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December 15

computable universe

Episode 1 of "Through the Wormhole" with Morgan Freeman has left me with a flurry of thoughts. Someone talked about reality as we know it to be a possible computer simulation of a "god" programmer... which leaves us with the eternal question - "Where did this godlike programmer come from?" - but this is not my question. What was stated was that the universe has a finite resolution or pixellation and if so, the entire universe can be computed or duplicated in a simulation. They talked about computers being able to perform realistic simulations in 5 years time (computers about 500 times more power than today's) so why not universe-scale simulations in hundreds of years given that the universe is 13 billion years old? My questions: does reality have a finite resolution? What if there are smaller subatomic particles than currently known to science - then the resolution would get finer not so? Would it ever be possible for any computer to simulate the entire working of the universe? How can this be, given that the computer is always made up of fewer elementary particles than the universe itself? Sandman30s (talk) 04:50, 15 December 2010 (UTC)

The limit is the size of the smallest possible black hole. Since black holes have no hair, anything smaller than that does not matter. What this means is that whenever there is too much "stuff" inside a given sphere to resolve it all on the surface of that sphere the mass is too much and it collapses into a black hole. Hence the surface area of the observable universe can easily contain all the information inside it.

Added: Where are the fnording links between Simulated reality and Holographic principle? Hcobb (talk) 05:43, 15 December 2010 (UTC)

Yes, the universe does appear to be pixelated. At a fine level many things are quantized and can only change in discrete amounts. Why this is is not known. Regarding the computer - it's pretty obvious that a computer can only simulate a universe that is smaller than itself - probably much smaller. This could mean that there is a huge chain of computers each simulating ever smaller universes. It's impossible to know. For all you know your entire life could be an RPG played by someone in our parent universe (sound kind of like religion and heaven, doesn't it?). However I should point out that currently computers are not getting faster, but they are getting more parallel, then again, reality simulation is a pretty parallel process - especially since the speed of light means that distant computation units don't have to talk. But it's impossible to know, so I've chosen to live my life as if I were real, and not a simulation. BTW the Simulated reality article is quite excellent. Ariel. (talk) 08:35, 15 December 2010 (UTC)

The "simulated reality" article is excellent in the sense that there's a large overlap between the type of people who edit Wikipedia and the type who are prone to that kind of superstition, so it gets a lot of attention. It's not science, though. It's essentially a form of religious belief. -- BenRG (talk) 09:08, 15 December 2010 (UTC)

It's excellent because it covered many possibilities and described the implications and limitations of each. If you define "religious belief" as a desire to explain the origin of the universe without evidence then sure, but to me religious belief also includes an element of worship, which this topic does not have. To me this topic is speculative, not religious. Ariel. (talk) 11:03, 15 December 2010 (UTC)

Well... it's entirely possible that the universe is discrete/finite in some way. There isn't what I'd call clear evidence for it, or against it. It's not even entirely clear what it would mean for the universe to be discrete/finite. The idea of "computer simulation" seems to me rather silly, since computers are physical devices whose existence and correct operation depends on the laws of physics. You might be able to ask "is the universe computable?", using an abstract mathematical notion of computability, but to ask "is the universe run on a computer?" suggests to me a certain failure of imagination.

"The limit is the size of the smallest possible black hole" doesn't make sense to me. You may be talking about the Bekenstein entropy bound, whose physical significance isn't entirely clear. I don't think there should be links between "Simulated reality" and "Holographic principle", since I can't see any connection in either direction.

Morgan Freeman is an actor whose main marketable skill appears to be his awe-inspiring voice. I haven't seen the show in question, but I'm going to go out on a limb and guess that it's full of cringeworthy nonsense. They mostly are, these days. -- BenRG (talk) 09:08, 15 December 2010 (UTC)

Cringeworthy? Nice word, lol. Thanks for the responses guys. Sandman30s (talk) 09:42, 15 December 2010 (UTC)

I question the claim that the Universe is pixellated. Pixellation implies that a continuous reality is identified only by samples and the intervening reality is invalid. Ignoring reality between samples is the source of Sampling error and the incorrect (aliassed) appearance of fine detail - see Nyquist–Shannon sampling theorem for a frequency-domain explanation. One encounters infinite (not quantised) precision in math identities such as the square root of 2 and Transcendental numbers such as e and the ratio pi, and in fractals. Is the claim saying that math does not apply to reality between the pixels? Cuddlyable3 (talk) 10:22, 16 December 2010 (UTC)

It's not that the intervening reality is invalid, but that things can only change by discrete amounts - which matches quantum physics quite well, and the "sampling error" does actually show up, in for example, things like blackbody radiation. Math is not a thing, it's an idea, so can take on any value desired - a physical circle on the other hand not have exactly Pi ratio of circumference to diameter, the ratio is slightly changed because the atoms have finite resolution. Ariel. (talk) 22:56, 16 December 2010 (UTC)

The answer to the OP's "Where did this godlike programmer come from?" given by this frequently-mentioned-here speculative philosophical paper is that: it came from us. WikiDao ☯ (talk) 21:10, 16 December 2010 (UTC)

The simulation of the entirety of reality brings up the problem of determinism vs. Free will. Of course, then there are the numerous chaotic components that fully exist even in a deterministic system. What about the potentially computable multiverses and possibility of retrocausality given the quantum Zeno effect? ~AH1^(TCU) 02:53, 18 December 2010 (UTC)

At least your brain is simulating a virtual environment based on the input it receives from the external world. What you experience is always the events in that virtual world, not the real world. It is just that the simulation mimics real world events (unless you are dreaming or hallucinating), that you are fooled into believing that whatever you are experiencing happens exactly like you are experiencing it in the real world. Optical illusions clearly demonstrate this fact.

The conclusion thus has to be that we are all algorithms that exist in a big universe that is running all these algorithms. The universe itself is presumably also just an algorithm. There may not be a physical world at all, it could be that all that exists is pure math. Count Iblis (talk) 22:21, 19 December 2010 (UTC)

Full name for "Issiki", Japanese Lepidoptrist active ~1930 - ~1960

Hi all,
Yet again, pet peeve is authorities without biographies. One "Issiki" is binomial authority for N. elongata, N. nipponensis, N. matsumurana, and many more. Who is this Moth-man? (nb: "Issiki" looks like Kunrei-shiki romanization. "いしっき" would probably more likely romamised as "Isshiki" - see Wikipedia:Manual_of_Style_(Japan-related_articles)#Romanization). Thanks again. --Shirt58 (talk) 11:03, 15 December 2010 (UTC)

Full name appears to be Shūchi T. Isshiki (in Hepburn romanization) – see these papers. Physchim62 (talk) 15:06, 15 December 2010 (UTC)

Nice work! I spent half an hour on that without any luck. Ginger Conspiracy (talk) 16:06, 15 December 2010 (UTC)

I don't know if it matters at this point, but your hiragana version of the name doubled the wrong consonant: it should be いっしき. ja:ヨトウガ mentions an 一色周知 who is presumably the same person, but there's no biography and no other mention in the Japanese Wikipedia. -- BenRG (talk) 21:37, 15 December 2010 (UTC)

どっ!--Shirt58 (talk) 12:59, 17 December 2010 (UTC)

It appears he is a Japanese biologist, I found an obituary for him (in Japanese here), I'll summarize some of it it if anyone's still interested.

He was born in Wakayama prefecture, educated first in Japan, professorship in Taiwan in the 1930s-50s then returned to Japan to do more teaching eventually passing away in 1978? at the age of 86. The main text doesn't say anything about his work, just the circumstance of the last few days of his life in hospital. It's kind of amusing if you're interested in this kind of thing. 173.183.68.27 (talk) 01:57, 16 December 2010 (UTC)

"ELSC0501: Error is occurring in displaying full Text PDF file."

"Because PDF file may be displayed normally, please act bellow."

"1. Search again because of the case of the close of the session."

"2. Change your browser's setting to accept Cookie because of the case that your browser doesn't accept Cookie."

Did all of the above, but still no joy for for me. --Shirt58 (talk) 13:44, 17 December 2010 (UTC)

Milk Powder

I want to know how milk powder are produced ?... I used to think it is produced from orignal milk but now I doubt it.. as it seems impossible to do that.... —Preceding unsigned comment added by 220.225.96.217 (talk) 12:54, 15 December 2010 (UTC)

We have an article, powdered milk. Feel free to come back here if you any unanswered questions from that article. CS Miller (talk) 13:08, 15 December 2010 (UTC)

Article was very helpful thanx.... :) —Preceding unsigned comment added by 220.225.96.217 (talk) 13:23, 15 December 2010 (UTC)

What if Newtonian mechanics were the correct model of reality?

How would a universe in which Newtonian mechanics were the correct model of reality differ from a relativistic universe? --J4\/4 <talk> 13:39, 15 December 2010 (UTC)

Let me paraphrase a (possibly apocryphal) story attributed to Johannes Keppler. Apparently, one of his students asked him "Wasn't it kinda stupid that people a few generations ago thought the sun moved around the Earth" and Keppler's response was "If they had been right, how would it have looked different?" The fact is that, for most people, living their lives as though Newtonian mechanics is reality works; which is why it is still a good, workable theory. After all, if I'm trying to calculate the torque in my car's engine or the energy evolved in a chemical reaction, Newtonian mechanics works quite well, and there's often little need during most people's day-to-day lives to invoke quantum mechanical calculations and explanations. Answering how the universe itself would appear different if the laws of quantum mechanics didn't work is kinda nonsensical; we might as well ask how things would look if "magic" were real. --Jayron32 13:58, 15 December 2010 (UTC)

I don't think it's quite on par with asking if "magic" worked. The theories give different predictions, unlike "magic". At this stage it is hard to imagine such a change because many of the questions and investigations we've asked since then only make sense in light of the theories themselves. (To ask what Bell's theorem would look like with quantum mechanics is obviously nonsensical, for you need the latter to even conceive of the former's existence, much less truth.) But one could say, "if Newtonian mechanics was correct, there should not be any black holes," for example, (if that is true, I don't know). One might even be able to come up with a cosmological model (steady state, expanding, big bang?) that is or isn't compatible with Newtonian mechanics, though I imagine that is a bit too much work for the Ref Desk. --Mr.98 (talk) 14:41, 15 December 2010 (UTC)

In a newtonian universe, objects can reach infinite speed in a finite amount of time. I wish there was a wikipedia page about this but apparently there isn't, so see http://plus.maths.org/content/outer-space-twos-company-threes-crowd 157.193.175.207 (talk) 15:09, 15 December 2010 (UTC)

In a relativistic universe, objects can reach infinity in finite proper time (always traveling at sublight speed). I think this is related to the Newtonian result. -- BenRG (talk) 04:19, 16 December 2010 (UTC)

Speed is acceleration times time. How can an object reach infinite speed without either infinite acceleration or infinite time? The former is ruled out because by Newton's 2nd law F=ma infinite acceleration could only be obtained by an infinite force (impossible) or a zero-mass object (impossible). Cuddlyable3 (talk) 09:52, 16 December 2010 (UTC)

The linked article does not in fact directly assert that the objects reach infinite speed in finite time. It says that they become infinitely separated in finite time. That must mean that the speed approaches infinity over that interval, but neither the speed nor the acceleration would have to actually become infinite at any moment before the actual singularity. Once you reach the time at which they are infinitely separated, presumably the whole analysis breaks down; for example, if the physical universe is modeled as R³, then there is no such thing as two infinitely separated points. --Trovatore (talk) 10:03, 16 December 2010 (UTC)

What do you suppose is the object's finite average speed during the acceleration to infinite separation? Did Newton have any reason to disbelieve that his stated laws apply throughout an infinite universe? Cuddlyable3 (talk) 10:48, 16 December 2010 (UTC)

Suppose for example that an object's position for t<0 is k/t, where k is some constant. Then its position approaches infinity as t approaches 0. The speed as a function of time is -k/t², which is finite for t<0. The average speed is infinite. There is a singularity at t=0 when the object "reaches infinity", but no singularity before that moment. That's the kind of situation being talked about here. Yes, it's weird, and the physical significance of it isn't clear. (Well, Newtonian physics is wrong, but the physical significance of the relativistic version isn't clear.) -- BenRG (talk) 14:13, 16 December 2010 (UTC)

There's something a little flaky about the claims on the webpage, though. Newtonian mechanics may be wrong, but I'm not aware of anything in it that contradicts conservation of energy. Nevertheless it appears that the total energy of this five-particle system is supposed to increase without bound prior to the singularity. There's a piece missing here; I don't know what it is. Maybe the linked page is just wrong? Or maybe it's leaving something out of the informal description. --Trovatore (talk) 20:47, 16 December 2010 (UTC)

Conservation of energy holds just fine in Xia's example of a non-collision singularity in a 5-body problem. The source of the craziness is that according to Newton's theory of gravity, between two point particles there's an infinite amount of potential energy available to be consumed. The gravitational potential energy between point particles of mass m and M is U= - GMm/r. So the potential energy at any finite separation is infinitely greater than the potential energy at r=0. Xia's construction basically shows a way to turn that infinite potential energy into infinite kinetic energy. Non-collision singularities in the Newtonian n-body problem are discussed in more technical detail here. Unfortunately, there appears to be only three sentences covering non-collision singularities in the article space, at n-body problem#Singularities of the n-body problem. Red Act (talk) 22:24, 16 December 2010 (UTC)

Ah, that makes sense. I hadn't realized they were point particles. --Trovatore (talk) 22:47, 16 December 2010 (UTC)

Black holes wouldn't exist, so they wouldn't have accretion disks emitting x-rays. So maybe they would be even darker neutron stars. Ginger Conspiracy (talk) 16:21, 15 December 2010 (UTC)

Stars themselves wouldn't exist. Newtonian mechanics doesn't have a means to adequately deal with nuclear processes like fusion and fission; it's not that its somehow wrong about them, it just completely doesn't deal with it. The big problem with Newtonian mechanics isn't its wrongness, its that it simply ignores or doesn't deal with many issues that make our Universe exist in any meaningful sense. The question doesn't make any sense because it assumes that modern physical theories have supplanted "classical" physical theories because the classical theories were "wrong". That isn't all that true. The classical theories work just fine. Its just that there are huge parts of the universe that the old theories simply don't deal with at ALL, so attempting to construct a universe where those phenomena which can only be explained by post-classical theories like quantum mechanics doesn't make sense. At all. Unless we go back to designing a universe that operates on epicycles and the Music of the Spheres, there just isn't a way to answer the OPs question in any meaningful sense. --Jayron32 16:44, 15 December 2010 (UTC)

Why is relativity necessary for fusion or fission? I thought they're a strictly quantum chromodynamic and electroweak-nuclear force interaction process independent of relativistic constraints. Ginger Conspiracy (talk) 18:09, 15 December 2010 (UTC)

Because relativity explains mass-energy equivalence. Quantum theory is useful for explaining the mechanics of nuclear reactions, but the core concept that mass and energy are two expressions of the same thing comes from relativity. And both relativity and quantum theory are post-Newtonian theories. The OP asks what would happen if the universe only worked by the laws of Newtonian mechanics. I was merely pointing out that it is a nonsensical question because Newtonian mechanics ignores major observable phenomena. It doesn't get these phenomena wrong, which is what the OP implied, it just doesn't deal with them at all. --Jayron32 19:00, 15 December 2010 (UTC)

Fission and fusion are not fundamentally much different from chemical reactions: you rearrange some particles into a new binding state of higher or lower total energy, either storing or releasing some energy in the process. I don't see why nuclear reactions require E = mc² any more than chemical reactions do. On the other hand, I don't see how the standard model of particle physics can work nonrelativistically, since all of its fundamental fields are massless and the massive particles that we see show up through secondary mechanisms. In particular, most of the mass of protons and neutrons is actually the strong force binding energy of the quarks. I don't know how one could make a nonrelativistic version of that mechanism, but I wouldn't be willing to bet that it's impossible. -- BenRG (talk) 04:19, 16 December 2010 (UTC)

Atoms would not exist. Hcobb (talk) 17:17, 15 December 2010 (UTC)

Why not? Ginger Conspiracy (talk) 18:09, 15 December 2010 (UTC)

In a purely Newtonian world, an electron circling a nucleus, as in the Rutherford model, would emit electromagnetic radiation as per the Larmor formula, losing potential energy in the process, causing the electron to spiral in toward the nucleus until it collided with it. See Bohr model#Origin. Red Act (talk) 20:09, 15 December 2010 (UTC)

Even if the universe was Newtonian except for nonrelativistic quantum mechanics, the masses of atoms would be significantly different, because the mass defects of the nuclei would be zero. Red Act (talk) 20:31, 15 December 2010 (UTC)

In a quantum but not relativistic world, chemistry involving heavier elements would also be different, because relativistic effects of atomic orbitals become significant in heavy elements. For example, gaseous Hg₂ would exist, and gold would appear white. See Relativistic quantum chemistry. Red Act (talk) 20:57, 15 December 2010 (UTC)

Wow! Thanks both Red Act and Jayron. Ginger Conspiracy (talk) 02:42, 16 December 2010 (UTC)

What distance is a Newtonian Light-year? If you answer that it is about 63 000 Astronomical units then how long does it take for the light of the Sun to reach the Earth and why is this not immediate? Cuddlyable3 (talk) 09:58, 16 December 2010 (UTC)

It would be the same distance. There are two possibilities:

1. Photons are particles, and NOT waves, and the speed would vary based on the relative motions of the emitter and receiver, i.e. light would act like small bullets which are launched at a certain speed, but which can be speed up or slowed down by the motion of what launched them.
2. Photons are waves, and travel in Ether.

It's not possible to have non-relativistic photons that are both particles and waves. Ariel. (talk) 20:57, 16 December 2010 (UTC)

Ariel there is contradiction between saying that the distance light travels in a year is always the same, and that the speed of light varies. Newton wrote in "Optics" that light is a particle. Wave/photon duality would only be an issue raised by Young long after Newton died. Cuddlyable3 (talk) 01:02, 17 December 2010 (UTC)

The distance as measured from the emitter. Not as measured by all observers. So I guess Newton was self consistent with his theory? Obviously Newtonian mechanics is not sufficient to explain things, this is just a "what if". Ariel. (talk) 03:19, 17 December 2010 (UTC)

No Ariel, in Newtonian mechanics there is no relativism of distance measurements, In his 1704 book Opticks, Isaac Newton reported Rømer's determination of the speed of light and he explained Newton's rings not in the modern terms of wave interference but instead supposed that the light particles were altered or excited by the glass and resonated. He would have considered neither quantum nor relativistic mechanics as useful explanations because the laws of classical mechanics seemed accurate in all circustances. Cuddlyable3 (talk) 20:43, 18 December 2010 (UTC)

I don't see any problem with building the basic tenets of quantum mechanics, such as wave-particle duality, on a Newtonian background. (Some parts of quantum mechanics wouldn't work, but many parts would.) You'd probably have to treat photons as actual particles with a non-fixed speed, but we can observe wave-particle duality with electrons and other massive particles traveling at non-relativistic speeds, so I don't see any reason the same couldn't be true of hypothetical photons having non-fixed speed. Dragons flight (talk) 04:48, 17 December 2010 (UTC)

If I traveled at exactly the same speed as the photon what would I see? (BTW This is the question that Einstein asked which led him to relativity.) Unlike regular particles, photons can not exist if their frequency is 0. Ariel. (talk) 06:05, 17 December 2010 (UTC)

binary stars in Centauri system

Do scientists know if alpha and beta Centauri are tidally locked with each other? Googlemeister (talk) 17:19, 15 December 2010 (UTC)

Um, I'm gonna say no, since Alpha Centauri is 4 light years from earth, and Beta Centauri is 525 light years away. --Jayron32 17:24, 15 December 2010 (UTC)

My bad, I mean Alpha Centauri A and Alpha Centauri B. Googlemeister (talk) 17:35, 15 December 2010 (UTC)

(ec) I assume OP meant alpha Centauri A and B. No they're not. The orbital period of the system is 79.9 years, the rotation periods of the two stars are 22 days and 41 days, respectively. If they were tidally locked, all of these periods would be the same. --Wrongfilter (talk) 17:36, 15 December 2010 (UTC)

Do we know of any tidally locked binary stars? Googlemeister (talk) 14:08, 16 December 2010 (UTC)

Yes: [1], [2]. (Google "tidally locked binary" for more; it looks like tidal locking has interesting effects on the convective mixing of the stars' atmospheres.) TenOfAllTrades(talk) 14:25, 16 December 2010 (UTC)

Earth Rotation

Assuming the earth is orbiting the sun in a circular motion, how many days would be in a year? —Preceding unsigned comment added by 96.61.186.193 (talk) 18:31, 15 December 2010 (UTC)

The orbit being circular rather than a non-circular ellipse doesn't change the length of the year. The orbital period (that is, the duration of the year) is a function of the distance from the earth to the Sun (see Kepler's laws of planetary motion#Zero eccentricity). There some more info at Earth's orbit. -- Finlay McWalter ☻ Talk 18:45, 15 December 2010 (UTC)

Also, the earth's orbit is nearly circular. It is literally an elipse, but only barely so. The orbital eccentricity of the earth is 0.016, which means that average deviation from a perfect circle is only 1.6%. I'd have to do the calculations, but I believe that both of the foci of the elipse of the Earth's orbit actually lie within the sun itself. --Jayron32 18:55, 15 December 2010 (UTC)

Yes, they do. Physchim62 (talk) 19:01, 15 December 2010 (UTC)

A body travelling in an elliptical orbit will move faster when it is closer to what it is orbiting and slower when it is further away. The average of that speed is how fast something in a circular orbit of the same length would travel at, giving the same length of "year" for both. Vespine (talk) 21:37, 15 December 2010 (UTC)

For the record, Earth rotates around its (shifting?) North-South axis while it revolves around the Sun, so this subsection should've been named Earth Revolution. 66.108.223.179 (talk) 23:53, 15 December 2010 (UTC)

Why didn't anybody try swinging a rock from a long enough string in a still enough place to notice that the rock kept alignment with the fixed stars instead of the Earth sometime shortly after the invention of string? Hcobb (talk) 00:01, 16 December 2010 (UTC)

You mean like a Foucault pendulum? Generally, one would need a reason to construct one. --Jayron32 00:04, 16 December 2010 (UTC)

Anyway, the answer to the original question is that we can't say, because the original poster didn't specify which particular circular orbit is intended. But if the intention is that the orbital radius would be equal to the average of the actual aphelion and perihelion distances, then the length of the year would be the same as it really is. --Anonymous, 01:45 UTC, December 16, 2010.

Siping rubber soles?

Our article on siping says that the inventor of the process originally used it to improve the traction on his shoes in a wet slaughterhouse environment. I can find plenty of information on siping automobile tires, but little on shoes. I would like to try siping my soles to improve traction on ice/snow. Can anyone advise me on ideal number / depth of cuts to make? How about the geometry? Thanks, SemanticMantis (talk) 20:43, 15 December 2010 (UTC)

*checks soles* Try v-shaped grooves three to four millimeters deep in a crosshatched pattern every centimeter or two, especially where the soles appear already worn, as you'll have more pressure there. Ginger Conspiracy (talk) 00:58, 16 December 2010 (UTC)

Thallium(III) hydroxide

What is its appearance? Gray? --Chemicalinterest (talk) 21:22, 15 December 2010 (UTC)

White. All thallium(III) salts are white unless the anion is coloured. Physchim62 (talk) 23:07, 15 December 2010 (UTC)

Really? IIRC oxide is not colored. --Chemicalinterest (talk) 23:15, 15 December 2010 (UTC)

The Properties list in the article you link to states "brown-black", C. 87.81.230.195 (talk) 01:39, 16 December 2010 (UTC)

That seems to be a confusion. Thallium(I) oxide is black, thallium(III) oxide is colourless (which means white, if it's an amorphous powder). Physchim62 (talk) 15:47, 16 December 2010 (UTC)

Grass as edible food source for humans

Other than feeding it to other animals and have them produce meat or milk, is there any artificial method to more efficiently turn grass into edible food for humans? Disregarding taste of course. ScienceApe (talk) 22:39, 15 December 2010 (UTC)

Grass organic matter could be burned and converted into energy, and the energy could be used to clone chicken meat. Disregarding the taste of course, because apparently cloned chicken meat tastes like wet sponge. 173.183.68.27 (talk) 22:43, 15 December 2010 (UTC)

Do you get to choose which species of grass are involved? Many species of grass have grains that are commonly eaten by humans. Wheat, barley, oats and rye are all even in the same subfamily (Pooideae) as many of the common lawn and pasture grasses. Corn and bamboo (which has edible shoots) are also in the "true grasses" (Poaceae) family. Red Act (talk) 23:22, 15 December 2010 (UTC)

Oh, rice is a grass, too. Three grasses – rice, wheat and corn – provide more than half of all calories eaten by humans. See Poaceae#Food production. Red Act (talk) 23:33, 15 December 2010 (UTC)

(ec)What are the aspects of grass that make it inedible? I assume we're talking about the "lawn grass" sense, not the larger group that includes cereals which are already commonly eaten by humans? Probably some enzymes exist that could break down certain components. For example, if cellulose is the problem, cellulase could convert it to glucose. Heck, if you have a high-cellulose-content grass, right there is a neat way to convert it to a sugar that could be separated for consumption. Can grass be fermented? I know a lot of college students seem to live on a fairly steady diet of ethanol. Or else that could free up other crops (corn, barley, etc.) to be used for human food (your grass wouldn't directly be turned into food itself, but it would lead to production of it). DMacks (talk) 23:29, 15 December 2010 (UTC)

Sure grass can be fermented, but it would usually be considered silage. — Preceding unsigned comment added by SemanticMantis (talk • contribs) 00:40, 16 December 2010 (UTC)

Remember that 'grass' normally refers to the leaves of Poaceae spp, but 'cereals' refers to their seeds. CS Miller (talk) 12:21, 16 December 2010 (UTC)

Right, and silage is made "using the entire green plant (not just the grain)". Obviously the types of plants and proportions of plant parts will vary, but fermented leaves of Poaceae spp. are a large component of silage. SemanticMantis (talk) 15:28, 16 December 2010 (UTC)

If you're just trying to make use of the grass clippings from mowing your lawn, the grass clippings can be composted, and then the compost can be used as fertilizer in your vegetable garden. Red Act (talk) 00:23, 16 December 2010 (UTC)

Yeah I'm just talking about regular lawn grass that you find everywhere, but can't be digested by humans. ScienceApe (talk) 01:29, 16 December 2010 (UTC)

Disregarding taste, fermenting your lawn clippings would allow you to gain some calories from ingesting them. If you are interested in efficiency, grass is not the way to go. Our article addresses many environmental concerns, including runoff of insecticides and fertilizers, as well as high water usage. I'd rather gain efficiency by not having a lawn, rather than finding ways to make grass into human food.SemanticMantis (talk) 15:39, 16 December 2010 (UTC)

Yes, I recall hearing a radio programme about grass being put through a machine which opened the cells and turned it into a green 'milk' which was fed as an effective health supplement to malnourished children in South America. I also recall hearing about one or two enthusiasts for the human consumption of grass in Britain. Edit: searching Google finds the Chayen Impulse Process, described here, http://books.google.co.uk/books?id=M42stMBW_VwC&pg=PA458&lpg=PA458&dq=chayen+grass&source=bl&ots=bmab0CI4id&sig=i369bvSAcT5WPzjAUBV0MqSwjJs&hl=en&ei=kjYKTfrYNZK0hAfWsdnIDw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCcQ6AEwAg#v=onepage&q=chayen%20grass&f=false but the radio program I heard was a lot more recent than that, and perhaps was done with just a small machine. Correction: it may have been leaf protein they were eating in South America, but that coulsd include grass perhaps. eg http://scholar.google.co.uk/scholar?hl=en&as_sdt=2000&q=chayen+grass+malnourished 92.28.247.44 (talk) 15:51, 16 December 2010 (UTC)

building on buoyant coral

I'm working on a relatively complex sci-fi concept, and I'm trying to develop the idea with a realistic (though implausible) explanation of how it works. Basically the goal is to have some sort of living biological system that grows in equilibrium with the other organisms that it consists of, at least one having a buoyancy in high-seas so great that were the system large enough, it could float a city above (and/or below) it. It's a little more complex than just a huge forest of microbial cork though, because building on it would obviously cause it to lose buoyancy (and raise the water level), so the system would have to be in a state of balance with the water level in that submerging it caused it to grow faster > buoyancy, or perhaps made it more buoyant for some other reason. That's why I think this would make more sense as being the result of biochemical relationships between a number of organisms, living at different levels above/below the water.

Some species of coral (or rather, the fossil remains of them) are known to float spontaneously when air slowly? replaces some of the water inside, but the buoyancy wouldn't be enough and the coral is obviously dead, so that doesn't really work. Given that this is sci-fi, I'm thinking more along the lines of splicing characteristics from a number of organisms together, so for example a coral-like bacteria could be genetically engineered to secrete something vastly less dense than calcium carbonate.

I'm basically at a road block, because I can't get my head around the process that would allow the system to modify its buoyancy dynamically with the amount of force applied to it, and simply "modifying coral to make it better" doesn't really seem like a good feasible premise for a sci-fi concept lol. Any ideas? I'm not much of a biologist so any examples from nature that I've missed would be great! Thanks! 173.183.68.27 (talk) 22:41, 15 December 2010 (UTC)

One of the advantages of sci-fi is the ability to branch out into fantastic, but realistic, life forms. I'm not sure I have a direct solution (maybe an organism that's a giant air bladder is part of the ecosystem?) but an author you should perhaps look to for inspiration is biologist Julie E. Czerneda. Her life forms are fantastically well detailed and researched, especially their ecological background. Her "Species Imperative" series really does a good job of inventing some spectacular ecosystems and life forms which still obey the basic rules of ecology. --Jayron32 22:45, 15 December 2010 (UTC)

The nautilus uses a neat system called a siphuncle to adjust its buoyancy, maybe you could design something around that. Mikenorton (talk) 23:01, 15 December 2010 (UTC)

See floating island for something sort of similar. Looie496 (talk) 23:35, 15 December 2010 (UTC)

Your system has muscular swim bladders. They are attached to the surface with long spiracles. Submerging the top of the spiracle stimulates the bladder to open, and exposing it to too much air stimulates it to close (but this stimulation is very slow, so it ignores waves). If the bladder stays fully open, it stimulates the organism to grow another, and if it stays closed for too long it atrophies. Be aware that normally the muscles in a bladder squeeze, which is the opposite of what you want, so yours has two contracting muscles on either side that pull it open instead. Additionally in the spiracle it has a sphincter that can close the bladder (so the pulling muscles don't have to be constantly working). Ariel. (talk) 00:39, 16 December 2010 (UTC)

A strange "living" island floating in the ocean features in the book Life of pi. It has a spongy floor with "trees" and pools of "clean water," but it's also like a carnivorous plant after the sun goes down. But it's not really "real" it's sort of a dream or metaphor or something related by the protagonist, it's hard to explain. I personally don't recommend the book, it was recommended to me but i didn't like. Actually i just thought to google it and there's a straight dope article about it. Vespine (talk) 04:55, 16 December 2010 (UTC)

Here's one idea that springs to mind, and is (kind of) feasible. When extra weight is placed upon the floating mass, more of it becomes submerged. As more is submerged, the outer shell of the submerged parts expand as water absorbs into them. This expansion causes the internal spaces to expand, and this expansion draws in more air through the parts which are above the water-line. When more air has been drawn in, the buoyancy stabilises. When weight is removed, the reverse happens. The outer shell dries out more, decreasing the size of the outer shell, which squeezes the air pockets more tightly, which cause less air to be held, and the buoyancy decreases. This system would provide a consistent level of buoyancy. Hope this helps! Zzubnik (talk) 10:25, 16 December 2010 (UTC)

December 16

What is a Hill sphere of Sun?

What is a Hill sphere of Sun? Basically at what distance from Sun object will orbit Galaxy center rather then Sun? If you can, please use AU when answering. 70.52.184.140 (talk) 02:47, 16 December 2010 (UTC)

I thought the article on comets might help and indeed under the heading of "single period comets" was the answer The Sun's Hill sphere has an unstable maximum boundary of 230,000 AU (1.1 parsecs (3.6 light-years)).. Vespine (talk) 04:41, 16 December 2010 (UTC)

I'm not sure that's accurate. The comet article cites a 1964 Paper by Chebotarev as the source for that figure - that paper is reproduced in English here - the relevant section is section 6 "solar gravitational sphere", pp621-622 of the original journal. There Chebotarev says "For the mass of the galaxy we assume the value M=1.3 × 10¹¹ solar masses." And indeed if one runs that through the formula given for a simple (non-eccentric) system given at Hill sphere, one gets a value for r of 225837 AU (with the value for the semimajor axis Chebotarev cites); that's consistent with the 230,000 value he gives.

But that paper is 46 years old, and it looks like the current estimates of the galaxy's mass are quite different. Looking first at Wikipedia's numbers - Milky Way says its mass is roughly 1.4×10⁴² kg, and the Sun article says its mass is 1.9891×10³⁰. Going by those figures, the mass of the galaxy is 7.038×10¹¹ solar masses, making the galaxy 6 times more massive than Chebotarev's numbers. Running that through the equation (with a slightly refined value for a, again from Sun) gives us a Hill radius of 130,261 AU (down from Chebotarev's 230,000).

But there's more. If you ask Wolfram Alpha for "mass of the galaxy" it says 6×10⁴² kg which it says is "based on 2009 velocity data from Mark Reid using the Very Long Baseline Array (VLBA)" (I guess that's the finding discussed here). That gives us a mass ratio of 30.2×10¹¹, making the Hill radius about 80,000 AU - that's about a quarter of Chebotarev's number.

I've done the math on this in a hurry, so I'd be grateful if someone could check my numbers. But it does look like Chebotarev's calculation is based on a very wrong estimate of galactic mass. -- Finlay McWalter ☻ Talk 19:41, 16 December 2010 (UTC)

Moreover, ask Wolfram Alpha "distance from the sun to the centre of the galaxy" and it says 2.349×10²⁰ m (it cites a bunch of astronomical sources). That's quite a bit lower than the values given by Wikipedia or Chebotarev; plugging that into the equation and we get an estimated Hill radius of 75,350. It's noteworthy that the estimated radius of the Oort cloud is around 50,000 AU. -- Finlay McWalter ☻ Talk 19:59, 16 December 2010 (UTC)

Wow, I'm going to bookmark you if I ever have any astronomy questions, great answer. Vespine (talk) 04:35, 17 December 2010 (UTC)

A poem and its related biological/neurological functions:

I just wrote this poem and am curious for someone to shed light on the biological function breakdown of the things I exclaim in it...

Entry004:

The tier on which love operates at its prime; a prime that has seemingly lasted forever, and has no plans of changing anytime soon: (In no particular order of importance..)

Getting to actually know her, her secrets, what makes her tick,, the like; and loving every part about them.

Evolving my golden standard in perfect sexual chemistry, and furthermore the best sex ever even beyond what I once deemed fathomable.

She is the absolute definition of beauty, be it both in pure hotness, cutest, or most gorgeous (Jewish accent)i. And is such a good fuck, yet also the mistress of making love all with a synergistically perfect” key-lock combo”

And all of these things intersect in spacetime…

A-A-W. Cuddlyable3 (talk) 10:51, 16 December 2010 (UTC)

Current electricity

Even though current is scalar why the directions are assigned? —Preceding unsigned comment added by 180.215.52.172 (talk) 10:56, 16 December 2010 (UTC)

One of the properties of a direct electric current is that it is accompanied by a magnetic field. The magnetic field is described by vectors and the orientation of these vectors is dependent on the direction of flow of the electric current. Therefore it is possible to identify the direction in which the electric current is flowing. Dolphin (t) 11:32, 16 December 2010 (UTC)

Scalars can be signed. Ginger Conspiracy (talk) 07:04, 17 December 2010 (UTC)

To say that perhaps a bit more clearly, current is not actually a scalar, it is a vector. In many applications it is possible to simplify things by working only with the magnitude of current and ignoring its direction, but even so it does have a direction. Looie496 (talk) 00:10, 18 December 2010 (UTC)

Current is certainly a vector. Consider applying an electric potential across an anisotropic conductor such as a piece of graphite: the direction of the current will depend on both the direction of the field and the orientation of the graphite (and in general will not be parallel with the field. --ColinFine (talk) 23:51, 19 December 2010 (UTC)

Prison Riot

in a Prison Riot do the guards get raped —Preceding unsigned comment added by 66.66.92.152 (talk) 13:39, 16 December 2010 (UTC)

I don't know. Which particular prison riot did you have in mind? I'd imagine that in some cases, guards get assaulted. No idea on the nature of the assault. --Jayron32 14:27, 16 December 2010 (UTC)

The Wikipedia article on Etiquette does not address the issue but such an action would conform less than favourably with the Manners that are due to a kindly person who tucks one in at night. Cuddlyable3 (talk) 16:19, 16 December 2010 (UTC)

A simple search for 'prison guards raped riot' finds [3] which suggests it's a common fear among guards that it may happen in a riot (it also mentions one riot where it happened among hostages which I guess includes guards), our article New Mexico State Penitentiary riot which mentions some some guards were treated for beatings and rapes (it also mentions several prisoners were tortured, burned and killed in the riot) and [4] on the 25 (or 26 if you include the fun one) worse riots which includes the New Mexico State Penitentiary riot (the only other prison related item in that list is the 1981 Irish hunger strike, it's perhaps not the best source considering it says the Kosovo is Serbia protest 2008#Protest in Montenegro was about Serbia recognising Kosovo). As Jayron said it obviously happens, whether it happened in any particularly riot, you'd need to look in to that riot. Nil Einne (talk) 17:01, 16 December 2010 (UTC)

Whip scorpion

What do whip scorpions do with their tails? The Wikipedia article says nothing about this, which is odd, since it is a pretty distinguishing physical characteristic of the creature in question and the origin of its popular name.

This site says they use them in self-defense. (How?) This one says it is a sensory organ. (What kind?) In general there seems to be a lot less discussion of this on the web than I'd expect.

What's the truth? Can someone find a solid reference and update the article with it? --Mr.98 (talk) 14:42, 16 December 2010 (UTC)

Interesting question. All the scholarly articles I can find on defensive behavior focus on the composition and effects of the chemicals released from the glands at the base of the tail. Seems like the defensive use of the whip is a bit of a red herring, although it may help them mimic regular scorpions to scare away predators. This article is probably a good source, but I can't easily find it online; Biologie der Geißelskorpiones (Uropygi Thelyphonida) J Haupt - Memorie della Società Entomologica Italiana, 2000 SemanticMantis (talk) 16:26, 16 December 2010 (UTC)

Just because its tail has a different shape than other scorpions' doesn't mean it won't have a stinger. The smaller tail likely allows greater agility for dual use as a feeler. Ginger Conspiracy (talk) 07:01, 17 December 2010 (UTC)

Whip scorpions do not have stingers on their tails. Cursory googling will give you plenty of references. SemanticMantis (talk) 16:49, 17 December 2010 (UTC)

Boat movement problem

If a boat is moving in upstream with velocity of 14 km/hr and goes downstream with a velocity of 40 km/hr, then what is the speed of the stream ?

I assume that this is a homework problem and you meant to say that the stream is flowing at the rate of 40 km/hr (although that's mighty fast, so maybe that's the boat and the stream is flowing at 14 km/hr). We won't do your homework for you but can help with how to solve it:

1) If both the boat and stream are moving in the same direction (downstream), then you just add the numbers together and that's how fast they are moving downstream.

2) If they are going in opposite directions then you subtract the smaller number from the larger, and that's how fast it's going, and whichever original direction number was larger, that's the direction it's going. So, if the upstream speed is bigger, then subtract the downstream speed from it and that gives you how fast it's going upstream. But, if the downstream speed is bigger, subtract the upstream speed from it and that gives you how fast it's going downstream. (This problem can also be done by adding two numbers, one of which is negative, but that's more complicated). StuRat (talk) 15:07, 16 December 2010 (UTC)

x-y=14
x+y=40
x= boat speed
y= stream

although i guess you could switch the variables —Preceding unsigned comment added by 173.166.164.91 (talk) 15:41, 16 December 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.

Just to clarify: if motion upstream is positive and motion downstream is negative, and x and y are as you define them above, so that x+y=14 km/hr relative to a stationary observer on the bank of the river, what would x-y be then? Is that what you are talking about, or is it something else? WikiDao ☯ (talk) 20:55, 16 December 2010 (UTC)

Paul Dirac Equations??

I was watching a BBC4 program last night regarding equations and was drawn in by the enthusiasm of, I assume, a Dirac fan.

He wrote down an equation that I believe represented some explanation to the overall understanding of matter/anti-matter but cannot find this equation listed in the Wikipedia page on Paul Dirac.

The equation is as follows:

i,gamma,p,spinner = m,spinner

Please advise where I have mis-understood what was being relayed and if this equation exists? —Preceding unsigned comment added by 86.10.74.128 (talk) 14:51, 16 December 2010 (UTC)

The equation you're looking for is the Dirac equation, which in natural units such that $\hbar$ and c are 1 can be expressed as

$i\gamma ^{\mu }\partial _{\mu }\psi =m\psi$ .

See also Dirac spinor. Red Act (talk) 16:48, 16 December 2010 (UTC)

A bomb’s flash, Why would it happen?

From the NYT: "the scientists found that a bomb’s flash would blind many drivers, causing accidents and complicating evacuation. " However, wouldn't the glass block the UV, therefore, not blinding drivers? 80.58.205.34 (talk) 17:18, 16 December 2010 (UTC)

It is more than just UV that burns, it is virtually the whole spectrum. The flash can melt the retina -even if your wearing shades..Effects of nuclear explosions--Aspro (talk) 17:34, 16 December 2010 (UTC)

Also, you're only considering permanent damage, but for someone driving, even momentary/short-term vision impairment is a problem. A bright visual flash can do that (consider your visual ability right after staring directly at a flashbulb, or a Flashbang grenade). DMacks (talk) 17:38, 16 December 2010 (UTC)

According to one of his memoirs, Richard Feynman shared your reasoning and watched the Trinity test through a windshield with no goggles. --Sean 19:52, 16 December 2010 (UTC)

About 40 years ago I read that AND he also described his observation point being about 20 miles from the initiation site. Considering the intensity of light falls off as the .... of the distance... etc. A windscreen (laminated with PVA as opposed to triplex as common in 1940 auto mobiles) provides little if any protection to flash blindness emanating from a bucketful of sunshine.

According to flash blindness, a 1-megaton bomb can cause temporary blindness at a distance of up to 13 miles. The Trinity nuclear test was only 20 kilotons, so it seems plausible that Feynman would be fine observing it directly at a distance 20 miles. Of course, it was certainly a non-trivial risk to decide to look at the very first detonation since he couldn't really be sure what the effects would be. Dragons flight (talk) 21:35, 16 December 2010 (UTC)

Or what the yield would be, for that matter. But it should be remembered that 20 kt was actually a very high yield for the bomb. It was expected that it would be far less efficient than that — most scientists involved had guessed it would be only a kiloton or two at most. --Mr.98 (talk) 21:50, 16 December 2010 (UTC)

It's of note that Feynman himself reported an impressive afterimage at 20 miles. If he was driving said car, and had no idea that a bomb was about to go off, would he have kept it together or would he have crashed it? We can't know, obviously, but it's worth noting that even in the Feynman scenario (ideal from a number of standpoints), it was still a pretty potent visual effect. --Mr.98 (talk) 21:48, 16 December 2010 (UTC)

Indeed. In Surely You're Joking, Mr. Feynman!, he recounts

"Time comes, and this tremendous flash out there is so bright that I duck, and I see this purple splotch on the floor of the truck."

While he wasn't completely blinded, he saw one heck of an afterimage. Even though Feynman was expecting the blast he still reflexively turned away from it; consider the effect on a motorist moving at speed and caught by surprise. 04:48, 17 December 2010 (UTC)

Does the volume of cylinder affects Pressure

Let consider I have a cylinder filled with compressed gas (let air), if half of gas is taken of would the pressure of remaining gas reduce. Here I mean that when the half of cylinder will be empty then the remaining gas will have some volume to expand inside the cylinder so will the pressure decrese..? —Preceding unsigned comment added by 220.225.96.217 (talk) 20:32, 16 December 2010 (UTC)

Yes. This is an example of Boyle's law, which is a special case of the ideal gas law that applies when the temperature is constant. Red Act (talk) 20:44, 16 December 2010 (UTC)

However if the gas is partially liquified due the high pressure than some of the liquid will evaporate filling the space and keeping the pressure constant, as long as there is enough liquid inside. 71.101.41.73 (talk) 03:08, 17 December 2010 (UTC)

Why fog is mostly seen in morning ?

Why fog is mostly seen in morning ?. and disappear as the sun shines.... does it because we can't see them in darkness of night... or is there some science behind that...? —Preceding unsigned comment added by 220.225.96.217 (talk) 20:37, 16 December 2010 (UTC)

The sun heats up the earth, which allows the air to hold more moisture, so the fog (floating water droplets) evaporate. --Sean 20:44, 16 December 2010 (UTC)--Sean 20:44, 16 December 2010 (UTC)

Fog happens when the ground is warm and moist and the air is cold. That situation is more common in the morning, but can also happen at other times of day if a mass of cold air moves into an area where the ground retains heat. Looie496 (talk) 21:12, 16 December 2010 (UTC)

See Fog#Types. The type of fog that develops overnight (and you can see in the morning) is called "radiation fog" and the one that's made by moving air masses such as a Warm front is called "advection fog". Alansplodge (talk) 09:30, 17 December 2010 (UTC)

@Sean - Air does not "hold" moisture. For a full explanation (and, for the OP, a clear and very accurate description of how fog is created) see here and here for a more in-depth background. Matt Deres (talk) 23:44, 17 December 2010 (UTC)

Fog is essentially a cloud on the ground. The Sun increases the temperature of the near-surface air in the last morning so as to decrease the relative humidity of the air so the fog droplets no longer form. Ice fog also often occurs in the morning as does black ice. ~AH1^(TCU) 02:33, 18 December 2010 (UTC)

Why on every Wathc they write Quartz ?

I have seen many watch from hand watch to wall clock and seen that all of them having written Quartz on them.. why so ... is there any component which is made of Quartz. or it is some kind of patent...? —Preceding unsigned comment added by 220.225.96.217 (talk) 20:39, 16 December 2010 (UTC)

See quartz clock. --Sean 20:44, 16 December 2010 (UTC)

Thanks to cheap quartz watch brands such as Swatch, having a quartz crystal is not the novelty it used to be, so the "quartz" labelling is not always shown. Cuddlyable3 (talk) 01:12, 17 December 2010 (UTC)

Though labeling tells you that it doesn't need to be wound in any way. The counterpart on older (wound) watches was a listing of how many jewels it contained. --Mr.98 (talk) 03:22, 17 December 2010 (UTC)

Yea, it's a bit like finding a radio that boasts "stereophonic sound !" ... you know you have an antique. StuRat (talk) 05:05, 17 December 2010 (UTC)

This is an excellent little video that describes how a quartz watch functions. --Mr.98 (talk) 13:47, 17 December 2010 (UTC)

It's a pretty video but gives no idea of the circuit needed to make the crystal oscillate, just connecting a battery won't do. It would also have helped to explain why 32768 Hz is chosen, it is 2¹⁵ cycles per second. Cuddlyable3 (talk) 20:54, 17 December 2010 (UTC)

Quartz watches are practically normal and have nothing to do with quality. I have a watch that cost 1 US dollar and it says "quartz" on it. --Chemicalinterest (talk) 14:34, 18 December 2010 (UTC)

Thallium(I) oxide production

Can it be made by burning thallium powder in air or would that also make the sesquioxide? --Chemicalinterest (talk) 22:04, 16 December 2010 (UTC)

I'm not a chemist but isn't it unlikely that simply combusting it in air will result in a significant amount of the (I) oxide? I would guess there will be a lot of other oxides, including nitrogen oxides. Vespine (talk) 23:27, 16 December 2010 (UTC)

I can't find the exact answer, but the reaction of thallium with moist air produces TlOH. The standard method for production the anhydrous oxide is by decomposition of the carbonate at 700 °C. To produce the sesquioxide, you seem to need an oxidizing agent that is stronger than air (e.g. Br₂), but I'm going on fairly sparse data there. Physchim62 (talk) 23:49, 16 December 2010 (UTC)

From doi:10.1006/jcht.1993.1128 Tl₂O made by Tl₂O₃ volatilized at around 1000 K in a stream of water-vapor/oxygen, which equilibrates with TlOH under those conditions. DMacks (talk) 10:30, 17 December 2010 (UTC)

Thallium(I) carbonate, I presume, is made by reacting thallium(I) oxide with carbon dioxide... --Chemicalinterest (talk) 12:09, 17 December 2010 (UTC)

December 17

Pterodactyls

Could someone explain for me in layman's terms, what the difference between a pterodactyl, pteranodon and a psterosaur is? I've seen all three terms used interchangably in writing in the past. Thanks. —Preceding unsigned comment added by 95.148.109.104 (talk) 00:09, 17 December 2010 (UTC)

Pterosaurs were the whole order of flying reptiles. Pterodactyloidea was a suborder of pterosaurs. Pteranodon was a genus of large flying reptiles. --T H F S W (T · C · E) 00:29, 17 December 2010 (UTC)

And I really wanted to answer that question! :) But yeah, he covered it. Crimsonraptor (talk) 00:37, 17 December 2010 (UTC)

In even more layman's terms... Pterosaurs is a term which includes a lot of different species of dinosaurs. Pteranodon is a sub-group of species within that group. Pteranodon is a sub-group within that group, which contains two species, which are usually the specific birds you think of when you refer to Pteranodons. --Mr.98 (talk) 14:38, 17 December 2010 (UTC)

"Birds", maybe, but not birds! --Sean 17:24, 17 December 2010 (UTC)

That's not layman's terms, it's just completely incorrect. THFSW had it right - none of the terms listed have ANYTHING to do with dinosaurs or birds. Please be more careful before you try correcting someone who knows what they're talking about. 64.235.97.146 (talk) 18:11, 17 December 2010 (UTC)

Untreated ringworm does... what?

Ringworm is apparently quite common in both humans and other animals. When humans get it (assuming a certain level of medical care is available) they can resolve the problem quite quickly with modern antifungals and such. But what happens if the dermatophytosis is left untreated, as one would expect for a stray dog or cat? Does the fungus just happily reside on the surface of the skin indefinitely? Does it eat deeper and deeper into the tissues? The ringworm article kind of sucks. The Masked Booby (talk) 01:35, 17 December 2010 (UTC)

I would imagine that ringworm may itself not be harmful in the long term, but it greatly increases the risk of secondary infections, due mostly to the fact that you are scratching it all the time. Those secondary infections could be a major problem, and could perhaps be too numerous and varied to list here. --Jayron32 02:25, 17 December 2010 (UTC)

There's an old story that claims that a ringworm around the abdomen will kill you when it completes a full circle. Not sure of that statement's validity. ~AH1^(TCU) 02:28, 18 December 2010 (UTC)

The same myth exists with shingles. Complete balderdash of course! Caesar's Daddy (talk) 08:25, 18 December 2010 (UTC)

Tiger cheese

Are there any carnivores whose milk is consumed by humans? LANTZY^TALK 03:36, 17 December 2010 (UTC)

Historically and prehistorically, it seems rather unlikely. You'd have to feed them meat edible to humans, whereas cows and such eat things we can't. Plus they'd be liable to be a whole lot less docile and prone to evil thoughts of eating their keepers. But hey, you may have hit upon a novelty product. Clarityfiend (talk) 04:55, 17 December 2010 (UTC)

But lots of carnivores eat things we wouldn't want to eat, like cats eating mice and dogs eating skunks (which might just curdle their milk :-) ). StuRat (talk) 05:02, 17 December 2010 (UTC)

Ugh! Finish all yummy mice, Tumak. Are Neanderthals in cave somewhere starving! Clarityfiend (talk) 05:24, 17 December 2010 (UTC)

People do drink dogs milk sometimes, here's a vid of a kid, but adults probably do it too (although maybe not directly). There is also pig cheese and presumably milk too. Ariel. (talk) 06:25, 17 December 2010 (UTC)

(Edit Conflict) Romulus and Remus legendarily fed on a wolf's milk, and I vaguely recall accounts (not necessarily verified) of more recent feral children similarly surviving temporarily on an adoptive canid or other wild animal's milk. 87.81.230.195 (talk) 06:37, 17 December 2010 (UTC)

Didn't the King James Bible have a verse in Genesis saying something like "Seven sons did milk a bear?" Edison (talk) 00:59, 18 December 2010 (UTC)

If you're going to call a bear a carnivore (hint, they're not, except Polar bears), then we should also consider Human milk, which many people consume as an infant, and occasionally later in life. Buddy431 (talk) 02:48, 18 December 2010 (UTC)

A couple more thoughts. The cost of keeping meat-eating critters is much higher than what you could possibly get back in the form of milk. On a more practical note, who're you going to get to milk a tiger? Clarityfiend (talk) 02:53, 18 December 2010 (UTC)

Is this whole thread somehow inspired by Tiger's Milk? --Trovatore (talk) 03:19, 18 December 2010 (UTC)

Crazy kid again... with more subjective thoughts that y'all will hopefully objectify

So through a little bit of work with a pencil and a sheet of paper, i wrote out an arbitrary word problem requiring simple algebra to solve. It was then I realized that if i were to translate this word problem into an equation that each kind of word in the english language (i.e. noun, verb, adjective etc.) would have a parallel mathematical meaning. In algebra class in middle school I was told that the word "of" just meant times. and that makes perfect sense. If was wondering... If I was to ask myself simply "What do I see in my room?" could I answer it in an equation form like ... I see a blanket then assign a variable to the blanket lts say (B) and a mattress then label that mattress L.. to answer my question I would now be able to say What I see = B + M... what I am curious about is going further. Let say I wanted to describe M in more detail by maybe.. saying that whatever function (mattress manufacturing and shipping and whatever else it took to get to my room) lead to the mattress being in my room and being part of my answer for what I see in my room...how would I combine certain aspects of my overall equation

Given

What I see in my room = B + M

M exists because of the function of why it's in my room M(x), x being whatever variables account for why the mattress is in my room.

So now I have

What I see in my room = B + M= B + M(x)

Is any of this correct at all?

Where can I find instructions on how to translate words into pure equations? — Preceding unsigned comment added by BloodWasPassion (talk • contribs) 04:39, 17 December 2010 (UTC)

What you're trying to do looks like the branch of artificial intelligence called knowledge representation and reasoning, which typically represents real-world information in semantic networks. It also touches on computational linguistics, in particular computational semantics. And all of this is a part of natural language processing. Red Act (talk) 05:15, 17 December 2010 (UTC)

How did the mattress get from L to M? You might enjoy Word problem (mathematics education) or Internet Relay Chat (e.g. [5]) more than the reference desk. Ginger Conspiracy (talk) 05:34, 17 December 2010 (UTC)

About Styrofan (construction Chemical from BASF )

Hi, This is Vinay from Bangalore India. can some one give me answers to the following: a) What are the chemical compositions of Styrofan b)Why & how Styrofan should be used in READY MIX CONCRETE what are the proportion c)How many types of styrofan is there & how many of them are for ready mix concrete PLZ SOMEBODY HELP ME ITS VERY URGENT TRIED LOOKING THE WHOLE INTERNET BUT COULD NOT FIND MUCH PLZ PLZ IF IT IS POSSIBLE TO MAIL THE ANS here is my id [removed]. looking forward for the ans

with regards Vinay —Preceding unsigned comment added by 59.97.26.3 (talk) 09:59, 17 December 2010 (UTC)

A) It's water-based styrene butadiene

B) It's a protective coating or binder used for fibre bonding or as an adhesive.

C) There seem to be 19 types

Zzubnik (talk) 10:15, 17 December 2010 (UTC)

I removed the poster's email address, per refdesk standard (ask-here, answer-here; avoid spam-harvesters, etc.) DMacks (talk) 10:22, 17 December 2010 (UTC)

This appears to be the internet resource you're looking for... Physchim62 (talk) 11:06, 17 December 2010 (UTC)

Maxwell's demon (MADE IN JAPAN)

A radioisotope thermoelectric generator

• http://neocoat.jp/neo/english/comparison.html

It seems like this revolutionary paint does not decompose under the sun (chemical heat absorption). Its high-tech molecules just vibrate and keep heat from entering your house.

Are they selling Maxwell's demon by the bucket in Japan? -- Toytoy (talk) 10:42, 17 December 2010 (UTC)

This is the sort of question where things can get very complicated. So, forget about this paint advert which attempts to baffle with science and read this simplified explanation of reflectance/ low emissivity. Low emissivity for use at high temperatures Wikipedia does have an article about low emissivity but it is not easy to take in at a single reading. Note also that high performance heat sinks, such as those found in top class sound systems and on radioisotope thermoelectric generators etc., are nearly always matt black.--Aspro (talk) 14:58, 17 December 2010 (UTC)

Maybe the best WP article is Radiant barrier--Aspro (talk) 15:31, 17 December 2010 (UTC)

I think there shall be a way to make a not-so-Maxwellian-demon heat shield:

• You have to have a material that is capable of phase or chemical change at about 25 deg C.
• The location must have very hot days (e.g., 35 deg C) and very cold nights (e.g., 15 deg C).
• The target room temperature is about 25 deg C.
• You have a great scientist to make this material a commercially successful paint.

During the day, the material absorbs solar energy and undergoes phase or chemical change. The change keeps the external surface from getting very hot. As a result, the house does not get too hot during the day. The paint layer has to be very very thick to act as a heat sink.

Then during the night, the external temperature drops very quickly. The paint releases heat and its phase or chemical change is reversed. Since the inside of the house is warmer than outdoors, the paint releases most of its heat to the cold outside air.

During winter days, this dark-colored material absorbs heat and heats up your home.

Then the paint releases heat to the outside during winter nights. You must have a good heater and a cheap source of fuel otherwise you will be very sorry ...

This certainly is not a solution for everyone of us. -- Toytoy (talk) 16:36, 17 December 2010 (UTC)

That has nothing to do with the paint, which was the subject of your question. Your prediction is now too far into the realms of a crystal ball to warrant further discussion. You have now shown you are just asking lots of questions here on the reference desks because you have nothing better to do. --Aspro (talk) 18:43, 17 December 2010 (UTC)

Is that not allowed? 81.131.62.210 (talk) 19:21, 17 December 2010 (UTC)

??? It's not a crystal ball to ask if something is scientifically feasible. He's not asking about the future. If you don't have anything to say about it... then just don't say anything! Don't be so arrogant as to proclaim that nobody can have anything to say about it. --Mr.98 (talk) 13:24, 18 December 2010 (UTC)

Cryogenic revitalization

Is it possible to revive someone many many years into the future after they have been cryogenically frozen?

We do not presently have the ability to do this, and it is unknown if we will ever be able to do that. Some people do freeze themselves (typically shortly after death), with the hope that future doctors will one day learn how to revive frozen people. See: Cryonics. Dragons flight (talk) 18:12, 17 December 2010 (UTC)

Also note that the freezing process causes ice crystals to grow inside the cells, which destroys them. Unless they find a way to completely prevent this, the chances of ever reviving someone so damaged is very low. StuRat (talk) 19:04, 17 December 2010 (UTC)

There are a few types of animals that are capable of freezing and then reviving -- their cells make a sort of antifreeze that prevents the formation of ice crystals. My sense is that if animals can do it, then sooner or later there will be a technology that allows it to be done to humans, but of course we're in the crystal-ball realm here. Looie496 (talk) 20:34, 17 December 2010 (UTC)

Freezer burn is a major problem in this process, and surgeon nanorobots could be one solution. ~AH1^(TCU) 02:22, 18 December 2010 (UTC)

Vitrification freezers are another. It's a freezer and a microwave; two appliances in one! The Japanese have the best, in the food processing (edamame/soybean preservation) industry, since ice crystals change the texture of frozen vegetables, too, by destroying cell walls. Ginger Conspiracy (talk) 13:44, 18 December 2010 (UTC)

I've always thought one of the biggest problem with cryogenics is that you'll be trying to revive someone who is not only frozen but who is already dead. We need to find a cure for death before we need to worry about defrosting. DuncanHill (talk) 13:48, 18 December 2010 (UTC)

Reviving a mammal who died because of hypothermia and has been preserved since (i.e. by cold) is possible. It takes an electric shock such as from a defibrillator, an artificial respirator, and a way to evenly warm them back up. If there has been severe ice damage, they won't revive. With moderate ice damage they will revive and die a horrible, really disgusting and painful death in less than a day. Light ice damage is survivable with a decreased expected lifespan and infertility in females (the ova are the largest cells, and thus most susceptible to ice crystal damage.) There seems to be a general agreement among researchers to discontinue cryonics research on mammals over a kilogram until vitrification technology improves such that ice crystals aren't expected to be a serious issue. Improvements have been slow and steady, but vitrification freezers are nowhere near human mass range yet. Ginger Conspiracy (talk) 08:14, 19 December 2010 (UTC)

RationalWiki's Cryonics article is much better than ours. Ginger Conspiracy (talk) 01:58, 19 December 2010 (UTC)

Error in Image

In the image File:Decay chain(4n+1,Neptunium series).PNG it says Uranium-223 inside the octagon it should say Uranium-233. 174.112.211.143 (talk) 21:01, 17 December 2010 (UTC)

Fixed it, thanks. --Sean 21:26, 17 December 2010 (UTC)

What percentage of the air expelled rearward from a jet engine actually thrusts an aircraft forward?

Seems like a pretty basic question, which would have the pretty basic answer of "all of it". But I've been looking around our articles and widely through google and can't seem to get the answer. What I am trying to determine is how much of the thrust comes from the exhaust from the jet engine pushing against the atmosphere behind the aircraft, and how much comes from the thrust pushing forward against the engine itself. How is it that in a vacuum a rocket/jet engine pushes itself forward even tho there is nothing behind it to push on? Anyone? —Preceding unsigned comment added by 222.152.15.198 (talk) 21:29, 17 December 2010 (UTC)

You don't need the mass you expel out the rear of the rocket to "push" against anything. The mere fact that you are expelling that mass is what propels you. Googlemeister (talk) 21:35, 17 December 2010 (UTC)

Do you mean that the mass is pushing against the engine to make it (and the aircraft) go forward? I'm not trying to be cute here Googlemeister. If I blow up a kid's balloon and then let it go it will fly around like crazy. Will it behave the exactly same in a vacuum as in my house? If yes, then I guess the answer to my question is that zero % of the air expelled rearward from a jet engine actually thrusts an aircraft forward.—Preceding unsigned comment added by 222.152.15.198 (talk) 22:30, 17 December 2010

Yes, it will behave much the same in a vacuum. That means 100% of the gas expelled from a rocket pushes it forward, but it's all done by Newtonian reaction, not by pushing against some external medium. You get the same effect by firing a gun (the reaction pushes you backward) or a firehose. The little maneuvering jets that astronauts use to fly around when they're outside a space station are quite like a can of hairspray, and indeed an astronaut could take a (big) can of hairspray with them and use it to move them - they just point it in the opposite direction to where they want to go and push the button. -- Finlay McWalter ☻ Talk 23:08, 17 December 2010 (UTC)

Let's say you're kneeling on a skateboard and you're holding a brick. You throw it forwards as hard as you can. What happens to you? You go in the opposite direction, and it's not because the brick is pushing against the air. See Newton's Third Law. --Sean 22:13, 17 December 2010 (UTC)--Sean 22:13, 17 December 2010 (UTC)

I think the answer to this question might not be simply 100% or 0%. Let's compare walking, flying in a jet, and flying in a rocket. In all three cases, some fuel is consumed, to get the energy to move something, to obtain an reaction in the opposite direction. In the case of walking, we burn food and move the earth very slightly. The jet burns fuel and moves the air. The rocket burns fuel and moves the fuel. Question is, can't the jet also be said to be expelling its fuel to some extent? It needs air in order to burn the fuel, but if the air was carried onboard, it would be a rocket, and its fuel would be part of what it was expelling. So, now I'm just confused by what the question means, sorry. 81.131.15.161 (talk) 06:49, 18 December 2010 (UTC)

Ahhhhh, wonderful wikipedia. Thanks for your input, but I'm sorry my clumsy question wasn't clear. What I was trying to find is whether the stuff coming out of the back of a jet engine propels the aircraft forward by pushing against the air behind it or does it propel the aircraft forward by by pushing against the engine? Finlay McWalter has cleared this up admirably, but I can tell you that reading wiki's relevant articles does not truly spell out the answer for people not au fait with the science terminology. Like me. —Preceding unsigned comment added by 222.152.15.198 (talk) 07:10, 18 December 2010 (UTC)

Here's the famous 1920 New York Times editorial that says rockets can't fly in space. 81.131.15.161 (talk) 08:29, 18 December 2010 (UTC)

But let's be fair. They did apologize for that... during Project Apollo. --Anonymous, 18:00 UTC, December 18, 2010.

Does gravity slow down time?

Someone said that clocks are faster in space than they are here on Earth. Supposedly standing next to a pyramid will slow down time by a fraction of a second. Is this true? ScienceApe (talk) 21:45, 17 December 2010 (UTC)

Yes, that is correct. Under Einstein's general relativity, time flows more slowly in a gravitational field. See also our article on gravitational time dilation. TenOfAllTrades(talk) 21:54, 17 December 2010 (UTC)

There are two different effects at work for the most famous clocks in space, the GPS system. 1) Being further from the Earth makes them run faster, gaining 45 microseconds each day. 2) Moving really fast in their orbits makes them run slower, losing 7 microseconds each day. Combined, they would gain 45 - 7 = 38 microseconds each day. Luckily, some smart people thought about this and made the necessary corrections. Details. --Sean 22:31, 17 December 2010 (UTC)

Gravitational time dilation is also the more important effect for satellites in geosynchronous orbit. But for something in a very low orbit, such as a space shuttle, relative velocity time dilation is the more important effect, so clocks on the space shuttle run slower than they do here on Earth. To the right is a graph of how the two effects vary with orbital radius. Red Act (talk) 22:47, 17 December 2010 (UTC)

The pyramids are no different than any other big chunk of rock in this respect. You might as well have mentioned Mount Rushmore. Even so, they're pretty much meaningless. Even our entire planet only changes time by a handful of microseconds per day. The pyramids are minuscule in comparison. APL (talk) 03:06, 18 December 2010 (UTC)

I just plugged in some numbers into the equation for gravitational time dilation. Compared to a stationary clock far from anything, a clock at the surface of the sun runs slow by about 0.18 seconds per day. So being next to the sun slows a clock so much that it's measurable with a cheap stopwatch. Compared to a clock far from anything, a clock at the surface of the Earth runs 60 microseconds slower per day. So being next to the Earth slows a clock by too little to measure with a stopwatch, but very easily enough to be measured with an atomic clock, which is accurate to about 10^-9 seconds per day. But a clock that's about 150 meters from the center of the Great Pyramid, which has a mass of about 5.9x10⁹ kg, will only run about 2.4x10^-15 seconds slower per day due to being next to the pyramid. So being next to the Great Pyramid slows a clock by vastly too little to be measurable by even an atomic clock. Red Act (talk) 08:28, 18 December 2010 (UTC)

My fuzzy potatoes

I bought a bag of sweet potatoes a couple weeks ago, and now they are moldy. I kept them in a cool place (around 60°F), so I was surprised by this. I frequently treat regular potatoes this way, and they don't rot nearly so quickly, but they do occasionally grow sprouts:

1) So, am I right in thinking that the regular potatoes stay alive after they are harvested, and that their immune systems stop decay, while sweet potatoes die and decay immediately thereafter ?

2) If so, what is it about normal potatoes that allows them to survive in my cupboard while sweet potatoes can't ?

3) I wanted to switch to sweet potatoes because they are more nutritious, but does this also make them more hospitable to mold ? StuRat (talk) 22:33, 17 December 2010 (UTC)

Moldy sweet potatoes and months-old "perpetual stew"? You won't need a pension. Re stew, see Bacillus_cereus#Pathogenesis 92.15.4.135 (talk) 14:08, 18 December 2010 (UTC)

Drench them in the same amount of anti-fungal treatment, ensure the RH is low and you probable wont notice any difference.--Aspro (talk) 23:28, 17 December 2010 (UTC)

RH ? Do you mean pH ? And do they really treat normal potatoes with an anti-fungal agent ? If so, why don't they use it on sweet potatoes, too ? StuRat (talk) 23:35, 17 December 2010 (UTC)

Relative Humidity. Roots store well if they are in a dry environment. It is pretty basic stuff they teach school girls in domestic science.--Aspro (talk) 00:16, 18 December 2010 (UTC)

Wikipedia even as an article -as it always does- on Domestic science. Wikipedia is an amazing resource, one should use it more often--Aspro (talk) 00:47, 18 December 2010 (UTC)

Mycotoxins are very harmful, You should throw them away and not eat them. Even the parts that look OK will have the toxins in them. 92.28.242.98 (talk) 23:57, 17 December 2010 (UTC)

Meh. Mold is everywhere, even if you can't see it. Unless things turn soft and yucky, the usual solution is to just cut away the moldy parts. Looie496 (talk) 00:03, 18 December 2010 (UTC)

Professor Sir John Berry would disagree with you. Read the section "Benefits as ephemera" in his article here http://www.spiked-online.com/Articles/00000002D29C.htm Risk, science and society. Unfortunately the diagram seems to be missing. "...Derived from data reported by Mongeau et al (12) on the production of carcinogens (furocoumarins) in infected parsnips {but also applies to other moldy food}. Healthy roots produce little of these toxins, but when infected they are found in greatly increased amounts throughout the parsnip, not simply in the visually altered areas....Cutting out the damaged bits of spoiled vegetables is not sensible". I've noticed that people I assume to be North Americans have such an uncritical attitude to food; yet a large proportion of cancers, heart disease, strokes etc are the result of food choices made in previous decades. 92.15.4.135 (talk) 13:56, 18 December 2010 (UTC)

(EC with 92 and Looie4961) I'm not aware of that practise and I'm not sure what the heck is meant by RH. But to start at the beginning... our concepts of "dead" and "alive" are much blurrier for plants than they are for animals (which can also be tricky) and become downright irrelevant when you start talking about bits and pieces of plants. However, there is usually a period of continued metabolism (usually the transformation of starch into sugars) followed by either an extended period of dormancy or a breakdown of the plant material by outside action (i.e. mold, bugs, potato chip manufacturers, etc.) So, when you harvest a tuber, there are already a number of things going on: there are all manner of microorganisms that have set up shop, but which haven't yet taken hold, there is internal metabolism changing the more complex carbohydrates into sugars, and there is a small release of water vapour, etc. What the mold wants is a warm, dark, damp environment in which to get on with its business. Between the ground and your pantry, it doesn't get as many of things as it would like: the spuds spend time out in the dry air, there isn't that much sugar available, and the skin is relatively dry. But time goes on: sugars increase, there is a buildup of moisture, you've stuck the spuds in a dark drawer, and the metabolism within the tuber is warming it slightly. The longer the potato sits, the more optimum the conditions get for the mold to grow until the inevitable happens. So, why would your sweet potatoes get moldy faster? The same reason you call them sweet: five times the sugar content! And not only odes that give mold a leg up on a normal spud, sweet potatoes also come from further away, meaning they've been out of the ground longer, been in the dark of a ship's hold for longer, and so on. Matt Deres (talk) 00:07, 18 December 2010 (UTC)

PS - my reference for the "five times the sugar content" thing ended up getting blacklisted; Google sugar content potato versus sweet potato and you'll find it. Matt Deres (talk) 00:09, 18 December 2010 (UTC)

My sweet potatoes and yams store very well for months in the kitchen. Perhaps you kept them in a plastic bag or other container which retained moisture. In the rural US, historically they were very easy to keep all winter, longer than regular Irish potatoes or apples. They are hard and relatively dry and stay that way. Your post is very puzzling. Exactly how did you store them? Edison (talk) 00:51, 18 December 2010 (UTC)

You're right, I left them in the plastic bag I got from the store, but I've now removed the survivors and they are now in 20% humidity. Hopefully that will solve this prob. StuRat (talk) 05:14, 18 December 2010 (UTC)

My thoughts too! So, I reiterate what I posted above: Relative Humidity. Roots store well if they are in a dry environment. I reiterate: It is pretty basic stuff they teach school girls in domestic science.---Aspro (talk) 01:04, 18 December 2010 (UTC)

There was no need to reiterate and there would have been no need to explain yourself at all if you had simply been more helpful from the outset. Your snide condescension is also out of place. Matt Deres (talk) 01:31, 18 December 2010 (UTC)

Agreed. StuRat (talk) 05:11, 18 December 2010 (UTC)

One of the issues which has not been discussed is where the OP gought the sweet potatoes from? Unless you know the provenance of the potatoes, they could have been MONTHS old by the time you bought them. A sweet potato which is a few hours out of the ground will likely be indistinguishable from one which is a few months out of the ground; there's no way to tell whether the sweet potato you bought at the SuperMegaMart has months of shelf-life left, or is just about to go off... --Jayron32 00:59, 18 December 2010 (UTC)

In a related Q, do sweet potatoes get worms ? Because some of them have a circular hole about a millimeter in diameter in them. At the store there were some small flying insects buzzing around them, so do the worms grow wings when they mature ? StuRat (talk) 05:22, 18 December 2010 (UTC)

I don't see why not. There are literally too many possible flys and their associated maggots to name which may infest sweet potatoes. Maybe some type of Drosophilidae? --Jayron32 06:55, 18 December 2010 (UTC)

Note that potatoes are an Andean crop which survives the winter underground. In regions subject to the depredations of war or oppressing armies (such as Ireland) they were often harvested throughout the winter so that a military force couldn't effectively seize them from the populace. And of course seed potatoes can be chopped up and replanted. So the life of the potato, under normal circumstances, really isn't in doubt. Wnt (talk) 05:17, 19 December 2010 (UTC)

December 18

Maize recycling...

How to present the recycling method of maize — Preceding unsigned comment added by Raunakstha (talk • contribs) 03:20, 18 December 2010 (UTC)

I'm not sure I follow. One doesn't usually recycle food. One usually eats it. Unless you mean composting food waste?!? I am thoroughly confused. Could you elaborate. --Jayron32 04:26, 18 December 2010 (UTC)

Never seen a corn field Jayron? The OP is almost certainly referring to the ~80% of the plant that's not edible - the stalk, leaves, etc. In rural China people collect it by hand and use it for heating fuel. That's not really what I'd call recycling, though. The Masked Booby (talk) 04:57, 18 December 2010 (UTC)

Then there's the silk, cobs, and leaves from the corn left after you eat it. StuRat (talk) 05:00, 18 December 2010 (UTC)

Roughly one-quarter of the world's food is wasted or uneaten. Perhaps the OP is referring to "recycling" and redistributing this food? ~AH1^(TCU) 15:48, 18 December 2010 (UTC)

MCAT en Français

Hello. Are there any plans of a French equivalent of the MCAT to be recognized by Canadian medical schools underway? Thanks in advance. --Mayfare (talk) 03:25, 18 December 2010 (UTC)

There are three francophone medical schools in Quebec, at the Université de Montréal, the Université Laval and the Université de Sherbrooke. Sherbrooke appears to run its own equivalent of the MCAT, the TAAMUS (Test d’Aptitude à l’Apprentissage de la Médecine à l’Université de Sherbrooke) [6], while Montréal [7] and Laval [8] don't mention anything about a specific aptitude test in their publicity. Physchim62 (talk) 12:52, 18 December 2010 (UTC)

Why does warm air hold more moisture than cold air

I've heard two explanations: that the warm air transfers more energy to the water, preventing it from forming water droplets; and that there is more space between air molecules in warm air, and droplets tend to form in the spaces between air molecules. Which is right, and could anyone knowledgeable elaborate on the explanations? Thanks a lot!74.15.138.27 (talk) 08:02, 18 December 2010 (UTC)

It has nothing to do with "holding". You are thinking about it wrong. There's always PLENTY of space in air (or any gas) to hold more molecules of anything. Indeed, gases at earth atmospheric conditions are on the order of 1/1000 as dense as solids or liquids, meaning that there is generally about 1000 molecular volumes of empty space around each molecule of a gas. So there's plenty of "room" in the air. The reason that warm air has a higher absolute humidity has to do with the competing forces which determine the phase of a substance:

• Intermolecular forces are the forces of attraction between the molecules of a substance. These forces are why solids and liquids exist at all.
• Heat is the energy of molecular motion. The faster molecules move, the greater the forces needed to slow them down.

Now, in a gas, there will always be a range of speeds of molecules. The higher the temperature, the greater number of molecules will be moving at faster speeds. Molecules which don't move fast "enough" to overcome the intermolecular forces will condense out of the gas phase. So the deal with warmer air is, warmer air has a higher percentage of water molecules which will be moving fast enough to avoid sticking to each other than colder air, which is why warmer air has a higher "carrying capacity" for water vapor. So, the first explanation you have is "closer" to the truth. The second one, about having more space between air molecules, is pretty much bullshit. If that were true, then there would be LESS impetus to form water droplets, because the molecules of water would be farther apart on average, and so the intermolecular forces trying to make them condense would be less effective. --Jayron32 13:18, 18 December 2010 (UTC)

ACMA blacklist

whats it — Preceding unsigned comment added by Kj650 (talk • contribs) 14:19, 18 December 2010 (UTC)

Information_published_by_WikiLeaks#Internet_censorship_lists explains it. SmartSE (talk) 14:50, 18 December 2010 (UTC)

The lists leaked by Wikileaks can be still be found at their website (or one of its mirrors): AMCA blacklist. Buddy431 (talk) 23:46, 18 December 2010 (UTC)

A lead on leads

Were leads ever made from lead? Reason for asking: I have some ancient resistors and they are corroded similar to lead. --Chemicalinterest (talk) 14:32, 18 December 2010 (UTC)

Electronic "leads" (pronounced LEEDS) are so named because they are the point of contact between a device and other devices, and thus "lead" (LEED) the connection between the two devices. This has nothing to do with the element "lead" (LED) per se. --Jayron32 14:36, 18 December 2010 (UTC)

From my reading of the question, the OP never suggested such a connection. Dismas|^(talk) 18:13, 18 December 2010 (UTC)

According to its article, it's soft and has poor conductivity, so it would have been an odd choice. Clarityfiend (talk) 21:31, 18 December 2010 (UTC)

The resistors are most likely carbon, not lead. -- kainaw™ 21:52, 18 December 2010 (UTC)

Although I appreciate learning extra facts and tidbits of scientific information, I don't think my question was answered. Did leads originally contain lead? --Chemicalinterest (talk) 22:30, 18 December 2010 (UTC)

I have seen them made from iron, copper and silver. I am sure that somebody tried lead, but the low melting point of lead makes the use very problematic if you solder. resistance is no problem when you only have 5mm length with 0.5mm diameter.--Stone (talk) 22:53, 18 December 2010 (UTC)

The answer is No. "Leads" on electrical components are named from O.E. lædan "cause to go with one, lead"[9]. The name of the metal "lead" has a different root W.Gmc. loudhom. Electrical leads (LEEDS) have nothing to do with the metal (LED), though one can quip that the terminals on a Lead–acid battery are stubby leads of lead. Cuddlyable3 (talk) 23:00, 18 December 2010 (UTC)

The solder used to join leads to components is likely to contain lead. DuncanHill (talk) 00:10, 19 December 2010 (UTC)

Well, yes. The leads (ledes) on electronic components are likely to be tinned with solder, which contains lead (led, or perhaps Pb). But the led is there to melt and make soldering easy, and the lede (most often copper, or Cu) is there to provide conductance and physical strength. Led would be useless as a lede because it melts easily and doesn't conduct well at all. PhGustaf (talk) 00:36, 19 December 2010 (UTC)

The coating or "tinning" of tin-lead solder on the copper wires coming out of the resistor make it much easier to solder them into a device. Bare copper would oxidize and have to be scraped clean immediately before it was soldered. The Pb metal would make a lousy conductor to use in attaching a component, because it is more prone to break than copper, has higher resistivity, and would be prone to melt and separate during soldering. Old time fuse wire, dating back to 1880 or earlier, contained lead, I believe, like solder. A short link of it would melt and interrupt the current when there was a short or a sever overload, before the copper conductors could overheat and start a fire. Edison (talk) 04:18, 19 December 2010 (UTC)

The Degradation of the Human Race by Doctors

Susceptibility to certain bacterial or viral diseases is inheritable in some persons. (A doctor will sometimes ask a patient what his father died of.) If these susceptible people get the disease to which they are prone, medical science will often be able to keep them alive longer than would have been the case in the pre-medical era. The disease-prone people will therefore live longer and will be able to have children or more children. As a result, the proportion of disease-prone people in the population will continually increase. As medical science advances, the problem will accelerate. The burden of supporting and treating the unwell will eventually become intolerable on those who are healthy. Can anything be done about this? How about mandatory sterilization of these persons? This would be one more of the Draconian measures that will be needed if human life is to continue on this planet.-- Diatom. 173.189.136.110 (talk) 15:07, 18 December 2010 (UTC)

This article speaks to your concern, but is focused on domestic dogs [10]. On the other hand, the fact that our medical practices may be decreasing negative selective pressure on deleterious human alleles could also result in broadening the evolutionary search space, allowing our descendants the possibility to develop beneficial mutations that would not be available without negative intermediate forms. Also, since you speak of human sterilization programs, you may enjoy reading up on ethics. SemanticMantis (talk) 15:36, 18 December 2010 (UTC)

I do not like the idea of enforced sterilization. But it may become a necessity as the lesser of two evils. And after all, there is always the possibility of adopting a child. As for waiting for mutations to counteract disease susceptability, the burden of supporting and treating a great many unwell persons may become intolerable. I am talking about a very long term effect - Long term versus shortt term is a known problem in ethics. Diatom. 173.189.136.110 (talk) 17:00, 18 December 2010 (UTC)

The fears about dysgenics have generally been considered over-exaggerated in modern medical contexts, and societies generally will not tolerate compulsory sterilizations anymore done in the name of eugenics. Consider whether you yourself would be happily compulsory sterilized if tomorrow DNA testing told you that there are a statistically higher chance that your offspring would be susceptible to some common virus or bacteria. The social medicine seems worse than the disease in most such cases. --Mr.98 (talk) 15:50, 18 December 2010 (UTC)

Mr.98, you refer to the Wikipedia article on compulsory sterilization. However that article does not deal with the increasing influence of medical science on prolonging life of disease-susceptible persons. That can be expected to continue, with more and more of these persons living longer and longer, and producing more children.

Compulsory sterilization has three aspects:

1. The sterilization of persons of a certain race. The Nazis did some of that.

2. The sterilization of persons who have an inheritable disease, without considering the affect medical science may have in continually increasing the proportion of such persons in the population.

3. The same as item 2, but taking into consideration how medical science allows such persons to continually increase in proportion to the population.

As for society usually being opposed to compulsory sterilization, society takes only a short term view of it. Diatom173.189.136.110 (talk) 17:47, 18 December 2010 (UTC)

Diatom, are you soapboxing? It is a very complicated issue with many factors and implications and a tragic history. I think the answers you have been given so far (above and below this post) have been quite good treatments of this difficult subject, and you should consider them more carefully before trying push further your point that "society" is taking a "limited" view of it. WikiDao ☯ (talk) 18:57, 18 December 2010 (UTC)

This process has, of course, gone on for a long time. Just blame the people who started using fires, enabling individuals with weaker teeth and stomachs to survive and beget children. Or those pesky weavers, who allowed people with insufficient body hair to survive the cold! Humans have always adapted their environment to their benefit, and then evolved to better utilise this environment. Doctors are part of our new environment. Immunity to a disease does not come for free - it comes at a biological cost. If this ability is not needed, it will vanish, and free resources that may allow us to evolve new features useful in our modern environment. Of course, sometimes changes in human lifestyle are slower than evolution. As a result, we still get fat on Big Macs, although for most of us there is little likelihood of ever experiencing life-threatening starvation. --Stephan Schulz (talk) 16:00, 18 December 2010 (UTC)

As for fire and weaving, a similar, partly successful, solution has been developed for disease susceptability. It is medical treatment. But that is often expensive, time consuming, and sometimes requires repeated treatment. There are somtimes serious side effects or infection. It would be muich better to eliminate the susceptability.

Regarding mutations, they are rare. I don't think there has been one in all of human history. Diatom.173.189.136.110 (talk) 20:11, 18 December 2010 (UTC)

Chances that you are not a mutant are negligible. According to this paper, there are 175 mutations per generation. Most of them are neutral, of course. Very few indeed give you superpowers ;-). --Stephan Schulz (talk) 20:24, 18 December 2010 (UTC)

(e/c) Right, but we can afford the expense of health-care (in an overall sense), the modern medical infrastructure has become a part of our environment to which we are adapting short-term (epigenetically, culturally, etc.) and long-term (genetically). Technology will improve those processes, at least eventually in ways that are acceptable to us and don't have unexpected bad consequences. I don't know what you mean by there having been no human mutations, though, you should go read an article or something. ;) WikiDao ☯ (talk) 20:27, 18 December 2010 (UTC)

(edit conflict) They are not rare. There are about 175 mutations per human genome per generation. [11]. Since ~98% of the human genome is not directly associated with protein coding, most of the mutations fall into innocuous regions that have no effect. Some fall on critical genes and the resulting embryo in not viable, leading to spontaneous abortion. But on average, you can expect every baby has around 1 gene (out of 23000) that has been mutated to be different from both their parents. In some cases the effects are profound and deleterious, but in many cases the effects are subtle and not obvious. Dragons flight (talk) 20:29, 18 December 2010 (UTC)

Well, it depends what you mean by "mutation". Every human being is different. They have a different face, for instance. Even identical twins are different - they have different fingerprints, for instance. So it could be said that every person is a mutant. But still, I think there will be a long, long wait for disease susceptability to disapear or turn into something beneficial from that cause. And it will only happen to one person at a time. Diatom.173.189.136.110 (talk) 20:42, 18 December 2010 (UTC)

Mutation has a very well-defined meaning, so we don't really get to choose. Some fairly well-known mutations are the development of Lactose tolerance and the Sickle cell trait. --Stephan Schulz (talk) 20:54, 18 December 2010 (UTC)

The most important thing to bear in mind when thinking about issues like this is that unless selection is extremely rigorous, its effects take dozens of generations (at minimum) to become significant. So in principle it may be correct that if current practices are continued for thousands of years, human vulnerability to disease might increase. But given the vast number of more pressing problems we face, it's hard for me to feel terribly stressed about this. Looie496 (talk) 18:52, 18 December 2010 (UTC)

And it is certainly not the case that people in places with better medical care and longer lifespans produce more children! In fact it is usually exactly the opposite: the more exposure to education, medicine, and wealth a population has, the more their reproduction rate declines. --Mr.98 (talk) 19:50, 18 December 2010 (UTC)

I don't like to ask - but are the Germans healthier than people in other countries, or is there no difference? Did their killing/murdering of disabled people have the effect on the German gene pool that they expected? 92.15.1.13 (talk) 20:01, 18 December 2010 (UTC)

Well, those unfortunate victims of the Nazis certainly did not pass along susceptibility to disease unless sthey had children earlier. Diatom.173.189.136.110 (talk) 20:26, 18 December 2010 (UTC)

This would not be measurable against the noise background, much less separable from other differences due to health system and living circumstances. Also note that eugenics was not limited to Germany, even if the Nazis were particularly ugly at it. --Stephan Schulz (talk) 20:17, 18 December 2010 (UTC)

We are just now entering the era when genetic modification is possible. I wouldn't be surprised to see medical treatments during the next century that routinely eliminate disease causing alleles. That seems a far more likely outcome than any form of forced sterilization. Dragons flight (talk) 20:09, 18 December 2010 (UTC)

The real genetic answer to why eugenics doesn't work is pretty simple. The kind of "weeding" you are talking about only works if there are no recessive traits. If there are recessive traits, then you have to "weed" out people who don't express the given condition as well, which is a vastly greater number than the "sick" population. The Hardy–Weinberg principle essentially makes it clear that if you only sterilize those who express a trait, it will never appreciably affect the total amount of expression in the total gene pool.

Now, what you can do is prevent expression in the form of aborting fetuses with expressed conditions. That is what is done on Cyprus in the instance of thalassemia — the number of carriers in the population remains constant, but the number of those born with the full disease zeroed out in a single generation, because of the use of amniocentesis and selective abortion. It's a controversial case, one that only seems to have gone over on Cyprus because the effects of expressing thalassemia are so violent were becoming such a drain on families and the health care system that people were basically not having kids. I doubt you could do that with the much more minor things you are describing above. The ethics are problematic, in any case, and you aren't actually affecting the "healthiness" of the gene pool — just the "healthiness" of those who get to be born.

Genetics is in any case far more complicated in most instances. There are relatively few conditions that are caused by strict Mendelian heredity. If you start adding in more complicated risk factors (e.g. genetic factors which put one at high risk for breast cancer), you start getting a much wider net of whom would have to be sterilized in order to achieve your "healthier" society. The sweep of eugenics would have to be much more radical than even the Nazis were able to accomplish under a fascist state. It's not feasible. It's not ethical. It's not really very sound science, either. --Mr.98 (talk) 21:43, 18 December 2010 (UTC)

I agree with most of the responses above, and would like to add that eugenics (or breeding, in the case of animals) also fails because what we choose as "healthy" genes may not be what is best for society. For example, eliminating the gene for sickle-cell anemia may cause malaria to spread. And some mental "diseases", like manic-depressive disorder, seem to lead to astonishing periods of creativity. And there may be many other hidden benefits to some of those mutations you dislike, that we haven't yet figured out. StuRat (talk) 00:08, 19 December 2010 (UTC)

I agree that the degeneration of the human genome in response to poor selection should take a very long time, though it is not infinite. The success of feral pigs in many regions should attest to the potential of humanity to shake off the legacy of domestication. In the very long term however we might need to consider the effects of increased background radiation from uranium which has been cracked into shorter-lived isotopes, which will almost inevitably tend to spread throughout the world over time. But it is fair to say that genetic modification should be able to reverse such effects.

I would also contend that genetic medicine can be differentiated from eugenics. The reason is that with the broad population data that is being gathered, it becomes possible to tell how long ago a mutant allele arose in the population. Sometimes it can be determined that it started fresh in the patient, parent, or grandparent; other times a longer estimate will be needed. By drawing a line between recently arisen mutations and longstanding alleles, it is possible to undo the damage from "disease alleles" whose fate, most likely, was to be expunged from the gene pool in any case, while recognizing the intrinsic value of alleles that have survived many thousands and often millions of years through having some special use. However, I'm not aware of this being a published or accepted sentiment. Wnt (talk) 05:12, 19 December 2010 (UTC)

Night vision of seagulls and other birds

I've often seen seagulls flying around after dark this winter. They may be confused by the very bright street lighting. 1) Do seagulls and other birds have good or any night vision? 2) I once heard it would probably kill a bird to disturb them from their roost after dark, as they would be unable to find another in the dark. Is this true? Thanks 92.15.1.13 (talk) 20:07, 18 December 2010 (UTC)

As a rule, most diurnal birds have middling-poor night vision. they are not night-blind, but probably don't have the visual acuity needed to fly through woodlands or underbrush safely. This may not be of too much concern for gulls, since they tend to frequent 'open sky' regions without too many obstacles to run into. And no, it won't kill a bird to disturb it from its roost at night, but it might harm itself if it smacks into a branch in the dark. --Ludwigs2 20:57, 18 December 2010 (UTC)

Some other birds to indeed have excellent night vision (see Bird_vision#Nocturnal_birds). Some gull species are highly adaptable. Nocturnal Scavenging by Gulls in the Southern North Sea is one study that mentions nocturnal activity (following trawlers and their discard) among Larus argentatus, Larus marinus, and Larus fuscus. The abstract concludes with "they should be regarded as neither nocturnal or diurnal by preference in this area". Perhaps it applies to other civilized areas with yet more tasty scraps too. ---Sluzzelin talk 21:16, 18 December 2010 (UTC)

Hi. I was summoned... :) According to this 1914 article by R. M. Strong (page 24) "It has been my experience that the Herring Gull has nearly as good darkness vision as man at least". Just so happens that I was reading that the other day, heh. Personally, I have seen Herring Gulls happily feeding in the streets in the middle of the night and heard their contact calls as they fly overhead before sunrise. They seem to see just fine. I also read an article recently where it was mentioned that GBB Gulls will raid tern nests at night.

As for other birds, I can tell you that Budgerigars have *very* poor dark vision. If they fall off their perches in the night, they struggle to find them again and will flap around their cages in a panic until the light is turned on. I've heard accounts of it being a similar situation with Cockatiels. --Kurt Shaped Box (talk) 23:59, 18 December 2010 (UTC)

"Hi. I was summoned..." From the vasty deep? 87.81.230.195 (talk) 12:39, 19 December 2010 (UTC)

December 19

Properties of liquid diamond

In recent news articles there's been mention of the possibility of diamond oceans at the centre of ice-giant planets like Neptune. What would it be like to travel as a submariner in such an ocean, assuming I had a magically strong bathysphere? What properties does liquid diamond have that would make the journey unique?

Sober discussion and wild speculation are both welcome.

Thanks Adambrowne666 (talk) 00:08, 19 December 2010 (UTC)

phase diagram of carbon. The liquid phase isn't really "diamond"

"Liquid diamond" cannot exist, given the type of bonding that exists in a diamond. Diamond is a "network solid" consisting of a single massive covalently bonded network of carbon atoms. In order to liquify, one would need to have discrete molecules of some sort, diamond just isn't organized that way. There could be liquid carbon, but it exists only at very high pressures and temperatures; under pressures less than 10 megapascals, (about 100x the pressure of Earth's atmosphere) it sublimes. Speaking of "liquid diamonds" is the fanciful sort of stuff you read in the science sections of newspapers, but such things don't really exist. --Jayron32 00:49, 19 December 2010 (UTC)

Yeah, good point; I didn't think of that. I suppose it's like calling water 'liquid ice'. I see here - carbon physics - that it's referred to as liquid carbon, as you say. Can we continue the discussion even so? Adambrowne666 (talk) 01:24, 19 December 2010 (UTC)

What do you want to discuss? The paper you just linked has a rather exhaustive and complete discussion of the properties of various phases of carbon. I am unclear what else you wish to learn... --Jayron32 01:29, 19 December 2010 (UTC)

Well, I think he was fairly clear the first time. He wants to know what it would be like to travel through it in a "magically strong bathysphere", and whether the answer would have to do with the medium's properties. I don't have any answer for that, but I don't see that it lacks sufficient specificity to be answered. --Trovatore (talk) 01:47, 19 December 2010 (UTC)

Jayron32: Not true, liquid diamond can exist - nanodiamonds. Consider dehydroadamantane, technically, the smalest molecular structure which can be called a diamond; an unsaturated carbon structure with delocalized lone electrons which, can have liquid properties under the right conditions. Think about it, a rock does not flow from a bucket, but crush it into fine silt, it flows freely from the bucket. It is not a true liquid, but it has similiar properties. I can't give you any properties of liquid dehydroadamantane, as no one has actually studied it, but I can tell you that it should behave as a highly reducing metallic liquid. Liquid diamond is a metastable substance, as it should irreversably polymerise into a hydrocarbon glass at STP. --Plasmic Physics (talk) 01:54, 19 December 2010 (UTC)

I don't see how you can call something diamond if it has (any significant amount of) hydrogen in it. Our article says dehydroadamantane is C₁₀H₁₄. --Trovatore (talk) 02:01, 19 December 2010 (UTC)

There are several degrees of unsaturation, C₁₀H₁₄ is not the most unsaturated adamanane frame. All diamonds have a "dirty" surface, covered by non-carbon groups. There is no formal cut-off ratio of carbon to other elements for molecule to be differenciated from a diamond, how many grains of sand makes a heap. The ratio can be simplified to a surface area to volume ratio. --Plasmic Physics (talk) 05:09, 19 December 2010 (UTC)

Halophiles

http://books.google.com/books?id=o8lOge_6TpsC&pg=PA101&dq=halophile+possibilities+for+industrial+process&hl=en&ei=NmYNTbaZG8L6lwfW16WeDA&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCYQ6AEwAA#v=onepage&q&f=false

(Under the header Extracellular Enzymes)

1. What does the term "Washing" mean?

2. How would halophilic enzymes be used in food processing?

3. (Page 103)

These compounds have industrial applications as stabilizers of enzymes, nucleic acids, membranes...

What would applications be that require for stabilizers of enzymes, membranes, etc.?

4. Reliable reference?

Thanks, Albacore (talk) 02:12, 19 December 2010 (UTC)

Your #1 and #2 seem straightforward to learn more detail, since the sentence gives you a citation for it:) Page 114 of your ref has a full bibliographic reference for the 2005 work by Ventosa. That author appears to have published extensively in the scientific journal world, so he's probably a reliable reference (but cf. #4, I don't know about the work you are reading that cites him). Also, the cites in the paragraph preceding the one you mention (main §5.4 intro) points to several other references that are described as in-depth reviews of these applications/fields (including an older one by the same Ventosa author). DMacks (talk) 04:37, 19 December 2010 (UTC)

Jet stream time lapse?

To understand how long-term changes in weather work, it would be very desirable to have some video showing the entire jet stream over the Northern Hemisphere, updated once a day, going on for at least a year, and preferably colorized as well with perhaps daytime high or average temperatures. Is anything like that in circulation? Can it exist, or is the jet stream too abstract to actually be placed on a map consistently in this way using data from multiple authorities? Wnt (talk) 05:23, 19 December 2010 (UTC)

Here are animated northern hemisphere jet stream maps with data available back to 2006. Red Act (talk) 06:17, 19 December 2010 (UTC)

networking

concept of bridge,switch and router plz help me some one....... sand mass. satraj2010@gmail.com — Preceding unsigned comment added by Satraj2010 (talk • contribs) 07:53, 19 December 2010 (UTC)

Please see Routing, Bridging (networking), Network switch, and Router. Further questions might be better suited to the Computing Desk. Ginger Conspiracy (talk) 08:00, 19 December 2010 (UTC)

physics

in a structure of an atom protons are positively charged then why dont they repel each other as every positive charge repel positive charge? —Preceding unsigned comment added by 218.248.64.182 (talk) 12:25, 19 December 2010 (UTC)

According to Atomic nucleus#Forces, The nuclear force is highly attractive at very small distances, and this overwhelms the repulsion between protons which is due to the electromagnetic force, thus allowing nuclei to exist. 90.195.179.14 (talk) 12:34, 19 December 2010 (UTC)

The nuclear force is actually repulsive at very close range, but becomes attractive at typical distances between particles in the nucleus. The comparison with electrostatic repulsion is shown here. If a proton ever gains enough energy to separate from its neighbours by three times its normal distance, then the charge repulsion will take over and the proton will leave the nucleus. Dbfirs 12:56, 19 December 2010 (UTC)

Science and God

Has science absolutely proven that God cannot exist? I know for a fact that the big bang theory does not, since no one can say where the material for it came from. But what about life? The Primordial soup could have resulted in forming organic molecules, but could they combine or react to form living cells? Thanks. --119.155.7.74 (talk) 13:59, 19 December 2010 (UTC)