Wikipedia:Reference desk/Archives/Science/2010 January 4

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January 4

Auxetics utilization in model?

Hey, you guys have helped me out a lot, hopefully the smart people at the refdesk can help me out on something else this time... I am making a model of a stretcher, weaving elastic cord in a 12" by 5" grid in squares about 1/4 inches in size. I wanted to incorporate this into it but seeing as my string is too small in diameter for using thread to work I am unable to practically do so. Is there any practical way to apply this to the entire model? Thanks, ♠The Ace of Spades^♣♥_♦ 00:43, 4 January 2010 (UTC)

jap heating

why dont japs insulate their homes and have central heatring —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 01:04, 4 January 2010 (UTC)

As in Jewish people or Japanese people? And is your don't meant to be distributed, so that japs neither insulate their home nor have central heating, or undistributed, in that japs fail to insulate their homes yet have central heating? DRosenbach ^{(Talk | Contribs)} 02:10, 4 January 2010 (UTC)

i mean japan and both they dont insulate their homes or have central heatring —Preceding unsigned comment added by Thekiller35789 (talk • contribs)

Do you have evidence, like written down somewhere, that says that Japanese people do not heat their homes or insulate them? Where does this information come to you from? --Jayron32 03:33, 4 January 2010 (UTC)

Having visited Dai Nippon during winter I noticed no lack of heating. If there is it may be that the Japanese are a rather stoical race and put up with such things, they are trying to save energy, or it might just be a cultural hold over from days when their 'traditional style' houses were almost entirely wood and rather combustible. Therefore having a large fire was not practical. Fire was taken very seriously (I gather) in old Japan. Not 100% sure but I think arson was a capital offence Also the more common occurence of earthquakes there caused serious problems if a house collapsed on a open fire. --220.101.28.25 (talk) 03:55, 4 January 2010 (UTC)

See here Japanese_houses#Heating for a discussion of heating arrangements --220.101.28.25 (talk) 04:03, 4 January 2010 (UTC)

none of that explains why they dont insulate their homes —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 05:41, 4 January 2010 (UTC)

And you didn't answer Jayron's request for a source that states they don't. Vimescarrot (talk) 09:11, 4 January 2010 (UTC)

I agree some evidence is needed. In any case the lack of central heating and poorly insulated homes is hardly unique to Japan if both really occur there. NZ homes are well accepted to be generally poorly insulated [1] [2] [3] and usually lack central heating. It's sometimes said people from very places with extreme winters have trouble adapting because of how cold our houses are in winter, e.g. [4]. There are some attempts to change both nowadays. [5] A variety of regulatory, traditional and cultural factors contribute and I expect it's difficult to say why except that that's the way things are done. The severity of the winter is likely one. It's clearly going to be far more difficult to have poorly insulated homes in Siberia or perhaps of greater relevance Canada, most of the northern US and most of the UK; then it is in most of NZ. Nil Einne (talk) 10:27, 4 January 2010 (UTC)

Two reasons: 1) Earthquakes. A system of complicated gas pipes in every home and the infrastructure to set one up, apart from the difficulty, would be a massive problem in the event of one of their plethora of quakes. An air con unit on the wall, well screwed-on, is not going to cause explosions or death. Agreed, insulation is non-existant in most places, especially on those single-pane double doors that so many of their apartments have. 2) Energy. Japan imports pretty much all of its energy. Gas would involve some sort of US-Japan pipeline. Oil is more feasible, and electricity to power heating and cooling aircon units is just far more practical. Bear in mind also that Japanese people tend to destroy and re-build houses once every 20-30 years, so the costs of putting all those systems of heating and insulation would also be considerable.

I assume you haven't quoted some kind of proof, as bizarrely requested above, because you have simply lived or visited there and noticed this about their homes. It's true by the way.

Lucas 83 13:59, 4 January 2010 (UTC) —Preceding unsigned comment added by Lukerees83 (talk • contribs)

Some possible reasons are given in this blog post. Nanonic (talk) 14:34, 4 January 2010 (UTC)

again that dosent explain why they dont have insulation —Preceding unsigned comment added by 67.246.254.35 (talk) 01:51, 5 January 2010 (UTC)

I think my post and the blog post given by Nanonic do to some extent. If this is true, it's the way things are done there likely for a variety of regulatory, traditional and cultural reasons and there's unlikely to be one simple reason you can give for why things are down that way. The simplest answer is probably to say they're done that way because that's the way things are done there. Also I forgot to add before, but presuming the situation is as Lucas described or something similar, the helpful thing to do would be to at least explain why you believe it is the case Nil Einne (talk) 11:12, 6 January 2010 (UTC)

Verification Needed - unlikely cite check.

I have doubts that anyone here would be able to verify this source, but I thought that I'd try anyway. If this post is not appropriate for this location, please notify me and I will remove it.

The citation information is:

• Staff (Aug 1, 1990). "FICS Awards Gold Medal To Dr. Press". Dynamic Chiropractic 8 (16): 1.

The relevant information that needs verification is that Dr. Press is the founder and first president of the FICS.

Thanks, DigitalC (talk) 01:07, 4 January 2010 (UTC)

I can't access that document myself but the FICS website states that he was the first president on it's website and past versions of the site state that it was founded at a meeting he convened. A precis of an article in Dynamic Chiropractic (with the full article lurking behind a forever cursed paywall) states he is "founder and past-president of the Federation Internationale de Chiropratique Sportive (FICS)". I don't know if that's what you're looking for? Nanonic (talk) 01:27, 4 January 2010 (UTC)

Hrmm and evermore strange, I've just found that Dynamic Chiropractic have some articles archived on their website and yet neither your article or the one above that is paywalled feature. Nanonic (talk) 01:37, 4 January 2010 (UTC)

Actually, that paywalled one is available here (if you scroll down). Unfortunately, this is not enough for some editors, so having a second source would be beneficial. I think a hard copy would be the only way to verify the info. DigitalC (talk) 02:01, 4 January 2010 (UTC)

Sounds like something that may be difficult to find but you should ask at Wikipedia:WikiProject Resource Exchange/Resource Request first. And perhaps read Wikipedia:WikiProject Resource Exchange too Nil Einne (talk) 10:13, 4 January 2010 (UTC)

cramped legs

Why do my legs get cramped when in a car, but not anytime else, even when im sitting?Accdude92 (talk to me!) (sign) 02:11, 4 January 2010 (UTC)

Perhaps you meant why do my legs get cramps and a possible response would be because they are cramped when you sit in a stuffed car -- when you sit on a couch, though, there is generally a lot of room for your legs to move, and even if they don't move, the mere fact that you have room to move them around may contribute to a lack of the sort of claustrophobic-like feeling that may accompany cramped situations. DRosenbach ^{(Talk | Contribs)} 02:37, 4 January 2010 (UTC)

You also tend to be stuck in one position for a lot longer in a car than when sitting elsewhere, especially if you are the driver - you can't really fidget, and your one leg is nearly constantly flexing to some degree or another. ~ Amory (u • t • c) 04:51, 4 January 2010 (UTC)

Unless you set your cruise control and do not need to change speed often because of traffic and such. That will depend on local conditions. Googlemeister (talk) 15:29, 4 January 2010 (UTC)

Animal intelligence

Could it be that animals know things (and I don't mean in terms of instinct) about the world, such as gravity, peer pressure, earth's orbit, the birth-life-death cycle, etc. but we just don't speak the same language? This is, of course, assuming said organism has a long enough lifespan to appreciate life in a way similar to the way we do, with past experience impressing upon future action. DRosenbach ^{(Talk | Contribs)} 02:35, 4 January 2010 (UTC)

The relevant articles are Animal cognition and Emotion in animals. They are quite detailed. Regarding your specific question about gravity - it is not well posed. A plant seed lacks a nervous system altogether, but it "knows" the local direction of the gravity field. However, no animals and only some humans are aware of Newton's law of gravity, let alone what a graviton is. --Dr Dima (talk) 02:57, 4 January 2010 (UTC)

The same applies to the notion of the Earth orbit. Both plants and animals have circadian and annual rhythms, as a direct result of Earth orbital motion; however, no animals and only some humans are aware of Kepler's laws, or even of the fact that the Sun, Moon, and the stars are not actually attached to the celestial spheres. --Dr Dima (talk) 03:20, 4 January 2010 (UTC)

Considering how hard it was for humans to figure out that stuff, even with our massive cognitive abilities, I don't see why we should assume animals know that kind of stuff. Animals know what they need to know to survive. Some of that is instinct, some of that is learned. To know about gravity in an abstract sense isn't necessary to survive unless you have a very peculiar society that rewards such abstract knowledge (which humans have only really had for a few hundred years out of our long existence as a species). Note that when we have taught animals how to better communicate, they say things like, "Banana me eat banana" and so forth. That isn't definitive, of course, but it doesn't really point towards the idea that animals have all sorts of advanced abstract intelligence just bubbling beneath the surface, which is fairly implausible anyway for the other reasons mentioned. This is not to say that animals are dumb—but their intelligences are quite different than humans'. --Mr.98 (talk) 04:00, 4 January 2010 (UTC)

This may be of interest Tool use by animals or Animal_cognition#Tool_and_weapon_use --220.101.28.25 (talk) 05:03, 4 January 2010 (UTC)Bold text

There's an important conceptual issue here. When we talk about "knowing" something, we must distinguish between implicit knowledge (expressed by performance) and explicit knowledge (expressed by giving the correct answer to a question). There is no doubt that animals have a great deal of implicit knowledge. When it comes to explicit knowledge, though, we face the problem that there is no way to ask an animal a question, so there is no way to probe for explicit knowledge as we would with a human. There have been many attempts to get around this issue, but they all run into difficulties of one sort or another. Looie496 (talk) 18:11, 4 January 2010 (UTC)

I think we would have to say that there is zero evidence that animals think about anything. I have a theory that early human life is not that different than animal life, as concerns consciousness. There was only a point when I became aware of thinking about anything. Prior to that my thoughts were amorphous. They had no form. It is at that borderline that I am making the distinction between "thinking" and "not thinking." My assumption is that animals never get beyond the way consciousness takes its form in the earliest years of human life. But this is utterly unfounded hyperbole spouted by yours truly, in the spirit of original research. Long live Wikipedia. Bus stop (talk) 18:34, 4 January 2010 (UTC)

It depends how you define "thinking". My dog clearly thinks about its dinner. It gazes longingly up at its food bin. It finds elaborate ways (sitting in my lap, for example) to express to me its desire to have dinner at what it considers to be the correct time. When I show her a toy that she wants, and then hide it when she isn't looking, she will first look confused, then search for it, knowing that it has to be somewhere. There is clearly learned cognitive activity going on here at a level that, say, a housefly is utterly incapable of. (When my dog dreams, she is clearly running, woofing, and having experiences as abstract and real to her as my dreams are to me.) I would call all of that "thinking." It is certainly not the same kind of thinking that I do in contemplating my dog. But to say, "humans think, animals don't" requires positing a hard line between human and animal thinking that I just don't see actually existing—similar to concluding that humans "don't know how to smell" when compared to the olfactory senses that a dog has. My dog clearly thinks about food, toys, intruders, keeping the "pack" together, and going on walks... but probably not too much more than that. As to how "conscious" she is... I'm not sure we understand what that means in humans in the slightest, really, so it's hard to say whether it exists in animals, whether it is a thing that you-have-or-you-don't or something else altogether. --Mr.98 (talk) 21:23, 4 January 2010 (UTC)

Healthy skepticism is good, but many people, including scientists, adopt the dogma that only humans can think. It seems that no amount of evidence can convince them otherwise. I think research increasingly demonstrates that while we are by far the most intelligent species on Earth, others know a thing or two about the world as well. When a crow solves a problem on first try and elephants go on a procession for a dead child, I wish they wouldn't dismiss the idea so easily. For your amusement, though I'm sure you'll chalk it off for off-stage coaching, I present this video.[6] Imagine Reason (talk) 02:34, 5 January 2010 (UTC)

Simple magic tricks work with dogs too. If you sit on the ground with your dog's favorite toy - then play 'fetch' (toss the toy so the dog runs off to grab it and bring it back) a couple of times. Now hold the toy above your shoulder and pretend to toss it forwards - but instead just drop it behind your back while flinging your hand forward as if tossing the toy. The dog rushes off after the invisible toy - looks frantically for it. You can then amaze your dog when you "magically" bring the toy out from behind your back. Most dogs can be fooled several times in a row before they figure out the trick. I'm not sure it proves anything about their thought processes though. SteveBaker (talk) 00:48, 6 January 2010 (UTC)

The real debate with animals is not about whether they "think" or not (what the hell does a brain do if it's not "thinking"?!). The debate is whether they are "conscious" or not. That seens to be really impossible to know (although I think it's very likely that higher animals are conscious thinkers). But there are scientists out there who actually doubt whether all humans have "conscious" thought - and some claim that consciousness itself may have evolved fairly recently in human history (in the last 10,000 years perhaps). The trouble is that we really don't have a solid definition for "consciousness" - and without that, we don't even know what we should be testing or measuring to prove or disprove this hypothesis. SteveBaker (talk) 00:48, 6 January 2010 (UTC)

See mirror test for some interesting work done on that very question. Matt Deres (talk) 21:49, 8 January 2010 (UTC)

Expansion in a matter of time

How could 16,000 gallons of water expand to 932 °F steam in a matter of seconds?24.90.204.234 (talk) 02:38, 4 January 2010 (UTC)

Drop it in the sun? Place it under a thermonuclear bomb? The rate of temperature increase is related to the difference in temperature between two areas. Very broadly speaking, if two areas are under a different temperature, the warmer will heat up the cooler (and vice versa) and the rate of change is related to how different the temperature is. So, if you want to heat something up about 1000 degrees very fast, place it in contact with something at say 10,000 degrees... --Jayron32 03:31, 4 January 2010 (UTC)

Actually, it was in a boiler aboard the SS Norway that 16,000 gallons of water expanded to 932 °F steam in a matter of seconds.24.90.204.234 (talk) 03:54, 4 January 2010 (UTC)

Alright then. It expanded to 932° F steam in a malfunctioning boiler. You've answered your own question. At atmospheric conditions, steam is about 1000x less dense (that is, 1 mL of water will generate 1 L of steam). So, 16,000 gallons of water, when converted to steam, at equilibrium with the atmosphere, would "want" to occupy 16,000,000 gallons of space. In a confined space, by Boyle's Law, that means it is at a pressure of 1,000 atmospheres instead. I doubt the boiler could withstand those kinds of pressures. 1,000 atmospheres equals about 15,000 pounds per square inch, give or take. So, imagine the weight of say, a half-loaded Mack Truck balanced on 1 square inch of space. Then put that weight on EVERY square inch of the boiler. No wonder it went KABOOM rather spectacularly... --Jayron32 03:56, 4 January 2010 (UTC)

See this previous discussion from the Science desk archives. Gandalf61 (talk) 10:26, 4 January 2010 (UTC)

There seems to be a major error here. According to the source the water was at 932° F before the event. Because the conversion of water to steam (a gas) requires a great deal of energy, the temperature of the resulting steam would have been much lower than 932° F. In fact, not more than a small fraction of the water would have vaporized before the temperature dropped down below the boiling point. Looie496 (talk) 18:03, 4 January 2010 (UTC)

This question was asked and answered at length a few months ago. Edison (talk) 19:40, 4 January 2010 (UTC)

Cause of death

Flogging seems to imply (but doesn't explicitly state) that loss of blood is the culprit. Is it? Clarityfiend (talk) 03:46, 4 January 2010 (UTC)

Shock is likely a greater influence than just loss of blood. Shock can occur when blood pressure or blood flow is restricted to many vital organs, if ones back is flayed sufficiently it can cause interruptions in blood flow which may result in serious shock, even if "loss of blood" is not as much as say, slashing a major artery. --Jayron32 04:00, 4 January 2010 (UTC)

Note that flogging is normally a form of punishment not intended to kill. A victim is likely eventually to lose consciousness due to blood loss, at which point the punishment loses meaning. Floggings on ships and in prisons were often observed by a doctor who would declare the condition of the victim. A case is recorded Gibson, Ian. The English Vice: Beating, Sex and Shame in Victorian England and After. London: Duckworth, 1978. of a sailor who was put in hospital after going unconscious half way through his alloted strokes; his captain ordered the flogging to continue as soon as the sailor was deemed able to feel it. Cuddlyable3 (talk) 23:45, 4 January 2010 (UTC)

Thanks. Clarityfiend (talk) 07:17, 5 January 2010 (UTC)

"protecting plastics" for cargo

Does anyone apply the protecting group philosophy to whole objects instead of functional groups? I was thinking of like putting a polymer on a certain object, adding some plasticiser... the polymer would be fairly resistant at pH 7 and against heat and moisture, and but when you add an acid/base catalyst (or maybe hydrogen or a reducing agent) the polymer bonds collapse to give you your original product? John Riemann Soong (talk) 04:32, 4 January 2010 (UTC)

Sounds like a messy way to do stuff. The protecting plastic would still exist, albeit in a different form. Disposing of packing peanuts and cardboard seems like an less messy prospect than standing in a puddle of goop that formerly encased your product... --Jayron32 04:38, 4 January 2010 (UTC)

I was thinking of actually protecting something during manufacturing (e.g. a sensitive part) while it underwent various transformations. John Riemann Soong (talk) 05:19, 4 January 2010 (UTC)

Etching, as a process, usually involves "protecting" the un-etched areas of the substrate with some sort of acid-resistant substance, such as a wax, which is later removed. See also Photochemical machining and Industrial etching and Etching (microfabrication) all of which have some methods which operate on the same basic principle; you first protect the areas you want untouched, then you chemically react away the unprotected parts, then you remove the protecting material. Is that the sort of processes you are asking about? There are also multi-pass printing techiniques where plates are treated with special chemicals which allow the ink/dye/toner to stick to certain areas of the plate and not to others, the treated areas are "protected" so they don't attract ink; such plates can then be cleaned and reused. --Jayron32 05:31, 4 January 2010 (UTC)

Yeah, that was sort of what I was thinking about (though not necessarily so nanoscale but that works too) -- I was thinking even two sets of polymers in the style of orthogonal protection. Does the world have any use for a polymer that is fairly tough and resistant ... except with one critical (and useful) weakness. Also, how would I encourage this polymer to fall apart "cleanly" (i.e. it is easily washed off) as opposed to clumps of disgusting stuff you have to chip away? John Riemann Soong (talk) 05:41, 4 January 2010 (UTC)

Electronics are sometimes covered with conformal coating to prevent moisture, dust, and impact damage... it is applied with a physical deposition (spray), not a chemical process, and is not usually ever removed. Nimur (talk) 19:24, 4 January 2010 (UTC)

what do you call this alkene? is it a good dienophile?

Is there a reasonable dehydrogenation reaction that would create a conjugation-stabilised product 2?

Trying to figure what you would call product 2. My IUPAC naming conventions are failing me right now, and never mind what the common name is called. I'm trying to use it for a Diels-Alder reaction. Is there a reasonable reaction (e.g. not reaction conditions like 500C) that would remove H2 from 1?**

Is it a good dienophile? I'm worried the phenyl group is too electron-donating ... how would it affect the transition state? What type of substitution pattern would it encourage if I say, used pyrrole as the dienophile? Also I'm worried about side products like ... the unsaturated C=O bond, polymerisation -- both via DA modes and enolisation....

**I initially thought of synthesising it via phenylacetaldehyde and potassium cyanide, hydrolysing the nitrile and eliminating water ... but some preliminary literature tells me phenylacetaldehyde polymerises very quickly -- Sigma-Aldrich only sells it at 90% purity! :o And oh, cis-trans isomerism is an issue. Any other ideas? John Riemann Soong (talk) 06:14, 4 January 2010 (UTC)

As far as naming, I'd call it 3-phenylacrylic acid. Then I looked it up, and its also called Cinnamic acid, which is readily availible commercially. I see no reason to make #2 when you can buy it probably as cheaply as #1. --Jayron32 06:30, 4 January 2010 (UTC)

Also see Phenylpropanoid for more on this general class of compounds... --Jayron32 06:33, 4 January 2010 (UTC)

It would appear that the entire class of molecules are all produced naturally from Phenylalanine. Also, I see several sources that call #1 in your synthesis "Hydrocinnamic acid" which would indicate that it is more common to work your reaction mechanism backwards; that is to hydrogenate cinnamic acid to make #1 rather that to dehydrogenate #1 to get #2... --Jayron32 06:37, 4 January 2010 (UTC)

Thanks so much! An issue is that I suspect I might need the cis isomer not the trans isomer ... the entire theme of my research is actually various derivatives of amino acids, so a phenylalanine reaction would be perfect.... the most immediate knee-jerk thing that comes to mind is some sort of stereospecific deamination of phenylalanine (or maybe stereoselective deprotonation of the benzylic proton), but I feel that would be really uncontrolled and unreliable. John Riemann Soong (talk) 07:12, 4 January 2010 (UTC)

Well, what are you doing with the Cinnamic acid? What's the next step? Is THAT product stereospecific? --Jayron32 07:14, 4 January 2010 (UTC)

I'm trying to Diels-Alder react cis-cinnamic acid with pyrrole to form troparil (and similar derivatives). (okay the product is missing a carbon, but I'm still curious -- I suspect the methylene carbon affects the conformation of the 7-membered ring and I wonder what would happen if it was removed. notably dopamine has the amino group 2 carbons away from the phenyl group but in troparil it's 3 carbons away.) Diels-Alder is pretty stereospecific, so yeah. Don't worry my interest in troparil is mostly academic. I work in a drug addictions lab in the medical school (as a lowly work-study undergrad), and I'm thinking it would impress my supervisor if I came up with a theoretically cheaper way to synthesise compounds that cost thousands of dollars per experiment to test each time -- just for the material alone!

(Also I figure practicing wouldn't hurt me since I might have no orgo courses until grad school. I'm also trying to find someone who's willing to supervise my experiment if my reaction conditions aren't too harsh...) John Riemann Soong (talk) 07:29, 4 January 2010 (UTC)

trans-Cinnamic acid is cheaply commercially available, or can be made using aldol or malonic-ester reactions (though I think the yield is often poor--companies probably have patented an improved process). I know many cinnamic-acid derivatives can be photoisomerized trans→cis. That's a cool reaction...it's reversible but it's not an equilibrium (either can be excited by light and undergo isomerization, but you can get reasonable yields of the clearly less-stable cis compound). DMacks (talk) 17:01, 4 January 2010 (UTC)

If you feed D-Phe to Phenylalanine ammonia-lyase, would it make the cis-isomer? Or not really? John Riemann Soong (talk) 22:04, 4 January 2010 (UTC)

Frozen organisms

What's the largest organism that can survive frozen in a block of ice? (My question is open-ended on what minimum survival time is meaningful. Let's make it 2 separate questions: what's the largest organism that can survive frozen in a block of ice for a day; and what's the largest that can survive for a month?) Comet Tuttle (talk) 06:28, 4 January 2010 (UTC)

A number of species of frogs are known to be able to overwinter completely frozen; they alter their blood chemistry right before going into hibernation in such a way that prevents formation of large ice crystals (which would have caused irreversible tissue damage if allowed to form). It is also likely that some species of freshwater fish in the permafrost belt can do the same, as some ponds there do freeze solid (Couldn't find a reference though). Among the warm-blooded, I remember a documentary with Sir David Attenborough showing a hibernating bat with an icicle hanging from it (no kidding!); the bat itself was cold (almost invisible in a thermal scan) but not frozen. If it freezes solid it dies AFAIK. --Dr Dima (talk) 08:45, 4 January 2010 (UTC)

OK, I found the refs I was looking for. Cold-climate fish and insects prevent the formation of large ice crystals by having Antifreeze proteins in their tissues. There is a whole bunch of references in the Antifreeze protein article. --Dr Dima (talk) 09:09, 4 January 2010 (UTC)

Not directly relevant to your question, but I think it is worth noting that viable microorganisms have been extracted from ice at least several hundred thousand years old (and some claimed extractions for millions of years). In addition, at least some bacteria remain metabolically active when imprisoned in ice provided that some form of food source is available such as an adjacent dust grain or concentration of organic impurities. Dragons flight (talk) 09:12, 4 January 2010 (UTC)

That's relevant, too — it sounds like microorganisms might be able to avoid death from cold damage, but larger creatures need antifreeze to live. Thanks! Comet Tuttle (talk) 22:11, 4 January 2010 (UTC)

Using anti-freeze to prevent freezing is different from surviving freezing, though. Imagine Reason (talk) 02:21, 5 January 2010 (UTC)

Yeah, especially if the animal using antifreeze is a dog...they don't seem to survive antifreeze too well :-) Nyttend (talk) 06:08, 5 January 2010 (UTC)

pull of gravity or magnetism or any force

Is it safe to say that no matter how close two objects, particles or any matter comes to each other the attractive or the repulsion forces will never be infinite? 71.100.1.76 (talk) 08:42, 4 January 2010 (UTC)

Yes, that's fair. Infinite force will not actually occur. Formulas that appear to lead to infinities will generally be approximations of reality that aren't actually valid in the vicinity of the expected infinity. Dragons flight (talk) 09:19, 4 January 2010 (UTC)

For the forces to be infinite, the two objects would have to be literally at the exact same position. But as the distances get shorter, the scale on which we're measuring them starts to make quantum mechanical effects very noticable. Objects at the quantum scale don't have a firm position - merely a fuzzy "probability cloud" centered on some point in space. This will prevent them from being positioned a literal zero distance apart because the probability of two objects being at the precise same point is infinity-to-one against - which makes it impossible. Hence no infinite forces occur - even though the math suggests that they might. SteveBaker (talk) 14:12, 4 January 2010 (UTC)

The words "any matter" include matter+antimatter interactions. Can we consider the force which would be needed to reverse a matter+antimatter annihilation that has occurred? Cuddlyable3 (talk) 23:27, 4 January 2010 (UTC)

The thought of antimatter did not occur to me when I asked the question but now thinking about it briefly suggests that mass probably becomes energy in the form of gamma radiation before force can become infinite or perhaps on the road to force becoming infinite. But its past my bedtime. 71.100.1.76 (talk) 01:43, 5 January 2010 (UTC)

In Cuddlyable3's case(Matter Antimatter Reactions), because $dE=\int _{C}F\cdot ds\Rightarrow d^{2}E=F\cdot ds$, so it can be seen that energy can viewed as infinite different forces acting on an object on different points, stressing the infinite. So I think in this case, the resulting force might really be infinite!The Successor of Physics 10:54, 7 January 2010 (UTC)

Frozen citrus fruit?

While travelling halfway across the USA this past week, I accidentally left some clementines in a bag in an unheated vehicle overnight. This morning, I decided to eat two for breakfast, and I found that one was distinctly squishy (so I called it my own Squishy :-) while the other seemed normal; the squishy one is now in the compost, and the normal one in my stomach. Is the nutritional value of clementines damaged when they're frozen whole in this way? What I saw on Google when I looked for "freeze" and "citrus" was generally (1) how to freeze citrus fruits optimally in your freezer, and (2) damage done to orchards by sudden frosts. Nyttend (talk) 14:02, 4 January 2010 (UTC)

If consumed straight after defrosting it would have been OK, just the texture destroyed, but the substances contained in it would have been the same. The cell structure would have been disrupted, and that would lead to rapid deterioration if kept. Perhaps you could have juiced it! Graeme Bartlett (talk) 21:24, 4 January 2010 (UTC)

I'm no expert but some nutrients (vitamins etc) can be be reduced by freezing, but if a piece of fresh fruit is several days/weeks old (even if stored in a coolroom) it will also have a reduction in nutrients. Freezing on the other hand can help preserve these until it is defrosted for consumption. Chemical reactions and growth of mold/fungus & decomposition are all accelerated by higher temperature. As you noticed and Graeme explained, the cell structure is damaged(ice cystals) and it became 'squishy'. Frozen_food#Effects_on_Nutrients has more details. --220.101.28.25 (talk) 03:32, 5 January 2010 (UTC)

Well, I didn't consume it immediately after defrosting — yesterday (the day after it was left in the vehicle), I spent all day in the vehicle with the heat on; after reaching my destination last night, I took it inside, so it had all of yesterday and all of last night to defrost. Thankfully, there was no mold or fungus visible; otherwise, I wouldn't have bothered finding whether it was squishy or not. Nyttend (talk) 04:36, 5 January 2010 (UTC)

LCD TVs and their Manufacturers

I'm curious about these things because I have heard that as far as their screens are concerned, each individual company doesn't make their own, and that pretty much all branded TVs get their screens from one of only 2 or 3 screen manufacturers, then sort of change the peripherals like the box and the remote control and put their own logo on it, then off to the shops with it. Can anyone be more specific on this and/or confirm it?

Effectively, if I've got it right, it would mean that between, for argument's sake, the 700 quid Sony model and the 400 quid Goodmans next to each other on the shelf, both same size, there would be very little difference in the actual viewing quality or life of the product. Lucas 83 14:12, 4 January 2010 (UTC) —Preceding unsigned comment added by Lukerees83 (talk • contribs)

Well, you're right that many brands share component manufacturers. Whether Sony and Goodmans do I couldn't say. My personal recommendation, though, is to find a store that runs a lot of screens side by side and start doing comparisons. Get up close and see if you can spot differences, then back up to your expected viewing distance and see if those differences still exist. If possible, see if the store will dim the lights in the area -- brightly lit stores don't reflect most home viewing environments. Finally, you've got to evaluate how much an incremental improvement is worth -- even if you can spot the difference in the Sony and the Goodmans, there's no objective answer as to whether the "viewing quality" is worth 300 pounds. — Lomn 16:40, 4 January 2010 (UTC)

Also, while there are only a few panel makers, there is more to a TV than the panel. Back-lighting can make a major difference to the resulting quality, as can the decoder. And it's quite possible that the makers perform binning, sending the best panels to premium customers, selling the average ones on the open market, and dumping the remainder to low-cost sweat shops. --Stephan Schulz (talk) 16:54, 4 January 2010 (UTC)

There are so many variables in the shops--screen settings, inputs, lighting--that I don't think it helps much to see the products in real life. Imagine Reason (talk) 02:19, 5 January 2010 (UTC)

Plantain herb

Hi My question is "can any part of Plantain herb be used to treat bedsore?" tahnk you.

Sabboor —Preceding unsigned comment added by Sabboor (talk • contribs) 15:39, 4 January 2010 (UTC)

Sadly, we do not give medical advice of any sort, and so will not answer this question. I note that the Plantago major articles notes that the plant was used as a battlefield field-dressing. This should not be taken as an indication that it is of any use for bed sores. --Tagishsimon (talk) 16:11, 4 January 2010 (UTC)

What people believed about science in earlier times

Hi there, I'm trying to find out what people believed in earlier times about science. For example, I want to know what the average person living in the middle ages thought about reproduction in the biological sense. I mean, how well did the average person understand the qualities of semen and that sex results in pregnancy? What did people back then think of the placenta? What about other body organs, like kidneys, livers, etc?

And then I want to know what the "learned" community at the time thought. Where can I find this information? Thanks.--70.122.123.222 (talk) 17:57, 4 January 2010 (UTC)

At Wikipedia, the article History of science and the category Category:History of science would be a good place to start. Most science disciplines also have articles titled "History of XXXX" where XXXX is the name of the science, for example History of biology. --Jayron32 18:56, 4 January 2010 (UTC)

The general topic you are interested in is what is usually called Medieval medicine. There are lots of books on this, if you want to pursue it further. If you want to know about specific organs, your best bet is to probably run a search like "'medieval medicine' placenta" through Google Books.

In a very brief summary... It's easier to say what the "learned" community thought, because they wrote down what they thought, and the medical and scholarly culture of medieval Europe in particular was heavily, heavily text-based. The basic European "learned" model of the medical body throughout most of what we usually call the Middle Ages is known as Humorism—a model derived from the work of Galen. (European scholars were of the basic idea at this time that the Ancient Greeks and Romans had discovered the real "truth" about science and medicine, and that all further work had been corruptions, and so they went back to these very old models for their knowledge, and did not try to innovate on them, or test them.) Around the 16th century this starts to change and you get a more "sack of guts" view of the human body, characteristic of Vesalius, that we see as being characteristic of the Early Modern period (scientific revolution and all that).

Things were less doctrinaire and more varied in the Islamic world (and more "modern" in many ways). At this time, the Islamic world was the real center of medical development, not Europe. The Islamic physicians thought the European ones were completely barbaric. See Medicine in medieval Islam for more information. --Mr.98 (talk) 18:58, 4 January 2010 (UTC)

And just to follow up on my own comment... there are lots of wonderful books written about Medieval science. It is weird stuff. It does not match up one-to-one with modern scientific concepts very well. If I can recommend a favorite that is easily readable and very rewarding, C.S. Lewis' The Discarded Image (1964) is considered quite a classic even by current scholars of the medieval period. ("Hey," you say, "that's about literature!" Well, yes, and no. One of the main points about really understanding medieval thinking that the categories we use today to delineate literature, science, etc., did not really exist in the same way back then. The medieval scholars saw a synthesis of "the whole organization of their theology, science and history into a single, complex, harmonious mental model of the universe," as Lewis put it.) --Mr.98 (talk) 22:08, 4 January 2010 (UTC)

You can also check out the Mishnah and Talmud articles for relevant dates, but they speak of this -- although it might be difficult to get across the language barrier if you don't read Aramaic, unless you speak to a Talmudic scholar or get an English-version, such as Artscroll. In general, the assertions made about science in general and reproductive medicine in specific seems to be generally accurate and most certainly coincident with the popular ideas of the time. The sages of the Talmud were in frequent debate and discussion with the wise men of the time of Greek civilization, and numerous reference is made to debates regarding the nature of the orbits of the Earth and the Moon. Medicinal information is provided, with most of it being arcane and silly next to modern standards of care -- but that was the popular notion of the time among other civilizations as well. Complete understanding of sperm and egg, or at least male + female portions of a fetus seem to be overt, and the placenta is revealed to have been known to both exist and be associated with the fetus. It cannot be known for sure, but there is no indication that the function of specific organs such as the liver/kidneys were known, although the halachic relevance of such information is dubious, and they may have had an inkling at the time, but the Talmud is not meant to be a science text. DRosenbach ^{(Talk | Contribs)} 14:05, 5 January 2010 (UTC)

Does the body need to "breath" oxygen?

I was watching Avatar (great movie btw), and in the movie the humans can walk around on Pandora (alien planet) without any protective clothing (their skin can be exposed), but they needed to be supplied with oxygen (presumably because the atmosphere has no oxygen). So it got me thinking about what a teacher once told me. He told us that the body needs to be surrounded by oxygen or otherwise you will die. Then some student asked him, "What about when we are in water?!" to which the teacher responded "There's oxygen dissolved in the water!". The point of this lesson was to explain to us why tar and feathering causes death. Because the tar "suffocates" the body. I'm not sure I buy that, I would assume it's because the tar is extremely hot.

But anyway let me ask this, if we were on a distant planet that was 100% nitrogen in its atmosphere composition. Would we be ok walking around naked as long as we had oxygen tanks to let us breathe (and the temperature was adequate as well of course)? ScienceApe (talk) 19:53, 4 January 2010 (UTC)

I'm not entirely sure of the answer, but it sounds like your asking if there are any issues with walking in an environment with no oxygen (i.e. would it damage the external parts of the body e.g. skin). I'm not sure of the answer to that question, so I'll leave it for someone else, but my speculation would be that, assuming the atmosphere is at a survivable temperature and you have an oxygen tank mixed at the correct concentrations, you could survive. I'll now hand over to experts to rip apart my answer :) Regards, --—Cyclonenim | Chat  20:07, 4 January 2010 (UTC)

Well, tar and feathering does not actually kill you. That's kind of the point of it—it is humiliating and unpleasant but it's not fatal. But on to the main question: no, and it sounds like a Goldfinger-derived myth, helpfully perpetuated by a clueless high school teacher. You do need to perspire or you can overheat, and this can be inhibited by coating your body in paint or latex or tar or whatever, but it has nothing to do with lack of exposure to oxygen --Mr.98 (talk) 20:08, 4 January 2010 (UTC)

Oh, and regarding tar and feathering, I'm almost certain that if it does turn out fatal, the cause of death would be shock, but I suppose if the tar permanently covered the mouth and nose of the victim, then it would cause suffocation (i.e no oxygen getting to the cells within the body) and then death. Regards, --—Cyclonenim | Chat  20:12, 4 January 2010 (UTC)

(Edit Conflicts) As far as I am aware from previous reading and can find from initial searching, the answer is, yes we would be OK. Our Human skin article suggests nothing to the contrary, and discussions by relevantly qualified scientists I have heard at Mars Society meetings have assumed that outdoor Martian conditions could be tolerated by use of a contact pressure suit and oxygen helmet, without the need for significant air-skin contact.

Tarring and feathering involves not merely cutting off oxygen to the skin, but also severe skin burning (because the burning-hot material adheres and is very difficult to remove). Nevertheless it is usually intended to cause pain and humiliation, but not necessarily death which, though it can indeed occur due to burning injury and shock, is often incidental. Permanently covering all of the skin with any sealing material may cause a slow buildup of problems by blocking its functions, including "insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates" as well as some excretion, but (contrary to the fictional scenario in the film Goldfinger) would not cause rapid incapacitation and death. 87.81.230.195 (talk) 20:17, 4 January 2010 (UTC)

"There's oxygen dissolved in the water!". Generally, yes, but we're talking tens of ppm (per this) as opposed to the concentration of oxygen in the air (around 16% or 160,000 ppm). I'd like to hear your teacher's justification for saying that though the skin needs oxygen in some mysterious way a dissolved oxygen concentration some sixteen thousand times less than that in the air would be enough to sustain life. Homoeopathic oxygen, perhaps? Tonywalton ^Talk 20:47, 4 January 2010 (UTC)

Your teacher was wrong. There is a possibility that after an extended time you might have some sort of skin issue, irritation or bacterial issues (since you are converting the bacterial colony from aerobic to anaerobic). But as far as life is concerned, your teacher was wrong. Tar might block sweat pores in the skin, and a person would then very easily overheat (and the tar is also hot). Ariel. (talk) 21:46, 4 January 2010 (UTC)

Not necessarily that hot. Per http://www.inchem.org/documents/icsc/icsc/eics1415.htm the melting point of coal-tar pitch is from 30C-180C (86F-356F). So a low-melting tar (up to say 50C/120F-ish) isn't even that hot. Even the basic premise ("tar and feathering causes death") that this teacher was trying to teach seems suspect. Tonywalton ^Talk 22:06, 4 January 2010 (UTC)

I have seen (at various times in the past) claims that the skin cannot be completely blocked from oxygen for extended periods. Often, it is in relation to a person having his or her entire body painted. Even though the person could breath, they suffocate. So, I do not disagree that there are intelligent people out there who believe that some skin must be exposed to oxygen at all times. However, there are many anecdotes that counter this argument, such as the Blue Man Group and people with rubber fetishes. It is possible that a person may overheat from an inability to properly sweat, but that doesn't apply if the skin is exposed to moving air that doesn't have oxygen. -- kainaw™ 22:01, 4 January 2010 (UTC)

And there are intelligent people who believe in Fan Death. Ariel. (talk) 22:06, 4 January 2010 (UTC)

Anybody remember the Opportunity Knocks show with the silver-painted muscle man (was it Tony Holland)? He appeared in a Speedo-type cossie, painted all over with silver paint, and Hughie Green made great play on the fact that the performer had to complete his act within three minutes (or some-such) or he would die from overheating due to blocked pores. I wonder if this was once one of those now-debunked pseudo-medical myths (like not putting flowers in a bedroom overnight because they'd "use all the oxygen", swallowed chewing gum "wrapping round your heart and killing you" or "not getting pregnant if you do it standing up"). Tonywalton ^Talk 22:29, 4 January 2010 (UTC)

Wow! I remember that! Well, clearly it made the act MUCH more exciting. If you knew that the guy was in no danger whatever, it would have been a lot less interesting. That show was on at about the same time as the Goldfinger movie - and was probably playing on the same misinformation. At the time of the movie, they made a big point of the fact that the actress actually had a small patch of her skin left un-painted (at the base of her spine - allegedly) so her skin could breathe. That alone raises huge red flags - can the oxygen intake from a small patch on one side of the body somehow travel around to keep the rest of the skin alive? How? It's truly a myth put about to make these entertainments seem much more dangerous than they really are. SteveBaker (talk) 00:22, 6 January 2010 (UTC)

Your teacher was wrong, probably because he or she watched the movie Goldfinger. Uncle Cecil dismissed this myth admirably in 1978, when he wrote, "It is now known that you do not breathe through your skin. You breathe through your mouth and nose." Comet Tuttle (talk) 22:13, 4 January 2010 (UTC)

Do not try the experiment at home or you too may gain a Darwin award. Some paints can be toxic applied to the skin. Here's a 2009 Darwin Award Winner. Dmcq (talk) 00:40, 5 January 2010 (UTC)

The danger is overheating, not 'suffocating'. Mythbusters looked at the 'Goldfinger myth' twice:[7][8]. Fences&Windows 01:28, 5 January 2010 (UTC)

Original research: Most teachers are wrong -- that's because teachers are invariably under-qualified. I'm now in 22nd grade, and I've found qualified professors to be severely outnumbered by nothing too far short of 10:1. DRosenbach ^{(Talk | Contribs)} 14:11, 5 January 2010 (UTC)

The Mythbusters actually tested this "Goldfinger" myth (twice) - and with mixed results. The first time, the victim felt pretty ill rather quickly - but it's not clear whether that was psychosomatic, or a consequence of some material in the gold paint that they used or what. However, the second time, they used a safer latex-based material and there was no problem. So it's pretty clear that the skin doesn't need to breathe...at least it can survive without exposure to the air for many hours at a time without problems. Your teacher's claim that dissolved oxygen in water is what saves a swimmer is just a clever guess - and I'm 100% sure it's wrong. I suggest you ask again but this time mention people who survive quite well swimming in tight-fitting neoprene diving suits for hours at a time...clearly those exclude both air and water from the skin - and they obviously aren't porous to either. IMHO, that statement clinches the argument - although I suppose it's possible that there might be longer term problems if your skin were kept away from the air for days or weeks. Avatar was an excellent movie - I didn't think they made it clear whether the masks were to provide oxygen or to exclude some other toxin...I rather suspect the latter was intended. People who lost their masks didn't gasp for air or turn blue (as you'd expect from oxygen deprivation) - so perhaps that's a reasonable interpretation. I need to see that movie again. SteveBaker (talk) 17:57, 5 January 2010 (UTC)

I seem to recall that the only human who was exposed to the atmosphere regularly was the evil base commander guy, who was so tough he could hold his breath for quite some time. I assumed it was supposed to mean that the air just wasn't rich enough in oxygen or something like that. --Mr.98 (talk) 17:31, 6 January 2010 (UTC)

Unknown animals

I know that this file is some type of screech owl (Megascops sp.) and that this file is a marmot (Marmota sp.), but I do not know what either species is, so if you can identify it for me and tell me, I would be much obliged. --The High Fin Sperm Whale (Talk • Contribs) 21:13, 4 January 2010 (UTC)

I don't know about the owl, but the rodent looks like an alpine marmot to me. Looie496 (talk) 22:26, 4 January 2010 (UTC)

Yes, it looks like an Alpine Marmot, only it lived near E. C. Manning Provincial Park, British Columbia, Canada. Alpine Marmots live in Europe. I think it is a Yellow-bellied marmot, but I could be wrong. And I still don't know about the owl. --The High Fin Sperm Whale (Talk • Contribs) 23:44, 4 January 2010 (UTC)

Those who know him well call him Marmota flaviventris. DRosenbach ^{(Talk | Contribs)} 14:14, 5 January 2010 (UTC)

Is the owl an immature Long-eared owl with its ears flattened? --TammyMoet (talk) 09:40, 5 January 2010 (UTC)

No, it is some type of screech owl. And I am now certain the marmot is a Yellow-bellied marmot Marmota flaviventris. --The High Fin Sperm Whale (Talk • Contribs) 00:00, 6 January 2010 (UTC)

So does anyone know what type of screech-owl it is? --The High Fin Sperm Whale (Talk • Contribs) 18:40, 6 January 2010 (UTC)

Nutrient Deficiencies

Perhaps this would be more appropriate over at the history section, but it's somewhat of a medical question as well. My understanding is that many (poor) Europeans during the Middle Ages didn't have a terribly good diet (though I admit that I was unable to find anything specific on the diet of the Middle Ages). This leads me to believe that they may have been deficient in some nutrients. Specifically, I was over looking at the Iodine Deficiency article, where I saw that this particular deficiency is common in areas that don't eat seafood (and don't iodize their salt), which would seem to describe many European peasants from the Middle Ages. So did these people just manage to live with goiter and the symptoms of other nutrient defficiencies? Or were there diets more balanced than I believe, and they gennerally got enough of whatever nutrients they needed, at least to ward off the worst symptoms? A similar problem seems to exist for people in high latitudes getting enough vitamin D before we started putting it in our milk, or in Eskimos getting enough vitamin C from their diet of animal products. Modern nutritian seems to put a pretty heavy emphasis on getting certain amounts of certain nutrients, and I suspect that many people were not getting all of these nutrients in different time periods and in different parts of the world (and still don't, in some places). So can we still function well enough to get by even if we're nutrient defficient in certain nutrients, or am I wrong about many people having defficiencies in the past (or both)?Buddy431 (talk) 21:21, 4 January 2010 (UTC)

Iodine – Yes, iodine deficiency and goiter were seen during the Middle Ages in Europe, according to the Network for Sustained Elimination of Iodine Deficiency. Goiter was so common that some women were painted with goiters. (http://www.iodinenetwork.net/Resources_Nutrition.htm) Some ancient people used seaweed for goiter. The people did live with goiters, but the main danger was cretinism, when mothers could not obtain enough iodine and the lack of iodine caused the babies to develop cretinism, mental and physical retardation. It is possible to live without iodine; its only known use is for making thyroid hormones.

Vitamin D – The body can make several times more vitamin D than you would find in a pill in just ten minutes out in the sun. There are very few foods that naturally contain vitamin D; like iodine, most vitamin D provided naturally by food comes from seafood. In some parts of the world, vitamin D deficiency has caused rickets in children and osteomalacia in adults.

Vitamin C – The Eskimos did not have to eat plant foods in order to have adequate vitamin C intake. Vitamin C was provided by some kinds of meat in their diets, especially raw meat (http://uclue.com/?xq=1716).

Reference Daily Intake – Not all nutrients must be at RDI levels to prevent deficiency diseases. "In human dietary studies, all obvious symptoms of scurvy previously induced by extremely low vitamin C intake, can be reversed by vitamin C supplementation as small as 10 mg a day" (Vitamin C, Wikipedia). "The uses and recommended daily intake of vitamin C are matters of on-going debate, with RDI ranging from 45 to 95 mg/day" (Vitamin C, Wikipedia). Therefore, the RDI is several times higher than the amount needed to prevent scurvy.

“So can we still function well enough to get by even if we’re nutrient deficient in certain nutrients?” It depends on the severity. It is recommended, for instance, that most people receive at least 1,000 milligrams of calcium a day. Teenagers should have 1,300 milligrams. Of course, we can get by with less calcium (look how many Americans have stopped drinking milk), but a suboptimal intake of calcium is likely responsible for high rates of osteoporosis. Many people are deficient in magnesium. Magnesium is essential to life (it is involved in many enzymes), but the deficiencies that people have are not life-threatening, even if they increase the risk of osteoporosis. “Am I wrong about many people having deficiencies in the past?” No, many people in the past did develop goiter or deficiency diseases due to inadequate nutrient intakes. Many people today continue to develop deficiencies in iodine and vitamin D in parts of the world.75.88.127.44 (talk) 23:13, 4 January 2010 (UTC)

OR aheadI recall a college lecture many years ago about vitamin A. It seems that at the beginning of WWII the British Government decided to see what the required intake of vitamin A was (to work out domestic food rationing levels and requirements for the armed forces). So they took a group of volunteers (conscientious objectors, but genuinely volunteering, I seem to remember) and put them on a diet as completely devoid of vitamin A as possible. At the end of WWII they had detected no deficiency symptoms at all. Of course as the Vitamin A deficiency article says, between ¼ and ½ million children go blind each year due to vitamin A deficiency - the difference being that vitamin A is stored (in the liver - the polar bear liver story is well-known). Adults who have previously had access to enough vitamin A can have stored enough to last for years while if you have never had enough vitamin A you haven't had the opportunity to store any. Tonywalton ^Talk 23:34, 4 January 2010 (UTC)

See also Rickets, which is reputed to have been fairly common in, for example, Britain up to WW2. Consider also that much of the higher child mortality rate in past centuries may have been due to such deficiencies, so the extant adult population was already partially selected from those who had not suffered and died from the worst deficiencies. 87.81.230.195 (talk) 03:44, 5 January 2010 (UTC)

In England, the condition of goitre was so common in one part of the country that it was known as "Derbyshire neck". --TammyMoet (talk) 09:37, 5 January 2010 (UTC)

One point not mentioned above is that deficiency diseases were not always attributed to getting too little of some vitamin, protein or mineral (or the foods they come from, before these nutrients were scientifically named). Sharecroppers in the rural U.S. who lived on a monodiet of corn (maize to the rest of the world) got Pellagra, and the devastating disease was variously attributed to a poison in corn, to too much sun exposure, to toxic atmospheres, to bad hygiene, or to bad heredity page 13 before 20th century controlled experiments disclosed the actual root cause as a nutrient deficiency. It was easier for the financial leaders of the southern society to attribute the killer disease to failure to wash up, or to poor genetic stock, than to failure to provide a varied diet to the poorest workers. In the Middle Ages "God's Will" was a satisfactory explanation for deficiency diseases, along with other nonscientific explanations. A supposed cure for goiter in the Middle Ages was the touch of a King's hand, or the touch of the hand of a dead person, or a toad dying in a sack tied alongside the goiter, or saying a magic phrase in some particular phase of the moon. [9] Iodine became an accepted treatment in the early 19th century. It was thought in the mIddle Ages that goiter might be due to impure water or hard work[10], and it is likely that those with a restricted diet worked hard and drank impure water in many cases. Treatment with seasponge ashes, containing iodine, dated back to the 13th century, but was not widely accepted as the effective remedy it was later seen to be. Edison (talk) 15:41, 5 January 2010 (UTC)

planet surviving being engulf by sun

Earth was said earlier to have possibility to survive being inside the sun. Is this possible for Venus to also survive inside a 5 to 7 billion year sun being taken inside the sun but not being destroy. Tango said Earth could also survive being engulf is this possible for Venus to too.--69.226.43.41 (talk) 21:29, 4 January 2010 (UTC)

Where were these things said? Cuddlyable3 (talk) 23:11, 4 January 2010 (UTC)

• At this if earth do but probably not then venus would be even unlikely. It say only if earth do then venus could have chance.--69.226.34.161 (talk) 01:31, 5 January 2010 (UTC)

If earth can, venus can (more or less), but I'm not convinced that earth can survive. Ariel. (talk) 23:13, 4 January 2010 (UTC)

At issue is the definition of "inside the Sun." The Sun has many layers that do not have extremely distinct boundaries. How may layers down does the Earth have to be before it is considered being "inside" the Sun? -- kainaw™ 01:37, 5 January 2010 (UTC)

Why is there an attractive force between the Moon and the Earth? Bus stop (talk) 01:44, 5 January 2010 (UTC)

Hypotheses non fingo. --Tango (talk) 03:08, 5 January 2010 (UTC)

Please see Gravity for the scientific reasons. If asking from a philosophcal POV, it's there so that we have tides, pretty, or if you prefer romantic, moonlight, and as a side effect also keeps us 'attached' to the suface of the Earth. --220.101.28.25 (talk) 04:00, 5 January 2010 (UTC)

I said there that the Earth wouldn't be instantly destroyed. Chances are it would be destroyed before the Sun shrank again, although there is some evidence to suggest it would survive in a much diminished capacity (no atmosphere, no water, most of the crust probably gone): planets have been found orbiting white dwarfs close enough that they should have been inside the red giant at that stage, suggesting they survived inside their star for a time. There is no qualitative difference between the Earth and Venus in that respect, although Venus being quite a bit closer means its chances of survival are quite a bit less. --Tango (talk) 03:08, 5 January 2010 (UTC)

According to [11] a red giant's envelope has a density of ~0.1 kg / m³, which is about 1/10 the density of air at the surface of the Earth. If that's correct, then an enveloped Earth would experience a drag of order 0.5*v²*(0.1 kg/m³)*pi*(radius of Earth)² ≈ 5.5×10²¹ N, or equivalently a torque of ≈ 8×10³² N-m. It's angular momentum around the sun is ≈ 2.6×10⁴⁰ J-s. So, to order of magnitude, it would take about 3×10⁷ seconds (400 days) for such a drag to rob the Earth of all it's angular momentum. I think this back of the envelope calculation shows that in order for the Earth to "survive" the few million years that the sun will be a red giant, it would have to remain far removed from the sun itself and in a region of space with a density probably less than say ~10 μg / m³. Dragons flight (talk) 07:22, 5 January 2010 (UTC)

The above post can be converted to English by replacing "it's angular" by "its angular" in 2 places. Cuddlyable3 (talk) 21:59, 5 January 2010 (UTC)

PS. For anyone that is curious, the current space the Earth travels in has a density of order 10^-20 kg / m³. Dragons flight (talk) 07:28, 5 January 2010 (UTC)

When a star turns into a red giant it throws off its outer layers, reducing its mass. That would cause planets to move further out. That density figure is presumably an average, so it would be significantly less near the edge. Your back of the envelope calculation also fails to account for the reduction in drag as the orbital velocity slows down - that could be a large factor. Whether those two factors are enough to multiply the survival time by a factor of 1,000,000, I don't know. The evidence for survival is empirical, rather than theoretical, and I haven't looked into it recently so there may be alternative explanations now. --Tango (talk) 21:47, 5 January 2010 (UTC)

I think that you may have confused two distinct scenarios for what happens to Earth following the expansion of the sun. In one scenario, the Earth survives the expansion of the Sun by not being engulfed, an rather by being slowly pushed to a higher orbit as the sun expels 30% of its mass in the process of expanding into a red giant. In this higher orbit, the Earth escapes the drag that would doom it to being engulfed. However, simulations disagree as to which scenario will come true. You can read about it at Risks_to_civilization,_humans_and_planet_Earth#Cosmology_and_space. Someguy1221 (talk) 07:34, 5 January 2010 (UTC)

redshift/blueshift hypothetical

I have a hypothetical question regarding redshift and blueshift of light.

If there was a hypothetical giant mirror that reflected all light, and there was a distant star moving towards the earth, but away from the mirror (if the earth and the mirror are stable with respect to each other), would the reflection show a redshift or a blueshift? Googlemeister (talk) 22:28, 4 January 2010 (UTC)

I assume we are observing the distant mirror from Earth. The image of the approaching star recedes from us so its light will be red-shifted.Cuddlyable3 (talk) 23:09, 4 January 2010 (UTC)

Redshift. I know what you're thinking - that the light eventually travels toward the earth, so if it was emitted directly from the star it would blue shift. But the two situations are not the same. The light leaving behind the star causes the star to speed up toward the earth (conservation of momentum), so the light looses energy, the star gains it. If the light was emitting in front of the star, the star slows down and the light gains energy. Ariel. (talk) 23:11, 4 January 2010 (UTC)

I don't understand Ariel's reasoning. The star emits light in all directions so that does not cause the star to accelerate in any direction. The OP stated that the star is moving towards the Earth. Light is electromagnetic energy that is lost by the star, spreads out and is never regained (except by return of a small amount along the path normal to the mirror). Cuddlyable3 (talk) 02:13, 5 January 2010 (UTC)

The star is accelerating. It just happens to be that it's accelerating the same in both directions, and it balances out. However this has no effect on the light leaving the star, which, from the point of view of earth, is still gaining or loosing energy. You normally think of red/blueshift as being due to the motion of the object (doppler effect). This is not so - light does not change in speed. The light changes color due to change in energy, not due to change in the velocity of the star. The light on one side gives the star energy (as measured from earth), and the light on the other side takes energy. Ariel. (talk) 02:23, 5 January 2010 (UTC)

Ariel no. "Accelerating the same in both directions" is nonsense and I don't know why you keep talking about the star accelerating which it does not do in the OP's scenario. Please read the article about the Doppler effect which is well founded in classical physics but which you seem to want to reject in favour of some weird "change in energy" of light.Cuddlyable3 (talk) 22:20, 5 January 2010 (UTC)

Ariel.'s argument is confusing but I think it makes sense; allow me to rephrase it. Each photon emitted in the direction of the star's motion (in your frame) reduces the star's KE (in your frame) and must therefore carry more energy in your frame than it would in the star's (where it does not carry away KE). Similarly light emitted "backward" must have less energy than "normal". The light emitted in all directions by the star thus shows a continuous variation in energy (and thus color, of course) with direction, and so long as any mirrors involved are stationary in your frame, the energy at which you receive it will be determined entirely by its direction of emission and not by its path to you. --Tardis (talk) 00:04, 6 January 2010 (UTC)

You don't need stars and giant mirrors - you can do this experimentally. Stand near a wall and listen to the Doppler shift from the echo of a passing ambulance siren (the echo, not the siren itself coming towards you). If an ambulance siren isn't available get a friend to run in the appropriate direction shouting "Nee Naa". The fact that the siren (or friend, or star, if you must) itself is moving toward you is irrelevant. Tonywalton ^Talk 23:42, 4 January 2010 (UTC)

Huh? How can motion of the source (siren, friend, star) relative to yourself be irrelevant to showing a Doppler shift? Cuddlyable3 (talk) 02:13, 5 January 2010 (UTC)

It's irrelevant for the doppler shift of the echo. For that, you only need to know the relative motion of the source and whatever the sound is bouncing off (and the relative motion of that thing and you, but the OP said the mirror was at rest wrt Earth). --Tango (talk) 03:13, 5 January 2010 (UTC)

Exactly. Sorry if I wasn't clear. Tonywalton ^Talk 23:08, 5 January 2010 (UTC)

Another way to think about it is to look at the total path length from the source to your eyes. If the total path length is increasing with time, you get a redshift; if it's decreasing, you get a blueshift. -- Coneslayer (talk) 16:36, 5 January 2010 (UTC)

So if the star is moving away from the mirror at speed x, and the mirror is moving away from the observer at speed x, then the resulting redshift would be equal for a star moving away at 2x? Googlemeister (talk) 16:45, 5 January 2010 (UTC)

Yes, I think so. In fact, that situation would be the same as looking at yourself in a mirror that is moving away from you at speed x - you would see yourself redshifted as if your image was moving away from you at 2x. That is, in fact, what you would see - an image of yourself that appears to be moving backwards. Apart from imperfections in the mirror, you wouldn't be able to tell that it wasn't a copy of you moving backwards, so it makes sense that the redshift would be the same. --Tango (talk) 21:51, 5 January 2010 (UTC)

Yes to both. In Googlemeister's scenario the star is stationary relative to the observer. Cuddlyable3 (talk) 22:28, 5 January 2010 (UTC)