Wikipedia:Reference desk/Archives/Science/2008 April 29

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[edit] April 29

[edit] Relation between isospin and up and down quark content

I wrote the following in the List of baryons

Up and down quarks each carry isospin 1⁄2. Due to Pauli's exclusion principle, quarks of the same flavor must have their isospin aligned. Three aligned up and down quarks would make a particle with isospin 3⁄2, while two up quarks (who must be aligned) and a strange quark would make a particle with isospin 1.

—Headbomb

And then I go on and detail explicitely what particles go with what isospin etc... Check it out if you want List of baryons#Isospin and up and down quark content.

I'm not 100% sure of myself, and I can't find reference on it. So if you can confirm that I understood things correctly, that would be great, and if you could provide me with a reference for this that would be even better (preferably a specific passage within a book, or an article specifically about this. Headbomb (talk · contribs) 00:01, 29 April 2008 (UTC)

I thought two quarks of the same flavour had to have opposite spin. That's what the first paragraph of the Pauli article seems to say as well. --Tango (talk) 20:32, 1 May 2008 (UTC)

[edit] Carbonyl chemistry

To be straight up: It's a homework question. But I have been trying to do it, to no avail. Can someone at least point to a correct direction? Here is the problem [1] Will the alkyne be the nucleophile? But surely the alpha carbons of CN and/or the ester would form the enolate/nucleophile. I'm also suspecting that it's intramolecular. Then there's also the methyl group that could form an enolate. So, I'm not even sure which is the nucleophile and electrophile. Any suggestions?128.163.224.47 (talk) 00:57, 29 April 2008 (UTC)

:My organic chem is a bit rusty but I don't think this is an enolate reaction. An enolate could not form on either molecule here. Could you give some info on what context this question was asked? What type of chem? Type of questions before and after? --Shniken1 (talk) 02:46, 29 April 2008 (UTC)

You could form enolate (or similar resonance-stabilized α-carbanion) at methyl of ketone or at CH between the two nitriles or at CH between the two esters. Or you could deprotonate the alkyne CH. Which is most acidic (especially remember to consider resonance stabilization)? Once you have a nucleophile (something that is not present until you deprotonate something here), gotta figure out what it could attack. What electrophile(s) are present and which are most electrophilic? Do enolates have a preference for certain types of electrophilic structures? Is there a reasonably good ring-size available by intramolecular attack? Shniken1's got a good point (and a good crutch for problem-sets:)...what similar problems have you already seen? DMacks (talk) 03:10, 29 April 2008 (UTC)
Consider the following: according to the diagram, the reaction occurs in basic solution. What Base might you use, since it is a catalytic base? How do you think base might effect the reactants? --Shaggorama (talk) 06:30, 1 May 2008 (UTC)

[edit] Matrix of structural similarity of proteins

Where can I get a matrix of structural similarity of proteins? CATH is probably what I want, but I am not sure how to proceed, probably because my background is Computer Science, not Biology.

What I actually want is a list of proteins IDs with their amino acid sequences, and a matrix in which cell i,j gives the structural difference between protein i and protein j, as a real number. --Masatran (talk) 10:11, 29 April 2008 (UTC)

Defining the 'difference' between two proteins in a biochemically-meaningful way is a nontrivially difficult problem. If you're interested in the primary structure only (just the amino acid sequence), you could adapt the protein-protein BLAST (blastp) algorithms to your task. They will boil your sequence-sequence similarity down to a real number, at least.
If you want to compare secondary or tertiary structure, you're in for a world of hurt. Determining how proteins will fold based only on their amino acid sequence is still an open problem in computational biology, and if you can do it successfully you will be showered with glory, riches, and possibly a Nobel prize. If you limit yourself to known 3D structures in a curated database (like the Protein Data Bank), you will still have to decide a basis for comparison. Are two alpha helices 'similar' if they have the same length and charge distribution, even if they contain completely different amino acids? TenOfAllTrades(talk) 12:32, 29 April 2008 (UTC)


Someone else asked the same question a while back. Check out http://folding.stanford.edu/ Folding@Home. As tenofalltrades explained folding is the key to understanding how proteins work. These guys are using computer time donated by people to do the computing of various folds for them. They've adapted their program to run on some game machines now and that helped a lot. Look at the "science" page for some basic info. --71.236.23.111 (talk) 13:02, 29 April 2008 (UTC)

[edit] Unknown animal: very tiny snake-like black thing.

I live in Minas Gerais, Brazil, and today I've found a very, very tiny snake-like thing in my room. It's not a worm, it has scales and everything, no legs, but it just very tiny. The scales are black, btw. It's about 7-8 cm long and 3mm thick, and moves like a snake. I guess it's an reptile of some sort. Any ideas? 189.15.70.185 (talk) 12:53, 29 April 2008 (UTC)

Sorry snakes freak me out, so I'll forego looking through the Wikipedia snake pages. As to the size, it's spring. That makes it highly likely that your tiny snake is a baby snake. I'd not wait to find out what it'll grow up into. --71.236.23.111 (talk) 13:13, 29 April 2008 (UTC)
I've seen snakes that small before Nil Einne (talk) 13:48, 29 April 2008 (UTC)
[2] & Leptotyphlops bilineatus for two examples of claimed to be smallest snakes in the world (I don't think they're the same thing). BTW neither have pictures. Nil Einne (talk) 13:53, 29 April 2008 (UTC)
Given the locations cited neither of those two seems likely in Brazil, but it makes the point that it might possibly be a full grown specimen. Have you tried this: http://pt.wikipedia.org/wiki/Lista_de_cobras_pe%C3%A7onhentas_do_Brasil  ? If you can't read Portugês you can look at the "Nome binomial" in the boxes and then look up the description on the English pages. --Lisa4edit (talk) 16:00, 29 April 2008 (UTC)
Well no, my point was more that such tiny snakes to exist (and apparently in several places). It may be some other kind of Leptotyphlops, they appear to be quite small in general although the others that I could find lengths for were 20-30 cm when full grown, not 8cm Nil Einne (talk) 22:43, 29 April 2008 (UTC)

[edit] Whistling teakettle

Why, just before it whistles, a teakettle suddenly becomes less noisy than before? It's as if fewer molecules are hitting the sides of the kettle. Thanks. Imagine Reason (talk) 13:21, 29 April 2008 (UTC)

I would guess that as the pressure builds up it retards boiling, then, as the steam escapes, the pressure lowers and rapid boiling continues. StuRat (talk) 16:42, 29 April 2008 (UTC)

Actually, the same thing happens when you boil water in an open vessel. See the explanation at The Straight Dope. --Rallette (talk) 16:49, 29 April 2008 (UTC)

[edit] Name of muscles on either side of the lower spine?

Today the results of an X-ray on my spine came back, and the doctor who examined the results told me that the "muscles on either side of the spine in my [lower] back" were spasmodic. I am going back some time next week to discuss further with my GP, but I was wondering, as the doctor never told me, what are the names of the muscles surrounding the lower spine? (I don't think this qualifies as asking for medical advice, as I am not asking for advice, merely the name of certain muscles) 88.104.246.77 (talk) 13:22, 29 April 2008 (UTC)

There are quite a lot, but they are listed here: Table of muscles of the human body#Back -- MacAddct  1984 (talk • contribs) 13:27, 29 April 2008 (UTC)
Thank you. It's quite a confusing list for someone who doesn't understand most medical terms, but it should help. I'll probably just ask my GP for what specific muscles are affected. 88.104.246.77 (talk) 13:32, 29 April 2008 (UTC)
(ec) There are a number of muscle groups in the lower back; balancing and walking erect take a fair bit of tweaking. Your best bet is to pull out a copy of Gray's Anatomy and have a look around. (Bonus—the entire 20th editing of Gray's is in the public domain and online: [3].) You'll want the myology section, perhaps starting with the deep muscles of the back and the muscles and fasciæ of the iliac region. Scroll down to the figures. (Many of our articles also use Gray's figures.) TenOfAllTrades(talk) 13:35, 29 April 2008 (UTC)
(ecII) Gray's Anatomy in online at Bartleby. The deep muscles are here, and the iliac are here. --Milkbreath (talk) 13:38, 29 April 2008 (UTC)
Interesting factoid: I was interested in getting higher-res scans of Gray's for Wikipedia and contacted Bartleby.com and got a curt response from the owner saying that Wikipedia was using the scans without his permission and that he held copyright over them (presumably because he colored in the 1918-edition pictures, or perhaps for doing the scans (which would not be legit)). I didn't pursue it any further, but I do have in the back of my mind that some day I'd like to get hold of a copy and do really nice scans of it. --Sean 17:55, 29 April 2008 (UTC)
Spinal erectors. Vranak (talk) 16:54, 29 April 2008 (UTC)

[edit] Time of Unconsciousness

How long does a person typically remain unconcious after being knocked out from head trauma? --Think Fast (talk) 15:07, 29 April 2008 (UTC)

There's no 'typical' length of time. It can range from 'a few seconds' to 'forever'. Even after consciousness is restored, the victim may be disoriented, nauseated, and headachey—the Hollywood picture of the hero leaping back to his feet to chase down the bad guy and defuse the bomb is very misleading. The trauma may also rupture blood vessels in the brain, leading to bleeding that requires surgical intervention. Permanent damage may also have occurred, with a wide assortment of neurological sequelae. TenOfAllTrades(talk) 15:51, 29 April 2008 (UTC)

[edit] Spin

Can someone explain to me what spin (physics) is? There is what most people would think of as spin, like what a basketball has when you put it on the end of your finger and spin it around with your hand and, apparently, there is another kind but the linked article does an poor job of explaining it to non-physicists. Maybe it is just too technical to explain to non-physicists but hopefully someone here can try. Recury (talk) 17:24, 29 April 2008 (UTC)

I think you might be looking for the Spin (physics)#Spin and magnetic moments section. If you take a spherical shell with a uniformly distributed surface charge density (or maybe it is a sphere with uniformly distributed volume charge density; can't remember) and spin it, characteristics of the magnetic field you get looks similar to that of a particle with spin. Even for neutrally charged particles like the neutron, the magnetic field looks similar to a spinning charge distribution (imagine perhaps two spherical shells with equal but opposite charges, one inside the other). I don't believe it is known (and perhaps it doesn't matter) whether or not the particle is actually spinning in the classical sense of the word; it simply looked like it to someone studying the electromagnetic properties of the particle, and that was the inspiration for using the name for that quantum number. --Prestidigitator (talk) 18:03, 29 April 2008 (UTC)
Wouldnt the net curl of such a field be zero? I had the vague impression that diamagnetic and paramagnetic properties required that the curl be non-zero. I havent studied it mathematically. thats just my intuition speaking.Em3ryguy (talk) 20:48, 29 April 2008 (UTC)
No, I suppose not. Thinking two dimensionally, each particle would be a sort of curl dipole and the whole material would be a sort of curl dielectric. If all the particles align then it would be as if there was a net curl on one side and the opposite curl on the other and any applied magnetic field would be either strengthened or weakened. Why didnt I see that before? Em3ryguy (talk) 00:57, 30 April 2008 (UTC)

[edit] Cross points on star/galaxy photographs

In many astronomy photographs, stars and galaxies will often have 4 points coming out of the star/galaxy. These points go up, down, left and right. What are these lines/points and what causes them? e.g. http://antwrp.gsfc.nasa.gov/apod/ap070516.html Thanks. --Rajah (talk) 18:36, 29 April 2008 (UTC)

Those are most commonly diffraction spikes from the internal structure of the telescope. — Lomn 19:01, 29 April 2008 (UTC)
Awesome. Thanks! --Rajah (talk) 19:58, 29 April 2008 (UTC)

[edit] Hot-tub - Spa - Water treatment options.

Briefly - I bought this brilliant Hot Tub for use in our garden in Scotland - and we love it - made in Carlsbad Calif. But the water treatment chemicals are Chlorine based - expensive - and they antagonise my skin - badly - so much so I don't use it as much as I would like. So, the manufacturers suggested I use their "Non-Chlorine" water treatment - but it still contains chlorine based chemicals - so that's a non-starter. Question - can I use a splash of ordinary household liquid bleach before each use, and then change the water every couple of weeks or so - I know that won't harm my skin, but could it harm the Tub/Pumps/Filters etc? You will understand that the manufacturer isn't keen as they want me to keep on purchasing their "product specific" (expensive) chemicals. Thanks. 92.10.186.2 (talk) 18:47, 29 April 2008 (UTC)

The non-chlorine chemicals I use in my spa are bromine-based. The other alternative I've heard of is an "ozonator", although last I checked those were out of my price range. --LarryMac | Talk 19:06, 29 April 2008 (UTC)
"Ordinary household liquid bleach" is often the same chlorine-based chemical as pool chlorine, just diluted more. So on the one hand, it would certainly not harm the pool equipment, but on the other hand, by the time you add enough to have any substantial effect on the water, you're at the same point as if you'd chlorinated the pool as normal. The reason people use "pool chlorine" is because it is more concentrated, so it takes less of this chemical than of laundry bleach to get the same chlorination level in the pool (no effect on the result) and/or because it also contains stabilizers that keep the chlorine active for longer (less chlorine needs to be added overall). There are lots of other pool-water sanitizing products...bromine is often used in hot-tubs (it's similar to chlorine but more stable at higher temperatures), ozone or silver are more expensive alternatives. DMacks (talk) 20:45, 29 April 2008 (UTC)
I would strongly recommend an ozonator. If you don't have wild crowds in your hot tub every night, the ozonator may be all the sanitizer you need routinely need (although you may still want to "shock" the tub occasionally). Some ozonators use germicidal lamps to make ozone; these will last several years and then need to be replaced. (Intheory, the lamp alone ought to be replaceable but in practice, it usually isn't.) Others use a corona discharge and they allegedly last a lot longer.
Atlant (talk) 22:55, 29 April 2008 (UTC)
Another option might be to just change the water more often. This might be a good choice if you can use the waste water to water your lawn, which should work if it's not full of nasty chemicals. One downside, for an outside hot tub the water you add is likely to be ice-cold if added by hose, requiring time and money to heat it electrically in the hot tub. On the other hand, for an indoor hot tub you may have a hot water supply line from your water heater which can provide cheaper preheated water using natural gas to heat it. However, getting the waste water from an indoor tub to the lawn could be tricky, requiring a siphon hose out the window.
Also, if you haven't yet experimented with reducing the quantity of chemicals in the water but still using the same ones, try that. Showering before you use the tub will also reduce the quantity of bacteria you introduce each time. StuRat (talk) 17:02, 30 April 2008 (UTC)

[edit] Alcohol consumption causes hiccups?

It is an established phenomenon in humorous comic books that excessive alcohol consumption causes hiccups. In real life, I have experienced it very seldom. I am experiencing it right now, but this is the first case in over half a year. My question is, how and why does this happen? JIP | Talk 19:38, 29 April 2008 (UTC)

There doesn't appear to be a solid explanation, but this page has some informed speculation. TenOfAllTrades(talk) 20:08, 29 April 2008 (UTC)
Drinking anything that has been chilled can cause hiccups. I think this is more likely the cause than alcohol.--Shantavira|feed me 07:19, 30 April 2008 (UTC)
It might have some relation with spicy/hot food that's consumed along with it (at least that's the practice in India). Also, may be, alcohol could be making the whole respiratory control less coordinated. But, both the explanations I gave are pure guesses.
Regards.
Ketan Panchal, MBBS (talk) 07:25, 30 April 2008 (UTC)
Oh, so now we're editing wikipedia whilst drunk, are we? ;) Ziggy Sawdust 17:05, 30 April 2008 (UTC)

[edit] Ostrich egg in microwave

Is this real or fake: http://www.youtube.com/watch?v=IMM7s5RRqT4 ? Has anyone else tested this and can we calculate what the egg/bomb's explosive force would be? Thanks. --Rajah (talk) 20:00, 29 April 2008 (UTC)

I don't understand why the entire oven would burst; if the egg were to explode, the shell would crack and the liquidy insides, (possibly boiled / gasified) would make a mess... but it seems very unlikely that the egg could detonate the oven. This is especially unlikely because microwaves are really not designed to be airtight; so the pressure would easily seep out, rather than building up and exploding. Many microwaves even have exhaust fans and vents to help air circulate. Nimur (talk) 04:43, 30 April 2008 (UTC)
I've "done the experiment" with a chicken egg, and they do have an amazingly high amount of explosive force when microwaved. In addition to the shell being able to contain a high force when equally distributed, the egg also cooked from the outside in, meaning the solid egg also contains and evenly distributes the force. Once a crack does develop, all of the force built up from the steam releases at once. It blew the door of the microwave open and made a mess, in my case, but no permanent damage was done. StuRat (talk) 16:44, 30 April 2008 (UTC)
Well, then I'll defer my speculation to experimental evidence! Nimur (talk) 16:48, 1 May 2008 (UTC)

[edit] HIF alpha expression

Is the HIFalpha protein consitutively expressed? I know ARNT is, but I can't seem to find out if HIFalpha is! Thanks 163.1.214.119 (talk) 21:51, 29 April 2008 (UTC)

This pubmed abstract seems to imply it is: http://www.ncbi.nlm.nih.gov/pubmed/11292861 and that is it normally degraded, but hypoxia induces it action. --Rajah (talk) 04:17, 30 April 2008 (UTC)
in fact, wikipedia's own article Hypoxia-inducible factors implies it's constitutively expressed. (citation needed, of course) --Rajah (talk) 04:20, 30 April 2008 (UTC)

[edit] Implosion bomb

Would it be possible to generate a powerful implosion by using a dust made from a material that binds with nitrogen? If so, what material could be used? This is just idle curiosity, and I don't plan on actually building one. — DanielLC 22:00, 29 April 2008 (UTC)

The times when I could remember how to reformulate shoe-polish are definitely over, but why would you want to have an implosion. The reason you have that in nuclear bombs from what I read is to get the material to critical stage. For nitrogen you could just use an explosion. (Bat-cave and cigarette-lighter should not be mixed!). If you want a dust explosion, there are very few things that won't do. Just depends on how fine and the right mix. Flour's a well-known one. Sugar has recently been sadly demonstrated by a sugar plant in Georgia. Lots of bang for supermarket buck. Don't try any of this at home or in "interesting" places like Iraq!!! --Lisa4edit (talk) 22:25, 29 April 2008 (UTC)
An implosion would be cooler, if only because it's not the way it's normally done. I forgot to mention, all products would need to be solid or liquid, rather than gas. The idea is that it spreads out trough the air, then is heated to a critical temperature and "explodes", but absorbs gas rather than releasing it. I think the dust staying solid might prevent it from working, as the middle of the dust wouldn't be able to oxidize. — DanielLC 22:52, 29 April 2008 (UTC)
As far as I can make out that would depend on the relative particle distribution in the dust-cloud and the ignition point. But even imagining the math behind that gives me a headache. Your best bet would probably be mixing an "accelerant" type chemical with the actual explosive agent. Given that you want to direct the explosive force inward (which makes it an implosion) you'd then have to add "projectile" material to redirect it outward again, unless you want to use all the force to compact material in the center; sort of like creating a glass drop or diamond depending on the oomph. If you could get your liquid component to form a bubble that would confine the dust and then have most of the force of the dust explosion go toward the center which is the math headache with relative velocities and energy transfer, that should work. You might run out of oxygen in the middle though. That means that one of your chemicals also has to release some. As basis for thought experiments you could visualize an old TV tube. Gas or liquid mist isn't that big a difference. Sorry, I'm more of a "trial and error" kind of person than a "what if", this is about as far as I can take it without going in to major research. --71.236.23.111 (talk) 23:41, 29 April 2008 (UTC)

I'm not trying to make an implosion with an explosive force around the center like they do with nukes. I'm trying to decrease the pressure in the center by turning the air into a solid, and letting the normal air pressure do the rest.

When I mentioned the products being solid or liquid, I meant the stuff that was produced by the reaction. If you get a reaction like 2Xx(s) + N2(g) -> 2XxN(s), it will make a dramatic decrease in pressure. 2Xx(s) + N2(g) -> 2XxN(g), on the other hand, will increase it. 24.7.180.224 (talk) 01:12, 30 April 2008 (UTC)

Nitrogen (N2) is one of the most stable molecules; you'd have a hard time getting a rapid reaction which consumes it. It is more often a stable by-product of other chemical reactions. Nimur (talk) 04:48, 30 April 2008 (UTC)
I think what he means is some sort of nitrate compound. I still don't really see how you'd get the implosion though. You'd need to do something that produced a rapid and very localized decrease in pressure if you were going to have it be even noticeable. I can't think of an easy way to do that with explosives but maybe I'm not very chemically imaginative. --69.110.41.71 (talk) 09:03, 30 April 2008 (UTC)
You could burn some kind of reactive metal in nitrogen. Magnesium, or Calcium dust can burn in nitrogen, and oxygen, just leaving the noble gases behind. But a lot of energy will be produced in the reaction. Graeme Bartlett (talk) 11:24, 30 April 2008 (UTC)
You want to turn the air into a solid? I get the idea, but good luck kid. If you want to decrease the air pressure, Try playing with the other easy variable in the Ideal Gas Law, temperature. You can implode a soda can pretty easily by heating it over a flame and then putting it open-end first into water: the heat decreases the pressure inside the can relative to the environment, and putting it end down in water isolates hot air inside from the cool air outside, creating a pressure differential that results in the walls of the can caving in. --Shaggorama (talk) 06:05, 1 May 2008 (UTC)

[edit] Rabbit.jpg

Now I have my own picture issue. Could a biologist please have a look at the Rabbit page or the Rabbit.jpg picture. I may be off, but that looks like meeting way too many criteria for Hare to be a rabbit. --Lisa4edit (talk) 22:11, 29 April 2008 (UTC)

The face-shape and ear-length certainly look more hare-like to me, but I am only familiar with British rabbits and hares, and I'm not an expert, so I can't say for sure. Do we have any experts? 78.32.74.31 (talk) 01:53, 30 April 2008 (UTC)
Well, it certainly isn't a European rabbit, seeing as the original caption says it was taken in Louisiana. Not being familiar with North American lagomorphs, however, I've no idea what species it might be. It probably should be removed from the Rabbit infobox (as I've just done) until it's been properly identified, though. —Ilmari Karonen (talk) 05:02, 30 April 2008 (UTC)
I see we are "just splitting hares" again. :-) StuRat (talk) 16:36, 30 April 2008 (UTC)

[edit] what's going on with evolution?

will there ever be a point at which evolution finds the perfect traits and all species become one single species with every evolutionary advantage given to it? —Preceding unsigned comment added by 86.139.48.3 (talk) 23:09, 29 April 2008 (UTC)

No, evolution is contantly occuring and the environmental pressures are always changing. Although we may wipe out all species on Earth--Shniken1 (talk) 23:24, 29 April 2008 (UTC)
No, the environment constantly changes and creatures should evolve to adapt to it. Besides having one species is not possible as species have diverged to different evolutionary pathways (I don't think a plant will evolve to a humanoid very soon). We might get a single species if we wiped out everything on the planet as Shniken1 says but I'm pretty sure that humans do not have the perfect traits.--Lenticel (talk) 23:44, 29 April 2008 (UTC)
will all niches become one niche?Em3ryguy (talk) 23:49, 29 April 2008 (UTC)
A common misconception that evolution moves towards the optimum. It moves toward the most suitable average. And every species had a lot of baggage that was once useful, no longer is, but doesn't harm that much either. Then there are the selection prinicples for mates. Those are a sea-saw between "new and adventurous" and "tried and true". Moreover environments are changing constantly. Yesterday resistance to bird flue and drug resistant TB wasn't interesting. Tomorrow it might single out the ones that keep standing. We could always head for becoming cockroaches though :-) --71.236.23.111 (talk) 23:53, 29 April 2008 (UTC)
Well really it's beyond the capacity of anyone (scientist or otherwise) to speak definitively about the eventual long-term course of biological evolution; but based on a lot of logic and observations, it stands to reason that there is no "optimum" organism which we are evolving towards. Sometimes evolution can even yield undesirable traits (e.g. short-term benefits with long-term repercussions) so it's really not accurate to say we're making consistent steady "improvement". Nimur (talk) 04:52, 30 April 2008 (UTC)
A really interesting question – perhaps it already exists as an organism – maybe the biome is it. Julia Rossi (talk) 05:10, 30 April 2008 (UTC)
An ecosystem or biome is not really an organism (under the non-Gaia hypothesis) but several different plants and animals that share a certain habitat. And that's neither ideal nor final in any way. There are plant successions. Invasive species and competitive, dominating plants (sorry forgot the word for that type, weed's not it.) Same with animals. And ecosystems are never stable. The most extreme ones include bromeliads in tall trees in the rainforest and hydrothermal vents one storm or an earthquake and the entire community is gone. Bogs gather leaf-matter that gathers and builds up the soil until it's higher than the water table. Then all the bog plants and animals go and the "dry ground" plants and animals move in. Citizens of Pompei were pretty well adapted to their environment until Vesuvius erupted. Then all of a sudden being a Thermophile was a much better suited organism. I hope my examples are clear enough. This is a very broad topic. Put very bluntly there is no such thing as an "optimum". --Lisa4edit (talk) 06:07, 30 April 2008 (UTC)
Nimur, could you give an example of such an evolutionary misstep? Thanks. --Sean 12:08, 30 April 2008 (UTC)
The simplest example I can think of is a predator-prey model where the predator develops a sufficient upper-hand. Maybe the wolf becomes faster than the rabbits; then, over-predation occurs, and the food source is exhausted. If the wolves evolve sufficiently fast, they can extinguish the rabbit population before a new equilibrium can be established. Here, a "positive" evolutionary step (faster wolves, better hunters) results in a negative outcome for their species (over-predation). Nimur (talk) 15:01, 30 April 2008 (UTC)
I'd say Giant panda. Their almost-exclusive diet of bamboo (which is not a very good food source) is really detrimental to their survival, especially with human encroachment on their territory. -- Kesh (talk) 23:11, 30 April 2008 (UTC)
There are plenty of examples in humans. Our bodies readily convert excess energy into body fat because for eons our ancestors were hunter/gatherers and would not eat as well or as often as we do today. Consequently a large portion of the population in developing countries, especially america, is suffering from obesity. Obesity can result in many detrimental health problems, such as diabetes. Evolutionarily, it used to be awesome that our bodies stored fat, but now it's sort of a problem because we eat too damn much. Some other gifts to humans from evolution are unwanted body hair (although I don't know if you'd call this a misstep though). You might say that being delicious was an evolutionary misstep for the chicken. --Shaggorama (talk) 05:57, 1 May 2008 (UTC)
As noted above the environment is constantly changing, which leads to more evolution. However, if we started with the given of a permanently fixed environment, I think we would eventually either get a stable situation or an oscillating system (say the prey becomes nocturnal, then the predator follows, then the prey becomes diurnal, etc.). StuRat (talk) 16:33, 30 April 2008 (UTC)
Sorry I'd disagree unless we're talking in a different hypothetical universe. If you have a stable system you get stagnation. (Funny we don't have a relevant page, non of the disambiguation links fully illuminates the concept. Work for future editors) The idea you proposed hits walls in so many places. Our universe is built on dynamic processes. At no level is there anything stable, from the smallest particle to the big wide whole. Earth is the way it is, rather than a barren rock, because it depends on dynamics. Think of rotation and revolution, plate tectonics, weather, water cycle, tide, ocean flow etc. etc. If you get dynamics you get change and change is never predictable. Uncertainty principle. Game theory describes some mathematical aspects of the predator - prey relation. Ignoring for the sake of the argument the processes required that lead to there being a predator and prey; any of the dynamic processes on earth cited above could throw a serious lug wrench into your oscillating process and that is if you don't get a large rock thrown at it from elsewhere. (Meteoroid) For stable oscillation your predator and prey would only be allowed to move in certain strictly defined patterns. Otherwise you'd automatically introduce chaos. The basic flaw with the idea in the OP's question is the concept that there is an "optimum". In a chaotic dynamic system that is impossible as far as I know. Anything that can be defined as an optimum can only be so temporarily. Remember what Feynman said : Complex problems have simple, easy-to-understand, wrong answers. :-)Lisa4edit (talk) 22:25, 30 April 2008 (UTC)

[edit] nitrogen again

could i get the price of nitrogen per gram? —Preceding unsigned comment added by 76.14.124.175 (talk) 23:47, 29 April 2008 (UTC)

At this point I'd suggest either google or refining dove droppings. What's the science in a price quotation? Several people have suggested links before. Although I usually am all in favor of being helpful and giving people a break, there is a limit and repetition gets tiresome. Even the most wide-flung definition of an encyclopedia would not include "commodities exchange information board". --Lisa4edit (talk) 03:33, 30 April 2008 (UTC)
And, you'll have a hard time purchasing nitrogen in units of grams. You'll usually buy it by the cylinder or by the ton. You should probably talk to a vendor to see if they have regulations about who they will sell to, as well; nitrogen is safe, but any compressed gas is potentially hazardous, since it is under pressure. Nimur (talk) 05:02, 30 April 2008 (UTC)
Nitrogen is not safe in quantity: if your supply tank contains enough of it to displace the air you're breathing, you can fall unconscious before you realize something's wrong, and suffocate to death in minutes. The reason you don't realize anything's wrong is that instead of a "low oxygen level" sensor, your body is equipped with a "high carbon dioxide level" sensor. The one is as good as the other if you're not getting oxygen because you're not breathing, but if you're in an oxygen-free atmosphere, you can exhale the CO2 normally. See nitrogen asphyxiation. (For essentially the same reason in reverse, CO2 in quantity is also not safe. See Carbon dioxide#Toxicity.) --Anonymous, 22:05 UTC, April 30, 2008.
There's also nitrogen narcosis, although that only occurs at high pressures. --Tango (talk) 21:08, 1 May 2008 (UTC)