Wikipedia:Reference desk/Archives/Science/2009 December 4

= December 4 =

Storks
Why do you get storks in places like Germany and Holland but not in Britain? Germany has a more severe winter than Britain, so that cannot be the reason. 89.242.105.246 (talk) 01:08, 4 December 2009 (UTC)


 * Storks are seen in UK, occasionally. However, UK is rather far west and north-west from their habitat (Central and Eastern Europe). They migrate south by one of three routes, AFAIK: western route over France, central route over Italy, or eastern route over Israel. If they were to spend the summer in UK, they would have to fly east to France and then south, which, I guess, they usually don't. --Dr Dima (talk) 01:42, 4 December 2009 (UTC)

name of physics book
What is the name of the physics book depicted here? In case you are wondering, that is Tiger Woods's car. Thanks. 67.117.130.175 (talk) 01:24, 4 December 2009 (UTC)


 * See this. hydnjo (talk) 01:42, 4 December 2009 (UTC)


 * It is “Get a Grip on Physics” by John Gribbin. Edit: the above link does not work for those of us for whom Google automatically redirects to Google.co.uk, so here is a UK version of it: 78.149.192.188 (talk) 11:24, 4 December 2009 (UTC)
 * Took a minor liberty and Wikilinked the name in your post, 78.149, as I'm a fan of Gribbin. 87.81.230.195 (talk) 12:55, 4 December 2009 (UTC)

Cat and dog ear fold.
What is the function of the small pleat on the ventral/posterior exterior margin of a cat or dog auricle? Presumably other Carnivora have this feature as well. It looks like this: ==-===--- where the skin doubles, and the interior fold is divided. The structure is visible in this image: http://en.wikipedia.org/wiki/File:Terrier_mixed-breed_dog.jpg. - Craig Pemberton 01:43, 4 December 2009 (UTC)
 * I'm going to go out on a limb and say that this fold has no appreciable function. My guess is that it is a vestigial trait left over from some other ancestral characteristic. I also have to admit that I am not at all qualified to make such an assumption so if someone else has evidence to the contrary you can safely ignore my answer. Presumably since some bats have quite gnarly ears, the folds play some role in sensing direction or attenuating certain sound, but a lot of bats also have smooth ears and hear just fine so it seems to suggest that this characteristic doesn't play a major role. Similarly it's hard to imagine the folds in human ears play a significant "functional" part of our hearing, if any part at all. Vespine (talk) 05:26, 4 December 2009 (UTC)
 * I seem to remember reading somewhere that the folds in human ears modify the frequency ranges of sounds coming from different directions, allowing a person to know where the sound is coming from (not just left or right but in front or behind, above or below). I must, like you, point out that I have no idea what I'm talking about really, though. 213.122.24.221 (talk) 17:58, 7 December 2009 (UTC)


 * I've always assumed that it has to do with turning the ears. That is, the fold is present when the attached muscle is relaxed, while it's straigtened out and the ear turns when the muscle tenses. StuRat (talk) 05:28, 4 December 2009 (UTC)

Rechargable Batteries
Just curious: which is faster? Draining a battery OR charging it? or can they be completed in roughly equal periods of time? I'm thinking draining a battery could potentially be faster because (I think?) batteries don't heat up when they lose power, only when they're charged, so the absence of a thermal consideration would allow for a faster rate of flow? Thanks! 218.25.32.210 (talk) 02:00, 4 December 2009 (UTC)
 * I guess you've never used a smart phone or semi smart phone then. Draining a battery can definitely result in it heating up. This happened even with my Panasonic VS2 which wasn't a particularly fancy phone, when using GPRS or when taking many photos nearly continously. In fact from some quick Googling I see it can happen with continous talking too which makes sense so I wonder if you could probably notice this even with completely non smart mobile phones in some circumstances so you may be able to try this yourself if you have a mobile phone (although it's obviously going to cost money in such circumstances). I'm thinking here of Lithium-ion batteries obviously but I'm pretty sure this would apply to most rechargable batteries. Obviously when it comes down to it, it's depends under what conditions. You could discharge or charge a battery at a very high rate but it may damage the battery or in some cases particularly lithium-ion batteries result in explosions. For example, you can get 15 minute fast chargers for NiMH batteries that are supposed to charge in about ~15 minutes but as the batteries get hot and it isn't particularly good for them to be charged so fast, many have a switch to allow slower charging. (Which would still be faster then most traditional chargers and I suspect even extremely fast charging is probably significantly better for the battery then overcharging that can happen with old unsmart chargers). Similarly most lithium-ion batteries have temperature sensors I believe and these help limit the rate of discharging and charging to prevent the battery getting too hot Nil Einne (talk) 02:39, 4 December 2009 (UTC)
 * Though I own a smartphone, 99% of my usage is text messages, so I had indeed never experienced what you relate. In terms of my original question, I'm really more interested in laboratory/theoretical conditions and the physics behind the results - though I thank you for your long and detailed response! :-) 218.25.32.210 (talk) 02:55, 4 December 2009 (UTC)

The question is relevant to designing an electric bus to run a fixed urban route. The goal is to have two busses, one always charging and the other always in motion. My assumptions are that the bus design sets no limit on the battery size or weight, the battery type (to be defined) cannot accept charge as fast as it discharges in use, and that any charging arrangement can be made available at the bus terminus. It seems that if the bus is equipped with battery capacity X times as much as needed to complete its route until the busses swap at the terminus, then the battery can be charged at 1/X times the current at which it discharged. That will be achieved by switching the battery cells from parallel for driving, to series for charging. Am I am right? X must be a smallish integer. Cuddlyable3 (talk) 14:33, 4 December 2009 (UTC)
 * What's the use of a bus if it's always in motion? Also are we talking a dedicated busway here or something? Or just completely empty roads? Nil Einne (talk) 15:59, 4 December 2009 (UTC)
 * There are services for swapping car batteries, you might want to look at something similar:. Fences  &amp;  Windows  16:06, 5 December 2009 (UTC)
 * By one bus being "in motion" I mean "in service", meaning it follows a predetermined circular route, stopping when needed to take on or unload passengers. I don't see how a distinction between dedicated busway or empty road affects the calculation. I don't see a future for the battery swapping machine that is an expensive investment, needs a critical interaction of man and machine, and has a lot of ways to go wrong. A bus that is demensioned to carry 40-60 people and serves a route of say 10-40 km can carry its batteries to be changed only when they they wear out after some hundreds of charge cycles.Cuddlyable3 (talk) 23:12, 5 December 2009 (UTC)

Hair
Why do girls typically have longer hair than boys? jc iindyysgvxc  (my contributions) 05:34, 4 December 2009 (UTC)


 * For the same reasons they wear lipstick when most men don't - cultural norms. Note that men having shorter hair than women on average is not universal to all cultures. In societies in which men traditionally wear turbans, their hair will be very long, perhaps even perpetually uncut such as with Sikhs. In those situations you may very well have most women, even with "long" hair, walking around with less hanging off their skulls than men! 218.25.32.210 (talk) 05:44, 4 December 2009 (UTC)


 * No, I'm pretty sure that girls are capable of growing longer hair than boys. It's not just a matter of how they cut it. So the OP's question stands. Some google found that estrogen and androgen have an effect on how long hair says in the anagen phase. Google for hormone and hair. Ariel. (talk) 06:32, 4 December 2009 (UTC)


 * Can you point to any WP:RELIABLE sources for your claim, or just a Googled bunch of blog entries from random Internet people? Tempshill (talk) 07:55, 4 December 2009 (UTC)


 * I have no real ref. But as evidence I point to the fact that women grow and retain a lot more hair when pregnant (and then it falls out a month or two after they give birth), and men get bald while women don't. It's clear that hair responds to hormones. Ariel. (talk) 23:52, 5 December 2009 (UTC)


 * I don't see any reason to expect Sikh men to have more hair then Sikh women. Both are expected to observe Kesh (Sikhism) AFAIK. Women may not wear turbans but unless that increases hair growth or reduces it falling out or something then it's fairly irrelevant. Now if you include facial har and body hair and perhaps because men tend to be slightly larger on average you could argue that all that means men would on average have more hair but a more sensible interpretation wouldn't include those factors IMHO so it seems they would have roughly equal amounts of hair. Also since no one has done so yet, I might as well link to Long hair Nil Einne (talk) 08:14, 4 December 2009 (UTC)


 * (after ec) Rate of hair growth does not differ significantly between men and women, but telogen (easily detached) hair does: (they studied both Africans and Caucasians).  -- Scray (talk) 08:22, 4 December 2009 (UTC)


 * As anecdotal evidence contradicting Ariel's contention, consider that I (a British white male) have in two separate periods of my life (ages ca 19-23 and 45-50) grown to and maintained my hair at near waist length with no difficulty: I've also encountered plenty of other adult males with hair as long or longer. There may be weak statistical trends in 'hair-length potential' attributable to sex, but the overwhelming bulk of the generally observed length differences is purely down to fashion. 87.81.230.195 (talk) 12:51, 4 December 2009 (UTC)
 * I found some data from the 1950s that suggests that women's head hair grows ever so slightly faster than men's - though only by about 0.02mm/day. Fences  &amp;  Windows  15:25, 4 December 2009 (UTC)
 * This may be a crazy idea, what if the reason females grew hair faster was because the hormones that signal hair growth in the body were spread out over more places in the male body than the female? Mac Davis (talk) 16:36, 5 December 2009 (UTC)

Green Laser Pointer
Recently I bought a green laser pointer thinking of high power etc. but when switched it on I saw that it does NEVER foucus single point but in nearly fifty or so points dividing the power all over. I thought that there should be some adjustment that could be removed but no. There is a lens type thing on front that can be slightly rotated ( causing points to dance here and there ) but no way I can foucs it to single point. What I should to it to make it SINGLE point ?

Jon Ascton   (talk)  07:56, 4 December 2009 (UTC)
 * You need to hold a suitable (separate) convex lens in front of it. MER-C 11:39, 4 December 2009 (UTC)
 * See the image in the article Speckle pattern. Cuddlyable3 (talk) 14:07, 4 December 2009 (UTC)

Restyl tablets
'''Question removed due to request for medical advice. If you are concerned for your health, please call emergency services.'''

activation energy and pri/sec/tert advantages
On paper (resonance structures), the benzylic / allylic site looks quite reactive, but from the bond energies table I see that a benzylic and allylic C-H bond is only about 15 kcal/mol weaker than a "normal" C-H bond. Same goes for C-X bonds (halide). Are there other effects at play (besides I guess bond weakness?) In fact choosing iodide as a leaving group over chloride seems to give a much bigger energy advantage than benzylic/allylic!

Btw, is iodide catalysis "true catalysis"? (Where in an alkyl halide SN2 substitution reaction you put some iodide in solution to speed it up.) What I understand is that iodide is a good leaving group but iodide is not that solvated (so you start out with higher energy, allowing it both to react and leave), but chloride is more solvated (so it ends up in lower energy) so in fact you've increased the energy gap between the reactants and the products, altering the equilibrium. John Riemann Soong (talk) 15:17, 4 December 2009 (UTC)

Organizing chemicals (practical)
I have been tasked with organizing the chemical room of a foodservice D.C. The chemicals are those you'd expect retaurants and other institutions to order - cleansers, chafing fuel, de-greasers, detergents, sanitizers, de-limers, soaps, etc. While they've never had a serious spill, there's no harm in taking some extra precautions, so I'd like to organize the room in such a way to minimize the risks associated with the accidental mixture of chemicals. For the first order of business, I've separated the strong alkalis, acids (of which there's only a few), and flammables (again, only a few) away from each other, keeping more innucuous items like soaps in between. What else ought I keep in mind? Should oxidisers like sodium hypochlorite be given special treatment? Would it be better to have the oxidisers near the alkalis or the acids - or completely separate? Let me emphasize: the actual risk of accidental mixture is very low, the substances are securely packaged and carefully stacked, and we're talking about commercial and light industrial mixtures here, not weapons grade stuff :). Matt Deres (talk) 16:14, 4 December 2009 (UTC)
 * Follow the normal rules of H&S, i.e. keep heavy items on lower shelves if not on the floor: items which are frequently used closer to hand than items which are infrequently used. Make sure the shelves are properly labelled with the item which is to be kept in that position, so all your plans are not set to nought by people who think they know better! --TammyMoet (talk) 16:24, 4 December 2009 (UTC)
 * I'm not worried about that stuff (though I appreciate the advice); I organize and design distribution centres as part of my job. I just want to make the room as safe as it can be, keeping potential chemical reactions in mind, as well as the normal stuff. And, to be honest, you don't necessarily want heavy stuff on the floor; something around hip height is best - would you rather pick up a frozen turkey from floor height or from counter height? Matt Deres (talk) 16:43, 4 December 2009 (UTC)
 * (ec) Even with "low grade" or light commercial chemicals, serious hazards may exist. For example, never mix bleach with ammonia or acid. Be sure to check the MSDS safety sheet for any chemicals - these safety sheets will have storage guidelines that will outline any safety issues associated with storage. Typically, acids and bases are stored in separate cabinets. Oxidizers are never stored near fuels. Pressurized gas falls into its own category, and gas cylinders have entirely separate safety requirements (often mandatory outdoor storage, depending on conditions). Above all, consult the MSDS sheets - these are very informative and will spell out any potential hazards in plain english. Some "benign" chemicals may have storage details that you did not know about. Nimur (talk) 16:44, 4 December 2009 (UTC)
 * The MSDS's are, of course, the ultimate guide. The problem there is that when you're dealing with hundreds of chemicals, it may be more useful to start with general guidelines and then work your way down, so to speak. It's a shame that the word "bleach" has more than one meaning; hydrogen peroxide is both a bleach and an acid so according to that poster, I should keep it away from itself :-). Matt Deres (talk) 18:12, 4 December 2009 (UTC)
 * As important as the location is the manner of storage: Flammables in a fire cabinet, liquid acids on a spill tray, gas canisters behind chains, etc. On the other hand, my local supermarket keeps liquid acid drain cleaner right above the liquid base drain cleaner and right near the bread! Rmhermen (talk) 19:20, 4 December 2009 (UTC)