Wikipedia:Reference desk/Archives/Science/2012 November 27

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November 27

forest extent in very ancient India

Hi, I`m interested in finding out the extent of forest cover in India ideally around 7,000 BCE (but willing to follow leads for a few thousand years either side of that) A map would be great but I can`t remember the name for this kind of map so am having trouble googling it. All pointers appreciated. Thanks. 184.147.123.169 (talk) 01:33, 27 November 2012 (UTC)

I doubt that the data exist to make comprehensive forest zone maps, but lake levels show that the monsoon was much stronger at that time than it is now, so you can expect that the forest zone covered most of the subcontinent. Even the Thar desert region had permanent lakes then. Searching Google Scholar for "holocene climate India" will get you into the literature, for what it's worth. Looie496 (talk) 04:12, 27 November 2012 (UTC)

Thanks very much, those search terms do help. 184.147.123.169 (talk) 01:27, 28 November 2012 (UTC)

You might also go about it from the other direction, look at these results for deforestation grazing india. μηδείς (talk) 17:41, 28 November 2012 (UTC)

Problems about determine habitable zone in 7.5 billion year future sun

I understand determining habitable zone in 7.5 billion year tip of RGB if difficult but I still have trouble understand why is it so difficult. The reasons is we don't know exactly how big the sun will be, the second reason is we don't know how bright the sun be. I thought calculate the luminosity is quite easy to determine It tell us to use the square root/square power rule. So 1000-3000 luminosity if you square root, the HZ is 45-60 AU. It is that easy. I do it is 3000 luminosity/45 AU square, the intensity is 1.xx just to play a wildcard. I still don't get the table What does Saturn (?) Uranus(?) or Jupiter (???) means. Is there anything else we need to know besides the luminosity and how big the sun will be in order to know the HZ. Do we know exactly how hot the sun will be and how much heat will the sun produce because I thought luminosity is the key idea to determine how much heat will star produce. When sun becomes a giant do me know exactly how hot the sun going to be, or what other issues about knowing it? --69.226.43.162 (talk) 02:09, 27 November 2012 (UTC)

We just had this exact question asked from Los Angeles in September: http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2012_September_18#how_to_figure_out_the_habitable_zones. Was that answer no good? Please let us know if the prior response was not helpful. μηδείς (talk) 05:50, 27 November 2012 (UTC)

Is just when a respondant said The main reason for uncertainty in the Solar System's habitable zone 7.6 Ga (billion years) from now is that we're not sure how much the Sun will expand when it reaches RGB, and exactly how bright it will be. he pointed out Jupiter and Saturn's could still be in HZ at that time. I tried to calculated it on my calculator I assume sun's expansion in 7.6 Ga is at least where Venus orbit is now, to at most where Mars orbit is now. The reason I think that is I never heard in my lifetime that Mercury will survive at tip of RGB, I didn't see the expansion of the sun's uncertainty make that much difference. I definitely know just because planets fit in HZ it doesn't mean the planet itself will be habitable that is quite obvious, I mainly describe the HZ by if the planets fit in habitable zone, not if the planets is actually habitable (it is not really that important).--69.226.43.162 (talk) 00:45, 28 November 2012 (UTC)

Neutron binding

Can two or more neutrons bind together via the strong nuclear force and become stable? From what I understand, a neutron is stable in an atomic nucleus because of the strong nuclear force generated by the protons and neutrons, but neutrons alone should also generate this force as well. So shouldn't they also be able to bind with each other and become stable? ScienceApe (talk) 03:48, 27 November 2012 (UTC)

That would be Neutronium. Our article describes observed and hypothetical properties of the various isotopes. In brief, two neutrons can form a strong attraction to one another, but cannot truly form a bound state. Someguy1221 (talk) 03:56, 27 November 2012 (UTC)

I thought neutronium is unstable outside of a neutron star's immense gravity field? ScienceApe (talk) 07:06, 27 November 2012 (UTC)

You're thinking of neutron degenerate matter. Neutronium can also mean a hypothetical element on the periodic table that would have atomic number zero, i.e. would be composed solely of neutrons. Double sharp (talk) 07:20, 27 November 2012 (UTC)

(edit conflict)Precisely, which is why no one has ever observed it directly in a laboratory. Although, you still have to decide what "neutronium" means – does it refer only to neutron-degenerate matter, or does it include "atoms" with an atomic number of zero? Regardless of what you call it, a system of just two neutrons will not form stable bonds through any means. And based on currently accepted models, the same goes for three, four, five, etc. What have been observed in the lab are very transient interactions between two otherwise free neutrons. Someguy1221 (talk) 07:20, 27 November 2012 (UTC)

For four neutrons (not just two), see Tetraneutron for more info. Clusters of three and five neutrons should not be bound, and should not exist for even a short time. Double sharp (talk) 05:05, 27 November 2012 (UTC)

Your two neutrons together is called a dineutron. Graeme Bartlett (talk) 11:36, 27 November 2012 (UTC)

But it appears it's not stable even though they are within the range of the strong force. Why is that? ScienceApe (talk) 17:25, 27 November 2012 (UTC)

Read Deuterium#Spin and energy for an explanation. Dauto (talk) 18:33, 27 November 2012 (UTC)

Diamond (thought experiments)

Theoretically predicted phase diagram of carbon

To keep it cheap and simple: If I have a pure diamond of the size of a soccer ball (D_SB) and

1. "Close to absolute zero" (i.e. space temperature) I increase the pressure on D_SB very, very, very slowly (to avoid heating) and uniformly until I reach pressures which are found in the center of suns. What will happen to the diamond structure?
2. I repeat the above experiment (with a second D_SB) without taking care of heat dissipation (lets say, we reach 5000-10000 °C). What will happen to the diamond structure? Thanks for answers. GEEZER^{nil nisi bene} 08:27, 27 November 2012 (UTC)

at 1 TP (10000000 atmospheres) it is predicted to form bcc-carbon and at high pressures metallic carbon could also exist. Graeme Bartlett (talk) 11:45, 27 November 2012 (UTC)

Slow compression: If the diamond does not change into bcc-carbon or metallic carbon, it will only be compressed. However, this does assume that the compression is exactly uniform (which it may as well be if it is very slow). If there are irregularities, they might shatter the crystalline mesh, as even the structural strength of diamond is no match to that kind of pressure. If the diamond changes its structure, say to bcc carbon, it may or may not form one new crystal, depending on the time it takes to form the bcc crystal.

The article on allotropes of carbon states that "There is an evidence that white dwarf stars have a core of crystallized carbon and oxygen nuclei." However, "it is more likely an exotic form of carbon." I take it as possibly degenerate.

Fast compression: There will probably be not much of a difference between different amorphous phases at that kind of pressure. Whether it is a liquid, a gas, or a plasma will not matter much. The carbon will be in a degenerated state of extremely high (relativistic) thermal motion and mean free path close to zero. However, if the compression is extremely fast, from zero to full pressure without any time in-between, chances are that you'd set off a carbon catastrophe. You should find a "volunteer" to do that for you, and be somewhere else when the experiment starts. Not "in a different room" or "in a different building." In a different city.

- ¡Ouch! (^{hurt me} / _{more pain}) 13:14, 27 November 2012 (UTC)

What exactly is a 'carbon catastrophe'? AndyTheGrump (talk) 15:06, 27 November 2012 (UTC)

Going from context (extremely fast compression of carbon), I'm assuming the meaning is setting off fusion in the carbon, and the 'carbon catastrophe' refers to the sudden start of carbon fusion in a white dwarf: carbon detonation. But I could be wrong of course. Fgf10 (talk) 18:18, 27 November 2012 (UTC)

Thanks Fgf10, that's the one. I think I had an iron catastrophe in the back of my head. - ¡Ouch! (^{hurt me} / _{more pain}) 09:12, 28 November 2012 (UTC)

Ah, I suspected as much, after thinking about it a bit more. Given that even a soccer-ball sized supernova might be a little, um, 'unfriendly', I can see why Ouch advises getting someone else to try it... AndyTheGrump (talk) 18:50, 27 November 2012 (UTC)

Being bored, I decided to calculate just how 'unfriendly' this would be! A regulation football has a circumference of 69 cm, translating to a volume of 5.5 l. A diamond this size, given a density of 3.5 g/cm², would weigh 19.4 kg. At a formula mass of 12.01, this means 1616.7 moles/football, or 9.7x10²⁵ atoms/football. Assuming the ideal case of all of these atoms fusing with their next-door neighbour, this leads to half that number of fusions. Carbon-carbon fusion has a number of options, but a quick look suggests that at least in stars, the most prominent reaction is the fusion to Mg, liberating 13.93 MeV each. All of these fusions in a diamond football, again assuming ideal case, will then liberate 6.8x10²⁶ MeV. So the bottom line? In a ideal case, your completely fusing diamond football will give you 25.9 kt of TNT equivalent. Call it a Fat Man with change (and a rapidly expanding Mg plasma and a load of gamma radiation), so yes quite unfriendly.... But a lot less than I was actually expecting! Fgf10 (talk) 21:47, 27 November 2012 (UTC)

Interesting calculation. So Ouch's 'different city' to be safe is probably about right for his football-sized diamond experiment. Since the yield is presumably proportional to the mass, the average engagement ring will only be capable of more local damage if detonated this way. I could probably do the maths myself, but maybe in the interests of romance, I'd best not... AndyTheGrump (talk) 05:19, 28 November 2012 (UTC)

Geezer: This is going O/T (for you asked about fast compression but not about the fast limit case) but meh. For some "real" yield, one could always add some crystalline deuterium. Pocket Tsar.

Andy: And you thought a divorce could end up messy... ;)

Since the next topic goes towards silicon compounds, we could investigate the yield of breast implants.

"Oooo, what a nice pair of WMDs..." - ¡Ouch! (^{hurt me} / _{more pain}) 09:12, 28 November 2012 (UTC)

Hehe, yes it's OT, but it's fun! An engagement ring? Say 2 carats? About 0.5 kt, still enough to ruin your day!

And Ouch? Silicones? That's going to be one hell of a calculation; silicon, carbon, oxygen and hydrogen? Way over my head! I'll stick to my dayjob, regenerative neuroscience is so much easier.... Fgf10 (talk) 09:50, 28 November 2012 (UTC)

No, no, not O/T ... I enjoyed reading the comments. They added color to thoughts about a tiny object in an otherwise cold universe... May even serve as excuse one day, if a Female requires attention in form of a diamond ring...  ;-) GEEZER^{nil nisi bene} 15:23, 28 November 2012 (UTC)

Hassocene

In 2008 there were plans at the GSI to synthesize the compound hassocene (Hs(C₅H₅)₂), the heavier homologue of ruthenocene and osmocene (see this presentation by Cristoph E. Düllmann). Does anyone have access to the results of the experiment? Was the experiment even conducted in the end? I haven't found any info on this. Double sharp (talk) 13:42, 27 November 2012 (UTC)

Nothing in SciFinder by that name or chemical formula. DMacks (talk) 19:24, 27 November 2012 (UTC)

I am fairly certain the Hassocene is the geological period from 1982 until 2000. μηδείς (talk) 03:34, 28 November 2012 (UTC)

The older archaelogical strata have a pretty solid Foundation layer, but towards the end there are some slowly-undulating areas of a weird silicone-like material. DMacks (talk) 04:04, 28 November 2012 (UTC)

<chortles> We're currently in the middle of the Hassocene-Beiberanian extinction event -- OBSIDIAN†SOUL 21:38, 29 November 2012 (UTC)

LOL. Is that related to the Bieberian Law of thermodynamics, that "in a closet system, gaiety can only increase with time"? - ¡Ouch! (^{hurt me} / _{more pain}) 07:12, 30 November 2012 (UTC)

Best ... reference desk jokes ... ever. μηδείς (talk) 21:57, 1 December 2012 (UTC)

walking vs running

which burns more calories? — Preceding unsigned comment added by PlanetEditor (talk • contribs) 14:46, 27 November 2012 (UTC)

Running. See [1] and [2]. Dismas|^(talk) 15:09, 27 November 2012 (UTC)

if they are done for the same duration. eg, walk for a day, run for a minute, then walking burns more.165.212.189.187 (talk) 18:31, 27 November 2012 (UTC)

Uh, that's not the same duration. Same duration would mean walk for a minute, run for a minute. Looie496 (talk) 19:17, 27 November 2012 (UTC)

That's a typo, I suppose. Anyway, does running/distance or running/time burn more calories than walking/distance or walking/time respectively? OsmanRF34 (talk) 20:18, 27 November 2012 (UTC)

Walking is simply a controlled fall, running requires lifting the body off the ground. The first is more efficient, and so burns fewer calories per distance. If you want to burn calories, rowing is the best low-impact all body exercise and the stair-master is the best low-impact calorie burning exercise. One gym I went to had to put a 20-minute limit on the stair master since some of the ladies were so skinny they were getting blown of their feet by the stage fans they used to cool the place. This does not constitute medical advice. μηδείς (talk) 03:29, 28 November 2012 (UTC)

Running for an hour definitely uses more energy than walking for an hour. Now running for a mile versus walking for a mile is a bit trickier, and might depend on the individual. The basal metabolic rate, which varies by the individual, must be considered, since the walker will take longer, and thus burn more calories in this way. So, someone with a high BMR might do better to go faster, to minimize calories burned in this way, while someone with a low BMR might want to go slower, to take advantage of the more efficient movement method. I suspect that, for the average person, a slow jog might be the most efficient method per mile. StuRat (talk) 08:31, 28 November 2012 (UTC)

That's a bit of special pleading StuRat. The person with the high BMR is not going to turn his off once he stops running--the BMR calorie consumption will continue over the same period in both exercisers. It's the difference in calories burned between running and walking the same distance that that matters. The BMR calories are going to be burnt no matter what at a rate of 24 hours per 24 hours. μηδείς (talk) 17:34, 28 November 2012 (UTC)

Power walking may expend more calories. ~AH1 ^(discuss!) 20:50, 29 November 2012 (UTC)

Mattress pad science

This might be the most ridiculous question so far posted but it's bugging me...

The wife and I have a thick (a couple inches) down pad that sits between the mattress and the fitted sheet on our bed. It is constantly sliding down the length of the bed so that after about a week, the pad is protruding off the foot of the bed by at least 5-6". And therefore, the pillows are also in a bit of a trench since there isn't any pad to push them up slightly. What causes the pad to slide down like this and so quickly? All we have to do is sleep on it and it moves down over the course of the week. Thanks, Dismas|^(talk) 15:01, 27 November 2012 (UTC)

If we first assume that your nocturnal motions induce small movements in the pad, we would expect the probability of finding the pad at a given position would follow a normal distribution. But you're reporting a systematic bias in one direct (footwards). I believe this is caused (in part) by the random walk the pad takes being constrained at one end but not the other. Random motions you induce in a headward direction are sometimes contained by the pillows and headboard, but not in the footward direct. So this induces a bias, and the pad's distribution is pushed footward. I confess I've always thought this process was called a drunk walk, because of the way an inebriate winds his way along the road - the walls of buildings constrain him, so rather than his position at any time being gaussian, random offsets tend to bounce him along one wall or the other. But we don't seem to have a drunk walk article, so I don't know what it's really called. -- Finlay McWalterჷTalk 16:02, 27 November 2012 (UTC)

Drunkard's Walk, which redirects to random walk. I've never heard it called "drunk walk" myself, but another redirect won't do any harm. Tevildo (talk) 23:24, 27 November 2012 (UTC)

Try this experiment: turn the mattress so the foot end is now the head end and see if it still happens, and then with just the pad. This will rule out (or not)surface features of the two materials like a lint brush goes easy in one direction but rough in the other.165.212.189.187 (talk) 18:35, 27 November 2012 (UTC)

I can't tell you why, but to stop it get some sticky velcro and stick it to the top end of the bed and pad, and the pad should stay put. Now if I could only find a way to stop my duvet from working its way down the duvet cover in much the same way as you describe! --TammyMoet (talk) 19:04, 27 November 2012 (UTC)

The shifting bedding can be simply due to the bed being slightly lower at one end, such that gravity is pulling you and your bedding downward whenever the lateral forces on the pad from your movements overcome the static friction between the pad and bed. It doesn't take a steep incline for this sort of thing to happen, and often times floors that appear level are actually not. I would try raising the apparent low end with some shims and see if that helps put a stop to the creeping pad. -Modocc (talk) 21:43, 27 November 2012 (UTC)

• This is very common, I have the problem all the time. The bedclothes ride down when you sit on the edge or side of the bed. You don't sit at the headboard. At night you can push away from the headboard, but you can't reall push effectively toward it. Hence the drunken walk away from the headboard. (Oh, and BTW, this doesn't even make it to the lowest third of ref desk question, let alone close to the stupidest.) μηδείς (talk) 03:20, 28 November 2012 (UTC)

Can separate universes be causally connected?

This is perhaps more of an issue of definitions, but I was arguing with my roommate last night about the idea of a multiverse. My position was that you could have two x-dimensional universes contained in a y-dimensional multiverse, and that these universes could theoretically exchange gravitons and be detected in this way (the manner of detection and interaction here isn't important), and that it makes sense to call each of these objects a "universe". But he was saying that if we can detect them at all then it's not another universe, it's just another part of our universe. In this case, what I'm calling a multiverse, he's just calling the universe. To him, a multiverse necessarily connotes entirely separate universes. Who has the more accurate definition, from a physicist's standpoint? Goodbye Galaxy (talk) 15:14, 27 November 2012 (UTC)

I am a physicist (at least, I carry the degree of one, which I obtained by battling other physicists in close quarters in the halls of a fine, accredited university). So, in principle, anything I say is "from a physicist's standpoint," even when I spout nonsense. It is my opinion that "multiverse" is a bunch of pop-science drivel. The term is ill-defined, and is primarily used to permit non-physical descriptions of hypothetical scenarios. For the sake of citing a reference, (as I've been drawn to the habit of spouting my opinions quite frequently this week), I'll recommend Richard Feynman's Six Easy Pieces, which I re-read recreationally during the Thanksgiving holiday. This book excerpts several of the best lectures from his course at Caltech. Feynman will fall back on this definition: physics is guided by experiment. Experiment trumps everything else. If you hypothesize a multiverse, or a Wakalixes, or whatever other ridiculous word you choose, you will have to describe what consequences you hypothesize. And then you will have to test for that consequence. In the absence of predictive hypothesis, corrected by experimental result, science degrades into Aristotelian drivel. So, ask yourself the more important question: if, as you hypothesize, there are some set of distinct regions of interacting matter, how would we test for that? And then, construct the test, and draw a conclusion, and let the language-experts fight over the proper name for your result. Nimur (talk) 16:01, 27 November 2012 (UTC)

That's a pretty non-answer, you have to admit. It is recognized as completely valid within the scientific community to spend some time thinking about abstract, not-yet-measurable things, with the idea that such things are what give you the ideas as to what kinds of experiments might be interesting to conduct. There are set technical definitions of universes within the multiverse theories, which is what the OP is asking about. He or she is not proposing a new theory of multiverses and doesn't probably need to be told that experimental results are important for determining which of many competing theories is actually true. Nobody disputes that experiments are necessary for determining validity between theories, but experiments are not the only source of inspiration for theories, and indeed many theories are in fact the source of inspiration for experiments. --Mr.98 (talk) 16:09, 27 November 2012 (UTC)

Most "multiverse theories" do not make scientific predictions. There is a difference between thinking abstractly, and thinking without any contraint whatsoever; this is what distinguishes physicists from religious teleologists. Nimur (talk) 16:12, 27 November 2012 (UTC)

Apparently it doesn't distinguish them, under your model, since many physicists do find it worthwhile to think about such things. What distinguishes them from religious teleologists is, I would argue, something else. There is a grand tradition in theoretical physics of taking big leaps that don't as of yet correspond with any experimental outcomes. Some of them work, some of them don't. There's no need to take your professional angst out on an OP. --Mr.98 (talk) 16:16, 27 November 2012 (UTC)

My very non-physicists' understanding is that it really depends on which flavor of multiverse theory you're talking about. In some of them, I believe, the non-interactiveness is key to the definition of what a universe is. In some I'm not sure it matters. My conclusion would be, generally, that if you're not being extremely precise about which theoretical framework you're talking about, it doesn't make sense to try and be precise about the linguistic terms. The linguistic differences only matter if you are actually reducing them to technical definitions. --Mr.98 (talk) 16:15, 27 November 2012 (UTC)

If you start from the perspective of real observers like we are, who have access to only a finite amount of information (due to finite brain capacity), you get a totally different picture. There are then identical copies of us located in different universes. Because the copies are exactly identical, you can't say that you exist in either one or another universe, you are in all of them. The identical copies are the same w.r.t. to their memomories, their bodies can be in different states. So, if you are not bald, then the amount of hair you have is not exactly determined unless you have measured this.

Different people live in different sectors of the multiverse. E.g. given what I know, Nimur could have a big beard or not. In my sector, those two different Nimurs exist. But from Nimur's perspective, these two sectors are different, he is a different person in the two sectors. Count Iblis (talk) 18:18, 27 November 2012 (UTC)

@ Nimur, your answer was perfect, if maybe a bit too charitable. (Not only do they not make testable predictions, there's no evidence for them, and there's not even a coherent description of one.) But otherwise perfect. μηδείς (talk) 22:11, 27 November 2012 (UTC)

There is evidence. E.g., in quantum mechanics, time evolution is unitary, no deviations have ever been detected, so there is no experimental evidence for models that postulate a non-unitary collapse of the wavefunction. Count Iblis (talk) 22:30, 27 November 2012 (UTC)

Doesn't that mean there is no evidence? -- Jack of Oz ^[Talk] 23:14, 27 November 2012 (UTC)

You need a real collapse of the wavefunction to get rid of the quantum multiverse, so far there is no evidence for this. Quantum mechanics has so far survived every experiment designed to falsify it. Take e.g. the double slit experiment, you can verify that electrons don't go through either one or the other slit, both possiblities are equally real (we refer to this as a "superposition" of the two possible classical possibilities, it is often said that the electron goes to both slits as once, but it's misleading to put it that way).

The question is then why we don't see such strange things happening in the macroworld. You could postulate that there is a real wavefunction collapse that causes superpositions of different classical states collpase into one or the other classical state. But you don't need to make such assumptions, so-called decoherence leads to the emergence of a classical world at the macro level. Also, there is no evidence that a real wavefunction collapse happens (this is something that could be unambigously detected in experiments). Count Iblis (talk) 00:09, 28 November 2012 (UTC)

That's not really evidence, it's based on taking an interpretation as fact and then insisting something that we can neither formulate coherently nor detect must be going on because we are sure of our interpretation. That compares almost exactly to the argument for phlogiston, although that theory at least made testable predictions. μηδείς (talk) 03:15, 28 November 2012 (UTC)

And what happened in the past can just as well be considered as events that are not real but exist in some other realm with which we cannot intereact anymore. So, by your logic, we shoud prefer the interpetation that says that the past actually is fictitious. The alternative interpretation that it isn't is, after all, just an interpretation with zero "real" evidence for it (you can't intereact with the past). Count Iblis (talk) 00:22, 29 November 2012 (UTC)

That's silly, Iblis. My grandmother was real and her effects and remains are real, she is just not alive now, which is no different from saying her corpse is not buried on Mars. You know this. μηδείς (talk) 21:54, 1 December 2012 (UTC)

What's the point of postulating a completely separated universe that cannot ever have a connection to ours? Isn't that like the flying spaghetti monster or your favorite God? And why would you need a word like multiverse? The concept of universe encompasses everything. Maybe at some parts of it the natural rules are completely different than what we know, and not yet discovered, but there is no "outside." OsmanRF34 (talk) 23:06, 27 November 2012 (UTC)

Right on. "In my Father's house (= the Universe) there are many mansions (= sub-universes)". -- Jack of Oz ^[Talk] 23:14, 27 November 2012 (UTC)

This has already happened. We can never send a message to the galaxies seen in the Hubble deep field. They now live in realities totally separate from our own, even though we see them clearly as they once were. Hcobb (talk) 23:18, 27 November 2012 (UTC)

there you go. Math being incorrectly interpreted. Like the traveling professor marvel in the wizard of oz.GeeBIGS (talk) 00:26, 28 November 2012 (UTC)

• The whole "multiverse" thing may or may not be hokum, but it's really just renaming the limits. If the Universe is "everything", how do you have more "everythings"? You don't, just just redefine what "everything" means: you can either give it a new name, or you can redefine the old terms. It is important to remember in this context that less than 100 years ago, it was widely assumed in the scientific world that the entire universe consisted of the Milky Way galaxy. In less than a century we've shown how completely ridiculously small the Milky Way is. In terms of scale, it's a bigger redefinition of the "universe" than anything Copernicus or Galileo came up with. And there are people alive today who lived in a world where the prevailing scientific thought was that everything in creation was in the Milky Way. So, whether or not there are, or are not, something like a "multiverse", if it were found that there was, it wouldn't be an unprecedented redefinition of creation. It wouldn't even be the first such major redefinition in the past century. --Jayron32 05:52, 28 November 2012 (UTC)

But here we have a clear case of different bits of one universe that mingled in chaos and void until some old dude turned on the lights and are now so far apart that they can never interact in any way again. Hcobb (talk) 12:32, 28 November 2012 (UTC)

As fun as this is to say, "ah, these guys must just be idiots!," the people who work on this aren't idiots, and it isn't just about linguistic semantics. Hugh Everett's many-worlds interpretation, for example, is an attempt to make sense out of quantum mechanics on a very deep level. Not everyone agrees with it, but a startling number of theoretical physicists do find it the most useful way to understand quantum phenomena. Those other "universes" are not simply areas of one bigger universe; they are alternate realities. I fear there is a lot of ignorance on exhibit in this particular thread. I don't claim to be an expert here but I know that the pat little "ah, misunderstood math!" and "mansions without houses" sorts of answers are just plain uninformed. I suppose I prefer Nimur's, "why even talk about it if we don't know their real" sort of response, though it is also unhelpful to the OP. It's a pity that one can't ask a question about a controversial theory on here without provoking a debate as to whether the theory is valid or not, especially from a lot of people who clearly don't know much about the theory. It is a bigger shame that we can't get a SteveBaker-like answer to this sort of thing, rather than a Yahoo! Answers chorus. --Mr.98 (talk) 23:56, 28 November 2012 (UTC)

Quantum entanglement + wormhole = ??? ~AH1 ^(discuss!) 20:46, 29 November 2012 (UTC) Shared noise. Hcobb (talk) 17:57, 30 November 2012 (UTC)

Is a covalent bond a cooper pair or a magnetic link?

Is a Covalent bond more like a Cooper pair or is it a magnetic link between two atoms as the electrons drop into reversed spins to cancel out their two magnetic fields? If so, isn't the photon emitted when a covalent bond is established simply the result of Magnetic reconnection? Hcobb (talk) 16:35, 27 November 2012 (UTC)

No, covalent bonding isn't anything exotic like that. It's just good old electrostatic interaction. Nothing fancier than Coulomb's law is needed to explain it. In a covalent bond, the electrons exist in a molecular orbital that has more electron density between the nuclei than around them. To put in in simplest terms, the negative electrons hang out in the space between the positive nuclei, and electrostatics keeps the whole thing together. There's a whole lot of Shroedinger's equations and wave functions and Hamiltonians and whatnot describing how the electrons hang out in that space; but basically they do, and that's what keeps it all together. It's the same forces that keep electrons around the nucleus of an atom, or stick the balloon to the wall after you rub it in your hair. It isn't magnets or anything like that. Cooper pairs are exotic low-temperature behavior kind of stuff. --Jayron32 05:43, 28 November 2012 (UTC)

An Ionic bond is held together by electrostatic interaction. The most famous covalent bond would be something like carbon-carbon, which is entirely electrically neutral. It is the magnetism of unpaired electrons, not their charges that is "neutralized" therein. Hcobb (talk) 12:29, 28 November 2012 (UTC)

What? That's a rather odd perspective. A non-polar molecule has a balanced charge, from an external point of view, but internally it is the electrostatic interactions between the nucleus and the electrons that holds it together. It isn't "magnetism", it's the localized concentration of electrons between the nuclei. Even in a C-C bond, the two Cs are held together by the electrons concentrated between them. You seriously need to reconsider what loony is teaching you basic chemistry and physics here if you think there's "magnetism of unpaired electrons" which is holding a C-C bond together. The forces holding ions to each other are identical to the forces holding a molecule together internally; it's just a difference in organization not in fundemental forces. --Jayron32 17:51, 28 November 2012 (UTC)

Agree with Jayron. All forms of chemical bonding are based ultimately on a combination of electrostatic interactions and exchange interactions. To the extent that magnetism enters into it, it is only as a secondary consideration. Dragons flight (talk) 21:40, 28 November 2012 (UTC)

Direct Evidence Against Sodium Channel Inactivation in Spike Frequency Adaptation

Hello. Is there any evidence against sodium channel inactivation in spike frequency adaptation (e.g. the failure to stop adaptation with the administration of a pharmacological agent that interferes with this inactivation)? Thanks in advance. --Mayfare (talk) 18:49, 27 November 2012 (UTC)

On the contrary, it is clear that multiple mechanisms contribute to SFA, and there is pretty strong evidence that sodium channel inactivation is one of them -- see for example http://jp.physoc.org/content/566/2/519.full. If you want to get into the literature on this topic, I recommend doing a Google Scholar search for "sodium channel inactivation spike frequency adaption" -- this will give you a number of relevant papers. Looie496 (talk)!~

Bombarding proton with neutron

What will happen if we bombard proton with a high speed neutron ? I shall be thankful if someone suggest me some articles related to my question in Wikipedia or anywhere else. Sunny Singh (DAV) (talk) 18:54, 27 November 2012 (UTC)

Many things might happen, but you're like to produce a bunch of hadrons. At high enough energies these hadrons are likely to form jets. Dauto (talk) 19:21, 27 November 2012 (UTC)

Can you mention some of those things that might happen ? Sunny Singh (DAV) (talk) 05:35, 28 November 2012 (UTC)

Stability of neutron and proton

I know the half-life of neutron is about 10 minutes, 11 seconds, when it is outside the nucleus- hence unstable. I want to know the half-life of proton when it is outside nucleus. Sunny Singh (DAV) (talk) 20:49, 27 November 2012 (UTC)

No one knows. Proton decay has never been observed, which implies a half-life of more than 10³³ years. Dragons flight (talk) 20:57, 27 November 2012 (UTC)

It has been estimated to be $10^{35\pm 1}$ years, see e.g. here. Count Iblis (talk) 21:05, 27 November 2012 (UTC)

In the Standard Model the proton is stable. In some Beyond the Standard Model theories like GUTs the proton is unstable but there is no exprimental evedence that protons decay, or hint that the theories that predict proton decay should be favoured over theories that pridect protons are stable. Dja1979 (talk) 22:52, 27 November 2012 (UTC)

Protons should decay even within the Standard model because of non-perturbative sphaleron effects. Dauto (talk) 23:56, 27 November 2012 (UTC)

The deuteron can decay this way to a positron and an anti-muon neutrino or to an anti-muon and an anti-electron neutrino. The deuteron lifetime due to this process is approximately 10^(218) years. Count Iblis (talk) 21:51, 28 November 2012 (UTC)

10^218 years? That's long enough that not a single decay would be expected to have occurred to any particle in the entire history of observable universe thus far. Dragons flight (talk) 00:12, 29 November 2012 (UTC)

For an interesting tangent in theoretical particle physics, see tetraneutron. ~AH1 ^(discuss!) 20:43, 29 November 2012 (UTC)

Why poisoning with ²¹⁰Polonium?

It's difficult to obtain and expensive, which limits the circle of suspects. Radioactive elements are also easier to detected and it also decays rapidly, so you have to hurry up once you obtain it. There are other more efficient poisons, with a lethal dose of less than 1g. Why not use traditional poisons? OsmanRF34 (talk) 23:41, 27 November 2012 (UTC)

To send a clear unambiguous message to others: "That's what will happen to you if you cross us". Dauto (talk) 23:50, 27 November 2012 (UTC)

The perpetrator might want two things: to be unambiguous or to keep everything under wraps. If it was the case of Arafat's death, couldn't an F16 be a better choice to deliver the same message unambiguously? Or to be as discreet as possible, use an easily available poison? I still see Polonium as a total overkill (excuse the pun). OsmanRF34 (talk) 00:14, 28 November 2012 (UTC)

An F16 lives no deniability. Dauto (talk) 00:21, 28 November 2012 (UTC)

Deniability leaves no chance for your unambiguous message. If Arafat was killed with Polonium, people will know that a state was behind it (which can only be the Israeli state, for obvious reasons). If they wanted it to look like a health issue, then, why not another poison? OsmanRF34 (talk) 00:31, 28 November 2012 (UTC)

It could also be a rival in the Palestinian movement, as was suggested at the time he died. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:00, 28 November 2012 (UTC)

I don't know about Arafat. I was thinking of Alexander Litvinenko. But the point is how to send a clear message AND still preserve deniability? That is a balance act that requires a specific choice of murder weapon, hence the choice of polonium-210. Dauto (talk) 00:48, 28 November 2012 (UTC)

"which can only be the Israeli state, for obvious reasons" — I don't think it's so obvious. Arafat was, at the very least, a known quantity. It strikes me as not at all clear that the Israelis would consider his death in 2004 to be a desirable thing (at an earlier point in time it would be more obvious). There are lots of potential candidates of people who would have benefited from his death either directly or indirectly by the confusion it caused within the Israeli-Palestinian relations. I'm not trying to start a debate, but I think you should expand your analysis as to whom "the state" behind the Polonium might or might not have been. There are lots of states (even some private companies) with the technical wherewithal to create Polonium-210. More difficult than the technology is the experience with handling it, but even that is probably wider than is commonly thought. --Mr.98 (talk) 16:01, 28 November 2012 (UTC)

It is also worth noting that very small amounts of Polonium-210 (i.e. 1/100000th of a lethal dose) can be easily obtained for industrial and research purposes for roughly $100. Given that it has been years since he died, it isn't that hard to imagine that someone could deliberately introduce traces of polonium after the fact to intentionally mislead an investigation. That is especially true when talking about the traces reportedly found on Arafat's effects, probably less so if they actually find it in his bones, which is after all the point of exhuming him now. Finding very small amounts of polonium now isn't really a guarantee that it was used to kill him, especially since many of his symptoms weren't generally consistent with what you expect from radiation poisoning (e.g. no hair loss). By the way, we have an article of the death of Yasser Arafat. Dragons flight (talk) 20:55, 28 November 2012 (UTC)

You only need about 50 nanograms of Polonium 210 to kill someone. The alpha radiation emitted by the decays don't exit your body, so it isn't easily detected. Count Iblis (talk) 23:52, 27 November 2012 (UTC)

Polonium poisoning is also difficult, if not impossible, to treat. Plasmic Physics (talk) 05:09, 28 November 2012 (UTC)

Recall Hamlet's words after killing Polonius: "Indeed this counsellor is now most still, most secret, and most grave, who was in life a foolish prating knave." In the Litvinenko case, I think this is precisely the message someone was sending through their choice of poison. By the way, the verb "prate" can here be read as having a double meaning: "to prattle" but also "to tell tales or inform against someone"; Shakespeare used it in the latter sense in Macbeth.--Rallette (talk) 06:43, 28 November 2012 (UTC)

What was the message from Litvinenko? If you are no longer or friend we go and kill you. We will do it any country. Going to a journalist or a foreign secret service will not help. We will do it in a way that everybody knows that it was murder. We will not be prosecuted or even questioned. We do not care if everybody knows that we have done it. Even if the dieing is on youtube and every other media we will not care.--Stone (talk) 07:45, 28 November 2012 (UTC)

Are you suggesting, Rallette, that the use of Polonium was an actual intended allusion to Polonius? μηδείς (talk) 19:22, 28 November 2012 (UTC)

Yes, actually, that was what I thought it must be, back in 2006. Of course I can't be sure, but I think it fits rather neatly.--Rallette (talk) 07:15, 29 November 2012 (UTC)

I suppose it's conceivable, but what it doesn't fit very neatly with is my image of the Cheka. Subtle allusions to a foreign writer that hardly anyone will even think of? Perpetrated by those humorless thugs? Kinda doubt it. But who knows; maybe they've been taking night classes. --Trovatore (talk) 07:47, 29 November 2012 (UTC)

On the contrary, the Russians seem to be very big on old-fashioned education, including the literary canon, and indeed take some pride in being able to insert apt references and quotes into their conversation. Take for instance the movies "Peculiarities of the National Hunt" and "Peculiarities of the National Fishing", which are extremely low-brow comedies, yet their names are an allusion to the opening paragraph of The Brothers Karamazov.--Rallette (talk) 08:17, 29 November 2012 (UTC)

Also, it has been pointed out that "Polonius" and "Polonium" are spelt identically in Russian: Полоний. --Rallette (talk) 08:26, 29 November 2012 (UTC)

I didn't say Russians. I said Cheka. The second point is mildly interesting, though. --Trovatore (talk) 08:27, 29 November 2012 (UTC)

Yes, I see your point! Although I can’t say I personally know any Chekists, still my image of Russian spies is rather different. The typical KGB man in my mind is the Soviet-era “cultural attaché” in a foreign capital, who unofficially represents the real power of the Kremlin, the Party, and the national security apparatus, as opposed to the regular diplomatic bureaucrats who work for the Foreign Ministry, far down the food chain. There used to be lots of them here in Helsinki, and they were most cultured and charming people, or so I’ve heard... But let me admit for the record that a major reason I believe in the Hamlet connection is, of course, that it makes me feel clever! But this is getting a bit OR, and I suppose belongs more in the Humanities desk.--Rallette (talk) 08:46, 29 November 2012 (UTC)

Hmm, that's not the image I ever had. The stereotype, here, is men in badly fitting suits, with comical accents, trying to appear Western. But I'm happy to admit that may just be a successful propaganda effort but on whose part? Let's see, whom would it benefit? :-) --Trovatore (talk) 10:25, 29 November 2012 (UTC)