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September 16

Gull

(okay, so there was a question in there...) ;)

Not really a question - but I just saw this photo and it took my breath away. How cool is this? Even the gull I raised from a couple of days old won't do this... --Kurt Shaped Box 01:00, 16 September 2006 (UTC)

How did you manage to mount it like that? cool! 8-)--Light current 01:04, 16 September 2006 (UTC)

Dunno - not my photo. You were referring to mounting the camera, right (as opposed to some form of sexual deviancy)? ;) --Kurt Shaped Box 01:18, 16 September 2006 (UTC)

No. Mounting of the stuffed gull of course! Is that deviant?--Light current 01:20, 16 September 2006 (UTC)

You sure it's stuffed? Just looks scruffy and a bit 'moulty' to me (as young gulls often are). --Kurt Shaped Box 01:23, 16 September 2006 (UTC)

I dont go out with young gulls, so I couldnt comment! 8-)--Light current 01:41, 16 September 2006 (UTC)

Looks lea-gull to me. --Kurt Shaped Box 01:53, 16 September 2006 (UTC)

Looks a pretty ill eagle to me!--Light current 02:33, 16 September 2006 (UTC)

It could just be a photoshop. Photoshoped pictures can look *really* real these days if done by an experienced photoshopper. (take a look at the photoshopped 'morphs' on this page http://www.humandescent.com/index3.shtml) Yaksha 02:02, 16 September 2006 (UTC)

Anybody notice how the bread looks like it was toasted with a clothes iron ? So we know the guy is a bachelor trying to lure young gulls into his grasp... :-) StuRat 02:42, 16 September 2006 (UTC)

Looks more like the gull is trying to swallow both the bread and the foolish feeders thumb.--Light current 03:56, 16 September 2006 (UTC)

Surely that's orange peel. How cool is this? 78%. Peter Grey 13:54, 16 September 2006 (UTC)

THe question I have is : who is taking the picture. If it's the person holding the bread, how the hell did s/he keep the camera so steady/ focussed etc?--Light current 20:51, 16 September 2006 (UTC)

That's what I was wondering too. The photographer has a whole gallery of similar pics at http://www.flickr.com/photos/elsie/sets/88049/ - some amazing stuff. Check this one out too - I've had it on my HD for ages and I can't remember where I found it: http://img133.imageshack.us/my.php?image=bethseagullhires5uzew4.jpg --Kurt Shaped Box 21:30, 16 September 2006 (UTC)

Looking at those pics it can only be a motor drive camera with auto focus etc.--Light current 01:00, 17 September 2006 (UTC)

Weird! Not the photo, but the response here. If you throw some bits of bread to gulls on the beach, a big flock gathers. Hold up bread, gull flys up to get it, snap picture. If it didn't turn out well, do it again and again until you run out of bread and/or fingers. The gulls aren't easily bored if there's food involved. I guess the equivalent for a city-dweller would be a pigeon or squirrel eating peanuts right at your feet, where you could reach out and touch it. --Wjbeaty 06:06, 17 September 2006 (UTC)

The gulls around here would never actually take food from a human's hand on the wing. They'll catch food in mid-air if you throw it to them and they'll come quite close if you place it on the ground but they are *very* careful never to enter our 'striking range'. When on the ground, they seem to calculate the distance that I'd be able to cover with a full length dive and stay just outside of that. Very wise birds - "beware the hand of man". The only one that comes closer is a gull that knows and trusts me... --Kurt Shaped Box 06:39, 17 September 2006 (UTC)

Photographing birds on the wing is very difficult, even at a distance. Imagine getting a good shot at a short distance like that. But photographing gulls like that under windy conditions (such as on a boat or a cliff) isn't too hard. They just hang in the air, inching closer to the person holding the bread.

Kurt (or should I call you 'Box'?), your gulls are on the ground and maybe that is too vulnerable a positiom for them. DirkvdM 07:27, 17 September 2006 (UTC)

Gulls are the masters of the updraft - it's like they're just floating there without any effort whatsoever. Forwards, backwards, sideways, they can just sort of 'slide' around in the air without flapping their wings at all (if you look closely, they do it with tiny flicks of the 'wrist'). On a hot summer's day, they love to ride the thermals and go so high as to be tiny dots in the sky. Then they glide slowly down. Thinking about it, in my garden, with nothing to catch a ride on, they'd have to swoop, dive and pull up at the last moment to take food from my hand - which is probably a pretty tricky manoeuvre for the sake of a piece of bread... --Kurt Shaped Box 12:39, 17 September 2006 (UTC)

Onions going green

There's a way to preserve onions that involves peeling the onions, and then leaving them in a jar filled with pure vinegar (normal vinegar, not white vinegar).

The vinegar soaks into the onions, and the onions are ready to eat after about a year. At the end, the onion pieces turn black (obviously due to the black color of the vinegar that gets soaked in.) After a few month, the onion pieces started turning black. However, i noticed many of them also turned green before going to black. Not like a dull green, but a bright and almost flourscent green. They'd stay green for a few weeks before starting to turn black also.

And before anyone tells me the onions have gone mouldy - i can assure you that's not the case. They're supposed to turn green. When preserving onions in vinegar, it's normal for them to start turning green.

I can't quite figure out why, no one really knows...and i'm having a bit of a hard time trying to get intelligent results by googling keywords like "green onions" Yaksha 02:02, 16 September 2006 (UTC)

Try searching under pickled onions. Unfortunately, our article on them is just a stub. StuRat 02:36, 16 September 2006 (UTC)

Garlic I've pickled has gone blue. The main changes a chemist would expect would be due to the acid of the vinegar causing changes or maybe something to do with metal ions bonding / breaking free from / swapping with different metal ions on organic molecules. Have a look at pH, denatured, chelate, chlorophyll, and colour for some background reading. Rentwa 07:21, 16 September 2006 (UTC)

Yeah..i know it happens to garlic too. I've seen garlic turn green when preserved in vinegar too. I pretty much guessed it was due to the acid in the vinegar and all, i'm a chem student myself. I had hoped someone here would be able to give a precise answer about exactly what in the onion did what to produce what product that caused the green-ness. thanks anyway Yaksha 12:05, 16 September 2006 (UTC)

If you're a chem student you can prepare various extracts and put them in a spectrometer :) . Rentwa 07:20, 17 September 2006 (UTC)

How to Build a Catapult

My sister needs to build a catapult for physics class. For her project, she needs to build a catapult that will be able to launch a tennis ball sufficently farther than the competition (her other classmates). Interestingly, grades will be determined by one's rank in distance compared to the competition. She needs to help with concepts and such, to keep this safe from that homework rule. :p

Here are the main points and rules:

Size restrictions: The maximum size of the base is 0.75 meters by 0.5 meters.

The maximum size of the movable rigid throwing arm cannot exceed .5m.

There must be a safety switch to ensure the mechanism can be fired from 2 meters away.

There are no weight restrictions. (This seems pretty important and useful.)

Any materials can be used.

Here are some questions:

What is a good place to start at when building the catapult?

What materials would be best for such a catapult? (springs, etc)

What are some sources (websites) that provide detailed instructions on creating a catapult that maximizes distance?

What are some general rules to follow?

And lastly, what are some good tips that can give the highest opportunity to have the best distance?

The key question that she wants to know is what is the best way to build a catapult that will allow her to win. :)

Please tell me if you have questions. Hopefully there are loopholes in the project that can be exploited. :P

--Proficient 03:39, 16 September 2006 (UTC)

I don't see a rule prohibiting tennis ball launchers, baseball launchers, nor any design like them. Also, backspin is a good thing. A friend built a fixed-arm catapult with approximately these dimensions that would through tetrahedral packs of four tennis balls ~300 meters (of course, the arm tended to bend slightly on these maxed-out throws). -- Fuzzyeric 03:58, 16 September 2006 (UTC)

Yes but these are not catapults and may be disqualified. I suggest following the Roman army design that uses torsion springs made of taut rope or sinew to store the energy. Were they callled ballistas?--Light current 04:05, 16 September 2006 (UTC)

I reckon one of these 2 babes may do the trick!

Catapult

Trebuchet at Château des Baux, France.

--Light current 04:17, 16 September 2006 (UTC)

Ahh but heres the site you want [1]--Light current 05:00, 16 September 2006 (UTC)

I would use bungee cords for the energy source. You can buy them at many stores, typically in the hardware/automotive section. Use a peg to hold the throwing arm in place, then add the bungee cords one at a time (you will need to have eyelets on the throwing arm for the bungee cord hooks, and eyelets on the base for the other end of the bungee cords). Make sure the base is very heavy, so it won't tip over when you pull the lubricated peg out with a rope from several feet away. You should have a "stop" that assures the object is launched at a 45 degree angle for max distance, this will take some testing. StuRat 06:10, 16 September 2006 (UTC)

Here is a rough sketch:

+-+
|S| \
|T|   \BUNGEE CORDS
|O|     \
|P|       \  BALL
+-+--ARM---+------+
+-+----------+
| HEAVY BASE |
+------------+

StuRat 06:27, 16 September 2006 (UTC)

Yeah you wouldnt want to jerk your dog would you? See bungee cord--Light current 06:15, 16 September 2006 (UTC)

Keep in mind that the more bungee cords you add, the harder it will be to pull the throwing arm down to the ready-to-fire position. One thought is to buy a boat trailer winch (the manual hand-crank kind) at a hardware store, and use it for cocking the firing arm. I bought one a few years ago for a project, and it was pretty inexpensive. Speaking of cost, though, what's your sister's budget? I suspect that every other student in the class is also turning to the internet, and researching old Roman catapults and stuff, and will come up with the same basic design. Want something different, and more dangerous? Use the power of compressed air for firing the thing. A big accumulator (air tank), some large-diameter hoses and a poppet valve, and a big pancake cylinder will generate way more force than a few bungee cords. It'll also make an exciting, loud noise and scare the crap out of the competition. It may be beyond your sister's technical abilities though... is she handy with tools? Does she have a MIG welder or know someone who does? --192.168.1.1 8:33 16 September (PST)

My instructions are to attach one bungee cord at a time, while the throwing arm is already in the firing position. Thus, you can apply maybe a dozen bungee cords, each stretched to the maximum, for a great deal of total force. StuRat 01:29, 18 September 2006 (UTC)

OMGLOL MIG Welder!! THis girls probably in primary school!(and probably doesnt understand the meaning of the term welding) I think Stu's idea is probably the most practical for a young girl.--Light current 16:49, 16 September 2006 (UTC)

Well, she wants to win, doesn't she?  :) I was going to ask what grade she was in, but forgot... I can see a high-school student maybe having access to one (a neighbor, a friend in shop class... ) A third-grader, though, probably not. Anyway, my competitive streak came out (and my innate tinkerer). Can I build this for her? We won't tell anyone! But if she wins, I get to share the prize. --192.168.1.1 11:03 16 September (PST)

She is a junior in high school (physics). I will tell her of these suggestions. I thank each one of you. Please feel free to add more comments and such. --Proficient 19:15, 16 September 2006 (UTC)

What scares me about this is that an unlimited amount of stored energy can be put into the device. With no material or weight limit, it could be powered by a piston driven by high pressure compressed air, with a pilot valve manually triggered which opens the large main air valve very quickly. A high voltage electrical circuit breaker in a substation uses such technology. Or it could be powered by a coil spring or by a torsion spring, also like used in substation circuit breakers and automatic throwover gear. Either the compressed air or the spring could have enough energy to lift a car off the ground, so the transfer of that energy to a tennis ball could result in perhaps lethal speed at launch, which would decay rapidly due to air resistance. One could build a catapult, the firing arm of which was capable of knocking off the head of anyone in its way if it fired inadvertently. If I wanted to win this contest at all costs and regardless of risks, I would get a spring such as is used on a car, and use a ratchet and windlass, or perhaps a car hydraulic jack, to cock it. Think a classic crossbow made into a catapult. If it came apart or fired prematurely, it could sever limbs. It would be apt to break and throw deadly parts in various directions to considerable distanced. The firing arm would be low mass to allow max acceleration, but strong enough to stand the acceleration and deceleration. A damping device would be needed to absorb the impact when the firing arm stops. The whole device would tend to jump in the air when fired, so I would design for low center of gravity with a massive baseplate. When the trigger released the firing arm, which would probably require a clever trigger mechanism to avoid binding, the firing arm would rotate from its rest position to, say, a 45 degree angle or something between 45 and 90, selected to achieve maximize range. It would stop by hitting the arresting device and the tennis ball would continue. The limiting launch velocity would be that which breaks the tennis ball or the mechanism. Design conservatively with a large safety margin. I would have written the rules to limit weight and materials to avoid the hazards inherent in this very open statement of rules. As always, these comments are purely theoretical: don't try this at home. Edison 19:41, 16 September 2006 (UTC)

You could also take some pointers from the recurve bow. That's basically the thing that made mongol bows so dangerous. Basically, if you just use one half of it you get a catapult, right? Btw, I once saw a video of atrebuchet flinging a car into the air. It landed tens of metres away. Pretty potent stuff! DirkvdM 07:41, 17 September 2006 (UTC)

Trebuchets don't scale linearly: throwing power increases somewhere between the square and the cube of size, so while a large trebuchet is more powerful than a large catapult, a small catapult is more powerful than a small trebuchet.

Back to the original competition: the rules limit the rigid part of the throwing arm to half a meter, but there's no mention on a limit on a sling. All medaeval throwing weapons had a sling on the end of the arm to increase range. Calibrating the release hook for the sling is something of an art, but if you get it right, you can easily double the range of your catapult. --Serie 19:38, 19 September 2006 (UTC)

On the subject of materials, I recommend something like cast iron (with possibly lead added) for the base and aluminum for the throwing arm. For the arm, you want something light and stiff, emphasis on light so it can accelerate quickly. Dipics 14:37, 22 September 2006 (UTC)

Effects of using spent perlite as soil conditioner to improve yield of corn

one of the by products in the manufacture of carrageenan is perlite - predominantly Si02 used in the filtration process. do you have technical papers citing the benefits of usig perlite as soil conditioner to improve yeild of corn? we generate about 3-4 mt/day and it will also help transform the waste into agricultural purposes and help the local farmers.

json of the philippines

Probably best to contact the Perlite association [2]--Light current 04:58, 16 September 2006 (UTC)

Perlite is used to lighten (improve drainage, aeration etc) heavy soils. I'm sure it would help agriculturally, although I think most of the data available will be from horticultural sources, try searching for perlite as a compost additive / ingredient for more info. It may be contaminated (depending on the details of your process). If the contamination is with organic matter it may encourage excessive microbial growth, which may be harmful. Rentwa 07:38, 16 September 2006 (UTC)

Black Rain

What was the black rain that happened after the Hiroshima blast? --Shanedidona 04:20, 16 September 2006 (UTC)

Probably nuclear fallout: radioactive fission products and unreacted fuel from the bomb. —Keenan Pepper 04:35, 16 September 2006 (UTC)

(edit conflict) A combination of water, ash and radioactive fallout such as isotopes of uranium, caesium, and lead. ---Sluzzelin 04:40, 16 September 2006 (UTC)

And probably other dust and debris which was sucked up into the mushroom cloud. --Fastfission 17:23, 16 September 2006 (UTC)

And anything thing that was vaporised in the original blast recondensing. Philc _T^E_C^I 17:27, 16 September 2006 (UTC)

It is very well described in the horrific Black Rain by Ibuse Masuji: Secker & Warburg, London 1971 -- Puffball 07:40, 22 September 2006 (UTC)

we have heard of 2 , 4 , 8 , 16 , 32 and 64 bit processors .why not there any processor that is of odd bit number?

is there any processors that are of 1,3,5,7 etc. bits or 6,12,24,48 etc.bits? why a 64 bit processor is better than 32 bit processor and how ?

You should probably try Computing rather than Science, but let me just say there are several different things "#-bit" could refer to: the number of bits in a byte, the number of bits in a memory address, the width of the computer bus... —Keenan Pepper 04:39, 16 September 2006 (UTC)

The GE-600 series (a.k.a. "Honeywell 6000 series") and the PDP-10 were 36-bit computers. The Ge-600 also had 6- and 9-bit addressables (which can make the second definition of byte difficult to apply). The CDC 6000 series used 60-bit words. The IBM 7030 had variable length bytes (1-8 bits). During the relevant time period, bytes can in all kinds of sizes, leading to the use of the phrasing n-bit-byte ("8-bit-byte").

The Motorola 68000 was degenerate in that there was no address pin zero, so the minimal actually addressable was 16-bits although the pointers had 8-bit resolution. (Dereferencing an odd address threw an exception.)

To answer your 32-/64-bit question, see 64-bit computers#32 vs 64 bit. -- Fuzzyeric 05:26, 16 September 2006 (UTC)

See Category:Data unit. There are certainly quite a few computer architectures which use data sizes which are not a power of two bits, but 31-bit is the only one I'm aware of which isn't an even number.

The main reason why a 64-bit processor is "better" than a 32-bit one is that it can address (or "use") more memory. A 32-bit processor can only use 4 GB of memory unless certain work-arounds are used; a 64-bit one can use 4 billion times as much. For current personal computers, there isn't much demand for more than 4 GB, but for servers and some scientific applications, the extra memory is very useful.-gadfium 05:20, 16 September 2006 (UTC)

The Electrologica X1 had a 27-bit word length. --Lambiam^Talk 11:54, 16 September 2006 (UTC)

help me to know more about the colour of the urine

I want to know what are the unnormal clours of the human 's urine ? Can it be green? does it's colour depend on what has been drunk?

Yes, it can be green, and it does depend on what you eat and drink, but it's not as simple as always being the same color as what you eat or drink. It can also be clear if you drink a lot of water. Yellow, of course, is normal. Red or brown indicates blood in the urine, and merits a visit to the doctor (hopefully it's just a bladder injection and some antibiotics will fix you right up). StuRat 06:40, 16 September 2006 (UTC)

Normal urine is a pale yellow: that color is a result of the presence of urochrome. Dilute urine, caused by increased fluid intake, can be colorless; concentrated urine, caused by decreased fluid intake, can be dark yellow

There are two relatively common abnormal colors that correspond with physical disorders. Dark brown ("tea-colored" or "Coca-Cola") urine can indicate a problem metabolizing bile in the liver - if this is the case it can be accompanied by a yellowing of the skin and eyes (jaundice), and by pale feces. Red or pinkish urine can indicate the presence of blood in the urine, which can be the result of urological probem.

Also, a "cloudy" urine may indicate an infection.:There are less common abnormal colors as well. Some of them are related to foods, vitamins or medications such as beets, B vitamins, pyridium, or rifampin

Green urine is very unusual, but can result from artificial colors such as methylene blue, or pigments produced by certain microorganisms that cause urinary tract infections.

Obviously, if anyone has an abnormally colored urine that isn't linked to an obvious specific cause, they should talk to their doctor about it. - Nunh-huh 06:43, 16 September 2006 (UTC)

It can also go green from an overdose of B-Vitamins. B00P 10:33, 16 September 2006 (UTC)

Porphyria (the madness of King George) can cause purple-pink urine, but most bizarely of all, the flourescent microbes found in seawater can give sea travellers glow-in-the-dark urine even if the sea water is thoroughly treated before drinking. smurrayinchester^{(User), (Talk)} 21:22, 16 September 2006 (UTC)

Hmm. Handy for pissing in the dark.--Light current 01:02, 17 September 2006 (UTC)

Your name would take on a whole new meaning. :) DirkvdM 07:53, 17 September 2006 (UTC)

Asparagus will often cause urine to be green colored. Check this link for all urine color changes, and also this page, which says that other foods, as well as some medicines, including Risanpin, an antibiotic, will cause urine to be green (or blue). ^BlankVerse 05:18, 17 September 2006 (UTC)

I recently saw a documentary on the possibility of missions to Mars and the preservation of water. Of course that meant distilling the urine for reuse. The leftover concentrated urine was gathered in a transparent (!) tank and looked very dark yellow of course, but with a definite reddish hue to it. Is that blood or what? DirkvdM 07:53, 17 September 2006 (UTC)

Urochrome--Light current 20:01, 17 September 2006 (UTC)

lexapro

is blurred vision a side effect of taking this medication? john

http://www.drugs.com/lexapro.html http://www.lexapro.com --GangofOne 06:49, 16 September 2006 (UTC)

Any strange effects (such as yours) whilst taking your meds should be reported to the doctor quickly.--Light current 09:06, 16 September 2006 (UTC)

Luminosity

I added the following to Barnard's star yesterday: It has a "visual luminosity just 4/10000 of solar, corresponding to a bolometric or absolute luminosity of 3.46/1000." This is based on this and this paper within it. But I'm uncertain if I have this right, as it suggests the first figure is a relative value and the second absolute, while our page on solar luminosity mentions no distinction. Also don't no why there's an order of magnitude difference, though I think I'm reading it write. Marskell 07:15, 16 September 2006 (UTC)

Dont worry. Someone will correct it if its wrong.--Light current 09:08, 16 September 2006 (UTC)

LOL. I don't like to edit that way. I'd rather know I'm right or not before I add the point; call it amateur responsibility. Marskell 09:31, 16 September 2006 (UTC)

So do I but its not always possible. Just edit in good faith OR put a question on the respective talk page pending your edit (or even afterward)--Light current 14:31, 16 September 2006 (UTC)

The visual luminosity is the total amount of visible light output from a star. The bolometric luminosity (which, I believe, is what astronomers usually talk about when discussing luminosity) is the total radiated energy output: visible light, ultraviolet, x-rays, infrared, radio, etc.

Barnard's star is smaller and cooler than the Sun, which means that its light output is redder than the Sun's and that it radiates less energy per unit of surface area. Also, a larger fraction of that output is down in the infrared, rather than visible light. So the total energy output of Barnard's star is about 0.346% that of the Sun. Because a larger portion of that output is in the infrared, Barnard's star's visual luminosity is even lower—0.04% that of the Sun. TenOfAllTrades(talk) 17:37, 16 September 2006 (UTC)

OK, thanks. I assumed something like this, but it often doesn't seem to be made clear when detailing luminosity. When luminosity states "In astronomy, luminosity is the amount of energy a body radiates per unit time" it makes no mention of the distinction, which is fine I suppose, insofar as the generic term is taken for absolute output. But the characteristics in star tables on our pages use the other figure and say "luminosity", not "visual luminosity", which strikes me as an error. Marskell 19:47, 17 September 2006 (UTC)

Weird strings during nuclear explosions

What are those things that rise or fall from/to the ground during some nuclear explosions? White trails of smoke, they look like. 81.93.102.3 11:31, 16 September 2006 (UTC)

Do you mean mushroom clouds ? StuRat 11:36, 16 September 2006 (UTC)

Not at all, but you can very clearly see them in http://en.wikipedia.org/wiki/Image:Mushroom_cloud_sequence.jpg - WHITE TRAILS. :) 81.93.102.3 11:54, 16 September 2006 (UTC)

If memory serves, they are rocket trails. Measuring gauges of some sort would be shot up on rockets just before the explosion.--Rallette 12:03, 16 September 2006 (UTC)

That seems to be correct; see Effects of nuclear explosions#Other phenomena. (But see also Rope trick effect, which can also produce curious lines in pictures of nuclear tests.) —Ilmari Karonen (talk) 13:55, 16 September 2006 (UTC)

Yeah, they are smoke trails from rockets that go off right before the blast. You can measure blast effects with them which would otherwise not appear on film in a quantitatively measureable fashion (like the shock wave and changes in air pressure). --Fastfission 17:21, 16 September 2006 (UTC)

If this is about the vertical striations each side of the cloud, I used to think this was an electrical discharge phenomenon due to the intense emp generated by the blast but looking at the photos linked to, it appears I was wrong.--Light current 01:21, 17 September 2006 (UTC)

You are all wrong, if you are talking about, as I suspect, pictures of early "ground burst" tests which sometimes show bright more less diagonal lines. In such pictures, you can sometimes see the vaporized remnants of cables which had been used to anchor the tower holding the bomb, or to anchor (un-manned!) blimps which held scientific instruments. This is discussed in Richard Rhodes, The Making of the Atomic Bomb.

It is true that some pictures also show electrical discharges related to atmospheric disturbances resulting from an nuclear explosion; these tend to look like lightning flashes, not straight line segments. ---CH 22:36, 19 September 2006 (UTC)

Sorry, just noticed that someone already linked to Rope trick effect. I think the mention of rockets is a third possible correct explanation. Looks like you would have to provide a link to a specific picture.---CH 22:40, 19 September 2006 (UTC)

name of species - or common name

resembles - to me at least - a snail, is very large - maybe 10" across, lives on land, only seen photo long ago, remember it being quite colorful

I am in no way a snail expert, but if you can find a photo, it would help those here that do have experience with zoology. --Russoc4 14:51, 16 September 2006 (UTC)

Maybe a flatworm or land planarian? Wikipedia:Reference desk archive/Science/May 2006#Any idea what this flat head worm slug thing is? --Kjoonlee 16:04, 16 September 2006 (UTC)

Sounds perhaps like one of the West Indian land snails famously studied by Stephen Jay Gould. Possibly either the genus Cerion or Poecilozonites. They don't have specific Wikipedia articles, but you can look at Bermuda Land Snail or try a Google search (e.g., cerion snail). --jjron 16:35, 17 September 2006 (UTC)

Thanks - ?but no thanks? - someone is not paying attention. I tried to be concise and clear. "RESEMBLING A SNAIL" - i.e. it has a LARGE shell, definitely not a worm or planarian. "VERY LARGE" - not almost microscopic. "LAND" animal - not aquatic. Definitely not a tiny West Indian snail. Much larger than the Giant African Land Snail. And no, I do not have a picture or name or anything - just a vague memory.

On Glass Cleaners, Ammonia.

In Windex brand cleaner and other glass cleaners, is there ammonia in solution with water or is it the ammonium ion in solution from ammonia containting compounds? --Russoc4 14:48, 16 September 2006 (UTC)

See Windex. Other glass cleaners are not necessarily the same, for example, some are based on white spirit.--Shantavira 17:39, 16 September 2006 (UTC)

So is ammonia used as a glass cleaner or not? If I just wanted to read a static answer in the article, I wouldn't be here on the ref desk. I'm looking for a more dynamic answer that doesn't just aimlessly redirect me to an article.--Russoc4 18:27, 16 September 2006 (UTC)

It says in the article that it is ammonia. --liquidGhoul 02:49, 17 September 2006 (UTC)

Ammonia is a very weak base, and so a solution of it would not normally contain very much of the ammonium ion. Further evidence is that ammonia smells, and the ammonium ion does not. Smell the Windex! --G N Frykman 20:55, 16 September 2006 (UTC)

Thank you Frykman. You've been most helpful. --Russoc4 21:09, 16 September 2006 (UTC)

Cancer stats

Where would I find a list of top incidents of cancers (prostate and breast) per county in the U.S.?

• By county, I'm not sure, but the American Cancer Society has a load of US cancer statistics by state at the very least. I have seen by-county maps out there before (they are sometimes quite remarkable) but I don't know offhand where they are. --Fastfission 17:29, 16 September 2006 (UTC)

Psychopathy prevalence

I am taking a criminology course in college and recently learned from the professor that statistics show psychopathy is more prevalent in the united states than in japan and other asian countries (controlled for population). I asked the professor why this was and the theory he came up with is that it could be genetically less prevalent in ethnic asians or that a more individualistic culture might be correlated with a higher incidence of psychopathy. Is there any statistical evidence for or against this theory (possibly the percentage of asian peoples diagnosed as psychopaths in the US)? Thank you very much for your time, any evidence would really liven up class discussions! -Timothy

Comment: I would call that hypothesis or conjecture instead of theory.

I don't know, though you might be interested in reading race and intelligence, but first check out the maps at Race Differences in Intelligence.--Shantavira 18:53, 16 September 2006 (UTC)

One potential confound to researching genetic differences among ethnic groups is that even in one country, different ethnic groups generally have cultural differences. Most clinical psychologists would point to a cultural explanation rather than a genetic one to explain differences among ethnic groups; this approach even has a name -- the sociocultural model. Also note it is simplistic to say that the U.S. has a higher prevalence of psychopathology; this may be true overall (I don't have it in front of me), but different disorders have different prevalences around the world. Schizophrenia has similar rates in all cultures. Also, there is a cultural component to the symptoms of some diseases -- for example, with major depression -- and some disorders are peculiar to certain cultures. --Ginkgo100 ^{talk · e@} 19:44, 16 September 2006 (UTC)

Whoa, I just realized I mistook the work "psychopathy" for "psychopathology". Very different things! Psychopathy, of course, is aka antisocial personality disorder, one of many types of psychopathology (mental disorders). --Ginkgo100 ^{talk · e@} 00:41, 18 September 2006 (UTC)

I suspect that the incidence of psychopathy is either overreported in the US (say by criminal lawyers hoping for leniency) or underreported in Japan (possibly due to the shame associated with such a diagnosis). StuRat 23:44, 16 September 2006 (UTC)

Two words: ascertainment bias. What an astonishing question. There are enormous cultural differences between the two societies. It is hard to think of a more culture-dependent imputed category than "psychopathology", which is originally a European concept wholeheartedly adopted and elaborated in North America. How could anyone imagine that the classification and ascertainment procedures would be the same in the two countries. Find another professor if he really believes that. alteripse 00:11, 17 September 2006 (UTC)

There is an essential difference between psychopathology – the study of various forms of mental illness – and psychopathy – a presumed personality disorder characterized by the inability to experience compassion or remorse. I doubt that the latter concept is originally European. --Lambiam^Talk 20:00, 17 September 2006 (UTC)

Thanks for pointing out that I wrote psychopathology when I meant psychopathy. The former is a very broad category roughly equivalent to "mental illness", while the concept of psychopathy (and the more common term psychopath) derives from European and American psychiatry. See Werlinder H (1978) Psychopathy: A History of the Concepts. Uppsala: Almqvist and Wiksell if you dont believe me. However, my answer does apply to psychopathy not psychopathology. alteripse 02:36, 18 September 2006 (UTC)

Thanks for the information guys. And no thanks for the completely unhelpful trolling alteripse. -Timothy

If you dont think my answer was a direct relevant answer to your question, you and your professor are well-matched. alteripse 17:25, 17 September 2006 (UTC)

Geez, Timothy. alteripse is the only self-identified medical professional who responded to your question, and s/he said exactly what I was going to say (but didn't because it'd already been said). Maybe some of it was strongly worded, but it wasn't trolling, IMO. No need to take offence for a WP editor casting aspersions on your prof. Anchoress 17:39, 17 September 2006 (UTC)

Project management

I would like to know of existing or recent case studies or experiences from community based projects in some Developing Nations with respect to methodologies in project management and evaluation. Preferably in the building/construction area.

Micro-climate in Nigerian houses

Please help me with information on housetypes of the pre-colonial Nigeria and how the various types of architecture of the three major geo-political zones (north, southeast and southwest)as well as the materials used helped in creating a tolerable micro-climate within the building.

Maybe some of these links can help you: Encyclopedia Brittanica African architecture, various articles by Uche Isichei, Article by Adesoji Jiboye in Anthropologist, 6(3): 169-174 (2004) pdf file! (html version).---Sluzzelin 05:56, 18 September 2006 (UTC)

ABS with a manual transmission?

It seems that I can't get an Anti-lock braking system (ABS) on a Toyota with a manual transmission. Anyone know why this might be? Is ABS avilable only on any cars with an automatic? I amazingly can't find much on this. -Ravedave ^{(help name my baby)} 20:15, 16 September 2006 (UTC)

There's no physical reason why you can't have ABS on a manual; most cars in the UK are manual and it's legally mandated that all new cars are fitted with ABS. I don't know why you can't get that combination from your dealer. --Yummifruitbat 20:35, 16 September 2006 (UTC)

I don't know either, because the lack of ABS means no stability control either. I wonder if there is something with the manual that costs more. -Ravedave ^{(help name my baby)} 20:38, 16 September 2006 (UTC)

I thought ABS was mandated in the US. Are you sure you aren't thinking of ASR or ESC? --Russoc4 21:12, 16 September 2006 (UTC)

To cut production costs, manufacturers like to limit the number of available combinations of options. For example, power windows and power locks almost always come together, even though there is no technical reason preventing one from being offered alone. StuRat 23:31, 16 September 2006 (UTC)

I have a 2000 Dodge Dakota pickup truck with manual transmission and 4-wheel ABS, so I know for a fact there is no incompatibility between a manual transmission and ABS. --Gerry Ashton 03:59, 17 September 2006 (UTC)

I wonder if it takes 2 Master cylinders on manuals.-Ravedave ^{(help name my baby)} 04:12, 17 September 2006 (UTC)

The service manual says the same master cylinder is the same for all 2000 Dodge Dakota models. --Gerry Ashton 04:18, 17 September 2006 (UTC)

Lack of ABS does not mean "no stability or control." See the section on "effectiveness." --Smack (talk) 17:46, 17 September 2006 (UTC)

here in Australia, Toyota supplies manuals with ABS.see www.toyota.com.au Downunda 23:31, 17 September 2006 (UTC)

Toyota is playing games here, I have cars from 1992, 1997, and 2003, all have manual transmissions and ABS (none are Toyotas). And to Smack, what he meant by 'no stability control' was that no ABS system usually means the car has no way to meter the wheels for electronic traction control. To Ravedave, cars require a master cylinder for brakes whether there is ABS or not, the ABS mechanism is actually often far away from the pedal mechanism, so they would have to offer manual transmissions only on cars without brakes... hmmmm... --Jmeden2000 15:04, 18 September 2006 (UTC)

histologia

CualSeptember 17September 17on las diferencias entre mastocitos y celulas cebadas?

• What are the differences between what and what? Esto es el Wikipedia inglés. --Nebular110 21:51, 16 September 2006 (UTC)

Son identicos. Celulas cebadas (literally "barley cells", mast cells in English) and mastocitos (mastocytes) are one and the same thing. ---Sluzzelin 22:33, 16 September 2006 (UTC)

¿Ha visto Ud. es:mastocito? Yo leo ...también son llamadas células cebadas. Hyenaste ^(tell) 01:51, 17 September 2006 (UTC)

You can ask a trick question in Spanish at the English science ref desk, mutilate it by replacing a letter with the date (twice) and still get an answer. Is that cool or what? DirkvdM 08:36, 17 September 2006 (UTC)

September 17

Geochemistry of ultrabasics.

How a rock can be named ultrabasic on the basis of chemical constituents? S.K.Pandey <email addr removed>

See Ultramafic rock ---Sluzzelin 01:47, 17 September 2006 (UTC)

Lactic Acid in Yogurt

how much lactic acid is there in commercial yoghurt? (question modified in part by Russoc4 02:26, 17 September 2006 (UTC))

Most references give 0.9%-1.1% as the range of acceptability. The acidification of yogurt continues during storage, so I assume that commercial yogurt has around 0.9% lactic acid when it leaves the factory. This UCLA link has a table showing the postacidification of yogurt for different storage temperatures.---Sluzzelin 02:27, 17 September 2006 (UTC)

How does radar work?

Let's say we send some radar waves toward an object, like so:

http://72.136.70.187/radar.jpg

If radar waves obey the law of reflection, how can the object be detected in the above situation? None of the radar beams are reflected back to their source.

Also, our article on radar says that the received power (that's reflected from the object) decreases with the fourth power of the distance. Why is this? I know that since the radar emitter sends out waves in all directions, the intensity of the waves decrease with the square of the distance. But since the target object reflects the waves directly back, and does not send it out in all directions like the emitter does, why does the intensity of the reflected beam decrease with the square of the object-receiver distance (instead of the emitter-object-receiver distance)? --Bowlhover 05:01, 17 September 2006 (UTC)

The diagram depicts "stealth technology" where an aircraft is covered with flat facets. As long as none of the flat mirrors face the emitter, and as long as none of the flat mirrors reflect each other (so they don't create "corner reflectors") ...then there will be very little reflected waves. And the 4th-power stuff only works if we model the distant target as a point-like reflector. Of course if the object is covered with curved metal surfaces, it will be a curved mirror, and will create virtual images which act as point-sources. --Wjbeaty 05:55, 17 September 2006 (UTC)

You unwittingly discovered one aspect of stealth it seems. :) Most surfaces will scatter the radio waves, so some of it will come back to the source. As for the fourth power, imagine looking at a light source through a cloud. The intensity will decrease with the distance, but also because of the scattering. I don't know why this would amount to the fourth power precisely (or is that an estimate for practical purposes perhaps?). Also, doesn't the intensity decrease with distance to the third power because the beam gets emited in three dimensions? DirkvdM 08:49, 17 September 2006 (UTC)

Suppose the target were a sphere, roughly the size of the wavelength of the RADAR wave. The intensity of the radiation incident on the sphere falls off like $1/r^{2}$. That radiation is then reflected over just less than $4\pi$ steradians (grazing waves are barely reflected). Thus, the reflected energy also falls off as $1/r^{2}$. Since the round-trip energy is attenuated twice this way, the result is $1/r^{4}$.

Now, why is this a reasonable model? Note that very few surfaces are optically reflective. Most surfaces have semi-transparent surfaces, so incident waves are incoherently scattered from several different depths in the material. This happens for RADAR waves and metals. The penetration depth is proportional to the wavelength, so a real surface looks like a bunch of randomized scatterers at variuos depths in the skin. Thus, the reflected radiation pattern is not purely specular but contains a large diffuse reflection component. This is captured at radar as $\sigma$, a coefficient indicating the tendency for the target to scatter incident radiation. Common radar wavelengths now are a few millimeters to a few centimeters, or equivalently gigahertz frequencies. So current radar will treat any rough features with these dimensions as a re-scatterer. So bolts, plate seams, and other similarly small features will act as scatterers (not reflectors). -- Fuzzyeric 22:31, 17 September 2006 (UTC)

Thanks to Fuzzyeric for explaining why power decreases with the fourth power. Also thanks to Dirk and Wjbeaty for telling me what's going on in my diagram. However, I have a question: in the example of the sphere, shouldn't radiation be reflected over just less than $2\pi$ steradians (instead of $4\pi$), because only half of the sphere is facing the radar emitter? --Bowlhover 01:21, 18 September 2006 (UTC)

Well, I hinted why this is the case ("grazing waves are barely reflected"), but ... Take a test ray and point it at the sphere. When the test ray passes through the center of the sphere, it will be retroreflected. We will measure displacements from this ray by measuring the angular displacement of the point of incidence at the center of the sphere. Move the ray slowly towards the edge of the sphere. When the displacement is less than 45-degress, the reflection is to the same side of the sphere as the incoming ray. When the displacement is 45-degrees, the reflection is at right angles to the incident ray. At larger displacements, the ray is "nudged" out of line, but ends up in on the other side of the sphere from the incoming ray. The only part of the forward scattering hemisphere that does not receive a reflected ray is the shadow of the sphere. (And, in Mie theory, even this isn't true due to diffraction around the edge of the sphere.) -- Fuzzyeric 13:17, 18 September 2006 (UTC)

Forgive my lack of knowledge, but I still don't quite understand. I'm pretty sure this is what you meant with the example of the sphere (am I correct?):

http://72.136.70.187/sphere_reflection.jpg

However, can you explain what you meant by "the only part...that does not receive a reflected ray is the shadow of the sphere"? Isn't half of the sphere in shadow? --Bowlhover 04:20, 19 September 2006 (UTC)

The diagram correctly illustrates my description. However, there are no rays that go through the sphere, so there's a shadow above the sphere in your drawing. However, Mie scattering, surface plasmons, and the formation of glories relies on more complicated behavior along the skin and/or through the target. This last bit is probably too much information...  :-) -- Fuzzyeric 15:57, 21 September 2006 (UTC)

Chemical, Molecular, and DNA Computers

Are chemical computers and molecular computers the same thing? If not, then what's the difference between them? Are all molecular computers DNA computers? If not, then apart from DNA computers, what other types of molecular computers are there (or will there be)?

(I've read the articles on them but I still don't understand.)

I would think that chemical computers would be the broadest category, with molecular computers being a subset of those, and DNA computers being a subset of those. StuRat 10:35, 17 September 2006 (UTC)

Chemical digital computers are currently not a practical possibility (and may never be). --Lambiam^Talk 20:11, 17 September 2006 (UTC)

Kids, help

My biochemistry is from a while ago. Am I correct in assuming 1 g carbohydrate = 4 kcal, 1 g protein = 4 kcal and 1 g fat = 9 kcal of energy when metabolized in humans. Anyone remember the value for glycogen? Thanks -- Samir धर्म 08:18, 17 September 2006 (UTC)

BINAS tells me that Cod liver oil is pure fat and 100 g metabolises to 3762 kJ. So that would be 37,62 kJ/g. I don't know what kind of calorie you're talking about (there's a small one and a large one - weird unit!), but assuming it's the large one, then it would be 37,62/4,185 = 8,989 kcal. Close enough. DirkvdM 09:10, 17 September 2006 (UTC)

My chemistry book confirms this: 1 gram of fat = 9.3 kcal (39 kJ), 1 gram of carbohydrate = 4.06 kcal (17 kJ). It doesn't give values for proteins, but I wouldn't be surpirsed if it was about the same as that of carbohydrate. It's only approximate though; it depends on the type of carb or fat (in this case glucose and glyceryl trioleate (olive oil) respectively). smurrayinchester^{(User), (Talk)} 14:49, 17 September 2006 (UTC)

The problem with glycogen is that it is never eaten in a pure form, which would theoretically be about the same in terms of caloric value as starch. alteripse 17:22, 17 September 2006 (UTC)

Long ago, I memorized the values you gave (1g carb = 4 kcal, 1g protein = 4 kcal, 1 g fat = 9 kcal) from a nutrition book. So my memory at least matches yours. --Ginkgo100 ^{talk · e@} 00:38, 18 September 2006 (UTC)

energy

i want to know about energy so that i can put it as the introductory part of my project -"conservation of energy"

-arjun

How about starting with Energy? Please sign your contribution with ~~~~. ColinFine 11:57, 17 September 2006 (UTC)

Also see energy conservation and conservation of energy, two quite different concepts. StuRat 07:07, 18 September 2006 (UTC)

Indeed. Many times it is easier to type it into the box before asking questions and attempting to look for the answer. --Proficient 05:36, 19 September 2006 (UTC)

Time

I was attempting to explain the concept of Time to my son today. I went your search engine, typed in the word "Time" and was floored by what I read. You guys better take a real good look at what some individual(s) wrote about what time is. The reference to George Bush and Dick Chenny (while comical) do not belong in Wikipedia. Just thought I would send this msg. your way.

It's already been fixed; it was just someone childishly vandalising an article. smurrayinchester^{(User), (Talk)} 15:06, 17 September 2006 (UTC)

Thank you, tell somebody again if you see something like that. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)16:39, 17 September 2006 (UTC)

Another user probably permanently scarred by Wikipedia vandals. And it was only there for 1 hour!  freshofftheufoΓΛĿЌ  07:00, 18 September 2006 (UTC)

If you want to be floored by the study of time, don't forget to check out timecube[3]! --Jmeden2000 14:57, 18 September 2006 (UTC)

twin paradox - curved space?

After reading about the twin paradox at http://en.wikipedia.org/wiki/Twin_paradox, I think I have a problem with the resolution. It says that the knoticable time delation of the moving object compared with the none moving one would distinguish which one it is that is moving only because of the acceleration of one twin in a switch in time frame.

What I don't understand is what if the space has a ring topology, then there would be no nessessary acceleration for the two objects to move in seperate directions, then to meet again and compare time. The topology of the universe seems not to be coverd in the artical.

Is it iMpossible for space to have a ring topology or is there a much simpler answer that I'm missing?

Thank you for your time in answering.

Colin

Curved space alone couldn't account for the time dilation without relativity, because the space would still need some kind of discontinuity in it for the dilation to occur. Rentwa 17:43, 17 September 2006 (UTC)

In flat, cyclic time (no accelerations, but if you go long enough in finite time you meet someone going the other way (which is a weaker requirement than "you get back to where you start")), if both participants accelerate with identical magnitudes but opposite directions then when they meet again, their clocks agree. However, in the twin paradox, only one twin experiences any acceleration at all (first to get up to speed, second to turn around, and third to stop) and the other experiences no acceleration at all. In the loop universe, the second twin accelerates to get up to speed and to stop, so we can still tell whose clock is slow. -- Fuzzyeric 22:46, 17 September 2006 (UTC)

I don't get what the paradox is in the "twin paradox". One ages more than the other, where's there a paradox in that ? If one could be frozen and thawed out later, the same thing would occur. Or, if one lives a rough life exposed to the elements they will also appear to age faster than one in a protected environment (although this is just the apparent age, not the true age). StuRat 01:18, 18 September 2006 (UTC)

But in relativity, whats apparent is the truth! But its an interesting view point you have.--Light current 01:32, 18 September 2006 (UTC)

It's called a paradox not because it's a logical error, but an apparent impossibility - "What? Two people born at the same time, in the same place, now have a thirty year age gap? That's impossible!" Confusing Manifestation 01:35, 18 September 2006 (UTC)

(Addendum) Oh, and then once you've had the concepts of special relativity explained to you, your next response is "ok, I'll accept that, but then if everything's relative to each other, how come if we look at it from the other twin's viewpoint we don't see the exact opposite happening?" - The answer to which is that the other twin has to accelerate and thus special relativity doesn't apply to him. Confusing Manifestation 01:37, 18 September 2006 (UTC)

THe conclusion from this is that altho velocities can be relative, accelerations are absolute in the universe. So you dont need to accelerate wrt anything-- you just accelerate! So in special relativity, I dont think an accelerating frame can be compared to a non accelerating one. Actually in the twins thing, its probably more to do with momentum.--Light current 01:42, 18 September 2006 (UTC)

I am distressed to see there is a lot of misinformation in the "answers" to several earlier questions involving relativistic physics, but since I am a latecomer, and tend to try to mention subtle points, perhaps there is no point in my trying to go into any detail.

Colin, your question involves taking a "discrete quotient" of Minkowski vacuum to "roll up" ("compactify" is the fancy term) one spatial dimension. "Twin paradox" thought experiments (of course, the "paradox" here is more apparent that real!) in such spacetimes have been considered by various authors. Try [4] and [5]. The correct short answer to your question is that global Poincaré group symmetry is broken by taking the quotient, while local Poincaré group symmetry is preserved. The local versus global distinction is fundamental in the theory of smooth manifolds.---CH 03:27, 18 September 2006 (UTC)

Ouch! :) Rentwa 14:17, 18 September 2006 (UTC)

I think relitivity is pointing to a lack of universal frame of reference. That would mean that you can not tell which twin of the two is moving, and all frames of referances can declare them selves as not moving at any point in time, and indeed that would be a correct claim, as there is no frame of reference that can say that it is not moving itself.

The time delation encountered by any frame of reference that has not acclerated must be the same. If they can meet twice without accelerating but still moving compared to each other, as it would be so in a circular space, then each can correctly observe and expect the other one to have more time delation.

All this means that no one can distinguish which is moving, yet their clock still must agree. How CAN is situation be possible?

Do animals prefer raw or cooked food, and can evolution cope with cooking?

A comment above about feeding sausages to gulls made me wonder what animals prefer. Has anyone any practical experience of gulls, dogs, cats, birds and so on prefering one or the other?

And since cooking is a very recent invention in evolutionary time, would anyone else agree or disagree with my hunch that since apes, mammals, and all predecessors back to single cells have not evolved to dealing with cooked foods, then we humans may not be able to totally cope with the carcinogens and acrylamide that is in food, not just burnt or browned food? 81.104.12.52 16:05, 17 September 2006 (UTC)

I think your postulate reflects a naive and overly simplistic understanding of evolution, cooking, and the differences between people and animals. Sorry. alteripse 17:19, 17 September 2006 (UTC)

Hey there! If you're gonna pick on the guy's theory, at least offer a reason why you find it so "naive and overly simplistic"! Seems like an interesting thought to me! In fact, the only "simplistic" notion expressed here is that there is some fundamental, physiological difference between people and animals. Of course, neurologically we may be vastly superiour to our closest cousins, but physiologically ... human beings are basically nothing more than another species of animal, and a rather weak, fragile species at that. In fact, (with the exception of our manual dexterity), we're actually physiologically inferiour to many animals in practical every sense. Loomis 18:01, 17 September 2006 (UTC)

Conjecture, that is. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:23, 17 September 2006 (UTC)

Except we can eat almost anything, something only shared by a few other mammals... Philc _T^E_C^I 19:10, 17 September 2006 (UTC)

Like hedgehogs - which, by the way, prefer cooked food. At least the dozen or so hedgehogs I've spent a lot time with will go for cooked food over raw food every time. --Kainaw ^(talk) 19:13, 17 September 2006 (UTC)

And gulls. Which can also eat rotting carrion and our rancid garbage with no ill effect. --Kurt Shaped Box 20:10, 17 September 2006 (UTC)

How do you know? They may go home and have a really bad stomach ache after eating those manky sausages. I believe it may be called ' **** stomach' 8-)--Light current 20:59, 17 September 2006 (UTC)

I should have just passed on answering it, but you are right, if I criticize it I should at least explain. The simplistic notions that seemed embedded in the question were the following:

1 Animals cannot eat cooked foods. What's simplistic? Of course they can eat it; they just can't build the fire to cook it.

Huh? I cannot see why I am supposed to believe that animals cannot eat cooked food: I've just asked if they prefer it, for goodness sake.

2 Animals would not prefer cooked food. What's simplistic? It's an untested hypothesis and I have a hunch that carnivores would prefer heated meat if given a choice. Someone somewhere has probably done the research and I will gladly admit I am mistaken if it showed otherwise.

Huh? again. I've just asked if they do prefer it or not. ?????

3 Evolution has selected us to be able to deal with carcinogens from cooking better than animals. What's simplistic? Evolution selects reproductive fitness and most effectively selects out traits likely to interfere with reproduction. With some exceptions, cancer (especially carcinogen-linked cancers) are diseases of the post-reproductive years and the assumption that evolution had made us less vulnerable to old-age cancers is pretty questionable. Secondly there is no evidence that we are less susceptible to cancer produced by cooking carcinogens than animals-- zero evidence.

Huh? yet again. I'm concerned that humans havnt had time to evolve to fully cope with cooking. I am aware that evolution is less forceful post-reproduction. Also my hunch is that human are still susceptable to cooking carcinogens. Why do you believe I believe things I dont believe? This is very bizarre.

4 Ability to deal with carcinogens is the largest survival effect of cooking. What's simplistic? The major advantages of cooking are enhancing flavor, killing parasites, denaturing bioactive proteins, retarding spoilage, and reducing the energy required for chewing and digestion. I suspect those advantages outweigh carcinogen risks as pro-survival factors by orders of magnitude. Armchair speculation about evolution requires thinking through all the likely effects at different stages in the life history.

OK, so I can be a curmugeon. Now do you see why I thought the question was based on some pretty simplistic assumptions? alteripse 21:49, 17 September 2006 (UTC)

No I don't. You've confabulated the assumptions out of nowhere. Surely you can't be a know it all.

OK, if you don't see the points it actually confirms my first suspicion when I didnt list the reasons, but you asked. Others can judge whether they find them convincing. At least I hope you dont mind that I reformatted slightly since you interpolated in my message and it messed up the numbering and flow. alteripse 01:59, 18 September 2006 (UTC)

You've invented out of thin air "the simplistic notions that seemed embedded in the question" which are pure baloney and which I don't in fact believe, and then you've used them to condem me. This does not make any sense at all. It is analogous to hearing someone remark for example they would like to go on holiday in Germany, inferring with your superior intellect that this must be because they are a covert-nazi and anti-jewish, and then condemning them on this basis. What utter nonsense.

Alteripse said what I was going to say. :( Oh well, I second everything he said. Doesn't it seem blatantly obvious to everybody?? That was actually pretty confusing. I was going to say all those things that had numbers. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:23, 17 September 2006 (UTC)

There is certainly a raw food diet/movement which believes humans are better off eating raw foods. I think most raw fooders are vegetarian, but there is mention of raw meat on the page. Cooked food certainly does contain carcinogens, and the benefits listed for cooking are mostly irrelevant for fruit and vegetables. —Pengo ^{talk · contribs} 02:33, 18 September 2006 (UTC)

The raw food diet movement is certainly a truckload of bullshi... rv, NPOV. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)02:37, 18 September 2006 (UTC)

Ah-ha! It has just occurred to me that the bizzarre remarks above may be due to one or two people who have quite wrongly and incorrectly decided that I am suggesting that people should eat only raw food. This is not the case - I eat plenty of cooked food myself. I'm going to eat some now.

No, no, don't worry. I don't know or have inferred anything about you, except that you know that there is a raw food movement and that food contains carcinogens. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)15:24, 18 September 2006 (UTC)

I'm not sure why, Alterprise, but you seem to have COMPLETELY misread the questioner's question. You make four points. The first two are based on a complete misreading of his/her question. S/he never said anything about animals prefering raw food over cooked food. Quite the contrary. The first paragraph of the question bears repeating here: A comment above about feeding sausages to gulls made me wonder what animals prefer. Has anyone any practical experience of gulls, dogs, cats, birds and so on prefering one or the other?. You then proceed with a brief summary of what you got out of the questioner's question in your first two points: "1 Animals cannot eat cooked foods." Huh? S/he just ASKED that question! "Do they prefer one or the other?" How can the question "do they prefer one or the other?" be transformed into the simplistic assumption that they do prefer one over the other? I'm afraid you've misread the question.

Same goes for the second point. "2 Animals would not prefer cooked food." Again: A comment above about feeding sausages to gulls made me wonder what animals prefer. Has anyone any practical experience of gulls, dogs, cats, birds and so on prefering one or the other? What the...? I'm afraid that once again you've misread the question. Again, I can't imagine why. It's written in such a simple, commonsense manner.

3 Evolution has selected us to be able to deal with carcinogens from cooking better than animals. No! That's the exact OPPOSITE of the point the questioner was making! "[W]e humans may not be able to totally cope with the carcinogens..." (emphasis added). Did you miss the "not" part?

4 Ability to deal with carcinogens is the largest survival effect of cooking. Once again, in the questioner's words: "have not evolved" (emphasis added). "Not evolved!" Again, the complete opposite of what the questioner is asking.

I'm really at a loss as to how such a relatively easy to understand question could be so badly and completely misread.

So let me (with the permission of the questioner) rephrase his/her question in even simpler terms: "Is it not a reasonable hypothesis, that the particular vulnerability to cancer in humans (as against other animals), can be attributed to the fact that we learned to cook our food, (and learned to prefer it that way,) much faster than evolution has allowed our bodies to physiologically adapt and defend against those particular cancer causing agents that naturally occur due to the "cooking" process?" Seems like a reasonable hypothesis to me. Of course it could be completely false, that's why it's simply a hypothesis. But I definitely don't see how the hypothesis "reflects a naive and overly simplistic understanding of evolution, cooking, and the differences between people and animals." Loomis 00:00, 20 September 2006 (UTC)

Speed of Radio

The speed of light is clocked at just under 300k metres per second. Yet when scientists speak of sending and receiving radio signals from spacecraft or perhaps even from places further distant, it always seems as if they're using the speed of light as a measurement of the speed at which radio signals travel. I'm no scientist, and I'm not quite sure exactly how radio signals travel, and what their relationship is to the speed of light. I've always been told that the "speed of light" is the maximum speed that anything can travel. If anything, I would only imagine that radio signals, would, at most, travel at speeds slightly less than the speed of light. Is this true? If so, how fast do radio signals travel? If they travel at the speed of light, how is it that they match this speed? Thanks. Loomis 16:28, 17 September 2006 (UTC)

Radio energy, like light, is carried by photons, and they always travel at the speed of light. Now the speed of light in a vacuum is the highest speed, but the speed of light in other media is a bit lower. For spacecraft in stellar space the two speeds are, essentially, the same. -- Finlay McWalter | Talk 16:32, 17 September 2006 (UTC)

Those photons tend to travel at the speed of light because THEY ARE light. Finlay says the speed of light in different media varies. Pretty much the denser an object is, the longer it takes light to get through it, if at all. The photons kind of go in one atom, and come out the other side to continue on its way. The more atoms, the longer it takes. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)16:42, 17 September 2006 (UTC)

Visible light is one part of the Electromagnetic spectrum, radio waves are part of the same spectrum (with lower frequency and longer wavelength). Everything in the electromagnetic spectrum travels at 'the speed of light'. Don't confuse the term 'radio signals' with the sound you hear from your radio - in simple terms, the signal is carried to your radio at the speed of light, but the sound you hear travels very much slower, at the Speed of sound, which is about 340m/s in air. --jjron 16:56, 17 September 2006 (UTC)

Ok, I may be no scientist, but I do know the difference between the speed of light and the speed of sound! No worries though, you couldn't have known that, so thanks anyway, you're help is much appreciated! Loomis 17:10, 17 September 2006 (UTC)

What he said was that the sound you hear travels at the speed of sound. Then there is also the transducer time to convert the radio frequency to electrical signals for the speaker. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:21, 17 September 2006 (UTC)

I'm not a scientist, but the way the speed of light is expressed above makes it look like it's 300,000 metres per second. Anchoress 18:12, 17 September 2006 (UTC)

It's actually 3 x 10⁸ m/s, or 300,000,000 m/s. I think someone got Kilo and Mega mixed up. smurrayinchester^{(User), (Talk)} 19:02, 17 September 2006 (UTC)

Yeah I know that. But I didn't know if '300k metres per second' was actually a way of expressing it, or if it was a mistake. Anchoress 19:08, 17 September 2006 (UTC)

Ok...you're right, it was 300 MILLION metres per second not THOUSAND. Now how does that affect my question? Loomis 21:25, 17 September 2006 (UTC)

It doesn't. But if you are here to learn (what else?) then isn't it nice if people point out to you you made a mistake and that the way you phrased the question doesn't make sense? Well, in scientific lingo, anyway. Using 'k' for 'thousand in other combinations has become colloquially accepted and actually does make some sense. DirkvdM 18:24, 18 September 2006 (UTC)

My mistake was akin to a typo. I saw nine digits, but mistakenly wrote a "k" for "thousand" rather than just writing "million". Also, as I said, I'm no scientist, and so "scientific lingo" is somewhat of a foreign language to me, albeit one that I'm reasonably familiar with. Take yourself, (please! Apologies to Henny Youngman!:-). Your mother tongue is Dutch, but at the same time you have an excellent command of the English language. I only wish I had as much fluency in my second language (French) as you seem to have in English. Yet occasionally, you do make the odd linguistic error, the type that only a non-native English speaker would make. Of course I understand what you're saying completely, so I'd consider it rather rude to correct your English, and I'd feel like quite the ass for doing so, so I just leave it alone. True "learning" is one thing. Pointing out other people's typos and the most minor of linguistic errors is quite another. Loomis 23:06, 19 September 2006 (UTC)

I would consider a correction of my English by a native speaker a great help. It's a courtesy, not at all rude (depending on how it is brought, of course) and I wish more people would do it. Especially if I make the same mistake more than once. Eg, StuRat recently pointed out to me that 'instead' is one word, not two ('in stead'), as it is written in most languages. I had always written it that way as I consequently noticed. I was thankful for the help. DirkvdM 07:39, 20 September 2006 (UTC)

Loomis, I wasn't typo-flaming you, and I'd appreciate it if you'd AGF a little bit, instead of being so sensitive. I truly didn't know whether or not the way you wrote it was correct, and just not familiar to me, OK? That's why I commented. Because I am here to learn. Just like everyone else here. Anchoress 07:51, 20 September 2006 (UTC)

Anchoress, even if I was being overly sensitive, my reaction wasn't directed at you at all. Only to those who assumed I didn't know the difference between a thousand and a million. Loomis 09:41, 20 September 2006 (UTC)

Huh? You said in the post just above (addressed to Dirk) that you considered it rude to point out people's typos. Since I was the one who pointed out the typo, who else could it have been referring to but me? Anchoress 18:34, 20 September 2006 (UTC)

Look. An order of magnitude out isnt bad for a non scientist. Even scientists are out by more than that some times. I dont know why you are arguing about it, but I do know its taking up a lot of space in the wrong place! 8-(--Light current 18:45, 20 September 2006 (UTC)

Anchoress, you're making a mountain out of a molehill. When I'm wrong, I'm the first to admit it. I just assumed by the sound of your language, (wrongly,) that your first two posts were basically a sarcastic snotty remark that I didn't know the difference between a thousand and a million. I was wrong. I'm sorry. Let's please put this silliness behind us.

Oh, and Dirk, I actually remember the "in stead" thing with Stu. In fact, I wouldn't say it's totally, completely inappropriate to use the two words separately. It's just never done when they follow each other. In other contexts, though, when the two words are separated by another, it's actually correct, as in the sentence "The apple was removed, and an orange was placed in its stead". I really don't see any rule in English that would prevent one from just expressing "in" and "stead" as two separate words, rather than the compound "instead". It's just that according to convention I suppose, when the word "stead" immediately follows the word "in", it always seems to be expressed as the compound: "instead". It's funny though, but you made another minor error in that same post. You used the word: "negativest" as a superlative of the word "negative". I opted for Jack's cheeky, less obvious way of correcting it, but I'm not sure if you caught it. If you really don't mind and don't find it rude to be corrected for such minor errors, I should point out that there is no such word as "negativest". The superlative form of "negative" is simply "most negative". :) Loomis 03:47, 21 September 2006 (UTC)

Thanks for the clarification on 'instead'. The use of the word 'negativest' was a joke. I suppose I should be a bit more careful with such jokes since people might think it's an error because I'm not a native English speaker. But then most of those people will probably have gotten to know me a bit and thus have some understanding of my sense of humour (that's EE, not a typo :) ). Btw, it's not just Jack who is that cheeky. And I did miss it, but I believe I didn't even read it, so that would explain that. :) DirkvdM 08:10, 21 September 2006 (UTC)

You're welcome. I just hope that the fact that you didn't read my post was for some other reason than that old "ignoring Loomis" thing. I hope we're over that. Also, I didn't quite get that "EE" remark. Your sense of humour can be quite cryptic and difficult to decipher sometimes! Another thing I should mention is that when I said that your minor errors are the type only a non-native speaker would make, I was serious, as certain other errors are more prone to be made by native speakers, such as (and listen closely Phil, you limey bastard! You should be teaching me how to speak proper English, not the other way around! :) using the non-existant phrase "should of" when what the speaker really means to say is "should have". I guess it's just because when we say it, it actually sounds more like we're actually saying "should of". A non-native English speaker with a good command of the English language would actually be less prone to make that mistake. Alright, so now that all that's cleared up Dirk, time for you to get off your lazy ass and get a job! :--) Loomis 12:00, 21 September 2006 (UTC)

Faster than light???

Hi

I am reading a book on the creation of the Universe. According to Inflationary Theory, at a certain point in time, there was an "explosion" that created an expanding Universe. What i dont understand is that within a fraction of a second after this "explosion", it seems that the Universe has expanded to a size larger than can be explained/allowed by the speed of light (because nothing can travel faster than it). What i mean to say is...the universe seems to have expanded faster than the speed of light and thus something must travel faster than light?

Hope someone can help me out Cheers Gregory J Davies 17/09/06

Faster-than-light#Universal_expansion has an explanation. -- Consumed Crustacean (talk) 17:01, 17 September 2006 (UTC)

It is accepted that during the inflationary epoch the universe expanded faster than the speed of light. The short answer for why this doesn't violate relativity is that no information or 'actual stuff' moved faster than light. You may also be interested in entanglement

What was the speed of light in that early universe?--Light current 20:03, 17 September 2006 (UTC)

Isnt the speed of light a universal constant? Philc _T^E_C^I 20:10, 17 September 2006 (UTC)

It is now, but there is speculation that it was different at the birth of the universe.--Light current 20:18, 17 September 2006 (UTC)

Moving the speed of light practically breaks the universe, I cant see how it is possible.... but if it was 0 at one point, through e=mc² you would get infinte mass from any energy, which could explain the big bang and stuff I guess. Philc _T^E_C^I 20:32, 17 September 2006 (UTC)

Erm... You'd get zero rest mass contribution to energy, but the inertial terms would still appear, so you'd have the rest of the Taylor series expansion at Relativistic mass#kinetic energy, most of which would diverge, suggesting the need to renormalize.

The fine structure constant is a constant that is one of the more famous candidates for non-constancy. This is still controversial and the best data so far is consistent with no change. However, there should be new data late this year that should finally be fine enough :-) to resolve the issue. -- Fuzzyeric 23:06, 17 September 2006 (UTC)

Inflationary epoch address this in its first titled section ("Explanation"). The observation is that space expanding is not the same thing as something (even light or information) moving and so the speed of light is not a limit to the effect. -- Fuzzyeric 22:53, 17 September 2006 (UTC)

To clarify a bit on what was said, according to inflation, nothing actually moved. Spacetime expands, but coherent objects do not move or expand. It is like the distance between objects increases, but they didn't really move. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:19, 17 September 2006 (UTC)

So can space expand just by the creation of mass, say?--Light current 00:11, 18 September 2006 (UTC)

Doesn't the speed of light depend on the medium in which it is traveling? For instance, light travels faster in a vacuum than it does in, say, water... correct? - R_Lee_E (talk, contribs) 01:41, 18 September 2006 (UTC)

Yes it does, but I dont think thats relevant to this argument. THe speed of light depends upon the medium constants mu_nought and epsilon_nought. These may have had different values at the beginning.--Light current 01:51, 18 September 2006 (UTC)

Variable speed of light theories? No, no, no. You should all read this excellent popular book:

• Weinberg, Steven (1977). The First Three Minutes. Basic Books. ISBN 0-465-02435-1.

A picture is worth a thousand words, so look for the figure illustrating "light cones in the large" in an expanding FRW dust model. The same point is made with more mathematics in books such as

• d'Inverno, Ray (1992). Introducing Einstein's Relativity. Oxford: Oxford University Press. ISBN 0-19-859686-3.{{cite book}}: CS1 maint: publisher location (link)
• Hawking, Stephen; and Ellis, G. F. R. (1973). The Large Scale Structure of Space-Time. Cambridge: Cambridge University Press. ISBN 0-521-09906-4.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: publisher location (link)

---CH 03:38, 18 September 2006 (UTC)

According to relativity, light is taken as pretty much the only constant isn't it? If c ever changed, the laws of physics would break down. — X [Mac Davis] (SUPERDESK|Help me improve)15:45, 23 September 2006 (UTC)

Tree identification

I recently went backpacking in the Sierra Nevada (US), in the John Muir Wilderness. We spent three nights in two places at about 10,000 feet, near the treeline. There was a sparse forest there, consisting mostly of one particular species of tree. I believed it to be some kind of fir, but after perusing our various articles on firs, I found that I was mistaken. The best picture that I have is this rather blurry one. Does anyone know what kind of tree this is? --Smack (talk) 17:33, 17 September 2006 (UTC)

Your link doesn't work, maybe you could upload your picture to Fileanchor? It is free and easy to use. Wikipedia also has an article on the Biology of the Sierra Nevada, with pictures, maybe one of the pictures will be your plant and you will be able to identify it from that. Gary 18:20, 17 September 2006 (UTC)

That article says that Western White Pine, Mountain Hemlock, and Lodgepole Pine grow at that altitude. Rmhermen 20:27, 17 September 2006 (UTC)

The link works now. I had omitted the file extension. Rmhermen: I think it's none of those. --Smack (talk) 00:16, 18 September 2006 (UTC)

Sorry for not responding earlier. That's a very nice picture! If the trees are none of those three species, I don't know what they are, though they are probably something closely related. Did you happen to look at the trees up close, to see things like whether they had short or long needles, or other distinguishing features? Gary 00:03, 23 September 2006 (UTC)

Yes, you bet I got a closer look; sorry for not mentioning my own observations. The bark is reddish-brown, redder than most trees I've seen, and broken by many fine cracks in a netlike pattern. The needles resemble like those of the Silver Fir, although they're dark green, as my picture shows. --Smack (talk) 05:07, 25 September 2006 (UTC)

Burmese Python

Would a hungry Burmese Python eat dead prey, or does it need to be alive? FireSpike 17:41, 17 September 2006 (UTC)

Burmese python is not specific on the matter, but it does say "As Burmese Pythons are opportunistic feeders, they will typically eat almost any time food is offered, and often act hungry even when they have recently eaten. This often leads to overfeeding, and obesity related problems are common in captive Burmese Pythons", which seems to suggest that they are not picky. ColinFine 18:11, 17 September 2006 (UTC)

With snakes, this often depends on what the animal is accustomed to. A python raised in captivity on dead prey may not even know how to kill live prey, and may be injured by it. Other animals may refuse anything not alive. --Ginkgo100 ^{talk · e@} 00:13, 18 September 2006 (UTC)

Fact check me?

I was wondering if a couple people with a scientific background could fact check me. I am working on a template message for new users violating WP:RS or WP:OR which explains the basic concepts. Have a look: Wikipedia_talk:Reliable_sources#Proposal:_Sources. Thanks --Darkfred ^{Talk to me} 23:08, 17 September 2006 (UTC)

Everything there seemed right to me. Made two corrections. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:15, 17 September 2006 (UTC)

I made rather a large number of changes 8-)--Light current 23:31, 17 September 2006 (UTC)

Yeah, put a box around it whydon'tcha. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)01:58, 18 September 2006 (UTC)

DAB Broadcast Range

Hi there.

I'd like to find out what the normal broadcast range is for DAB radio, as I'm considering purchasing a unit. I live in Ireland (east coast), but I'd like to pick up UK stations too. I can't pick these up on FM, so would I be able to receive them on DAB?

Cheers

NaLaochra 23:29, 17 September 2006 (UTC)

This seems to give some info on DAB.[[6]] Not sure if you can pick up UK DAB tho. Probably not. Have you considered listening to UK radio over the internet?--Light current 23:38, 17 September 2006 (UTC)

Yes, I always use internet radio, but it's a bit of a pain having to listen off the web the whole time; it's not much good for the kitchen! Thanks for the help NaLaochra 00:22, 18 September 2006 (UTC)

September 18

Future of plant genetic engineering

What do you think is the future of plant genetic engineering? I've read things about the dangers of GM crops, such as golden rice that has become prevalent in china, and a type of corn made by a company called epicyte that can be used as a contraceptive. What are some active GM plants out there, and does anyone know any GM horror stories (or potential GM horror stories?) Thanks! Dave 130.207.180.27 00:28, 18 September 2006 (UTC)

You seem to be looking for horror stories and totally look over the tearing greatness that genetic engineering has brought us. Aside from the fact that the "unscientific" genetic engineering that brought us apples, and oranges, pumpkins, and cabbage, detoxified almonds (they used to have a compound that when digested produced 10x the lethal dose of cyanide for an adult), genetic engineering is possibly the greatest technology that has ever evolved from the human race. Read a bit on Norman Borlaug, easily one of the greatest people who ever lived, credited with saving billions of lives through genetic engineering. It is easy to complain and talk about the bad things, when you know you have at least one meal per day, and are not among the 25,000 to die of starvation everyday. Also, what is wrong with the golden rice, that is to help with the problem of VAD? — [Mac Davis](talk) (New! SUPERDESK|Help me improve)02:43, 18 September 2006 (UTC)

Mac Davis, genetic engineering has a specific meaning. Please do not confuse it with plant breeding or artificial selection — which are NOT genetic engineering by any stretch of the imagination. Norman Borlaug, although a proponant of GMO, worked largely on HYV hybrid varieties without the use of genetic engineering techniques. The other benefits you talk of are not from genetic engineering but from ordinary plant breeding. To say we should turn a blind eye to the problems of genetic engineering because of the benefits is plain stupidity. —Pengo ^{talk · contribs} 03:00, 18 September 2006 (UTC)

Sorry, how embarressing. I was referring to the GM crops, obviously. However, I do believe that purposefully altering the genes of a plant make plant breeding a subset of genetic engineering. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)03:15, 18 September 2006 (UTC)

One "horror story" is that of the weed Lactuca serriola, which gained herbicide resistance from being contaminated by GMO lettuce. It's not that much of a horror story really. Another is of some GMO corn produced in the US (See Bt_corn#The_StarLink_corn_controversy). There are probably not many real horror stories relating directly to GMOs. The key issues, in my mind, is that of the patenting of life (biopiracy); the loss of genetic diversity (countered partially by seed banks and seed exchange groups and networks); and the placing of a large amount of trust in seed corporations, which farmers have become reliant on as they cannot replant their own seed. These issues are the same for hybrid varieties as much as they are for GMO, and are not safety issues as much as they are food security issues. —Pengo ^{talk · contribs} 03:14, 18 September 2006 (UTC)

Biopiracy will surely be a fiery issue when it gets in the forefront. That is going to be scary, and probably in my lifetime. Yikes!! — [Mac Davis](talk) (New! SUPERDESK|Help me improve)03:21, 18 September 2006 (UTC)

If you don't want it to occur within your lifetime, I suggest you take up smoking. :-) StuRat 06:34, 18 September 2006 (UTC)

Can't you think of any slower ways to die? DirkvdM 18:57, 18 September 2006 (UTC)

The potential of any GM plant spreading worldwide without any ability to stop it is indeed frightening. Even if grown in a greenhouse, preventing workers from taking out pollen on their bodies or clothes or carrying a seed in the tread of their shoes is nearly impossible. Such crops would need to be given the highest levels of biocontainment treatment, similar to how anthrax and bubonic plague are treated in research labs, to prevent dispersal. Such treatment would make GM foods completely impractical. StuRat 06:42, 18 September 2006 (UTC)

The potential could be good or bad. If it were doing more harm than good (who could be the judge of that?), than that would be "bad." But if it was a vitimin-rich protein-packed, high calorie crop, that didn't kill off too many species (who could be the judge of that?), than that would be "good." — [Mac Davis](talk) (New! SUPERDESK|Help me improve)15:22, 18 September 2006 (UTC)

I agree that most GM modifications are beneficial, but the potential for such GM plants to spread uncontrollably is still troubling. This can lead to wiping out non-GM varieties, thus forcing people to consume the GM variety, against their will. If some negative side effect is later found in the GM variety, it may be difficult to get the original variety back. Perhaps an "assassin virus" would then need to be programmed to go after the GM variety to wipe it out in the wild. StuRat 16:45, 18 September 2006 (UTC)

I have a cure for this problem, from the movie Jurassic Park. In that movie, the "lysine contingency" refers to the fact that the cloned dinosaurs were genetically engineered to lack the normal ability to synthesize lysine, a critical amino acid. While captive, these animals would be provided with lysine in their diets. If they escaped, however, they would die in short order from a lysine deficiency. Similarly, some defect (perhaps multiple defects) should be programmed into the GM plants, so that escaped varieties would die naturally. Legislation should be passed making such protections mandatory, preferably at the worldwide level. StuRat 16:59, 18 September 2006 (UTC)

Most GM plants are prisoners of their poor design. Built to resist one and only one species of insect or fungus, they are more able to get attacked by another pest, or by any mutation of the original ones : what do you think happened before in South America : people bought GM seeds, their plants were soon attacked and the people are poorer. Now when you buy stocks of GM engineering companies, you get rich. Right ? See also [7] -- DLL ^{.. T} 18:28, 18 September 2006 (UTC)

The problem is we know so little of what we're doing in that field that we don't even know what the horror stories might be. If you do something bad you can usually rectify it with equal effort. But some things propagate themselves in a feedback loop. And life is the greatest expert at feedback. Once something starts it can be unstoppable, spreading exponentially. That's why we still haven't managed to exterminate loads of diseases - miss one bacterium and in a few years it will be all over the place again. And if we inadvertently create some disease (or something that creates a disease or gives it a breeding ground to evolve or something I can't think of (!)) then that can be as hard to stop as malaria. Of course I'm talking about plant diseases here. And if farmers the world over would switch to certain plants because they give a much bigger yield then that will reduce biodiversity, nature's best counterforce against the spread of diseases, because some varieties might not be affected and thus take the place of the ones that died - the same mechanism that diseases use to become resistant to antibiotics. Life is a constant battle between species and the ones with the greatest biodiversity stand the best chances of survival.

As an illustration think of what has happened with the introduction of species to new environments (rabbits in Australia, that sort of thing). Most will not survive in the wild, but the ones that do won't have any natural enemies and will spread like wildfire. And with gm we may create species that don't even come close to what life on Earth has seen so far. Maybe not yet, but if we continue we'll get there for sure. DirkvdM 18:57, 18 September 2006 (UTC)

I think there may be a misinterpretation here about GM plants. They aren't completely new plants engineered from scratch, but more typically very close to an existing plant, with perhaps one gene added to provide disease resistance, produce a valued nutrient, etc. Therefore, they retain all other characteristics of the original plant, such as resistance to all the same diseases as the original. However, if the new, more disease resistant plant becomes widespread, this will put pressure on the disease causing organisms to evolve a counterattack. The original plants will be particularly susceptible to these new "super bugs". StuRat 19:11, 18 September 2006 (UTC)

Yeah, I know, I was just taking it a little further. GM is sort of evolution on steroids. So if it becomes popular, a new species may be created in a much shorter time. And if that is taken further still, we might create something that would normally never have evolved (on Earth), something that not only has no natural enemies in one spot, but anywhere on Earth, so we couldn't even introduce one. Of course we could fabricate one, and that will lead to a 'natural' selection of who is the cleverest GM engineer. Of course this could also be used for warfare, so we had better start with it real quick before 'the enemy' beats us to it (who is it this time? Oh yeah, terrorists). DirkvdM 06:27, 19 September 2006 (UTC)

Turpentine

I went to the article on turpentine looking for some sort of confirmation of the story that the stuff can enter through your skin and stays in your blood (or collects in your ankles) and never leaves your body.

A. Is this true? Or where does this idea originate?

However, looking at the article, I discovered that Wood turpentine and Mineral turpentine are different things, and looking at the shelf of my local hardware store, I notice that there is also Mineral turpentine substitute which is different again from mineral turps. (The article seems to confuse the two — which is partially my fault).

B. What's the difference between these substances?

C. And does anyone feel like sorting out the articles to reflect these differences?

—Pengo ^{talk · contribs} 02:39, 18 September 2006 (UTC)

I looked around and didn't find this particular myth, but if it exists, it probably comes from painters and their practice of mixing turpentine with all sorts of nasties, such as lead. --Zeizmic 12:08, 18 September 2006 (UTC)

Mineral turpentine substitute just sounds to me like a sloppy way of saying "mineral turpentine (substitute for wood turpentine)". I can't think of many instances in life where I've needed a substitute for a substitute. Well there was this one time in grade 5...  freshofftheufoΓΛĿЌ  14:27, 18 September 2006 (UTC)

The labels of the two seemed to have different ingredients, but i only glanced. There's also "low odor turpentine" which may or may not be the same as any of the above. —Pengo ^{talk · contribs} 09:04, 19 September 2006 (UTC)

Metals, non-metals, and semi-metals

Looking at the Periodic table, it's pretty clear which elements are considered metals, non-metals, and transition metals. After all, there's a big old streak running from Boron to Polonium. What I'm not entirely clear on is why, that is, why those guys on the top like covalent bonds and the guys on the bottom like metalic bonds. At first I thought that it could be electronegativity -- maybe the higher electronegativities would favor covalent bonds because in covalent bonds, the electrons are more localized -- but a quick look down one of the columns refutes this.

My next thought was that as you go down a column, the atom gets larger and larger and has more and more complex valence shells -- maybe the fact that the shells are held further away from the nucleus allows the electrons to be shared more easily amongst all the nuclei (leading to a metalic bond), and maybe as these shells get more full, this has less of an effect (an attenmpt to explain why lead is metalic while polonium is not). This explanation seemed plausible, but not great.

Any ideas?

for a start...i think Polonium is sort of metallic, or at least metalloid. I don't think it's a non-metal.

But Polonium would be less metallic than lead. this is because lead is physically smaller than Polonium. Polonium has two more protons than lead, and two more electrons. The two extra protons make the nucleus stronger. However, the two extra electrons go into the same shell...meaning Polonium has the same number of shells as lead.

This means in Polonium, there is a stronger nucleus holding on to the same number of shells of electrons. This means the outer shell of Polonium is held more tightly than the other shell of lead...hence Polonium would be less inclined than lead to shed off its valence shell electrons (which is what metallic bonding involves.)

may i suggest you read the articles here on Metals and Periodic_tableYaksha 07:20, 18 September 2006 (UTC)

Classification as metal/semiconductor/insulator is based on band gap and valence band. The effect is primarily one of delocalized bonds and their energy spectra. The physics of electronic band structure is not simple. In metals, the conduction band has no gap separating it from the valence band, so electrons may be promoted from a localized orbital (essentially attached to a single nucleus) to a delocalized orbital (essentially smeared out over a large volume). In semiconductors, valence electrons may be promoted to the conduction band by providing a small energy, for instance thermal energy at room temperature. Insulators have such a large bandgap that essentially no electrons are in the conduction band at room temperature. -- Fuzzyeric 14:06, 18 September 2006 (UTC)

distinguish between network bridge,repeaters,routers,ethernet hub,bluetooth and gateways?

i need the answer of dis question in proper format. please help me with this

What's great is you don't even try to disguise this as something other than a homework question. Benbread 10:43, 18 September 2006 (UTC)

Read the articles. o_o --Proficient 05:48, 19 September 2006 (UTC)

Questions about allergies

I was diagnosed with an allergy to penicillin (and another drug, sulfa) at a young age. My father recently suggested that the diagnosis might have been wrong, and that I should get tested again, because penicillin is such a useful drug and so on. Is it likely that it could have been misdiagnosed? (He claims that the doctor seemed rushed and "unprofessional".) Alternatively, is it possible to "grow out" of such an allergy? Would re-testing be worthwhile?

Second, my boyfriend is allergic to most seafood (with exceptions for some processed fish, like canned tuna) and some nuts (allergic to almonds, brazil nuts, and walnuts, but not pistachios, peanuts, macadamia nuts or cashews). Do you see any connection between these allergies? Fish and nuts are said to have high levels of omega-3 fatty acids. Is it possible that that's the allergen? If so, is he in danger of not getting enough omega-3? What sort of factors would cause him to be allergic to some nuts, and some fish, but not others?

Thanks in advance! --Grace 07:12, 18 September 2006 (UTC)

I agree that you should be retested, as allergies do change with age, and the doctor might have misinterpreted the results originally. StuRat 10:06, 18 September 2006 (UTC)

Reactions to substances vary and not all are "allergic". Reactions which indicate an allergy with a high degree of certainty include hives and swelling of mouth or throat, especially with a change of voice or narrowing of the larynx. The likelihood of a similar or worse reaction upon next exposure is fairly high. At the opposite end of the spectrum in terms of risk is a vague red rash which is a common part of many viral infections and which is sometimes amplified by concurrent use of ampicillin. The problem with labelling someone penicillin-allergic is that the penalties for being wrong in either direction are so asymmetric. If someone is erroneously told she is allergic to penicillin, there is rarely any penalty for avoiding it and lots of people react positively to their "specialness". If someone is erroneously told she is not allergic to penicillin and is prescribed it in the future she could develop a worse reaction with throat swelling and very rapid death. This severe reaction is called anaphylaxis and doctors consider contributing to someone's avoidable death a Bad Thing. So this enormous asymmetry of consequences leads to many people being labeled penicillin allergic erroneously. This is well-recognized by doctors and there are published guidelines for deciding how likely it is that a person is really allergic based on the nature of the original reaction (not based on the parent's estimate of the "professionalness" of the doctor). The major disadvantage of being erroneously labeled penicillin-allergic is that you get prescribed more expensive antibiotics which migh incur other risks. There are ways to test for penicillin exposure with small risk if someone needs treatment and no alternative antibiotic seems appropriate. Why not have this conversation with your doctor?

As for your second question, allergies seem to be formed primarily against specific proteins in foods rather than against omega-3-fatty acids, so your boyfriend has many other possible sources of the fatty acids. We have no idea why people become allergic to certain food proteins and not others-- be glad it is limited. Best wishes. alteripse 10:33, 18 September 2006 (UTC)

Your boyfriend is allergic to some of the most common food allergens. Besides tree nuts, fish, and shellfish, the other most common food allergens are peanuts, soy, milk, eggs, and wheat. I sympathize, having certain shellfish allergies myself. One of the hardest things about it is explaining it to restaurant staff. You would think they would hear it all the time, but they are frequently rather stupid about it, either not understanding the concept of a food allergy or acting "put out" that you ask for special non-deadly food. --Ginkgo100 ^{talk · e@} 04:34, 19 September 2006 (UTC)

Thanks all, very helpful! -Grace, not logged in

Fishy coincidence

Take two rivers not too far away from each other, say you consider the Po and the Rhône River, which both give water to the Mediterranean Sea. You have a look at what fishes live in these two rivers, and say you discover that the carp lives in both rivers. Question: how is this possible? With the exception of salmons, no fish can live both in fresh water and in the sea (I am not sure if NO fish can, but of course SOME fish cannot). So how is it that two rivers which are not connected by some fresh water channel contain the same species of fish? Of course this does not depend on Man. I have asked a biologist friend, but her answer does not really satisfy me, so I am posting it here. And I will tell you what her answer was, but I would like to see some other opinion first. Cthulhu.mythos 08:55, 18 September 2006 (UTC)

Well for the example you give, the Alps are only ~15 million years old, so the freshwater fish could have been part of a connected watershed earlier than that. Though I haven't checked on carp in particular, most fish families are far older (100s of millions of years), so it wouldn't be surprising to find carp on both sides. After ~15 million years though, you'd expect to see a variety of descendant species unique to each side as well as a few ancestral species that survived in both places. Dragons flight 09:22, 18 September 2006 (UTC)

I agree. The two rivers may have had a confluence at some point in the past, such that one was a tributary of the other. I suppose that, if it can be established that the same species existed in both rivers prior to development of boats by people, this would even constitute evidence that the two bodies of water were, indeed, once connected. StuRat 10:02, 18 September 2006 (UTC)

Mmmmh. I see. Now I will tell my friend's answer. She said: well, once upon a time during Pangea, or anyway durind a time when the two rivers were somehow connected, there was the carp's great-great-great-granmother, which was not yet a carp. Then continents drifted and blah blah and the two rivers became separated. So we have two ancient rivers with the same archeofish. As the two rivers wetre once connected, they cannot be too much far away, hence the climate must have been about the same in the two rivers, hence the two archeocarps will undergo the same evolutionary processes, as they live in very similar environments. What you get is the same carp in the two rivers.

Looks like we need an article on fish falls.--Shantavira 11:02, 18 September 2006 (UTC)

Now what does not satisfy me is that I do not believe that the same evolutionary processes must happen, of course the two great-great-great-granchildren will be similar species, but I see no reason for them to be the very same species (interfecundity, in perticular). Then what she replied was: they will just like two different races of carp, not really the same carp but very very similar, like "Caucasian" and "Asian" for Man. Cthulhu.mythos 10:24, 18 September 2006 (UTC)

What your friend describes is called convergent evolution, and does happen, but I don't know if it happens with fish. Morwen - Talk 11:09, 18 September 2006 (UTC)

No, it's parallel evolution. I agree that there is a logic flaw in what the teacher said, though. While parallel evolution can produce similar traits from a single proto-species in similar environments, it never produces exactly the same species. StuRat 11:12, 18 September 2006 (UTC)

Agree, especially if you're talking about a length of time like that since Pangaea. In cases like this there are often more simple explanations that are easily overlooked, e.g., major and rare floods allowing the rivers to be temporarily connected, rising and falling sea levels, coming and going of ice ages, etc. Whether these can necessarily explain this specific example I don't know, but they do explain a lot of similar cases. While these things may be rare or a long time ago on our time scale, in geological and evolutionary terms they are not - a once-in-a-thousand-years flood is actually pretty common, and the last ice age at about 10,000 years ago was a mere eye-blink ago. --jjron 13:46, 18 September 2006 (UTC)

Why does evolution or connection have to be involved? What about the possibility of a visitor from Po to the Rhone becoming interested in the carp, and then bringing a few back with him to place in the Po? Man could have easily accomplished this thousands of years ago. - Rainwarrior 15:54, 18 September 2006 (UTC)

I believe the original question was asking for reasons that didn't involve human interference. Of course human involvement is a possibility in a case like this, but if there was evidence that the fish were in both rivers prior to human occupation of the region then there would have to be a natural cause. --jjron 16:19, 18 September 2006 (UTC)

Freshwater systems used to be a huge source of diversity, and endemism was common within them. However, man has basically destroyed the fresh water systems of the world, and most are overrun by introduced species which outcompete native species. Naturally, crossing to different river systems occurs through large flooding (which can occur to a huge scale, but is rare), and previously connected rivers. Remember that rivers are constantly changing, and can split apart, merge, or whatever. They are rapidly changing, much faster than continental change. --liquidGhoul 16:30, 18 September 2006 (UTC)

It is still possible to see man as the origin of a plain identity of carps in both rivers. They belonged to the same empire during centuries, and you may carry freshwater fish a long time in a bucket. I'm thinking of a Roman war veteran who was allowed some part of Provence and wanted to fish his old Po carps to have his foreign wife accomodate them in the Po valley fashion. -- DLL ^{.. T} 18:38, 18 September 2006 (UTC)

Arowanas are obligatory freshwater fish; they cannot tolerate sea water, yet they are found on different islands and continents around the world. They evolved long ago, when the landmasses were connected, and were carried along when the continents and islands broke apart.[8] Cutthroat trout, an American species, diverged into numerous subspecies, each peculiar to a separate river basin, more recently. During the Ice Age, their ancestor was able to travel "over the mountains" into different rivers.[9] By the way, many other fish, such as the barramundi perch, can tolerate both fresh and salt water. See fish migration. Of course, the carp themselves could be introduced species, not natives. --Ginkgo100 ^{talk · e@} 20:09, 18 September 2006 (UTC)

Flies

I read the article on here about flies. I was wondering if anywhere in the article does it say if they go to the bathroom at all? I'm just curious about this.

Sure they do. The insect article is probably better than the fly article for this, especially the Morphology and development section. They have a digestive system ending in an anus, and an excretory system (read about Malpighian tubules for this). --jjron 14:07, 18 September 2006 (UTC)

Flies do not have a designated area where they go to excrete. Therefore, no bathroom. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)16:17, 18 September 2006 (UTC)

I find them in my bathroom often enough, so I reckon they do ;) --jjron 16:25, 18 September 2006 (UTC)

They go to the toilet less often if you keep it clean.Edison 16:58, 18 September 2006 (UTC)

Or is the question if flies ever bathe? They use their own saliva for that, don't they? (Or was that dogs?) DirkvdM 19:08, 18 September 2006 (UTC)

What do you think flyspecks are? alteripse 23:28, 18 September 2006 (UTC)

Things for correcting their bad eyesight? 8-)--Light current 23:36, 18 September 2006 (UTC)

indium oxide

Hello everyone,
does anybody knows the thermal conductivity of indium (III) oxide around room temperature ? I already searched in a few scientific databases and handbooks without results... Thank you ! David Berardan 11:56, 18 September 2006 (UTC)

[[10]] is our page on it--Light current 22:01, 18 September 2006 (UTC)

Thanks, but I already read that page :-) ... and it didn't give me the answear :-( David Berardan 07:51, 19 September 2006 (UTC)

I know it doesnt have the answer, I was just saying that is our page on it. Google search also negative. Sorry. Can you measure it? thermal conductivity--Light current 08:01, 19 September 2006 (UTC)

I imagine I will have too ^^. I am just a bit impatient, cause my thermal conductivity measurement device is currently broken down ! When I can measure it I will complete the article (but In2O3 being very hard to densify, it probably won't be a very precise value). David Berardan 19:49, 19 September 2006 (UTC)

Well, an approx value (if published in a reliable source WP:RS) is better than no value I suppose.8-)--Light current 20:48, 19 September 2006 (UTC)

spot goo

how come if i squeeze a spot sometimes it just goes pff like a wet fart and sometimes it goes pop and i have to clean the mirror?

Hmm interesting question. Could be to do with the excess pressure built up inside.--Light current 14:24, 18 September 2006 (UTC)

Are you talking about squeezing a pimple ? I understand how they would be filled with puss, as this is left over from your skin fighting the small bacterial infection which caused the pimple. I'm not sure why their would be air inside a pimple, as seems to be described, as well. StuRat 16:32, 18 September 2006 (UTC)

Puss is a cat. Pus comes in zits.Edison 16:58, 18 September 2006 (UTC)

Here pus pus. Doesn't it depend on the size of the zit? And probably the strength of the skin.--Shantavira 17:08, 18 September 2006 (UTC)

I can't believe I've put any thought into this at all, but I'd guess that there are two factors coming into play here: one would be the size of the pimple (or specifically the amount of pus that is trapped) and the second would be the hardness of the plug that has formed at the surface. If the material blocking the pore has hardened significantly, it will not be easily dislodged. Exerting additional pressure when squeezning the pimple might cause it to pop, with the result that the additional pressure also causes the pus to shoot out with more velocity. --LarryMac 19:18, 18 September 2006 (UTC)

A bit like opening Champagne bottles (though attempting pimple sabrage would be ill advised). Rockpocket 04:50, 19 September 2006 (UTC)

SOLAR PANEL PROJECT

HOW DO WE MAKE A HOME MADE SOLAR PANEL ?

THIS IS FOR A GRADE 5 PROJECT.

PLEASE REPLY URGENTLY §

Here's a link with some information you might find helpful. And turn off the caps lock please, it is impolite. It's like you're yelling.

http://scitoys.com/scitoys/scitoys/echem/echem2.html

Gary 14:03, 18 September 2006 (UTC)

You forgot to reply urgently!  freshofftheufoΓΛĿЌ  14:07, 18 September 2006 (UTC)

XD --Proficient 06:28, 21 September 2006 (UTC)

egg drop

What is the best egg drop design that you know of?67.177.19.69 13:03, 18 September 2006 (UTC)mule

The article on egg drop competitions says that commonly used materials include sand and styrofoam. I'm sure there's more than one way to do this, though. Gary 14:09, 18 September 2006 (UTC)

Parachutes are always more fun, though. StuRat 16:15, 18 September 2006 (UTC)

A chicken? DirkvdM 19:14, 18 September 2006 (UTC)

Aerogel, if you've got a particularly well-equipped egg dropping club.  freshofftheufoΓΛĿЌ  03:42, 19 September 2006 (UTC)

Aerogel is harder than polystyrene or sand isn't it? — [Mac Davis](talk) (SUPERDESK|Help me improve)04:01, 19 September 2006 (UTC)

You may be right, some types may be. Carbon aerogel is supposed to be extremely elastic though.  freshofftheufoΓΛĿЌ  06:38, 19 September 2006 (UTC)

Some vacugels are lighter than air. (Vacugel: very experimental aerogel, sintered under vacuum and then hermetically sealed.) Sea also SEAgel. -- Fuzzyeric 01:45, 20 September 2006 (UTC)

I'm very good at this. What you want to do is first isolate and prtect the egg by putting it in a styrofoam cup and packing it with cotton balls making sure to position the egg vertically. Then put this is a coffee can and pack the inside of the can around the egg-cup with crumpled up paper, making sure that the egg-cup cannot move around inside the coffee can. Then, on whichever end of the coffee can you want facing down, put a paper bowl on the bottom with the bottom part of the bowl facing down. Pack the empty space with more crumpled up paper (loose leaf paper works well). After this, duct tape popsicle sticks onto the coffee can facing down, these will break off and absorb some shock. Finally, to make sure your device falls straight, attacht a string to the top of the device and tie lond bits of paper or playing cards. That will stabilize it as it falls, making sure that the end with all of your crumple zones hits the ground. Two more helpfull hints, put your egg in a sealed plastic bag so if it does break, it won't get egg all over your device. The second is that parachutes are notoriously difficult to make work properly. I've only seen one person successfully pull off a parachute retarded egg drop. Deltacom1515 01:50, 23 September 2006 (UTC)

Does this not explain it? — Michael J 16:15, 23 September 2006 (UTC)

Speech to text conversion

I could not find any article related to speech to text conversion under speech processing.

There is a link in the Speech processing article that leads directly to Speech recognition. --LarryMac 13:36, 18 September 2006 (UTC)

ID Card size

What is the logic behind such an odd size od Id-1 cards that have a size of 85.6x53.98mm?

1. Where did you get those numbers?
2. Maybe the dimensions originated in inches. 85.7 mm is 3 3/8 inches, and 53.98 mm is 2 1/8 inches. --Smack (talk) 17:15, 18 September 2006 (UTC)

• It's an ISO standard size for ID cards!

ISO/IEC 7810:2003 specifies:

    * four different sizes of identification cards with a nominal 
      thickness of 0,76 mm and dimensions of:
          o ID-000 25 mm x 15 mm,
          o ID-1 85,60 mm x 53,98 mm,
          o ID-2 105 mm x 74 mm,
          o ID-3 125 mm x 88 mm;
    * the conditions for conformance;
    * the dimensions and tolerances of the identification cards;
    * the construction and materials of the identification cards; and
    * the physical characteristics of the cards such as bending stiffness, 
      flammability, toxicity, resistance to chemicals, dimensional stability, 
      adhesion or blocking, warpage, resistance to heat, surface distortions, 
      and contamination.

ISO/IEC 7810:2003, together with a standard for test methods, provides
for interchange between various types of identification card
processing devices and systems.

No idea just why these numbers, though! --jpgordon^∇∆∇∆ 21:12, 18 September 2006 (UTC)

I'm sure that the logic behind those numbers is "that's the size almost all ID cards were when they officially wrote up the standard". Credit cards and ID cards and whatnot have been essentially standardized for decades, and everything from wallets to card readers to the little static-proof ATM card sleeves all assumed the sizes would stay that size. This is kind of a cop-out answer, but it would take a lot of research to figure out who used that size first and how it became a widespread standard. I wouldn't be too surprised if it was the first social security cards or some such. -- Plutortalkcontribs 13:54, 19 September 2006 (UTC)

Especially the senseless precision – 53,98 mm instead of 54 mm, a difference of 20 µm and less than 0.04% – is curious. Assuming a modest variation in the measured heights of existing ID cards, on the order of 1 mm, would require averaging over several thousands of measurements before the estimated average gets a precision anywhere near that. While very close to 2⅛ inch (= 53,975 mm), the width 85,60 mm is clearly less than 3⅜ inch (= 85,725 mm). If we stick to powers of two for the denominators, it could be 3451/1024 inch in mm, rounded to two decimals, but no lesser power will do. --Lambiam^Talk 20:50, 19 September 2006 (UTC)

Hot and Cold as Sensations...

Has there been any research done as to how exactly the sensations of hot and cold manifest themselves? Clearly, with sufficient exposure, either can be quite painful. Yet the sensations are vastly different. Something that is hot is, well, a burning sensation. And something that is overly cold is a kind of biting sensation. Why is this? There must be some explanation on both a cellular and neurological level. After searching for a bit, I still wasn't able to find the answers I was looking for. Maybe you guys can help. Thanks. - R_Lee_E (talk, contribs) 16:36, 18 September 2006 (UTC)

See this archive. — [Mac Davis](talk) (SUPERDESK|Help me improve)18:08, 18 September 2006 (UTC)

Ah...you beat me to it Mac. --Russoc4 18:12, 18 September 2006 (UTC)

Ah. This helps. Thank you much. - R_Lee_E (talk, contribs) 21:45, 18 September 2006 (UTC)

The archive doesn't answer why we perceive the feeling of hot and cold as we do (i.e. burning vs biting). That is an interesting question and more to do with interpretation of the signal in the brain, rather than nociception at the periphery. Interestingly, though, when human skin is exposed to extreme noxious cold (like, of example, dry ice or liquid nitrogen), the resulting pain is often descibed as a "burn" and, i can confirm, the immediate acute pain is "burn like". Thus, my hypothesis is that the human thermosensory system is more "tuned" to warn us of hot temperatures, since we are more likely to be exposed to noxious heat in a natural environment, than noxious cold. Consequently "hot" is more immediately painful than "cold", within the ranges we are normally exposed too. Its only when you get to extremely cold temperatures, that the cold interpretation becomes as acute as the hot response. Why then, as Seejyb reports, we have "about 30 "coldness" nerves for every "warmth" nerve", is a puzzle, however. But this expanded "thermo-space" for cold detection, could provide a mechanism through which a more moderate cold respose is mediated. Rockpocket 04:43, 19 September 2006 (UTC)

Thanks for the response(s). Makes alot of sense. Though, I suppose all of existence must be regarded as an "interpretation of (a) signal in the brain." Much respect to the Man, Descartes. - R_Lee_E (talk, contribs) 01:46, 20 September 2006 (UTC)

When you're talking about "burning" and "biting", you're not just talking about heat and cold perception. A stimulus that is sufficiently severe to be perceived this way is also provoking a pain response, which is conveyed by means of sensory neurons that are morphologically different from heat and cold afferent neurons, to different centers in the brain. In other words, extreme heat and cold evoke more than one type of sensation at once. Interestingly, temperature and pain perception follow the same neural pathway from the peripheral nervous system to the diencephalon-- the spinothalamic tract.--Mark Bornfeld DDS 17:39, 19 September 2006 (UTC)

Yes, that is a very good point. I was oversimplifying. Clearly there is cross-talk between the thermosensation and pain sensation signaling. Rockpocket 07:35, 20 September 2006 (UTC)

On a related note, if a substance is cold enough, exposure to it will create a sensation indistinguishable from burning. People who work with stuff like liquid nitrogen have to be careful. It's really weird.

Solvents

We are going to have to identify an unknown organic compound tomorrow in lab using IR Spectroscopy and it's observed melting point. When choosing a solvent to do recrystallization, we are to pick one from 1. Water, 2. Ethanol, and 3. Hexane. Is it safe to assume that water will dissolve polar compounds, hexane will dissolve non-polar compounds, and ethanol will dissolve both? --Russoc4 18:16, 18 September 2006 (UTC)

It is not 'safe' but I would call it a 'rule of thumb'. There are some organic compounds which will not dissolve in any of those.

watts into kwh

My alarm clock runs at 5 watts, or 5 joules per second. Would this mean that it consumes 1/200 kwh?— Preceding unsigned comment added by ChowderInopa (talk • contribs)

Yes, per hour. In one hour it consumes 5 watt-hours = 5/1000 or 1/200 kwh. Fan-1967 20:24, 18 September 2006 (UTC)

Usually people count kWh when they receive their monthly electric bill, so kWh/month may be a more useful unit. Your clock uses .005 kWh/hour * 24 hour/day * 30 day/month, or 3.6 kWh/month. If electricity costs you $0.10/kWh, that's a whole $0.36 you spend every month keeping your clock going. Foobaz·o< 02:13, 19 September 2006 (UTC)

First you divide the Joule by seconds. Then you multiply that by hours. And then you divide by months again. Or days. Or years. This is almost as bad as the imperial units system. Just stick to one unit for time, the SI unit 'second'. Then you'll only have joules and watts and it's clear what you are talking about (energy and power). DirkvdM 06:35, 19 September 2006 (UTC)

Unfortunately, no electric company actually bills in Joules, which is the real measurement. If I have the math correct, 1 kwh = 3600 seconds × 1000 joules/second = 3,600,000 Joules. Kind of a difficult conversion factor in calculating your bill. Fan-1967 14:10, 19 September 2006 (UTC)

butterflies

What do you call a group of butterflies?

Honestly I never seen them in more than 2s--Light current 21:46, 18 September 2006 (UTC)

a swarm of butterflies or a rabble of butterflies. search google under "collective noun"

They should only be called a swarm if it is a very bad horror film. Here are a myriad of other possibilities. MeltBanana 22:48, 18 September 2006 (UTC)

It's not on the list, but a "brothel of butterflies" really rolls off the tongue. Hyenaste ^(tell) 23:45, 18 September 2006 (UTC)

10/10. Excellent work. JackofOz 09:04, 19 September 2006 (UTC)

List of collective nouns for fish, invertebrates, and plants. Weregerbil 11:33, 19 September 2006 (UTC)

Why Do Men Have Nipples?

Simple question; likely a difficult answer. - R_Lee_E (talk, contribs) 21:46, 18 September 2006 (UTC)

Because God is good? --Trovatore 21:57, 18 September 2006 (UTC)

We has this one a few months ago.--Light current 21:59, 18 September 2006 (UTC)

Nipple#Male_Nipples... -- Consumed Crustacean (talk) 22:45, 18 September 2006 (UTC)

How would you feel and look if you didn't have any nipples? bibliomaniac15 00:14, 19 September 2006 (UTC)

Most people can feel and look without the using their nipples. As far as I know. MeltBanana 00:26, 19 September 2006 (UTC)

Yes, but it feels so much better when you do use them. Seriously. JackofOz 09:07, 19 September 2006 (UTC)

Ok, since the reference desk has wandered into chaos, and primally contains sarcastic and rude remarks for plain and simple questions (this question/answer-thread isn't that bad...Just look at the above entries) - I will try to answer your question. At least the easy answer: Both male and female nipples develops at a stage in the pregnancy when the babys gender is still undetermined. The genitals develop later. --Petteroes 11:57, 19 September 2006 (UTC)

Isn't it, more precisely, when the fetus is female, rather than undetermined? Steven Gould has an essay on this, I recall... Marskell 12:32, 19 September 2006 (UTC)

Freudian slips are very telling. "Primally" is spot on when it comes to nipples. My contribution, fwiw, was not meant flippantly, which is why I said "seriously". Whenever this question comes up, I remind folks of the sexual function of men's nipples. I know, I know, there's a difference between the biological purpose behind how they developed, and what they're good for now that we've got them. I'm more interested in the latter question. JackofOz 13:15, 19 September 2006 (UTC)

Stephen Jay Gould discussed this in an essay entitled Male Nipples and Clitoral Ripples in which he basically explains that the fetus has to have the roots of both genders' characteristics, so men have nipples because women have breasts, and women have clitorises because men have penises. Fan-1967 14:15, 19 September 2006 (UTC)

Info on an american polar-expedition...

Hope you guys could help me out here. A long time ago I read an article in a science magazine about an american expedition with an exceptionally big tank, an armoured wagon that weighted too much for the enviroment it was going to explore, and eventually got itself stuck in the snow. I reckon it was during the early stages of The Cold War - around 1946 - 1956. I think the target for the expedition was to reach the central parts of Greenland, or the North Pole. The expedition was widely concidered a failure.

Does anyone know the name of the expedition?

fluid behind our cats ears

moved from Wikipedia talk:Questions

We have a four year old golden calico male.Our cat goldie keeps building up pockets of fluid behind his ears.He has had three hematobin operatoins.He also has asthma.He has been on full time antibiotics and prednisone.I hear that they are a very rare species because of their genetics.Can you please help us solve this problem.We love this cat very dearly and hate to lose him.We have heard rumors that golden calico males usually only live up to five years old.Please help SINCERELY JIM KERR. —The preceding unsigned comment was added by 24.105.219.35 (talk • contribs) .

First, let me clarify that a Golden Calico is a breed, not a species. Second, this "fluid behind the ears" doesn't sound like a life threatening issue from your description. Can you describe the quantity ? I would think the treatment would be to lance the skin and allow the fluid pockets to drain. StuRat 23:55, 18 September 2006 (UTC)

Calico is not a breed, it is a description of a coat pattern, and it only occurs in females. You see, the colors are on the X chromosome, and the calico patchiness comes from the alternating patches of x-chromosome silencing (i.e. barr bodies) in the young embryo. Thus Goldie could only be a "he" if he has klinefelter's syndrome, and Golden Calico can not be a breed unless this particular breed is parthenogenic...Tuckerekcut 01:36, 19 September 2006 (UTC)

Now that I have read your question more closely (sorry Jim), I have decided that your cat probably is a klinefelter male, which would corroborate your details. You can read about klinefelter's syndrome here on wikipedia, perhaps a description of the human phenotype will help you better understand the prognosis of your cat, there is also some info at Tortoiseshell cat. It may very well be that the problems you mentioned regularly go along with being XXY and a cat. I will also add that your cat's condition would probably be better described as a genetic disease than as a "rare species" or otherwise.Tuckerekcut 01:46, 19 September 2006 (UTC)

There's more than one way to have a male tortoiseshell (see Laura Gould's Cats Are Not Peas for the story of George, a rare fertile male calico who turned out to be an XXY/XY mosaic). On the more serious question, it sounds like the cat in question needs a vet more than Wikipedian's opinions. (By "hemotobin" do you mean "hematoma"? Your vet should be able to tell you why this is recurring), - Nunh-huh 06:49, 19 September 2006 (UTC)

I suppose thare are many possibilities, but straight klinefelter's is the most likely, at about 1/1000 live births. (How much more likely? I don't know how many chromosomes a cat has, but the likelyhood of being mosaic for two karyotypes like this is about 100 times the number of chromosomes in a typical cell, if this cat were a human, that would be about a 1 in 4600 chance, giving a total chance of having an mosaic x nondisjunction in a male of about 1 in 4.6x10^6.) If this cat were a human, I would recommend having him karyotyped, but that is not particularly cheap. As Nunh-huh said, a vetrinarian is your best bet, she will know if these symptoms are normal for your cat's disease.Tuckerekcut 11:57, 19 September 2006 (UTC)

38 chromosomes for cats. I can't see much benefit in karyotyping, other than assuaging an intellectual curiousity. Better to spend the bucks getting veterinary care.- Nunh-huh 16:49, 19 September 2006 (UTC)

About the same benefits as with a Down's patient. With a full karyotype you know exactly what's going on (i.e XXY vs X/XY mosaic in the cat, as with 47 X(x/y) +21 or 46 X(x/y) der(N;21) or some mosaic with one of those in the Down's patient). Sometimes it helps the family to get a solid, definite cause. But sometimes even that results in little benefit.Tuckerekcut 02:40, 20 September 2006 (UTC)

September 19

Work, lifting vs walking - 7th Grade Physics

Yes, this is a homework problem for the kiddo; however, I am not understanding the concept trying to be taught here, so thought I'd see if someone can lead me in the right direction (38 Yr old CompSci Major slinks off to the corner and cries....) The problem is this - A woman lifts her 100-netwon child up 1 meter and carries her a distance of 50 meters to the crib. How much work does the woman do?

Because of Work = Force x Distance, I can see that the woman lifting her child exerts 100 joules by lifting the child 1 meter. How do we account for the 50 meters that she walks? Surely she is doing some work? But would the work exerted simply be 100 newtons times the 50 meter walk? 1001001 00:56, 19 September 2006 (UTC)

No! She is doing no work in carrying the child (assuming she is not bobbing up and down as she walks-- we will assume this) 8-)--Light current 01:49, 19 September 2006 (UTC)

While the horizontal movement requires energy, it is not work in the physics sense, except for the acceleration and deceleration of the combined mass of woman and child, which are probably only over short distances. If there are no figures for the mass of the woman, or the accelerations, (and it 7th grade) it's probably meant to be assumed negligible. (Probably bonus points for identifying the assumption.) Peter Grey 01:56, 19 September 2006 (UTC)

Peter, I basically agree with you, but I would say that most of the work she does is due to microscopic accelerations and frictions in her muscle cells, and that this does count as physics work (in real life, not for the kid's class). I would also argue that the work she does carrying the child probably far outweighs the work she does lifting the child. Almost certainly, though, the teacher wants the student to pretend no work is being done in the carrying. (Not that going for the extra credit isn't a good idea.) --Allen 02:25, 19 September 2006 (UTC)

TMI--Light current 02:33, 19 September 2006 (UTC)

I pretty sure that the question is asking how much work is being done only against gravity, and only whatever affects the baby - which I personally think should be stated very clearly in the question. Of course, some energy is expended in the part of the force that's counteracting friction in the vertical and horizontal directions, as well as all those biological processes mentioned before, plus the work necessary to lift the weight of her arms and etc. This was one of the toughest things for me to understand myself in middle school, because you have to understand that all of that "off-to-the-side" work is being ignored. All that they care about is the work against gravity. As another example, holding a pen up needs impulse and energy is being used in your hands/arms to create the impulse, but none of that energy is actually going into the pen (neither potential nor kinetic), so it doesn't count as work. Also note that heat transfer is being ignored too (though it'll eventually start playing a role in a future course, once you get into heat engines and gas laws and such). —AySz88\^-^ 04:25, 19 September 2006 (UTC)

Well put, AySz88. In my opinion, trying to teach kids, without explanation, that they're not doing any work as they carry things around, even though they intuitively know they are, is an unhelpful oversimplification. Light current, that's why I don't think it really is TMI. It's just enough "I" that kids can understand what the lesson is driving at without being sidetracked by apparent absurdities that aren't really there. --Allen 04:51, 19 September 2006 (UTC)

Just wanted to add my thanks to this - I really didn't understand what the question was going for, but it makes sense now. I think that I can even explain it to the kiddo now. (and they say raising kids doesn't generate work, HA!) 1001001 05:08, 19 September 2006 (UTC)

Isn't this a nice (and educative) example of how physics is a model of reality and not reality itself? An much used modelling 'error' is to assume no friction. Let's say the baby is lifted onto a table on wheels. Assume no friction in those wheels. It takes energy to get the table going, but stopping it 'releases' that energy again. In a modelled world, that is. I'm no physicist, so I'm not sure if that example was a good one, but the first sentence touches on the core of the problem, right? DirkvdM 07:08, 19 September 2006 (UTC)

Hmmm, one thing still bugs me about my example. If there were any energy lost by friction, that would go into heat, but what about the 'releasing' of energy by stopping. Where does that 'come from'? I assume this depends on which system you look at and whether it is open (to what?) or not, but I can't wrap my head around it. (Suppose my head isn't big enough. :) ) DirkvdM 07:12, 19 September 2006 (UTC)

THe energy of motion is of course 1/2 mv^2 and when you stop the trolley the energy goes into stretching your arms or dragging you across the floor creating heat by friction. And no, I woulddnt agrre with your last statement. 8-)--Light current 07:41, 19 September 2006 (UTC)

Yeah, I understand that. That's the reality bit. But I meant that in the model, if you pick up the baby and then put it back down, you end up with the old situation. But if you move the table and stop it, something has changed, namely the location of the table. Also, you excert energy twice. Maybe I should be thinking about energy as a vector. The model sort of assumes that the energy is 'won back' because it worked in opposing directions. (And in reality that would (to some extent) be possible if you slowed down with a dynamo.) So the two situations are 'energetically equal' (or how should I put that), despite the fact that a change has occured. This makes me think of something different, which I will ask a separate question about below (space travel). DirkvdM 08:45, 19 September 2006 (UTC)

Wouldn't the work be zero, according to the old saying "A woman's work is never done?"Edison 14:42, 19 September 2006 (UTC)

You should certainly not think of energy as a vector. If you're thinking that energy has a direction, you're probably thinking about momentum instead (which does). If I may quote myself here, I discussed some of the physiological aspects of this situation about two months ago. In this case, the important thing to say is that the woman does so much work on the child. She may do plenty more work on her own tissues, the floor, the air, etc., but that's not the (implied) question. --Tardis 16:41, 19 September 2006 (UTC)

Tylenol Overdose

A health question: I was recently told that taking more than the extra dose as said on the bottle of tylenol is a serious health risk; I have been feeling bad lately so I have been taking 4 Tylenol extra strength 500 mg tablets twice daily, double the twice daily two tablet dose...is this a health hazard? Thanks! ChowderInopa 03:03, 19 September 2006 (UTC)

Yes, taking more than the recommended dose is a health hazard, so is not going to the doctor when 1g of acetominophen/day is not enough to alleviate your pain. You should schedule a visit with a physician. In case you are curious, acetominiphen overdose has a slow onset and can lead to a very slow, very painful, very irreversible failure of the liver.Tuckerekcut 01:26, 19 September 2006 (UTC)

Thanks, this is only for today though...As in, for months I have not had any medicine, now when im feeling sick I took double starting this morning, then a friend said that was crazy and I should throw it up...but then i responded that it was just 8 pills in one day. All I am asking is, a one or two time double dosage during one day isnt a serious problem is it? By the way I am a 200 pound male, so the effects should be dampened. I mean it sounds like you are saying continual abuse hurts the liver, which i of course agree with, but just doing so today isnt horrible correct? This is not merely a context specific question, I am curious for general double doses with any medicine. Thanks! ChowderInopa 03:03, 19 September 2006 (UTC)

In your case, I would not recommend taking a double dose again, in some people without other obvious pathologies, taking the dose that you took even one time could cause clinically relevent, albeit minor and ephemeral, symptoms, especially if compounded by alcohol (be it in your beer or your cough syrup). The general case is even more fuzzy. For instance lithium can cause severe life threatening complications in certain circumstances if a patient takes a double dose. Other medicines have an even smaller theraputic ratio, (adriamycin/doxyrubicin comes to mind, but these things are not likely to be self-administered). In general, monoamine oxidase inhibitors and drugs for bipolar disease have some of the narrowest theraputic ratios, I believe. This information is all trivial, though. If you feel that you have a medical problem, see a doctor. She will be in a much better position to tell you what is healthy for you specifically. Also, please sign your edits with four tildes in the future. Tuckerekcut 02:12, 19 September 2006 (UTC)

No, I feel great and feel no problems whatsoever, I was just curious to make sure I hadnt done something completely stupid, like knock myself into a coma. How many would that generally take? 10 pills? 20? In the movies you always see a bottle full, but that seems to be way too much compared to what you are saying could hurt me... ChowderInopa 03:03, 19 September 2006 (UTC)

I have heard of people dying from as little as 8, which is only double what you're taking. You're at a much higher risk of harming yourself if you are in a weakened state (i.e. if you are sick) because your body is weak and may react strongly to the drugs that you (over) induce. Tylenol are generally pretty safe, which is why they're so easy to put on the market, but there is a reason that the warnings are there in the first place so there's no reason to deliberately put yourself in danger. I'm the kind of person that refuses to take any medicine, especially pain killers, unless it is really needed to help increase the speed of recovery. I can handle a little bit of pain and discomfort, and when it get's bad enough that I can't, I know that it's time to get some kind of treatment.  freshofftheufoΓΛĿЌ  03:27, 19 September 2006 (UTC)

I don't know if you've actually received a medical opinion or not yet. In Australia, acetaminophen is known as paracetamol, and the typical healthy adult dose is 1 or 2 500mg tablets 4 times daily, with a maximum dose of 8 tablet (or 4g) daily. If you have other health problems the safe dose for you may be less than this. Read the packet instructions on your tylenol. It will probably say something like this. If you exceed the dose, it means at least 2 things: 1.) it is not treating the illness you are using it for; and 2.) you risk toxicity, including irreversible liver damage. Either way - the most sensible course of action is to see your doctor. Best wishes, Mattopaedia 04:10, 19 September 2006 (UTC)

we do have an article on acetaminophen, you know... but the posters are right. Overdosing on paracetamol can nuke your liver, leading to a nasty death. --Robert Merkel 05:00, 19 September 2006 (UTC)

MPTP article image

Is the image in our MPTP article correct? If not, what needs to be done to fix it? On the talk page, a visitor has called the image's accuracy into question, but no one watching the article is qualified enough to fix a chemistry diagram. Thanks for any help you can give! Foobaz·o< 02:00, 19 September 2006 (UTC)

According to chemfinder, ChEBI, and University of Akron's Chemical Database both the formula and the structure (diagram) are correct.---Sluzzelin 05:45, 19 September 2006 (UTC)

the diagram is correct, it is just that the name is misleading. Xcomradex 10:54, 19 September 2006 (UTC)

Freezing to death

Would a warm or cold blooded animal (assuming that they are the same size, like a large toad and a rat) freeze first?--Peta 04:32, 19 September 2006 (UTC)

I figure the toad would freeze first, because it isn't producing as much heat of its own, and is probably starting from a lower temperature to begin with. But it might not freeze to death first, because some toads have weird abilities to live through freezings. --Allen 04:58, 19 September 2006 (UTC)

It depends, in part, whether the Ectotherm/poikilotherm was warmer or colder than the homeotherm at the time of the competition. The terms warm- or cold-blooded refer to the mechanism of thermoregulation, not the actual temperature of the organism itself. (that said, its likely the toad would freeze first, unless it was particularly toasty to begin with). Rockpocket 05:06, 19 September 2006 (UTC)

Are roast duck susceptable to the Mpemba effect? — [Mac Davis](talk) (SUPERDESK|Help me improve)05:35, 19 September 2006 (UTC)

As Allen said, there are some cold blooded animals which can freeze, and still live (I know of snakes and frogs). So the question as to which would die first, it is dependent upon the species. It would be interesting (though horrible and cruel) to see which would die first between the Wood Frog and the Arctic Fox. --liquidGhoul 05:47, 19 September 2006 (UTC)

Warm blooded animals have a constant temperature. Cold blooded ones don't. So the toad's temperature seems to be one piece of information that's missing. But even if they started off at the same temperature the rat would use its metabolism to keep it warm, so the toad would freeze faster. All this assuming were talking about live animals here and I don't know how much heat a toad can store. It would have to be one hot toad to compensate for the rat's metabolism. That said, I wonder what happens to coldblooded animals under freezing conditions. Do they all manage to survive freezing? Or do they dig themselves in at a warmer spot or something? DirkvdM 07:24, 19 September 2006 (UTC)

I can't speak for all, but it is certainly true for frogs. During winter, the tree frogs in my area will bury themselves under leaf litter, compost to keep warm. A lot of the ground dwelling frogs bury themselves underground, and some can just take it (Common Eastern Froglet seems to be able to live in absolutely freezing conditions). Mind you, this isn't Canada, the coldest it gets is -7 celcius. --liquidGhoul 08:47, 19 September 2006 (UTC)

Some cold blooded animals use antifreeze to keep from freezing, some find warm spots to survive, others die, but leave eggs that can survive freezing temps. However, the evidence that warm-blooded animals can handle cold better is in the relative scarcity of cold blooded animals in arctic environments. The problem with cold-blooded animals is that, while they may survive freezing temps, they can't do anything at those temps, like eat, breed, migrate, etc., which is a problem in places where temps are almost always below freezing. StuRat 12:38, 19 September 2006 (UTC)

Space travel

In the 'walk, lifiting vs walking' questions a few posts back it is claimed that it requires no more energy to move a baby than the energy needed to pick it up. In reality energy is expended because of friction. But take space travel, where the friction is negligible. Would it be possible to make a spacecraft that consumes no energy because it can regain the stopping energy when it reaches its destination? Of course, energy has to be put into the sytem for the first acceleration, but if the spacecraft shuttles back and forth it can use it's stopping energy to start again in the opposite direction and thus consume no more energy than for the first flight. This sounds wrong, but I can't find the flaw. DirkvdM 08:54, 19 September 2006 (UTC)

Is it possible? No. Hmm… *thinks again* Well, yes, actually. If the spacecraft could use its kinetic energy to "charge its batteries", or something, when it slows down at the destination, it could use that energy for going back. This is what electric automobiles usually do when you brake – instead of using the brakes, they start to charge the batteries with the movement of the wheels (which also slows the vehicle down). —Bromskloss 10:19, 19 September 2006 (UTC)

No, it's not possible, for two main reasons: The first is theoretical, no energy conversion is 100% efficient (second law of thermodynamics). Your theoretical spaceship would have to perform several energy conversions to 're-use' its deceleration energy, so something will always be lost in the process. The second is practical - I know of no technology which allows you to 'recover' some of the energy used for deceleration in space. Remember that, in space, there is no difference between decelerating and accelerating, both use energy. You need a certain amount of energy to accelerate to your 'cruise speed', and the same amount again to decelerate. And even if you did come up with a technology which would allow you to 'recover' some of your energy (perhaps some kind of drag against the magnetic field of a star which would induce a current in a wire?), the second law will still get you in the end.

Also, to be pedantic, there is some (very very small) amount of friction in space. Space contains particles, and these hitting your ship will slow you down. However, there are very few particles in interstellar space (tens of atoms per cubic meter, if I remember the figures correctly off the top of my head), so the friction they exert is nearly negligible. — QuantumEleven 11:40, 19 September 2006 (UTC)

Oh, come on. Of course the energy conversion isn't perfect, we all know that. I don't think the questioner was thinking of actually go out and build the spaceship! As for deceleration is acceleration, that is very true, but this time we might have a planet to crash into – freeing a lot of energy. You might wan't to "crash" smoothly, of course, but if done well (again, perfect conversion) you would still get the same energy. —Bromskloss 12:49, 19 September 2006 (UTC)

Yes, but that's exactly the problem - crashing on a planet will stop you, obviously, but I know of no way how this energy can be 'recovered', it's wasted as heat and terrain deformation. The energy is there, but it's not in a useable form (unless you want to use the heat of re-entry to boil water to turn it to steam to turn a turbine to produce electricity... but then you have to carry all this extra equipment around, so your ship is heavier, which needs a bigger heatshield... you can see where this is going, it's just not practical). — QuantumEleven 15:09, 19 September 2006 (UTC)

OK, you're clearly on a more practical level in this discussion than I am. Boiling water with the heat would have been perfectly satisfying for me. One could also imagine landing on a very high (many kilometers) platform that is not firm (as to avoid a crash), but gives way with only a little resisting force and takes care of the energy the spacecraft gives to it by pushing it down. —Bromskloss 21:32, 19 September 2006 (UTC)

This reminds me of a quite funny thought experiment: suppose you were to bore a tunnel straight through the earth that came out at exactly the other side of the globe (assuming this would be possible, of course). You could then jump into the tunnel and be accelerated until you passed the center of the earth, from which point on you would be decelerated by exactly the same amount. At the other end of the tunnel, you would stop and could just step out into the open. -- Ferkelparade π 11:50, 19 September 2006 (UTC)

Actually, it is possible, and it's being done for ages now. The moon's been going to and fro from Earth's sunside to the other side without ever having needed to charge it's batteries. It is, maybe, not a very practical way of making space ships fly, but it is certainly very economic. David 12:12, 19 September 2006 (UTC)

Note that spaceships do reuse the energy going one way and use it for the return trip, by using the destination star's, planet's, or moon's gravity to turn the ship around (possibly after many orbits). Also, the ship may even gain velocity by using the slingshot effect. They don't come to a "stop", of course, in either case, but can get close enough to make good observations and maybe drop a probe, then return back home. StuRat 12:15, 19 September 2006 (UTC)

Ah, you're right. Clever. And that probe, you could even go down in it yourself. —Bromskloss 12:49, 19 September 2006 (UTC)

That's true, you can use gravity assist to get some "free" (it's not completely "free" as you alter the trajectory of the body you're passing near, but the effect is so small it can be ignored) acceleration or deceleration. However, you can't slow down very far this way, so you still have to shed the rest of your speed some other way, either with rocket engines or aerobraking, neither of which obviously nets you any energy. — QuantumEleven 15:09, 19 September 2006 (UTC)

What do you mean when you say that you can't slow down very much? Relative to the body you use for gravity assist, you can't slow down at all, actually. You can only change the direction of your movement. —Bromskloss 21:32, 19 September 2006 (UTC)

Gravity slingshots do address this when you can use them, but it's important to realize that you always have the problem of conservation of momentum. If you're going to stop when you get to Alpha Centauri, something else has to gain that momentum. If this is fuel that you carry with you, you'll have to give it energy to get it moving (in your reference frame). What you'd "want" to do would be push off of a counterweight you left behind at Earth, and then pull on it again when you got there. But this would require a light-years-long tether, or else some magic like a tractor beam, and so has its own problems. --Tardis 16:30, 19 September 2006 (UTC)

The reason it is impossible is that, even theoretically, energy will be lost (due to the second law).

Um, what do you mean? I can't see why you would loose energy (apart from practical imperfections, of course) or what Newton's second law has to do with it. —Bromskloss 21:32, 19 September 2006 (UTC)

Read the articles on the second law of thermodynamics and Newton's laws

The third answer is that, due to the absence of appreciable friction, accelerating an object in space requires using Newton's third law. (See the second paragraph in the Overview at rocket.) That is, fling something backwards away from the ship. Since the center of mass of the rocket/exhaust system is unaccelerated by this maneuver, if you want to travel arbitrarily great distances, you have to let the exhaust escape. Having done this, your ability to subsequently accelerate (to stop at the destination, for instance) is reduced because you have less stuff left to use as exhaust. If, for example, your exhaust were a lead brick and you attached an infinitely long, internally frictionless rope to it, you could throw it away at the start of a maneuver, then grab the rope at the end and recover (most) of your kinetic energy. But the example is strongly unrealizable except for very short maneuvers (say, the length of the capsule).

Semi-relatedly, there are very low energy transfer orbits in the Interplanetary Transport Network. Some of these transfers are free, and others are surprisingly low-energy. -- Fuzzyeric 19:01, 19 September 2006 (UTC)

If there is a large mass at the point of destination that can be used as an anchoring point, then you could stretch a large rubber band between two poles and have the ship fly into the band. Just as the ship would be about to be catapulted back, you secure the stretched band, storing energy. At departure time, use as a catapult. --Lambiam^Talk 21:19, 19 September 2006 (UTC)

Global Warming/ Ozone layer

Seeing as the ozone layer is closing, does that mean global warming will stop? If not, what does it have to do with global warming?

thanks!

The hole in the ozone layer has nothing to do with global warming. The ozone layer is a region of the atmosphere that shields us from ultraviolet radiation coming from the sun, and prevents you from sunburning too easily and getting skin cancer (amongst other things). Global warming is the result of increased amounts of greenhouse gases (such as CO₂) which 'trap' more of the sun's heat, changing the global climate. I recommend you browse through some of the articles I've liked to for more info. Hope this helps! — QuantumEleven 11:33, 19 September 2006 (UTC)

The confusion is that both are caused by air pollution. The hole in the ozone layer was caused by CFCs, which used to be in every spray can and air conditioner. They have been largely eliminated now due to government actions, and this explains why the ozone hole seems to be closing. The greenhouse gases which cause global warming have not been stopped, however, thus global warming continues to worsen. There are two main reasons why there is no agreement to reduce greenhouse gases:

• The Bush administration is denying that anything needs to be done and has rejected the Kyoto Protocol, which would have addressed this issue.

• Unlike CFCs, a significant portion of greenhouse gases are produced by third world countries, which can't afford to eliminate them. They are produced by agriculture, heating homes, etc.

However, since action on stopping the use of CFCs did fix the ozone hole, it's reasonable to think that reducing greenhouse gases would reduce global warming. We've now seen evidence that human intervention can affect the atmosphere, for good or for bad. StuRat 11:59, 19 September 2006 (UTC)

Sidenote: the fact that most greenhouse gas production takes place in third world countries is caused by the fact that those countries house the vast majority of mankind. DirkvdM 18:56, 22 September 2006 (UTC)

Of course the ozone hole had decreased in some years before CFC's were discontinued, and the Earth has been warmer than this before the industrial age began adding more greenhouse gasses. The Climate is more complex than many are willing to admit.

No no it wasn't. The ten year average is the highest in history, as far back as reliable estimates can be made via the current methods. And we are indisputably at the high point of recorded temperatures. --Darkfred ^{Talk to me} 16:22, 19 September 2006 (UTC)

Most people seem surprised when to find that current levels are relatively low, at least from a long-term perspective - understandable considering the constant media/activist bleat about current levels being allegedly "catastrophically high." Even more express surprise that Earth is currently suffering one of its chilliest episodes in about six hundred million years.[11] On the 650,000 year time scale, it is following pattern remarkably well.[12] On the 20,000 year time scale it is pretty hot.[13] Regarding post-Industrial Revolution[14], this is for sure the hottest time (how hot is disputed). However, the point is often brought up that only a few decades before the Industrial Revolution was the CO₂ ppm measured as higher than current. (Thenard, 1812 Traité élém. de chimie, 5 edit., vol1, p. 303. | Value: 385.0 ppm) (W. Kreutz 1941, Kohlensäure Gehalt der unteren Luft schichten in Abhangigkeit von Witterungsfaktoren,” Angewandte Botanik, vol. 2, 1941, pp. 89-117 | Average 1939-41: 438 ppm) The current value is around 381 ppm. I see you have mentioned "as far back as reliable estimates can be made via the current methods"—that is where opinon comes into play often more than scientific objectivity.— [Mac Davis](talk) (SUPERDESK|Help me improve)16:53, 19 September 2006 (UTC)

The problem with examining the whole 650,000 year timescale is that different studies have had radically different results. As far as the last 20,000 years the results are undeniable. You mentioned C02 levels, according to ice cores testing, (where the granularity of testing is in 10-100 year range) we are at a 300,000 year high. The high 1800s numbers are during the heydey of Coal consumption, the problem is the numbers have never returned to their pre-coal/pre-industrial levels. By propping up the less reliable statistics you are basically just giving political ammunition to the "do-nothing" crowd, when there IS a concensus on the danger even from the scientists who have recorded the outliers. --Darkfred ^{Talk to me} 14:54, 20 September 2006 (UTC)

Although the Bush administration has its own motives for denying, there is an extremely heated controversy on almost all parts of the anthropogenic global warming hypothesis. Back to the original question, the ozone layer is a thin dynamic blanket that absorbs some parts of the ultraviolet spectrum. Relation to climate seems negligible at current. — [Mac Davis](talk) (SUPERDESK|Help me improve)16:46, 19 September 2006 (UTC)

While there have certainly been climactic variations in geologic history, that fact is unrelated to human-caused global warming, which most scientists and national governments accept as a serious problem. If the scenario is true, then failure to heed the warning signs in time would have serious consequences. Oceans could rise due to melting glaciers and ice shelves: just a few feet of rise could destroy the fresh water reservoirs for the country of Kiribati. The city of Venice would become uninhabitable. Other inhabited lowlands such as coastal Louisiana and parts of Florida would have to be evacuated. Durova 22:27, 19 September 2006 (UTC)

Climate change can be a serious problem [in some aspects] as you say, however it is not as if it is not going to happen if we stop CO₂ emissions. — [Mac Davis](talk) (SUPERDESK|Help me improve)00:12, 20 September 2006 (UTC)

I'm going to be rude, and rather than refuting what you've said, Mac Davis, I'm going to suggest that you're buying in to tobacco and oil company sponsored propaganda. I don't know how you could say our CO2 levels are anything but at an all time high. By funding a large number of organisations, Exxon helps to create the impression that doubt about climate change is widespread —Pengo ^{talk · contribs} 15:13, 20 September 2006 (UTC)

Also note that the rate of change of global temps is at least as significant as the current level of global temps. Normally, global temps would only change slowly, allowing people time to adapt (moving slowly inland as the coasts flood, for example). However, rapid change can lead to disasters. There may be some rare natural causes of such rapid temp changes, too, such as a supervolcano or large meteor. Of course, those events can be catastrophic to life on Earth too, just ask the dinosaurs (oops, you can't !). :-) StuRat 00:33, 20 September 2006 (UTC)

I would have to disagree that humans or climate change could cause a supervolcano or meteor impact. — [Mac Davis](talk) (SUPERDESK|Help me improve)04:00, 20 September 2006 (UTC)

Mac Davis, you are setting up a straw man here. No-one has claimed that humans or climate change causes a supervolcano or meteor impact. Gandalf61 14:50, 21 September 2006 (UTC)

I think he was joking. StuRat 04:05, 22 September 2006 (UTC)

Perspective viewpoint

What are the main gaseous products of volcanoes? And how much do they produce per year? Are these greenhouse gases? How much of these gases does the human race produce? 8-)--Light current 04:04, 20 September 2006 (UTC)

A clue: Volcanic activity releases about 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year. SO2 output shown here: [[15]] Looks like at least 10 megaton per year to me --Light current 04:21, 20 September 2006 (UTC)

I believe SO2 is more 'greenhousey' than CO2 and water vapor is the worst! So how now?--Light current 15:21, 20 September 2006 (UTC)

Magma

does magma contain magnetic material?

It can. For example, moving molten iron can react with the Earth's magnetic field and cause a weak magnetic field to form. Most magma, however, is not magnetic. StuRat 11:49, 19 September 2006 (UTC)

Indeed. If there is some kind of metal in it. --Proficient 06:30, 21 September 2006 (UTC)

I don't believe that most metals can be magnetized. Only certain metals, like iron, can be. StuRat 04:03, 22 September 2006 (UTC)

Ferromagnetism--Light current 04:06, 22 September 2006 (UTC)

Fidel Castro's eyes

Why do the irises of Fidel Castro's eyes appear completely black in recent pictures? Does some drug dilate the pupils that much? If so, how can he stand daylight?

Ken

The man is barely alive. 'Intestinal surgery' usually means something really bad, like stomach cancer or some such thing. As well, he might be on a hose-pipe of morphine. --Zeizmic 12:59, 19 September 2006 (UTC)

the magnetic field can effect to FO ( mazut oil) using in burner

My manufacturer has one boiler made in UK, produced by Wellman Robey, this boiler uses FO (mazut oil) for burning, I make the maximum magnetic field by the Neodyme magnets in the input type of the oil line to the boiler , I hear that this system will be saved the oil after the magnet treatment ,but the oil used the same, not reduced. For the burner using the DO, it's OK, Why? Please give me the answer. Thanks. Ngocthuan_06 , 13:30 (UTC) 19,SEPT,2006

The "magnets on a fuel line" scheme is an urban legend at best. They never have any effect. There are, of course, countless shady companies with these worthless products. DMacks 14:17, 19 September 2006 (UTC)

I have the fuel saver from USA for the truck used the Diesel Oil, this product uses the magnet treatment for reducing the dimension of the fuel drop, from 300Micron into 3 micron, the fuel will be burned completely.The fuel reduced about 15% for my truck in highway You can find out it by go to google.com, type fuel saver [[User:Ngocthuan_06] 14:30, 19 september 2006 (UTC)

I'm not really sure why you appear to be answering your own question, but DMacks has summed up the situation nicely. Magnetic "fuel savers" are hoaxes. If they weren't, they'd be standard equipment with every car manufacturer who likes bragging about fuel economy. — Lomn 15:57, 19 September 2006 (UTC)

The question posed (as I interpret it) was: "It works fine for diesel oil. Why does it not work for fuel oil?" --Lambiam^Talk 21:30, 19 September 2006 (UTC)

I think that any products are selling in USA, it must be checked the quality and purpose. I bought one fuel saver for fuel car, and one for truck, my truck is OK , it reduce 15% of DO in the highway, and 6% in city.But my car, it can not go over 70km/h, the speed can not increase but I still open the throttle(it means the fuel is increased but the speed is saturated), but if below 65km/h, it can reduce 20% of fuel in the highway. And now I get this for the FO burner, but no effect . I pose the question, why is it the difference of the same hydro carbon molecules but one is effected with magnetic field, one don't >User:Ngocthuan_06 00:51, 20 September 2006 (UTC)

The additive is reducing the octane of your fuel, destroying its performance while slightly increasing mileage rating. This will also damage your engine, your manual states a minimum octane. Plus, for a 6% increase in fuel efficiency (which I doubt) you are paying $15. This is NOT a good deal, you could simply have paid for 50% more fuel. --Darkfred ^{Talk to me} 14:59, 20 September 2006 (UTC)

because neither are being effected by the magnetic field. Xcomradex 00:18, 20 September 2006 (UTC)

Ayup. Can't rule out observer bias in the driving case: you know the magnet's there, and you unintentionally drive in a more fuel-efficient manner. OTOH, you could believe all this hooey, and think about the differences between what form of energy you get from a piston engine and a combustion furnace: maybe magnets increase the expansion that occurs during burning but don't increase the heat output. "I think that any products are selling in USA, it must be checked the quality and purpose" is entirely false—there are as many unscrupulous quack vendors selling useless, counterproductive, dangerous, and even illegal things are there are gullible people willing to pay for them. DMacks 01:53, 20 September 2006 (UTC)

indeed, i'm sure these[16] have been tested for "quality and purpose". Xcomradex 03:03, 20 September 2006 (UTC)

Contact glue

I bought some superglue with instructions along the lines of applying glue to both of the surfaces to be affixed, waiting 10-40 minutes and then pushing both surfaces together. I want to know what is going on here - why can't I just apply glue to one surface, push the other suface against it and leave them overnight to get acquainted. --Username132 (talk) 14:12, 19 September 2006 (UTC)

The strength of the bond depends on the amount of pressure the two objects are under whilst the glue dries. The stronger the pressure, the stronger the bond.

What you're talking about isn't superglue, but a type of contact glue (I haven't found a Wiki page on it yet). I have used it for many years, and, yes, it does work best if you apply it to both sides, leave them both to dry for a little bit (10-40 min sounds good, less if the ambient temperature is warm) and then press them together hard. The strength of this type of glue depends on the force with which the two objects are pushed together. After you've pressed them together you then need to leave it for a bit to set properly. You can, of course, just apply the glue to one side, press the two together without waiting, and leave it overnight, it will still work, but the joint won't be as strong. — QuantumEleven 14:51, 19 September 2006 (UTC)

The products I've used call themselves "contact cement" and several wiki pages (including glue) have redlinks to contact cement as well. So I guess: 1) that's this thing's official name, and 2) we there isn't a wiki page for this thing. DMacks 18:51, 19 September 2006 (UTC)

The "why" is that glues set by evaporating solvent and polymerizing (or engaging in other, more complicated chemistry). If you press the parts together soon, then the evapoartion can take a long time and therefore the time to set can become unduly long (possibly infinite). -- Fuzzyeric 18:42, 19 September 2006 (UTC)

Rubber cement is a common name. Rmhermen 21:24, 19 September 2006 (UTC)

No, I'm afraid that rubber cement is something different again. I have used both, and they are very different beasts... — QuantumEleven 14:42, 20 September 2006 (UTC)

Rows of teeth...

An adult human can grow only 2 sets of teeth...Why is this? And why can animals (e.g. A shark), grow many sets of teeth?

Presumably, due to evolution. Some animals (i.e. shark, crocodile) lose their teeth a lot because they like to feast on large, live prey. They have to bite down on an animal struggling for it's life, and some of the teeth or lost. If the teeth didn't grow back, that would be one toothless shark. For humans, we don't have to worry about that problem. We never bother to grow teeth after they've been lost.— [Mac Davis](talk) (SUPERDESK|Help me improve)17:05, 19 September 2006 (UTC)

I've actually heard speculation that wisdom teeth were evolved in order to replaced lost teeth. This explains why many modern day humans don't have room for these teeth, because they haven't lost any others. --best, kevin [kzollman][talk] 19:29, 19 September 2006 (UTC)

I grew three sets. Maybe I should've feasted upon live prey while I had the chance. AEuSoes1 19:36, 19 September 2006 (UTC)

What do you mean, you don't do that now? *slurps in the last, gory piece of flesh* —Bromskloss 21:16, 19 September 2006 (UTC)

"and the people did feast upon the lambs and sloths and carp and anchovies and orangutans and breakfast cereals and fruit bats and large chu--" – b_jonas 14:21, 20 September 2006 (UTC)

I understand what you guys are saying, yet it still doesn't tell me why we don't grow more than two sets. IS there a reason? Or is it something no one can explain? Its very weird and I have no idea what the answer is! HELP MEEEEE!

It's not that humans don't grow more than two, it's that other animals do. We don't grow more because we don't need to. That is to say, evolutionary pressures are not sufficiently strong to have mutant genes like mine more reproductively advantagious. Although I do attribute my attractive set of straight cavity-less teeth to the fact that my last set came in when good dental hygiene practices were finally engrained into my prepubescent psyche. AEuSoes1 21:47, 19 September 2006 (UTC)

Are your last teeth falling out? What sense of "why" do you mean? After all, why don't we grow an extra set of eyes for when the first set starts failing? And why don't we grow a pair of eyes in the back of our heads? Why can't we fly? It's so very weird. WHY? WHY? --Lambiam^Talk 22:01, 19 September 2006 (UTC)

Evolution is based on epending the minimum amount of energy, whilst spending it well so that it increases the chances of survival to the point that it was worth the change. Since we have survived just fine as a species with only 2 sets of teeth, we have no need for any more. Philc _T^E_C^I 22:08, 19 September 2006 (UTC)

I would say the cost of growing new teeth includes the possibilities of impacted teeth, infection, abscess, and death. We need to grow one new set of teeth, or else either babies would have impractically large teeth or adults would have useless tiny teeth. (I know someone who never got their adult teeth, and those baby teeth are almost useless as an adult.) But, growing more teeth would have more of a cost (potential death) than a benefit, so we don't do it. StuRat 00:01, 20 September 2006 (UTC)

Urrr, what? Naturally we grow a second set, and rarely (never) have I heard this result in death... Philc _T^E_C^I 17:51, 20 September 2006 (UTC)

Just because you haven't heard of it doesn't mean it doesn't exist: [17]. It certainly happens more rarely now, however, because we have dentists. If we had them during the majority of human evolution, we may have evolved differently. StuRat 20:22, 20 September 2006 (UTC)

Also, baby teeth can be considered a temporary solution, as they are smaller, weaker, and take a much less firm hold on our gums than adult teeth do. Allowing succesive rows of adult teeth to grow in would certainly cause many more problems. I guess we should ask our resident freak AEuSoes1 how it worked out for him.  freshofftheufoΓΛĿЌ  01:45, 21 September 2006 (UTC)

As far as I recall, it was just a little embarassing to be losing teeth when I was eleven. I don't think that all teeth were replaced and I'd probably have to do a bit of investigation with my old dentist and his x-rays to see how many it was. AEuSoes1 08:19, 21 September 2006 (UTC)

Ok, my reply was a bit toungue in cheek, I dont doubt that it could kill you, but then everything can kill you, it just doesnt, because its unlikely. And there must have been an evolutionary advantage of early humans with 2 sets over the ones with one set, one thing is your jaw changes shape dramatically from when your first teeth form, to when your second set do. Philc _T^E_C^I 21:51, 22 September 2006 (UTC)

Ear Throat connection - Eustachian Tube

If a very bitter oily liquid is dropped in the ear, can It taste bitter in the mouth?

Depends if the molecules can permeate the eardrum somehow (or you got a perforated eardrum). Otherwise I would say no.--Light current 15:33, 19 September 2006 (UTC)

Are you saying that if a bitter liquid somehow got past the eardrum, a bitter flavor would be tasted? Do you have a source for that? It is interesting if true, and if so I'd like to read more about it. Gary 00:16, 20 September 2006 (UTC)

No source. Its obvious that if the stuff get beyond the eardrum into in the eustachian tube that leads to the throat anh hence to the mouth nose etc. Therfore you may taste/smell it.--Light current 00:41, 20 September 2006 (UTC)

No, it isn't going to happen. — [Mac Davis](talk) (SUPERDESK|Help me improve)16:42, 19 September 2006 (UTC)

Many people have a perforated eardrum. Via the Eustachian tube, material from the external ear can enter the mouth and be tasted. Contrariwise, some of them can puff on a cigarette and blow smoke out their ear. Edison 04:54, 20 September 2006 (UTC)

Here's your reference:

the middle ear lies in the petrous part of the temporal bone. It contains the three ossicles. Laterally lies the tympanic membrane (eardrum). Medially lies the inner ear. … Anteriorly, the Eustacian tube communicates with the pharynx. _{Oxford Hadbook of Clinical Specialties 4th Ed. 1995. ISBN 0-19-262537-3}

So, yes, things can pass from the middle ear to the pharynx, and thereby the mouth, where they may be tasted. If the eardrum is perforated, it follows therefore things placed into the external auditory meatus (ie your earhole) will be able to be tasted should they pass through to the mouth. The quandry arises in the case of an intact eardrum - how do you get the taste to go through? Light current's idea of permeation is interesting, but I don't know that enough would get through to have an appreciable taste in the throat - so I don't think that's the whole story. My theory is neurological. The mucous membrane of the middle ear is supplied by a bunch of nerves called the tympanic plexus, which mainly originates from the tympanic branch of the glossopharyngeal nerve, and, you guessed it, the glossopharyngeal nerve also carries sensory information from the pharynx and the posterior ⅓ of the tongue. That is, a lot of taste information gets to the brain via the glossopharyngeal nerve. Now, here's where Light current's idea kicks in. Any substance that can diffuse through the eardrum, (and it really only has to get to the inner surface of the eardrum, which is covered by the mucous membrane of the middle ear, and therefore innervated by the glossopharyngeal nerve) might cause a degree of chemical irritation to the mucous membrane, which would generate a sensory impulse the brain could well interpret as a taste - the brain's differentiation of smell, taste and oropharyngeal stimuli being a bit fuzzy. --Mattopaedia 13:30, 20 September 2006 (UTC)

Gold reacting with Mercury

Dear Sir, Gold whien in contact with Mercury is changing the colour to silver. What is to be done to get back the colour of Gold. With Regards, Ajaya Babu Potluri

The gold metal isn't just turning a silver color, it's actually dissolving in the liquid mercury, forming an amalgam. The "Mining" section of that article mentions distillation as a way to remove the mercury. Google for gold mercury separate for more info. DMacks 16:19, 19 September 2006 (UTC)

Is this a homework question of a practical question, if practical DO NOT attempt to repair this yourself, you are obviously not a metallurgist, attempts to do this at home could result in permanent brain damage. --Darkfred ^{Talk to me} 16:26, 19 September 2006 (UTC)

Then all youll be fit for is WP ref desk work. Like us! Duh! 8-)--Light current 20:51, 19 September 2006 (UTC)

Huh? whuaa? --Darkfred ^{Talk to me} 21:29, 19 September 2006 (UTC)

Stop sniffing that mercury vapor--Light current 21:34, 19 September 2006 (UTC)

my mercury tastes funny. Xcomradex 21:40, 19 September 2006 (UTC)

Yeah, it seems a bit off to me too. Better switch to some of that sweet sweet lead. DMacks 21:48, 19 September 2006 (UTC)

nothing beats a shot of gallium on a warm summers day Xcomradex 22:52, 19 September 2006 (UTC)

Hey, it worked for Isaac Newton, allegedly. Confusing Manifestation 01:06, 20 September 2006 (UTC)

In seriousness now. If this is damage to a family heirloom cause by breaking a thermometer, a jeweler could fix this by reforging the item, basically heating it till it glows, the mercury will boil off. This should be done under a vapor hood, while wearing a mask. --Darkfred ^{Talk to me} 23:00, 19 September 2006 (UTC)

The title is wrong, isn't it? Nether Gold nor Mercury react very well, let alone with each other. It's an alloy, not a chemical reaction. DirkvdM 08:57, 20 September 2006 (UTC)

Satellite

Is Satellite a Vector?

from Hatim Bharmal email address: <email removed to prevent spam>

Could you give us some context? It may be helpful. — [Mac Davis](talk) (SUPERDESK|Help me improve)18:58, 19 September 2006 (UTC)

Do you mean is an artificial satellite a biological vector? Peter Grey 20:36, 19 September 2006 (UTC)

In none of the meanings of satellite that I'm aware of is it a vector in any of the senses I know. (One meaning is the Satellite moth species, which in theory could be a disease vector, but is not as far as I know.) --Lambiam^Talk 22:14, 19 September 2006 (UTC)

A satallite has vectors, like a velocity vector and an acceleration vector! --Amanaplanacanalpanama 00:32, 20 September 2006 (UTC)

I'm going to interpret the question as "do satellites in orbit travel along a constant vector (straight line) ?". In that case, under Newtonian physics, the answer in no, they follow an elliptical orbit. According to relativity, however, I believe space is curved (by gravity) around massive objects like planets, and the path they follow is actually straight, so could be called a "vector". StuRat 14:55, 20 September 2006 (UTC)

Even if you didn't consider relativity, would it be un-scientific to imagine an elliptical vector for the satellite?  freshofftheufoΓΛĿЌ  01:39, 21 September 2006 (UTC)

laws of motion

if you were to push an immovable object with all your might, how hard would it push back?

With the exact same force as you were applying to it. However, this would never really happen so I suppose you could say it could push back with any force as it is outside the scope of the laws of physics (as far as I know) 80.229.152.246 20:08, 19 September 2006 (UTC)

See normal force. — [Mac Davis](talk) (SUPERDESK|Help me improve)20:20, 19 September 2006 (UTC)

Unless the questioner is addressing God, then Irresistible force paradox would be the article to see. —Bromskloss 21:11, 19 September 2006 (UTC)

See Newton's laws of motion. It's not possible to have an immovable object. By Newton's 2nd law, if you apply a force to an object, it will accelerate. By Newton's 3rd law, it will push back as hard as you push it - as the first reply said. Whilst it's not possible to have an immovable object, it is possible to have an extremely heavy one, say a large wall connected to the Earth - where the acceleration caused by your muscular force will be miniscule. Richard B 21:49, 19 September 2006 (UTC)

Presumably you'd be pushing the Earth with your feet in the other direction with the same force. Otherwise, you'd also be accelerating in the opposite direction. So effectively you're keeping the Earth in its place. --Lambiam^Talk 22:19, 19 September 2006 (UTC)

If you take the reference frame of the object (so it doesn't seem to be changing its motion), if you push on the object, it would appear to push back with more than the force that's pushing it. It also would seem like the entire universe accelerated - but that's only because your reference frame is accelerating. An accelerating frame of reference makes things strange. —AySz88\^-^ 22:35, 19 September 2006 (UTC)

Anyone can move the Earth by jumping up and down. Of course, the planet will move a smaller distance than the person. Edison 04:56, 20 September 2006 (UTC)

Yes, but it's not like the Earth moves all at once as a rigid body. It's probably better to say that anyone can launch seismic waves into the Earth by jumping up and down. Melchoir 05:43, 20 September 2006 (UTC)

Also, the Earth and you would move back to the same position due to the gravitational attraction between you, no? 80.229.152.246 16:16, 20 September 2006 (UTC)

"Protein molecules of the ninth configuration?"

In the movie The Ninth Configuration, a character says:

"In order for life to have appeared spontaneously on earth, there first had to be hundreds of millions of protein molecules of the ninth configuration. But given the size of the planet Earth, do you know how long it would have taken for just one of these protein molecules to appear entirely by chance? Roughly ten to the two hundred and forty-third power billions of years. And I find that far, far more fantastic than simply believing in God."

So I have a couple questions. What exactly is a protein molecule of the ninth configuration? Do we have any articles that talk about these kinds of proteins specifically? And does anyone know if what the character claims has been proven/disproven/discounted since then (the book the movie is based on was written in 1978)? Recury 19:56, 19 September 2006 (UTC)

I have no clue what the character in the movie is talking about, but you might be interested in the article Origin of life. --Allen 20:28, 19 September 2006 (UTC)

I have never heard of a protein molecule of the ninth configuration. I am thinking this figure comes from the 9 human essential amino acids. Also, the figure cited I would think is not very reliable ("the kind that you make up, not look up"). Besides, it wouldn't take that long for a few atoms to hook up in the right way—that's 10²⁵¹ years. That's several orders of magnitude greater than the estimated lifespan of the universe. Heh. — [Mac Davis](talk) (SUPERDESK|Help me improve)20:31, 19 September 2006 (UTC)

Probably fictional. Peter Grey 20:33, 19 September 2006 (UTC)

It might be useful to look at what the Intellegent Design folks have to say about this. This is a film, and the purpose of films are to entertain, although they can have the effect of provoking thought. I always ask people who calculate these odds exactly how did they do these calculations. How do you compute the odds of something when you do not know what the conditions are. What are the odds of rolling dice and coming up seven? What are the chances of throwing a peice of metal in water and having it catch fire? What are the chances of a planet existing with an oxygen atmosphere? How do you calculate these odds without knowing the conditions?

You don't, because of the randomity, the ignorance. I tried to keep from saying the number was bullshit, but I guess it is evident. — [Mac Davis](talk) (SUPERDESK|Help me improve)21:21, 19 September 2006 (UTC)

thats mostly bollocks (nineth configuration??) wrapped around an actual nugget of truth, the Levinthal paradox. Xcomradex 21:37, 19 September 2006 (UTC)

Having read the essential amino acids and Levinthal paradox articles, it seems pretty likely to me he is applying the Levinthal paradox to essential amino acids to make his argument for ID. If my memory of the film is right, he does mention that the amount of time it would take is longer than the lifespan of the universe, which I guess is the point of the argument. Which "configuration" is supposed to be ninth out of nine is beyond me. Recury 22:07, 19 September 2006 (UTC)

which, as mentioned in the levinthal paradox article, is a pretty weak argument. Xcomradex 22:51, 19 September 2006 (UTC)

In addition to the other flaws already mentioned, limiting the places where life could possibly evolve in the universe to just Earth is also wrong. Life could evolve anywhere in the universe with the proper conditions. Had it evolved somewhere else, instead of on Earth, we would be on that planet and the silly ID folks there would then limit their calcs to that planet, and not include Earth as potential site for life to evolve. StuRat 23:51, 19 September 2006 (UTC)

But it most likely wouldn't be "us." Some "thing" else. — [Mac Davis](talk) (SUPERDESK|Help me improve)04:39, 20 September 2006 (UTC)

But whoever is there would think of themselves as "us". StuRat 14:37, 20 September 2006 (UTC)

Science Projects on the Titanic

i have been trying to find examples of science projects on the Tiatance for 4th grade. Can this site help me?

Yes it can probably. Next question?--Light current 21:44, 19 September 2006 (UTC)

• I'd say something about buoyancy is probably what you will be looking for. - Mgm|^(talk) 21:53, 19 September 2006 (UTC)

Depends whether the questioner is looking for something about the sinking, or about the design of Titanic. We need more info from the questioner.--Light current 21:56, 19 September 2006 (UTC)

Icebergs could be a good topic for a fourth grade science project. Durova 22:16, 19 September 2006 (UTC)

Attempt to build a lifesize model out of popsicle sticks! You can go half size if you are lazy. — [Mac Davis](talk) (SUPERDESK|Help me improve)22:37, 19 September 2006 (UTC)

(meta) What surprises me is that Google gives me three hits on "tiatance". (/meta) An interesting angle might be the cold embrittlement of materials. This was relevant for the Titanic (see RMS Titanic#Faults in construction) and much more recently for the Space Shuttle Challenger disaster (see Richard Feynman#Feynman's later years). Feynman's icewater and O-ring demonstration is probably more feasible for a school science project than would the equivalent iron embrittlement demonstration, but the basic science is similar. -- Fuzzyeric 23:22, 19 September 2006 (UTC)

You could do something on the searching for, recovering, identifying and forwarding of remains (then vs. now). [18] - Nunh-huh 23:31, 19 September 2006 (UTC)Edison 05:00, 20 September 2006 (UTC)

Build a spark transmitter and send Morse code signals. Measure how much of a block of ice floats below salt water.Edison 05:02, 20 September 2006 (UTC)

redox reaction help

can someone help me, i need to predict and balance the reaction k+ s8---> i just need the products, thanks--69.140.210.163 22:40, 19 September 2006 (UTC)--69.140.210.163 22:40, 19 September 2006 (UTC)

This isn't the homework-helpers'-hut, mister. I'm wondering, is that a potassium ion (K⁺) or the potassium metal (K₂)? I haven't worked with theoretical redox equations in a year so I might be wrong in thinking that it should be either one. Hyenaste ^(tell) 23:21, 19 September 2006 (UTC)

Dude, we don't do your homework for you. Try the redox reactions page. It shows you how to do it. And make sure you get different charges at the end. Potassium should be oxidized and sulfer should be reduced.

Is potassium metal K2? i did not know that, and can't help but suspect it false. why does elemental potassium exhibit metallic properties on the bulk scale if the bonding is localised into K2 units? these bulk properties suggest delocalised bonding, like the other metals. Xcomradex 00:16, 20 September 2006 (UTC)

Oops, I was wrong. I saw a K and S and jumped straight into K₂SO₄, got frustrated with my inability to still be able to solve it in my head, and my response fell apart from there. Hyenaste ^(tell) 00:32, 20 September 2006 (UTC)

Hint: knock off the O's and you're done i'd say. Xcomradex 00:53, 20 September 2006 (UTC)

16K + S₈ → 8K₂S? Hyenaste ^(tell) 01:02, 20 September 2006 (UTC)

That would be my answer. Xcomradex 01:25, 20 September 2006 (UTC)

car

who invented the car?

See Automobile... many people invented the parts necessary for it, and carriages already existed so it is complicated. --Darkfred ^{Talk to me} 22:43, 19 September 2006 (UTC)

I don't think it was invented. I think it evovled over time. Have you checked the article Car? Himanyo 22:47, 19 September 2006 (UTC)

copycat :) --Darkfred ^{Talk to me} 23:03, 19 September 2006 (UTC)

Most cars did indeed evovle; only Volvos evolved. :--) JackofOz 23:08, 19 September 2006 (UTC)

Did not! Clearly cars, like television, represent intelligent design and content. Thus cars and television were invented by God and anything found in or on them is the literal truth of God. (<sprain> Ouch!) -- Fuzzyeric 23:26, 19 September 2006 (UTC)

Karl Benz in 1885 received a German patent for adding a gasoline engine to a carriage. More specifically for making and selling it to the public, but custom carriages had already been made by others, and steam cars were commercially available even earlier. --Darkfred ^{Talk to me} 23:14, 19 September 2006 (UTC)

September 20

Health Care Supply in Canada 12 years ago and today

Hello,

Thank you to anyone willing to help me out.

I'm looking for the number of medical school seats in canada in 1994, and the number available now. Does anyone have that information or a lead on where I can look for that information?

A most sincere thank you,

Matthew LR

Some information is available from Statistics Canada; for instance, they report 265 graduates in 2003 with earned doctorates (and a further 270 at "other graduate level") from "health, parks, recreation and fitness" programs, which includes medical residency programs. I think it's fair to assume most of these are med school; how many people get a doctorate in push-ups or camping? Multiply this by the length of medical school (6 years?) and it's a good back-of-the-envelope estimate. Their ESIS program may have more information, or could help with the historic info. This article might also be a good place to search. --ByeByeBaby 15:23, 21 September 2006 (UTC)

Breast removal

If I cut off a girl's breasts, what will happen to her? What will she look like? (Yes, I know she's not going to be able to breast feed, but are there any other negative effects?) --Bowlhover 04:19, 20 September 2006 (UTC)

See Mastectomy. --Allen 04:21, 20 September 2006 (UTC)

Massive blood lost (defined as over a liter) seemed to be ignored. — [Mac Davis](talk) (SUPERDESK|Help me improve)04:37, 20 September 2006 (UTC)

Surgery should only be done with the informed consent of the patient, and only by those medically qualified, using all applicable standards of sterile technique and anesthesia. And what would happen to you if she cut off your breasts?Edison 05:05, 20 September 2006 (UTC)

What about the Amazon warrior women? Or is that a myth?--Light current 05:39, 20 September 2006 (UTC)

Yes, I believe that is a myth, that Amazon women removed one breast to improve their ability to pull back an archer's bow. The existence of the Amazons may even be a myth, although there does seem to be some supporting historical and genealogical evidence. StuRat 13:01, 20 September 2006 (UTC)

That particular part of the myth is particularly hard to believe. It would take enormous breasts to interfere with archery at all, and in those rare instances they could be bandaged. Durova 13:31, 20 September 2006 (UTC)

Please discuss this question with your therapist. Please. 69.142.89.10 08:07, 20 September 2006 (UTC)

Im not a doctor (obviously?) but I would have thoght that the poor girl could bleed to death!--Light current 21:59, 20 September 2006 (UTC)

Your name isnt Shylock is it?--Light current 15:59, 20 September 2006 (UTC)

How did you know my name? --Bowlhover 04:01, 21 September 2006 (UTC)

Well...when I asked the question, I was thinking of torture rather than surgery. The Lord's Resistance Army loves to mutilate people, and I wonder what happened to the girls they abducted. --Bowlhover

She will look a lot like Agatha of Sicily a.k.a. Saint Agatha.

Atlant 01:14, 21 September 2006 (UTC)

about non watson and crick base pairing

it is known about watson and crick base pairing in DNA molecules but are there any other non watson and crick base pairing in DNA molecule please give me some informations on it.

it is quite common in RNA. not sure about in native DNA, but it can obviusly occur in DNA-like molecules containing unnatural bases. Xcomradex 07:20, 20 September 2006 (UTC)

See base pair, and follow the links in the 'See also' section. TenOfAllTrades(talk) 12:44, 20 September 2006 (UTC)

Attached to the normal base pairs, you might find DNA methylation, acetylation, or other epigenetic information. —Pengo ^{talk · contribs} 14:56, 20 September 2006 (UTC) (my RfA)

Can you prove existance of colors if you can only see B/W?

I was wondering on the subject on how the design of our human sensors and brain affects our understanding of the universe. Related to this I came up with this abstract question and would like ask the world for input:

If I have nothing but a black & white television, is it possible to prove the existence of color transmission? -- Let's say I suspect that there is a television transmitter sending out in full color somewhere, could I prove its existence using only my B/W television?

Thanks,213.199.128.152 09:14, 20 September 2006 (UTC)Jonas Sig

No, not with a b/w television. Reception in colour requires a very different technology. That was a very practical question. The abstract question you hinted at in the title would be a more interesting one.--Shantavira 09:28, 20 September 2006 (UTC)

To answer the abstract question, yes, a color blind person can prove the existence of color, by looking at a spectral analysis of various colors. That is, they can see that different frequencies are produced by different light sources. Now, they might have no idea how these frequency differences are perceived by those with normal vision, but they would certainly know that colors (frequency differences in light) do exist. StuRat 12:02, 20 September 2006 (UTC)

Color does not exists. It's a sensory fiction created by the biological system known as the eye and the brain. Just ask yourself this question: if no living creatures have eyes, does color exists? 210.49.155.134 12:14, 20 September 2006 (UTC)

The universe does not exist. It's a fiction created by information processing systems. Just ask yourself this question: if no living creatures exist, does anyting exist? --Lambiam^Talk 17:02, 20 September 2006 (UTC)

This is as much a question of philosophy as it is of science. With the television example, no, a B/W television can’t prove the existence of color transmission. However, televisions aren’t such a good analogy for eyes.

Firstly, we have to look at how color is seen. Color is the result of different waves lengths of light. Our eyes has cells which can respond to certain specific wave lengths. Information from many, many cells which respond to certain wave lengths are passed into our brain, where the brain puts together the information and tells our conscience mind what ‘color’ something is.

Now, if we defined color as being the different wave lengths of light, than the existence of color can be proven to a color blind person, as explained by StuRat.

However, if we define color as being the perception of color. So that it is an illusion created by our brain (based on the information received from the eyes) for our conscience mind, then color is completely meaningless for a color blind person. And it would be impossible to prove this perception to be color blind person, since color would be a creation of how the mind interprates sensory information.

In biology, color is defined in terms of the wave lengths of light – so yes, scientifically, ‘color’ can be ‘proved’ to a blind person. And yes, even if no living creatures have eyes, color would still exist because light still has different wave lengths.

But in some schools of thought – people will say that yes, science explains to us what color is in terms of light, but people define what color is. And if color cannot be perceived, then it is not color.

A good question to consider is, do you believe 'ultraviolet' exists? What does it take to prove ultraviolet rays exist to you? After all, ultraviolet refers to light of certain wavelengths. Just like the way “green” refers to light of certain wavelengths. But...is ultraviolet a color too then? you are blind to ultraviolet rays like the way a blind person is blind to the difference between different colors, what would you accept as a proof for the existence of ultraviolet? Yaksha 12:50, 20 September 2006 (UTC)

The claim ":However, if we define color as being the perception of color. So that it is an illusion created by our brain (based on the information received from the eyes) for our conscience mind, then color is completely meaningless for a color blind person. And it would be impossible to prove this perception to be color blind person, since color would be a creation of how the mind interprates sensory information." is somewhat dubious. As for most subjective phenomena, detection of prior basis for the phemonema can be ascertained by double-blind subject categorizations. Or, in less obscure language, one can perform a sequence of experiments on so called "color sighted" people (equiv., "psychic") where the subject is required to identify which of several objects is most similar to the "colored" object. Persistent correct classification, especially across a large selection of "color sighted" people, especially if the experimental design were sufficient and the probability of the sequence of same answers were unlikely to occur by chance, would be a mechanism of the proof of the existence of "color" to a skeptical "achromatic" person.

In fact, this is how achromats perceive color perception in others. They recognize that there is an objective reality to the attribute "orange" (say) that color sighted people persistently apply to specific objects, even though the achromat doesn't perceive any distinction between that object and the "green" object everyone's currently fawning over... -- Fuzzyeric 16:18, 21 September 2006 (UTC)

Perhaps not a very satisfying answer, but if you were to filter the colour signal to show only the red, then only the blue, then only the green, you could see each layer of the colour image on your black and white set. This answer, of course, doesn't look at the perception side of colour. However, we seem to believe bees can see ultraviolet colours even if we have no concept of what that perception may be like (or even if bees "perceive" anything, or if they're some sort of automata). Science is pretty shakey on the subject of consciousness and qualia. All we can do in that department is infer along the lines of "my brain looks like this when I see pink, so if that fish over there has a similar brain pattern when it sees pink, then we must be on the same wavelength." (no pun intended) —Pengo ^{talk · contribs} 15:05, 20 September 2006 (UTC) (my RfA)

Perceived colors do not map monotonically to the spectral wavelength of electromagnetic energy. Metameres are colors perceived identically, but having different physical bases. Many colors, defined by hue and saturation, are in the interior of the CIE color space, and can be created by mixtures of 2 or more spectral colors. These combinations are infinite in number. Also, color perception is influenced by prior exposure of the observer's eye. Stare at a color for say 30 seconds, and you will perceive its complementary color in an afterimage. Repeat the experiment, and after staring at a color, stare at the complementary color, and you will perceive a supersaturated color, more vivid than the pure spectral wavelength pruduces. Add a surround of the original viewed color, and the perceived color becomes even more vivid. Perceptual psychologists have techniques of convergant and discriminant validation to investigate the validity of sensation and perception experiences. They can determine that the same observer reports the same physical stimulus with the same label "red" and applies different color labels to different physical stimuli, and that different observers apply the same labels. They can systematically map stimuli to responses.Edison 17:00, 20 September 2006 (UTC)

I'm surprised that nobody has mentioned the fact that colorblind people do not see in black-and-white. The reason why they are colorblind is simply that the part of their vision system that would normally differenciate the colors doesn't function properly. As hinted above, most colorblind people can look at samples of colors that are considered to be of the same intensity (i.e. brightness/darkness) but of different colors, and clearly see that they are different colors. They would not have the ability, though, to determine which colors they represent, only that they are both of a similar intensity. To actually see something in black and white would involve a much more complex visual system, though would obviously be of no benefit. A friend of mine became mostly colorblind as he got older (and may eventually go completely blind), and he describes his vision now as a mess of indecipherable colors and images, as he progressively loses the ability to interpret the input coming from his eyes.  freshofftheufoΓΛĿЌ  01:31, 21 September 2006 (UTC)

There is a rare form of colourblindness where the vision becomes completely achromatic. In this case people do see in just black and white. The condition is usually from birth, but in one case a painter lost his vision, and for sometime couldn't even bring himself to eat anything ordinarily colourful (like a banana) because it was too odd and disturbing to eat a gray fruit. He also lost his ability to even imagine colour, although he rememebered it existing. The case was described in an Oliver Sacks book, Island of the Colourblind.—Pengo ^{talk · contribs} 15:03, 21 September 2006 (UTC)

Surface area of a pin

Hii my physics teacher asked me how to calculate the surface area of a pin, how the heck could u do that!!

Take a close look at it, is it a series of cylinders and cones ? If so, draw a diagram, then take measurements and do calcs for those primitives, being sure not to count areas twice where the primitives meet. Here is one possible way to model it (not drawn to scale):

+---+
|   +---------------------+ 
|   |                     |   >
|   +---------------------+ 
+---+
 CYL1       CYLINDER2      CONE

Accurately measuring the diameter could be tricky, you might need a vernier micrometer for that. StuRat 11:29, 20 September 2006 (UTC)

I hope it's not a safety pin () but more like a standard pin. The task can be split in three parts: (Step 1) deciding on an appropriate geometric model for your pin (for example the one suggested above by StuRat); (Step 2) estimating the parameters of that model (lengths, diameters, ...), preferably by taking measurements; (Step 3) doing the actual calculation using formulas for the surface areas of various geometric shapes. For step 1, stick to shapes for which you have a formula (see the article on surface area and various articles on shapes). You could go for a standard pin with a spherical head. I'd include a picture in the written report. Since the assignment is about calculation, I would not go overboard in doing the measurements with ultra-high precision. --Lambiam^Talk 14:20, 20 September 2006 (UTC)

Physics professors often give students questions like this to teach them how to do back-of-the-envelope calculations. My professor once asked on a test how much water a person drinks in a year, and there is a famous story about a mathematician who calculated the number of piano tuners in Chicago. Here's an article about these types of calculations: http://en.wikipedia.org/wiki/Back_of_the_envelope Gary 18:22, 20 September 2006 (UTC)

Fermi problem is another name of these, as Enrico Fermi was well known for them (he's apparently the one behind the piano tuner question—a physicist, not a mathematician). --Fastfission 23:49, 20 September 2006 (UTC)

I wonder if the answer is to find the volume first (easy - just drop lots of pins in a small measuring cup with water), and then to measure the pin length, divide the volume by it - that would give you the area of the cylinder's cross-section. That would give you the radius, and you are done. All of this assumes cylindrical shape, of course. --Ornil 20:58, 21 September 2006 (UTC)

Far too experimental: Paint the pin and a test unit area. Remove each mass of paint by solvent extraction. Weigh each mass of paint. Assert that the surface area is the ratio of the masses. For improved precision, dilute the paint first.

Far too hot: Heat the pin to a biggish temperature, like 1 kK. Measure the total thermal radiation of the pin. (Proportional to surface area minus small correction factors for self-visibility.)

Variant: coat the pin with a thin layer of fluorescent or phosphorescent paint. Also coat a test area. Measure the total fluorescent/phosphorescent emission of the pin (when excited) and compare to that of the test area.

Far too difficult: Heat the pin to a biggish temperature, like 1 kK. Insert into a well stirred quenching liquid. Measure the temperature profile for the liquid. Melt the pin into a sphere. Repeat the experiment. The repetition allows you to directly calculate the heat transfer coefficient between the pin and the fluid. Consquently, you may calculate the area of contact in the first experiment.

Far too phishy: Offer to give the makers of the pin some money if they'll tell you the surface area of the pin. -- Fuzzyeric 02:37, 22 September 2006 (UTC)

Piano tuners

How many pianos? How many people want em tuned? How many can afford it? So how many tuners can that business support? Is that the logic?--Light current 23:52, 20 September 2006 (UTC)

Pretty much. As I recall, it required estimates on things like the population of Chicago, the average size of a household, the proportion of households with a piano, the frequency with which pianos are tuned, and the number of pianos the tuner can tune in a year. Put them together, you get your answer. Confusing Manifestation 03:31, 21 September 2006 (UTC)

What kind of bug is this?

I found a bug. Is it identifiable? It was captured in New England, not too far from the coast, if that helps. grendel|khan 12:23, 20 September 2006 (UTC)

Looks a lot like a western conifer seed bug (Leptoglossus Occidentalis) [19][20]. Weregerbil 14:26, 20 September 2006 (UTC)

As both you and the random university entomologist that I emailed concur, I shall be fixin' that image to illustrate the article. Thanks! grendel|khan 18:11, 20 September 2006 (UTC)

Energy when cycling

Yesterday I was cycling along a route I normally run, when I started wondering - why is cycling easier than running? You're going faster, and carrying more weight (moving the bike frame as well as yourself), but using the same legs and cardiovascular system to generate the energy - so surely you should get tired more quickly. Yet it feels easier. Obviously there's some energy not-loss, in that your energy is just going into moving forwards, wheras running also uses energy to push upwards with every step, but is that all the difference? Or is cycling more efficient/am I just imagining the difference in tiredness? Our article on Cycling didn't seem to cover the energy input. --Mnemeson 13:10, 20 September 2006 (UTC)

As long as you don't ride up an incline, the weight of the bike is not directly relevant to the amount of work needed. You have to counter the force of friction and of the deformation of the tubes, which is higher for a heavier bike, but still small if the bike is in good condition. On the other hand, when walking on a strictly horizontal plane, various body parts also have an up-and-down motion component, which does involve work, and this gets stronger with a running gait. Going up a steep incline, walking is easier than running or cycling (at least for me). --Lambiam^Talk 13:32, 20 September 2006 (UTC)

(edit conflict) :Walking requires constant lifting and lowering (or bobbing) of the body to swing the legs. THats where the energy goes in walking (on the flat)--Light current 13:35, 20 September 2006 (UTC)

This is precisely why Ug invented the wheel (which was followed by a rather crazy epoch until someone else invented the brake).--Shantavira 14:56, 20 September 2006 (UTC)

Yeah but it took him a while to realise it should be round. The square wheel he first invented still required extra energy. We still have some of those original wheels on out local buses. 8-)--Light current 15:16, 20 September 2006 (UTC)

Which reminds me of a B.C. cartoon in which we are in the waiting room of the patent examiner's office. Through a window we see carts with square wheels go by in the streets; in the room someone is sitting with a model cart on his lap that has triangular wheels. As the proud inventor explains to his neighbour: "It eliminates one bump."  --Lambiam^Talk 16:49, 20 September 2006 (UTC)

Square wheel production continues today but they are used mostly on shopping carts. I believe there was a Scientific American article in the 1960's looking at the efficiency of bicycling versus running or walking, which showed the calories burned by mile to be way lower for the cycle. For one thing, you are not having to move your center of mass up and down with every step like running.Edison 17:04, 20 September 2006 (UTC)

Hasn't it anything to do with the fact that a bicycle preserves forward momentum much better than walking does? That is, when you're walking, you have to constantly add energy to have the same velocity, and that energy-cost is much lower on a bike. More energy can be directed towards acceleration instead, thus you go faster. Oskar 23:05, 20 September 2006 (UTC)

Mind you, the equilateral curved polygon gives a smooth ride if you use it as a roller.--Light current 17:34, 20 September 2006 (UTC)

Do you mean the Reuleaux triangle? (It sounds like something Inspector Clouseau might say.) While having a constant height in all orientations, its centre does bob up and down a bit – if I remember correctly by something like 7%. --Lambiam^Talk 00:47, 21 September 2006 (UTC)

Well yes! Or anything similar with more 'sides'--Light current 02:16, 22 September 2006 (UTC)

Cycling is the most efficient form of transport. More effcieint than walking or a car (taking into account energy used by the car of course). I think the scientific term for the energy conservation mechanism found in a moving bicycling is called "rolling along". —Pengo ^{talk · contribs} 00:46, 21 September 2006 (UTC) (my RfA)

Thanks for the answers, you guys :) --Mnemeson 01:38, 22 September 2006 (UTC)

Glycemic response

After doing much research on Glycemic index at WP and other sites, a question seems to emerge. Is there any way for a person who suffers from exaggerated insulin response but is otherwise healthy to improve their response to normal foods, aside from reducing glycemic load in meals? --Jmeden2000 14:40, 20 September 2006 (UTC)

I believe many small meals instead of a few big meals helps to distribute the load on the pancreas more evenly. StuRat 15:26, 20 September 2006 (UTC)

As always, get your nutritional info from a registered dietitian and your medical advice from a doctor , nurse, or diabetes educator. Now what do you mean by "exaggerated insulin response?" Are you diabetic? How do you know your body has an abnormal insulin production after a meal? Do you have hypoglycemia, diagnosed by yourself or a doctor, and how was it diagnosed? Anyone can buy a glucose meter for $30 or so at a drugstore and do a finger-stick to test blood sugar premeal, say an hour after, and 2 hours after, etc. Never use someone else's meter or lancets, since hepatitis and other illnesses have been spread thereby. Edison 17:13, 20 September 2006 (UTC)

I am otherwise healthy (according to my doctor) but I experience lethargy after eating a meal of high GI foods, typical of a blood sugar swing. It isn't health threatening but it's disruptive to my work, so I am trying to learn more about it to know if I need to change my diet, behavior, or both so that I can perform better. --Jmeden2000 19:38, 20 September 2006 (UTC)

The lethargy is healthy and normal, the bodies response to the sugar you are eating in the meal. Xcomradex 21:43, 20 September 2006 (UTC)

If its just the high GI foods that wipe you out, why not stick largely to low GI foods then? Mattopaedia 09:44, 21 September 2006 (UTC)

So see above. Buy a Freestyle Flash meter or similar, and test your fasting glucose (premeal) the after the meal 1 hour, 1.5 hours, 2 hours, 2.5 hours, etc up to say four to six hours after eating, and you and the doc will know more than you do now. Edison 14:37, 21 September 2006 (UTC)

a question about seed

can u tell me what sort of plant has the biggest seed and where they r found?

thanx ~spike

A coconut ? StuRat 15:30, 20 September 2006 (UTC)

The words biggest seed are a really good google search term. See Coco de mer. Weregerbil 15:40, 20 September 2006 (UTC)

Capacitance Time Delay Circuit

What formula should be used to solve the following ?

An open circuit exists with a 500 kOhm resistor and 35 microfarad capacitor in series with a 30 volt battery. Once the switch is closed and the circuit is energized, how long until the circuit will acquire 63.2% of it's final charge ?

         /SWITCH   R=500 kOhm   C=35uF
+-------/  --------/\/\/\-------| |----+
|                                      |
|                 |   |                |
|             - | | | | +              |
+---------------| | | |----------------+
                | | | |
                  |   |
                 30 volts

This is a homework problem, although not mine, but somebody I'm helping. Also, I want the formula, not the answer. (However, if you want to give the answer, I won't object too strongly.) :-) StuRat 15:38, 20 September 2006 (UTC)

THe formula for voltage across the capacitor is Vc= 30* [1-exp(-t/RC)]. The figure of 63.2% is a special one as you may see from the equation and the cap charges to this level in a time that is known as one time constant which is equal to RC (ie t=RC). Because [1-1/e]= 0.632.--Light current 15:50, 20 September 2006 (UTC)

Answer 17.5sec--Light current 15:54, 20 September 2006 (UTC)

Thanks...glad to see you have interests other than going to find a man in a bar. :-) StuRat 19:04, 20 September 2006 (UTC)

Welcome! I have many interests, but I must still be a sad person to be spending so much time here. 8-))--Light current 19:11, 20 September 2006 (UTC)

Did you try RC circuit (which needs a bit of a reorganization...)? :p —AySz88\^-^ 17:04, 20 September 2006 (UTC)

---

Question Status: Answered

StuRat 19:28, 21 September 2006 (UTC)

A Question Of Bread

In the UK/Netherlands, the cheapest bread money can buy is 28p/€0.39. Is this bread nutritionally inferoir to bread of two or three times the price? --Username132 (talk) 15:43, 20 September 2006 (UTC)

I wouldnt eat that stuff. It wont be wholemeal or anything for that price.--Light current 15:56, 20 September 2006 (UTC)

Sounds like conjecture to me. What do you propose it's made of? --Username132 (talk) 16:18, 20 September 2006 (UTC)

Flour--Light current 16:24, 20 September 2006 (UTC)

We have always referred to cheap fluffy white bread as "balloon bread" and buy whole wheat instead. "Wheat bread" is a misleading advertising trick term, since balloon bread is made of wheat. The whole grain is supposed to have some nutritional value, but at least it is higher in fiber. Still, cheap white bread will keep body and soul together and if money is tight, something is to be said for the most grams of complex carbohydrate per unit cost. Bakery outlet stores sell all kinds ofday old bread for a small fraction of the grocery store cost, and most bread is day old by the time it is consumeed anyway.Edison 17:18, 20 September 2006 (UTC)

Is a $20000 car 100 times worse than a $2000000 car? Is a $100 dollar pair of jeans half the quality of a $200 pair?

I would guess that the more expensive bread would advertise that it uses better raw ingrediants, 'organic' ingrediants, ...etc. But whether this makes the more expensive bread nutritionally better, no one really knows. Personally, i wouldn't ever buy the cheapest food - because when it's that cheap, it's target customers are really poor people, which means the quality probably is worse. but at the same time, i wouldnt' bother to buy the more expensive food, because when it's that expensive, it's just fancy-ness.

I should also point out that more expensive food is something nutritionally worse. Here, the most expensive breads are the ones that tastes the best...which also happens to be the ones with the most preservatives and oil. Yaksha 07:54, 21 September 2006 (UTC)

The bread I buy (Allinson wholemeal) is rather expensive if you look at the price per bread. But I don't. I look at the price per weight. The bread may cost twice as much as average bread (75 eurocents per half bread), but it also weighs twice as much, so will (ceterus paribus) have twice the nutritional value. I consider most breads to be 'gebakken lucht' ('baked air' - it seems that is English too). Also, I prefer my bread to stay in one piece when I smear pâté on it. :) DirkvdM 08:30, 21 September 2006 (UTC)

Water window ph4 - ph 9

Water window or de:Wasserfenster from pH 4 bis 9, we need help on the discussion here [[21]], The pH of wastewater leaving manufacturing plants and wastewater purification plants, as well as potable water from municipal drinking water plants, must be within a specific pH "window" as set forth by local, state or federal regulatory agencies. This value is typically between 5 and 9 pH, but can vary from area to area. source, :[[22]].

The question: is it a term used in the field or should the article be removed? reg. Mion 16:55, 20 September 2006 (UTC)

I have not heard of this term before, but it seems logical enough.--Alex 13:04, 21 September 2006 (UTC)

Micrometeorites and radiation

Assuming the Apollo missions did go to the moon, how did the astronauts survive the intense radiation and the numerous fast moving micrometeorites? --Light current 17:38, 20 September 2006 (UTC)

There weren't as many as you think, that's all. If there was too much radiation or even one small rock the system would have crashed. — [Mac Davis](talk) (SUPERDESK|Help me improve)17:44, 20 September 2006 (UTC)

How many small holes were there in, say, the lunar lander module? And why didnt these particles that caused them puncture the spacesuits?[23]

Radiation dangers are here [24]--Light current 17:48, 20 September 2006 (UTC)

Your links answer your question. The Apollo missions were short. Note that the "from space" example (not the lab example) is a 1mm "crater" after 6 years of exposure, and the Apollo missions spent around a week outside of the Earth's magnetic field. — Lomn 18:17, 20 September 2006 (UTC)

Yes the Apollo astronauts were incredibly lucky:

• not to have been hit by micrometoeries of any damaging size
• not to have been out and about during a solar flare
• not to have got more of a dose (a life times worth wasnt it?) of radiation than they did.

However this points up the difficulties of long spaceflight: something that seems to have been forgotten by the general pubic most of whom think that holidays on the moon are just around the corner. 8-(--Light current 18:28, 20 September 2006 (UTC)

Well, "incredibly" is not really the right word. That implies that particularly adverse odds were withstood, which really wasn't the case. The vast majority of the time, damaging micrometeorite collisions do not occur. The vast majority of the time, solar flares are not present in a particular region of space. And the radiation dosage taken was something like two or three years' worth, fully expected and not life-threatening. Are you correct that something like a Mars mission carries more inherent risk? Sure. But engineers are also aware of that, and can take measures unnecessary during the Apollo era. If you want to talk about "lucky", though, your radiation dangers link also answers this: takeoffs and landings compromised the bulk of the mission risk. — Lomn 18:50, 20 September 2006 (UTC)

You can see solar flares coming, and predict them accurately enough, there are no serious radiaton risks, the link you gave, expressed that a 2 year trip would reach NASA imposed limits, these are usually well below levels you can become affected by. As they dont what to risk even an outside chance, so the odds are even if you recieve a lifetimes worth of radiation, deemed as safe for an astronaut, you'll till be fine. And also that the magnetosphere is a lot bigger than you might have thought. Philc _T^E_C^I 18:55, 20 September 2006 (UTC)

I agree the magnetosphere is the primary protection mechanism against radiation and charged particles, near the earth. But it doesnt extend as far as Mars. Does Mars have a magnetic field? Also a quote from the ref.

"A big solar event during one of those missions could have been catastrophic," said Cary Zeitlin, a radiation expert at the National Space Biomedical Research Institute at Baylor College of Medicine in Houston. "The risk was known. They gambled a bit." My bolding --Light current 19:03, 20 September 2006 (UTC)

My point is that such a statement is analogous to "A wreck while driving from coast-to-coast could be catastrophic. The risk is known. Truck drivers gamble a bit." And yet most truck drivers complete their routes without incident. It's not that the risk does or doesn't exist; it's placing said risk into proper context. — Lomn 19:30, 20 September 2006 (UTC)

Alternately, the apples-to-oranges comparisons need to be stopped. The topic originated with Apollo, and references such as the gambling above refer to Apollo, but you're referring to Mars. Nobody is claiming that the Apollo approach is suitable for Mars, or that it is being considered for such. — Lomn 19:33, 20 September 2006 (UTC)

OK. The points Im making here are:

• Travel to the moon was very risky (because of possible meteorite damage).Astronauts WERE v.lucky!
• safe travel beyond the earths near environs (and its protective magnetosphere) is going to be a lot more difficult than most people think.

People think that because we've managed to get to the moon, all problems are minor, and its just a slightly longer journey to Mars. Any spacecraft for this sort of trip is going to need some pretty good (and massive) shielding against radiation and meteorites. It's probable that the only way of doing this is to build the spacecraft in earth orbit, as we would never be able to launch it all in one go!--Light current 20:49, 20 September 2006 (UTC)

I'm still going to have to disagree with your assessment of relative meteorite risk. There has never been a significant meteorite impact on a manned spacecraft and, as far as I know, no such impact on an unmanned telemetry-capable craft either, and that's with 40-plus years of manned flight (much of it continuous due to space stations). Empirical data , therefore, suggests that the chance of catastrophic event on a week-long Apollo mission is pretty low. For that matter, there's probably a greater chance of incident in near-Earth orbit due to all the man-made junk floating around than in cislunar or interplanetary space. More spacecraft have been lost due to collision damage from their own debris than from that of extraplanetary origin. — Lomn 21:41, 20 September 2006 (UTC)

That is very interesting! I m sure I saw a TV programme illustrating the high micro meteorite risks.--Light current 21:52, 20 September 2006 (UTC)

You are correct in thinking that the lack of adequate protection from radiation does pose a significant complication for long-term habitation beyond the Earth's viscinity. For this reason some proposed lunar or martian settlements comprise metal habitats sent from earth that are buried in the regolith, the local material providing the bulk of the radiation shield. This page shows estimated radiation on the surface of Mars, which vary between 10 and 20 rems (about half the dosage one would get in the ISS and 2 or 3 times what you'd get on Earth [25]). And that's unshielded doseage (what you'd get if you lived ontop of Olympus Mons wearing a polkadot bikini for a year). Explorers on mars would get a lot less in practice, because a) they'd be at lower altitudes for some of the time (depending on the mission profile and base location) b) they'd be in some kind of suit which would afford some protection c) they'd only be outdoors for a few hours a day, and would spend the rest of the time in the rad-shielded hab watching Battlestar Galactica and d) they'd probably (at least in the forseeable missions) be there only a month or two. Explorers would likely receive more radiation during the long flight to and from Mars than on its surface. This is one argument for running trips to Mars via a chunky permanent station in the Hohmann transfer orbit; each individual mission to and from Mars wouldn't have to spend energy accelerating and decelerating a heavy radshield - they'd just accelerate and decelerate themselves (and their supplies, spacecraft etc.). Higher exposure incidents (particularly for solar flares) call for chunkier mars-habs and a beefier Hohman station, and you'd just no go outside during a solar storm. Per radiation poisoning, doses in the ranges you might expect to be achieveable (say ~5 rems a year for a 2 or 3 year mission) are probably going to elevate the astronauts' cancer risks (and you can bet they'll be closely monitored for the rest of their lives) and its certainly much more than is permitted for occupational exposure, but it's still below the threshhold for proximate health problems. -- Finlay McWalter | Talk 23:13, 20 September 2006 (UTC)

About the impact danger, what realy astounds me is that one spacecraft (which one was that again?) flew through Saturns rings and survived.

Spacecrafts for manned Mars missions are designed with a 'radiation free' room that astronauts can survive in during a passing solar flare. The big problem is their functioning depends on weight (eg lead) to stop the radiation, and that is precisely something one wants to keep down when sending a spacecraft. Another problem is that weightlessness for more than a year will cause weakening of the muscles, which will make the trip pointless if it means the astronauts can't do any work in the week or so they get before they return. Unless they stay until the Earth and Mars are in the right positions again and return a year or so later, but then they'd need a whole support system set up on Mars first.

That said, what's the point in manned Mars missions anyway? For above reasons they would cost loads more than sending robots (no life support needed and and more expendable, so crafts don't have to be as full proof). Sending, say, ten robots for the same price would give us much more info. I suppose democracy gets in the way here (give the people instead of the scientists what they want), especially in the US, where people were made to believe that the USSR's landings on the Moon 'didn't count' because they weren't manned missions, so the US government could claim that the US had won the race to the Moon (which was also presented as 'the big goal', which was also a load of bull - sorry about the rant :) ). DirkvdM 08:54, 21 September 2006 (UTC)

Em momentum transfer

I read somewhere that there is a drive that can cause momentum transfer in air molecules to produce propulsion useing micro-waves. Its called an EM drive i think, not like in the biefeld -brown effect where the air molecules are ionised and collide with air molecules.

Proplusion with momentum transfer in air molecules needs a starting force, what kind of Em waves can create a momentum transfer with air molecules? Are there more than one type and what kind of frequency is needed.

Robin

See EmDrive, and the caveats therein. -- Finlay McWalter | Talk 22:22, 20 September 2006 (UTC)

uuuuuuuuuum that didnt anwer my question, i asked if EM waves can cause moemtum transfer in air molecules, this says nothing about that. its just about the EM drive but it sounds quite different from how i heard it described in another article. but the question still stands.

Robin

your question is unclear. if you are asking can EM fields cause air to move, then yes, eg. rotational spectroscopy or microwave. Xcomradex 23:35, 20 September 2006 (UTC)

Thank you , yes i was asking if EM waves or fields can move air, and it looks like the answer is yes. Robin

A photon has momentum and will transfer some or all of its momentum to an atom if it interacts with that atom. So the answer is yes. EM waves can "move" air molecules. 202.168.50.40 00:17, 21 September 2006 (UTC)

Another way to say that is that light makes air hotter, and therefore moves it, due to the definition of heat. — [Mac Davis](talk) (SUPERDESK|Help me improve)05:22, 21 September 2006 (UTC)

It's not just heat; if a beam of light interacts with air, the air (or perhaps its container) will be propelled in the direction of the beam as well as heated. Heat is molecular kinetic energy with an average momentum of 0; it is possible to heat something without moving it, and to move it without heating it. A beam of light will do both because photons are more efficient at carrying energy (to be precise, their ratio of non-rest (or "kinetic") energy to momentum is greater) than all massive particles. This means that after all the momentum is transferred, there's still some energy left over that can't accelerate anything, so it heats it instead. (In reality, of course, not all of the beam will be absorbed, and new radiation will be being emitted all the time.) Hope this helps. --Tardis 18:15, 21 September 2006 (UTC)

Excitation of the vibrotational spectrum of air molecules doesn't make them move (translate), it makes them vibrate or rotate, and therefore get hotter. Translational motion of molecules has less energy than these modes. (Diatmoic nitrogen gas with 0.1 eV of translational energy is moving ~800 m/s, which is about 5-times the mean free velocity of air molecules.) Compton scattering and Raman scattering are common forms of inelastic scattering of light. Compton scattering doesn't apply to neutral atoms. Raman scattering has a typical efficiency of 10^-7 * 10^-3 (interaction probability, momentum transfer fractions, respectively) although there are nonlinear effects at high intensity that can make this a bit higher. Nevertheless, moving air by this method is an extremely inefficient method (watts in, nanowatts out). -- Fuzzyeric 19:26, 21 September 2006 (UTC)

Basic Law of Electrostatics

What is a simple way to expain thislaw to a 3rd grade student?

Are you talking about Coulomb's law? If so, I would say that, if two objects have opposite charge, they attract just like gravity, but with amount of charge, rather than mass, determining how strongly they attract. And if two objects have the same charge, they repel, just like gravity in reverse. Now if the student wants more detail about inverse-square laws in general, take a look at Inverse-square law, especially the diagram at the top. The idea of radiating flux lines can be useful to understanding why force decreases with distance the way it does. --Allen 23:32, 20 September 2006 (UTC)

Human evolution

Now and then I hear people (very credible people) say that since the rise of agriculture and civiliazation, human evolution has essentially stopped. Is this really true? I mean, we're getting taller, we're getting older, we're getting smarter all the time. I find it hard to believe that all of these things are simply results of an advancing society with better dietary conditions and so forth. Is that all it is? How about a more concrete example: the lactose-tolerance gene. That is a fairly recent genetic improvement that has spread across the world from northern europe. Isn't that a textbook example of evolution?

However, I am not a doctor, nor a scientist, so it's very possible (probable even) that I've got it all backwards. Can someone explain what exactly has changed during the last few millenias that would supposedly stop the mechanisms of evolution for humans? Oskar 23:00, 20 September 2006 (UTC)

Spread of genes isnt really evolution, possibly an example of evolution in progress. But any changes that have taken place on a timescale shorter than at least several hundred thousand years are not going to be evolution really, so any differences between us and cavemen, are purely due to conditions, diet, social stuff, etc. Philc _T^E_C^I 23:03, 20 September 2006 (UTC)

I thought that micro-evolution (ie spread of individual genes) and macro-evolution (major changes in species) was the same thing in modern evolutionary biology. That is, a genetic change that passes natural selection in a race is evolution, no matter how small the improvement. Is that not accurate? Oskar 23:09, 20 September 2006 (UTC)

Evolution is not stopping. Some of the natural selective pressures have been taken away, such as the need for good eyesight. That in and of itself changes the frequency of certain alleles. If you think of evolution as some progression towards bigger and better things, that's not what evolution is and may be part of the problem. InvictaHOG 23:07, 20 September 2006 (UTC)

This is what I'm thinking! So what are the arguments for of these people that claim that evolution has stopped? I mean, unless they're not figments of my imagination. I seem to recall the argument that since we are no longer isolated in small tribes, but in much larger communes, that any big evolutionary change will be quickly diluted and disappear. The evolutionary incubator, so to speak, has gone away. I may be imagining that too (damn those imaginary scientists!), but that is what I've heard people say. Is it all a misunderstanding on my part? Oskar 23:14, 20 September 2006 (UTC)

Well, without strong differential reproduction pressures you're not going to deviate terribly far from the mean, to use a statistical analogy. But "diluted" is the wrong metaphor to use (it is not actually a melting pot) and "disappear" is probably wrong (in fact the biggest evolutionary change of modern society is that many genetic combinations which would otherwise be more likely to disappear can be accomodated for). If you mean, "we'll never be able to see the same change take over the entirety or even the majority of the species very quickly," that's true, but that isn't really different from any species with a large, stable population ("big" changes usually occur with things like founder's effect and in other small populations). There are shifts in allele frequencies, of course (there have to be, if you are reproducing) but you're not going to get radical changes in them unless there are reproduction pressures which favor one against another. --Fastfission 23:43, 20 September 2006 (UTC)

(EC) There is a common equivocation between evolution-as-getting-better and evolution-as-change. When biologists talk about evolution, they mean simply change in gene frequencies among certain populations. Since Europeans/North Americans are reproducing at slower rates than members of other nationalities, I feel confident that gene frequencies amongst human populations are changing, perhaps very rapidly (by geological standards). Before humans were capable of radically modifying their environment, change in gene frequencies often corresponded to humans becoming more adapted to their environment. This usually resulted in what we would call improvements, like better immune systems, etc. So, in early human evolution both evolution-as-getting-better and evolution-as-change where occurring together. Now however, our bodies are undergoing evolution-as-change, but not perhaps evolution-as-getting better. In fact, there may be some reason to think our bodies are getting worse because people who otherwise might have died out are now able to reproduce. --best, kevin [kzollman][talk] 23:20, 20 September 2006 (UTC)

"I find it hard to believe that all of these things are simply results of an advancing society with better dietary conditions and so forth. Is that all it is?" As for getting taller, older, smarter, pretty much. All three of those things correlate directly with things like diet, medicine, public health, education, and luxury. Now whether there are not also smaller long-term gains across the population — it would be a very subtle effect, if it was one, because evolution works sloow. Evolution works on the scales of hundreds of thousands of years — improved diet, medicine, public health, education, and luxury are only what? Two hundred years old, max? And these changes are what, a hundred or so years old? Almost definitely an environmental issue. (But the question of "are humans evolving?" is a totally different one from that one.) --Fastfission 23:37, 20 September 2006 (UTC)

While evolution hasn't 'stopped', but there has been a change of perspective. The agricultural revolution was only a few thousand years ago, and the whole period of recorded history is compared to the entire stone age, at least hundreds of thousands of years, so in the very short historical period human biology seems to be 'standing still'. Also, humans have the power to alter their environment far more profoundly than any other species, and while this does not eliminate evolutionary pressure, it does mean that we respond by both biological evolution and cultural/technological evolution. Peter Grey 23:52, 20 September 2006 (UTC)

Agreed!--Light current 23:55, 20 September 2006 (UTC)

Also, evolution can never stop, it being the genetic change of an organism. As for the first sentance, "credible" does not always mean "correct." — [Mac Davis](talk) (SUPERDESK|Help me improve)05:25, 21 September 2006 (UTC)

I'm afraid I don't understand what you mean. Evolution is not usually about organisms, but about populations. Although statistically unlikely, it seems possible to me that a population could maintain gene frequencies over several generations, and thus not experience any evolution. Can you say more about what you meant? --best, kevin [kzollman][talk] 06:05, 21 September 2006 (UTC)

You might be interested in the concept of higher evolution (from which there is a link for more info), although it is only a stub.--Shantavira 06:28, 21 September 2006 (UTC)

"Now and then I hear people (very credible people) say that since the rise of agriculture and civiliazation, human evolution has essentially stopped. Is this really true?"<<<the rise of agriculture and civilization would have removed most evolutionary pressures from humans. If people are saying humans haven't evolved since agriculture and civilization, then they are quite right. Since agriculture and civilization where only about 10 thousand years ago at most, which is a blink of an eye in life history. In terms of evolution of species, not much happens in 10 thousand years, it's a very short period of time.

If the question was merely whether humans are still evolving...then it's quite a debated issue. Microevolution - so the change in gene frequency over generations, is certainly happening. But whether the human race in general is still changing is a question that doesn't really have an answer. Lots of hypothesis and beliefs, but there's never been any large scale research done.

And quite possibly there never will be, due to the contraversy it would bring, especially because most religions believe humans where made by god, and therefore we have never evolved and shouldn't be evolving. If the topic interests you, i recommend you try and get your hands on some old New Scientist magazines. Try public libraries or university libraries - it's one of the most popular science magazines. It had in the last year quite a few large article asking exactly your question - whether humans are still evolving - http://www.newscientist.com/channel/earth/mg18925422.700-editorial-are-we-still-evolving.html, http://www.newscientist.com/channel/being-human/mg18925421.300-are-we-still-evolving.html, http://www.newscientist.com/channel/being-human/mg18725174.600-human-brains-are-still-evolving.html.

And there's one article on brain size which is open for public view: http://www.newscientist.com/channel/being-human/dn7974-human-brains-enjoy-ongoing-evolution.html enjoy. Yaksha 07:38, 21 September 2006 (UTC)

Though it should be noted that New Scientist is not a terribly reputable science magazine, and has published some utter nonsense in recent years. --Fastfission 20:27, 21 September 2006 (UTC)

some. But it's pretty easy for general audience to read, and at least where i am, very easy to get hold of Yaksha 03:20, 22 September 2006 (UTC)

Sound waves and momentum transfer

What is the difference between sound waves and other air molecule momentum transfers such as overpressure shockwaves, or just air pumps. why is some waves propagating by air molecule momentum transfer called sound and others are not. Would a vibratiing peice of metal causing air vibrations and levitating something be called acoustic levitation?

thanks

Sound is defined as what we can hear. Anything else is just compression waves! 8-| --Light current 23:59, 20 September 2006 (UTC)

i thought that what we couldnt hear was still souund, either ultra or infra sonic?

thanks

Sound is what sounds like sound to you--Light current 00:34, 21 September 2006 (UTC)

What I'm sure Light current means to say, is that "sound waves" are basically waves that happen to fall into the range of frequencies that are audible to humans. Since other animals such as dogs can hear much higher frequencies than humans, those waves can also be considered sound waves. If a piece of metal vibrates at a frequency within the range of human hearing, you will be able to hear it and thus it will make a sound. Of course high-frequency waves can be called ultrasound (not ultra-sonic or super-sonic, which is a speed as opposed to a frequency), and low-frequency sounds can be called infrasound (not infra-sonic), but in many cases it's not useful to think of vibration as merely types of sound.  freshofftheufoΓΛĿЌ  01:06, 21 September 2006 (UTC)

Just to correct. Ultrasonic and infrasonic refers to frequency of sound. While terms for speed are subsonic, supersonic and hypersonic implying speeds less than, greater than and more than five times the speeds of sound respectively.nids(♂) 10:53, 21 September 2006 (UTC)

Fundamantally there are three types of waves we know about (or believe we do): mechanical (this includes sound waves), electromagnetic and (we believe) gravitational. So in answer to your first question, there is not fundamental difference between the phenomena you asked about.

Acoustic levitation is acoustic levitation. The first order effect in acoustic levitation is parking a mass at a node of the acoustic field so that the field minimizes the work done on it. Displacing the mass away from the node causes a restoring force, similar to the force in the Casimir effect. The air molecules in acoustic levitation oscillate in position, but do not have a net collective displacement. A rock, thrown through the air, has a net collective displacement. A pump produces a net collective displacement, not positional oscillation. Consequently the mechanism whereby a pump lift an object by flinging air at it is different from the mechanism where an acoustic field can hold an object at a position of minimal energy. In the first case, momentum is transferred to the object to oppose gravity. In the second case, energy is transferred to the object to oppose its moving off the node. -- Fuzzyeric 19:34, 21 September 2006 (UTC)

Has anyone ever held a seagull?

Has anyone here ever held a seagull? What do they feel like? I see them sat around and they look like they're really warm, soft and fluffy.

Theyre aggressive and could peck your eyes out tho!--Light current 00:00, 21 September 2006 (UTC)

Especially the male ones. Oops, minus 20 points. Clarityfiend 00:29, 21 September 2006 (UTC)

Shit I forgot!--Light current 00:32, 21 September 2006 (UTC)

Assuming that we can generalize from parrots to seagulls, what you'll find is that the tactile impression you get from touching a bird varies a lot across the bird. The downy head and body feathers are soft and fluffy but the long wing flight feathers and tail feathers are stiff and make crackly noises not unlike crinkling very stiff paper. Also, birds vary in "cuddliness" depending on how they are raised. Our sun parakeet, adopted by us a few months ago, spends a lot of time snuggled up with my wife, often falling asleep inside her shirt! She (the parakeet!) also very often likes to be petted, to have her beak rubbed, or, occasionally, to be aggressively played with including flipping her over on her back and then letting her hang from your fingers.

Atlant 01:25, 21 September 2006 (UTC)

Baby gulls are cuddly. I've raised a couple of young'uns myself and they do love to be held and snuggle (they like the 'inside the shirt' thing too). When they grow, they stop liking it and become quite aloof. Gulls are not social preeners, you see - even mated pairs keep a respectful distance, aside from during the 'physical act of love' itself (much like some human couples, heh)... --Kurt Shaped Box 12:09, 21 September 2006 (UTC)

Mentioning the word or alluding to it: Minus 20 points! Sorry!--Light current 01:39, 21 September 2006 (UTC)

What's the in-joke? Mattopaedia 10:27, 21 September 2006 (UTC)

Start with the 4th question of Sept. 10, then switch to Miscellaneous and look at the 2nd question of the 17th. Clarityfiend 00:03, 22 September 2006 (UTC)

Well, believe it or not, I saw someone hold a seagull today. It literally just fell from the sky and landed on a busy street in the city. And old man went and lifted it away and sat it out of the way of the crowds. IT didn't seem to creat much of a fuss.

It was probably sick and/or dying. I once picked up an adult great black-backed gull with a broken wing and it fought like hell and was screeching and whining all the way as I wrapped it up in my coat and carried it home. --Kurt Shaped Box 20:22, 21 September 2006 (UTC)

"Do you think [the seagull had] a message on him like that dude in Con Air?"

Atlant 14:01, 22 September 2006 (UTC)

Calling The Future

Will this prove that time-travel is possible?

I create a message like:

"If time-travel exists, would a time-traveller email or call me on my mobile phone(insert number here) at (let's say a minute after the time I posted the message to stop fraudulent cases). I will not reply to the email or answer the phone."

I would need to keep the message on a medium that will last for many centuries or thousands of years. The internet would be ideal, as I can imagine the message would be constantly archived and backed-up for many many years.

So theoretically, if i put my email address or mobile number on the message I should be able to discover if time-travel is possible and only within a minute.

What would make the theory impractible?

ImbalancedZero 23:53, 20 September 2006 (UTC)

you assume the medium lasts forever, and that someone finds it, reads it and understands it and considers you important enough to answer. all big calls. Xcomradex 00:04, 21 September 2006 (UTC)

Has a future Wikipedian left a message on your talk page yet?

Seriously, that would rely on the people capable of time travelling finding your message, coming back in time to right after you left it, figuring out how to use a phone, and calling you on it. Either that, or else calling you from the future on a phone the waves from which could travel in time, and arrive in a form recognisable to current technology. In principle an interesting idea, but in practise I think there are too many obstacles. --Mnemeson 00:07, 21 September 2006 (UTC)

This is a message from the year 2262 to tell ImbalancedZero that time travel is possible. Thank you.

People have tried this sort of thing at least once; a few years ago someone held a big conference, inviting all future time-travelers to stop by. They did their best to publicize the invitation in as many permanent media as possible. Sorry I don't have a link for you; but if memory serves no time travelers showed up. Maybe next time. --Allen 00:15, 21 September 2006 (UTC)

The conference you mention is the Time Traveler Convention at MIT. No-one from the future turned up. Rockpocket 03:54, 21 September 2006 (UTC)

The trouble comes afterwards when you try to convince others that sentient beings from the future are contacting you. —Pengo ^{talk · contribs} 00:22, 21 September 2006 (UTC) (my RfA)

What you mean by 'sentient beings' earthling??--Light current 00:24, 21 September 2006 (UTC)

Presumably we'll have radiated or adapted into different species by the time the laws of physics have changed adequately for time travel to be possible. —Pengo ^{talk · contribs} 00:37, 21 September 2006 (UTC)

I guess the media wasn't so permanent Allen 8P --Agester 01:36, 21 September 2006 (UTC)

Can the future caller reverse the charges? Peter Grey 02:08, 21 September 2006 (UTC)

Ask yourself this - if you were a time-traveller, would you bother to reply to messages in the past? Imagine the chaos it would cause.

and also ask yourself this - if timetravelling became possible, it would no doubt be heavily regulated. That kind of technology is the kind of stuff they'd hole up in the military and the government, the public isn't even likely to know about it until a long time after...when adequet technology has been made to regulate time-travell. In which case...do you think people would really be allowed to contact the past whenever they want? And do you think the government would simply choose a random person in the past to contact?

Further more, there're a lot of theories about how time travel works. Some people will say if you can travel into the past, you can change it, contact people in the past. Other's will say it's impossible - travelling in the past will take you to a different past where you have always travelled to the past. Just think about all the time-travel paradoxes. Others will say it'll never be possible to travel into the past, even if you can time-travel, you can't change what's already happened. Which means if a time-traveller has never visited you, there never will be a time-traveller who can. For any RPGamers here, just think Final Fantasy 8 scenario when it comes to doing things in the past. Yaksha 07:47, 21 September 2006 (UTC)

Everything is used illicitly or illegally eventually. Everything. Strict rules, laws, regulations, oversight, and even social mores aren't foolproof, and they definitely aren't foolproof forever. Even if it took a million years for someone to get around the Timecops, they would still be able to go back in time to whatever year they wanted to. -- Plutortalkcontribs 12:10, 21 September 2006 (UTC)

I suppose. But if i was going into the past illegally, no way in hell would i show up at such a high-profile event claiming to be from the future.

And i wouldn't publically claim to be from the future at all. Maybe i'd contact some ancesters, or famous people in the past. But i wouldn't be so careless as to answer a random "hey time traveller contact me" message from a random person whom i didn't know. Yaksha 14:06, 21 September 2006 (UTC)

No law is foolproof but the law of physics. And it is this what stops the timetraveller from visiting us. —Pengo ^{talk · contribs} 15:06, 21 September 2006 (UTC)

It is still an open question among physicists whether time travel is possible. One interpretation that avoids the paradoxes is that when you travel to the past and say, prevent your own parents from meeting each other, you split off a separate universe, i.e. you stop the birth of the "you" in that universe, but that does not make you vanish, because you are from a different universe. Clarityfiend 16:46, 22 September 2006 (UTC)

Tell the time-traveller that a government minister with no known family has died and left his unclaimed millions in you bank and you will split the fortune if they impersonate his long-lost great-great-great-great nephew. They will/have not be/been able to resist leaving a message for you. Gandalf61 15:33, 21 September 2006 (UTC)

Actually, with inflation what it is, the Millions would No Doubt be worthless by the time they got the money Back to the Future. smurrayinchester^{(User), (Talk)} 17:41, 22 September 2006 (UTC)

Maybe you should tell the time-traveller you have some antique items instead of money? Since they would be worth more in the future, not less --Yaksha 02:01, 23 September 2006 (UTC)

It might help to first legally change your name to Sarah Connor. Peter Grey 12:17, 22 September 2006 (UTC)

Buy life insurance first, lots and lots of life insurance. Clarityfiend 16:46, 22 September 2006 (UTC)

Time travel is absolutely possible. I myself do it every day. Even as I write here, I find myself traveling forward through time at the rate of one second every second. Dipics 18:19, 22 September 2006 (UTC)

September 21

Hurricanes and Tropical Storms in Europe

Here in Spain we are all watching the news with ex-Hurricane and now Tropical Storm Gordon about to arrive in Galicia (frankly this is seeming surreal, I believe it is heading for France/South England afterwards). 1) Is this a serious indication that something is going very wrong with our climate? 2) Is it possible that in the near future we will see major hurricanes hitting the coasts of Spain/Portugal/France/UK/Ireland and killing us? Thank you in advance for information even if worrying ==ALang==

Hey ALang - storms crossing the Atlantic is nothing new, the remnants of Hurricane Floyd created the Great Storm of 1987 (killed about 20 in the UK). They don't usually get this far with any intensity, but whenever there's a big storm we get the tail end of it, it just usually manifests itself in the form of a few clouds. The Atlantic would need to get significantly warmer in order for such storms to form over it with any reliability or regularity. We'll probably die due to the Azores falling into the Atlantic and creating a huge tidal wave long before hurricanes threaten us in a big way :) --Mnemeson 00:34, 21 September 2006 (UTC)

Oh, and it turns out we have an article on European windstorms - hopefully another like 1362 won't come along soon. Okay, much of my answer could be technically right, due to use of the word 'hurricane', which has a precise definition, but read the article on windstorms, it's a lot more helpful. I'm gonna go off and sing 'Captured in a windstorm'... --Mnemeson 00:40, 21 September 2006 (UTC)

Though, of course, it should be mentioned that it could be an indication of a changing climate, although not (by itself) a particular reliable one. There are still many people who argue that any irregularities in climate that have appeared recently could merely be signs of an active weather process that cycles over decades or centuries, though do you really want to risk letting them be wrong?  freshofftheufoΓΛĿЌ  00:55, 21 September 2006 (UTC)

Hurricane Florence almost hit Newfoundland the other day, that's pretty far north for a hurricane. User:Zoe|(talk) 02:48, 21 September 2006 (UTC)

A single event is no indication of climate change, unless it is something that could normally never have happened, and 'never' is a big word. It would take several events to draw such a conclusion, such as not one hot summer but several in rapid succession, as we are experiencing in the last decade or so (actually, almost every summer is a record breaker by pre-1990's standards - what more proof could one wish for?). As for your second question, hurricanes are being reported in places where there never were any before, such as off the Brazilian coast (or thereabouts - vague recollection). I'm no expert, but I believe hurricanes are caused by temperature differences between sea and air and with the weather becoming more erratic unexpected things might happen. Hurricanes in Europe is just one possibility. Droughts and floods, which are very likely to become more frequent are a much bigger threat. DirkvdM 09:31, 21 September 2006 (UTC)

Hurricanes are caused by the latent heat of condensation over warm sea waters, unlike polar lows, a.k.a cold fronts, which depend on thermal differences between air masses. Titoxd^(?!?) 03:20, 25 September 2006 (UTC)

Yeah, you are talking about Cyclone Catarina, which is the only observed tropical cyclone to reach hurricane intensity in the Saffir-Simpson Hurricane Scale to form in the South Atlantic (although hurricanes impacting South America aren't rare, we have a featured list about it). Hurricane Ioke hit Alaska the other day, albeit as an extratropical cyclone. About Europe, though: it seems we are forgetting Hurricane Vince, which is the only hurricane to impact the Iberic Peninsula in record; however, hurricanes hitting Great Britain after extratropical transition are not that rare. Just have a look at the 1985-2005 cumulative cyclone track map and you'll see that they aren't that rare. Titoxd^(?!?) 03:20, 25 September 2006 (UTC)

Rubbing Alcohol and Blindness?

When I look at a bottle of rubbing alcohol it says: "Do not consume (no kidding!) Consumption may lead to blindness or death". I can accept without really understanding that doing such a stupid thing as drinking wood alcohol can, along with a whole bunch of other awful things, kill you. I've just always been curious as to why "blindness" in particular is singled out as a very possible result. What is the particular and to me, rather peculiar connection between consuming rubbing alcohol and blindness? Loomis 02:30, 21 September 2006 (UTC)

This is interesting. I typically associate rubbing alcohol with isopropyl alcohol (the Wikipedia article mentions ethanol preparations, as well). However, neither are classically associated with blindness. I associate blindness with methanol (wood alcohol) because exposure commonly results in blindness. So, I can't answer your question. However, if the bottle actually contained methanol, the warning would be apt because it commonly damages the optic nerve. InvictaHOG

Yeah IPA doesnt blind you but can cause other problems (even sniffing it is bad). I remember seeing or hearing the COSHH data on it. Is this the same thing as surgical spirit?--Light current 02:54, 21 September 2006 (UTC)

Ok, I hadn't realized that there were different kinds of rubbing alcohol. Apparently, I was wrongly using the terms "rubbing alcohol" and "wood alcohol" synonomously. In any case, I'm concerned with the type that is apparently connected to blindness, which would apparently be methanol, or wood alcohol. I'm still curious as to why blindness is a particularly specified danger. Loomis

blindness is one of the permenant non-fatal effects of consuming methanol, and takes very little. maybe thats why? and i remember reading about a study where they placed 'warning: fatal' and 'warning: causes permenant disfigurement' on bottles, and they found the latter a more effective deterrent. Xcomradex 04:19, 21 September 2006 (UTC)

The incidence of irreversible blindness seems to be high among survivors of methanol poisoning. Every year you can read about incidents worldwide caused by drinking home-made spirits with toxic amounts of methanol; many victims remain blind or partially blind for the rest of their lives. It's probably not methanol itself that is toxic, but one of its metabolites, specifically formaldehyde and formic acid. Blindness may result from accumulation of formic acid inside the retina.---Sluzzelin 09:30, 21 September 2006 (UTC)

To answer what I think is the actual question here ("What is it about methanol that causes blindness, and not, say, seizures, or skin discoloration, or burning of the esophagus, or any number of other possibly disfiguring or dangerous consequences?"), I'll point to our methanol article, and the "Health and Safety" section in particular, and this quote: "It is toxic by its breakdown by the enzyme alcohol dehydrogenase in the liver by forming formic acid and formaldehyde which cause blindness by destruction of the optic nerve." Note to self: Improve that sentence. It then links to an article in the DoE's "Ask a Scientist" archive with some better details. You can keep asking "yeah, but why?" all the way down, but hopefully this is a sufficiently substantive answer. An aside, one thing I've always found interesting is the treatment for methanol poisoning: getting the patient drunk on ethanol (although usually IV, not the fun way). -- Plutortalkcontribs 12:03, 21 September 2006 (UTC)

Thanks, Plutor, for finally identifying my actual question, in a way I was apparently unable to. Loomis 00:19, 22 September 2006 (UTC)

Of course, now that we have fomepizole, we don't have to worry about IV ethanol. InvictaHOG 17:28, 21 September 2006 (UTC)

Worry? Who was worried? I was looking forward to it, myself. -- Plutortalkcontribs 10:38, 22 September 2006 (UTC)

Shape and Finish of granite rocks in Texas Canyon in Arizona

Recently we drove through Texas Canyon on I-10 near Benson, AZ. The rocks in the canyon are very interesting and one can't help wondering how they were shaped. None of the rock have sharp edges; they rounded and smooth and give the appearance of being finished either by man or by nature. My sister-in-law says the rocks were rounded over the eons by rushing water. I'm not sure how they were finished so smoothly but suspect they where shaped by nature. They appear to have been formed as giant bubbles of lava or magma. Can anyone help us conclude how these beautiful rocks came to be??

Are the rocks attached to the ground or loose ? StuRat 11:55, 21 September 2006 (UTC)

Texas Canyon, AZ

well, 6000 years ago they magically appeared from the void ;-) more seriously, do they look like the Moeraki Boulders in New Zealand? Xcomradex 04:15, 21 September 2006 (UTC)

Granite is a volcanic rock, but it also sounds like they may have been ground to me. I can think of two likely ways:

• They might have been run over by glaciers (during an ice age) and dragged underneath them, being ground against other rocks in the process.

• They might be in an area subject to massive flooding on a regular basis at some point in the past. The boulders would bounce around on the ground underneath a torrent of water, and be ground down in that manner. StuRat 05:23, 21 September 2006 (UTC)

If the image we have of Texas Canyon is any indication of the rocks you're talking about, I'd say sandy wind (i.e. sandstorms) would do the trick.  freshofftheufoΓΛĿЌ  06:07, 21 September 2006 (UTC)

Some of those rocks have a rather erotic shape, maybe I should open a rock porno site, LOL. StuRat 11:53, 21 September 2006 (UTC)

There appears to be almost no geologic information on this. Since it is called a canyon, and they loosely use the term 'granite', I would assume that water was the main smoothing agent. --Zeizmic 12:02, 21 September 2006 (UTC)

It looks rather like a large lady reclining. THe rock at the top is the head.--Light current 15:12, 21 September 2006 (UTC)

According to this, it's not granite! Rather, it's quartz monzonite. Water does the trick quite well. --jpgordon^∇∆∇∆ 16:55, 21 September 2006 (UTC)

The easy answer is "erosion". The hard answer is what type of erosion (wind, water, ice?). --Fastfission 20:41, 21 September 2006 (UTC)

Much of the rounding is a result of exfoliation, a common development in granitic rocks (quartz monzonite is not really very different from granite). The final bits of smoothing probably result mostly from wind and some flash flood erosion, as suggested above. No glaciers in this area. The rocks in Texas Canyon are roughly 70 million years old (the time they were forced into pre-existing rocks as molten magma - Granite and quartz monzonite are not volcanic - meaning erupted onto the earth's surface; they solidify hundreds or thousands of feet below the surface, allowing their crystal grains to grow to visible sizes.). Cheers Geologyguy 17:59, 22 September 2006 (UTC)

Antimatter

I have read the article on antimatter and for some reason I still dont understand the process in which they make it. Please someone explain to me the process so I can understand it fully. Thanks in Advance for all your help.67.126.143.78 04:32, 21 September 2006 (UTC)

Looks to me like the antimatter article's main weakness is that it doesn't explain where the antiprotons come from. I don't know the details myself, but here are a few diagrams [26] [27] and a PDF of a review [28]. And here's a cool video showing what happens after the antiproton is created. --Allen 04:46, 21 September 2006 (UTC)

Antiproton describes one way of creating them. (Ain't Wikipedia wonderful?) It takes a lot of energy, while positrons (i.e. anti-electrons) are relatively easy to find, even occurring naturally. There are also antineutrons, if you're feeling ambitious. The big problem is keeping them around long enough to form antimatter atoms, since they have the annoying tendency to encounter their normal matter counterparts and vanish in a burst of energy. I believe they use magnetic fields and near vacuums to accomplish this feat. Clarityfiend 04:51, 21 September 2006 (UTC)

It is kind of confusing. The physicists do some particle physics equations to determine what happens when they break apart particles, and smash them together. They end up trying to do what is intheory experimentally and isolate the antiprotons from the mix with penning manipulation. — [Mac Davis](talk) (SUPERDESK|Help me improve)05:29, 21 September 2006 (UTC)

Do anti-matter fall upwards?

Do anti-matter have negative kinetic energy?

Ohanian 11:32, 21 September 2006 (UTC)

No to both of the above. You're maybe thinking of exotic matter.

Really it's all about conservation of energy and E=mc².

See http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/antimatterFall.html "Does antimatter fall up or down?" "In theory, antimatter dropped over the surface of the Earth should fall down. However, the issue has never been successfully experimentally tested. ..." from the Physics FAQ --GangofOne 02:03, 22 September 2006 (UTC)

Do herons swim?

Do Grey Herons swim? My bird books (and Wikipedia) don't say they swim, but they don't deny it either. A friend of mine said he saw one swimming on our local pond, but I think it is more likely to have been wading, or else he saw something else.--Shantavira 09:59, 21 September 2006 (UTC)

I have no scientific information, just original research. For what it's worth: I frequently watch grey herons hunt in a river near where I live. On several occasions I've seen one of them gliding over the water, and then landing on top the water and floating for a few seconds before taking off again. It didn't look like it was wading, and the water seemed too deep and the current too strong for that. ---Sluzzelin 10:37, 21 September 2006 (UTC)

Do they swim? i would say the most likely answer is no. Animals swim mostly for food or to escape. Unless the Grey Heron needs to swim for food, it's very unlikely to swim since it is able to fly. And it can cool itself by wading - which it does, and has no need to swim. If the Grey Heron naturally swim for any other reason, it would be a behavioural oddity, and would most likely be well-noted.

a related question would be whether they can swim. In which case i'd say yes. Some animals that don't live in water can swim naturally, others can't at all. Most animals can to a certain degree --> that is, they're not good swimmers like a penguin, but they're not going to drown. Considering how swimming is quite common amoung birds - i'd say a bird that wades and eats fish will most likely have some ability to swim. So it's not going to kill it self if it accidentally slips while wading, or accidentally wades too far into deep water.

if you're really wanting to find a sure answer, i recommond doing some reading about Ciconiiformes, the order that the Grey Heron belongs to. There'll probably be information avaiable about Ciconiiforms behaviour in general. And if you find textbooks saying Ciconiiforms can/do swim in general, then i think you'll have your answer. Either that or do some general reading about bird behaviour. Simply because i doubt anyone's gone out to scientifically observe every species of bird and see whether they can/can't and do/don't swim, and Grey Heron's aren't anything particularly special. Yaksha 14:34, 21 September 2006 (UTC)

What about this picture?---Sluzzelin 14:42, 21 September 2006 (UTC)

As waders, their feet are not webbed. What your friend probably saw was the heron floating. It was probably not using its feet in any way, as they would be pretty useless in propulsion. Also, if it is a "pond", that sounds shallow enough to wade. --liquidGhoul 14:40, 21 September 2006 (UTC)

I think the picture clinches it. Thanks Sluzzelin. --Shantavira 17:44, 21 September 2006 (UTC)

There's a heron plague in Amsterdam and indeed I see them regularly around where I live, next to a canal. All sorts of birds swim in the water, but I've never seen a heron do that. They fly by or stand on houseboats, but never in the water, which is about 2 m deep. DirkvdM 09:00, 22 September 2006 (UTC)

Here's another picture, and the same picture magnified. I did some more research on hobby ornithologists' websites, and there are numerous reports of swimming grey herons. That being said, almost every mention is accompanied by the expression of surprise at seeing such a sight. So it's a common uncommon phenomenon. ---Sluzzelin 16:22, 22 September 2006 (UTC)

matter

what are the different changes that take place in matter? waht are the signs or evidences of a chemical changes? what are the examples of physical changes and chemical changes? why?

One example is the change in synaptic strength that takes place in your brain matter when you actually try to answer these questions by reading textbooks and the like. This particular change is also called learning. Not much changes on the level of synaptic strength when you merely copy any answers that might be posted here. ---Sluzzelin 11:22, 21 September 2006 (UTC)

That was both scathing and clever. Hyenaste ^(tell) 18:34, 22 September 2006 (UTC)

Copper sulfate

As a crystal of copper sulfate is heated, does its weight increase or decrease ?

The mass of it would not change. The weight of it would not change. See conservation of mass, and next time do your own homework. — X [Mac Davis] (SUPERDESK|Help me improve)18:25, 21 September 2006 (UTC)

Not to sound stupid but doesn't copper sulfate crystal (blue) involve H2O in some way and heating it would evaporate the H2O and leave white copper sulfate. Or am I messing up high school chem again? 62.194.90.163 18:37, 21 September 2006 (UTC)

Yes, some Copper Sulfate is really a hydrate (and is blue). If heated the Hydrate (water) is driven off and the mass will decreate as a consequence. The color will change also.

The molecules having been accelerated, Relativity predicts a small increase in mass. (Too small to matter.) Of course, some of them might evaporate, or otherwise change state. (Not too small to matter.) -- Fuzzyeric 19:38, 21 September 2006 (UTC)

I did this exercise in high school chemistry. Water molecules are driven out of CuSO₄ • 5H₂O as it is heated, so it does in fact lose mass. Hyenaste ^(tell) 20:20, 21 September 2006 (UTC)

i second Hyenastes answer. Xcomradex 21:39, 21 September 2006 (UTC)

OTOH Anhydrous copper sulfate is white and would not lose any weight as there is no water in it.--Light current 22:06, 21 September 2006 (UTC)

Depends on how much you heat it, and for how long, really. --Serie 23:21, 21 September 2006 (UTC)

You mean:

At 650 °C copper(II) sulfate decomposes into copper(II) oxide (CuO), Sulfur dioxide (SO2) and oxygen (O2).? Well yes!--Light current 23:36, 21 September 2006 (UTC)

• Still, the weight or mass of copper sulfate wouldn't change. It would be the mass of the remains after heating that changes compared to the starting material. But if you put evaporated water and copper sulfate together, you still have conservation of mass. - Mgm|^(talk) 23:25, 21 September 2006 (UTC)

Well of course you do!.But this is obviously a homework question where the simple answer is wanted by the teacher!--Light current 01:36, 22 September 2006 (UTC)

Hepatitis?

Sorry about the graphic nature of this question, thought about it, and theres no "nice" way to put this (hows that for an intro?). Anyways, after a bowel movement, when wiping sometimes either the toilet paper is lousy or ill be wiping to vigrously maybe. But Ill start to bleed. Now is there any risk of left over fecal matter entering my blood stream through the open cuts? Cant you get like hepatitis from fecal matter entering your blood stream? or E.coli or something?

Thanks!!!

Very little risk. I suggest using a wet wipe or putting moisturizer on the TP. That allows you to get clean without creating so much friction. StuRat 17:14, 21 September 2006 (UTC)

I will echo this. Can certainly happen - you can get all kind of horrible nasty infections from bacteria (such as E. Coli) in your bowel entering your blood stream. However, the mechanism you describe is low risk. Furthermore, hepatitis is not caused by bowel bacteria - the most common forms are due to viruses that are transmitted by other people to you. InvictaHOG 17:26, 21 September 2006 (UTC)

Just make sure you're not sharing your toliet paper! :) I would see a doctor about it. You bleed everytime?? — X [Mac Davis] (SUPERDESK|Help me improve)18:29, 21 September 2006 (UTC)

It is true that the various hepatitis viruses can be transmitted in feces. However, if it is your feces that is carrying the hepatitis, you are not at risk for transmission, since you already are infected in that case.

Regardless, any bleeding in the digestive tract from the mouth to the anus has the potential to cause a transient bacteremia-- i.e., a brief period where bacteria circulate in the bloodstream. For most people, this poses little risk, and the bacteria are quickly cleared from the circulating blood. In fact, transient bacteremia is a common event for almost everyone. However, those people with certain predisposing conditions (e.g. rheumatic heart disease, mitral valve prolapse with regurgitation, heart valve prosthesis, joint prosthesis, or history of glomerulonephritis, can develop serious systemic infections as a consequence of bacterial seeding.

By the way, although rectal bleeding is commonly caused by benign conditions such as hemorrhoids or anal fissures, all instances of blood in the stool should be treated as suspect until proven otherwise--Mark Bornfeld DDS 18:34, 21 September 2006 (UTC)

shark's name

I am looking for the name of a type of shark. I was wading here in Charleston, SC and I thought I saw a very large catfish swimming around my legs. I reached in and grabbed it. When I pulled it out of the water, I noticed it had no scales, so I assume it was a small shark. It was gray, had a small dorsal fin, and a rather flat nose/mouth (not pointed like great whites). I thought it was a catfish because it had long "whiskers" coming out of the corners of its mouth. I've been searching through shark images on Google, but I can't find anything that looks like it. Any ideas? --Kainaw ^(talk) 20:30, 21 September 2006 (UTC)

Your description is vague, and it could have been several species. An easy way for a layperson to tell a shark from a bony fish is by looking at the gills. If it has multiple gill slits, it's probably a shark; if it has a hard round cover over the gills (the operculum), it's probably a bony fish. If it was indeed a shark, it might have been a juvenile nurse shark, which has barbels like a catfish, or perhaps a species of catshark. I assume this was in the ocean, not in fresh water. --Ginkgo100 ^{talk · e@} 20:40, 21 September 2006 (UTC)

Thanks. It definately was a nurse shark. I saw in the article that it has a "sluggish behaviour", which is probably the reason I was able to catch it with my hands so easily. I guess it was a juvenile as it was only about 2 feet long. Knowing the species, I've been able to assure my wife that it is not dangerous. So, she isn't bothered by going back in the water. She wouldn't take my argument: If I was able to pick it up, look it in the face, then let it go and not get bit, it must not be a dangerous shark. --Kainaw ^(talk) 00:29, 22 September 2006 (UTC)

Bruce. Remind me not to sell you medical insurance (Pick it up. If it doesn't bite your face off, it must not be dangerous???) Clarityfiend 17:08, 22 September 2006 (UTC)

empirical formula

ok i have this problem:find molecular formula of a fully combusted hydro carbon that produced 7.2 grams of water and 7.2 liters of co2 at stp. wats the empirical formula. ok so idivided 7.2 liters co2 by 22.4 to get .321 moles and 7.2 g h20 by 18.02 toget .4 moles then divide both by .321 to get 1 co2 and 1.25 h2o and muliply both to get 4 as coefficient of co2 and 5 coefficient of h20. therefore the empirical formula is c4h10. Can somone please tell me if im right and if not how to doit correctly and how to get the grams of o2 required to completely combust the hydrocarbon and molecular formula of hydrocarbon. please help im stuck for an hour --69.140.210.163 20:36, 21 September 2006 (UTC)

Excellent! Now you need to work out the number of moles of butane, write the balanced equation of its complete combustion to get the molar ratio of butane:oxygen, work out the moles of oxygen and then multiply by 32. The formula you have is the molecular formula as well as the empirical formula, because you can't have an odd number of hydrogen atoms in a hydrocarbon. --G N Frykman 20:59, 21 September 2006 (UTC)

Advantages of skimmed milk?

Is skimmed milk to prefer to semi-skimmed milk or whole milk? The fat is mostly saturated isn't it? But if you take away the fat, what happens to the fat soluble vitamins in the milk? Jack Daw 21:16, 21 September 2006 (UTC)

Vitamin A and D are fat soluble. Skim milk is allowed to contain up to 0.5 grams of fat per cup. That amount would carry vitamins A and D and allow for their absorbtion. Vitamin A, however, may be negatively effected by UV light in transit. Regardless of the saturation of the fat with hydraogen, fat has a LOT of calories, and has few positive nutritional benefits. (source: http://healthletter.tufts.edu/issues/2003-04/asktufts.html) JBKramer 21:26, 21 September 2006 (UTC)

It has a very clear nutritional benefit and you have already mentioned it. It has lots of calories. It is only in some modern cultures where getting too many calories is a problem. Rmhermen 01:51, 22 September 2006 (UTC)

And, of course, nearly everyone here (English speakers with Internet access) is in one of those cultures. StuRat 03:38, 22 September 2006 (UTC)

Some fats and fatty acids, like omega 3 fatty acids, are healthy. However, these tend to be found in plant and fish products, not in meat or milk. So, fat from those sources should be limited. StuRat 03:35, 22 September 2006 (UTC)

I'm an English speaker with Internet access and I consider energy in my food a good thing as long as I burn as much energy. If you're a lazy bastard who eats loads of junk food (irrespective of whether you speak English or have internet access), maybe milk won't be good for you unless it's deformed by extraction of much of its nutritional value. Then again, if you value your health so much that you worry about that, then why don't you change your lifestyle such that drinking proper milk won't harm you? That would make sense, wouldn't it? Eg sell the car and get a bike (save the planet in the process). Btw, energy is properly expressed in joules. The calory is archaic. DirkvdM 09:14, 22 September 2006 (UTC)

Certainly there are many people in the world who have to spend most of their time thinking about what they can do to get enough calories every day, but I can't believe you have to worry about that, any more than you have to worry about not being able to get enough sodium each day. On the contrary, you would have to make a serious effort to keep from getting enough calories and sodium each day. StuRat 15:14, 22 September 2006 (UTC)

There's more to the question of fat consumption than lack of exercise. Even someone who gets a proper amount of exercise still will benefit from a diet high in "good fats" and low in "bad fats", like saturated and trans-fats. Since milk is high in bad fats, it then makes sense to remove some of them, or limit your milk consumption, while simultaneously increasing your consumption of good fats from other foods, like fish and nuts. StuRat 14:53, 22 September 2006 (UTC)

And, unlike some other low fat foods, where they use some rather questionable chemistry on the food, skim milk just has the cream skimmed off the top, so I would hardly call it "deformed". StuRat 15:09, 22 September 2006 (UTC)

Milk has the unique characteritic of being food that is expressly meant to be food. So whatever is in it, common sense dictates that it must be healthy. I'm not going to let dietists double-guess evolution for me. DirkvdM 07:31, 24 September 2006 (UTC)

Point light displays

Do point light displays (such as this one) go by any other name? I can't find an article for them on Wikipedia, so I want to start one. However, I'm afraid an article already exists by another name. Thanks, --JianLi 21:26, 21 September 2006 (UTC)

• I've made a stub, point-light display, to be redirected if anyone finds an existing article. --JianLi 21:50, 21 September 2006 (UTC)

unidentified insect, need help

I have recently come across a very strange looking insect in my basement. I live in western North Carolina, U.S.A. Anyway, the insect looks to be related to the grasshopper. It is brown in color. It's a little more compact than the ordinary grasshopper. It doesn't appear to like daylight. It's not a cricket. The insects back legs are very big, almost "meaty". And here's the strange part: It leaps backwards! It jumps the opposite direction from the direction it's head is pointed. I asked a neighbor what it was, and he called it a back-hopper. Sadly, I have found no documentation on such an insect. I know it exists, therfore I'd like to be able to identify it, get some information, and even a photo. Someone has also told me that it is a wood-destroying insect so it has raised my interest that much more. Please forward any information on the subject.

Thanks, Dean

If you have a photo, you can try asking "BugGuide.net" or "What's that Bug". http://www.boingboing.net/2006/07/24/online_bug_identific.html --Kjoonlee 01:28, 22 September 2006 (UTC)

If it looks like a grasshopper, it might be in the Orthoptera. (Orthoptera includes "crickets, grasshoppers and katydids" according to WTB. I'll try having a look through the Orthoptera articles. --Kjoonlee 01:40, 22 September 2006 (UTC)

I had a look, but couldn't find anything mentioning pointed heads or backward leaps. --Kjoonlee 02:49, 22 September 2006 (UTC)

One suggestion: Perhaps it has a "fake head" on it's tail, making it appear to be hopping backwards. If you capture one, look closely at the end that appears to be the tail, and see if there is a less obvious head at that end. StuRat 03:26, 22 September 2006 (UTC)

Your description reminded me of the cave crickets (aka camel crickets) who shared our basement flat in Virginia. I remember them hopping in all directions and usually when I least expected it. Here's a google image search, is this your bug? ---Sluzzelin 06:52, 22 September 2006 (UTC)

Milk --> cheese?

What happens to milk after you drink it? does it turn into cheese?--Light current 23:41, 21 September 2006 (UTC)

A protein called rennet solidifies the milk, and you can then digest it as if it is a food. Juveniles have much more rennet than adult mammals. So, in a way, yes it does turn into cheese, as it was this protein (and may still be, can't remember) which probably caused the first cheese to be made, and had been used for centuries after. People used to get cow or sheep stomach lining, and, as it contained rennet, would use it solidify milk into cheese before it was ingested. --liquidGhoul 00:11, 22 September 2006 (UTC)

Some cheeses are still made with animal rennet. Rmhermen 01:48, 22 September 2006 (UTC)

September 22

Animal Respotory System

What animal breaths through its mouth and its anus? Amber Could it be the sea cucumber? I don't know if they breathe through their mouth, but they do have organs inside their anus to extract oxygen from the water. Gary 03:26, 22 September 2006 (UTC)

some primitive animals have only one hole that acts as both the mouth and the anus. and i guess they're probably able to breath through it. Yaksha 03:33, 22 September 2006 (UTC)

One-holers generally have a high enough surface area and a low enough oxygen need that they absorb oxygen by diffusion through the skin. --Serie 20:40, 22 September 2006 (UTC)

I know some people who talk through their anus, and you can't talk without breathing, can you? DirkvdM 09:19, 22 September 2006 (UTC)

I don't know. Maybe you should try. See how long you can talk for without breathing. (disclaimer: i take no responsibility regarding what happens when people follow my suggestions.) --Yaksha 12:32, 22 September 2006 (UTC)

Worms

What happens if you cut a live worm in half?--Light current 02:11, 22 September 2006 (UTC)

It depends on the worm. The group of animals called "worm" is polyphyletic. A lot of the best known worms will live (both halves) and regenerate the lost body parts (like the earthworm and at least some flatworms), but I doubt all do. --Allen 02:39, 22 September 2006 (UTC)

I think Light current means earthworms. In that case, and if you live in southern Ontario, nearly all of the worms you see crawling out of the ground will live if you cut them in half. (Trust me, I've done this before many times!) --Bowlhover 03:22, 22 September 2006 (UTC)

Yeah Im certainly not talking about tapeworms 8-)--Light current 17:03, 22 September 2006 (UTC)

and i guess if you're really sadistic, get some earthworms, and start cutting. And see how big a 'piece' has to be before it becomes unable to regenerate into a full earth worm. IIRC, for worms which can regenerate, they only will if you cut between certain parts. There are some bits where if you cut, you don't get two worms...just one new worm and a dead bit. Yaksha 03:29, 22 September 2006 (UTC)

If you cut an earthworm in half, only one side has a clitellum, so doesn't that factor in? At the very least, it certainly wouldn't be able to reproduce anymore.  freshofftheufoΓΛĿЌ  05:48, 22 September 2006 (UTC)

Wouldn't it just grow a new one? I've seen photos of people who've cut up worms (not sure what type though) into many pieces, and later photos showing all the pieces growing bigger. I don't know...go try XP --Yaksha 12:16, 22 September 2006 (UTC)

Here is our article about regeneration in general, though it doesn't talk about earthworms specifically. --Allen 05:49, 22 September 2006 (UTC)

...and here is the answer given when a similar question was asked a few months back.--Shantavira 07:37, 22 September 2006 (UTC)

...which I have therefore added to the reference desk faq. DirkvdM 10:01, 22 September 2006 (UTC)

Hey thats great Dirk. Thanks for doing the 'FAQ' thing 8-)--Light current 17:00, 22 September 2006 (UTC)

Ah, it looks like I was wrong about earthworms, then. I'm not so sure about that poster who said that the flatworm cut has to be lengthwise, though; I'm pretty sure you can separate the tail from the head and both halves will fully regenerate. --Allen 16:42, 22 September 2006 (UTC)

No, only half wrong after all. Sorry I didn't look that up before. --Allen 16:47, 22 September 2006 (UTC)

I know some people who talk through their anus, and you can't talk without breathing, can you? DirkvdM 10:01, 22 September 2006 (UTC)

The connection is not immediately obvious to me. In any case, maybe you should seek new friends. --Lambiam^Talk 16:14, 22 September 2006 (UTC)

Ooops, I dont know how this got here. It was meant for one thread up. I like lateral thinking, but this one went off the scale in that respect. :) DirkvdM 18:25, 22 September 2006 (UTC)

Yes, when thinking laterally, one has to be careful that the ideas do not come out of ones ears and hit people in the wrong place 8-)--Light current 20:07, 22 September 2006 (UTC)

No, although worms have the ability to regenerate, and move about for a while afterwards (in an attempt to confuse any predators), almost always both halves die. Philc _T^E_C^I 17:34, 22 September 2006 (UTC)

OMG another classic! Can you imagine trying to confuse your predators by wriggling about if you had just been cut in half. I mean whats the point? LOL! 8-)--Light current 19:59, 22 September 2006 (UTC)

Maybe you should read the response I gave Allen, who also didnt understand what I meant, though he expressed this in a much more polite manner. Philc _T^E_C^I 20:48, 22 September 2006 (UTC)

I am being polite. I thought your answer was very funny . THats all. No offence!--Light current 21:24, 22 September 2006 (UTC)

OK it wriggles about to deter predators just in case it manages to regenerate? Is that what you mean?--Light current 21:29, 22 September 2006 (UTC)

Ok, sory, if you meant no harm, the I've just misenterprated what you said. All is cool.. And yeh, thats the jist of what I mean, except one half always dies, and its this half that wriggles, in the hope that the half which can survive will get away as the predator is distracted. Much like some salamanders and their tails. Philc _T^E_C^I 21:39, 22 September 2006 (UTC)

I don't understand. They regenerate and then die? And what's the evolutionary advantage to confusing predators if you can't live long enough to reproduce? --Allen 17:49, 22 September 2006 (UTC)

No, they can regenerate, but its not a 100% success rate, if you cut a worm in half you cannot count on it regenerating. It will often die before it manages. The advantage of continued movement after seperation is that if one half is to small to survive it will continue to move, thus distracting a predator from the other half that may survive. Philc _T^E_C^I 18:19, 22 September 2006 (UTC)

I see; thanks. --Allen 19:34, 22 September 2006 (UTC)

Does it?

Does white absorb more heat than black?

No--Light current 02:34, 22 September 2006 (UTC)

Things appear "black" during the night because they don't reflect a lot of light. Black objects appear black during the day, also because they don't reflect a lot of light. And if light is not reflected, it has to be absorbed. Therefore, black objects absorb more light than objects with any other colour. --Bowlhover 03:16, 22 September 2006 (UTC)

which means it's black that absorbs more heat than white. a "experiment" teachers often show students in primary school is that they put many piles of ice outdoors where the sun can shine on them. Then they cover the piles of ice with different colored pieces of cloth. And the pile under the black cloth generally melts the quickest, and the white one the slowest. Yaksha 03:26, 22 September 2006 (UTC)

Yes. No. Maybe. The question is ill-posed. Everything being equal (and this is saying a lot, as we will see), the answer is a qualified no.

Given an infinite amount of time, any two object, regardless of their color or other physical properties, exposed to the same radiant source will achieve approximately the same temperature -- the temperature at which the black-body radiation of the objects matches the incoming radiation. These temperatures will not be the same because real, physical objects do not emit exactly the black-body spectrum. See the discussion at Color temperature about assigning correlated color temperature to fluorescent lights. The black-body radiation article shows a plot of the emission spectrum of an incandescent bulb, which shows slight deviations from the ideal spectrum. The solar spectrum also shows deviations from the ideal spectrum due to absorbances caused by the atoms out of which it is made. (Helium was discovered by noting details of these departues from ideality in the sun's spectrum.) Consequently, the total emission energy of two distinct objects at the same temperature can differ, sometimes significantly, therefore they will achieve different asymptotic temperatures when exposed to the same source.

When a painted, asphalt street is heated in the summer, one may note that the black asphalt is too hot to walk on, but the painted lines are cool enough to walk on. This is sometimes taken to imply that the black absorbed the heat more than the reflective/white/yellow paint did. This implication is incorrect. The black asphalt has a vastly higher heat capacity and thermal transport coefficient (in contact with your foot) than does the paint. In short, the paint is the same temperature as the asphalt, but when it starts transferring thermal energy to your foot, it runs out of energy far faster than the equivalent volume of asphalt would. The same effect can be seen when bare-handed handling the space shuttle heat tiles. The tiles don't contain much energy when they are heated (difference between temperature and heat capacity) and second, they conduct heat very poorly internally, so you can easily deplete excess heat where you are touching the material, but thermal energy a millimeter away takes a very long time to transfer to the cool spot and continue heating your hand. Thus, material heat capacity and internal heat transport properties are significant when evaluating the heat absorbed by objects when you intend to contact them.

If an illuminated object doesn't have a mechanism to convert electronic transitions into rotational, vibrational, or translational modes ("kinetic modes"), then a white object will absorb energy faster than a black object but will not express that energy as heat. The reason is that the "white molecules" absorb twice as much recoil momentum as the "black molecules", so the white molecules are made to translate more rapidly than the black molecules. Raman scattering is a mechanism for converting photon scattering events into kinetic modes. The zero-phonon line and phonon sideband represent an additional mechanism which is a consequence of collective electronic modes in a material. Brillouin scattering is a more directly coupled mechanism for transferring scattered photonic energy into collective motions of the molecules. Most real materials have several mechanisms to convert scattered photons and electronic modes into kinetic modes and thus, unlike the description at the front of the paragraph, real black materials do not store the absorbed energy in modes that don't produce heat. Real black materials absorb the energy and turn it into vast amounts of heat. In comparison, the momentum recoil is tiny. For example, a 400 nm photon contains enough energy to cause a water molecule to recoil at 5800 m/s; it's momentum would only make that water molecule recoil at 0.055 m/s. Consequently, if there is no mechanism to convert photon scattering or electronic excitation in kinetic modes, then the white molecules recoil with twice the momentum of the black molecules (and the black molecules store huge amounts of energy in non-inetic modes, i.e. not as heat). If there is/are such mechanisms, then the black molecules express huge quantities of absorbed energy as heat. Note that the final temperatures are not affected by these considerations; the asymptotic temperatures are unchanged, but we expect black objects to reach those temperatures vastly faster. Also, some materials may exhibit some consequences related to this feature so that they heat unusually slowly -- rarefied noble gases do not have rotational or vibrational modes, and do not easily exhibit collective modes, and therefore only very slowly convert electronic excitations into heat.

So, the answer to your question is: "it depends". Depending on how you're going to measure hot, the color may be correlated with other physical properties like heat capacity or thermal conductivity which could limit the transfer of heat to the measurement device (perhaps a thermometer, hand, or foot). The black object and white object may have sufficiently diverse graybody spectra that their asymptotic temperatures under identical illumination are different. Unusual properties of the black material may make it difficult for the material to express internal energy as heat and so it may take vastly longer for the black object to catch up to the white objects temperature.

Nevertheless, in the absence of exceptional behaviours such as those I've listed, you may assume that (1) the black object gets hot much faster than the white object, (2) they are both trying to reach the same temperature, and (3) either one may feel hotter due to details of heat transfer through and out of the materials. -- Fuzzyeric 03:50, 22 September 2006 (UTC)

Black absorbs more light energy than white, and radiates this as heat. So although there is a minor misunderstanding in this, black objects will get hotter in the sun. Philc _T^E_C^I 17:31, 22 September 2006 (UTC)

So its 'no' then? THought so! 8-)--Light current 20:00, 22 September 2006 (UTC)

Yeh, the answer is no, but the difference is I thought he might like to know the origins of the myth, and that its not complete rubbish, its just misquoted. Philc _T^E_C^I 20:50, 22 September 2006 (UTC)

Ah well Ive not heard of the myth. So...--Light current 21:26, 22 September 2006 (UTC)

Fair enough, its just things like people often say they dont want a black car, because it "absorbs" more heat, but it doesnt, it absorbs more energy, and radiates it as heat, a lot of which is trapped inside the car. Philc _T^E_C^I 21:30, 22 September 2006 (UTC)

If its trapped within the car, how does it radiate it?--Light current 21:32, 22 September 2006 (UTC)

You have to remeber in this case the car is not treated as a single object, black objects, such as bashboard, or black paint radiate heat, some of this goes into other objects within the car, or the air in the care, some of it is radiated out of the 'car' system completely. So, you see, parts of the car are radiating heat everywhere, not the whole car radiating heat out of itself. Maybe my initial explanataion was a bit to simplified to exaplain that point completely, sorry. Hope you understand now! Philc _T^E_C^I 13:29, 23 September 2006 (UTC)

P.S. Fuzzyeric, has posted a more indepth reply to your question below, as he seems to be more learned on this subject. hehe. Philc _T^E_C^I 13:30, 23 September 2006 (UTC)

Nope. The black object's temperature increases faster in the sun, but it does not reach a higher final temperature than a white object.

(Why do I know this? I and a friend I met in college performed a sequence of experiments to settle this. This was after five years of collecting evidence about which way this should work, which is why I am able to explain the theory at some length. The least confounding experiment involved several thermocouples, a half dozen hotdogs painted white, and a half dozen hot dogs painted black. The paint was selected to have equivalent (to within 5%) heat capacity and thermal conductivity. The black painted hot dogs's temperature rose more rapidly than the white painted hot dogs (initially). However, the asymptotic temperatures of all the hot dogs were identical. No hot dog showed thermal overshoot.)

The black object does not "get hotter in the sun". The black object is initially hotter in the sun and the difference in the temperatures may increase briefly before going to zero. Unavoidably, the difference goes to zero.

And to Light current: The black paint absorbs the energy, transfers it to the metal body through conduction, which then provides the heat to the plastic and glass portions of the vehicle, also by conduction. The glass radiates the energy both into and out of the cabin and the metal and plastic surfaces in the cabin will radiate heat into the cabin. (They also radiate heat to the outside of the car, but most of that escapes to the ground, trees, buildings, et al. On an especially hot day, you can see air, heated by conduction with the car's surfaces, convectively rising from the car.) However, the glass in the cabin is an excellent infrared reflector, so that heat does not escape through the windshield. More and more energy enters the cabin (by conduction from the rest of the car's body and by directly shining through the windows), but most of that energy is trapped until the interior is so hot that the windows and car's body are no longer an effective insulator (like a thermos) and the excess heat leaks away by conduction. -- Fuzzyeric 04:02, 23 September 2006 (UTC)

I dont doubt the results of your experiments and these results are interesting. THe only thing you may have overlooked here is the emissivity of the paints. Im assuming the emissivity of the black dogs was near to unity whereas the white ones would have lower emissivity (how much lower is hard to say). If both sets of dogs reached a steady equal temperature, then it is obvious that no net energy was flowing into or out of the dogs. But, one would expect the black dogs to be radiating more heat energy due to increased emissivity and therefore taking in more heat energy. THe temperature of each set of dogs (neglecting convection, conduction) will be given by solving the eqaution for zero net energy loss/gain. So i dont get it, unless the 2 sets of dogs had equal emissivities.!--Light current 13:43, 23 September 2006 (UTC)

The difference in kT is small in experiments like the car or the hot dog. Thus, the difference in blackbody spectrum is small. These two objects are not blackbodies and do have some spectral content at various frequencies. For blackbodies, the peak emission wavelengths are 9.7 um (1030 cm^-1) at 300 K (80 F) and 9.1 um (1100 cm^-1) at 320 K (116 F). The total emitted power increases from 460 W/m^2 (300 K) to 590 W/m^2 (320 K). The point is that very little new spectrum is relevant going from the lower to the upper temperature, although the change in power is huge. So, we may expect that paints using similar formulations will have similar mid-/long- IR spectra and should have equivalent emissivities for the range of temperatures tested. Also, empirically, the near constancy of emissivity of paints is observed. Q.v. 1 (black paints: 0.88, white paints: 0.87-0.92). The differences, ~ 4% will result in ~4% change in emitted power at the same temperature. However, the full change in emitted power is +28% for +20 K (from the numbers above) so the difference in temperature will be < 3 K. (Quite a bit less since the emitted power is not a linear function of the delta-T.) Remember also that the visible spectrum of materials is not particularly related to its IR spectrum -- glass is trasparent in visible and reflective in the room temperature band (near 1000 cm^-1) ref -- so the visible blackness or whiteness of a material has very little relation to its IR reflectance.

Of course, this only takes account of the paint. The hot dog material is the same in both cases. Since the paint thickness is about the wavelength of the light, it's semitransparent for most of the emission spectrum. So any difference in the paint spectra will be averaged out a bit by the hot dog spectra. It is thus feasible to expect < 1 K differences in the final temperatures of the two hot dogs. Larger fluctuations can be driven by differential convection (if there's any wind at all) and so this difference is insignificant in practice. -- Fuzzyeric 20:04, 23 September 2006 (UTC)

Thanks for that exhaustive explanation of the theory. So it seems your experimental results confirm the theory. Im not too concerned now, since you have indicated the very similar emissivities of both paints and maybe the lack of relevance of the paints anyway due to their thinness cf wavelength of the IR. So basically you showed that similat bodies (as far as IR is concerned) heated up the same amount? But for some reason the black one got there more quickly. --Light current 20:15, 23 September 2006 (UTC)

Yes, the similar bodies race to the same temperature. The black body gets there faster because it retains more of the incident energy as heat. The white reflects more of the incident energy as light, so gets there slower. -- Fuzzyeric 05:57, 24 September 2006 (UTC)

Well sunlight is of course a relatively broadband source of electromagnetic radiation.--Light current 04:02, 25 September 2006 (UTC)

Do Bugs "Hybernate"?

Up here in the great white north (Canada), it's just starting to get a bit nippy. Of course we'll have some "Indian Summer" when it'll warm up again for some reason for a couple of weeks (curious! but that's a different issue).

In any case, the mosquitos are mostly gone by now. But they'll of course be back in full form annoying the hell out of us next spring.

I know certain birds, like robins, can't take our winters and so they "fly south", and certain others seem to be more hardy about the whole thing, like sparrows, crows, pigeons etc.

But what about the bugs? The mosquitos, the spiders, the houseflies, the earthworms, the moths? Certainly an earthworm doesn't "crawl south" for the winter!

Seriously though, each species must somehow survive our incredibly long winter, by laying dormant in some sense. What do the worms do? What about mosquitos and the houseflies? Do the adults somehow deposit their larvae or eggs or whatever in some reasonably protected, reasonably warm spot and then die, only to have their offspring hatch next spring? I can't see how the adults can survive the entire winter "hybernating", but I may be wrong.

Another odd thing is that while during the summer, all the bugs mentioned tend to annoy us and somehow manage to creep into our homes, curiously, over the winter, the only pests seem to be the spiders. It could be the dead of winter, -30°C, far too cold for a weakling mosquito to handle, but somehow a spider will manage to appear crawling on the ceiling. How do they do it? Loomis 02:38, 22 September 2006 (UTC)

I'm no entomologist, but I read that some larvae can live much longer than adults can. I guess some adults hybernate, some eggs wait over the winter, and some insects wait as larvae.
PS. Spiders aren't usually pests. :) --Kjoonlee 03:02, 22 September 2006 (UTC)

Some bugs go into tons or tonnes or something like that, like wooly bears. — X [Mac Davis] (SUPERDESK|Help me improve)03:04, 22 September 2006 (UTC)

I don't have an exact answer for your question, but i do know that insects do not hibernate. Hibernation is something that warm-blooded animals do. The entire point of hibernation is that in winter, it becomes simply absurd to maintain the normal body temperature (as warm blooded animals do), so they hibernate. Animals that never maintain their own body temperature has no need to hibernate.

as for what insects do, i guess they just find a place warm and stay relatively dormant. which is why you don't see them around in winter. Some insects can keep their core temperature sort of warm by vibrating their flight muscles. A lot of insects do this when they need to fly in winter - they vibrate flight muscles to warm up before taking off. Bees do this collectively - so all the bees in a hive will do this at the same time, which is used by bees to keep their hive at a decent temperature during winters so all the individual bees don't get frozen to death.

i'm not sure what happens to other insects, but insects (and spiders) really don't have a very high energy requirement. For a warm-blooded animal, the vast majority of what we eat goes into keeping us warm, staying warm is VERY tiring. For something like an insect, the only time it really needs much energy is when it's growing, or when it's producing young, which both happen in the warmer seasons. When an insect just needs to stay alive, it really doesn't need to eat a lot. If you've ever kept something like a cricket or a spider as a pet, you'll know you really don't have to feed it an awful lot to keep it alive.

as for the spider --> spiders come indoors in winter because they're looking for a warmer place. Some are probably able to be active in very cold temperatures. Generally, cold-ness is more dangerous to warm-blooded animals than cold-blooded ones. Cold-ness kills animals because it causes the water in their bodies to freeze (very bad), or the proteins that are needed to push forward vital chemical reactions and drive metabolism stops working (also very bad.) Aniamsl adapted to the cold have chemicals that prevent water from freezing, or adaptations so that the important parts don't freeze, and specialized proteins that can still carry out their functions even when it's very cold. How do you think fish survive in very cold waters?

about larve. Eggs and larve and stuff are generally very resilient. Similar to plant seeds. As i said - cold is dangerous because it freezes water and stops metabolic reactions. If something doesn't have much metabolism in the first place, they can stay dormant very easily in very cold temperatures. Yaksha 03:13, 22 September 2006 (UTC)

• I'm positive they don't "hybernate". Whether they hibernate is another question altogether.- Mgm|^(talk) 12:27, 22 September 2006 (UTC)

• Hybernate = To hibernate in Hyderabad. :-) StuRat 14:45, 22 September 2006 (UTC)

• I scrolled past quickly and saw a "Hy..e..na..te" in bold and thought someone asked a question about me. Stupid spelling mistakes. :( Hyenaste ^(tell) 18:29, 22 September 2006 (UTC)

I found the book I had read six years ago, and will now correct, clarify, and elaborate.

Water bears are also known as tardigrades, a name that means "slow seppers." They are very small—from one to 20 could fit on a pinhead. Some live in the sea, between particles of sand and mud. Others dwell in fresh water. But most live in places that are sometimes wet and at other times dry—like muddy puddles, insdie a moss plant, or in the rainwater gutters of buildings. They can survive here because, as the dampness dries out, the water bear turns into a special resting stage called a tun. It simply dries out, shrivels up to about one tenth its size, and becomes inactive, almsot like an egg. This tun stage can surivve for many months, even yeras. When the moisture return, the water bear "hatches" out of its tun stage, and carries on living!"

The book was Animals of the World. I loved that book when I was eight! — X [Mac Davis] (SUPERDESK|Help me improve)18:05, 22 September 2006 (UTC)

M>S in Engineering from your University

Sir My daughter is doing B.E in Electronics&Telecomunication from Pune University [India] with 60% marks.She wants to do M.S from your University.We want to know what are the procedures for admission. Will you help us. Thanking You Tanveer Asma Trading Corp Yavatmal[M.S] India 445001

Our website is not a university. It's an encyclopedia, where you look up information if you're curious about something. --Bowlhover 03:31, 22 September 2006 (UTC)

the university of wikipedia? its got majors in edit warfare, seagull science and bagelometry Xcomradex 03:34, 22 September 2006 (UTC)

There is something called Wikiversity. I'm not really familiar with it, but it aims to have some things in common with a university. You can't earn a degree from it, though. --Allen 03:39, 22 September 2006 (UTC)

I think Wikiversity is simply a collection of information that's more organized than Wikipedia. --Bowlhover 04:11, 22 September 2006 (UTC)

60% doesn't sound very good. There is a lot of competition for most university slots, and I doubt if those grades would be sufficient. Universities will sometimes overlook poor grades for those who live in the area or have relatives who attended or who contributed large amounts of money to the university. Unfortunately, it doesn't sound like any of these apply here. Also, consider that, if she is struggling where she is, that will likely only get worse if she studies abroad, and then has language and culture issues to deal with, too. My suggestion is that she focus on improving her study skills and grades where she is, before attempting a move. StuRat 03:45, 22 September 2006 (UTC)

Wikiversity is different. It aims to provide learning materials. Tests, class ideas and the like. It probably seems more organized because it's new, smaller, and subject to a lot less rules because of it. If you take some time to learn the basics, Wikipedia isn't all that complicated either.- Mgm|^(talk) 04:58, 22 September 2006 (UTC)

I don't believe the questioner is asking about Wikiversity. They are obviously under the assumption that since Wikipedia is an American company, most of the users would be too, and thus "your Universities" means "American Universities". If your daughters grades can't get her easily into a good international university, consider looking into international exchange programs at her school. It seems there is some sort of sister-schoolship with the University of Calgary, though I'm not sure if they have any courses for your daughter. You should check at the university international student center for options.  freshofftheufoΓΛĿЌ  05:40, 22 September 2006 (UTC)

Of course, Calgary is in Canada, not the US. StuRat 06:16, 22 September 2006 (UTC)

The user may also have searched for a particular university on a search engine, found the Wikipedia article on that university, and mistaken Wikipedia for the university's website. Apparently this happens from time to time. -- SCZenz 07:45, 22 September 2006 (UTC)

genetics

Which relationship is genetically stronger? with a sibling(eg;sister-sister) or with a parent (eg; mother-daughter)?
----Jane

In either case the two individuals share basically 50% of the genome. I'm assuming "full sibling" here. See our article Heritability (although not what I'd call a Good Article). --Lambiam^Talk 09:13, 22 September 2006 (UTC)

That's not entirely accurate. The parent-child relationship is guaranteed (barring any extremely rare abnormalities) to share 50% of their genome. Siblings however, have no such guarantee. It's possible (but unlikely) that two siblings will share no DNA -- that they have each inherited a different half of their parents genome. It's similarly possible that they will have identical DNA (identical twins). It's almost always somewhere in the middle, and I bet it's usually pretty dang close to 50%. -- Plutortalkcontribs 10:34, 22 September 2006 (UTC)

Identical twins happen fairly often (1 in 150 births), while identical non-twins should only happen 1 in every 2^46 births, or 1 in every 70 trillion sets of siblings. This means it's probably never happened yet. Genetically unrelated siblings should also happen in around 1 in every 70 trillion sets of siblings. So, these are unlikely enough that we can ignore them. Identical twins don't occur by random distribution of chromosomes that happen to match, however, but when a single embryo splits into two. So, I would conclude that siblings, with parents who are unrelated, would be slightly more genetically related, on average, due to the portion which are identical twins, than parent and child, assuming the child's parents are unrelated. StuRat 14:37, 22 September 2006 (UTC)

It's also worth noting that male siblings share a Y chromosome precisely (up to mutation), and female siblings share one X chromosome precisely. (A brother and a sister have no such special correspondence.) Furthermore, there is the subject of mitochondrial DNA, which ties you more closely to your mother and siblings (and equally so), but not to your father. I wonder if the insanely unlikely "completely different siblings" case (aside from sex chromosomes and mitochondria) would be more likely to result from pairing of two pairs of gametes that were formed in the same meiosis than from lucky genetic recombination? --Tardis 15:14, 22 September 2006 (UTC)

What is the word that means 'linking a memory to a smell'?

I used to know the word (and have forgotten what it is!) so when I see it again, I'd know what it is.

I know it is not 'Proust Effect' nor 'Olfactory'.

So I want to get as many options as I can here - so the way I remember it, the word describes how a memory is triggered by a smell. I used to use it to describe how walking past men who were Hugo Boss's Innovate would give me flashbacks of my ex.

Thanks for your help ! Mavis ----09:10, 22 September 2006 (UTC)----

There is the term "involuntary memory" (Proust's mémoire involontaire). Although not explicitly confined to smell, the vividness of memories evoked by scent stands out; see also Limbic system#Practical application (sic!). --Lambiam^Talk 09:57, 22 September 2006 (UTC)

Sometimes it's called the Madeleine effect, again after Proust.--Rallette 10:00, 22 September 2006 (UTC)

And I meant madeleine with a lower case m, of course, a pastry not a person.--Rallette 10:07, 22 September 2006 (UTC)

A pastry or woman can also have a strong smell that triggers memories..."That's right, I was supposed to go buy deodorant for Madeleine". :-) StuRat 14:25, 22 September 2006 (UTC)

Why do you associate pastries with women. Are you still a mummy's boy? 8-)--Light current 05:58, 23 September 2006 (UTC)

A more general term is context dependent memory; could that be what you're looking for?

It looks like someone forgot to write that article. :-) StuRat 05:55, 23 September 2006 (UTC)

Hmm .. still one of the above. ARGH. the sense of frustration is creeping in .. it's like the feeling of having something at the tip of your tongue but not being able to utter it .. Mavis

(Semi-) Random relevant phrases: "The primary olfactory cortex, which receives information about smells from nerves in the nose, links directly to the amygdala, which controls expression and experience of emotion, and the hippocampus, which controls the consolidation of memories." "Odor-evoked memories" "an ambient odor would trigger a better memory" "demonstrated the relational memory organization through appropriate transitive inferences" "a general declarative memory capacity" "recognition of the odor in the olfactory process will simultaneously evoke the correlated memory" -- Fuzzyeric 05:52, 24 September 2006 (UTC)

Thermometers

I have two thermometers here, neither of which type is listed in our thermometer article. The first is a bath thermometer, with a glass tube part filled with a bright red liquid, so it is obviously not mercury. What is it? The other thermometer is a Toblerone-shaped piece of polished slate, with a plastic strip along one side. There is a numbered scale along the plastic strip, but only one number is visible at any time. Is there are name for this type of thermometer and how does it work?--Shantavira 12:40, 22 September 2006 (UTC)

The red stuff is alcohol, this is mentioned in the Mercury article at least. MeltBanana 12:57, 22 September 2006 (UTC)

The second sounds like a liquid crystal thermometer. For the second, could you describe the strip more clearly? If you hold your finger on the strip where you expect the human body temperature to be, does it light up in addition to the current room temperature? JBKramer 12:58, 22 September 2006 (UTC)

I agree that #2 is definitely a Liquid crystal thermometer. The fact that it's mounted on a triangular prism of slate is weird, though. -- Plutortalkcontribs 13:36, 22 September 2006 (UTC)

Yes, you're right. Thanks. I guess a liquid crystal thermometer can be mounted on anything. I figured the stone was intended to stabilize it, but it's mainly decorative. I shall add the thing about alcohol to the thermometer article later on.--Shantavira 15:31, 22 September 2006 (UTC)

Is fire plasma?

Is fire an example of a plasma? My understanding is that it is not, since the gas would need to be ionized, and ordinary fire is not nearly hot enough to accomplish that: but there are conflicting sources on the web: for example, yes 1) [29], no: 2) [30] and [31]. (There's a corresponding disagreement on the fire article.) Antandrus (talk) 14:58, 22 September 2006 (UTC)

Flame is not a plasma. Electrons remain trapped in their orbatal. The color of fire comes, if I remember correctly, from the black body radiation of the heated particles. JBKramer 15:11, 22 September 2006 (UTC)

I think you may have remembered the last bit incorrectly. The colour of a flame is caused by excited electrons falling back to lower energy states, thereby emitting photons. That's why a flame goes yellow when you sprinkle some kitchen salt on it: it is the colour of the sodium D emission lines. Of course, as the temperature goes up and the electrons get really excited, the average energy of the photons also goes up, just as it would for black-body radiation. --Lambiam^Talk 16:54, 22 September 2006 (UTC)

both wrong. see flame.--Deglr6328 00:14, 24 September 2006 (UTC)

That makes sense. So what leads to the common misconception? --Allen 16:36, 22 September 2006 (UTC)

There is some degree of ionization in a fire, so it all depends on how much ionization one requires to classify a phenomenon as a plasma. It's similar to trying to decide whether Pluto is a planet or not. StuRat 16:53, 22 September 2006 (UTC)

Dwarf plasma? --Lambiam^Talk 16:55, 22 September 2006 (UTC)

conception/ovulation

After ovulation, how long is the unfertilized ovum responsive to fertilization before it breaks up and becomes a part of the uterine lining?

Apologies for previous wrong answer. Implamentation must take place within 6-12 days from ovulation. Still working on fertalization timing. PMID 10362823 JBKramer 15:15, 22 September 2006 (UTC)

I can find no good studies relating to the actual fertalization of the egg, as opposed to timing for intercourse/implamentation. Intercourse is most effective 6-1 days before ovulation, while implmentation is most effective 6-12 days after ovulation. JBKramer 15:20, 22 September 2006 (UTC)

By what measure is "intercourse" "effective"? probability of fertilization? And what is "implamentation"? did you mean implantation? From what I know, a sperm lasts about 4 days in the accomodating fluids of the uterus and fallopian tubes. An egg that has been released from the ovary takes about 6 days (often longer, usually not shorter) to travel to the uterus. Once the egg reaches the uterus, it is reabsorbed, causing a hormonal cascade that leads to the shedding of the uterine lining. Fertilization must take place while the egg is in the fallopian tube (but not implantation, that would lead to an ectopic pregnancy). Thus the window of conception-producing sex is about 4 days prior to ovulation to about 6 days after ovulation: a 10-day window.Tuckerekcut 15:47, 22 September 2006 (UTC)

PMID 7477165, widely cited, disagrees with your 10-day window. m:dick disagrees with your spelling (f)lame. JBKramer 16:05, 22 September 2006 (UTC)

6-1 ? StuRat 15:48, 22 September 2006 (UTC)

Six to one.

That would normally be written as 1-6, so I'm wondering if they meant something else, like 6-10, with a missing 0. StuRat 16:50, 22 September 2006 (UTC)

JBKramer: Referencing my Guyton & Hall Textbook of Medical Physiology, Tenth Ed. (Saunders 2001, Page 941), "The ovum remains viable...after it is expelled from the ovary for no longer than 24 hours. Therefore sperm must be available soon after ovulation...intercourse must occur sometime between 4 and 5 days before ovulation and up to [a day] after ovulation..." It seems that my measure of 6 days for the travel down the fallopian tubes (gleened from my Ob/Gyn course notes) was inflated and incorrect. With this new information it seems that a 4-6 day window is more likely. However your discussion of implamentation still doesn't make any sense to me. I still don't know if you mean the impl[e]mentation of something (perhaps implementation of an IVF protocol?) or implantation. I pretty much assumed that you meant implantation, but I was unsure because you used the word three times. That's why I asked. By the way, the article you mentioned, it is only cited 20 times on PMC.Tuckerekcut 19:02, 22 September 2006 (UTC)

ID Card size2

I am posting this question again because i could not get any satisfactory answer. What is the logic behind such an odd size od Id-1 cards that have a size of 85.6x53.98mm?

Maybe because it is small enough to fit nicely in most people's hands and still large enough to hold a fair amount of information? Possible scenario: somebody (probably English) issues a popular ID card (3 3/8" x 2 1/8"); others like it and start imitating it. Logic? What's logic got to do with it? Why do people drive on one side of the road? Somebody started it and then everybody else went along.

Here's another thought. Maybe somebody used the other side of playing cards, back when only one side was printed on? The sizes are pretty close (3 1/2" x 2 1/2"). Or it could just be a form of Parallel evolution - it's just a pleasing size. Clarityfiend 17:01, 22 September 2006 (UTC)

The previous time was not the first time the question was asked: Wikipedia:Reference desk archive/Mathematics/April 2006#ID Card size. The reason you can't get a satisfactory answer is because we don't have one. We are flummoxed. Rarely has the reference desk been so perplexed as by this question. We'd love to be plussed, but the fact is, we're all nonplussed. Sorry. The members of the ISO 7810 committee who might have known the rationale all died mysteriously within days of each other through a variety of accidents and natural causes briefly after the standard had been adopted. --Lambiam^Talk 17:22, 22 September 2006 (UTC)

Plussed, eh? Does that mean, if we were minussed, then we'd be nonplussed? Wait - what happens with the zero? Can we be both plussed and nonplussed at the same time? Clarityfiend 19:57, 22 September 2006 (UTC)

I suspect it has to do with a hard conversion vs. a soft conversion between Imperial measurements and Metric measurements. With a hard conversion, the original (in this case Imperial) measurement is exactly multiplied by a very precise conversion factor, and the number of significant digits is important. So you get a seemingly precise answer such as 3-1/2" --> 85.6mm. With a soft conversion, the answer need not be so exact, the conversion factor has fewer significant digits, and so 86mm would suffice. Whoever opted to convert the Imperial measurements of an ID card to the metric system opted to use a hard conversion. As to why, that's the unknown. Often in fields like Land Surveying a hard conversion with many significant digits is necessary, so that the survey is accurate to tenths of a foot over an area of many miles.

A different example would be, say, electrical conduit. A 12mm conduit is approximately the same as a half-inch conduit. If an electrical job was being converted from english to metric, I wouldn't take the half-inch measurement, multiply it by 25.4, get 12.7mm, and thus say 12.7mm conduit would be used; there's no such standard size available.

This is not a satisfactory solution unless you can give plausible imperial measures whose hard conversion results in these values. Personally I tend to think 337/100 inch and 3451/1024 inch are not plausible, but maybe you can make a case for them. Another reason why imperial measures are less likely is that this is an ISO standard. ISO standards are based on the SI system. For example, the ID-2 card has A7 format: 2^−13/4 m × 2^−15/4 m, and the ID-3 card has B7 format: 2⁻³ m × 2^−7/2 m. They could easily have picked A8 format, which is 74 mm × 52 mm (2.913 inch × 2.047 inch). --Lambiam^Talk 21:00, 22 September 2006 (UTC)

This is interesting. The dimensions are very close to the Golden ratio. Clarityfiend 20:02, 22 September 2006 (UTC)

The golden ratio is about 1.618034. The aspect ratio of the ID-1 card is 1.585773. Not that close. If they had wanted to achieve the golden ratio, they could have gone for 83.62 mm by 51.68 mm, with an aspect ratio of 1.618034. The aspect ratio of the other cards (ID-2 and ID-3) is the square root of 2: 1.4142. --Lambiam^Talk 21:21, 22 September 2006 (UTC)

Well, the ISO 7810 constellation of standards appear to have been standardized in the past few years. (Irritatingly, the article doesn't give a history of the standard.) The standard appears to have codified the general sameness of the dimensions of credit cards which have definitely varied very little since the Diner's Club card in the 1950s (personal experience). ... which were roughly sized to match business cards and trade cards. ... which were the same size as the pockets in wallets. ... which were designed to carry calling cards. Wallet directly asserts this history for dimensioning to calling cards and then dimension standardization following the release of credit cards in the early '50s. "Rules of Etiquette & Home Culture", 1882 (quotation) suggests 1.25" x 3" (76.2 x 31.75 mm) as a small card, so it is not inconceivable that a "medium size" could be close to ID-1 dimensions.

Nevertheless, the answer is, "because those are the dimensions of the Diner's Club card." And there may not be a much better documentable answer. -- Fuzzyeric 03:44, 23 September 2006 (UTC)

Submarine Periscopes

Ive often wondered how the periscope is designed to slide up and down without letting any water in into the sub, especially at great depths. Any answers?--Light current 17:16, 22 September 2006 (UTC)

At great depths you don't slide your periscope up and down. You only do that at depths up to the length of the periscope. --Lambiam^Talk 17:26, 22 September 2006 (UTC)

[after ed con]The periscope is only used at very shallow depths, so there isn't much of a problem with water pressure. There is a close fitting seal (and I assume quite a lot of grease) to prevent water penetration. When the sub is at any depth, the water pressure will actually help seal it.--Shantavira 17:27, 22 September 2006 (UTC)

[edit conflict]Yeah but the waters still trying to get in even if the scopes down?--Light current 17:29, 22 September 2006 (UTC)

Rotating face mechanical seal

Speaking of periscopes, did you know that it was once proposed, as a countermeasure against submarines, to teach seagulls to defecate on raised periscopes? It's true! (and I can't believe I added a seagull-related answer to the Ref Desk!)

You did and thats minus 20 points to you! Congrats! Anyway thats a load of bird crap!--Light current 19:27, 22 September 2006 (UTC)

Yes, and now I feel bad. But another example came to me: Think hydraulic cylinder, like you see on bulldozers, backhoes, and so on. There is a simple o-ring style seal on the cylinder, keeping the hydraulic fluid in. Hydraulic systems operate at very high pressures, up to 2,000psi. So they keep the fluid inside, whereas a periscope seal keeps the fluid outside. But both depend on a smooth machined surface sealing with a flexible o-ring type seal.

Is there a g**l conspiracy? There's another one just a few questions down. Was Alfred Hitchcock onto something? Clarityfiend 20:08, 22 September 2006 (UTC)

There is an infestation that needs to be eradicated!--Light current 20:10, 22 September 2006 (UTC)

O yes. That rings a bell. 8-)--Light current 19:55, 22 September 2006 (UTC)

Involuntary/Voluntary memory

I am a bit flummoxed by the whole part. Can somebody explain to me the differences and frequencies further? Are involuntary memories as common in the normal person as I? Every second of life for me is filled with involuntary memories. — X [Mac Davis] (SUPERDESK|Help me improve)18:14, 22 September 2006 (UTC)

Your question is not well phrased. Could you clarify?--Light current 19:30, 22 September 2006 (UTC)

Try not dipping your madeleines in tea. While there is a large variety between individuals (and for a given individual between different periods of life) in the incidence of involuntary memories, every second sounds rather high. You may be talking about something else. An involuntary recollection intrudes with great strength and usually vividness upon your consciousness. It's more than "Oh, that reminds me of ...", it is almost like re-experiencing. Some people never have this, some regularly, but not more than a few times a day. --Lambiam^Talk 20:25, 22 September 2006 (UTC)

Cognitive psychology research has shown that memory is less like a playback of a recording, and more reconstructive. People can be quite certain of details of an incident or a person's description which were not there in the original incident. So one could have involuntary "recall" of memories all the time, with much of the detail invented. Example: One recalls how his family had a cow on the farm when he was little, and remembers seeing the big black and white Holstein cow getting milked in her stall. Then a parent corrects him to the effect that it was a Jersey, and now he can remember seeing the little brown and white cow getting milked. Attention and effort, with such techniques as repetition, the Method of Loci or other mnemonic,techniques are useful for retaining memories.Edison 21:15, 22 September 2006 (UTC)

How do you remember? Do you have to try? With almost every word I type I associate it with a past experience or objects, events, or trivia. — X [Mac Davis] (SUPERDESK|Help me improve)03:08, 23 September 2006 (UTC)

Sounds like it might not make for the greatest productivity; more like daydreaming. Have ADHD?Edison 15:13, 23 September 2006 (UTC)

Blood Physiology

Naqa inc 18:20, 22 September 2006 (UTC)×Blood PhysiologyWhat would be the simplest answer to the question : "Why is it necessary to control blood sugar ?" The answer should not mention diabetes mellitus or any diabetes. Assume its a 40 marks question.this was our assignment but we cannot seem to agree on hypo-/hper-glycemia.

That's a big question, and it would help to know what grade (or level, or whatever the gradations are called in your region) you are in. Perhaps you could write out your answers, and I/we can tell you where you are wrong or need elaboration. That said, we aren't going to do your homework for you, so dont expect something you can copy and give to your teacher.Tuckerekcut 19:08, 22 September 2006 (UTC)

The question you are asking can be read from several angles. From a physiologic standpoint, the evolutionary benefit from maintaining a tight blood sugar range can be approached from a conservation of energy standpoint. When the blood sugar gets too high, it is freely filtered in the urine and provides an osmotic load which keeps water from being reabsorbed by the renal tubules. A person can urinate a significant portion of their calories, often resulting in weight loss and wasting. Dehydration is also common due to water loss. If blood glucose is too low, there are significant consequences to the brain, which uses glucose preferentially as a fuel source. Too little glucose leads to seizures and coma.

From a molecular biology standpoint, elevated blood glucose leads to glycosylation of plasma proteins, resulting in the multiple consequences which are typically associated with diabetes mellitus. There are many other answers to the question from a variety of standpoints and it will depend what you are looking for. InvictaHOG 22:26, 22 September 2006 (UTC)

Do gulls swim?

I've seen them floating on top of the water but they seem to end up going wherever the current takes them. Can they actually 'swim' as such? --84.67.79.146 19:13, 22 September 2006 (UTC)

They have webbed feet... that certainly suggests that they swim in a duck-like fashion. – ClockworkSoul 21:31, 22 September 2006 (UTC)

They have webbed feet but it looks like they can only just paddle and tread water a bit, unless the water is completely still. I wouldn't really call it 'swimming'. --84.69.49.184 23:11, 22 September 2006 (UTC)

They can swim if necessary, but as they are a bird of the open sea and need to cover large distances there is little incentive to swim anywhere when they can fly. It's a matter of energy use. If I am in my local park and throw some bread, ducks will fly over if they're any distance away, but swim if it's only a matter of yards. Swans and geese, being quite heavy, will always swim over. If there is a gull around it will invariably fly, in fact it prefers to catch bread on the wing rather than come down for it. Coots use an interesting hybrid tactic: they run.--Shantavira 06:46, 23 September 2006 (UTC)

AIDS after WWII in Europe

Hello, I read in a book called The Tipping Point about how after WWII in German mining towns it was noticed that a lot of children were dying of an immune deficiency disease, and that people now speculate that it may have been a precursor to the AIDS virus. I wanted to find more background on this but haven't found much information regarding this occurence, so I was hoping that someone else knows what I'm referring to. Thanks! Andromeda321 19:28, 22 September 2006 (UTC)

Starvation, overwork, stress in general, and extreme cold also hamper proper immune system functioning.Edison 21:18, 22 September 2006 (UTC)

http://www.nytimes.com/books/97/08/24/reviews/970824.24ryanlt.html this may help. BTW I knew nothing about it but search inside a book at amazon is a very useful for this kind of research. MeltBanana 21:30, 22 September 2006 (UTC) Actually it probably will not help much as it barely mentions it, you will probably have to buy his book. MeltBanana 21:34, 22 September 2006 (UTC)

There are many conditions which cause immunodeficiency, so it's not a good idea to call them all "AIDS", which is a specific type of immunodeficiency caused by the HIV virus. StuRat 03:17, 23 September 2006 (UTC)

Suppose another acute one comes into existence, what would we have to call that then? AIDS 2.0? The sequel? TNG? DirkvdM 05:22, 23 September 2006 (UTC)

The "A" does not stand for "acute" (as in SARS) but for "acquired". I think, though, that any disease not caused by a close relative of HIV can no longer be called "AIDS", even if it matches the clinical description (AIDS was originally defined by its symptoms, not its cause, since its cause was unknown). I think that now that the cause is known, it no longer makes much sense to keep around a term defined by a clinical history, and if language were rational (or, perhaps less flatteringly, "rationalistic") the term "AIDS" would simply disappear, to be replaced by "HIV disease" or some such. But language isn't rationalistic, and attempts to impose rationalism on it rarely have happy outcomes. --Trovatore 20:14, 23 September 2006 (UTC)

Battery life

About 20 yrs ago I bough a (Philips CD 650) CD player that is still working. With the player came a remote control powered by Philips type 035 (alakaline?) batteries. Altho I dont use the remote a lot, I'm pleasantly surprised that the batteries are still powering the remote OK. Is this some sort of record?--Light current 19:51, 22 September 2006 (UTC)

Probably close, although a Google search for "battery record" gives at least one result of someone claiming longer (34 years). The alkaline battery was only invented 47 years ago, and this is far longer than the life of any standard cell battery I've ever heard of. You might want to toss them, though, especially if you have kids. Old batteries corrode and leak, and before 1996, alkaline batteries had Mercury in them. -- Plutortalkcontribs 11:32, 23 September 2006 (UTC)

They are quite safe, not leaking, and still operating the remote! I dont intend eating them either, but thanks for the answer.--Light current 11:50, 23 September 2006 (UTC)

If I wrote to Philips with this wonderful news, do you think they would give me a new CD player?--Light current 14:56, 23 September 2006 (UTC)

light acting as waves

dear sir / mam

i just wanted to know that if light acts like particles, and as waves than why doesnt it collide like particles. for example, when you shoot two laser beams across each other , it never deflects or even collide, where as waves do collide and particles also collide. so ya, i am confused. your help will be highly appreciated.thank you shaneel deo165.196.194.137 20:16, 22 September 2006 (UTC)

First of all, you might find our article wave-particle duality helpful. When you shoot two laser beams across each other, I think some interference would take place, but maybe not enough to notice, but don't take my word on that. --Allen 20:24, 22 September 2006 (UTC)

Interesting question! What happens if two photons collide! --Light current 20:28, 22 September 2006 (UTC)

I think when two photons interact, that interaction is going to look like wave interference, not particle collision. Photons don't have size or exact location, so I don't see how they could ever collide in a billiard ball sort of way. --Allen 20:33, 22 September 2006 (UTC)

Look up scatttering of light by light. I don't know much about it, but I think it could be naively described as "photons colliding". --Trovatore 20:39, 22 September 2006 (UTC)

In the standard model, in particular the subtheory of quantum electrodynamics, photons only interact with electrically charged particles such as electrons. Why nature behaves like she does we can't know; all we can do is make the simplest models we can that conform to our observations. In the best model we currently have, photons do not interact, and such interaction has not been observed. --Lambiam^Talk 23:01, 22 September 2006 (UTC)

Yeah, now that you say that I feel like I should have known. What about interference, though, like in the double-slit experiment? I guess that's not considered interaction? --Allen 00:32, 23 September 2006 (UTC)

Right; that is simply the result of adding the amplitudes, and the wave equation is linear, so if there is no quantum collapse or other interaction the photons proceed as if they had never encountered another photon. --Lambiam^Talk 01:52, 23 September 2006 (UTC)

Hey, hang on! Bare photons may not be able to directly interact with each other, but in QED, photons are constantly producing virtual electron pairs and re-annihilating. One photon can strike an electron from another photon and get re-emitted in a different direction -- not as if the two photons had never encountered. Melchoir 08:27, 23 September 2006 (UTC)

Can you sketch a Feynman diagram of this? I don't understand what it means for a photon to be re-emitted by an electron. --Lambiam^Talk 14:53, 23 September 2006 (UTC)

Well... I can describe one pretty easily. Electron loop in the middle, two photons in and two photons out. Melchoir 19:18, 23 September 2006 (UTC)

I fear there is a misunderstanding in the original question, specifically the part stating "waves do collide". When two or more waves "collide" they simply pass right over one another. During the overlap they may reinforce or cancel one another, but once each wave moves beyond the others, it reforms it's original shape once again. StuRat 03:13, 23 September 2006 (UTC)

I see such interaction regularly in the canal I live at. When a boat passes by and the bow waves bounce off the walls, the original and reflected waves interact to form checkered paterns. Some nice examples can be seen at Ripple tank. DirkvdM 05:39, 23 September 2006 (UTC)

Limestone vs Siltstone for aggregate

Hi,

I was wondering if anyone could tell me if siltstone is suitable for aggregate. And if it is and you had Limestone to choose from as well, which is better and why?

Thanks in advance.

Limestone is commonly used for roads etc as hardcore but I dont know if its better that siltstone. Usually gravel is used as aggregate--Light current 21:45, 22 September 2006 (UTC)

Is it possible for a man to have multiple penises?

Is this a real condition that some men have or not?--68.90.188.227 22:04, 22 September 2006 (UTC)

Yes it is. See diphallia. Hyenaste ^(tell) 22:06, 22 September 2006 (UTC)

(edit conflict) It has been documented, and if I recall correctley their is a caste made of one such occurance of this should you wish to see it. The owner claimed both functioned well, and he was happilly married. Hehe. Philc _T^E_C^I 22:08, 22 September 2006 (UTC)

September 23

Fate of the Universe

Well, I just researched the Big Crunch/Freeze/etc... and I didn't find anything specifically answering my question... Which is: "Once the universe ends in the way that it does will it be reborn again like another Big Bang or just end completely without any life existing ever again?" It's a scary question for me to think about, but I'd like to know the answer anyway. Any theories present? -MF14

Our current understanding of physics does not allow us to extrapolate beyond the demise of the universe as predicted by current cosmological theories about the ultimate fate of the universe. It is hard to imagine how some possible observation of a physical event might lead to a new understanding of physics that would allow such an extrapolation. In some string-theoretical models there is an analytical continuation beyond what would be a singularity in Einstein-like models, but the current status there is that the theories "aren't even wrong". If you like scary theories, then the Big Rip is my favourite; a lot more chilling than the Big Freeze, for which one can imagine some scientific way out. --Lambiam^Talk 01:18, 23 September 2006 (UTC)

Interesting. The Bose-Einstein condensate addendum to the heat death of the universe (which is only hinted there) isn't mentioned in the ultimate fate of the universe article. Yet, here it is: Fermion-boson fate of universe theory. Fixed. -- Fuzzyeric 03:01, 23 September 2006 (UTC)

Either way dude, I wouldn't let it affect your long term plans. ;) --AstoVidatu 02:55, 25 September 2006 (UTC)

If you want something to worry about, consider the rogue asteroid problem ie Impact_event--Light current 02:59, 25 September 2006 (UTC)

Covering answers on a worksheet

I want to photograph a homework sheet and send the photo to my friend, but I don't want him to see the answers. Is there a quick and easy way to block the answers? I tried copying & pasting blank portions of the page onto the answers (using an image editor of course), but the photograph is not of uniform brightness. Also, this method takes too long. --Bowlhover 00:33, 23 September 2006 (UTC)

Snopake out the answers before you scan it ! 8-)--Light current 00:38, 23 September 2006 (UTC)

In case anyone is confused about this answer, like I was before doing a Google search, apparently the Snopake company made correction fluid before they became a stationery company. --Allen 00:41, 23 September 2006 (UTC)

Thats right, they used to move right along! I should have said Tippex--Light current 00:46, 23 September 2006 (UTC)

But erasing the answers and re-writing them will take even longer than copying & pasting blank pieces of the photo. --Bowlhover 00:56, 23 September 2006 (UTC)

Just wondering, why does it have to have a natural gradient of shade? Hyenaste ^(tell) 01:04, 23 September 2006 (UTC)

I don't have a scanner, so I used my camera to photograph the worksheets. The main source of light in these photos is the camera's flash, and since it's so close to the sheet, the distance to the centre of the sheet is less than the distance to its sides. Taking account of the inverse-square law, this represents a significant difference in brightness. --Bowlhover 01:36, 23 September 2006 (UTC)

You could turn the flash off and use a bright external light, instead. StuRat 05:49, 23 September 2006 (UTC)

Why not load it into MS Paint or something and use the spray paint tool to cover them. Anchoress 01:03, 23 September 2006 (UTC)

Which colour should I spray-paint the answers with? I'm pretty sure that no matter which colour I choose, it will end up looking like this. --Bowlhover 01:36, 23 September 2006 (UTC)

Do you want to send him the questions without the answers, but don't want him to see that you are hiding the answers from him? The best bet might be to tell him that your imaging techniques aren't working, and to dictate the problems to him. If you have photoshop, you could use the stamp tool to create a gradient similar to the background, maybe other paint programs have a similar tool...Tuckerekcut 01:16, 23 September 2006 (UTC)

No, I'm not trying to hide anything from him. (Some of these homework sheets were handed out days ago, and he won't believe that I didn't even start any of them.) My friend needs to print the homework out and do it, and I don't want it to look like this. Also, no, I don't have photoshop. I have the Gimp, though. --Bowlhover 01:36, 23 September 2006 (UTC)

If I understand you, you don't really care what your friend sees, as long as he does not see your answers. The problem, though, is that you don't want the teacher to see these weird light-colored squares on your friend's answer sheet, after he has turned it in, right?

In that case, you can use MSPAINT, and use the cut-paste commands... capture a square of the blank background page, copy it, then paste it back in and move it so it covers up one of the blanked-out regions. Repeat until you have all of the answers blanked out. It will not be perfect, but it'll have the correct background color instead of being white. 192.168.1.1 7:51 22 September 2006 (PST)

This is actually what I did, except with Gimp instead of MSPAINT. However, the "blank" background does not have a constant brightness. So if I copy a square and move it to another location, the contrast will be obvious. --Bowlhover 03:41, 23 September 2006 (UTC)

Another suggestion: Go to a copy center, like Kinko's, make a straight copy, use liquid paper on the copy, let it dry, then copy that. Copiers don't distinguish between various whites as much as a digital camera will. The total cost should be less than a dollar. StuRat 03:02, 23 September 2006 (UTC)

Don't use cut and paste, use the clone tool. Gimp has it. The fact that there's a gradient makes it a bit more difficult, but as long as you clone parts of paper along the same gradient line it's very difficult to notice the difference. It takes a little practice to make it look perfect, but I've been fiddling with pictures like that for years, and as long as I have a 1-inch section of relatively clear base texture I can blank out anything. There are a lot of techniques to make it easier, one might be to unify the brightness of the entire photo using an inverted mask or something like that, but you don't seem to have the time to do that.

A useful tool for this purpose is the GIMP Resynthesizer plugin, which provides a "smart remove selection" tool. However, I agree that for this purpose it's overkill — just adjust the levels until the black is truly black and the white truly white, and then you can just cut out the parts you don't want. You'll have to do the adjustment anyway, if you want the resulting image to look like the original after printing. —Ilmari Karonen (talk) 19:38, 23 September 2006 (UTC)

Of course, no matter how well you blank the answers out, there are always ways for your friend to find out what you did.  freshofftheufoΓΛĿЌ  04:13, 23 September 2006 (UTC)

What ways ? StuRat 05:49, 23 September 2006 (UTC)

That's what I'd like to know. Police always claim they have fail-safe ways of finding out (possibly analyzing patterns in the code segments?), although I'm not sure how much that applies to non-compressed media.  freshofftheufoΓΛĿЌ  07:55, 23 September 2006 (UTC)

Whatever you do to blank the spaces, first clip the white to make it even (and very white!). Basically, you shift the white point that way. Use the histogram or 'levels' or whatever it is called in Gimp and move the right slider to the left (if it works the same as in Photoshop). Another way to do this might be to increase the contrast. DirkvdM 06:03, 23 September 2006 (UTC)

Wouldn't it be easier to call up your friend and read out the answers which you want him to know ? Wikicheng 07:38, 23 September 2006 (UTC)

Here's some general advice on using a digital camera as a copier:

• Don't take the picture with the camera too close to the document to be photographed. Keep a distance of about 5 ft (1.5 m) between the camera and the document. Optically zoom in the document if necessary. This reduces geometry distortion and will result in more uniform illumination.
• Make sure that the document to be photograph lies flat.
• When you shoot the picture, leave some space around all sides of the document to make sure that the edges and the corners of the document are visible. This will be helpful if you need to correct the orientation or perspective distortion of the image.
• If you use autoexposure, point the camera at something a little darker (e.g. a grey sheet of paper placed next to the document to be photographed) and lock the exposure. If you point your camera at a mostly white sheet of paper, your picture will be under-exposed for your purpose. As an alternative, manually adjust the exposure compensation until you get the desired exposure.
• If you're photographing a black-and-white document, convert the picture taken into a grey-scale image to reduce the file size.
• Adjust the color curve so that most of the pixels will be clipped to white. You may also need to adjust the curve at the other end so that printed text will look more black.
• You can compensate for non-uniform illumination using a gradient mask (radial or linear, as appropriate) and selectively brighten only a portion of the image, if you're familiar with how it's done in photo editing.

Science Question

How can i get more information about salamanders from your site,like their habitat, what they eat things i can ues to do a report"""""""""

You should sign your comments with four of these: ~. The key is usually on the top-right top-right of your keyboard.

Nice 'correction'. :) DirkvdM 07:36, 24 September 2006 (UTC)

Don't you mean the top left? DirkvdM 06:05, 23 September 2006 (UTC)

No its in the middle right on my KB--Light current 06:06, 23 September 2006 (UTC)

Well it's bottom right on mine, between the alt-gr and the ctrl. No wonder folk have difficulty finding it.--Shantavira 06:55, 23 September 2006 (UTC)

I meant top-left, even though they're on the top-right of my Japanese keyboard haha. I'm all messed up in the head!  freshofftheufoΓΛĿЌ  07:52, 23 September 2006 (UTC)

As for your question about salamanders, remember that there are many many different kinds of salamanders, so there's no easy answer to something like "where do salamanders live?". About the only thing you can assume is that most of them live close to, or in, water. Check out the articles for individual species/suborders for more specific information about each type of salamander: Cryptobranchidae, Hynobiidae, Ambystomatidae, Amphiumidae, Dicamptodontidae, Plethodontidae, Proteidae, Rhyacotritonidae, Salamandridae, and Sirenidae.  freshofftheufoΓΛĿЌ  04:20, 23 September 2006 (UTC)

Sliding...erm, thing (physics)

An object travels toward a 25-degree ramp at 18m/s. It travels 16.2m along the ramp. Find the force of friction. Is there enough information in this question to get the answer? BenC7 05:58, 23 September 2006 (UTC)

P.S. Not homework.

TRavels up the ramp and then stops at 16.2m? I think youre gonna need the weigt of the object for friction calculations.--Light current 06:04, 23 September 2006 (UTC)

Ah wait a mo. Some the kinetic energy of the object has been dissipated as heat caused by friction. THe remainded has gone into the potential energy of the object now at rest. You can work out how much energy is lost due to friction by subtracting the PE from the KE. THis however does not give you the force of friction.--Light current 06:11, 23 September 2006 (UTC)

You do know the vertical displacement, which is what matters for the potential energy at the point where the block stops... you can then assume that if all the potential energy became kinetic energy, you could solve for terms of your velocity in terms of the mass... then you could do some kinematics to solve for the acceleration, when given the displacement, and rewrite that acceleration as a force in terms of Newton's Second Law. The only change of velocity there would be due to the deceleration caused by the force of friction, no? Titoxd^(?!?) 06:23, 23 September 2006 (UTC)

No: you also have to remember the component of gravity acting down the slope that will add to the frictional force in decelerating the object. THis is a very interesting question! Is the ramp sloping up or down? I assumed up.--Light current 06:32, 23 September 2006 (UTC)

It's not that interesting. The slope can be either down with very strong friction, or up with less friction. To know the force, you need to know the mass (it's proportional to it) - if you only want to know the friction coefficient, you're good to go (let m be the mass, it will cancel). For each case, you know the changes in kinetic energy and potential energy. The difference (or sum, depending on how you look at it) is the work done by friction. Divide by the distance travelled, and you have the force. -- Meni Rosenfeld (talk) 06:42, 23 September 2006 (UTC)

Of course Work = Force x distance moved. So the answer is that there does appear to be enough information to slove the problem! So solve it!--Light current 06:49, 23 September 2006 (UTC)

Again, that depends. The mass is not given. So you can express the force as a function of m, and you can find the friction coefficient as a number, but you cannot express the force as a number. -- Meni Rosenfeld (talk) 07:09, 23 September 2006 (UTC)

The question also didn't explicitly state that it hits the base of the ramp at 18 m/s, so it could lose some speed due to friction, before it arrives. If we allow for this possibility, then we can't answer the question in any way. StuRat 09:44, 23 September 2006 (UTC)

Yes yes. Well all previous respondents assumed that we had frictionless travel before it hit the ramp other wise as you say the solution could not be obtained.

In fact this can be deduced from the question in that since it travels toward the ramp at a given speed, we must assume that speed is constant: An object travels toward a 25-degree ramp at 18m/s.(constant velocity is implied) So, as long as it is traveling towards the ramp, its doing 18m/s. THis eliminates any possibility of energy loss before it hits the ramp!. I hope that explains our position! --Light current 11:21, 23 September 2006 (UTC)

I'm not sure you can make that assumption. If that were the case, why wouldn't they state it simply as: "An object starts up a 25-degree ramp at 18m/s" ? StuRat 13:52, 23 September 2006 (UTC)

Its badly phrased by the physics /mechanics teacher. An object hits a ramp at 18m/s would be best.--Light current 13:55, 23 September 2006 (UTC)

I prefer my way. Your way might involve some transfer of energy to the ramp from the impact of "hitting". StuRat 16:15, 23 September 2006 (UTC)

I think there is not enough information. The vertical reaction force F = mg with which the ramp pushes back to your sled can be decomposed into two orthogonal vectors of, respectively, magnitude F·cos α (directed upwards normal to the ramp) and F·sin α (directed backwards along the ramp), where α stands for the slope angle of the ramp. If μ denotes the coefficient of friction, the force of friction X is then X = μF·cos α. The total backwards-directed force G has then magnitude G = μF·cos α + F·sin α = mg(μ·cos α + sin α). The deceleration is then a = G/m = g(μ·cos α + sin α). The distance s travelled until the object reaches zero speed equals s = v²/(2a) = v²/(g(μ·cos α + sin α)), where v is the initial velocity. We may assume that g is known, and s and v are given (assuming that all forward speed gets translated into speed along the ramp!), and we have to find the value of X = μF·cos α = μmg·cos α. We have two equations (s = v²/(g(μ·cos α + sin α)) and X = μmg·cos α) with four unknowns (μ, α, X, and m). --Lambiam^Talk 14:21, 23 September 2006 (UTC)

α is known. And I have already discussed what happens with m. And doing this using energy considerations is much easier. -- Meni Rosenfeld (talk) 14:31, 23 September 2006 (UTC)

It has been my experience that those who are good at math, such as physics teachers, often have poor language skills. This question is yet more confirmation. Edison 15:17, 23 September 2006 (UTC)

That's why I take pride in being equally poor at both. :-) StuRat 16:15, 23 September 2006 (UTC)

The question is (was) for a grade 11 physics student who I am tutoring. He recounted the question to me from an exam he had just taken, saying that he was confused because there did not appear to be enough information. After trying to work it out myself, and seeing you guys have a go, I think it is safe to deduce that you cannot work out the force of friction from the information given. So it is possible that either there was a mistake in the original question, or it was not remembered properly. I probably would have felt a bit silly as a tutor if you could work it out! BenC7 01:23, 25 September 2006 (UTC)

Potential energy and mass

Hi everyone.

When two Deuterium nuclei merge into a Helium nucleus, energy (and lots of it) is released.

It is often explained by saying that the meass of a Helium nucleus is less than twice the mass of a Deuterium nucleus, and the difference in mass is converted to energy according to the famous E=mc².

However, why is this explanation necessary? There is a strong nuclear force acting between the protons and neutrons. When these get closer together, an energy equal to the difference in potential energy - that is, the integral of the force between the two points - is converted to other forms. This is the same as the calculations of potential gravitational energy in classical mechanics (of course, the nature of the force is different), and should be enough to explain the released energy.

What does it mean? Does it mean that the energy released is the change in mass plus the change in potential energy? Or does it mean that the additional mass is itself the potential energy? Does this apply to other forces as well? For example, when two distant, massive objects are moving away from each other, do their masses increase because of the additional gravitational potential energy? What kind of mass is this? Inertial, gravitational, both, or something else? If this is so, is there even such a thing as "potential energy", or are there only changes in mass?

Taking this into account, and the idea that the relativistic mass of an object increases when it is in motion, would it be correct to say that every form of energy is actually mass? From which it can be concluded that mass and energy are the same thing?

I will be grateful if anyone can clear that up, or direct me to references which will. Thanks. -- Meni Rosenfeld (talk) 06:31, 23 September 2006 (UTC)

Conservation of mass-energy--Light current 06:36, 23 September 2006 (UTC)

Wrong link, but I've managed to find the right ones, and they're helpful, thanks. Let's see if I got this straight:

• The additional mass is itself the potential energy (I'm not too clear about how that might be, but whatever).
• It applies to other forces as well.
• This mass is both inertial and gravitational.
• There is no "abstract" potential energy which appears only in calculations, but only observable differences in mass.
• Mass and energy are the same thing.

Right? By the way, does this apply only to special relativity or to general relativity as well? -- Meni Rosenfeld (talk) 06:55, 23 September 2006 (UTC)

So potential energy is always manifested as mass?--Light current 07:03, 23 September 2006 (UTC)

Yes. All forms of energy contribute to the mass of the system by the infamous formula m = Ec⁻². There is a well-known quip that when you climb a mountain, your mass increases. In doing so, you however convert energy stored in your body as fat or ATP to "height" energy (E = mgh) as well as to heat that is lost to the environment. So, theoretically, there should actually be a (miniscule) mass loss. --Lambiam^Talk 11:28, 23 September 2006 (UTC)

And I believe that the Sun loses something like 4.25 million tonnes per second in radiated energy. Richard B 15:21, 23 September 2006 (UTC)

I think this is why it becomes harder and harder to accelerate when you approach the speed of light - your kinetic energy starts making a significant contribution to your mass. Clarityfiend 18:21, 23 September 2006 (UTC)

O, now I understand! When I try to run really fast it's always as if I hit a wall. --Lambiam^Talk 22:16, 23 September 2006 (UTC)

Okay, thanks everyone. -- Meni Rosenfeld (talk) 15:39, 23 September 2006 (UTC)

Well actually you answered most of it yourself! So thanks to you!--Light current 16:11, 23 September 2006 (UTC)

Say not: "when you climb a mountain, your mass increases." Say instead: "when you climb a mountain, the mass of the planet-person system increases." --GangofOne 00:33, 24 September 2006 (UTC)

Center pivot irrigation

Why is Center pivot irrigation argriculture laid out on a square grid? Surely there would be more efficient ground usage on a hexagonal grid. -- SGBailey 07:05, 23 September 2006 (UTC)

Thought I saw some pics of this using hex grid. Or was that oil tanks?--Light current 07:24, 23 September 2006 (UTC)

I agree that it would be more efficient in a very large field, but not in small rectangular fields, because the hex grid would tend to leave half a circle out at each edge. Also, the non-irrigated areas might be useful for storage, farm equipment, crops that require less moisture, livestock, offices, housing, etc., so don't assume it's all wasted. StuRat 09:04, 23 September 2006 (UTC)

In addition, the length of the piping leading to the watering stations might be significantly longer per irrigated area, since the pipes would either need to be doubled or placed at an angle to reach all the points in a hexagonal grid:

                                                 WATER
 *---*---*----+-*-+-*-+-*------*---*---*-------- SUPPLY
 |   |   |    | | | | | |     / \   \            LINE
 *   *   *    * | * | * |    *   *   *
 |   |   |      |   |   |     \   \   \
 *   *   *      *   *   *      *   *   *
 RECT GRID     HEX GRID        HEX GRID

Then again, my diagram seems to indicate that the total length is the same is they are placed at an angle. StuRat 09:23, 23 September 2006 (UTC)

Here are pics (also) showing hex grids: [32][33]. There may be a relationship with the local price of (arable) land. If land is dirt-cheap, the simplicity of working with a square grid may prevail. If land is at a premium, you want to use it to the maximum extent. --Lambiam^Talk 11:13, 23 September 2006 (UTC)

The simple reason, at least in Nebraska, is that country roads are laid out on a one-mile grid. It's much easier to lay out land in rectangular patterns, and the roads were laid out before center-pivot irrigation came along. If the fields were hexagonal and the roads had to zigzag around the fields, then driving around in the country would be very annoying. ;-) —Bkell (talk) 19:04, 23 September 2006 (UTC)

Nostrils--how long and why?

I ve had difficulty for some time with my left nostril. (Been to the doctors a number of times- so no need to advise I go see one). Any way I was wondering how long each nostril is before it (preumably) joins up with the other one. Why do we have two nostrils anyway? (Oh, and please dont say: In case one gets blocked 8-) )--Light current 13:16, 23 September 2006 (UTC)

Why not say the correct answer ? I frequently have one sinus and nostril blocked, and the other is clear. StuRat 13:46, 23 September 2006 (UTC)

Same as my problem. But mines always the left sinus/nostril. Snap! 8-)--Light current 13:48, 23 September 2006 (UTC)

That is the answer basically. I think I heard them say it on Beakman's World once. Just think of the trouble's you'd be having now if you only had one nostril.  freshofftheufoΓΛĿЌ  14:34, 23 September 2006 (UTC)

OK but how far do they go before joining up into the airway?--Light current 14:35, 23 September 2006 (UTC)

I can only guess from this picture, but they appear to converge quite close to your pharynx, right in the middle of your ears. I had no idea there were so many holes in the front of my head.  freshofftheufoΓΛĿЌ  14:40, 23 September 2006 (UTC)

Yeah picture is unclear. I belive tho' that you can get ito the sinuses by probing round the labarynth of passages in there and there is a procedure for cleaning out the sinuses via the nose. Somone who had it done said it felt a bit like having your brain sucked out 8-)--Light current 14:49, 23 September 2006 (UTC)

If somebody dressed like an ancient Egyptian offers to clean out your sinuses with a large hook, I'd look elsewhere. :-) StuRat 16:10, 23 September 2006 (UTC)

Id be shouting 'Mummy!, Mummy!'.. please dont make me a mummy'--Light current 16:14, 23 September 2006 (UTC)

Tube shoved up one nostril. Water turned on. Dish held underneath the other. Been there, seen it, had it done when I was 10. Not pleasant. --G N Frykman 17:29, 23 September 2006 (UTC)

What sort of water do they use? Saline?--Light current 00:37, 24 September 2006 (UTC)

Who says we all have two nostrils? Don't do cocaine, kids. Rockpocket 04:40, 24 September 2006 (UTC)

Seriously, though. It is highly likely there is a lot more going on with the human nasal septum than just a barrier to divide the nasal cavity into two. In rodents for example, there is a vomeronasal organ (VNO), a septal organ of Masera [34] and a septal organ of Gruneberg [35], all of which are associated with the nasal septum. In humans, there is disagreement over whether there is an active VNO on the septum, but there certainly is a small, regressed pit where one used to be. There is still much to be learned about human olfaction, but recent work from Linda Buck and others are beginning to suggest there there are unusual types of olfactory receptor neurons, and the smart money is that they are, at least in part, associated with these unusual organs associated with the septum. So, i would say that there may well be a very important reason we have two nostrils - because the seperator is functional. We just don't quite know in what way yet. Rockpocket 04:56, 24 September 2006 (UTC)

You've found the missing link between Humans and Dolphins! --192.168.1.1 10:14, 23 September 2006 (PST)

Why does some hair stop growing at a certain length?

Here's a question i've always been curious about: why does some hair stop growing at a certain length, while other hair will continue growing "indefinitely". For example, human head hair can be grown down to the toes (and beyond? Note that indefinitely is in quotes above because its possible a maximum length for human hair does exist, but I'm not sure), but if i cut my cats' fur, it will always grow back to the same length it was originally. Is this a function of the hair follicle itself "sensing" the length (via the weight perhaps??), or is it simply because the hair is shed at a fixed interval, which means the individual hairs cannot grow beyond a certain length before they are removed? The latter seems like a good theory, but human eyebrows are fixed length and dont seem to "shed".

Note that I know that the commonly-held belief of hair growing back thicker or longer every time it is shaved is false...no matter how many times you shave an eyebrow, it will always grow back to the same length and shape.

--65.105.3.194 16:22, 23 September 2006 (UTC)

You may know about one myth, but you've been fooled by another! I'm sure it's detailed somewhere along the lines in the hair and hair follicle articles, but hair doesn't stop growing at a certain length, it falls out at a certain lenth. There's a continuous cycle of hair growth, and when the time comes (signalled by a chemical message, apparently), it just falls out. Notice that short hairs almost never fall out! Most human hair has a max length, but only in a few rare cases can humans grow hair "indefinitely". Some kind of mutation I guess.  freshofftheufoΓΛĿЌ  16:30, 23 September 2006 (UTC)

How was I "fooled" by another? In my question I asked whether falling out was the reason. Also this answer is self-contradictory; why would a short hair never fall out...if falling out is the only way that hair length is regulated, wouldn't short hairs fall out more often than long ones? I'm willing to accept that a certain type of hair will grow at a constant speed and fall out after a constant period of time, thus regulating the length (this seems to be what happens with my cats hair for example), but it seems like in some instances this isn't the case (such as an eyebrow, which will grow back at a rate similar to the rest of the hair on the body when shaved, but then seems to stop without falling out). --17:33, 23 September 2006 (UTC)

Sorry, I might not have been clear. The question you ask about hair is actually a pretty common one. It's almost as if there's an urban myth that hair stops growing at a certain length. Short hair never falls out, because hair doesn't usually fall out until it gets longer. The hairs that fall out naturally are usually the longest ones.

Once again, with eyebrows it only appears that the hair doesn't grow. You lose a fair percentage of your eyebrows every day when you sleep (the long ones) and it is constantly regenerating. Apparently there is a relatively long phase at the end of an eyebrow hair's existance in where it doesn't grow much, but it's not that much different than any of the other hairs on your body.  freshofftheufoΓΛĿЌ  17:45, 23 September 2006 (UTC)

This is much clearer now, thanks. --24.159.108.105 19:44, 23 September 2006 (UTC)

It does seem odd that head hair would ever grow long enough to be in the way, particularly by becoming a tripping hazard. It's hard to see what type of evolutionary advantage such hair could possible offer. StuRat 17:11, 23 September 2006 (UTC)

Perhaps it was a mutation which occured after humans had developed the ability to cut their hair. It may have spread as a result of being attached to another beneficial mutation and because the hair could be cut, it was not a detriment to survivability. --65.105.3.194 17:41, 23 September 2006 (UTC)

An old roommate of mine hair that would "stop" growing after it reached her shoulders; she's never been able to grow it longer than that. This might seem freaky, but freshofftheufo apparantly has more than two eyebrows. Considering that temperature can affect the rate at which hair grows (that's the function of goosebumps), it and possibly other factors may also affect the rate at which other hairs grow so that perhaps body hairs grow a bit faster after you've just shaved because it's colder (or hotter?) but once the hair gets to a functional length the sensory demand for faster growth diminishes and the hair's growth rate stays slow until it falls out. AEuSoes1 20:17, 23 September 2006 (UTC)

I can assure you I have two very well formed eyebrows thank you very much! I was only pulling my information from the hair follicle article, where it states that eyebrows have a 9 months telogen phase at the end of the growth cycle in which the hair doesn't grow (as much?). Maybe I was interpreting the information incorrectly.  freshofftheufoΓΛĿЌ  05:21, 24 September 2006 (UTC)

I haven't had a haircut for about 15 years and my hair doesn't grow beyond my shoulders. Also about 15 years ago I stopped using shampoo to stop the fallout (which worked). A friend once told me my hair has split ends (figures, I love splitting hair :) ). So maybe split ends are nature's way of preventing hair from getting too long and shampoo undoes that. Did your rommate use shampoo and if she did, what kind? Maybe something 'light' like baby shampoo? DirkvdM 07:51, 24 September 2006 (UTC)

She still shampoos as far as I know. She's also black and repeatedly straightens her hair as well as trims it periodically to keep the split ends out. I'm trying to recall what she uses but I can't remember. She stopped sleeping with me and I stopped talking to her so I don't think I'll ask. AEuSoes1 08:36, 24 September 2006 (UTC)

Nuclear fusion in stars - iron

I've been told that the reason why elements heavier than iron are not produced in stars is because the fusion reaction becomes exothermic for iron nuclei. Can anyone explain why this is, and why such elements can be created in a supernova? Thanks 80.169.64.22 17:12, 23 September 2006 (UTC)

Isn't the most common hydrogen to helium fusion reaction also exothermic ? That's what keeps the Sun hot, isn't it ? StuRat 17:30, 23 September 2006 (UTC)

Iron is such a stable element (pays its bills, doesn't drink, is always on time for work) that there aren't any(?) ways to convert it to heavier elements that don't require adding energy. If you examine the diagram in Island of stability, you can see iron securely located in the "Stable Mountains". However, during a supernova, there's plenty of energy to go around! Clarityfiend 18:01, 23 September 2006 (UTC)

If I understand the articles about iron and nuclear fusion correctly, that's actually not true. It can be converted into nickel, but I don't really get what they mean by disintegration in the article. - Dammit 18:35, 23 September 2006 (UTC)

since it's the most stable element, eventually everything in the universe will end up as iron. THere was a nice popular science book about this called The Iron Sun.--Light current 18:46, 23 September 2006 (UTC)

That's weird. If ⁶²Ni is more tightly bound than ⁵⁸Fe (the iron isotope previously thought to be the most stable), why would it disintegrate (break down into lighter elements) so much faster? Clarityfiend 19:12, 23 September 2006 (UTC)

Heger and Woosley simulated various stellar collapse phenomena to estimate population production. Fig. 2 there has a region labelled "nickel photodisintegration" for very massive star collapse. Fig. 3 there shows suppressed formation of heavy elements. Figs. 4 and 5 show that this suppression is reduced for smaller initial masses. It is known that the silicon burning process can more or less allow jumping straight from ²⁸Si to ⁵⁶Ni. ⁵⁶Ni converts to ⁵⁶Fe in a couple of days. Note that ⁶²Ni is not accessible from any of the ⁵⁶Ni precursors by the alpha process and so would have to be results of synthesis of heavier elements which decay via beta radiation. Since silicon burning occurs so late in the process (last weeks before implosion) there's not enough time for enthalpically unfavored production of heavy isotopes and multiple decay to produce significant quantities of ⁶²Ni. Additionally, at such late times, the temperature in the star is high, ~ 3 GK. The island of stability shifts to slightly lower masses because heavy nucleii keep boiling off nucleons. -- Fuzzyeric 21:40, 23 September 2006 (UTC)

The Supernova article talks about what we're discussing. It confirms what I read somewhere: during the last stages, you end up with shells of increasingly heavy elements, an outer layer of hydrogen over a layer of helium over a layer of carbon...all the way down to a core of iron. Always liked that image. Clarityfiend 00:13, 24 September 2006 (UTC)

It goes like this:

If you compute the mass of a neutron and the mass of a proton individually, they come out to certain values. If you multiply each of these by two and add them together, though, this value is larger than the actual observed mass of a Helium nucleus (two protons and two neutrons). As the subatomic particles have fused, some of the mass has been converted into energy. This release of energy is what makes the reaction take place, and is what powers the very sun itself. This missing mass, or packing fraction, is most noticable between Hydrogen and Helium, but is still noticable as one moves up the atomic scale. That is... until Iron-56 (gasp)

At Iron-56, fusing nuclei together no longer releases energy, but necessitates it. Thus, when a star has gotten this far, it finds itself out of fuel and explodes (usually) in a nova or supernova. So much energy is present at this time that many atoms are driven "uphill" past Iron-56 to form heavier elements such as Zinc, Uranium, etc. Hope this explains things. See also Helium fusion, Fusion power, and best of all, read Atom: Journey Across the Subatomic Cosmos by Isaac Asimov where he explains this quite skillfully and in great detail. An excellent read overall, as well. Cheers, Dar-Ape (talk) 18:54, 23 September 2006 (UTC)

Also, check out this graph: Image:AvgBindingEnergyPerNucleon.jpg —Keenan Pepper 19:00, 23 September 2006 (UTC)

So from the graph, iron is bound to be the most stable and populous element in the universe?--Light current 21:44, 23 September 2006 (UTC)

Most stable doesn't imply most populous. There is more hydrogen-1 in the universe than any other nuclide, even though it's one of the least stable, simply because enough stars haven't been burning long enough. —Keenan Pepper 04:03, 24 September 2006 (UTC)

No I meant it will be. THats why I said 'bound' 8-)--Light current 01:48, 25 September 2006 (UTC)

And also, more complete data indicates that ⁶²Ni should win based on binding energy but won't due to its not being on the alpha ladder from ²⁸Si through ⁵⁶Fe. This article adapts Fewell's plot of data from The 1983 Atomic Mass Table. -- Fuzzyeric 05:13, 24 September 2006 (UTC)

So it's like the Bates Motel of fusion. Clarityfiend 17:59, 24 September 2006 (UTC)

Order of magnitude values

A probably silly question from a math dummy: on scales that use an order of magnitude between whole numbers (e.g., the Richter scale) what are the values for each decimal? With metallicity, a scale is used where +1 equals x10 solar and -1 equals 1/10th solar metallicity. If O.O = solar, does 0.1 = double solar, 0.2 = triple, etc.? What doesn't make sense to me is you reach x9 at 0.8 and the next order of magnitude at 0.9. Or, on scales like this, is there some other formula for increasing/decreasing values? Marskell 17:41, 23 September 2006 (UTC)

These scales are called Logarithmic scales, the article will probably make it a lot clearer to you. - Dammit 17:55, 23 September 2006 (UTC)

Or not. Basically, 0.1 translates to an increase of 10^0.1, 0.2 to 10^0.2...1.0 to 10¹. In other words, it's not a linear increase, it's an exponential one. So the difference between a 3.3 earthquake and a 3.4 one is smaller than that between a 3.4 and a 3.5. Clarityfiend 19:27, 23 September 2006 (UTC)

Or maybe either one depending on the particular scale? Clarity (sorry if this is really stupid) but 10^0.1 is simply equal to 10 yes? Thus any #.1 is redundant? Marskell 21:50, 23 September 2006 (UTC)

According to my calculator 10^0.1 is about 1.26 - Dammit 22:02, 23 September 2006 (UTC)

If you are using Windows XP, start the calculator (Start -> All programs -> Accessories -> Calculator). If the calculator has 27 keys, click on View, then click Scientific, so that you have 58 keys. To find a linear number that corresponds to a logarithmic number, type 10, then the x^y key, then the logarithmic number, then the enter key. So a metalicity of 0.1 would be about 1.26 times Sol, and a metalicity of 0.2 would be 1.58 times Sol. On other calculators, the key to use may be labeled x^y or just ^. --Gerry Ashton 22:55, 23 September 2006 (UTC)

I assure you WinXP isn't the only OS with a calculator. :) DirkvdM 07:54, 24 September 2006 (UTC)

10^0.1 = 1.26, 10^0.2 = 1.58, 10^0.3 = 2.00, 10^0.4 = 2.51, 10^0.5 = 3.16, 10^0.6 = 3.98, 10^0.7 = 5.01, 10^0.8 = 6.31, 10^0.9 = 7.94, 10¹ = 10. Notice that it goes up 0.26 in the first interval, but a whopping 2.06 in the last. Clarityfiend 23:55, 23 September 2006 (UTC)

Thx all. Marskell 05:59, 24 September 2006 (UTC)

One quibble: it's not that meaningful to use subtraction to say that it "goes up 0.26 in the first interval, but a whopping 2.06 in the last". It's a multiplicative scale, so the right way to think of it is that when it goes from 0.1 to 0.2 it's being multiplied by 1.259 (1.259 × 1.259 = 1.585), and when it goes from 0.2 to 0.3 it's being multiplied by 1.259 (1.585 × 1.259 = 1.995), and when it goes from 0.3 to 0.4 it's being multiplied by 1.259 (1.995 × 1.259 = 2.512), and so on, up to 0.8→0.9 = 6.310 × 1.259 = 7.943, and 0.9→1.0 = 7.943 × 1.259 = 10.000. (In other words, it's just a tenth-scale version of the way when we go from 1.0 to 2.0 it's a factor of 10, and from 2.0 to 3.0 it's another factor of 10, meaning that from 1.0 to 3.0 was a factor of 100. But this doesn't mean that 2.0 to 3.0 was "a whopping 90".)

Where does that magic number 1.259 come from? It's the tenth root of 10, or 10^0.1, or in other words, the number which, when you multiply it by itself 10 times, you get 10. —Steve Summit (talk) 04:05, 25 September 2006 (UTC)

User:Molecular Hamiltonian/monobook.js

Could someone please delete this? this is the 2nd time I've created a monobook that has kept me from editing. Since this monobook doesn't do anything other than crash my browser, could someone please delete it for me? since I can't edit it while logged in, I'm kind of at a loss--172.148.167.123 20:30, 23 September 2006 (UTC)

• In the mean time, I'll be using this one--Laplacian Operator 20:35, 23 September 2006 (UTC)

Tried deleting but page has been protected from editing for some reason. Youll have to contact an admin.--Light current 20:39, 23 September 2006 (UTC)

Okay, I deleted it. Can you log in and post here just to confirm that you're that user? -- Consumed Crustacean (talk) 20:49, 23 September 2006 (UTC)

Thanks, same person, no problems, from now on I'll be more careful with my monobook (; Molecular Hamiltonian 20:55, 23 September 2006 (UTC)

maps

where in the world can you find a map of where peacocks are living today?— Preceding unsigned comment added by 74.107.171.198 (talk)

'Bout time somebody asked this question! - R_Lee_E (talk, contribs) 22:53, 23 September 2006 (UTC)

Well I guess it's about time somebody answered it then. First off, peacocks don't survive long without their friends, the peahens. So what you want to search for is Indian peafowl. This and the peafowl article have some information about their range. If you search Google and Google images for "indian peafowl map" it comes up with several results that will answer your question.--Shantavira 13:53, 24 September 2006 (UTC)

September 24

Landmines in films

Hello

In films, whenever someone steps on a landmine there is a 'click', and it doesn't explode until they step off the device. This seems unlikely to me, a more sensible plan would be to make the mine explode as soon as it is stepped on. All the info I've seen seems to agree with this. Is this just another Hollywood myth, or is there some basis for it? Maybe early landmines worked like this.

Thank you!

Bill --82.163.182.64 00:02, 24 September 2006 (UTC)

I've often had the same thought. StuRat 03:34, 24 September 2006 (UTC)

Anti-personnel mine gives the impression that there is no such delay on directy trigger land mines, and it does seem like something Hollywood would like to exploit. Not every movie does, mind you. I don't remember any scenes like that in Saving Private Ryan, although there may have been a one-second delay after triggering or something like that.  freshofftheufoΓΛĿЌ  05:28, 24 September 2006 (UTC)

You can read about this fallacy in S-mine#Usage. dpotter 05:43, 24 September 2006 (UTC)

Now that that is cleared up, a little anecdote. During army training a sergeant (or such) demonstrated to new recruits that a tank mine is harmless to people by stepping on one. To drive the point through, he started jumping, which turned out not to be such a bright idea. Who said evolution no longer works in humans? :) DirkvdM 08:05, 24 September 2006 (UTC)

We were told (in the NZ Army) that the click is bs, if you actually step on a mine you won't know till it blows. and we were also told an interesting point about antitank mines, the trip pressure is set high enough so people don't fire it, (eg. the barmine is 140 kg) but if you get a healthy infantryman (lets say 90-100 kg), rifle (3.5 kg), pyrotechnics (say 1 kg) water (upwards of 2 kg), pack with personal ammo, gear and section ammo (easily 30-40 kg)... pretty soon you get into the region where that mine is not so much an anti-tank mine as an anti-soldier mine. Xcomradex 08:57, 24 September 2006 (UTC)

Excellent, thanks for the help Bill 82.163.182.64

Gulls vs. Magpies - update

Not really a question, but an anecdote. I threw some food out for the birds yesterday (pieces of *cooked* sausage, for anyone that cares), expecting the usual flock of gulls to fly down and feast. A magpie flew down first and started to eat, blissfully unaware of the large herring gull walking up behind it. The gull almost nonchalantly picked up the magpie by the neck, turned through 180 degrees and deposited it, unharmed on the ground, then walked towards the food. The magpie chattered in protest a few times, then backed off, standing around and folornly watching the gulls chow down. Wish I'd had my camera. --Kurt Shaped Box 01:59, 24 September 2006 (UTC)

LOL, that's rather rude behavior StuRat 03:32, 24 September 2006 (UTC)

So the answer is : unmentionable seabirds can be gentle if they want. The question is tho': dont you like sausages?--Light current 02:07, 24 September 2006 (UTC)

They'd fallen on the floor twixt grill and plate. No way was I going to eat them - you should see the state of my carpet. --Kurt Shaped Box 02:10, 24 September 2006 (UTC)

Many accept the 5 second rule as a matter of faith if not of microbiology. Some restaurants have the deep-fat fryer rule: if it came from the fryer and it hits the floor, another pass through the fryer will make it edible again.Edison 19:39, 24 September 2006 (UTC)

I saw two gulls fighting over a massive live crab in Travemünde dock. Truly amazing creatures. --Asterion^talk 01:12, 25 September 2006 (UTC)

Energy Needed

How do I calculate for example how much energy I would need to send a 500 ton object hurtling throgh the air at 7.2 miles/s? It's coming out of a really big cannon.67.126.240.99 05:20, 24 September 2006 (UTC)

Read kinetic energy. You must figure out which of the varieties of ton and mile you have to use in converting to metric equivalents. The energy needed does not depend on the size of the cannon. --Lambiam^Talk 08:15, 24 September 2006 (UTC)

That's some big ol' cannon you got there boy. Even a supercannon can't fire a payload of more than about 10 tons. Look at the figures in our spacecraft propulsion article instead.--Shantavira 11:21, 24 September 2006 (UTC)

$E_{k}={\begin{matrix}{\frac {1}{2}}\end{matrix}}mv^{2}$

http://www.onlineconversion.com/energy.htm will do the unit conversions for you. Using British (long) tons and using an electric rail gun? I figure it would cost about $950,000 at my electric rate, if I plugged and chugged correctly. The web site will also convert to kilotons of explosive.Edison 20:06, 24 September 2006 (UTC)

Bath oils

Hello, I just wanted to know how to make bath oils. It's for my science project, and it has to have Aloe Vera in it. thankyou. From, sheen

Probably the easiest is to get some baby oil and some aloe vera gel from the pharmacy and mix the two. You can basically use almost any vegetable oil: olive oil, almond oil, grapeseed oil, canola oil, some of which are cheaper than others. If you have fresh aloe leaves, take off the skin to get the gel (pulp). The skins contain a powerful laxative, so don't lick your fingers. It is easier to mix in the oil (slowly, a few drops at a time!) into the gel than the other way around, othewise you may be stuck with gobs of aloe goo in the oil. Finally, you could mix in a bit of gentle liquid bath soap. Googling "make your own bath oil" may give you further ideas, like on how to scent the oil. --Lambiam^Talk 08:36, 24 September 2006 (UTC)

Urinate

Why is it that I cannot urinate when ever there are people around? What can I do to allow myself to be able to urinate easily even when people are around? Someone please help me...

The inhibition about going to the bathroom in front of people may be a natural protective mechanism, because when you're doing your business, you're vulnerable. Your protective instinct may be extra-strong. For men, using urinals might also introduce an extra element of 'performance anxiety' and a need to hurry and not just stand there like a tool, and that can make it harder to go. Try using the stall to pee and just staying in there until you go no matter how long it takes. Then you can gradually inure yourself to going with other people in the room, and once you've mastered that you can go back to the urinal. Anchoress 06:41, 24 September 2006 (UTC)

This is called paruresis. There are a few ideas mentioned in the article. I find that discreetly tickling the tip of my penis (I'm assuming you're a man! Anchoress, I thought you were a woman!) stimulates it to function in this circumstance. Also taking an end or corner stall makes it easier.--07:26, 24 September 2006 (UTC)

Anchoress's answer and advice didn't make me think she was a man. Women often know more about men than men know about men.---Sluzzelin 07:35, 24 September 2006 (UTC)

How would a woman know about this particular problem may I ask? To my knowledge women do not indulge in communal urination whilst standing or whilst being watched. Do they?--Light current 03:08, 25 September 2006 (UTC)

And of course the advice about staying there till it flows is clearly ludicrous. Men who 'hang out' in toilets for longer than about 30 sec are viewed by other customers as highly suspicious (as they could be doing a George Michael.--Light current 03:17, 25 September 2006 (UTC)

If you're a man, how would you know (per your own statement). If you're a woman - yeah, right. :) Just imagine a guy stating that men understand women better than they themselves do. I think by now it's time for men's lib. DirkvdM 08:11, 24 September 2006 (UTC)

You're right in pointing that out. I probably should have written "Women often know more about men than I know about men." (which implicitly answers your implied question) :) ---Sluzzelin 08:20, 24 September 2006 (UTC)

There is a muscle involved during urination, and this muscle acts like a valve which controls the flow. It opens when it is relaxed, if I recall correctly. This point becomes important in the design of washrooms. For example, urinals with partitions between them offer more privacy than those without, which influences the washroom occupancy rate. --HappyCamper 17:31, 24 September 2006 (UTC)

How about closing your eyes and imagining you are all alone?--Light current 03:14, 25 September 2006 (UTC)

air conditioners

isn't it true that they make things warmer instead of colder because they have fans in them?

First you must understand that "cold" is not an actual thing. It is the absence of "heat". Air conditioners work by moving heat around. Air conditioners work by taking the heat out of a room and putting it somewhere else, usually outside of the building it is in. Air conditioners do have fans in them, and all electric motors generate heat, but this heat is insignificant to the temperature of the room. See the article on air conditioners for a more indepth response.--Russoc4 15:16, 24 September 2006 (UTC)

...And you could say the same about refrigerators. Anything that consumes energy converts some of it into heat.--Shantavira 16:12, 24 September 2006 (UTC)

Neither is "heat" an actual thing. It's merely the effect of the motion of particles. Those particles are still moving when there's "cold", but at a slower rate. Wouldn't it be just as true to say that heat is the absence of cold, as it is to say that cold is the absence of heat? JackofOz 23:30, 24 September 2006 (UTC)

I only disagree with one point made above. The amount of heat is in no way insignificant to the temperature cooling. In Tokyo (and other large cities such as Hong Kong), the air conditioning of large buildings creates what is being called here as a concrete island, because the heat released by AC exhausts cannot circulate properly when exuded into the city air (which is crowded with other buildings). The heat produced is significant, raising the temperature of the entire downtown region of Tokyo a few degrees just a few years ago.  freshofftheufoΓΛĿЌ  00:40, 25 September 2006 (UTC)

There's a number of reasons for this microclimate effect, though, beyond air conditioning. Cities absorb the sun's heat into brick, concrete and (especially) asphalt. Windows often act as mirrors, rereflecting solar heat. Automobiles produce loads of heat; an internal combustion engine is just a well-controlled continuous gasoline explosion. People tend to be warmer than air temperature, and Tokyo has it's fair share of people. --ByeByeBaby 03:12, 25 September 2006 (UTC)

Emphysema

My girlfriend is 14 (yes cute, I know) and she has told me that she has genetic alpha 1-antitrypsin deficiency, and that doctors put her life expectancy at 25 tops from pulmonary emphysema. She accepts it as a part of herself, has lost hope, and that she is going to die in less than ten years, however I have faith in medicine and am watching of developments in the area. I've done some research at PubMed and the like, and there doesn't seem to be anything she can do but take the weekly injections of the alpha 1-antitrypsin harvested from blood donors. She does not want to suffer any more past her projected death date. Lung transplant wouldn't work because, aside from possible death, it isn't a cure, because the problem is the deficiency not the smoking. I have seen liver transplant as a "cure," but every time it was specifically mentioned of the other problem of the liver not secreting the substances properly leading to concentration, then liver failure. I don't see why a liver transplant wouldn't fix the problem, because it is the liver that is not producing the alpha 1-antitrypsin. If the procedure worked out well would she be fine? She can't die before adulthood—that's unacceptable. Don't tell me to consult a doctor for medical advice, and don't tell me to read the article. I'm not a newbie. Thank you much. — X [Mac Davis] (SUPERDESK|Help me improve)16:20, 24 September 2006 (UTC)

When I read these sorts of posts on the Wiki, as a human being I want to reach out and offer you some sincere food for thought. However, there are many times where talking in person with someone more informed would be much, much more appropriate. It sounds like you are in a complicated and unique situation, and it sounds like you need to sit down and have a serious and genuine conversation with someone you trust. At minimum, you should feel that this person is capable of giving you mature insight with respect to your thoughts and concerns. I suspect you might find that process to be more meaningful than what could be offered over the internet. --HappyCamper 17:17, 24 September 2006 (UTC)

Life is almost unbearable sometimes, and this sounds like one. What would one do if he had 10 years to live? Before the 1920s, diabetics had less life expectancy than that, but insulin came along in time for some. With genetic engineering and stem cell research there is some chance of an effective long term treatment coming along over that time span, provided it is a disease receiving some research dollars. Be aware that today you can be more informed than some specialists in a field if you keep up to date on legitimate internet publications. Keep the hope for a cure or effective treatment alive, and enjoy each day. Ten well spent years can be better than 30 wasted ones.Edison 20:13, 24 September 2006 (UTC)

I have no useful advice, and I'm sure you, Mac, would be able to collect information about her disease much more efficiently than I. I just want to remind you to realize, on the other hand, that she has to live and deal with her deficiency, and it may not be easy for her to talk about it in a completely rational way, so you shouldn't force her to. Advances in science will continue whether she (or probably, her parents, for they are likely the most influencial authority figures to her on the subject of her health) pays attention or not. If it's an issue of "now or never", then nobody can stop you from trying to help, but if the only thing you can contribute are maybes and in the futures, you might just end up causing more strain on your relationship. It sounds unfortunate that she "doesn't want to suffer [live] past her projected death date". Maybe it's your duty to inspire her.  freshofftheufoΓΛĿЌ  00:35, 25 September 2006 (UTC)

She does not want to be alive in the hospital for months or years just to prolong her life, which is perfectly understandable. — X [Mac Davis] (SUPERDESK|Help me improve)03:34, 25 September 2006 (UTC)

Since you asked us not to, I won't suggest you get that important information from a person able to answer you the best, but if you aren't a newbie you should know that if an accurate and full answer fact-based answer is truly important to you, you won't get it here. If you aren't much older than your girlfriend, what you may need is the sympathy other editors have offered. From what little I know, I suspect your description includes at least one or two erroneous assumptions, but I don't whether the error(s) lie in your understanding of what she told you, her understanding of what she was told, or unusual features of her case (and of course, the erroneous assumptions may in fact be mine). Be skeptical and help her look for other perspectives. alteripse 00:43, 25 September 2006 (UTC)

Reading your description, the pessimism expressed by your girlfriend is out of proportion to my experiences with the disease. There are several reasons for this. First, the life expectancy (without knowing her degree of deficiency) is much closer to 40 years, especially if she does not smoke. Second, lung transplantation, while not a cure, is certainly a viable option that should not be taken off the table! Your instincts about liver transplantation are right on - if she develops liver failure and undergoes successful transplantation, she will not have to worry about the lung disease. Liver transplants are much more successful than lung transplants in the long term. As for options on the horizon, AAT deficiency is an attractive target for gene therapy. The small amount of enzyme needed to be replaced makes it likely that there will be therapy available to mitigate the lung disease within the next 15 years. The liver disease, obviously, will still have to be dealt with given the different mechanism of disease (though it is less predictable). All in all, it's a tough disease but one with many more options than seem to have been acknowledged! InvictaHOG 01:38, 25 September 2006 (UTC)

Thank you for everything—your comforting, advice, sincerity. The reason I said the two "Don'ts" are because I am already in the process of consulting several experts. About the liver transplantation, I am asking if a successful live transplant will cure it period, almost regardless of the situation. — X [Mac Davis] (SUPERDESK|Help me improve)

Diffusion & Concentraton

Why do molecules move from a region of high concentration to a region of low concentration?

Don't know if there is a more specific answer, but entropy seems to come into play. 1001001 16:46, 24 September 2006 (UTC)

Probability. Let's say the two regions are the same size and that there are 100 molecules in region A, only 10 in region B. Over time, Brownian motion moves half the molecules from one region to the other. So what happens? 50 move from A to B, while only 5 move from B to A. Clarityfiend 17:15, 24 September 2006 (UTC)

You can also talk about the concentration gradient in the system, which drives the system towards equilibrium. The "probability" explanation is related to results in statistical mechanics, whereas this one is more related to thermodynamics. Very interesting stuff might I add. Read up on chemical potential and the second law of thermodynamics too. --HappyCamper 17:20, 24 September 2006 (UTC)

There are lots of ways to think about your question....

The simple answer: it's a lot easier for a bunch of things to randomly spread out than to randomly come together. "Spreading out" = "moving from high concentration to low concentration". Another way to think of it is: Imagine a bunch of peanuts and a bunch of styrofoam together in a box that's continually shaking. Just because they're (pretty much) randomly moving around, the peanuts will tend to go where there aren't many peanuts, simply because they're going (they're moving from a place where they are to where they aren't).

If you want to ask another "why?", I think you start coming across things like "what is space?" and "what is a position?" and "why does time move towards the future instead of the other direction?" and "what is movement?". —AySz88\^-^ 01:29, 25 September 2006 (UTC)

Selectively-permeable membrane

A selectively-permeable membrane is made into a bag and is filled with a 5% sugar solution. The membrane is permeable to water but not to sugar. The bag is then placed into a glass containing a 10% sugar solution. What will happen to the size of the bag?

See osmosis. Hope you get an A. 1001001 16:48, 24 September 2006 (UTC)

Ask yourself what you think will happen to the concentration of the water, not just the sugar, and you will probably figure out the answer. Gary 17:43, 24 September 2006 (UTC)

Chemical composition of wine

What is it? From which elements/molecules/compounds does wine come from? --Fbv65edel / ☑t / ☛c || 17:48, 24 September 2006 (UTC)

Wine is not a chemical, it is a mixture of many ones, the flavours possibly from esters, the active compund would be ethanol. Philc _T^E_C^I 18:05, 24 September 2006 (UTC)

Aha. Thanks for your help. --Fbv65edel / ☑t / ☛c || 18:25, 24 September 2006 (UTC)

The most abundant chemical in wine is hydrogen oxide. --Lambiam^Talk 18:55, 24 September 2006 (UTC)

Hehe, fair enough, when I read that I thought you meant hydrogen per oxide, and I was thinking, "eh, that stuff pretty poisinous" shouldnt the hydrogen oxide page be a disambig between HO and H₂O? Philc _T^E_C^I 19:01, 24 September 2006 (UTC)

No I think you'ld become quite pale after drinking H2O2, and then you'ld dye! 8-)--Light current 03:36, 25 September 2006 (UTC)

I think you mean H₂O₂. There is also hydroxyl, which is the radical -OH. I don't think we need disambiguation. The term "hydrogen oxide" is not common. For increased jocular effect, use dihydrogen monoxide (DHMO). --Lambiam^Talk 19:31, 24 September 2006 (UTC)

Scientific American had an article on the chemistry of wine in the last decade or two. Very complex. You could probably search their online index, and then find the issue in a library or big city used book store. alteripse 00:24, 25 September 2006 (UTC)

Thin Layer Chromatography

I'm a little stumped here. We're going to use TLC in lab this week on a mixture of aspirin, acetaminophen, ibuprofen, and caffeine (all analgesics). I need to predict the R_f values for all 4 compounds. This means that whichever compound travels farther on the chromatography paper will have the higher R_f value. To do this I must determine the relative polarities of the molecules. I tried looking up water solubilites and I could either not find them or I found conflicting sources, so I have to resort to using the structure of each:

	Aspirin
	Acetaminophen
	Ibuprofen
	Caffeine

I think that aspirin and acetaminophen are more polar than caffeine and ibuprofen, but I'm not sure on the exact order of them, in decreasing polarity. Can anyone help me out? --Russoc4 18:19, 24 September 2006 (UTC)

Hmm...well, this is really an homework exercise, but some things you want to be concerned with, are the functional groups on each molecule, their relative size, and their relative solubility in the solvent you will be using. As a tip regarding aspirn and acetaminophen, there should be something about attachements to the benzene ring which would give the answer away...In particular, the -OH and -COOH parts. Come back if you have more questions :-) --HappyCamper 18:25, 24 September 2006 (UTC)

Well, on aspirin, there is a carboxylic acid and ester group on the same side of the benzene ring. On the acetaminophen, there is an amide and secondary amine on one side, with an OH on the other side. Does this mean that aspirin is more polar because they are on the same side? --Russoc4 18:32, 24 September 2006 (UTC)

Also, this website gives water solubilities in decreasing order as caffeine, ibuprofen, aspirin, then acetaminophen. The wikipedia article for caffeine says that it is slightly soluble while this website says its very soluble. Vague answers you give me here are not going to help much. Also, I don't consider a prelab like this to be as trivial as "homework". They expect us to research the topics and collaborate with others. --Russoc4 18:54, 24 September 2006 (UTC)

Let me tell you why I'm hesitating with this one. TLC depends on the solvent and on the solid phase. Are we using water here? It seems to be the case. TLC is a very flexible and powerful technique because you can play with both the solvent and the solid phase.

I find the ordering of solubilities given above a bit odd. Ibuprofen has a large organic group attached to the carboxylic acid. I would expect aspirin to be more soluble than ibuprofen, as it has more polarizable groups.

I keep on having this image of acetaminophen being a zwitterion in solution, but this seems unfavorable. If this were the case, in some sense it would be more "polar" than aspirin. I think the your initial reasoning you had isn't unreasonable. Think by analogy: which is more polar - cis-dicholoroethene, or trans-dichloroethene? I'd settle with aspirin for the same reason, but at the same time emphasize that from structural considerations alone, it should be expected that the bands would be close together. --HappyCamper 20:12, 24 September 2006 (UTC)

As someone said above, the solvent is pretty important (I'm assuming that you are using finely divided silica as the solid phase). If I were a lab teacher (still), I would use hexane as the solvent, as it would allow me to use shorter TLC strips, but I'm cheap that way. But you are more likely to be using a short organic solvent than water, so if you are going to look up solubilities and base your answer on those, then the water solubilities would probably tell you the affinity for the (polar) solid phase, whereas the the solubility in hexane will tell you how well that affinity will be "opposed".Tuckerekcut 20:25, 24 September 2006 (UTC)

It seems that the solvent is going to be 95% ethyl acetate and 5% acetic acid (which will be neither extremely polar nor extremely nonpolar). Also, we are going to synthesize aspirin, and will be given the other 3 to use as references in identifying the spots, but we still need to guesstimate the Rf values. I think I am going to list them as aspirin, acetaminophen, caffeine, then ibuprofen. --Russoc4 20:44, 24 September 2006 (UTC)

Note that the solvent above is not the stationary phase, which will be silica --Russoc4 21:15, 24 September 2006 (UTC)

something worth looking up for each will be the Partition coefficient, which will give you an idea of relative polarities. Xcomradex 22:09, 24 September 2006 (UTC)

I'm very familiar with this experiment, I assign it every year (though I only require my students to deduce the polarity information from their results!). Without giving the answer away, here are a few guidelines:

• The order of Rfs is independent of the eluent, and only dependent on the polarity of each molecule.
• There is no perfect number you can point to and say "That tells you the polarity. Remember, barium sulfate is much more polar than caffeine, but it's much less soluble! About the best things are partition coefficients (very hard to find) and for solvents you can use dielectric constant to some extent.
• The best way to judge polarity is to look at the balance of polar groups (O-H, N-H, C=O) vs nonpolar groups (C-H, C-C). If you have a lot of the former and few of the latter, your molecule will probably be pretty polar, and vice versa. This isn't perfect, because (as usual) things aren't as simple as that (this approach is flawed for at least one of the above molecules), but it would show a good effort if you try that.
• Acetaminophen does have a zwitterionic resonance form, and it is indeed minor, though it explains why an amide group is quite a polar group.

Some tips: Check that your spots are visible under UV before you run the plate (the ibuprofen doesn't show up well and often needs spotting several times), and don't pick up the TLC tank while the plate is running. Good luck! Walkerma 04:19, 25 September 2006 (UTC)

dc or ac?

At the same voltage, say 220 Volts, which is more dangerous to human beings. AC or DC?? Also, Which would be more fatal to humans, HVDC transmission lines or HVAC ones.nids(♂) 18:50, 24 September 2006 (UTC)

My phyics teacher always said its current that kills you not voltage anyway, but to answer the question, with AC the current is contantly passing through 0 so there would be less in total than with the same DC which is remains contstantly high. To answer question I assumed equal current. Philc _T^E_C^I 18:55, 24 September 2006 (UTC)

The current does reverse with ac, but you cannot therefore say that less cuurent is supplied. The rms current of the ac should be compared to the dc value to see which is greater. Im not saying that one isnt more dangerous than the other though.--Light current 00:07, 25 September 2006 (UTC)

I elaborate my question. Consider Human body to be a form of resistance. Take R dc= R ac for the moment, (even though there is a difference by the factor of 1.2). Now a person accidentaly touches a AC power line with 220V supply, and another one touches a DC power line with 220V suppy. Which one of them will be more fatally injured.nids(♂) 19:02, 24 September 2006 (UTC)

You can't be "more" or "less" fatally injured -- that's like being "a little bit pregnant"! :-) —Steve Summit (talk) 20:40, 24 September 2006 (UTC)

I thought there was a difference between the level of fatal injuries and Pregnancy.:)nids(♂) 20:52, 24 September 2006 (UTC)

I used to think that pregnancy is like a step function, but injury is like a continuous function, where we can have different levels.nids(♂) 20:54, 24 September 2006 (UTC)

You can't be "somewhat fatally injured". In terms of how life-threatening injuries can be, "fatal" is the top level. --Lambiam^Talk 21:06, 24 September 2006 (UTC)

It seems you dont know what fatal means, well it means causing death. And Lambiam has a point in saying your dead or youare arent, you cant be more or less dead. Hope that clears things up. Philc _T^E_C^I 22:17, 24 September 2006 (UTC)

Ahem! But to try to answer the question, one may consider 220 vac to be more dangerous becuase its peak value is 311V and is therefore more likely to drive higher peak currents through the body than 220v dc. But I think the distinction is pretty pointless as the current derived from much lower voltages (eg even 9v directly across the heart muscle or applied below the skin surface) can be lethal.--Light current 00:16, 25 September 2006 (UTC)

Based on what is written about this in our articles War of Currents (see in particular the section "Edison's propaganda") and Electric shock (see "Issues affecting lethality"), the verdict appears to be inconclusive: both are about equally dangerous. --Lambiam^Talk 19:06, 24 September 2006 (UTC)

Thanks for the link to Electric shock. But i think that there should be some conclusiveness now, atleast after a century after the debate started. Thanks anyways.nids(♂) 20:15, 24 September 2006 (UTC)

Thomas Edison's demonstrations were pretty conclusive that at voltages such as this AC is more deadly. Many animals, dogs up to elephants, were tested. This is not to say that 220 DC is even remotely safe. When you are talking HV such as 138kV, 500kv, etc, I expect that either would be quite deadly, that is, I would not expect anyone to survive even momentary contact, because of the arcing and burning and the enormous current in the fault through the victim having an explosive effect. A charred hunk of burned flesh would likely be all that was left even if the fault were interrupted as quickly as 6 cycles.Edison 20:22, 24 September 2006 (UTC)

Your namesake went overboard in his attempts to demonstrate that DC was safer than AC. Can we be sure the experimental set-up of his demonstrations was bias-free? --Lambiam^Talk 20:50, 24 September 2006 (UTC)

Yes, he was my Teacher's Teacher, and he did not lie as to the truth of electricity. Edison 04:21, 25 September 2006 (UTC)

One thing I read that seems plausible; if you grab a live wire with AC you can let go, whereas with DC the current will override neuromuscular control such that you can't let go--the muscles are clamped tight. Very bad. --GangofOne 21:03, 24 September 2006 (UTC)

I know people who grasped 240 V AC and could NOT let go. So we learned to touch it only with the BACK of the hand to avoid the involuntay contraction of the musculature. As always, do not try this at home.Edison 04:24, 25 September 2006 (UTC)

So considering these effects, can we say that DC is more dangerous (if not fatal).nids(♂) 21:29, 24 September 2006 (UTC)

No, you can't. It's an ill-formed question. The voltage and frequency both enter in to it. At some voltages, it's true, DC induces a neuromuscular grab reflex making it impossible to let go, so DC could be said to be more dangerous at those voltages. At some voltages and frequencies, the inductive coupling of AC will be more effective at inducing disruptive currents in the heart muscle and inducing cardiac arrest, but at other voltages and frequencies, it might be less effective (particularly due to skin effects). At really high currents and voltages, the burns will kill you whether your heart stops or not.

I think that ac also induces a neuromuscular grab reflex making it impossible to let go. Any induced currents in the heart due to current traversing some other path will be minisule and can be neglected. We dont have a transformer here just a big, slightly resistive, blob with some nice conducting channels (blood vessels). So if I sent some current from one of your feet to the other foot, most of it would go via the groin area. Nothing of any significance would be 'induced' in the heart. I therefore doubt that this form of electro'cution' would cause immediate death whatever the current. --Light current 00:24, 25 September 2006 (UTC)

The bottom line is that electricity is potentially dangerous (that's a little punny joke there, but it's true) and can kill you, period. The question of whether AC or DC is more dangerous probably wouldn't even come up if it weren't for those old, historical current wars. If you're asking out of curiosity, please settle for this. If you're asking because it's a homework question, ask your teacher which book's ill-founded pronouncement on the question your teacher considers "correct", and use that. (Or if you're courageous enough, tell your teacher that the question is ill-formed and that you refuse to answer it, and explain why.) —Steve Summit (talk) 21:56, 24 September 2006 (UTC)

This question was out of my curiosity. The frequency for the AC 220V is the normal 50Hz that is supplied(In the countries with 220V distribution). I dont trust my teachers and i have seen the consequences of correcting them. Some of my outstanding Physics teachers didnt even had their basic concepts clear. One of them went out of the way in explaining that AC is more dangerous in all circumstances and they also gave absurd reasons for that, but i know that they were wrong. Now, I dodnt even bother to correct them. I thank you all for the great response.nids(♂) 22:56, 24 September 2006 (UTC)

One more point I didn't mention is that in one respect, 50-60 Hz is said to be the most dangerous frequency you can use, i.e. one of the nasty AC effects is apparently magnified, for organisms of our size, at about that frequency range. (But I don't remember the details.) —Steve Summit (talk) 23:09, 24 September 2006 (UTC)

I havent heard that, and I cant think of a reason why it should be so. THe only thing thet could be magnified is the current, and since the body is basically resistive (not reactive) that aint gonna happen. Unless its to do with a heart preffered fibrillation frequency 8-)--Light current 00:29, 25 September 2006 (UTC)

Oh well maybe not:

Ventricular fibrillation, despite its appearance as a random waveform, has a clear dominant frequency with a narrow bandwidth and a peak in the power spectrum around 9 to 12 Hz, which changes with time, drugs and ischaemia.--Light current 00:34, 25 September 2006 (UTC)

Please believe this: AC or DC can be lethal, even at voltages below the 220 V described here. Thomas Edison and his henchmen proved that at various voltages such as 120V, 240V, and 400V, AC was more likely to cause sudden death than DC. But 200 V DC can cause grevious burns. A funny difference between DC arcs and AC arcs, based on observation, at voltages above 120 V: AC hums, while DC hisses.Edison 04:33, 25 September 2006 (UTC)

pyrex comosition

sorry if this appears to be a repeated question i did not put a heading last time. Does anyone know the chemical compostion of pyrex, like water is h20, as it did not have it on the article, just a chart. I need it for work.

Pyrex is a brand name for borosilicate glass (I wrote that before even reading the pyrex article). It is "about 70% silica, 10% boric oxide, 8% sodium oxide, 8% potassium oxide, and 1% calcium oxide" (that part i copied). Don't forget that this is an encyclopedia, just type in "pyrex" or "borosilicate glass" into the search pane to get more info.Tuckerekcut 20:13, 24 September 2006 (UTC)

Also, glass is amorphous, so it doesn't have repeating crystal structure. Nor is it a pure substance, It is more of a mixture, so there is no precise chemical formula. That would be like asking for the chemical formula of milk.Tuckerekcut 20:17, 24 September 2006 (UTC)

not all glasses are mixtures though, eg. fused quartz. Xcomradex 22:04, 24 September 2006 (UTC)

cell biology: cytolysis vs. plasmolysis

We got any cell biologists here? Can someone go over to the Lysis article and figure out what the right thing to do is with this note someone tacked on at the very end (down beneath the "See also" section):

Correction from mentioned above. In a hypertonic environment, plasmolysis occurs, which is nearly the complete opposite of cytolysis that occurs in hypotonic environments. Cytolysis does not occur under normal conditions in plant cells because plant cells have a strong cell wall that contains the osmotic pressure, or turgor pressure, that would otherwise cause cytolysis to occur.

Thanks. —Steve Summit (talk) 20:36, 24 September 2006 (UTC)

I'm not a cell biologist, but I gave it a try. --Allen 02:56, 25 September 2006 (UTC)

Managed Care

Does a physician "gatekeeper" work for or against the patient? 207.200.116.204 21:06, 24 September 2006 (UTC)

It depends on whether they have taken a Hypocritic Oath :)  --Lambiam^Talk 22:53, 24 September 2006 (UTC)

Is this homework? The intent of course is that they will work "for" the patient to obtain necessary medical care while preventing access to "unnecessary" care. Even when performed in good faith and honesty, there are at least two potential problems: (1) a patient may not always agree with what his/her doctor deems unnecessary care, and (2) if the financial incentives are strong enough to limit care, they will corrupt judgement and tempt the physician into having to choose between deciding on behalf of the patient or on behalf of the insurance company. The high tide of strict gatekeeping in the US was in the mid-1990s when some managed care companies directly subtracted the costs of consultation and tests from the amount that would be paid annually to the primary physician: i.e., any service the patient needed that he could not provide was in a sense directly charged to him. After some scandals and lawsuits this form of gatekeeping has been largely abandoned in the US, and few managed care companies penalize primary physicians for seeking specialist consultations or tests. The newest form of managed care interference with medical decisions is "performance pay", where doctors are judged by various objective measures of the care of their patients and are rewarded or penalized by how they rank (or patients may be penalized for seeking care from a doctor who ranks more expensively). Sounds OK until you think for a minute what it means if your doctor has to decide whether treating you is likely to help his statistics or hurt them, since every system like that will be "gamed" and it is not always easy to judge good medicine by countable parameters. alteripse 00:20, 25 September 2006 (UTC)

The issue of circumcision is notable here. Long story short, several different groups have supported it (many times for hidden motives), and now the physicians are the most prominant. Because they make several hundred to a thousand dollars per circumcision. The reality in the United States now is more "do you want your child's penis to fit in" rather than saftey. — X [Mac Davis] (SUPERDESK|Help me improve)03:38, 25 September 2006 (UTC)

Don't embarrass yourself-- you have no idea what you are talking about and you are flat wrong. Do not listen to propaganda from the circ/anticirc warriors. alteripse 03:41, 25 September 2006 (UTC)

Thermodynamics

I am trying to help my son with his homework and I am lost. Use the laws of thermodynamics to defend the statement that 100 percent of the electrical energy that goes into lighting a lamp is converted to thermal energy. Please help. Thanks!!!

At the lightbulb a part of it is converted into light and the rest into heat (thermal energy). My guess is you simply have to say that when the light hits an object it is converted into heat since the energy cannot magically leave the system. - Dammit 21:24, 24 September 2006 (UTC)

Even light is a form of Thermal energy with wavelength less than 700nm. So all the electrical energy is actually converted to thermal energy.nids(♂) 21:26, 24 September 2006 (UTC)

Or perhaps you are after the first law of thermodynamics, particularly conservation of energy. Xcomradex 22:00, 24 September 2006 (UTC)

Use the first law of thermodynamics plus the fact that the internal energy of the lit lamp (once it is up to temperature) is constant. So the increase in the internal energy of the system is zero. Then you have: heat in = work out. Or, in this case: heat out = work in. In a formula: $\Delta Q=\Delta W\,$. The heat energy given off to the environment is therefore equal to the electrical energy input. --Lambiam^Talk 22:50, 24 September 2006 (UTC)

copper

What is the purpose of a layer of copper or aluminum on the bottom of stainless steel cookware?

It helps in proper dissipation of heat, since copper is a much better conductor of heat than steel.nids(♂) 21:27, 24 September 2006 (UTC)

Thermal Conductivity - note the relative positions of copper, aluminum, and stainless steel on the Thermal Conductivity chart. 71.96.28.140 21:30, 24 September 2006 (UTC)

Ideally the entire piece would be made of copper/aluminum, but that would bring the price way up.  freshofftheufoΓΛĿЌ  00:15, 25 September 2006 (UTC)

Why do I have so much trouble picking up women in bars?

I'm really into attractive older women (say 40-ish, blonde and MILFy) but I never seem to have much luck. I'm 19 and they never seem to take me seriously, even when I turn on the charm (I'm pretty good at 'pulling' women of my own or similar age). Any tips? --84.69.92.146 22:18, 24 September 2006 (UTC)

You're asking about this on Wikipedia? No wonder why they don't take you seriously. :P I'm not sure if us Wikipedians should either. :-) --HappyCamper 22:54, 24 September 2006 (UTC)

We don't tend to shy away from questions here, so give him a chance. The obvious reason has to do with motives. Women in their 40s generally aren't searching for a sex-relationship (that does not mean they don't want to have sex). Women in their 30s and 40s, if single, straight, and within the range "average" personality types, often would seem to be more interested in things like marriage, commitment, and security (i.e. money). Since it's difficult to see any of these things in a 19 year old man, they do not treat you seriously. Men tend to seek entirely different things, a lot of them being related to boobs. It is probably an instinct left over from our animal days, when a strong and reliable male was required to protect the female and her babies, and the more well-established the male, the better. Even successful women -- i.e. those who have established a level of security and a stable career for themselves -- seem only to be interested in successful men. If you really can't get off on anybody under the age of 30, try hanging around divorce groups and places where women complain about their fat, balding husbands.  freshofftheufoΓΛĿЌ  00:12, 25 September 2006 (UTC)

Yeah, youre just too young, poor, inexperienced, unsophisticated etc to attract these women.--Light current 00:38, 25 September 2006 (UTC)

Very simply, what charms 19 year old women is unlikely to charm 40 year old women, especially since they will almost certainly see through any element of deception. (Not accusing you of dishonesty, "charm" is always full of deception and disrepect.) (The 19 year olds see through it, too, but they might be flattered by it; 40 year olds will need a lot more to be impressed.) Peter Grey 02:21, 25 September 2006 (UTC)

The Fundamental Equation of Sex: 19 goes into 40 more times than 40 goes into 19. This should work in your favor. Edison 04:38, 25 September 2006 (UTC)

Have you considered using the internet to find the kind of person you're looking for? There are undoubtedly women of that age interested in having relationships with much younger men, but tey probably make up a smaller number of them. With the internet, you can narrow down your search to just that fraction that might be interested in a relationship with a 19-year-old. --Robert Merkel 04:45, 25 September 2006 (UTC)

Pffffft. I'm almost 40, blonde, etc etc, but I would NEVER consider someone who'd refer to me as 'MILFy'. And believe me, at our age, we can tell when that's what you're thinking, even if you don't say it. Get a little bit of respect for your elders, stop even thinking of us in those objectifying terms, and maybe we'll go to bed with you. A tip: at our age, we've learnt that the most important thing in a sexual or romantic relationship is respect. And we can tell if we're not getting it. And anyone who'd call me a MILF doesn't qualify as respectful in my book. Anchoress 04:59, 25 September 2006 (UTC)

Let me tell you how to pick up 40 year old chicks! Now listen up.

• take a $100 bill and wave it in front of her.
• take out a cigarette lighter and burn the $100 bill.
• tell her "Wait. There's more."
• burn another 12 $100 bills in front of her.
• Tell here you want to take her for a ride in your brand new Porche.

Easy! 202.168.50.40 05:02, 25 September 2006 (UTC)

Again, Pfffffffft. I'm not a hooker, but I'd be more likely to go to bed with him if he gave me the $1300. Like I said, respect. And a dude who doesn't respect his own hard-earned cash isn't gonna get any poontang from me. Anchoress 05:04, 25 September 2006 (UTC)

static and dynamic lung volumes

Can you define static lung volumes and dynamic lung volumes?

I don't know what this is, but maybe you could find something from a medical dictionary? Maybe this would be of help. --HappyCamper 22:56, 24 September 2006 (UTC)

Dynamic lung volume refers to a partial lung volume which can be inhaled or exhaled in a certain amount of time. An often used Dynamic volume is the FEV1, which is the amount of air expired in the first second of expiration. Static lung volumes refer to the volumes of air inhaled or exhaled without reference to time, such as the tidal volume.Tuckerekcut 23:07, 24 September 2006 (UTC)

plasma (4th type of matter)

why are substances on earth found in the state of plasma?

You didn't like any of the examples listed in our Plasma article? —Steve Summit (talk) 23:05, 24 September 2006 (UTC)

A source for bimetal strip coils

I am looking for a company that sells the bimetal coils that are used in old thermostats. I am tinkering with something and need a bimetal coil to regulate temperature, but don't want to spend $20 on a thermostat just to scavenge a bimetal strip(the whole thing probably won't cost $20). Preferably copper-steel, but I'm not picky. --Crazy Wolf 23:02, 24 September 2006 (UTC)

Can you not make your own by spot welding a strip of copper to a strip of steel?--Light current 23:51, 24 September 2006 (UTC)

I'd prefer buying them so that they are all the same shape and reactivity. --Crazy Wolf 00:07, 25 September 2006 (UTC)

i would imagine is probably cheaper to rip apart the thermostat. what you want sounds specialised, which means people will make you pay through the nose for it in my experience. Xcomradex 01:44, 25 September 2006 (UTC)

Castrated ejaculation?

When a castrated adult (with testes removed) ejaculates, the liquid that comes out is clear and a lot more thin (not globby). What is it exactly? Something is definitely missing, since the testes are not present. What remains in post-orchidectomy ejaculate?--Sonjaaa 23:19, 24 September 2006 (UTC)

Semen sans sperm?

from page on semen The bulk of the semen is composed of seminal plasma, the fluid portion of semen. This fluid is contributed by the accessory male reproductive organs. Some 60% of the volume of ejaculate is produced by the seminal vesicles, and most of the remainder is generated by the prostate. A small amount of viscous mucus secreted by the bulbourethral glands contributes to the cohesive jelly-like texture of semen. --Light current 23:52, 24 September 2006 (UTC)

Treatment of MCAD

How is MCAD treated? The article doesn't say. Also, is it impossible for people with MCAD or similar diseases to lose fat? Jack Daw 23:57, 24 September 2006 (UTC)

The treatment of MCAD deficiency consists primarily of avoiding prolonged fasting and stress-induced catabolic states in early childhood. In other words, IV glucose is used in the event of a vomiting illness. There has been some advocacy of supplemental carnitine on theoretical grounds, but this is not universally recommended and there have been no conclusive studies to support it. Risk of metabolic decompensation and acute liver or heart failure seems to decrease with age. alteripse 00:05, 25 September 2006 (UTC)

September 25

Aeroplane advertising

Occasionally you see aeroplanes advertising by towing banners behind them. The banners always seem to stay vertical, rather than twisting and turning in the wind as you might expect - is this due to particular aerodynamic properties of the banner, or just the way it's attached to the plane?

Thanks, --Noodhoog 02:20, 25 September 2006 (UTC)

Very high SPLs at bass frequencies

Can very high SPLs (>100 dBA)at bass frequencies induce heart palpitations?--Light current 03:53, 25 September 2006 (UTC)

That is the goal, and yes. Edison 04:40, 25 September 2006 (UTC)

Force Dynamics

Problem: 'A box is given a push so that it slides across the floor. How far will it go, given that the coefficient of friction os .20 and the push imparts an initial speed of 4.0 m/s?'

...i don't see how i can solve this if i am not given the mass of the box.

Neither do I! 8-)

Go ahead and try the problem anyway, substituting "M" where you'd otherwise put the mass of the box. The M's should cancel out. --Allen 04:06, 25 September 2006 (UTC)

God, I hated freshman physics!Edison 04:41, 25 September 2006 (UTC)