Wikipedia:Reference desk/Archives/Science/2013 September 4

= September 4 =

Question about atomic repulsion.
If electrons are what repulse atoms, what happens if the atom has no electrons? Sincerly, camerontregantalk 08:02, 4 September 2013 (UTC)


 * Then the positive charge of the naked nucleus would cause the atoms to be repulsed; or if you believe that the free neutron stands in as element number zero, then a neutron gas would be near impossible to contain, as temperatures anything higher than a few pico-Kelvin, it would simply diffuse through the walls of any containment vessel. Plasmic Physics (talk) 08:31, 4 September 2013 (UTC)


 * In a neutron star, that's what happens. Without the repulsive force of the electrons, the material collapses in on itself.  If there is enough mass, you get a black hole - but for more sane objects, you'd get a solid material.  An effect called  quantum degeneracy pressure stops it from collapsing any further - and that's due to the Pauli exclusion principle which basically (very basically) stops identical things from being at the same place.  SteveBaker (talk) 16:05, 4 September 2013 (UTC)
 * Given that neutron stars will only form with huge (at terrestrial scale, and still pretty damn big in stellar terms) masses, and still involve some slightly odd physics, I think "sane" is a bit of an overstatement. MChesterMC (talk) 08:52, 5 September 2013 (UTC)


 * There is no need to invoke neutron stars, just try enriched californium. It readily outgases neutronium gas. Plasmic Physics (talk) 09:28, 5 September 2013 (UTC)

Flat feet
Is there any situation where flat feet/fallen arches would be an advantage? Thanks ツ Jenova   20  (email) 10:21, 4 September 2013 (UTC)
 * Yes. You would be rightfully exempt from most physical exercises, e.g. running, because the lack of friction between the feet and the ground for you would be unfair so that's that. That is, if your flat feet were that serious. ☯ Bonkers The Clown  \(^_^)/  Nonsensical Babble  ☯ 10:40, 4 September 2013 (UTC)


 * Back in World Wars I and II, it could have gotten you out of army service. Nowadays, it appears that "flat feet are perfectly functional and may even be an advantage in sports", and among US Army recruits, the flat-footed suffer fewer training injuries than those with high arches, according to the New York Times article "The Maligned Flat Foot: Some See an Advantage". Clarityfiend (talk) 12:20, 4 September 2013 (UTC)


 * That's strange...I'd always heard the opposite, that flat feet affected balance, carrying loads, walking distances, and increased injuries overall, disqualifying people from the army. Thanks ツ Jenova   20  (email) 12:55, 4 September 2013 (UTC)


 * A lot of the problem for the army back when that was an issue was that they only had one design of boot - and it didn't suit flat-footed people. Since they did a lot of marching around back then - it was a huge issue.  (Sorry - I don't recall where I read that). SteveBaker (talk) 13:18, 4 September 2013 (UTC)
 * Perhaps you read it in our amazingly-well-cited section on toe anatomy and physiology, which references U.S. Army studies of comparative foot sizes - including the seminal post-war work, "Foot Dimensions of Soldiers" (1946) that distilled all knowledge learned about flat-footed American GIs of the second World War? It's almost encyclopedic, the amount of information available here!'  Nimur (talk) 14:51, 4 September 2013 (UTC)


 * On a related topic, is this the top view of the left foot, or the under view of the right foot? The article toe anatomy and physiology says right...Thanks ツ Jenova   20  (email) 16:23, 4 September 2013 (UTC)
 * The caption is correct; Plate 269 is the plantar view of of the right foot ("looking up"). There's a little bit of symmetry, and the uninitiated might easily confuse it with a top-view of the left foot; but you can verify a few easy features: the navicular bone is on the insole and is visible; the calcaneus (heel) is plainly visible.  You can see the diagram has labeled the plantar (bottom) attachments for the flexor tendons, but not the extensors; (and you know which direction toes flex on a healthy human's foot - they curl downward, hopefully!)  Plate 268 is the dorsal ("top") foot surface; compare the visible extensors, the talus bone (ankle); and so on.  Nimur (talk) 20:38, 4 September 2013 (UTC)


 * Thanks for clearing that up ツ Jenova   20  (email) 08:47, 5 September 2013 (UTC)


 * My father found his lat feet an advantage in that they exempted him from the US military draft. μηδείς (talk) 00:54, 7 September 2013 (UTC)

Projects that cannot complete during the life of the people who started it.
We were talking (above) about a space mission to the nearest star...how it would certainly take hundreds of years to get there.

This made me think about the problem that whoever designed and launched this hypothetical probe - and (importantly) whoever came up with the funding for it - would never see their project do much more than disappear from our solar system.

This makes be think that it would be very hard to get funding for a long-term project that would produce no results until after everyone who had anything to do with it was dead.

Are there any projects like that underway right now that will eventually come to a definite conclusion - but not within the lifespan of anyone who was involved with making it happen? I'm having a hard time thinking of even a single one!

SteveBaker (talk) 18:08, 4 September 2013 (UTC)


 * Not a science project, but John Cage's As Slow as Possible is currently being performed in Halberstadt, Germany, and that will last until around 2640. More scientifically, one of the motivations for archiving astronomical data, including data from crappy old photographic plates, is to permit detection of changes that occur over long periods of time. This is, however, not a concrete experiment with a definite expected conclusion. --Wrongfilter (talk) 18:23, 4 September 2013 (UTC)


 * A while ago someone here mentioned Beal's seed germination experiment . Currently running; the guy who started it is long dead. Several other candidates at that "longest running experiment" thread from a few months ago. SemanticMantis (talk) 18:38, 4 September 2013 (UTC)


 * Yes - but both of those examples produce benefits to the instigator from day one. I'm trying to come up with something where the original people who started the project have to do it entirely altruistically because they know for sure that they won't live long enough to see any of the results. SteveBaker (talk) 18:58, 4 September 2013 (UTC)
 * The Cologne Cathedral was started in 1248, suspended in 1473, and finally completed in 1880. The first usable part (AFAIK) was consecrated in 1322, 74 years after construction started. The people who constructed it may, of course, have drawn spiritual satisfaction from the mere act of building. --Stephan Schulz (talk) 19:07, 4 September 2013 (UTC)
 * That's a good one actually. I wonder if the people who started it expected to see it finished in their lifetimes?  Of course, they probably expected to get credit for kicking it off once they made it to heaven...so perhaps this wasn't a truly altruistic effort. SteveBaker (talk) 20:33, 4 September 2013 (UTC)
 * (reply to Steve) I don't think your assumption that the originators will not "see any of the results" is right, because surely any project like sending a probe to a star will have many (1) technical (eg testing that different propulsion and communication technologies work), and (2) secondary goals (such as making observations of the solar system and its surroundings on the way). In fact, any such project will inevitably consist of a series of probes over decades to test and refine different sub-systems, and practically speaking individuals will be devoting their careers to designing specific features of those various probes, with only the larger "institution" (hopefully) surviving to see the project to completion. Compare say with the Apollo program, in which "land a man on the moon" served as a large motivating goal, but individual engineers and groups were perhaps only trying to wheedle out 2% power from the Saturn rockets, or make the space helmet look cooler. Ditto, for the current Mars probes, which have the motivating goal of finding life on Mars/sending a manned mission to Mars. Or, if one were to get poetic/philosophical, physics, which has the motivating goal of "explaining" all natural phenomenon.
 * The point being: the fact that one won't see the end of a larger project in ones lifetime/career, doesn't mean that one won't get any results, and a measurable sense of achievement, in that lifetime. Abecedare (talk) 19:28, 4 September 2013 (UTC)
 * You might be right - if this hypothetical space probe was gathering data along the way - then it wouldn't be a total bust for the people involved.
 * I also wonder whether this is the solution to the Fermi paradox. Alien species aren't talking to us because each individual knows that he (she/it?) won't get a response within their lifetimes - so it's not worth the effort of talking to us when that money could be better spent on gold-plated antennae and tentacle polishers.  SteveBaker (talk) 20:33, 4 September 2013 (UTC)
 * Well, there is the Voyager Golden Record, which will certainly not reach any aliens in the lifetime of the team that assembled it. But, as with a cathedral, just the act of assembling and sending it is a powerful statement to the current generation. --Stephan Schulz (talk) 21:25, 4 September 2013 (UTC)

Why doesn't Wikipedia provide medical advice?
moved to talk page μηδείς (talk) 18:53, 6 September 2013 (UTC)

what hormone is responsible for the facial fat sexual dimorphism in prepubertal children?
Is it progesterone or some form of progestin? Estrone or estriol? 64.134.65.22 (talk) 19:09, 4 September 2013 (UTC)

I mean, girls have more facial fat at 6-8 yo, way before puberty. Is this due to adrenarche? 64.134.65.22 (talk) 19:10, 4 September 2013 (UTC)

Ionized water - is there any truth to this claim?
Hi. I recently came across this article detailing an Irish technology involving treating water with nitrogen that supposedly increases yields by up to 30%. I find it a bit suspect because of its fantastic claims and the fact that none of the people mentioned have Wikipedia articles. Is there any truth to the science behind the claim? Thanks. ~ AH1 (discuss!) 19:24, 4 September 2013 (UTC)
 * Well, the technology is bullshit, and bullshit is good as a fertilizer, so the technology must be good as a fertilizer due to the transitivity of the subset operation. No, seriously, if you apply electromagnetic radiation to water, you'll warm the water up a bit, and you might electrolyze a bit of it into hydrogen and oxygen gasses which will then bubble out of the water (see Photocatalytic water splitting), but neither of those is going to have any significant effect on plants that are watered with that water.  Red Act (talk) 20:06, 4 September 2013 (UTC)


 * I guarantee it's bullshit. Magical "energized" water...hell no!  If they'd made just one, narrow claim - it might have been credible - but when they start piling claim upon claim, it's clear that this is a ridiculous scam.  It's remotely possible that this process produces a tiny amount of nitrates - but if it's using only "pennies" of electricity to process "thousands of gallons of water" then it's not going to be enough to matter.  Electricity costs in Limerick (Ireland) are about 10 pence per kilowatt hour.  So let's allow that this tiny box can put that much electrical energy in to chemical conversion of water and nitrogen into hydrogen and nitrates.  How much nitrate would that be when diluted into a few thousand gallons of water?  Nitrogen is very hard to break apart - it takes a lot of energy.  Sadly, I don't see an easy way to calculate how much could possibly be converted...we need a chemistry expert here.  SteveBaker (talk) 20:24, 4 September 2013 (UTC)


 * "Professor Austin Darragh says, 'Vi-Aqua makes water wetter...'." Nothing to add at the moment, I just liked that line :) Someguy1221 (talk) 20:35, 4 September 2013 (UTC)
 * I recall some stuff used in model railroading that was alleged to "make water wetter". What it actually did was interfere with water's tendency to form a surface "skin", which is especially noticeable on very small bodies of water. The stuff seemed to be something akin to soap, and was certainly not something I felt like ingesting. But everybody trying to sell something has got a gimmick... especially when the product is a humbug. ←Baseball Bugs What's up, Doc? carrots→ 21:54, 4 September 2013 (UTC)
 * See Surfactant, incidentally. Tevildo (talk) 23:24, 4 September 2013 (UTC)
 * this is a very good site compiled by a real chemist which discusses the myriad of water "scams", including ionized water. Vespine (talk) 22:56, 4 September 2013 (UTC)
 * Agree this appears to be a scam.  Notable for appearing in a formerly respectable source.  In concept the claim of using electricity, even radio to do nitrogen fixation is not plainly impossible; you want N2 + 3H2O -> 2NH3 + 1.5 O2.  But the resulting highly alkaline ammonia water would not necessarily be appreciated by plants in a direct application.  (Sort of interesting though, how much of potential pH difference hides in the choice of which major atmospheric gas the hydrogen attaches to)  In any case, there is the not insignificant problem that in reality doing industrial nitrogen fixation is not easy, nor do radio waves have anywhere near the energy difference one expects to see unless you have practically mystical catalysis going on. Wnt (talk) 02:01, 5 September 2013 (UTC)
 * They are claiming to achieve complete nitrification, not just fixation. So that would be nitrate, not ammonia. Someguy1221 (talk) 02:16, 5 September 2013 (UTC)

So I calculated it out. The conversion of nitrogen to aquous nitric acid costs 18kj/mol (it's surprisingly small because a nitrate ion does not have too much more energy than a nitrogen molecule, although this is a multistep process with rather significant thermodynamic barriers). If we assume perfect effeciency, which is assuming a lot, it would take 5000kj of energy to get an amount of nitrate containing 1kg of nitrogen. If we assume a kilowatt-hour costs 10 cents, then this actually only costs 14 cents per kilogram. To buy an equivalent amount of nitrate fertilizer from wholesale providers would cost about $6 (you have to place an order for tens of metric tons to get that kind of a discount, though). So their hope has merit, but I sincerely doubt that these guys managed to beat the fertlizer industry to the tune of 4300% relative efficiency, 15 years ago, and have yet to receive serious interest from independent scientists or businesspeople (who have been looking for easy ways to perform these reactions for over 100 years, by the way). Someguy1221 (talk) 02:46, 5 September 2013 (UTC)
 * That's odd... come to think of it, if you're content to get pure nitrate and neutralize it with some kind of cheap alkali, why can't you get the theoretical efficiency? I would have imagined that with a sufficiently contorted set of winding tubing forming a countercurrent exchange that you could bring N2+O2 to a temperature where equilibrium is favorable to nitrogen oxides and back again with little loss.  The resulting smoggy mixture, bubbled up through water, ought to leave behind nitrous and nitric acid. Wnt (talk) 06:55, 5 September 2013 (UTC)
 * Because it's never favored. The closest thing to what you describe is the Birkeland–Eyde process, which has only a 4% yield at 3000oC, and is extremely inefficient in terms of energy consumption. Someguy1221 (talk) 07:07, 5 September 2013 (UTC)
 * And bear in mind that this thing is the size of a biscuit tin (let's say, less than 1 cubic foot) and can continuously cope with the flow from a garden hose! SteveBaker (talk) 16:34, 5 September 2013 (UTC)
 * You do realize that in 50 years a hobbyist doing tabletop microfluidics is going to look through these archives and implement stuff like this as a lark? He may even present you with a working model. :) Wnt (talk) 23:53, 5 September 2013 (UTC)
 * In 50 years, I'll be 108 years old...I very much doubt anyone will be presenting me with anything! SteveBaker (talk) 12:54, 6 September 2013 (UTC)
 * You never know. What I do know is that your odds of being hale and healthy then are a lot better than your odds of winning the lottery, and there are people who play it anyway (though I'd never accuse you of such gullibility!) Wnt (talk) 19:44, 6 September 2013 (UTC)

why the veins blood is dark more than arteries blood?
Why the blood of the veins is dark comparing to the blood of the arteries? the reason connected to the oxygen? 95.35.210.39 (talk) 21:16, 4 September 2013 (UTC)
 * From having had blood drawn from both veins, it's pretty obvious that blood from veins is a darker, richer red. That stands to reason, as the veins are carrying various waste products from the cells. That might be another good reason to draw blood from veins rather than from the relatively pure arteries. The Blood article says (without citation) that veins' blood's blue appearance under the skin is an optical illusion. ←Baseball Bugs What's up, Doc? carrots→ 21:52, 4 September 2013 (UTC)
 * From blood, oxygenated blood is brighter than deoxygenated blood. "Hemoglobin is the principal determinant of the color of blood in vertebrates. Each molecule has four heme groups, and their interaction with various molecules alters the exact color. In vertebrates and other hemoglobin-using creatures, arterial blood and capillary blood are bright red, as oxygen imparts a strong red color to the heme group. Deoxygenated blood is a darker shade of red; this is present in veins, and can be seen during blood donation and when venous blood samples are taken." --Stephan Schulz (talk) 23:30, 4 September 2013 (UTC)
 * Schulz is correct. Heme is an uncommon and very powerful dye; there's nothing else in blood with anywhere near so much color.  Other fun variations can be seen in blue Fugates, but here it's the strained ligand interaction with carbon dioxide rather than oxygen that matters.
 * The obvious problem with drawing blood from arteries is that they tend to be under pressure... Wnt (talk) 06:58, 5 September 2013 (UTC)


 * The blood from veins are dark in color because of the presence of "carbaminohemoglobin"(deoxygenated), a respiratory pigment darker than "oxyhemoglobin"(oxygenated). Benison talk with me 16:28, 5 September 2013 (UTC)


 * Good point! We have an article on carbaminohemoglobin.  I should explain the carbon dioxide actually binds to the hemoglobin protein rather than the heme; its binding and the increase in acidity from increased CO2 levels tend to release the oxygen.  Methemoglobin is yet another variation, with the iron in a different oxidation state.  Carboxyhemoglobin, in carbon monoxide poisoning, gives the blood a bright red color.  I hadn't thought about the fact that oxygen and CO2 can be associated with hemoglobin at the same time, though not so happily: because the variations at the heme are what matter most, it isn't literally the binding of carbon dioxide that changes the color of the blood, but the loss of oxygen, unlike with carbon monoxide. Wnt (talk) 17:44, 5 September 2013 (UTC)

about taking blood test from the veins / arteries
What is the reason that we used to take the blood for a test from the veins and not from the arteries? Is there any biochemical reason or it's happen only because it's more easy to take from the veins? If we take a blood test from the arteries will it show us the same results? 95.35.210.39 (talk) 21:22, 4 September 2013 (UTC)
 * I'm sure there are many reasons. One of them will be evident if you ever have blood drawn from an artery: It hurts like hell, and you have to apply pressure for a while to prevent excess internal bleeding. Much less of an issue with veins. ←Baseball Bugs What's up, Doc? carrots→ 21:46, 4 September 2013 (UTC)
 * Veins are closer to the surface and thus easier to reach, are lower pressure, and have thinner walls. There may be other reasons too. Shadowjams (talk) 23:04, 4 September 2013 (UTC)
 * Arterial flow is harder to stop. μηδείς (talk) 00:11, 5 September 2013 (UTC)
 * In addition to reasons already stated (Arteries contain a muscular layer that makes it more painful to have blood drawn from them; risk of blood loss due to higher blood pressure; difficulty with bleeding; and accessibility) there is a risk of interrupting blood supply to vital tissue when an artery is punctured, and morbidity can result. In general, the expected results from venous and arterial blood are expected to be indistinguishable, with the exception of measurement of blood gasses, which is pretty much the only reason blood is routinely taken from arteries (partial pressures of arterial oxygen and carbon dioxide are clinically useful). There may also be instances in which arterial blood is used because it's easy for the physician to obtain (when veins are scarred or can't be accessed, or when there's an arterial line already in place, which is often the case in an ICU where a patient is on a respirator). - Nunh-huh 22:57, 5 September 2013 (UTC)

Something from nothing
Did space exist before the Big Bang? If nothing existed in it, then would it have been as infinite as it is now, or sufficiently tiny to accommodate the first particle. Is the size of space determined by the matter that fills it? russ (talk) —Preceding undated comment added 23:54, 4 September 2013 (UTC)
 * It's not clear whether "before the Big Bang" makes sense at all. You might get a better intuition if you mentally take the logarithm of the time after the big bang.  That is, think of 1 second after the big bang as being as long after 0.1 sec as 0.1 sec is after 0.01 sec, which is the same interval as from 0.001 sec to 0.01 sec, and so on backwards.  That moves the big bang itself to a point "infinitely far" in the past. --Trovatore (talk) 00:07, 5 September 2013 (UTC)
 * Oh, as to how that relates to your real question: If the universe is infinite now (which is an open question), then it always has been infinite, where "always" is to be understood in the sense above &mdash; that is, at any positive time after the big bang.  If you extrapolate back to the big bang itself, then the distance between any two world lines goes to zero, so in that sense you would have just a single point at the big bang, but infinite space at any time afterwards.  That's a strange-seeming discontinuity, but if the big bang itself "never happened" (that is, is infinitely far in the logarithm-of-the-past), then who cares? --Trovatore (talk) 00:10, 5 September 2013 (UTC)


 * The size and dimensions of what you call "space "is sape by what they call particles . Because actually the space content noting and endless . And for example when the particles are attracted by the gravity, they are attracted to it in power indefinitely at smallest size , so time flip dirction and multiplies the particl , so you got 3 dimension and it also depends on the strength of the attraction of the particles themselves . But again " space " made ​​of nothing and have infinity dimension and length . Thank water nosfim

Neither space nor time existed before the big bang. Space and time exist relative to measurable entities and changes (there is so much space between x and y, so much time elapses between this and that). Likewise, had the big bang occurred in space and time there would be a reason why it occurred now and not then, here and not there. The big bang is like the south pole. you can walk north from it, but there is nothing south of it. μηδείς (talk) 00:16, 5 September 2013 (UTC)

Time symmetric models have also been proposed like this one where the time evolution from the initial inflating patch is invariant under time reversal. So, we would then exist in both 13.7 billion year after and "before" the big bang, our copy on the other side of the big bang evolves backward in time relative to our positive time direction (but that copy will experience our negative time direction as his positive time direction). Count Iblis (talk) 00:25, 5 September 2013 (UTC)


 * We have Big_bang, which includes links to some theories. The answer is that no one knows. Stephen Hawking's theory is that the big bang was basically time zero, and there is no such thing as "before the big bang". There are many theories that posit some manner of universe existing before the big bang in which there may be space and time. All of them, except the ones postulating a universe that is infinitely old or cyclic, also have an issue with explaining "what came before". Someguy1221 (talk) 00:44, 5 September 2013 (UTC)


 * Roger Penrose - whose hobby sometimes seems to be betting against Hawking - has proposed and championed conformal cyclic cosmology. Gandalf61 (talk) 10:02, 5 September 2013 (UTC)