Wikipedia:Reference desk/Archives/Science/2012 January 16

= January 16 =

Ice fossils
Can fossils be formed in ice? Whoop whoop pull up Bitching Betty 02:29, 16 January 2012 (UTC)


 * I don't think so, if by "fossils" you mean where the bone is replaced by minerals. That requires that the minerals be transported in by a liquid.  Of course, an animal can be frozen as long as the ice remains, so that's even better than a fossil, but not likely to be as old. StuRat (talk) 02:36, 16 January 2012 (UTC)


 * I meant ice as the minerals, not the medium. Whoop whoop pull up Bitching Betty 18:28, 16 January 2012 (UTC)


 * I don't understand. How can ice be minerals ? StuRat (talk) 22:53, 16 January 2012 (UTC)
 * Maybe minerals embedded in the ice. Though I would think they are too diluted to do anything. ←Baseball Bugs What's up, Doc? carrots→ 00:51, 17 January 2012 (UTC)
 * I think that water serves as the solvent for minerals that replace the structural details of a once-living organism in the process of fossilization. I would think that pure ice would not be able to contain the detail of fossils as normally understood. I think it may be theoretically possible to have impure water containing any type of contaminant participating in a variation on fossilization in which contaminants serve to record detail, and which would have to be maintained at a temperature that will keep it in its solid state. But that makes me consider yet another difficulty—how would molecules of water move into place in a fossilization process if they were frozen? Bus stop (talk) 01:16, 17 January 2012 (UTC)


 * You mean permineralization, but with ice crystals instead of minerals filling in the spaces between tissue? In a way. Freezing is pretty much the same process as permineralization. The water is trapped within the tissues that then solidify. These can form casts. But they're quite useless aren't they? as the original tissue still exists anyway.


 * Ice (and water) is too plastic and ephemeral. Global temperatures fluctuate too much. By the time the organic tissues begin to disappear for the ice cast to be of any value, the ice itself will have long rearranged themselves again or have gone.


 * While you can technically have more macroscopic trace fossils preserved in ice (like a footprint), I doubt it would also last for more than a few years. You cant exactly overlay it with another "stratum" of ice and still expect it to be recognizable either.--  Obsidi ♠ n   Soul   01:31, 17 January 2012 (UTC)


 * Well, they can identify individual yearly layers in the ice, and count them to tell how old a given sample is. So, theoretically, they could also make out a footprint, but the problem is they wouldn't know to look for it.  Perhaps if there was something that would reflect a signal between the layers, like a thin layer of ash from a volcano, the footprint might be a bit more visible.  Also, in places where interesting footprints are expected, like by a cave entrance, the scientists might make the effort to search for them. StuRat (talk) 05:43, 17 January 2012 (UTC)


 * True, but then you'd have to rely on more serendipitous factors as well. Like the ice having to maintain constant temperature - unlikely when talking in geochronological terms. They can't be buried too far or compacted - pressure = heat. While stratigraphic sequence is still preserved even after that, the trace fossil is not. They most likely wouldn't survive in interglacials as well. Not to mention collection problems. The only places where I can reasonably expect these criteria to be met is in space. If ever exopaleontology/exoarcheology become valid sciences, ice fossils would probably be common. On the other hand, if the ash falls on the footprint and then solidifies, that can theoretically make a perfectly recognizable trace fossil - a mold. Again with the stipulation that the ash wasn't warm in the first place.--  Obsidi ♠ n   Soul   06:14, 17 January 2012 (UTC)

Information transfer Faster Than Light - DIY
Not a physicist, so maybe this is an old question, but I didn't find a good saerch query response.

There is an insanely simple method for communicating faster than light, and I wonder whether it violates some obscure physics rule or equation.

It's this: run a string that cannot stretch or break (hypothetical material) out a REALLY LONG WAY, like a billion miles, or maybe Earth to the Moon. Put a person on each end. Send signals in real time, with zero delay, along the string by a series of tugs, like Morse Code, only by pulling on the string. That's it. If it really can't stretch, then the far end will feel the tug from the near end at precisely the moment it is pulled. There will be no delay for signal transmission regardless of the distance between the two points.

I know - it is technically ridiculous. But, purely from an idea standpoint, wouldn't it in fact constitute sending information faster than light?

If not: why not?

Dave — Preceding unsigned comment added by 24.113.99.57 (talk) 02:38, 16 January 2012 (UTC)


 * Nope, those type of waves don't move faster than the speed of light, they may be more like the speed of sound. Any real-world string will have some elasticity, so it will stretch when you pull on it, until eventually the far end catches up. StuRat (talk) 02:44, 16 January 2012 (UTC)
 * A similar thing has occurred to me too in the past, except I envisaged pushing and pulling a long rigid rod. I concluded, as you say, that far from being instantaneous, the transmission of information would be at the speed of sound in the material, just like if you whack an iron girder then the vibrations would travel along it at the speed of sound. But what about some hypothetical absolutely rigid material, with no little atomic "springs" inside it? Does the restriction about speed of information preclude such a material from existing (independently of other objections)? 86.181.172.222 (talk) 03:02, 16 January 2012 (UTC)


 * You have to consider carefully what 'rigid' means. The forces that bind atoms together in a solid material are electromagnetic in nature, and therefore mediated by photons&mdash;and so limited by the speed of light.  In other words, if I wiggle an atom at one end of the rod, the next atom down the line has no way of 'knowing' what I did to the first atom until my wiggle is transmitted – no faster than the speed of light – through electromagnetic interactions.  Your hypothetical 'absolutely rigid' material is an impossibility.  TenOfAllTrades(talk) 03:10, 16 January 2012 (UTC)
 * Sorry, but you're ignoring my provision "independently of other objections" which I expressly put in to ward off this kind of answer. Say there was some other novel type of matter that was not composed of atoms but of some completely rigid stuff. Can we say that this substance can't exist solely because it would violate faster-than-light transfer of information? 86.181.172.222 (talk) 03:16, 16 January 2012 (UTC)
 * Restating your question as "If superluminal communication were possible, would superluminal communication be possible?", the answer would be yes&mdash;but not terribly informative. Once one starts invoking non-physical imaginary materials, we're out of science and into science fiction.  In the real universe, forces are mediated by force carriers limited by the speed of light.  TenOfAllTrades(talk) 03:24, 16 January 2012 (UTC)
 * Yeah, I guess .... but I was hoping there might be a more interesting answer! 86.181.172.222 (talk) 03:40, 16 January 2012 (UTC)
 * I think the answer is quite interesting! Prior to twentieth century understanding of physics, who could have predicted that material properties like tensile-strength and elasticity would have hard upper limits?  And... that these limits would be governed by properties of electricity and magnetism?  It's a fair bet that Archimedes' lever gedankenexperiment never took account of this limitation - even though he probably knew a lot about electrostatics!  The really interesting part of the answer you received is that we now understand this connection.  Nimur (talk) 05:20, 16 January 2012 (UTC)
 * Science Fiction has suggested other forms of "matter" (sometimes from an alternative "super-dense" universe) with "magic" properties, but such inventions really don't belong in the universe as we know it. We know about Supersolids and Bose–Einstein condensates, where atoms don't behave conventionally, but "super-rigidity" has never been found or postulated by experts.  The nearest anyone has found to super-rigidity" is possibly on the surface of a cool Neutron star, and light certainly behaves strangely there, but this is because of the high gravity, not because shock waves are transmitted instantaneously.  The only other forms of instantaneous communication that I've heard suggested are quantum entanglement (where the "effects due to entanglement travel at least thousands of times faster than the speed of light", but it doesn't actually work, even in theory, as faster-than-light communication), and telepathy (believe whatever you wish about that).    D b f i r s   09:10, 16 January 2012 (UTC)


 * It seems others have already provided an answer, but allow me to link to the same question in the Physics FAQ which gives the same answer, hoping you or other readers will find the FAQ useful. &#x2013; b_jonas 12:11, 16 January 2012 (UTC)


 * I will just note that when people say "real world substance," they don't mean, "oh, this is just an engineering problem." They mean, "any substance that acted in such a way would violate the rules of physics." It violates non-even obscure physics rules and equations for the reasons given above. It does so by deliberately ignoring what rigidity means on a physical level. --Mr.98 (talk) 14:26, 16 January 2012 (UTC)

Another answer is based on the relativity of simultaneity. If a force were to be able to act instanteneously accross a finite distance, then in your frame momentum would be consererved, because the change in momentum of one object would be the opposite of the change in momentum of the other object, and his would happen at the same time. However, in the frame of someone moving relative to you, the two mometum changes will happen at different times, so momentum would not be conserved. The only way to conserve momentum in all frames, is to have momentum conserved locally, at each point in space-time. Count Iblis (talk) 13:44, 16 January 2012 (UTC)


 * From Quantum entanglement, "Quantum entanglement is a form of quantum superposition. When a measurement is made and it causes one member of such a pair to take on a definite value (e.g., clockwise spin), the other member of this entangled pair will at any subsequent time[7] be found to have taken the appropriately correlated value (e.g., counterclockwise spin). Thus, there is a correlation between the results of measurements performed on entangled pairs, and this correlation is observed even though the entangled pair may have been separated by arbitrarily large distances.[8]" so if you did the following experiment: 1) Entangle two pairs of atoms, pair #1 and pair #2, 2) Carry one atom from pair #1 and one atom from pair #2 on a spaceship out 10 light minutes away from the laboratory on Earth where the other atoms from pair #1 and pair #2 are 3) Out at the remote location on the spaceship, flip a coin in your floating spaceship and slap it against the wall. If it comes up heads, cause the spin of your pair #1 atom with you to change and shine a red light back to Earth. If it comes up tails, cause the spin of your pair #2 atom with you to change and shine a blue light back to Earth. 4) Back on Earth, where the atoms are being watched and a telescope is pointed in the direction of the spaceship, the observers on Earth will know the result of the coin flip by way of the atom, practically 10 minutes before they get the message by way of the light, no? 69.243.220.115 (talk) 16:54, 16 January 2012 (UTC)
 * This idea has been bandied about since Bell's early work, but I don't think it works out. The problem, as I understand it, is that you can't arbitrarily decide what state to collapse it into, nor can you know if the other person has already collapsed the state. So you can't send a signal this way; you can't even send an "empty" signal (you can't say, "when I collapse the state, then you'll know the deed has been done" — because you can't detect if the state has already been collapsed, or if your measurement collapsed it). You can compare the states and find they are the same — but that requires slower-than-light communication. But I'm not a physicist, so someone surely can elaborate more on this, or correct me... --Mr.98 (talk) 17:44, 16 January 2012 (UTC)
 * I'd say you pretty much covered it. Truthforitsownsake (talk) 18:19, 16 January 2012 (UTC)
 * Is the FTL nature of quantum entanglement not confirmed experimentally? If so, then that (set up the test the way they did that does work to confirm it). If not, why is it believed by scientists to be true? I haven't carefully read the entire article and am not highly trained in physics, and so might not even be able to understand it all. 69.243.220.115 (talk) 19:20, 16 January 2012 (UTC)
 * From the article, "Experimental results have demonstrated that effects due to entanglement travel at least thousands of times faster than the speed of light," with a ref to this article in Nature, which seems pretty unambiguous about it. But again, I'm not a physicist... --Mr.98 (talk) 19:42, 16 January 2012 (UTC)
 * So if the effect is experimentally confirmable, use the same method they used to confirm it to send information FTL. 69.243.220.115 (talk) 19:47, 16 January 2012 (UTC)
 * It doesn't work that way, for the same reason I explained. The experiment looks roughly like this: we separate entangled particles. We both agree to check it at the same exact time. We check them. Then we telephone each other and confirm that the states are the same. That is, it takes slower-than-light communication to know what the states are (we can't set them), and it takes slower-than-light communication (the telephone call) to know that we did it at exactly the same time, and using our very precise time measurements regarding when we checked the state to calculate the speed. There's no FTL information passing there. If I screwed it up and checked it a week earlier, the person on the other end would have no way to know that unless I told them... via something slower than the speed of light (e.g. the telephone). We cannot arbitrarily set the state, we can only read it. There's no information traveling FTL here. The key distinction you have to make here is whether information is being exchanged FTL, not whether there is FTL phenomena. The latter is not necessarily prohibited by SR, but the former is, and there isn't currently a way to do it within the current laws of physics.--Mr.98 (talk) 19:51, 16 January 2012 (UTC)
 * So you on Earth and the guys out 10 light minutes away have really good clocks synchronized and agree to look at your atoms at a specific time. You look at the appointed time and see that yours is "up" or whatever state your equipment can measure, and that "information" leads you to believe that at that point in time, the state of the atom 10 light minutes away is also "up" and then 10 minutes later you get the confirmatory color of light beam, but you knew that 10 minutes earlier than the light beam told you because you looked at your entangled atom. True, it didn't involve any setting by the guys in the spaceship. They couldn't tell you anything they wanted, but it still seems like a kind of information, you knowing what the state of an atom 10 light minutes away was before any slower-than-light means could tell you. 69.243.220.115 (talk) 20:13, 16 January 2012 (UTC)
 * There's no information communicated FTL; that's the key part of SR. Zero communication. Case in point: if a meteor destroyed the other station, you'd have no way of knowing unless some STL communication took place as well. Another way to think about this, is how your situation above is any different than if instead of entangled particles, you simply have duplicate photographs in sealed envelopes. You can both open the envelopes and say, "oh, look, it's a photo of a dog," and you can say, "well, according to our system, he has a photo of a dog, too." But neither of you get to choose what the photos are (nobody does, technically), and there's no way to use them to pass any information between the two of you. The photo is itself a "piece of information," as it is, but you can't pass information this way. If all you're saying, at this point, is, "isn't it cool that particles are entangled?," then I agree, but trying to find a convoluted way to argue that this allows FTL communication is just not going to pan out, sorry. This stuff has been hashed over at length by more clever people than you or I, including folks who had strong vested interests in trying to come up with FTL communication schemes. :-) --Mr.98 (talk) 20:25, 16 January 2012 (UTC)
 * I see now. Your envelope analogy is very good. 99% of the time, I remember to just not bother trying to think of ideas that work and that someone else will always have thought of it first if it is a good idea :) 69.243.220.115 (talk) 20:58, 16 January 2012 (UTC)


 * I was interested above to read "the effects due to entanglement travel at least thousands of times faster than the speed of light". Although my understanding of this is very hazy to say the least, I'd always imagined that these effects did not actually entail anything "travelling" anywhere, and that they were therefore instantaneous. The Wikipedia article says that the "thousands of times faster" is experimentally confirmed. Is it still an open question whether the effects are instantaneous? But, while writing this, another thing has occurred to me, which is that there is not actually any such thing as simultaneity, right? So how do we determine this question anyway? Now my head hurts. 86.181.206.2 (talk) 12:49, 17 January 2012 (UTC)
 * My reading of that statement is that there are limits to the precision of our ability to measure simultaneity. Simultaneity is when we say two events occur at the same time. It's a non-trivial thing to measure precisely, and there are technical (and theoretical, but I don't think those experiments approach those) limits to our ability to measure precise times. (Relatedly, see relativity of simultaneity.) Saying it propagates at least 1000 times faster than the speed of light is highly encouraging to the idea that it propagates instantly. The deeper question is whether the property (e.g. spin) was the same all along — e.g. is it like an envelope, which has a photo in it even if you haven't opened it. This is a deeper quantum question about the nature of the uncollapsed wave function. Too deep for me, but my understanding of the Bell test experiments is that it has been more or less confirmed that the properties are not there until you look for them (there are no "local hidden variables" — the particles don't just secretly have the information with them). But there are still multiple interpretations of that data available. This is exactly where the analogy with the envelope breaks down — in the quantum case, there isn't a fixed photograph inside the envelope until somebody looks. Then both envelopes have the same photographs inside of them. This is what Einstein thought was "spooky." It doesn't make a lot of sense in a macroscopic world, but that's true of most of quantum mechanics. Being spooked by it is a sign that you actually are taking it seriously, I think. --Mr.98 (talk) 13:13, 17 January 2012 (UTC)
 * Thanks! The "relativity of simultaneity" thing is puzzling me still. If there are events A and B, then according to the article you linked (and according to what I previously understood), some observers may see A before B, some may see B before A, and, presumably, some special-case observers will see them both happen at precisely the same time. So in the case that A and B happen to be quantum-entangled events, how does the question of whether they are simultaneous even make sense? 86.181.206.2 (talk) 14:05, 17 January 2012 (UTC)
 * The relativity of simultaneity should not come into effect unless the two observers are in different inertial frames. Given that they are both on Earth and their labs are presumably "still" I don't think it really comes into play. If one of them was in a very fast traveling rocket then you'd have a much harder time saying which even happened before the other. Generally these sorts of SR effects don't come into effect unless one of the frames is moving at a significant fraction of the speed of light. But they are interesting to think about, nonetheless. What the relativity of simultaneity emphasizes (and the only reason I linked to it here as food for thought) is that the definition of simultaneity is based on two events happening at the same time. The problem is, according to relativity, what time it is varies according to your inertial frame. In a Newtonian view, saying something happened "at the same time" implies that there is one universal time somewhere out there, but that isn't the case. There are local times, and they can vary from other local times. In the case of this experiment, though, this probably doesn't matter too much except maybe in a few decimal places far at the end of the time measurement. But I'm not 100% sure of this; knowing where you are and when something happened very precisely can be very tricky in physics. --Mr.98 (talk) 14:22, 17 January 2012 (UTC)
 * Do you mean to imply that there is some theoertically sound and exact way of establishing simulaneity by ensuring that everything is "still" (in some appropriate sense), and this obviates all the relativistic objections that simultaneity is actually not well defined? On a more practical level, though I can't do the maths, I would have thought that even the slow speeds of normal experience might be relevant when distinguishing between something travelling, over a short distance, thousands of times faster than light, and something instantaneous. The difference must be only some vanishingly small fraction of a second. But I am speculating because really this is well beyond my knowledge. 86.181.206.2 (talk) 14:38, 17 January 2012 (UTC)
 * Well, my knowledge of SR and inertial frames isn't perfect, so I could be pretty off on that. This also strikes me as a not-totally-normal use of SR since even if the two observers are not in the same reference frame, they are not "communicating" in the same way you would in a typical SR situation. But the more I ponder over it, the less confident I am that you could, even theoretically, distinguish between absolute simultaneity and very-very-very-very close simultaneity. Even if you could measure time to arbitrarily low values (which you can't, not even theoretically), being able to distinguish between entanglement acting instantly or ridiculously fast is probably not possible. Even if you had one experimentalist on the other side of the universe from the other, you probably couldn't distinguish it from being many billions times the speed of light and being actually instant. (Before one rushes off to make that experiment, keep in mind it would take billions of years for the results to be received from each station.) --Mr.98 (talk) 18:53, 17 January 2012 (UTC)
 * As far as I know, simultaneity is perfectly well-defined within a single reference frame. As long as you both have good clocks you can synchronise them by relying on the speed of light being constant. Just send a pulse of light from A to B, where it hits a mirror and goes back to A. A times how long it takes the light to get there. Halve that and you have the time it takes light to travel from A to B (1 minute, say). B then says to A "According to my clock, it's 12:00am". When A receives that message it knows that, according to B's clock, it is now 12:01am so A can set its clock to 12:01am too and then you have an easy way of knowing when events are simultaneous. (Note, you have to do it like that rather than just having A and B starting off in the same place, setting their clocks, and then walking away from each other because as soon as they start moving they aren't in the same reference frame and all bets are off [unless you measure the movement very carefully and do some relativistic calculations and compensate for the error, I suppose].) --Tango (talk) 00:05, 18 January 2012 (UTC)
 * "simultaneity is perfectly well-defined within a single reference frame". So, for example, if I have two alarm clocks not moving relative to each other, then will all observers also not moving relative to the clocks agree that the alarms go off at the same time? Does that not mean that the two events really are simultaneous, in some absolute sense, and anyone disagreeing because they are moving is just looking at things from "a distorted perspective"? Like I could say two lines really are parallel, but you might not see them that way. 86.181.206.2 (talk) 00:28, 18 January 2012 (UTC)

Persistent BO
I have some cotton T-shirts that are getting a few years old now but still in pretty good condition so still wearable. The problem is that within only a couple of hours of putting them on they can start smelling of BO from the armpits, usually as soon as they get the slightest bit of sweat in them. It doesn't matter how they're washed or how often they're washed it still happens. I don't have bad BO in general and other T-shirts I wear don't have this problem even older ones. What would cause this and why are only some T-shirts affected? Any suggestions about how it could be fixed? Dob in a Nerd (talk) 03:19, 16 January 2012 (UTC)


 * Is it possible it's tighter than the other T-shirts you wear ? I find having good air flow to the pits is essential to them keeping dry.  If they stay wet, then they start to stink. StuRat (talk) 04:33, 16 January 2012 (UTC)


 * Interesting. Well I would say that they are probably fairly tight ones and I don't think I have this problem in any looser fitting ones, however I do have as old or older ones just as tight that don't smell either so it can't be just that. Dob in a Nerd (talk) 04:47, 16 January 2012 (UTC)


 * I've also noticed that certain fabrics tend to cause BO more than others. Cotton usually isn't bad (presumably because it wicks away moisture), but nylon and other artificial fabrics are.  Are you sure there's no nylon in it ?  Also, I suggest you wash them with bleach, as plain detergent will probably remove most of the stink, but leave enough bacteria to "seed" your pits and start them stinking quickly.  StuRat (talk) 04:54, 16 January 2012 (UTC)


 * Yes agree that the synthetics tend to smell more quickly in general. But these are definitely cotton, just checked two of them. Can't use bleach cos they're colours and specifically say not to bleach but I have tried those stain removal sprays with little effect but will try again. Dob in a Nerd (talk) 05:06, 16 January 2012 (UTC)


 * There is "color-safe bleach", although perhaps "oxidizer" is a better name than "bleach". You could also pour alcohol directly on the pits, but be sure they are rinsed thoroughly before drying, or they could catch fire.  StuRat (talk) 05:14, 16 January 2012 (UTC)


 * OK thanks for your suggestions I might give it a try. If anyone else has got any ideas still happy to hear them. Dob in a Nerd (talk) 06:55, 16 January 2012 (UTC)


 * It might be that there is odorous material trapped in the fabric, and when it heats up (as a result of your body heat) the smell comes out. So it's not you that smells, but the t-shirt.  Soaking in vinegar is sometimes suggested to remove smells from fabrics. --Colapeninsula (talk) 11:06, 16 January 2012 (UTC)


 * Changing to a biological washing powder should solve the problem for you. You may need to make a solution of the powder first and paste it onto the affected areas, let it soak for a while (not dry out though) and then wash. Using washing powder that has enzymes in it (biological washing powder) will prevent this problem happening. --TammyMoet (talk) 12:06, 16 January 2012 (UTC)


 * I do use an "enzyme powered" detergent possibly the dearest one on the supermarket shelf that usually tops comparative independent tests of washing powders in this country so it's not that and that's not preventing it, however I haven't tried making the concentrated paste thing first and letting that soak in so I will give that a try thanks. Dob in a Nerd (talk) 03:25, 17 January 2012 (UTC)

Time is stopped
What is the time? That is a big question.The matter move from a place to another place,but time never change.The change just a feel people thought,because you are you in this situation.Time like space and place .We just a geust in the situation of time.So giving up the concept of thime.You will be liberated by the new opinion.That is my view about time. — Preceding unsigned comment added by 123.138.31.86 (talk) 04:15, 16 January 2012 (UTC)
 * What's your question? We do have an article called Time, if that would help. ←Baseball Bugs What's up, Doc? carrots→ 04:32, 16 January 2012 (UTC)
 * We also have an article on the human perception of time, which is probably less well-understood than the actual physics-descriptions of time. In physics, definitions of time as a dimension or as a variable in an equation tend to be axiomatic, so there's really not much to explain.  Nimur (talk) 05:25, 16 January 2012 (UTC)
 * The nature of time can also be a very interesting, complicated and challenging topic in physics. See List of unsolved problems in physics and Arrow of time.  Red Act (talk) 05:58, 16 January 2012 (UTC)

Hyperbolic lines around radio towers
While walking through the National World War II Museum today, I saw a map in one of the exhibits. The caption said something about planes finding their way to France for the D-Day bombings and such. The map, besides having an outline of the coasts of England and France, had various radio navigation towers on it with hyperbolic lines drawn around them. The caption didn't mention them or explain in any detail how the pilots used them. So what were these lines and why would they be hyperbolic and not circular? Thanks, Dismas |(talk) 05:37, 16 January 2012 (UTC)


 * See Decca Navigator System. AndyTheGrump (talk) 05:45, 16 January 2012 (UTC)
 * G was the World War II phase navigation system used by the RAF, that later evolved into Decca (post-war)... but I don't know what the actual chart you saw was, so all this is a little speculative.
 * I don't think that Decca was ever used in the United States (at least, non-experimentally). 1940s-vintage American aeuronautical NAVAIDs were usually nondirectional beacons, LORAN, and eventually VOR.  I presume in Occupied Europe, the navaids were German, not British; but the physics is the same for all Hyperbolic navigation navaids.  (NDBs would have circular radiation patterns, so iso lines aren't drawn on sectional charts).  RAF and American AAF pilots probably used British or American equipment dialed to German stations.  One of the most important post-War technology development thrusts was spurned by the realization that enemy bombers could use our own NAVAIDs, resulting in the technology that we now call the Emergency Broadcast System.  (The beeping noise on television was just for testing.  In an actual bomber-air-raid emergency, the TV station would be spoofing as a radar tower or malformed NDB in the wrong state).  Nimur (talk) 06:13, 16 January 2012 (UTC)
 * Would that spoofing actually be a part of the Emergency Broadcast System, or just something else that was also implemented (or considered)? I can't find anything about it in the EBS article, but it would be neat to cover if it we had reliable sources for the design, testing, or implementation of such a system. TenOfAllTrades(talk) 23:18, 16 January 2012 (UTC)
 * Some more information at CONELRAD. I'll see if I can dig up a more authoritative reference.  Nimur (talk) 23:38, 16 January 2012 (UTC)
 * Official handbook for station-operators (2007): AM & FM Emergency Alert System Procedures. Steps 5 through 9, for participating stations, to enable your tower to transmit data from the National Activation system.  The FCC and FEMA will jointly decide, under direction of the White House, what signals to transmit out of your tower.  Additional information, Emergency Communications, from the FCC.
 * And, Special Temporary Authority, for ad-hoc, emergency use of radio towers. Nimur (talk) 23:57, 16 January 2012 (UTC)

Tau-catalysed fusion
Wouldn't tau-catalysed fusion be even more efficient than muon-catalysed fusion, because taus are over fifteen times more massive than muons and would therefore bring two deuterium or tritium atoms over fifteen times closer to each other than muons do? Whoop whoop pull up Bitching Betty 19:15, 16 January 2012 (UTC)


 * I don't know, but it's worth noting that a tau's lifetime is seven orders of magnitude shorter than a muon. So that's lowering the threshold of usefulness substantially, no? --Mr.98 (talk) 19:49, 16 January 2012 (UTC)


 * The tau appears to have a 17.39% chance of decaying into a muon anyway when it finally does decay though. The alpha sticking problem seems to be more of a critical issue with muon-catalysed fusion, not sure if taus will stick to alpha particles as often as muons do. If they don't, then it would make more sense to produces taus. I guess it all depends on which can produced more efficiently, muons or taus. ScienceApe (talk) 11:02, 17 January 2012 (UTC)


 * If taus are 15 times more massive than muons, presumably that means they take 15 times more energy to make. If muon-catalysed fusion uses more energy than it produces, then tau-catalysed fusion would be even worse. --Tango (talk) 12:18, 17 January 2012 (UTC)


 * Is there anything that decays and produces taus? ScienceApe (talk) 12:57, 17 January 2012 (UTC)
 * Yes, of course. Anything that is heavy enough to produce a tau particle in its decays will occasionally produce them. But other things like protons and neutrons are much more likely to be produced. Dauto (talk) 19:47, 17 January 2012 (UTC)
 * To clarify Dauto's "of course": it is a general principle in particle physics that any way of decaying that doesn't violate any conservation laws will sometimes happen (it may happen with an incredibly low probability, but it will happen sometimes). It's worth noting that a tau is about twice the mass of a proton, though, so there aren't many particles heavy enough to decay into a tau on their own (but you can certainly make them by colliding particles together so that the kinetic energy contributes as well). --Tango (talk) 21:27, 17 January 2012 (UTC)


 * Didn't realize Taus were actually bigger than Protons. Curious, could anti-protons work? ScienceApe (talk) 03:20, 20 January 2012 (UTC)
 * I can't find any mention of a particle made up of a proton and an anti-proton, which makes me think it would be incredibly unstable. I would expect the proton and anti-proton to annihilate each other before either of them could fuse with anything. --Tango (talk) 16:03, 21 January 2012 (UTC)
 * If you are capable of producing antiprotons efficiently enough to make them useful for fusion, you may as well just use antimatter annihilation as your energy source. It's way more efficient. Law of Entropy (talk) 01:47, 22 January 2012 (UTC)


 * No it's not. Producing antiprotons will never be an energy source since it will always take much more energy to produce antiprotons than you will get out of proton-antiproton annihilation. ScienceApe (talk) 02:00, 23 January 2012 (UTC)


 * Note: "If you are capable of producing antiprotons efficiently enough..."  Point being, instead of getting the comparatively tiny energy from a catalyzed nuclear reaction, just completely consume the antiproton, if you are generating them efficiently.  If making the antiproton is inefficient, then you shouldn't be using it to catalyze fusion in the first place.Law of Entropy (talk) 09:15, 24 January 2012 (UTC)


 * The tau requires more energy to produce, has a much shorter lifetime and suffers from a more serious alpha-sticking problem (Being heavier it moves more slowly making it easier for the alpha particles to capture it). Dauto (talk) 19:47, 17 January 2012 (UTC)

climate data
Anyone know where on the internet I can get climate data for Hampshire, England, preferable Petersfield. I need temperatures, rainfall and wind direction averages for each month, and within the next few hours if at all possible. The internet only gives me tomorrow's weather and climate change stuff.

148.197.81.179 (talk) 22:19, 16 January 2012 (UTC)
 * Have you tried searching pubmed? Might be your best bet.  N o f o rmation  Talk  22:23, 16 January 2012 (UTC)

That's a collection of biomedical journal references, apparently. i can't see the connection myself. 148.197.81.179 (talk) 22:42, 16 January 2012 (UTC)
 * Derp, I meant google scholar. Sometimes I forget that science exists outside of biology :).  N o f o rmation  Talk  22:43, 16 January 2012 (UTC)


 * This site gives temperatures, rainfall, sunshine hours but no wind speeds I'm afraid. Mikenorton (talk) 22:57, 16 January 2012 (UTC)

I've just found the temperature and rain data, half an hour of searching on the Met Office site. Now all I need is the wind data. 148.197.81.179 (talk) 23:01, 16 January 2012 (UTC)

6 hours left to find it... 148.197.81.179 (talk) 01:57, 17 January 2012 (UTC)