Wikipedia:Reference desk/Archives/Science/2015 October 16

= October 16 =

exposure to sunlight create which nutrients in human body
OP want knowledge — Preceding unsigned comment added by Mahfuzur rahman shourov (talk • contribs) 03:51, 16 October 2015 (UTC)
 * Vitamin D. GangofOne (talk) 04:09, 16 October 2015 (UTC)


 * Not having a clear idea in head how to look this up properly, I tried a web search for photochemical "other than vitamin D", coming up with leads like  and  (the latter says it's "not clearly known"; the former seem more positive).  It's a difficult experiment to carry out, because there's no way to put a radioactive label on photons and watch where they go!  Maybe RNA-Seq could witch out some new leads... but a study like  this shows that that is no cakewalk either, because the changes from UV will be far-reaching, and I imagine some of the other known effects also are pretty widespread in the transcriptome.  (Unknown effects probably, though not certainly, actually would affect proteins and biochemistry, touching on transcription only by an indirect route)  If you really think hard about the problem likely you can think of something smarter to try... Wnt (talk) 15:10, 16 October 2015 (UTC)

What happens in slow-motion when the 9/11 planes collided with the WTC towers?
I hate to be morbid, and I haven't been able to find the info I'm looking for. What happens on-board the plane—in slow-motion—as the 767 planes collided with the tower? Does the sort of concussion of impact kill everyone on board instantly, and are the passengers in the back of the plane effectively dead before the plane completes its disintegration? Is the plane turning into a molecular pancake, all while pushing itself forward into the center of the building?

And finally, wouldn't aviation and construction engineers want to know this kind of information and use it for some sort of purpose (if only for a better knowledge of high-speed impacts)? Reflectionsinglass (talk) 06:05, 16 October 2015 (UTC)
 * You don't need 9/11 to get this kind of information, see:, there are other videos of this online (some with narration), I picked the most complete one. At the speeds involved everyone on board was killed instantly. As soon as the front of the plane hit, a shock flowed through the body of the jet, and everyone on board was thrown forward (relative to the body of the jet) with tremendous force and would be killed or knocked unconscious when they hit what was in front of them. In theory someone in the aisle who had nothing in front of him could survive their journey all the way to the front - which would have taken under 1/5 of a second at most. Ariel. (talk) 06:43, 16 October 2015 (UTC)
 * This |slow motion visualization of the collision models the breakup of a plane as it penetrated the tower structure. Passenger bodies are not simulated specifically but being approximately 60% water (15 liters/adult, see Composition of the human body), they would have become Aerosol similar to the fuel and Boiling occured. Bestfaith (talk) 18:52, 16 October 2015 (UTC)

https://www.youtube.com/watch?v=_vobOib9iTg This is a YouTube video that helps explain what happens to people when a plane goes down. In an event that your plane goes down and crashes, it is livable. You are suppose to put your hands behind your head, place your chin to your neck, and brace for the impact. When you are talking about crashing into a building, it is more complicated. Our body is filled with cells and they can not handle extreme speeds and will explode/die. You are mostly to die instantly. Kmmi227 (talk) 18:46, 20 October 2015 (UTC)

Vacuum energy
The mention of vacuum energy made me notice something odd in that article. They say that there is a minimum energy between anything and anything of E = hv/2, where h is Planck's constant and v is the frequency, and so that adds up to an infinite amount of energy permeating all space. But I'd think that the minimum energy only applies when that energy level is less than if the two objects don't interact. I suspect that's actually implicit in the frequency - if you have H2 I'd expect it to wiggle back and forth faster than Xe2. But that energy isn't "in the vacuum"; it's just energy that you can't extract by bonding the atoms together in some interaction. I also feel like this ought to be somehow equivalent to the Heisenberg uncertainty principle, namely, that the uncertainty in the position/momentum of the bound objects tells you precisely how much "zero point energy" must remain - is this true? Wnt (talk) 14:26, 16 October 2015 (UTC)
 * See Quantization (physics). The notion that energy is quantized is that energy exists only in a discrete set of values, and not at an inbetween values.  The easiest model of quantization to understand is probably the Bohr model of the atom, but that's a highly specialized view of quantization restricted to 2 particle systems.  If you take the basic principle, however, all forms of energy are quantized.  -- Jayron 32 14:50, 16 October 2015 (UTC)
 * I understand that much. The thing is, when a Bohr atom is in its ground state, I don't call that "vacuum energy".  It's just the limit on how much energy you can get out of an electron and proton by dropping them next to each other.  (Incidentally, the Bohr radius actually can be calculated from the Heisenberg principle, though there are an alarming number of "~"s in this calculation.  I don't understand why such a fundamental law is so frequently written with "~"s.) Wnt (talk) 14:56, 16 October 2015 (UTC)
 * You don't have to call it vacuum energy, but the concepts are related. Vacuum energy is essentially the ground state of the empty universe.  If you want to get to the "whys" of vacuum energy, the answer is "we have no clue".  Zero-point energy is the theoretical prediction made by quantum theory as to what vacuum energy should be, and yet experimental measures of that vacuum energy show that the prediction is WAY off.  This so-called Vacuum catastrophe is, in some ways, the quantum mechanical equivalent to the ultraviolet catastrophe within classical mechanics.  Currently, there is no solid model which eliminates said catastrophe.  -- Jayron 32 15:13, 16 October 2015 (UTC)
 * Well, if the ground state of an atom is part of it, then there should be an infinite amount of "vacuum energy" in one hydrogen atom, since the electron could fall infinitely close and tight to the proton, if there were no Heisenberg principle. But to me, this is less meaningful than how much wood a woodchuck could chuck...  the electron can't do that, you can't picture how it would act to do it.  Which is like trying to picture how the particles in a zero-energy oscillation would move (or rather stand still with zero observed motion), with no uncertainty principle, again acting as mathematical points or something.  Nature has never shown us a point particle, or anything with zero dimension; it doesn't exist except as a textbook platitude.  And if the theory can't make consistent predictions that only seems to confirm it.  So why do people credit it as a meaningful idea? Wnt (talk) 16:41, 17 October 2015 (UTC)
 * I'm not sure I understand your question but I'll blather a bit anyway. The vacuum energy isn't energy of particles or between particles; it's energy of the underlying field. As the article says, the vacuum is something like a bunch of harmonic oscillators. (Classically, it's like a rubber sheet, and if you distort it there's a restoring force given by something like Hooke's law.) Since the world is quantum they're quantum harmonic oscillators. Quantum harmonic oscillators can have energies of 1/2, 3/2, 5/2, ... times a base energy. At those energies we say there are 0, 1, 2, ... particles (bosons). That's what particle count means in quantum field theory (at least for bosons), and that's why it's an integer. If there are n particles in a certain state, the energy is n+½ times a base energy (=hν). The ½ is the vacuum energy. It does derive ultimately from the uncertainty principle applied to the state of the quantum field. Why not just ignore it, since you can't convert it to anything else? I think there's a convincing argument (which I don't understand) that gravity can't tell the difference between vibrations of the field that represent particles and vibrations that represent vacuum energy, without violating some important principle (possibly locality). When talking about nongravitational forces you can ignore it: it doesn't figure into the mass of hydrogen atoms vs free protons and electrons, nor, despite popular belief, the Casimir effect. -- BenRG (talk) 09:01, 17 October 2015 (UTC)

Using pluripotent stem cells for hair regrowth
This article claims that hair can be grown by using human pluripotent cells to create dermal pappilae and use them to become hair follicles on scalp. Is it for real ?http://www.eurekalert.org/pub_releases/2015-01/smri-usc012715.php — Preceding unsigned comment added by 175.101.24.136 (talk) 15:49, 16 October 2015 (UTC)
 * Read the linked source carefully, it doesn't say they transplanted hair folliciles on to the scalp. In fact, it says transplanting the dermal papilla cells on to the scalp (well on to human subjects, I presume they meant the scalp but I'm not sure) was the next step. And it was from 2015. Even if they have found the partner they were looking for, given the approvals etc needed, it's fairly unlikely they've actually transplanted the cells yet. And in the unlikely event they have and it was successful, it would still be long way from being a commercial option, if it ever becomes one. I don't know what you mean by "is it for real". The study, which is linked your source is a real published paper, and as a peer reviewed paper published in a decent journal it's resonable to assume that the results were real. That doesn't of course mean it will ever lead to a viable treatment. Notably, while I didn't read the paper that carefully and I'm not certain I'm understanding what I did read, it sounds like they are using embryonic stem cells. If I'm right, this will likely be controversial in certain places. More significantly perhaps, I presume this means the cells will not normally be from the same human subjects, so it seems likely there will be a strong risk of an immune response. It seems unlikely taking antirejection/immunosuppressants for a hair transplant will be consider viable and seems to agree. That source notes there's current research into methods of transplanting hair from another donor without causing an immune response, and I guess there may be additional things you could try with embryonic stem cells but it still seems a big hurdle. The alternative would be trying to do the same thing, but starting from autologous adult stem cells. At a guess, perhaps that's the long term plan. Either way, it seems a long time away from being a viable treatment, if it does ever work. Nil Einne (talk) 16:43, 16 October 2015 (UTC)
 * Note that the problem with human baldness is usually not complete absence of hair; rather that the hair that does appear is vellus hair for quite a while, before the follicle finally gives up the ghost. So if that's the underlying motivation behind this work, growing new hair from stem cells wouldn't seem to address the basic problem, which is that the whole follicle is still there, but is being shut down somehow. Gzuckier (talk) 05:57, 20 October 2015 (UTC)
 * From my reading, this work may have been more of a "can we do this" and "what does it tell us about how hair develops" sort of experiment (than with a definitive eventual therapeutic goal although since they plan transplants in humans, I suspect there is some consideration of the possibility. You're right that I don't think they really considered DHT resistance or anything of that sort, at least not in the paper I read. Nil Einne (talk) 16:10, 20 October 2015 (UTC)

What species does this fish belong to?


Can anyone tell me the name of the fish? I am really curious to know the scientific name of this fish. Thank you. Supdiop ( T 🔹 C ) 17:01, 16 October 2015 (UTC)


 * What's with the weird psychedelic pics ? It looks to have a fin made partially for walking, in front, so that makes me think of some type of walking fish, but not a mudskipper due to the position of the eyes.  Perhaps a climbing perch:  ?  StuRat (talk) 19:44, 16 October 2015 (UTC)


 * It swims like normal fish, like a gold fish. My friend told me it is a baby shark but I don't think it is a shark because it doesn't have any features like electric pulse detector and has gills like normal gold fish. I intentionally blurred out other parts. Sorry. It's a cool looking fish, it's actually cute, it doesn't look dangerous at all. Supdiop ( T 🔹 C ) 19:58, 16 October 2015 (UTC)


 * Walking fish don't walk often, they usually swim. They do have the option of walking, though, when water levels are too low to swim, etc. StuRat (talk) 21:21, 16 October 2015 (UTC)


 * Where is it? How big is it? Can we see non-distorted photos please. DrChrissy (talk) 20:14, 16 October 2015 (UTC)


 * It is 5 to 6 inches long. It's a baby. Mature ones are little bigger. I am uploading new one soon. It is very very sensitive to movement and sound, in other way, it's sensitive to vibrations. Supdiop ( T 🔹 C ) 20:54, 16 October 2015 (UTC)


 * I uploaded a new version. See it. Supdiop ( T 🔹 C ) 21:03, 16 October 2015 (UTC)


 * It has beard, really, there are 4 or 5 hair like structures under it's mouth. Maybe they are used to detect vibrations. Supdiop ( T 🔹 C ) 21:09, 16 October 2015 (UTC)


 * Why the distortions (the bottom pic is now even more distorted than before and I can no longer see the "foot") ? If it has barbels, then maybe it's a catfish.  Also see the other fish described at the barbel link.  StuRat (talk) 21:14, 16 October 2015 (UTC)


 * Yes, it is a Catfish, the description correctly fits this fish. Thanks. ( T 🔹small>C ) 21:26, 16 October 2015 (UTC)


 * It has no foot, it's a small fin which is under its body. Thanks Supdiop ( T 🔹small>C ) 21:30, 16 October 2015 (UTC)


 * Good. I couldn't see it clearly due to the distorted pics.  I will mark this Q resolved, but you can remove the tag if you have more Q's about the fish. StuRat (talk) 21:41, 16 October 2015 (UTC)
 * See this. It is shark catfish. Thank you Supdiop ( T 🔹 C ) 22:13, 16 October 2015 (UTC)


 * We have an article Shark catfish but it does not look much like that. DrChrissy (talk) 22:32, 16 October 2015 (UTC)
 * There are many sub species of shark catfish, I think. If you search for shark catfish on google images, you will get that fish photos. Thanks Supdiop ( T 🔹 C ) 00:01, 17 October 2015 (UTC)
 * Well, there are dogfish people and shark catfish people, i guess.Gzuckier (talk) 06:00, 20 October 2015 (UTC)

Pork for dinner
Folklore aside, will individual wolves attempt to eat adult hogs? I can imagine a wolfpack attempting to take down one or more pigs/boar/razorbacks/etc., but an individual wolf? Nyttend (talk) 23:34, 16 October 2015 (UTC)
 * Two Russian gray wolves attack two young adult male wild boars. |video Bestfaith (talk) 23:44, 16 October 2015 (UTC)