Wikipedia:Reference desk/Archives/Science/2010 June 20

= June 20 =

Oxidation of antimony
Would the antimony in a pewter spoon be oxidized as it is dissolved in hydrochloric acid? --Chemicalinterest (talk) 00:46, 20 June 2010 (UTC)
 * Yes it should oxidize to SbCl3. FWiW 67.170.215.166 (talk) 05:18, 20 June 2010 (UTC)
 * Antimony is pretty inert to non-oxidizing acids such as hydrochloric acid, although you might get a slow reaction due to dissolved oxygen. Physchim62 (talk) 08:46, 20 June 2010 (UTC)
 * Here's one source of Sb reactivity towards acid - no reaction with dilute acids (does react with dilute nitric acid). Also here  . The oxide does dissolve and is produced by heating in air. 77.86.115.161 (talk) 10:52, 20 June 2010 (UTC)
 * "Dilute acids have no effect on Sb; concentrated oxidizing acids react readily, e.g. conc HNO3 gives hydrated Sb2O5, aqua regia gives a solution of SbCl5, and hot conc H2SO4 gives the salt Sb2(SO4)3." . If you look at the electrode potentials, you will see that elemental antimony will not reduce H+ to hydrogen. Physchim62 (talk) 11:06, 20 June 2010 (UTC)
 * Sorry to the art appreciators, but I want to dissolve a fine pewter spoon in hydrochloric acid to get the reducing agent tin(II) chloride. I know the copper will be left behind, but will the antimony? That was the context of my question. --Chemicalinterest (talk) 11:09, 20 June 2010 (UTC)
 * Yes, excluding any antimony in the alloy that was already oxidised.. Haven't you got any lead free solder? It's usually almost all tin plus very small amounts of silver or copper.77.86.115.161 (talk) 11:12, 20 June 2010 (UTC)
 * No, I only have lead solder. --Chemicalinterest (talk) 11:42, 20 June 2010 (UTC)
 * Yes, the antimony should be left behind. There's very little antimony in pewter anyway, usually less than 1%, just enough to harden the tin. So your tin(II) chloride should be 98–99% pure (at least when it's fresh), which should be perfectly adequate for your purposes. Physchim62 (talk) 11:18, 20 June 2010 (UTC)

Why don't Harleys ever have headlamps in other shapes?
In March, I promised a Harley dealer that I would buy a Harley once any model came with headlights in shapes other than circulars. Apparently, I will never buy a Harley then. But that was the dealer's opinion. What's with 2010 Harleys looking the same as the 1960 Harleys? I promise, they would make great time machines because they wouldn't look as out-of-place in the past as a DeLorean would.

But will Harley motorcycles ever get a different headlamp shape in any future model? Or will the 2060 models be just as at-home in 2010 as the 2010 models are today? The Harleys reek of old-schoolness, and just like so many things in life, that style ought to get old sooner or later.

PS: I tried calling the customer care phone # for Harley-Davidson but their offices were already closed. That's why I asked here instead. --Let Us Update Dusty Articles 01:10, 20 June 2010 (UTC)


 * Unfortunately, the Official Reference Desk Crystal Ball is currently out-of-order, so we are unable to answer your question. We apologise for the inconvenience. --Tango (talk) 01:31, 20 June 2010 (UTC)
 * Okay, I can see the part of being unable to answer when Harleys will ever have headlight shapes other than circular-types, but why don't they have other headlight shapes already? At least that's a past/present question, so you don't need a crystal ball for that. --Let Us Update Dusty Articles 01:38, 20 June 2010 (UTC)
 * Just a guess from a marketing angle: One of the Harley's most essential characteristics is that it looks like a Harley. If one didn't have a single big round headlight, it wouldn't look like a Harley any more.  A 2010 Harley is expected to look like a 1960 Harley, or a 1940 Harley for that matter.  PhGustaf (talk) 01:54, 20 June 2010 (UTC)
 * Does a Ford need to look like a Ford? --Let Us Update Dusty Articles 19:03, 20 June 2010 (UTC)
 * PhGustaf is right: 2010 Harleys are supposed to look like a 1940 Harley. New technology is integrated, often at great cost to keep it looking like it is not there. For instance, the ABS doesn't use the "grate sensor" that the Bosch system typically uses. Instead, they use special bearings with a pickup on the outer ring. The only visible part is an extra wire. Pretty smart.
 * So, I'd expect to see Harley come out with HID lamps that fit the old-style housing, rather than moving forward on looks. You can see this on bikes like the Rocker C and on bikes that aren't aimed for the main market- I'm talking about the V-Rod here. In fact, the V-Rod doesn't have an entirely round headlight, it's more of a teardrop shape.
 * WP:TLDR applies. tedder (talk) 04:34, 20 June 2010 (UTC)
 * Oh, TL;DR? In that case, at what part of my original post did you stop reading at? --Let Us Update Dusty Articles 06:30, 20 June 2010 (UTC)
 * TLDR was in regard to my reply, not yours. I figured it rambled enough that I lost you tedder (talk) 09:04, 20 June 2010 (UTC)
 * Nah, I've been trying to solve that age-old question for who knows how long. After nurturing my curiosity for a long time, there'd be no way that your answer(s) would be rambles. I'll be Googling for images of concept Harleys now; depictions of what they may look like in 2020, 2030, and 2040. If I have trouble, I'll check back here to see if you or anyone can find links to them. --Let Us Update Dusty Articles 09:51, 20 June 2010 (UTC)
 * The same reason as the odd firing order characteristic of Harleys; if it went hmmmm or wheeeee, instead of blat-blat-blat, it wouldn;t be a Harley.  Acroterion  (talk)  16:42, 20 June 2010 (UTC)
 * A simple answer: Because people buy them. If twenty years from no people only buy 5-wheeled purple-fringed dingbats with triangle headlights, then Harley will make...No, they wouldn't. Can you see a Hell's Angel on a bike with purple fringe? 75.41.110.200 (talk) 05:23, 21 June 2010 (UTC)

smelly vitamins.
what, exactly, makes multi-vitamins smell they way they do? why are some so pungent and others not? i assume it's the amount of variety of ingredients, but most have that same "vitamin smell" not matter what they contain. —Preceding unsigned comment added by 67.83.46.55 (talk) 08:24, 20 June 2010 (UTC)
 * Is it yeast which is a good (and I suspect common) basis for a multivitamin pill..? 77.86.115.161 (talk) 10:18, 20 June 2010 (UTC)
 * Multivitamins without yeast also smell. B vitamins have a quite horrible smell, for one. -- Aeluwas (talk) 10:42, 20 June 2010 (UTC)
 * Which of the B vitamins are responsible for the smell?77.86.115.161 (talk) 10:48, 20 June 2010 (UTC)
 * Yeast extract is the main component of the vast majority of Vitamin B supplements, and it does have quite a distinctive smell. You can get it as brewers yeast tablets. If you can, try and take a smell of these tablets to see if that's the smell you're referring to. --TammyMoet (talk) 14:29, 20 June 2010 (UTC)


 * Try Marmite!  MacOfJesus (talk) 14:15, 21 June 2010 (UTC)

butterfly / moth
I found this butterfly / moth (picture) just sitting on the pavement today, at risk of getting stepped on so I carefully moved it to my garden on a card. It seems weak and just sits on the card now, it doesn't move around or anything except for its antennas. It tried once to fly and just fluttered to the ground and landed on its back. I have two questions
 * a) What species it is?
 * b) Is there anything I can do to help it? I feel very sad about this. If I just let it go it will fall to the floor and probably get stepped on.

Thank you for your help 82.43.90.93 (talk) 12:46, 20 June 2010 (UTC)
 * Cinnabar moth. Maybe you can get it to take some honey, or sugar water? --TammyMoet (talk) 14:33, 20 June 2010 (UTC)
 * Is it possible that it has laid it's eggs and will die anyway (anyone know when these lay their eggs?)
 * In the UK, usually around June since, according to Richard South, the caterpillars "feed[s] in July and August on ragwort (Senecio jacobaea)" - which they certainly do as I know from collecting and raising them as a youth.
 * The male and female of this species look very similar, and I can't tell which yours is. If you're concerned about helping it to reproduce (assuming it hasn't already) the best course would be to take it to somewhere that ragwort is growing, preferably in as close to a rural/unpolluted situation as possible, and leave it on a plant - you may see some of the very colourful caterpillars there. The moth, incidentally, is one of the few British species that habitually fly (in a rather weak fashion) in the daytime. 87.81.230.195 (talk) 02:37, 21 June 2010 (UTC)
 * Of course you could just let it die, it could possibly be a weak, unfit or diseased individual. Just as squishig a bug in the past could have dire consequences on life in the present, if it just happens to be a direct ancestor of say: the human race. In the same way, you playing "God" with nature and helping a weak or unfit individual to breed and possibly then compete with other individuals which just might have otherwise gone onto evolve into another intelligent race in another billion years, but will instead not flourish because of your direct actions. In a slight variation of, but still quite fittingly called "butterfly effect". Of course i'm not "serious", but it's a thought isn't it? Vespine (talk) 05:54, 21 June 2010 (UTC)

uv / urine
http://www.amazon.co.uk/Urine-Off-Finder-Black-Light/dp/B001I0617W

Does this only work for cats? 77.86.115.161 (talk) 15:36, 20 June 2010 (UTC)
 * Cats, dogs, rats; probably more. Any particular animal in mind? Try googling for blacklight giraffe urine etc. Be aware though: urine is a bit difficult to detect using a black light. The room must be very dark, and it's easy to get false positives from other substances. 88.112.56.9 (talk) 18:42, 20 June 2010 (UTC)
 * ok so does healthy human urine fluoresce (noticeably - not in a uv spectrometer), and if so what causes it? And what does coffee/tea/milk/cocoa do? 77.86.115.161 (talk) 19:30, 20 June 2010 (UTC)
 * All urine (including human) fluoresces under UV light -- in fact, there are special UV fluorescence kits for detecting urine stains. Don't know what causes it, though; prob'ly a trace component that I don't remember. FWiW 67.170.215.166 (talk) 05:24, 21 June 2010 (UTC)
 * The presence of natural fluorophores in human urine is the cause of its fluorescence. The major ones include, 4-pyridoxic acid, riboflavin and various pterins and porphyrins. Fluorescence is observed mostly within the 300 nm - 450 nm excitation wavelength range, and it is highly variable between different individuals. Rockpock  e  t  11:36, 21 June 2010 (UTC)
 * Thanks> 77.86.115.161 (talk) 12:04, 21 June 2010 (UTC)

Risk of catastrophic methane explosion in Gulf of Mexico
This article and this video say that a methane gas buildup under the Gulf of Mexico ocean floor will explode with devastating consequences... Is this credible or is it just fear mongering? Thanks very much for your input! --User298576392 (talk) 18:04, 20 June 2010 (UTC)
 * Why would methane explode? The ocean isn't filled with oxidizers. The ocean would also carry away the heat from the methane, preventing it from reaching an ignition temperature. --Chemicalinterest (talk) 18:21, 20 June 2010 (UTC)


 * In all honesty - it walks and talks like a conspiracy theory.77.86.115.161 (talk) 19:33, 20 June 2010 (UTC)


 * The article doesn't say that the methane will ignite, just that there may be enough to create a vast bubble that would rise all at once and generate a tsunami when it reaches the surface. Seems unlikely to me, but let's at least get the story straight. Looie496 (talk) 23:17, 20 June 2010 (UTC)
 * Yeah, let's get the story straight – or as straight as you can get bovine excrement! Methane deposits are commonly associated with oil wells, and this one is no exception, but any substantial quantity of methane would sit on top of the oil. If there was going to be some "supersonic tsunami" (doncha just lurve the alliteration), it would already have happened. Physchim62 (talk) 23:46, 20 June 2010 (UTC)
 * I checked my universities' Geology department on this, To Quote the PHD who incidently was a survivor of the rig in Ixtoc I oil spill "Its Crap" Weaponbb7 (talk) 21:17, 21 June 2010 (UTC)


 * I haven't read the article, but this sounds similar to a limnic eruption? Is the bottom of the Gulf supersaturated with methane (I don't know)? If so then perhaps a volcanic eruption or something else to mix the cold/warm waters (e.g. underwater rock shelf collapse) might allow a massive methane burp. Just throwing out some possibilities/theories. TheGoodLocust (talk) 22:26, 21 June 2010 (UTC)
 * The methane still won't ignite because there's not enough free oxygen down there to allow combustion; and since it won't ignite, it won't make much of an explosion (a BLEVE at most rather than a real detonation), much less a tsunami. 67.170.215.166 (talk) 02:39, 22 June 2010 (UTC)


 * Ignite? I never said it would ignite, but a massive enough methane burp might look like an explosion. Unlike the limnic eruptions we've seen in some places (e.g. Nyos), such an eruption would probably not cause as much loss of life since I think the methane would float up into the air rather than suffocating those the ground. TheGoodLocust (talk) 03:40, 22 June 2010 (UTC)


 * Mud volcano? This sort of stuff happens all the time - hot gas seeps, cold gas seeps- methane is down there and under high pressure, and occasionally comes out forcefully; but it sounds like somebody has taken exaggeration to a whole new level.  The ocean will not explode and there will not be a tsunami because of a gas seep.  Oil and gas reservoirs do have seismic signatures: they are usually so small and faint that they are called "microseismic."  Could a hydrocarbon reservoir event ever result in enough seismic activity to cause a tsunami?  Unlikely.  Could reservoir-induced seismicity be hazardous?  Sure.  The bigger worry in this case would be environmental contamination if hydrocarbons leaked to the surface - methane is a greenhouse gas, and liquid hydrocarbons can seriously contaminate surface and coastal ecosystems.  Nimur (talk) 15:32, 23 June 2010 (UTC)


 * There are deposits of methane clathrates on the sea floor near the rig, and those could pose a significant risk to shipping and even the global climate if they release methane in large quantities&mdash;see clathrate gun hypothesis. There are also reports that methane clathrates could release from the East Siberian Shelf this year, where warm temperatures have persisted, and where methane clathrate releases also occurred in 2008. For related topics, see Paleocene-Eocene Thermal Maximum (the event described in the article that I would not consider a reliable source and would even consider alarmist), Storegga Slide, and Arctic methane release. There is a real possibility that BP will fail to cap the spill, and ideas being sent to BP do not get to the company executives at all. Now if a hurricane passes over the spill region while operations are being done to cap the leak or likewise methane escapes from the sea floor, then that's another story... ~ A H  1 (TCU) 17:23, 23 June 2010 (UTC)
 * In this case, the quantity of methane is far short of that necessary to set off the clathrate-gun chain reaction. FWiW 67.170.215.166 (talk) 01:22, 24 June 2010 (UTC)

Why is the power output of a series-connect array of solar cells so affected by partial shading?
I am trying to understand why, in a series-connected array of solar cells in which one cell is faulty or shaded, the power output of the array should fall by more than the power of the one "lost" cell. To my thinking the current corresponding to the maximum power point (Impp) will be the same in each case (with or without the lost cell), so each "live" cell will continue to produce its same power output. Can someone please explain the physics of the disproportionately large decrease? Many thanks. 89.211.215.17 (talk) 18:07, 20 June 2010 (UTC)
 * I think the cell has resistance, so it functions like a resistor, impeding the current from flowing. If it was just a piece of metal, it would have almost no resistance and so the power output would only go down 1 cell. --Chemicalinterest (talk) 18:19, 20 June 2010 (UTC)


 * I'm fairly certain that the 'silicon' is acting as a Photoresistor as well, in addition to the photo-voltaic effect.77.86.115.161 (talk) 18:19, 20 June 2010 (UTC)


 * In series you can only get the current from the total that every cell can produce. If one is reduced somehow by shading etc, the max current is reduced, and the other cells are not used to their full capacity, the could make a higher current, but the reduced one limITs it. Graeme Bartlett (talk) 11:30, 21 June 2010 (UTC)

Remote video camera
Hi. I want to set up a video camera outside, so that I can watch the footage on my TV. I am therefore going to need a setup where I can receive the pictures remotely. My TV has SCART, HDMI and RF inputs and my PVR has a S-Video, SCART and RF inputs (it would be nice to be able to record the video, but not crucial). I also have a camcorder that I could use for the vidoe capture, which has HDMI and S-Video outputs. I have done loads of searches for "remote camera", "RF wireless camera", "remote webcam", "wireless camera" etc, etc but I can't find anything obvious. It would be nice if the picture could be encrypted between the camera and the receiver, but again not critical. Any thoughts would be greatly appreciated. Thanks GaryInLondon (talk) 19:31, 20 June 2010 (UTC)
 * Have you tried connecting an S-video cable from camcorder to PVR, and a SCART cable from PVR to TV? Cuddlyable3 (talk) 20:44, 20 June 2010 (UTC)
 * Interesting that your searches didn't work. There are lots of wireless video systems available, mainly designed for security purposes -- try searching for "wireless security camera" or "wireless surveillance camera".  If you really need to be able to use your existing camera, though, that's out of my knowledge range. Looie496 (talk) 23:23, 20 June 2010 (UTC)
 * Another search is "wireless video sender" or just "video sender" eg - these can be got at relatively low price for transmission of standard video signals - the issue is that they require a power supply, and typically are built for indoor use only. Using one could still have much wiring though.77.86.115.161 (talk) 23:36, 20 June 2010 (UTC)


 * Are you sure this has to be on your TV set? Doing this with a computer would be vastly easier.  There are tons of WiFi "web cams" out there which would do this job perfectly - so long as you don't mind watching the results on a computer screen.  You could even watch it over the internet while away from home.  If you absolutely must see it on your TV, there are ways to get the video output from your computer to drive the TV. SteveBaker (talk) 02:54, 21 June 2010 (UTC)

Seeing the past
If you traveled faster then the speed of light, could you see the past? --92.244.142.112 (talk) 19:33, 20 June 2010 (UTC)
 * Yes (if it were possible to do so). But you can look back in time without traveling faster than light. Kittybrewster  &#9742;  19:53, 20 June 2010 (UTC)
 * How can you look back in time? Bus stop (talk) 19:56, 20 June 2010 (UTC)
 * Light takes a finite time to travel to your eyes, so the further (distance) out you look, the further back in time you see. e.g. we can see what very young galaxies looked like in the early universe just by having very powerful telescopes looking out to vast distances. Zunaid 19:59, 20 June 2010 (UTC)
 * Hence, a light year is a measurement of distance rather than an amount of time. Kittybrewster  &#9742;  20:04, 20 June 2010 (UTC)
 * By that reasoning we see our hand as it looked in the past. The light took time to travel from our hand to our eyes. Bus stop (talk) 20:45, 20 June 2010 (UTC)
 * True. Maybe the OP wanted to know why we can't travel faster than light? Assuming there are no wormholes which I certainly assume in the absence of evidence for them. Kittybrewster  &#9742;  20:51, 20 June 2010 (UTC)

Nicéphore Niépce invented a way to see the past, now we can see it moving and even reconstruct a historic event in 3-D, and maybe soon we will be able to step into one. Cuddlyable3 (talk) 20:40, 20 June 2010 (UTC)
 * And by this reasoning we are not really seeing the past. We are seeing an artifact that relates to the past. Bus stop (talk) 20:49, 20 June 2010 (UTC)
 * Television beats Paul Revere any day. Kittybrewster  &#9742;  21:32, 20 June 2010 (UTC)
 * If you could travel faster than light, you could not only see the past (which is possible anyway as others pointed out), you could go to it. Looie496 (talk) 21:49, 20 June 2010 (UTC)
 * Indeed but you might have to leave your mass behind. Kittybrewster  &#9742;  21:52, 20 June 2010 (UTC)

Using a tachyonic antitelephone you can send signals into your own past. Count Iblis (talk) 23:22, 20 June 2010 (UTC)


 * Let's be super-clear about this. There is no such thing as a tachyon.  The laws of physics as we understand them do not permit faster than light travel - and it's highly unlikely that there are wormholes.   So if you want a clear science-based answer - and not science fiction - then the boring answer is that because you cannot possibly travel even as fast as light - let alone faster - we simply cannot say what you'd hypothetically be able to see.  It's an utterly meaningless question - and any attempt to answer it is absolutely guaranteed to be bogus. SteveBaker (talk) 02:50, 21 June 2010 (UTC)
 * We might not be able to describe what you'd see outside the window of your superluminus ship, but once you arrived at, say, Proxima Centauri fifteen minutes later, it's safe enough to say that you could see into your own personal past with the appropriate telescope. Even if you'd be too far away at that point to resolve enough details to actually pick yourself out.
 * Sure, our question-asker is not likely to ever pilot such a ship, since they're probably completely impossible, but there's educational value in these sorts of hypotheticals. For instance, understanding this concept may lead them to wonder what would happen if the Centaurians simply put up a giant mirror for us. APL (talk) 03:38, 21 June 2010 (UTC)
 * Woah, I never thought of that. So if WASP-12b was highly polished, archeologists could use Hubble to see the Romans? 81.131.52.86 (talk) 09:52, 21 June 2010 (UTC)
 * Well, kind of. The timing works out more or less.  I don't know how to do the math to figure out how big of a telescope you'd need to see individual Romans in a giant disco-ball nine-hundred light-years away, but I'm pretty sure it would be far bigger than anything we could ever hope to actually build. APL (talk) 20:41, 21 June 2010 (UTC)
 * Viewing Earth through a flat perfect mirror at 900 ly is the same as viewing Earth directly from 1800 ly. To resolve features separated by 0.1 m at that distance you need an angular resolution better than 0.1 m / 1800 ly ≈ 10−20 radian. To get that kind of resolution at visible wavelengths (400–700 nm) your telescope's diameter needs to be at least 700 nm / 10−20 ≈ 0.01 ly. The mirror needs to have at least half the diameter of the telescope. -- BenRG (talk) 01:47, 23 June 2010 (UTC)


 * To OP (and Steve, whom I'm sure knows this), you actually can have faster-than-light particles (tachyons) in some models, except for us forward-time folk they look exactly like forward-time particles. In one model for antimatter, a positron is simply an electron going faster-than-light backward-in-time, which is the cause of the antimatter weirdness that we observe in our forward-time universe. That said, a tachyon can't slow down to slower than the speed of light any more than we can speed up faster than it.
 * A thought experiment: if a person was going backward in time from 2012 to 2008 in the middle of the city, what would he look like, how would he behave, were you to see him on the street in 2010 inside his time-machine-telephone-booth? SamuelRiv (talk) 03:57, 21 June 2010 (UTC)
 * I keep hearing about these models in physics but I've yet to see any of them in a Victoria's Secret show. Yes, that was my useless comment for the night. --mboverload @ 08:35, 21 June 2010 (UTC)


 * Positrons aren't tachyons. A tachyon is (by definition) a particle whose momentum is spacelike (implying faster-than-light motion) or a wave whose mass-squared is negative. Positrons have timelike momentum (slower than light) and positive mass-squared. One can say that particle-antiparticle pairs are related by a time inversion, but this isn't related to the arrow of cause and effect, birth and death, etc., which is the same for both. -- BenRG (talk) 01:47, 23 June 2010 (UTC)

Ammonia-based life
What substances would be poisonous to ammonia-based life but harmless to humans? --75.25.103.109 (talk) 23:47, 20 June 2010 (UTC)
 * I had a hunch but don't really know much about hypothetical "ammonia based life", took me all of about 5 seconds to verify: Googling the term found our article Hypothetical_types_of_biochemistry which confirms the most obvious answer would be simply oxygen. If this was a homework question, you fail. Vespine (talk) 00:07, 21 June 2010 (UTC)
 * nitrite reacts very quickly with ammonia to produce dinitrogen. Graeme Bartlett (talk) 11:21, 21 June 2010 (UTC)