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April 21

tongue map

hey everyone. In biology class I've got to find a tongue taste map for the lab investigation in taste we are doing. the professor says not to use wiki, so I need an accurate tongue map from a reliable source. Any idea where I can find one? <3 ~Liviya —Preceding unsigned comment added by 76.235.111.187 (talk) 00:45, 21 April 2010 (UTC)

Did you try typing "tongue map" into google images? --Jayron32 00:48, 21 April 2010 (UTC)

Have you tried a printed encyclopedia? APL (talk) 00:56, 21 April 2010 (UTC)

It may be of interest that recent articles in the popular scientific media (sorry, can't immediately find a linkable reference, but New Scientist is a likely source) have asserted that the hallowed 'map' of highly differentiated taste areas on the tongue was based on a very old and flawed study that has now been discredited. Apparently the 'buds' for the various tastes are only weakly concentrated in different areas, and these concentration areas vary between individuals. You might want to follow up this line (don't just take my unsupported word for it) and surprise (or possibly gratify) your professor. 87.81.230.195 (talk) 01:05, 21 April 2010 (UTC)

Oh! Good point. If you look at the Tongue map article, you'll see that the "research" section of the article has two cites (footnotes) that link to articles explaining that tongue maps have been discredited. (The Nature article is a pay article, I'd try the Scenta article.)

With a little google searching I was also able to fine this article. APL (talk) 01:24, 21 April 2010 (UTC)

Ouch! That's going to make for a tough class! Our article also mentions how this falsified concept is still taught in schools. I suggest you read the references that say that it's discredited very carefully - so you are sure of your facts, find a "Tongue Map" someplace (so you can reasonably claim that you did your assignment no matter that the entire premise of it is incorrect) - and carefully write about how it's wrong. If you are doing a 'lab' and are planning on testing whether the maps are right or not - be aware that anyone who has looked at one of these maps is an invalid test subject as they are pre-conditioned to expect what they found when they did their assignment. Good luck with that! SteveBaker (talk) 04:54, 21 April 2010 (UTC)

The tongue taste map is a good example of a scientific misconception or a lie-to-children. ~AH1^(TCU) 00:19, 22 April 2010 (UTC)

It's a good scientific misconception, but I'm not sure it's a "lie to children". It's not an oversimplification of some scientific truth, nor is it an intentionally incorrect to help students learn some other material. It's simply an error.

You'll notice that the Lie-to-children article actually lists the tongue-map as an example of something that is not a lie-to-children. APL (talk) 00:57, 22 April 2010 (UTC)

I never took the tongue map seriously. I did an experiment of my own several times by placing salt, and sugar on various spots on my tongue. I was able to taste it regardless. --Kvasir (talk) 16:24, 24 April 2010 (UTC)

toba bottleneck

I was wondering if any thought has been given to the loss of technology during the toba eruption and bottleneck. IE. construction of the pyramids, astrology, etc.  ???? —Preceding unsigned comment added by 68.34.218.91 (talk) 01:45, 21 April 2010 (UTC)

Yes. It's in the article, Toba eruption#Genetic bottleneck theory. ~ Amory (u • t • c) 04:21, 21 April 2010 (UTC)

The article Toba catastrophe theory does not mention pyramids or astrology. The only direct evidence of how the Toba eruption must have devastated the life of people living at the time of the eruption has been found in Malaysia. A large and long-established "palaeolithic workshop" named Kota Tampan, had been found [1]. 'Pompeii-Like' excavations in southern and northern India shed light on the kind of human settlements existing before and after the Toba super-eruption 74,000 years ago.[2]. The earliest known Egyptian pyramid was constructed much later 2630 BCE–2611 BCE. Cuddlyable3 (talk) 09:06, 21 April 2010 (UTC)

No, of course not - as you say way too far off, for one, and beyond impossible to determine. But the question as I read it was asking "Hey, if the population of humans didn't plummet into such a bottleneck, would maybe we be more advanced now?" The answer, of course, is nobody can ever know, although it could make a good sci-fi/fantasy novel. ~ Amory (u • t • c) 14:30, 21 April 2010 (UTC)

There's a theory that pyramids were constructed as early as 10,000 years ago, during the Age of Leo. See that article for more information on astrological ages but it does not mention events prior to the end of the ice age. ~AH1^(TCU) 00:16, 22 April 2010 (UTC)

information disinformation. Cuddlyable3 (talk) 13:20, 23 April 2010 (UTC)

cleaning up chemical spills

i notice in this vid

http://www.youtube.com/watch?v=f5M3rUqaEYs

he spills concentrated acid and powdered sodium hydroxide. how exactly is this cleaned up? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 02:01, 21 April 2010 (UTC)

Sodium bicarbonate solution for acid, vinegar for alkali, then hose down the area with lots of water. (Careful, don't burn yourself!) 24.23.197.43 (talk) 22:24, 21 April 2010 (UTC)

I expect that this could be very dangerous advice. If there are significant quantities of sodium hydroxide then poring vinegar on will produce a fast exothermic reaction that will probably splatter sodium hydroxide everywhere. I could be wrong but I would be very cautious with this advice. -- Q Chris (talk) 14:52, 22 April 2010 (UTC)

You might want to dilute them first, with water, then add the chemicals to nuetralize the acidity and alkalinity. StuRat (talk) 15:01, 22 April 2010 (UTC)

Using sodium bicarbonate you may neutralize both base and acid. The CO3 part can react with acids to form CO2 gas, and the H can react with bases to form water. --Cheminterest (talk) 21:29, 26 April 2010 (UTC)

Wrongly cleaned copper nickel coin resulting in light copper colored stains.

How do I remove light copper colored stains on a copparnickel coin due to contact with washing detergent?02:05, 21 April 2010 (UTC)

I first tried to clean the coin with backing soda, salt and a aluminum foil like with silver without any improvments. Then I tried with vinegar with no result there either. With toothpaste all the dark brown stains disapeared and only the light copper colored stains remained. Also tried with lemon juice, nothing. The same with handsoap.

I've also heared using about 25% diluted amonia. Could that be something to me or have I permanently destroyed the coin?83.233.65.220 (talk) 02:05, 21 April 2010 (UTC)

I appreciate all the answers I'll get.

Thanks

Presuming this is some kind of old, valuable coin (or you presumably wouldn't be asking!) - you probably destroyed most of its' value the instant you started cleaning it. Collectors of antiquities like for them to have all of their original 'patina' and cleaning things like this doesn't improve their value at all. The more you do, the worse you are making it. Salt and toothpaste are both abrasives and that's a definite no-no! I think you should quit while you can. SteveBaker (talk) 03:07, 21 April 2010 (UTC)

He might just be the obsessive type thinking "I'll be darned if this stain is gonna beat me !". StuRat (talk) 05:15, 21 April 2010 (UTC)

The only other thing I can think of to try is tomato juice. StuRat (talk) 05:16, 21 April 2010 (UTC)

How would washing detergent cause a copper colored stain? The dark stains are from corrosion presumably, but the copper one? Perhaps you cleaned the coin so well you removed the surface plating, and you are revealing the copper underneath? What kind of coin is it? If it's not plated but rather a Cupronickel alloy, is it possible the black stain was nickel corrosion (the nickel leached out of the alloy)? Although nickel oxide is usually green, it could be black. And once you cleaned it off you have a section with just copper and no nickel? Just guessing, but try to figure out what the stain is made off. Ariel. (talk) 09:14, 21 April 2010 (UTC)

@SteveBaker Your right it's a rare and valueable defects characterized cupronickel coin worth about $30-$70 US I've seen it being put out for. I whished I'd known not to try to wash it, but now I know and will never make that mistake again. @StuRat You're also right "I'll be darned if this stain is gonna beat me !" :) I now have nothing to lose so I'll try to use tomato juice depending on if Ariel can help me with salvaging the coin. @Ariel I used a ultrasonic cleaner with washing detergent containing 15-30% zeolites, 5-15% non-ionic, anionic and <5% soap, phosphonates, perfume and enzymes. Only the one side of the coin is affected and that's the one in direct contact with the detergent. I think that you are closest or right on of what have happened to my coin. The coin is made of a cupronickel alloy 75% copper 25% nickel. I'm 99% sure that the stains on my coin is copper because of its color now when you have told me about leaching and the "black". Is it possibe to remove this copper except damaging the nickel futher?83.233.65.220 (talk) 20:55, 21 April 2010 (UTC)

Thanks all of you who helped me with this subject. It has been very enlightning and hope that you will be kind enough to help me further.

When you clean the tarnish off an old coin, this instantly destroys most of its antique value. Also take a look at numismatics if you are interested. However, if you wish to make the coin appear new (and unvaluable), a slow method of un-tarnishing the coin involves using ketchup (tomato acid) or mustard (vinegar). I've also discovered a new method of instantly removing the tarnish from a coin today: place the coin in a bowl with a small quantity of tap water at the bottom, then pour salt over the coin. Drop some cola (phosphoric acid) over the coin into the water, until it starts to mix. Next, take half of a lemon and squeeze a few drops of lemon juice over the coin—the tarnish should come off instantly, then repeat with the other side. However, since salt is abrasive, this process should also work without the salt, but I haven't tried that myself. To re-add the tarnish to the coin, which would make it look old again but not in its original state, either place the coin on a paper, cardboard or wooden surface for several days, or leave it in a shallow dish of water overnight, but don't add additives to the water. However this method may cause any fingerprint stains on the coin to become more visible, so the coin should always be held by the edge. Hope this helps. ~AH1^(TCU) 00:08, 22 April 2010 (UTC)

The best stuff I know for cleaning that dark stuff off of copper, brass and other similar kinds of metal is "Duraglit" - it's a weird kind of cottonwool-like stuff that's impregnated with who-knows-what. It comes in a can about the size of a soda can - with an airtight lid. Rubbing a thumb-sized chunk of this stuff on a grungy-looking 1 cent coin makes it look like it's just been minted. It's claimed to be non-abrasive. I use it in car restoration...where keeping things crudded up with "patina" isn't so popular. SteveBaker (talk) 01:02, 22 April 2010 (UTC)

I have to disagree with the idea that the more tarnish on a coin the more valuable it is. On the contrary, a coin in "mint condition", meaning no tarnish or wear at all, is the most valuable. However, if the level of tarnish is incongruous with the wear, then that might bring the value down, as it's obviously been "messed with". So, I think removing the weird stain on the coin won't destroy it's value. Think of it like restoring an antique. As long as it's done properly, it can increase the value. Do a shoddy job, and the value drops. StuRat (talk) 03:46, 22 April 2010 (UTC)

I absolutely agree that there is no idea that dirty coins are worth more. What is expected is that the degree of tarnish is appropriate to the age and degree of circulation that the coin has undergone. So a coin that's been preserved in "mint" condition since it was first struck (and which therefore has no tarnish) might well be worth more than a worn and tarnished coin of the same type and age - which in turn would be worth more than a worn and cleaned coin - which in turn might be worth more than a coin that was so heavily corroded that it was almost unrecognisable. But in none of those four situations would cleaning the coin increase its value. SteveBaker (talk) 14:12, 22 April 2010 (UTC)

The American Numismatic Association says the following:

8. Should I clean my coins?
The short answer is “NO!” Cleaning a coin often presents an enigma. A coin that has circulated and shows signs of wear has an altered appearance if it has been cleaned. In essence, what you would have is a coin that is bright but worn. Generally, a coin will lose some of its value after being cleaned. Most experienced numismatists are able to spot a cleaned coin fairly easily. If a coin is so corroded that it is unrecognizable, you may try a solution of mild dish soap and distilled water. Rinse the coin thoroughly with distilled water and allow the coin to air dry otherwise you should leave coin cleaning to professional services such as NCS.

— American Numismatic Association, General FAQ

AlmostReadytoFly (talk) 08:54, 22 April 2010 (UTC)

They don't seem to cover the current case, where a coin has more tarnish than it's wear would indicate. In such a case, cleaning it until it matches might increase the value. StuRat (talk) 15:16, 22 April 2010 (UTC)

Self-replicating molecules

I hear a lot of talk about self-replicating molecules being a precursor to life on Earth, but despite working in chemistry, I have yet to see a self-replicating molecule. I'm not talking about DNA, that needs a rather complex system of enzymes to replicate during cell division. What is an example of a simple molecule that can make a copy of itself? Or do people mean something else when they talk about a 'self-replicating' molecule? 24.150.18.30 (talk) 02:22, 21 April 2010 (UTC)

Chemistry is not my strong subject - but you might want to read about the work of Julius Rebek who is a pioneer in this field. Our article on Self-organization (especially the sections on chemistry and biological self-organizers), the Abiogenesis article has a lot of information about RNA as an alternative to DNA as a way for the process of evolution to be 'kick-started' (see also RNA world hypothesis) - and in that context, Error threshold (evolution) is a really interesting article. The general concept of Autocatalysis and Autocatalytic sets is very relevant to this topic. There are also entire families of Peptide nucleic acid, Threose nucleic acid and Glycerol nucleic acid that are candidates for this kind of behavior. PAH world hypothesis is also interesting. Yet weirder possibilities are explored in Iron-sulfur world theory. SteveBaker (talk) 03:24, 21 April 2010 (UTC)

Polymer. Cuddlyable3 (talk) 08:37, 21 April 2010 (UTC)

And since when did your plastic shopping bags acquire the ability to self-replicate, Cuddlyable3? ;-) 24.23.197.43 (talk) 04:35, 22 April 2010 (UTC)

Ribozyme. --Mark PEA (talk) 15:50, 21 April 2010 (UTC)

If you're asking for a truly self-replicating molecule (i.e. replicating w/o external assistance), one example would be a prion.24.23.197.43 (talk) 04:33, 22 April 2010 (UTC)

Correction: prions don't really self-replicate the way DNA does, they only transform protein molecules into more copies of the prion. My mistake. 24.23.197.43 (talk) 04:40, 22 April 2010 (UTC)

Sunset color on a different planet

Considering we can't see one from the planets (excluding titan in that, but we can't see anything from the surface of titan, or rather we can't see the sun, well, I suppose we could, but we'd have a hell of a time getting a sunset there.) that have an atmosphere like Earth's and also aren't deadly to anything short of tungsten (see Venus, crushed a lot of spaceships down there), I'd like to come up with a theoretical planet for this one. The planet's size is three earth masses, and it orbits a star with a spectral class of K2V. The atmospheric composition is 29% Oxygen, 61% Nitrogen, 9% Carbon Dioxide, and 1% other gases such as methane, argon and helium. For referencing the star size in the sky, it orbits just on the inner edge of the habitable zone, and the star is about 0.89 solar masses. Now, based on these hypothetical values, can anyone think of what a sunset would look like on the planet, if either a human or something with very close to human vision were to see it? If you have to ask, no, it's not for an astrophysics paper or anything, just a book I'm writing. If you need more information, I'll probably have to come up with something. 173.50.148.216 (talk) 04:07, 21 April 2010 (UTC)

You may be interested in this image I've put up here - it's a sunset from Mars. As to your question, I haven't the foggiest idea, but you'd also need 1. the radius of the planet (to calculate gravity) and 2. a better definition of habitable zone, as it's not entirely clear what that would be for such a situation. ~ Amory (u • t • c) 04:16, 21 April 2010 (UTC)

Oooh, purty

Ah, I'm afraid I can't figure out the radius of the planet. Saying three earth radii would be incorrect, as I'm certain that's too big. As for the habitable zone, it's about close enough that most of the non-polar area is tropical, and not boiling off its oceans (the rest of the non-polar area is a sand desert. The planet is large enough that further north and south of the general 'antarctic and arctic zones' you start finding frozen carbon dioxide and liquid methane (though I don't know if that would freeze sooner or later than CO2, so take that with a grain of salt). Now, I would say that the gravity in multiples of Earth is about 3.02, but then Jupiter ended up with something like 2.0 or some odd completely unexpected number that I would've expected out of a planet much smaller. Gravity seems to be a tricky thing. Perhaps 13.6m/s2 is a good value for the acceleration due to gravity.173.50.148.216 (talk) 04:29, 21 April 2010 (UTC)

I think you need to calculate the color of the sky using Rayleigh scattering and Mie scattering equations - then figure out which colors will be refracted the most and thereby bent around the curvature of the planet by the setting star. Of course the spectral characteristics of the star and dust/liquid droplets suspended in the atmosphere would play into this too. That's going to be pretty tough to figure out. I don't think anyone predicted the weird orange-sky with blue sunsets on Mars before the first photos of it were taken. SteveBaker (talk) 04:46, 21 April 2010 (UTC)

Assuming it is being observed by a human eye, the sky and sunset should be pretty similar to how it is on Earth. The Rayleigh scattering should be pretty much the same as on Earth since the visible spectrum is very narrow, so it will all the affected the same way with just the simple dependence on wavelength that we see on Earth, which results in a blue sky and red sunsets. Mie scattering caused by larger particles happens fairly evenly across the spectrum, if memory serves, so that will result in the sky looking overcast to varying degrees. It is dust in the atmosphere that causes the red Martian sky and the sun isn't blue at sunset, it has a blue halo. The halo exists for the same reason we have a blue sky, but Mars only has enough air for Rayleigh scattering to outweigh the dust when the light is going through the much greater amount of air between the observer and sun at sunset. So, in summary, I think the most important factor is what dust/ice/etc. is in the atmosphere. Atmospheric pressure will be a factor too, but only in determining how bright the different colours are. --Tango (talk) 18:44, 21 April 2010 (UTC)

Not really directly relevant to the question, but if the mass of the planet is 3 times Earth's and the gravity is 3g on the surface, then radius would be about the same as Earth's (so triple the density). Keep in mind that gravity is proportional to m/r², and mass is proportional to r³ρ where ρ is the average density. Rckrone (talk) 05:29, 21 April 2010 (UTC)

Volcanic ash vs other jet engines

The volcanic ash destroys turbojets but are Ramjets theoretically immune to this due to the simple design? —Preceding unsigned comment added by 74.105.225.192 (talk) 04:41, 21 April 2010 (UTC)

Yes - I believe that is true. SteveBaker (talk) 04:47, 21 April 2010 (UTC)

Agree --BozMo talk 06:20, 21 April 2010 (UTC)

I don't think anyone has tried pouring ash into an operating ramjet. They do not offer a solution to the present air transport crisis because not even Concorde at Mach 2 flew fast enough for a ramjet to be useful. However it is comforting to think that an ICBM should make it through the ash plume. Cuddlyable3 (talk) 08:31, 21 April 2010 (UTC)

ICBMs are solid fuel rockets. No one flies ramjets, they are test engines only. Ariel. (talk) 09:19, 21 April 2010 (UTC)

At top speed, the SR-71 was effectively ramjet-powered: the turbine core of the engine wasn't producing any thrust. --Carnildo (talk) 00:28, 22 April 2010 (UTC)

That's not entirely accurate: the turbine core was still drawing air into the afterburner, helping the latter to function as a ramjet. This configuration could be classified as a "turbo-ram ejector" or a "topping-cycle ramjet". BTW, many surface-to-air missiles and some cruise missiles use true ramjet propulsion. FWiW 24.23.197.43 (talk) 04:47, 22 April 2010 (UTC)

What about piston engine powered propellor planes? Count Iblis (talk) 16:01, 21 April 2010 (UTC)

These still have to intake a huge amount of air, which is contaminated by volcanic ashes. If the filter was not developed with this purpose in mind, it will clog and the motor will stop working.--ProteanEd (talk) 16:11, 21 April 2010 (UTC)

Car engines are piston engines...not much different (in principle) from aero engines. I've said it a half dozen times in the past week - but the US Geological Survey folks say that if you are driving your car through volcanic ash, you should change your engine oil, oil filter and air filter every 50 to 100 miles(!)...so, no - piston engined aircraft are definitely no better off (and quite possibly much worse off) than jet engines in these kinds of conditions. SteveBaker (talk) 18:40, 21 April 2010 (UTC)

Additionally, car engines are mostly operated at a fairly small fraction of their peak power (low RPMs/low throttle). I would definitely expect this to be true of a research vehicle in an ash cloud. Piston aircraft engines are continuously operated closer to their peak power. Since the amount of air going through the engine is roughly proportional to power output, the aircraft is going to be even worse off than a car. -- Coneslayer (talk) 18:52, 21 April 2010 (UTC)

A rocket plane may be a more practical alternative for flying through an ash plume. StuRat (talk) 13:16, 21 April 2010 (UTC)

I guess the other alternative would be pulse jets - those (typically) only have one moving part - but like ramjets, they are ungodly noisy, and therefore probably unusable as a replacement for turbofan jet engines. SteveBaker (talk) 18:43, 21 April 2010 (UTC)

In theory I guess some form of geometric filter of the inlet air is possible. Obviously not a mesh, but perhaps a tight corner which flung all the larger particles out (centrifuging glass out of air) and only left smaller ones which would be carried by the flow. No doubt in some corner of the universe some civilisation coping with massive aviation on a volcanic planet has sorted it out. Meanwhile for us the development and research cost just isn't worth it. --BozMo talk 20:13, 21 April 2010 (UTC)

I dunno - the $2 billion that the airlines alone have lost during the last 6 days would pay for an awful lot of engine research! SteveBaker (talk) 00:47, 22 April 2010 (UTC)

Too much pressure drop, BozMo. 24.23.197.43 (talk) 04:42, 22 April 2010 (UTC)

blood-vessel building

I am curious about how blood vessels have such regular arrangements within the body, especially since angiogenesis factors can create new blood vessels. What guides their order? Especially the development of the heart -- it seems sort of curious how you get one vessel to coil around the other without having them merge. John Riemann Soong (talk) 04:54, 21 April 2010 (UTC)

Just checking some stuff now, there seem to be a myriad of factors that play a role in vasculogenesis, most notably various Vascular Endothelial Growth Factors (VEGF). That article's point, however, is that you also need the right receptors. There's also a protein discovered a year ago that ends up being responsible for differentiation into different vessel types. Essentially, it seems that initially there's just endothelial tissue, but by week 4 the embryo is starting to develop more specific cells for veins and arteries. This is mostly done through a process called sprouting angiogenesis, wherein endothelial cells "sprout" off the main vessel, then connect back, expanding the original. ~ Amory (u • t • c) 14:12, 21 April 2010 (UTC)

I think it's called angiogenesis and the regular arrangement is really just for the large bore vessels we fondly refer to as arteries and veins. When you take a step down to arterioles and venules (not to mention metarterioles, capillaries and the same levels of lymph vessels), there are no names (except for vague reference to specific plexi) because there is such variation. I'd say the large vessels are so consistent because they body relates to them as much as it would to an organ -- they are necessary for survival. Then again, there's always transposition of the great vessels if you'd like to peruse some variation. DRosenbach ^{(Talk | Contribs)} 02:47, 22 April 2010 (UTC)

Genotype and drug resistance

If a creature is resistant to a drug, its genes are certainly modified in a way that the creature exerts resistance. Here, i wonder whether that particular gene which is mutated codes for a different protein which is obviously new for the bodily functions. Cockroach has always been a wonder to me as it quickly adapts or is resistant to many types of poisonous drugs when administered against it. please explain the phenomenon behind the 'genotype and drug resistance' and also let me know if cockroaches are 'special'in evolving better - Anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 09:21, 21 April 2010 (UTC)

When a species evolves some kind of resistance to drugs or disease or whatever, that change will likely be a genetic one (there are a few other possibilities - for example: a new kind of gut flora might be picked up from the environment somehow that is subsequently passed from one generation to the next). If genetic then it would have to be in genes that are expressed in some way (versus "junk DNA") - which means that either some new protein will be formed or some "normal" protein will cease to be formed, or (most likely) there will be a very small change to an existing protein. SteveBaker (talk) 13:04, 21 April 2010 (UTC)

Also note that more complex animals can exhibit behavioral changes to adapt to a toxin. These can then be passed down from generation to generation. For example, some monkeys eat charcoal as an anti-toxin. Of course, avoiding or limiting exposure to the toxin is far more common. StuRat (talk) 13:12, 21 April 2010 (UTC)

Also, there is no reason to believe that roaches evolve better than any other animal. Dauto (talk) 14:14, 21 April 2010 (UTC)

Remember that individuals don't evolve, populations do. A certain cockroach will not see a change in its DNA, but many many generations later, the population living under your or my sink may have a higher proportion of those with resistance. ~ Amory (u • t • c) 14:16, 21 April 2010 (UTC)

(after edit conflict) See Xenobiotic metabolism. There are many enzymes in the body that detoxify various substances, and each of the genes for these enzymes can have different alleles in the population that result in slightly different enzyme activities. Thus, individuals in a population will have different combinations of genes for drug metabolizing enzymes that give them a unique enzymatic profile. The most likely explanation for development of drug resistance in a given organism is NOT a new mutation that somehow generates a novel enzyme that can break down a particular compound, but rather selection for those genotypes that most effectively neutralize the compound. It's a great example of population genetics and natural selection. Cockroaches are not (to my knowledge) any different than the rest of us in terms of drug metabolism; they just have faster generation times and are the subject of external selective forces that magnify a process that would otherwise happen very slowly. --- Medical geneticist (talk) 14:22, 21 April 2010 (UTC)

is clozapine antiaromatic?

The seven membered ring seems to be ... does the molecule try to "prevent" this by making the protic nitrogen between the two rings sp3, e.g. basic? John Riemann Soong (talk) 11:02, 21 April 2010 (UTC)

I'm not sure yet, but in my searching on Wikipedia I've discovered that the seven member ring appears to be an Azepine derivative. There are many derivatives of this, and they all would appear to have the same problem. Buddy431 (talk) 14:22, 21 April 2010 (UTC)

Here's (I think it's free) a paper discussing Azepine and Dibenzazepine. Yes, it appears that they are antiaromatic (presumably Clozapine would be too). They can partially relieve this by protonating the nitrogen and forming a Homoaromatic cation. Funky stuff. Buddy431 (talk) 14:30, 21 April 2010 (UTC)

Very interesting. I wonder what significance the enamine motif comes into play. I'm kind of puzzled by the 7-membered cyclisation step in the article's given synthesis of clozapine, I would expect the amide center to be very non-electrophilic (being an amide, having a phenyl ring donating into it + enamine donating electrons by proxy). John Riemann Soong (talk) 18:17, 21 April 2010 (UTC)

John, thanks for bringing this up. It has reminded me to fix the image at Clozapine, which incorrectly shows a planar diazepine ring.

The structure of clozapine has been determined by X-ray diffraction: Acta Cryst. (1982). B38, 1750-1753 and J. Chem. Soc., Perkin Trans. 2 (1976) 1415-1420. The ring is actually puckered, as is the case for all the diazepines I've come across. When I made File:Clozapine-3D-vdW.png in 2006, I didn't know about antiaromaticity and Accelrys Discovery Studio Visualizer incorrectly minimized the ring to a planar geometry.

Hückel's rule says that molecules with (4n+2) π electrons (in a planar, conjugated ring) are aromatic, whereas those with (4n) π e⁻ are antiaromatic, where n is an integer. Clozapine has 8 π e⁻, which is 4n with n = 2, and is thus Hückel antiaromatic. Addition of two more π e⁻ would result in an aromatic dianion (10 π e⁻, 4n+2 with n = 2), and removal of two of the eight π e⁻ would give an aromatic dication (6 π e⁻, 4n+2 with n = 1).

Ben (talk) 19:56, 21 April 2010 (UTC)

Hmm I do wonder because depending on how you draw the benzene ring (or interpreted a resonance structure), you can make it seem like it has 6pi or 10 pi electrons. Of course this is at cost to benzene's own ability to have multiple resonance structures, so there's a tradeoff. Also, you can draw resonance structures such that you have one big ring of 16 pi electrons. Do you know what I mean? (Or should I draw them in chemdraw?) It's these alternate aromatic-looking ring structures, in competition with the antiaromatic ones, that intrigue me. John Riemann Soong (talk) 21:29, 21 April 2010 (UTC)

How can you make a benzene ring have 10 pi electrons?

Ben (talk) 18:36, 26 April 2010 (UTC)

Fish trachea

Do fish possess a trachea? Should the vertebrate trachea article be renamed to tetrapod trachea? -Craig Pemberton 15:18, 21 April 2010 (UTC)

No, and no. The trachea connects the mouth with the brachii in the lungs. Fish don't have lungs. Even lungfishes don't have tracheas. The article name is fine. -- Flyguy649 ^talk 16:55, 21 April 2010 (UTC)

Thank you. That means article title is misleading because it suggests that a trachea is a vertebrate synapomorphy. -Craig Pemberton 17:52, 21 April 2010 (UTC)

No really. The naming is to distinguish between vertebrate tracheas and invertebrate tracheas. -- Flyguy649 ^talk 18:31, 21 April 2010 (UTC)

Scientific Principle

What's the name of the scientific principle where the conclusion of a study seems obvious after it's proven but it seemed unlikely prior to study? TheFutureAwaits (talk) 16:50, 21 April 2010 (UTC)

That's not a scientific principle, but perhaps it's covered by the expression "hindsight is 20-20". StuRat (talk) 16:54, 21 April 2010 (UTC)

Peripherally related, look at disruptive technology / disruptive innovation. For example, after the computer mouse, its concept seems obvious and its implementation seems trivial - but before Douglas Engelbart, nobody really thought about controlling a numerical calculating machine with your bare hands! Nimur (talk) 17:11, 21 April 2010 (UTC)

That's not even remotely true! The mouse was neither invented first - nor marketed first - nor in common use first! I used touch-screens (invented in the 1940's), trackballs (invented in 1952) joysticks (invented in 1944) and digitizing tablets (invented in 1888!) in college and in my first job around 1977 - long before the mouse (invented in 1963) appeared on the market in 1981. The significant difference Engelbart made was in reducing a $500 device to a $10 device that achieves 20% of the functionality of the most common alternative - (which at the time was probably the digitizing tablet). Nowadays, the little digitizing tablets you find on laptop computers (now we call them "touch-pads") are comparable in price to the mouse - but have lost most of their functional benefits because they are only used to (poorly) emulate a mouse. You couldn't describe the mouse as a significant breakthrough - either scientific or technological. The only real claim to fame is cheapness. SteveBaker (talk) 18:20, 21 April 2010 (UTC)

Well, the use of a mouse in an operating system GUI was a significant breakthrough. Comet Tuttle (talk) 21:07, 21 April 2010 (UTC)

Interestingly there are commercial examples as well of ideas which people thought they hated but which were successful in practice. Selling sandwiches in Service Stations is one (all the market research implied the association of a service station with the unpleasant taste and smell of fuel would make it impossible). However it turned out to be commercially very successful (albeit with airconditioning in the shop). --BozMo talk 17:18, 21 April 2010 (UTC)

There is no such "principle." --Mr.98 (talk) 17:53, 21 April 2010 (UTC)

Psychology refers to this as Hindsight bias. ☯  Zenwhat (talk) 18:03, 21 April 2010 (UTC)

Thanks Zenwhat, that's exactly what I was looking for. And Mr. 98 maybe don't be so quick to dismiss questions in the future! TheFutureAwaits (talk) 21:09, 21 April 2010 (UTC)

He didn't dismiss the question. He simply pointed out (correctly) that this is not a scientific principle. Dauto (talk) 22:15, 21 April 2010 (UTC)

Though in all fairness I probably could have been more creative and less literal in interpreting what was intended by "scientific principle"—I thought the OP was implying that it was some basic principle of science that it would work in this way (that is, a statement about science rather than one provided by science, in this case, psychology). I see now that a different meaning was intended. --Mr.98 (talk) 01:28, 22 April 2010 (UTC)

Muscle tingling after exercise?

Why might a person feel a pleasurable tingling sensation in the muscles worked, after strength training?

This Yahoo answers page attributes it either to reduced blood-flow, dehydration, or decreased oxygen supply, but all these things affect the extremities -- not the muscles worked during exercise (like shoulders, chest, or abdominal muscles).

To clarify, the sensation feels similar to a massage and seems to occur near the end or after recovering from delayed onset muscle soreness. 96.255.178.76 (talk) 17:59, 21 April 2010 (UTC)

I'm feeling this right now a bit in my lower legs and feet. I have run for half an hour about 20 minutes ago and I'm now sitting in front of the computer. I think this is just the blood flow. During the exercise this was at a huge level compared to rest. If you stop running then the blood won't flow at the usual resting rate immediately. This is also very clear from my heart rate. During the exercise it was about 160 bpm and now it is 58 bpm but in rest it should be about 40 bpm. Count Iblis (talk) 19:20, 21 April 2010 (UTC)

40 bpm, are you sure? That seems really low to me, I thought that 60 was more common, unless you are an Olympic class athlete. Googlemeister (talk) 19:43, 21 April 2010 (UTC)

I've had a resting heart rate below 50 at least since primary school. My primary school teacher told us one day how to measure the heart rate. and I was the one with the lowest in class, which my teacher verified. I also noticed that I actually don't need to put my finger on my wrist to feel and count my heart rate; I can usually feel my heart beating in my body. When running this is very convenient, no expensive heart rate monitors ae needed, I can just look at my watch for ten seconds and count the number of beats.

I don't think I'm an Olympic class athlete. My recuperation time is way more than that of top sporters. My heart rate takes quite a long time to return to the resting value. I will typically exercise two or three days in a row. On my resting day, my resting heart rate will be slightly higher e.g. 43 bpm instead of 40 bpm. A top sporter will be able to pack my three day training effort into a single day and still be fully recovered only a few hours later. So, unfortunately, I've a long way to go before I become as fit as Miguel Indurain "His cardiac output is 50 litres a minute; a fit amateur cyclist's is about 25 litres a minute. Also, Indurain's lung capacity was 8 litres, compared to an average of 6 litres. In addition, Indurain's resting pulse was as low as 28 BPM". Count Iblis (talk) 20:57, 21 April 2010 (UTC)

Well mine comes out at 72bpm, so I must be in lousy shape :(

Count Iblis, the Yahoo seems relevant to your case, because it's cardio exercise and you feel the tingling in your extremities. I'm talking about strength training where the tingling isn't in the extremities, but the particular muscles that were worked on. 96.255.178.76 (talk) 21:33, 21 April 2010 (UTC)

The resting heart rate's normal range varies by age. It could be up to even 95 bpm and still be normal. However in the tachycardia range at rest is when it becomes dangerous to the body for prolonged periods. ~AH1^(TCU) 23:51, 21 April 2010 (UTC)

PDF

how do i make a pdf form writable so i can fill it out on the computer instead of printing it out? —Preceding unsigned comment added by Tom12350 (talk • contribs) 18:21, 21 April 2010 (UTC)

Specifically, there are means of adding editable form fields to PDFs such that someone with the free Reader software can fill out the page electronically. I'm not familiar enough with the software to comment on how exactly that's done. Then there are intermediate solutions, with varying effectiveness, like importing the PDF into a word processor and typing over it. Generally, though, if you have a PDF you've downloaded from somewhere, there is no provision for changing it. — Lomn 20:32, 21 April 2010 (UTC)

Well, the ordinary use model is that it should not be changed. That's not the same thing as saying it can't be changed. See PDFedit for software specifically designed for that purpose. I haven't tried it and can't tell you how well it works. --Trovatore (talk) 20:47, 21 April 2010 (UTC)

Adobe Acrobat has a "typewriter" feature which works pretty well for filling out forms (it lets you just add text wherever you want). Unfortunately you have to have (or have access to) the expensive, full-featured version of the program for that to work. Googling a bit, there are suggestions as to how to use Microsoft Word to do something like this, though how good it will look, I don't know. This site claims to allow you to easily fill out PDF forms that do not have form fields, as does this software... I haven't used either, personally. There's no real difficult technical reason that this shouldn't be doable for free. --Mr.98 (talk) 20:47, 21 April 2010 (UTC)

In addition, Acrobat allows you to add form fields to make it into a proper form (there's also an automatic conversion thing, but from my experience it doesn't work very well) so it can then be filled in by people with just the reader if you get the settings right. I'm not BTW particularly sure why this is on the science desk since it's better suited to the computing desk Nil Einne (talk) 23:49, 21 April 2010 (UTC)

That's true, though that's generally only good for if you have a form you want others to fill out. It's a whole lot of hassle for a form you're filling out yourself (Typewriter works a lot better for that). Agreed that this should be moved to computing. --Mr.98 (talk) 01:23, 22 April 2010 (UTC)

Personally I prefer the form way so it's easier to change and edit in the future including from Reader if necessary, but then again I'm a stickler for these sort of things. Depending on the complexity of the form and how accurate you want it to be it doesn't take that long, say 10-20 minutes Nil Einne (talk) 14:29, 25 April 2010 (UTC)

Foxit Reader also has a typewriter mode, and is free. -- Coneslayer (talk) 13:56, 22 April 2010 (UTC)

That is good to know for future reference! --Mr.98 (talk) 21:51, 22 April 2010 (UTC)

Force of a magnet on metal

Is there a way to calculate the force induced on a piece of metal by a magnet (assumed it is a simple dipole), if you know the magnet's field strength, the distance? There is one more variable necessary, one that makes the reaction of aluminium and iron different. I think it is called 'magnetic permeability', but I might be wrong. But given that variable as well, how would you find it? KyuubiSeal (talk) 19:17, 21 April 2010 (UTC)

It is not easy to write an equation which accurately states the strength of attraction to a piece of metal from a permanent magnet or electromagnet. It is not as simple as using Ohm's Law to calculate the current through a specified resistance, since geometry is critical. There are complicated edge effects due to fringing. In practice, a magnet which fits smoothly against the metal will lift far more than one which is not an exact fit. The strength of the the magnet, the thickness and nature of the metal, and the shape of the poles are important. As you note, the distance from the magnet poles to the surface is important. See Magnet# Calculating the magnetic force which gives some simple cases but not quite the situation you described of a dipole separated from a piece of metal. Edison (talk) 19:41, 21 April 2010 (UTC)

Cast iron object unknown

Hello. Can someone help identify the type of thing this cast iron object is.

object

other side

Very faint markings on the second side appear to say "DINNY" ? Sf5xeplus (talk) 19:52, 21 April 2010 (UTC)

Could you give us an estimate for the size and weight? I am having trouble telling the size.

It looks like a cover plate for a hole in a flat metal sheet. Graeme Bartlett (talk) 22:04, 21 April 2010 (UTC)

The squared sheets maybe A4. Could it be a gearbox? The short arc may be an idler gear control. Swing it (the idler gear) out of the way, then bring the other long arc lever (controlling the driven gear) to the opposite extreme, then swing the idler gear back -to re-engage. Magically, the contrivance now revolves on the opposite direction.--Aspro (talk) 22:21, 21 April 2010 (UTC)

The short arc is better suited for a safety stop that blocks the main (longer) arc movement. NVO (talk) 08:24, 22 April 2010 (UTC)

Is it flat or rounded? If it's rounded, I've seen similar plates on axles of lorries. --TammyMoet (talk) 08:36, 22 April 2010 (UTC)

~10" diameter , ~1/2" rim thickness (less inside rim), it's flat.

Where on a truck? Did you mean the plate that covers the differential - eg File:T138 podvozok.jpg - that's usually curved like you say? or something else. Sf5xeplus (talk) 11:00, 22 April 2010 (UTC)

Yes that's the one. --TammyMoet (talk) 13:53, 22 April 2010 (UTC)

I think it is a cover plate through which two levers protruded with which an operator could control a mechanism. That is what others seem to be saying above. I don't think it has to be automotive in origin, though gear shift and clutch do seem to be a possibility, as suggested by others above. Bus stop (talk) 11:12, 22 April 2010 (UTC)

How would one calculate the total entropy of the sun?

How would one calculate the total entropy of a star, for example the sun?

I was adding an entry to Orders_of_magnitude_(data) (which also covers information and entropy -- or should do). The entropy of the sun is quite interesting in its own right as the entropy of a great big physical thing; but, also, as something to compare with the entropy of a one-solar-mass sized Schwartzschild black hole.

Using the Black Hole entropy formula, and 2.0 × 10³⁰ kg for the mass of the sun, the Black Hole entropy works out as about

1.4 × 10⁵⁴ J K^-1 = 1.0 × 10⁷⁷ nats = 1.5 × 10⁷⁷ bits.

For the sun, Bekenstein (1973), Black Holes and Entropy, Physical Review D 7 2338 gives a figure for the entropy as about

10⁴² erg K^-1 = 10³⁵ J K^-1 = 7.2 × 10⁵⁷ nats = 10⁵⁸ bits.

Other sources say "about 20 orders of magnitude less than a solar mass black hole" or "about 22 orders of magnitude less".

So: how does one calculate the entropy of a star? I believe it's a standard question on some astrophysics courses, to calculate the entropy of the sun, and compare it to the entropy of a neutron star of the same mass. But I haven't seen any answers.

It's straightforward to calculate what the entropy of the same mass of helium and dissociated hydrogen would be at S.A.T.P.

There would be about (3/4) * 2.0 * 10^30 / (1.0 * 10^-3) = 1.5 * 10^33 moles of dissociated Hydrogen, and (1/4) * 2.0 * 10^30 / 4.0 * 10^-3 = 1.25 × 10^32 moles of Helium. If they were at S.A.T.P., the standard molar entropy would be about 100 J K^-1 (126.0 J K^-1 for Helium), which would give a total of about 1.6 * 10^35 J K^-1 = 1.6 * 10^58 bits

Of course, the temperature of the sun is not 25°C, nor is its pressure 1 atm.

According to the Sackur-Tetrode equation for a monatomic gas, S = N (ln (V / N Λ³) + 5/2) nats, where Λ is the thermal wavelength, Λ = h / sqrt(2π m kT)

Plugging in m=1.67 × 10^-27, T=15 × 10⁶ I get Λ=4.49 × 10^-13 m Then with N = 1.5×10³³ * Avogadro's constant, = 9.0×10⁵⁶, and V = 1.4×10²⁷, I get S=9.0×10⁵⁶ * 19.2 nats = 2.5×10⁵⁸ bits.

Is that along the right lines? Are there other contributions I've missed?

I guess there should also be a contribution from the electrons, since it will be a plasma. The mass being (1/1836) smaller would give a thermal wavelength 43 times larger, so 3 ln 43 = 11.2 nats fewer per particle, so about 8 nats per electron, taking the total entropy up to about 3.5×10⁵⁸ bits.

So the numbers seem to be in about the right ball-park (if I haven't made any numerical errors), but does anybody have a reliable source or lecture notes for the method that would be more dependable? Jheald (talk) 21:37, 21 April 2010 (UTC)

You also need to add the contribution of the photons. If I remember correctly, the entropy density of a photon gas is 4/3 u/T where u is the energy density, which in turn can be related to the Stefan-Boltzmann law via sigma T^4 = c/4 u. Count Iblis (talk) 22:04, 21 April 2010 (UTC)

Thanks. Right, so again taking V=1.4×10²⁷ m³ and T=15×10⁶ K, I get U = 4σVT⁴/c = 5.4×10⁴⁰ J calculation, so S = 4U/3T = 4.8×10³³ J K^-1 calculation = 5.0×10⁵⁶ bits.

So important, but not as important as the contribution from the protons and electrons. Jheald (talk) 12:03, 22 April 2010 (UTC)

This model homework solution (problem 3.15), extending an earlier problem 1.17c (cf our Equipartition of energy#Stellar physics), finds that a star has a heat capacity C = -(3/2) Nk, giving an entropy S = constant - (3/2) N K ln(T).

This suggests that the entropy is smaller the larger the temperature is. (Based I think on the faster the particles are going, the further down the gravity well they must be, so the more negative the gravitational part of their energy must be). I'm not at all sure whether or not this and the previous calculation - which basically ignored gravity - can be compatible. Would need to think more about this. Jheald (talk) 20:52, 22 April 2010 (UTC)

Note that you are using some effective volume in the calculation. It is that volume which is relevant here. In principle you can model the whole Sun and then you will see that gravity determines the size of the star which then turns out to depend on the core temperature. Count Iblis (talk) 03:18, 23 April 2010 (UTC)

I found a nice discussion in qualitative terms of the entropy changes in star formation here which gives a good big picture, and touches on the negative heat capacity (how removal of heat from the system actually increases its temperature; the star contracts, its entropy falls, but that is more than made up for by the increase in entropy in the rest of the universe on transferring the heat there.

You're right. The two calculations should be marryable together. The first simply uses an approximate static picture, of a constant temperature and pressure inside an effective volume to give a ballpark estimate. The second captures more of the dynamic responsiveness of what's going on, and (I think) probably lends itself reasonably easily to a simple model of the temperature and the pressure falling off with distance in a spherically symmetric way. The Wallace paper linked [3] I think has the equations, but I haven't yet had time to go through it, to check whether it comes to a numerical answer, and how this compares to the rough-and-ready estimate in the first calculation above. Jheald (talk) 12:46, 23 April 2010 (UTC)

April 22

Dry ice engine

I built a dry ice engine (sort of like a steam engine) that works by exposing dry ice to ambient temperatures. It does not really run very fast even when I put shavings in water because the water often freezes. What I'm worried about is under what circumstances the dry ice can sublime. Can it sublime in an open container if I increase the temp of the container using solar radiation? 71.100.1.71 (talk) 06:18, 22 April 2010 (UTC)

Sublimation is the change from solid to gas, without melting and going through a liquid phase. Under normal pressures, dry ice always sublimes to CO2 gas. --Phil Holmes (talk) 08:37, 22 April 2010 (UTC)

Do you realise, that when the pressures are matched, it will not run as fast as a steam driven engine anyway? Carbon dioxide is a heavy molecule and therefore will not expand as fast as steam. You can work out the viscosity from these equations [4]. To get a more practical comparison, take three balloons. Fill one with carbon dioxide the second with air and a third with (say) methane; and all to the same pressure (diameter). Use a felt tip pen to identify the gases within. Let them all go at once. You will see very clearly just how viscous the carbon dioxide is. --Aspro (talk) 10:43, 22 April 2010 (UTC)

You mean let them go with the opening not tied, right? Otherwise you would be seeing the difference in density. I would put my money on Hydrogen in either case, for it to rocket faster or rise faster. Edison (talk) 20:08, 22 April 2010 (UTC)

Right! Just let them deflate. I would put my money on hydrogen as well (but I suggested methane, because mains gas is commonly available). This property of hydrogen, is why it used as the working gas for the Super High Altitude Research Project and of course - fuel for rockets. Hydrogen and fluorine would be better, as the mass is lower still – but I digress. I think this viscosity point, would help the OP not to bust a gut by trying to get too much from his apparatus.--Aspro (talk) 22:13, 22 April 2010 (UTC)

Hydrogen is readily available, if you have a tank of dilute sulfuric acid with a couple of large carbon electrodes and a source of DC current as I do. In generating stations from the 1930's onward it was common to have giant high voltage generators filled with hydrogen, since it insulated and convected heat and had very low viscosity to interfere with the rapid rotation of the armature. It seemed nonetheless like madness to fill a big sparky generator with hydrogen (a la Hindenburg disaster) but the absence of oxygen in the generator enclosure allowed a successful and efficient operation of the generators. Edison (talk) 04:42, 23 April 2010 (UTC)

Galactic feature

On this cool website[ http://www.chromoscope.net/] you can see our Galaxy in all sorts of wavelengths. I'm curious: what's the feature above the galactic centre, visible in X-ray, hydrogen-alpha and microwave, but only vaguely in visible? --TammyMoet (talk) 08:33, 22 April 2010 (UTC)

You are probably referring to Galactic halo. We don't have much of an article on it, unfortunately; so library seems like the only option for now. --Dr Dima (talk) 09:29, 22 April 2010 (UTC)

I could be mistaken but I think the bright orange star under the blue stars in the region you are talking about is Antares, part of Scorpio. in X ray one of the objects you are talking about looks like a galaxy to the left of the top blue stars, maybe in the region of Messier_107 but i don't think it's that, i'm having a bit of a look and I can't see any big galaxies right there near scorpio.. I have to run away but i'm sure with some more digging you might find it.. Vespine (talk) 09:39, 22 April 2010 (UTC)

I just re read both posts and I'm not sure I'm talking about the same thing you are :) Vespine (talk) 09:41, 22 April 2010 (UTC)

If you look at it in microwave you can see a huge lump which looks like it's split off from the galaxy. In hydrogen-alpha it looks like two swirls, only one of which corresponds to the ?Antares region. It's within the Galactic halo, but is a clearly defined feature, and I wondered if someone could point me at more details for it, as it's not there in visible light. Oh and I don't know how to split off the new post from the bottom of this - can someone sort it out for me please? Thank you! --TammyMoet (talk) 10:49, 22 April 2010 (UTC)

I think you're referring to the North Polar Spur. It's thought it may be due to supernova remnant(s) that happened in our local part of the Galaxy. Unfortunately there doesn't seem to be a Wikipedia article on it. See [5] for more info -- Stuart Lowe (Developer of Chromoscope) 130.88.24.249 (talk) —Preceding undated comment added 14:28, 22 April 2010 (UTC). Apologies for not dating it; someone said 3 tildes inserted the date but they obviously didn't. (16:41, 22 April 2020)

Thanks for this but I'm still confused. If the blob at the side of it is Antares, isn't Antares in the southern hemisphere of the sky? I had thought it might be the rho Ophiuchus nebula, but I can't judge the scale well enough to determine whether the rho Oph nebula is part of the Antares O-B association, which would mean this blob is not that one. On a related topic, can anyone point me in the direction of a 3-D map of the Galaxy? Thanks. --TammyMoet (talk) 15:31, 23 April 2010 (UTC)

I've now had a chance to follow some of the links from our Milky Way article, and I concur with Vespine that the bright orange star is Antares. However, the hydrogen-alpha blob seems to be next to it, and I've not managed to track that down at all. (BTW thanks for sorting me out!) --TammyMoet (talk) 14:10, 22 April 2010 (UTC)

Just insert a ==New heading== in between. (done)

Just felt curious about one thing though, when we observe through X-rays the picture seems to be like torn up or clawed, as in like a punch or a strike from a tiger paw or something like that, which we cannot observe in any other image. what makes it so?

electromagnetic wave - atom - electrons

How can i make an arrangement to knock off electrons from an atom by making an electromagnetic wave of a particular wavelength,say radio wave, incident on the material? —Preceding unsigned comment added by Randeep d (talk • contribs) 10:25, 22 April 2010 (UTC)

How long do you want the electron to stay knocked off? If you want to "permanently" knock it off, or ionize the atom, that is much more difficult than "temporarily" knocking an electron into a different energy state. If you just want to knock electrons around, you can use a semiconductor and use the electromagnetic wave to bump electrons into conduction bands. You can do this with a lot of things; a photodiode is pretty cheap and safe, and whenever light (electromagnetic waves in the visible spectrum) land on it, it will produce a voltage, because electrons are getting "knocked" into conduction bands. To completely ionize gas is more complicated. You can make ionized gas in a lot of ways, especially if the gas is already at high (effective) temperature and low pressure. This happens to some extent inside a fluorescent light bulb, (and to some extent, inside an incandescent lightbulb too). A vacuum tube operates on the principle of freely flowing, thermally activated electrons, and could be considered a sparse plasma, where the quantity of excited electrons is controlled by an input electromagnetic signal. If you move up to higher and higher frequencies, your radiation will be able to knock electrons off of atoms in almost any condition. For example, a microwave oven, using microwaves, can ionize grapes (the grapes, being saturated, impure watery spheres, form conduction channels; as large currents start to flow, an effective high voltage electric potential builds up, locally concentrating the electric field near the grape, resulting in dielectric breakdown that ionizes the air and portions of the grape). (The jury is out on whether this is safe). Watch out with ionizing radiation in general, though, because if you have enough energy to ionize atoms, you have enough energy to potentially harm yourself. Radio waves usually do not have enough energy to really ionize anything. Nimur (talk) 12:02, 22 April 2010 (UTC)

As Nimur says, ionising atoms requires high energy/short wavelength photons - ultraviolet or shorter. And anything that can ionise your target substance can also ionise your own cells, which is potentially very harmful. You might want to take a look at our article on radiation shielding. Gandalf61 (talk) 12:14, 22 April 2010 (UTC)

It's worth stating that the microwave/grape experiment does not technically use ionizing radiation. As Gandalf just pointed out, direct ionization occurs at higher frequencies than microwaves operate at. The grapes ionize as a secondary effect due to dielectric breakdown. Nonetheless, this experiment can be harmful for other reasons, not the least of which is a fire hazard. There are other, safer (read: "safer", not necessarily "safe") ways to get a similar breakdown: a spark gap can be formed using a piezoelectric barbecue igniter. Or you can buy one of those plasma globe toys - because they have an evacuated gas chamber, they can operate at much lower, safer voltages. Nimur (talk) 15:01, 22 April 2010 (UTC)

Didn't Einstein get a Nobel for explaining something like this viz the "Photoelectric effect?" Edison (talk) 04:37, 23 April 2010 (UTC)

so can i use a low intensity uv ray to knock out electrons..?? Which semionductor material shall i use & what about the distance betwen the radiator & the exciter module & will it be safe to use low intensity uv rays for the purpose..?? —Preceding unsigned comment added by Randeep d (talk • contribs) 12:34, 23 April 2010 (UTC)

You can use regular visible light, as I explained above, to activate the photoelectric effect. You can buy photodiodes on the internet, or at a local electronics store. DigiKey is one such vendor. This one is about $1 per unit, and should be sensitive to either infrared or visible light. UV is more hazardous, not to mention harder for a hobbyist to produce, but there are definitely photodiodes that respond only to UV. Nimur (talk) 14:08, 23 April 2010 (UTC)

Wouldn't a Photomultiplier tube be more fun than a photodiode? Edison (talk) 23:52, 23 April 2010 (UTC)

A dim Sparky?

(REVISED) I needed electric put in for a fan and had a person come in to run the electric for it. PROBLEM started when he noticed that 9 wires was going throught the 1/2" conduit. We removed the ground wire in which he decieded to run 2 more wires through, but they got stuck and we had to repull wires down and back through the conduit which got stuck. We spent 12 hours with just getting 1 wire through the (black), and found out that we could not use groung wires because they were used for the GFI brakers. these kept on popping when ever he connnected the common wire so he had to reattach all the wiring to the correct wires he had cut and did not label so that each room would work properly.(4) BEDROOMS I still did not have the wiring for the fan, or the conduit. I put in the box and the conduit for the fan, but I still have to get the common from the bathroom which does not have a GFI braker connected in the box in the basement, I hope this will work?? While here had to talk to someone else about this issu. If he were a licenced electrican should have know about GFI brakers. Instead my son-in-law fiquired out the problem and solution. But now that person who was here wants to charge $4oo SHOULD I say Yes and pay HIM or Not —or LOWER HIS PRICE?? —Preceding unsigned comment added by 24.15.246.106 (talk) 15:51, 22 April 2010 (UTC)

This isn't really a science question, and I'm not sure that it's really a Ref Desk question, but here goes:

You are free to negotiate a fair price. Either of you are free to take the other to court depending on how the payment process goes. The usefulness of either procedure will vary depending on where you are. Generally, though, for purposes of deciding fair payment, I'd consider the following:

1. Did he quote a price for the job beforehand? No Quote
2. Was the intended job completed?JOB WAS NOT COMPLETED
3. Did he consult with you before doing the additional work? he did but he wasn't to sure if it would worK. HE SHOULD OF THOUGHT OF IT BETTER.
4. Was the additional work relevant or necessary (to the job at hand, or to the safety of the house)?unnecessary

Particularly if the fan isn't wired yet, it may be reasonable to agree to pay him for the work done once the original job is complete. — Lomn 18:22, 22 April 2010 (UTC)

It sounds like he is not qualified enough to be allowed to finish the job!--Aspro (talk) 18:28, 22 April 2010 (UTC)He does this on the side (he does hvac)He consulted an electrician friend about the GFI AFTER HE HAD PROBLEMS RECONNECTING WIRESBACK UP.

One thing to think about is his side: He'll say, it's not my fault the wires got stuck, that's how your house was laid out, and I stuck by it and didn't give up till I finished the job (or as much as was possible). I am not telling you what to decide, I'm playing devils advocate a little, so you see his side, and maybe that can help you decide. Ariel. (talk) 19:07, 22 April 2010 (UTC)

Also, there are other ways of running wires if they won't fit through a conduit like that. The simplest would be to remove all the ground wires, and run a single fat one through the conduit, and then split them again after. You can theoretically do that with the white (neutral for those of you not in the US) wires too, but it's probably not to code. Don't do that with the black (hot, or what would be red in europe) one though. The correct way to handle that is a sub-panel. You run one large wire, then attach to a sub-panel with a small number of breakers to handle the rest. Ariel. (talk) 19:07, 22 April 2010 (UTC)He did pull the ground which still left 8 wires in the 1/2 in conduit.

Note: He said we did not need the green ground so that is what we used for pulling up the 2 wires for the fan. WE HELPED him throught the day to try to resolve the problem with getting wiring finished but to only got worse, finally got it done. that day

BTW, I'm not sure why the breaker kept popping when he hooked up the ground - is it a GFCI breaker? But that's is not normal, and possibly dangerous (sounds like electricity is flowing through the ground, and that's not normal), and I have to agree with Aspro that he sounds like he's over his head. Ariel. (talk) 19:16, 22 April 2010 (UTC)

Yes,. He is talking about ground-fault circuit interrupters not current trips. As he is using the $ sign, I presume he is in the US. Most states (I think) now require companies to be licensed to do this kind of work and a sparky with such a permit would not make this sort of mistake. --Aspro (talk) 19:25, 22 April 2010 (UTC)

Anything said here is just as general information and not technical advice or consultation, per the rules of the Reference Desk. The explanation you gave does not really make sense as stated:"We spent 12 hours with just getting 1 wire through the (black), and found out that we could not use groung wires because they were used for the GFCI, and the bracker kept on popping when ever he connnected the groung so he had to reattach all the wiring to the correct wires he had cut so that each room would work properly." You pulled out 8 wires and tried to pull in 10, but could only pull in 9? How many circuits did the 8 conductors represent originally? By "groung" do you mean neutral? The National Electric Code (U.S.) has strict limits on how many conductors of what size and insulation type can be installed in a given conduit size. Table 3 of the NEC says how many conductors can go into a conduit of a given size. See [6] for instance, which implies that 9 #14 XHHX (such as THHN) in a 1/2 inch conduit. Fewer could go in if the wires were larger, such as #12, or if the insulation were different, such as THW. Sometimes you have to run another conduit, or sometimes the loads can be reassigned to conductors, if a circuit is lightly loaded. Do not get creative if you don't know what you are doing. Only a licensed electrician should be doing the work for you. Edison (talk) 20:03, 22 April 2010 (UTC)

In rural or boondock parts of the US they do not use conduit, they use plastic jacketed "Romex" wire. There is also flexible metallic conduit called "Greenfield" and metal jacketed wire called "BX." A competent electrician can always run a circuit to where it is needed, but it may require some patching and painting of walls or ceilings, or removal and replacement of baseboards, or someone going up into the attic or down in the crawlspace to run wires. Edison (talk) 23:49, 23 April 2010 (UTC)

Romex is not "rural or boondock". Romex is pretty much universal for home use in the US (although not for commercial). Ariel. (talk) 07:23, 26 April 2010 (UTC)

Abnormal daisy

Hello, I posted a question on mutants versus developmental abnormalities here. Maybe someone could take a look. Bye, Apdency (talk) 17:54, 22 April 2010 (UTC)

what do they do with the glass slides after a skin scraping test

do they throw them out or reuse them —Preceding unsigned comment added by Tom12350 (talk • contribs) 18:31, 22 April 2010 (UTC)

They cost about seven cents a piece. So on that basis it would cost more to wash and autoclave them, than use a new one each time.--Aspro (talk) 18:41, 22 April 2010 (UTC)

i agree it would be cheaper, but not all doctors are rational people? —Preceding unsigned comment added by Tom12350 (talk • contribs) 19:23, 22 April 2010 (UTC)

But they have to dispose of them as hazardous medical waste, which is expensive, so that might shift the economics some. Ariel. (talk) 19:23, 22 April 2010 (UTC)

what do you mean? —Preceding unsigned comment added by Tom12350 (talk • contribs) 22:41, 22 April 2010 (UTC)

We mean: that it is the opinion of some of us, that it is cheaper in pure financial terms, that the slides are used only once, and then get thrown away. In poorer countries, they could well get recycled.--Aspro (talk) 22:57, 22 April 2010 (UTC)

In the United States they are all thrown in a "sharps box" - same place the used needles are placed - and disposed of as hazardous medical waste. I cannot answer what happens in other contries. 65.96.208.10 (talk) 01:37, 24 April 2010 (UTC)

Orgasm

This might be an urban legend type of thing, but I remember hearing something about rats that were given the ability to make themselves orgasm by pulling a leaver, and they kept pulling the leaver until they starved to death.

1. is this story true and is there a Wikipedia article on it?
2. could the same technique to give a rat an orgasm be applied to humans?

Thanks 82.43.89.71 (talk) 18:48, 22 April 2010 (UTC)

What do you mean by 'leaver'? It dosen't make sense to me. Chevymontecarlo. 18:53, 22 April 2010 (UTC)

He means lever. In some parts of the US the regional accent is such that it's pronounced leaver rather than lever. (Although the spelling doesn't change of course.) Ariel. (talk) 19:19, 22 April 2010 (UTC)

I'm confused, do you mean "lea-" as in "lead" or as in "lead"? ;-) AlmostReadytoFly (talk) 08:54, 23 April 2010 (UTC)

See:Pleasure center for more info of this experiment. Dr Robert Heath was one of the first researchers that did experiments on human subjects. [7]--Aspro (talk) 18:55, 22 April 2010 (UTC)

Peter Milner and James Olds did the rat experiments. Besides the Wikipedia article on the Pleasure center, see Life magazine's article on electrical stimulation of the brain and pleasure from March 8, 1963 "Behavior by electronics" by Robert Coughlin. The Olds experiments are discussed on page 100. The rat would press the lever 8,000 times an hour until fatigue, hunger or thirst forced a brief interruption for a sip and bite and a short nap, then he would be right back at it. One rat went on like this for 3 weeks straight. Some of Olds' rats, after a series of marathons lasting "hundreds of days" seemed in better health than their contro rats. Edison (talk) 19:33, 22 April 2010 (UTC)

That was quite interesting to read, especially how he used the same methods for mind control, with some talk on how to mind control humans too. But it's also interesting that nothing seems to have come of this research. You would think after 40 years we would have these devices commonly available, but no. So much for the rule that every new technology eventually gets used for war, or to control others. Ariel. (talk) 20:21, 22 April 2010 (UTC)

Thank you everyone for the links :) I'm interested in how their brains were stimulated; did they put electrodes on their heads or was more invasive surgery involved? 82.43.89.71 (talk) 20:10, 22 April 2010 (UTC)

The method used is roughly (and don't try this at home):

Shave the head, give broad spectrum antibiotic, give 'local' anaesthetic, cut and fold back a flap of skin and remove a small section of skull. Then guide gold wire via an X-ray monitor. Wire is held in a jig to keep it steady. The subject has to be awake so that the exact position can be a confirmed by the subject. Gold is used: because it is inert in a way that stainless steel is not when passing a current. Actually, if your interested in electrical stimulation of the brain, the guy that I think started it all off was Wilder Penfield. His biography here on Wikipedia does not do his work real justice. Surf around the web for more detailed information.--Aspro (talk) 20:56, 22 April 2010 (UTC)

For interest, the science fiction author Larry Niven portrays illegal use of such addictive technology, called 'Wireheading' as a serious social problem in several novels and stories in his 'Known Space' future history series. 87.81.230.195 (talk) 21:10, 22 April 2010 (UTC)

By the way, it seems logical that the rats were indeed obtaining pleasure by stimulating the part of the brain that the researchers dubbed the pleasure center; but I don't think the researchers ever alleged that the rats were giving themselves orgasms. Comet Tuttle (talk) 21:21, 22 April 2010 (UTC)

I'd like to point out that while this was certainly an important experiment, the results were not quite as shocking as they are often portrayed. As I understand it, the rats were given a choice of two levers to press: one would give them food, the other would give them stimulation of the septal area of the brain (a reward center). The parameters were set such that the rats needed to spend virtually all their time pressing the food lever to get enough food to survive. The outcome was that they spent some time pressing the reward level anyway, and therefore didn't get enough food. When rats are given reasonable amounts of food for each lever press, they don't starve in this way. In fact, rats won't continue to press a reward-stimulus level forever without stopping even if there is no penalty for doing so -- eventually they satiate on it. (Also Comet Tuttle is right that this has nothing directly to do with orgasm. Also I'm dubious about the gold wire business -- I've implanted stimulating electrodes in the brains of rats a bunch of times, and always used stainless steel, in part because gold wire is so soft that it bends too easily. But the techniques have changed over time, and you'd have to look at the orginal paper to see what they actually did.) Looie496 (talk) 23:33, 22 April 2010 (UTC)

The original paper will probable just say 'gold wire' but actually be referring to wire that has been plated in 'pure' gold. In the past, pins and screws for holding shattered bones together had to be gold plated. The were just called gold pins and gold screws without any reference to the substrate material. Even to day, such things as stents are often still gold plated, because they are more inert. [8]. The data sheet for your stainless steel electrodes will probable state that it is 316LVM which is considered the modern medical grade. [9] (ladies; look on your body- piercing information leaflet, it will (should) be mention there as well if it is stainless steel). Beware: if you brake a leg in some countries and get it pined, you might need to go back under the knife for a second time to have them removed again after the bones have knitted, as not every surgeon in the world uses this grade (check beforehand). For electrodes in rats, 316LVM is (I would think) OK for short term use. In humans, I think it is still gold plating for the terminals due to the problems you can run into with the interaction between electrode and tissue; although the use of other materials are being explored. --Aspro (talk) 10:00, 23 April 2010 (UTC)

Descriptions above are not accurate in every case. Many experimental techniques have been used for stimulation of animal and human brains Rather than wire, which would basically short out to the scalp, the skull, and diffuse brain tissue, I recall people making electrodes which had glass insulation around the conductor. Tiny holes would be drilled through the rat skulls, and microelectrodes would be inserted using a stereotaxic apparatus, based on an atlas of rat brains. One article I found at Google Books said the rats with the pleasure electrodes would cross a shock grid on the floor to get the reinforcement, that rats who were starving to death would not cross to get food (old research methods were not always pretty). I once heard Milner give a lecture in which he showed cross sections of rat brains showing the pleasure centers, and related pathways, and cited the poem: "In Xanadu did Kubla Khan, A stately pleasure-dome decree: Where Alph, the sacred river, ran, Through caverns measureless to man, Down to a sunless sea." The fit of the words to the slides was eerie. Edison (talk) 04:25, 23 April 2010 (UTC)

Passive immunity in humans

How is passive immunity in humans only temporary? Chevymontecarlo. 18:56, 22 April 2010 (UTC)

Did you read passive immunity? It means that the antibodies are not made in the recipient, but rather are given from someone else. So once they run out the immunity stops. Ariel. (talk) 19:21, 22 April 2010 (UTC)

Yes, did I spell it wrong? The lack of a spellcheck function on the Windows machine I'm using is becoming annoying...at least on my MacBook it spell checks everything I type! :) Chevymontecarlo. 19:26, 22 April 2010 (UTC)

(Switch to using FireFox - it has spellchecking even under Windows) SteveBaker (talk) 20:03, 22 April 2010 (UTC)

I am guessing there are other meanings to this other than the one I am thinking about... Chevymontecarlo. 19:27, 22 April 2010 (UTC)

Eustachian Tube

How does pseudoephedrine help clear up excess mucus in the Eustachian tube? --Reticuli88 (talk) 19:30, 22 April 2010 (UTC)

Pseudoephedrine#Mechanism_of_action. --Dr Dima (talk) 19:54, 22 April 2010 (UTC)

nicotine gum expiration

i got some nicotine gum about 8 months ago. it has no expiration date on it. i used some today and it does no have any potency or "tingle". i felt no effects from it. is it expired. it used to work well 8 months ago —Preceding unsigned comment added by Tom12350 (talk • contribs) 20:12, 22 April 2010 (UTC)

It's heat liable (unlike raw nicotine). Have you stored it in a warm place?--Aspro (talk) 20:27, 22 April 2010 (UTC)

about 76-80 degrees —Preceding unsigned comment added by Tom12350 (talk • contribs) 00:19, 23 April 2010 (UTC)

Hello. If it doesn't tingle, then you definitely need new gum. You, as someone who is familiar with relieving nicotine cravings, would be able to tell if it was good by judging its effectiveness. You said it didn't work. ;) Mrdeath5493 (talk) 07:40, 23 April 2010 (UTC)

Frequency of STDs in population

Recently a woman tried to pick me up, who was a complete stranger I had never seen before. It made me wonder - what on average are the chances of getting a sexual disease from an unprotected coupling with a) a random member of the population in the UK, and b) a promiscuous member of the population in the UK? I recall this poster http://bedazzled.blogs.com/bedazzled/2007/03/vintage_vd_post.html Actually, she was a young foriegn lady who from her pronounciation, did not appear to have been in the UK all that long. 78.149.175.91 (talk) 20:39, 22 April 2010 (UTC)

This page estimates that about 24% of people in the US have some sort of STD. Presumably the rates will be similar for the UK. Keep in mind, though, that even if you have sex with someone with an STD, the chances of contracting it are much less than 100% (probably on the order of 1% with a latex condom, with a wide variation depending on the disease, whether she is symptomatic, etc.). Buddy431 (talk) 21:44, 22 April 2010 (UTC)

Isn't it likely that random strangers who seek to have sexual relations with as many people as possible are likely to have STDs? Edison (talk) 04:13, 23 April 2010 (UTC)

Epidemiology of herpes simplex lists numbers for Herpes (both HSV1 and HSV2) in a rather scattered manner. In some countries, HSV1 is present in as much as 80-90% of the population (and contrary to popular belief, both HSV1 and HSV2 can be found orally and genitally). Depending on how you define "STD", and depending on where you are right now, you may already have one. --Jayron32 05:16, 23 April 2010 (UTC)

Pumping seawater into the volcano crater

Would pumping a lot of seawater into the crater of the recent volcano have had any good effect? What would happen? Thanks 78.149.175.91 (talk) 20:48, 22 April 2010 (UTC)

Probably a very large explosion. The heat energy of any respectable volcano is sufficient to flash-boil into steam far more water than puny humans could shift its way. It was seawater getting into the innards of the 1883 Krakatau and ca 1600BCE Thera eruptions that caused their final explosions to be much more powerful than they otherwise would have been.

Possible results might include blowing a few cubic miles of Iceland into what vulcanologists technically call "smithereens", and sending Tsunamis to devastate much of the coastlines of the North Atlantic. So, not good, really. 87.81.230.195 (talk) 21:05, 22 April 2010 (UTC)

Also, underwater volcano still erupt, so it is not like a bit of water will stop the volcano from spitting out ash and lava. Googlemeister (talk) 21:28, 22 April 2010 (UTC)

For an entertaining fictional presentation of this idea, see Jules Verne's "The Mysterious Island". PhGustaf (talk) 21:36, 22 April 2010 (UTC)

We had this exact discussion just a few days ago - I suggest you check back through the archives. SteveBaker (talk) 00:50, 23 April 2010 (UTC)

Now, to be fair, sea water has been used to stop lava flows from volcanoes, see Eldfell#Lava-cooling_operations, where pumped seawater was used to redirect lava flows away from a population center. However, stopping a river oozing rock is a different proposition than stopping a massive explosion; they are VERY different events. As mentioned a few days ago, a volcanic eruption of the type going on at Eyjafjallajökull will be entirely, 100%, unaffected by spraying it with sea water. Eruptions of this type are so large that nothing humans could muster would have any effect on it at all. It would be no more effective than pissing on it. --Jayron32 03:08, 23 April 2010 (UTC)

I agree with your assertion that it's been used to divert slow-moving lava flows far from the heart of the volcano. That's very different from what our OP is contemplating - which is pumping seawater directly into the caldera - which is a complete non-starter as an idea. SteveBaker (talk) 12:59, 23 April 2010 (UTC)

Part of me really wants someone to try pumping vast amounts of seawater into an erupting volcano, just for the fun of it. It's the same part of me that's getting impatient with the Yellowstone super-volcano and the San Andreas fault. I like big, loud geology! DuncanHill (talk) 14:59, 23 April 2010 (UTC)

Ha! You're such a catastrophe tart. 87.81.230.195 (talk) 17:38, 23 April 2010 (UTC)

Time machine

Hey everyone. My friend told me about a Discovery Channel program he'd seen, about how some scientists have taken the "first steps" towards making a time machine (haven't actually seen it myself). If I remember my high school Physics correctly, it is impossible to make a time machine because that would entail traveling faster than the speed of light, which is impossible because a) Celeritas is the fastest anything in the universe can go and b) Even reaching celeritas with a non-massless particle would require an infinite amount of energy, as energy also has mass ($m=E/c^{2}$). Can anyone clarify? 76.229.198.48 (talk) 20:52, 22 April 2010 (UTC)

We have a whole article on this: Time travel. See also Category:Time travel once you're done. Comet Tuttle (talk) 21:13, 22 April 2010 (UTC)

You're correct, with the caveat faster-than-light travel is just one way to travel in time that won't work. There are also other ways which won't work. Or, strictly speaking, those other ways are presumed not to work because (a) traveling backwards in time wrecks causality, and (b) the laws of physics seem to very neatly protect us from most possible ways of traveling backwards in time, so we suspect that the remaining ones are impossible, too (for a similar argument, see cosmic censorship hypothesis). Paul (Stansifer) 00:25, 23 April 2010 (UTC)

If that's the same programme I've also seen, the guy is Ronald Mallett. There's an extended discussion on his experiments on the WP article about him. ― ___A._di_M. (formerly Army1987) 09:28, 26 April 2010 (UTC)

I can time travel and do it on a regular basis, can only ever manage to go forwards though, one day at a time —Preceding unsigned comment added by 62.172.58.82 (talk) 14:34, 23 April 2010 (UTC)

But you don't jump one day at a time. You time travel with a speed of one day per day (there may be times where it seems from your point of view that you jumped around 8 hours). Should the SI unit for the speed of non-instantaneous time travel be s/s? Or maybe dimensionless? PrimeHunter (talk) 16:37, 23 April 2010 (UTC)

A recent article in Discover (magazine) postulates the possibility that the arrow of time is a lie. ~AH1^(TCU) 21:45, 23 April 2010 (UTC)

One stuffy nasal passage suddenly clearing itself... what physical mechanisms are at play?

This happens often enough to me that I assume it's a general characteristic of having a cold, and not some freakish personal medical event. When I have a stuffy nose, often only one side or the other is "stuffed up" - such that I can breathe through one nostril but not the other. Oftentimes, if I lay down such that the "stuffed" nostril is higher and the free nostril is closer to the bed and wait, eventually - and quite rapidly when it actually happens - the "stuffed" nostril will clear without any discharge.

I've always found this 1~3 second clearing process to be both peculiar (as one can certainly feel it happening) and interesting. Can anyone shed any light on exactly what is happening here? 61.189.63.145 (talk) 22:35, 22 April 2010 (UTC)

I always used to think a clogged nose is dried up snot or something like that. But actually it's inflamed blood vessels that swell up and block the passage. If you need temporary relief, try getting your hart rate up. For me if I run up and down some stairs about 5 times both passages open totally. Unfortunately they close again, but they will stay open at least long enough to blow your nose. Do NOT blow your nose while doing the running. The pressure from blowing will swell it up again. Wait until they are fully open, then blow your nose (if you need to). Ariel. (talk)

But of course we NEVER offer any medical advice. Edison (talk) 04:11, 23 April 2010 (UTC)

(ec)Yes, we are on(over?) the boundary here, Mr Edison. I thought that part of the effect here is that the "running" or other exercises releases natural adrenalin/epinephrine which has an effect similar to cold tablets, which often contain pseudoephedrine. It appears that both 'snot' and 'blood vessels' are involved, see Pseudoephedrine#Mechanism of action reduces snot (mucus) and vessel swelling (vasoconstriction). --220.101.28.25 (talk) 04:26, 23 April 2010 (UTC)

It is a normal and usually unnoticed feature of human physiology (and thus not in itself a medical question) that the inner tissues of the two nostrils swell and shrink slightly and oppositely in the Nasal cycle, so that while one nostril is, say, somewhat constricted but slowly widening, the other is a little dilated but slowly narrowing. Without a cold or similar infection that also swells the tissues, as Ariel mentions, neither usually becomes completely closed, but with one the more constricted phases can close one nostril completely while the other is still somewhat open, and a relatively short time later the positions reverse. The more sudden clearance probably occurs when the mucus is trying to drain due to gravity and its surface tension finally breaks. 87.81.230.195 (talk) 17:28, 23 April 2010 (UTC)

ghosts

I donot believe in ghosts ,then why i am afrid of it .Is this in our evolution —Preceding unsigned comment added by True path finder (talk • contribs) 22:52, 22 April 2010 (UTC)

My guess is you were told to be scared of them as a child, and you are unable to remove the fear even though logically you don't have it. To fix that, try to confront the fear over and over, and each time see that nothing bad happens, and even better give yourself a reward. This way you will change the association from "scary" to "reward". Ariel. (talk) 23:27, 22 April 2010 (UTC)

I recommend you read scientific scepticism and become a sceptical thinker. I'm sure your fear of ghosts will vanish. Dolphin (t) 23:31, 22 April 2010 (UTC)

It won't. Not from that. Fears are not logical. Ariel. (talk) 00:10, 23 April 2010 (UTC)

I disagree. Fears are perfectly logical. SteveBaker (talk) 00:42, 23 April 2010 (UTC)

Some are, some aren't. Phobias are irrational fears. On the other hand, being afraid of jumping out of an airplane is entirely logical (especially if it's off the ground and you don't have a parachute). StuRat (talk) 13:56, 23 April 2010 (UTC)

Humans aren't naturally nocturnal animals. We've evolved to be active in daylight. We're also 'pack animals' - we aren't generally loaners. It's not surprising then that when we're forced to be unnaturally alone and in the dark, we're nervous and our senses are heightened as we try our best to figure out what's around us. Sadly, our primary sense is sight - and robbed of that, we're pretty much left only with hearing - so the slightest sound could be a predator or something untoward like that. Modern man hasn't lost that evolutionary history - however, we are generally unwilling to acknowledge that we have all of this ancient stuff driving our behaviors. Primitive religions (and even some modern ones) tell us that the dead are all around us in "spirit" form - and some of us believe that too. We also have Pareidolia - a strong tendency to take random-looking shapes and make human faces or figures out of them. So what little sight we have left in the darkness is misinterpreted by our brains to make "ghostly" figures.

So we have a good explanation for everything we feel. Sadly, that doesn't stop us from feeling it because it's hardwired into our bodies at the genetic level. When you are alone in the dark - make a game of working out what the heck that noise was - what is that weird looking shape? You know for 100% sure it's not a ghost. Carry a flashlight in your pocket...when you see something you don't understand - stop - try to guess what it "really" is - then use the flashlight to confirm your guess. Do this enough and I guess you'll eventually stop making the assumption that there is something nasty there and start suspecting it's something innocuous instead.

SteveBaker (talk) 00:42, 23 April 2010 (UTC)

I'd like to add to Steve's assertion from a biological point of view. Humans are most vulnerable to predators at night (humans' ancestors did have natural predators, after all) when they are sleeping. It is in the night, therefore, that the sympathetic nervous system is most active, naturally. The sympathetic nervous system is responsible for emergency reaction, i.e., unmeditated, fast, fight-or-flight action. If we didn't have this, our ancestors would have been trying to figure out what the heck is going on rather than feeling the urge to run away from the funny noise in the bushes while they were being attacked and eaten. If we see something in the dark, we tend to be afraid of it even if we don't know what it is--the human who runs away from a misshapen bush lives another day, the human that sits and stares at the stalking leopard is eaten. I have to disagree with Steve's method of dealing with this fear--this amount of evolutionary hardwiring can't be conditioned out so easily. You can no more control your instinctive responses than you can control mine. --Douglas —Preceding unsigned comment added by 69.210.136.92 (talk) 03:25, 23 April 2010

I believe fears and phobias are partly evolutionary hardwiring, partly learned and partly peer-pressure. Education and positive-reinforcement experiences are widely used, successfully, to combat fear of flying, fear of heights etc. Superstitions that endured for centuries have been largely eradicated by education in the developed world. Where education is insignificant or non-existent, superstition persists, often as a means of dealing with fears. Dolphin (t) 03:48, 23 April 2010 (UTC)

The only reason anyone has to fear ghosts is that they represent some secret nameless fear deep in your psyche. In short, it's useful psychologically to fear something, and that something manifests itself in the whole 'ghost concept'. It's dark, muddy, and mystical territory, so I can't really go into any more detail. Suffice to say it relates to how you view yourself, in the context of your family, your ancestors, and the whole population of the world, deceased as well as alive. Vranak (talk) 02:55, 23 April 2010 (UTC)

There may well be some innate fear of "things that go bump in the night" along with ghosties and ghoulies. Spooks seem far less scary out in broad daylight. The distant ancestors of modern humans spent the night in trees or caves hoping that a predator or evil spirit would not "get them." Night fears may be a form of free floating anxiety. Isolation may be a factor as stated above. Edison (talk) 04:09, 23 April 2010 (UTC)

See ghost. Some fears are not rational as the fear itself may cause the outcome being feared to actually materialize. This is an example of a self-fulfilling prophecy. ~AH1^(TCU) 21:44, 23 April 2010 (UTC)

April 23

Eyjafjallajökull: Tephra color

Some images and videos of the recent eruption show tephra with distinct black or white coloring. I have two questions about this:

• What is the difference in composition between the differently colored tephra?
• Why are the two spatially separated instead of being one big gray cloud ? Also some videos show purely white or mostly black ash clouds; why does the composition and mix seemingly change with time ?

Abecedare (talk) 02:49, 23 April 2010 (UTC)

Just a WAG, but the white doesn't look like tephra, it looks more like cloud, i.e. condensed water vapor, which may be forming at the boundary conditions between the hot air surrounging the ejecta and the cold, damp air due to melting ice and/or the local humidity. Hot + cold + water vapor = cloud, so that may be more of what is happening with the white stuff. The black is the pyroclastic material itself. --Jayron32 02:59, 23 April 2010 (UTC)

Query: WAG="Wild ass guess"? --220.101.28.25 (talk) 03:08, 23 April 2010 (UTC)

That's right. StuRat (talk) 13:50, 23 April 2010 (UTC)

That could be the case, especially since the volcano is/was topped by a glacier, which would be a prime source for immense amounts of steam. That would also explain the spatial delineation, for the temperature in the immediate vicinity of the erupted ash would be too high to allow for steam condensation and cloud formation. Does anyone know for sure ? Abecedare (talk) 03:24, 23 April 2010 (UTC)

There have been several reports that the white clouds are water vapour and the darker clouds are ash. I can't find one offhand - but it's very clear that this is what's going on. SteveBaker (talk) 12:55, 23 April 2010 (UTC)

Not to be too pedantic, but the clouds are not water vapor. Vapor is a gas, which is invisible. The clouds in the pictures, like all clouds and fog, is an aerosol of liquid water droplets suspended in the air. It is the product of condensing vapor, that is of the water gas collecting into tiny microscopic droplets, that makes clouds visible as white puffy things. --Jayron32 00:53, 24 April 2010 (UTC)

Invertebrate stomach

The article on the stomach does not describe its distribution outside of the vertebrates. The link from Chordata to digestive canal incorrectly redirects to human anatomy so that is of little help. Echinoderms are said to have "stomachs" but it seems doubtful that that structure is homologous with the human stomach. Could someone knowledgeable about this subject help me fill in this gap in Wikipedia? -Craig Pemberton 03:50, 23 April 2010 (UTC)

Be bold. DRosenbach ^{(Talk | Contribs)} 14:32, 23 April 2010 (UTC)

Milk protein denaturation

Why is NOT the protein in milk coagulated/denatured on boiling? I am not sure if the question is already asked, please let me know. - Anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 04:53, 23 April 2010 (UTC)

In of milk, the primary protein is casein. The Wikipedia article on casein itself describes the reason why it does not coagulate. --Jayron32 05:10, 23 April 2010 (UTC)

Thanks. The reason for not being denatured is given but coagulation part is vague. "Casein is not coagulated by heat" but WHY? In industries, an optimal temperature of 43 °C for 4-6 hours is used for preparation of curd (coagulation process?). I wish to know the relation between "In milk, casein is a salt of calcium" and coagulation. May i also know the function of casein? 125.21.50.214 (talk) 06:03, 23 April 2010 (UTC)

Since milk has only one function: nutrition, I would suspect that Casein is the structure it is for ease of digestion. Coagulation is caused by crosslinking between denatured proteins. Denaturing is specifically the loss of tertiary structure. Casein's peculiar organization (it has lots of proline and no cysteine) means that there really isn't any tertiary structure to speak of. It is the breaking of Disulfide bond from a single molecule and the random reforming of those bonds between neighboring molecules that leads to the crosslinking in coagulation. No cystein = no disulfide bonds = no coagulation upon denaturing. Casein, with lots of proline and no cystein, is basically a randomly wrapped somewhat floppy chain of peptides, with nothing holding into any particular tertiary structure. So there is nothing to denature there. The reason it is a calcium salt in milk is because casein's isoelectric pH is much lower than milk's native pH, meaning that it is a negative ion in milk. Being a negative ion, there needs to be a positive counterion which balances its charge, and the most common positive ion in milk is calcium. Hence, it is a salt of calcium in milk. --Jayron32 15:01, 23 April 2010 (UTC)

Cheese is created through heating with the addition of the enzyme rennet (originally sourced from the lining of animal stomaches) and usually addition of acid (sometimes directly in acid-set cheeses, more often indirectly as by-product of intentional bacteria growth) Yum, cheese! See cheesemaking for more including which cheeses must have mold as well. Rmhermen (talk) 13:32, 23 April 2010 (UTC)

Based on my experience with hot chocolate if you bring a pot of milk to boil it will develop a skin of denatured protein on the surface... cyclosarin (talk) 15:13, 24 April 2010 (UTC)

Why exactly do pet parrots mimic (or attempt to learn, if you believe that) human speech?

Is it basically them trying to fit in with humans? WP's talking bird article doesn't explain anything about why. Thanks. --95.148.106.230 (talk) 07:57, 23 April 2010 (UTC)

Birds mimic so that they can learn what sounds they should make, hopefully from more experienced birds of the same species. Graeme Bartlett (talk) 12:47, 23 April 2010 (UTC)

According to this source birds call or sing:

• Calling or singing to attract a mate.

• Calling or singing to establish the bird's territory

• As an indication of the readiness of either or both partners for mating activity

• Maintain a bond between male and female bird

• As a way of communication between parent and young

• As a means of warning it's[sic] mate or other members of the flock of danger

• As a means of gathering a flock together or finding each other

• As a means of encouragement to fellow flock members (such as the case of geese flying and calling to other members to keep up

• As a tactic of intimidation to predators or other birds

• Birds do practice their songs, calling and talking through repetition. Cuddlyable3 (talk) 12:59, 23 April 2010 (UTC)

To answer the Q, rather than talk about why birds sing in general, let me start by saying that some species of birds imitate all sounds they hear. They probably do this to impress potential mates with how fit they are, if they can imitate any sound they hear. This also applies to mimicry of human speech. Of course, if they are rewarded when practicing this (say with food), they may do it even when there's no mate around to impress. StuRat (talk) 13:46, 23 April 2010 (UTC)

Also, since parrots are social animals, when a bird is raised with humans his whole life, he thinks that he is human too. That is one reason they imitate us. --The High Fin Sperm Whale 18:24, 23 April 2010 (UTC)

Many parrot owners don't actually realize this - but pet parrots will often consider the human with which they interact with the most to be their mate. This is basically the reason behind the violent, jealous 'one person parrots'. --Kurt Shaped Box (talk) 04:41, 24 April 2010 (UTC)

See also: Alex (parrot). GeeJo ^(t)⁄_(c) • 19:07, 23 April 2010 (UTC)

Many birds mimic the sounds they hear in their environment, presumably as a means of making themselves more attractive for mating purposes. Also presumably, they have done this for thousands of years prior to the appearance of humans in their environment.

There was a fabulous episode of a TV series on this subject, I think by David Attenborough. One of the exhibits was a bird that had lived all its life in a forest in which logging was taking place. This bird was a brilliant mimic of the sound of a chain saw! Dolphin (t) 05:41, 24 April 2010 (UTC)

gravity-south pole

Is the value of gravity same all around the earth? Is that like things/creatures at the south pole has lesser gravity comparitively because it is at the bottom of the earth (seems like clinging to it, things will fall off):-)? How is the south pole affected by earth's rotation/revolution? Is gravity because of earth's rotation (too)? Is the escape velocity same all around the earth? I dont understand physics well!!!125.21.50.214 (talk) 11:29, 23 April 2010 (UTC) anandh.

see here--BozMo talk 11:37, 23 April 2010 (UTC)

The south pole is only the "bottom" of the Earth by modern mapmaking convention (some old maps put East at the top). Gravity doesn't care about up and down; it just pulls everything towards everything else, so there's nothing gravitationally special about the South Pole. Earth is by far the biggest thing near us and gravity is very weak, so, to a first approximation, gravity just pulls us towards the center of Earth.

Now, earth's rotation does have an effect. The centrifugal force caused by Earth's rotation (same thing that causes your arms to be pulled out if you spin around in place fast) causes things to be lighter, the closer they get to the Equator. But things are only 0.3% lighter there than at the poles, so it's not something that you'd notice. Paul (Stansifer) 12:31, 23 April 2010 (UTC)

The shape of the earth has an effect too - the poles are closer to the center of the earth than the equator - hence more gravity there. There are also differences due to mountains - which get you further from the center (hence less gravity). Deposits of denser or less dense rock will also make a difference to local gravity. See Gravity anomaly, Physical geodesy SteveBaker (talk) 12:53, 23 April 2010 (UTC)

The radius of the Earth varies from 6,357 km at the poles to 6,378 km at the equator, and (6,378/6,357)² = 1.0066, so this reason only increases the gravity at the poles by 0.66% compared to the equator. Actually it'll be slightly less than that due to the pull of the equatorial bulge itself, but that's harder to compute. Combining that with the centrifugal effect, which is more accurately 0.35%, we see that you weigh no more than about 1% more when at the poles. --Anonymous, 03:45 UTC, April 23, 2010.

9 volt battery

I often test if 9 volt batteries are still good by touching them on my tongue and seeing if they give a small shock. Would touching a 9 volt battery to a hypothetical persons penis/clitoris produce an orgasmic effect? 82.43.89.71 (talk) 12:22, 23 April 2010 (UTC)

Wikipedia has an article on Nine-volt battery. Connecting the male and female terminals is inadvisable as it leads to premature discharge. Cuddlyable3 (talk) 12:50, 23 April 2010 (UTC)

Premature discharge? Cue rimshot. Kingsfold (talk) 16:14, 23 April 2010 (UTC)

No - if that worked then every sleeze-bag on the Internet would be selling devices that do exactly that. SteveBaker (talk) 13:01, 23 April 2010 (UTC)

That is quite independent of whether it works, and they do. --Stephan Schulz (talk) 13:48, 23 April 2010 (UTC)

See Erotic electrostimulation. PrimeHunter (talk) 16:24, 23 April 2010 (UTC)

Touching the device to the hypothetical person might constitute battery, but we cannot give legal advice. The current from the battery would depend on the resistance. Salt on the skin would likely lower the resistance. We do not seem to have an article on Salt and battery. Alessandro Volta tested his batteries (or "piles") in a similar manner, but by using other parts of his own body. This might be considered "self abuse," and if done to the eyes like by Volta, Ritter or Charles Darwin, might cause you to go blind. Some 19th century writers, going in the opposite direction, speculated that sexual intercourse might be pleasurable because of the electricity generated by the act. 19th century quack "doctors" did lots of truly scary electrical experiments, sticking electrodes about everywhere to prevent "spermatorrhoea," which should absolutely not be imitated. In the late 19th century doctors attempted to treat "female complaints" with electricity, either DC or AC, with mixed results. By the 1970's women started using batteries not directly but instead to power vibrators, and found this an effective way of obtaining orgasms[10]. Edison (talk) 22:30, 23 April 2010 (UTC)

Global warming.

Cenozoic global temperatures (right-to-left)

This subject has me thoroughly confused! The sea level is rising, caused by melting ice, caused by global warming, caused by increase of carbon dioxide in the atmosphere. That is what it seems to me that scientists have stated. Am I right? If not, then ignore the rest! cdiac.esd.ornl.gov/trends/co2/contents.htm claims that atmospheric carbon dioxide concentration jumped from 275 ppm in 1750 to 367 ppm at present. A WHOLE WHOPPING 33%! TERRIBLE? But that is still only .0367% of what we breathe in. Of course I realize that the increase itself is increasing. BUT: mistupid.com.chemistry/aircomp. gives the present level as 330 ppm. Answers.com gives 380 ppm, Wikipedia gives 387 ppm and Physlink 314 ppm. And if I had searched further I would no doubt have found still different figures! AND: Whilst the increase from 1750 to Physlink is only 14%, the discrepancy between Wiki and Phys is an enormous 23%. When I did chem. anal. half a century ago, if I had come up with such varied answers, my employers would have kicked me out on the spot! LASTLY: National Geographic some years ago stated that (I think) some few million years ago the carbon dioxide in our atmosphere was 5x the present level. AND LOOK WHAT HAPPENED: WE DID!!!!!! Not feeling at all comfortable with a PC, nor with how to reply to an answer (vide my query re EMP weapons in Smolensk a few days ago), could some kind soul PLEASE tell me, step by step, how to go about this? Thank you!!!220.253.193.132 (talk) 13:01, 23 April 2010 (UTC)

I suggest you start with Carbon dioxide in Earth's atmosphere BozMo talk 13:05, 23 April 2010 (UTC)

Some points:

1) Yes, CO₂ levels were higher at times in Earth's history, but so were sea levels. The problem isn't really so much that we are headed to an inherently dangerous level of carbon dioxide, but that we have chosen to build on the shores of oceans around the world, which means that billions of people will be subject to increased flooding.

2) Yes, the level of carbon dioxide is a tiny portion of the atmosphere in total. If the atmosphere was all greenhouse gases, then we would have a planet like Venus, which would kill off all people (and most life) on Earth.

3) Variations in measurements around the Earth can be expected to be larger than those measured in a laboratory setting. There will be variations by location and date, as well as due to different measurement methods. However, all the numbers you listed show an increase; that's the most important part. StuRat (talk) 13:33, 23 April 2010 (UTC)

Just pointing out that StuRat in #1 above says "the problem" is coastal flooding, whereas of course there are many, many other problems. Our Effects of global warming article discusses some. If you take an eons-long view, then it probably doesn't matter to you that, for example, as this article discusses, higher temperatures in the Pacific Northwest are giving the bark beetle a longer seasonal life each year, which has allowed them to kill 10 times as many trees as they have historically — a million years from now, who's going to care about this particular problem, true; but there are knock-on effects from these problems of today that make a lot of people care today. Comet Tuttle (talk) 17:07, 23 April 2010 (UTC)

"...all the numbers you listed show an increase..." It's not like these guys have forgotten how to do statistics. Countless studies show a significant rise that can't be contributed to randomness. At this point in the debate it isn't really a question of whether CO2 is the culprit. It is, and it is making temperatures rise. What is still up for debate is hanging a world catastrophe on changing temperature. If you want to argue against Global Warming give them their entire argument save the global disaster. Yes CO2 is rising due to us, and yes it will probably impact the climate. No matter how strong the correlation of the data and no matter how certain we are that it is our own fault, these facts don't necessitate drastic climate changes that lead to a series of uncontrollable steps where very bad things happen.

Nowadays, you won't find too many reputable sources screaming Armageddon. They have backed off that claim for now, and for good reason. It is pretty uncertain what will happen in the future, even with all the data we have. However, I found a few claims on the Global Warming quite interesting:

"In a literature assessment, Smith and others concluded, with medium confidence, that:

-climate change would increase income inequalities between and within countries

-small increase in global mean temperature (up to 2 °C by 2100, measured against 1990 levels) would result in net negative market sector impacts in many developing countries and net positive market sector impacts in many developed countries

-the aggregate market sector impact (i.e., total impacts across all regions) of a small increase in global mean temperature would amount to plus or minus a few percent of world GDP."

Conclusions like these point to a growing realization that it isn't very likely anything good will come of Global Warming, but the first one seems a little shaky. In my opinion, no one should be trying to speak this conclusively. It is very easy to be wrong when correlating broad trends with temperature. That should be your main line argument, not questioning the research.

Mrdeath5493 (talk) 17:16, 23 April 2010 (UTC)

Atmospheric CO₂ concentrations lower than 387 ppm are likely outdated. Global concentrations have increased more from 1800 to today (+107 ppm) than it has between the peak of the last ice age to 1800 (+100 ppm). ~AH1^(TCU) 21:40, 23 April 2010 (UTC)

Perpetual motion machine

In string theory, the basic building blocks of matter are said to be tiny vibrating strings. The frequency to which they vibrate determines their properties.

Where do they get the energy for this vibration? If they vibrate forever, they are perpetual motion machines. If they don't, what will the universe look like when all strings have ceased to vibrate? What will be these strings' properties? --13XIII (talk) 14:20, 23 April 2010 (UTC)

Note that only the type of perpetual motion machine where "you can pull energy out and still have it run forever" is impossible. Having an object move forever without removing energy is fine, in a frictionless environment. One of Newton's laws, after all, is that "An object in motion stays in motion, unless another force acts upon it". StuRat (talk) 14:47, 23 April 2010 (UTC)

But doesn't the movement itself remove energy from the string? Since vibration means mechanical oscillations about an equilibrium point, the string would vibrate back and forth. Accelerate back, decelerate, accelerate forth, decelerate, etc.--13XIII (talk) 15:22, 23 April 2010 (UTC)

No. Under Newtonian physics the vibration would give off heat, but strings are too small for those laws to apply. Quantum mechanics rules at those scales. StuRat (talk) 15:32, 23 April 2010 (UTC)

It is not necessary for something that appears to "vibrate" to be accelerating and decelerating. It could be an effect of dimensional perspective. Imagine a merry-go-round spinning. Due to your dimensional limitations, you cannot see the main mechanism. You can only see one horse on it. Further, you can only look it from the side and you cannot sense any sort of depth. What you end up seeing is a horse moving back and forth - but it is not accelerating/decelerating. It is rotating. -- kainaw™ 17:38, 23 April 2010 (UTC)

In a simple piano-string vibration...during acceleration towards equilibrium, the string gains kinetic energy. The acceleration comes from the potential energy of the string being away from equilibrium. During deceleration, the kinetic energy is converted back to potential energy as the string moves past the equilibrium state. There's no net loss of energy, just change of its form. DMacks (talk) 17:56, 23 April 2010 (UTC)

There certainly is a loss of energy from a vibrating piano string, some of which becomes air vibrations (sound). StuRat (talk) 19:34, 23 April 2010 (UTC)

Vibrating objects do radiate away their vibrational energy until they reach equilibrium with the environment. Quantum mechanically, though, the lowest energy state still has some vibrational motion, because of the uncertainty principle. Even in a vacuum, a system can remain in that vibrational state "forever" (though not really forever, because there are probably other allowed decays with extremely long half-lives, like spontaneous fusion or proton decay).

The other thing, though, is that the premise is false. The known particles aren't different vibrational states of strings (assuming that known physics can be reproduced within string theory at all, which still isn't known). They are different vibrational states of the vacuum, but that's already true in ordinary particle physics. It has nothing to do with the stringiness of the strings. I don't know why so many of the popularizations make a big deal about string vibration. Probably it's because then they can talk about the physics of music, a very old and well-understood topic, and pretend that they're teaching string theory. -- BenRG (talk) 19:28, 23 April 2010 (UTC)

If vibrators give off heat, that may explain my singed pubes.--79.76.130.158 (talk) 21:22, 23 April 2010 (UTC)

Atoms are constantly bouncing off each other, but they don't loose any energy by doing so. Energy lost by one atom is gained by another, which then goes to another - as long as no energy leaves the system, it can do this forever. Vibration is the same - it moves one way, stores energy in tension, then retrieves the energy on the way back, and does it over and over. As long as no energy is lost from the system it can do it forever. (With the macro objects friction steals energy.) The only reason perpetual motion machines don't work is that there is friction which steals energy. Otherwise they could actually go on forever (as long as you don't try to do anything with them.) Ariel. (talk) 22:34, 23 April 2010 (UTC)

Antimatter bomb

Assuming equal amounts of fuel, would an antimatter bomb be more powerful than an atomic bomb? What would the explosion from an antimatter bomb look like? --71.144.122.18 (talk) 14:36, 23 April 2010 (UTC)

It would be on the order of 10,000 1000 times more powerful. If you decreased the amount of antimatter to get a similar yield, then it would probably look similar to an atomic bomb. However, a large anti-matter bomb, if it was possible, might rupture the crust of the Earth, causing volcanic effects absent in an atomic bomb. StuRat (talk) 14:42, 23 April 2010 (UTC)

How did you find your way here, without finding your way to Antimatter weapon first?--Aspro (talk) 14:46, 23 April 2010 (UTC)

Modern fission weapons will fission about 40% of their fuel; each atomic fission converts (roughly) 0.1% of its mass to energy; therefore about 0.04% of the total fuel mass is coverted to energy. (See Mass–energy equivalence#Efficiency.) Fusion weapons do better (efficiency-wise), converting about 0.3% of their fuel mass to energy. A matter-antimatter weapon, in contrast, ideally converts 100% of its fuel mass to energy. On a weight-for-weight basis – neglecting the mass of any containment, triggers, delivery system, etc. – the matter-antimatter bomb will deliver 300 times the energy of a thermonuclear fusion bomb and about 2500 times the energy of a fission bomb.

As for the appearance of the explosion, I'm not sure — perhaps StuRat has sources for his statements above? I'll note that the output of an antimatter bomb will (initially) consist of very high energy (~1 GeV) gamma rays, instead of the MeV gammas and hot plasma of a fission or fusion explosion; does someone know how efficiently that energy will couple into the bomb casing, or to adjacent air, earth, and buildings? My gut instinct is that for a ground burst of equivalant energy the appearance will be comparable (at any distance where an observer would live to tell about it), but I suspect there will be marked differences at very high altitude or in space (where escaping gamma rays won't be absorbed by surrounding matter). TenOfAllTrades(talk) 15:02, 23 April 2010 (UTC)

Shouldn't that 300 be 333 ? StuRat (talk) 15:13, 23 April 2010 (UTC)

It should be if you're making unreasonable assumptions about the precision o f the value 'about 0.3%', yes. Otherwise, no. TenOfAllTrades(talk) 16:23, 23 April 2010 (UTC)

According to Pastafarianism, will the universe be destroyed by equal amount of pasta and antipasta coming into contact with one another ? :-) StuRat (talk) 15:07, 23 April 2010 (UTC)

So does that mean that an antimatter bomb would have an effect for 10,000,000 kilometers in every direction, since the largest nuclear weapon caused destruction up to 1000 kilometers away? --71.144.122.18 (talk) 14:59, 23 April 2010 (UTC)

First of all, blast radius is not directly related to bomb energy yield. See blast radius. More often, yield energy is proportional to (blast radius)² or even in some cases, (blast radius)³. For the mathematically uninclined, this means that increasing the energy of the explosion will only increase the blast radius "a little bit." In fact, when modeling nuclear weapon yield, many practical, realistic estimates place the proportionality closer to E_yield = (blast radius)⁵: in other words, you need 100,000 times as much energy to generate a blast 10x as large (measured by spatial radius). More energy does mean more destruction in general, but the relationship defining "how much more" is very complicated. Nimur (talk) 15:21, 23 April 2010 (UTC)

No, not at all:

1) First, what nuclear weapon caused destruction 1000 km away ?

2) Let's use Ten's 300 times more powerful figure, since the maximum current bomb you refer to is likely a thermonuclear bomb, not a simple atomic bomb.

3) (See Nimur's comments above about blast radii.) StuRat (talk) 15:26, 23 April 2010 (UTC)

The Tsar Bomba makes claims that it broke windows and was felt 1000 km away, but those claims are uncited. The mesured zone of total destrucion was a much smaller 35 km radius. Googlemeister (talk) 15:45, 23 April 2010 (UTC)

Also note one practical effect of the diminishing returns from larger bombs is that many small bombs are far more destructive than one big bomb, where the total mass of explosives is equivalent. StuRat (talk) 15:57, 23 April 2010 (UTC)

So what would the blast radius be of an antimatter bomb with 500,000 kg of fuel (roughly 20 times Tsar Bomba)? Ignore the problems with building and dropping such a bomb, because this is for a sci-fi story which takes place far enough in the future that they've been solved. --71.144.122.18 (talk) 16:38, 23 April 2010 (UTC)

The bomb won't be 100% efficient as a lot of the energy will be lost in the form of neutrinos. Protons and anti-protons consist of quarks, so you get mesons when they decay. But then you can get mesons consisting of a quark and the anti partner of another type of quark. This will then decay into a muon and a neutrino. The energy lost in the form of neutrinos should be easy to estimate, the article on the antimatter bomb gives a figure of 60%.

Now, I think the effects of explosions should be universal in the sense that whenever you deposit a large amount of energy very quickly in some small volume, then the effects far away from that region should not strongly depend on the details of how that energy was deposited in a first approximation.

This then means that you can just as well use this calculator to compute the effects of an asteroid impact with the same kinetic energy. You should then, of course, disregard typical effects associated with impacts, like that of ejecta. But perhaps an underground explosion would be similar also in these respects. Count Iblis (talk) 17:14, 23 April 2010 (UTC)

For example, a 3*10^11 Megaton TNT explosion should cause the following effects at 10,000 km distance. The seismic effects should be:

The major seismic shaking will arrive at approximately 2000 seconds. Richter Scale Magnitude: 12.3 (This is greater than any earthquake in recorded history) Mercalli Scale Intensity at a distance of 10000 km:

VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.

VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.

The effects of the air blast should be:

The air blast will arrive at approximately 30300 seconds. Peak Overpressure: 295000 Pa = 2.95 bars = 41.9 psi Max wind velocity: 370 m/s = 828 mph Sound Intensity: 109 dB (May cause ear pain) Damage Description:

Multistory wall-bearing buildings will collapse.

Wood frame buildings will almost completely collapse.

Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient collapse.

Highway truss bridges will collapse.

Glass windows will shatter.

Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

Count Iblis (talk) 17:29, 23 April 2010 (UTC)

If Iblis's math is correct on the amount of Mtons, then this blast would exceed the power of the Chicxulub crater impact that allegedly killed the dinosaurs by 3000x. Googlemeister (talk) 18:24, 23 April 2010 (UTC)

Just one small note. It's not correct that if a perfectly efficient antimatter bomb was possible, it would convert 100% of the mass of the antimatter into energy. The correct number is 200%, since an equal amount of normal matter would necessarily be converted. --Anonymous, 03:51 UTC, April 24, 2010.

Also, (unlike a nuclear fission/fusion bomb) it's certain that 100% of the antimatter will react with regular matter and be converted to energy - it's not like there could be antimatter 'left over' that could be scattered as fallout - as is the case with an atom bomb. So in that sense, it is 100% efficient. The issue is whether the resulting energy is emitted in ways considered useful for destruction of the target. That's where the difficulty lies. Also, a less-than-fully-efficient atomic bomb may actually cause you enemy more trouble because 'dirty fallout' that's still full of radioactive plutonium/uranium could easily kill more people and cause a larger area to be uninhabitable than a 'clean' bomb that would convert 100% of radioactive material into unreactive byproduct. SteveBaker (talk) 16:48, 24 April 2010 (UTC)

Penguins

How would the creationists today explain the flightless yet winged penguins? --Reticuli88 (talk) 14:44, 23 April 2010 (UTC)

I don't think that any explanation beyond "That's just the way God made it" is necessary for some people. --Jayron32 14:49, 23 April 2010 (UTC)

They use the wings to help them swim. --71.144.122.18 (talk) 14:52, 23 April 2010 (UTC)

Perhaps they evolved to survive The Deluge? Nimur (talk) 15:24, 23 April 2010 (UTC)

Maybe they would rather formulate it "God works in mysterious ways" if others try to point out seemingly illogical things. PrimeHunter (talk) 16:47, 23 April 2010 (UTC)

Or better yet "Who are you to question God ?", which implies that it's a sin to question God, and by extension God's representatives (the Church). StuRat (talk) 17:33, 23 April 2010 (UTC)

Us creationists take the easy way out of tough questions :)) Rimush (talk) 17:38, 23 April 2010 (UTC)

Penguin wings are anything but useless. They couldn't swim without them. --The High Fin Sperm Whale 18:21, 23 April 2010 (UTC)

See for example [11] and [12]. Gabbe (talk) 19:01, 23 April 2010 (UTC)

If you call the wings "flippers" then their construction makes pretty good sense from either point of view.APL (talk) 21:23, 23 April 2010 (UTC)

The whole problem here is that creationism is a pseudo-science. It claims the trappings of a science without following the scientific method (that's the definition of a pseudo-science). Because of that, creationists can just make up any story they like - they are (evidently) not required to provide proof of anything they say in order to keep their believers happy. Hence, asking these kinds of questions doesn't really allow you to prove or disprove anything whatever. SteveBaker (talk) 01:00, 24 April 2010 (UTC)

No explanation is necessary. I mean, their wings are used for balance, and for swimming. Just because they can't use them to lift off, it doesn't mean that they weren't invented by The Deity, or what have you. Besides, in the deadly Antarctic winter, having longer extremities is not good for your survival prospects. You want short little stubby wings so you don't lose copious amounts of body heat. Vranak (talk) 14:30, 24 April 2010 (UTC)

Well, that's not really true. Science can explain why penguins are birds - they evolved from other birds. They have wings because that's what birds have. They have evolved some features for survival in the extreme cold, others for swimming and so on...but (interestingly) they have not lost all of the features that birds evolved for flying (wings - and the huge chest muscles required to flap them). We can completely explain more or less every aspect of why a penguin is like a penguin is. The trouble for the ID "explanation" is to ask why penguins are like birds at all. Why don't they have propellers or water jet engines like a jet ski? The ID/creationism approach doesn't offer any degree of explanation whatever...the answer can only be "because the designer decided to do it that way". Since this designer produces some extraordinarily crappy designs sometimes - we have to wonder at his/her/its' sanity. I think an explanation is required - and the ability for science to provide one is a compelling thing. Why choose to believe a pseudoscience that can't explain a single fact about the nature of plants and animals beyond "well, just because the designer did it that way". That's a crappy system! I could understand choosing an "intelligent design" answer if there were no credible alternative - and that's why intelligent people believe in it hundreds of years ago when we had no better explanation. But now we have a really comprehensive, elegant explanation that fits all of the facts perfectly, choosing the ID/creationism answer is no more than pathetic dogmatism. SteveBaker (talk) 01:45, 25 April 2010 (UTC)

Exoplanet naming scheme

Why do there seem to be two schemes of naming exoplanets? Science fiction has named planets "Name of star I", "Name of star II", "Name of star III"... for many decades now. Real exoplanets, however, are named "Name of star b", "Name of star c", "Name of star d"... Why is this? There has been a simple naming scheme for decades, so why was a new one invented instead? JIP | Talk 15:16, 23 April 2010 (UTC)

• Extra-solar planets from the Institute of Physics Reports on Progress in Physics (2000) has this to say: "Object names such as 70 Vir (for 70 Virginis) reflect standard astronomical (constellation-based) nomenclature, while other designations reflect discovery catalogues or techniques variously labelled with catalogue running numbers (e.g. HD 114762) or according to celestial coordinates (e.g. PSR 1257 + 12). The International Astronomical Union is in the process of formulating recommendations for the nomenclature of extra-solar planets (cf Warren and Dickel 1998), meanwhile the de facto custom denotes (multiple) planets around star X as X b, c, . . . , according to discovery sequence."
• Following the reference above, W.H. Warren, from the United States Naval Observatory / NASA Marshall Space Flight Center / Hughes STX, had this to say to the IAU General Assembly in 1997: Nomenclature for Extrasolar Substellar Objects: A New Challenge _{HTML version}. Primarily the issue lies in defining a unique and unambiguous way to refer to a specific object which is currently on the edge of detection. If somebody else detects "something else", which might actually be found later to be the same substellar object, we must find a way to ensure that two independent nomenclatures can somehow merge together.

Ultimately, the problem is one of consistency. We don't really know what we are looking at when we see a "stellar wobble," for example. Because extrasolar planets are on the current edge of detectability, we can't be certain of the parameters (including orbital distance, or even sequence number from the star, in the case of multi-planet extrasolar systems). So, to be sure that we refer to the same object, the name is determined by when it is first observed, rather than some parameter (like distance from its star). After significant scientific observation, we might find that (the hypothetical) α-Vir-a, discovered before (hypothetical) α-Vir-b and α-Vir-c, actually lies between those two in orbital radius. Nimur (talk) 15:50, 23 April 2010 (UTC)

Does this mean that extrasolar objects are, when they are first discovered, named with letters, and after they have been confirmed to be planets and their order is known, they get Roman numerals, but it's just that in real life, we have never actually got to the confirmation stage? If this is the case, then I can see the point. But why do the letters start with b? If it's to allow for a to be discovered later, why don't they start in the middle of the alphabet then? JIP | Talk 20:10, 23 April 2010 (UTC)

The method of naming planets with Roman numerals is contained only in science fiction. Even if the order were known for certain, the letter designation would still be used. As the convention of using Roman numerals preceded the discovery of the first extrasolar planets, we can see it as an attempted guess at future planetary nomenclature that, so far, has not panned out. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 20:37, 23 April 2010 (UTC)

I think in response to JIP's question about starting with b - this is because in some conventions, α-Vir-a refers to the star, in other words, to the "primary" at α-Vir. α-Vir-b therefore refers to the first substellar object (either an extrasolar planet, a brown dwarf, or some other "UFO") detected at the location of the α-Vir system. I agree that this nomenclature is not ideal. Nimur (talk) 22:23, 23 April 2010 (UTC)

The star already has a designation: α-Vir. Why make α-Vir-a mean the same thing? Or does α-Vir refer to the entire system? JIP | Talk 06:45, 24 April 2010 (UTC)

In binary systems (those that have two stars) that have only one designation like this, the two stars are givin capital letters so there's α-Virginis A and B. In this sense, the designation for the system is "α-Virginis" and that of the star is A, B, etc. I'm not sure why exoplanet nomenclature starts with b. It's possible that the scheme originally assumed that the principal body would be A/a and subsequent bodies would be B/b, C/c, but then we have examples like 16 Cygni Bb, 30 Arietis Bb, and HD 178911 Bb. BTW, "α-Virginis a" would be the designation of a planet orbiting both α-Virginis A and α-Virginis B (since that is a binary system) though I don't believe this kind of orbit has been detected yet. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 19:23, 24 April 2010 (UTC)

III

What does the (III) in something like Nickel(III) mean? —Preceding unsigned comment added by 76.230.229.37 (talk) 15:23, 23 April 2010 (UTC)

That is called the oxidation state, and is roughly derived from a simplified description of the number of electrons exchanged in the ionic bond. Nimur (talk) 15:26, 23 April 2010 (UTC)

In other words, it refers to a nickel atom with three less electrons than neutral nickel, or alternately a +3 oxidation state. Most metals have multiple oxidation states, so it is usually necessary to indicate which oxidation state a metal has in a particular compound (for example, to distinguish between a +2 charged nickel ion and a +3 charged nickel ion). The roman numeral is omitted in unambguous cases, which are basically group IA and IIA metals, and a few random other ones (Aluminum is always +3, Zinc is always +2, and silver is always +1, so we omit the roman numerals for those as well). Other than IA, IIA, Aluminum, Zinc, and Silver, you should always include the roman numeral beside the metal name in a compound to indicate which oxidation state the metal is in. --Jayron32 15:33, 23 April 2010 (UTC)

The use of Roman numerals in parentheses following a chemical element's name of symbol is part of Stock nomenclature, a naming system for chemical species.

Ben (talk) 15:45, 23 April 2010 (UTC)

When did chemistry textbooks used in high school switch from some other nomenclature (like prefixes to indicate oxidation state) to the Roman numerals? I seem to recall a different system. Edison (talk) 22:21, 23 April 2010 (UTC)

The older system used the "-ic" and "-ous" suffixes for the oxidation states. Thus, Cu¹⁺ = cuprous and Cu²⁺ = cupric. The problem with that system is that its relative to the element in question; so while Cu²⁺ = cupric, Fe²⁺ = ferrous (since Fe³⁺ = Ferric). So, you still can't tell from the name directly what the actual oxidation state is. However Copper(I) and Copper(II) are unambiguous. Plus, what do you do with an element like Manganese, which has at least 3 common oxidation states (2+, 4+, and 7+) and a slew of other less common, but documented ones. The roman numeral system is MUCH clearer. --Jayron32 00:45, 24 April 2010 (UTC)

IUPAC has been standardizing nomenclature and advocating for standardized chemistry education since around 1913 - but I can't find a definitive date for the introduction and mainstreaming of the roman-numeral system for inorganic compound names. Textbooks may have changed many years after recommendations were made. I learned both systems, and I strongly prefer the numeric system - the "ic"/"ous" system requires much more memorization. As far as elements with more than two oxidation states, there are additional prefixes: per- and hypo-, and there are also common names for certain compounds (for iron oxide, there is ferric and ferrous oxide, also known by common names, including wustite, hemtatite, magnetite, maghemite, and so on). This system reeks of the alchemic origin of chemistry - cryptic code-words and poorly-explained, vaguely latin-ish prefixes and suffixes to designate astrological significances loosely tied to the specific process for generating specific compounds. Nimur (talk) 06:03, 24 April 2010 (UTC)

So the old chemistry set bottles labelled "Cupric Sulphate" and "Ferric Ammonium Sulphate" would now be called what? Edison (talk) 03:28, 25 April 2010 (UTC)

Copper(II) sulfate and Ammonium iron(III) sulfate, respectively. Interestingly, both Cupric sulphate and Ferric ammonium sulfate (but not Ferric Ammonium sulphate) redirect to the correct articles. Buddy431 (talk) 05:27, 25 April 2010 (UTC)

The basic assumptions of GR

The basic assumptions of GR are not clear. Steven Weinberg discussed this in his 1972 text. One assumption is nonlinearity. Imagine a satellite attracted to the earth and the sun. In Newtonian theory, the force on the satellite is the vector sum of the forces due to the earth and the sun. According to Weinberg, the force would contain a third term, the attraction to the gravitational fields of the sun and the earth. It is not clear how one calculates this force, nor has anyone tried to verify it. It is critical that we discuss basic assumptions. —Preceding unsigned comment added by Sanford123445 (talk • contribs) 18:14, 23 April 2010 (UTC)

I'm sorry, what is your question? Gabbe (talk) 18:51, 23 April 2010 (UTC)

In newtonian physics, gravity is considered instantaneous, and the force is directly toward the object. In relativity gravitational force moves at the speed of light, so the force is actually directed to where the object was, not necessarily where it is now. Frame-dragging can also cause the direction of gravitational force to be different from where newtonian physics expects. I hope I understood your question. Ariel. (talk) 22:49, 23 April 2010 (UTC)

Empty balloons

Ignoring the casing, how much extra buoyancy would a rigid balloon "filled" with a perfect vacuum give over, say, a hydrogen or helium balloon? And since I'm here, a follow-up question: Ignoring the prohibitive cost and availability issues, could you construct a buoyant "vacuum balloon" out of carbon nanotubes which would remain rigid against atmospheric pressure? GeeJo ^(t)⁄_(c) • 18:27, 23 April 2010 (UTC)

Looks like the density of helium is 0.2 g/L, and the density of air is 1.2 g/L. This means that helium is already around 85% as buoyant as vacuum. Hydrogen is around 0.1 g/L, which is even closer. Paul (Stansifer) 18:42, 23 April 2010 (UTC)

There have been a number of lengthy discussions here about this topic. here is one from 2006 and here is one from 2007. APL (talk) 19:19, 23 April 2010 (UTC)

And "ignoring the casing" completely changes things. If you count the casing, the extra buoyancy is totally negated by the container needed. It's difficult to even get a vacuum balloon that's lighter than air, much less lighter than a hydrogen balloon. StuRat (talk) 19:26, 23 April 2010 (UTC)

I asked myself this question once, many years ago. So, in different units:

1000 cubic feet of a vacuum has a lifting power of 80.7 lbs.

1000 cubic feet of hydrogen has a lifting power of 76 lbs.

1000 cubic feet of helium has a lifting power of 74 lbs.

The shell would have to therefore need weigh no more than 4,7 lbs. just to equal the lifting power of hydrogen. I came to the conclusion that using Carbon fiber-reinforced polymer (there was no such thing as nano-tubes back then) it would just be possible to construct a sphere of 1000 cubic feet displacement, with enough strength to withstand a mild vacuum. However, it would be very susceptible to suffering from sudden and catastrophic crushing if it was subjected to the slightest deformation. In other words: providing that the skin was in 'pure' compression -it would withstand atmospheric pressure. Larger spheres would of course displace a larger ratio of air for the given mass of carbon fibre skin. Yet the vulnerability of the skin to crumpling, makes any likelihood that this would be practical proposition outside of a laboratory very remote, to my mind at least. Carbon nano-tubes promise to be stronger and more ridged but I imagine that even hydrogen would be safer to use in any practical application. Also, because of the higher pressure differential present with a vacuum system, it would also lose buoyancy faster than hydrogen and helium. A helium dirigible takes a long time (days) to lose noticeable lift due to a puncture. I later had thought that it would be better to replace the air with water vapour. A slug of ²³⁸plutonium (plus lead shielding) would produce enough joules of heat to keep a large version of such a craft, aloft for years. Hey! and it would be immune to volcanic ash. --Aspro (talk) 19:56, 23 April 2010 (UTC)

Also, you said "mild vacuum", which I would take to mean a pressure lower than 1 atmosphere but significantly higher than 0. To get the extra bit of lifting power, you need something pretty close to a true vacuum or else you might just as well use hydrogen. --Anonymous, 03:55 UTC, April 24, 2010.

I just used the word 'mild' to indicate it was to the practical limitation one faces due to the plastic 'out-gassing' and I have no recollection now of what that was, nor what we could achieve with fibre bonding resins such as epoxy. The difference though, is a loss of lift which is a magnitude or more too small to bother about. Another problem that appears when trying to scale up to larger sizes, is that being under compression the skin will tend to resonate. This would be in the form of waves, with the direction of amplitude on radial axes. The number of waves dependant on the size and thickness of the skin(and air density, etc., etc.). Then there is the problem that greater air pressure at the bottom will tend to flatten the sphere at that end. This causes peek of higher stress around some of the resonance nodes. All this modelling convinced me, that the only application where these new materials have made a real contribution to mankind is than we can now buy some really good fishing rods.--Aspro (talk) 08:57, 24 April 2010 (UTC)

Number of mammals in the world

I was curious how many mammals there are in the world, not species, but individual citizens of my class, from the smallest infant bat to the largest blue whale. My estimates would put it in the billions, assuming that most mammalian species have less than a million members and there are at most 50 mammalian species as populous as us, but that's basically a guess.--Prosfilaes (talk) 18:53, 23 April 2010 (UTC)

I don't have a source, but I recall hearing that the mouse / rat is the most populous kind of mammal with ~200 billion individuals. Dragons flight (talk) 18:58, 23 April 2010 (UTC)

For the more common domestic mammals, there are 1.3 billion cows, 0.4 billion dogs, 2 billion pigs, and 1 billion sheep. As you can see, these numbers are totally swamped by small mammals like mice and rats. Googlemeister (talk) 19:04, 23 April 2010 (UTC)

 ! These sorts of numbers should not be proliferated without a source! Nimur (talk) 22:24, 23 April 2010 (UTC)

Laugh. I'm inclined to agree. Vranak (talk)

Which is interesting, if a little problematic without a definition of which type of kind we're talking about. But given that, I'd guess I'm looking at under a trillion mammals, all told, unless there are way more squirrels and bats than I'd assume.--Prosfilaes (talk) 19:13, 23 April 2010 (UTC)

Oil Depth

How deep down and wide does an oil patch or field have to be to be considered worthwhile to drill? —Preceding unsigned comment added by 71.137.251.25 (talk) 19:40, 23 April 2010 (UTC)

That will depend on a lot of factors, so we can't give a very satisfactory numeric answer. Some considerations are; pressure of the oil in the well (higher pressure means less cost to get oil out), price oil is expected to fetch when production comes online (if you have a higher sale price, you can be less efficient), level of impurities in the oil (it costs money to get out stuff you don't want), viscosity of the oil (high viscosity needs to be heated for it to flow well), transport distance to refinery (cheaper to ship oil 5 miles then 500) and method of transport (pipeline, ship etc... cost different amounts). Costs are higher for offshore oil, and while a small patch might be worthwhile if it is 200 ft down, the same patch would not be worthwhile if it was 8,000 ft down, or under 2000 feet of water. Googlemeister (talk) 19:50, 23 April 2010 (UTC)

The ease with which the oil can be produced is crucial to the viability of an oil accumulation, this will depend on both the nature of the oil (light v. heavy) and the permeability of the rock that forms the reservoir. There have been very large oil discoveries that are unlikely ever to be produced due to poor reservoir permeability, such as the Ellida discovery offshore Norway, lots of excitement at the time [13] but no indication that it will ever be produced.[14] Mikenorton (talk) 21:45, 23 April 2010 (UTC)

Hydrocarbon exploration is the task of guessing how much oil is under the ground. Of course, it is almost always easier to get oil if it is shallow. If the oil flows to the surface, that's even better! If it's very deep underground, it's much more expensive to locate and extract it. So, a very complicated set of estimations takes place when somebody thinks they have found some oil, especially if it's very deep underground. Remember, we don't ever really know how much oil is underground until we drill it and extract it; and drilling costs money - so the whole process always boils down to "do we think there is enough oil to outweigh the cost of drilling?"

First, the location is determined as carefully as possible, using a combination of geology, stratigraphy, seismic imaging, exploration wells, and dumb luck. (The percentage of each ingredient varies from company to company, and region to region - in some parts of Saudi Arabia, you don't even really need to look, and wildcat wells, drilled at purely random locations by wealthy oilmen who enjoy casino roulette games, turn up wet often enough to be profitable). Other people do not like making financial decisions based on guess-work, so they prefer a scientifically-informed guess.

In geologically interesting parts of the world, like the Gulf of Mexico, the oil is very deep and far below the water and hidden underneath pesky salt diapirs. The probability of finding petroleum under 4 miles of seafloor below an 8000 foot deep ocean is very low, unless you know where to look. That is where the magic of seismic imaging comes in: using extremely low frequency sound waves, a sonic image of the rock layers is produced, and with a little geology and a lot of luck, you might be able to identify a reservoir. Next, a series of 3D models are designed to estimate how much fluid could possibly have been produced in that region, and the physics of the flow is modeled with very large computers. These extremely accurate numerical physics calculations that are basically giant "for-loops" modeling the fluid dynamics of the entire reservoir over many possible parameters; or focusing the seismic images; and so on. The software can take many months to run, meanwhile earning millions of dollars of profit for contract geophysical processing companies. When the programs are done, the results are plotted on to huge reels of paper (well, it's all digital now, but some still print out the seismic). Next, a geologist uses colored pencil on these printouts and draws the edges of where they believe the reservoir is. Then a numerical physicist computes a precision volume integral bounded by the color pencil sketch, and a petrophysicist multiplies this resulting volume by a porosity value and an extraction factor ("percentage efficiency" of getting oil out of the ground). We now know "how much oil is in the reservoir." If the fluid physics matches the seismic images, a businessman makes a risk analysis and decides whether the color-pencil drawings and the numerical calculations are probably correct. If they are all in order, things move on to the next step. Now the business man calls his economics team, who guess what the price of oil is going to be for the next few years. And the petroleum engineers look at the geophysical results and estimate what kind of expensive technology is needed to drill this prospect, and how quickly the oil can be brought out of the ground. An easy decision is made: if the total value of the volume of extractable oil, integrated over the production curve estimate for the next few years, will cost less than building the rig and operating the boats, then the well will be profitable. At this point, the businessman responsible for this prospect calls up his boss and asks to borrow the company's 600 million dollar drilling rig to float out to his new hydrocarbon prospect. If things go great, the physicists and geologists were right, the well is wet and oil and natural gas flow. If the contractors are lucky, nothing goes wrong and nobody dies in a horrible fiery explosion and the $600 million dollar rig doesn't sink, creating loss of life, an ecological catastrophe and an economic disaster, and everbody profits. Nimur (talk) 15:26, 24 April 2010 (UTC)

Of course, if the oil accumulation is too shallow, you may have to worry about biodegradation of the oil.

As a geologist, I'd just like to point out that I've only used my coloured pencils twice in the last ten years, I spend my days sat in front of a computer workstation where I look at, and interpret the seismic images using specialist software that's been around for more than 20 years. Mikenorton (talk) 15:40, 24 April 2010 (UTC)

I admit it was an unfair jab at the geologists; really I intended to point out the ironic juxtaposition of extremely accurate and extremely inaccurate techniques in the estimation of geologic and economic risk parameters. Everybody, including the physicists, engineers, and economists, have a few "color pencils" in their toolbox to draw over the uncertain estimates. Nimur (talk) 15:46, 24 April 2010 (UTC)

That's OK, I've worked with lots of geophysicists over the years, some of them have difficulty coping with the often enormous uncertainty involved in the geological model, whereas geologists are used to that sort of thing - I was once asked to estimate the age of the formation at the bottom of a proposed well and I replied "definitely Phanerozoic", meaning that I wasn't even sure whether it would be Mesozoic or Paleozoic, but that's just how it is sometimes in frontier exploration. Mikenorton (talk) 15:56, 24 April 2010 (UTC)

GLYCOLYSIS video(s) in µm/Å-scale

Ok, I'm just learning about GLYCOLYSIS today. I'm watching many of the 10 Step Processes done in excellent 3D graphs and chartworks. My question, and note, I don't know a thing about Microscopy. Just naming off some randoms here: Transmission Electron Microscopy Area (TEM), or Positron emission tomography (PET). These types or others, do we even have the capability to watch the 10 Steps of Glycolysis, and/or just basic MitochondriaWorks with Microscopy/Video? If I'm doing video searches, if there are such videos, what to type on me search? Cheers, --i am the kwisatz haderach (talk) 19:57, 23 April 2010 (UTC)

an example of what kind of videos I'm looking for is this youtube vid done on CELL BIOLOGY by:phoenixfilmandvideo. It was made back in 1981, and has a very Cecile B. Demille 10 Commandments-like Narrator. It's chunking together basic Cell Biology infos in just 17 mins. The Microscopy parts, he just skims over. I'm looking for videos where it breaks down each segment, with way smaller in there. Even if not on the Nets, do you have an suggestions on pretty good Biology DVD's with MUCHO-MUCHO ELECTRON MICROSCOPY FEEDS? --i am the kwisatz haderach (talk) 22:39, 23 April 2010 (UTC)

What's the point in some reflexes?

I can see how some reflexes e.g. how the pupils react to changes in light are beneficial to us. But others, I can't see how they would convey any evolutionary advantage at all! For example the knee jerk reflex, the brachioradialis reflex... how can reflexes such as these help our survival? Thanks RichYPE (talk) 20:15, 23 April 2010 (UTC)

I believe they're side-effects of other, more useful reflexes. For instance the knee-jerk reflex is part of the feedback loop that helps us stand upright without consciously worrying about balance. Unfortunately, The Patellar reflex article only dedicates about a sentence and a half to this. APL (talk) 21:14, 23 April 2010 (UTC)

As I understand it, the knee-jerk reflex triggers naturally every time you take a step, causing your lower leg to extend and therefore exert a force to support your weight. It is an essential part of walking. This doesn't mean that every reflex has a function, though -- some might be relics of evolutionary history. Looie496 (talk) 23:25, 23 April 2010 (UTC)

Hi guys thanks for your responses, are there any sources you can cite as I would like to look into this further. Thanks RichYPE (talk) 15:45, 24 April 2010 (UTC)

I would say that all reflexes are protective by definition as they are instinctive in a physiologic way. The knee-jerk reflex is a just a great example of a reflex that has been misappropriated by the nomenclature, in that we call it a knee-jerk because of the way in which it as a reflex, as representative of all or most reflexes are working in the body. But if you're standing against a wall and you doze off and your knees buckle, your quadriceps is extended by the pulling motion of the tendon over the knee area and your Golgi tendon organ is activated by this tension. It then sends a message for your quadriceps to flex, thereby re-establishing equilibrium. DRosenbach ^{(Talk | Contribs)} 02:24, 25 April 2010 (UTC)

Abdomen

Is there a term for the area of abdomen between the belly button and the groin? (ie the bit that hangs below your belt)--79.76.130.158 (talk) 21:27, 23 April 2010 (UTC)

Left lower quadrant (abdomen) or right lower quadrant (abdomen)? ~AH1^(TCU) 21:33, 23 April 2010 (UTC)

The supra pubic area? —Preceding unsigned comment added by 86.4.186.107 (talk) 21:52, 23 April 2010 (UTC)

Wait, you wear your belt around your belly button? I thought belts were worn just over the hips. —Preceding unsigned comment added by 99.254.8.208 (talk) 22:24, 23 April 2010 (UTC)

MY wife and I have this debate. I wear my pants around my hips, and her waistband crosses her belly button. Its apparently not a settled matter... --Jayron32 00:31, 24 April 2010 (UTC)

Hypogastrium --Arcadian (talk) 00:40, 24 April 2010 (UTC)

Ok then, what is the reason for protruding hypogastrium in older women, when they are not necessarily fat?--79.76.130.158 (talk) 11:28, 24 April 2010 (UTC)

Poor tone of abd muscles, esp from previous stretching during pregnancy. It's called a paunch. Also fat, even when limbs are not obviously fat. alteripse (talk) 11:34, 24 April 2010 (UTC)

Ok how can this tone be improved? Sit ups?--79.76.130.158 (talk) 12:52, 24 April 2010 (UTC)

Yes, though crunches may be better. See also leg raise. Abdominoplasty (surgical procedure) is also a rather drastic possibility. --220.101.28.25 (talk) 18:53, 24 April 2010 (UTC)

scuba

how long air will a scuba tank give u? and what compression is used on it? —Preceding unsigned comment added by Tom12350 (talk • contribs) 22:13, 23 April 2010 (UTC)

Diving_cylinder#Breathing_Time --Aspro (talk) 22:24, 23 April 2010 (UTC)

Note that your dive time is usually limited not by the air in your tank, but by your careful adherence to the dive tables or to your dive computer; you have to come up before decompression sickness becomes inevitable. Here is a long FAQ about tank filling, with a little picture of their fill station, and lot of information for technical diving. Comet Tuttle (talk) 22:38, 23 April 2010 (UTC)

The pressure is about 2,900 to 4,400 psi. Ariel. (talk) 22:53, 23 April 2010 (UTC)

The OP seem to be asking for a ball park sort of generalisation. Since a lot of people never get beyond trashing around ( a technical term for a certain swimming style) in depths of no more than 30 feet, for some 20 minutes at a time, on a 70 l tank. Adherence to decompress times is unlikely to take up much time at all. Beyond this however, it is as Comet Tuttle above points out – a more complex question.--Aspro (talk) 23:00, 23 April 2010 (UTC)

yes i just need a generalization. i heard that but it might be hard to control the flow of 2000 PSI tank? does it use a flow regulator? —Preceding unsigned comment added by Tom12350 (talk • contribs) 00:00, 24 April 2010 (UTC)

SCUBA specifically refers to the combination of a pressurized tank and a diving regulator. I have seen an instructor breathe out of an unregulated cylinder by carefully cracking the valve (which is stupid and dangerous). If you dive to shallow depths (where the fun stuff is, anyway), you can get as much as 40 minutes or an hour out of a 3000 psi tank. Your breathe-rate varies by at least a factor of two based on how calm and controlled you are - inexperienced divers waste air and run out long before they otherwise would. At greater depths, you typically consume air faster (because the regulated pressure is higher); but this also depends on controlled breathing. It is possible, but dangerous, to breathe less often when you are breathing high pressure air - your oxygen partial pressure is higher and you can "survive" longer off of each breath; this extends the down-time, but contributes to a variety of hazardous conditions, including decompression sickness. If you need more down-time, technical divers carry multiple bottles and/or use other gas mixes. As has been pointed out, in most deep dives, the limiting factor is not quantity of air, but safety due to compression hazard and nitrogen narcosis, oxygen toxicity, and decompression sickness. Nimur (talk) 01:52, 24 April 2010 (UTC)

The person at the lower right just breathed out.

where does the air you breathe out go? also why is it dangerous to breathe out of a unregulated cylinder ?

To question 1: It depends on whether or not you are using a rebreather or an open-circuit Scuba set. Rebreathers trap exhaled gas, while in open-circuit systems your exhaled breath just bubbles away. And breathing from an unregulated cylinder is very dangerous because it is unregulated. A sudden burst of high-pressure air into your head can cause all sorts of damage to your lungs and breathing system. Having your lungs pop like a balloon because you opened the valve on the cylinder too far doesn't sound like a good idea. Also consider the Newton's third law of motion problems with opening the valve too far. Doesn't sound like fun to me... --Jayron32 04:36, 24 April 2010 (UTC)

Of course our article Scuba diving will be of interest. Comet Tuttle (talk) 06:33, 24 April 2010 (UTC)

how does the air "just bubble away. " is there an exit valve? what about on the scuba fireman where?

The mouthpiece has a second set of valves, including a demand valve and a backpressure valve. The diagrams in our article illustrate how complicated all of this is - but basically, the air is delivered at the correct pressure when you breathe in; and when you breathe out, those valves close and your exhaled air blows out an outlet valve and bubbles into the water. The design of all of these valves is necessarily complicated to make sure that both the correct pressure is delivered, and that water is unable to flow into the mouth or the air tank. Nimur (talk) 22:46, 24 April 2010 (UTC)

The 'U' in 'SCUBA' stands for "underwater" (Self Contained Underwater Breathing Apparatus) - so the things that firemen wear isn't SCUBA gear. SteveBaker (talk) 01:21, 25 April 2010 (UTC)

muscle fuel

I can start walking any time I want, so there must be some sort of fuel stored in each individual muscle cell, ready to be used any time. I can keep walking for hours at a time, or I can run for ten minutes, before I have to stop. Did the muscle cells start with enough fuel in each one to work for that long, or are they being refuelled through the blood while I'm walking? If they are being refuelled, is there a fuel storage area in my body where I keep the extra fuel after digesting it but before distributing it to a cell? —Preceding unsigned comment added by 99.254.8.208 (talk) 22:18, 23 April 2010 (UTC)

Now that's a good question. Look at Glycogen and Mitochondrion.--Aspro (talk) 22:32, 23 April 2010 (UTC)

Aerobic vs. anaerobic exercise may be helpful as well. Short runs are typically anaerobic sprinting, while long, endured exercise is more commonly aerobic. These are qualitatively different metabolic processes and utilize different biochemistry to release energy. Nimur (talk) 01:55, 24 April 2010 (UTC)

THe only usable form of energy is adenosine triphosphate. Glycogen and glucose only form and reform the hydrogen bond between the last two phosphate ions. 99.13.216.93 (talk) 02:34, 24 April 2010 (UTC)

True, but ATP is the last step in many long processes which produce energy for cells. Its like saying that your lights come on because you flip the switch on the wall, and then ignore the process that got the energy to the switch. ATP is the ultimate source of energy for cells, but the role of substances like Glucose and Glycogen in the transport and storage of energy cannot and should not be understated. --Jayron32 03:17, 24 April 2010 (UTC)

The fuel is glycogen and it's stored in your muscles and liver. So in that case, the fuel storage area will be the liver. Your body refuels its glycogen reserves by converting stored fat in the body. --41.177.6.108 (talk) 09:31, 24 April 2010 (UTC)

Fat is not to any significant extent converted to glucose (which is a necessary intermediate for making glycogen). See Glyconeogenesis, especially the section Entering the pathway. The glycerol part of triglycerides can be converted to glucose, but the fatty acids cannot. --NorwegianBlue ^talk 10:12, 24 April 2010 (UTC)

Yet it seems I can exhaust the supply in the muscles and liver by jogging for an hour, and some refuelling in the form of juice or other sugar is needed for continued exertion. Is it like a car with a very small gas tank? Edison (talk) 03:32, 25 April 2010 (UTC)

April 24

Energy used in travel

How many joules of energy are expended by each of the following 16 entities? (Additional details for each of the 16 entities: Please deal with entity variations by providing minimum and medium and maximum values; or please specify a typical specimen and provide a value for that specimen. Please assume that there is no wind in the air and no current in the water.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC)
[I am inserting the underlined text. -- Wavelength (talk) 03:34, 24 April 2010 (UTC)]

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.. --Jayron32 03:34, 24 April 2010 (UTC)

None of these questions is a homework question. I am simply curious about all of them. -- Wavelength (talk) 03:39, 24 April 2010 (UTC)

In that case, these are insansely complex problems anyways. The work done by each body in traveling one kilometer. Its a rather complicated problem, since in a perfect frictionless system, the work = 0 if the movement is at a constant velocity. So the work done in traveling one kilometer is the work done overcoming friction. These systems are fantasticly complex; you could calculate joules of energy consumed in traveling that distance for some of these. For example, given a car with a fuel efficiency of 30 km/gallon of gasoline you could calculate the mass of gasoline burned and then the joules of heat released in burning that gasoline from the Heat of combustion value for gasoline. For the human examples, there are ways of calculating "food energy" consumed per minute for various activities, but these are usually pretty inaccurate measurements. Still, you can find calculators online that will do this for you. Then you just need to convert from food calories to joules. --Jayron32 03:49, 24 April 2010 (UTC)

Remember that in both air and water, drag is really important as speed increases (drag increases with the square of the speed). So the speed needs to be known for all the mechanical systems. There are also questions of efficiency. Some engines are more efficient at high speed -- airplane engines are more efficient at the low temperatures of high altitude. The air is also much thinner there. At 1 km altitude, air friction would be quite high and the engines not as good. An aircraft blog I visited earlier gave an economy of ~2.7L/100km/passenger for a Boeing 777-300ER and ~3.1L/100km/passenger for an Airbus A330 and that's overall with most of the flight at ~10km altitude and Mach 0.82 or so (see comment 9 here). -- Flyguy649 ^talk 04:28, 24 April 2010 (UTC)

Also, another difficulty is that airplanes weigh anywhere from a couple hundred pounds to over a million pounds. The An-225 would use an absolutely incredible amount more energy than the CriCri, and the engines are optimized for completely different altitudes. The same (in terms of the weight) goes with automobiles (though not as extreme) and the other things you mention. Even amongst airliners, there will often be a significant difference between types. Falconus^{p t c} 05:02, 24 April 2010 (UTC)

My clarification about "entity variations" applies to all those variations. -- Wavelength (talk) 21:31, 24 April 2010 (UTC)

Extended content

Energy used in travel: by a man walking How many joules of energy are expended by a man walking along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a man running How many joules of energy are expended by a man running along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a man bicycling How many joules of energy are expended by a man bicycling along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a man swimming How many joules of energy are expended by a man swimming along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a man pedaling a pedal boat How many joules of energy are expended by a man pedaling a pedal boat along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a man rowing a rowboat How many joules of energy are expended by a man pedaling a rowboat along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a horse with a rider How many joules of energy are expended by a horse carrying a rider along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a horse with a carriage How many joules of energy are expended by a horse pulling a carriage along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a motorcycle How many joules of energy are expended by a motorcycle traveling along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by an automobile How many joules of energy are expended by an automobile traveling along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a bus (omnibus) How many joules of energy are expended by a bus traveling along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a ferryboat How many joules of energy are expended by a ferryboat traveling along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a steam locomotive How many joules of energy are expended by a steam locomotive traveling along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a diesel locomotive How many joules of energy are expended by a diesel locomotive traveling along a distance of one kilometer in a straight line on a flat and horizontal surface at sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by an airplane (aeroplane) How many joules of energy are expended by an airplane flying along a distance of one kilometer in a straight line at an altitude one kilometer above sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC) Energy used in travel: by a helicopter How many joules of energy are expended by a helicopter flying along a distance of one kilometer in a straight and horizontal line at an altitude one kilometer above sea level? (Additional details are under the main heading, above.) -- Wavelength (talk) 03:24, 24 April 2010 (UTC)

16 questions from Wavelength collapsed, all identical except for the vehicle. Comet Tuttle (talk) 06:30, 24 April 2010 (UTC)

Could they please be removed? They're screwing up the Table of Contents 82.43.89.71 (talk) 23:41, 24 April 2010 (UTC)

They were not a problem to the Table of Contents until they were collapsed in a recent revision. If they are removed, the discussion will be hanging without the complete context. If the collapsing is not going to be undone, the main heading can be reworded to say "Energy used in travel (collapsed subheadings non-functional in links)", that is to say, including the links in the Table of Contents. But I prefer that the collapsing be undone. -- Wavelength (talk) 05:45, 25 April 2010 (UTC)

Are you sure this is what 82.43 is referring to? My guess is the complaint is about the very large TOC due to the 16 additional items (that's about a whole days worth), not the inability to navigate to the individual sub-questions; and that problem occured both before and after the collapsing Nil Einne (talk) 06:35, 25 April 2010 (UTC)

Why no plastic beer bottles?

Why do I never see beer in plastic bottles sold anywhere? Why are they either in aluminum or glass? --70.179.176.30 (talk) 04:09, 24 April 2010 (UTC)

Beer is often sold in plastic bottles at punk/skinhead/metal/etc. gigs. It hurts the singers and band members less when people hurl the bottles at their heads. Also makes it harder to use bottles as weapons when the crowd start beating on each other. :) --Kurt Shaped Box (talk) 04:20, 24 April 2010 (UTC)

(edit conflict) Well, not demonstratably true. For over a decade Anheuser-Busch has sold beer in plastic bottles, and they weren't the first, Miller started some time before they did. Plastic bottles are not as popular as beer sold in cans or glass, tradition being what it is, but they certainly exist. You see them a lot more at major events like ball games or rock concerts, where glass is a concern for safety reasons. However, you can find them in grocery stores and other places where you can buy beer. --Jayron32 04:22, 24 April 2010 (UTC)

I'm pretty sure that I've bought plastic 500ml bottles of Bud in England before, FWIW. --Kurt Shaped Box (talk) 04:29, 24 April 2010 (UTC)

Aye, well, most bottled water is sold in plastic. :) --KägeTorä - (影虎) (TALK) 18:18, 24 April 2010 (UTC)

http://www.packaging-gateway.com/features/feature79/ has some comparisons and consumer info. You can do your own research with Google on beer plastic bottles. PrimeHunter (talk) 04:38, 24 April 2010 (UTC)

Interesting link — it seems to claim the major reason is that more oxygen gets into the bottle while it's on the shelf; but I thought plastic was airtight, and don't particularly see why the cap on a plastic bottle would let in more oxygen than the cap on a glass bottle. Comet Tuttle (talk) 06:28, 24 April 2010 (UTC)

Interesting enough, it also mentions cost. I presume this is in comparison to aluminium cans rather then glass bottles but don't really know. This [15] mentions cost as a factor in 2001. As an aside, plastic bottles are common in stadiums as has been mentioned, but while not as dangerous as glass, they still pose a threat, particularly of course when full and sealed. Stadiums sometimes limit bottle size (even for brought in bottles) as a result. Similarly, tap beer with paper or plastic cups for the beer [16] Nil Einne (talk) 07:24, 24 April 2010 (UTC)

The plastic is not airtight! The plastic allows diffusion of gas, depending on the exact material this diffusion is varying. The oxygen diffuses into the beer and changes the taste by oxidation reactions. There are certain surface treatments necessary for beer bottle to lower this diffusion. There is a book about the properties of polymers which has a good introduction [17] --Stone (talk) 08:12, 24 April 2010 (UTC)

For me, drinking beer from a plastic bottle would be like drinking water from a muddy puddle. It's just not preferred, when inert glass is available. Vranak (talk) 14:25, 24 April 2010 (UTC)

Glass and aluminium cans are much more recyclable than plastic - going to plastic bottles would be a retrograde step. SteveBaker (talk) 18:04, 24 April 2010 (UTC)

To me the Q shouldn't be why beer isn't commonly sold in plastic bottles, but why soda-pop is. It goes flat much faster in plastic, because the plastic isn't airtight, and the bottle may also leach chemicals out of the plastic, into the contents. StuRat (talk) 18:18, 24 April 2010 (UTC)

Similar question: Why in the US is water not sold in 2 liter bottles? This came as a shock to me when I tried to buy it, and had to settle for two 1 liters. Staecker (talk) 22:43, 24 April 2010 (UTC)

Because it comes in gallons. Like milk. How it's decided what is sold in gallons and what is sold in liters is one of the great mysteries of life.

Of course ...while I can understand a single serving, it feels pretty crazy to buy an entire gallon of tap water that someone has put into a bottle. I get that stuff literally piped into my house! APL (talk) 03:15, 25 April 2010 (UTC)

I suspect that the answer is that US manufacturers tend to stick with traditional units (ounces, pints, quarts, and gallons; in this case), until they reduce the size and want to hide this fact from consumers. Then they switch to metric to maximize deception and confusion. This happened with car engines, where a muscle car engine went from 455/460 cubic inches to 5.7 L, so nobody would notice that it was now 3/4 as big. This prevented consumers from trying to pay 3/4 as much. I wonder if any company has then done the reverse, and switched back to traditional units, when they next need to deceive consumers about another decrease in size. StuRat (talk) 07:18, 25 April 2010 (UTC)

Catabolic breakdown of muscles

Hello. I've heard many a bodybuilder say that catabolism starts breaking down muscles after about six hours of fasting. However, it seems quite exaggerated to me, so I've come here to seek a scientific answer. For an average person, how much time without eating does it take for the body to start breaking down muscles noticeably to feed itself?

(By "noticeably", I mean to the point that the bodybuilder may lose the muscle mass he has gained by working out during the day, or more). Thank you guys! --95.120.13.224 (talk) 08:35, 24 April 2010 (UTC)

Since they aim to get their fat to muscle ratio to the minim I expect their energy reserves are low. This is an area that the military have long been interested in, maybe another wikipedian knows of a good s reference. You might find of interest some of the things gone into on this site [18]. Fasting adds a complication because metabolism tends to slow down under these conditions.--Aspro (talk) 09:39, 24 April 2010 (UTC)

We may simplify anabolic/catabolic relationships as follows (for an average adult): 1. For about 3-4 hours after a mixed meal, glucose and amino acids and free fatty acids are coming from the gut into the blood; insulin levels are high and glucose is actively moved into liver, kidneys, and muscle, where it is stored as glycogen in all three, and amino acids are moved into muscles and incorporated into protein. From about 4 to 16 hours after a meal, insulin levels fall gradually, and blood glucose levels are maintained by glycogenolysis from liver and kidneys (not muscle), and there is little net uptake or output of amino acids from the muscle. By 16 hours (with wide variation), liver and kidney glycogen is depleted (not entirely gone) and insulin levels are low enough to allow catabolism of both fat and muscle for purposes of making glucose by gluconeogenesis. This is also when ketogenesis from fat breakdown begins. See Cori cycle. This is somewhat oversimplified, as there is considerable overlap between end of glycogenolysis and start of gluconeogenesis, but perhaps is a useful way to think about it for clinical and physical culture purposes. alteripse (talk) 11:13, 24 April 2010 (UTC)

It seems to me that the time frame would change dramatically based on activity levels, with each step taking far longer when asleep than while running a marathon. So, what activity levels were assumed for those values, Alterprise ? Also, doesn't the nature of the last meal matter, with sugars being digested far quicker than fats ? StuRat (talk) 11:19, 24 April 2010 (UTC)

Overnight resting. The major fuel source for muscle activity is muscle glycogen, which is used in muscles during exercise, and not for ordinary between-meal blood glucose maintenance. This partial separation reduces the exercise effect on whole body metabolic balance but amplifies it for in-muscle glycogen balance. Speed of digestion has an early effect which is why I specified mixed meal, but has little effect on the timing of the later stages. We use cornstarch to prolong digestible glucose intake in people whose glycogenolysis and gluconeogenesis is defective but it only adds a couple hours at best. So does a huge high fat meal. alteripse (talk) 11:27, 24 April 2010 (UTC)

Number of cells in a human body

How many (approximately) cells are there in a (an average, adult) human? RJFJR (talk) 13:10, 24 April 2010 (UTC)

Close to 50 trillion cells. However, that conflicts with Human_flora#Gut_flora which declares it to be about 10 trillion cells and Cell (biology) at a 100 trillion. Is this assuming a standard human of 70 kg I wonder? Looks like we will have to do a little proof correcting on these articles. --Aspro (talk) 13:38, 24 April 2010 (UTC)

Do you mean total number of cells, or number of Human cells? I've read somewhere (sorry, no reference yet) that the number of non-human cells (for example, bacteria in the gut and on the skin) out-number the cells that actually have your own human DNA.24.150.18.30 (talk) 15:11, 24 April 2010 (UTC)

The OP's word "in" an average human must include gut flora. Cuddlyable3 (talk) 15:39, 24 April 2010 (UTC)

And do we include dead cells ? A good portion of the skin is dead, so that makes a diff. StuRat (talk) 15:20, 24 April 2010 (UTC)

This must be a harder thing to estimate than it at first appears, as I can't find any references to this in my human physiology text books nor on any of the human genome sites, etc. To give the OP a figure could we say: The average human adult is composed of cells numbering between the magnitude of 1 x 10^13 and 1 x 10 ^14. --Aspro (talk) 16:10, 24 April 2010 (UTC)

Well, Human_flora#Gut_flora and Cell (biology) are compatible, as there are indeed roughly 10 times more non-human than human cells in a human. So Cell (biology) apparently counts all the cells that are inside a person. --Stephan Schulz (talk) 20:06, 24 April 2010 (UTC)

What is strange here is that humans are colonies of cells. So, you have intelligent colonies of cells that have difficulties estimating how many cells they themselves consist of :) . Count Iblis (talk) 20:46, 24 April 2010 (UTC)

Katla

Hi. If Katla were to erupt, how much water vapor would be released into the atmosphere and how much sea level rise would occur from the melted glacier (I previously calculated a figure of 0.3 mm)? Considering both the vapor released into the troposphere and stratosphere, what would be its equivalent CO₂e warming effect as an increase in equivalent carbon dioxide concentrations in ppm? Finally, would the net result from the combination of the ash, sulfur, and vapor ejected from the volcano produce net warming or cooling of the Earth globally in terms of surface temperature, or is this indeterminate? Thanks. ~AH1^(TCU) 13:43, 24 April 2010 (UTC)

I believe volcanoes typically cool the Earth, since the additional sunlight and heat reflected back into space from the ash clouds outweigh all the other factors. StuRat (talk) 15:17, 24 April 2010 (UTC)

I agree. To get a significant warming effect, you need to have an enormous eruption in which huge quantities of CO2 are emitted. Then, because of the long atmospheric lifetime of CO2 (far longer than that of the dust and aerosols), you can get a warming effect. Note that H20 only has a short atmosheric lifetime. I think that even supervolcano eruptions are not large enough; they will still produce a net cooling effect. But large flood basalt eruptions, such as the one that formed the Siberian Traps, will lead to a net warming effect. Count Iblis (talk) 15:52, 24 April 2010 (UTC)

CO2 lives in the upper atmosphere for thousands of years. So I'd expect there to be a short-term cooling effect due to the light colored clouds produced by the volcano - but that effect can't last for more than a year - so the longer term effect can only be to contribute to global warming. SteveBaker (talk) 01:15, 25 April 2010 (UTC)

Stratified Italian soda + cold cream => Salt fingers??

A fluid mechanics professor and myself are a bit stumped on this question:

Go to your local cafe, order an Italian soda. Make sure the barista/server pours the soda in very gently so that the syrup & soda remain as stratified as possible. Now get the carafe of cold half & half & pour in 1-2 tablespoons. The cream is significantly denser than the soda and sinks quickly. However, the syrup is denser than the cream and so the cream is stopped abruptly at the syrup/soda interface. (Side note: the breakdown of large -> small turbulent structures at this point is really cool!)

After ~10 seconds, small fingers of cream appear to drop into the syrup layer ... and look a LOT like salt fingers (see wiki article + links on those). Salt finger theory relies on the lower layer being cold and the upper layer being warm such that thermal diffusivity causes displacement instability (i.e. a bit of warm upper fluid is randomly displaced downward, quickly loses its heat to the ambient cold layer, and continues to fall downward because its density just increased through loss of heat).

In the case of the Italian soda, the cream (upper layer) is COLD and the syrup (lower layer) is warm/room temperature. This SHOULD be a STABLE configuration provided that the syrup is indeed denser than the cream, because any parcel of fluid that falls into the syrup should get warmer, lose density, and rise back to the point of equilibrium. Yet these fingers clearly fall into the syrup.

I thus present this conundrum to the reference desk. I highly recommend you try it!

128.193.45.125 (talk) 20:46, 24 April 2010 (UTC)

I'm afraid I haven't been able to get you a complete answer. Poking around the web, I find these figures for the specific gravity (density) of

• Half and half: 1.031 g/cc at 4.4°C, and 1.024 g/cc at 20.0°C;
• Pure water: 1.000 g/cc at 4°C, and 0.998 g/cc at 20°C;
• The densities for the flavor syrups will depend on the manufacturer and the particular syrup. For Torani brand, there appears to be between 15 and 23 grams of sugar per 30 mL (1 fluid ounce) serving; you'll have to find the tabulated densities for sucrose solutions (the primary contribution to the sugars is cane sugar: sucrose.

Hopefully you'll find what you're looking for. TenOfAllTrades(talk) 21:30, 24 April 2010 (UTC)

Here's my guess: the syrup curdles the cream, creating globules (curds) that are denser and therefore fall into the syrup until the density finds an appropriate equilibrium. Any chemists out there know if syrups are acidic enough to do this?128.193.45.125 (talk) 22:11, 24 April 2010 (UTC)

You might be right - but I suppose there is another possibility. I suspect that the syrup and the cream are very similar in density - with the cream being very slightly the denser. As the cream descends through the liquid, the density gradient will reduce the downward force on the cream to the point where there isn't enough density difference to provide a force that will overcome the viscosity of the liquid. Hence, I'd expect the cream to stop moving just before it's at the right density level. What we have now is a slightly unstable situation - but without enough energy in the overall liquid to overcome the viscosity barrier. But there is still small-scale random motion going on - so it's only a matter of time when two or three streams of liquid flow that happen to be heading in the same direction join and together provide enough energy to overcome the viscosity of the syrup. Hence, the cream breaks through in these "fingers" that appear more or less at random. Once they get started, they can be self-sustaining and will eventually allow the cream to flow to the very bottom.

It would be interesting to get an accurate measure of the densities of syrup and cream...but because either can absorb water and other 'stuff' in this complex mixture, it may be that they absorb other parts of the liquid at different rates. Any system as complex as this is going to be very tough to analyse.

SteveBaker (talk) 00:32, 25 April 2010 (UTC)

First human

This may sound oversimplified, but evolutionarily speaking, would the mother of the first homo sapien have been a different species than her offspring? Spellcast (talk) 20:49, 24 April 2010 (UTC)

Strictly speaking no. Because to breed, both parents would need to be of the same species in order to produces fertile offspring. Yet, I have this feeling that some one will post... Yeah But !... --Aspro (talk) 22:14, 24 April 2010 (UTC)

Here is the Yes But bit Neanderthal#Interbreeding_hypotheses. --Aspro (talk) 22:24, 24 April 2010 (UTC)

Yeah but "able to reproduce with fertile offspring" isn't really a satisfactory definition of species. See Species#Definitions_of_species for 14 different definitions of what constitutes a species, of which "fertile offspring" is just one. Most of these definitions would say that the mother was indeed the same species as her child, assuming that she was pretty much like her child in most respects. Which would make the child not the first homo sapien, leading to a paradox. Conclusion: there is no single definition of what exactly constitutes a species, and you have to be comfortable with some blurry boundaries between one species and another. Staecker (talk) 22:41, 24 April 2010 (UTC)

Species is a fuzzy, fluid concept, so there's really no point in trying to establish a final cut-off on who was human and who was just a dirty ape. Vranak (talk)

Interesting argument by Dawkins here Count Iblis (talk) 23:21, 24 April 2010 (UTC)

Ah yes, I'm glad you linked to that interesting article, which I now recall reading years ago. Dawkins' mention of ring species is quite useful in applying here. Spellcast (talk) 01:30, 25 April 2010 (UTC)

Yes, an excellent article by Dawkins. Thanks Count Iblis. It reinforces the notion that a new or different species is identified in retrospect rather than at its first appearance. When a number of creatures are determined to be different to other similar creatures we say they represent separate species of the same genus. It won't necessarily be unambiguous so there is likely to be learned debate about where the boundary lies between the two species. (Genetically, there are millions of differences within any one species.) There is also likely to be speculation about how many thousands of years ago the two species diverged. It certainly won't be possible for the mother of a new-born to say Whoops, I've given birth to the first member of a new species. Dolphin (t) 07:00, 25 April 2010 (UTC)

If we had a solid definition of what is a human - some kind of a bright-line measurement (or set of measurements) - then you could say that the mother of "the first human" was (by definition) not human. However, we don't have a measurement like that. When we look back through the hominid fossil record, we see slow, continuous, change from something that's clearly an ape-like non-human to something that clearly is human with perhaps a couple of million years between those two fossils. We cannot put a stake in the ground and say that at on April 12th on 2123456 BC there was a sudden change between the "obviously not human" and the "obviously human" in the fossil record.

Evolution isn't like that...well, mostly it's not like that. If we look at a specific attribute of what makes us what we are, there are abrupt changes. The one I usually trot out at times like this is the evolution of lactose-tolerance in adults. There is a very specific change on chromosome 2 that flips a switch between lactose tolerance and lactose intolerance - there is no halfway house here. You are either one or the other. So we know for sure that the first lactose-tolerant human child was born of a lactose-intolerant human mother (probably around 4,000 to 6,000 years ago in some part of the world where people started to farm sheep and goats on a large scale).

So if you found some single, special feature of humanity that was controlled by an "on/off" gene like that - then you'd be able to point to that specific baby that had that specific gene and say "definitely human" - and to the mother of that baby and say "definitely not human". But we don't have such a specific gene...if we did, we'd probably be able to point to a specific skull in a long line of them in a museum someplace - and say "that one is human - that one isn't" - but we can't do that, so there is no single gene that we've chosen to mean "human" or "non-human".

That's not to say that we couldn't do that - we could look at our nearest relatives (chimps, gorillas, etc) - find a gene that we have that the chimps and gorillas don't have - and label that "the human gene". But doing that would be extremely controversial. Suppose we picked a particular gene on the long arm of chromosome 7. A child born with a rare genetic condition called "Williams disease" might well be missing that gene. Are we then going to label that child "not-human"? Of course not! But if we picked a bright-line definition of "human" then this kind of thing would happen all the time. I don't think we have the cold-hearted scientific rigor to do something like that.

Our modern definition of "human" is something like "born of a human mother" (although "born from an egg produced by a human mother" might be a better choice if we were to develop artificial wombs or something in the future). But that definition leaves us with a very definite "chicken and egg" problem.

So we have to accept that "humanity" isn't a black-and-white thing. There have been animals around in the past that have been "almost human" and others that are "somewhat human" - but nowhere has there been a step where a "definitely not human" gave birth to a "definitely human" child. What happened was that a "49.9% human" mother gave birth to a "50.1% human" child, the child looked, behaved and performed more or less identically to his/her brothers and sisters - looked like his/her mommy - maybe was slightly better at the "walking upright" thing - maybe fractionally more intelligent - maybe a tad less hairy...but not so much that you'd notice.

In the end, like so many RD:Science questions, this is not about science - it's about the definition of a word. What the OP is asking is a matter of linguistics. I recommend reading Chicken or the egg - an odd article - but actually very meaningful in the context of this question.

SteveBaker (talk) 00:13, 25 April 2010 (UTC)

See http://www.onelook.com/?w=homo+sapiens&ls=a. - Wavelength (talk) 00:25, 25 April 2010 (UTC)

...and in what way does that help? All of those dictionaries say things like "The primate species of mammal to which modern humans belong. Homo sapiens is Latin for knowing man or wise man."...but that completely fails to draw a bright line between this species and other, older species. It also fails in that the word "species" is a totally fuzzy, inadequate term. There is nothing in any of these definitions that would allow you to say "This creature is a human...that one isn't"...and that's what it would take in order to provide a "Yes" answer to our OP's question. Without such a 'bright line' definition (which would undoubtedly have to be genetic in order to be useful) - the answer is a clear "No" - there is no small step along the way from ape to human at which you could say that the mother was non-human and the child was human. SteveBaker (talk) 06:59, 25 April 2010 (UTC)

April 25

relation between the expansion of orbits and of the universe

It seems quite reasonable that because orbits like the Moon can expand that such expansion could the explanation for the expansion of the Universe since orbits seem to be a Universal phenomenon, pun intended. Indulging this line of thought consider that somewhere then there must be a center about which everything orbits which probably contains the center of mass as well. What science denies that such a center exists and that orbit is only a local phenomenon and not one that is totally universal? Plain vanilla with chocolate chips (talk) 05:28, 25 April 2010 (UTC)

I'm sorry - but what you are suggesting makes zero sense.

Why would you think that the gradual expansion of the moon's orbit would have anything to do with the expansion of the universe? The gradual increase in the moons' orbit is caused by gradual consumption of the moons' kinetic energy as it raises tides - there is no such mechanism happening in the universe as a whole. You can't just say "Thing A is expanding because of reason B, hence the expansion of thing C must also be because of reason B."

So I'm not going to "indulge this line of thought" - because it's 100% wrong. There doesn't have to be a "center" about which everything orbits or a "center of mass" because this whole orbital theory of yours is not remotely true:

• We know the universe is expanding because we see redshift in light from distant galaxies.
• Einstein field equations of general relativity explain why this is happening in mathematically specific form.
• General relativity is an exceedingly well tried and tested theory.
• Furthermore, many experiments - including the decisive observations of the cosmic background radiation) prove conclusively that space has been expanding ever since the big bang.

To be credible, your "explanation" would have to explain why Einsteins' field equations are somehow incorrect and explain why we observe all of the other effects of general relativity and somehow find another explanation for all of those experiments which you are (in effect) saying must be false.

Science does not allow you to just come up with a mental model that (to you) explains something you don't understand. You also have to tie that in to all of the other aspects of physics that relate to that idea. You won't be able to do that - which is why we know you're wrong.

I suggest you carefully read Metric expansion of space which explains what we know - how we know it - and (crucially) which experiments have been done to show that these theories correctly explain our observations...but "orbits" have nothing whatever to do with that.

SteveBaker (talk) 06:48, 25 April 2010 (UTC)

Gravity is often depicted as an indentation on a grid. How do you express the moon's expanding orbit on this grid? Does the grid become flatter and flatter in the area of the moon's orbit and it so what happens if it becomes entirely flat? Same question for the Universe assuming there is a center around which everything else orbits? Would not this flatter and flatter grid represent the expansion of the Universe as the area of orbit furthest from the center just like we see in galaxies? Plain vanilla with chocolate chips (talk) 09:06, 25 April 2010 (UTC)

I would be inclined to agree partially with the original post in that the earth revolves around the sun, the solar system aroung the galaxy and the galaxies around some greater point, what is that point?

Physics-Question regarding Vacuum

What happens when a fan is switched on inside a perfect vacuum? Imagine a glass room that is completely sealed. Perfect vacuum is maintained. A battery is kept in and a fan be connected to it. If we switch it on with any remote controller, will it run or what happens?

It is very easy to answer this question without having to achieve a vacuum. Simply remove the fan blades and run the electric motor. Without a load on the motor it runs at its zero-load speed. Contrary to what you might imagine, the unloaded electric motor doesn't keep accelerating forever. Electric motors have an equilibrium speed determined by their power source and their system of magnetic field and wiring. With no load, the motor will run at its no-load speed. When the motor is loaded, such as with a fan, it runs at a speed somewhat slower than its zero-load speed. Have a look at Synchronous motor. Dolphin (t) 06:25, 25 April 2010 (UTC)

Also, I suspect that the motor may overheat, since it lacks moving air to cool it. Radiation cooling is still possible, as is conduction cooling to the case, but probably wouldn't be sufficient to cool a motor designed to use forced air cooling. StuRat (talk) 07:02, 25 April 2010 (UTC)

If the motor has internal friction (as all "real" motors do) - then the fan would run quite a bit faster than it would in air - but the system would quickly reach an equilibrium at which point all of the electrical energy coming from the battery would go into overcoming friction. If you imagine a totally frictionless motor - then it would either continue to speed up faster and faster so long as you kept a charged battery connected to it...or it would cease to draw power from the battery when it reached a certain maximum speed. (Which of these things would happen depends on the design of the motor). SteveBaker (talk) 07:07, 25 April 2010 (UTC)

There is a limit on how fast the magnetic polarity of the motor's electromagnets can be swapped, which must occur at least twice per revolution (and for most motors, a lot more). This in turn limits the speed of the motor. CS Miller (talk) 09:14, 25 April 2010 (UTC)

If we're talking about the portable battery operated fans that we use in our motor-homes, hobby shacks, etc. then it would be a cheap-an'-cheerful brushed DC motor . It would speed up a bit with no load but the back Electromotive force being generated would limit its maximum speed . As the article Brushed DC electric motor explains As As an unloaded DC motor spins, it generates a backwards-flowing electromotive force that resists the current being applied to the motor. The current through the motor drops as the rotational speed increases, and a free-spinning motor has very little current. It is only when a load is applied to the motor that slows the rotor that the current draw through the motor increases. So it would run a bit cooler without load, but without some gas present to aid cooling, it would get hotter and hotter. The cheap-an'-cheerful bearings are unlikely to be lubricated with vacuum grease (nor employ dry running ceramic ball bearings) so there goes your hope of maintaining a perfect vacuum. The insulating vanish on the windings would start out-gassing with the rising heat too. The plastics would also 'out-gas' and you'd lose perfect vacuum that way too. You would lose vacuum faster than you could pump out the vapours and thus the motor would then start to lose heat. A quick consideration of the tribological effects of the vacuum and one has to ask what happens as the lubrication evaporates and the bearings dry. Without their lubrication (and protective oxide layers) the metal will (or may, depending on different things) start to form many temporary 'micro-welds' creating heat and the micro-weld particles and rough surfaces produced from this, increasing the friction. The carbon brushes will also wear out and fail in a very much sorter time when run in a vacuum. Another phenomena you might witness as the commutator spins: that without the presence of air to quench all those little sparks, a low voltage Corona discharge may lead to speed loss due to shorting. Putting all that together: The fanless fan, would most likely seize first, and if there is no current trip, the windings will (in places) short and glow about 'cherry red' (at which point it will be radiating heat more efficiently), until the conductors sublimate into space/vacuum and an open circuit condition is achieved. If NASA could ignore these problems, it could buy most of its stuff from RadioShack and space exploration would be a lot cheaper. --Aspro (talk) 09:38, 25 April 2010 (UTC)