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November 25

Frolov (the inventor of the Frolov breathing apparatus)

The Wikipedia disambiguation page for "Frolov" does not indicate which, if any, of the Frolovs listed is the inventor of the Frolov Breathing apparatus (for which Google provides numerous entries, but nothing quickly seen that shows a first name or gives any biographical information). Can the author of the Frolov disambiguation page (or anyone else) provide an answer? I started out on this search to get some sense of the reliability (or value) of the device, for which most of the info readily available on the Web is either out and out hype for the product or testimonials of dubious value. A bio of the inventor would help instill confidence (or lack of it) in various health claims for the device. One related issue: A Russian language article pushing the device claims (rather unbelievably, I thought) that 200 years back earth's atmosphere contained 38% oxygen rather than the 19% it contains today,and that human organisms were intended to live under such conditions. That claim was what first made me skeptical about the whole thing, in part because, even if the claim about atmospheric composition were true, human organisms go back tens of thousands of years, not 200. I would welcome comments on all of this. TIA T —Preceding unsigned comment added by Jkwikijk (talk • contribs) 00:42, 25 November 2008 (UTC)[reply]

Yea, the time frame seems way off for the higher oxygen level. It should be more like 200 million years ago. It's hypothesized that higher oxygen levels may have allowed larger land animals to exist. Any animal so large now would have to move slowly or wouldn't be able to get enough oxygen. StuRat (talk) 01:20, 25 November 2008 (UTC)[reply]

Czarek Tomczak (talk) 10:16, 2 April 2014 (UTC) See the Buteyko breathing technique that is somehow related to how Frolov device works. This is the only wikipedia page I could find.[reply]

Chicken head movement

As in this video, is there a good reason why chickens hold their heads like this? Nadando (talk) 03:11, 25 November 2008 (UTC)[reply]

One evolutionary advantage is that by being able to keep its head stationary while walking, the chicken could easily detect movements in its surroundings. This is useful both for avoiding danger and for finding prey. --Bowlhover (talk) 06:54, 25 November 2008 (UTC)[reply]

Also, when they walk, they keep their heads completely stationary and then jerk it forward very fast. This allows them to use parallax to provide depth-perception, mimicking other animal's two forward-facing eyes. — Sam 96.237.124.247 (talk) 14:00, 25 November 2008 (UTC)[reply]

Its funny, I read the title of this thread, and I thought: its because the guy is going to pay her. Am I alone on this, or did anyone else chuckle at the title?!? --Jayron32.talk.contribs 21:04, 25 November 2008 (UTC)[reply]

It appears as though you are alone. 3/23/10

Three colors in a LCD projector

This happened when I was attending a seminar. As a staff, I was sitted on the far side of the projector so I could see the glow of the projectors lens. When I trailed my eyes, I momentarily see the lens's light trailing distinct sections of red, green and blue not blurry and blended like a rainbow. I repeated the eye movement from left to right and right to left and the same result happens. I think that the trailing effect is like making light figures by twirling a flashlight. However, I can't explain the fact that the light "scatters" into sections. I'm pretty sure that I did not eat magic shrooms for breakfast or licked a poison toad so I think I'm sane that time.--Lenticel ^(talk) 05:29, 25 November 2008 (UTC)[reply]

What you saw was probably a DLP projector. Single-chip DLP projectors actually use a rotating color wheel to create RGB color, so they're showing the colors not quite at the same color, but one after the other in sequence. If you look past it really quick you'll see a rainbow effect. (In my experience, a small minority of people seem to be really bothered by this effect, but most of us don't notice it in the projected image unless we're moving our eyes back and forth like crazy.) APL (talk) 06:48, 25 November 2008 (UTC)[reply]

A good read. I think a learned a thing or two regarding projectors.--Lenticel ^(talk) 08:01, 25 November 2008 (UTC)[reply]

What's going on here is actually rather cool. TV's show a sequence of still images - we all know this. A 'conventional' cathode ray tube TV shows the red, green and blue images simultaneously. But a projector (unlike a regular TV) shows an entire image in red, then an entire image in green then an entire image in blue. Then the picture clicks over to the next still picture. The reason this is a problem is the cool part. When our brains see a fast sequence of still pictures, we don't just kinda fail to notice that the images are still - we actually EXTRAPOLATE the in-between images in our heads - we imagine that the image is moving smoothely by calculating where everything would be between the still images we were shown. This is a useful visual trick - imagine the caveman running after a rabbit with a rock in his hand intent on rabbiticide. All the time he can see the rabbit, he can estimate where to throw the rock in order to bring it down. But if you were in a forest with the rabbit darting in and out of the trees, you'd keep in losing sight of it (not unlike the gaps between the still images of the TV picture)...so your brain extrapolates the position of the rabbit so we know (roughly) where it'll reappear and we'll still be able to hit it with the rock.

OK - so we're extrapolating. That means taking the position of the object at time t₁ and the position at t₂ - and from that we can figure out the position at time t₃. But with the projection TV - drawing a new Red/Green/Blue picture every 16 milliseconds, the green colored version of a moving object is at the same position as the red colored version - but about 5 milliseconds later in time. The blue version is also in the same place but 10 milliseconds later in time. So our poor brains can't extrapolate the position of the R, G and B images as if they were one moving object - it doesn't make sense for an object to sit still for 10 milliseconds...then jump forwards within 6 milliseconds...then stop still for another 10 milliseconds. Real world rabbits just don't stop dead behind trees like that. So the best interpretation our brains can come up with is that there are actually THREE completely different objects - one red, one green and one blue - each of them is only visible briefly, once every 16 milliseconds - but that's OK - we've evolved to deal with that.

So - when the object moves quickly - it 'breaks up' into three separate objects and 'reforms' into a single object when it slows down again. You don't notice this when you watch a regular TV image - because the camera has a certain amount of motion blur - so that objects tend to be so streaky/blurry at that speed that you really can't accurately get a position for it - and the color separation is MUCH less noticable.

BUT - if you move your head/eyes quickly across the screen - the object is moving across your visual field very quickly - and you see the 'breakup' effect.

The exact same thing happens in computer games (where there is often no motion blur) if the computer can't manage to update the graphics at the same rate that the monitor repaints the picture. Even if you're viewing it on a CRT monitor. If the monitor refreshes 60 frames a second - and the computer only recalculates at 30 frames a second...then moving object 'stay still' for two 60Hz frames - then jump forwards. Again, it seems wrong and our poor brains see two objects chasing each other across the screen. If the computer falls back to 20 frames a second then you MAY see three objects tracking along...but at about 15 frames a second, our visual system realises what's going on and we see a single object moving jerkily. But the frequency at which this happens varies from person to person and depends on the lighting conditions...and all sorts of other things.

Another problem with 'sequential' color displays is what happens when you blink. If you blink quickly you may miss one or two of the three colors. This can result in the entire screen flashing cyan, magenta or yellow (if you blink really quickly and miss one color) or red, green or blue (if you blink more slowly and miss two colors). I personally find this REALLY annoying...but a lot of people don't seem to notice it at all...perhaps they have slower eyelids?!?

SteveBaker (talk) 01:29, 26 November 2008 (UTC)[reply]

you misspelled interpolate —Tamfang (talk) 06:32, 26 November 2008 (UTC) [reply]

Are you trying (tangentially) to tell me that you think I should have said 'interpolate' instead of 'extrapolate'? If so, then you need to explain why because I thought very carefully about which word to use - and 'extrapolate' is (IMHO) the correct one in this context. If we were 'interpolating' we'd see the image at t=0 and again at t=1 and from that, figure out where the object was some time in the past at t=0.5 (say). That's not what the brain does because the position at t=0.5 isn't very interesting anymore. Instead we're taking the data from the images at t=0 and t=1 and using that to figure out where the object is right now - at t=1.5...not where it was back in the past. There are some rather subtle experiments that show this. That being the case, the correct term is 'extrapolation', not 'interpolation'. SteveBaker (talk) 20:31, 26 November 2008 (UTC)[reply]

If the question is "where the rabbit is now", yes, that's extrapolation. My eye was caught by the emphatic phrase "we actually EXTRAPOLATE the in-between images"; a point beyond the endpoint(s) is not in-between, is it? —Tamfang (talk) 23:59, 4 December 2008 (UTC)[reply]

Black holes

Hi, i was just curious as to what would happen if you put a man inside a black hole? I guess the force of gravity might crush a person? but if so, what would happen to the debris?? 79.75.233.111 (talk) 07:19, 25 November 2008 (UTC)[reply]

For the love of God, Montresor!!! --Dr Dima (talk) 07:45, 25 November 2008 (UTC)[reply]

Literary references will not be tolerated (or understood, anyway) on the Science refdesk. Scray (talk) 11:51, 25 November 2008 (UTC) [reply]

Check out Black hole#Effects of falling into a black hole for the ~~gruesome~~ technical details. It looks like spaghettification might get you first. However, if you can avoid that, this describes how to prolong your remaining time. Clarityfiend (talk) 07:50, 25 November 2008 (UTC)[reply]

Spaghettifiction is very significant for stellar mass black holes (ie. ones formed when a big star dies). For supermassive black holes (such as are at the centres of galaxies) you can get far inside the event horizon before the tidal forces become significant, eventually they will get you though (infalling radiation that's been blueshifted to very high energy x-rays and gamma rays might get you first, though, I can't remember the details). --Tango (talk) 13:33, 25 November 2008 (UTC)[reply]

Fingerprints in electronic devices

Does fingerprint's locks (see here). also work with amputated fingers? Mr.K. (talk) 12:01, 25 November 2008 (UTC)[reply]

Yes, and with special rubber-cast copies. There's ongoing research to develop an alternative that uses infrared light and recognizes the unique pattern of blood vessels in the hand instead. EverGreg (talk) 13:19, 25 November 2008 (UTC)[reply]

After googling this a bit, it seems there's already blood-vessel readers on the market. EverGreg (talk) 13:22, 25 November 2008 (UTC)[reply]

Follow-up question And what would happen is a loose my password? How would I be able to access my data?Mr.K. (talk) 17:14, 25 November 2008 (UTC)[reply]

That's not really the worst problem. The difficulty is that making a functional copy of a fingerprint (lifted - for example - from the nice shiney surface of someone's car while they are inside that supermarket with the fingerprint scanner at the checkout). You can grab the print using your cellphone camera for example...you'd never get caught doing it. Edible gelatin fake fingertips can then be manufactured using only the stuff you'd find in a typical kitchen - the instructions are all over the Internet. If it looks like you might get caught using one - you stick the finger in your mouth and eat it! So - the REAL problem is how will you cope with the fact that criminals are using your fingerprint for identity theft! Now you really CAN'T change your 'password'. Fingerprint readers are a dumb idea. I strongly advise everyone to avoid them like the plague! SteveBaker (talk) 00:59, 26 November 2008 (UTC)[reply]

Its even easier than that. Mythbusters fooled a fingerprint reader with nothing more complicated than a decent scanner and printer. Lift the print in the standard manner (fine black dust and scotch tape work quite well), copy it onto the computer, and play around with the contrast levels in the copy. They were able to fool the scanner without much problem. Some of the more advanced fingerprint scanners have sensors for temperature and/or pulse detection (to prove its a live person), but the most common ones don't... --Jayron32.talk.contribs 04:06, 26 November 2008 (UTC)[reply]

The photographic approach doesn't fool the temperature and pulse detectors - or the ones that measure skin conductivity. But it's easily possible to fool even the super-fancy devices with a thin gelatin-molded fingerprint stuck to your real finger. Temperature, pulse and conductivity readings are close enough to fool the detector into making a reading of the print - and the print matches perfectly so it lets you in. Do a google search for fake fingerprints or something - you'll find sites where people have gotten through the most expensive military-grade fingerprint scanners that way. These devices are practically useless for anything but the most casual use. SteveBaker (talk) 20:08, 26 November 2008 (UTC)[reply]

To directly answer, though, if you lose your finger, you regain access the same way as on any other system you lose a password to. Specifics vary by the service in question, but most stuff has some sort of recovery mechanism. — Lomn 14:11, 26 November 2008 (UTC)[reply]

Logic Gates

Is there any single Integrated Circuit(IC) which can implement all the logic gates? —Preceding unsigned comment added by 210.212.192.18 (talk) 12:03, 25 November 2008 (UTC)[reply]

Yes -- though the question appears backwards from the norm. An IC is a much higher level construct than a logic gate, as anywhere from a few to a few billion gates compose an IC. I'm more familiar with questions like "what's the minimum subset of logic gates required to construct all other logic gates?" or "what's the minimum subset of logic gates that is functionally complete?" (a rephrasing) — Lomn 13:58, 25 November 2008 (UTC)[reply]

I think an IC that included all the logic gatss would have to have an AND, an OR, a NAND, and a NOR. —Preceding unsigned comment added by 98.16.67.220 (talk) 22:54, 25 November 2008 (UTC)[reply]

NAND alone is a base of propositional logic, as is NOR. Obviously, then, NOT and AND or NOT and OR are also bases. NOT, AND, OR is the standard base. The proof is fairly simple with an induction over the construction of propositional formulas (=digital logic circuits). --Stephan Schulz (talk) 23:09, 25 November 2008 (UTC)[reply]

The question asked about gates in an IC. There is no such thing as a NOT gate in an IC. In fact, it is a contradiction in terms to talk about a NOT gate - how can it be called a gate when there are no open-shut conditions? —Preceding unsigned comment added by 98.16.67.220 (talk) 00:34, 26 November 2008 (UTC)[reply]

Eh? What?!?! There are plenty of chips that perform the NOT function - we typically call them "INVERTERS" - but the logic function is there - you feed in a 'true' and out comes a 'false'. You feed in a 'false' and out comes a 'true'. That's the definition of NOT! In fact, that 4011 quad NAND chip pictured here is easily used as a NOT gate. Just take your input signal and wire it to BOTH inputs of one of the gates (pins 5 & 6 for example) and the output (pin 4) will be the NOT of the input. SteveBaker (talk) 00:51, 26 November 2008 (UTC)[reply]

An inverter isn't a gate. A gate requires at least two inputs. When these inputs meet the required conditions, the gate opens or closes, and the output changes. These conditions are indicated by the name AND or OR. If all the inputs to a gate are connected together, it is no longer a gate - it is an inverter or a non-inverting driver.

That's utter, utter, utter bullshit! To quote from Logic gate: "A logic gate performs a logical operation on one or more logic inputs and produces a single logic output." - the article talks about NOT gates all over the place! We even have an article with the title "Inverter (logic gate)". Check out this data sheet from Integral: www.alldatasheet.com/datasheet-pdf/pdf/126173/INTEGRAL/IN74AC04.html - it's entitled "IN74AC04 - Hex Inverter High-Speed Silicon-Gate CMOS". A google search for "Inverter gate" produces 200,000 hits. I used to be a hardware designer - I built massively complicated graphics chips from the early 1980's into the mid 1990's and I've never heard anyone say that an inverter isn't a gate. What makes something a 'gate' is that the signal has to cross some threshold to trigger it...as opposed to (say) an analog inverter which produces a continuously varying output for a continuously varying input. Pah - you speak nonsense! SteveBaker (talk) 20:23, 26 November 2008 (UTC)[reply]

>IN74AC04 - Hex Inverter High-Speed Silicon-Gate CMOS< isn't at all an example of what you're trying to prove. "Silicon-gate" in this case has nothing to do with a logic gate, it's the gate electrode of a field effect transistor. In some CMOS fabrication technologies the gate electrode of a FET is fabricated with doped polysilicon (rather than a metal oxide), hence it's a "silicon gate". While of course FETs can be used to construct logic gates, they can as easily be used to make analog circuits. ([1], [2]) 87.115.77.76 (talk) 22:15, 27 November 2008 (UTC)[reply]

And you'll kindly note, Steve, that I've not sneered or belittled or abused you the way you have 98.16.67.220, even though your argument relies on nothing more than a poorly-sourced Wikipedia article and a datasheet you plainly don't understand. Please learn to treat others with some tiny modicum of human dignity. 87.115.77.76 (talk) 22:22, 27 November 2008 (UTC)[reply]

Certainly - take any single-chip microprocessor - you can to program it to perform almost any logic function you could imagine! OK - that's probably not what you're asking - but there are lesser programmable parts - PAL's, FPGA's, etc. These are much more like simple 74-series TTL devices - they have a bunch of different basic logic gates inside - and a way to 'rewire' them (sometimes permanently - sometimes in a reprogrammable way). They are very effective at collecting together lots of and's, or's, xor's, nand's and not's, they can implement flip-flops - all of the 'basic' logic functions, certainly - and they have become amazingly cheap. SteveBaker (talk) 00:44, 26 November 2008 (UTC)[reply]

If you want to implement AND, OR, NOR, NAND, NOT, XOR functions with the same IC, the easiest way is to use a 4 gate NAND chip as is shown above. See NAND Logic for how to contruct all gates from Nand gates, its also possible to use nor gates.--Dacium (talk) 03:55, 27 November 2008 (UTC)[reply]

Thank you for your comment, 87.115.77.76. I ignored the abusive poster. But for others, here is my view on this question of terminology. An electronic gate is either open or closed. An inverter is always open – the output always responds to the input. My viewpoint is based on a rational consideration of the function of the circuit element. As for the authorities quoted, they have sought to establish consistency of terminology where it did not exist in the things referred to. I have never unquestioningly accepted the viewpoint of authority when it seemed to me wrong. If that makes me a heretic,so be it. I always have a shadow of doubt about everything, and am always ready to consider the reasons for opposing viewpoints and change my views if I am convinced. This terminology question is a very small matter, but it has been said that great ideas sometimes begin as heresy. To read of a person who stood by his viewpoints against powerful authority in very important matters, refer to Giordano Bruno in Wikepedia. What a hero that man was. What dedication to truth. Another great thinker was Rene Descartes, who wrote, "... I entirely gave up the study of letters ..., being resolved to seek no other science than that which I might find within myself, or in the great Book of the World.

Inverters are logic gates, I know of no source saying otherwise, please cite one if you do. Perhaps you're thinking of a switch or a tristate gate. By the way you'd need 5 NAND gates so the 4011 wouldn't do the job. You can get hex NAND drivers or some other things to do the job but it would be cheaper to use two 4011s. Dmcq (talk) 18:21, 1 December 2008 (UTC)[reply]

Marmosets

Can marmosets be kept as pets? Thanks 124.30.235.62 (talk) 12:26, 25 November 2008 (UTC)[reply]

Any animal (including humans) can be kept as a pet. That doesn't mean it will make a good pet or that it is legal where you live. -- kainaw ™ 12:52, 25 November 2008 (UTC)[reply]

The legality of it will need to be discussed with a local animal control officer or something. Once you've established that it's legal in your area I would recommend talking to local vets to see if you can find one that will treat it. It's no good having a pet that no vets will agree to treat.

But before you do any of that read this : Caring for Marmosets & Tamarins. Here's ominus sample : "Hand-raised, bottle-fed babies are quite charming, but with the onset of sexual maturity, they become unpredictable, aggressive and dangerous to humans - including their owners. Consequently, people should be discouraged from keeping them as pets."

Hope this helps. APL (talk) 13:46, 25 November 2008 (UTC)[reply]

Many pets become nasty upon sexual maturity, which is one of the reasons we have them fixed. Can marms be neutered ? StuRat (talk) 14:59, 25 November 2008 (UTC)[reply]

What a pity kids can't be charming, especially to those who feed them and care for them. —Preceding unsigned comment added by 98.16.67.220 (talk) 14:04, 25 November 2008 (UTC)[reply]

Heh, reading the above comments, the thought occurred to me that kids, like marmosets, may become "unpredictable, aggressive and dangerous" upon sexual maturity. Oh, teenage rebellion... ;) —Lowellian (reply) 04:49, 29 November 2008 (UTC)[reply]

Monkeys make tough pets. There is an interesting article on this here. --98.217.8.46 (talk) 14:56, 25 November 2008 (UTC)[reply]

A few species of marmosets are endangered or threatened. Honestly, I think it's best to leave them in the wild.Calamus Fortis 16:23, 25 November 2008 (UTC)[reply]

Don't try to keep a racoon as a pet. When they are young they are alright. They are quite intelligent, and unlike a dog or cat they can pick things up in their front paws. But as they mature they can be hostile to humans and may bite even the person who raised them. —Preceding unsigned comment added by 98.16.67.220 (talk) 23:00, 25 November 2008 (UTC)[reply]

There really is a problem with ALL exotic pets and wild animals as pets. Things like dogs, cats and goldfish have been living with humans - and undergone selective breeding (which is essentially a form of evolution) to make them fit into human lifestyles. Pretty much everything else hasn't been through that and is likely to react badly as a result. If you want something a bit unusual - think 'farm animals'. SteveBaker (talk) 01:57, 26 November 2008 (UTC)[reply]

Small exotic pets are fine, like fish, since they can't hurt you (with a possible exception for fish with teeth). StuRat (talk) 00:53, 27 November 2008 (UTC)[reply]

Opinion Question

Brett Favre aside, most athletes whor etire and try to come back end up doing rather poorly. Indeed, it's often hard for athletes to to retire, from what I've heard, becasue they're so used to the crowds, the cheering, the adrenaline rushes; so much so that I've heard some call it an addiction.

Could this be why people in general "live in the past" at times? Human nature does seem to cause us to need reliable patterns, but the way some do it, it makes me wonder. For instance, our neighbors when I was a teenager had a situation where for at least a few weeks, the woman's ex-husband would drive by the house 1-2 times and honk his horn at them. My dad would just say the guy should "get a life," but I wonder if the fellow could actually have gotten so much pleasure out of it that, he was actually addicted. It's hard to imagine why else he would think about it so much. Just like the athlete who wants to keep playing.

Of course, then there are those who actually think it is the past for a few moments, because of dementia or something, but I'd think such people would be acting upon that in their minds, actually talking to people and imagining things as if it was years ago, not just driving by a house and yearning for the peson to come back.Somebody or his brother (talk) 13:00, 25 November 2008 (UTC)[reply]

I'm sorry, but your question appears (after many readings) to be a request to discuss opinions about this topic. This is a reference desk, not a discussion forum. If you are looking for a reference about this topic, please ask again and limit your question specifically to the reference you are looking for. -- kainaw ™ 13:15, 25 November 2008 (UTC)[reply]

Never mind, then; it's probably a question that psychologists really don't know the answer to.

I would rephrase it as "Could people who are said to be 'living in the past' addicted to former circumstances in the same way that athletes are said to have trouble leaving the applause, cheering, adrenaline rush, etc. of their former playing days." However, looking at the nature of an addiction, it really could be seen as too gray an area.(And there would probably be someone who, without my using an example, would say it was asking for medical advice :-) Somebody or his brother (talk) 13:28, 25 November 2008 (UTC)[reply]

There are studies on sports psychology. this is the textbook for one of the classes here. It includes the psychology of leaving the sport - nicely phrased as "career transition." -- kainaw ™ 13:35, 25 November 2008 (UTC)[reply]

Formula #1 racing driver Jack Brabham doesn't seem to stay still; but on comebacks, some sports people return for financial reasons and it's what they feel they do best. (I'm thinking boxers here.) As psychological flashbacks go, Ian Thorpe recalled exactly re-living a race when swimming in the home pool. Julia Rossi (talk) 01:30, 27 November 2008 (UTC)[reply]

Near-death experiences

Why is it that certain mammals, such as small rodents and the Dutch, defecate in certain circumstances shortly before death? the skomorokh 13:10, 25 November 2008 (UTC)[reply]

Loss of muscle control caused by whatever is killing them is one possibility. Another is as part of the fight-or-flight response - that article talks about a "General effect on the sphincters of the body", that will include the anal sphincters which control bowel movements. I'm not sure what that effect is, but it could well cause an involuntary bowel movement (cf. the common phrase "shitting oneself" to mean being very frightened). --Tango (talk) 13:38, 25 November 2008 (UTC)[reply]

It may be an evolutionary response to attacks by a predator, as some predators will skip prey that smells bad, since this could be a sign of a disease which the predator could catch. StuRat (talk) 14:51, 25 November 2008 (UTC)[reply]

Very interesting chaps, thank you very much. the skomorokh 19:43, 25 November 2008 (UTC)[reply]

How could it have an evolutionary advantage if the mammal is soon to be dead? Zain Ebrahim (talk) 08:12, 26 November 2008 (UTC)[reply]

I didn't say it's a reaction to whatever is killing them, that was what Tango I said. I'm saying it's a fear response that occurs before it's even touched The prey animal's defecation works (sometimes) by convincing the predator, like a bear, not to kill the stinky prey, which it judges may be diseased, and instead it may go off to look for healthy prey. Most predators can smell prey long before they kill it. StuRat (talk) 00:27, 27 November 2008 (UTC)[reply]

But the OP is specifically referring to defecation shortly before death, not defecation when being attacked. Could these be related somehow? Zain Ebrahim (talk) 07:00, 27 November 2008 (UTC)[reply]

Yes, if this defense mechanism fails to shake off the predator, then the prey is killed, so the defecation had occurred shortly before death. StuRat (talk) 15:06, 27 November 2008 (UTC)[reply]

Further to that, though it seems reasonable to use stench as a defence, some animals like to roll in dead, stinky stuff, so would that really work? Julia Rossi (talk) 08:17, 26 November 2008 (UTC)[reply]

It certainly doesn't work 100% of the time, it's more of an act of desperation. That rolling in strong smelling stuff is likely to disguise the natural scent. I've seen predators, like dogs, do that, presumably so they can sneak up closer to the prey (before it smells a dog and starts running). StuRat (talk) 00:27, 27 November 2008 (UTC)[reply]

Because they get scared-shitless? --Shaggorama (talk) 16:36, 26 November 2008 (UTC)[reply]

Also, if a prey animal knows that a predator is tracking it's scent, leaving a big steaming pile may be distracting enough that the predator can't pick up the scent again, or at least it may take a few minutes, giving the prey more time to escape. StuRat (talk) 00:40, 27 November 2008 (UTC)[reply]

Hang on one minute, I have to go back to Zain's point: the OP never asked about being killed, the question was about dying (e.g. by natural causes?). Zunaid 12:42, 28 November 2008 (UTC)[reply]

Actually, it said "before death". I don't see that this excludes predation, however. StuRat (talk) 14:35, 28 November 2008 (UTC)[reply]

windmill turbines

hi, I am a student of electrical engg. Well, induction generators are used (if not, suppose to be) for wind turbines. Then, how does it get the magnetizing mmf? Even though it is singly excited, it requires reactive power to create its magnetic flux. Maybe it feeded on the grid for that, but imagine it directly connected to a load. —Preceding unsigned comment added by 218.248.70.235 (talk) 14:48, 25 November 2008 (UTC)[reply]

See induction generator. An induction generator connected directly to a load, with no external source of excitation, doesn't work. 198.29.191.149 (talk) 18:44, 25 November 2008 (UTC)[reply]

Quantitative CO2 IR spectrum

Do you know a website where one can get a quantitative infrared absorption spectrum of carbon dioxide? webbook.nist.gov has only relative data (without concentration and light path length information; it has quantitative data for some other compounds). Thanks in advance! Icek (talk) 15:13, 25 November 2008 (UTC)[reply]

mouth-to-mouth resuscitation

When did mouth-to-mouth resuscitation begin to be widely used in first aid? I'm reading a manuscript which is about the experiences of an Italian sailor in the Second World war in which he claims that mouth-to-mouth resuscitation was performed on a shipmate who was rescued by the British Navy. Did the British Navy employ this technique in those years? --JAXHERE | ^Talk 16:30, 25 November 2008 (UTC)[reply]

Have you seen our article, History of CPR? That may answer some of your questions. --Tango (talk) 16:43, 25 November 2008 (UTC)[reply]

Red caviar

When salmon or trout roe is bottled as red caviar, how long will it last and be edible? Does trout caviar usually come from wild trout, or is it harvested in conjunction with trout farming operations? Thanks for any information you may provide. —Preceding unsigned comment added by 80.101.134.43 (talk) 16:49, 25 November 2008 (UTC)[reply]

Wow, no replies at all. That doesn't happen here very often. I'm still interested, especially if someone can lead me to info on the shelf life of red (or trout) caviar. —Preceding unsigned comment added by 80.101.134.43 (talk) 09:25, 27 November 2008 (UTC)[reply]

Why not try doing a search for "trout caviar" and "shelf life"? That's what anyone here would do for you. Search engines are your friend. --jpgordon^∇∆∇∆ 16:02, 27 November 2008 (UTC)[reply]

What to be done

We don't give medical advice on the reference desk. See a doctor if you have bleeding problems. --98.217.8.46 (talk) 17:25, 25 November 2008 (UTC)[reply]

was a wheel (by an axel) distinctly created at a single earliest moment?

so wheel-like things have been used for a while. I heard (or saw in a film) that the ancient egyptians rolled stones on rolling ... rollers. But there was no axel. It seems like the addition of an axel (let alone axle) would have HAD to have been an intelligent choice of at least one EARLIEST, first designer in a FIRST construction somewhere. Is this understanding of mine correct? —Preceding unsigned comment added by 86.217.99.209 (talk) 17:28, 25 November 2008 (UTC)[reply]

Are you asking if someone invented a wheel? If so, the answer is yes. In fact, it's likely that several people independently invented wheels. — Lomn 20:15, 25 November 2008 (UTC)[reply]

Wheels have been used a long, long, time, but they weren't necessarily used in the way we commonly think of today. Keep in mind that the efficiency of wheels varies directly with the quality of roadways available, so shifting things with wheeled transport wasn't always the slam-dunk improvement we consider it now. It's difficult to prove, but it seems likely that the first wheels were used in pottery making and that other early uses were also horizontal, as in a mill. You are correct (if I understand you correctly) that the invention of the axle was probably nearly as important as the invention of the wheel. Matt Deres (talk) 21:20, 25 November 2008 (UTC)[reply]

In a four-wheel vehicle, an important adjunct to its wheels is making the front wheels steerable. In a simple horse-drawn wagon, this is accomplished by having the front axle turn about a vertical axis situated at the center of the axle, thus steering the wheels. By this means, when the driver directs the horse to the left or right, the horse turns the front wheels into alignment with the new direction of travel. The rear wheels follow with no difficulty. The ancient Romans didn't know about steerable front wheels. When a driver took one of their wagons around a curve, a component of motion of the wagon was sideways. This dragging sideways was exhausting for the horse. That has been suggested as the reason the Romans built long-distance roads in a straight line, even when it meant going over a small hill instead of around it. The name of the inventor of steerable front wheels is lost in the mists of antiquity. The use of a tie rod to make front wheels steerable was a later important improvement; it allowed the front axle to be immovably attached to the body of the vehicle with springs for the front axle. An unsprung vehicle is very uncomfortable to ride in, even on today's roads. —Preceding unsigned comment added by 98.16.67.220 (talk) 23:49, 25 November 2008 (UTC)[reply]

Flatulence

What foods would LEAST likely cause flatulence in a healthy adult? --Emyn ned (talk) 17:31, 25 November 2008 (UTC)[reply]

Our article on flatulence has some good information, including a listing of foods and spices that promote and reduce flatulence. jeffjon (talk) 19:44, 25 November 2008 (UTC)[reply]

According to a LiveScience article, swallowing (of air) can also cause flatulence. ~A H 1^(TCU) 00:24, 29 November 2008 (UTC)[reply]

Relativity

If electromagnetic radiation didn't exist, would the predictions of special relativity still hold true? —Preceding unsigned comment added by 76.68.247.230 (talk) 18:33, 25 November 2008 (UTC)[reply]

Well, considering we'd be living in a totally different physical universe, the answer is probably "no" on some level. But if you mean, can you make sense of special relativity without ever referring to EM radiation... you probably could, as it affects more than just EM radiation. For example, time dilation can be easily observed with muons, or really anything that you can accelerate to extremely fast speeds. But it really wouldn't make sense without reference to EM radiation—you can say, "oh, a baseball going .9 the speed of c will have certain effects", and just say that c is an arbitrary number. But it's not—it's the speed of light in a vacuum. It's not a random speed. Removing all EM radiation would make Special Relativity rest on a lot of very arbitrary numbers. And Einstein wouldn't have liked that at all! --98.217.8.46 (talk) 19:54, 25 November 2008 (UTC)[reply]

I am having a really hard time imagining a universe without electromagnetic radiation. How would anything at all happen? EM is kinda integral to the whole system that produced it all; it's not like you could just pluck it out of the system and expect ANY aspect of physics, let alone something as specific as special relativity work. Its kinda like asking "what would you have grown up like if your parents never had sex". The question is rendered impossble to answer because it contains internal assumptions which are patently illogical (i.e. it assumes you COULD exist had your parents never had sex). --Jayron32.talk.contribs 21:00, 25 November 2008 (UTC)[reply]

Indeed. EM radiation is a natural consequence of electromagnetism, without which you couldn't have atoms, so the universe would just be a mass of electrons, hydrogen nuclei and helium nuclei (possibly with a trace of lithium, if memory serves). In fact, without EM, everything would probably collapse into neutron stars and black holes. --Tango (talk) 23:59, 25 November 2008 (UTC)[reply]

And would the said electrons, neutrons, muons etc. experience things like time dialation? —Preceding unsigned comment added by 76.68.247.230 (talk) 06:48, 26 November 2008 (UTC)[reply]

Yes - I think so. If you were in a place in our universe that was completely dark, a solid vacuum, almost impossibly cold and surrounded by a few hundred feet of very pure lead - there could (just maybe) be no EM radiation there for a while. There is no reason to think this would make any difference whatever to the laws of nature. Of course you'd be had pressed to test that because inserting anything that's not at absolute zero into our chamber would result in low energy photons being radiated and spoiling the experiment. This makes measuring anything at all completely impossible.

However, if you were thinking of a universe where EM radiation simply wasn't possible because of some weird difference in the fundamental laws of nature - then all bets are off. Different fundamental laws means that all speculation is pretty much meaningless. Ordinary matter probably couldn't exist...nah - we can't even make a sensible guess.

SteveBaker (talk) 00:33, 26 November 2008 (UTC)[reply]

True, not having EM radiation would imply completely different laws of physics, and so maybe my question, in the way that I phrased it, becomes meaningless. But the heart of my question is this: does Special Relativity depend on the existance of EM radiation or something akin to it? I mean, most or all of the thought experiments that Einstein used made use of the interesting properties of light, so one would think that the answer is yes. But to think that the very nature of motion is altered by the presence of photons seems ridiculous. —Preceding unsigned comment added by 76.68.247.230 (talk) 04:11, 26 November 2008 (UTC)[reply]

The nature of motion wouldn't be dependent on the presence of photons but on the nature of them. Dependence on presence would be asking "does Special Relativity hold in the dark?" — Lomn 14:05, 26 November 2008 (UTC)[reply]

But if photons didn't exist period, then it would appear that motion would instead follow Newton's equations, which seems hard to believe. —Preceding unsigned comment added by 76.68.247.230 (talk) 22:06, 26 November 2008 (UTC)[reply]

Sorry to sound rude can (I can think of no other way to put this) but your question is meaningless. EM radiation does exist. If we imagine a universe without it we have no way of deciding what laws would pertain in that universe. Martin Hogbin (talk) 15:33, 29 November 2008 (UTC)[reply]

Why is refrigeration of tin a bad idea?

I recently heard that cans of vegetables, soups, etc., that are partly used should not be placed in the refrigerator. The person didn't know why, but had heard that, unlike aluminum, it wasn't safe.

Do you knwo why this would be? The article on tin only states that tin itself is harmless, but some chemical reactions with it may be. Does the cold of the refrigeration cause some to leak into the food or something?(Not being a chemist, I don't know if this is it, but seeing that the temperature for conversion to a certain type is only 13 C makes me wonder if that has something to do with it.)

Thanks.Somebody or his brother (talk) 18:47, 25 November 2008 (UTC)[reply]

Problem #1: Cans of vegetables, soups, etc. aren't made of tin. They are made of steel, or aluminum. Sometimes, the steel is coated with tin to reduce corrosion. But they are primarily steel or aluminum.

Problem #2: Your refigerator is cold, but its also a rather damp place. There's lots more ambient mosture in your fridge than in the rest of your house. Water facilitates oxidation (aka RUST) and so leaving that half-eaten soup can (which, being opened, has exposed untreated steel to the moist environment in the fridge) will cause it to rust much faster. --Jayron32.talk.contribs 20:26, 25 November 2008 (UTC)[reply]

I see, thanks; I guess I always consider them "tin cans" just as a generic term, but that makes sense that they'd be steel by now.Somebody or his brother (talk) 20:38, 25 November 2008 (UTC)[reply]

I think there's another factor involved as well. With acidic foods, once the can has been opened, the food, the acid, the metal and now oxygen are available to react. Such reactions can quickly give an off-taste to the unused food. This can happen either in a fridge or out on the counter. Both a) refrigeration and b) storage in a non-reactive container will prolong the life of the food. For example, the instructions on a can of pineapple pieces (a very acidic food) are "After opening, refrigerate contents in glass jar or plastic container."

When dealing with moist foods such as soup or pineapple, the extra moisture inside the fridge may make no significant difference. CBHA (talk) 00:52, 26 November 2008 (UTC)[reply]

I think that if anything, putting something in the refrigerator would slow down any chemical processes. Maybe the cause has something to do with bacterial spores landing in your opened can? I'm inclined to think this is just an old wives' tale.69.125.228.48 (talk) 06:49, 26 November 2008 (UTC)[reply]

I agree that the refrigeration part is unlikely to be the culprit. The fact that the contents of your can is exposed to oxygen, however, is. I assume that refrigeration gets mentioned, because it delays symptoms ordinarily that would ordinarily keep you from using the food, like a dried out surface, discoloration and the like. That means you'd eat stuff out of a refrigerated can (or tin for BE) that you'd probably no longer consume if it had been left out on the counter for the same amount of time. While the inside of your can may be coated with resin (with it's own inherent health problems) to avoid contact between metal and food, seams are often uncoated. Both uncoated seams and uncoated metal surfaces of your can will react with acidic contents of your food. (Don't nail me to this I very nebulously remember oxalic acid being mentioned in this regard. Maybe someone with a chemistry background can fill in the details.) As I said above you are more likely to keep food for longer in your fridge, there's more time for this to happen and produce undesirable compounds. The processes are aerobic, so while your can is sealed they don't have the air necessary for the reaction to take place. Just pour out the contents into a bowl or plastic container before you put it in the fridge. Alternatively line your can with a freezer bag that's BPA free and then put the contents back into your can. 76.97.245.5 (talk) 09:02, 26 November 2008 (UTC)[reply]

Many "tins" now are already lined with a thin plastic coating. Bazza (talk) 15:24, 26 November 2008 (UTC)[reply]

It's kind of complicated, but...as was said earlier, once a can is opened, the contents of the can are exposed to the atmosphere, in particular to oxygen and carbon dioxide, as well as to bacterial/mold contamination. Due to the potential for spoilage, it's clearly not safe to keep an opened can at room temperature. It's also not safe to keep an opened can in the refrigerator, even if it is resealed or covered well enough to keep bacterial contamination out. Why this is, however, has NOTHING to do with refrigeration, or temperature at all.

So, what's the concern? The fact that the liquid containing can is now exposed to oxygen and carbon dioxide, but we're not concerned about the tin coating on the steel can, or even about the steel beneath it. What we are worried about is the lead-containing solder that holds the can together. The action of acid and oxygen on the solder can leach the lead into the liquid contained in the can! Consuming the liquid then brings that lead into your body. One cans worth probably won't hurt anyone, but lead never leaves the body, so over time, this could be a dangerous practice. As for a plastic coating on the inside of the can - do you want to take the risk that the plastic isn't scratched? (Sealed cans don't have oxygen or carbon dioxide in them, and are perfectly safe)Bobzchemist (talk) 16:06, 26 November 2008 (UTC)[reply]

If you want a reference, British government healthy eating advice from the Food Standards Agency [3] recommends "Don't store food in an opened tin can, or re-use empty cans to cook or store food. This is because when a can has been opened and the food is open to the air, the tin may transfer more quickly to the can's contents." --193.172.19.20 (talk) 10:45, 27 November 2008 (UTC)[reply]

If the tin is lined with plastic, note that some types of plastic may contain the cancer-causing agent Bisphenol A which can leach into water when heated, and has been banned in Canada if I remember correctly. ~A H 1^(TCU) 00:20, 29 November 2008 (UTC)[reply]

Sinusitis

Is there an extreme way to treat sinusitis? Such as using a laser and burning the lining of the sinuses in order stop it from producing muscus all together? Is that possible? What would be the drawbacks of burning away the lining? --Emyn ned (talk) 18:53, 25 November 2008 (UTC)[reply]

The treatment of sinusitis, including surgical treatment, is covered in our article. - Nunh-huh 19:45, 25 November 2008 (UTC)[reply]

I know. I read the article before I wrote this question. There is no mention of lasers in it thus my question above. Let me know if I am missing something...--Emyn ned (talk) 20:00, 25 November 2008 (UTC)[reply]

There's nothing particularly special about lasers; ablated mucosa is ablated muscosa. The article discusses surgical ablation of the mucosa of the maxillary sinus by ordinary means; you'd have to consult MEDLINE to look for recent thoughts on laser treatment; for example J Laryngol Otol. 2006 Dec;120(12):1026-32. "Computer-assisted surgery of the paranasal sinuses: technical and clinical experience with 368 patients, using the Vector Vision Compact system." Stelter K, Andratschke M, Leunig A, Hagedorn H. - Nunh-huh 20:23, 25 November 2008 (UTC)[reply]

Type of illusion where one treats Wii sport like regular?

When I went to try my cousins' Wii bowling game, I experienced an illusion, and I've been trying to search what kind it is. I got close to the TV, as I need to, and because it looked enough like a real bowling alley, I moved my hand back and threw as if hefting a real bowling ball - you can probably imagine the force with which that ball went down the alley. :-)

I know what I did involved muscle memory, and my muscles being tricked into thinking it was a real bowling ball. But, it's a little of a couple types. It was optical in the sense I relied on sight, but it was tactile in the sense the neurotransmitters in my brain, while they weren't saying, "This is a bowling ball you have," were saying, "You need to throw it like a bowling ball."

is there a name for this type of illusion? Thanks.Somebody or his brother (talk) 20:35, 25 November 2008 (UTC)[reply]

Immersion. We call a virtual experience where you actually do feel you're a part of it "immersive". And (of course!) we have an article about it: Immersion (virtual reality). SteveBaker (talk) 02:04, 26 November 2008 (UTC)[reply]

(anthropology/biology) universals that turn women on?

I was reading the line "Penelope Brown and Levinson extended Grice's theory by showing how people all over the world use politeness to lubricate their social interactions", and I was like... I'd like to 'lubricate' my social interactions, if you know what I mean. It's probably not what they meant, but surely politeness turns women on. More generally, what are scientific principles that turn women on? my impression

secretly be a muscled adonis (though this is just visible through your quality shirt)
ride a horse (????)
use tools. like, put up a shelf with a power drill. (???)
sweat with honest work. (construction workers?)
have a great sense of humor, make eye contact.
pay attention, be interested in them in a way no one else is.

but there my 'tips', such as they are, er...run dry. So, does anyone have good, strong, scientific ... moisterizing tips for the fairer race? —Preceding unsigned comment added by 86.217.99.209 (talk) 21:02, 25 November 2008 (UTC)[reply]

You could start by not being me. In fact, I can tell by personal experimentation that not being me has always been the best way to get a woman sexually aroused. --Jayron32.talk.contribs 21:07, 25 November 2008 (UTC)[reply]

It depends on the woman. But yeah, having a great personality and a great body, those sure can help, I imagine. Some of those things seem unnecessary. I'm not sure all women find horses all that appealing in practice. I think you left off a fairly obvious one:"have a very secure economic situation" (aka, MONEY), as that seems to impress a lot of women (and is one of the few things there that can easily be traced to more "evolutionary" origins). --98.217.8.46 (talk) 21:14, 25 November 2008 (UTC)[reply]

The things that attract people to each other are not confined to the evolutionarily advantageous. You can probably think of several real-life examples where a pairing just makes no sense and (perhaps even stranger) where the couple stays together even though it's obvious to all concerned that the match is not a productive one. People get turned on by strange things and there's no accounting for taste. Being good-looking, financially secure, funny and in good health should all seem to indicate a person would make a good mate, yet we all know ugly, unemployed bastards that somehow manage to get dates. Matt Deres (talk) 21:30, 25 November 2008 (UTC)[reply]

if you're talking about actual science, there's a decent number of studies attesting to sexual selection on the basis of facial and bodily symmetry. -- Nunh-huh 22:18, 25 November 2008 (UTC)[reply]

Ah the eternal question, please notify me if you manage to find the answer.--Lenticel ^(talk) 23:24, 25 November 2008 (UTC)[reply]

Political or financial power, or being any kind of leader of men, turns women on. This is undoubtedly a stone age instinct; powerful men and leaders could better ensure the survival of a woman and her offspring. A light-hearted rascal is also attractive to women; I don't know how to account for that. —Preceding unsigned comment added by 98.16.67.220 (talk) 00:11, 26 November 2008 (UTC)[reply]

For some reason, being a complete jerk seems to work rather well... Women like to be friends with nice guys and go out with jerks, don't ask me why. --Tango (talk) 00:27, 26 November 2008 (UTC)[reply]

Observer bias - the 'other' guy is ALWAYS a jerk! SteveBaker (talk) 04:06, 26 November 2008 (UTC)[reply]

Not sure, but perhaps it's some sort of motherly instinct in which the girl will try to "fix" the jerk's attitude in their relationship. Nice guys don't need that kind of help so they ignore them (you might want to make another thread about this section though).--Lenticel ^(talk) 01:15, 26 November 2008 (UTC)[reply]

All stereotypes aside for a moment, there's nothing quite like someone who's comfortable in their own skin, who's relatively self-aware and takes an interest in other people. Even unassuming so-called plain guys with these attributes stand out imho. It's like another dimension. Julia Rossi (talk) 02:13, 26 November 2008 (UTC)[reply]

Stars and Planets

2 questions really, 1) what is the difference between a planet and a star? and 2) are the lives of all stars and planets finite? I mean i heard that the sun will die eventually, any idea when? does that mean even planet earth is not imune to dieing eventually?! —Preceding unsigned comment added by 79.75.254.37 (talk) 22:09, 25 November 2008 (UTC)[reply]

Both are huge balls of matter. The difference is that the amount of matter in a star is so great that nuclear fussion occurs. Yes, the Sun is middle-aged. In about 5 billion years, it will turn into a red giant, possibly engulfing the entire Earth (scientists aren't sure). Even if the Sun doesn't swallow up the Earth, the Sun is gradually getting warmer. In about 1 billion years, it will be too hot and all life on the planet will die off. See the articles on Planet and Star for more information. 67.184.14.87 (talk) 22:26, 25 November 2008 (UTC)[reply]

A star is a mass of incandescent gas. A planet is broadly any object which is in orbit around a star. Also see Stellar evolution for more information on the life cycle of stars... --Jayron32.talk.contribs 22:31, 25 November 2008 (UTC)[reply]

In a binary star system, is it possible for a star to orbit another star? That is, the center of gravity lies inside one of the stars? 67.184.14.87 (talk) 22:51, 25 November 2008 (UTC)[reply]

I don't see why not. It's quite common for one of the stars to be much larger than the other, so as long as they are fairly close together (also not uncommon) one would orbit the other. The only think I'm not 100% on is that both those common things occur at the same time, but I would expect them to. --Tango (talk) 23:36, 25 November 2008 (UTC)[reply]

Keep in mind that a billion years is a very long time. The first dinosaurs showed up 230 million years ago — less than 1/4 of a billion years. --98.217.8.46 (talk) 22:49, 25 November 2008 (UTC)[reply]

Indeed, it's about 7% the age of the entire universe. When the sun finally dies it will have been around for well over half of the universe's existence. --Tango (talk) 23:36, 25 November 2008 (UTC)[reply]

It will still be a sad day though. I wouldn't want to be in my early 20's when the sun ultimately dies. —Preceding unsigned comment added by 79.75.254.37 (talk) 00:05, 26 November 2008 (UTC)[reply]

It will take place over the course of billions of years, so it's not really an issue (the Earth becoming uninhabitable may be a little shorter, maybe 1000s of years, I don't know, but still more than a lifetime I'd expect). --Tango (talk) 00:21, 26 November 2008 (UTC)[reply]

There's nothing remotely going on to make the earth uninhabitable in a time scale of 1000s of years. Even the worst predictions in the worst possible models of human-caused climate change don't reduce the earth to a barren rock in 1000s of years. Earth will probably not become uninhabitable for life in several hundred million years, probably closer to 1 billion years. --Jayron32.talk.contribs 03:43, 26 November 2008 (UTC)[reply]

I believe Tango was saying that the Sun's death will make the Earth uninhabitable over the course of 1000s of years, not that the Earth will become uninhabitable in that amount of time from now. --Sean 15:06, 26 November 2008 (UTC)[reply]

Indeed, I was making a wild guess on the amount of time it would take for the Earth to go from being completely habitable to completely uninhabitable (and the wonderful this is, my guess is almost certainly correct before those terms are so vague I can just define them in such a way as to make me right!). --Tango (talk) 21:35, 26 November 2008 (UTC)[reply]

Ah... Sorry. I thought you meant "1000s of years from now" and not "1000s of years from when things start getting uncomfortable to getting uninhabitable". Mea culpa... --Jayron32.talk.contribs 02:24, 27 November 2008 (UTC)[reply]

Water marbles

http://www.youtube.com/watch?v=vCeAfKCC2ng http://www.youtube.com/watch?v=x_kYkFy5-jI

I know these "water marbles" are real, as I've played with them before, but is this the correct way to make them? And if Calcium bicarbonate doesn't exist in a compound form, then then how does that part work? Furthermore, can I buy it at the store or make it myself with calcium carbonate, or would it need to be bought online? I really want to make these but I want to wait until I know exactly what I'm doing. Thanks! Reywas92 ^Talk 22:48, 25 November 2008 (UTC)[reply]

I've no idea about the answer to your question, but that is really cool! Thanks for the link! --Tango (talk) 23:55, 25 November 2008 (UTC)[reply]

Looks like a sham to me. --Scray (talk) 00:42, 26 November 2008 (UTC)[reply]

I agree. It's interesting how many of these sham science videos are on YouTube though, no? --98.217.8.46 (talk) 00:45, 26 November 2008 (UTC)[reply]

No! It's not a sham! I have played with these balls before. They are really interesting and feel like gel. It's really amazing how they are invisible in water, but they are real! Reywas92 ^Talk 00:51, 26 November 2008 (UTC)[reply]

(after edit conflict)

I'm pretty sure that they're not real. For one thing, these supposedly unrelated videos seem to be taken in the same kitchen under different lighting conditions. But more importantly, look at the how "marbles" themselves look. They're perfectly ridged, all perfectly spherical, all exactly the same size, and pretty strong. (Look at his fingers when he holds one between thumb and forefinger, he's squeezing pretty hard.) Also, in one of the videos, he accidentally drops a marble and it bounces, just like you'd expect a glass one to do. (Look to the right of the screen at 2:32)

Not only that, but the explanation seems like gibberish to me. What does it mean for a substance to "loose its Polar hability"?!?

I would expect real Sodium Acetate to do something more like this. (And get quite hot.) APL (talk) 00:50, 26 November 2008 (UTC)[reply]

No! It's not a sham! I have played with these balls before. They are really interesting and feel like gel. It's really amazing how they are invisible in water, but they are real! Reywas92 ^Talk 00:52, 26 November 2008 (UTC)[reply]

I'm only saying that I think that these videos are a sham. I fully belive that you have played with some sort of "water balls" that were really neat. But I don't at all belive that the videos you linked are anything other than a prank.

(I am not at all a chemist, though. So feel free to assume I'm an idiot.) APL (talk) 00:58, 26 November 2008 (UTC)[reply]

Here's another video of real Sodium Acetate. Very cool, but nothing like the "water balls" video. APL (talk) 00:54, 26 November 2008 (UTC)[reply]

I don't know all the science to it; "lose its Polar hability" may be wrong, but they are not just glass and are real. From all the places I've read, they are two different applications of sodium acetate. Reywas92 ^Talk 00:56, 26 November 2008 (UTC)[reply]

Not just the "Polar Hability", but what is the white powder identified as "Calcium bicarbonate"? Is it "Calcium carbonate"? I suppose it could be, that's a white powder, but it's not the same thing. APL (talk) 01:01, 26 November 2008 (UTC)[reply]

Presumably Calcium bicarbonate, precipitated into solid form for the first time by previously unknown science. Algebraist 01:45, 26 November 2008 (UTC)[reply]

It's a special kind of science that only works in kitchens that look exactly like that one. APL (talk) 03:09, 26 November 2008 (UTC)[reply]

This video Seems a bit more credible, but I still am not sure what he's got there. APL (talk) 01:35, 26 November 2008 (UTC)[reply]

Why do you think that's more credible? He gives no instructions - makes no actual claims - and whatever happens is happening off-camera. Those could be blobs of Jello. Extraordinary claims demand extraordinary evidence. SteveBaker (talk) 02:46, 26 November 2008 (UTC)[reply]

Oh, That's easy, I think it's more credible because absorbent 'plastic' things that grow to several times their size when left in water for an hour or so are real thing. It's entirely credible that you could make some soft, gooey spheres that way. It's a hell of a lot more credible than the idea that you could mix Sodium Acetate and unobtainium on your stove and get a bunch magic crystal spheres.

Of course, now that I've found those hyrdoponic spheres at deal extreme.com (see below) I'm sure that's what the video I linked to was of. So I was right. The video I linked is probably real. It shows something perfectly mundane, of course. APL (talk) 03:02, 26 November 2008 (UTC)[reply]

Here we go!. I'll bet these are what you're thinking of. Very cool. And for the low, low price of $2.58! APL (talk) 01:46, 26 November 2008 (UTC)[reply]

So - to summarize the known facts to date:

There is no such solid as Calcium Bicarbonate - yet BOTH supposedly independent video's claim to use it,
"polar hability" is a made up term,
Salt is 'iodized' not 'ionized'...they put iodine in it to stop the grains from sticking together. (Jeez!)
the two videos (while supposedly submitted by different people) are clearly filmed in the same kitchen
we see the "water ball" bounce like a very hard solid - despite the claim that these things are slightly squishy.
The two sets of instructions use totally different methods and very different ingredients to produce this very strange result.
How could it REMOTELY be possible for such a simple process made with common household ingredients (well - except for the unobtainium-calcium-bicarbonate) not be so well known as to be all over the 'home chemistry' web sites.
The second set of instructions tell you to heat the vinegar to 550 degrees for 10 minutes. Now - I'm going to be generous and assume he's talking Fahrenheit - but 550F is 288C !! How can you get a liquid composed of water (boiling point 100C) and acetic acid (boiling point 118C) to a temperature of 288C ?!?
Generously assuming the pot did get up to 550F (and I don't think a stovetop ring would do that) - taking it straight off the stove top and putting it onto the glass shelf of a refrigerator would result in fairly instant shattering of the glass - unless it's a plastic shelf - in which case it's gonna melt for sure.
None of the usual YouTube wannabies who claim to have reproduced the results have MENTIONED the difficulties of getting their stoves up to 550F or obtaining calcium-bicarbonate. Hence we may deduce that they are lying...so we may discount their stories.

Yeah - this is utter, utter, utter, bullshit - and it's done so ineptly that it falls apart at the first touch of scientific inquiry. I can't tell in what way Reywas is confused/duped/bullshitting-us - but I discount his report. SteveBaker (talk) 02:39, 26 November 2008 (UTC)[reply]

I few quick fixes: Calcium silicate is the chemical they use to prevent caking in table salt. It is iodized as a public health measure to reduce the incidence of goiter69.125.228.48 (talk) 06:54, 26 November 2008 (UTC)[reply]

Good catch on the temperature. I feel stupid for missing that one.

Please notice that Reywas92 might not be trying to con us at all. He may honestly have played with some spheres at some point, and has mistaken the spheres in these hoax videos for the spheres he remembers. He may be thinking of the plant potting spheres I linked above, or he may be thinking of something entirely different, But I don't think he's claiming that he's ever seen spheres manufactured out of Sodium Acetate. That's why he asked. APL (talk) 03:02, 26 November 2008 (UTC)[reply]

Indeed - that's why I said 'confused/duped/bullshitting-us' rather than "OUTRIGHT LIAR" - he could be confusing some other effect - or perhaps he was duped with the plant potting balls - we have no way to tell. It's certainly notable that the refractive index of those plant potting beads is almost exactly the same as water - which makes them seem to vanish. You might even be able to do a bit of kitchen chemistry to make a liquid with an exact refractive index match to enhance the effect. That's undoubtedly the origin of the hoax...combine the interesting (and very real) weird behavior of Sodium Acetate (try Googling "Hot Ice" for some non-hoax examples)...and you have fertile ground for not-so-scientifically-literate hoaxers. SteveBaker (talk) 03:56, 26 November 2008 (UTC)[reply]

Yes, the videos are pretty bad. I take no responsibility for anything in them, but I know that the water marbles shown in various videos are the ones I've played with. The balls both bounce and are slightly squishy. You are completely right that the refractive index was the same as water so they are invisible. I don't know how my marbles were made or anything, but these videos are them, and they are likely made with sodium acetate somehow, with unknown veracity of the videos otherwise. What I played with was a toy and not plant potting balls, but they may be similar. Also, I feel insulted by you calling me 'confused/duped/bullshitting-us'. How about curious? Reywas92 ^Talk 04:19, 26 November 2008 (UTC)[reply]

Well - I guess this is how it is:

The consensus of the ref-deskers is that we don't doubt that there exist squishy hygroscopic balls with a refractive index close to that of water that would closely simulate these mythical 'water balls'. Indeed, we believe you can buy them - and here is a link: [4]
But we do SERIOUSLY dispute that they can be made in any of the ways indicated in the videos...we dispute that they are some bizarro new phase of water or whatever the heck is being claimed.

So - assuming we're correct about those two facts (which, quite honestly, is beyond doubt at this point) then it logically follows that either:

You are telling us that someone showed you some squishy balls in water - and didn't say that they were made with a simple process involving household ingredients - then (because you say that you "know that the watermarbles shown in various videos are the ones you've played with") you must have been confused by those ridiculous videos.
You are telling us that someone showed you some squishy balls in water - and told you that they'd made them in the kitchen in ways similar to those in the videos - then you have been duped - the person lied and you believed them.
You are telling us that you know for a fact that these balls were made in ways similar to the movies - then you are bullshitting us because there is no conceivable way to even follow the instructions - let alone come up with a product such as they describe!

I don't any way to know which of those things it is - so I said that you are either confused, duped or are bullshitting us. I don't think I'm being unreasonable by saying that...and (since we try to assume good faith around here) - I'd prefer to assume you're either confused or were duped. I'm sorry if that upsets you - but sometimes the truth is hard to bear.

SteveBaker (talk) 06:19, 26 November 2008 (UTC)[reply]

Actually, Someone showed me a small container of the balls which was made as a toy and called something like Dinosaur Eggs. I'm asking my friend if he still has it so I can look up the company and product. I know these balls are the ones shown in the movies, so I wondered about their origin. I asked about the videos to see if I could learn anything about what I had played with. Apparently the videos are not completely accurate, but that's why I asked you about them before wasting my time trying to make them. You might call that getting duped, but I don't. I'm not upset, I just didn't learn how to make the balls. Reywas92 ^Talk 15:39, 26 November 2008 (UTC)[reply]

My primary conclusion last time this came up about a month ago, unchanged by the recent revelations is that most of the people posting the videos on youtube (not commenting on the OP) are clearly bullshitting and with one clear purpose. They're trying to fool people into wasting their time and perhaps being laughed at by looking for the non-existant calcium bicarbonate. I guess the people who posted these videos think it's funny, I just think it's lame Nil Einne (talk) 13:15, 26 November 2008 (UTC)[reply]

Incidentally, there seems to be rather a lot of blog and forum traffic that about creating "water balls" from Sodium Acetate and powdered calcium bicarbonate, so I can see why that might make someone think that this is a commonly known fact. The problem is, all of that talk, all of it, appears after these videos appear. As far as I can tell this (wrong) idea was completely unknown before these videos came out. In fact, most of the people talking about this effect try to impress each other with the nonsense phrase "polar hability".

I'm sure whoever made these videos is getting a great laugh out of all this. APL (talk) 13:56, 26 November 2008 (UTC)[reply]

http://revver.com/video/1004979/invisible-ball/ Here's exactly what I played with. Basically, How do I get it/make it? Reywas92 ^Talk 16:00, 26 November 2008 (UTC)[reply]

I'd bet money that your 'invisible balls' were made from some combination of one or more of these, possibly with another cross-linking agent:

and Calcium lactate or calcium chloride

A thick enough gum solution slowly poured into a slowly stirring calcium (lactate or chloride)) solution will break up into large balls of gelled gum that will be firm but squishy and maybe clear. The faster you stir, the smaller the balls will be. Molecular gastronomy uses this trick to make solid/gelled alcoholic drinks, but I can't find the reference.Bobzchemist (talk) 16:38, 26 November 2008 (UTC)[reply]

November 26

'Writing about Vampires' seeks Comprehensive list of Disease Involving Sunlight

I'm a writer who is currently writing somewhat about vampires but what I really need is a comprehensive list of diseases involving sunlight to help with my current research needs. Thanks in advance. —Preceding unsigned comment added by 70.238.136.205 (talk) 01:24, 26 November 2008 (UTC)[reply]

This isn't bad: make sure you click the link to see the table. - Nunh-huh 01:29, 26 November 2008 (UTC)[reply]

For some people, going into bright sunlight triggers sneezing. See Photic sneeze reflex. I'm pretty sure this is not classified as a "disease" but it might be of interest anyway. CBHA (talk) 04:05, 26 November 2008 (UTC)[reply]

A disease you might want to check out that I remember being characterized as particularly vampiric is porphyria, which messes with the enzyme pathway that makes hemoglobin. Photodermatitis is sometimes a symptom. --Shaggorama (talk) 16:14, 26 November 2008 (UTC)[reply]

Tuberculosis sufferers were once thought to be vampires. See Tuberculosis#Folklore. - Draeco (talk) 05:19, 27 November 2008 (UTC)[reply]

Seasonal Affective Disorder (SAD) sufferers experience depression and other mood changes in the winter. Seasonal Affective Disorder is believed to be related to the much lower levels of sunlight in winter. CBHA (talk) 05:58, 27 November 2008 (UTC)[reply]

Xeroderma pigmentosum is a classic example of such a disorder. – Clockwork Soul 08:03, 29 November 2008 (UTC)[reply]

Black holes

Hi, A thought just occured to me while i was brushing my teath; what would happen if a human being was situated next to a black hole and stretched out their arm so that only their arm fell beyond the black hole's event horizon. Would they lose their arm? or would the black hole suck them in completely? 79.75.254.37 (talk) 01:27, 26 November 2008 (UTC)[reply]

The black hole gravity will pull hard on the arm, so if it is big enough to pull more than a few millimeters, the arm will drag the rest of the human in as well. However the tidal force and gravity would be expected to be huge as well, so even in an orbit around the hole you can expect to be spagettified. Graeme Bartlett (talk) 01:39, 26 November 2008 (UTC)[reply]

Being within armsreach of a sizeable black hole's event horizon is not a really comfortable situation! Between the spaghettification and being cooked by the gamma rays being emitted by stuff entering the hole...then the severe time, space and mass dilation effects of moving so rapidly...the fate of your arm is really the very least of your problems! SteveBaker (talk) 01:45, 26 November 2008 (UTC)[reply]

I saw a documentary about it... DMacks (talk) 02:11, 26 November 2008 (UTC)[reply]

An event horizon is not a magical shell where you don't feel the black hole's gravity outside of it, but you do feel it inside of it; F = mg still applies. For a small black hole with a high gravity gradient, see Steve Baker's answer. For a large one, the event horizon will be very large (such as the size of Pluto's orbit), and you won't feel much when you stick your arm in, but even if you then had your arm amputated, your space ship will require nearly infinite energy to escape the hole's gravity. If you find yourself in this situation, it's probably best to just keep your arm on so that you can carry out your final activities intact. --Sean 15:35, 26 November 2008 (UTC)[reply]

What does "nearly infinite" mean? — DanielLC 16:01, 26 November 2008 (UTC)[reply]

If we assume that the black hole is large, and thus the tidal forces are small, and that there isn't enough other matter falling into the black hole in order to harm you, and that you are magically (or otherwise) hovering above the event horizon, then you would actually never experience your arm passing the event horizon because this event is at t = ∞ in your reference frame! That can be seen from the Schwarzschild metric. As your arm moves closer to the event horizon, the time dilation in your arm compared to the rest of your body will certainly cause strange effects.

Note that the situation is quite different for falling observers.

Icek (talk) 15:32, 26 November 2008 (UTC)[reply]

But the problem with that explanation is this 'magical hovering' bit - we simply can't let you get away with that - even in a thought-experiment. Once you stick your arm through the event horizon - you can't have it back because in order to escape the black hole, it would have to be moving faster than the speed of light relative to the black hole. You may not see anything different when you do that - but we know that light from your arm can't get back either - so if you didn't notice an abrupt change when you stuck it in there (which I agree, you don't) then it must be that there was only just BARELY any light coming from your arm BEFORE you stuck it into the event horizon. So there must be something very odd happening to you BEFORE you stick your arm across the event horizon in order for that not to be very noticable.

But remember - in the absence of 'magic' - in order to avoid the rest of your body getting stuck in the hole too - when you're just a foot or two outside the event horizon - you have to be moving at 99.9999999% of the speed of light relative to the black hole! The event horizon is just the place where you can't escape even by moving at the speed of light. In the region close to the event horizon, you can only avoid falling in if you're going 99.9999999% of the speed of light...sure, it's possible to escape falling in theory - but severely difficult in practice!

So we can deduce that you are orbiting the black hole just the slightest smidgeon below lightspeed (relative to the black hole itself). That is insanely fast! At those speeds (and - inevitably - in a circular or elliptical orbit) you only have to glimpse a particle of matter falling into the hole to be completely cooked by the resulting high energy gamma radiation. This really isn't a good way to run your life!

SteveBaker (talk) 20:02, 26 November 2008 (UTC)[reply]

Unfortunately, such a kind of orbit is not possible; at 1.5 Schwarzschild radii the orbital speed already reaches the speed of light, and no closer free-falling orbits are possible! (the time dilation factor for circular orbits in the Schwarzschild metric is

{\sqrt {1-{\frac {3\;r_{s}}{2\;r}}}}

) Icek (talk) 22:46, 26 November 2008 (UTC)[reply]

Are CD jewel cases recyclable?

I'm moving all my CDs to flip albums and I have sacks of discarded jewel cases. Just curious if CD jewel cases are recyclable? The clear plastic is obviously different from the gray Cd holder part. But I don't see any plastic classification symbols anywhere. --68.88.175.36 (talk) 03:21, 26 November 2008 (UTC)[reply]

These cases are probably polycarbonate, this is one of the plastics that are not recycled much. However there would be other people who would like to use the cases as they are to store CDs, so I think you will be able to give them away easily. Graeme Bartlett (talk) 10:17, 26 November 2008 (UTC)[reply]

Are you sure of that? I know the CDs and DVDs are polycarbonate but I'm not so sure about the jewel cases. From the examples given in the linked article and the properties, it seems a bit odd to me they would use something like polycarbonate for jewel cases which are meant to be cheap, not especially hardy and mostly disposable. I've comes across various people suggesting they are type 6 (polystyrene) or one person suggested type 5 (polypropylene) which seems more likely to me. Specifically this [5] which means one of the slim line cases having a type 6 code and says it's confirmed from a government website. This website about manufacturing them [6] also suggests they're polystyrene. The (usually black) insert may be different from the clear/jewel part though, not sure (however there are those with transparent/clear inserts which I presume are the same at least Nil Einne (talk) 13:01, 26 November 2008 (UTC)[reply]

The best idea as others have said is to give them to somebody that can reuse them - libraries are often after jewel cases as people borrow their discs and bring the cases back broken. However, they definitely can be recycled - at least here in the UK. The company I work for sends all its scrap CDs and any excess jewel cases (including the paper inlays and black plastic parts) to a company on merseyside who recycles the lot - see this website: http://www.polymerrecycling.co.uk/cd.html I think they take them for free as well although you would have to pay to ship them there.62.25.96.244 (talk) 13:24, 26 November 2008 (UTC)[reply]

Lights

If two identical spotlights shining on the floor overlap, the intensity of the overlapping region doubles. If light is a wave, whhy would this happen? Wouldn't the light interfere with itself? —Preceding unsigned comment added by 76.68.247.230 (talk) 04:12, 26 November 2008 (UTC)[reply]

Because spotlights aren't coherent light. Unless the two beams of light are of the same wavelength, they won't interfere with each other. Spotlights feature a wide spectrum of wavelengths, and these don't interfere any more than a room full of musical instruments all playing at the same time (i.e. an orchestra) would interfere... --Jayron32.talk.contribs 04:40, 26 November 2008 (UTC)[reply]

It's not just the variety of wavelengths. Even a pair of Sodium lamps (which basically emit only two frequencies) don't interfere. The real reason is that the light isn't 'coherent'. Imagine a good old fashioned tungsten filament lamp - or a florescent tube maybe...each little part of the filament or of the glowing surface is giving off a little bit of light...right down to the individual atoms - each one is emitting light. But nothing is keeping the lightwaves they produce in synchronism - so at any given instant, some of the tiny light emitters that make up one 'lamp' are at the crest of their waves while others are in the trough and others are at the halfway point. Nothing forces them to stay together. Even if they were 'together' at the start, the shape of the filament/tube is such that the sources of all of these lightwaves are starting out at different places and radiating outwards in all directions...so they might interfere constructively here - and destructively there. As Jayron says - in the case of a white lamp - the light is coming out at all different frequencies too - and that complicates matters still further.

So the light that comes out of such a crude device is a horrible mixture of interfering lightwaves...it's a complete mess. But on the average of quadrillions (at least) of individual glowing atoms - there is light. OK - now add a second lamp...now you're averaging over two quadrillions instead of one quadrillion...but the results are much the same...except that there is now twice as much light energy. But even a pair or completely monochromatic light sources don't form interference patterns unless the light is 'coherent'.

To get some nice interference going, you need something like a laser - which (by devious means) produces 'coherent' light - where all the waves are in perfect synchronism and all at one very specific frequency. Laser light does indeed interfere in situations like your thought experiment - and if you could hold the lasers still enough and peer at the ground with a microscope - you'd see tiny interference patterns.

SteveBaker (talk) 19:46, 26 November 2008 (UTC)[reply]

Fuel consumption with a cold engine.

My car (a turbo-charged MINI Cooper) manages about 40mpg (US gallons) when I drive it carefully. I'm aware that car engines use more gas when they are cold - but today I found out how much more...and I'm astounded!

The car has a miles-per-gallon gizmo - but it's basically useless because it either averages over the entire life of the car - or it swings wildly moment by moment and tells you nothing useful. So I've always known my average MPG - but didn't get a good feel for how it varied over a journey.

Well, this morning, I was kinda low on gas - so I switched the car computer over to tell me "available range" (really: "miles remaining until you're out of gas"). It's not a mode I use much...but it turns out to give you a much better idea of what's going on. It's a 17 mile trip to work - and when I left home, it said I had 77 miles worth of gas in the tank. After just about 8 miles, I glanced at the gauge and noticed to my horror that it had dropped to 55 miles(!)...22miles off of my 'available range' but only 8 miles travelled!!

By the time I got to work (about 9 miles further) the gauge showed 50 miles left - so the first 8 miles of my trip used four and a half times more gas than the second half! Almost the entire trip is on freeways and I leave early enough to miss all the traffic.

Having an enquiring mind - instead of filling up the tank - I repeated the experiment on my drive home - and got very similar results. But it was astounding how fast the 'available range' dropped in the first mile alone. This was a good test because I was doing the trip in the reverse direction so the first half of the first trip was the second half of the second trip.

Tomorrow I'm going to make a note every mile...graphs need to be plotted! The world needs to know!

So here is the question...what the heck makes a cold engine use FOUR TIMES as much gas as a warm one?!? I can think of a few small things (like the engine oil isn't as runny) but that doesn't seem enough to account for the difference!

SteveBaker (talk) 05:37, 26 November 2008 (UTC)[reply]

Perhaps your gizmo got some glitches. I think you need an alternative way of measuring your fuel consumption (If you have the time to find one, sorry I have no idea what would that be) to compare with the data your gizmo provides.--Lenticel ^(talk) 05:50, 26 November 2008 (UTC)[reply]

If your car is new enough, you can get an aftermarket MPG display. I've been thinking about getting one, just for kicks. But the ones I've seen are a bit pricey. Doesn't answer the original question though. APL (talk) 14:12, 26 November 2008 (UTC)[reply]

The cheapest solution might be to write it up as a nice idea for Mythbusters -- they've done the small-quantity fuel efficiency sort of thing a few times before, as I recall (maybe suggesting that cold weather has an abnormally large effect can even call those previous experiments into question, too!) — Lomn 14:26, 26 November 2008 (UTC)[reply]

About the only way the engine could actually be burning that much more fuel is if the cylinders are missing (a lot). If that was the case the vehicle would be running very roughly and stalling. So, it must be the inaccuracy of the device. I'd compare this to the "time remaining" bar during a download. At the beginning, it tends to be highly inaccurate, but it gets more accurate the longer the download runs, as it's able to average info over a longer period to more accurately figure the current download rate. StuRat (talk) 14:53, 26 November 2008 (UTC)[reply]

Without knowing the details of how your car's "miles remaining" calculation works it's impossible for me to be certain, but I can think of at least a couple of confounding factors here which might explain your readings. When you turn your car on, it may be using the average fuel efficiency for your previous trip to calculate its "miles remaining". (Alternatively, it may use a factory-set 'default' value.) Once the car starts moving, the efficiency measurement is reset, and new calcuations are based on the current trip's data. Early in your trip, you will accumulate a lot of low-efficiency time: starting the car, stopping and starting at intersections, hard acceleration to get on the freeway and merge. By the time you reach the end of your journey, most of your time and miles are under efficient constant-speed conditions. Even counting the little bit of city driving at the end, the overall average efficiency for the mostly-highway trip will be good. You will see a similar effect on your journey home.

This is not to say that most automobile engines aren't appreciably less efficient when cold. Particularly in winter conditions, engine oil is quite a bit more viscous than it is at normal operating temperatures, and the engine has to work hard against that sticky, sludgy goo. But it generally takes very little time for a car to warm up when it is being driven. TenOfAllTrades(talk) 16:01, 26 November 2008 (UTC)[reply]

Answers above question the accuracy of the "miles remaining" information. Comparing that gauge information to when you have to fill the tank should give you a very good sense of how reliable the information is, IMO.

When I used to keep careful records of gas mileage, I was surprised at the dramatic difference between summer and winter gas consumption. It seemed too drastic to make sense - after all, so I thought, once the car has warmed up in the first part of a trip summer versus winter should not make a "lot" of difference. Parhaps my mistake was in underestimating just how much fuel was used in the warmup period. Unfortunately I did not have a "miles remaining" feature. CBHA (talk) 19:15, 26 November 2008 (UTC)[reply]

I think the way to discover whether there is something odd about the gauge (which is certainly possible) would be to drive the car from cold - then stop, turn off the engine, wait a minute - then jump back in and drive the exact same route again - but with the engine hot at the outset. If I'm right and it really is a cold versus hot engine situation - then the second time around would show normal consumption rates throughout the trip. I'll give it a try over the weekend.

But I do know that cold engines use more gas - that's a fact for sure - but what surprises me is the magnitude of that effect.

SteveBaker (talk) 19:30, 26 November 2008 (UTC)[reply]

Are you factoring in the gas used by starting the engine? --Carnildo (talk) 22:59, 26 November 2008 (UTC)[reply]

I didn't look at the 'miles to go' gauge until after I'd started the engine (because that's when it tells you you're low on gas) - so the cost of starting the engine was not a factor. SteveBaker (talk) 14:51, 29 November 2008 (UTC)[reply]

Though there are a number of salient difference, a internal combustion engine is still basically a heat engine so an appeal to the Carnot efficiency can be illustrative (if not entirely accurate).

Carnot:

E=1-{T_{Low} \over T_{High}}

In this case, T_Low is roughly the temperature of the air-fuel mixture prior to ignition, and T_High is the temperatures of the vented exhaust after it has finished all delivering all the useful work it can. For T_Low lets take something around room temperature, say 300 K (27 C). I don't know, T_High, i.e. the gas temperature, but I do know one doesn't want the engine block as a whole to go much above 100 C (373 K), so maybe the gas exits at around 400 K (127 C)? That would give a thermodynamic efficiency of 25%. Now suppose we lowered these values to simulate starting on a cold day. If you take -13 C (260 K) and 50 C (327 K), that gives a thermodynamic efficiency of 20%, or in practical terms it might take about 1.25 times as much fuel to deliver the same amount of useful work. Of course cold also adds other variables like more viscosity engine oil, but ultimately, I think this is the right order of magnitude. I would guess an engine that is warming up probably uses 15-50% more fuel than a warm engine and not the 300% more fuel that your experiment suggested. Dragons flight (talk) 23:29, 26 November 2008 (UTC)[reply]

(The reason you don't want the engine block going over 100C is that it's water cooled. If the water gets even close to 100C, tiny steam bubbles form in the hotter regions of the engine block (close to the cylinders, presumably). Those bubbles are excellent insulators - so they greatly inhibit further heat from being transferred from that spot on the block to the water - that local hot-spot distorts the metal and is the major cause of a cracked block...which is generally totally terminal for your engine! So the 100C operating limit (it's generally more like 85C) is not an efficiency thing - it's a not-destroying-your-engine thing! SteveBaker (talk) 14:51, 29 November 2008 (UTC)[reply]

Yes, I know the limit exists because the engine is water cooled, but it is still an efficiency thing. IF the components of your engine were capable of running hotter, then the fuel would be used more efficiently. Dragons flight (talk) 22:46, 29 November 2008 (UTC)[reply]

I guess this is OR (if educated guessing is research) but the computer knows to a high degree of precision (a fraction of a spritz) your fuel consumption but is not so good on your remaining fuel volume. And the fuel management box could be fast-warming your engine/exhaust system. In the old days that was done by leaning the mixture. That would lead to inefficiencies, too.

An alternative testing method is switch to instantaneous-fuel-use mode and get to max BMEP (~3000 rpm. Best fuel economy, fast enough for drag effects to show but still a safe, cold-engine speed) for long enough for the mpg reading to stabilize (very steady on the throttle). Do this at the beginning and end of your trip. Compare and discuss :-) Saintrain (talk) 01:48, 28 November 2008 (UTC)[reply]

Modern fuel-injected engines deliberately run "rich" for the first few minutes in order to "light off"/"light up" the catalytic converter. That is, by running rich, unburned fuel makes it as far as the catalytic converter and burns there, rapidly warming up the catalyst to proper operating temperature. You, of course, see this as really poor fuel economy for a few miles.

Atlant (talk) 23:53, 30 November 2008 (UTC)[reply]

Endorphins and interest in sports

Does lack of interest in a sport lead to a failure of the body to produce endorphins while playing when they would normally be expected? Vice-versa? (As a child, I noticed that I was not only the least interested in sports of anyone in any of my gym classes, but also the least able to cope with pain from an injury.) Neon Merlin 07:54, 26 November 2008 (UTC)[reply]

An interesting theory. As for myself, I might be interested in playing a sport, but find watching strangers play sports to be as dull as watching paint dry; I simply can't make myself care who gets which ball into which basket/hole/crevice. StuRat (talk) 14:45, 26 November 2008 (UTC)[reply]

I saw a good discovery channel show on a phenomenon that equated competitive desire within sport to testosterone levels (in both men and women). It discussed a correlation between testosterone and overall desire to "compete" (in any area). Other than a means of keeping the body fit, sport is primarily an outlet for these competitive desires, especially in a decidedly VERY uncompetitive youth that most western societies establish. In a sport like American (or in my case, Canadian) football, some degree of injury (usually just soft tissue; the type of thing that won't be life-long) tends to occur in every outing, for example. From experience, I could always tell who would be most successful as being those that were most willing to "play through" those non-life-long injuries (not display any of the behavioural indications that an injury has been sustained, like holding an injured area or limping), not because of peer pressure or social expectation or rational reward, but rather just because of that internal competitive desire.NByz (talk) 20:50, 26 November 2008 (UTC)[reply]

It's been shown that athletes have higher basal endorphin levels and response (Inder et al, "Elevated basal adrenocorticotropin and evidence for increased central opioid tone in highly trained male athletes." The Journal Of Clinical Endocrinology And Metabolism [J Clin Endocrinol Metab] 1995 Jan; Vol. 80 (1), pp. 244-8.), so lack of playing could definitely decrease your central opioid tone. If you're asking whether a "naturally" decreased endorphin tone causes decreased sports interest, that's tough. I don't know of any studies that approach the question in that way, most likely because you would have to study children from early in development all the way to adulthood...a very ambitious undertaking. - Draeco (talk) 23:22, 26 November 2008 (UTC)[reply]

Boundries of longitude and latitude for western europe 1955-1990

I wanted to know what the boundries for Western Europe would be as far as latitude and longitude? I am needing these to know what a person would meet criteria for a US Military medal criteria. Many medals have a boundry criteria for an award of a medal in a theater of operations. Like the European-African-Middle Eastern campaign Medal, they have a boundry. I need to know the exact latitude and longitude of Western Europe from the above time periods —Preceding unsigned comment added by 70.212.140.156 (talk) 08:09, 26 November 2008 (UTC)[reply]

It probably depends a LOT on who is doing the defining. I would say that before 1989 or so, the eastern boundary of Western Europe was the eastern boundary of West Germany; eastern and southern boundaries of Austria, and eastern boundary of Italy. The question is whether to include such countries as the Scandanavian countries (politically yes; geograpically probably considered "Northern Europe"). Our article on Western Europe includes a half-dozen or so maps that define it in slightly different ways. --Jayron32.talk.contribs 11:38, 26 November 2008 (UTC)[reply]

4d rotation of 3d objects

Last year I've read the novella 'Flatland' by Abbott. Then I came along another website telling stories in a way similar to Flatland, e.g. 3d beings messing with 2d ones and 4d beings with 3d ones. In one section, a 3d human lifts a 2d book out of the plane where 2d beings live, flips it over (rotates it 180 degrees in 3d space) and puts it back. The book is reversed/mirrored. 2d beings are confused as no rotation in a 2d plane can make this happen. Similarly, the 4d being does the same to a 3d book and upon inspection we find that the book was mirrored. Unfortunately I can't recall that website but I hope you get the idea.

Well, after that I read in a short story (by Asimov, if I remember correctly) that such a rotation would mirror the molecules and if a man were to undergo that procedure, his amino acids would turn from L to D and sugar molecules D to L and in the end he may be starved.

Yet in another message board(!) I read that such a rotation would not only mirror the molecules but also turn every particle into its antiparticle thus upon returning to the 3d world the object would be annihilated into gamma rays.

Sorry for the lenghty intro but visualising these is really hard for me. So,

1- Does such a rotation mirror the molecules forming the rotated object?

2- Does it also turn the particles into antiparticles?

3- Could a 4d being watching us from "above" interact with our 3d universe to accomplish such tricks?

4- Are the questions already moot as the electromagnetic interactions essential for seeing, touching and rotating matter are confined to our 3d universe so there is no way a 4d being could watch us or interact with our objects?

5- Also invalid as such feats would violate conservation of energy?

5- Or not moot at all because there may be 4d photons, other 4d force carriers, etc for the 4d being to observe and interact with our universe? 3d beings may or may not observe those forces directly but they would observe the effects and not finding a cause, maybe they'd call it "dark energy"? .. Ok that one was pure speculation, but I couldn't help writing!

Thank you!! 78.176.16.183 (talk) 12:10, 26 November 2008 (UTC)—Preceding unsigned comment added by 78.176.16.183 (talk) 12:08, 26 November 2008 (UTC)[reply]

I think the answers to 1 and 2 would be yes. For 3 the answer would also be yes, but it could also be done in three dimensions with a non-orientable wormhole. J kasd 13:42, 26 November 2008 (UTC)[reply]

The answer for (1) is yes, for (2) it's no (see Parity (physics)), the other points are moot because we don't know 4d beings or the hypothetical space they inhabit. The conservation of energy shouldn't be violated by mere mirroring. Icek (talk) 15:05, 26 November 2008 (UTC)[reply]

Addendum: You might also be interested in reading C-symmetry, T-symmetry and CPT symmetry. Icek (talk) 15:07, 26 November 2008 (UTC)[reply]

Just as a footnote - Abbots flatland really sucks - and I think I know the other book you're talking about...and it sucks too. Go out and grab a copy of "The Planiverse"...it's a MUCH better description of a 2D world. I absolutely guarantee it'll bend your mind! You can easily spend a half hour looking at each of the many illustrations - trying to figure out how (for example) the 2D steam engine works - or why the 2D house is built the way it is. Abbot's book is just awful by comparison. SteveBaker (talk) 18:42, 26 November 2008 (UTC)[reply]

Flatland's not bad, it's just not much good as a description of a 2d world. As a satire of Victorian society (the main point), it's ok. Algebraist 19:04, 26 November 2008 (UTC)[reply]

Um...it's kinda sexist...actually, outrageously, PAINFULLY sexist. It's embarrasing to read...you just want to grab the author by the throat and tighten your grip until he goes limp and finally quits this talk! His view of the 2D world is wrong in many regards (think about his descriptions of houses with doors and windows)...he kinda flips back and forth between a top-down 2D world and a side-on 2D world without proper consideration of what this actually MEANS. I dislike it greatly. Get a copy of Planiverse and you'll immediately see what I mean. SteveBaker (talk) 19:23, 26 November 2008 (UTC)[reply]

I haven't read the book for a while, but my recollection is that while the narrator (being a victorian gentleman) is outrageously sexist, the book itself is not. Algebraist 19:25, 26 November 2008 (UTC)[reply]

The narrator actually struck me as a little more progressive than his Flatland society, reflecting Abbott's own views on Victorian treatment of women(and the "criminal classes" represented by irregular polygons). Back to the general subject, the idea of a fourth spatial dimension large enough for rotation of objects is pretty speculative in itself, but another work I might recommend on the subject is The Annotated Alice by Martin Gardner, which discusses varying interpretations of what "looking-glass" matter(either antimatter or oppositely-chiral molecules) would do when in contact with "normal" matter. 69.224.113.5 (talk) 21:10, 26 November 2008 (UTC)[reply]

By the way, the "Asimov" story mentioned above is actually Technical Error, also published under the title The Reversed Man, by Arthur C. Clarke. --Anonymous, 02:15 UTC, December 3, 2008.

"Brain Balance" autism treatment

I can't seem to find much about this (http://www.brainbalancecenters.com/) treatment regime, except for posts on autism activism sites. Would this approach be described as 'evidence-based' or 'alternative'? Messiahxi (talk) 18:37, 26 November 2008 (UTC)[reply]

If you can't find much, especially on sites like PubMed, that's a very good clue that it's more to the alternative part of the spectrum. -- Aeluwas (talk) 18:40, 26 November 2008 (UTC)[reply]

indeed... as is the fact that it was founded by Dr. Robert Melillo, who is apparently a Chiropractic Neurologist. I was just wondering if anyone had specifically heard of this program. Messiahxi (talk) 18:56, 26 November 2008 (UTC)[reply]

A quick flip through the site reveals absolutely nothing about what, specifically, they actually DO. For people at the autistic end of the spectrum, some kind of treatment that actually works would be a truly wonderful thing - and clearly the parent of an Autistic kid needs to explore all of the options to help the child out.

But at the more 'normal' end, "curing" Asperger's syndrome is considered by most people who have it (me included) to be a REALLY BAD IDEA. Almost every adult who is at the more mild end of the spectrum will tell you that as bad as the downsides are - they are easily outweighed by the up-sides. If there were a magic pill that would cure my Asperger's - I wouldn't even consider taking it...not for one moment! So I get a little upset when people talk about "curing" children of the syndrome...aside from the fact that this site doesn't look too convincing to me, I worry that they may actually be destroying the potential that Aspergers offers. Aspergers (and Autism) is an actual difference in the structure of the brain - you can't simply use therapy and nutrition and whatever else they do to "fix" that. What you can do is to cause the child to suppress the beneficial things in order to "fit in" - which is a terrible, awful thing to do.

What us Aspies REALLY need is a comprehensive testing program so that "sufferers" can be identified earlier in life - and placed on the appropriate slot in the spectrum (Normal...Mild Aspergers...Severe Aspergers...Autism...Profound Autism). I didn't find out why life seemed so difficult until I was nearly 50 years old! What a SPECTACULAR difference it would have made if I'd known when I was in my early teens...I can't tell you the number of things I screwed up in interpersonal relations simply because I didn't know. Now I do - I positively cringe at some of the things I did that I now know to avoid. Once identified, we need to be taught the set of social skills and body language that everyone else takes for granted (most are mere 'conventions' that are quite teachable to someone with the intense ability to focus that characterises an Aspie). I've been through a 1 week course - and it's INCREDIBLE how much that helped. They didn't try to cure anything - just to tell me what other people know instinctually and apply automatically that I have to learn explicitly and think about consciously. That's why knowing is a HUGE part of what an Aspie needs on a day-to-day basis.

Case in point from yesterday. My kid (who is in college) phones me up at work (which is unusual) and tells me all about some text book that he needs and why he needs it and how he's going to pick it up - and oh, by the way, since we recently moved house, is the billing address on his credit card OK? So I listen carefully, answer the questions he asked, say goodbye and put the phone down. Then - my "training" kicks in. Why on earth did my kid ask me all of that crap? I don't need to know it. Then the alarm bell goes off..."Hold on - this must be one of those 'hidden agenda' things that I'm so useless at spotting!"...so I think hard about what OTHER message was buried in the phone call - and BINGO!...he wants me to offer to pay for the book. The point being that I totally lack that part of the brain that tells me what the other person might be thinking (I've heard this area of the brain called "the mirror neurons" because they function as a copy of the other person's thought processes. I simply don't have the ability to put myself in my son's position of needing to ask for a favor and not wanting to come right out and demand money. (Which is unfortunate - because an Aspie needs to be told exactly what you want because he/she can't know any other way!) But - because I've had the training - I know that when a conversation goes oddly, then there is something I'm missing about how the other person is thinking...and sometimes I can work out what it is and fix it. But when I didn't KNOW I had this problem (or, more exactly - when I didn't know that everyone else DIDN'T have this problem) - I'd never have thought to call my son back and ask if I could pay for the book.

(Of course, from my perspective - I'm just wondering why the heck there has to be all of this machiavellian double-talk going on in the world. If you want me to do something - JUST SAY SO FOR CHRISSAKES!)

SteveBaker (talk) 19:12, 26 November 2008 (UTC)[reply]

If it helps you at all, Steve, I'll tell you right now that every time a kid calls home from college, he's looking for you to pay for something, so you may as well just begin your conversation with "how much and how soon?" Matt Deres (talk) 21:26, 26 November 2008 (UTC)[reply]

Also, doesn't it seem strange that your son hasn't yet figured out how to get what he wants from you? Even if he wasn't aware of the Asperger's, you'd think (or at least I would) that he would intuitively have figured out what he needed to do? My daughter figured out how to wrap me around her finger in pretty short order. Matt Deres (talk) 21:31, 26 November 2008 (UTC)[reply]

Perhaps he has. He did, after all, get his dad to buy the book. APL (talk) 21:43, 26 November 2008 (UTC)[reply]

I can’t tell you how many times I’ve wished that people would just say what they mean, and I don’t have Aspergers as far as I know! (the mores the pity) --S.dedalus (talk) 21:37, 26 November 2008 (UTC)[reply]

I've wished the same thing, and I have been tested for Aspergers and found not to have it. I have no problem playing the game, but I really wish I didn't have to... --Tango (talk) 21:44, 26 November 2008 (UTC)[reply]

Firemaking in the 1700's.

Hello, I was wondering how fires were started and candles were lit in the 18th century. I searched for matches but found they were invented in the 19th century. I have asked a few people and they didn't know but guessed at flint or two sticks, however,I thought this was quite primitive for the 18th century and would like a certain answer to how fires were produced. Thank you. 82.27.54.8 (talk) 19:16, 26 November 2008 (UTC)[reply]

They used a tinderbox. —Jeremy (talk) 19:18, 26 November 2008 (UTC)[reply]

This was discussed here circa May 19 2008. Link? Edison (talk) 03:43, 27 November 2008 (UTC)[reply]

An easy and once common way to light candles, fires, etc, was to use an already lit candle, fire, coals, etc. The question is how did one start a fire when there wasn't a flame or smoldering embers somewhere around already. A minor point, sure, but the most common way to light a candle in the 18th century was probably to use a flame or embers already handy (depending on location and circumstance of course). In earlier times than the 19th century, when starting a fire was more difficult, it was common to "borrow" fire from your neighbor/friend/kith. Making fire might be of interest. Pfly (talk) 06:40, 27 November 2008 (UTC)[reply]

Good point. My grandmother lived as a girl in a house where there was no electricity. A collection of rolled up pieces of scrap paper she called " tapers" was kept near the fireplace, and one could be lit from the remaining coals in the fireplace to light a kerosene lamp or a pipe. I supposed this saved the cost of a match. Edison (talk) 17:20, 28 November 2008 (UTC)[reply]

November 27

Chicken head stabilization

I just thought this gizmodo story [7] is very cool and was surprised I can't really find more information on this behavior. Can anyone confirm that this is not an elaborate hoax and maybe offer some more videos/info on the subject?

I've handled chicken before but don't recall them doing that, but then, i wasn't paying much attention. Thanks. —Preceding unsigned comment added by 70.79.159.37 (talk) 06:45, 27 November 2008 (UTC)[reply]

That's regular chicken behaviour. The chicken is clearly used to being handled which accounts for the calm display of head stability. If you've ever had a chicken travel in a car with you it works even better. The possible reason for the head stabilising behaviour has, I think, been answered in a previous question somewhere. Richard Avery (talk) 08:31, 27 November 2008 (UTC)[reply]

Is that behaviour unique to chickens, as a matter of interest? --Kurt Shaped Box (talk) 10:43, 27 November 2008 (UTC)[reply]

Here's the same guy demonstrating the phenomenon with a non-chicken. [8]

Part of me wonders if that is real. There's something a little unnatural about the way these birds look and move and I'm not just talking about the heads. There's something computer generated looking about their heads and bodies. Maybe I'm just being paranoid. But the shapes and movement seem wrong, and the depth of field seems wrong. --98.217.8.46 (talk) 07:10, 28 November 2008 (UTC)[reply]

Why are limes seedless?

A bartender told me that all the limes she has seen are seedless while lemons contain seeds. Why is that? Did seedless limes arise naturally or were they bred for that trait, and if the latter, why not breed seedless lemons also? --Mathew5000 (talk) 10:00, 27 November 2008 (UTC)[reply]

Seedless lemons are rare but do exist: new varieties were reported recently[9][10], although the NYT shows up a 1911 reference to a seedless variety which I imagine did not catch on for some reason.[11]. The most common variety of (largely) seedless lime is the Persian lime, which is believed to be a hybrid[12], and which is propagated by grafting. The first article I linked mentions that one problem with seedless fruit is that it is difficult, requiring many years of breeding, to ensure that it really is seedless and not just rarely seeded. It takes a long time to selectively breed trees in general due to the time it takes before they are able to fruit; limes are a lucky hybrid. —Preceding unsigned comment added by 193.172.19.20 (talk) 11:04, 27 November 2008 (UTC)[reply]

Another thought. Is there much of a demand for seedless lemons? AFAIK, people don't generally eat them 'straight' (do they?)... --Kurt Shaped Box (talk) 11:10, 27 November 2008 (UTC)[reply]

I do. I'll eat a few slices after dinner to "cleanse the palate". StuRat (talk) 14:57, 27 November 2008 (UTC)[reply]

Any citrus works well for that. I use oranges. -- kainaw ™ 19:01, 27 November 2008 (UTC)[reply]

However, restaurants don't usually give me orange slices for that purpose, but the lemon wedges in my drink work well. StuRat (talk) 06:13, 28 November 2008 (UTC)[reply]

Hooray for kumquats! bibliomaniac 1 5 20:57, 27 November 2008 (UTC)[reply]

Also after poetry, especially Keats.

I'm inspired:

"Have a citrus slice, after eats,
 and also have one, after Keats." StuRat (talk) 14:39, 29 November 2008 (UTC)[reply]

Lots of people like lemon wedges in their iced tea or other drinks, and for squeezing over their fish, mozzarella in carozza, etc. And the seeds must bother at least a fair number of these people, or high-end joints wouldn't serve said wedges in a prophylactic cheesecloth that keep the lemon seeds out of the drink/main course. - Nunh-huh 03:55, 28 November 2008 (UTC)[reply]

Well, never underestimate the importance of pointless doohickeys that are meant to project high-class... I doubt people care all that much about the seeds. The cheesecloth just makes us feel fancy and justified in paying that much for our lobster... --07:02, 28 November 2008 (UTC) —Preceding unsigned comment added by 98.217.8.46 (talk)

Thanks for the answer, 193.172.19.20! --Mathew5000 (talk) 23:49, 27 November 2008 (UTC)[reply]

Bromelain from Pineapples

Hey all, For my A-level Biology coursework, I've got a task about the effect of bromelain on Jelly. I've read that there are two types of bromelain (stem and fruit), but am unclear on the difference between the two, other than where they're found. Can anyone help? Many hugs, Amzi (Talk To Me) 10:08, 27 November 2008 (UTC)[reply]

Trying to make jelly with raw pineapple pieces is doomed to failure in my experience! It liquefies around the fruit. Graeme Bartlett (talk) 11:28, 27 November 2008 (UTC)[reply]

Turns out that pineapple has enzymes (oh yeah, that'd be bromelain) that destroy the gelatine (not surprising given that gelatine is primarily protein, and bromelain is a protease). If you want to make pineapple jelly you have two options: use a gelling agent unrelated to gelatine; or (better) use something that prevents the enzyme from wrecking the gelatine - if you heat your jelly mix with some pieces of a bell pepper you can then gel it with gelatine. I doubt it helps Amzi though. --121.127.209.126 (talk) 12:02, 27 November 2008 (UTC)[reply]

The coursework involves heating it to a high enough temperature to denature the enzyme - I think about 75 degrees Celsius is about the temperature you need to heat it to - so the jelly will set after all. 86.128.107.146 (talk) 17:01, 27 November 2008 (UTC)[reply]

if you read the bromelain article it explains the difference between stem and fruit enzyme. Graeme Bartlett (talk) 05:36, 28 November 2008 (UTC)[reply]

is this for real??? -- Bruce Lee plays ping pong with nunchuck

Is this video for real?? How could they fake it:

http://uk.youtube.com/watch?v=9QHslHpK4-Q

Thanks! —Preceding unsigned comment added by 86.217.99.209 (talk) 10:36, 27 November 2008 (UTC)[reply]

I'm not convinced it's really Bruce Lee -- the video is so small, it could be a look-alike in a track suit. Remember Forrest Gump? Tom Hanks really wasn't a ping pong champion. And the fact that its a commercial really makes me believe it was faked. --70.130.54.91 (talk) 15:02, 27 November 2008 (UTC)[reply]

I don't know about Bruce Lee, but legendary cricketer Donald Bradman honed his skills using a cricket stump to hit a golf ball repeatedly against the curved surface of the family's water tank when he was growing up. So it might be possible to use a nunchuck for ping pong but whether it's Bruce Lee for real is hard to tell. Julia Rossi (talk) 05:20, 30 November 2008 (UTC)[reply]

Note that the Bruce character is filmed from a rear angle, his face is rarely shown close up and hardly ever frontal, unlike the opponent(s). You can get a glimpse of his facial features around 00:35 and 00:52, and he doesn't look like Bruce Lee. Some of the ball movements don't look quite natural, "Bruce" doesn't even follow the ball's movements with his eyes, sometimes looking 90 degrees away, and it's a commercial. I don't know how they "faked" it, but one likely scenario is having the Nunchaku-Ka and ping pong player mime their motions without a ball at all. Air ping pong, if you like. Maybe they improvised, maybe someone was shouting instructions while filming, maybe it was thoroughly choreographed. The ball could have then been added later by some variety of computer animation. ---Sluzzelin talk 06:19, 30 November 2008 (UTC)[reply]

The mystery of illusion is a bit more transparent in this clip, by the way. Enjoy! ---Sluzzelin talk 06:37, 30 November 2008 (UTC)[reply]

It's probably faked the same way they faked the tennis matches in the movie Wimbledon (see the special features on the DVD). Watch the video closely and you'll see two high, bouncing shots on "Lee's" side of the table that look a little unnatural. The scene is choreographed and the actors go through all the motions without a ping-pong ball. The ball is then added in using CGI. This works great until you need a slow-moving ball, where it becomes difficult to get the motion right. --Sub-nav5019 (talk) 18:42, 1 January 2009 (UTC)[reply]

Why would any of you doubt Bruce Lee's powers and abilities?

Ok, to clear the air. I led the team that created this viral campaign at JWT Beijing. This was a viral campaign to promote the Limited Edition Bruce Lee N96 for Nokia.

The person is not Bruce Lee but a chinese national who has won multiple Bruce Lee lookalike contests in China. He is also a student of Jeet Kune Do.

The video was shot using a background sound of people playing ping pong so that “Bruce” and the ping pong player / players know when to “hit” the ball.

The ball was later superimposed into the video + sound and all.

Hope this clears the air. I glad that you enjoy it. We had lots of fun making it.

Perturbation theory in quantum mechanics

I have a question about perturbation theory. If we expand the exact state as

|n\rangle =|n^{(0)}\rangle +\lambda |n^{(1)}\rangle +\lambda ^{2}|n^{(2)}\rangle +\cdots \ ,

with |n⁽⁰⁾> the eigenfunction of the unperturbed H₀. Normalizing the exact state gives to first order in λ (supposing |n⁽⁰⁾> was normalized):

\langle n^{(0)}|n^{(1)}\rangle +\langle n^{(0)}|n^{(1)}\rangle =0\ .

The usual reasoning goes on saying that, "since the overall phase is not determined in quantum mechanics, without loss of generality, we may assume <n⁽⁰⁾|n> is purely real." But with "overall phase" only the phase of |n> is meant, isn't it? Changing its phase would change the phase of |n⁽⁰⁾> with the same amount, so that their inproduct remains unchanged. This would mean that it is not in general possible to assume that <n⁽⁰⁾|n> is purely real. What am I missing? MuDavid 12:55, 27 November 2008 (UTC)[reply]

The problem has been solved. The "overall phase" may be a function of λ (which seems pretty crucial, so maybe our article should be changed to reflect this), and by choosing this function the right way, <n⁽⁰⁾|n> can be made purely real. Bransden and Joachain explicitly say the phase may be a function of λ, but they do not stress that's what makes the argument. MuDavid

13:54, 27 November 2008 (UTC)[reply]

Natural selection in humans

If, due to some freak tectonic shift, the entire Eurasian and African continents shifted overnight so that Sub-Saharan Africa was located where Northern Europe is now, and vice versa, how long would it take before natural selection made the two populations physiologically resemble what the other one formerly was? (i.e., how long before most of the Africans now living in a cold climate had white skin, and the Europeans now living in a very hot climate had black skin) 69.177.191.60 (talk) 16:55, 27 November 2008 (UTC)[reply]

It probably wouldn't happen. We would just use sunscreen and vitamin supplements to negate the effects of having the wrong colour skin for your climate (in fact, with a decent diet, the vitamin supplements probably aren't even required). --Tango (talk) 17:01, 27 November 2008 (UTC)[reply]

I've read that the genetic shift from dark skin to light is estimated to take ~10000 years. Of course, as Tango says, that was before the advent of modern technological and medical advances. Dragons flight (talk) 05:58, 28 November 2008 (UTC)[reply]

And involved much smaller populations. With small populations you have things like founder's effect and etc. With very large populations you get regression to the mean. --98.217.8.46 (talk) 06:53, 28 November 2008 (UTC)[reply]

For natural selection to operate, people would have to die as a result of their skin color. We have ways to prevent that now. Of course, a small portion of the people would likely ignore all the medical warnings and go without vitamins or sunscreen, and die as a result. So, we might eventually get changes in skin color, but only if this effect was quicker than natural genetic drift and the effects of intermarriage. StuRat (talk) 06:09, 28 November 2008 (UTC)[reply]

Well, technically they wouldn't have to die, they'd just have to not reproduce, and others would have to out-breed them. But yeah, same difference, not gonna happen in today's world, population is too big and we don't tolerate that sort of thing. --98.217.8.46 (talk) 06:52, 28 November 2008 (UTC)[reply]

If the freak tectonic shift also ended technological civilization, there would certainly be selection for dark skin in the new Africa, but I don't think the population of the new Europe would necessarily evolve to "white" skin. The Indians of Canada and Alaska have been there for over 10,000 years and they don't have white skin. —JerryFriedman (Talk) 23:06, 3 December 2008 (UTC)[reply]

dissassociation of salts

Do salts necessarily disassociate completely when dissolved in water? Our article does not say. Or is there an equivalent of pKa for salts to describe their tendency to disassociate? ike9898 (talk) 17:13, 27 November 2008 (UTC)[reply]

They don't necessarily dissociate completely. And there absolutely an equivalent of pKa, and it's calculated the same way. It's usually called the solubility product constant. See solubility equilibrium. --Bennybp (talk) 17:37, 27 November 2008 (UTC)[reply]

Salt solubility in non-aqueous solvents

Is there any freely accessible information anywhere on the solubility of common salts in non-aqueous polar solvents (e.g. alcohols, ethers)? 69.177.191.60 (talk) 17:19, 27 November 2008 (UTC)[reply]

Our article, Sodium chloride includes a table of its solubility in various liquids. I expect out articles on other salts will have similar data. --Tango (talk) 17:36, 27 November 2008 (UTC)[reply]

I believe the CRC Handbook of Chemistry and Physics has that information. I guess that's "freely available" if you check your local library - typically the reference section. It can be a bit hard to find the information though. --Bennybp (talk) 17:42, 27 November 2008 (UT

Engineering handbook in English, German and Japanese

I would like to find three general handbooks in these three languages. What are the most common works?--Mr.K. (talk) 18:17, 27 November 2008 (UTC)[reply]

You don't say which kind of engineering you have in mind? I'm not an engineer, but in the field of mechanical engineering I sometimes turn to the Mechanical Engineers' Handbook, which is in a library near me. Engineering is such a vast subject that for any particular topic a general handbook is likely to point you somewhere else. Xn4 (talk) 03:13, 28 November 2008 (UTC)[reply]

In the meantime I found two German general engineering handbooks. There are this and this one. Engineering is surely a very vast field. However, there is plenty of common stuff. Physics', mathematics', material science's books for engineering are not uncommon. I need handbooks that unite all this common ground. Mr.K. (talk) 16:17, 28 November 2008 (UTC)[reply]

Jacuzzi Question

When I'm sitting in the jacuzzi with a cigarette, the water start to bubble when I blow out the smoke. Does anyone know why this happens? Thanks in advance. 99.230.51.61 (talk) 23:11, 27 November 2008 (UTC) —Preceding unsigned comment added by 99.230.51.61 (talk) 23:10, 27 November 2008 (UTC)[reply]

Are you sure you're not passing gas? —Cyclonenim (talk · contribs · email) 23:11, 27 November 2008 (UTC)[reply]

The water bubbles whenever the bubbles are switched on, it has nothing at all to do with your cigarette. See confirmation bias. --Tango (talk) 23:12, 27 November 2008 (UTC)[reply]

Sorry, I said what I meant wrong. When I blow the smoke over the jacuzzi I hear the bubbles a lot louder. Why? 99.230.51.61 (talk) 23:39, 27 November 2008 (UTC)[reply]

The ears and mouth are connected, so it's possible to act of blowing somehow affects your hearing. Try doing it without the smoke, just blow, and see what happens. --Tango (talk) 23:54, 27 November 2008 (UTC)[reply]

I've done that. Also, the sound gets quite a lot louder. 99.230.51.61 (talk) 00:01, 28 November 2008 (UTC)[reply]

All sounds rather dubious to me. The smoke is not going to be in a large enough amounts to affect the bubbles or things like air pressure, and it will be rapidly rising away from them at that. My humble suggestion is some sort of placebo effect and confirmation bias. --98.217.8.46 (talk) 06:46, 28 November 2008 (UTC)[reply]

Do you mean the sound gets louder when you blow without smoke? If not, then it's probably just your imagination playing tricks on you (combined with confirmation bias). If it does get louder without smoke, then it could be a genuine effect on your hearing (it won't have any effect on the actual volume of the sound, though). --Tango (talk) 13:31, 28 November 2008 (UTC)[reply]

November 28

Chemistry 1310

When 3.77 g of compound A (molar mass = 121.0 g) reacts with a few grams of compound B (molar mass unknown), 6.98 g of product C is produced. Analysis shows that C is actually a simple addition compound (that is, AB) and that the yield of product was 76.3% based on A. If A is the limiting reagent, what is the least amount of B that must be used to prepare the maximum amount of C obtainable from 3.77 g of compound A? —Preceding unsigned comment added by 128.61.26.178 (talk) 00:45, 28 November 2008 (UTC)[reply]

Do your own homework. Then you will learn somethng. —Preceding unsigned comment added by 98.16.67.220 (talk) 01:35, 28 November 2008 (UTC)[reply]

Or at least show us your attempt to solve it, if you want our help. StuRat (talk) 06:03, 28 November 2008 (UTC)[reply]

A psychology question - when do we feel we've "seen all the examples"

Suppose I have a collection of items, say N of them. The objects might be episodes of a TV show, collectible figurines, whatever. (In my case, they are snippets of information I show on a website - a different one each day or week).

Suppose I present them one by one to a subject, who doesn't know how big N is.

My basic questions are :

How soon will the subject begin to feel that they've seen all the objects, and lose interest?
How can I order the presentation to hold the subject's interest for as long as possible?

Any ideas, even partial, even "this is called 'Phenomenon X' so look it up yourself" would be welcome! mike40033 (talk) 03:44, 28 November 2008 (UTC)[reply]

I think you may have a bad assumption there, that people will only lose interest after they feel they've seen all the objects. While that may be true for some, others may lose interest the first time they see a repeat, or even before that. For an example, when I checked out my friend's cable TV, which has just about every channel there is, I only flipped through the channels until I felt I had a good sample of what was out there, then lost interest.

As for holding interest, you want each object to be more interesting than the last. As an example, let's try a joke:

"My garage is so big I can fit a boat in there, or even a yacht. I have a Nimitz class aircraft carrier in there at the moment." - Stays interesting because successively more absurd items are listed.

"My garage is so big I can fit a Nimitz class aircraft carrier in there, or a yacht. I have a boat in there at the moment." - Starts out interesting, but quickly gets dull.

There is an interesting problem with trying to make each object more interesting than the last, however. It's something I like to call Fantasy Island syndrome. That TV show started out to be quite reasonable. For example, they would bring a couple of separated High School sweethearts together again, and maybe there would be a romance. However, the network felt the need to have each episode trump the previous, so that they became more and more absurd. Toward the end Mr. Roarke had apparently become God instead of the original owner of a quirky resort. Then the show was canceled. So, beware that you can only outdo the previous object so many times, before you hit a wall. StuRat (talk) 05:40, 28 November 2008 (UTC)[reply]

Related point, from a statistical perspective. If your subject has seen n of the N objects, his maximum likelihood estimate for N will be n, although some authors have argued for a point estimate of 2n. HTH, Robinh 08:04, 28 November 2008 (UTC)

I believe that quite a lot of research work has been done on this. The makers of collectible card games (Pokemon, etc) have to solve this problem. They want to keep people looking out for 'new' cards - but they don't want to have to design and print too many different designs. So they have to introduce new es once in a while. But it's not enough to simply add a new card at full production run once in a while - it's necessary to have a new card that only shows up very rarely - that you'll only ever see once. That leads you to think that some cards must be very rare indeed (because you've seen some that are fairly rare) - and therefore, if you wait long enough, there may be an even rarer one coming along. This kind of trick is also used in computer games to keep things seeming new...if you get waves and waves of the same enemy coming at you time after time, it gets boring fast - but introducing a rare 'new' thing (and then not bringing it up again) makes you want to keep playing in order to see the next rare thing.

So I'm pretty sure there is some science behind this - I don't know (in detail) how they plan this stuff out - but I believe there is (somewhere) a comprehensive answer.

20:16, 28 November 2008 (UTC)

Is that anything to do with a law of intermittent returns that keeps people say, watching test cricket? There's also another "law" operating built into that one which means that the minute the fan is distracted, something exciting happens and they miss it. Incentive has a useful intro and maybe anything to do with reward anticipation, Julia Rossi (talk) 21:49, 28 November 2008 (UTC)[reply]

Are you impuning test cricket? Gadzooks!

I recall reading somewhere about the question of how often a slot machine has to pay to keep gamblers interested. This is probably well-researched. Whether much of the research is published is another matter. CBHA (talk) 22:34, 28 November 2008 (UTC)[reply]

Neva CBHA, not moi, but since you mentioned it's allure (more or less) it would be an interesting study to find stats of the efforts televised cricket must make to keep people glued to the screen: replays, minute detail of technicalities according to the bowling style,, new/old ball, batting stance/angle/averages, stump tweaks, slip and field positions and their rationale, dropped catch/great catch, wind direction, crowd behaviour, the finer points of lbw, including all those diagrams of field arrangements and runups, and findings of a player's state of mind, form, god it goes on and on. Not to mention the romance of the game. This kind of open-endedness means people simply must stick around to find some kind of closure or decide on balance it's going one way or the other, and opt for a conversation with the person next to them. Now there's a study in delayed gratification. Julia Rossi (talk) 07:27, 29 November 2008 (UTC)[reply]

Great article, Julia, I only wish I'd created it myself [13]. :-) StuRat (talk) 18:48, 29 November 2008 (UTC)[reply]

PS, puts a new spin on the idea of "test" cricket, non? Julia Rossi (talk) 07:34, 29 November 2008 (UTC)[reply]

To an American, a "test cricket" is a grasshopper used in an experiment. StuRat (talk) 18:48, 29 November 2008 (UTC)[reply]

Overlap of electron orbitals in violation of Pauli Exclusion Principle?

Electron orbitals (s,p,d, etc.), visualised in the conventional way as probability distributions centred on the nucleus, are frequently shown SEPARATELY in textbooks as spheres, dumbells, etc. Many diagrams appear to indicate that the probability function reaches inwards fairly close to the nucleus in all cases (I realise there is a finite probability of 'finding' any 'orbital' electron in almost ANY position). If this is taken at face value, then does this not mean that for atoms with several orbitals (more than one s-orbital, or an s- and a p-orbital, for example), the orbitals OVERLAP, and therefore, for example, a p-electron could be found in the space that could also be occupied at another time by an s-electron? To make myself completely clear, I am imagining an atom with dumbell-shaped p-orbitals and a spherical s-orbital, and cannot think how to draw the two orbitals without them passing through one another. Bearing in mind the restriction on electron numbers in an orbital set by the Pauli Exclusion Principle (2), this indicates my visualisation is wrong, but I don't know what the correct visualisation is. Is it perhaps the case that the orbital diagrams are completely hypothetical , being merely solutions to the Schrodinger equation, and that no atoms (other than Hydrogen?) actually have anything like these textbook distributions I have referred to, the truth being that the orbitals hybridise in some complex way? If so, do the conventional diagrams have any value? I asked a University chemistry lecturer this question 40 years ago, but he was unable to answer it. It has been nagging me ever since, and this forum is the first real opportunity I have had to obtain a solution. Pigmailion (talk) 10:41, 28 November 2008 (UTC)[reply]

Your visualisation is correct, the orbitals do overlap (indeed each electron has a positive probability density at almost every point of space), and the Pauli principle is not violated. All the Pauli principle says here is that no two electrons can have exactly the same quantum numbers; it says nothing about how the position-distributions are related. Algebraist 13:43, 28 November 2008 (UTC)[reply]

Thank you. Would this imply that I need to free myself of the concept of electron energy levels being rigidly related to distance of the electron from the nucleus? It seems that a 'valence' electron could spend some of its time closer to the nucleus than what I would call an 'inner-shell' electron. Although, as I understand it, one free electron in space is physically indistinguishable from any other, does a particular single electron in a given atom preserve its quantum identity indefinitely in the absence of external stimuli, or is there the possibility of two electrons spontaneously exchanging quantum states (leaving the atom overall unchanged)?Pigmailion (talk) 15:23, 28 November 2008 (UTC)[reply]

I think your mistake is that you're thinking of the wave function of a two-particle system as two one-particle wave functions superimposed on one another in some sense. That's not how it works at all. Wave functions (unlike every other kind of wave found in physics) live in the configuration space of the system, not in physical space. When your system consists of a single particle whose internal state (like spin) can be neglected, there's a one-to-one correspondence between points in space and (a particular orthogonal decomposition of) states of the system, so you can think of the wave function as living in space and draw it as such. But in a two-particle system the configuration space is six-dimensional.

To be a little more concrete, let me work this out for the much simpler problem of noninteracting spin-0 fermions in a one-dimensional infinite square well. (Spin-0 fermions are impossible in relativistic QFT but perfectly fine in nonrelativistic traditional QM.) In the one-particle case the Schrödinger equation is

\partial _{t}\Psi (x,t)=-ik\partial _{x}^{2}\Psi (x,t)

with the side condition that

\Psi =0

at the boundaries of the box, which I'll take to be at

x=0

and

x=\pi

. The solutions are then normalized linear combinations of

\Psi _{n}(x,t)=e^{ikn^{2}t}\sin nx

where n ranges over the positive integers. In the two-particle case the Schrödinger equation is

\partial _{t}\Psi (x_{1},x_{2},t)=-i(k_{1}\partial _{x_{1}}^{2}+k_{2}\partial _{x_{2}}^{2})\Psi (x_{1},x_{2},t)

.

If the particles are distinguishable then the solutions are linear combinations of

{\begin{array}{ll}\Psi (x_{1},x_{2},t)&=(e^{ik_{1}n_{1}^{2}t}\sin n_{1}x_{1})(e^{ik_{2}n_{2}^{2}t}\sin n_{2}x_{2})\\&=e^{i(k_{1}n_{1}^{2}+k_{2}n_{2}^{2})t}\sin n_{1}x_{1}\sin n_{2}x_{2}\end{array}}

.

But if the particles are indistinguishable fermions then we have the side condition that

\Psi (x_{1},x_{2},t)=-\Psi (x_{2},x_{1},t)

, and in order to satisfy that we have to limit our solutions to antisymmetric combinations of the above, i.e. to

\Psi (x_{1},x_{2},t)=e^{ik(n_{a}^{2}+n_{b}^{2})t}(\sin n_{a}x_{1}\sin n_{b}x_{2}-\sin n_{b}x_{1}\sin n_{a}x_{2})

.

Note that we no longer have solutions with

n_{a}=n_{b}

. The lowest energy state is the one with

\{n_{a},n_{b}\}=\{1,2\}

. Do the wave functions of the two particles overlap? It's a meaningless question because the particles don't have individual wave functions. There's just one wave function and it's defined over a two-dimensional configuration space, even though the physical space of the problem is still one-dimensional. The exclusion principle is manifested in the fact that the wave function is zero along a "diagonal" line in the configuration space, which has no analogue in physical space. Note also that the single-particle wave functions overlap completely in this example and can't be classified according to their distance from any particular location. -- BenRG (talk) 17:21, 28 November 2008 (UTC)[reply]

A less technical explanation is that "two orbitals overlap" means their associated electrons can be in the same place. That doesn't require that they are there at the same time. More importantly, the possibility of being in the same place doesn't require that they have the same angular momentum and energy (comparable to "velocity and direction" in more conventional object motion) when they are there. DMacks (talk) 03:06, 29 November 2008 (UTC)[reply]

Possibility of life on another planet which does not Evolve

Given that one assumes the appearance on another planet (in another solar system) of an initial single 'living' organism, can we question the NECESSITY of some ubiquitous features we find on planet earth? For example, is there an inevitability that more than one living organism exists on this other planet?
Is it conceivable that the control mechanisms for building the body of the first-appearing organism do not have, or need, to provide reproductive abilities? I am imagining a stable environment in which the sole (very simple?) organism on the planet metabolises, grows, maybe repairs or discards damaged parts (having a fairly uniform internal structure), and lives for a considerable time. Maybe there would be some difficulty in this case of deciding whether the organism was alive! Is the answer to this question linked to the necessity of supposing that more than one organism would be expected to appear on a planet where life develops?
Secondly, can we imagine another planet whose environment is very uniform and very stable over a long period, such that, given some initial period of evolution of (a number of) organisms, natural selection operates in such a way as to eliminate all significant deviations from the existing population structures caused by mutation and genetic drift. Would this not result in a planet with species that changed very little over large timescales? Or is the very nature of interaction between species chaotic, regardless of environmental stability? Does the huge number of species that have existed on this planet(most of which are extinct) result mainly from the instability of this earth's environment, and is not therefore something we should necessarily expect to find elsewhere in the cosmos, or is it an inevitable consequence of life's chemistry? Pigmailion (talk) 11:42, 28 November 2008 (UTC)[reply]

I recommend reading Solaris, it discusses a situation not unlike what you have just described. --131.188.3.21 (talk) 12:52, 28 November 2008 (UTC)[reply]

Reproduction has been part of every definition of life that I've seen (it's a very difficult thing to define, but the definitions have certain things in common). As for life without evolution, it is certainly possible for a species to stay essentially unchanged for millions of years, there are examples on Earth. For an entire ecosystem to be unchanged seems unlikely (although presumably not impossible). Natural selection only affects characteristics that improve or hinder an organism's chance of reproducing, a lot of characteristics don't do that so aren't affected. Those characteristics would be susceptible to genetic drift, so there would be some changes going on over long enough time scales. Interactions between species could also be relevant (you can get "arms races" between species, eg. a plant develops harder and harder flesh so an animal develops harder and harder teeth). Earth's environment probably isn't any less stable or uniform than that of other planets capable of supporting life as we know it, so I expect most ecosystems would include evolution on a similar scale to that seen on Earth. --Tango (talk) 13:06, 28 November 2008 (UTC)[reply]

Continental drift seems unusual, and serves to change the environment considerably, including climate and the level of isolation of land species. The sometimes cloudy/sometimes clear nature of the sky on Earth also seems unusual. Most other planets either always have clear skies or always have a thick cloud cover. This means that long term changes in the cloudiness of the sky (due to volcanoes, meteors, etc.) can affect evolution in ways it can't on other planets. StuRat (talk) 14:21, 28 November 2008 (UTC)[reply]

It's unusual in our solar system, but then so are planets capable of supporting life as we know it. Planets capable of supporting such life are likely to be more Earth-like than other planets in our solar system. --Tango (talk) 15:11, 28 November 2008 (UTC)[reply]

I had a similar thought to the one organism concept. However, I thought it more plausible that one colony of single celled organisms, like coral, could exist where the individual cells do evolve, but any cells that split off from the colony are unable to survive on their own. This could eventually lead to one colony spread around the planet. StuRat (talk) 14:28, 28 November 2008 (UTC)[reply]

There would be strong evolutionary pressure for cells to become independent because doing so would reduce competition for resources. Even if the situation you describe can develop, I don't think it can be stable. --Bowlhover (talk) 06:06, 30 November 2008 (UTC)[reply]

Here's an example: Picture a colony of single celled organisms that develops sexual reproduction, yet is incapable of motion, and requires that two cells be adjacent, so the genetic material can be exchanged through the cell walls. Any cell that split off from the colony would be incapable of reproducing. StuRat (talk) 18:12, 30 November 2008 (UTC)[reply]

Disease transmission from old books (and other artefacts)

I'm a collector of old books, residing in England. Some of my books are 300 years old. At that time, and much later on, I guess there were a number of fairly common disease organisms around, which are now much rarer, that could have been transmitted via contact with a book that had been in contact with an infected owner. Does anyone know of a modern case of infection (by a nowadays rare organism) from an old book? I could also extend my question to ask whether there is any evidence of disease transmission through books and other secondhand items (computers, toasters, cars, etc. etc.) that change ownership today. It strikes me that, if hospitals have to go to great lengths to sterilise equipment, that organisms can readily be transmitted in this way. I'm not a hypochondriac, just curious about the survival times of various disease-causing organisms in the normal human environment. Pigmailion (talk) 13:54, 28 November 2008 (UTC)[reply]

Most disease organisms can't survive for more than a few hours outside the body. I would think the longest lasting organisms would be eggs of a parasite, that, when ingested, might hatch. However, I doubt if even they would last 300 years. StuRat (talk) 14:08, 28 November 2008 (UTC)[reply]

Most ... but not all. See endospore. Gandalf61 (talk) 14:26, 28 November 2008 (UTC)[reply]

Golden staph is considered a big bogey in hospitals where human to human contact is what it requires. It's considered "an incredibly hardy bacterium, as was shown in a study where it survived on a piece of polyester [hospital curtain] for just under three months." Science fiction and mummy's curses account for other misinformation, though the section Possible causes] lists some moulds. Julia Rossi (talk) 21:38, 28 November 2008 (UTC)[reply]

Anthrax spores, according to the article can last for many decades and possibly centuries. Richard Avery (talk) 08:11, 29 November 2008 (UTC)[reply]

Single or multiple breasts

Are there any validated examples of women "born with" (i.e. later developing) either just one or more than two (natural) breasts? If so, why would this be? —Preceding unsigned comment added by 209.161.213.199 (talk) 14:03, 28 November 2008 (UTC)[reply]

Extra nipples (supernumerary nipples) are quite common in both men and women. Extra breasts (including nipple, areola, and fat) are rather more rare, but so-called accessory breasts are not unheard of. (The term for the condition is polymastia.) TenOfAllTrades(talk) 14:45, 28 November 2008 (UTC)[reply]

erath gravity

what is the power needed to escape the erath atmosphere by considering the efect of hight on gravity bat not the airodinamic? --אזרח תמים (talk) 14:37, 28 November 2008 (UTC)[reply]

I think you're talking about gravitational potential energy. The formula for it is

U=-G{\frac {m_{1}m_{2}}{R}}

(it's negative because you need to add more energy in order to get free). If we plug in the mass and the radius of the Earth, the energy (in Joules) required to get an object from the surface of the Earth to infinite distance is 62.5 million times the mass of the object (in kilograms). If the object is, say, a person weighing 70kg, the energy required is about 4 gigajoules (equivalent to about a tonne of TNT). If you don't want to get all the way away from the Earth but just high enough that you are out of most of the atmosphere, it's significantly less. Low Earth orbit starts at about 200km above the surface (that's roughly where it becomes possible to have reasonably stable orbits without the atmosphere being a problem - orbits do still decay, just fairly slowly), the energy required to get an object to LEO is the energy required to get it from the surface to infinity, minus the energy required to get it from LEO to infinity. The energy required to get it from LEO to infinity is the same formula as above, but with R replaced by R+200km, so for the 70kg person we get the difference as 133 megajoules, or about 33kg of TNT. --Tango (talk) 15:10, 28 November 2008 (UTC)[reply]

tanks--אזרח תמים (talk) 16:04, 28 November 2008 (UTC)[reply]

You're welcome. --Tango (talk) 16:58, 28 November 2008 (UTC)[reply]

How much additional energy would be needed to add orbital velocity to the person, besides getting him to the specified altitude of 200 km, from which he would fall back down? Edison (talk) 17:15, 28 November 2008 (UTC)[reply]

Excellent point, I forgot to mention that! Orbital speed at 200km is about 7.8 km/s, plug that into E=1/2 mv² gives (for the 70kg person above), an additional energy requirement of about 2 GJ, or half a tonne of TNT. When you factor in things like gravity drag (essentially the energy required to maintain your current altitude while you're climbing) and atmospheric drag, the actual amount of energy required to get from the surface to orbit is going to be greater than the sum of those values. You'll notice that the energy to get into orbit is nearly 20 times greater than the energy required just to get to the right altitude - that's why sub-orbital flight is so much easier than orbital flight (and hence why companies like Virgin Galactic are just doing straight up and straight down flights for the public with about 6 minutes in space rather than actually taking them into orbit). --Tango (talk) 17:41, 28 November 2008 (UTC)[reply]

What you are calculating is the potential and kinetic energies a mass would have once it reaches orbit or escape velocity. The actual energy expended when using, for instance, a rocket to reach required velocities will be much greater. Remember, you are lifting and accelerating a large amount of fuel in order to propel a much smaller mass, and the potential and kinetic energies of that fuel needs to be taken into account. Probably the easiest way to approach the problem, is to find the required Delta-v, then use Tsiolkovsky's rocket equation to calculate the total energy required.—eric 22:17, 28 November 2008 (UTC)[reply]

Indeed, I'm assuming some form of 100% efficient propulsion, a (ideal) space elevator, say. Rockets require far more energy than the naive calculations I have presented would suggest. --Tango (talk) 22:30, 28 November 2008 (UTC)[reply]

PCR Primers

If I ran a PCR reaction and one of my primers was not working, for whatever reason, is there any possibility to have no bands appear under UV light after gel electrophoresis? Donek (talk) 17:21, 28 November 2008 (UTC)[reply]

Usually you'll see your primers at the bottom of the lane, but (for example) they can be obscured by loading dye. It also depends on what you're using to visual nucleic acid (ethidium bromide, SYBR green, etc), and how you visualize your gel (exposure time, etc). --Scray (talk) 17:38, 28 November 2008 (UTC)[reply]

I'm using dntp's as well as the dye. Might either obscure this? I'm using ethidium bromide to visualise and only exposing the gel for a moment's glance and throwing it away as not getting results. How do I test if a tube labelled as containing a certain primer actually contains a primer at all? Donek (talk) 18:15, 28 November 2008 (UTC)[reply]

You should always have a positive control, and having multiple controls will allow you to know which of your reaction components is working properly. In addition, your gel imaging station should support integration (prolonged exposure) because you might miss your result otherwise. --Scray (talk) 18:25, 28 November 2008 (UTC)[reply]

I have been getting positive results for all other reactions except one. This outcome occurs in a repetitive fashion. I use positive and negative controls and I am using bromo-blue as the loading dye. I have suggested to other students (one phD) and two lecturers that there may be a problem with the primer but they have said that there would have been evidence of this, maybe what you initially suggested. I'm going to go in to test it anyway tomorrow but I don't know how likely I am to be right. I don't understand why it would work for all other reactions but not one in particular, especially in a repeating pattern. I can only think it could be the primers at fault. Donek (talk) 20:54, 28 November 2008 (UTC)[reply]

I would think hard about every single thing that is different between your positive controls and your experimental reaction. Additionally, I would search for a PCR troubleshooting page, just to explore ideas, e.g.: [14]. Hope this helps! --Scray (talk) 00:48, 29 November 2008 (UTC)[reply]

That's a great link, thanks. One more question. What would be observed under UV light if only one primer was added to the mix? Donek (talk) 14:00, 29 November 2008 (UTC)[reply]

There would be very little if any signal. You're staining with ethidium bromide, which intercalates between the bases in double-stranded nucleic acids. Unless the primers form primer-dimers, they wouldn't stain incredibly efficiently. Perhaps more importantly, however, if only one primer, rather than a primer pair, was added to the PCR mix, the resulting amplification would be linear (1, 2, 3, 4, 5, ..., N) rather than exponential (1, 2, 4, 8, 16, ..., 2^N) leaving you with very little amplification product and lots of unused primers in the end. – Clockwork Soul 18:08, 29 November 2008 (UTC)[reply]

November 29

caffiene

can caffiene be smoked? —Preceding unsigned comment added by 76.14.124.175 (talk) 02:23, 29 November 2008 (UTC)[reply]

In the world of shisha there are ads for blends of caffeinated tobacco. I don't know anything about the actual dosage or effect. ---Sluzzelin talk 06:10, 29 November 2008 (UTC)[reply]

I can think of at least three other alkaloids – nicotine, morphine (as opium), and cocaine – that are smokable, which suggests that it's possible, but I know of no instances where caffeine is subjected to the same process. I would strongly advise against attempting it, however. Seriously. Caffeine overdoses can be fatal. – Clockwork Soul 08:18, 29 November 2008 (UTC)[reply]

I agree, we should be looking for ways to make smoked drugs into something edible, like coffee, instead, as smoking anything causes lung cancer. Pass the special brownies and grow those tomacco plants, please. StuRat (talk) 14:33, 29 November 2008 (UTC)[reply]

It is not true that “smoking anything causes lung cancer”. --Mathew5000 (talk) 15:23, 29 November 2008 (UTC)[reply]

Well, whilst I don't agree with the certainty with which StuRat stated it, it's kind of true that smoking (not inhaling) anything can cause cancer. When you smoke, you burn something, almost always inefficiently. When you do this, you produce carcinogens. Carcinogens cause cancer. —Cyclonenim (talk · contribs · email) 16:25, 29 November 2008 (UTC)[reply]

(ec) It's a pretty good approximation to 'true', however. Burning just about any organic material at low temperatures generates a number of carcinogenic products of incomplete combustion; this includes nasty polycyclic aromatic hydrocarbons like benzo[a]pyrene. I suppose that for some smoked products the user does not typically inhale particularly deeply, providing a modest amount of protection to the lungs; in those cases carcinogens would be largely deposited in the nose, mouth, lips, and throat, leading to oral and nasopharyngeal cancers. TenOfAllTrades(talk) 16:40, 29 November 2008 (UTC)[reply]

You are arguing that smoking anything should cause cancer, theoretically. But empirical data refute the claim; a 2006 study found no statistical association between smoking marijuana and lung, head, or neck cancer.[15][16] --Mathew5000 (talk) 19:16, 29 November 2008 (UTC)[reply]

It's rather dangerous to rely on a single study to draw a conclusion. Your remark could just as easily have said – correctly – that "a 2006 study found a statistically-significant association between smoking marijuana and lung cancer": PMID 18238947. Looking at PubMed, the best I can say is there's not a good scientific consensus one way or another. I don't see any clear-cut results from the last couple of year's publications, and there's a review in Arch. Intern. Med. that summarizes the data up to 2006 pretty well: PMID 16832000. Essentially, there's good data to support the conclusion that heavy marijuana smoking is linked to a number of clinical and histopathological markers of premalignancy, but the step to a demonstrated increase in lung cancer (or not) isn't there yet. Most of the studies I've looked at today don't seem to be sufficiently large or well-controlled. My two cents. TenOfAllTrades(talk) 20:14, 29 November 2008 (UTC)[reply]

I think it's also fair to compare the level of exposure that a "heavy" marijuana smoker gets to the amount that a "heavy" cigarette smoker when considering carcinogenic effect. I've known plenty of people who smoke 40 cigarettes a day (2 packs), but I've never met anyone who smokes 40 joints per day. --Sean 20:42, 29 November 2008 (UTC)[reply]

Agreed. While I stick by my claim that all smoking causes cancer, most pot-heads may be lucky enough to be below the exposure level which would cause a statistically-significant effect that can be easily measured. StuRat (talk) 18:03, 30 November 2008 (UTC)[reply]

It's also possible that smoking tobacco exposes a person to more or more powerful carcinogens then smoking marijuana dosage being equal. This doesn't imply that all smoking causes cancer is wrong Nil Einne (talk) 11:43, 1 December 2008 (UTC)[reply]

Cost of an additional degree of heating

Let's say the average temperature outside is 30 °F. Now, let's say that someone can tolerate an indoor temperature of 70 °F but feels better with, say, 71 °F, and would feel even more comfortable with 72 °F or 73 °F. For a single-room studio apartment, how much more will it cost to heat that additional one degree over a month? Just a little bit, or a lot? What about an additional, say, two degrees? Or three? Basically, I'm trying to figure out whether it's worth it to turn up the thermostat or just keep shivering or wearing uncomfortably bulky clothing to save on heating costs. —Lowellian (reply) 04:28, 29 November 2008 (UTC)[reply]

The monetary answer depends strongly on how well insulated the apartment is. In general, conductive heat loss is directly proportional to the temperature difference, so if you have a 40° F difference between inside and outside then increasing it by 1° F will make you lose heat 41/40 = 1.025 times as fast. Which means using ~1.025 times as much heating and increasing your bill ~2.5% from what it otherwise would be. Most other factors (such as convective heat losses if you have a draft, or secondary sources of heating) will tend to imply this a lower limit, and the actual cost increment could be higher. Dragons flight (talk) 05:49, 29 November 2008 (UTC)[reply]

Please ignore Dragons flight's answer. It's completely incorrect. Heat loss isn't "directly proportional to the temperature difference"...Heat loss increases as the SQUARE of the temperature difference (per Newton's law) - which is why turning your thermostat down by a small amount produces much bigger gains than you'd expect. So going from 40 to 41 is a 5% increase in cost - not 2.5%. Read what I wrote below. SteveBaker (talk) 14:36, 29 November 2008 (UTC)[reply]

Steve, are you sure it's the square and not, as User:Dragons flight says, "directly proportional"? According to Wikipedia's article on heat transfer, "Newton's law of cooling, states that the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings, or environment." —Lowellian (reply) 19:17, 29 November 2008 (UTC)[reply]

Not an answer but a tip: if you sit still for a longer period of time, instead of warming the whole apartment you could buy an electrical foot warmer. I use one and I find that with warm feet, my whole body stays warmer. Lova Falk (talk) 09:17, 29 November 2008 (UTC)[reply]

Counter-tip: wool socks aka "boot socks". I keep a pair laying by the couch, if I'm feeling cold I put them on. You're absolutely right that keeping the feet warm is a big part of the puzzle. Franamax (talk) 12:02, 29 November 2008 (UTC)[reply]

The thing is, once my feet are cold, no socks can make them warm again. It rather feels as if the socks insulate the icy skin of my feet. I've heard that alternating foot baths (that is, alternating hot and cold water) do wonders for cold feet, but it is way too much hassle. Lova Falk (talk) 15:56, 29 November 2008 (UTC)[reply]

Because we don't know how efficient your heater is - or how well your house is insulated - or how much electricity/gas costs where you live - we can't answer the question as a direct amount of money. What we can do is tell you how much your electricity/gas bill will increase as a percentage of whatever you're paying now. Newton's law of cooling says that the rate at which heat is lost increases as the square of the difference in temperature between the inside of your house and the outside air. That fact is true regardless of the amount of insulation you have - or how your heating system works. So when the temperature outside is (say) ten degrees below what it is inside - then you are losing ten-squared=100 "units" of heat - which your heater has to replace using 100 "units" power you have to pay for (I'm being deliberately vague about what a "unit" is because that depends on all of those things that we don't know). If you increase the thermostat setting by just one degree then the difference is 11 degrees and you'll lose eleven-squared=121 units of heat. So the cost of increasing by one degree in a 10 degree temperature difference is to add 21% to your heating bill! However, if the weather outside is just one degree below your thermostat setting (1x1=1 unit of heat loss) - and you increase the thermostat by 1 degree then your (very small) 1 unit heating bill will go up to 2x2=4 units! Your heating bill will quadruple in a 1 degree temperature difference. (But then it was such a small bill in the first place - you may never notice).

As the temperature difference between inside and outside get bigger (eg because the weather got colder) then the cost of adding one degree gets smaller. If you live in deepest Alaska and the outside temperature is zero degF and you keep your home at a toasty 70 degF then you are already using 70x70=4,900 'units' of heat...if you wind the thermostat up one degree in that situation then you'll be using 71x71=5041 'units' - which is only about a 3% increase in your heating bill.

Insulation and having an efficient heater are vitally important because they reduce the cost to you (and to the environment) of adding one 'unit' of heat to your house.

The same rules apply when airconditioning a house too.

SteveBaker (talk) 14:31, 29 November 2008 (UTC)[reply]

Newton's law of cooling is linear not quadratic. Please ignore Steve's answer. It's completely incorrect. Dragons flight (talk) 22:02, 29 November 2008 (UTC)[reply]

From Physical Calculations (J.J.Tuma, c.1983), Sec. 6(6) Overall Heat Transfer, (a) Wall Transfer: quantity of heat Q transferred in the interval t through three stages is Q = A(T_a - T_b)t divided by (rec(h₁) + rec(k) + rec(h₂)) where A = transfer area, T_a, T_b are internal and external temperature, h₁ and h₂ are convection coefficients (air space) and k is thermal conductivity of the wall. (Sorry I haven't figured out <math> yet, also rec(x)=1/x) This implies a linear relationship (T_a - T_b), but then we need to examine k. My impression was always that thermal conduction varied with e ^(-kT), so I'd be interested in a resolution here. Franamax (talk) 01:58, 30 November 2008 (UTC)[reply]

And I might be wrong on the minus, and it should be a delta-T that I'm completely wrong on - so you can understand my complete confusion on this. :) Franamax (talk) 02:10, 30 November 2008 (UTC)[reply]

The rate of cooling, dT/dt, is indeed proportional to the temperature difference:

dT/dt = -k(T-T0), where the negative sign indicates temperature is decreasing

e^(-kt) can easily be found by rearranging the equation and integrating to solve for T:

dT/(T-T0)=-k dt

ln (T-T0)=-kt + C

T = (Ta-T0)e^(-kt) + T0, where Ta is the initial temperature of the cooling object

It is the temperature of an object left to cool that obeys this equation, not the rate of heat exchange. Since this rate is what matters in the case of a room being maintained at a constant temperature, the power spent by the heating unit should be linear, not exponential. --Bowlhover (talk) 05:35, 30 November 2008 (UTC)[reply]

I've been away from the Reference Desk for awhile, and when I return, I'm disappointed to see it devolve into this. "...please ignore the previous answer"... "...complete and utter nonsense..."... Reference Desk regulars, let's keep in mind that this is the Science Desk. There is no reason to ignore anything - incorrect or inaccurate discussion can still be educational - if nothing else, it shows that smart people can disagree about precise factual claims; more precision leads to more squabbling over the details. Let's not forget that Newton's Law of Cooling, like all other laws of Science, are mathematical generalizations based on empircal data. Models are not always correct; and they are very often inapplicable. Before throwing the differential equations around, it would be more productive to consider this situation qualitatively. Raising the thermostat will cause the furnace to turn on more often. How much more often? It will depend on the rate of cooling, and it will also depend on the differential rate of efficiency of the furnace to re-heat the room. (I suspect that turning on the furnace entails "overhead" - so heating from 70 to 71 degrees may actually take negligibly less energy than heating from 65 to 71). The consequence of this result is that the range of the thermostat's dead-zone has a bigger impact to the heating budget than small variations on the temperature setting. The total on-time of the furnace (and hence, the bill) might not change much for a single-degree change on the thermostat dial. Nimur (talk) 02:53, 1 December 2008 (UTC)[reply]

THC absorption (repost)

Reposting removed question (see Wikipedia talk:Reference desk#Removed medical advice (THC absorption)). Zain Ebrahim (talk) 11:43, 29 November 2008 (UTC) [reply]
Ages ago, I learned (from somewhere, heck if I can remember) that when smoking marijuana, it is more effective to "hold it in" for as long as possible after inhaling to maximize the amount of THC taken in. Now... is this tactic effective? Does holding it in increase the amount of THC intake versus a quick inhaling followed quickly exhaling (as in "regular" breathing)? I guess an effective way to test this would to smoke same amounts of the same strain of marijuana with the same method of delivery over an identical period of time in each test on different days... except, there are other variables involved (food in the system, surroundings and comfort, mood, etc) and it may prove difficult to properly record or quantify any results (it's a lot of work for a part-time stoner to try and process with any consistency while under the influence). --Abin Sur (talk) 17:32, 24 November 2008 (UTC)[reply]

From the literature circulated in my church group, something like 90% of cannabinoids are absorbed immediately in the inhalation process. Brief holding-in would increase the absorption to some degree. Holding your breath for any amount of time will tend to reduce your blood oxygen, which could enhance the effect - however holding in the smoke is mostly part of the ritual, since it proves you're not being greedy and over-toking. Anyway, that's what I've heard at my church group, I never touch the stuff myself :) Franamax (talk) 11:54, 29 November 2008 (UTC)[reply]

According to "Cannabis in medical practice" [17], holding your breath for up to ten seconds increases absorbed THC, but not any longer than that. Also, holding your breath for longer increases exposure to tar and carbon monoxide. Fribbler (talk) 15:07, 29 November 2008 (UTC)[reply]

You're right, Abin Sur, your query did not run afoul of any applicable guidelines; its removal was unwarranted. If I recall correctly what I've read, THC absorption drops off sharply after five seconds or so. There are some high-quality references in Volcano Vaporizer, some of which address this what you're curious about. —Scheinwerfermann ^T·_C17:49, 29 November 2008 (UTC)[reply]

Hydrogen peroxide and yeast

When mixed together do they react or is the hydrogen peroxide a catalyst for the yeast? —Preceding unsigned comment added by 89.241.68.206 (talk) 15:15, 29 November 2008 (UTC)[reply]

Oxygen is released because of the yeast's catalase enzyme. Catalase breaks the peroxide into hydrogen and oxygen. Fribbler (talk) 17:41, 29 November 2008 (UTC)[reply]

While true, there won't be a great deal of catalase in the yeast medium. Peroxides, including hydrogen peroxide, are actually somewhat toxic at the cellular level, and won't be very good for yeast cells. – Clockwork Soul 18:00, 29 November 2008 (UTC)[reply]

Food Safety

This question relates to a prior discussion, now archived. Wikipedia:Reference desk/Science#Why is refrigeration of tin a bad idea?

Are food cans sealed with solder that contains lead? I understand from our article that they once were. Are they still?

Thanks. CBHA (talk) 17:37, 29 November 2008 (UTC)[reply]

No, they aren't soldered at all any more. StuRat (talk) 18:39, 29 November 2008 (UTC)[reply]

Plant Propagation

What factors (physical, biological, genetic) affect the ability of a plant cutting placed in water to grow roots.

Soft-tissue plants such as Saintpaulia, Coleus root very readily. What are the issues with tougher plants, and can they be overcome?

Just for example, I'm trying to root Schefflera cuttings (not because I need another Schefflera, just to see if it can be done.) After about five months, they still look healthy but there is no sign of growth. Ficus cuttings, put in water at the same time, have small roots.

Thanks, CBHA (talk) 18:43, 29 November 2008 (UTC)[reply]

Have you used that hormonal rooting powder? SteveBaker (talk) 20:32, 29 November 2008 (UTC)[reply]

Yes, it was used on the Schefflera and the Ficus. CBHA (talk) 20:35, 29 November 2008 (UTC)[reply]

Thanks for your responses. I guess I did not make my question clear. What was revolutionary with the surgery she performed was not that she did it from a remote location or even the technology that made that possible. Instead, what was revolutionary was the innovative nature of a surgical technique she devised to conduct the surgery. It's a technique that she apparently perfected and which is not on record as having been performed before anywhere in the world.

PlatoSelfstarterone (talk) 19:40, 1 December 2008 (UTC)[reply]

Ground-breaking Cardiac Surgery Technique.....

A female doctor from Michigan devised a new heart repair surgical procedure. She remotely (from her home), led and directed a team of other surgeons at a San Diego hospital, to perform the surgery on a 26 year old male patient. The surgery was performed sometime in November 2007. It was even rumored that the new procedure might be named after her. Does anyone out there know the name of this doctor and the name and/or type of procedure she performed?

PlatoSelfstarterone (talk) 19:12, 29 November 2008 (UTC)[reply]

2007 seems a bit late for that to be terribly ground-breaking (unless the innovation was that she did it over dial-up :) ). See Remote surgery. --Sean 20:45, 29 November 2008 (UTC)[reply]

The technology used is shown here. http://www.mybuzza.co.za/ It is revolutionary. ;o) CBHA (talk) 20:59, 29 November 2008 (UTC)[reply]

Feeding the seagulls

I was throwing bits of stale bagguette to a seagull this afternoon. I suppose that they were too hard or rough for him to swallow because every time I threw him a chunk, he'd pick it up, take it over to a puddle, swish it around in the water a bit until it was all soggy and soft and then swallow it and come back for more.

Has anyone else seen seagulls do this, or is this something that this one seagull has figured out on his own, do you think? --84.68.183.229 (talk) 19:32, 29 November 2008 (UTC)[reply]

I've seen ducks do the same thing. --Tango (talk) 19:34, 29 November 2008 (UTC)[reply]

I can't answer your question but I'm surprised by it. My experience is that if I feed one seagull, approximately 83 others appear. CBHA (talk) 19:38, 29 November 2008 (UTC)[reply]

This one was already pecking around in my garden for worms or something before I fed him. I don't think that the other gulls saw him eating the bread. --84.68.183.229 (talk) 19:48, 29 November 2008 (UTC)[reply]

Psychoneuroimmunology

Is there an easy way to find out which universities offer a degree in Psychoneuroimmunology? Also when such degrees first became available?

Would such a degree be a Doctor of Medicine degree or a Doctor of Philosophy?

Thanks, CBHA (talk) 19:42, 29 November 2008 (UTC)[reply]

I believe such specialism is only possible after studying a medical degree such as an MD, MBBS etc. I don't think there is a specific degree in psychoneuroimmunology but rather you train to become a psychoneuroimmunologist, like an immunologist or neurologist. Therefore, you would be a Doctor of Medicine. The specialism has existed for around 40 years. —Cyclonenim (talk · contribs · email) 20:06, 29 November 2008 (UTC)[reply]

While there will be doctors specialising in it, there will probably also be researchers with PhD's working in the field too having done their first degrees in pharmacology, (bio)chemistry, psychology, etc. (and then specialising for their PhD and subsequent work). It's also not uncommon for people to have both an MD (or equivalent for their country) and a PhD if they are involved in medical research. --Tango (talk) 22:54, 29 November 2008 (UTC)[reply]

Please Be Patient And I Thank You For Your Time

Awhile back, I believe some people did not take this seriously, so I am hoping everyone will taking this 'question' seriously (this time around).

I also want to give notice to this because this was some new information that had not be included. I humbly thank you.96.53.149.117 (talk) 22:18, 29 November 2008 (UTC)[reply]

We attempted to give you a serious answer and you refused to accept it. Our answer isn't going to be any different this time - chest hair is perfectly normal and there is absolutely no reason to believe it is a recent phenomenon. --Tango (talk) 23:01, 29 November 2008 (UTC)[reply]

I see absolutely no reason to suspect that any hair on your chest is unique to you or unique to the last 100 years. --98.217.8.46 (talk) 01:10, 30 November 2008 (UTC)[reply]

As before and before that... If you believe you have some sort of physical problem, this is a medical issue. See a doctor. If this is not important enough to you to see a doctor, you must not consider it truly unique or special - so why should we? -- kainaw ™ 01:17, 30 November 2008 (UTC)[reply]

Yes, such hair is absolutely normal. When you get old, you can also look forward to hair growing out of your ears and eyebrows that never stops, too. It seems this hair was put there primarily for God's amusement. StuRat (talk) 02:37, 30 November 2008 (UTC)[reply]

Evidence that not all hair is entirely useful: [18]. Sometimes, hair just gets in the way. --Jayron32.talk.contribs 03:42, 30 November 2008 (UTC)[reply]

. . .indeed it does [19]

I think I finally understand what the questioner is trying to ask, but has failed to do so properly. He appears to be under the impression that he has some special kind of pubic hairs on his chest. Also, he appears to be under the impression that chest hair in general is a recent step along the evolutionary ladder. So, since short chest hairs are recent and he now has big chest hairs, he must be one step past the rest of the world on the evolutionary ladder. In fact, he is no longer a simply homo sapien. He is a completely new species, perhaps a homo pubicium. -- kainaw ™ 14:05, 1 December 2008 (UTC)[reply]

What does "higher mammal" mean?

Is it related to their ability to think or some other classification? Can you point out a sample list of these animals? Thank you =) Louis Waweru Talk 22:59, 29 November 2008 (UTC)[reply]

I've never heard of a strict definition of the phrase, it's usually used quite loosely. I think it usually refers to intelligence, at least partially - humans and primates would almost certainly be included. Intelligence is very difficult to define, though, which makes such a classification pretty much useless for any serious work. --Tango (talk) 00:05, 30 November 2008 (UTC)[reply]

It could also mean placental mammals, as opposed to marsupials and monotremes. StuRat (talk) 02:32, 30 November 2008 (UTC)[reply]

Accession number needed for BLAST

I would like to compare the gene sequences of PCAF and GCN5 (Homo sapiens, both) using BLAST. BLAST requests accession numbers. Here is the page of the NCBI entry for PCAF: [20] - it gives the number 8850. When I use this number in NCBI BLAST, it using a different gene sequence (something unrelated to PCAF. Why is this? Where is the correct accession number? --Seans Potato Business 08:00, 30 November 2008 (UTC)[reply]

When I click on the link, I see a page for KAT2B, which I see is also known as PCAF. Is that not what you get?Calamus Fortis 01:33, 30 November 2008 (UTC)[reply]

Also, here is the data for GCN5, also known as KAT2A. [21] Calamus Fortis 01:38, 30 November 2008 (UTC)[reply]

Well thanks; that's fine and dandy, but I need accession numbers that I can put into NCBI BLAST. I don't see them on those pages. --Seans Potato Business 08:00, 30 November 2008 (UTC)[reply]

I think I may have found what you need. At the very bottom of the page for the genes, there is a number associated with the nucleotide sequence. For PCAF, it's AC099057. For GCN5, it's AC105024.8. Could that be what you need?Calamus Fortis 15:30, 30 November 2008 (UTC)[reply]

Lipid and Phosphate Granules

On your diagram of a section through a yeast cell on the yeast article, within the cell are two granules, on lipid and one phosphate. What do these granules do and is there any significance to the phosphate granule being within the vacuole.

Thanks in advance 84.13.17.47 (talk) 23:42, 29 November 2008 (UTC)[reply]

If nobody here rises to the occasion with an answer, you may want to post this Q on the yeast talk page, instead. StuRat (talk) 02:29, 30 November 2008 (UTC)[reply]

November 30

Shooting the ISS out of the sky

Just a goofy question I had. What would be the minimum technology necessary to shoot the International Space Station out of the sky? (I've no interest in doing so, personally.) It looks like a rather fragile thing up there, though I suspect its great height and relatively fast speed would mean you'd require some sort of fairly sophisticated anti-satellite weapon to do so. But it is pretty large compared to most satellites, so maybe it would be an easier target? Or maybe you could shoot a missile somewhere into its path that would just shoot out a lot of debris? I'm sure some of you mad scientists out there have even better ideas... --98.217.8.46 (talk) 01:16, 30 November 2008 (UTC)[reply]

The ISS is in a fairly low orbit, which is why it moves so fast. USA 193 was destroyed at a similar altitude (and therefore similar velocity), so such technology does exist - that's just one example, though, so there's no way to know how reliable it is. The ISS being so big would make it an easier target compared to other satellites in a similar orbit. --Tango (talk) 01:43, 30 November 2008 (UTC)[reply]

If don't want to develop a real anti-satellite weapon, any ICBM can reach the ISS altitude, and I'd imagine that with a nuclear warhead you'd only have to get close so steering and guidance would matter less. Dragons flight (talk) 04:01, 30 November 2008 (UTC)[reply]

You would have to get closer than you might expect - without an atmosphere you don't get the same blast wave doing damage over a wide area. --Tango (talk) 13:29, 30 November 2008 (UTC)[reply]

Though the EMP would fry the ISS's electronics and cause it to drop out of orbit fairly quickly (because there'd be no way of making course corrections - assuming that there's no 'fire booster rockets manually' lever behind a break glass somewhere), wouldn't it? --Kurt Shaped Box (talk) 15:38, 30 November 2008 (UTC)[reply]

You don't need to make course corrections to stay in orbit, once you're in orbit your momentum keeps you there. You might hit space debris which could do damage, though (I'm not sure how much debris there is that intersects the ISS orbit). Eventually it would de-orbit due to atmospheric drag since the loss of attitude control would make it impossible for craft to dock and use their rockets to boost the orbit (which is done periodically), but that would take months at least, probably years (they boost every few months, but I'm sure they don't leave it to the last minute). They may even be able to use gyroscopes to maintain basic attitude control without electronics, I don't know. --Tango (talk) 16:04, 30 November 2008 (UTC)[reply]

Well, I was hoping for the most low-tech solution. A nuclear ICBM ain't that! My thought was, what if you had some very primitive sounding rocket, could you get it high enough and have it create some sort of debris field that the ISS would be forced to go through, or something like that. --98.217.8.46 (talk) 16:29, 30 November 2008 (UTC)[reply]

Our article on sounding rockets says they can easily get high enough, and there's no reason you couldn't put an explosive charge in one to create debris. I'm not sure you would get enough debris to reliably cause an impact, though - it's going to spread out pretty quickly and then fall down (since it isn't in orbit), so you need to get the timing very precise. I'm not sure sounding rockets are that accurate. --Tango (talk) 16:36, 30 November 2008 (UTC)[reply]

See, that's what I want to hear about. ;-) --98.217.8.46 (talk) 16:51, 30 November 2008 (UTC)[reply]

What do you mean shoot it "out of the sky"? There was some controversy a while ago when Russia blew up one of their satellites, but the problem was that it was still in the sky, and had created a lot of dangerous debris. — DanielLC 16:54, 30 November 2008 (UTC)[reply]

Are you sure you're not thinking of 2007 Chinese anti-satellite missile test? While both Russia (well actually the USSR) and the US have blown up their satellites with missiles before it appears to be the most recent case I'm aware of involving a destruction using missiles for demonstration/testing purposes. See Anti-satellite weapon. The only other recent case is USA 193 although officially that was because of the risk the satellite may pose. There was this [22] but if the destruction was intentionally (which we don't know) it was designed to be able to self-destruct and definitely wasn't shot by a missile Nil Einne (talk) 11:35, 1 December 2008 (UTC)[reply]

2012

What are the governments saying about it?

What governments? What topics? There are millions of people working for governments around the world and they may be saying billions (if not trillions) of things about 2012. You must limit your question to something that can be answered within the confines of a reference desk. -- kainaw ™ 01:22, 30 November 2008 (UTC)[reply]

I assume you're talking about 2012 (film). Those hollywood people love disaster movies, no matter how far-fetched. -- JSBillings 01:37, 30 November 2008 (UTC)[reply]

i meant, what is the US gov. saying about 2012 if anything at all...ok i know wikipedia is known for saying 2012 is just hype and paranoia...but guys,... it's scary how all those calendars from dif. cultures coicide on the date and also that strange galactic occurrence... if there is such a hype, why doesn't NASA educate the public? i mean...they don't say anything....thats kinda weird, right? —Preceding unsigned comment added by 75.68.165.235 (talk) 02:25, 30 November 2008 (UTC)[reply]

What galactic occurrence? Dragons flight (talk) 02:45, 30 November 2008 (UTC)ou her[reply]

Didn't you hear this? We will be passing through the exact, perfectly defined and perfectly known geometric plane of the milky way on April 1st 2012, exactly at 11:11 (a.m.). --Stephan Schulz (talk) 09:14, 30 November 2008 (UTC)[reply]

What time zone? --128.97.245.27 (talk) 04:41, 1 December 2008 (UTC)[reply]

On April 1st, 11:11 occurs simultaneously in all time zones. --Stephan Schulz (talk) 10:04, 1 December 2008 (UTC)[reply]

There is none, but there certainly are a fair number of conspiracy theories that predict the date 2012 as the end of the world, or Armageddon, or whatever. Their proponents allege various cultures/mavens/seers all agree; you can choose from the Mayans, Edgar Cayce, Native American myth, Our Lady of Fatima, Nostradamus, Medjugorie, etc., etc., etc. Suffice it to say that, to the extent that governments are rational, they have nothing to say about it, and that the question belongs on the pseudoscience desk, not the science desk. I believe the NASA component of the conspiracy alleges they've discovered "Planet X" that is due to collide with Earth in 2012... -Nunh-huh 02:52, 30 November 2008 (UTC)[reply]

See ZetaTalk on that one. Algebraist 02:55, 30 November 2008 (UTC)[reply]

It's important to note that there are LITERALLY a million or so distinct belief systems and religions out there; and a significant number of these have specific dates for the end of the world. Every decade or so a new one comes up. This is just the next one on the docket. It will pass, like the hundreds of predictions before this, without event, and we will promptly forget it and move on to the next one. If anyone wants to read more about the end of the world, Eschatology is as good of a Wikipedia article as any on this. --Jayron32.talk.contribs 03:37, 30 November 2008 (UTC)[reply]

ZetaTalk lady is, without a doubt, not of sound mind. And I'm not intending that as an insult, it is completely serious. It's actually somewhat sad to hear her on the radio, as well as frightening (not for fear of doomsday, of course). -- Consumed Crustacean (talk) 09:53, 30 November 2008 (UTC)[reply]

People have been predicting that the world would end in their lifetimes for thousands of years. You might enjoy this list of failed end-of-the-world predictions. (Well, the ones in the past have failed; the ones in the future will fail in a few years.) -- BenRG (talk) 13:36, 30 November 2008 (UTC)[reply]

And on April 1st no less :) -hydnjo talk 14:47, 30 November 2008 (UTC)[reply]

Wouldn't you be MORE worried if your government, which is supposed to be focused on the 10 million ACTUAL problems in the world today, like the totally failing economy, terrorism overseas, multiple wars, genocide, ecological disasters, YOU NAME IT, was instead wasting its time, and YOUR MONEY, looking into whether the coincidence of multiple religions allegedly having similar dates that their calendars loop over was somehow a national security threat? How would they even evaluate that? What would you be expecting them to do? Stock up on shamans? Now take a look at the people who are saying it will be the end of the world. Are they reputable? Are they recognized experts anywhere except for rather crackpot places? Do you really want an acidhead like Daniel Pinchbeck taking government money and directing government policy? (Here's a nice article on him and his ilk if you have the time.]) The government has got limited time and limited money. They use things like "actual science" as a way of determining which of the million potential issues they should be spending it on. Science itself purposefully limits the sorts of things it can worry about to those which have a hope of being reliably determined, because it too has limited attention and limited resources. The 2012 thing, even if you imagine it to be some sort of real thing, is not a great thing for the government to be wasting its limited resources on, especially at a trying time like this. The people who are promoting the idea that there is some sort of disaster are people who all directly profit from people being scared of it. Be wary. --98.217.8.46 (talk) 16:32, 30 November 2008 (UTC)[reply]

but guys, isn't our solar system supposed (scientifically) to be in a special place and alignment that day? (21, dec.?) i mean...it's not just religions...what do reputable scientistssay about the alignment , pole shift , photon belt and stuff?I read that it's supressed scientific knowledge...

Look, let's make a bet. If you lose, come to my birthday party on Dec. 21, 2012 and bring me a gift. If you win, you would obviously not need to come.

Please point out specific claims made by specific authors and the Reference Desk will examine them. For an article on 2012, see http://www.universetoday.com/2008/05/19/no-doomsday-in-2012/. I suppose you already know that nearly every time the Reference Desk received a question like yours, I linked to all previous questions relating to 2012.

Reputable scientists are not likely to waste their time on crackpot theories, so I don't think you'll succeed in finding out their opinions. If you trust the people here, though, many (not including me) have considerable scientific knowledge and are qualified to comment on information you find, as long as you are specific. --Bowlhover (talk) 19:24, 30 November 2008 (UTC)[reply]

thank u guys...u r noble...I used to be a wikipedian...lol, this sounds like a tragic story...I even had a user page and stuff...i should use it again. so...is there NOT going to be a SPECIAL astronomicalevent going on on that date? I mean...doesn't mainstream science basically admit that that is a special date astronomicaly?

It's quite possible that something fairly interesting astronomical will happen around then, but not as interesting as the doomsayers are trying to make out. If this is the date I'm thinking of, the "planets will all align and cause massive gravitational effects like tides the size of mountains" is more like "roughly half of the planets will be kind of within a 90° wedge shape while the rest will be fairly randomly scattered, with a gravitational effect less than that of a full jumbo jet flying overhead". Confusing Manifestation(Say hi!) 22:33, 30 November 2008 (UTC)[reply]

thank u guys, I luv u and wikipedia! :) --Cosmic girl (talk) 00:22, 1 December 2008 (UTC)[reply]

Not quite a government, but some within the Republican Party are already considering Sarah Palin as a Presidential candidate for that year's election, so make of that what you will from an apocalyptic standpoint. 69.224.113.5 (talk) 00:46, 1 December 2008 (UTC)[reply]

And who knows, maybe Canada will have Stef Carse as PM by then. And the name of the President of France will be something easier to spell. Then they can go to war over who controls Montreal Nil Einne (talk) 11:10, 1 December 2008 (UTC)[reply]

Piperidine,

wat are the effects of absorbing(smoking,eating,ingecting) Piperidine into the blood? —Preceding unsigned comment added by 76.14.124.175 (talk) 02:29, 30 November 2008 (UTC)[reply]

Our article on Piperidine does not directly answer this question, but it is VERY well referenced. If you find and read those references, you could find more information. Alternately, here is an MSDS for Piperidine. Cheers! --Jayron32.talk.contribs 03:33, 30 November 2008 (UTC)[reply]

Why not freeze food twice?

Why aren't you supposed to freeze food twice? Here people argue that bacteria in thawed food procreate faster... which begs the question why that should be so. Shouldn't the cold temperature just after taking the food out of the freezer (and the first minutes after putting it back in) be even colder than regular storage temperature and, if anything, slow bacteria down? --Ibn Battuta (talk) 03:19, 30 November 2008 (UTC)[reply]

When you freeze food, you break cell walls/cell membranes in the cellular structure of the food. This causes 2 problems:

Freezing multiple times increases cellular damage, which produces mushier, less palatable food
Cellular membranes are actually pretty good barriers against bacteria. When these are broken, and their contents dumped out, it provides a more nutritious medium for bacterial growth. Thus, thawed food has a greater potential for bacterial growth than never frozen food.

Those are probably the best two reasons NOT to freeze multiple times. Fresh food is of course the best to eat; the closer to "alive" it is, the tastier AND safer it is... --Jayron32.talk.contribs 03:31, 30 November 2008 (UTC)[reply]

"the closer to 'alive' it is, the tastier AND safer it is..." - So I'm sure you eat all your meats raw and never touch baked goods like pastries and cakes? I find your generic platitude rather unhelpful and oversimplified. Dragons flight (talk) 03:50, 30 November 2008 (UTC)[reply]

If you take it to mean the time between the death of the animal or plant and the time to cook, all other things being equal, older food will tend to accumulate more bacteria. Of course, some foods (like Blue Cheese... yummmmmmmm) benefit from a healthy dose of microbes. But given a simple question of whether a slab of meat or an apple or some other unprocessed whole food is safest to eat, it is always safer to eat said food closest to when it is killed (for the animal) or picked (for the fruit). Over time, microbes will tend to accumulate on the food and, if uncontrolled, will tend to degrade the quality and safety of the food. --Jayron32.talk.contribs 20:03, 30 November 2008 (UTC)[reply]

Many people prefer aged beef, which is purposely allowed to go though some degradation. ike9898 (talk) 02:33, 1 December 2008 (UTC)[reply]

Other things aren't equal though. Cooking and processing food will kill and remove bacteria, which can dramatically improve food safety and longevity. For many foods, the result is safer than even if you ate the food as fresh as is possible. For safety, recently killed is usually far less important than how the food has been handled/preserved/cooked since it was killed. Dragons flight (talk) 20:59, 30 November 2008 (UTC)[reply]

You are 100% correct. --Jayron32.talk.contribs 02:18, 1 December 2008 (UTC)[reply]

There was a Straight Dope with a quite detailed explanation about this a couple of years ago, here's the link. Maelin (Talk | Contribs) 04:37, 30 November 2008 (UTC)[reply]

grant for study and visit st buddhist temples are over the world

i am interested to know and visit st buddhist temple,any agencies is ready to give grant to vist st buddhist temples?SAJITH 07:33, 30 November 2008 (UTC)

Why would someone give grants for that? --Mr.K. (talk) 18:02, 30 November 2008 (UTC)[reply]

What are st buddhist temples - it looks to me like you are calling Buddha a Saint. Although, I'm guessing English isn't your first language and you meant to type "visit at" when all you need is "visit."

As for grants, nobody's going to give you money just to visit. Are you in college? Perhaps you can devise some reason to study such temples, like for a Masters degree. (Or, even as an undergraduate project in some places. See College of Wooster and their Independent Study program, which gives such grants.) It has to be something that is seemed worthy to study. For instance, the architecture of them. Or, for sociology, peoples' habits upon entering. Things like that.

However, be forewarned, visiting "all over the world" will be seen as too broad by most, unless you really want to make it like a PhD. thing. Say, for instance, your professor in SOciology learns you want to study how people approach Buddha in different cultures. He or she will suggest something along the lines of people raised in the Orient versus Westerners who convert. And, he or she will expect you to have some hypothesis that you are trying to prove.

So, can you get grants to visit temples? Sure, but you're going to have to put a lot of work into it.Somebody or his brother (talk) 02:54, 1 December 2008 (UTC)[reply]

Publicly accessible free scientific lectures?

I saw on iTunes U, that I can download some to my ipod and found a couple of them INCREDIBLY interesting! Is there some free website where I can view/hear lectures by respectable scientists talking about new potential discoveries? Most of the ones on youtube are by fakes. I am interested in physics and biology, and am wondering if there are real lectures anymore? or if there is no real audience for that any more and there won't be any faraday lectures like the 1700s.

The only lectures so far which are plentiful and meet this criteria is global warming lectures, but I don't get enjoyment about hearing my 10th lecture on it. I like physics and biology personally, and no disrespect to climate scientists. 65.41.148.101 (talk) 07:53, 30 November 2008 (UTC)[reply]

Addendum I already know about OCW, and I love it! I am looking for an OCW style (in terms of quality and accuracy and no side-goal of trying to push a POV, but the only goal to educate), geared towards bright inquisitive minds who are temporarily under a 48 hour WoW ban, or similar. 65.41.148.101 (talk) 07:55, 30 November 2008 (UTC)[reply]

Here you can find some excellent neurobiology lectures. [23] Lova Falk (talk) 12:30, 30 November 2008 (UTC)[reply]

Ok, these aren't new but you might find these lectures by Richard Feynmann interesting: http://vega.org.uk/video/subseries/8 Jdrewitt (talk) 13:08, 30 November 2008 (UTC)[reply]

MIT offers many free online lectures from their courses in a wide variety of departments. Take a look: http://ocw.mit.edu/OcwWeb/web/courses/av/ – Clockwork Soul 07:51, 1 December 2008 (UTC)[reply]

Water pressure

Why does water pressure increase with depth. I have the general idea: there's water above pressing down, an analogy with pressing on jello shows why there would be an increase in lateral pressure with depth. But where's the origin of the water pressure that's pushing up on an object in water?

See bouyancy. If that article doesn't float your boat, come back and ask a follow-up Q. StuRat (talk) 17:59, 30 November 2008 (UTC)[reply]

Well, I've read through the article, and I haven't seen anything that really answers my question. I know that bouyancy is caused by this pressure difference, and I know that this is in turn caused by the difference in the weight of water above a point, but I don't get why water pushing down on an object will cause an upward force.

At a lower depth, there is more water on top, pushing down. This causes pressure from the top, which in turn squishes the water molecules together, causing the water to be denser. Since the water is denser, it has more bouyancy ability, and thus it is able to float denser objects, as well as cause the water pressure to push on them from all sides, thus squishing them and causing it not to float. ~A H 1^(TCU) 23:43, 30 November 2008 (UTC)[reply]

No. Water density doesn't change significantly with depth. You're thinking of a gas.

Try this: (as a thought experiment: don't actually do it.) line down on a partially-filled waterbed in its frame, place an empty waterbed mattress on top of yourself, well spread out. Now fill the top mattress with water to a depth of 10cm. do you think you will feel pressure? Why? how much? Why is this different than when the two mattresses contain air? Is the pressure different that what you would feel if you wer wrapped in a dry suit and held 10cm beneath the water surface? -Arch dude (talk) 01:14, 1 December 2008 (UTC)[reply]

As for why water pressure can push upwards, water resists the compression force exerted by the water above it, just as the ground exerts a normal force that prevents gravity from pulling objects through. The downwards force of gravity equals the upwards force because the water isn't moving; it is in mechanical equilibrium. --Bowlhover (talk) 04:50, 1 December 2008 (UTC)[reply]

I think I get it...now for a related question. If I were to construct a hut at the bottom of the ocean, would the water pressure in this hut be the same as the surrounding? Intuition says yes, but wouldn't there not be the weight of the water above pushing on it?

If the water can flow through it, then the pressure would be about the same throughout it. However, it would be slightly higher at the bottom of the hut than the top. StuRat (talk) 09:13, 1 December 2008 (UTC)[reply]

I'm saything that water can't flow through it.

OK, if you have a tank at the bottom of the ocean, which has been sealed since it was moved there from the surface, one of three things will happen:

1) The much greater pressure outside will cause the tank to collapse until the pressure is equalized.

2) The tank will collapse somewhat, and subsequently the pressure will increase a bit.

3) The tank is strong enough to resist any significant collapse. This would be easiest with thick metal and a spherical shape that distributes the forces evenly. In this case the pressure inside would be approximately the same as on the surface.

If you had constructed the tank at the bottom of the ocean, then the pressure inside would be the same as the outside, unless you pumped out some of the water inside to reduce the pressure. StuRat (talk) 13:59, 1 December 2008 (UTC)[reply]

If you constructed the tank at the bottom of the ocean, why would the pressure inside be the same as the pressure outside? Afterall, the weight of the water above no longer has an effect on the water inside the tank.

Thoughts, feelings and reality.

I'm not completely sure if this belongs in the science section, but nonetheless I'm looking for a scientific answer. I was just wondering, can thoughts influence or alter reality? For instance, let's say I'm going to do an exam and I think I will fail, will the probabilities of approving the exam change? Similarly, can feelings influence or alter reality? Note that I'm talking about reality, not the perception of reality. Thanks in advance. ― Ann _{( user | talk )} 12:09, 30 November 2008 (UTC)[reply]

Would self-fulfilling prophecy be an answer? And for an answer from me personally: yes, absolutely. Thinking you will fail an exam, can cause stress which leads to certain reactions in your body (and already on this level, thinking has changed reality, because the body now shows a number of physical reactions, such as a higher heart rate, muscular tension, faster respiration etc), which can influence how you perform on your exam. One of the results of stress mentioned in the article on stress is an inability to concentrate, and that would make it less probable that you pass the exam. Lova Falk (talk) 12:24, 30 November 2008 (UTC)[reply]

Thinking you will fail an exam can also cause learned helplessness, which in turn may lower the amount of effort you put into it. --82.21.25.219 (talk) 12:26, 30 November 2008 (UTC)[reply]

I see your point. Homever, those are reactions caused by the thoughts, not the thoughts themselves. Perhaps I phrased my question poorly, but I'm specifically asking about the thoughts. Let's suppose that I think I will fail such exam, but I don't feel stressed, my heart rate is fine, my respiration is normal, etc. Could reality be influenced or altered simply by mere thoughts? ― Ann _{( user | talk )} 13:59, 30 November 2008 (UTC)[reply]

In the sense that you're asking, no, science has no evidence to support telekinesis or other mind-alters-world phenomena. Absence of evidence is not evidence of absence and all that, but there have been plenty of opportunities to validate such claims and they've all struck out. — Lomn 14:21, 30 November 2008 (UTC)[reply]

Surely absence of evidence is evidence of absence. Maelin (Talk | Contribs) 14:30, 30 November 2008 (UTC)[reply]

No, it's not. We have an absence of evidence that there is extraterrestrial life elsewhere in the universe, but that's more a statement about the difficulties of collecting such evidence than it is that there isn't any out there. --98.217.8.46 (talk) 17:46, 30 November 2008 (UTC)[reply]

If you have an absense of evidence, then you have evidence of absense existing ;) —Cyclonenim (talk · contribs · email) 19:43, 30 November 2008 (UTC)[reply]

If you're referring to thoughts effecting anything other than the person with those thoughts, and not indirectly through said person, it's technically possible thanks to the butterfly effect, but what actually happens has no relation to what you were thinking. It will tend to be something equally unsurprising as what would have happened. By the way, conspicuous absence of evidence (i.e. absence of evidence when evidence would be expected) is evidence of absence. — DanielLC 16:43, 30 November 2008 (UTC)[reply]

This seems like an interesting answer. Now you have my curiosity sparked. Could you please explain this a little further, particularly regarding how it would work? ― Ann _{( user | talk )} 17:09, 30 November 2008 (UTC)[reply]

Also, if a tree falls in a forest... ~A H 1^(TCU) 23:39, 30 November 2008 (UTC)[reply]

To me it seems confusing to separate thoughts and reality. Thoughts are real and have influences, causing an "alternate" reality compared to not having those particular thoughts. Exactly what effect they have is another question, and depends on many factors. But as to whether thoughts have an effect on reality--of course they do, they are part of reality. The question strikes me as a bit odd--doesn't reality include your thoughts, feelings, perceptions, and so on? Don't these influence your actions? Don't your actions influence the world around you? In short I don't understand the difference between the question "can thoughts influence or alter reality?" and the statement that some things, like stress, are reactions "caused by the thoughts, not the thoughts themselves." It sounds like you are asking whether thoughts can alter reality without causing any reaction to happen. How can there be an effect without a cause? Pfly (talk) 07:36, 1 December 2008 (UTC)[reply]

Instituto Conmemorativo Gorgas

How could I link Instituto Conmemorativo Gorgas to other pages like the one on William Crawford Gorgas and pages related to infectious diseases of the tropics, publica health and history of medicine?

Jorge Motta, MD, MPH

Like this: William C. Gorgas. --Cookatoo.ergo.ZooM (talk) 18:46, 30 November 2008 (UTC)[reply]

You need to go into "edit" to see what was done there, which is this: [[William C. Gorgas]], double square brackets surrounding the article name. SpinningSpark 18:56, 30 November 2008 (UTC)[reply]

Is it correct to say this (see below)?

Let's say that I want to know how to determine the gravitational force on the Earth due to another massive body. Isn't it then correct to say, "To weigh the earth, the gravitational force experienced by the Earth due to another massive body is measured"? 203.217.34.128 (talk) 16:28, 30 November 2008 (UTC)[reply]

To strictly describe the force attracting the Earth to the other body, yes. However, you would also want to determine the force attracting the other body to Earth, in order to determine the acceleration of the two bodies toward each each. StuRat (talk) 17:55, 30 November 2008 (UTC)[reply]

Newton's third law says the force attracting the other body to Earth is equal in magnitude and opposite in direction to the force attracting the Earth to the other body.
If you use the term "weight" to describe the attraction between the Earth and, for example, the Sun or the Moon, then I would say there is scope for much confusion here, as the Earth simultaneously has many different "weights". "Gravitational force" or "gravitational attraction" would be better terminology. Gandalf61 (talk) 19:58, 30 November 2008 (UTC)[reply]

Leaking batteries

What is the white crystalline stuff that leaking AA batteries sometimes leave behind and what is the best way to remove it from the appliance, e.g. is it okay to use a mild solvent?--Shantavira|^{feed me} 16:53, 30 November 2008 (UTC)[reply]

If it is regular alkaline batteries you are using, the electrolyte is potassium hydroxide and the white crystals are compounds that this alkaline chemical is forming with the metals (often copper) that it is attacking. I would recommend chipping off the larger pieces with a small screwdiriver or other tool and then polishing the battery contacts with a fine abrasive, I use a fibreglass pencil. You can use an electronics solvent such as Electrolube's ECSP to clean up any electrolyte on the circuit boards. If it is a bad attack there is a good chance that the corroded battery contacts disintegrate or break off while you are cleaning them and you will have to replace them. It is likely in any case that the protective plating on the contacts has been corroded away and they are more likely to oxidize and give you problems in the future (you will have to clean them now and then). A lot of Q&A sites, such as this one from Hewlett Packard recommend a 50:50 solution of water/white vinegar. This makes sense chemically as the acetic acid in the vinegar will tend to counter the alkaline electrolyte but I would not recommend it. Anything acidic being splashed around inside electronics is likely ot result in further damage if you do not take extreme care. SpinningSpark 18:38, 30 November 2008 (UTC)[reply]

Interesting. Thank you.--Shantavira|^{feed me} 08:57, 1 December 2008 (UTC)[reply]

Medical opinion (but not advice)

After seeing the picture below on the local news (in Spanish) about the burns of an Afghan girl, I was wondering: are this injuries recent or is the picture after a ´healing´? Is there any chance that this girl will have a somehow normal skin? (link: here, disturbing image!)--Mr.K. (talk) 18:23, 30 November 2008 (UTC)[reply]

I'd say those pics are after healing. It may be possible to restore an approximately normal appearance with a series of skin transplants, but this is well beyond the scope of what the average Afghan family can afford. StuRat (talk) 19:42, 30 November 2008 (UTC)[reply]

I'd say they're in the late stages of healing, judging by the fact there are still some scabs there. However, some of what appears to be scabbing may actually be an infection, hard to tell from the image. Anyway, StuRat has it about right. Skin grafts could reduce the image and help restore a normal look but it'd be difficult to make it anywhere near perfect, and Afghans cannot usually afford such operations. —Cyclonenim (talk · contribs · email) 20:19, 30 November 2008 (UTC)[reply]

Telling sunrise from sunset

Let's say I have a color photo where the sun is on or near the horizon, and I don't know anything about the time it was taken or the surrounding terrain which would allow me to tell if this is a sunrise or a sunset. Is there a way to discern which it is from the lighting or color of the sky alone? 69.224.113.5 (talk) 18:24, 30 November 2008 (UTC)[reply]

If all the people in the picture are still drinking then it is sunset. If they are laying unconcious on the beach or look like they have a hangover, then it is sunrise. For a serious answer, there is a daily change in the F layer but the change is only visible at radio wavelengths, as far as I know there is no effect on the visible spectrum. There might possibly be meteorological clues, but I leave that to a met expert to answer. SpinningSpark 18:53, 30 November 2008 (UTC)[reply]

According to sunset:

"The sunset is often more brightly colored than the sunrise,[citation needed] with the shades of red and orange being more vibrant. The atmosphere responds in a number of ways to exposure to the sun. In particular, there tends to be more dust in the lower atmosphere at the end of the day than at the beginning. During the day, the sun heats the surface of the Earth, lowering the relative humidity and increasing wind speed and turbulence, which serves to lift dust into the air. However, differences between sunrise and sunset may in some cases depend more on the particular geographical features of the location from which they are viewed. For example, on a west-facing coastline, sunset occurs over water while sunrise occurs over land."

Also see the previous discussions at [24] and [25]. Ignore the last answer in the first link; even the rising or setting Sun can completely overwhelm light pollution.

On a completely irrelevant answer, ignoring the color of the sky, if you used a digital camera to EXIF data can probably give you a 'time taken'. —Cyclonenim (talk · contribs · email) 20:16, 30 November 2008 (UTC)[reply]

One more difference: mirages of the Sun occur more frequently during sunrise than during sunset because they can only exist when the layer of air above the surface is hotter than the overlaying air. --Bowlhover (talk) 20:02, 30 November 2008 (UTC)[reply]

A similar question was once asked on Talk:Sunrise, but I'm not sure the responses there are much help. -- Coneslayer (talk) 17:10, 1 December 2008 (UTC)[reply]

If you can upload the picture somewhere we can take a look. Might be other clues in the picture. -----J.S (T/C/WRE) 21:02, 1 December 2008 (UTC)[reply]

Where does today end and tonight begin ?

Weatherforecastwise, that is. 6 PM ? StuRat (talk) 20:43, 30 November 2008 (UTC)[reply]

I don't think there is a rule for this. 6pm is plasuible. Dusk is another good choice. I think it is just casual expression. -- SGBailey (talk) 22:35, 30 November 2008 (UTC)[reply]

Sunset would be a good guideline. Add 30 min fudge factor either way and you should be a-ok. -----J.S (T/C/WRE) 02:00, 1 December 2008 (UTC)[reply]

This is an unsupported personal understanding, but I always assumed that morning was 6:00 AM - 12:00 Noon; afternoon was 12:00 Noon - 6:00 PM, evening was 6:00 PM - 12:00 midnight, and overnight was 12:00 midnight - 6:00 AM. Day(morning + afternoon) is thus 6:00 AM - 6:00 PM and night(evening + overnight) is 6:00 PM - 6:00 AM. --Jayron32.talk.contribs 02:17, 1 December 2008 (UTC)[reply]

I have found myself saying "good evening" when at the start of an evening activity, even if it starts in what would be afternoon normally. (Say, a church service starting at 5 PM, saying it a few minutes before.) However, I think that's because it is unusual, to me at least, to say "good afternoon."

However, if you are looking at a technical definition, I would say dusk is the most likely, because unlike the definite AM and PM, evening is more of a state of mind. And, in the witner, at least to me, if it's 6:30 PM it can feel like 10:00 at night. Like Yogi Berra said once, "It gets late early out there." Just like, psychologicall, if a person has been up all night studying, there doesn't feel like there's been a break between night and the next day; they might say "good evening" to the guy delivering pizza at 1 AM even though, technically, it's "good morning."Somebody or his brother (talk) 02:45, 1 December 2008 (UTC)[reply]

I don't think I would usually describe 6pm as night unless it's rather dark. Perhaps it's because I grew up in Peninsular Malaysia which is in the UTC+7 timezone but uses UTC+8 so it isn't even close to being dark at 6pm and here in Auckland it seems to be getting dark way to early during winter. Agree dusk or around sunset time is a more likely definition although I guess that's somewhat problematic near to the poles where I think people would still consider there to be a night time and a day time even if it doesn't get dark or is forever dark Nil Einne (talk) 10:51, 1 December 2008 (UTC)[reply]

In calculations for working out the Jewish calendar, the day begins at 6.00 p.m. Simonschaim (talk) 09:26, 1 December 2008 (UTC)[reply]

In the UK all the newspapers used to publish daily "lighting up times", this used to be shown in calendars too. No one seems to bother any more but the Royal Observatory website still shows the details, basically half hour after sunset. SpinningSpark 11:44, 1 December 2008 (UTC)[reply]

There is also the definition of three different versions of twilight at the bottom of that page. SpinningSpark 11:47, 1 December 2008 (UTC)[reply]

Distortions of sunrays and starlight by atmosphere: what can we conclude?

If Earth did not have an atmosphere surrounding it, the photons from the sun ("sunrays") and the stars could hit the ground unobstructed, traveling in a straight line from celestial light sources to Earth. However, the atmosphere is a mix of gases (oxygen, nitrogen, etc.). If I picture the atmosphere's molecules as tiny billard balls floating about in space and the photons as bullets mostly whizzing past the billard balls but sometimes getting absorbed by or ricocheting off them... what can I conclude about the density of the atmosphere. Most photons must be getting through unobstructed otherwise a glance at the sky would seem like seeing underwater with your eyes open or seeing nothing at all.

Does the degree of visual acuity, or lack of it, permit an extrapolation of the number of molecules in a given volume of air? Would that be easier to do in the daytime or at night, gauging the blurriness of stars? What data does one need to do the extrapolation -- for an example, is there such a thing as a cross-section of an O₂ molecule? Is it possible to conclude that out of 3x10⁶ photons, 2x10⁶ (grabbing a number out of thin air -- sorry for pun) will get through to my retina unimpeded?--Goodmorningworld (talk) 23:20, 30 November 2008 (UTC)[reply]

There are really two factors at play: Rayleigh scattering and astronomical seeing. The first covers most of what you are discussing and addresses in general the ability of molecules to scatter light. For example you could measure the ability of the atmosphere to scatter light by comparing the intensity of direct sunlight to the intensity of blue sky. That, plus some other assumptions could get you a density estimate. However that bulk scattering is not the principle source of the blur or twinkling in stars which arises mainly due to atmospheric turbulence. Dragons flight (talk) 00:22, 1 December 2008 (UTC)[reply]

Cough-induced abdomenal reflex

During medical examinations, in addition to testing for the knee jerk reflex, sometimes they test for this thing where they ask you to cough, and listen with the stethoscope for some kind of reflex in your abdomen at the places where I imagine your ovaries would be (except I'm male, so I don't have any ovaries). What's this phenomenon called? Is there an article on it? Cough reflex doesn't talk about it; and none of the other ones on the list of reflexes seem to be relevant. Also, what is the place they are listening to called? --71.106.183.17 (talk) 22:46, 30 November 2008 (UTC)[reply]

I don't know of an exact match for what you describe. In examining a man for evidence of inguinal hernia, one can insert a digit into the inguinal canal and ask the patient to cough (or bear down - the goal is to increase intra-abdominal pressure). If one feels pressure at the fingertip, then a defect in the abdominal fascia may be suspected. If scrotal contents are enlarged and inguinal hernia is suspected, one may listen over the scrotum for bowel sounds (which should normally be absent).

Alternatively (no coughing involved in these) when renovascular hypertension, aka renal hypertension is suspected one may listen over the renal arteries for a vascular sound or bruit that would suggest renal artery stenosis (can you believe what a wiki-mess this is?). Similarly, one can listen for bruit over the inguinal ligaments when vascular disease of the iliac or femoral artery is suspected. --Scray (talk) 23:03, 30 November 2008 (UTC)[reply]

The inguinal canal seems to be totally internal to the body. How can you "insert a digit into the inguinal canal'? Or is "pressing on the skin near the inguinal canal" what is meant?

What diameter approximately is the inguinal canal?

Are new internal body parts still being discovered? When I went to school, there were heart, lungs, liver, kidneys, stomach, gall bladder, appendix, and tonsils. Some people had "intestines", but that was a lower class thing. And that was it. Now practically every time I read this Reference Desk, some other internal body part crops up. It's getting out of hand.

CBHA (talk) 06:46, 1 December 2008 (UTC)[reply]

(regarding the inguinal canal) In men, the scrotum provides loose skin and a path for a finger to reach the inguinal canal. The diameter is between 1 and 2 cm.

(regarding body parts) Just about everyone has intestines - even upper-class people. --Scray (talk) 12:21, 1 December 2008 (UTC)[reply]

radiant barrier

I read the wiki artical about radiant (attic) barriers and followed one of the suggested links (http://www.fsec.ucf.edu/en/publications/html/FSEC-EN-15/index.htm) but I was unable to find the answer I was looking for. Specifically, can one make their own rediant barrier for their attick by adhering aluminum foil (from the supermarket) to a backing (e.g. carbboard or kraft paper) and then securing this aluminum-side down to the roof trusses? If so, how efficient would this be? Is there something more efficient than aluminum foil?

Thanks

That article reads like an advertisement. You might like to look at Thermal insulation and go from there. Foil doesn't only reflect, it heats up, so layers and thicknesses come into it. If you want to improvise, there's Space blanket a kind of foiled sheet material available for people trekking in the wide outdoors and emergency insulation. Julia Rossi (talk) 01:12, 1 December 2008 (UTC)[reply]

On second thoughts, space blankets are aluminium on plastic and I'm not sure if they are durable or temporary. Your foil on cardboard sounds better than that. Julia Rossi (talk) 03:15, 1 December 2008 (UTC)[reply]

One thing to be aware of when insulating an attic is that you must not block air flow out of the attic, since this is needed to prevent moisture buildup. This moisture leads to all sorts of problems like mold, insects, and wood rot. StuRat (talk) 05:44, 1 December 2008 (UTC)[reply]

The advice in the article seems sound. I'd go for the stuff with a thin bit of insulation in between two reflective sheets which you can probably get in your local DIY store. Dmcq (talk) 16:49, 1 December 2008 (UTC)[reply]

December 1

Taste of Food Additives

I have a bottle of "lemon juice, made from concentrate". The complete ingredient list is water, lemon juice concentrate, sodium benzoate, sodium metabisulfite, and lemon oil. (Another brand lists water, lemon juice concentrate, sulfites, and lemon oil.)

I don't like to use this stuff to make lemonade because I don't like the taste of the resulting product.

The question is, do sodium benzoate and sodium metabisulfite give any taste to foods they are added to? The articles on these compounds have no mention of taste.

To put this another way, if sodium benzoate (or sodium metabisulfite) were added to water in the concentrations likely to be used in lemon juice, would the mixture have a taste different than water?

As a side issue, the article on sodium metabisulfite says that "when mixed with water, it releases sulfur dioxide (SO2), a pungent, unpleasant smelling gas that can also cause breathing difficulties in some people." Is a residue of this nasty stuff likely to remain in the reconstituted lemon juice?

CBHA (talk) 03:39, 1 December 2008 (UTC)[reply]

There are another three possibilities I can think of:

1) It's the lemon oil. This comes from the skin, which is also called lemon zest. It has a rather bitter taste (not sour, as in lemon juice). So, why do they include it ? Because it's cheaper to toss the whole lemons into the machine than peel them first.

2) It's the concentration process:

2a) The particular method of concentration may involve heating the juice to drive off water. This heating can cause the breakdown of some molecules in the juice and change it's flavor.

2b) The concentration itself, regardless of method, may also be a problem. Some of the molecules in lemon juice may be bound to water molecules, until the water is removed, and then may react with other molecules, as a result.

3) The water added during the reconstitution process may alter the flavor, based on minerals in the water, such as chlorine. StuRat (talk) 05:37, 1 December 2008 (UTC)[reply]

No idea regarding sodium metabisulfite but the taste do change when you add sodium benzoate to your fruit juice. I son't know how to describe the change in taste but it seems to be "less natural tasting". If you will consume the fruit juice within one day then you should not use these chemicals. However, if you plan to store it on two to three weeks then you should add the preservatives even though they compromise the taste --Lenticel ^(talk) 06:52, 1 December 2008 (UTC)[reply]

Also note that a lot of people (especially asthmatics) are allergic to sodium benzoate, so be careful when using bottled lemon juice for anything.--Shantavira|^{feed me} 09:06, 1 December 2008 (UTC)[reply]

Nova and Supernova

I'm trying to figure this out: If I'm calculating the distance to a nova in a far-away galaxy, but I mistake it for a supernova, will my incorrect calculations be shorter, the same, or longer than the actual distance? My guess is that it should be longer than the actual distance because supernovae come from stars that are more massive than those of novae, and it will be more luminous. Am I right? Thanks!--el Aprel (^facta-_facienda) 04:08, 1 December 2008 (UTC)[reply]

Yes. The typical maximum absolute magnitude for a nova is -8, while supernovas have brightnesses around magnitude -18. --Bowlhover (talk) 04:36, 1 December 2008 (UTC)[reply]

Motorcycle Dynamics

In scenes on TV and film of motorcycle riding, there is often a shot where the rider somehow tips back the cycle so that the front wheel is off the ground. I saw one of these tonight on the Compendium of Scientific Information (CSI), Miami division.

The implication is that the rider does this to go faster. Is there any real speed advantage in getting the front wheel off the ground, or is it just a cool trick to enliven a chase scene?

Is there a way to steer a cycle when the front wheel is up?

It seems to me it would take a lot more force to raise the front wheel from the ground to 30 degrees up than from 30 degrees to 60, or from 60 to 90 degrees. Do people trying to ride a motorcycle on the rear wheel risk tipping over backwards?

Thanks, CBHA (talk) 07:21, 1 December 2008 (UTC)[reply]

Well, in a perfectly abstract world, as soon as the front wheel comes of the ground, all the weight is on the rear wheel, thus increasing traction. So the motorbike can accelerate faster without slipping. In a non-perfectly abstract world, this a) increases aerodynamic drag, b) makes it nearly impossible to steer and 3) is a very unstable position, so you need to be very careful with the power control to void falling on your ass. In other words, I suspect it's purely for show. I've never seen this in real races, either. --Stephan Schulz (talk) 08:11, 1 December 2008 (UTC)[reply]

I don't see it as a method of achieving rapid acceleration but rather a result of rapid acceleration. In fast motorcycles and some race cars, the torque created about the rear wheels under full accel is enough to lift the front end off the ground. StuRat (talk) 09:09, 1 December 2008 (UTC)[reply]

See Wheelie. You may also find Bicycle and motorcycle dynamics interesting—it's a good, thorough article, even if it doesn't cover wheelies. -- Coneslayer (talk) 12:47, 1 December 2008 (UTC)[reply]

Time and causality

This is basically some daydreaming of mine, but I was wondering what seasoned theoretical physicists (and amateurs such as myself) thought of it.

The gist: we experience a global sense of linear (past->present->future) time and associated causality every day. But is there any reason, other than Occam's razor, to assume time is actually linear, even in the local sense? Supposing causality worked in any direction, including future->past, wouldn't we still experience causality in a linear fashion? If the future changed the past, we wouldn't know of a different past, and hence had no way to know a later event influenced an earlier one. From a purely theoretical point of view, is there anything prohibiting bidirectional time? And if there isn't, then wouldn't it also be safe to assume tachyons and related concepts could exist?

--Link ^(t•c•m) 10:47, 1 December 2008 (UTC)[reply]

There is an argument that the perception of time must, of necessity, be in the same direction that entropy is increasing. A laymans explanation of this can be found in Stephen Hawking's book A Brief History of Time. The argument goes something like this: to form a memory, a finite amount of energy must be stored in a structured way. But any local structuring of energy (decreasing entropy) must involve the transport of energy to form the structure, and globally (in the universe as a whole) entropy must be increased by the second law of thermodynamics. It is impossible to see into the future (remember the future) without breaking the second law. Since the second law is currently considered a fundamental law of nature that is ablsolutely true in all cases then the answer is that there can only be one path for time to take (for a given observer in a given frame). SpinningSpark 12:03, 1 December 2008 (UTC)[reply]

See also, arrow of time. There are a number of equations used in the sciences which are, as far as we know, unidirectional in time (cannot be reversed). --98.217.8.46 (talk) 14:54, 1 December 2008 (UTC)[reply]

Thanks for the replies. The entropy explanation seems valid. So basically, under the assumption that the second law of thermodynamics is true, it is impossible to change the local past in any way, provided that the universe is indeed a closed system (so no external "something" decreases entropy locally), right?

Still, the Second Law seems to be at least partly incompatible with the Poincaré recurrence theorem. I find this all quite mind-boggling, which is exactly why I love reading and thinking about it!

--Link ^(t•c•m) 15:51, 1 December 2008 (UTC)[reply]

Strain Gauges

Could anyone step me in the right direction as to where a strain gauge would be used in Clinical Neurophysiology (eg EEG, EP, NCS, EMG) or the very least in neurology? Moffo (talk) 15:52, 1 December 2008 (UTC)[reply]

Looks like one type of strain gauge is used to measure blood flow and tissue swelling; see Strain gauge#Other gauge types. --—— Gadget850 (Ed) ^talk - 16:25, 1 December 2008 (UTC)[reply]

Might it be used to measure intracranial pressure on a continuous basis, as opposed to manometry via spinal tap? The pressure sensors sometimes inserted through the skull, for instance. (This certainly does not constitute medical advice!) Edison (talk) 21:08, 1 December 2008 (UTC)[reply]

Herpes research

There are a very large number of individuals infected with herpes in this country and I suppose throught the world. What are the chances of a cure in the near future(5 years)?— Preceding unsigned comment added by 129.112.109.252 (talk)

That's impossible to predict. It requires people to make predictions of future events, and until someone invents the time machine, or the crystal ball, or something like that, it would be difficult to determine. There are drugs like Valtrex that are known to effectively control the symptoms of herpes, and which also have been shown to reduce (but not eliminate) the transmission of herpes from infected persons. See our article on Herpes simplex for more info. --Jayron32.talk.contribs 18:10, 1 December 2008 (UTC)[reply]

Although there is no way to predict if we'll have a break through in the next five years, I find it unlikely that someone will come across a cure in that time. I believe that most hope lies in vaccination, which has already proved effective in several trials. —Cyclonenim (talk · contribs · email) 18:12, 1 December 2008 (UTC)[reply]

Viruses are almost never cured. AS Cyclonemin, our best hope is a vaccination and/or treatments that reduce it's contagiousness in individuals who have it. -----J.S (T/C/WRE) 20:55, 1 December 2008 (UTC)[reply]

Less known cell line resources

Hello, all. I'm trying to locate a particular cell line that is commonly used in my area of research (HaCaT), but all the usual non- and for-profit resources don't seem to have it. This particular cell type is used fairly commonly in the existing literature, so I would really prefer to use it if possible. Before I go begging a possibly competing lab for a vial of some of theirs or seeking alternative lines, does anybody here have any suggestions regarding means that I hadn't considered? Cheers! – Clockwork Soul 19:42, 1 December 2008 (UTC)[reply]