Wikipedia:Reference desk/Archives/Science/2010 March 11

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March 11

Spinach and strength

It says on the article that spinach doesn't make you stronger because of a miscalculation in its iron content. But if it did have a lot of iron, would it make you stronger? I never heard of iron making a person stronger before.. ScienceApe (talk) 00:31, 11 March 2010 (UTC)

Please take a look at Human iron metabolism. Inadequate iron causes Iron deficiency anemia and will make one weaker. On the other hand, iron overload is toxic and won't make you stronger. 88.242.232.209 (talk) 01:11, 11 March 2010 (UTC)

_{You'll just get overwrought. Richard Avery (talk) 07:52, 11 March 2010 (UTC)}

As opposed to cast down. Gwinva (talk) 08:01, 11 March 2010 (UTC)

Steel yourself against such ironic posts. Cuddlyable3 (talk) 10:58, 11 March 2010 (UTC)

Ferrous to answer this question, we need more information. SteveBaker (talk) 13:30, 11 March 2010 (UTC)

Ore you could experiment. Googlemeister (talk) 14:23, 11 March 2010 (UTC)

Popeye#Spinach says that "Early references to spinach in the Fleischer cartoons and subsequently in further stories of Popeye are attributed to the publication in 1870 of a study by Dr. E von Wolf which, because of a misprint, attributed to spinach ten times its actual iron content.[34] The error was discovered in 1937 but not widely publicized until T.J. Hamblin wrote about it in the British Medical Journal in 1981." - so the whole thing is down to a misprint. (That is so sad - the millions and millions of suffering children who were practically force-fed this disgusting so-called food by parents who were desperate to help them in later life...and it's all some simple misprint.) SteveBaker (talk) 13:40, 11 March 2010 (UTC)

I find spinach very tasty. So does my two year old. Dauto (talk) 14:42, 11 March 2010 (UTC)

Yeah, Steve, I think you're focusing too narrowly on a particular error here and missing the big picture, probably because of your personal dislike for the veggie. Spinach doesn't have as much iron as they thought, and anyway the notion that most people need more iron is a bit dated (iron is a necessary but rather toxic mineral and it's easy to get too much). But that doesn't mean you shouldn't eat it! Leafy greens have all sorts of things most people don't get enough of, starting but definitely not stopping with just plain fiber.

I also enjoy spinach, mainly raw. Try a salad made of spinach leaves, red bell pepper, a few Kalamata olives and a little feta. Possibly some avocado although that makes it less Greek. Pour some olive oil over the top, and then squeeze half a lime on it; you could sprinkle a little salt if you absolutely have to. Really really good! --Trovatore (talk) 20:41, 11 March 2010 (UTC)

Ah - one of those recipes. Basically, smother the noxious food item with as much strong smelling & tasting stuff as possible in order to avoid having to taste it! You can get your nutrition from all manner of other leafy greens - various cabbages and lettuces, brussel sprouts, bean shoots, leeks - you name it. You don't need spinach for health. SteveBaker (talk) 01:21, 12 March 2010 (UTC)

Most lettuce I find too mild. Iceberg in particular I don't want anything to do with. You can tell that its antioxidant content is low, just because it's not strongly colored. Antioxidants tend to be pigments (all those double bonds).

Cabbage, on the other hand, I just don't like. Brussels sprouts, broccoli, all those cruciform vegetables cruciferous vegetables, are palatable when cooked, but I don't care for them raw, and I think raw is probably best.

But my favorite leafy greens are the ones packaged as spring mix or herb salad — I like those even better than spinach. Still, spinach beats ordinary lettuce hands down. --Trovatore (talk) 02:02, 12 March 2010 (UTC)

Oh, and the recipe I gave is certainly not about drowning out the taste of the spinach — the spinach taste comes through, and I like it. If I didn't, I suppose iceberg would be OK. (Except I don't like the texture of iceberg, and since it has no taste, the texture is the only thing it does have.) --Trovatore (talk) 02:06, 12 March 2010 (UTC)

Steve, now I'm curious — do you taste phenylthiocarbamide? I was having a hard time imagining how anyone who objected to the taste of spinach, could even remotely tolerate cabbage. According to one of the articles I was clicking through yesterday, PTC tasters (like me; stuff's absolutely foul) are less likely to like cabbage. If you can't taste it, that could explain the difference in perception. --18:17, 12 March 2010 (UTC)

I'm not likely to go around tasting chemicals with long, dangerous-sounding names! I have no idea whether I can taste that stuff or not. Actually, my problem with spinach is that it really doesn't taste of very much at all...the texture bothers me some. But it's well-understood that taste is quite different between individuals. I know (for example) that most fish have almost zero flavor for me. People around me will be saying "Wow! This fish is so fresh!" - and I'm thinking "It tastes of almost nothing - just like almost every other fish I've ever tasted.". SteveBaker (talk) 01:49, 13 March 2010 (UTC)

Interesting -- it really doesn't taste of very much at all...the texture bothers me some is almost exactly what I'd say about lettuce (well, most lettuce). I like spinach precisely because it has more taste, and doesn't have that unpleasant pseudo-crunchiness. It's true though that spinach that's been left in the fridge too long acquires a very unpleasant slimy feel -- if that's what you associate with spinach, you just need to get it fresher. --Trovatore (talk) 02:46, 13 March 2010 (UTC)

I ate raw spinach and got Salmonellosis. 88.242.232.209 (talk) 23:04, 11 March 2010 (UTC)

Nothing in this life is free of risk. Yes, bacterial contamination is an ongoing issue. It would be a pity if that stopped people from eating veggies. --Trovatore (talk) 23:44, 11 March 2010 (UTC)

Raw spinach is great, that nasty stuff that comes in the can is fit only for a minor ingredient in lasagna. Googlemeister (talk) 14:09, 12 March 2010 (UTC)

I don't know that I've ever had canned spinach. I used to eat a fair amount of frozen spinach when I was a kid. My mom would boil it up and cut it liberally with mayonnaise. I really liked it, but I don't think you'd call that nutritionally recommendable. (Better than no veggies at all, but still better not to add that much fat and sodium.) --Trovatore (talk) 18:12, 12 March 2010 (UTC)

I think your mother knew what she was doing: doesn't the fat greatly increase the quantity of fat-soluble vitamins you get from the spinach, which are the chief benefit of cooked spinach to my mind? Better to eat your spinach with a little fat than with no fat. 86.178.167.166 (talk) 02:07, 13 March 2010 (UTC)

A little fat might help absorb carotenoids, according to our article on them. (Most people get enough vitamin K so that's not really a consideration.) But there's a difference between a little olive oil and a big old clump of mayonnaise. Just the same, it really was tasty. --Trovatore (talk) 02:14, 13 March 2010 (UTC)

For people that like spinach they might also like Amaranth or Callaloo as its known in the UK.

And please! Stop asking questions about food... it keeps me raiding the kitchen and putting on weight!--Aspro (talk) 18:47, 12 March 2010 (UTC)

If you're raiding the kitchen for raw spinach, I'm guessing that'll be OK. --Trovatore (talk) 20:34, 12 March 2010 (UTC)

Yeah - the projectile vomiting will solve the problem completely. SteveBaker (talk) 01:49, 13 March 2010 (UTC)

Re: the point above about broccoli being better raw, I would be careful before making such assumptions. I recall being told once about a study which found broccoli was best if lightly steamed, not raw. I can't seem to find that at the moment and if you do a research you may come across a widely reported study which I think is this [1] about raw broccoli being better then cooked (in particularly the bioavailibility of one compound being significantly lower). While a good study, it does use somewhat artificial example of 'raw' & 'cooked' "1 kg of raw broccoli was crushed with a blender and incubated at room temperature for 2 h prior to serving to the volunteers. One kilogram of broccoli was microwave cooked at 1000 W, crushed with a blender, and immediately serve." (Unfortunately it doesn't seem to say cooked for how long.) I'm not really sure why the crushing, it may given the small sample size (it's always going to be difficult to draw any definite conclusions from a sample size of 8) to try and prevent differences due to how well the participants chewed. Unfortunately that has the problem that there may be natural differences in how well people will chew the products if raw or cooked and incubating the broccoli for 2 hours after crushing is likely to cause differences compared to what most people consume when they eat raw uncrushed broccoli. Of course it may simply be crushing broccoli is common in the Netherlands.

In any case, this other study [2] found boiling was bad, but steaming, stir-frying and microwaving did not significantly reduce the content although this was of the vegetable instead of testing how it was absorbed like the earlier study did. This [3] mentions broccoli and other vegetables and goes briefly into the complexity.

Suffice to say as with most of these questions about which one is better health wise, it's unlikely to be a simple thing (although boiling the shit out of the things ala English and deep frying is unlikely to ever be good). In any case, even when raw is better, it doesn't automatically follow that it'll be better to just avoid the vegetable altogether, it may still be beneficial to eat it, along with other cooked and raw vegetables to ensure a variety of different nutrients.

(Personally I do enjoy raw brocolli on occasion, along with raw baby spinach, raw lettuce)

Nil Einne (talk) 15:57, 15 March 2010 (UTC)

Fluorescence in polar and nonpolar environments

It's said polar environments give emission with longer wavelength (i.e. red-shift) because "reorientation of polar solvent molecules compensates for charge separation", from my lecture notes. Why is that? My prof is so horrible and he has even worse notes. I looked at the wikipedia page for fluorescence but it doesn't explain these topics. —Preceding unsigned comment added by 142.58.129.94 (talk) 01:05, 11 March 2010 (UTC)

It sounds like you might be talking about Solvatochromism. Basically, a compound can absorb light, and in doing so, is changed to a higher energy form, that has different properties and structure than the lower energy form. Depending on the dipole moment of the lower and higher energy states, a polar or non-polar solvent may stabalize one or the other forms. This means the wavelength of light absorbed is dependent on the polarity of the solvent. Some compounds have a high degree of solvatochromism, such as Brooker's merocyanine.

However, I've never heard of fluorescence being related to solvatochromism, and the statement from the lecture notes means nothing to me. Perhaps a bit of context is needed: what are you studying right now? What class is it (i.e. upper level physical chemistry vs. freshmen biology)? What's in the solution (I assume you have a solution, as you're talking about polar and non-polar wavelengths environments)? Buddy431 (talk) 02:15, 11 March 2010 (UTC)

nitrile gloves

why do nitrile gloves smell like diarrhea? —Preceding unsigned comment added by 67.246.254.35 (talk) 01:34, 11 March 2010 (UTC)

Psychology. Namely, yours apparently. You believe them to smell like diarrhea, so they do to you. I think they smell something like nitrile gloves. --Jayron32 02:21, 11 March 2010 (UTC)

no iv asked others and they agree —Preceding unsigned comment added by 67.246.254.35 (talk) 03:24, 11 March 2010 (UTC)

I have to agree with Jayron32, they smell like nitrile. It's plastic-like mixed with a bit of sulfur. -- Flyguy649 ^talk 03:44, 11 March 2010 (UTC)

whatever the smell why do they smell that way shouldn't they be inert? its synthetic rubber —Preceding unsigned comment added by 67.246.254.35 (talk) 06:08, 11 March 2010 (UTC)

I'm not sure of the physiology behind smell, so don't know whether smell and reactivity should be related. However, rubber definitely isn't inert - e.g. it burns fairly readily (and smells awful when it does so!). 131.111.248.99 (talk) 11:42, 11 March 2010 (UTC)

yes i know rubber burns. u know what i mean by inert it shouldn't smell. obviously if u burn it it will. why does nitrile smell bad shouldent it just smell like latex or rubber? —Preceding unsigned comment added by 67.246.254.35 (talk) 23:22, 11 March 2010 (UTC)

advances needed to truly democratize the Internet?

I saw an article headline yesterday stating that most people consider the Internet (and by implication internet access) an inherent right. That led me to consider the recent events in western China where the government essentially pulled the plug on the Internet altogether. Similar events have happened in Iran lately. It seems, above and beyond any firewall/filter/proxy shenanigans, that if you go high enough up there is always someone who can just pull the plug and blackout a large swath of the Earth.

So, that led me to wonder about what sort of distributed hardware would be needed to prevent (or mitigate) this wholesale silencing? Knowing very little about the underlying structure of the Internet, the best idea I could come up with was interlinking WiFi hotspots that use solar/manually rechargeable battery sources. You would need an awful lot though to perpetuate a network on any useful scale... and there's certainly nothing to stop your favorite local authority figures from confiscating/banning such devices, so I readily admit it's not a very good idea. I know Wikipedia is not a crystal ball, but I hope I've given enough solid background to qualify this as a reasonable technology question. Succinctly put - how does the series of tubes become ownerless? 218.25.32.210 (talk) 01:37, 11 March 2010 (UTC)

By getting larger and being owned by many people. The problem isn't that they need to be "ownerless"—it's that you need them to have lots of owners, all of whom are interested in maintaining autonomy, none of whom want to be shut down by the government. (Or so a classical capitalist would argue.) If your entire economy is linked up to a lot of different service providers, that provides a rather resistant incentive against pulling the plug.

As for the technical suggestion... are you suggesting that the internet itself would be constituted solely on the WiFi linkages between individual machines? I don't think that would be robust enough unless you had an extremely high density of participating machines, and even in such a case, the density would have to be limited to local cities. It certainly wouldn't link up the world that way—China and Japan would never be linked by WiFi alone, since there is nobody sitting in the middle of the ocean with Wifi (or certainly not enough to have a worthwhile connection). Maybe at the edges you would have satellite connections or something, but you're going to be concentrating your infrastructure somewhere. (Concentrating it all in satellite connections is not necessarily a great idea if you afraid of governments, either—satellites can be shot down, can fail, can probably be hacked, etc.)

I'm not sure the answer to this is technological in nature, or at least not limited by the networking technology. Connecting countries requires big cables. A government presumably knows where these are. They could, in theory or in practice, shut them down or monitor their use. Increasing the number of cables can make this harder, but not impossible (it is still a finite number of cables). Increasing the number of participants would make shutting them down more problematic in some countries (but not all). A more robust solution might be to mingle political traffic with economic traffic in an invisible way (e.g. through encryption)—with a goal to make it so the government can't shut down political speech without a significant sector of their entire economy. (Note that I would not call this "democratizing" the internet. You are making it more robust, but that's not the same thing as "democracy.") -Mr.98 (talk) 03:26, 11 March 2010 (UTC)

Additionally, the novel Cryptonomicon proposes something along these lines, relying primarily on strong encryption as the means to ensure long-term communications/economic freedom. --Mr.98 (talk) 04:27, 11 March 2010 (UTC)

(e/c) This is actually not strictly a science question, but I'll answer it anyway. the internet was designed from its inception to be (technically speaking) a surveillance system. What I mean is that the client/server architecture is geared towards more-or-less static sites which are viewed by an assortment of viewers. Pragmatically, what this means is that anyone with the proper access can restrict and monitor everything that is viewed - the static servers have to advertise their locations on the web so that viewers can find them, so authorities always know where people are going to be looking. for an analogy, a campus I know was specifically designed with one building for all student groups and meetings, and that building was designed with (physical) firewalls that could be closed so that campus police could quickly and easily isolate and contain any student protests.

Peer-to-peer networking has started to break that client/server architecture up a bit - there were some people using peer-to-peer to get information and videos out during the Iran election troubles, and we all know the problems that the music industry has been trying to gain authoritative control over. but even with peer-to-peer a dedicated group with the proper access can track down, monitor, and suppress internet traffic. There's really nothing anonymous on the internet: best you can hope for is to throw enough sand over your electronic tracks to confuse anyone watching.

Internet democracy (should such a thing ever be tried) would require some legal guarantees to certain kinds of internet privacy and freedom. this has been specifically excluded in nations like China, Iran, and the US where the government explicitly retains the rights to monitor digital communications. I think the EU has some (weak) guarantees in place, but I suspect it will be decades before legal ethics catches up with changes in technology, so I wouldn't hold my breath. --Ludwigs2 03:40, 11 March 2010 (UTC)

How about dial-up ? That is, if the people in China can call outside the country and connect to an ISP there, they can stay online. Of course, there are long distance fees for that, but hopefully only pennies a minute. During their next Tiananmen Square massacre, they could connect up to get the real news and download their pics. Now, China could always block all international calls, but that would certainly hobble the economy. They might just block calls to phone numbers owned by ISPs, though. It would be nice if everybody outside China had a way that, when they get a call from China, it would just hook them up to the Internet automatically. I suppose China could also develop snooping software that would listen to every call, and disconnect anything that sounds like data transmission, but that would probably also knock out faxes, which are used in business. StuRat (talk) 06:14, 11 March 2010 (UTC)

So the problem is that if a government decides it doesn't want its people talking to the rest of the world - then nothing involving wires or optical fiber would solve the problem (if it is a problem...which we can discuss) because those wires can be cut/filtered/monitored at the borders. Radio signals (like Ham Radio's Packet radio) are lacking in bandwidth - and can still be monitored - and perhaps even jammed. What is needed is a wireless - narrow-beam technology that's hard to intercept, impossible to filter and impossible to jam. That would require some kind of "direct-to-satellite" approach where you'd send your data via narrow-beam radio signals or lasers aimed at a satellite and the results would be beamed back using normal transmission mechanisms. Such a system would be horrifically expensive - and would require someone with deep pockets to launch and maintain the satellites. The problem with that is how it gets paid for. Individuals couldn't pay for it using credit cards because those kinds of transactions are easily spotted in the local banking system. It would have to be advertising-funded, but that still leaves the system open to blocking by a government banning the sale of products and services that advertise over this subversive communications system.

The real solution is that people who don't want an oppressive government who shuts down their internet have to get rid of that government. In the end, that's the only way. If you have an oppressive government then all of the technological solutions in the world won't help because they can simply ban use of whatever device is required to access it - clamp down on the importation or manufacture of such gizmo's and use secret police to track down and imprison people found using them.

Bottom line: This isn't a technological problem - and you can't solve it with technology either.

SteveBaker (talk) 13:25, 11 March 2010 (UTC)

It isn't an issue of 'cutting wires'; the issue is that the internet relies on identifiable numeric addresses as distribution points. If you know what addresses are used for distribution, you can control them. wireless and satellite systems will not solve the problem unless they somehow bypass the IP infrastructure of the net, because otherwise a source will still have an identifiable internet location that can be blocked. --Ludwigs2 18:02, 11 March 2010 (UTC)

If you're happy with high latency, IP over Avian Carriers and sneaker net (which can use IP over Avian Carrier technology with a slightly different physical layer) offer very high bandwidth with modern data storage technology. Very small high capacity memory cards are incredibly easy to smuggle across borders, so very little packet loss (which is important when each packet is gigabytes in size). But the latancy sucks. --Polysylabic Pseudonym (talk) 04:34, 12 March 2010 (UTC)

Cooking oatmeal

Why does it seem to take longer to cook oatmeal when you add the sugar before microwaving than if you cook it, then add the sugar? —Preceding unsigned comment added by 66.112.225.118 (talk) 05:43, 11 March 2010 (UTC)

Sounds like another homework question. To brake the bonds so that the crystals dissolve, is in this case Endothermic. You can even freeze water with a mixture of photographers hypo!--Aspro (talk) 08:38, 11 March 2010 (UTC)

Note:, you’d still better read up on it. This is only half of what you need to know but was provided in case your completely stuck, but it is not the whole answer.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. --Aspro (talk) 08:57, 11 March 2010 (UTC)

I'm sorry but this really doesn't sound like a homework question to me, more like a question arising from some piqued curiosity, from observing what happens to porridge in the microwave. I'd personally appreciate a good answer to this question - and my homework days are long gone! So would you please tell me, even if you won't tell the OP? --TammyMoet (talk) 10:06, 11 March 2010 (UTC)

It is important to understand this phenomena before mixing together substances that may cause one’s bench apparatus to undergo rapidly disassembly. So I will link to a pdf of a Dissolution Reactions Pre-Lab Script for your further edification - the answer is out there -enjoy! [4]--Aspro (talk) 11:20, 11 March 2010 (UTC)

(edit conflict) I agree with Tammy: this seems unlike a homework question. Here's my explanation, 66: when you heat something up, its temperature will rise to a different extent, given the same amount of energy, depending on the material. The energy needed to raise a certain amount of a substance by a certain number of degrees is called its specific heat capacity. Water takes about 4.2 joules to raise one gram by one degree Celsius, for example. When you cook the oatmeal alone, you only need to put in enough energy to heat up the oatmeal to the right temperature. You then add room-temperature sugar. But when you add the sugar into the oatmeal and cook the mixture, you've got to put in energy to heat up the sugar too - I'm not sure how its SHC compares to water or oatmeal, but still, it's going to mop up some of the energy that would previously have just heated the oatmeal. You need to put more heat energy into your food, to get it to the same temperature as your plain oatmeal, as a result. Since microwaves operate at constant power (energy transfer per second), you just leave it on for longer. In a nutshell: you have to heat up the sugar too. I could possibly have explained it without the SHC link but it would make interesting further reading for you. Brammers (talk) 11:54, 11 March 2010 (UTC)

Sugar is a poor absorber of microwave energy – instead it will take up heat from the water in the porridge. The specific heat capacity of the sugar will only take a few seconds worth of power (each spoonful = about 5 grams, or in other words a very, very small percentage of the whole total SHC). As the pdf suggests: the braking of bonds simply requires more energy than any energy released by the sugar molecules entering the solute and thus slows down cooking. However, the cooking instructions that I have seen on the side of the boxes always seem to be very generous as to cooking time required. Nor have I ever seen any suggestion to increase cooking time if sugar (or salt if you live in Scotland) is added first. Porridge isn’t so touch or go as a soufflé. The difference, I would imagine, is so small as to be unnoticeable unless set as a homework question. Maybe if one was cooking a very big goldilocks and the three bears size pot of it, it might be more noticeable but then microwaving that amount is a very inefficient use of power. I am asuming that this involves pre-steamed Quaker Oats type oatmeal, as ordinary rolled oatmeal takes so long to cook that the effect would be very difficult to measure. --Aspro (talk) 12:35, 11 March 2010 (UTC)

This is the original poster. This is not a homework question jeez. And it doesn't seem to be significantly colder after cooking the same amount of time, it just takes longer for the oats to expand and remains soupy longer. I was wondering why. 66.112.225.58 (talk) 05:18, 12 March 2010 (UTC)

In that case you may be witnessing what might best be understood by read Osmosis. In short: Sugar is hygroscopic. That means is will slow down the hydration of the oatmeal. By how much I don’t know, but if you prepare two bowls at exactly the same time, one sugared and one without, then leave both of them at room temperature. Both will hydrate whilst cold but you might find the sugared bowl ‘remains soupy longer’. So it might not be the cooking time that’s slowed but the hydration time that’s delayed. --Aspro (talk) 15:56, 12 March 2010 (UTC)

This may also be relevant to the fact that burning sugar does not work. ~AH1^(TCU) 01:00, 14 March 2010 (UTC)

expansion of the universe

If exponential expansion of the universe can not be ascribed to a polar force of gravity then how about a force like centripetal force; i.e., expansion being due to the universe spinning? 71.100.11.118 (talk) 09:49, 11 March 2010 (UTC)

Spinning relative to what? How do you explain the expansive force at right angles to the plane of the alleged spin? Cuddlyable3 (talk) 11:02, 11 March 2010 (UTC)

I'm continually amazed that people come up with these 'classical' ways to try to explain such phenomena. Do you really think scientists wouldn't have already thought of trying such a simple explanation? Of course they did! But it had some horrible flaw and was discarded in favor of the much less intuitive answer that we have today. If there were a simple "classical" explanation, then Occam's razor would certainly have us using it instead of the theory we currently subscribe to.

In this case, there are a bazillion problems - there would be coriolis forces (which we do not observe) - there would be the question of where the center of rotation would be - because the expansion of the universe would look very different from the perspective of someone out on the edge of this rotating object than to someone who just happened to be in the middle. The idea that the earth would just magically happen to be in the precise center of the expansion is just vastly too improbable and smacks of geocentricism - which went out the door in the 16th century! Also, the universe is three-dimensional (at least) - if it were spinning about (say) a "North-South" axis like the earth does - then the expansion would only be in a plane parallel to the "Equator" - but here in the real universe, all objects are moving away from us - including the ones vertically above and below us which would experience no centrifugal force in a simple rotating universe. There are (I'm sure) dozens of other reasons why this explanation won't fly. But since all it takes is one flaw to destroy a hypothesis - this one is busted and needs no further investigation. SteveBaker (talk) 13:01, 11 March 2010 (UTC)

All it takes to fix one flaw is some handy dark matter! Also, I like your tautology "[geocentricism] smacks of geocentricism". Aaadddaaammm (talk) 13:53, 11 March 2010 (UTC)

There is a simple classical (i.e., non-quantum) model of the accelerating expansion, and it does involve a "repulsive force" that's proportional to distance like the original poster imagines. That's not the problem. It's not hard to write down a law that fits the data; the question is, why that law? There are two terms in the force law; what physical principle leads to those terms being present and other terms being absent, and what principle sets the value of the constant factors on each term (the force constants G and Λ)? Quantum field theory does seem to predict a lower bound for a certain unitless combinations of those constants, but the prediction is ludicrously higher than the observed value; no one can find a reason why the real-world value should be so small. That's the problem.

Centrifugal force doesn't work because it would lead to expansion only perpendicular to the rotation axis, which isn't what's observed; but the other problems Steve mentioned don't exist. Rotating cosmological models don't have a center of rotation, just as the expanding models don't have a center of expansion. The rotation axis has a direction but not a position. But we wouldn't be any better off anyway if the data supported a rotating cosmology, because we still wouldn't know why it's rotating at that particular rate along that particular axis. If there were evidence that the universe was rotating, physicists wouldn't be asking, "hey, what if the universe is rotating?"—they'd be asking "why is the universe rotating?". And that's what they're asking now: why is the expansion accelerating? And, incidentally, why isn't it rotating? -- BenRG (talk) 20:49, 11 March 2010 (UTC)

Well whenever there is an explosion in the universe like a supernova things slow down and come to rest. I assume this is in part due to the gravity of the remnants in the presence of empty space. The classical model of exhaustion of the energy from the explosion fits and this is what you would expect from a theory like the Big Band. This leaves a lot of questions that require lots of speculation just like a blind man trying to work his way through unknown territory ahead.. One idea I can't find considered is the possibility the things like permissivity might change in opposition to thinking according to classical physics. The idea applied here would mean that a greater distance can be traveled in the same amount of time the further from the Big Bang in time and space the distance is or that gravity has a polar force we can call anti-gravity. What are the flaws in these theories other than that they step on the toes of the classical or current model? 71.100.11.118 (talk) 15:01, 11 March 2010 (UTC)

Always ask, is there a way to falsify my theory? Until you've done that you've not a scientific theory. Imagine Reason (talk) 15:35, 11 March 2010 (UTC)

If the universe were spinning, that would assume that the universe is spherical or something similar, but the current theory is that the universe is flat and has infinite volume so there is nothing for it to spin relative to except for perhaps time as space is contained inside (but then again time might not exist outside the universe or there may not even be an outside). ~AH1^(TCU) 00:30, 14 March 2010 (UTC)

nuclear candle

sir, can we model a nuclear fuel rod by using a common candle.many articles referring to CANDLE are found like. Potential of CANDLE reactor on sustainable development and strengthened proliferation resistance ETC

REGARDS SCI-hunter (talk) —Preceding undated comment added 11:07, 11 March 2010 (UTC).

CANDLE is in capital letters because it's an acronym, it stands for "Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy-producing reactor" - which has to be one of the most contrived acronyms I've ever seen! (But, I suppose, more memorable than a CASONFNDAPSDLOEPR reactor). Anyway, it has nothing whatever to do with wax cylinders with a bit of string up the middle. If you're still interested in "CANDLE reactors" then you can read more about them here. SteveBaker (talk) 12:45, 11 March 2010 (UTC)

Also known as a Traveling wave reactor --Aspro (talk) 12:51, 11 March 2010 (UTC)

From what I read - it seems to be a particular kind of TWR (ie not all TWR's are "CANDLE reactors" - but all CANDLE reactors are TWR's) - but the literature is very opaque if you're not an expert (and I'm certainly not!). SteveBaker (talk) 13:02, 11 March 2010 (UTC)

As both burn from one end to another ( like a candle) there is plenty of opportunity for confusion. I have put “CANDLE reactor” on the CANDLE disambiguation page but will hold off creating and redirecting it to the TWR article. --Aspro (talk) 13:10, 11 March 2010 (UTC)

okay i understand wax candles have no significance with a CANDLE in above reference i have made.But can i have any reference of modeling a fuel rod's nuclear reaction by a candle.Modeling neutrons in reactor by air around candle,the products of nuclear reaction by flame in a candle.Even if no proof is availaible,is that comparision apt.

Thanks in advance 218.248.11.214 (talk) —Preceding undated comment added 21:27, 11 March 2010 (UTC).

No, I don't think so. They are very different physical processes. --Mr.98 (talk) 22:57, 11 March 2010 (UTC)

I agree - there is really no kind of analogy at work here. SteveBaker (talk) 00:50, 12 March 2010 (UTC)

Shielding against Electro magnetic induction

How do you design a Faraday Cage to shield against interference from heavy C Band radio frequencies and what is the recommended material for the cage. —Preceding unsigned comment added by Shielding Buff (talk • contribs) 11:47, 11 March 2010 (UTC)

I believe a Faraday cage must be made of an electrically conductive material, so a wire mesh would be used. As for the ideal spacing of the wires, I will let others answer that. StuRat (talk) 13:33, 11 March 2010 (UTC)

The cage has to completely enclose what you are trying to shield. The rule of thumb is that the size of the holes is 10% or less of the wavelength. So for a 6 GHz C band wave, you would have a wavelength of 5 cm and a mess spacing of 5 mm. (Or do you mean citizens band ?) Thick copper plate would do the job, but steel plate would be cheaper. Security screen mesh or the fine grade of chicken wire should do. If you leave a hole, the em wave will travel over the surface and in through the hole via diffraction. So the tin foil hat is ineffective. Graeme Bartlett (talk) 18:33, 12 March 2010 (UTC)

Birds fall out of the sky?

What could cause the phenomenon described in this article? [5]

Aaadddaaammm (talk) 13:42, 11 March 2010 (UTC)

A large release of gas in a localized area, not enough oxygen for the birds to breathe. —Preceding unsigned comment added by Fire2010 (talk • contribs) 14:01, 11 March 2010 (UTC)

(edit conflict)Turbulent weather is typically the reason for raining animals. The following is an extract from the article:

Doppler Image from Texas showing the collision of a thunderstorm with a group of bats in flight. The color red indicates the animals flying into the storm.

In the case of birds, storms may overcome a flock in flight, especially in times of migration. The image to the right shows an example where a group of bats is overtaken by a thunderstorm.. The image shows how the phenomenon could take place in some cases. In the image, the bats are in the red zone, which corresponds to winds moving away from the radar station, and enter into a mesocyclone associated with a tornado (in green). These events may occur easily with birds in flight. In contrast, it is harder to find a plausible explanation for rains of terrestrial animals; the enigma persists despite scientific studies.

Zain Ebrahim (talk) 14:03, 11 March 2010 (UTC)

Who knows. turbulence of the type described above is vanishingly rare in Somerset, UK. As the article says it is reported to have happened happened in several places in the world in the last year or two. There seems to be a strong clue in the second paragraph where it is reported that many of the birds had broken wings, beak, legs and internal damage. In my experience it requires more than gravity to cause that sort of damage in a bird, particularly a smallish bird like a starling. The report contains a likely scenario for the horrendous carnage incident and the force of the birds flying downwards in a panicked attempt to evade a predator could account for the birds' injuries. What is more interesting is the end of the report where the witness describes what she found. ... "like a scene from a horror film like Hitchock's 'The Birds'", well, no, because all the birds were alive in the film. Richard Avery (talk) 14:09, 11 March 2010 (UTC)

The OP's link refers to a "whoosing sound", which makes me think of strong downward winds, perhaps a microburst. StuRat (talk) 14:35, 11 March 2010 (UTC)

Hmm some interesting possibilities. The predator evasion theory doesn't sit too well with me - I give these little birds more credit than flying into the ground to avoid being eaten. I noticed that bit at the end too, Richard - it's kind of the opposite of "The Birds". Aaadddaaammm (talk) 14:53, 11 March 2010 (UTC)

A lot of birds did (fictionally) die in the film, from smashing themselves into buildings and such to get at the people inside. Deor (talk) 17:44, 11 March 2010 (UTC)

A bird falling out of the sky is one of the imageries used in the Dutch film De Vierde Man to symbolise the death of the black widow's 2nd husband. --Kvasir (talk) 18:04, 11 March 2010 (UTC)

The bird of prey theory sounds silly to me, too. StuRat (talk) 17:56, 11 March 2010 (UTC)

Birds falling out of the sky is nothing, try | fish falling out of the sky. --Kvasir (talk) 18:00, 11 March 2010 (UTC)

Fish falling out of the sky is easier, that pretty much has to be from a waterspout. StuRat (talk) 18:03, 11 March 2010 (UTC)

Although this sounds logical, and is the answer usually resorted to by meteorologists and others attempting to explain away anomalous falls, most of the many instances of such fish, etc falls seem to have occurred with no waterspout, or even the sort of weather in which waterspouts commonly occur, in evidence. (I have no alternative explanation, but I am unconvinced from a long interest in Forteana that the waterspout one holds water.) 87.81.230.195 (talk) 22:10, 11 March 2010 (UTC)

Interesting. I was reading Kafka on the Shore and I couldn't explain why the author put in so much supernatural occurrances in the story. Maybe Murakami was inspired by Fort. It reminds me of Magnolia where it was raining frogs in the end. I concluded that coincidents and interconnectedness among characters were so great that the rain of frogs became plausible and remind us anything was possible. Back to falling fish in Australia, the incident occurred hundreds of miles from any river or ocean btw. --Kvasir (talk) 05:54, 12 March 2010 (UTC)

The smaller the object the farther it can be carried by an updraft. Sand grains are carried all the way across the Atlantic Ocean from the Sahara Desert to the Carribean. Small fish can probably be carried hundreds of miles, but a great white shark ? Not so much. StuRat (talk) 19:18, 12 March 2010 (UTC)

Why do birds fall out of the sky every time you walk by? Just like me, they long to be close to you. Deor (talk) 21:33, 11 March 2010 (UTC)

Could perturbations in the flow of the Gulf Stream have to do with it? ~AH1^(TCU) 00:24, 14 March 2010 (UTC)

Pressure in a liquid

Imagine a small particle inside a liquid. The pressure of the liquid will exert forces on it. There will be a downward force caused by the weight of the liquid above it, and an upward force caused by the water below the particle resisting the weight of the water above it, both forces equal in magnitude. My question is, are there any horizontal forces? I would imagine that the answer is yes, but I can't think of any way that the forces would arise... 173.179.59.66 (talk) 14:31, 11 March 2010 (UTC)

Yes, if the particle is floating in equilibrium, then the forces on all sides are equal. To help visualize this, think of a hole halfway up a can full of water: a stream is pushed out by the horizontal forces. Now think of two bricks with wet mortar in between. In gets squeezed out, right ? Well, think of the water above the hole in the can as one "brick" and the water below the hole as another. StuRat (talk) 14:39, 11 March 2010 (UTC)

That's exactly the explanation I'd give - but now I think about it, how do two exactly opposing forces (up and down) produce a force at 90 degrees to both? Aaadddaaammm (talk) 14:55, 11 March 2010 (UTC)

The stuff you are squeezing is a fluid (lots of small mobile particles), not a single solid. Consider if you have two spheres stacked but not quite perfectly aligned. As top one falls, it falls off to the side because the force (gravity, straight down) is acting a little sideways rather than straight at the bottom one. Another way to think is that the particles are all in constant motion in every direction. As the side comes closer, they cannot move that way but up/down is still available. And they may also bounce at an angle off the side, continuing to move up/down but coming back to center left/right. Fluid statics might have some info. DMacks (talk) 17:36, 11 March 2010 (UTC)

Boiling water

When boiling water, I've seen small bubbles form, sticking to the side of the pan. The same thing happens (sometimes) when I leave a glass of water sit for a while. Why is this? 173.179.59.66 (talk) 14:56, 11 March 2010 (UTC)

They are formed from the dissolved atmospheric gases coming out of solution. That’s why once formed they don’t grow any more. I.e., More oxygen and nitrogen can dissolve in cold water than warm at standard atmospheric pressure.--Aspro (talk) 15:01, 11 March 2010 (UTC)

see also nucleation157.193.173.205 (talk) 15:59, 11 March 2010 (UTC)

Is it true that freezing recently boiled water gives very clear ice cubes, for the reason Aspro mentions? --Dweller (talk) 15:58, 11 March 2010 (UTC)

Yes, boiled water does give clearer cubes for this reason; boiled distilled water is even better. In the days before domestic freezers, the companies that made large blocks of ice (which they then sold for people to put in their cool-boxes) kept ice clear by placing a tube in the center of the freezing can and bubbled air slowly through the water. This kept the dissolved minerals in constant circulation. Because it is the minerals and other foreign particles in water that serve as nucleation sites, the bubbles that did form, just floated up to the surface and burst. --Aspro (talk) 16:43, 11 March 2010 (UTC)

Did they want the ice clear just for cosmetic/marketing reasons? --Sean 13:13, 12 March 2010 (UTC)

A. I have no other reason to think that clear ice just looked nicer and gave the impression of being ‘pure’. Once one company did it I suppose the others had to follow suit. It guess this was not done for bulk ice used for railroad freezer wagons (for transporting meat). These used tanks of brine at each end and a fan driven off the axil to circulate the cold air within the wagon. Cloudy ice would not have mattered one iota. --Aspro (talk) 15:10, 12 March 2010 (UTC)

Okay, is there a physical explanation to why cold water holds more gas than warm water? 173.179.59.66 (talk) 16:11, 11 March 2010 (UTC)

This explanation is probably incomplete, but the basic reason is that warm water doesn't trap gas well. When warm, the water molecules are moving around more, with less static positions. The more energetic gas molecules have an easier time escaping under these circumstances. Cold water moves less, and is more organized in structure, so any gas that gets trapped has a harder time leaving. In both cases, the air molecules are occasionally dissolving, the only difference is that they are released more quickly by warm water, while cold water traps and holds them. —ShadowRanger ^(talk|stalk) 16:30, 11 March 2010 (UTC)

Cool, thanks. While we're on it, is there a significant pressure dependancy on a liquid's ability to trap gasses? 173.179.59.66 (talk) 17:20, 11 March 2010 (UTC)

Well, if the gas is under pressure, then it will dissolve more rapidly, and the final equilibrium will have more dissolved gas than water of the same temperature would have under lower pressure. In all cases it's a balance; how much gas is going in vs. how much is going out. —ShadowRanger ^(talk|stalk) 17:24, 11 March 2010 (UTC)

This sounds like some great potential content (if we can WP:V to get to the real underlying reasons) for Solubility#Factors affecting solubility. DMacks (talk) 17:27, 11 March 2010 (UTC)

I can't let a gas-coming-out-of-solution thread go by without linking to the fascinating Lake Nyos disaster. --Sean 13:17, 12 March 2010 (UTC)

On the subject of water, ice and important gases trapped therein: methane hydrate.--Aspro (talk) 15:16, 12 March 2010 (UTC)

Temperature of Diet Coke

I like Diet Coke. I normally drink it from plastic 2 litre bottles. Sometimes from 330ml cans. Occasionally (very occasionally) from those dinky glass bottles you see in American films and soaps, but are rarely sold here.

Anyway, it's my perception that Coke from glass bottles and cans is considerably colder when I drink it than it is from the plastic bottles. This, of course, all from the same fridge and the same position in the fridge.

Is this a flaw in my perception or is there some reason why it may be true? I had considered that it might be the volume of the container, not just its material that's the issue, but hey, you're the Scientists. --Dweller (talk) 15:08, 11 March 2010 (UTC)

Have you tried transfer some from each container into a couple of the same type of drinking vessels and then judging? It might be that your lips on the lower heat conductive bottle is affecting your perception.--Aspro (talk) 15:17, 11 March 2010 (UTC)

Interesting. I don't drink directly from the plastic bottle, but often drink direct from the can. So, I should pour from a plastic bottle into a chilled empty can, for a rigorous comparison? --Dweller (talk) 15:39, 11 March 2010 (UTC)

Maybe ask a friend to pour some coke from a chilled can into one glass and some from a chilled plastic bottle into another identical glass. Then you taste each and compare. I think that would be rigorous enough. Zain Ebrahim (talk) 15:43, 11 March 2010 (UTC)

I ask a friend to pour some

Coke from a chilled can into one glass and some Pepsi from a chilled can into another identical glass.

Verdict - Chilled Coke taste better to me.

and again

Coke from a not chilled can into one glass and some Pepsi from a not chilled can into another identical glass.

Verdict - Not chilled Pepsi taste better to me.

Conclusion - Chilled Coke and not chilled Pepsi.

manic

Would it be double blind if the friend marked which glass was which (say a sticker with #1 for the can an #2 for the bottle or vv) and left the room before you entered? Googlemeister (talk) 15:46, 11 March 2010 (UTC)

If you look at the three-dimensional clay model of the sensory homunculus ( just over half way down on this page), you will see that the lips contribute a great deal of the sensory information and so could over rule neural pathways in other parts of mouth and oesophagus. [6] This is why holding a piece of pair under the nose of someone who is blindfolded and whist giving them a slice of apple to eat. They will report that they are an eating pair because smell tends to over rules the sense of taste. (do they do these types of experiments in skools any more?)--Aspro (talk) 15:54, 11 March 2010 (UTC)

Here's a link to just the pic: homunculi.jpg. StuRat (talk) 18:12, 11 March 2010 (UTC)

All this talk about double-blind tests ... what's wrong with using a thermometer?157.193.173.205 (talk) 15:58, 11 March 2010 (UTC)

I thought someone would ask me that. Thermometers don't get on with me. I've never had a thermometer for home use that was both readable (mercury thermometers for me are the Emperor's New Clothes; so are Magic Eye pictures.) and reliable (the electric-stick-in-your-ear one we recently bought at great expense and fanfare resolutely refuses to give the same reading twice. We tend to take an average of three). --Dweller (talk) 16:02, 11 March 2010 (UTC)

I can confirm at least that Magic Eye pictures do "work". They aren't that exciting, but you really can, with some effort and unpleasantness, see realistically 3D images in them. Woooo. No comment on thermometers. --Mr.98 (talk) 01:58, 13 March 2010 (UTC)

You are comparing drinking from a chilled glass bottle or chilled can with drinking from a glass at room temperature, and you wonder why one feels colder than the other? Perhaps it is because the can is chilled but the glass is not? --Normansmithy (talk) 16:07, 11 March 2010 (UTC)

Okeydokey, I'll chill the glass and see. Thank you. --Dweller (talk) 16:12, 11 March 2010 (UTC)

Let see if I can guess the next question: Help! How do you un-stick a lip that's got frozen to a glass?!!!--Aspro (talk) 16:17, 11 March 2010 (UTC)

Well? !! What’s the answer Dweller? Or have you suffered a brown out?--Aspro (talk) 18:54, 11 March 2010 (UTC)

I have a feeling I must be missing something here or this is too obvious. Glass and metal have much, much faster thermal transfer rates than everyday plastics. When you touch the plastic lip of the 2L bottle to your mouth very little heat will be lost from your body. On the other hand, a metal or glass container will act as a kind of heat sink and provide you with a much cooler mouth feel. 64.235.97.146 (talk) 19:30, 11 March 2010 (UTC)

Yes you hav emissed something: the first reply!”It might be that your lips on the lower heat conductive bottle is affecting your perception.”--Aspro (talk) 21:16, 11 March 2010 (UTC)

If you don't have a scientific measure of the actual temperature of the liquid then it's likely that what's happening is that those very large bottles are getting cold on the outside and (let's say) for about an inch into the liquid - but that the majority of the liquid in the center simply isn't getting cold by the time you take it out of the fridge to drink it. The cans and bottles not only have smaller amounts of thickness of liquid for the fridge to chill - but also they both conduct heat better than plastic, so the contents get cool faster for that reason too. The way to test this supposition is to try drinking from one of the small 16oz plastic bottles that coke sometimes comes in. In that way you'd be controlling all aspects of the experiment except the volume of the container. SteveBaker (talk) 00:45, 12 March 2010 (UTC)

someone above said "Maybe ask a friend to pour some coke from a chilled can into one glass and some from a chilled plastic bottle into another identical glass. Then you taste each and compare." saying that is rigorous enough. ahahahahahahaha. So hilarious. The real answer is just buy a fast eleoctronic thermometer, and alternatively put it into the two two vessels, and see if the temperature is different. The above was cute though :) 82.113.106.93 (talk) 13:23, 12 March 2010 (UTC)

The premise is that the temperature is in fact the same, but the human perception of the temperature differs. The above advice could be used to determine if it is the perception only, or if the actual temperature that differs. Googlemeister (talk) 14:00, 15 March 2010 (UTC)

Fermi problem: neurons vs. transistors

So, I was thinking the other day about the sheer number of transistors that a successfully replicating yearly (via their biological symbiotic species, humanity), and I got to wondering: are transistors the fastest-growing species of life on Earth? Certainly they are being pretty successful. But a professor recommended comparing like-for-(relatively)-like. Thus, I'd like to know if anyone could help estimate the relative numbers of 'operational' neurons vs. 'operational' (or still capable of operation) transistors on planet Earth.

I have no idea where to begin answering this question, but trust some of you might be able to Fermiment some figures.

Thanks, 130.209.241.193 (talk) 15:12, 11 March 2010 (UTC)

Hmm. I think your prof. has sent you off on a tangent, the successful answer of which, will add little to the sum of human understanding. --Aspro (talk) 15:28, 11 March 2010 (UTC)

This page from 2006[7] suggests 10^19 transistors were made per year in 2006, although this has probably increased by a few orders of magnitude. You could probably extrapolate. You could try and count the number of microprocessors and estimate how many transistors they are likely to have, but remember that far more microprocessors are in embedded applications than in personal computers (on the other hand a simple microcontroller may have 10^5 while a new Intel processor may have 10^9), and don't forget RAM. Neuron will tell you there are about 10^11 neurons in the brain, and world population has lots of statistics. --Normansmithy (talk) 16:22, 11 March 2010 (UTC)

If you want to extrapolate figures for the present day, Moore's Law will help you calculate the increase in transistors per device, and you can multiply this by the growth in the number sold. I'm sure you can guess rough death rates for transistors and neurons. --Normansmithy (talk) 16:31, 11 March 2010 (UTC)

You'd have to squint pretty hard to see transistors as a life form. They're being made by humans, not other transistors. Paul Stansifer 17:53, 11 March 2010 (UTC)

I have to agree with Mr. Stansifer above. I'm not really sure if there is a meaningful question here. Transistors are not a life form by any definition of which I am aware. Certainly they do not grow, reproduce, consume raw materials, produce localized decreases in entropy, nothing. I am quite open to the idea of artificial life, but a minor electrical component is not it, in my opinion. Nor is a neuron a species either, though it is alive. I suggest reframing your question, if possible. — Knowledge Seeker দ 19:10, 11 March 2010 (UTC)

Ditto; ditto etc., ... Good scientists (IMO) have been those who have been able to identify the questions that are worth answering. Might I suggest, you suggest to your prof. to “post here, ” his reason why you should waist ‘spend your limited time’ on this? Just take a step back and think... there are billions of more important avenues of inquiry and speculation. Think your prof. is doing you a disservice to encourage you to travel down this route, a route which yields no meaningful insight to anything. It can only produce a non-sequitur.--Aspro (talk) 19:39, 11 March 2010 (UTC)

surely this would make hydrogen the most successful lifeform? Hydrogen obviously isn't life, but nor are transistors. They exhibit none of the characteristics listed here.--92.251.227.109 (talk) 19:42, 11 March 2010 (UTC)

It's weak - but arguable. Transistors cause humans to make more transistors. That's more like a virus than a proper "living thing" - and their descriptions are held as memes rather than genes...but they spread in similar ways. Person A buys an iPhone, person B sees it and becomes infected by the meme - causing him to buy one and thereby cause another iPhone to be manufactured. Eventually, people become immune either because they already had one or because their minds become immune to an old, tired meme. The iPhone evolves into the iPhone-II. Survival of the fittest applies - so poor phone designs die and good ones reproduce. Yeah - it's a hell of a stretch.

But as of a few years ago, I recall that someone had figured out that the total amount of memory devices ever manufactured was not equal to the storage capacity of a single human brain. So even if you could consider them to be in some manner like a lifeform - they are horribly outnumbered. SteveBaker (talk) 20:14, 11 March 2010 (UTC)

On that note, prions and definition of life may be of interest. Fire, tropical cyclones, and even the Universe may potentially be considered forms of life based on its current definition. ~AH1^(TCU)

Free Particle

The free particle article only dealt with a particle of well defined momentum, so I thought I'd clarify a few things here, and get them added to the article, however I ran into problems with my understanding of the maths. This is quite elementary QM so I am a bit concerned by how trouble some it has been.

I guess this is a little bit of spot the mistake.

For well defined momentum, the momentum $p=\pm {\sqrt {2mE}}$, allowing us to define a propogation operator $U(t)$ where $\left|\psi ,t\right\rangle =\mathrm {U} (t)\left|\psi ,0\right\rangle$ defined by the schrodinger equation.

$\left|\psi ,t\right\rangle =\mathrm {U} (t)\left|\psi ,0\right\rangle =e^{\tfrac {-i\mathrm {H} t}{\hbar }}\left|\psi ,0\right\rangle =\int _{-\infty }^{\infty }dp\left|p\right\rangle \left\langle p\right|e^{\tfrac {-i\mathrm {E} (p)t}{\hbar }}\left|\psi ,0\right\rangle =\int _{-\infty }^{\infty }dp\left|p\right\rangle \left\langle p\right|e^{\tfrac {-ip^{2}t}{2m\hbar }}\left|\psi ,0\right\rangle$

thus

$\psi (x,t)=\left\langle x|\psi ,t\right\rangle =\left\langle x\right|\mathrm {U} (t)\left|\psi ,0\right\rangle =\int _{-\infty }^{\infty }dp\left\langle x|p\right\rangle \left\langle p\right|e^{\tfrac {-ip^{2}t}{2m\hbar }}\left|\psi ,0\right\rangle =\int _{-\infty }^{\infty }dx'\int _{-\infty }^{\infty }dp\left\langle x|p\right\rangle \left\langle p\right|e^{\tfrac {-ip^{2}t}{2m\hbar }}\left|x'\right\rangle \left\langle x'|\psi ,0\right\rangle$

since

$\left\langle x|p\right\rangle ={\tfrac {1}{\sqrt {2\pi \hbar }}}e^{\tfrac {ipx}{\hbar }}$

therefore

$\psi (x,t)={\tfrac {1}{2\pi \hbar }}\int _{-\infty }^{\infty }dx'\int _{-\infty }^{\infty }dp\,e^{\tfrac {ip(x-x')}{\hbar }}e^{\tfrac {-ip^{2}t}{2m\hbar }}\psi (x',0)$

given that the particle is initially localised at $x=0$, therefore $\psi (x,0)=\delta (x)$

$\psi (x,t)={\tfrac {1}{2\pi \hbar }}\int _{-\infty }^{\infty }dx'\int _{-\infty }^{\infty }dp\,e^{\tfrac {ip(x-x')}{\hbar }}e^{\tfrac {-ip^{2}t}{2m\hbar }}\delta (x')$

performing first the integral over p

$\psi (x,t)={\sqrt {\tfrac {m}{2\pi i\hbar t}}}\int _{-\infty }^{\infty }dx'\,e^{\tfrac {im(x-x')^{2}}{2\hbar t}}\delta (x')$

and then x

$\psi (x,t)={\sqrt {\tfrac {m}{2\pi i\hbar t}}}\,e^{\tfrac {imx^{2}}{2\hbar t}}$

thus the probability

$P(X=x)=|\psi (x,t)|^{2}={\tfrac {m}{2\pi \hbar t}}$

the probability distribution is independent of $x$, and infinite everwhere at $t=0$ despite the boundary condition that it was localised at $t=0$. Help! —Preceding unsigned comment added by 129.67.39.49 (talk) 16:10, 11 March 2010 (UTC)

Your inital state wave function is not normalized correctly, I don't think.Dauto (talk) 19:28, 11 March 2010 (UTC)

One thing that jumps out is that $\int _{-\infty }^{\infty }dx'\,e^{\tfrac {im(x-x')^{2}}{2\hbar t}}\delta (x')=e^{\tfrac {imx^{2}}{2\hbar t}},$ rather than 1. Rckrone (talk) 19:37, 11 March 2010 (UTC)

True, for some reason when writing I was thinking of $\delta (x-x')$, I have corrected the mistake.

I'm not sure if the math is right here or not, but it's worth thinking about what result you expect to get for this problem. If you start out with a particle truly localized at a point, then it's evenly distributed across the whole momentum space (it can't really be represented by a distribution at all). After any non-zero time t, the distance it would move is proportional to the momentum, so it would be evenly distributed across the whole position space (again not really representable with a distribution), so I don't know if you can expect a sensible answer. Rckrone (talk) 22:38, 11 March 2010 (UTC)

I think the math is fine. I get the same result. The classical analogue is infinitely many particles flying apart from a point with momenta evenly distributed in momentum space. The density falls off like 1/t. Total energy (or probability) is "conserved" inasmuch as it's always infinite. This also shows up in the low-density nonrelativistic limit of big bang cosmology (with the same 1/t falloff). To get nice time evolution you need to start with a nice normalizable wave packet, as in the example at the end of Wave packet#Mathematics of wave packets. -- BenRG (talk) 23:03, 11 March 2010 (UTC)

I haven't checked the math, but the result seems plausible. If you recall the Heisenberg uncertainty principle, no particle can have both definite momentum and definite position. If you insist that the particle is truly in a momentum eigenstate, then it must have equal and uniform probability of having any possible position. Or in the limit of truly infinite space, the "normalized" wavefunction goes to zero everywhere. Dragons flight (talk) 01:16, 12 March 2010 (UTC)

Ok, in that case can you help me understand the interpretation. I thought that due to uncertainty, asserting that at t=0 the particle is localized meant that by definition in p-basis the wavefunction included a non-zero probability for all possible momenta. So that any result in x-basis is allowed by heisenberg uncertainty (since nothing is known about the momentum). And thus I would have expected the delta function to spread like a guassian growing in width over time; as for a given x, the number of momentum eigenstates that permits the particle to have reached x grows with t. Also this fits with the recquirment that probability flows continuously; which the answer derived above does not seem to. —Preceding unsigned comment added by 129.67.39.49 (talk) 03:35, 12 March 2010 (UTC)

Your solution is essentially correct for all times except $t=0\,$. To see why that happens you should use a gaussian as intial condition instead of the delta function.

$\psi (x,0)=\left({\frac {2\pi }{\alpha }}\right)^{1/4}\left({\frac {\alpha }{\pi }}\right)^{1/2}\exp \left\{-\alpha x^{2}\right\}$.

That initial condition will converge to the delta function you used when the limit $\alpha \rightarrow \infty$ is taken, except for the extra normalization factor $\left({\frac {2\pi }{\alpha }}\right)^{1/4}$ that was missing from your solution (as a mentioned on my earlier coment). That factor cancels the infinity you found on your solution. If you use that initial condition and do a calculation similar to the one you've done before, you get

$\psi (x,t)=\left({\frac {2\pi }{\alpha }}\right)^{1/4}\left({\frac {m}{m{\frac {\pi }{\alpha }}+2\pi i\hbar t}}\right)^{1/2}\exp \left\{-\alpha x^{2}\left({\frac {m}{m+2\alpha i\hbar t}}\right)\right\}$

When the limit $\alpha \rightarrow \infty$ is taken the expression above coverges to your solution (times the extra normalization factor) for all times except $t=0\,$ when it converges to the initial condition. Dauto (talk) 16:29, 12 March 2010 (UTC)

What about the expanding gaussian? If you want to see the expanding gaussian you must keep second order terms in the expansion of the exponential argument.

$\psi (x,t)\sim \left({\frac {2\pi }{\alpha }}\right)^{1/4}\left({\frac {m}{2\pi i\hbar t}}\right)^{1/2}\exp \left\{-\alpha x^{2}\left({\frac {m}{2\alpha i\hbar t}}\right)\left(1-{\frac {m}{2\alpha i\hbar t}}\right)\right\}$

And we can now get the expression for the probability

$P(X=x)=|\psi (x,t)|^{2}=\left({\frac {2\pi }{\alpha }}\right)^{1/2}\left({\frac {m}{2\pi \hbar t}}\right)\exp \left\{-{\frac {m^{2}}{2\alpha (\hbar t)^{2}}}x^{2}\right\}$

Which has the gaussian you were looking for. Dauto (talk) 03:32, 13 March 2010 (UTC)

Too much Potassium in diet

what are the negative effects of having too much potassium in one's diet? Also, are there are any negative effects of having too much chlorine in one's diet?--92.251.227.109 (talk) 19:34, 11 March 2010 (UTC)

Not sure about too much potassium in the diet, but Wikipedia has an article on Hyperkalemia, which is too much potassium in the blood. Does that article help? Zain Ebrahim (talk) 19:43, 11 March 2010 (UTC)

See Potassium_chloride#Biological_and_medical_properties. --NorwegianBlue ^talk 19:44, 11 March 2010 (UTC)

I already read that article, but it only talks about overdoses, not simply consuming more than you should.--92.251.227.109 (talk) 19:48, 11 March 2010 (UTC)

Chlorine in the diet is always in the form of compounds ( chlorine is too reactive to exist in it’s atomic form). Most of them are better avoided ( I avoid over generalizing by calling them all toxic). I think ( off the top off my head0 that too much potassium will just be pissed out. Although pottasium nitrate ( for curing bacon etc.,) has been linked tio cancer .--Aspro (talk) 19:47, 11 March 2010 (UTC)

Ah right that's very helpful thanks! What would happen to someone with kidney failure who could not urinate, who took in a lot of potassium?--92.251.227.109 (talk) 19:48, 11 March 2010 (UTC)

That is indeed a problem. They try to limit their potassium intake, and also may use potassium binders, such as sodium polystyrene sulfonate. See Sodium_polystyrene_sulfonate#Medical_use. StuRat (talk) 19:55, 11 March 2010 (UTC)

If they can’t piss it out: Their potassium/sodium balance would be servilely compromised -is the short answer to that . Can you expand on that. Remember: we don’t give medical advice. --Aspro (talk) 19:58, 11 March 2010 (UTC)

Have you read Renal_failure yet? --Aspro (talk) 20:00, 11 March 2010 (UTC)

I hear Obama is trying to get something through congress to help people with medical problems the same way as here in Europe. Do you have to ask these questions because your American?--Aspro (talk) 20:06, 11 March 2010 (UTC)

I'm not American I don't have kidney problems. I just dined at a friend's who used a 1:1 mix of potassium chloride and sodium chloride instead of regular sodium chloride table salt and I got curious. Also I have my own opinions of government run healthcare services after some stuff the Irish government pulled (forced every insurer to pay a state-owned insurer money, forcing some companies out of the market).--92.251.227.109 (talk) 20:10, 11 March 2010 (UTC)

Here in the UK we have products under the such names as “Lo Salt” with 60% or less sodium. Remembering what I said about medical advice: Unless one has kidney, heart or diabetes problems, this modified form of salt should be OK. Even then, it depends on the individual case. In my view it is better just not to see a doctor in the first place-- ignorants is bliss- but from a doctor’s point of view “this behaviour is not very profitable” Large amounts of potassium salts will also stop the heart but no normal person will want to drink this amount. It ( the cardiac muscle) will just not be able to re-polarise – but that’s for another time. --Aspro (talk) 20:29, 11 March 2010 (UTC)

Erhummm.., I have just re-read that post above...
”I just dined at a friend's”

One can just imagine it.....”Heard you had 92.251.227.109 round for dinner last night... AND WHAT did he think of your culinary skills?

Hmm well! He thought my choice of table salt very interesting! Ho! Ho! Ho! --Aspro (talk) 20:54, 11 March 2010 (UTC)

I actually attended a lecture at Columbia University Medical Center recently given by nephrologist Dr. Len Stern, who spoke a great deal about the terrible effects of high potassium diets. He showed a graph of what is termed an "ideal protein diet" and how it results in a much greater potassium intake than is ideal. So, while I cannot describe the effects of such a diet and cannot comment on particulars, you may take the initiative and find Dr. Stern's email address from Columbia's website and ask him for the details. DRosenbach ^{(Talk | Contribs)} 00:47, 12 March 2010 (UTC)

Going by the amount of potassium found on food package nutrition data labels about 3.5 grams of potassium is required with a 2,000 calorie diet per day or about 1.2 grams per a 1 in 3 meal plan per day. 1.2 grams of potassium chloride when weighed out looks like a quarter teaspoon. since both potassium and chloride are part of your electrolytes they are required by your body. As a personal note when I eat foods that are low in potassium according to this recommended amount I get chest pain. When I add enough potassium to bring my meals up to the recommended amount the chest pains not only go away but I sleep like a rock. I'm also careful to be sure the potassium is completely dissolved and spread throughout the meals such as by dissolving it in water and then using the water to cook or as a solvent or even to stay hydrated throughout the day. This last item is important because potassium unlike sodium will produce lesions in tissue instead of helping lesions heal like sodium. 71.100.11.118 (talk) 02:40, 12 March 2010 (UTC)

Chemical compounds with many elements

What is the chemical compound with the most chemical elements inside it? --84.61.135.112 (talk) 20:34, 11 March 2010 (UTC)

It's probably not near the highest, but DNA must have quite a few. StuRat (talk) 20:44, 11 March 2010 (UTC)

DNA is a very complicated molecule, but it doesn't actually have too many elements in it. I think is just has Nitrogen, Oxygen, Hydrogen, Phosphorus, and, of course, Carbon. Maybe it has some sulfur in it too, but it only has about 5 or 6 elements at the most. --The High Fin Sperm Whale 20:50, 11 March 2010 (UTC)

I assume you mean distinct elements, as opposed to "atoms per molecule"? DNA definitely wins on the latter, but probably not the former. Nevertheless, I suspect a carbon-based molecule would win for overall diversity, since carbon chains allow for a near infinite number of attachment points. You'd need to construct it artificially, but you could theoretically stick most of the (non-noble) periodic table on a long enough carbon chain. —ShadowRanger ^(talk|stalk) 20:55, 11 March 2010 (UTC)

Fluoride is a very reactive halogen and will encapsulate most compounds . Is this the the tree your barking up?--Aspro (talk) 20:58, 11 March 2010 (UTC)

Of the top of my head it’s most things from Hydrogen to Uranium.--Aspro (talk) 21:01, 11 March 2010 (UTC)

If metal alloys are valid answers, one of those? Googlemeister (talk) 21:02, 11 March 2010 (UTC)

Here is a molecule (CAS #289501-11-7) with 9 different elements: C33 H40 Cl N O P S Si . I name: Phosphonium, [(3S,4Z)-4-chloro-3-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-5-(2-methyl-4-thiazolyl)-4-penten-1-yl]triphenyl-, iodide (1:1) 24.150.18.30 (talk) 02:17, 12 March 2010 (UTC)

And another (CAS # 807332-34-9), with 10: C76 H62 Br2 Cu2 N4 P4 Pt S2 . 2 Cl O4 Platinum(2+), bis[(5-bromo-1,10-phenanthroline-κN1,κN10)copper][μ3-[1,2-ethanedithiolato(2-)-κS:κS,κS':κS']]bis[μ-[methylenebis[diphenylphosphine-κP]]]-, diperchlorate (9CI)

I don't think that you will find one with much more than 10, but I'm also not sure how you would do an exhaustive search for it.24.150.18.30 (talk) 02:17, 12 March 2010 (UTC)

It depends on how you define a compound. There are many minerals, for example, with astoundingly complex crystal structures. Some varieties of Tourmaline for example have up to 15 elements. --Jayron32 04:37, 12 March 2010 (UTC)

I searched a crystallography database and the highest number of elements in one compound was 22: Johnsenite-(Ce) of the Eudialyte group and "Ca₂(Y_1.53Dy_0.10Er_0.09Yb_0.08Gd_0.07Ce_0.02Tb_0.02Fe_0.02La_0.01Nd_0.01Sm_0.01(PrEu)_0.01Ho_0.01Tm_0.01Lu_0.01)((Si_3.87Al_0.13)O₁₂)CO₃·H₂O" from "G. Giuseppetti C. Tadini M. Oddone, Neues Jahrbuch für Mineralogie. Monatshefte, (1989) p153". There were about a thousand hits with more than 10 elements, and 50 hits with more than 15 elements.

These things sort of push the traditional definition of 'chemical compound' a bit, since they often have flexibility in the proportions of certain elements that are chemically and/or structurally similar.

As illustrated by some of the responses above, there are many "proper" compounds without such flexibility (non-stoichiometry), especially in coordination complexes with organic ligands. These combine the huge variety of carbon-based compounds with metal atoms that can have many different atoms bonded to them simultaneously - often six, sometimes more.

Ben (talk) 15:28, 12 March 2010 (UTC)

Here's the complex with the most different elements that I could find on the Cambridge Structural Database: Eur. J. Inorg. Chem. 2007, 2721–2728: C₈₀H₁₀₃B₂Cl₁₆Co₄CsF₈N₁₂NiORu₃S₃.

Ben (talk) 15:34, 12 March 2010 (UTC)

Organic compounds probably tend to have fewer elements, as Methionylthreonylthreonylglutaminylarginyltyrosyl...glutaminylglutaminylserxisoleucine (C₁₆₉₇₂₃H₂₇₀₄₆₄N₄₅₆₈₈O₅₂₂₄₃S₉₁₂) contains many atoms but only five individual elements. Also, how can an element have a decimal subscript for their atoms, or is it similar to the empirical hypothesis that water could be H_1.5O? ~AH1^(TCU) 23:54, 13 March 2010 (UTC)

Addicts - do they prefer to be cured?

I've never been addicted to anything, except perhaps tea. Would an addict, such as an alcoholic, like to be perfectly cured and lose all interest in or cravings for alcohol? Or is their desire for alcohol so strong that they would prefer to stay an alcoholic even if a perfect cure is available? 78.146.0.232 (talk) 21:40, 11 March 2010 (UTC)

Before or after they are cured? Depending on the alcoholic, they may or may not be aware of the consequences of their alcoholism. And they may or may not have a reason for drinking; in many cases it's a form of self-medication for depression. If they are aware of the damage they are causing and lack an ongoing reason to drink, then clearly then most of them would presumably welcome a cure that removed all physiological and psychological cravings. On the other end of the spectrum, they might not, or they might return to alcohol even after the cure is applied, as the ongoing reasons for self-medicating have not been addressed. —ShadowRanger ^(talk|stalk) 21:45, 11 March 2010 (UTC)

Elaborating: By and large, people don't prefer being addicted. But if they have reason to quit, the pull of alcohol isn't overriding their free will all the time, or even for particularly long periods. The problem is that in normal circumstances, staying sober means the alcoholic must maintain perfect control at all times; one slip up can undo all their work. If a cure could be devised to immediately remove dependence, that would make it *much* easier to stay sober. —ShadowRanger ^(talk|stalk) 21:48, 11 March 2010 (UTC)

As an example of someone who might not take the cure: I know someone (details unspecified for privacy reasons, I'll use singular "they" to describe) who drinks about a liter of wine a day (down from two liters, which had been the usual amount for decades). I doubt they have been fully sober for more than an hour a day in over a decade. But they don't see any consequences from their actions, as their significant other is an enabler who denies there is a problem, and their siblings drink more than they do. On top of that, they grew up a victim of sexual abuse and have never come to terms with it. The wine is likely treating depression resulting from the abuse, and the consequences of the drinking are relatively minor (today, though the decreased inhibition led to some awful behavior when they were younger). Since they don't see a problem, and the drinking is treating an underlying condition, they might resist a cure. —ShadowRanger ^(talk|stalk) 21:54, 11 March 2010 (UTC)

Is there more alchohol in a liter of wine, or a 6 pack of beer? Googlemeister (talk) 22:02, 11 March 2010 (UTC)

Depends on the wine and beer, but generally wine is something like 11.5% alcohol and beer is something like 4%. A standard beer can is 12 oz of liquid, thus a six pack is some 2.88 oz of alcohol. A liter of wine (33.8 oz of liquid) is 3.89 oz of alcohol. So the wine wins in the alcohol content contest. But again, answers may vary depending on type of wine and beer, and amount of beer in the six pack. --Mr.98 (talk) 22:36, 11 March 2010 (UTC)

In the particular case in question, the wine of choice is a dry red wine, with 12.5-13% ABV IIRC. So the daily intake of alcohol is about 4.25 oz. One drink is usually considered to be about a half ounce of alcohol, so this is about 8.5 drinks. The reduction from 17 drinks per day to 8.5 does not appear to have affected the level of inebriation (low level, but noticeable, particularly into the early evening), so it's likely that the person in question's liver has been damaged such that metabolization of alcohol occurs more slowly. —ShadowRanger ^(talk|stalk) 23:32, 11 March 2010 (UTC)

The answer to your question is both. Yes they would like to be cured. Yes they have such a strong craving that they would like to continue to abuse it. That ambivalence is at the heart of any addiction when it has reached the point that the person recognizes it is hurting them. alteripse (talk) 12:10, 12 March 2010 (UTC)

Would your question apply only to substance addiction, or would it include addiction to non-substances such as Internet addiction? ~AH1^(TCU) 02:54, 13 March 2010 (UTC)

Mix 'n' Match genetic sequencing

Chimpanzees and humans, for example, are said to have 99% of their genes in common. Dodos and mammoths have some but not all of their genes available from dead specimens.

Would it be possible to replace the missing genetic material with material from a related living species such a a pigeon or elephant, and get a living creature as a result? If not, why not?

Is it currently technologically possible to synthesise a sequence of genes just from chemicals in a laboratory, put them in an egg, and get a living creature as a result? 78.146.0.232 (talk) 22:11, 11 March 2010 (UTC)

Well, you have two issues here. One is whether you can fill in missing spots of DNA. I am not particularly sure this is possible but I wouldn't put it totally beyond very clever computational geneticists who happened to be very lucky about what was missing. If it was something specific to the species, and you had no other samples, then I imagine you would be out of luck. If it were something common, then you are OK. The second is whether you can take that raw DNA and make a living creature out of it. At the moment, the answer is, "it's really hard," but in another fifty years or so it probably won't be so hard. The relevant article part seems to be Extinction#Cloning; see in particular the case of the Pyrenean Ibex, which was made un-extinct for a short amount of time, on the basis of one very good tissue sample. --Mr.98 (talk) 22:55, 11 March 2010 (UTC)

I've read some articles on genetic sequencing that claim an incredibly high success rate at reconstructing DNA from fragments. I believe similar proposals have been made to resurrect the Woolly Mammoth by filling in gaps in a reconstructed genome with DNA from an elephant, then replacing the DNA in an elephant embryo and bringing it to term in an elephant surrogate mother.[8][9] It's supposed to be possible, just extraordinarily expensive (Less plausible proposals involve using frozen mammoth sperm to impregnate a modern day elephant). Similarly, resurrecting Neandertals might be possible, but the ethical concerns make it highly unlikely to occur in my lifetime. A note: Dinosaurs died out far too long ago to leave DNA that could be reconstructed by the technique in question, so no, Jurassic Park won't be happening soon. —ShadowRanger ^(talk|stalk) 23:24, 11 March 2010 (UTC)

It's hard to believe that you'd have a problem here. Let's say that 99% of the DNA in your sample is destroyed. What that means is one of two things: EITHER...

1. 99% of cells have ruptured or something and have no useful DNA inside and the remaining 1% of the cells are intact...so just find a good cell and then use Polymerase chain reaction to make the stuff by the bucketful...OR...
2. Each cell only has 1% of it's DNA left intact...but if you take the DNA from a million cells, you can find any given stretch of the DNA in lots of different cells so all you need to do is to sequence the fragments and write some rather simple software to stitch it back into an intact strand.

I can't think of any but the most contrived set of circumstances in which you'd need to take DNA from another species. Just find another cell in the same creature - the odds of the same bit of DNA being missing from every single cell in your sample seems astronomically unlikely. The only way I could imagine there being "gaps" would be if a spectacularly large amount of damage had been done and the sample size was microscopic. SteveBaker (talk) 00:31, 12 March 2010 (UTC)

The sample size may indeed be microscopic, as in the Jurassic Park scenario, where the blood in the gut of a mosquito preserved in amber is the source. And, while dino DNA can't survive by being frozen like a mammoth's, that doesn't mean there's no way it could survive. Here's one possible case: [10], [11]. StuRat (talk) 00:54, 12 March 2010 (UTC)

The problem with that idea is that you have no idea what the DNA you find there is from. You could go to a lot of trouble and wind up resurrecting a Jurassic lizard or a frog or something! You'd have no idea how to turn the DNA back into a living animal because we have no concept of how to deduce what kind of animal you'd get from what kind of DNA - so you wouldn't have a way to know what kind of cell to implant it into - or what kind of animal to provide a surrogate womb. I suppose if the DNA was sufficiently similar to (say) a modern bird then you might maybe be able to guess that you have a dinosaur of some kind - but if it's similar to a modern reptile - then you might just have DNA from a Jurassic Gecko. Given the ratio of numbers of large dinosaurs versus small animals like frogs - the probability of that super-rare-mosquito-in-amber-stomach-contents being blood from a T-Rex are absolutely astronomically small. SteveBaker (talk) 16:02, 13 March 2010 (UTC)

While a T-Rex would be wonderful, I'd still think many biologists would consider a resurrected Jurassic frog to be quite a coup. Also, by the time the technology is at such a state that we could do this, I'd expect the reconstructed DNA genome to tell us fairly precisely what type of animal we have. StuRat (talk) 03:24, 14 March 2010 (UTC)

I see a couple problems with the idea of filling in the gaps of an extinct species with another:

1) If you have gaps in the extinct species, then how do you know that the missing DNA is identical to the donor species ?

2) If the species of interest has badly degraded DNA, you may only have tiny fragments left, maybe only a base pair or two each. With such small strands, it may be impossible to determine where each fits into the sequence, and thus to figure out where the gaps are. Just like decoding a cypher, you need sequences of a certain length to even begin the process. StuRat (talk) 01:18, 12 March 2010 (UTC)

The severity of Stu's first objection depends on whether the goal is a perfect copy of the extinct animal or a viable approximation. —Tamfang (talk) 22:06, 12 March 2010 (UTC)

It is indeed possible to synthesize DNA de novo; see our article on Mycoplasma laboratorium for the most ambitious project currently going. It might be conceivable to resurrect an extinct lifeform by inserting genes into a closely related living species, for example bringing back the passenger pigeon by editing the genes of an existing pigeon. For distant species it's almost certainly out of the question -- there are huge numbers of interactions between genes, and there are also commonly substantial differences in the non-coding DNA that lies in between the genes. Looie496 (talk) 22:34, 12 March 2010 (UTC)

A further problem, mentioned by Mr.98 above, is that the developement of a genome into a viable organism depends on its continuous and complex interaction with exactly the right actively co-operating environment (in the case of a mammal, its mother's womb), which provides exactly the right physical conditions, chemical substances and chemically (hormonal and enzymatic) cues at all times. This process frequently goes wrong even in normal circumstances, hence the occasional birth of deformed offspring and the frequent early death and reabsorbtion of embryos at an early stage (I believe that in humans this runs at around 30% of all pregnancies, most of which remain unsuspected by the mother). In the case of an extinct species sufficiently 'different' from an unextinct one as to be interesting, this environment is by definition not available, and it is very unlikely in most cases that any living species could approximate it closely enough to result in a viable organism, still less one that would not differ from the 'original' in phenotypically significant ways. 87.81.230.195 (talk) 03:56, 13 March 2010 (UTC)