Wikipedia:Reference desk/Archives/Science/2008 November 27

= November 27 =

Chicken head stabilization
I just thought this gizmodo story is very cool and was surprised I can't really find more information on this behavior. Can anyone confirm that this is not an elaborate hoax and maybe offer some more videos/info on the subject?

I've handled chicken before but don't recall them doing that, but then, i wasn't paying much attention. Thanks. —Preceding unsigned comment added by 70.79.159.37 (talk) 06:45, 27 November 2008 (UTC)


 * That's regular chicken behaviour. The chicken is clearly used to being handled which accounts for the calm display of head stability. If you've ever had a chicken travel in a car with you it works even better. The possible reason for the head stabilising behaviour has, I think, been answered in a previous question somewhere. Richard Avery (talk) 08:31, 27 November 2008 (UTC)


 * Is that behaviour unique to chickens, as a matter of interest? --Kurt Shaped Box (talk) 10:43, 27 November 2008 (UTC)


 * Here's the same guy demonstrating the phenomenon with a non-chicken.


 * Part of me wonders if that is real. There's something a little unnatural about the way these birds look and move and I'm not just talking about the heads. There's something computer generated looking about their heads and bodies. Maybe I'm just being paranoid. But the shapes and movement seem wrong, and the depth of field seems wrong. --98.217.8.46 (talk) 07:10, 28 November 2008 (UTC)

Why are limes seedless?
A bartender told me that all the limes she has seen are seedless while lemons contain seeds. Why is that? Did seedless limes arise naturally or were they bred for that trait, and if the latter, why not breed seedless lemons also? --Mathew5000 (talk) 10:00, 27 November 2008 (UTC)


 * Seedless lemons are rare but do exist: new varieties were reported recently, although the NYT shows up a 1911 reference to a seedless variety which I imagine did not catch on for some reason.. The most common variety of (largely) seedless lime is the Persian lime, which is believed to be a hybrid, and which is propagated by grafting.  The first article I linked mentions that one problem with seedless fruit is that it is difficult, requiring many years of breeding, to ensure that it really is seedless and not just rarely seeded.  It takes a long time to selectively breed trees in general due to the time it takes before they are able to fruit; limes are a lucky hybrid.  —Preceding unsigned comment added by 193.172.19.20 (talk) 11:04, 27 November 2008 (UTC)


 * Another thought. Is there much of a demand for seedless lemons? AFAIK, people don't generally eat them 'straight' (do they?)... --Kurt Shaped Box (talk) 11:10, 27 November 2008 (UTC)


 * I do. I'll eat a few slices after dinner to "cleanse the palate". StuRat (talk) 14:57, 27 November 2008 (UTC)


 * Any citrus works well for that. I use oranges. --  k a i n a w &trade; 19:01, 27 November 2008 (UTC)


 * However, restaurants don't usually give me orange slices for that purpose, but the lemon wedges in my drink work well. StuRat (talk) 06:13, 28 November 2008 (UTC)


 * Hooray for kumquats!  bibliomaniac 1  5  20:57, 27 November 2008 (UTC)


 * Also after poetry, especially Keats.


 * I'm inspired:

"Have a citrus slice, after eats, and also have one, after Keats." StuRat (talk) 14:39, 29 November 2008 (UTC)


 * Lots of people like lemon wedges in their iced tea or other drinks, and for squeezing over their fish, mozzarella in carozza, etc. And the seeds must bother at least a fair number of these people, or high-end joints wouldn't serve said wedges in a prophylactic cheesecloth that keep the lemon seeds out of the drink/main course. - Nunh-huh 03:55, 28 November 2008 (UTC)


 * Well, never underestimate the importance of pointless doohickeys that are meant to project high-class... I doubt people care all that much about the seeds. The cheesecloth just makes us feel fancy and justified in paying that much for our lobster... --07:02, 28 November 2008 (UTC) —Preceding unsigned comment added by 98.217.8.46 (talk)


 * Thanks for the answer, 193.172.19.20! --Mathew5000 (talk) 23:49, 27 November 2008 (UTC)

Bromelain from Pineapples
Hey all, For my A-level Biology coursework, I've got a task about the effect of bromelain on Jelly. I've read that there are two types of bromelain (stem and fruit), but am unclear on the difference between the two, other than where they're found. Can anyone help? Many hugs,  Amzi  ( Talk To Me ) 10:08, 27 November 2008 (UTC)
 * Trying to make jelly with raw pineapple pieces is doomed to failure in my experience! It liquefies around the fruit. Graeme Bartlett (talk) 11:28, 27 November 2008 (UTC)
 * Turns out that pineapple has enzymes (oh yeah, that'd be bromelain) that destroy the gelatine (not surprising given that gelatine is primarily protein, and bromelain is a protease). If you want to make pineapple jelly you have two options: use a gelling agent unrelated to gelatine; or (better) use something that prevents the enzyme from wrecking the gelatine - if you heat your jelly mix with some pieces of a bell pepper you can then gel it with gelatine. I doubt it helps Amzi though. --121.127.209.126 (talk) 12:02, 27 November 2008 (UTC)

The coursework involves heating it to a high enough temperature to denature the enzyme - I think about 75 degrees Celsius is about the temperature you need to heat it to - so the jelly will set after all. 86.128.107.146 (talk) 17:01, 27 November 2008 (UTC)
 * if you read the bromelain article it explains the difference between stem and fruit enzyme. Graeme Bartlett (talk) 05:36, 28 November 2008 (UTC)

is this for real??? -- Bruce Lee plays ping pong with nunchuck

 * Is this video for real?? How could they fake it:
 * http://uk.youtube.com/watch?v=9QHslHpK4-Q
 * Thanks! —Preceding unsigned comment added by 86.217.99.209 (talk) 10:36, 27 November 2008 (UTC)
 * I'm not convinced it's really Bruce Lee -- the video is so small, it could be a look-alike in a track suit. Remember Forrest Gump? Tom Hanks really wasn't a ping pong champion. And the fact that its a commercial really makes me believe it was faked. --70.130.54.91 (talk) 15:02, 27 November 2008 (UTC)
 * I don't know about Bruce Lee, but legendary cricketer Donald Bradman honed his skills using a cricket stump to hit a golf ball repeatedly against the curved surface of the family's water tank when he was growing up. So it might be possible to use a nunchuck for ping pong but whether it's Bruce Lee for real is hard to tell. Julia Rossi (talk) 05:20, 30 November 2008 (UTC)
 * Note that the Bruce character is filmed from a rear angle, his face is rarely shown close up and hardly ever frontal, unlike the opponent(s). You can get a glimpse of his facial features around 00:35 and 00:52, and he doesn't look like Bruce Lee. Some of the ball movements don't look quite natural, "Bruce" doesn't even follow the ball's movements with his eyes, sometimes looking 90 degrees away, and it's a commercial. I don't know how they "faked" it, but one likely scenario is having the Nunchaku-Ka and ping pong player mime their motions without a ball at all. Air ping pong, if you like. Maybe they improvised, maybe someone was shouting instructions while filming, maybe it was thoroughly choreographed. The ball could have then been added later by some variety of computer animation. ---Sluzzelin  talk  06:19, 30 November 2008 (UTC)
 * The mystery of illusion is a bit more transparent in this clip, by the way. Enjoy! ---Sluzzelin talk  06:37, 30 November 2008 (UTC)
 * It's probably faked the same way they faked the tennis matches in the movie Wimbledon (see the special features on the DVD). Watch the video closely and you'll see two high, bouncing shots on "Lee's" side of the table that look a little unnatural. The scene is choreographed and the actors go through all the motions without a ping-pong ball. The ball is then added in using CGI. This works great until you need a slow-moving ball, where it becomes difficult to get the motion right. --Sub-nav5019 (talk) 18:42, 1 January 2009 (UTC)
 * Why would any of you doubt Bruce Lee's powers and abilities?

Ok, to clear the air. I led the team that created this viral campaign at JWT Beijing. This was a viral campaign to promote the Limited Edition Bruce Lee N96 for Nokia.

The person is not Bruce Lee but a chinese national who has won multiple Bruce Lee lookalike contests in China. He is also a student of Jeet Kune Do.

The video was shot using a background sound of people playing ping pong so that “Bruce” and the ping pong player / players know when to “hit” the ball.

The ball was later superimposed into the video + sound and all.

Hope this clears the air. I glad that you enjoy it. We had lots of fun making it.

Perturbation theory in quantum mechanics
I have a question about perturbation theory. If we expand the exact state as
 * $$ |n\rang = |n^{(0)}\rang + \lambda |n^{(1)}\rang + \lambda^2 |n^{(2)}\rang + \cdots \, $$

with |n(0)> the eigenfunction of the unperturbed H0. Normalizing the exact state gives to first order in λ (supposing |n(0)> was normalized):
 * $$ \lang n^{(0)} | n^{(1)} \rang + \lang n^{(0)} | n^{(1)} \rang =0 \ .$$

The usual reasoning goes on saying that, "since the overall phase is not determined in quantum mechanics, without loss of generality, we may assume  is purely real." But with "overall phase" only the phase of |n> is meant, isn't it? Changing its phase would change the phase of |n(0)> with the same amount, so that their inproduct remains unchanged. This would mean that it is not in general possible to assume that  is purely real. What am I missing? MuDavid 12:55, 27 November 2008 (UTC)


 * The problem has been solved. The "overall phase" may be a function of λ (which seems pretty crucial, so maybe our article should be changed to reflect this), and by choosing this function the right way,  can be made purely real. Bransden and Joachain explicitly say the phase may be a function of λ, but they do not stress that's what makes the argument. MuDavid [[image:Da Vit in Chu Nôm.jpg|17px|Da Vit]] 13:54, 27 November 2008 (UTC)

Natural selection in humans
If, due to some freak tectonic shift, the entire Eurasian and African continents shifted overnight so that Sub-Saharan Africa was located where Northern Europe is now, and vice versa, how long would it take before natural selection made the two populations physiologically resemble what the other one formerly was? (i.e., how long before most of the Africans now living in a cold climate had white skin, and the Europeans now living in a very hot climate had black skin) 69.177.191.60 (talk) 16:55, 27 November 2008 (UTC)


 * It probably wouldn't happen. We would just use sunscreen and vitamin supplements to negate the effects of having the wrong colour skin for your climate (in fact, with a decent diet, the vitamin supplements probably aren't even required). --Tango (talk) 17:01, 27 November 2008 (UTC)


 * I've read that the genetic shift from dark skin to light is estimated to take ~10000 years. Of course, as Tango says, that was before the advent of modern technological and medical advances.  Dragons flight (talk) 05:58, 28 November 2008 (UTC)
 * And involved much smaller populations. With small populations you have things like founder's effect and etc. With very large populations you get regression to the mean. --98.217.8.46 (talk) 06:53, 28 November 2008 (UTC)


 * For natural selection to operate, people would have to die as a result of their skin color. We have ways to prevent that now.  Of course, a small portion of the people would likely ignore all the medical warnings and go without vitamins or sunscreen, and die as a result.  So, we might eventually get changes in skin color, but only if this effect was quicker than natural genetic drift and the effects of intermarriage. StuRat (talk) 06:09, 28 November 2008 (UTC)


 * Well, technically they wouldn't have to die, they'd just have to not reproduce, and others would have to out-breed them. But yeah, same difference, not gonna happen in today's world, population is too big and we don't tolerate that sort of thing. --98.217.8.46 (talk) 06:52, 28 November 2008 (UTC)


 * If the freak tectonic shift also ended technological civilization, there would certainly be selection for dark skin in the new Africa, but I don't think the population of the new Europe would necessarily evolve to "white" skin. The Indians of Canada and Alaska have been there for over 10,000 years and they don't have white skin. &mdash;JerryFriedman  (Talk) 23:06, 3 December 2008 (UTC)

dissassociation of salts
Do salts necessarily disassociate completely when dissolved in water? Our article does not say. Or is there an equivalent of pKa for salts to describe their tendency to disassociate? ike9898 (talk) 17:13, 27 November 2008 (UTC)


 * They don't necessarily dissociate completely. And there absolutely an equivalent of pKa, and it's calculated the same way. It's usually called the solubility product constant.  See solubility equilibrium.  --Bennybp (talk) 17:37, 27 November 2008 (UTC)

Salt solubility in non-aqueous solvents
Is there any freely accessible information anywhere on the solubility of common salts in non-aqueous polar solvents (e.g. alcohols, ethers)? 69.177.191.60 (talk) 17:19, 27 November 2008 (UTC)


 * Our article, Sodium chloride includes a table of its solubility in various liquids. I expect out articles on other salts will have similar data. --Tango (talk) 17:36, 27 November 2008 (UTC)


 * I believe the CRC Handbook of Chemistry and Physics has that information. I guess that's "freely available" if you check your local library - typically the reference section. It can be a bit hard to find the information though. --Bennybp (talk) 17:42, 27 November 2008 (UT

Engineering handbook in English, German and Japanese
I would like to find three general handbooks in these three languages. What are the most common works?--Mr.K. (talk) 18:17, 27 November 2008 (UTC)


 * You don't say which kind of engineering you have in mind? I'm not an engineer, but in the field of mechanical engineering I sometimes turn to the Mechanical Engineers' Handbook, which is in a library near me. Engineering is such a vast subject that for any particular topic a general handbook is likely to point you somewhere else. Xn4  ( talk ) 03:13, 28 November 2008 (UTC)


 * In the meantime I found two German general engineering handbooks. There are this and this one. Engineering is surely a very vast field. However, there is plenty of common stuff. Physics', mathematics', material science's books for engineering are not uncommon. I need handbooks that unite all this common ground. Mr.K. (talk) 16:17, 28 November 2008 (UTC)

Jacuzzi Question
When I'm sitting in the jacuzzi with a cigarette, the water start to bubble when I blow out the smoke. Does anyone know why this happens? Thanks in advance. 99.230.51.61 (talk) 23:11, 27 November 2008 (UTC) —Preceding unsigned comment added by 99.230.51.61 (talk) 23:10, 27 November 2008 (UTC)
 * Are you sure you're not passing gas? —Cyclonenim (talk · contribs · email) 23:11, 27 November 2008 (UTC)
 * The water bubbles whenever the bubbles are switched on, it has nothing at all to do with your cigarette. See confirmation bias. --Tango (talk) 23:12, 27 November 2008 (UTC)

Sorry, I said what I meant wrong. When I blow the smoke over the jacuzzi I hear the bubbles a lot louder. Why? 99.230.51.61 (talk) 23:39, 27 November 2008 (UTC)
 * The ears and mouth are connected, so it's possible to act of blowing somehow affects your hearing. Try doing it without the smoke, just blow, and see what happens. --Tango (talk) 23:54, 27 November 2008 (UTC)

I've done that. Also, the sound gets quite a lot louder. 99.230.51.61 (talk) 00:01, 28 November 2008 (UTC)


 * All sounds rather dubious to me. The smoke is not going to be in a large enough amounts to affect the bubbles or things like air pressure, and it will be rapidly rising away from them at that. My humble suggestion is some sort of placebo effect and confirmation bias. --98.217.8.46 (talk) 06:46, 28 November 2008 (UTC)
 * Do you mean the sound gets louder when you blow without smoke? If not, then it's probably just your imagination playing tricks on you (combined with confirmation bias). If it does get louder without smoke, then it could be a genuine effect on your hearing (it won't have any effect on the actual volume of the sound, though). --Tango (talk) 13:31, 28 November 2008 (UTC)