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April 5

Lifespan of cats

this is my first reference desk question but what is the average lifespan of a cat? yuckfoo 03:01, 5 April 2007 (UTC)

I don't know precisely, but cats kept indoors as pets can live somewhere around 15 years, while outdoor pet cats and wild/feral cats don't live nearly as long. StuRat 03:15, 5 April 2007 (UTC)

The average lifespan of a cat is nine times the median age of cats when they die. 202.168.50.40 03:03, 5 April 2007 (UTC)

Maximum life span says the record is 34. Clarityfiend 03:21, 5 April 2007 (UTC)

can we add this to the cat article once we are sure about it yuckfoo 03:19, 5 April 2007 (UTC)

For domestic cats, estimates range from 10-18 years [1], 10-12 years [2] and 9-15 [3] though factors such as whether a cat is permitted to go outside will influence their average lifespan. [4] Rockpocket 06:52, 5 April 2007 (UTC)

The Impact of the Immune System on the Nervous System

Hey. I've been exploring a bunch of topics on the development of cephalization in humans, and I recently came across "neuroimmunology." I have seen a few studies on how the nervous system can impact the immune system but none for the reverse. I wouldn't readily assume that the immune system would have such an effect (unless it was detrimental as in autoimmune disease), but is there any literature on the subject? Thanks. Robinson0120 05:09, 5 April 2007 (UTC)

I'm not sure how you define "impact", but there is certainly evidence that key molecular players in the immune system can have a role in neuronal signaling. Major histocompatibility complex molecules have been implicated in synaptic development and plasticity. (PMID 16698261) In addition MHC-binding peptides have been shown to activate neurons of the vomeronasal organ and thus act as putative pheromones. (PMID 15528444) Rockpocket 06:42, 5 April 2007 (UTC)

Sorry, I was vague. I was looking more along the lines of behavioral modification, but pheromones and plasticity look like great starting points. Thanks for the input! Robinson0120 07:02, 5 April 2007 (UTC)

Instructables web site

I know that the Wikipedia is an encyclopedia and frowns on articles that include a "how to" section (except maybe a list of useful formulas, etc.) so I went looking for sites that could help me figure out stuff like how far apart I can spread the fork on a bike to fit a new axle and came across a site that is just what the Wikipedia is not and does not want to be. Its the Instructables web site. So my question is how come the Wikipedia does not have an article on this very extremely useful site? Nebraska bob 05:26, 5 April 2007 (UTC)

Because you haven't created one yet ? Seriously, go ahead and add it, it sounds like a good addition to Wikipedia. StuRat 05:47, 5 April 2007 (UTC)

Well, Stu this would be my first article and I want to start off doing it right. Even though this is a wiki there are some things you have to live with which the first editor does like the name of the article for instance. So what should I use for the title, "Instructables web site" or just "Instructables"? (Thanks for the vote of confidence, which I do not deserve BTW. I created the "Instructables web site" article page and put a REDIRECT tag on "Instructables" in preparation for development but a couple of BOTS immediately posted SPEEDY DELETION TAGS stating the subject is not "notable." . Nebraska bob 12:25, 5 April 2007 (UTC)

Excuse me, but I'm not a bot, and I'm pretty sure Longhair isn't either. You created an empty page that included an external link and a broken redirect. That is a textbook candidate for a speedy deletion tag. I've since commented on your talk page about what you might want to start with and even offered to search for sources myself. --Onorem 12:53, 5 April 2007 (UTC)

You are how the things under your control act. (Mighty jumpy if you ask me.) Nebraska bob 13:00, 5 April 2007 (UTC)

You really need to put together at least a couple of paragraphs and one solid reference (perhaps testing it out in the Wikipedia:Sandbox) before you paste that into the edit box to create the article - that way there is never a time when it looks like someone just stuck a random link onto a page for promotional reasons (which is probably why your first attempt was killed). However, there is a good chance that your article would get deleted anyway if the web site in question is deemed 'non-notable'. You should first check up on Wikipedia's standards for this in WP:NOTE...or more specifically: Wikipedia:Notability (web) - I strongly suspect that this site is not going to meet the guidelines...but I confess I'm not all that familiar with it. SteveBaker 14:49, 5 April 2007 (UTC)

Forgotten just how I came across this site... probably from a search for something... oh yes if a rear triangle could be spread 30mm... Anyway a few things caught my eye that I may have seen somewhere else and so I started browsing. You know sometimes policy in general is probably a good thing if you do not let it go to your head. After all it is possible to sacrifice usability for showmanship or so called professionalism. Anyway I found the site to be notable (unlike even some of the very good RC sites) simply because it is a wiki (or actually a user blog where other can comment on the stuff you have contributed but not flush it, for others but only for themselves, down the can.). That said it is notable to me and maybe to others but that will not change the fact that it is notable to me. If the Wikipedia wants to go "High Brow" hey that's fine with me. Just find it strange the first time I stick my toe in the water it gets bitten off by a couple of piranhas. Nebraska bob 15:07, 5 April 2007 (UTC)

You have to put this in context. The problem is that tens of thousands of web site owners have had the idea of creating a Wikipedia page that points to their web site (and says almost nothing else) - relying on Wikipedia's page rank score (which is astronomical) to boost their own ratings on Google, etc. In fact, this doesn't work (for technical reasons to do with how Wikipedia presents outside links) - but that doesn't stop people from trying. The result of this is that dozens and dozens of these things get created every hour of every day. There simply isn't time and/or effort to carefully examine each one to see if it's valid or not - so they tend to get speedily deleted without much care. Sadly, your article looked 100% identical to the other gazillion 'junk articles'...whether you planned to eventually expand it or not. That's why I suggested that you write a good chunk about the web site BEFORE you create the article - so it starts off as a substantial chunk of text. However, even if it were a substantial article, that's not enough to meet the 'notability' criteria...so it might be problematic even if you spent a lot of time on improving it. It's unfortunate that this has badly affected your first experience with Wikipedia - but I ask that you consider it from our point of view. We simply cannot allow the kinds of abuse that your initial effort looks so much like. If you had created an article about (say) a car or a bird or a Romanian emperor or...almost anything other than: (i) a web site, (ii) a living person or (iii) a band - it would not have been deleted. But those kinds of subject are subject to continual abuse 24/7 and the consequences for those with something serious to say are rather nasty. SteveBaker 16:16, 5 April 2007 (UTC)

You might try to create an article about HOW TO web sites in general in order to avoid the perception of bias. Of course you would include the instructables site and maybe add some others like wikihowCzmtzc 15:53, 5 April 2007 (UTC)

Okay, I'm working on composing an article off-line and will upload it as soon as Eric Wilhelm, (instructable's owner) can send a history file.

Here are some notability references:

• Time:

“step-by-step instructions for making things you never knew you wanted”

• The Village Voice

“you’ll find detailed, well-illustrated, friendly instructions for constructing your own at instructables.com”

• Lifehacker

“This is a great place to start if you’re looking to find a cool DIY project to try out”

In the meantime I suggesst everyone have a visit and explore... Lots of fun! Nebraska bob 16:34, 5 April 2007 (UTC)

You may not know this, but you can also create pages in your own user area, like say, User:Nebraska_bob/instructables, just by adding a slash and word after the web address at your own home page. Pages you create in your own user area generally go unmolested, (unless you invite people to molest them). This will allow you to test all the links and get the page up to a high quality standard to avoid the problem of it being immediately deleted when you first create it (because it's not yet perfect). StuRat 19:52, 5 April 2007 (UTC)

Alcohol's effect long-term effect on growth

Does ingesting ethanol during puberty really stunt one's growth (i.e. diminish one's final adult height)? Anti-drug websites claim so, but they'll claim anything they can get away with. Academic sources are preferred. Thanks, ^L_Wizard @ 07:26, 5 April 2007 (UTC)

I'm a teacher. Kids that I've known who came to school drunk were shorter than others. Coordination and motor control are damaged from alcohol use in young, whose brains have not fully developed before 23 years of age (female average) and 25 years of age (male average). Size tends to be related to diet from birth to age three. Genetics is also important. Poor diet in adolescence still affects height. I suspect the science would show Alcohol provides no benefit to children, and will harm health, but as to restricting size, I can omly go on observation. DDB 11:52, 5 April 2007 (UTC)

Alcohol affects smaller people more than larger people. It could be that they were all drunk, but only the smaller ones showed symptoms. Think outside the box 12:08, 5 April 2007 (UTC)

Also note that this refers to alcohol abuse ("getting drunk"). Small amounts of alcohol (such as naturally occurs in food) can be metabolized by the liver before any damage is done. StuRat 19:42, 5 April 2007 (UTC)

The need for a balance in relation to Energy articles

Hi, I notice that Nuclear power by country is a featured list, and that Nuclear power is included in the 2006 Wikipedia CD Selection, or is a candidate for inclusion in the next version. But what about the important and broad topic of Renewable energy?

Are there any comparable high-quality renewable energy articles? Or is it possible to get an indication of renewable energy articles which are potential candidates and just need some further work?

It seems very one-sided to be showcasing nuclear power and not renewable energy -- Johnfos 09:47, 5 April 2007 (UTC)

Renewable energy tends to fall into categories of Solar Energy, Wind Power, Water Power Generators or Geothermal Power. There are advantages and disadvantages of each.

Geothermal is not yet used anywhere in industrial size, although some baths are powered by it, and plans are being made. It requires a substantial water supply.

Solar power is not yet cost effective, and does not run for an entire day.

Wave Power generators have been blocked on ecological grounds. Water power through dams is less popular as fresh water increases in value.

Wind Power has been blocked on ecological grounds, and is unreliable.

One brilliant idea is a km high tower which uses convection currents through a green house to turn wind turbines. It has been promised at most state elections in Australia since '96 but to little effect. DDB 11:44, 5 April 2007 (UTC)

I think you are way out of date in your assessment of renewables. Please take a look at Renewable energy commercialization, Renewable energy commercialization in Australia, Wind power in Germany, Solar power plants in the Mojave Desert and Deployment of solar power to energy grids to see what has been happening recently.

But I'm not asking for a debate about renewables vs nuclear. I'm writing about WP articles in these areas, and asking if there are any renewables articles that are seen to be of high quality, in the same way that some nuclear articles have been identified as being of high quality. Or if there are any renewables articles that could be high quality articles if a bit more work was put in. -- Johnfos 12:14, 5 April 2007 (UTC)

It takes a lot of time and effort to get an article to featured status and only a very few editors can be bothered with the amount of hassle and red-tape involved. So the matter of which articles are pushed to featured status is not a decision made by Wikipedia as a whole - it's a matter of whether (typically) a single individual editor has enough passion for the subject, knowledge about it (and, rather crucially) books on the subject sitting on his/her bookshelf so that the article can be sufficiently well referenced. Hence the spread of articles deemed good enough for the CD selection is not so much determined by an attempt to get a balanced view of the universe of knowledge (although that is a consideration) as it is by the set of articles that particular editors had an interest in. Only a few hundred editors out of the millions who come here manage to get an article to featured status and less than a tenth of one percent of articles ever get to that level. Worse still, the quality bar for featured status is rising all the time - and many former featured articles have been downgraded in light of 'modern' standards. SteveBaker 14:38, 5 April 2007 (UTC)

Many renewable energy sources have their uses, although no single renewable source has the ability to replace all nonrenewable sources at this time. I believe only a few places have sufficient geothermal energy to power industry, such as Iceland and Yellowstone National Park in the US. Solar power can be quite useful for places which are "off the grid", especially in desert environments. Wind is similarly most useful only in a few places with consistently strong winds. Hydroelectric power (dams with turbines), however, has been used for many years to power cities around the world on an industrial scale. Other forms of renewable energy have their places, too, like wave and tidal power. Wood, ethanol, and other biofuels do tend to create greenhouse gasses, just like fossil fuels, but are good alternatives in other ways, like energy security. But, back to the original question, we would be very pleased if you would take on one or more of the renewable energy articles and improve it to featured article status. StuRat 19:38, 5 April 2007 (UTC)

Worldwide installed capacity and prediction 1997-2010, Source: WWEA

As with any energy source, renewables have their advantages and disadvantages, and we need to work with these. But I must say I'm surprised by some of the comments above in relation to wind power, such as this "Wind Power has been blocked on ecological grounds, and is unreliable" and this "Wind is similarly most useful only in a few places with consistently strong winds" How then do you explain the graph shown, or the installed capacity of 20,621MW in Germany in 2006, and the fact that Denmark gets 20% of its electricity from the wind? Thirteen countries around the world now have over 1000 MW of wind generating capacity and more wind farms are planned in most of these countries.

I'm not trying to be argumentative in saying this. I'm just trying to bring a few basic facts to the fore, which help to underscore the growing importance of renewables.

As for a possible feature article on renewables, I appreciate the comments made. I'd be prepared to put significant effort into Renewable energy, but would need more guidance as to specific areas that need to be improved. Would anyone be willing to provide some comments in relation to that article please? -- Johnfos 01:29, 6 April 2007 (UTC)

Wikipedia:Featured article criteria lists some suggestions. After that you would probably get more help from Wikipedia:Peer review. Shinhan 19:13, 6 April 2007 (UTC)

Hepatitis B vaccine

Are all three of the doses of the Hepatitis B vaccine (given over the course of 6 months) identical? —LestatdeLioncourt 12:16, 5 April 2007 (UTC)

Some googling (look for keywords like hepatitis b vaccine schedule) suggests that the schedule for Hep B vaccination can be rather flexible, and in some places Hep B vaccines are combined with vaccines for other maladies.

For the three-jab Hep B-only vaccination, the three inoculations are identical in composition and dosage. TenOfAllTrades(talk) 15:24, 5 April 2007 (UTC)

Cardiac Cycle

Many books/online sources etc refer tot he cardiac cycle in 2 phases: systole and diastole (ventricular), with diastole encapsulating atrial systole (PQ interval). Some sources say that it begins at SL valve closure (others say after ventricular pressure reaches maximal) and ends with AV valve closure (ventricular systole initiated). Could someone clear up exactly where and when each phase begins/ends (have read wiki!).

And on a related note, could someone please explain to me exactly when day begins, as opposed to night? Some sources say that it begins when there is light enough for someone with normal vision to read unaided, and ends when light is insufficient for reading, Others relate it to the position of the sun with respect to the horizon. Could someone clear up exactly where and when each phase begins/ends (have read wiki!). --62.16.173.45 20:05, 5 April 2007 (UTC)

Is that hard to distinguish in Norway?

Hearing tests

what is the advantage of the absolute bone conduction test in comparison with other tuning fork tests, i.e. rinne's test and weber's test?

Weber test, Rinne test, absolute bone conduction (bottom of page 4) --JWSchmidt 21:51, 5 April 2007 (UTC)

It's not exactly an advantage - it's a different test. Listening to a tuning fork requires that eardrums are working and nicely flexible. Very, very overly-simplistic: The bone conduction test tests the inner parts of the ear only. So if you can't hear the tuning fork - but you can hear the bone conduction test - then your outer ear is faulty - if you can't hear either of them then your inner ear is the problem. SteveBaker 04:24, 6 April 2007 (UTC)

Why does hot water clean better than cold?

I was curious why hot water (with detergent) cleans better than detergent in cold water. Not necessarily laundry, but also housecleaning and sidewalk cleaning. --24.249.108.133 16:56, 5 April 2007 (UTC)

I would guess because it has more energy in it, the water molecules have a higher KE, which is what temperature is—more bumping and rubbing around? [Mαc Δαvιs] (How's my driving?) ❖ 17:37, 5 April 2007 (UTC)

When dealing with fats, they gradually become more liquid and less solid as they are heated up. The more liquid they are, the easier it is for them to be washed away by water. StuRat 19:24, 5 April 2007 (UTC)

Also, when the detergents are supposed to do a chemical reaction (e.g. a redox reaction in case of acidic or basic detergents), the Arrhenius equation tells us that mnost chemical reactions happen faster at higher temperature. User:sanders_muc 85.127.180.138 20:06, 5 April 2007 (UTC)

Solubility of most substances increases with temperature. If you make a substance more soluble, it will be easier for it to dissolve in water and be carried away. Johntex\^talk 20:38, 5 April 2007 (UTC)

(edit conflict) As well, the goal is often to dissolve the dirt, not just physically move it away, and solubility often increases with temperature (see how much and how fast you can dissolve sugar in hot tea vs iced tea). DMacks 20:39, 5 April 2007 (UTC)

Also, hot water has less surface tension allowing it to penetrate fibres better. —The preceding unsigned comment was added by 209.53.180.29 (talk) 23:02, 5 April 2007 (UTC).

What if... Earth was frictionless?

Here's one of those silly Wiki hypotheticals. What would a frictionless or very low friction planet be like? (like all surfaces were super smooth and slick) --24.249.108.133 17:03, 5 April 2007 (UTC)

it would be like asteroids (game). Seriously. -- Diletante 17:07, 5 April 2007 (UTC)

I love that game! and lets just say there would be no need for car breaks as they wont work XD Maverick423 17:29, 5 April 2007 (UTC)

Just as a note, cars would break fine. It's the braking that would be an issue.

To the original question, though, consider an ice rink, and then expand it globally. That's what a low-friction planet would be like. — Lomn 18:38, 5 April 2007 (UTC)

Continuing that direction (sorry:) hockey goals don't slide around because they are anchored below the surface. Even if there weren't a non-frictionless sublayer, one could use an expanding bolt to fix things in place. That would allow one to move around in a controlled manner by gliding from fixed object to fixed object, similar to how a mountain climber moves from hand-hold to hand-hold. DMacks 18:44, 5 April 2007 (UTC)

Actually car brakes would work perfectly fine. The car would never move anywhere, though, no matter how fast the wheel spun, because the planet surface would have no static friction. If you study the wheel movements, you'll notice that the wheel needs high friction at the contact point with the ground, and low friction at the contact point with the axle. Nimur 21:03, 5 April 2007 (UTC)

You could never drill or set the expanding bolt. But there would still be wind, and we would blow all over the place. :) —The preceding unsigned comment was added by Zeizmic (talk • contribs) 22:15, 5 April 2007 (UTC).

The exhaust/intake would provide a small force to move the car. Planes would fly perfectly fine, would "frictionless Earth" have drag? What other effects would that cause? -- atropos235 ✄ (blah blah, my past) 00:24, 6 April 2007 (UTC)

Who said anything about drilling? One gun, two bullets: get two holes in the ground. Two sticks, now you've got two things to hold, and you can move around in any direction from them...even just one would be enough if the pole didn't rotate freely in its hole. If you've got strong enough arms, you can keep your legs motionless and still cross-country ski. You could even drill if you had a counter-rotating mass to keep you stationary (or an air jet or somesuch)...consider the tail rotor on a helicopter. DMacks 02:16, 6 April 2007 (UTC)

Sorry - won't work. You make a hole in the ground - but the total lack of friction between particles of dirt and rocks would cause the hole to fill back in almost as soon as you made it. In fact, dirt and sand would be like a liquid - we'd sink in up to about our chests in the dirt - think 'quicksand'. Buildings and roads and anything that's heavier than the soil beneath would sink without trace. This is a pretty silly question. SteveBaker 04:21, 6 April 2007 (UTC)

IT sounded like we were talking about the surface being frictionless "like an ice rink", not "the whole material of the earth is frictionless including lack of cohesion". DMacks 04:25, 6 April 2007 (UTC)

Really interesting insights! My original concept imagined all surfaces coated with frictionless nano particles. --24.249.108.133 17:22, 9 April 2007 (UTC)

How do satellites orbiting the earth avoid colliding with each other?

There are thousands of satellites in near-space orbit. How do they not hit each other? Is there a navigational database to track them? Can satellites change their orbit in order to prevent foreseen collision with other satellites or space debris?141.213.90.148 17:10, 5 April 2007 (UTC)

Suppose that there are 10⁵ satellites in orbit (unlikely), and that each of them is a square sail 10 meters on a side (100 m² in area: very large) presenting itself perpendicular to its motion (for best collision chances), and that they all orbit in circular orbits between 200 and 250 km in altitude (many are much higher) at a speed of 8 km/s with an inclination of no more than plus or minus 15° (many are polar). Then the volume of space they peruse is that bounded by the (two-cut) spherical caps between the minimum and maximum latitudes at the minimum and maximum altitudes. The mean radius of the earth is about 6370 km, so the area of our orbital region is a bit more than the average of $2\pi (r+h_{1})(2(r+h_{1})\sin 15^{\circ })=1.40\times 10^{8}{\mbox{ km}}^{2}$ and $2\pi (r+h_{2})(2(r+h_{2})\sin 15^{\circ })=1.43\times 10^{8}{\mbox{ km}}^{2}$, so call its volume $7.1\times 10^{9}{\mbox{ km}}^{3}=7.1\times 10^{18}{\mbox{ m}}^{3}$. Our ridiculous fleet of oversized satellites traces out a total of $8\times 10^{10}{\mbox{ m}}^{3}/{\mbox{s}}$, so even if they were not almost all travelling in the same direction we should expect collisions to occur on about the same order of time as it would take them to sweep out the entire volume: 88.8 million seconds, or about 2.8 years. (Recall that we made the probability much higher by restricting the orbits and using a rather large number of giant satellites.) In other words, they manage to not hit each other because they would have to try very hard to hit each other. It won't happen by chance. --Tardis 17:50, 5 April 2007 (UTC)

While the probabilities of collision are very low, satellite orbits are very carefully catalogued. The UN, among other organizations, maintains a thorough listing that is publicly searchable. See International Designator, and note the external links at the end. Note also that military satellites are generally not in public databases. — Lomn 18:46, 5 April 2007 (UTC)

It's also worth noting that while Tardis references the big sky theory, it's primary caveat (namely, that it's far less effective if conditions are restricted) applies in full force. There are comparatively few classes of orbit suitable for most satellites, and geostationary orbits in particular are subject to relatively high volumes of satellites. — Lomn 18:50, 5 April 2007 (UTC)

But, of course, objects in geosynchronous orbits aren't moving at all (relative to the Earth's surface) or are moving at the same speed and direction (relative to the Sun), so they can't hit each other. A bigger concern than satellites hitting each other is all the space junk out there in essentially random orbits. This includes nuts and bolts, tools, spaceship components, etc., that were intentionally discarded or accidentally lost. There are databases of such objects, but many are also unlisted. StuRat 19:20, 5 April 2007 (UTC)

Lots of stuff is carefully tracked and catalogued by the government, military, and commercial contractors. Take a look at this cartoon animation by Analytical Graphics, which demonstrates the ability to monitor not just satellites, but debris and dust, via radar. Nimur 21:37, 5 April 2007 (UTC)

“ China has acknowledged that it tested an antisatellite missile on January 11 when it targeted and destroyed an aging Chinese weather satellite. Along with fueling debate on global space control, the incident has raised concerns that the debris could jeopardize satellites in low-Earth orbit (LEO), including the International Space Station (ISS). ”

More details from the AGI website... Nimur 21:36, 5 April 2007 (UTC)

I put the animation on YouTube in case anyone wants to see it without a 50 MB download. Nimur 23:35, 5 April 2007 (UTC)

Nuclear Shelter

hey guys well i was checking out some stuff about nuclear shelters however i want to know what kind of walls will make it 100% radiation proof? besides that, is it logical to have a window in one? wont radiation go in through a window? and if not then how will a person inside it be able to renew the air already inside so as to not sufficate? Maverick423 17:26, 5 April 2007 (UTC)

100% stoppage is virtually impossible. That said, have you checked fallout shelter? Gamma rays are the deepest penetrator (that is, anything stopping them will stop alpha and beta particles as well. — Lomn 18:23, 5 April 2007 (UTC)

Not virtually impossible, theoretically impossible on many orders assuming you want a physical wall. Even, all baryonic matter is radioactive. Keep in mind there are several different types of radiation, and nuclear radiation. Try reading the articles! You should get enough out of them to know. [Mαc Δαvιs] (How's my driving?) ❖ 21:44, 5 April 2007 (UTC)

A window is definitely out. Some type of well filtered air intake could work, however, as most of the radioactivity is in particles floating in the air, not in the air itself. If you can remove those particles, you can get breathable air. Another approach would be to have a supply of compressed air and/or reuse the air with equipment to remove the CO² from the air and split it into carbon and oxygen, the latter of which is then returned to the air. Some combo might be best, such as using stored air during the first few days or weeks, when fallout would be heaviest, then going with filtered outside air after that. StuRat 19:10, 5 April 2007 (UTC)

While it is impossible to build a wall that is guaranteed to stop absolutely 100% of incident radiation, it's relatively straightforward to construct a wall which will block a large enough fraction of radiation to preserve and protect the soft and squishy living matter inside. A meter of concrete or soil will probably protect you adequately from radiation at any distance from a nuclear blast that doesn't physically destroy your shelter. The half value layer for lead and 1 MeV gamma rays [5] is 9 millimeters; ten centimeters will attenuate incident gamma rays to 1/2000 of their original intensity.

Windows are possible, but costly and a weak point; you'll want to look into a thick layer of lead glass. It's used regularly in the radiology and nuclear industry. Most fallout radioactivity comes from radioactive solid material affixed to dust particles; you'll want to have a HEPA-filtered air system to remove the bulk of these particles. As others have noted, our article on fallout shelter should give you a good summary of the important construction considerations. TenOfAllTrades(talk) 14:55, 6 April 2007 (UTC)

field lines

respected sir/madam,

i have a wireless router(wr) connected to the modem.i wanted to ask you what was the pattern of field lines created by wr & acc. to it what could be the best position for convenience122.162.99.104 17:31, 5 April 2007 (UTC)

Perhaps radiation pattern can help you? -- mattb @ 2007-04-05T19:03Z

The best position for your conveniece could be iether the bolw or the cistern, but not both! —The preceding unsigned comment was added by 88.109.246.75 (talk) 01:24, 6 April 2007 (UTC).

Huh?Edison 04:38, 6 April 2007 (UTC)

Ha. Fvasconcellos 22:47, 6 April 2007 (UTC)

Driver programs for wireless lan cards can usually display the strength of the received signal (this is similar to the signal strength display on most mobile phones). You can use that to experiment with different placements. Note also many buildings have iron in the beams which is an obstacle for reception. – b_jonas 10:52, 9 April 2007 (UTC)

Burying carbon dioxide

There are plan for some coal-based power plants to catch the carbon dioxide resulting from burning the coal and stash it away somewhere where the sun doesn't shine so that it cannot contribute to global warming. Am I missing some facts or is this raw political nonsense? Wouldn't it be far safer (outgasing), cheaper (no or nearly no preprocessing) and easier (no gas involved) to bury some sewer sledge with the same carbon content instead? 84.160.247.123 18:32, 5 April 2007 (UTC)

The key is carbon versus carbon dioxide. While sewer sludge may well be rich in carbon, that carbon isn't CO₂ and so isn't capable of contributing to a greenhouse effect. As for how CO₂ would be captured and buried... beats me. I have no idea if that's raw political nonsense or not. — Lomn 18:56, 5 April 2007 (UTC)

See also Carbon capture and storage and Carbon dioxide sink. DMacks 18:59, 5 April 2007 (UTC)

(After edit conflict) Right, carbon is not carbon dioxide, but the idea is to take away carbon that takes part in the carbon/carbon dioxide cycle to compensate for the coal that wasn't part of it previous to burning. The carbon of the sewer sledge will become carbon dioxide via bacterial decomposition soon enough. (And I didn't really expect an answer on the 'political nonsense' part here, not in the science section anyway.) 84.160.247.123 19:07, 5 April 2007 (UTC)

I would expect that, proportionally, comparatively little sludge is converted to CO₂. — Lomn 21:33, 5 April 2007 (UTC)

Oxydizing sewage is the main thing a sewer plant does, aside from concentrating and dehydrating the sledge. If it is not done by the plant it's done by the unlucky river or lake downstream. Of course, main portions are minerals and water but, what is easier and cheaper to bring deep down and keep it there: 1kg of artificially compressed and cooled gas or, say, 50kg of sledge? 84.160.225.164 22:47, 5 April 2007 (UTC)

Sledge is solid/liquid and will have minimal impact on the atmosphere compared to CO2, which is immediately released. Carbon sequestration can turn the evil coal-burning powerplant into something that emits virtually nothing, but is still cheap and safe. I'm not sure what oxydizing sewage means, but it doesn't mean that all the carbon in it is converted to CO2. Sewage is typically aerated near the end of the journey so it's not totally devoid of oxygen so it doesn't suffocate fish, to destroy some of the nasty anaerobic microorganisms present, and to allow other microorganisms to further process the sewage. -- atropos235 ✄ (blah blah, my past) 01:11, 6 April 2007 (UTC)

Oxidizing sewage is turning it into carbon dioxide http://en.wikipedia.org/wiki/Sewage_treatment#Aerobic_digestion. As it takes a while to build a power plant, deep down depositing of sewer sledge (= carbon containing material whose carbon would otherwise be converted into carbon dioxide within a short time) could start well 3 years ahead, so the net balance of carbon dioxide in the atmosphere would be the same. But I see the point: the evil coal burning plant would still be an evil coal burning plant, it's not so much about reducing the net release of carbon dioxide to the atmosphere but to make the guilty power plant look better. 84.160.225.164 10:33, 6 April 2007 (UTC)

shape of ionic compounds

I was tutoring chemistry, and drew a simple picture of NaCl, where the Na ions and Cl ions formed a lattice with the atoms alternating Na - Cl - Na - Cl etc., chessboard fashion (so no Na was orthogonally adjacent to another Na). Then a problem occurred to me: I had absolutely no idea what the shape of, eg. Magnesium Chloride was. There are two Cl ions for each Mg ion. How do they arrange themselves into a lattice? The Mad Echidna 19:14, 5 April 2007 (UTC)

I was part-way through writing the answer, when I happened to look at the page for your specific case, magnesium chloride and saw that there was a whole section of "Structure" information in the infobox in the upper-right portion of that page...see especially the Crystal Structure information and links. DMacks 19:18, 5 April 2007 (UTC)

Cubic crystal system may help also, it's a common way to categorize a lot (all?) ionic compound crystal structures. Nimur 21:07, 5 April 2007 (UTC)

For this particular case, the link Cadmium_chloride#Crystal_structure seems most useful (found following DMacks's idea), although it takes a while to 'see' where everything is. Skittle 22:33, 5 April 2007 (UTC)

Thanks folks for these answers, and sorry for not checking myself. It didn't quite dawn on me that the structure might be given for individual compounds, so I had only searched for the general term "ionic lattice". Even so, if I had searched for Magnesium Chloride, I would probably have missed the structure section in the infobox anyway. So I'm glad I asked. Fascinating how the lattice "knows" to just knock out a neat layer and leave everything else intact. The Mad Echidna 16:51, 7 April 2007 (UTC)

Lambertian verus Batwing radiation

Where can I find a comparative description for Lambertian versus Batwing radiation patterns. Nebraska bob 20:38, 5 April 2007 (UTC)

Lambertian reflectance is probably the same as radiation: it is isotropic, meaning the emitted light is the same at all angles. This might be described as a diffuse light source, as opposed to a spot-light or specular lighting. Batwing seems to be more of a "marketing" term, presumably for lighting and LEDs, as well as some antennas. This LED[6] seems to generate this batwing pattern. Nimur 21:18, 5 April 2007 (UTC)

Also, schematic of a batwing beam pattern and a technical article and a datasheet with graphs. Nimur 21:23, 5 April 2007 (UTC)

Open to Suggestions

Hypothetically, lets suppose that I live with a family member who for practical purposes displays obvious signs of unhappiness with his job and his life. Lets further suppose that he runs his own business, but it is in finiacial trouble because the mans unhappiness with his job has resulted in serious slide in business. Those around this person believe that he probably suffers from clinical depresseion, but the man in question refuses to believe it and, having a background in medicine, would likely know how to spot and stop any attempt made to treat such a condition. Furthermore, lets suppose that his co-workers, friends, and family are trying to help him, but are not sure what should be done to get the man back to his former self. Would anyone have any suggestions about what should be done? I'm desperate here, so I'll take any advise I can get. 70.254.22.164 22:32, 5 April 2007 (UTC)

May I ask why you are desperate for this hypothetical situation? − Twas Now ( talk • contribs • e-mail ) 01:34, 6 April 2007 (UTC)

I've lost friends to military moves. I would rather not lose my house and my parents to a divorce. Thats why I ask. I relaise that Wikipedia doesn't offer medical or legal advice, I just want some brainstorming help so I can try and save what little I have left. 70.254.22.164 03:05, 6 April 2007 (UTC)

Since this calls for speculation, I've answered here: [7]. StuRat 02:03, 6 April 2007 (UTC)

I would suggest that you talk with a psychologist, psychiatrist, therapist, or social worker. Be prepared to spend a bit of money; it's worth it. Obviously, the person who really needs help is this "hypothetical family member", but equally obviously, having that person talk to the psychologist etc. is not an immediate possibility. But (a) a professional might be able to help you figure out how to get this person the help they need, and (b) let's face it, you do need help, too -- otherwise you wouldn't be asking the question!

Good luck. (And thanks for caring.) —Steve Summit (talk) 03:15, 6 April 2007 (UTC)

We cannot give medical advice or psychological counseling. That said, a person the depressed person trusts who is not a direct family member can sometimes be helpful in getting them to a psychiatrist or psychologist. Their trusted medical doctor is an extremely good choice to push them to get the help they need. A priest or minister or rabbi might also be useful. Depression can result from a bad situation which counseling can help or can reflect chemical imbalances correctable with medication. Edison 04:37, 6 April 2007 (UTC)

I didn't think about having a clergyman take the matter up with my "hypothetical family member", although that does sound like a good idea. On this issue of medicine: we tried that once, but our family members' medical background came to his defense; when he relized that we were trying to get him to take an anti-depressent medication he got very angry with us and accused us of trying to interfere in his life. If there was a way to get him to take the medacine without relising what it was we likely would have figured out how by now :/ 70.254.22.164 06:50, 6 April 2007 (UTC)

My psychiatrist takes referrals directly from religious leaders, as well as family doctors. For hereditary depression which comes out in the forties, a few pills are a life saver! Problem is that many self-medicate with drugs or alcohol, and deny they are depressed. This tends to lead to violence and suicide. I know many, many men who should take the pills... --Zeizmic 15:02, 6 April 2007 (UTC)

My advice will be rough but honest. There are two issues here. People you love and care about have issues in their lives. That's one. You might suffer in consequence, in yours. That's the other. The more others are not calm and thoughtful and running on copmmonsense, the more you yourself have to be - two dramatics tend to make a situation worse not better, and misery loves to influence others to support them (see Karpman drama triangle and Transactional Analysis).

A good solution here is for you to grow to the point that you can see things here from a more heightened perspective. (See transpersonal psychology for example.) Here are some truths that apply:

1. Each person has their own path. You can hope for the best, and work for the best, but you are not living their life, nor their yours. You cannot say for certain whether something that looks like a disaster really is or not. You don't know what lessons they will draw nor how it'll pan out, and you can't predict what's for the best or whether allowing or avoiding suffering is best.
2. Your best role is to be a reminder to them that whatever else, the core emotional needs are safe. They are loved, they are cared for, they will be supported no matter what, they have not failed so badly that it means they are worthless, rather they have tried stuff and learned. They can focus on what they want stepo by step, in the same way as a cardianc or stroke victim relearns stuff.
3. if there is genuine psychological issues, then support may be useful. Traditionally US doctors are very heavy handed on medications compared to European. Consider whether this is life stuff they are learning, or brain chemistry. Often depression is simply the recognition that ones historic mental agenda is doomed or dead ends... and its solution is to accept it as a good thing to know, and the body suggesting taking time to look within at it.
4. Don't buy in that mood means everything. It may not.
5. Not every relationship lasts forever. Loss may be one of your tasks to handle, and if separation is best for them, then your role may be to love them even so, and understand the sadness and necessity.

Some ideas. I hope you find a path through it. Remember, all the above apply to you. Split of no, you are human, and valued. You know this, inside. FT2 ^{(Talk | email)} 01:54, 11 April 2007 (UTC)

date format history

While exploring a Salado Indian ruin(about 600 years old)in central Arizona recently I came across graffiti with a date formatted as: 6/18/19. I am wondering if that date format was in use at the time indicated or is this a later, bogus entry. Thank you. macinyartMacinyart 23:08, 5 April 2007 (UTC)

I'm pretty sure that would have been added later, probably June 18th, 1919, but possibly June 18th, 1819. StuRat 01:35, 6 April 2007 (UTC)

What did the graffiti look like? Spray paint? Stone carving? − Twas Now ( talk • contribs • e-mail ) 01:59, 6 April 2007 (UTC)

If you are just asking if they used that sort of date notation then, the answer is probably yes. My guess is that it became common to use abbreviated dates like that sometime in the 19th century, with the rise of the bureaucratic state and the need to constantly fill out forms. But that's just a wild guess. --24.147.86.187 02:45, 6 April 2007 (UTC)

Candles were sometimes used by hikers to leave dates and initianls on rock walls in caves. I saw some that were 90 years old when a Scout many years ago. Edison 04:32, 6 April 2007 (UTC)

Thank you for your responses, in fact I am interested in whether the graffiti dated in 1919 was placed there at that time (using that date format) or whether it was written much later by a more modern prankster. It appeared to be in pencil, but I did not touch it, since that is sort of the rule when looking at antiquities. I know that simply finding out that the date format in question was used in 1919 proves nothing, but it makes its presence have a bit more credibility. I plan to put images taken that day on my website soon and wanted as much credibility as I could get. There were other examples of modern graffiti (as compared with those images done by the Salado) but this one was the best. Some of the art like works done by the Indians are remarkable and charming. These are heiroglyphs rather than petroglyphs and the artist utilized pigment rather than "pecking" the design in the rock. Great stuff. Thanks again for the responses. macinyartMacinyart 17:16, 6 April 2007 (UTC)

On a vaguely relevant point, I have at hand a British book "Railway Tickets, Timetables and Handbills" by Maurice I. Bray. It shows a number of late-19th-century tickets date-stamped with forms like "22 JA 96" and "17 SEP 90" and "NO 26 86". None of them use all-numeric dates, but they all use 2-digit years. So we can say at least that that convention was established in at least one country before 1900. --Anonymous, April 7, 2007, 10:11 (UTC).

Indeed, I have British postage stamps from the Victorian period which have cancels dated e.g. 15 JA 70. -- Arwel (talk) 23:12, 9 April 2007 (UTC)

Mushrooms

I always knew they were some kind of fungus but I recently discovered that fungi have a seperate kingdom than plants. So basically that means that fungi, including mushrooms are not plants!? so what do their cells look like, do they have the things that plant cells have and animal cells lack? do they have cell walls? photosynthesis capabilities?
So basically, we eat three things: animals, plants, and fungi?

Try reading up on fungi. Perhaps the main thing which distinguishes them from plants is that they don't do photosynthesis to get energy from the Sun. Instead, they mostly get their energy from decaying matter (although there are parasitic/carnivorous fungi). BTW, we also eat things that aren't plants, animals, or fungi, such as the bacteria used to make cheese, yogurt, etc. StuRat 01:26, 6 April 2007 (UTC)

Fungi are actually more closely related to animals than they are to plants! Check out Eukaryote#Differences between eukaryotic cells for some more info. − Twas Now ( talk • contribs • e-mail ) 01:31, 6 April 2007 (UTC)

Also, mushrooms are only the "fruit" of the fungus organism, the main part of which is underground and called mycelium. Pfly 03:28, 6 April 2007 (UTC)

It is odd that fungi are not considered to be plants - but when you consider things like yeast - which behaves much more like an animal than a plant, it's perhaps not so odd. But like with so many questions we get here, we shouldn't be surprised at the oddness of the choice of name...it's just a name. The fact that scientists decided to exclude them from the name plant is about as arbitary as the decision to exclude Pluto from the list of planets or the Chimpanzee from the genus Homo. It's just a name. SteveBaker 04:00, 6 April 2007 (UTC)

I don't agree that it's "just a name", since you seem to be saying it's an essentially arbitrary decision, like whether Pluto was classified as a planet. There are good reasons for most of the scientific classifications, such as similarity in form, genetics, and ancestry. There are a few cases where species may have been misclassified, but the classification of the majority of species are not in question. StuRat 04:07, 6 April 2007 (UTC)

I agree. Not being able to produce its own carbon through photosynthesis is a huge difference. In general, reproducing with spores is different too. Some things are arbitrary, but this is like classifying the stars from planets. There are clear distinctions. --Wirbelwindヴィルヴェルヴィント (talk) 05:35, 6 April 2007 (UTC)

It is just a name. What we recognize as "fungi" are polyphyletic. Fungus is a way of life, not a taxon. − Twas Now ( talk • contribs • e-mail ) 05:41, 6 April 2007 (UTC)

You misunderstand what I'm saying. I'm not saying that fungi should be classified in the same branch of the classification hierarchy as grass, trees, daisies, etc - I'm sure the present classification is 100% reasonable. I'm saying that our questioner finding it strange that 'Mushrooms Are Not Plants' is an arbitary fact of how the word "Plant" has been defined. If scientists had chosen some new term ("photoplant" say) to denote the organisms that photosynthesise and that are therefore not animals or fungi - and chosen to use the word "plant" to informally encompass both fungi and 'photoplants' (as most non-scientists would certainly do) then this question would never have arisen. The question is not about the nature of biological classification - no layman would be too surprised to find that fungi have their own branch in the classification system - the question is why such "obviously" plantlike things (to a layperson) are not called "plants" by scientists. That is a question about why scientists chose to use some particular word for some particular branch of the classification scheme (which is entirely a matter of history and linguistics) - it's not in any way a question about the biology of fungi. In that sense, it's no different from the "problem" of whether Pluto is a planet. The discussions about Pluto were not questions about it's mass, size, orbital characteristics...it was a discussion about what the historical/linguistic implications of the term 'planet' is. How many textbooks would have to be rewritten - how many signs in museum display cabinets would have to be corrected. No new science was involved. Choosing to exclude Pluto from the arbitary term "planet" was every bit as arbitary as using the common word "plant" to describe only photosynthetic organisms rather than using it's more common meaning which includes fungi. It's just a word. SteveBaker 15:54, 6 April 2007 (UTC)

I believe there was some new science that went into the Pluto decision, such as discovering that several Kuiper belt objects are similar in size to Pluto. This, combined with Pluto's peculiar highly elliptical orbit at a high inclination (out of the plane in which most planets orbit) caused speculation that Pluto was actually an Kuiper belt object captured by the gravity of Neptune. Thus, it's classification as a planet was called into question. StuRat 01:30, 7 April 2007 (UTC)

For what it is worth, the OED agrees with you. After defining "plant" as 1. an organism of kingdom Plantae, and then 2. "green plants", multicellular and photosynthesizing, there is a note about how bacteria used to be classes in kingdom Plantae but are not now, and that ..in the broadest (non-technical) sense, the term still may include fungi (and lichens), which are now classified in a separate kingdom, but were formerly regarded as lower (non-vascular) plants, together with algae and bryophytes.

Also, the requirement of photosynthesis for plants fails in some cases, such as Monotropa uniflora, which while clearly a kind of flowering plant, do not photosynthesize and behavior more like fungi -- in fact tricking other plants into thinking it is a friendly fungus, and receiving food from them. Pfly 19:55, 6 April 2007 (UTC)

Cravings

Why do women in labor have unreasonable cravings for inedible things (e.g. paint)? —The preceding unsigned comment was added by 209.53.180.29 (talk) 23:32, 5 April 2007 (UTC).

I don't know about inedible things, but their cravings for unusual foods are likely to provide vitamins and minerals needed for the baby (and later, for lactation). StuRat 01:23, 6 April 2007 (UTC)

Do you have any evidence for that rather startling statement Stu? —The preceding unsigned comment was added by 88.109.246.75 (talk) 02:06, 6 April 2007 (UTC).

I assume you're being facetious. :-) StuRat 03:41, 6 April 2007 (UTC)

Well, he didn't ask you for personal evidence, if that's what you mean! —Steve Summit (talk) 03:47, 6 April 2007 (UTC)

It's not in 'labor' - it's pretty much throughout pregnancy. It's an unconscious effort to get sufficient intake of odd-ball vitamins and minerals and such. With my wife it was Toblerone bars wrapped in crusty French bread...at 3am...on a Sunday...when the nearest store that was likely to be open and have anything approximating the required ingredients was 40 miles away. Yep - it's definitely not an urban legend. What's utterly miraculous is that the ladies seem to be able to somehow know precisely that certain foods contain whatever dietary thing is missing. They aren't reading the ingredient list...it's gotta be some amazing unconscious memory for the vitamin and mineral content of all of these obscure foods...very, very strange. SteveBaker 03:56, 6 April 2007 (UTC)

Gonna have to put a big tag on the claim that the pregnant woman has some near miraculous instinct telling her that if she doesn't get dill pickles and ice cream RIGHT NOW the baby will be missing earlobes or have a pointy head. Is there any scientific data to back up the claim, interesting as it is? In some cultures pregnant women eat clay. Correcting a dirt deficiency? Edison 04:30, 6 April 2007 (UTC)

It's not that pregnant women gain some instinct; we all have such an instinct. It just becomes more urgent, and the things needed change from those usually needed. Isn't it generally accepted that people tend to feel a need for things they need? Like thirst when thirsty, hunger when hungry, a craving for bananas (if you have previously eaten bananas) when low in potassium, etc? Skittle 17:58, 6 April 2007 (UTC)

I agree that this seems unlikely - but the existance of cravings during pregnancy is exceedingly well documented...and it's evidently an evolved behavior because other mammals and birds exhibit it. The only explanation that has been put forth is a subconscious need to get some trace substance that is needed for fetal development. What is very stange is the extreme specificity of the craving. In my wife's case, no other chocolate than Toblerone would remotely satisfy her "need". But I certainly agree that it is dubious to claim that their brains have somehow memorised the exact content of a bazillion different foods and are homing in on the one thing that best matches this need...however, I don't know of any other explanation. But if we do buy into this explanation, it's not a "dirt deficiency" that's causing women to eat dirt - it's some obscure mineral - or trace element - or salt - that's likely to be present in dirt. It's weird - but it's hard to deny when you see it happening right in front of your eyes...and in that LONG 3am emergency drive to the Toblerone and French Bread store, you have plenty of time to reflect on the oddities of human biology and evolution! SteveBaker 15:34, 6 April 2007 (UTC)

Yes, that's actually an important nutrient for fetal development. "Then the LORD God formed man of dust from the ground" (Genesis 2:7). See also pica. DMacks 04:35, 6 April 2007 (UTC)

There are also some parrots that eat clay, apparently needing whichever mineral the clay has. StuRat 13:16, 6 April 2007 (UTC)

There are no scientific studies that have demonstrated the exact reason behind pregnancy cravings, but experts tend to suggest that it is associated with one or more of the following:

• A manifestation of a biochemical signal that the mother is lacking specific nutrients (the nature of the specific food craved appears to be culturally influenced).
• A result of altered hormone levels in pregnancy inducing olfactory and/or gustatory cravings.
• In the case of pica, the result of an iron or zinc deficiency.

The body of literature on the subject can be accessed here [8] Rockpocket 05:56, 6 April 2007 (UTC)

It is known that psychological cravings have nothing to do with "what the body needs," and we are very interested in finding out what is the cause of cravings. It isn't the same as being thirsty or hungry. [Mαc Δαvιs] (How's my driving?) ❖ 23:18, 6 April 2007 (UTC)

Really, do you have a source for that? My reading of the literature suggests the mechanisms driving craving are not known, so I would be interested to read about the experiment that demonstrates it has "nothing to do with" what the body needs. Rockpocket 00:10, 7 April 2007 (UTC)

I believe food cravings are due to a number of factors:

1) As stated previously, people tend to crave foods which contain nutrients their bodies need. This ability, providing a huge evolutionary advantage to those who possessed it, would have be strongly selected for. In pregnant or lactating women, many nutrients are removed from the body of the mother, causing her to crave foods which will replace those nutrients.

2) During most of human evolution, certain nutrients, such as salt, sugar, and fat, were in such short supply that we developed an almost insatiable desire for foods containing these things. Since few people encountered foods rich enough in those items to suffer from the problems caused by an oversupply, and many suffered from nutritional problems as a result of not having enough, our evolution guided us towards excessive consumption of these items in modern times.

3) Psychological factors can also play a part. For example, "comfort foods", which we associate with a pleasurable experience in the past, can cause the memory or feeling from that experience to return when we again consume those foods.

StuRat 01:12, 7 April 2007 (UTC)

There aren't many neurones which grow during life (it used to be thought none did). The sinuses contain some of them. In his book "Why zebras dont get ulcers" Robert Sapolsky hypothesises this is about parent bonding, and that the emergence of new tastes is due to new sensory neurone growth in the nose area. I might have that slightly wrong, but the general idea's about right. FT2 ^{(Talk | email)} 02:05, 11 April 2007 (UTC)

Olfactory sensory neuron regeneration (every 40 days or so in humans) is an interesting subject. The data in mouse seems to suggest that new neurons project to the same glomeruli in the olfactory bulb as the ones they replace, suggesting the retain a similar odor activation profile. However, this paper [9] suggests that regenerating neurons in the subventricular zone do populate the olfactory bulb in a manner influenced by odor environment. These become granule cells and result in a improved olfactory memory. This would suggest that the olfactory system is plastic enough to "adapt" to odorspace, but perhaps not at the level of the sensory neuron. Rockpocket 06:45, 11 April 2007 (UTC)

Population growth

If a city's population increases from 1,000,000 to 1,100,000 in 5 years, how do I calculate annual growth rate? im asuming 2% (one fifth of 10% in 5 years) close but not exactly the right answer, it should be a little less right?

Right. It would be calculated as follows:

{(1,100,000/1,000,000)^(1/5) - 1} x 100 = 1.924...%
See Compound annual growth rate for more info. adam the atomTEC 23:47, 5 April 2007 (UTC)

Yes, and the reason is that population growth is generally considered to be proportional to the current population, all other factors being constant. For example, a city with twice the population likely has twice as many babies born each year, and also twice the immigration, as there are twice as many jobs to be had and twice as many people to invite their relatives to live with them. StuRat 01:21, 6 April 2007 (UTC)

It is an example of exponential growth, which in early stages closely approximates linear growth, but which may vastly exceed linear growth in middle stages. DDB 08:50, 6 April 2007 (UTC)

Starlings - how do they know where the worms are?

As I was stood waiting for my bus today, I watched a couple of European Starlings pecking around on a nearby patch of grass. At first, it looked to me as though they were just wandering around and probing the ground randomly with their beaks - but they would frequently (maybe once in every four pecks) pull an earthworm from the ground. This suggests to me that the starlings were *not* just sticking their beaks into the soil at random and somehow knew the position of the worms beneath the soil (take a small pocket knife and stab it into the ground a few times - what are the odds of hitting a worm by chance?). How were they doing this? Any ideas? --Kurt Shaped Box 23:58, 5 April 2007 (UTC)

Worms leave little tunnels behind, which likely collapse noticeably when a bird pecks at the ground above them. The birds could then follow the tunnel to the worm with continued pecks. StuRat 01:18, 6 April 2007 (UTC)

I think I've heard that they can hear the worms burrowing through the soil, if they're close enough to the surface. —Steve Summit (talk) 03:05, 6 April 2007 (UTC)

Yes, they can hear the worms burrowing. Most birds eating worms use their ears to locate the prey. —The preceding unsigned comment was added by 195.236.222.1 (talk) 12:18, 6 April 2007 (UTC).

I don't know about starlings, but I have found a few references to a study by ornithologist Frank Heppner regarding how robins find worms, and the conclusion he came to is that they do it by sight. A brief item relating to the study can be found here (in the section titled The Eyes Have It. --LarryMac 20:10, 6 April 2007 (UTC)

April 6

shit

Is shit flammable?

Yes, but not in wet form. It needs to be dried first, before being lit. DDB 08:45, 6 April 2007 (UTC)

Dried Cow dung is sometimes used as a fuel in the Third World. — QuantumEleven 11:40, 6 April 2007 (UTC)

Of course dried cow dung burns so well because it is mostly plant fiber. —The preceding unsigned comment was added by Czmtzc (talk • contribs) 12:45, 6 April 2007 (UTC).

I read an article a couple years ago about a power plant in Russia using retirement home used diapers as a fuel source (instead of coal). --Kainaw ^(talk) 13:53, 6 April 2007 (UTC)

Thats a whole load of shit and I find it a bit hard to believe!  :-)

I believe dried camel dung can also be used for fuel in the deserts. —The preceding unsigned comment was added by 88.110.208.218 (talk) 18:04, 6 April 2007 (UTC).

And bison dung was used by the Native Americans on the Plains. Corvus cornix 18:33, 9 April 2007 (UTC)

Do birds reject sick offspring

Baby birds are often found on the ground. Do they fall from the nest or were they pushed? Is there any evidence that adult birds can detect illness or deformity in chicks and reject them? A practical reason to know the answer is for use when deciding whether to try to reunite a wild chick with its parents, when for instance you have cared for it for a brief time.—The preceding unsigned comment was added by Haulpak (talk • contribs) 07:43, 6 April 2007 (UTC).

I think it's rather the siblings. Their chance of survival increases if they have less siblings to share the food with, and hence, a very strong one might push a weak one out of the nest. From the point of evolution, this makes sense, but don't ask for a reference as I can't remember where I read this. Simon A. 08:20, 6 April 2007 (UTC)

Here is a nice overview of this behaviour in cockatiels. Rockpocket 08:17, 6 April 2007 (UTC)

They were probably pushed. The culprit could have been a brood parasite, a selfish sibling, or a mother. See also, bruce effect. Are baby birds really often found on the ground? I've never seen any. --JianLi 01:16, 8 April 2007 (UTC)

The bruce effect describes a mammalian behaviour (birds are not mammals). Rockpocket 18:55, 8 April 2007 (UTC)

Oops, my mistake. But it still is a good example of a situation where a mother's and baby's interests are in conflict. --JianLi 19:08, 8 April 2007 (UTC)

Bouyancy in dead sea

In the dead sea, we can float without any equipment by "lying" on the surface. What will happen if we "stand" on the surface of the water? Will we float? IF no, what must be the desity of the sea water? Is it possible to achieve such density in nature/ by human?Invisiblebug590 10:21, 6 April 2007 (UTC)

Your posture is irrelevant to floating, what matters is the "amount" of you above the water's surface. If you were to "stand up" in the Dead Sea, you would still float, but the only bit of you above the water's surface would likely be the top of your head. Take a look at our article on buoyancy - if you increase the density of the water you're swimming in, more of you would protrude from the surface of the liquid. As far as I know, the water in the Dead Sea has the highest density of any body of water on Earth, however, there are other liquids with higher densities, such as mercury - but you certainly don't to go swimming in mercury, as it's poisonous! Does that answer your question? — QuantumEleven 11:38, 6 April 2007 (UTC)

I've seen a picture (an old picture!) of a worker in a mercury mine lying on -- not in -- a pool of mercury. —Steve Summit (talk) 22:59, 6 April 2007 (UTC)

Do you mean this one (scroll down a tenth of the way)?

No, but that's a nice one, too. —scs

Mercury has tremendous surface tension, so I wouldn't be surprised if someone could stand on it without sinking in. --Bowlhover 04:29, 7 April 2007 (UTC)

More than just the top of your head would stick out, even in fresh water. In Dead Sea water I believe the head and shoulders stick out. Note that the denser the liquid, the harder it would be to "stand up", as you become top-heavy. Because the lack of friction with the liquid allows your feet to slide out from under you, it would be impossible to stand up in mercury. StuRat 13:10, 6 April 2007 (UTC)

Anecdotal data point - it's impossible to stand up in the Dead Sea (with only your head above the water), as your legs rise to the surface every time you try to put them below you. To answer the OP, you still need a surface between yourself and the water to float standing upright on the Dead Sea - it's not just about the bouyancy but about the distribution of weight on the surface. Feet aren't wide enough to keep you upright on the water, at its current bouyancy. Natgoo 14:25, 6 April 2007 (UTC)

I don't buy User:Natgoo's explanation. The density of your body is pretty constant - there shouldn't be a net force pushing your legs to the surface unless they are less dense than your torso. Furthermore, in the Mythbusters episode where they attempted to show whether quicksand really sucked you down (as per bad movies!) they created a 'fluidised bed' of fine sand by pumping water up from beneath. The resulting "liquid" was a suspension of sand in water that had a considerable density - more than the dead sea - but still liquid enough to permit swimming in the stuff. One of their presenters was easily able to 'stand' in the artificial quicksand and he floated around with the liquid only just reaching his chest. You might be amused to watch this demonstration of a 'non-newtonian fluid' which evidently has pretty high density...[10]. SteveBaker 15:24, 6 April 2007 (UTC)

The density of your legs and your torso should be roughly the same, which is why buoyancy dictates that your legs should follow your torso to the surface (your torso is already there; the force pushing your legs up is that which is already holding up your torso). The only way you can remain vertical in the Dead Sea is by keeping your body ramrod straight, and even then you can only hold it for a few seconds. Perhaps the difference between the Dead Sea and the Mythbusters experiment is the complex chemical composition, and the flow, of the DS water? Natgoo 18:05, 6 April 2007 (UTC)

Doods... you're stuck on buoyancy and you're forgetting about gravity, which acts as a destabilising force on upright objects in fluid (think of a bowling pin or a log in water). The fact that people in Mythbusters could stay upright in quicksand is probably because the particulate made it easier to resist tipping over. Anchoress 18:43, 6 April 2007 (UTC)

Right. As anyone who's tried to design a boat knows, something floating in water is stable only if its center of gravity is below its center of buoyancy. But that's obviously not so for a biped standing in a liquid so dense that only the legs are submerged! —Steve Summit (talk) 22:57, 6 April 2007 (UTC)

Yeah - but look at this picture of someone actually floating in the dead sea (see right). It's clearly not dense enough that the guy's center of gravity is above the surface of the water. We're not thinking of someone floating up to their knees or something - that's completely the wrong mental image. 16:37, 7 April 2007 (UTC)

Nice pic! Thank you.

The side discussion about CG/CB had to do with Natgoo's statement that "it's impossible to stand up in the Dead Sea (with only your head above the water), as your legs rise to the surface every time you try to put them below you." If you were in a fluid so dense that the volume displaced by just your shins and feet were sufficient to support you, you could try to stand, but it would be very difficult -- you would have to (as Natgoo also suggested) try to "keep your body ramrod straight". It's not that your legs would tend to fly up due to higher buoyancy or anything, it's just that your body would tend to fall down. —Steve Summit (talk) 18:36, 7 April 2007 (UTC)

shit

What is the chemical formula of human shit(faeces)? Invisiblebug590 10:26, 6 April 2007 (UTC)

What is the chemical formula of the human diet? What comes out is just as complex and varied a combination of things. There is no single chemical formula. alteripse 10:48, 6 April 2007 (UTC)

The color is mostly due to bilirubin and biliverdin. Cellulose is a major component, depending on your diet (much healthy plants with low nutritional value). Some mucus also, so it doesn't go 'clank, clank' when dropped. 84.160.225.164 11:01, 6 April 2007 (UTC)

Chemical formulae are for describing chemical compounds, but faeces is a mixture of different substances. Hence there is no singular formula. - SpLoT // 14:49, 6 April 2007 (UTC)

There's gases, dead intestinal cells, dead bacteria, digested organic matter, nondigested matter, and other mentioned things. bibliomaniac15 20:37, 7 April 2007 (UTC)

Electron Microscopes

Can anyone explain in terms of Higher Tier GCSE level how an electron microscope works, surely you would end up seeing the atoms in the lens and not the object/atom you want? —The preceding unsigned comment was added by 84.13.132.232 (talk) 11:51, 6 April 2007 (UTC).

All "seeing" works by bouncing a smaller particle off of a bigger particle — I see a stapler on my desk because tiny photons are reflecting off of it and hitting my eye. The problem is that when you want to see very small things, the size of a photon of visible light becomes relevant — blue light has a resolution of 400 nm which is pretty small but when we are talking about things like the size of an E. coli bacteria (1 nm µm across or so) that ends up not being enough to really see very much. So instead of using photons, an electron microscope uses electrons as the particle that is bounced off of the object; electrons can have much smaller wavelengths depending on how fast you shoot them (de Broglie's formula relates a particle's wavelength to its velocity), and thus can make out objects that are much finer. As for seeing individual atoms, you can do it, if you set the wavelength of the electrons to be small enough (.1 nm or so). But in any case what's important is that you can adjust the resolution by varying the velocity of the electrons. That's my understanding of it, anyway. --24.147.86.187 12:06, 6 April 2007 (UTC)

It might be useful to compare an electron microscope with the computer monitor you are viewing now. It doesn't ever really show an object, like a sphere, but rather shows a series of 2D dots which approximate the object. Our brains fill in the missing data (usually, but not always, correctly). Our brains are actually quite good at filling in missing visual info, as the signal that comes in from the retina is much worse than you would think. In addition to the blind spot in each eye, there are also numerous locations where you looked at the Sun or a flash bulb where damage was done. Yet our brains fill in those spots with whatever's around them without us noticing. Normally this is good, but it's sometimes bad, as when a hidden car is in the blind spot. StuRat 13:02, 6 April 2007 (UTC)

No bacterium is just a nanometer across; E. coli is about a half-micron across. 1 E-9 m says that DNA is already 2 nanometers across. But optical microscopes still have problems because the wavelength of visible light is not much smaller than the target, creating all sorts of image-distorting wave behavior. --Tardis 16:03, 6 April 2007 (UTC)

My bad — I misread the Greek script on the image. --140.247.251.165 16:20, 6 April 2007 (UTC)

The answer to your question depends on the type of electron microscope that you're talking about. The type that most closely mirrors a conventional optical microscope is a transmission electron microscope, which passes a beam of electrons through a sample and forms an image out of the electrons which reach the other side. In such a microscope, there are no physical lenses of the type that you would find in an optical microscope; as you've intuited, the electron beam would hit the glass and be absorbed or scattered, leaving nothing with which to form an image of the sample. Instead, the beam of electrons in an electron microscope is focused, bent, and manipulated using electric and magnetic fields. Carefully shaped electromagnetic fields can have the same types of effects on an electron beam as cut and polished glass does on a beam of light—and electromagnetic fields propagate perfectly well inside the vacuum of an electron microscope. (Our article on electron optics, unfortunately, is still a stub—experts in the field are invited and encouraged to flesh it out.) TenOfAllTrades(talk) 14:39, 6 April 2007 (UTC)

Static Electricity

Sometimes, when you go to bed at night and you move your feet around quickly against the sheets, you see an interesting effect. What is happening? --Mayfare 12:33, 6 April 2007 (UTC)

You seem to know the answer already, you're seeing a static electricity discharge between your feet and the sheets. I've noticed this happens when the sheets are just out of the dryer, and hence full of static charge. StuRat 13:05, 6 April 2007 (UTC)

The charge may come from yourself, as you walk on cheap carpet, you may build a charge which you discharge getting into bed. Also, some blankets and some sheets can collect charge as Stu suggested DDB 14:12, 6 April 2007 (UTC)

Thanks for your responses. --Mayfare 17:36, 6 April 2007 (UTC)

graphing forces

forces can be indicated on a graph paper by the use of? —Preceding unsigned comment added by Deasedanielle (talk • contribs) 14:49, 6 April 2007

Floating vectors ? StuRat 00:57, 7 April 2007 (UTC)

A pencil?--Shantavira 08:01, 7 April 2007 (UTC)

Disciplined mental effort, coupled with sound education and a little luck, given that your teachers really were right. DDB 11:33, 7 April 2007 (UTC)

Geriatrics

Hi, I have a question: would anyone, especially a geriatric doctor or someone who works in an elder care setting be able to provide a comprehensive and high school level list of vocabulary terms that would apply to general elder care and the problems associated with it. I have a few terms like reluctant patient and I know the basics but a good advanced list would really help my score. Thanks in advance! --Uchihah 15:01, 6 April 2007 (UTC) Uchihah

Sponge bath? :P Vitriol 16:14, 6 April 2007 (UTC)

Try asking a Personal Support Worker and/or a geriatric doctor. --Mayfare 17:38, 6 April 2007 (UTC)

a topic related to taxonomy of angiosperm

please give me details about a topic related to taxonomic tools that is, COMPUTERS AND GIS (Geogrophical information system)59.94.115.227 16:00, 6 April 2007 (UTC)

Belly button problem

In the human or other mammals, where does the umbiliacal cord connect to inside the baby before birth. And how is this pathway shut off after birth? —The preceding unsigned comment was added by 88.110.208.218 (talk)

See the articles about the umbilical vein and umbilical artery. DMacks 19:26, 6 April 2007 (UTC)

So in other words you mean:

Inside the fetus, the vein courses alongside the falciform ligament and then to the liver's underside. At the transverse fissure, the vein divides into two vessels, one larger than the other. The larger of the two is joined by the portal vein, and together they enter the right lobe of the liver. The smaller vessel, now called the ductus venosus, diverges away from the liver and joins with the inferior vena cava. Whatever that means!

Why didnt you say so? —The preceding unsigned comment was added by 88.110.128.130 (talk) 23:33, 6 April 2007 (UTC).

Because DMacks assumed you could read on your own. Which, apparently, you can. − Twas Now ( talk • contribs • e-mail ) 04:40, 7 April 2007 (UTC)

Composition

What is the composition of the isotope C-12? —The preceding unsigned comment was added by 76.64.52.108 (talk) 18:59, 6 April 2007 (UTC).

Carbon, specifically the isotope with 6 neutrons. DMacks 19:09, 6 April 2007 (UTC)

And 6 protons Czmtzc 19:21, 6 April 2007 (UTC)

And 12 electrons. − Twas Now ( talk • contribs • e-mail ) 04:39, 7 April 2007 (UTC)

Six electrons, not twelve. But in addition to the six protons and six neutrons, there are bunch of thingees in the nucleus that hold it together. These are the virtual particles that embody the nuclear strong force. Of course, this force may be a mere artifact of deeper interaction amongst the quarks and gluons the comprise the protons and neutrons. -Arch dude 05:12, 7 April 2007 (UTC)

Oh damnit, what was I thinking? There goes my university degree in biochemistry… − Twas Now ( talk • contribs • e-mail ) 09:09, 7 April 2007 (UTC)

relative atomic mass

Explain why the relative atomic mass of carbon, referenced on the periodic table, is not exactly 12? —The preceding unsigned comment was added by 76.64.52.108 (talk) 19:01, 6 April 2007 (UTC).

Explain why we should do your homework for you. Please at least try to use this bazillion-page encyclopedia to look up answers for yourself and then ask about what's confusing. DMacks 19:10, 6 April 2007 (UTC)

It is not homework. Don Mustafa

The atomic mass of an element is the average mass of all of the isotopes for that element weighted by the relative abundance of each isotope. --Czmtzc 19:17, 6 April 2007 (UTC)

Ironically, the mass of carbon 12 is exactly 12 amu, since the definition of atomic mass unit is one-twelfth of a carbon-12 nucleus. Now that I think about it, I'm not sure if it's the nucleus or the whole atom with electrons too, but that should be reasonably negligible, less than one percent. The original question, though, is referencing isotopes. Nimur 20:15, 6 April 2007 (UTC)

Made-up example: if I have 50% Cl-34 and 50% Cl-35, the average atomic mass of the chlorine atoms I have would be 34.5 --Bowlhover 05:36, 8 April 2007 (UTC)

mass of fractions

Why would you want to avoid calculating the mass of fraction of an atom? —The preceding unsigned comment was added by 76.64.52.108 (talk)

Why would you want to avoid doing your own homework? --LarryMac 19:49, 6 April 2007 (UTC)

It is not homework --Don Mustafa

—The preceding unsigned comment was added by 76.64.133.10 (talk) 13:36, 7 April 2007 (UTC).

I would guess because it probably isn't much use to you—most of the atom is empty space anyway, and all but the nucleus is ignored. So you would be finding the mass of part of the nucleus, and that would be unnecessary since you already known the masses of the nucleons. [Mαc Δαvιs] (How's my driving?) ❖ 23:20, 6 April 2007 (UTC)

But the mass of the atom is less than the mass of the nucleons, because of the energy needed to bind them together. —The preceding unsigned comment was added by 68.117.135.99 (talk) 04:58, 7 April 2007 (UTC).

Binding energy increases the mass of the atom, does it not? --Bowlhover 04:39, 8 April 2007 (UTC)

Some people spend huge energies on finding a prime number larger than the largest known one, or the 10 zillionth number in the decimal expansion of π. These aren't of much practical use either, but they're justified on scientific grounds. JackofOz 06:25, 8 April 2007 (UTC)

Normalized Mean Square Error

I am instructed, without further context, to calculate a normalized mean squared error for one of my data processing projects.

I am struggling to decide which is a better "normalization":

$error={\frac {1}{N}}\sum _{i=1}^{N}(x_{i}-x_{exact})^{2}$

or

$error={\frac {1}{N}}\sum _{i=1}^{N}({\frac {x_{i}-x_{exact}}{x_{exact}}})^{2}$

I will be comparing several different fast methods for calculating the $x_{i}$. I know the $x_{exact}$ and want to obtain relative errors for each method, to determine which is "optimal." Which normalization technique will result in a more straightforward comparison between different values? Any other suggestions? Any suggestions? Nimur 20:25, 6 April 2007 (UTC)

The two values will differ by a constant factor of ${x_{exact}}^{2}$. In a sense, it's really just a unit conversion issue: for example, if $x$ is measured in meters, then the former value will be units of meters², while the latter will be in units of ${x_{exact}}^{2}$. It would seem to me that, if the instructions explicitly call for a normalized value, then what they mean is probably the latter; if they meant the former, they would just say "mean squared error" without any additional qualifiers. —Ilmari Karonen (talk) 01:13, 8 April 2007 (UTC)

Heat transfer in space

If i was to be closer to the sun in space and I was to be standing in the shadow the temperture would be cold and if I was to step out in the sunlight I would burn, on earth the shadow would still be warm but in space does the heat travel into shadow AT ALL? Wuld there be a definitive line of hold and cold? —The preceding unsigned comment was added by 86.136.246.197 (talk) 23:25, 6 April 2007 (UTC).

There is a much more dramatic difference between shadow and light when close to the Sun in a place without an atmosphere, yes. With no atmosphere to transport the heat to you from the bright areas, the only heating would be from the blocking object, which would eventually warm up and radiate heat onto you (although still less than you would get from direct sunlight). Also, space around the Sun isn't quite empty, and particles might still strike you on the far side of the object, if you are in turbulent currents of the solar wind, for example. StuRat 00:49, 7 April 2007 (UTC)

Heat is transferred by: Radiation, Conduction or Convection. Without air or water or some other fluid, there is no convection - so we're left with radiation and conduction. No air means less conduction of heat into the air. If you imagine a big rock on (say) Mercury - then how does heat get from the sunlit areas to the shadows? Well, bright light reflecting off the surrounding landscape will slightly illuminate the shadows - so some radiation does make it into the shadow, not as much as on earth because we aren't getting any light scattered from the atmosphere. But unless we're looking really deep under the rock or in a cave or something we're getting some radiation from the brightly lit surroundings. Then there is conduction - so some heat from the sunlit side of the rock will be conducted through the rock and will warm the shadowed side. But rock doesn't conduct heat all that well - so heat is coming in there rather slowly. However, temperature is also determined by energy loss - so our rock will lose heat as well as gain it - no air means that the shadowed side of the rock isn't losing as much heat as it would on earth because heat isn't being conducted/convected away by the air. It's a complicated question - but undoubtedly it's going to be a heck of a lot colder in shadows and a heck of a lot hotter in sunlight when there is no atmosphere. SteveBaker 16:29, 7 April 2007 (UTC)

Proof of global warming

Does this not underline (get it?) today's events?

71.100.6.150 23:34, 6 April 2007 (UTC)

OK those are your underpants, now what about the females?

What makes you so sure I can't darn well pack a bra? Be 'shamed your self young feller! 71.100.6.150 00:18, 7 April 2007 (UTC)

I like how it goes from 18th century (1700s) to 1900. Skipped the whole 19th century there! --24.147.86.187 00:20, 7 April 2007 (UTC)

Yep, them peoples back then were a lot closer to the Victorian age and wearing less bulky clothes did not occur to them somehow to be the right solution. That's were the saying "... just don't seem right somehow..." comes from. 71.100.6.150 00:33, 7 April 2007 (UTC)

So the moral is "don't get your panties all in a bunch over global warming" ? StuRat 00:42, 7 April 2007 (UTC)

Don't quote me but its probably more like "Take you panties off over global warming." 71.100.6.150 00:48, 7 April 2007 (UTC)

Yeah will we all be wearing no panties at all in a few years if global warming continues?

Yes. It will be the garment industry versus global warming. 71.100.6.150 01:10, 7 April 2007 (UTC)

See also: Microkini], post hoc ergo propter hoc. [Mαc Δαvιs] (How's my driving?) ❖ 01:31, 7 April 2007 (UTC)

A Google image search on Microkini, reveals that more than one women has found that a reduction in clothing size can provide relief from heat caused during Ovulation by basal body temperature which can be exaggerated by Global warming. Nebraska bob 03:52, 7 April 2007 (UTC)

Greenhouse Gases

I am interested in the partition of greenhouse gas emissions by sectors, and the only reference I found within Wikipedia is this diagram:

Are the numbers in this diagram totally agreed upon? Or is there much variance between different sources? Does the emission from vehicles account really to only 14% of the total emission? Gidip 23:57, 6 April 2007 (UTC)

I don't know, but I know it does not seem almost anything is totally agreed upon regarding things having to do with the anthropogenic global warming hypothesis. Sometimes they can get more precision than order of magnitude estimates for global carbon producers and reservoirs, and I would not be surprised if that chart was based on only the US. [Mαc Δαvιs] (How's my driving?) ❖ 01:26, 7 April 2007 (UTC)

Thanks Gidip 01:19, 8 April 2007 (UTC)

April 7

Primordial soup

I was reading through abiogenesis in my biology textbook and Wikipedia, but couldn't find any specific details on it. Are there any findings that substantiate such an environment? bibliomaniac15 01:06, 7 April 2007 (UTC)

The existence of life on Earth substantiates the concept that, at some point in the past, there must have been a specific set of conditions in which early lifeforms could spontaneously arise and evolve. − Twas Now ( talk • contribs • e-mail ) 04:34, 7 April 2007 (UTC)

Panspermia contests this, but there have been attempts to reproduce abiogensis directly. -Arch dude 04:56, 7 April 2007 (UTC)

However, if terrestrial life originated from an extraterrestrial source, there must have been a specific set of conditions in which early lifeforms could spontaneously arise and evolve. − Twas Now ( talk • contribs • e-mail ) 09:08, 7 April 2007 (UTC)

There have been experiments that take the kinds of non-biological things that would have been around in the early earth - added sparks to simulate lightning - and those experiments have produced basic amino acids - and those amino acids do spontaneously form short chains and such. The question for abiogenesis is whether it is possible - by pure chance - that such a chain could form something that could replicate itself - perhaps an RNA molecule. That's all it takes - once you have thet, the well-understood processes of evolution gets us from there to animals and plants. So the problem is: What is the probability of something like a short RNA strand forming spontaneously? Bear in mind that this could have happened at any time over millions of years in any of the quadrillions of gallons of water in the oceans and in any of the molecules in each gallon of that water. The number of opportunities for that to occur are truly astronomical - and it only had to happen ONCE in the entire history of the earth. The event could be spectacularly rare. Indeed, it must be fairly rare because we don't see new RNA-like molecules forming all the time in modern earth. That being the case, it is not possible that a laboratory experiment could reproduce this event - you might well need an entire planet full of soupy amino-acid-laden water and to cook it for a hundred million years in order to make this happen. We can only deduce that it did indeed happen...once. There is some evidence that it may in fact have been so spectacularly rare that it did only happen once - if it had happened lots of times then I suspect we'd see multiple kinds of DNA in modern organisms that showed absolutely no common amino acid sequences whatever...we don't see that - so I strongly suspect that this was one single astronomically unlikely event. SteveBaker 16:10, 7 April 2007 (UTC)

The only thing is, what evidence do we have for such a soup? If such a concoction existed, why don't we find a nitrogen-rich layer of earth? Where in all the strata we have unearthed have we found remnants of such a world? Saying that because we are here, there has to have been spontaneous generation of living beings is a rather biased view. And how would only one single strand of RNA suffice to create what we have today, even if it overcame the odds? Infinite Monkey Theorem, it seems. bibliomaniac15 20:32, 7 April 2007 (UTC)

We have experiments that show that an amino acid 'soup' will arise when the mixture of gasses and water that we believe would have existed in pre-biotic times is stimulated with UV light and an occasional spark of electricity - the sun and lightning storms respectively. This shows that unless there is no reason whatever why the oceans of early earth would not have had the necessary ingredients for the spontaneous formation or an RNA molecule at some time in the past. Once the one single molecule existed, it would replicate until the oceans had a LOT of these peculiar molecules floating around in them. Once that happens, the molecules are competing for resources (the free floating amino acids for example) and they are mutating (because RNA copying errors would be relatively frequent - and survival of the fittest would also be there - so evolution kicks in and the rest is really well known. Why don't we find a "nitrogen rich layer"? Well, because the land surface is a mess of shifting tectonic plates that slide over and under each other. Whenever a plate goes under, it gets melted back into magma and mixed up...since the events we are talking about are so very old, not one scrap of the earths surface from those ancient times still exists for us to examine. No firm records of that era can possible have survived. We can only do experiments, calculate probabilities and produce believable mechanisms. This is less than satisfying as solid proof goes - but it's the only explanation we have that doesn't rely on supernatural intervention - which we generally rule out using Occams Razor. If there were a competing theory (which didn't require magic or whatever) then there would be a lot of interesting debate about it - but there really isn't. The Panspermia hypothesis is (in a way) a competing theory - but even if life arrived on earth on a meteorite or something, it still had to start SOMEWHERE - and we're back to needing an abiogenesis mechanism to make that work. SteveBaker 07:16, 8 April 2007 (UTC)

Direct evidence? The answer is basically no. Very, very few rocks survive for over 3 billion years, and those are so heavily metamorphosed that no complex organics would be expected to survive. However, we can make a variety of arguments about the simple ingredients of that world. We know for example that it had low oxygen and very high carbon dioxide (e.g. 1000 times modern). We know there would have been much greater volcanic activity (providing a potentially interesting energy source). We know liquid water was abundant (just as is it today). Various simple organic precursors (e.g. methane, ammonium, hydrogen) would have been created naturally in that environment. Work like the Miller-Urey experiment has shown that the synthesis of complex organic molecules and polypeptide chains is plausible (at least in small concentrations) from these raw ingredients. With neither oxygen nor microbes to break them down, some of those organics should have persisted in the environment for a long time and this gives rise to the classical idea of an organic "soup". Given the existence of complex life today, many scientists are willing to make the leap that somehow the accumulation of such organics eventually gave rise to cellular life, but we have very little evidence to show how this occured. Some parts are fairly easily. For example, lipids are easy to make and will spontaneously roll themselves into balls, effectively enclosing cell like spaces. RNA (once generated) can both act as genetic material and catalyze reactions, in a way similar to how proteins function today, though proteins are more efficient. In the presense of sufficient nuclei acids, RNA can also easily duplicate itself. This has led to speculation that an "RNA world" might have existed in the early development of life. Dragons flight 21:08, 7 April 2007 (UTC)

There weren't microbes or oxygen to break them down, but keep in mind that there was no ozone layer to protect such substances from the UV rays of the sun. The Miller/Urey experiment is interesting, but a) only two percent of the resulting sludge was amino acids, b) only 2 amino acids were actually created, c) these compounds reacted with the other chemicals created, and d) they used a carefully controlled apparatus to create these compounds. As for "RNA world," the chances that one RNA molecule spontaneously generates is big enough, what are the chances that there are two identical ones? bibliomaniac15 01:29, 8 April 2007 (UTC)

I agree that the classic Miller/Urey experiment left something to be desired - but we don't know the exact conditions - and other experiments using other starting conditions produced quite different results. So it's peossible for four amino acids to have formed instead of two given a different value for some concentration or a different temperature or whatever...it's not a huge stretch of the imagination at least. You don't need two RNA molecules to exist - a single strand is enough (see RNA virus for some examples of single-stranded RNA)- its complementary strand will form spontaneously from the first half - then they unzip and each half makes another complementary strand to match. That part is OK - there is even some evidence for such simple "organisms" (iffy terminology!) still exist (see Nanobe for example). The really, really unlikely part is that very first strand forming with exactly the right properties to replicate spontaneously with enough precision to make working duplicates over enough generations for evolution to cause it to survive more robustly. But even at low concentrations, given the enormous volume of the earths oceans and the veast time-span during which it could happen - it's really not so very unlikely. Suppose we estimate that there is a mole of reagent in every cubic meter of primordial soup and that 'candidate' reactions happen every millisecond or so...yeah there are lots of reasons why the numbers might be a lot lower than that - but stick with me for a moment.

• The oceans contain 1.37x10¹⁸m³ according to 1 E+18 m³.
• Avagadro's number (the number of molecules in a mole of reagent) is 6x10²³.
• A billion years is 3x10¹⁹ milliseconds.

So there could easily have been 2.4x10⁶⁰(!) attempts at this happening before we got a result. That's an insanely large number! If it only has to happen once - then the odds can be long indeed! Furthermore - since we could have ended up being brought into existance on any planet during the entire life of the universe - the timeframe and volumes of reagents is MUCH more than that. SteveBaker 07:50, 8 April 2007 (UTC)

Monarch Butterflies

Do Monarch butterflies help to cross pollinate flowers and plants? IF they don't, which butterflies do? —The preceding unsigned comment was added by 67.186.153.196 (talk) 01:18, 7 April 2007 (UTC).

Yes, as do pretty much all butterflies ; simply said, if it goes from flower to flower, it carries pollen, if it goes to two flowers of the same species then it helps cross pollination. Pro bug catcher (talk • contribs). 02:19, 7 April 2007 (UTC)

Umbilical cord

A developing fetus is connected to the mother via three blood vessels in the umbilical cord. My question is: whose are they? If you were to take tissue samples from the fetus and do genetic analysis, you'd obviously get fetus DNA. Presumably the placenta is the mother's tissue. But where does the baby start and the mother end? What is the interface like (gradual, discrete, etc.)? Thanks! --TotoBaggins 01:54, 7 April 2007 (UTC)

The umbilical cord develops from the embryonic allantois; it will have the baby's DNA. As you've correctly deduced, the placenta is indeed entirely Mom's. The interface is at the chorion (on the fetal side) which forms chorionic villi that project into the decidua (mother's side); this is interface where nutrients and blood gases are exchanged in the placenta. TenOfAllTrades(talk) 02:56, 7 April 2007 (UTC)

Awesome answer; thanks! --TotoBaggins 03:28, 7 April 2007 (UTC)

No, the placenta is not entirely maternal; in fact, the functional placenta is almost entirely fetal, with a rather minor maternal component. The chorionic villi comprise the majority of the functional placenta. These villi are entirely fetal in origin, which is the rationale behind using chorionic villus sampling to screen the fetal genome. Maternal tissue only plays a role in support (the maternal decidua basalis is the supportive structure to which the fetal placental component attaches) and in placental circulation (the spiral arteries of the maternal endometrium penetrate the developing chorionic villi and bathe the fetal tissue in maternal blood). The interface between fetal and maternal components of the placenta is rather distinct: the decidua basalis (maternal) is separated from the chorionic villi by a cytotrophoblastic shell that is derived from fetal tissue (the trophoblast) and is several cells thick. Also, it is a common misconception that the allantois gives rise to the umbilical cord. True, the allantois begins as an evagination of the gut that extends into the body stalk (the umbilical cord anlage), but the umbilical cord itself is made mostly of extraembryonic mesoderm and Wharton's jelly. The allantois regresses into the embryo to give rise to the urinary bladder and median umbilical ligament. To answer the original question: the blood vessels of the umbilical cord are fetal, as TenOfAllTrades said. --David Iberri (talk) 22:14, 7 April 2007 (UTC)

Dinosaur age

How old could a dinosaur become? —The preceding unsigned comment was added by 62.78.246.132 (talk) 09:07, 7 April 2007 (UTC).

There were many different species of dinosaur, so this question is a little like asking "how old can a mammal become" - it all depends on whether you look at a shrew or a whale (note to experts - yes, I know that mammalia is a class and dinosauria is a superorder, so the analogy is not exact). Dinosaur lifespans probably covered a wide range, with the larger species having longer lifespans, as they would take more time to grow to maturity. This page] gives a range of "tens of years to hundreds of years", and makes some comparisions with the maximum lifespans of modern reptiles in captivity; whereas this page suggests a typical dinosaur lifespan of about 40 to 50 years, based on growth rings found in fossil teeth and bones. Gandalf61 11:12, 7 April 2007 (UTC)

Just to provide some additional info, this page lists the life spans of the huge Apatosaurus, Brachiosaurus, Diplodocus, and Supersaurus as roughly 100 years; smaller dinosaurs die sooner. This page says the life span is 75-300 years, though I doubt 300 years is accurate. --Bowlhover 05:15, 8 April 2007 (UTC)

Turtles can reach a great age. cf Tortoise DDB 11:24, 7 April 2007 (UTC)

And of course it is widely believed that birds evolved from Dinosaurs - some species of parrot can live for 100 years in captivity. SteveBaker 16:00, 7 April 2007 (UTC)

WARTS

DEAR SIR, MY WIFE's DOCTOR HAS DETECTED WARTS ON HER VAGINA AND ANUS FOR WHICH SHE IS UNDER GOING THE TREATMENT. VAGINIAL WARTS AEE ALREADY FINISHED BUT STILL THEY ARE ON HER ANUS. I WOULD LIKE TO KNOW FROM WHERE DOES SHE CAUGHT THIS VIRUS AS I AND MY WIFE NEVER HAD SEX WITH ANYBODY ELSE AS SHE HAD IT ONLY WITH ME AND I ONLY WITH HER AND NOBODY ELSE AND STILL THERE IS A VIRUS. I WOULD LIKE TO SPECIFY THAT WE HAD ANAL, ORAL, AND VAGINIAL SEX.

THANKING YOU GAGAN

It depends on the type of warts. You would be best to seek advice from a medical professional—your family doctor, or at a walk-in clinic if you're too embarrassed. TenOfAllTrades(talk) 12:15, 7 April 2007 (UTC)

For what it's worth, we have an article HPV, the set of viruses that cause warts. Friday (talk) 17:54, 7 April 2007 (UTC)

Noting, of course, that there are other causes of genital warts and wart-like symptoms (some are listed in that article). See your doctor to be sure. TenOfAllTrades(talk) 18:12, 7 April 2007 (UTC)

It is not necessary to have had sex with someone in order to catch a sexually transmitted virus. As everyone says, it is better to ask your doctor or physician why the symptoms are still persisting and if it is normal for this to happen. That will put your mind at rest, as his/her answer will either be 'yes', in which case there is no problem, or 'no', in which case he/she will find another method of treatment. ScouseMouse - スカウサーUK! 23:11, 7 April 2007 (UTC)

Though in my experience most doctors will give you a condescending look, the "you can pretend if you want to but we all know what this means" sort of look. The "I don't actually know anything about you or your life but I'm going to presume that I do because I'm the one with the M.D., and this ain't no television show where doctors actually give a shit about ferreting out statistically unlikely causes." But maybe that's just my experience with doctors, which I admit is fairly infuriating. Statistical medicine works some of the time, but not all of the time, and when it fails it fails miserably. I wish more doctors seemed to care about that. Which is just a long way to say, you can ask your doctor for alternative possibilities, but don't expect them to really offer them up, or think they are necessary. They are going to tell you "they are spread by sex with people who have them" and no matter how much you inquire to the hypothetical that such might not have been the case, they'll just look at you like you're an idiot. --24.147.86.187 01:12, 8 April 2007 (UTC)

Two things occur to me. First, 99% of people "just can't imagine" where they got an STD, so if your doctor acts like she has heard it before and is a bit skeptical as to your amazement, and seems reluctant to engage in unprovable speculation about other alternatives, you shouldn't be surprised. Second, doctors being human beings, they often respond the way your attitude and signals tell them you expect them to respond. alteripse 17:34, 8 April 2007 (UTC)

Packing density

What is the packing density of grains with different regular shapes? E. g. how much air is in a bag of table salt? I'm quite sure that people have made mathematical models for these problems - is there a wikipedia article about the topic that I didn't find? Icek 13:45, 7 April 2007 (UTC)

Try crystal structure and lattice model (physics), for explanations at an atomic scale. For more mathematical explanations, some of which are not quite as applicable to this question, try some of the links listed at lattice. − Twas Now ( talk • contribs • e-mail ) 22:35, 7 April 2007 (UTC)

Interestingly "packing density" is a specific concept in crystallography (that's what I thought when I saw the title of this question), that uses a hard sphere atomic model to estimate how much "free space" exists in various crystal structures. Your example is a little trickier since, in practice, there's no way of knowing the exact size and shape of any grain of salt. Solid NaCl arranges itself into an FCC lattice and will cleave along the major faces, leading to the rectangular prism shape of salt grains, but with the grains oriented in all manner of directions and coming in varying sizes, any model for the free space in a bag of salt would have to be statistical in nature.

That's a long-winded way of saying "I don't really know", but hopefully the crystallography links can give you some useful information. -- mattb @ 2007-04-07T22:42Z

You might start at sphere packing and close-packing. —Steve Summit (talk) 23:59, 7 April 2007 (UTC) (Yes, I know you said "grains" and not "spheres", but it's a start.)

Thank you for the answers, but I already knew about crystal lattices and sphere packing. I hoped someone would know something about statistical models of e. g. a heap of cube-shaped grains. Btw, I measured and weighed a sample of ascorbic acid (grain size roughly 0.1 mm) and arrived at a space filling fraction of 0.56. Icek 17:59, 8 April 2007 (UTC)

Pen Lasers or 'Penned' Lasers

Those pen lasers, are they true "lasers" or are they just fancy, more sophisticated mini-flashlights?--JLdesAlpins 13:52, 7 April 2007 (UTC)

As it states in the article you linked "Most inexpensive laser pointers use a deep red laser diode [...]", so yes, they are actual lasers. --LarryMac 15:00, 7 April 2007 (UTC)

LarryMac, sorry if I don't always take what others write at face value and seek to doublecheck others' statements. This must be a scientific bug in me. One has to always be wary of marketing claims...--JLdesAlpins 15:20, 7 April 2007 (UTC)

See also our article on laser diodes. TenOfAllTrades(talk) 15:02, 7 April 2007 (UTC)

Sorry for hijacking the question, but I've always wondered: why does light from laser pens (...or in fact, lasers in general), reflect in all directions when hitting a boundary, such as a wall? Surely if all the laser's photons are heading in (ideally) exactly the same direction, the laws of reflection should make all the photons reflect through the same angle? Is it because the boundary is not a perfect reflector, and is atomically "bumpy"? Thanks, Icthyos 15:36, 7 April 2007 (UTC)

Yeah - when the laser reflects off almost any surface, the teeny-tiny bumps will scatter the light off in all directions - which is why you can see where the laser is pointing. It's no different from other kinds of light in that regard. The light rays coming from the sun are very nearly parallel when they reach us - if all reflections were 'perfect' - it would be almost impossible for us to see anything! SteveBaker 15:58, 7 April 2007 (UTC)

The beam is coherent, but it has a non-zero cross-section. In fact, it has the cross-section of the laser, more or less. Therefore it is hitting a small area of the wall, not a point on the wall. Unless this small area is an optically flat mirror, different parts of the spot will affect the photons differently. For the same reason, you do not see your reflection in that same wall. -Arch dude 16:08, 7 April 2007 (UTC)

The beam has roughly the cross section of the exit point of the resonant cavity waveguide unless it is further shaped by optics (it often is). -- mattb @ 2007-04-07T22:26Z

And with all the laser pointers I've used in the past, none of them are really that straight. The light all have an angle that you can clearly notice if you shine it far away when it's dark. The circle always increases. So with that imperfection built in, the light should also scatter slightly radially even with a perfect surface. --Wirbelwindヴィルヴェルヴィント (talk) 17:43, 7 April 2007 (UTC)

Perpetual Motion Machine Idea

What is the fatal flaw with the following "pereptual motion machine"? A pendulum with a magnetic bob swings between two attractive magnets that are positioned near the top of each swing. However, the pendulum mechanism is also to attached to a kind of magnetic shield that is thrust between the bob and the attractive magnet towards the peak of its swing, thus cutting off the attractive force and allowing the magnet to fall. —The preceding unsigned comment was added by 76.211.141.7 (talk) 19:04, 7 April 2007 (UTC).Z

Well, one fatal flaw is that your innocent-sounding "some kind of magnetic shield" doesn't actually exist! If you could find a shield for magnetism (or, equivalently, a shield for gravitation) you could make quite a few very interesting devices!

More seriously, even if you did have a magnetic shield, how do you know that it wouldn't have some magnetic properties of its own? If thrusting the magnetic shield into the gap between two magnets also required force, it could (and almost certainly would) end up canceling out the gain you hoped to get from the device. —Steve Summit (talk) 20:17, 7 April 2007 (UTC)

If human intervention is needed, for example to insert the magnetic blocker, then it's not a pertual motion machine. But Steve: the "magnetic blocker" could be another magnet with the same polarity as the bob. --Bowlhover 04:07, 8 April 2007 (UTC)

What about air resistance? This would have to be done in a vacuum, would it not? -Wooty Woot? contribs 04:08, 8 April 2007 (UTC)

No, the idea is to use the magnetic force to overcome air resistance and friction. --Bowlhover 05:03, 8 April 2007 (UTC)

The interesting and important thing about perpetual motion machines is that they quite simply cannot exist because of that boring old first law or thermodynamics. In the end it's a big waste of everyone's time to debumk each and every wild-assed idea for one. The reason it won't work is that the universe won't let it. Precise details of why are unimportant. SteveBaker 07:03, 8 April 2007 (UTC)

Except that the precise details are precisely what we were asked for ... there was no suggestion that the thing ought to work. Steve Summit thought the question was worth answering. If you think it's a waste of time, then I suggest picking a different question to answer. --Anonymous, April 9, 2007, 02:57 (UTC).

I don't think so. It would be really awesome to find one. [Mαc Δαvιs] (How's my driving?) ❖ 02:47, 9 April 2007 (UTC)

Now this is the guy that Steve Baker's comment should be addressed to, not the original poster. --Anonymous, April 9, 2007, 02:57 (UTC).

I thought it was the second law that prevented that from ocurring? Titoxd^{(?!? - cool stuff)} 03:01, 9 April 2007 (UTC)

Point. "First law: you can't win. Second law: you can't break even. Third law: you can't quit the game." As to perpetual motion machines, which one applies depends on whether you're talking about the kind generates energy output or the kind that just keeps running forever. --Anon, April 9, 05:45 (UTC).

Where do birds get their blood cells from?

I was wondering if the bones of birds are hollow, how do they produce red bloodcells and B-cells? Do they have another organ dedicated to this task or can their bones still produce blood cells even though they are hollow?PvT 19:49, 7 April 2007 (UTC)

The bones of birds aren't hollow; they just have a bunch of air pockets in them. There's still enough marrow to generate blood cells. bibliomaniac15 20:33, 7 April 2007 (UTC)

Thanks for the answer PvT 20:38, 7 April 2007 (UTC)

There are other hematopoietic organs involved as well. See also Bursa of Fabricius (the "B" in "B-cell"). --David Iberri (talk) 21:43, 7 April 2007 (UTC)

Voice power

Does being a fat person help in any way to have a powerfull voice? If yes how does it work?Bastard Soap 22:54, 7 April 2007 (UTC)

Well, it would depend on what you mean by 'fat'. Having large, strong lungs, backed up by large, strong stomach muscles would certainly help if you needed a strong voice, but just being clinically overweight would not really help at all. Pavarotti is certainly a large man, but then, so is Forrest Whittaker. ScouseMouse - スカウサーUK! 23:04, 7 April 2007 (UTC)

There is an article in the register about "Why are opera singers fat?" it discusses some of the theories but not in much depth. http://www.theregister.co.uk/2006/06/23/the_odd_body_opera_singers/ —The preceding unsigned comment was added by Sifaka (talk • contribs) 00:25, 8 April 2007 (UTC).

The article about Maria Callas reports on theories relating her voice decline to weight decline.  --Lambiam^Talk 00:43, 8 April 2007 (UTC)

I've never accepted those theories about her. Despite the stereotypical image of opera singers, the vast majority of them are not fat, and don't need to be. A strong voice comes from good voice training, admittedly helped by naturally solid physical attributes, but obesity as a necessity is a myth. I suspect the reason many earlier opera singers were overweight was because they typically commanded much higher salaries than other mortals, and could afford more food. Singing for a whole evening is a very physically strenuous activity, so having a good meal after the performance would be natural, and if this is followed by going more-or-less straight to bed and having little or no exercise other than for the voice, it would tend to produce obesity. JackofOz 06:19, 8 April 2007 (UTC)

gluconeogenesis/glycolysis regulation

PFK-1 regulation: insulin activates PFK-2; increasing F2,6BP formation while also inhibiting FBPase-1 activity. Increased F2,6BP activates PFK-1. My question is does [F2,6BP] inhibit FBPase-1 (directly- not through decreased insulin)?

Not an expert, but I want to help. Fructose 2,6-bisphosphatase doesn't seem to help. Try this I found on pub med. http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=45462&blobtype=pdf The two proteins in question were crystallized together. (they seem to gave good R values) This means it is a direct interaction. They also seem to discuss how the inhibition may work, but I only gave the article a cursory look. Sifaka ^talk 00:23, 8 April 2007 (UTC)

April 8

Understanding the Feline Way of Picking Food

I have three cats. Every day, I keep for them two bowls of dry food. I noticed that the food level in the two bowls, during the day, is decreasing at a similar rate. When I spy on them, it seems that they are purposedly picking food from the one bowl which has more food at that time. Why could that be? Why not finishing one bowl then attacking the other?--JLdesAlpins 00:39, 8 April 2007 (UTC)

In nature they need to protect their food or it could be stolen. Given the choice of two food morsels to protect, it would make sense to protect the biggest one, so perhaps that instinct is still with domestic cats. StuRat 01:38, 8 April 2007 (UTC)

I don't know about your cats, but mine will start to complain if I feed him the same brand of food more than once or twice in a row. Maybe yours just like some variety, too. —Ilmari Karonen (talk) 02:20, 8 April 2007 (UTC)

Alternatively, if the bowls both contain the same food, maybe they find it easier to eat from the larger pile. After all, they have no hands, and the feline mouth, while capable of it, isn't really adapted to fishing bits of dry kibble from the bottom of a bowl. Or maybe they just instinctively pick the pile that looks more appetizing, which might well be, in the absence of any other differences, the larger one. I doubt cats have the capability for the kind of abstract rationalization that would allow them to convince themselves that the piles really are homogenous and of identical consistency, even if one of them looks intuitively like a better meal than the other. And even if they did, why would they care — it's not like any other eating strategy is actually any better than the one they're actually using. —Ilmari Karonen (talk) 02:30, 8 April 2007 (UTC)

In most public restrooms, there are two rolls of toilet paper, so that if one runs out before an attendant can replace it, a hapless stall user will not be left high and dry (or something).

In many such restrooms, the second roll is concealed in a dispensing device and does not drop down until the first roll is consumed. In some restrooms, however, both rolls are equally accessible (i.e. on two simple dispensers, without any fancy, expensive cascade mechanisms).

When both rolls are equally accessible, you will notice that they are used up at a nearly equivalent rate, such that they run out at almost exactly the same time, thus negating most of the utility of the scheme.

I submit that the reason for this phenomenon is the same as for the two bowls of cat food. —Steve Summit (talk) 02:36, 8 April 2007 (UTC)

Another less likely possibility is that they can't find the food in a bowl that's almost empty. I don't believe cats have color vision, which makes it hard for them to find certain items that are the same shade as the background. I've been amazed at my cat's inability to find certain foods on the floor. It sniffs around the area, but can't seem to locate food that I can see as plainly as daylight. StuRat 04:12, 8 April 2007 (UTC)

Instead of believing, you could look it up. For example, here: www.straightdope.com/classics/a2_004.html Or even here. Cats do have color vision; it just isn't as good as ours. (So, yeah, they may have trouble picking out small objects by sight sometimes.) --Anon, April 4, 2007, 05:44 (UTC).

As I have read from a book of a Sahara explorer, some snail-eating foxes have the habit of picking only a few snails from a bush (so they can reproduce until the next meal) and traveling miles to visit other bushes. If they had eaten all the snails from a given bush, the snail population would have died out (and a little later, the foxes too because of starvation). Maybe there is some reason in the case of the cats too. In their natural habitat they eat live food, so they must spare some of it. --V. Szabolcs 12:06, 8 April 2007 (UTC)

Information entropy of the universe

What is the total quantity of information entropy in the universe? Is it increasing or decreasing? NeonMerlin 02:05, 8 April 2007 (UTC)

see Entropy#Entropy and cosmology. Jon513 13:55, 8 April 2007 (UTC)

Total Entropy is constantly increasing. Entropy is a measure of disorder - chaos - whatever. The tendancy for entropy to increase is very evident in daily life - things break - things that once worked stop working - tidy things get untidy. It's very rare for disorderly things to spontaneously get organised. It takes work - energy - to make something more organised than it was. Extracting energy disorganises things - so creating a little pocket of better organisation causes more disorder elsewhere...so whilst you can locally reverse the flow of entropy - on a global scale, it increases continually. SteveBaker 17:47, 8 April 2007 (UTC)

microbiology

why are eukaryote diseases more difficult to treat than prokaryote diseases? —The preceding unsigned comment was added by 4.152.24.220 (talk) 03:05, 8 April 2007 (UTC).

Many diseases, including infectious ones that you are asking about, rely on drugs exploiting the differences between human cells and cells of infectious organisms. For example, one of the first antibiotics, penicillin, worked well and was well tolerated because it inhibits the synthesis of bacterial cell walls, which human cells lack. In general, because humans are eukaryotic, there are fewer differences between humans and other eukaryotic organisms than there are between humans and prokaryotic organisms. The more differences between host and infectious organism, the easier to treat. I'm sure there are other good reasons, but this is a major one. --David Iberri (talk) 04:28, 8 April 2007 (UTC)

Evangelical christians with dilated eyes

I was just watching the movie Jesus Camp, and noticed something a bit strange. Many of the children (and some of the adults) have extremely dilated pupils, like they were on MDMA or something like that. One of my friends recently became a born again christian, and I noticed the same thing happening to him... huge dilated pupils. When people feel this way, I'm thinking it must be the body releasing endorphins that make them feel that way, which allows them to feel like jesus is inside of them, and that leads to the dilated pupils. Has anyone else noticed this, or have any thoughts on it? 67.142.130.20 03:12, 8 April 2007 (UTC) Anonymous

Its caused by the Jesus juice. Seriously, pupil dilation is a autonomic response and therefore if one could imagine that is there is such a thing as the Holy Spirit then it is not a huge leap of "faith" to imagine it could influence the release of neurotransmitters during spiritual possession. Of course, it could simply be a type of mass hysteria and resulting physiological effect. Alternatively they could be whacked out of their mind on alcohol or be brain dead. Rockpocket 05:47, 8 April 2007 (UTC)

Yellow moon?

As I was walking back home last night/this morning (~6:30 UTC), I noticed that the moon was yellow-orange. The lunar eclipse happened weeks ago, so what else could account for this?

Thanks. 137.99.165.83 06:08, 8 April 2007 (UTC)

When the moon is at a lower angle in the sky, its light has to pass through more atmosphere, which scatters the higher wavelength light (like the sun at sunset). Pollution makes this worse (more crap in the air to scatter light), and can be so bad that the moon appears oddly coloured even when at a pretty high angle. -- Consumed Crustacean (talk) 06:28, 8 April 2007 (UTC)

Human carry electric

A man carry electric which could be felt when we touch him like we feel mild electric shock. What is cause ? —The preceding unsigned comment was added by 89.148.17.212 (talk) 06:33, 8 April 2007 (UTC).

One way to generate that charge is by rubbing socks on some carpets, due to the triboelectric effect. Another way for a charge to build up is if a person maintains insulated above ground, such as riding in a car for a length of time. Then the person will get out and it'll discharge when he or she touches something like the car frame. I also get it wearing my dockers shoes and walk around in one specific store, and I have never figured out why. --Wirbelwindヴィルヴェルヴィント (talk) 07:11, 8 April 2007 (UTC)

The soles of your shoes and the carpet material in the store are widely spaced on the triboelectric series? —The preceding unsigned comment was added by 88.110.155.118 (talk) 18:50, 8 April 2007 (UTC).

Magic mushrooms - effect on non-humans

Does anyone know if magic mushrooms have a psychedelic effect on living creatures other than humans? On a more general note - do animals and birds ever actively seek out and consume naturally occurring psychedelic substances? --Kurt Shaped Box 07:34, 8 April 2007 (UTC)

According to Animals and Psychedelics: The Natural World and the Instinct to Alter Consciousness, Giorgio Samorini, Park Street Press, (ISBN 0892819863), literally hundreds of animals seek out hallucinogenic substances (and plenty more get wasted by accident, ruffied by Mother Nature, or by nasty men in white coats). A few examples: a type of ant will suck a hallucinogen from the abdomen of a lomechusa beetle. Male mandrills will get high on the root of a iboga root then hang around until the are tripping nicely before before fighting it out without another male over territory. Of course, in addition to experimenting on themselves those crazy scientists in the 60s tried out lots of drugs on animals. It appears elephants and LSD don't mix too well [11], but cats get a groove on (note: if you are of a sensitive nature, don't click here) and dogs that ingest magic mushrooms "frequently snap at invisible flies, may be extremely depressed, stagger when walking and become comatose." [12] Not unlike a trip I once had. Rockpocket 09:09, 8 April 2007 (UTC)

A friend of mine had a cat who ate some of his mushrooms. This was a few years ago, but the cat was acting strangely, with a wobbly walk. − Twas Now ( talk • contribs • e-mail ) 15:17, 8 April 2007 (UTC)

A friend of mine had left some LSD tabs lying around and his cockatiel chewed some of it. The poor thing spent the rest of the day wandering in circles on the floor, occasionally fluttering a couple of feet into the air and squawking and spending a long time staring intently into the middle distance. He couldn't get near the bird to put it back in its cage - it absolutely freaked when he approached it. --Kurt Shaped Box 19:06, 8 April 2007 (UTC)

What a sad waste of acid [Mαc Δαvιs] (How's my driving?) ❖ 02:45, 9 April 2007 (UTC)

Does it help to be fat to play the tuba?

(following on from the question above) This may just be a TV/movie/cartoon stereotype but generally, whenever I see guys playing the tuba on TV, more often than not, they are the fattest guys in the orchestra. So, is there any real advantage to being fat when playing this instrument? --Kurt Shaped Box 07:44, 8 April 2007 (UTC)

You can lay it on your stomach? PitchBlack 07:58, 8 April 2007 (UTC)

I think it's just for the comedic effect. Tuba is often used in "funny" songs and a fat guy playing it makes it look even more ridiculous. Even if it's not a comedy in question, fat guy + tuba may have become such a strong stereotype that directors use it anyhow. --Nitku 17:24, 8 April 2007 (UTC)

That's the great unmade Jackass skit, isn't it? Johnny Knoxville hiding in some bushes and going 'Ooompah! Ooompah!' on a tuba whenever a fat guy walks past, in time with his steps, until someone punches him... ;) --Kurt Shaped Box 22:46, 8 April 2007 (UTC)

The first page of a Google Image Search for "tuba player" does not support a hypothesis that they are fatter than average. --TotoBaggins 17:34, 8 April 2007 (UTC)

Brainiac:_Science_Abuse had a section in one of their series to see if a obese or a underweight person would survive longest in given situations (heat, cold, wind, water, etc). I'd love to have seen which was best at surviving a tuba audition, although i suppose it would come more down to talent :p 80.229.228.229 19:36, 8 April 2007 (UTC)

It would be interesting to find out if the 'fat tuba guy' idea has become so universally accepted that they'd choose a fat guy over an equally skilled skinny guy at a tuba audition just 'because'... --Kurt Shaped Box 22:42, 8 April 2007 (UTC)

I played tuba when I was in high school (a few years ago). I don't believe we were more overweight than any other representative sample of the band (although we did have one HUGE kid). Actually, we tended to be a little more in shape in marching band (or so I like to think) since we had to lug that thing around. I suppose being LARGER (not necessarily fatter) could facilitate carrying it. It is possible that fatter kids may better play the tuba than other brass instruments due to the size of the mouthpiece; I had trouble playing anything with a mouthpiece smaller than a trombone/baritone mouthpiece, and I didn't even have a fat face. :) --Bennybp 21:01, 8 April 2007 (UTC)

Anecdotal, but one of the finest tuba players I know is a rather short ~90 lb woman. -- mattb @ 2007-04-08T22:50Z

I concur with Bennybp's assessment that it probably helps to be larger/stronger as far as transport goes, particularly when marching with a sousaphone. That's not to say that mattb's 90 lb. female tuba player couldn't carry a sousaphone, but on average you'd expect it'd be easier for someone with a large base and a few extra pounds of muscle and/or fat to not be overwhelmed by the 25+ pounds of instrument on their shoulder. As far as actual playing goes, I don't know enough about anatomy to say whether lung capacity has any real correlation to body size. I suspect not (at least as far as fat goes), but does anyone care to comment on that? Eric (EWS23) 12:35, 9 April 2007 (UTC)

I haven't seen it on TV, but at every high school and middle school band concert I've seen it's always the fat kids on the baritone and tuba. [Mαc Δαvιs] (How's my driving?) ❖ 02:43, 9 April 2007 (UTC)

Extinction

I saw the original 60's film "Planet of the Apes" tonight on TV, and got me thinking about extinction. And I thought:

1) Is there a reason why we should preserve species and not just let them die out?

2) Would it be possible to get DNA from living species now, and be able to create living copies of it in the future, incase they ever became extinct? (WHEN they become extinct)

If number 2 is possible, there should be a place/laboratory/museum where they have multiple DNA's from each species they were ever able to get DNA from (that is, if they haven't already). Any views for or against this idea? PitchBlack 07:57, 8 April 2007 (UTC)

1) That is a matter of opinion. Many people consider there to be an inherent value in biodiversity, others don't. However, ecosystems tend to be pretty finely balanced. So there remains the possibility that if we permit a certain species to die, its absence from the ecosystem could cause a chain reaction which could severely effect us humans. See, for example, the concern over the mysterious disappearing bees in the USA. [13]

Note: also see here: Colony Collapse Disorder. zafiroblue05 | Talk 00:27, 9 April 2007 (UTC)

2) We could try to clone some animal species by nuclear transfer, but would need a host egg and a mother in which to gestate the embryo. See here and here for info about current attempts at this and the problems they face. The Svalbard Global Seed Vault is being built at the moment to house seeds in case of a doomsday scenario and a similar Frozen Ark project has been launched in the UK for endangered animals. Rockpocket 09:30, 8 April 2007 (UTC)

You also need to take into account probably technical difficulties, consider the pandas, there aren't any physical barriers but it still is very hard to make them get it on.Bastard Soap 10:48, 8 April 2007 (UTC)

1) I can think of a number of reasons to keep non-competitive species around. For example, if a plant provides some sort of medicinal value, keeping it around might be very advantageous. However, realizing that a species is non-competitive pretty much means that it can never survive naturally.

2) We already pin hopes on this with the collection of cord blood. --Tbeatty 11:02, 8 April 2007 (UTC)

I don't think there is any reason to conserve organisms to keep them alive if they deserve to die and can't adapt, unless of course we need it. How much "reason" there is in the world is a matter of philosophy. [Mαc Δαvιs] (How's my driving?) ❖ 02:41, 9 April 2007 (UTC)

The problem with that, of course, is that when we realise that infact we did need a particular extinct species it will be too late. Rockpocket 04:16, 9 April 2007 (UTC)

If we didn't want to change nature we'd let whatever was set to die out, die out. [Mαc Δαvιs] (How's my driving?) ❖ 14:36, 9 April 2007 (UTC)

Emotional Crying

Why do we produce tears when we're in a strong state of emotion? (sadness, happiness, anger) I looked at the article on "tears" but all I see is that it's because of a "different chemical makeup" but it doesn't actually explain how or why it happens.

Like when our eyes get too dry, our brain notices and does doody-dah-bahbooloo and releases tears to lubricate them. So, when we're emotional, how is our brain reacting, and why does it ultimately react by making us tear?

Another question I think of when thinking of this is how can people focus and force themselves to cry? I'm occasionally able to do it, but me knowing that I, or others are capable of doing it does not let me know why it's possible, or why it's allowed to be done. PitchBlack 08:24, 8 April 2007 (UTC)

Not completely sure, but simply, such states of emotions activate the parasympathetic nervous system inducing secretion by the lacrimal glands.

Actors often "force themselves" to cry. I believe they do it by either getting sufficiently emotionally in tune with the script that they get affected by it, or by remembering something similar in their own lives that caused them to cry and letting that do the work. JackofOz 01:15, 9 April 2007 (UTC)

Just like how we have facial expressions, body language, and changes in speech, it is to let others know how we feel. That's what I've always thought. [Mαc Δαvιs] (How's my driving?) ❖ 02:39, 9 April 2007 (UTC)

Exactly right. We feel the emotions in our bodies, and express them (ie. communicate them to others) in various ways. JackofOz 03:58, 9 April 2007 (UTC)

could electrons be splitted ?

is it possible to split an electron. if possible then how and what is emitted while electron splits up ? —The preceding unsigned comment was added by 202.56.7.139 (talk) 11:39, 8 April 2007 (UTC).

Good question. The answer is no, we have no evidence that it is ever possible to split an electron, and we have some good theoretical reasons to believe that an electron is indivisible. Our article on the electron says "The electron is in the class of subatomic particles called leptons, which are believed to be fundamental particles (that is, they cannot be broken down into smaller constituent parts)." Gandalf61 12:13, 8 April 2007 (UTC)

From experiments in particle accelerators it is known that electrons show no internal structure down to a size of 10^-18 meters. Icek 18:10, 8 April 2007 (UTC)

Also known as 1 attometer --172.130.96.204 22:24, 8 April 2007 (UTC)

NOx Production

How many tonnes of NOx are produced daily by human activity? Tobes ^(talk) 13:26, 8 April 2007 (UTC)

[Nitrogen oxide] has some information on the subject but not number of that sort. Perhaps some of the links at the bottom can help you. Jon513 13:49, 8 April 2007 (UTC)

Atmospheric NO_x is at least sometimes measured in terms of just the mass of the nitrogen involved. The NO_x produced by human activity amounts to about 33 Tg of nitrogen per year,[14] which is equivalent to about 90,000 tonnes per day. MrRedact 16:41, 8 April 2007 (UTC)

DVD/CD Writing

Do CDs/DVDs write better if they are hot or cold? Becuase when i take them out i find they are always hot, but then again after extensive game playing they are also hot... —The preceding unsigned comment was added by 85.210.157.80 (talk) 15:26, 8 April 2007 (UTC).

Your question is similar to "does water hydrate you better if it is warm or cool? Because after it is in your belly it is always warm". The CD's are hot, in both cases, because they have just been spinning at incredibly fast speeds. You should always keep your CD's around room temperature. − Twas Now ( talk • contribs • e-mail ) 15:56, 8 April 2007 (UTC)

It's warm inside your computer's case (that's why it has fans) and the drive's motors, when in operation, also generate heat. Even when I'm not doing anything, my computer's CPU is still at a fairly steady 45°C/113°F. So while the drives don't deliberately heat the discs – indeed, excessive heat will shorten their lifespan, and very high heat may warp the disc and make it unreadable – there's not a whole lot that you can do about the ambient 'waste' heat they pick up. TenOfAllTrades(talk) 15:56, 8 April 2007 (UTC)

They are also heating up because there is a pretty bright laser shining on them. But whether the peculiar light sensitive dyes in writable CD/DVD's work better at different temperatures - I don't know. The fact is that once it's inside the drive it's going to be warm come-what-may so you don't really have a choice. Store them on their sides at room temperature though - keep them out of the sun. SteveBaker 17:23, 8 April 2007 (UTC)

I believe I've also read to store burned cds and dvds horizontally, because the ink can run after several years. And don't store them with too much weight on them, so spindles are a pretty good bet, since they keep them horizontal and the casing is what holds up whatever you stack. --Wirbelwindヴィルヴェルヴィント (talk) 18:45, 8 April 2007 (UTC)

...what are you talking about? Ink? Spindles? Or is this a joke? [Mαc Δαvιs] (How's my driving?) ❖ 02:38, 9 April 2007 (UTC)

I wouldn't call it 'ink' - it's a dye. SteveBaker 05:13, 9 April 2007 (UTC)

Genetic disorder transmission

In the movie X-Men 2 (possibly not the most realistic portrayal of genetics, but still), one of the characters claims that the "mutant gene" (stupid name for a gene, given that any gene be mutated) can only be passed on by males. Of course, if the gene was on the Y-chromosome, then this would be possible, but since females do not have a Y-chromosome, they could not become mutants. So, more generally, are there are genetic conditions which can only be passed on by one sex, but expressed by either? Laïka 19:58, 8 April 2007 (UTC)

There are a few diseases mentioned in the article on mitochondrial DNA. Mitochondrial DNA is inherited only from the mother because the mitochondria of the sperm cell are destroyed after they enter the ovum (sometimes a paternal mitochondrion can survive, but this is rare in humans). Icek 20:53, 8 April 2007 (UTC)

Outside mitochondrial DNA, no. Genotypically speaking, if it can be expressed by either sex it can "be passed" on by either sex (though there are some hypothetical scenarios involving sex-specific uniparental disomy though could confound that, I suppose). However, there are some phenotypes that could result in that sort of scenario. For example, a autosomal-dominant gene mutation that had a sole phenotype of extremely abnormal oocyte development would - in practice - only ever be passed down the male germline since females that expressed it would be infertile. Similarly, a dominant gene that had a phenotype resulting in abnormal semen composition might only be passed on by females, since males that expressed it would be infertile but the female phenotype might be rather inconsequential. There likely are such disorders, though I can't think of any specific examples off the top of my head. Come to think of it, any X-linked recessive disorder that resulted in death in males before puberty would essentially have the same result: both sexes express the allele (at least in some cells) but only females will pass it on. Rockpocket 22:02, 8 April 2007 (UTC)

Natural Environment

I regret that such an important concept received such a poor article (I myself don't have any knowledge to improve it). It seems that the expression "natural environment" has two different meanings in the article:

1. In the opening paragraph, "the natural environment" (with definite article) is described as all natural things on earth.
2. in the Terminology section, "a natural enivronment" (with indefinite article) is described as any region or landscape with little human intervention.

These two meanings are quite different from one another. Do they really exist in parallel? If someone could improve the article and make things clearer, that would be great. Gidip 20:08, 8 April 2007 (UTC)

Is the problem with the use of "the" vs "a"? Or whether nature includes humans or not? Pfly 06:33, 9 April 2007 (UTC)

The problem is that two different meanings are described, but there is no clear distinction, and the article doesn't clearly mention that there are two different meanings. So, are there really two different meanings, or is it just a broad term, without any clear definiton? Or maybe I've misunderstood everything? Gidip 12:51, 9 April 2007 (UTC)

Vinageroon

Looking deadly is an over-rated survival strategy - this little guy is doing just fine with cuteness. Rockpocket 01:14, 9 April 2007 (UTC)

I am looking for info. on a Texas arachnid known as the "vinageroon". Can find nothing on them, but know they exist because have seen them. They exist in the desert areas along with the scorpions. The common name comes from their toxin made up of acetic acid.

Vinageroon Greglocock 21:18, 8 April 2007 (UTC)

That's a horrible-looking beast! You would think that after 4x10⁹ years of survival of the fittest everything would look that deadly. Thank God for koala bears. :) --TotoBaggins 01:07, 9 April 2007 (UTC)

They're not bears, but give them 4x10⁹ years and they may yet evolve into bears. But probably not. JackofOz 01:11, 9 April 2007 (UTC)

Wow, that is one awesome bug!! Yeah I know it's an arachnid, but I'm calling it a bug. Anchoress 03:52, 9 April 2007 (UTC)

Oh God, how'd you like to find that one in your bed when you wake up? Oh, and look, they spray acid! a combination of acetic acid and octanoic acid when they are bothered. The acetic acid gives this spray a vinegar-like smell, giving rise to the common name vinegaroon. Other species spray formic acid or chlorine. [Mαc Δαvιs] (How's my driving?) ❖ 14:35, 9 April 2007 (UTC)

A question on " self "

A little blurb came up in my mind a few years ago, and is still with me to this day.

If who I am, is formed (in simpel terms) by my neural net. And this neural net is constantly changing, adapting, reconnecting and restructuring itself. Then aren't I in a fact being reborn over and over again? Only with little changes in stead of large ones? Changes so small that nobody would doubt that PvT is still PvT? Countless of other PvT's have existed and died, are no longer here. Yet nobody mourns them.

So if I am in a constant state of flux then when am I me? And what then does it mean to die?

Are there any branches of science/philosophy that touch this subject? I've been trying to read the article on the philosphy of mind and such. But they are rather, bulky.PvT 21:36, 8 April 2007 (UTC)

Philosophy of the mind is all about questions on this — you are essentially asking questions about the nature of consciousness and its relation to the self. But yeah, it's bulky, if bulky you mean "full of specialized terminology and obscure concerns based on very old debates some of which are still relevant and some of which seem less so." As for branch of science, cognitive science is an interdisciplinary approach to questions like this, building on philosophy, linguistics, neuroscience, psychology, etc. You might try Steven Pinker's How the Mind Works, which is a readable popularization of cog sci and phil of the mind. --24.147.86.187 22:33, 8 April 2007 (UTC)

There's also Self (philosophy), which I haven't read fully but looks at first glance like it should probably be merged with Self (psychology). --Allen 02:40, 9 April 2007 (UTC)

Wow, and there's Self (sociology) too. I'm skeptical about whether we can or should separate these different senses of the word. --Allen 02:45, 9 April 2007 (UTC)

If who I am, is formed (in simple terms) by my neural net. --that's a mighty big if. Pfly 06:44, 9 April 2007 (UTC)

Really. Who I am is formed by my butterfly net. − Twas Now ( talk • contribs • e-mail ) 06:55, 9 April 2007 (UTC)

Intelligent, non-Terrestrial Life?

Does it exist somewhere in the universe?--172.131.75.193 22:25, 8 April 2007 (UTC)

Nobody knows. At the moment all we have are guesses, but there is no solid evidence of it as of yet, and no strong reason to think that intelligent life has existed simultaneously with the intelligent life on this planet (i.e., did not evolve sentience and then kill itself off as the human race has threatened to do at many points in its feeble and geologically-brief existence). --24.147.86.187 22:30, 8 April 2007 (UTC)

The International Space Station is manned isn't it? Vranak

Yeah, but I'm pretty sure life didn't evolve on it :). Splintercellguy 00:14, 9 April 2007 (UTC)

As 24 says, no one knows. There is no evidence that there is or has been intelligent life elsewhere in the universe. For that matter, there's no evidence for extraterrestrial life of any kind, aside some from some controversial, unconfirmed claims of Martian microbes. That being said, the universe is a huge place: with some 200 billion stars in our galaxy, and some 100 billion galaxies in the visible universe, many people the chances are very high that not only life, but intelligent life would evolve elsewhere in the universe. Of course, even if it did, the enormous distances might preclude any contact between our species. — Knowledge Seeker দ 03:37, 9 April 2007 (UTC)

Obviously - we don't know. I strongly suggest you read about the Drake equation. That is a rational effort to put together an estimate for the probability and number of intelligent races in the universe. The trouble is that this equation has an awful lot of unknown terms in it (eg What is the average number of earthlike planets orbiting each star? We don't know because our technology isn't good enough to detect earthlike planets orbiting other stars.) - depending on what semi-informed guesses you plug into that equation, you can get answers anywhere from it being very unlikely to there being tens of thousands of extraterrestrial civilisations out there. SteveBaker 05:10, 9 April 2007 (UTC)

Unknown Plant Picture

Can this photograph be identified? Thegreenj 22:42, 8 April 2007 (UTC)

No idea, but googling 'blue flower' sure turns up a lot of beautiful pictures. I'd thought it might be ragweed, but I guess not. Anchoress 00:08, 9 April 2007 (UTC)

Could it be lupin? The pic in the article doesn't look the same, but some of the internet pics do. Also check lobelia, spiderwort and pickerel weed. Anchoress 00:53, 9 April 2007 (UTC)

Looks to be in the family Boraginaceae; good chance of Echium genus. try those as search terms.Polypipe Wrangler 01:54, 9 April 2007 (UTC)

Morphological Crystallography,the Tschermak forms and the 48 simple forms in mineralogy

• Hi ,i have been astonished by this subject on my mineral science class last monday about this topic.
• What are the Tschermak forms? , are they related with Gustav Tschermak von Seysenegg? And what are them in the first place?. Does they only belong to the isometric form (crystal forms classes) system on morphological crystallography?--HappyApple 23:54, 8 April 2007 (UTC)

Can the octet rule be explained in terms of more fundamental behaviors of sub-atomic particles?

Can the octet rule be explained in terms of more fundamental behaviors of sub-atomic particles? --71.162.233.206 00:41, 9 April 2007 (UTC)

This sounds like homework to me! Pauli exclusion principle, no? [Mαc Δαvιs] (How's my driving?) ❖ 02:36, 9 April 2007 (UTC)

Actually I did look at the article on Pauli's exclusion principle but did not make any connection between the two. Still haven't figure out how PEP explains the octet rule. (And no, it's not homework — I don't have homework.) --71.162.233.206 03:18, 9 April 2007 (UTC)

My memory of quantum mechanics and such is pretty weak, but I believe it has to do in part with electron orbitals—one s and three p orbitals can hold eight electrons, and fully occupied orbitals are in general associated with increased stability. The reasons those orbitals exist arises from wavefunctions and quantum mechanics, I believe, but I cannot remember more. Perhaps someone more well-versed in this area could comment (and improve the article)! — Knowledge Seeker দ 03:29, 9 April 2007 (UTC)

Take a look at Atomic orbital#Qualitative characterization. Here's my explanation:

Every shell is numbered by the number n. For every n, there are as many subshells as there are numbers between 0 and n-1. So for example the first shell, n=1, has 1 subshell numbered l=0 (l represents the subshell number). For n=2, there are two subshells, numbered l=0 and l=1. The electrons inside each subshell all have a magnetic quantum number; this describes the shape of the electron's orbit. All numbers from -l to l could be taken as values. This gives 1 unique orbit to the first shell, 4 to the second, and 9 to the third. But because electrons also have one additional property, called the spin, that can either be positive or negative, the total number of electrons that can be held is 2 for the first shell, 8 for the second, and 18 for the third.

Although the 3rd shell has 3 subshells, the 4th has 4, etc., in the outermost electron shell only the bottom two subshells are used. This is because an electron in an outer subshell will have more energy than one in an inner subshell, and atoms always try to have the lowest possible energy. Subshells beyond the second one will only be used if they're not in the outermost shell (remember that electrons in the outermost shell have a lot of energy, too).

So the outermost shell can have 2 used subshells, with the first one containing 1 possible value of the magnetic quantum number and the second one containing 3 possible values. With 4 different orbitals and each electron having either a positive or negative spin, there can be a maximum of 8 electrons with no two electrons having the same properties (if they did, they would be the same particle). Obviously there can't be any more chemical reactions with a full shell.

I hope this helps, but feel free to point out any errors or make my explanation clearer; I'm far from being an expert! --Bowlhover 05:03, 9 April 2007 (UTC)

Artichokes polish aluminum?

I was just cleaning up after dinner, and I noticed that that aluminum lid for our cook pot was bright shiny and silvery. The pot is fairly old and is usually a dull gray color. We had boiled artichoke in it tonight and as usual, the inside of the pot is stained dark. I did add salt to the water that we boiled with which is different than usual. So what would it be about the combination of Salt, steam, and essence of artichoke that would polish the pot lid so bright? -Czmtzc 01:25, 9 April 2007 (UTC)

Easter osmosis ?

I have a chemistry/biology question related to my Easter dinner (do I have you hooked yet ?). One dish was sliced ham (precooked and injected with salt brine) heated with canned yams, canned pineapple rings, and some brown sugar. As always, it's quite good during Easter, but something bad happens to the leftovers. The ham slices left floating in the yam/pineapple juice seem to lose their water content (but retain all their salt) and become shriveled up, almost like bacon. I'm looking for an explanation of what's happening here. I would have expected, that since the ham is much saltier than the yam/pineapple juice, the ham would have absorbed water, not given off water. Perhaps the higher sugar content in the juice is able to suck more water out of the ham than the salt sucks in ? StuRat 03:53, 9 April 2007 (UTC)

I don't know exactly why it became like that but fresh pineapples are very good meat tenderisers because they contain some enzyme or something, so maybe you have some half digested meat floating around? --antilived^{T | C | G} 04:42, 9 April 2007 (UTC)

Earth Re-Entry

Is there anyway to re-enter Earths atmosphere without heating up, for example could you inflate a large ballon in space then slowly re-enter or maybe slow yourself down with engines? This reminds me of SpaceShipOne and how it re-enters could the same process be used for an orbital craft? —The preceding unsigned comment was added by 67.127.97.132 (talk) 04:47, 9 April 2007 (UTC).67.127.97.132 04:48, 9 April 2007 (UTC)

The problem is that in the uppermost layers of the atmosphere, there is very little air resistance - so parachutes, wings and balloons won't have much effect in slowing you down. By the time you reach layers where there is significant resistance, you're falling so fast that you get into all of the heating/burning up problems. SpaceShip One didn't get very high - nowhere near orbital altitudes. So it had less far to fall - less time to build up speed - so when it did re-enter the denser parts of the atmosphere, it was going a lot slower than (say) the Shuttle does. You could certainly slow yourself down using engines - but the amount of fuel you'd need to slow down would be about the same as it took to get you up there in the first place. When you see the size of the fuel tanks and boosters that the shuttle needs to get up there - and imagine needing about that much to get back down again...then imagine the amount of extra fuel you'd need on launch to get the re-entry fuel up there as well as the spacecraft - you can see that it rapidly gets out of hand. Heat tiles and the older 'ablative' heat shields are a cheap and (relatively) easy way to do the job. SteveBaker 05:00, 9 April 2007 (UTC)

I agree with most of that response, but not that the amount of fuel would be equal. This is because air resistance is hurting when a rocket is trying to gain speed during launch but actually helps when trying to reduce speed for landing. Perhaps a lower thrust mechanism, like an ion engine, could therefore be used to lower the ship to the surface at a safe speed. StuRat 06:17, 9 April 2007 (UTC)

Even if aerodynamic heating were not a factor during atmospheric reentry, the thermosphere is about 2,000°C (3,600°F). − Twas Now ( talk • contribs • e-mail ) 07:06, 9 April 2007 (UTC)

Well, yes, but the air is so thin there that very little heat would be transferred to a descending rocket. StuRat 08:14, 9 April 2007 (UTC)

Yes, and the International Space Station has orbited in the thermosphere for years without getting significantly heated, as the main heat transfer mechanism is radiation. You might be interested in project ARCHIMEDES by the German Mars society. They are planning to enter Mars' atmosphere by balloon in 2010. Icek 12:43, 9 April 2007 (UTC)

An object which had a large surface area relative to its mass would not heat up as much as did the Space Shuttle or the Apollo capsule from atmospheric friction. This is why when the most recent Space Shuttle disaster occurred and it broke up, nylon bags with computer equipment inside, a videocamera with a tape of the early reentry, and plastic containers with worms from biology experiments landed intact. MOOSE was an early project to allow an astronaut to reenter with only a shield-like disk and a space suit as protection: the kilograms per meter of surface area would have been less than for a normal spacecraft reentering. Edison 14:11, 9 April 2007 (UTC)

Wirenetting allowing blackbirds, not magpies

Every year, a couple of blackbirds builds a nest by my house. And every year, their young/eggs are eaten by magpies. Although that is the course of nature, I would like to find a way to shield their nests from the magpies. I am thinking about some kind of wire-netting. Do you think this would be feasible? How large should the holes be to allow blackbirds, and not magpies?

Thanks in advance

Søren 83.73.238.25 07:06, 9 April 2007 (UTC)

Protein digestion

Can protein form a white substance when becoming digested in the stomach, looking like the white of a cooked egg yolk? Thank you for your help

CorinneQ 07:21, 9 April 2007 (UTC)Corinne Quinones

I would guess yes, as many forms of protein start out looking like that. Besides ovalbumin, there's also chicken and many other sources of protein. StuRat 08:08, 9 April 2007 (UTC)

Thank you very much for your help, I really appreciate you taking the time to answer me StuRat =)

CorinneQ 08:12, 9 April 2007 (UTC)Corinne Quinones

You're quite welcome. StuRat 08:15, 9 April 2007 (UTC)

Wake imaging

I am looking for OPEN source material on the subject of " Wake imaging "

That is, the detection of surface or sub-surface craft using Synthetic Aperture Radar.

Rather than open a new subject page, I would be grateful if you could let me know where in Wiki I might find any related data SPECIFICALLY on wake imaging

(I have reviewed the material held on Synthetic Aperture Radar and related discussion on Doppler beam sharpening etc.)

Thanks

Goatman81 09:40, 9 April 2007 (UTC)

I am looking for OPEN source material on the subject of " Wake imaging "

That is, the detection of surface or sub-surface craft using Synthetic Aperture Radar.

The wake of a ship or submarine is the long lasting disturbance in the water caused by its passing.

Rather than open a new subject page, I would be grateful if you could let me know where in Wiki I might find any related data SPECIFICALLY on wake imaging

(I have reviewed the material held on Synthetic Aperture Radar and related discussion on Doppler beam sharpening etc.)

Thanks Goatman81 09:50, 9 April 2007 (UTC)

Gun

Any idea how does a light pen work?Any what about the GUns that used to come with the video games that can detect the images or moving image that we shoot on the TV??210.212.194.209

Check out light pen--Shantavira 10:46, 9 April 2007 (UTC)

The old NES light gun (NES Zapper) used an interesting method. When you pulled the trigger the screen would be momentarily blanked and white boxes indicating the hit zone for targets would be drawn. The sensing mechanism was a pretty basic photodiode behind some cheap optics in the back of the gun. -- mattb @ 2007-04-09T15:15Z

Motion Sensors

How does a motion sensor for games, work? if i start with the controller upside down it knows! is is mercury switches or something else. Also how can games consoles tell were you are pointing light guns, wii nunchuks etc. on the tv? —The preceding unsigned comment was added by 84.13.132.232 (talk) 10:31, 9 April 2007 (UTC).

Check out motion sensor.--Shantavira 10:47, 9 April 2007 (UTC)

It depends! There are many ways to realize motion sensors. A lot of modern applications use MEMS accelerometers and gyroscopes. The Wii controllers you refer to both use monolithically integrated MEMS accelerometer chips and a CMOS SoC image sensor: [15], [16] [17]. You could conceivably use some kind of mercury switch scheme, but on top of being bulky, fragile, inaccurate, and unable to really measure acceleration, it might not be a fantastic idea to put a toxic heavy metal into children's toys, especially ones that are going to be thrown around (I'm pretty sure nobody uses mercury switches in thermostats anymore, either). -- mattb @ 2007-04-09T14:18Z

Name that celestial body

So, I've seen a star/planet in the sky a few times over the past month, and I was hoping someone could tell me what it is. I'm in Salt Lake City, Utah, and the object was almost directly due south at about 5 a.m. MDT (23 UTC), and not too far off the horizon, probably about 30 degrees or so. It had a reddish glow/tint, leading me to speculate that perhaps it was Mars, but really that's a pretty baseless guess. I've never been very good at reading various star charts, so I'd appreciate some help. Of course, if you'd also like to "teach a man to fish..." as the saying goes, then feel free to provide me a link and tutelage either on this page or my talk page. Cheers! Eric (EWS23) 12:14, 9 April 2007 (UTC)

It was not Mars, but the much brighter Jupiter. See http://www.fourmilab.ch/yoursky/ for an online starchart program, enter your time and location (5 a.m. is 11 UTC), and look south. The symbol that looks like "4" is Jupiter, and at magnitude -2 it's much brighter than any star.

Mars should also be visible from your location, but you'll have to go to an open field and scan the eastern horizon just before sunrise to see it. --Bowlhover 12:46, 9 April 2007 (UTC)

Apologies for the UTC error...that's what I get for being up so early in the morning. Eric (EWS23) 13:27, 9 April 2007 (UTC)

Dyssomnia vs Insomnia

What is the difference between dyssomnia and insomnia? Thanks a whole bunch!!!!58.153.97.57 14:38, 9 April 2007 (UTC)

Try reading our encylopedia articles on dyssomnia and insomnia, you can use the search box on the left side at the top of the page next time. [Mαc Δαvιs] (How's my driving?) ❖ 14:52, 9 April 2007 (UTC)

Electric Cas vs not driving

Hi, I dont drive but recently find myself lusting after electric cars. I was wondering, given that normally i take the bus to work (i'm supposed to cycle but everytime i get a puncture it takes me about a month to get round to fixing it), what are the pros and cons environmentally speaking? Some of these cars can apparently do the equivalent of 300 mpg which can't be far off what one person "does" in a bus. Also, is there an argument that if you buy an electric car (which in the UK are extrememly rare) you're both rasing awareness (people see you driving) and help lower the cost of future electric cars, which are obviously both environmental good deeds? So what are our thoughts people - bus vs electric car? I'd love to hear your comments....87.194.21.177 14:58, 9 April 2007 (UTC)

Chicken or the egg?

I know the chicken or the egg dilemma is usually a philosophical problem, but from a scientific perspective which one actually came first? Heycos 15:09, 9 April 2007 (UTC)