Wikipedia:Reference desk/Archives/Science/2007 June 16

= June 16 =

discharging batteries
what is it called, and why do some people seem to discharge batteries in their watches and cause lightbulbs to blow?Sabeha 01:37, 16 June 2007 (UTC)


 * Are you talking about short circuiting? Doing this to a watch battery will have no observable effect on a lightbulb.  Someguy1221 01:47, 16 June 2007 (UTC)

i'm not sure. some people can't wear watches because the battery always dies too soon, and the time is always off no matter how often they reset the time. certain small appliances tend to malfunction when these people are around them. also, these same people have bad luck where lightbulbs are concerned. they (the lightbulbs, not the people) burn out quicker than they should.Sabeha 02:38, 16 June 2007 (UTC)


 * Something like street light interference? --Wirbelwind ヴィルヴェルヴィント (talk) 03:34, 16 June 2007 (UTC)


 * If you're talking about people who have some sort of ability to discharge batteries or cause light bulb filaments to fail, it's probably just superstition or some new-age pseudoscience like electrosensitivity. -- JSBillings 18:28, 16 June 2007 (UTC)


 * Can anyone cite any research published in refereed journals which substantiates this? Otherswise I would tend to chalk it up to an urban myth or superstition. Lightbulbs all fail eventually. Watch batteries all run down eventually. Who has gone around and recorded the frequency of liht bulb failure or the duration of battery life and fould repeatable effects depending on what individual is present? One light buld phenomenon to mention is that utilities regulate the voltage on the various feeders via tapchangers in the substations, or capacitor banks and voltage regulators on the feeders. It sometimes happens that one of these gets the voltage increased (intentionally or inadvertently) so that the line voltage as thge customer receives it goes from, say 116 volts to 126 volts. This can cause many bulbs in the house to pop the next time they are turned on, because they were near the end of life anyway, and the filament could not stand the higher voltage. If Aunt Nelly lives on a line which experiences such a routine voltage increase, then you or she might notice that every light Nelly turn on pops all of a sudden. Now she seems to have mystic poweres. All coincidence. Edison 18:32, 16 June 2007 (UTC)

thermotropic crystals and mood rings
hello. i was wondering if there is a way (in theory even) to calibrate thermotropic crystals to a color other than green (at 82 F): let's say brown? and then in that, is it possible to have a more focused color spectrum like dark brown - brown - milk brown? or if thermotropic crystals are totally out of the question, what other substances/chemicals reflect specific color wavelenghts based on heat?

I sing atlantic 05:29, 16 June 2007 (UTC)


 * To answer your first question&mdash;yes, absolutely. Stick-on aquarium thermometers (the thin black plastic rectangle kind that goes on the outside of the tank) are made with several liquid crystal strips; each strip exhibits a colour change at a different temperature.  (See thermotropic crystal and liquid crystal thermometer.)


 * I don't know if your second request can be met with liquid crystals, but you may be able to find a suitable alternative in our article on thermochromism. TenOfAllTrades(talk) 14:02, 16 June 2007 (UTC)

heat and sound
hey friends ... please give me something on effect of sound(compression and rarefractions) on transmission of heat through gases.(air) Reveal.mystery-dedicated to find new things


 * The sound waves carry energy, and dissipate along the way (that is, the energy of sound waves is gradually converted to heat). So yes, sound waves can contribute to transmission of heat in gas. Can you be any more specific with your question please? Best wishes, Dr_Dima.

indeed thanx for ur answer on sound and heat topic ,actually i m trying to experiment the transmission of heat in normal air and transmission of heat through air in presence of sound of various frequencies/amplitude. Reveal.mystery


 * I would expect a very loud sound might tend to mix up the air a bit and thus increase the rate at which heat transfers. StuRat 19:01, 18 June 2007 (UTC)

Hypersensitivity Classification
Hi. I'm looking for a comprehensive comparisons of the different types of hypersensitivity. Of particular note is the difference between type I and type III, which I keep getting mixed up. A few examples of each would also be very helpful! Many thanks for your time. 193.188.46.254 07:30, 16 June 2007 (UTC)


 * Our hypersensitivity article seems to cover those bases. - Nunh-huh 07:33, 16 June 2007 (UTC)

Panama canal
I was wondering several things about the Panama canal... how is it possible for the Atlantic and the Pacific to have different "sea levels"? (don't know if that's the correct way to say that) And, what would happen if the Panama canal didn't have those gates separating small portions of water from each ocean? Would we have a tremendous "water fall", flooding several regions of the world? --Taraborn 07:54, 16 June 2007 (UTC)


 * If you were to remove the gates, the lake in the middle would drain, but no tremendous water fall. According to Lake Gatun, the whole lake only has 5.2 cubic kilometers of water, but the total surface area of water on the Earth is 361 million square kilometers.  So if you spread the contents of the lake over the whole surface of Earth's oceans, you'd get less than a millimeter rise in ocean level.  Someguy1221 08:19, 16 June 2007 (UTC)


 * As this cross-section map shows, the locks in the Panama canal are not required because of different sea levels, but are needed to raise ships up to the level of the central Gatun Lake. Note that the horizontal scale on the diagram is shortened - the Gatun Lake, which was made by damming the Chagres River, is actually more than 20 miles long and makes up about half of the total length of the canal. Gandalf61 10:28, 16 June 2007 (UTC)


 * Aha, so it is because of a lake between the oceans, not because of different "heights" of the masses of water. Thanks. --Taraborn 10:52, 16 June 2007 (UTC)
 * No. The "gates" form locks, which are used to raise and lower the ships in order to get them over the substantial ridge that separates the two oceans. Gatun lake serves as part of the waterway, but its primary purpose is to store teh water needed to operate the lock. The number of ships the canal can handle depends on the amount of water available to run the locks. Your original question is relevant for a sea level canal such as the Suez canal.


 * It's worth noting that there is a mean sea level difference between the two ends of the Panama canal, albeit a small one&mdash;mean sea level is about 24 cm higher on the Pacific side. As well, tides on the two sides are not the same height, nor are they precisely in sync.  A lock or two might still be necessary to discourage large currents flowing back and forth.  TenOfAllTrades(talk) 14:12, 16 June 2007 (UTC)

The original poster asked how it is possible for the sea level to be different on the two sides. I believe the explanation is ocean currents. If a current is driving water toward the land, it'll turn to follow the coast, but it'll rise higher as it does so, just as water that you swirl around in a glass rises up the sides. Specifically, this area is where the Equatorial Counter Current hits Central America, so it makes sense for the sea level to be slightly higher in the Pacific here. Similarly, why are there tidal variations on the two sides when the gravitational effects from the Moon are the same? Because the tides are the result of the water actually moving around in response to gravity, and its ability to do that depends on the shape and depth of the sea floor, and the interaction of the tidal currents with other currents.

Would it cause a great waterfall and flooding disasters if the canal was at sea level without locks? No, the differences in level are way too small. Ignoring tides for a moment, the sea level difference is 24 cm according to the page cited above, or about 10 inches; the canal is about 78 km or 48 miles long. That is a difference of 1 part in 325,000: it might generate a current like you get in a river, but even that would be pretty sluggish. The tidal variations cause temporary changes in sea level of more than 100 times the mean difference, so the figure would then be about 1 part in 2,500 and I think that would be able to form a substantial current, which could erode the canal. As Ten said, they might want to put in a lock to prevent that effect.

One potentially bad thing that would be possible if there was an end-to-end current through the canal is ecological effects. Fish and other forms of sea life from the Pacific would ride through into the Caribbean and, if they survived there, would become introduced species.

--Anonymous, June 16, 16:51, copyedited 22:20 (UTC).


 * Note that the Suez canal has no locks, even though it is twice as long as the Panama canal, and there must be tidal differences between its two ends. The shorter Corinth Canal through the Isthmus of Corinth also has no locks. Gandalf61 19:07, 17 June 2007 (UTC)

Muscles
Could some one tell me the adaptations taking place when you keep a muscle tense for long periods? For example you can take a person holding a handgun. Bastard Soap 10:04, 16 June 2007 (UTC)


 * Are you writing a story in which one person needs to hold a gun on another for hours? &mdash;Tamfang 01:51, 17 June 2007 (UTC)


 * Anybody that's holding a handgun tensely doesn't know what they are doing. Root4(one) 04:39, 17 June 2007 (UTC)

No story here guys, I just wanted to know what does the body do to be able to sustain longer periods in tense positions.Bastard Soap 10:02, 17 June 2007 (UTC)

walking power source
on a forum i visit, one of the people mentioned that sometimes lightbulbs would explode around him. several other people mentioned flickering or exploding bulbs, smoke detectors going off for no known reason, etc. i asked them if their batteries ever seemed to die down too quickly and if the time always seemed to be 'off' on their watches. they told me that they could not wear watches for that reason. one person said that her microwave oven, digital clocks and dvr would not work correctly for her, but would work for her husband. i have heard of such things happening to some poeple, but am unable to find anything about it. i am trying desperately to get an answer as to why this happens.Sabeha 11:50, 16 June 2007 (UTC)


 * Before trying too desperately, you might want to consider the possibility that these forum claims are fraudulent or exaggerated. —Steve Summit (talk) 13:50, 16 June 2007 (UTC)


 * Perhaps they are illusionators? Nimur 19:13, 16 June 2007 (UTC)

of course there is SLI, which sounds similar to the first part of your description :) There are also reportas of similar things, but not usually as obvious, happening around adolescents :) Maybe what you have read is an exagerated version of this, written by people who want to impress you :) HS7 14:01, 16 June 2007 (UTC)


 * Yes, as Steve says, it could be interesting to know what this forum is, to get some idea of what type of people are making these claims, and how reliable the claims may be. Say the lady whose electrical equipment doesn't work for her but does for her husband - well, gee, I know heaps of people like that, but it's not some mystical force, it's just that they don't know how to use modern technology! Some of the claims sound highly dubious; I'd want some evidence that the claims are real and that it really does happen, before I'd worry about 'why it happens'. --jjron 14:23, 16 June 2007 (UTC)


 * I suggest you encourage such people to prove their claims and get rich at the same time Nil Einne 15:48, 16 June 2007 (UTC)


 * See Observer bias - how many lightbulbs do you walk past everyday? Probably dozens if not hundreds. No-one ever notices all the hundred of bulbs not blowing, but everyone notices the one bulb that does! Laïka  17:46, 16 June 2007 (UTC)


 * Some people feel an overwhelming need to be "special" - and if they aren't special they'll either consciously or subconsciously make up something. If these people really had this power, we'd know about it big-time.  Imagine someone like that walking down the street at night with lights winking out around them - or walking through a supermarket with all of those overhead lamps failing left and right - these are people who would have to go to bed at 7pm when it gets dark because they can't keep any light sources in their house working!   So - we know that either they are lying - or they are picking up on some coincidental (perhaps quite rare) thing that happened to them - and blowing that up into something they can talk about on a forum system to make themselves feel important.  If other people latch on to it and say it happened to them too - then you just know that this causes the original poster to lose his/her feeling of special importance and start exaggerating in order to regain their status as a 'star' of the conversation.  Truly - we KNOW this can't be true.  There have been plenty of tests of claims that humans can put out mysterious energy fields and so on and not one of them that has been done under proper, rigerous scientific conditions has shown any kind of an effect.  Then there is of course James Randi's offer of a million dollars to anyone who can prove that they have this kind of power.  I suggest you point out the possibility of earning a million bucks merely by demonstrating these 'abilities' under laboratory conditions - and let's see how fast they all back down from their claims because they know in their heart of hearts that this is all nonsense. SteveBaker 23:24, 16 June 2007 (UTC)


 * Besides that need to be "special", another big part of these kinds of claims -- and a reason for their extraordinary endurance -- is the delicious thought, irresistible to some people, that the entire medical/scientific establishment is grossly wrong, that there's this fantastic secret right under everyone's noses, that only the special few can appreciate, because everyone else is too hidebound by tradition and conservatism to admit the possibility. —Steve Summit (talk) 00:28, 17 June 2007 (UTC)


 * I blame the modern educational establishment. Most science classes spend huge amounts of time rote-learning various scientific facts, which are readily ignored or rejected by stubborn-minded individuals. Instead, the scientific process should be emphasized, with specific facts as case-in-point examples.  Science is about verifying observations and generalizing the explanations.  "Paranormal" is an oxymoron - if these things actually happened, then they would be normal and we could all observe them.  From there, it would just be a matter of effort to explain them.  Nimur 09:47, 17 June 2007 (UTC)


 * I've had that experience, but I've assumed there was a logical real world explanation. At various times throughout my life, when I would pass by certain light standards (street lights), they would go out while I was walking under them, then turn back on. This happened with one particular street light every day for two years. It didn't flicker on and off regularly, I had it in view for several blocks before passing under it. It's happened with other light standards also. But I always assumed there was a poor electrical connection somewhere that my footfalls shorted out with vibrations. Or maybe I'm just special. ;-) Anchoress 10:06, 17 June 2007 (UTC)


 * That's exactly the point. If what you say is true, it must be repeatable.  This will enable a full investigation of the cause (which will probably be pretty mundane).  Sadly, that will de-mystify and de-specialize you (and the lightbulb).  If it is not repeatable, than you are suffering from observer bias.  Nimur 10:13, 17 June 2007 (UTC)


 * Anchoress: Let me say this to you very directly...I'm deadly serious. This has never happened to me - I've never once seen a light flicker on and off at the precise moment I walked under it.  So if you can do this as repeatably as you claim (every day for two years!) - then take along a friend with a video camera and record it happening a dozen times - be sure to show the light for a couple of minutes before you walk under it and for a minute or two afterwards.  Then switch places and record your friend walking under the exact same light in the same way at the same time of the day and demonstrate that it doesn't flicker on and off like it does when you walk beneath it (which will eliminate the poor electrical connection theory).  OK - now you have some pretty good evidence that you are special and have a paranormal ability - so write down exactly what you did to make the video and send your write-up plus the video off to James Randi (care of ) - and if it is as you say then you'll easily be able to prove to him that it happens under carefully controlled scientific conditions.  When you've done that he'll cheerfully hand you a cool 'million dollars  - and I'm pretty sure you'll subsequently make hundreds of millions more from TV appearances, book and movie rights - so it's definitely worth the effort to do this.  Now - I know you could use a million dollars (who couldn't!) - so now you have absolutely no excuse - I insist that you must either put up or shut up!  I've very serious about this - either admit here and now that this is a lie (or at least a gross exaggeration) - or prove to the world that it's true and become rich and famous in the process, please keep us informed of your progress and you can thank me for my help by donating 10% of your future psi-created wealth to the WikiFoundation...thanks. SteveBaker 14:05, 17 June 2007 (UTC)


 * Hey, Steve, no need to come down on Anchoress like a ton of bricks! I assumed from her smiley that she didn't really think she was "special" (though of course we all are, in our own ways), but rather that "there was a poor electrical connection" or something.
 * I think we've all had lights go off as we passed by a bit more often than can comfortably be explained by coincidence. Gas discharge lighting is weird stuff, bordering on magic.  (I'm an electrical engineer, and I've never seen a convincing explanation of some of the odd aspects of even ordinary fluorescent lights, let alone sodium and mercury vapor.)  Those things have almost as many screwy failure modes as Windows computers; they're always popping on and off for no reason at all.  I don't have too much trouble imagining that some ephemeral effect induced by an ordinary passing homo sapiens -- electrical field, gravitational field, pheromones -- could tip a flaky one over the edge. —Steve Summit (talk) 14:25, 17 June 2007 (UTC)
 * P.S. Before you come down on me like a ton of bricks, let me say that, yes, I have read our Street light interference article, and I concede that my speculation here is somewhat outside the mainstream. But I hasten to add that the "ephemeral effects" I'm imagining would be wholly scientific and (in principle) explicable, not anything like paranormal. —Steve Summit (talk) 14:35, 17 June 2007 (UTC)
 * Anchoress isn't claiming an intermittant random effect - the claim is every day for two years (for one particular light) and many other lights over extended periods. Unless we have someone here who is "special" - this is WAY beyond normal experience.  I'm quite happy with claims that it happened once or twice over two years - maybe once a month for two years - but every day?!  Just think about the odds here!  Sure, we know that lights flicker as they die - but they don't take two years to die and be so stable in their behavior that a human passing maybe 10 feet below is enough to set it off.  Please - stop and think about the mechanisms that would have to be involved!  It's quite utterly beyond credibility - unless there is some completely unknown effect at work. SteveBaker 15:37, 17 June 2007 (UTC)


 * OT convo rem'd by author Anchoress 17:52, 17 June 2007 (UTC)
 * My request is neither unreasonable nor irrelevent - you didn't have to make this claim - yet you did so and I genuinely want to understand why. I'm not attacking you - you answered a question on the Wikipedia Science help desk and I'm asking for some evidence that what you are saying is good information to pass on to our readership:
 * Is it a reasonable request? Yes - it's reasonable because you claim you could reliably do this "every day for two years".  This should make it very easy indeed to reproduce for the camera.  We know it's not a faulty bulb because you say that you could see that it wasn't flickering from a long distance away and it happened absolutely repeatable - which is statistically so unlikely that we may discount that hypothesis.  Given these as facts - this is a badly understood phenomenon.  If it's true then we have a responsibility as scientists to investigate it.  If you could make it happen that reliably (I know of nobody else who claims to have done this every day for a week - let alone every day for two years!) - then you could certainly film it happening.  Having a friend try (and fail) to make it happen would eliminate the (highly unlikely IMHO) theory that a bad electrical connection is disturbed by vibrations from your feet.  I very much doubt that anyone here can come up with a reasonable scientific way for this to happen thats in any way consistent with the facts as you present them.  Vibrations would just as frequently cause the light to go off and stay off - or to come on when it was formerly off - or for passing cars to vibrate it on and off, etc.  Plus you say this has happened with many different lights on many different occasions - I just can't believe there could be that many street lamp connections that are so amazingly 'touchy' that something as light as a footfall several feet away would make it go on and off again.  So we're left with paranormal means - or that you are exaggerating the facts.
 * Is it irrelevent? No - if it happened rarely - or sometimes the light cut out before you got there or after you passed by then we could say that the light was flickering because it's a bad bulb or an intermittant connection or something.  But no -  you go to great pains to tell us that neither of these things is the case.  Filming it happening lots of times - and with a long pre-roll and post-roll would be proof that you were indeed the cause of this effect and it was not just some random statistical thing.
 * So I again request that you either withdraw your claim to be able to reliably produce this effect on many hundreds of repeated trials under the circumstances you claim - or you provide proof. I absolutely will not withdraw my request - it's not a personal attack - it's a request that this important phenomenon be either investigated or claims for it happening be withdrawn. SteveBaker 15:29, 17 June 2007 (UTC)
 * But if "every day for two years" was a while ago, if the flakey bulb's been replaced (or moved on to a different mode of flakiness) by now, of course she can't.
 * But we can call on everybody reading this: next time you have a street light go on or off as you pass underneath it, be scientific:
 * Walk away and walk back under it again. Is it repeatable?
 * Have someone else walk underneath it. Does the same thing happen for them?  If not, are they of a significantly different height?  Weight?  Sex?  Fragrance?
 * Observe the light from a distance. Is it going on and off spontaneously?
 * If the light is going on and off spontaneously, walk under it as many more times as you can, with an irregular period. Is there significant correlation between your walking and it cycling?
 * Then report back here with your results, or email me, or something. —Steve Summit (talk) 15:43, 17 June 2007 (UTC)


 * OT convo rem'd by author Anchoress 17:52, 17 June 2007 (UTC)


 * I don't think any of those comments were intended as a personal attack; the wording was harsh, but this is the science reference desk. If claims made by any editor do not pass a criteria of scientific credibility, verifiability, and repeatability, then they do not belong on this desk.  Pseudoscience must not be passed off as real science.  Nimur 22:54, 17 June 2007 (UTC)
 * This isn't worth a long side debate, but please note that
 * Anchoress did notclaim or imply pseudoscience, and
 * SteveBaker pretty much called her a liar.
 * Anchoress and I have both given credence to SLI; I insist on harsh treatment for me, too! :-) —Steve Summit (talk) 23:06, 17 June 2007 (UTC)
 * You (Steve Summit) only claim that there is some kind of highly intermittant and random effect - I have no problem with that. This is easily attributable to randomly flickering bulbs combined with observational bias.  No problem there - nothing special going on that we can't explain statistically. But User:Anchoress is claiming a highly repeatable observation and goes out of her way to clearly exclude any random effect.  That's an entirely different matter...and either it's a lie or it certainly needs investigating.  I don't want to call anyone a liar...I want to point out that (a) this is easy for someone who claims to produce the effect to prove it to the world and (b) there is a million dollars sitting there for the taking.  Given those facts - why doesn't anyone who makes these claims ever take the necessary step to prove it?  I think the answer is crystal clear to anyone who reads User:Anchoress's last (self-deleted) post.  She has not claimed a supernatural or pseudo-scientific reason.  Yet I don't think any of us could concieve of a reason why this could possible, even remotely be happening if we have only known scientific principles to work with.  So either there is some effect that appears to be quite new to science - or we have something more like observational bias going on.  The only explanation anyone has put forward doesn't pass muster.  A loose connection somewhere in the cable leading to the bulb that vibrates loose and disconnects whenever a specific person walks up to one side of it 100% of the time - and then reconnects when they've passed by 100% of the time - and yet is unaffected by traffic - never goes off and stays off - never once fails to do this in over 700 trials?!?!  Wow!  That's quite some strange loose connection!  Some suggested perfumes and pheremones - nope - I bet the wind was blowing pretty strong on some of those 700 days - and was dead calm on others.  The human body deflecting EM radiation in some freakish way?  Well for starters you're so far away from the bulb, it ain't gonna happen - and in any case, cars and such would have a much greater effect.  I mean - really - is there ANY effect that we could imagine that could so reliably reproduce this?  There truly isn't. SteveBaker 05:05, 18 June 2007 (UTC)
 * I think we've about beat this to death, but a few last points:
 * I suspect the effect is not purely "intermittent and random". I hypothesize that discharge lamps can get into an intermittentish mode in which subtle and somewhat distant events -- almost analogous to Lorenz's hypothetical butterfly wing causing a hurricane halfway around the globe -- can trigger an extinguishment, or a relighting.
 * You can't scold Anchoress for failing to rise to the $1,000,000 challenge, because she didn't and doesn't claim that the effect she thought she observed was paranormal.
 * "Loose wires" have been mentioned only by way of example; they're hardly the only failure mechanism we can imagine. Indeed, most of the time when gas discharge lamps are going intermittently on and off, I believe it's due to problems in the ballast, or the starting circuit, or the arc itself.  All three of these tend to involve bizarre constructions (involving exotic effects which have been redesigned for cheap manufacture) which are subject to truly bizarre failure modes.
 * I don't think you can completely discount electric field effects involving a human body. Yes, the field of a human body is quite small, but remember, in another thread on this very desk, we had no trouble agreeing that a human body could interact with an electromagnetic phenomenon in a significant way.  (Yes, I know, the frequencies and field strengths are rather different in FM radio transmission versus electric discharge lighting.  Maybe even radically different.  But not necessarily 100%, apples-and-orangutans different.)
 * Finally, I'm not asserting that there is an effect. I do agree that most of the time it's almost certainly observer bias.  But I'm not convinced that there isn't a significant interaction some of the time.  I don't expect to convince anyone (like other Steve) who's properly skeptical, or who has read and agreed with our Street light interference article.  But please, if anybody encounters a light that goes on or off repeatably as you walk by, please document and report it!  Perhaps we can truly get to the bottom of this one day...
 * —Steve Summit (talk) 00:10, 19 June 2007 (UTC)


 * Why is this still continuing? Perhaps the light is just flickering very slightly and you can't notice unless you are on top of it. Could be due to an intermittent power source, or just a bad bulb. Anchoress never said she was actually looking at the light directly, she had it in view on her way to wherever. As you approach a light source, your eye becomes more sensitive flickering.--GTPoompt (talk) 14:40, 18 June 2007 (UTC)


 * In some locations they hook street lights up with motion detectors to save electricity. If they install the motion detector the wrong way, the light is on until it detects motion, then turns off until it no longer detects motion.  If you are taller or walk on a slightly different part of the sidewalk, you may set off the motion detector while others don't. StuRat 18:48, 18 June 2007 (UTC)

Popcorn
I've just had some microwaved popcorn today and I want to know why when it pops, it bursts into the shape that it does. Why does its volume increase fivefold and why does it form all those nodules on the outside. This doesn't seem to happen when rice or wheat is puffed for breakfast cereals, so why does maize behave differently? -russ 16:03, 16 June 2007 (UTC)


 * We have a decent explanation in our Popcorn article, in the How popcorn pops section. --Steve Summit (talk) 16:12, 16 June 2007 (UTC)


 * The exact shape that a particular kernel explodes and coalesces into would depend mostly on the initial distribution of starch and water. To describe it accurately would be a very difficult computational task, as it involves numerous phase changes, fluid dynamics for a rapidly expanding viscous substance, and mechanical interference from gravity, the walls/floor, and other kernels.  Nimur 19:01, 16 June 2007 (UTC)


 * That's true, but russ wasn't asking about about the exact shape. Why does popped popcorn have the sort of shape it does?  I don't know, but I just had an idea.


 * Consider the problem of peeling an orange and laying the peeling flat. You can't do it, of course; orange peelers as well as cartographers and oragamists know that you can't cut and fold a flat surface into a spherical one, or vice versa.  When you peel an orange, you tend to get some jaggedy shapes, which you can of course reassemble into a rough, hollow spere without the orange's flesh inside.  (When you try to peel the globe and lay it flat, you end up with a similarly-shaped jagged rendition called the Goode homolosine projection.)


 * Now, imagine a small sphere which, instead of having its skin peeled off, is trying to expand. At one level it's trying to expand uniformly at all points and in all directions, and if the stuff it were made out of were perfectly flexible and expansive, this might be possible.  But as we've just read, the stuff an exploding popcorn kernel is made out of is busy cooling and coagulating.  Once it's no longer gelatinous, it can't expand/stretch perfectly, so it begins to tear, instead.  But the pattern of the tearing is sort of a three-dimensional analog of the way the two-dimensional peeling of an orange tears. —Steve Summit (talk) 19:16, 16 June 2007 (UTC)


 * Different types of popcorn can pop in very different ways. There are some which pop up not too differently than rice or other cereal grains. The standard pop corn, at least in the USA, is no doubt a particular varietal chosen because it makes a particularly interesting shape and texture. --24.147.86.187 23:16, 16 June 2007 (UTC)


 * I see we never really answered the second half of the Original Poster's question, namely "This doesn't seem to happen when rice or wheat is puffed for breakfast cereals, so why does maize behave differently?" And it's not just rice and wheat that are different; I've had puffed corn as a breakfast cereal that was mostly spherical and reasonably regular, looking nothing like popcorn.
 * I suspect the fundamental issue here is that grain puffing is a chaotic process. Like snowflake formation, it's subject to several different external and internal forces, with subtly correlated interactions.  A slight difference in the hull strength, or the starch/water ratio, or the kernel homogeneity, or the temperature or pressure at which you do the puffing, and you can get a very different response. —Steve Summit (talk) 15:07, 17 June 2007 (UTC)

Wow! I didn't realise it would all be so complicated. I am still not quite clear on where its extra volume comes from. Is it like a sponge: full of millions of tiny holes filled with air? -russ 20:55, 17 June 2007 (UTC)


 * Yes. No mass is added (in fact, significant water mass is lost as steam), so the resulting popped corn has much less density than the starting kernels.  You can verify this by weighing (... or measuring the mass of...) the before- and after- products.  Nimur 22:56, 17 June 2007 (UTC)

Fusion
Is it possible for nuclear fusion to occur at absolute zero and the free energy be converted directly to electricity instead of to heat? Ugly bag of water 19:13, 16 June 2007 (UTC)
 * No. Nimur 20:40, 16 June 2007 (UTC)
 * First of all, you would have to get the materials to reach absolute zero, which is impossible for theoretical and practical reasons. Next, you would have to make the substance undergo nuclear fusion, which is not trivial in the slightest; especially at absolute zero.  Finally, you would need to figure a way to turn fusion into electricity; this sort of energy conversion does not exist by any current techniques, so you would need to invent a theory and an implementation.  Finally, probably the biggest difficulty would be getting sponsorship for cold fusion research, which has been widely discredited due to historical blunders by a few scientists.  This means that even good science in that field is difficult to take seriously.  Nimur 20:44, 16 June 2007 (UTC)


 * As a minor aside, shouldn't you be an ugly bag of mostly water? Nimur 20:45, 16 June 2007 (UTC)
 * I certainly am that according to the Universal Translator and Data's explaination of the crystals' name for humans. But that name was based on the product's of combustion and not on molecules of water that come to be evaporated from freeze drying in a vacumn, such as we have in space. While others may prefer to think in terms of their remains being composed of only a few ashes of combustion I prefer to think in terms of a freeze dried rememberance a loved one might put on display. Ugly bag of water 23:13, 16 June 2007 (UTC)
 * A quick google search] suggests that the ST:TNG line is based on an earlier quote by Gregory Corso, without the "mostly". —Steve Summit (talk) 15:54, 17 June 2007 (UTC)
 * Interesting. The number of personal coincidents regarding Corso astounds me. But no doubt when you drop both the "mostly" and the reference to humans, ugly bags of water were hanging from front bumpers long before consideration of reference to either of one's self. Ugly bag of water 71.100.3.132 18:11, 17 June 2007 (UTC)


 * It heat is just the motion of particles, wouldn't absolute zero mean they weren't moving? If that's the case, how are you going to get the nuclei close enough for the nuclear force to kick in and have them fuse? Much less overcome the Couloumb barrier? It doesn't make any sense to me, there's a reason why we generally have to get things really HOT to undergo fusion, and that has to do with having the nuclei smash into each other at high speeds. --24.147.86.187 11:32, 17 June 2007 (UTC)

My understanding is that even at the immensely high temp, pressure and density at the core of the sun that there is still a very low probability of a collision sufficient to result in fusion - its just that there are so many nuclei and the release energy so great that even one millionth of a percent of collisions resulting in fusion is sufficient to produce enough energy for the sun to glow. Although I'm stating a condition of absolute zero I'm not referring to classical Cold Fusion per say. In answer to your question I would think magnetic and electrostatic fields might come into play as a means of doing to the nuclei what high temp, pressure and density do at the core of the sun. Admittedly the capability of the magnets and electric terminals that would make up the device would have to be enormous. If fusion could be made to occur I would expect that the energy released would initially be extracted from the coolant rather than as current meaning the cooling system would have to have extreme capability as well. The question, however remains how to do the job of high temp, pressure and density at the focal point of an electric and a magnetic field when the focal point is at (or as close as possible) to absolute zero. Ugly bag of water 12:52, 17 June 2007 (UTC)
 * You need lots of energy for fusion to occur - you need to whack one hydrogen atom into another with enough force to make them fuse - and you need enough of those collisions to happen statistically in order to get a useful amount of energy out. At absolute zero (which you can never reach by the way) - there is (by definition) zero energy available.  Even at an attainable fraction of a degree above zero, Your hydrogen atoms are pretty much stationary (that's what temperature is - the speed that the atoms are moving).  If virtually no movement is going on between the atoms hardly any collisions will happen and even when two atoms do happen to collide - they are going so slowly that they'd just gently rebound and head off in opposite directions.  There is nowhere close to being enough energy to cause fusion to occur.  So - given that fusion is utterly impossible at low temperatures - it's pointless to speculate about how you'd extract energy from it. SteveBaker 13:44, 17 June 2007 (UTC)


 * What happens when a stream of nuclei from a super collider hits hydrogen at the lowerest temperature that can be produced? Does it bounce off? And what happens to the streem if it travels through the highest temperature hydrogen plasma possible? Is there any chance that fusion will result? Ugly bag of water 17:14, 17 June 2007 (UTC)


 * The stream of nuclei is at an amazingly high 'temperature' (although temperature is a slippery term - let's go with "it has a lot of energy"). So when your high energy nucleii slam into the frozen hydrogen - you'd certainly expect some fusion events.  But this isn't a "low temperature event" it's amazingly high temperature because the stream of nuclii is presumably coming out at some significant fraction of the speed of light and has a 'temperature' that's effectively off the chart.  Whacking such a beam into hot hydrogen would result in even higher energy collisions - and thus even higher numbers of fusion events. Of course a super-collider won't be able to produce very many of these high energy neutrons - and it takes an insane amount of energy to power one of the darned things - so you certainly won't be producing much net energy out of such a machine. SteveBaker 17:33, 17 June 2007 (UTC)


 * You also get new physics at ultra-low temperatures - Bose-Einstein condensation and Fermi condensation being the most relevant, as atoms in a condensate kinda lose track of where they are. For converting the energy released directly into electricity, see beta decay; which, yes, is governed by an entirely different force, but does at least provide for the movement of charge. -Eldereft 17:28, 17 June 2007 (UTC)


 * In summary, my original answer still stands. No. I like that sort of concise certainty; it doesn't leave any loopholes though, so if I'm ever proven wrong I will have to just admit it instead of obfuscating it. Nimur 23:01, 17 June 2007 (UTC)


 * Hmm...I thought cold fusion was long disproved.  bibliomaniac 1 5  BUY NOW! 01:52, 18 June 2007 (UTC)


 * I was more pointing out that ordinary intuition can fail outside of the "middle world". The one true and correct answer is no, but that does not preclude the fun of dabbling in some other somewhat esoteric physics. -Eldereft 04:37, 18 June 2007 (UTC)


 * This is a completely different cold fusion being discussed here, not the kind "caused" by electrolysis. The original question could be rephrazed to "near absolute zero"  which is thoeretically achieveable.  I would like to know what happens at very low temperature with the Bose-Einstein condensation smearing the nuclei over each other.  Surely this will increase the chance of an encounter, or do they still find a way to avoid each other, even when their wave functions are overlapping? GB 02:25, 18 June 2007 (UTC)


 * Not really - the individual nuclei are delocalized in a condensate, meaning their wave nature is more prominent. A nice introduction to the phenomenon can be had from the 2001 Nobel Prize winners - the individual articles link to their Nobel lectures. In short, it is less a matter of small hard nuclei avoiding each other through probability (nuclei are small) and Coulomb repulsion like at ordinary low temperatures and becomes more a matter of losing the interactions all together. Like a superfluid, there are no available lower energy states for a BEC to decay to, providing for a total lack of friction. Plus, the first fusion event would immediately kick the system back into "normal" behavior both by the addition of heat and because the members would no longer be identical. -Eldereft 04:37, 18 June 2007 (UTC)

Cranial nerves and the brainstem
Kolb & Wishwaw: Fundamentals of Human Neuropsychology, 2003, write: "Also leaving or entering the brainstem are the 12 sets of cranial nerves." Does the optic nerve really enter the brainstem??? In the Wikipedia article on the optic nerve, the brainstem is nowhere mentioned. Lova Falk 19:21, 16 June 2007 (UTC)


 * Not claiming expertise on this, but Optic nerve says "Most of the axons of the optic nerve terminate in the lateral geniculate nucleus..." Lateral geniculate nucleus helpfully says it is part of the brain, but nowhere says whether it is part of the brainstem. (Could someone qualified in anatomy make it say so explicitly if that is in fact true?) Brain stem says "Superiorly, the superior colliculus marks the rostral midbrain. It is involved in the special sense of vision and sends its superior brachium to the lateral geniculate body of the diencephalon." and "Some taxonomies describe the brain stem as the medulla and mesencephalon while others include diencephalic regions."   Does that qualify, or is it just a misguided synthesis, constituting original research? Edison 20:45, 16 June 2007 (UTC)


 * The lateral geniculate nucleus is part of the thalamus, and you might be just right, because the thalamus is part of the diencephalon..." Lova Falk 20:52, 16 June 2007 (UTC)


 * Cranial nerves I & II (olfactory and optic) do not originate in the brainstem. Cranial nerves III - X, & XII do originate in the brainstem. Cranial nerve XI originates in the cervical spinal cord. The cranial nerves are classified not on the basis of their origins, but because of their general location. - Nunh-huh 03:09, 17 June 2007 (UTC)


 * Thank you! Lova Falk 06:59, 17 June 2007 (UTC)

norepinephrine
What diseases are associated with the dysfunction of this neurotransmitter in particular.Ĵêńńí
 * (Removed broken link to this section)
 * Have you looked at norepinephrine? Nimur 20:57, 16 June 2007 (UTC)

Removing duplicate header

what kinds of disease are associated with this neurotransmitter in paticular. --Ĵéññý


 * See above. Nimur ŇîṃűŖ 21:36, 16 June 2007 (UTC)

Plants and drugs
Does any body know why should some plants produce hallucinogens? What evolutionary advantage is obtained by getting people high? Bastard Soap 21:47, 16 June 2007 (UTC)


 * The plants aren't necessarily trying to get people high. Most mammal brain chemistry is pretty similar in respect to the neutrotransmitters that'll drive them crazy. --24.147.86.187 23:12, 16 June 2007 (UTC)


 * The benefit to the plant is likely that an animal who eats it thinks it has been poisoned and refrains from eating that plant again. &mdash;Tamfang 02:00, 17 June 2007 (UTC)


 * The question may not be answerable. Since there are plants that don't get people high and there are plants that do, attributing it to evolutionary advantage and creating a reason ex post facto is not scientific as it cannot be tested.  For example, I could surmise the exact opposite as Tamfang and say that animals enjoy the experience and spread the seeds.  But it's not scientific as almost any answer that supports the status quo (i.e. the plant exists) is untestable.  --Tbeatty 03:28, 17 June 2007 (UTC)


 * Very well put Tbeatty. To every thing there is not a purpose.--Shantavira|feed me 07:08, 17 June 2007 (UTC)
 * Such hypotheses are not even wrong. This is my new favorite direct wikilink.  Nimur 09:28, 17 June 2007 (UTC)

Well due to evolution nearly everything has to have a purpose. If the hallucinogens where useless the plant would be wasting large ammounts of energy in synthesising them and probably it would have been knocked out of existence by a less wastefull plant Bastard Soap 10:11, 17 June 2007 (UTC)


 * Oh geez - what a terrible set of answers! This is the SCIENCE DESK!  I don't know whether User:Tamfang is right or wrong - but of course this could be studied and understood if the answer were important enough.  It's just ridiculous for User:Nimur to suggest that this is an unfalsifiable hypothesis - it's clearly amenable to scientific study - although we may not have studied it enough to come up with a firm answer yet.  I agree with User:Bastard Soap - User:Shantavira's statement that "To every thing there is not a purpose" is a nice sentiment - but quite wrong in this context: Plants that waste energy producing chemicals they don't need would be rapidly out-evolved by plants that don't do that.  Hence there is certain to be a benefit to the plant in having these chemicals around or they'd have evolved to lacking the gene to produce it.  We don't have to understand what the purpose of chemical is in order to understand that it only persists in because there is such a purpose.  User:Tbeatty's argument (which is essentially that "if it was a good strategy, then all plants would do it") is obviously nonsense - some plants have big red flowers and some don't...does that mean that big red flowers are not an evolved trait?!?  There is room in a typical habitat for many different and competing strategies - that's the only reason there is variety within a single environment in the first place.  Some plants achieve their goals in different ways - and for some there may not be any benefit from repelling large animals using these chemicals because they grow rough indigestible leaves or because they are covered in spikes or because they are too tall for the animal to reach...something else makes them not need the chemical - so they didn't evolve to have it.


 * If I had to speculate, I'd say that the addictive nature of these chemicals is likely to mean that the plant is using it as an attractant - getting large herbivores addicted to eating you isn't really a good strategy unless you want to get eaten in order to spread seeds or whatever. But as [[User:24.147.86.187 correctly points out - it's possible that these chemicals act completely differently on the specific animals that the plant is trying to attract or repel.  They may only happen to have an unintended side-effect of being addictive hallucinogens to large mammals (what effect do these chemicals have on leaf-cutter ants for example?  Maybe it's a lethal poison - maybe it's something important to the ability of some bird to digest the fruit but not the seeds inside...I don't know and I suspect User:Tamfang doesn't know either).  You'd also want to know where the chemical is concentrated - the answer would be different if the chemical was mostly in the leaves versus mostly in the fruit.  It's hard to imagine any evolutionary benefit to having your leaves eaten - but attracting animals to eat fruit is a well-known means for getting seed spread far from the parent plant.


 * It's also likely to be wrong to come up with a single sweeping answer. Did amanita muscaria evolve their hallucinogenic chemicals for the same reason as the papaver somniferum and cannabis sativa?  I doubt it.


 * If you wanted to understand this, you'd need to study the plant in its natural habitat - see how it spreads seeds - what animals are present in its environment and how they react to these chemicals in order to form a better idea of why the plant evolved those specific chemicals. One would also want to study the chemical pathways involved in order to be sure that these chemicals are not mere byproducts of some other process that the plant undertakes for some other reason.  A genetic study of closely related plants that don't produce these chemicals would allow one to come up with a rough estimate of how long ago this feature evolved - that could be compared with the animals that were known to be around at that time in order to get some idea of what evolutionary pressure caused the plants to do this. SteveBaker 13:28, 17 June 2007 (UTC)


 * I think you missed the point. You certainly mischaracterized mine.  Evolution studied in hindsight will always yield some evolved advantage.  As you said everything has evolved.  And everything can be explained as an advantage.  But everything being possible means nothing in terms of science.  There is advantage to having it, and advantage in not having it.   If everythhing is possible, you might as well attribute it to God.  Scientific hypothesis however is almost always based on it's predicitve ability.  Predict the next hallucinogenic plant.  Predict the non-hallucinogenic plant that is forced out by the hallucinogenic plant.  Without a way to test the hypothesis, there is no science.   It's simply history.  --Tbeatty 16:27, 17 June 2007 (UTC)
 * I'm not 100% sure I understand you here - but we can certainly predict (and test our predictions) in systems where the evolutionary time scale is manageable. You can predict that use of a new antibiotic will initially have great effect on killing bacteria - but over the years the bacteria will evolve resistance to it and it'll become less effective.  We've seen this happen - and have even had some success in predicting how long it'll be until that happens (although the business of genetic change is a bit haphazard - so it's not an exact thing).  Predicting the future evolution of toxicity in a plant would be a lot harder.  For one thing, the timescales are too long.  A bacterium can reproduce in minutes - but a plant may require a couple of years to grow to maturity and produce offspring.  But also, you don't know in advance how the plant will react to whatever change you make to its environment.  Suppose you did an experiment lasting 5,000 years where you introduced a species of leaf-cutter ant to a colony of non-toxic plants that grow in parts of the world where those ants are not present.  Eventually, you'd expect the plant colony to evolve some kind of a defense - but you couldn't predict which random mutation would happen first - it's a matter of chance whether the plant might produce an halluciongen - or a poison - or an ant pheremone - or tougher leaves - or recruit a symbiote like maybe an ant-eating wasp by providing some kind of symbiotic benefit to the wasp.  Which one of those things happens first would depend only on which gene or genes mutated first - you just don't know.   So in order to answer questions like this, you have to rely on looking back into history and making deductions about how this chemical pathway arose.  Generally, you find that the chemical they are using is similar to some other, harmless, chemical that's used for some completely different process within the plant - which changed into a poison or whatever by a simple substitution that could be controlled by a small random change in the plant's DNA.  But we can't predict randomness - so what you are asking is essentially impossible.  SteveBaker 17:22, 17 June 2007 (UTC)
 * Note that it is possible to test what evolutionary advantage a gene or it's protein product conveys by creating a knockout or knockdown. This is not always simple, especially when you're trying to detect something which may have a complicated effect like a hallucogenic compound given that you'd need to replicate the natural conditions fairly well. But for example, we know that nicotine appears to be an important natural insecticide . Often this may not be necessary since you can reliably predict the importance of a compound by comparing plants with and without the compound as well as by observing the effect of the compound on the organisms which interact with it. We can also analyse how and when these compounds evolved and how organisms that interact with the plant have evolved in response. Note that these is a big difference in the predicted outcome between the two proposals. If tbetty is right and the organisms likes the compound then we would expect the organism to eat the plant a lot more. On the other hand, if tamfang is correct and the organism thinks it's been poisoned then we can surmise the organism will avoid the plant for this reason. Perhaps these predictions are of no interest and not science to tbetty but the fact remains, when we test these predictions of the benefit of said compounds we usually find we right. I'll use a simple example. We know that Cashew nut is a seed with minimal external protection. However it does have a compound (urushiol) which is a toxin to many organisms which may otherwise consume said seed. We know that for the plant, organisms eating its seed is not good. For most people, they would be willing to given high confidence then to the prediction that this toxin co-evolved with the evolution of the largely unprotected seed as a method of defense against herbivores who might otherwise eat said seed. More importantly, they would expect that it is preserved for this reason. We could of course test whether a cashew plant without this compound is more susceptible to herbivores eating its seed in a variety of conditions which hopefully would go somewhat to satisfying tbetty's concerns about why the compounds is maintained. But this sort of experiment has difficulty attracting financial support. BTW, it is true of course that we can't actually test why something evolved in the first place, and it is a valid point that even many evolutionary biologists would agree on. But evolutionary biologists are usually more interested in the how not they why. I note that bastard soap did't say anything about historical. So if tbetty wants to get technical, it would have been far better to say something like. "We know that hallucogenic compounds appear to convey evolutionary advantage X in to the plant in the present day. We therefore expect that these compounds may have evolved for this reason. However as it's not possible to test why these compounds evolved in the first place this prediction can't be called a scientific theory" Nil Einne 20:47, 17 June 2007 (UTC)
 * Coincidences do happen with the limited configureation of organic molecules, and wasteful plants aren't necessarily out-evolved.. there could be secondary advantages and anyway it's not likely to make much difference to the strength of the plant whether it secretes one oil or another --⁪frotht 20:42, 17 June 2007 (UTC)


 * Back to the original question, plants have evolved complex secondary compounds as herbivore (mostly insect) deterrents, and the complexity they have reached due to this arms race, combined with the fact that they're made of the same precursor compounds (amino acids, sugars, etc) as our hormones, mean some simply happen to be psychoactive or medicinal in humans. On an evolutionary scale, we've been a side show to their fight for survival against pathogens and insects. These substances are not made for us and there is no use trying to explain their existence in terms of what they do to us, or justifying their abuse because of their occurrence in nature. Bendž|Ť 22:08, 17 June 2007 (UTC)


 * Rubbish, I think, as crazy as it may be, that the fact the plant is hallucinogenic may just be a coincidence and not an evolved trait. I don't know if anyone here understands the mechanism here well enough to comment. I agree with Tbeatty's take on this situation. Certainly I think it is incorrect to say the plant is wasting "vast amounts of energy" quite possibly the hallucinogenic component is just a by product of the plant's other processes. Someone else mentioned something about "addictiveness" which is also incorrect, most psychedelic hallucinogens are not physically addictive. And lastly, a whole bunch of these plants would have evolved without much interaction with humans or other animals who eventually learned how to extract the 'goodness', ome which has to be dried or smoked or whatever, which must have already by then evolved. Vespine 23:07, 17 June 2007 (UTC)


 * I don't think any of us are arguing that these plants evolved this chemical in order to deal with humans - their biggest concern is insects and herbivores. So the fact that humans are - or are not - affected by these substances - or that we have to process the plant first in order to produce whatever by-product it is - is largely irrelevent. SteveBaker 04:55, 18 June 2007 (UTC)

A few comments:


 * The quantity of a hallucinogen absorbed by insects eating the plant may make it a deadly poison, to them.


 * Some "drugs", like alcohol, are merely waste products and serve no purpose for the organisms which produce them.


 * We can make some very strong arguments for why certain traits have evolved, such as sickle-cell anemia in humans, which appears to have evolved as a defense against malaria. StuRat 14:07, 18 June 2007 (UTC)

Noise in hi-res cameras
I read that noise increases along with the resolution of a digital camera. Is this entirely because of the shot noise inherent in such small CCDs, or are there other causes as well? Neon Merlin  23:27, 16 June 2007 (UTC)
 * Most commercial digital cameras aren't CCDs anymore, they are CMOS image arrays (although I know that some astronomy cameras still are).  Also, signal-to-noise (S/N) ratio is much more meaningful metric.  Just a guess, but I suspect the size of the frame isn't changing with resolution, but the number of pixels are growing.  That means each pixel is smaller.  The signal from each pixel is therefore also potentially smaller.  But noise that isn't related to pixel area (power supply?) is the same per pixel.  I suspect there is other noise that is proportional to the area of the pixel and that there is also signal gain with each generation so I have no idea how much S/N degradtion there really is.  --Tbeatty 03:21, 17 June 2007 (UTC)


 * Yes, provided the sensor size and technology remains the same. The size of each pixel is shrinking as they cram more and more pixels into a tiny CCD, and thus each receive less light and have less signal, therefore lowering the SNR. That's why DSLR produce far cleaner images, as the pixels are far larger, and therefore receive more light and have a higher SNR. Also, except for some Cannon DSLR and webcams, most digital camera out there are still CCD based. --antilivedT 04:21, 17 June 2007 (UTC)


 * I think camera buyers should take a good look at what NASA has to say on the subject of camera design: - those are very wise words! SteveBaker 12:27, 17 June 2007 (UTC)