Wikipedia:Reference desk/Archives/Science/2011 April 1

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April 1

milk

will putting milk thru a coffee filter remove radioactive iodine — Preceding unsigned comment added by Wdk789 (talk • contribs) 00:59, 1 April 2011 (UTC)

No. --Tagishsimon (talk) 01:04, 1 April 2011 (UTC)

why not — Preceding unsigned comment added by Wdk789 (talk • contribs) 01:29, 1 April 2011 (UTC)

Because iodine in milk doesn't form into large particles the size of coffee grounds. StuRat (talk) 01:36, 1 April 2011 (UTC)

The idea is that you can't separate radioactive iodine from normal iodine whithout the use of some very expensive equipment. Secondly, iodine is removed by chemical means which essentialy ruins the milk, rendering it undrinkable in any case. Plasmic Physics (talk) 01:41, 1 April 2011 (UTC)

what about a laboratory filter? — Preceding unsigned comment added by Wdk789 (talk • contribs) 01:45, 1 April 2011 (UTC)

I asked this here, and apparently it's hard to filter iodine. You could freeze the milk for about 2 months and 99.5% of the radioactive iodine will be gone by then. 70% will be gone after 2 weeks. Ariel. (talk) 01:54, 1 April 2011 (UTC)

To give an idea, as I've just added to the article, coffee filters pass particles under about 10 to 15 micrometers. Now by comparison iodine has a Van der Waals radius of 198 picometers (1.98 Angstroms). 1 micrometer = 1000 nanometers = 1 000 000 picometers, so the holes in a coffee filter are about 76,000 times larger than an iodine atom. Wnt (talk) 02:04, 1 April 2011 (UTC)

As stewed rat says, the iodine in milk is not present as crystals that can be filtered, it is dissolved. Similiarly, you can't filter table salt out of solution. Be carefull with your understanding of what filtration is. Plasmic Physics (talk) 02:13, 1 April 2011 (UTC)

Perhaps I should offer a bit more background for clarity. It's very common in research to encounter a .22 micron (220 nanometer) filter, which is still 1000 times larger than the iodine atom. By that point it gets quite hard to pass large amounts of fluid (depending of course on the amount of sediment). At smaller sizes molecular sieves are used, but generally in a different way - because it's no longer practical to wait for everything to pass through, instead they delay the molecules that can pass through them as they're dripped through in chromatography. When you get down to that scale, you generally rate them by the size of the molecule that can go through, such as 1000 daltons. Iodine is smaller than even that! Animals are equipped with gap junctions that work more like traditional filters though, because the cells with them are only 4 nm apart, the time delay isn't a big deal. (There are also tight junctions between cells that work like filters with a size that sometimes can be regulated).

But when you get down the the size of atoms, materials made out of atoms are weird to filter with. You can see ion channels set to pass specific sizes, but which won't pass anything larger or smaller than what they're set for. There's even a specific iodide channel in the thyroid,^[1] but alas we don't have an article for it. And if you go smaller than that - well, a filter that passes half of one of the smaller atoms won't pass anything; besides, any two surfaces half an atom apart are either going to spread out and accept solvent between them, or stick together and be held by Van der Waals forces.

The talk of biological channels suggests a possible practical solution, though I don't know if it works: live kelp and other seaweeds absorb iodide into themselves with great avidity, and one could hope that they might suck up radioactive iodide if left in milk for some time (before, presumably, dying) ... unfortunately you have to have a source of clean, live seaweed to start with! Wnt (talk) 02:50, 1 April 2011 (UTC)

Would you still be inclined to drink the milk following this method? Plasmic Physics (talk) 03:55, 1 April 2011 (UTC)

Well, it depends how desperately I want "cold" milk. And it's a proposal for an experiment, not a guarantee of success. ;) Wnt (talk) 05:24, 1 April 2011 (UTC)

In honor of the day, could the iodine in milk be reacted with ammonia to form nitrogen tri-iodide crystals, which might be more readily filtered out of the milk? Edison (talk) 04:00, 1 April 2011 (UTC)

I like the taste of ammonia even less than kelp. Plasmic Physics (talk) 04:10, 1 April 2011 (UTC)

a old civil defense movie said radioactive fallout was the size of table salt, why couldn't i filter it? would a activated charcoal filter work? what about this filter http://www.parowanprophet.com/Nuclear_War_Comes/water_filter_instructions.htm — Preceding unsigned comment added by Wdk789 (talk • contribs) 06:07, 1 April 2011 (UTC)

That movie is obviously... wrong. Fallout can be any size, fallout includes material of any size material, light enough to be carried by the wind. Is the iodine present in the milk as a result of fallout or a contaminated food cycle? Plasmic Physics (talk) 07:39, 1 April 2011 (UTC)

Think! If it was the size of table salt, how would it get into your milk at all, staying that size? 95.112.203.81 (talk) 10:53, 1 April 2011 (UTC)

Even if it's the size of table salt, it will dissolve in the milk. Filtering only works for particles which stay together, and don't dissolve. --87.169.34.172 (talk) 20:56, 3 April 2011 (UTC)

fallout, i think — Preceding unsigned comment added by Wdk789 (talk • contribs) 08:00, 1 April 2011 (UTC)

It's not fallout. A normal reactor makes iodine as it runs. If containment is breached (and the fuel melts) the iodine basically just evaporates into the air, so the particles are the size of atoms. In a bomb with fallout, sand and debris get irradiated and then the dust goes everywhere, it's different. Ariel. (talk) 10:43, 1 April 2011 (UTC)

With milk, I should be worried more about Strontium-90 because biologically it behaves like Calcium and has a much longer half life time. But I don't see how it should be distributed in larger amounts through the air. It is more likely to be washed away into the sea. 95.112.203.81 (talk) 11:09, 1 April 2011 (UTC)

Also, it should be noted, both iodine and coffee are brown. Coffee filters are designed specifically to pass brown liquids. As a test, take cream directly from the fridge; you will see that most of it won't pass through the coffee filter. Good <ahem> day. 71.95.147.208 (talk) 21:15, 1 April 2011 (UTC)

so would this work http://www.parowanprophet.com/Nuclear_War_Comes/water_filter_instructions.htm — Preceding unsigned comment added by Wdk789 (talk • contribs) 03:08, 2 April 2011 (UTC)

No, but that's not the whole of the truth. It surely won't work with milk. The instructions make up a very crude kind of ion exchange device. If there was heavy fallout from a nuclear bomb and you have no other water than freshly contaminated surface water then this might be a last resort. If you have access to water from a well then this has already been done naturally as the water seeps through the ground until it appears in the well. 77.3.139.229 (talk) 08:43, 2 April 2011 (UTC)

Our nearest neighbouring solar system

What is the nearest solar system to our own, and based on present technologies, how long would it take for us to send astronauts there? Flaming Ferrari (talk) 01:13, 1 April 2011 (UTC)

About 40,000 years with our currently fastest spaceships, if I recall correctly. --Belchman (talk) 01:32, 1 April 2011 (UTC)

According to this 2006 article, Epsilon Eridani is the next stop for the most intrepid real estate agent, a mere 10.5 light years away. However, our article states that the planet is "unconfirmed". Clarityfiend (talk) 01:31, 1 April 2011 (UTC)

The Proxima Centauri system is closest, but we have no way, with our current technology, to send astronauts there (alive). Also, we don't know if planets are present there. StuRat (talk) 01:34, 1 April 2011 (UTC)

I'm not an expert, but doesn't a solar system require a system of orbiting bodies, not just a star(s). Ergo, does a triple star with no suspected planets (Proxima Centauri) qualify? Plasmic Physics (talk) 01:45, 1 April 2011 (UTC)

I don't think we would be able to detect small planets. And how about asteroids, comets, etc ? What precisely is required to be a solar system ? StuRat (talk) 03:26, 1 April 2011 (UTC)

We can now detect planets that are pretty small, but only if they pass directly between the star and us (thereby dimming its light slightly). That's a low-probability occurrence. Looie496 (talk) 04:12, 1 April 2011 (UTC)

And saying 40,000 years with our fastest spaceships is misleading. We could design spacecraft that could get there faster (at a significant cost), but since we would still be talking about much longer then a human lifespan, we never bothered making something like that. Think about it like this. Our furthest mission we sent out was aimed at Pluto (5 light hours away). The nearest star is more then 7000x further. If the furthest you had to travel in your life was 1 mile, you wouldn't need to bother with a car or plane, you could make do with a bicycle and a wheelbarrow (which are far cheaper assuming you don't get one of those $5,000+ racing bikes). If you wanted to go 7000 miles away, then you might want to look into building some faster transportation. I would imagine 1% c would be possible with current technology if cost was not an issue. Googlemeister (talk) 13:09, 1 April 2011 (UTC)

You also need to taked development time into account. Even with unlimited funds, I don't think 0.01c would be possible in less than a few years. --Tango (talk) 18:23, 1 April 2011 (UTC)

Of course. We have the proven technology to build a building with a height over 2500 feet, but if we were starting to build one today, it wouldn't be done for at least a year. A 1% c spacecraft would be an engineering challenge greater then a tall building, but of course, in a different way. Googlemeister (talk) 14:17, 4 April 2011 (UTC)

And another problem is, if you designed, built and launched such a ship on it's multi-century journey, it would surely be passed by later, faster ships. This rather takes away any incentive to build the initial slow ship. StuRat (talk) 18:27, 1 April 2011 (UTC)

There have been good short stories about explorers heading out to a nearby star system in "cold sleep" only to wake up and find a prosperous centuries old colony. APL (talk) 01:05, 2 April 2011 (UTC)

That would seem preferable to the sleepers since most of the hard work of setting up the colony would already be done. Googlemeister (talk) 14:13, 4 April 2011 (UTC)

Googlemeister, I think you seriously underestimate the difficulty of the engineering involved. Even if cost were no issue, with current technology an attempt to build a craft capable of carrying humans to another star system would certainly fail. We don't know enough yet to design systems that can be kept operational and keep a human crew alive for such a long journey. We can barely manage 50% success at putting unmanned probes on or into orbit around Mars, and that is much easier. We need to learn a lot more about engineering spacecraft before such a long journey will be possible.--Srleffler (talk) 06:06, 8 April 2011 (UTC)

Jacob Barnett: amount of carbon created in the early universe

There's a 12-year-old prodigy who's got doubts about an aspect of big bang theory (check Google news today). Can anybody suggest what he means by this? (particularly the last two paragraphs -- the first grafs are fairly common):

"There are two different types of when stars end. When the little stars die, it's just like a small poof. They just turn into a planetary nebula. But the big ones, above 1.4 solar masses, blow up in one giant explosion, a supernova," Jake said. "What it does, is, in larger stars there is a larger mass, and it can fuse higher elements because it's more dense."

"So you get all the elements, all the different materials, from those bigger stars. The little stars, they just make hydrogen and helium, and when they blow up, all the carbon that remains in them is just in the white dwarf; it never really comes off.

"So, um, in the big-bang theory, what they do is, there is this big explosion and there is all this temperature going off and the temperature decreases really rapidly because it's really big. The other day I calculated, they have this period where they suppose the hydrogen and helium were created, and, um, I don't care about the hydrogen and helium, but I thought, wouldn't there have to be some sort of carbon?"

"Otherwise, the carbon would have to be coming out of the stars and hence the Earth, made mostly of carbon, we wouldn't be here. So I calculated, the time it would take to create 2 percent of the carbon in the universe, it would actually have to be several micro-seconds. Or a couple of nano-seconds, or something like that. An extremely small period of time. Like faster than a snap. That isn't gonna happen."

"Because of that," he continued, "that means that the world would have never been created because none of the carbon would have been given 7 billion years to fuse together. We'd have to be 21 billion years old . . . and that would just screw everything up."63.17.54.2 (talk) 03:33, 1 April 2011 (UTC)

I'll add to my own question. He seems to be saying that the earliest epoch of supernovae isn't early enough to have produced enough carbon to create planets by the time the earth was created, OR that the earliest epochS (plural) of supernovae wouldn't have cumulatively produced enough carbon.63.17.54.2 (talk) 03:41, 1 April 2011 (UTC)

Well, "earth made mostly of carbon" is his first mistake, it's only the 15th most abundant element. Looks like boy genius still has a thing or two to learn ;) lol.. (j/k) Vespine (talk) 03:58, 1 April 2011 (UTC)

I'm embarrassed that I didn't notice this big red flag -- obviously, the earth is "iron-centric" (so to speak) not carbon. But maybe the reporter transcribed him wrong or something -- maybe he's saying there aren't enough heavy elements in the big bang chronology? Otherwise, this is just embarrassing for him that he got quoted with such a huge error. This kid is phenomenally good at math ... he's very impressive. It's weird he could get wrong a basic fact like "amount of carbon in early planet formation." (Note: This is NOT an April Fool's Day joke -- you can look this up on Google.)63.17.54.2 (talk) 04:11, 1 April 2011 (UTC)

No i know, i did read about this kid, he did calculus by the time he was 8, sounds like a very clever kid, but i think the story is way over hyped. Carbon IS the 4th most abundant element in the universe, after H, He and O, but i'm not aware that this is a "problem". We have articles on Formation and evolution of the Solar System, Big Bang nucleosynthesis and Abundance of the chemical elements, I don't see anyone saying there's a discrepancy between what's observed and what's expected. Maybe there is, but I'll need more then a tabloid news story to convince me, whether the claim is made by a 12 year old or not. Vespine (talk) 04:17, 1 April 2011 (UTC)

Here is a Youtube video of the child in question: "Jacob Barnett talk about Einstein... And eats lunch". Now, with due respect (I mean, he is twelve) - the guy's not exactly out-doing Einstein. Really, he's just mumbling regurgitated jibberish that sounds like he just finished reading Chapter 3 of a Generic Pop-sci Cosmology book. Yes, it's fantastic that a guy this young is thinking about physics - but he's not exactly "innovating" cosmology as much as "misunderstanding" it. We get this sort of thing on the reference desk a lot. Loads of people are thinking about relativity and the formal mathematics that describe it; and loads of people find it to be a conundrum. And a few think they've resolved the conundrums by disproving modern theoretical physics. (See our RefDesk archives for innumerable examples). But this doesn't mean that all these enthusiasts are actually "smarter than Einstein." It's disappointing to see major media outlets like Time Magazine reporting that this is the new discovery that's going to shatter physics. Such reporting over-inflates a novice physicist's accomplishments. The kid's got a lot to learn - he may well develop a formal theory - but what we have right now is jibberish. Mr. Barnett has neither the necessary experience nor the access to the astrophysical data that would qualify him to make such sweeping assertions about the composition of stellar supernovae. If we were to subject his assertions to the proper scientific channels - that is, peer review in journals, and rigorous experimental and observational testing of his claims - the entire story would collapse. But, the media loves to take "boring" science topics and turn them into juicy human interest stories... Nimur (talk) 05:38, 1 April 2011 (UTC)

The kid is clearly confused. What's not clear is what is he confused about? He seems to be aware that larger stars release heavier elements when they explode but for some mysterious reason he is concerned about carbon's abundance. Dauto (talk) 06:32, 1 April 2011 (UTC)

I'm not sure exactly what he is trying to say is the problem, but he is clearly referring to the carbon creation bottleneck in big bang nucleosynthesis. Because there are no stable nuclei of mass 8, carbon-12 was not significantly created during the big bang. As a result, we assume that essentially all carbon in the universe had to come from supernova. He is correct that if the big bang were somehow slower, such that nucleosynthesis could last longer, then you could create appreciable carbon during the big bang. As far as I know though, there is no evidence of that (and at least some evidence against it). Dragons flight (talk) 07:06, 1 April 2011 (UTC)

Commenters elsewhere have suggested he's been coached by Creationists -- Creationists who (according to the commenters) include in their quiver of ignorance a "not enough carbon" arrow. His wikipedia page (!?) makes reference to a connection to a Christian school ... AND he's been celebrated on TV by one Glenn Beck. So maybe he's being exploited by "young-earth" morons.63.17.37.103 (talk) 02:16, 2 April 2011 (UTC)

Also, his family lives in Indianapolis -- a hotbed of ignorant fundamentalist Christians, as anyone can verify by going to lots of public places there and reading the inscriptions on the white trash's t-shirts.63.17.39.192 (talk) 07:55, 2 April 2011 (UTC)

See Jacob Barnett.63.17.37.103 (talk) 03:31, 2 April 2011 (UTC)

I did the prodigy thing long ago (sort of) - don't be fooled. The thing about mathematics is that it is quite easy to learn it quickly up to about the calculus level, provided you get good instruction to help you over the hiccups in understanding - to provide the step-by-step help of how actually to use the notation and work it to get a result. The way that kids usually learn it is simply inefficient - you just barely get into the swing of it in an hour, then you have half a week to forget what you learned, then you muddle through it the wrong way the next session and so on. I wish that schools would consider teaching groups of children the entire year's math class in a few weeks devoted entirely to that one subject, to improve efficiency. But standard instruction practices aren't so inefficient for learning about the real physical world, so those topics are more difficult for a prodigy to excel with. (the difference is that mathematical facts are connected, so if you learn 1, 2, 3, 4, and 5 in a day and practice working problems 1->2->3->4->5, you drill them all into your head at once; but physical facts are almost unrelated to one another) Moreover, to the degree that prodigies are good at devouring a book and regurgitating its contents, they are vulnerable to believe just pure balderdash when they read it - there's a lack of reasoned adult discrimination and skepticism about what sources to trust and which to recognize as obvious scams. Wnt (talk) 06:45, 2 April 2011 (UTC)

The question is "Can anybody suggest what he means by this?", NOT "Is he a genius?" or "What is your personal experience of having been (sort of) a math prodigy?" 63.17.37.103 (talk) 06:59, 2 April 2011 (UTC)

I think what he's saying^[2] is that he still hasn't read about Population III stars. So he thinks it would have taken an extra 7 billion years for the carbon to form to produce planets like ours (some hedging there; as quoted he is wrong about the Earth being made out of carbon, etc.; more likely something was left out).

From WP re Population III stars: "Their existence is proposed to account for the fact that heavy elements, which could not have been created in the Big Bang, are observed in quasar emission spectra, as well as the existence of faint blue galaxies." WHAT does this have to do with whether there was enough carbon 7 billion years ago to form the earth? Face it: The kid is being coached by "young-earth" Christian fundamentalists to spout a supposed contradiction in big bang theory. 63.17.39.192 (talk) 08:04, 2 April 2011 (UTC)

He was saying that the Big Bang was 21 billion years ago rather than 15 billion years ago (hmmm, that's not exactly 7...). Is that "young earth creationism"?? Wnt (talk) 11:35, 2 April 2011 (UTC)

No, he isn't. He's saying there's a big contradiction in the math, whereby the standard model shows 13+ billion years, but the supposed carbon content suggests earth would have to be 21 billion years old, and thus the Big Bang 28 billion. He's saying the math is phony -- as do the "not enough carbon" advocates of young-earth, in arguing AGAINST the Big Bang as an event. The point isn't the time that's passed, but the inaccuracy of the math that supports the standard model.63.17.33.200 (talk) 10:13, 4 April 2011 (UTC)

P.S. Jacob Barnett is up for deletion, if anyone has an opinion. Wnt (talk) 07:25, 2 April 2011 (UTC)

3D for one-eyed Jacks

Is there any 3D TV technology which would work for somebody with vision in only one eye ? StuRat (talk) 04:56, 1 April 2011 (UTC)

No. Is this an April Fool's joke? No current technology can synthesize depth perception in humans who only have one eye. We do not speculate about hypothetical technology on the Reference Desk. Nimur (talk) 05:29, 1 April 2011 (UTC)

As there are numerous monocular cues to depth perception, the question is quite reasonable, and your dismissal of it seems rather abrupt. -- ToE^T 11:04, 1 April 2011 (UTC)

Wiggle stereoscopy is one possibility, but it would probably yield headaches quicker than 3D glasses. -- ToE^T 11:13, 1 April 2011 (UTC)

Good answer. As an aside, many of the concerns about spending too much time watching 3D video based on binocularity is that current methods only use binocular cues, which trains the brain to ignore the monocular cues, since they don't work properly. SemanticMantis (talk) 13:47, 1 April 2011 (UTC)

You may also be interested in reading our Autostereoscopy article. While it does not specifically mention applicability to monocular 3D, several of the technologies would seem to apply. Has anyone here ever seen a Philips WOWvx screen which uses lenticular lenses? (Unfortunately, our Lenticular printing article gives a "morphing" example and not a "3D" one, but imagine such a thing with an LCD display behind it so that a different perspective is shown when you move your head.). -- ToE^T 14:29, 1 April 2011 (UTC)

Other possible technologies are Holography and Volumetric display (e.g. true-3D displays which use a 3D grid of light-emitting points). These produce an image that can be viewed from multiple viewpoints to "see around the corners". There are really 2 definitions of 3D displays: the limited stereoscopic sort where you can only see from 2 positions (one for each eye), or true 3D where you can actually move around an object (or equivalently, rotate it) to see multiple sides of it like examining an actual 3D object/sculpture. --Colapeninsula (talk) 13:22, 4 April 2011 (UTC)

Thanks for all the answers, so far. StuRat (talk) 23:31, 6 April 2011 (UTC)

Prevost theory of heat exchange

Prevost theory of heat exchange Statement & explanation pls.. —Preceding unsigned comment added by 114.79.154.72 (talk) 07:12, 1 April 2011 (UTC)

Early versions of the caloric theory of heat involved two "fluids" - a caloric fluid that was produced by hot objects, such as a fire, and a frigoric fluid that was produced by cold objects, such as ice. In 1790 Swiss physicist Pierre Prévost argued that there was only a single fluid involved - caloric fluid - and that cold objects cooled their surroundings because they absorbed more caloric fluid than they produced. See here and here for more details. Gandalf61 (talk) 08:30, 1 April 2011 (UTC)

parasite chain

I recently read the news that they discovered virophages, small viruses that can only replicate when they co-infect a cell with another virus. They basically function as parasites to that virus. When reading this I was wondering how long the longest 'parasite chain' we know is. Example: when a human is infected with a tapeworm, which in its turn has bacteria in its bowel, this would be a three-level chain. I know you have plenty of external parasites like lice, but in this case I am specifically referring to endoparasites, life within life.

I've been doing some quick google searches but that didn't turn up with anything, and wikipedia was no help either. Of course, since I am interested in the longest chain of parasites, liberty with the term parasite is warranted. Bacteria and viruses are also allowed. —Preceding unsigned comment added by 131.211.27.97 (talk) 09:07, 1 April 2011 (UTC)

I don't know, but a large parasite like Cymothoa exigua or Emerald cockroach wasp might help add a level to your chain. Ariel. (talk) 10:46, 1 April 2011 (UTC)

The longest chain likely involves Ichneumonid wasps. See a nice story about their lifestyle here: [3]. Note that you will find longer chains with parasitoids, which kill their host, compared to parasites, which do not. A parasitoid that targets parasitoids is known as a hyperparasitoid, so this class by definition has a length 3 chain. Googling /hyper-hyperparasitoid/ returns some hits, but many are from amateur blogs, and don't contain detailed species info. SemanticMantis (talk) 13:43, 1 April 2011 (UTC)

Pressure at the seabed

If you dropped a weighted 1 litre bottle or balloon of air into the sea above the Challenger Deep, by how much would it be compressed by when it eventually reached the seabed? After leaving it down there for a while to cool down, how close would this be to becoming liquid air? Thanks 92.15.8.176 (talk) 11:01, 1 April 2011 (UTC)

What temperature was the air before you dropped it? I have assumed 300K. By my calculations, the density of air at Challenger Deep temp and pressure would be 1208x greater then that on the surface. Assuming your balloon can tolerate this change (a bottle would not), it should be .827 mL at the bottom. I don't know if this would make liquid air since I don't have the appropriate graph handy showing the state of air at the various temps and pressures. Googlemeister (talk) 13:01, 1 April 2011 (UTC)

According to this, nitrogen cannot be liquified at temperatures above 147 degrees C, which is the critical temperature for that gas - as air is a mixture, things will be a little different but it suggests that the contents of the balloon (or squashable plastic bottle) will remain in a gaseous state. Mikenorton (talk) 14:02, 1 April 2011 (UTC)

Typo alert: the critical point for N₂ is minus 147 °C. The critical pressure is about 34 atmospheres, so at 1208 bar it would be a supercritical fluid rather than an ordinary gas (this is a gradual matter, but I doubt it would behave much like an ideal gas). –Henning Makholm (talk) 14:17, 1 April 2011 (UTC)

Thanks for spotting the typo, now fixed. Mikenorton (talk) 15:07, 1 April 2011 (UTC)

1208 bar was used with ideal gas properties. If the air starts to behave as a non-ideal gas at some higher pressure, then my volume is not going to be accurate. Googlemeister (talk) 14:52, 1 April 2011 (UTC)

(EC) The density of liquid air is about 870 kg/m³, which is about 710 times greater than the density of air, which is about 1.225 kg/m³ at sea level. But the article section Challenger Deep#History of depth mapping from the surface mentions a pressure of up to 1099 times the pressure at the surface (which is the same as air pressure at the surface). Boyle's law becomes increasingly inaccurate as the pressure of air approaches that of liquid air, but 1099 is a fair bit greater than 710, so it's fairly safe to say that a balloon full of air that's been pulled down to that depth would indeed turn into liquid air. 1 l of air at the surface would turn into 1/710 l = 1.41 ml of liquid air. Red Act (talk) 15:03, 1 April 2011 (UTC)

As indicated above, the contents under those conditions (the critical pressure for air being just over 37 atmospheres) would be a supercritical fluid, which is not a liquid in any normal meaning of that word. Mikenorton (talk) 15:40, 1 April 2011 (UTC)

I stand corrected. Red Act (talk) 04:26, 2 April 2011 (UTC)

The 1208 or 1099 bar down there makes the roughly 0 bar of space seem mild and harmless. If Red Act is correct, could there be pools of liquid air down there, with water floating above it like oil over water? 92.15.8.176 (talk) 15:15, 1 April 2011 (UTC)

I would expect it to mix into the water and actually be indistinguishable from what is usually described as "gasses disolved in water" at more familiar lower pressures. Roger (talk) 15:37, 1 April 2011 (UTC)

And even if it didn't, it would rise above the water, 870 kg/m³ being less dense than water (1000 kg/m³ at surface pressure, increasing very slightly with pressure). –Henning Makholm (talk) 15:59, 1 April 2011 (UTC)

As pointed out by others above, the ideal gas law will not be a good approximation at such high pressures. Van der Waals equation should work much better. Dauto (talk) 04:43, 2 April 2011 (UTC)

Butterfly effect

Consider going outside, flapping your hands violently and then wait for some months until CNN reports that some tornado has hit some particular town in the US. Then, if one assumes that flapping your hands caused the tornado, you could formulate this assumption as saying: "had you not gone outside and flapped your hands, that particular town would not have been hit by the tornado".

Let's look at this precisely. Consider the exact physical state of the Earth that corresponds to you going outside, flapping your hands, which evolves under time evolution to a final state corresponding to that town being hit by the tornado. Then we can consider an alternative initial state corresponding to you not going outside and flapping your hands, but everything else is left the same. Such a state would then not evolve to the final state where the town is hit by a tornado.

One can then object to this analysis by invoking quantum fluctuations. Both intitial states will actually evolve to some complicated superposition of "classical states". So, in both cases, you end up with a probability distribution over the possible states of the weather, and in both cases there is some probability that the particualr town will be hit by a tornado. Only if the probabilities are significantly different, can we say that flapping your hands outside caused the town to be hit by the tornado.

So, what does a fully fledged analysis from first principles show? Can the effect of flapping your hands be more dominant than the effect of quantum fluctuations as far as long range weather patterns is concerned on some time scale? Obviously, if you take the time scale too long, quantum fluctuations will dominate, take it too small and the effect of the hand flapping won't have led weather patterns to diverge much relative to the counterfactual initial state, so there may be some intermediary time scale on which there is a significant effect...

Count Iblis (talk) 16:03, 1 April 2011 (UTC)

No!190.148.136.60 (talk) 16:58, 1 April 2011 (UTC)

Yea, tornadoes don't form from slight air movements that grow over time. They start from temperature and humidity differences which cause supercells to form. So, while your analysis method seems reasonable, in general, it doesn't apply to this particular example. Perhaps a better example would be if you divert a small stream and wonder if this diversion will cause a new Grand Canyon to develop, or fail to develop. If you diverted the Colorado River too late, the Grand Canyon would have already formed, and, there being a big hole in the ground, water would have found a way into it to continue the erosion, in any case. Had you diverted it too soon, then, over time, as the course of rivers change, it would have likely find it's way back to a location where conditions were suitable for the formation of a Grand Canyon (not necessarily in the exact same spot, though). StuRat (talk) 17:37, 1 April 2011 (UTC)

The formalization of your question is something like the following: "Is the occurrence of a tornado Lyapunov stable with respect to a small perturbation of air caused by waving your hand?" I think most aeronautical engineers, global climate modelers, and complex systems theorists would say a resounding "yes", based on gut intuition (meaning that your hand-waving does not alter the course of the tornado's formation or non-formation); but to derive that gut intuition from first principles is downright impossible. In other words, most scientists will tell you the following: waving your hand had some effect on the weather. However, the effect was so small, that it is unlikely that it affected bulk air mass motion in a significant way; as a single event, your hand-waving activity did not alter the course of the weather. Read our Lyapunov stability article, read about techniques to mathematically model complex systems, and read about bifurcation theory, which formalizes the parameters that cause the outcome of a complex system to split into one of two states (e.g., "tornado happens" vs. "tornado does not happen"). As you can see, "affecting the system" by waving your hand is not synonymous with "causing a tornado." Nimur (talk) 21:28, 1 April 2011 (UTC)

Or read our article on the Butterfly effect, noting that the first paper on the effect was titled Does the flap of a butterfly’s wings in Brazil set off a tornado in Texas?. Our article explains why the answer could easily be yes. In short, I don't think the intuition of scientists who are familiar with chaos theory accords with yours. The basic reason is that atmospheric flow is very turbulent, and turbulence is generally believed to imply dynamical chaos, and therefore sensitive dependence on initial conditions (i.e., lack of Lyapunov stability). Looie496 (talk) 22:00, 1 April 2011 (UTC)

Admittedly, I am not an expert in the dynamic modeling of atmospheric weather phenomena. As Looie496 correctly points out, my intuition should not be interpreted as scientific fact. Nimur (talk) 22:37, 1 April 2011 (UTC)

In the OP's thought experiment, two different degrees of hand flapping are considered as alternative initial states. One can think of "degree of hand flapping as an input variable with a continuous range from "no flapping" which won't cause a tornado, to "super-gigantic hand flapping" which would manage to start a tornado. However the possible degrees of hand flapping are not continuous because they are quantised. Somewhere in the range there is a quantum step that makes the difference between tornado or no tornado. (This argument has to assume that thermal vibrations are deterministic.) Cuddlyable3 (talk) 12:30, 2 April 2011 (UTC)

The whole point of chaos theory is that perturbations, no matter how small, result in drastically different end states if you wait long enough than if those perturbations weren't there. As a weather system was where chaos was accidentally discovered, the Butterfly Effect is a nice catch-phrase illustration. Regardless of little consistencies and stabilities in your own town on a particular day, at some scale weather is chaotic, so you flapping your arms today would mean that, in a year or so, a tornado that was going to hit Kansas on Tuesday now hits it on Wednesday.

However, by the very same principle, there is no way to know, nor reason to care about, what would have happened had you not flapped your arms, for the reason that regardless of this, there was a tornado, and tornadoes happen regularly in Kansas. The very chaotic nature of weather systems gives it paradoxical stability - if you try to mess with the weather in a deliberate fashion, you will pretty much fail completely. (can someone help me remember what this is called, this chaotic/nonlinear resilience, which supposedly is featured into the London bus system?) SamuelRiv (talk) 07:35, 5 April 2011 (UTC)

Ok., but one should be able to say that the tornado wouldn't have been within some bandwith in time and space, had I not flapped my arms some time earlier. This assumes that the weather is exactly described by a deterministic model (which is chaotic). If we now take into account quantum fluctuations, then if you wait long enough after the arm flapping, you can no longer say that there is either a tornado or no tornado inside that bandwith, you have a probability for this, which is fundamental. The arm flapping may influence this, but this can be completely insignificant. So, for the statement to be true, one has to be sure that quantum fluctuations won't have washed out the effect of the arm flapping.

A dumbed down estimate can perhaps be give as follows. Since we consider thermal fluctuations to be deterministic, these are not relevant, so this suggests that it is easier to describe the system in terms of the molecules it consists of, instead of using some effective hydrodynamical description. In the classical description, you can say that the perturbation due to the hand flapping amounts to a shift in phase space of the system due to the displacement and change in velocity of a large number (n) of molecules.

The quantum fluctuations can be described in a dumbed down way as follows. You can think of phase space as being fuzzy, it is effectively divided in cells of volume h^3N, where N is the number of molecules. The effective uncertainty in a component of the position vector of a molecule is approximately the thermal de-Broglie wavelength of ${\frac {h}{/sqrt{mkT}}}$, while the uncertainty in the momentum components is ${\sqrt {mkT}}$.

Then, I think, we should compare the displacement in phase space due to the momentum change of the n molecules of 3 n m v to the displacement due to assigning each of the N molecules in the atmosphere a random uncertainty in momentum of magnitude ${\sqrt {mkT}}$, which amounts to a displacement of ${\sqrt {3mkTN}}$. Putting in tsome estimated numbers, I find that the latter distance is about 14 times larger, so this suggests that quantum fluctuations always dominate... Count Iblis (talk) 00:43, 6 April 2011 (UTC)

I see that I made a few mistakes here :( . I'll correct them tomorrow. Count Iblis (talk) 00:51, 7 April 2011 (UTC)

'Carbonating' a drink with N2O

Could a drink feasibly produced with nitrous oxide dissolved in it rather than carbon dioxide? I figure it wouldn't taste the same, but would the gas even go into solution?

Thanks, Daniel (‽) 17:00, 1 April 2011 (UTC)

Nitrogen is used to serve draught Guinness among other beers. --TammyMoet (talk) 17:24, 1 April 2011 (UTC)

Nitrous oxide is usually regulated. Medical-grade stuff is hard to get a hold of; almost everywhere else you can buy the gas, it will have a small amount of added sulfur to prevent huffing (a stupid, but common, problem). N2O has other hazards, including spontaneous decomposition and ignition. Finally, worth noting that CO2 works to form carbonic acid in solution (adding a sharp "tangy" taste); I don't think N2O will have that effect, but it can and does dissolve in water in small quantities. It is also common to see N2O in food as a whipped-cream propellant - the gas bubbles in and "aerates" the whipped cream. I'm not sure where those food processors and manufacturers get a hold of unadulterated gas - it's probably not easy. Nimur (talk) 17:49, 1 April 2011 (UTC)

Of course, other acids can be added. In the case of citric acid, it's probably better for you than carbonic acid, too. Also, does the N₂O form nitric acid ? StuRat (talk) 18:12, 1 April 2011 (UTC)

Whipped cream is made with Nitrous oxide if it comes from an can (Would not work with sour carbon dioxide). So drink a can of Whipped cream or by a small propellant bottle for a Whipped cream maker which looks ver similar to the ones used for making sparkling water.

.--Stone (talk) 21:17, 1 April 2011 (UTC)

The Henry's Law data for carbon dioxide and nitrous oxide are pretty similar: about 0.034 vs 0.024 for the solubility constant (respectively), and 2400 vs. 2700 for the temperature dependence constant. [4][5] I'm not so sure about the biological effects of having N2O coming out of solution in your stomach, however - it can't be buffered to a bicarbonate salt, and I haven't looked up relative anaesthetic potency. Wnt (talk) 11:47, 2 April 2011 (UTC)

I'm not sure where those food processors and manufacturers get a hold of unadulterated gas. Are you talking about the US? In Australia it's not hard for a catering or related business to buy food grade nitrous from a wholesaler. Vespine (talk) 23:19, 3 April 2011 (UTC)

List of nuclear reactors using MOX fuel

Hello, what is the list of nuclear reactors using MOX fuel in Japan? and in the world?--88.160.13.244 (talk) 18:54, 1 April 2011 (UTC)

Japan, as of January 2011: 1. Genkai 3, 2. Ikata 3, 3. Fukushima I 3, 4. Takahama 3 .[6][7] As of January 2011 there were 21 MOX fuel plants in France. I don't have other numbers handy. There are other MOX reactors in Belgium, France, Germany and Switzerland [8], as of 2009, at least. --Mr.98 (talk) 16:25, 2 April 2011 (UTC)

Info needed on Broyer Canyon, Brown County, Nebraska

Other than it's location [9], I can't find any info, such as it's history, and, specifically, who it was named for. Any help would be appreciated. StuRat (talk) 19:08, 1 April 2011 (UTC)

Also, going to the satellite or hybrid view, and zooming in as far as you can without losing the satellite image, there appears a white linear feature to the ENE of the canyon. This feature runs from the SW to the NE and looks to be man-made. It looks to be about 10 meters long. What is it ? StuRat (talk) 19:14, 1 April 2011 (UTC)

How about telephoning the Ainsworth Public Library and asking if their reference librarian can direct you to a book on local history? I've found that many small town libraries have local historians and/or local history book repositories that aren't published/available in the "outside world." As far as your mysterious white linear feature - well, the aerial photo is blurry, so it could be anything: a photographic glitch; a man-made structure; an exposed pipe or power line; a light-colored sand/gravel pit; it's not possible to tell from the aerial photo. Nimur (talk) 20:56, 1 April 2011 (UTC)

I'll second Nimur on checking the local library. As for the white object, it has some height to it, so I'd rule out glitch or depression - I'd say a building, or it's about the right size and shape to be a trailer, though I have no idea how it would've gotten there. Kmusser (talk) 17:28, 5 April 2011 (UTC)

Stanless Steel Grades

I've scaned several articals and charts pertaning to the various grades of Stainless Steel and could not find which grades of stainless steel a magnet will not stick to. If you could please E mail a chart that shows this or direct me to where I can view and down load a chart.

Thanks,

Peter Corcoran —Preceding unsigned comment added by 72.164.33.18 (talk) 20:22, 1 April 2011 (UTC)

Most austenitic steels will be non-magnetic, while most ferritic and martensitic steels will be magnetic. --Carnildo (talk) 01:39, 2 April 2011 (UTC)

300 series stainless has a higher iron content and is semi-magnetic. 400 series stainless is very slightly magnetic. To have an unnoticable magnetic characteristics, you would have to get nickel-chrome alloys like inconnel, hastalloy or waspalloy. The high nickel and chrome stainless steels are very expensive, though. They are aerospace materials that are used mostly for aircraft and spacecraft parts —Preceding unsigned comment added by 108.67.181.74 (talk) 04:04, 2 April 2011 (UTC)