Wikipedia:Reference desk/Archives/Science/2008 October 9

= October 9 =

Sending Sound Wave or Voice Messages to the Past?
Is it possible to send sound waves or voice messages to the past? For example, sending sound through time where the sound could be picked up by a local telephone. Can we build a technology to do this? 72.136.111.205 (talk) 00:19, 9 October 2008 (UTC)


 * No. --98.217.8.46 (talk) 00:29, 9 October 2008 (UTC)


 * Currently, humans have absolutely no ability to send anything through time. It's possible we never will. Calamus Fortis  01:17, 9 October 2008 (UTC)


 * Backwards through time...no. Forwards...yes.  Relativity allows 'fast-forwarding' of time.  From everything we know about the nature of time, there is absolutely no way to send anything back in time. SteveBaker (talk) 01:47, 9 October 2008 (UTC)


 * If Extrasensory perception worked, you might send the voice message by "mental telepathy" to someone in the past who had the right "gift," by some means beyond the knowledge of present science. Sending a sound vibration to an eardrum or making a voice frequency currents flow in phone wires or sending a telegraph message or affecting a computer circuit would require a transfer of energy, which would seem to violate the conservation of mass and energy in the universe both at the present and in the past. Jumping into the realm of science fiction, I suppose a way around this would be if the person 100 years ago left a message that he would send a message to the future, amounting to a certain amount of energy, and you sent a message with an identical amount of energy to the past, and somehow the messages cancelled, conserving mass and energy. That notion would work for letters or for time travellers of equal mass. Of course, any influence from the present to the past would alter the course of events, meaning that things might proceed a little differently in that time space continuum than turned out in ours. Edison (talk) 03:51, 9 October 2008 (UTC)


 * The whole idea of time travel is logically inconsistant anyways. If someone could travel in time as freely as in space, it would presuppose some "meta-time" that itself behaved exactly like real time is supposed to behave, but doesn't cuz you are traveling through it.  There's a database of causality, and if it isn't time, its something that behaves exactly like it... --Jayron32. talk . contribs  04:13, 9 October 2008 (UTC)


 * There can be an almost infinite number of parallel universes, with every possible outcome of each quantum choice-point oiccurring, so there is no problem of causality. If I send a message to Kennedy to duck when Oswald shoots, then only that time-space continuum has a second Kennedy term as president, and ours is not affected. If the bread falls jelly side up in one continuum, it falls jelly side down in another. I doubt time travel being possible, because to the best of my knowledge, no chrononaut from the future has ever held a press conference. Edison (talk) 05:42, 9 October 2008 (UTC)


 * Well, never had a reliable press conference. (There have been claimed chrononauts, e.g. John Titor). --98.217.8.46 (talk) 11:30, 9 October 2008 (UTC)


 * (undent) Well, WRT the parallel universe problem, that still presupposes a "branching" causality, which can still only be traced in a forward direction. That forward moving coordinate is still behaving exactly like time.  --Jayron32. talk . contribs  18:10, 9 October 2008 (UTC)
 * I suppose that in branching causality, a choice point would be whether or not the chrononaut arrived at a certain time and place. Edison (talk) 18:46, 9 October 2008 (UTC)


 * There is a problem with the branching 'many worlds' hypothesis for time travellers (I've been thinking a lot about this recently because I've been geeking-out on the latest Neil Stephenson book "Anathem"). So let's review what is generally said about this:


 * The theory says that in every possible instant in which a quantum event happens (Schrodinger's cat either dies or doesn't die - to pick a typical example), then the universe splits into two copies that are identical in every way except for that one event. So now there are two universes - one with a live cat in the box and another with a dead one.  OK - so now, the "future-you" builds a time machine - goes back in time and yanks the cat out of the box when nobody is looking 10 minutes BEFORE the experiment is started.  The idea is that your arrival into the past caused another fork in the universe back before the cat did or did not die - so now there is a third path...that the cat was never in the box in the first place.  The future-you who jumped back in time didn't come from the "cat not in the box at all" future - but from...oh - but wait...from BOTH the cat-is-dead and cat-isn't-dead universes?   Since those two universes are identical in all other respects - it's pretty reasonable to assume that both of you make identical time machines and jump back to an identical past...at a time when there were VASTLY fewer copies of the universe.  Since an insanely large number of quantum events have happened throughout the universe between the cat experiment and the time machine being turned on - there are an insanely large number of time travellers all jumping back to the exact same copy of the universe at (typically) the exact same point in space and time.  Only very few potential time travellers would fail to make it back because (through random quantum effects) were too grief-stricken by the pointless death of the kitty - or were just ABOUT to turn on their time machines when a cat leaps onto it and destroys it just seconds before launch.


 * But the fact remains that an almost infinite number of universes have been 'forked' from what was a single universe in the past at the moment in time to which the time machine is aimed. Hence a nearly infinite number of almost identical time travellers would pop into existance at more or less the same instant!


 * This is a big problem for the 'branching' many worlds concept. The reason I mentioned Anathem is because Stephenson has proposed in it an alternative means for the 'many worlds' thing to happen.  I haven't finished thinking my way through the implications of it yet (and all the heavy thinking it requires is slowing my reading of the book to a crawl!) - but essentially he envisages an infinite number of universes proceeding down every possible path through "configuration space" - requiring them to converge as well as diverge!  So two universes that have differed only in some very subtle manner could 'collide' and become one universe in which those past differences have quite utterly ceased to matter.  This eliminates my complaint rather neatly.  But it's not (I think) quite what most many-world-theorists had in mind.


 * SteveBaker (talk) 04:37, 10 October 2008 (UTC)

So...In Stephenson's book (which, we must emphasise, is fiction) - he proposes that we look at the multiverse in "configuration space". Imagine plotting a graph of (say) the cost of gasoline versus (say) the number of sunspots visibile on the sun...two totally unrelated things. Each point on your graph paper represents one possible combination of price and sunspot count - and if you plot these two things over time - you get a curve that traces around in some bizarre shape - looping back on itself, etc. Well, if you didn't limit yourself to 2D graph paper - you could plot more properties of more things - on 3D graph paper, you could plot price of gas against sunspots against the Dow Jones index. With 4D graph paper, you could add the popularity of the current US president...and if you had a truly INSANE number of dimensions for your hypothetical graph "paper" - you could plot the position, mass, spin, momentum, etc for every single fundamental particle in the entire universe. Since every possible configuration of the universe would be represented by a point somewhere in our bazillion-dimensional graph paper, we can draw a line on that graph that represents the progress of our universe through time...one of Stephensons' characters calls this a "Narrative". We could also plot the narratives of other possible universes through configuration space. OK - so that's Stephenson's idea of configuration space.

When you look at a classical (non-quantum) view of the universe - in which every event is entirely deterministic - the Narrative for our universe would be a L-O-N-G wiggly line snaking it's way through configuration space - looping around a region that's somewhat compact on the bazillion-dimensional graph because so much of the universe is relatively stable. But in a quantum universe like ours where events that are truly random happen and weird superposition phenomena exist - that line branches...just as in the many-worlds interpretation of quantum theory. But viewed in configuration space, it's also possible for two of these Narrative branches to merge back together - if two versions of the universe that differ only by the location of one fundamental particle happen to arrive at the same point in configuration space because that particle ended up in the same place in both of them - making the two universes identical in every respect. This is rather nicer than the conventional "many worlds" picture where universe split into copies of themselves - but never come back together again.

So what we have in Stephenson's rather clever model is that every conceivable point in configuration space (even some crazy, impossible-seeming ones) "exist" in some sense - and each one changes over time by threading a line through that bazillion-dimensional graph - sometimes splitting into two because of quantum randomness - other times merging together because two universes that have (potentially) very different origins and history happen to wind up with identical configurations. (One might argue that this would mess with the memories of living creatures in those universes - but if they have different memories to start with then the two universes can't merge because they are different. Only if every record of past history is somehow erased could two universes join back together.  But because configuration space is 100% full of these snaking "narratives" - there are (paradoxically) exactly as many rejoinings as there are splits!

Now - what about time-travel? Well, when a creature who is in a universe that's winding through its narrative line decides to jump "back in time" - they take themselves to a point in configuration space where the universe has a bunch of particles representing the time traveller. That's close (in configuration space) to the narrative that the time traveller's universe passed along - but it's not the same. If the time traveller is super-careful not to kill his grandfather or do anything else to "change the future" (a very tough proposition!) then when he finally leaves the past to return to the present, the universe with the narrative that contains his particles in the past will eventually merge with the narrative of the universe he came from - and he will truly have "done no damage" to the present. If, however (much more likely!) he displaces an air molecule and that has a "butterfly" effect that causes greater and greater divergence of the narrative of this universe from the one he remembers - then perhaps the two narratives will never be able to rejoin.

It could also happen though that he could kill his own grandfather - thereby causing the "new" narrative to diverge still more from our own - but in a million years, the consequences of the time traveller never having lived might be utterly erased by the passage of time such that the original time-line and the new one would become identical in every respect - and rejoin.

But in this peculiar interpretation of the multiverse (which I find exceedingly compelling) - time travel not only might exist - but it definitely does exist - in the sense that somewhere in configuration space, there must be a universe where I suddenly pop into existance for no obvious reason with memories of being a time-traveller. Since all possible configurations "exist" - then for all practical purposes, time travel can happen even if the laws of physics prohibit it. Of course there are also versions of the universe where I pop back into a nearly identical narrative - but my ears have turned to lime jello...or the world of the "past" is entirely populated by giant intelligent pink rabbits.

This is a very weird view of the multiverse - but it's kinda compelling.

SteveBaker (talk) 12:51, 10 October 2008 (UTC)


 * true, an interesting model. and as you say, if all possible universes exist, then there must be an infinity of universes where time travel was invented, and the travelers spilled over into the neighboring universes. but that comes up against the next problem: the chances of us living in a universe where nobody pops up from a parallel where they invented time travel would seem to be close to zero; yet that's where we are. (inspired by the logic that since model universes can be created inside computers or such so much more easily and go through their life cycle so much more quickly that there must be so many more of them, that in all probability we would have to be in one of those, not in the "real" universe.)Gzuckier (talk) 05:48, 11 October 2008 (UTC)


 * I don't know that we can conclude that time travel "must" be common enough in the infinity of universes to say that we should expect to have seen time travellers. Also, I'm not suggesting that time travel can actually exist - it can't - the laws of physics don't allow that.  What I'm suggesting is that the APPEARANCE of there being time travellers is perfectly possible - in the sense that  (due to some quantum weirdness - or because Stephenson's model of configuration space is true) people could pop into existance with a complete set of memories that are clearly from the future and may indeed perfectly predict who will win the superbowl for the next 20 years.  Such an event would be totally indistinguishable from real time travel.  The John Titor incident is somewhat chilling though - he was pretty convincing as a time-traveller.  This raises two difficult questions:  Firstly, perhaps we HAVE been visited by a time traveller.  Secondly, we didn't believe him - what makes you think we'd believe anyone who was a genuine time traveller? SteveBaker (talk) 01:45, 12 October 2008 (UTC)

The present exists. The future and past are both ideas. You can't travel to an idea. WAS 4.250 (talk) 20:30, 15 October 2008 (UTC)

Sterling Silver Allergy
If I were allergic to sterling silver jewelry, how long would I have to wear a ring around my finger to find out? 98.223.89.7 (talk) 02:32, 9 October 2008 (UTC)


 * I can't comment on sterling silver per se, but I can anecdotally report that my wife is allergic to gold. Its not the impurities in, say, 14K gold, its the gold itself.  She's been tested an everything.  The higher the Karats of the gold, the worse her reaction is.  Even a few second contact with 24 karat gold gives her hives.  So it is at least possible to be allergic to a metal like that.  As far as how long YOU would take to break out, well, that depends entirely on YOU.  Such facts of body chemistry are unique to each individual, and individual reactions cannot be predicted, especially over the internet.  If you have questions about possible allergies you may have (and metal allergies are very real), you should see a dermatologist or an allergist and get tested.  That is the only way to really know.  --Jayron32. talk . contribs  02:43, 9 October 2008 (UTC)


 * This is interesting. How can an inert metal like gold (especially higher purity) trigger an allergic reaction? Sjschen (talk) 03:47, 9 October 2008 (UTC)


 * No idea on the mechanics, and if I had never seen it myself, I would not have believed it. We are both chemists by training, and understand the chemistry of gold.  Gold is not entirely inert, and there is something there that triggers an allergic reaction in my wife.  This is partially a wag, but there may be something about the surface texture of the gold that triggers the reaction; it may not need to actually dissolve into the skin, but the contact triggers a histamine response in my wife.  Like I said, it shouldn't work that way, but I can only say that something about gold (and not the alloyants in lower purity gold jewlery, but the gold itself) that triggers the response in my wife.  --Jayron32. talk . contribs  04:08, 9 October 2008 (UTC)
 * That's really interesting, especially as you can both take a scientific view on it. Have you tried double-blind experiments? Have you tried the experiment with and without her using whatever soap or lotion she uses on her hands? The latter to examine if the gold somehow acts as a catalyst. There apparently exist gold-based room-temperature catalysts for the oxidation of CO, for instance. EverGreg (talk) 08:28, 9 October 2008 (UTC)
 * I know that Gold can be ionized by a strong oxidizer such as conc. nitric acid, but I doubt sweat and lotions can do anything close to that. Maybe the gold catalyzed rxns in the lotion or soap is indeed the answer. Sjschen (talk) 22:28, 9 October 2008 (UTC)
 * Just as a totally apocryphal story, I once met a woman with a similar problem, but in her case it was lupus and not an allergy (she had a ring tattooed on her finger instead of wearing a wedding band because of a similar problem). My guess is that's more an issue of skin sensitivity and not the metal in itself.  One option to test if it's a true allergic symptom is to see if it responds to antihistamines (i.e. diphenhydramine or somesuch), but it's more likely to be Contact dermatitis or some other sort of hypersensitivity than a true allergy.  SDY (talk) 12:41, 9 October 2008 (UTC)
 * Yeah, your terminology is probably more correct than mine. I was probably using the term "Allergy" too broadly.  The fact is that she has a reaction to gold (she has a platinum wedding band, and that causes no problems for her, and neither does silver or other costume jewlery), and whatever that reaction is is unpleasant for her, as gold causes an itchy rash.  The solution for me is I just buy her cheap jewlery.  Its a win-win situation for all of us!--Jayron32. talk . contribs  13:10, 9 October 2008 (UTC)


 * The original question actually asked how long to wear a ring until they find out. Well pure silver or gold is very weak and usually have alloys in it.  Some people are very allergic and can only wear stainless steel, titanium, platinum, palladium, or tungsten, though sometimes I've read forum posts of people who're allergic to those, except I've never heard of a tungsten allergy.  Also, there are some online sellers (often in China) who sell what they claim are sterling silver rings and they turn out not to be.  Are you ready for IPv6? (talk) 13:53, 9 October 2008 (UTC)


 * (Not a RefDesk-quality answer...) Jayron, does this happen with other forms of gold, and on other parts of the body? Has she, for instance, "merely" set a gold coin on her arm and got the same reaction?  Just curious.  Maybe this should be moved to a talk page somewhere.  --DaHorsesMouth (talk) 22:25, 9 October 2008 (UTC)


 * Jayron: I really think that if you are both scientists then a double-blind experiment is called for - and I'm very surprised you haven't already tried it. Too many scientists think that science ends at the laboratory door.  A while back, my wife was spending a small fortune on bottled water - I maintained that she couldn't tell the difference between the cheap stuff and the expensive stuff - so we did a double-blind experiment.  It turned out that not only could she not tell the difference between brands - but she couldn't even tell the difference between the good stuff and tap-water.  That experiment saved us a fortune!  In your wife's case, I think it's highly likely to be some kind of psychosomatic thing.  Gold is just too inert to be a true culprit here.  You need two similar sized rings - one gold, one of something else.  It should be easy to figure out a double-blind methodology here - have one person take two small boxes labelled "A" and "B" and put one ring into each box - using a coin toss to decide which goes into which box and noting which was which - but not letting the other person know.  Then the second person secretly does a coin flip and either swaps over the labels or does not (without looking inside).  Then, both of you close your eyes - you pick out the ring from the box marked "A" and rub it onto her skin on her left arm - take the one from "B" and rub it onto her right arm - each time putting the ring back into the same box and closing the lid.  Neither of you knows which ring was in which box until the results are in - then you can look into the box to find out - you should really do the experiment several times to be sure the result wasn't a flook. SteveBaker (talk) 04:10, 10 October 2008 (UTC)
 * Yeah, try this conversation on for size "Hey honey, you know that festering rash you get everytime you wear gold? Yeah, that really itchy shit that gets all pusy and nasty?  Say, lets do that on purpose".  I'll stick to buying her sterling silver jewlery and keep marital harmony going, thanks... --Jayron32. talk . contribs  04:22, 10 October 2008 (UTC)

I may have mentioned this before. I have a friend who has a weird reaction to gold, but only when she drinks alcohol. The skin around her wedding ring goes quite markedly blue. The whole ring finger and that side of her hand is affected. The skin touching her other jewellery or any other material does not do this. To prove the gold is playing some part, she once held a gold chain in the palm of her other hand while she was drinking wine, and her palm also went blue. She removed the chain, and the blue gradually receded, but the ring hand was still blue. It never happens when she's not drinking. I was spooked the first time I saw it. -- JackofOz (talk) 04:37, 10 October 2008 (UTC)


 * I have seen that before. That is generally due to the formation of copper compounds (which are blue) due to the presense of copper (as a hardener) in most gold jewelery alloys.  Apparently, some people have skin chemistry capable of dissolving the copper out of these alloys.  My wife has a very different reaction, which is distinctly either allergy, or dermatitis. --Jayron32. talk . contribs  04:45, 10 October 2008 (UTC)
 * I know you maintained that it was gold alone that caused your wife's allergy, but is she also allergic to nickel? a two-factor effect with gold + nickel could be one hypothesis. EverGreg (talk) 21:11, 10 October 2008 (UTC)

Perpetuating genes
Are there any known ways I can perpetuate my genetic stock without myself reproducing? Any that won't contribute to overpopulation? Also, are there any known ways of determining whether my genetic stock is above-average and worth making an effort to perpetuate? I have Asperger Syndrome, if that makes any difference. Neon Merlin  03:20, 9 October 2008 (UTC)


 * You could store your own semen. There are many sperm banks and other services that will do this for you.  If you are female, you could also have eggs extracted and stored, but that involves invasive surgery, and is far riskier and less pleasant than the male method for extraction of reproductive genetic information.  --Jayron32. talk . contribs  03:22, 9 October 2008 (UTC)


 * Note that the technology for long-term storage of unfertilized eggs is very new and has resulted in very few live births (I think I read about a first within the last year, but most IVF clinics don't do it yet). The exact reason why is not all that clearly understood, but freezing and the fertilization process don't work all that well together.  Fertilized eggs can be stored easily, as can semen.  SDY (talk) 08:47, 9 October 2008 (UTC)


 * You're asking some pretty tough questions, and it's hard to give suggestions here without bias. I suggest looking at genetic diversity, natural selection, and genetic testing to start you on the path to finding your own answers. Sjschen (talk) 04:01, 9 October 2008 (UTC)


 * An alternative is to support one's extended family as they have much the same genes as yourself. This is a tried and tested way of propagating genes in the animal world, with examples ranging from insects to mammals. EverGreg (talk) 08:34, 9 October 2008 (UTC)


 * This was what I was going to recommend. If your sister reproduces (if you have a sister), it's pretty similar genetic stock as your own, so at times it might be worth (from an evolutionary point of view) working to enhance her reproductive fitness even at the detriment of your own. See kin selection. --98.217.8.46 (talk) 11:20, 9 October 2008 (UTC)


 * As for "above average"... what do you really mean by that? You'd need to define your system of genetic worth first. It's not intuitive, and frankly we would probably disagree on what traits were most "desirable" and even some that were less "desirable". In the long run though your individual concerns about the worth of your genetics will play little role in the overall gene pool unless your reproduction rate is significantly differential from the average (either you produce more or they produce less). See eugenics. --98.217.8.46 (talk) 11:20, 9 October 2008 (UTC)


 * Although encouraging your relatives to reproduce will perpetuate your stock without your reproducing, it will still contribute to overpopulation. Theoretically, you could try to prevent other people from reproducing, but that would have a negligible effect on the portion of people who are related to you. Your only real solution is to go ahead and reproduce, and counter the effect on overpopulation by preventing others from having kids, or by increasing the capacity of the world. Because people in poverty reproduce more, I suggest donating to a charity that helps stop poverty, such as microcredit. If you donate a significant amount of money, it will be overkill, but I recommend that you do so anyway. — DanielLC 14:43, 9 October 2008 (UTC)


 * "Goodness" for a gene is really determined only by it's ability to spread and continue. Genes which don't make it into the next generation for some reason are "bad".  So there is no way to indirectly measure goodness or badness of someone's genes.  If they succeed in reproducing (preferably as many times as possible - and continuing for as many generations as possible) - then they are functioning well.  A decision to not have children (no matter how socially good that is) is an indication that your genes have already failed in their goal to reproduce.  Sooner or later, someone will come along with a higher sex drive or a higher maternal/paternal instinct that manages to overpower any hint of a desire to keep the earth's population in check.  When that happens, their genes will spread faster than yours and your genes have failed and were therefore not as "good" as the ones that wiped them off the face of the gene pool.  However, humans are (IMHO) gradually seeing more influence from memetic evolution than genetics.  Memes are also able to propagate, evolve and reproduce - and in humans, a meme can have a greater role in driving us than our genes do.  So perhaps the 'meme' that's telling us to save the planet is more powerful than the gene that's telling us to fill the planet from edge to edge with human beings.  It is arguable, therefore, that you are doing a better job of passing on your best memes to the next generation than you are at passing on genes.  So - become a teacher, or a writer or a musician - or merely answer questions on the ref desk in a way that reinforces the ideas (memes) that are worth passing on. SteveBaker (talk) 03:53, 10 October 2008 (UTC)


 * You might find Nature versus nurture an interesting read as well. SDY (talk) 15:05, 10 October 2008 (UTC)


 * in the Big Picture, you in all probability do not carry any genes which are not represented in the entire human gene pool at least several million times. and furthermore, if you did carry any rare mutations, the vast majority of them would be deleterious. so you can rest assured that even if you die without issue, your genetic components will not be lost to humanity. Gzuckier (talk) 05:41, 11 October 2008 (UTC)

Is our planet's core mostly iron because of boyancy?
?? 98.221.85.188 (talk) 04:18, 9 October 2008 (UTC)
 * Inner core is a pretty good read. One of the main driving forces behind the assumption that the core is mostly iron is that we know what everything else in the solar system is made of, and we know what our planet should be made of, and there's not nearly enough iron anywhere else on the planet to match the rest of the solar system.  Ergo, the iron has to be somewhere, so its gotta be in the core.  At least, that's how our article explains it.  Its a fairly logical analysis of the situation.  --Jayron32. talk . contribs  04:33, 9 October 2008 (UTC)
 * However, from the article Earth's magnetic field: Citing oceanic basalt 3He/4He ratios [5] and other evidence, J. Marvin Herndon et al contend that the inner core of the Earth is not iron but much denser atoms. --Ayacop (talk) 18:27, 9 October 2008 (UTC)
 * That's not what our articles say though. Our articles claim that the core is mostly Iron. And besides, what would these denser atoms be? 98.221.85.188 (talk) 14:37, 10 October 2008 (UTC)

Balancing equations
I can't for the life of me balance this equation: H2S + SO2 ---> S8 + H2O. The S8 in the product's side is throwing me off! I thought I knew how to do this, until I attempted this problem. Can someone explain to me how to do this? I've been at it for far too long! —Preceding unsigned comment added by 134.241.222.116 (talk) 05:16, 9 October 2008 (UTC)
 * Note that that there must be twice as much H as O on the right. The S is just along for the ride. The coefficients are not low. I guarantee the equation will balance. Edison (talk) 05:30, 9 October 2008 (UTC)


 * In other words, if the left hand side of the balanced equation is AH2S + BSO2 where A and B are integers, then you must have A=2B in order to get the hydrogen and oxygen to balance, and also A+B must be a multiple of 8 so that you have a whole number of S8 molecules on the right hand side. Gandalf61 (talk) 09:06, 9 October 2008 (UTC)

I still can't get it! Can you just tell me what it is? —Preceding unsigned comment added by 69.16.88.147 (talk) 11:15, 9 October 2008 (UTC)


 * Also note that, since A=2B, A+B=2B+B=3B. Since 8 is not divisible by 3, the fact that 3B must be a multiple of 8 implies that B itself must be a multiple of 8.  In particular, the smallest value that could possibly be a solution is B=8.  Why not try plugging it in and see if it works out?  —Ilmari Karonen (talk) 11:45, 9 October 2008 (UTC)


 * To restate the above, since the water/SO2 ratio requires there to be 3 sulfurs on the left side of the equation, and the S8 is on the right, the answer must involve a number of sulfurs that is divisible BOTH by 3 and by 8. The lowest number that works for that is 24, so try to work out a solution that involves 24 sulfurs.  That should put you in the right direction.  An alternative method would involve solving this via the half-cell method.  The reaction is a Synproportionation reaction, where sulfur in 2 oxidation states react to form a third oxidation state of sulfur.  Track the oxidation numbers and see for yourself.  You could try setting up two half-cell equations and balancing each and recombing them.  This method is described here and an example is put forward here.  If the brute force method using 24 sulfurs doesn't work, try the half-cell method.--Jayron32. talk . contribs  13:03, 9 October 2008 (UTC)


 * My recommendation to my students - ignore the requirement for integers until the end. After balancing the oxygen and hydrogen, you have 3 sulfur atoms on the left, with S8 on the right. So you require 3/8ths of S8.  At the end, you can't have fractions, so then multiply everything all the coefficients by 8.  I find this method a lot more intuitive than some of the above. --Bennybp (talk) 14:56, 9 October 2008 (UTC)

I think I got it! Is it 16-8-3-16? If so, thanks for all your help! If not, then I give up. —Preceding unsigned comment added by 69.16.88.147 (talk) 15:50, 12 October 2008 (UTC)
 * Yes, that's correct. It's easy to check; on the left you have 16×2=32 H, 16+8=24 S, and 8×2=16 O; on the right you have 3×8=24 S, 16×2=32 H, and 16 O.  You're done!  --Tardis (talk) 03:49, 14 October 2008 (UTC)

Ovulation
Why does the human body temperature increase whilst ovulating?90.210.162.166 (talk) 08:20, 9 October 2008 (UTC)
 * You may want to read Wikipedia's article on Ovulation. Having read it myself, I could posit an educated guess that ovulation is controlled by pituitary hormones, as mentioned in that article.  The pituitary gland also controls metabolism and homeostasis in the body, and one of its main jobs is the regulation of your body temperature via metabolic control.  My guess is that changes in body temperature are an indication that the pituitary is firing up in some way, which is a likely indication that it has released whatever the pre-ovulatory hormones are.  This is largely a guess based on some intuitive readings of the articles on Ovulation and the Pituitary gland, but it makes sense to me.  Does anyone else have a more concrete answer? --Jayron32. talk . contribs  12:52, 9 October 2008 (UTC)
 * From "Review of Medical Physiology" (William Ganong), the temperature rise at ovulation is probably due to the increase in progesterone secretion. Progesterone is thermogenic (i.e. increases metabolic rate and generates more heat). Axl  ¤  [Talk]  18:03, 9 October 2008 (UTC)

True or False? Attack of the mutant 6 foot man eating catfist?
There is this story about a scientist who found a man eating catfish. As reported in the Newspaper.

http://www.thesun.co.uk/sol/homepage/news/weird/article1784470.ece

Is this story scientifically true? Ohanian (talk) 10:50, 9 October 2008 (UTC)


 * Well it certainly doesn't seem scientifically supported. All evidence given seems to be from what local natives and one reporter say—which generally means it is anecdotal evidence, the stuff of legend (no matter whether your locals are in India or Missouri). Personally I would want to see why the reporter fellow ruled out animals better known to have attacked humans in the past (crocodiles, snakes, etc.) before jumping to a new theory. --98.217.8.46 (talk) 11:10, 9 October 2008 (UTC)


 * Ha ha I read that as a scientist finding a man who was eating a catfish, rather than a man-eating catfish. I'd go with 98.217's reasoning, though a man eating a catfish would be pretty plausible - if not exactly newsworthy. 194.221.133.226 (talk) 12:29, 9 October 2008 (UTC)


 * The Sun isn't really world renowned for its fact-checking. APL (talk) 12:48, 9 October 2008 (UTC)
 * If you see the cover of The Sun at supermarkets, it's usually hypin some biblical prophecy that it says is about to happen. Are you ready for IPv6? (talk) 13:58, 9 October 2008 (UTC)
 * You should have put an "NSFW" warning on that. ;-) Axl  ¤  [Talk]  18:07, 9 October 2008 (UTC)
 * I have seen catfish which weighed 50 pounds, and reliable witnesses have told of seeing larger ones living at the bottom of U.S. rivers just downstream from hydroelectric dams, eating the chopped fish who went through the turbines. As bottom feeders, catfish would certainly eat human bodies which had been placed in a river. All in all, it seems plausible but certainly not proved by a photo in a tabloid. I would have no trouble believing a report of one half the weight they claim. I could place a minnow that large in someone's hands in a Photoshopped picture. Seeing is not believing.
 * I don't know that much about catfish in general, but I can't quite imagine one eating a live human. I know that they would eat dead meat, so a dead human body wouldn't be that unlikely, but the live human...nonetheless, we could have a story about three 6 foot men eating a catfish, judging by that picture :-)  Nyttend (talk) 22:01, 9 October 2008 (UTC)
 * 6-foot and 161 lbs may be a record for that species of catfish but some species get much larger. The record Mekong giant catfish was "9 feet in length and weighing 293 kg (646 lb)." Rmhermen (talk) 23:42, 9 October 2008 (UTC)

Snopes has a couple of stories about huge catfish that may be of interest. Matt Deres (talk) 00:28, 10 October 2008 (UTC)

Quantum: why for entangled state but not separable states
I think there should be no difference between the entangled states and separable states (entangled states are just quantum states with special "pattern" and nothing else), so I speculate: if we measure one of the two entangled particle, the other will collapse instantly (just like this experiment), then how about measuring one of the two separated (non-entangled) particle? If we measure one of the two particle in separable state, does the other separated particle also collapse instantly? do whole of the other separated particles in our unverse collapse together with it (as the distance doesn't matter) simutaniously simultaneously and instantly? Can I say that all the other separated particles in our universe will actually collapse but just our sensor/device can't distinguish wheather whether they have collasped or not since they are in separable state? - Justin545 (talk) 12:07, 9 October 2008 (UTC)


 * Don't take too seriously the stuff about "the other particle collapsing instantly across arbitrary reaches of time and space." That's not something you can experimentally detect, it's just a feature of one particular mathematical formulation of quantum mechanics, and probably it should be taken to mean that that formulation doesn't correspond very well to reality. -- BenRG (talk) 21:34, 11 October 2008 (UTC)

Wave Function Collapse of Entangled Separable State

 * Suppose we have two particles $$A$$ and $$B$$ their respective states are
 * $$|\psi\rangle_A=\sqrt{0.2}|0\rangle_A+\sqrt{0.8}|1\rangle_A$$
 * $$|\psi\rangle_B=\sqrt{0.3}|0\rangle_B+\sqrt{0.7}|1\rangle_B$$
 * The state of the composite system of $$A$$ and $$B$$ is
 * $$|\psi\rangle_A\otimes|\psi\rangle_B=(\sqrt{0.2}|0\rangle_A+\sqrt{0.8}|1\rangle_A)\otimes(\sqrt{0.3}|0\rangle_B+\sqrt{0.7}|1\rangle_B)$$
 * $$|\psi\rangle_A|\psi\rangle_B=\sqrt{0.06}|0\rangle_A|0\rangle_B+\sqrt{0.14}|0\rangle_A|1\rangle_B+\sqrt{0.24}|1\rangle_A|0\rangle_B+\sqrt{0.56}|1\rangle_A|1\rangle_B$$
 * If we try to measure the state of particle $$A$$ of $$|\psi\rangle_A|\psi\rangle_B$$ and get state $$|1\rangle_A$$, it means $$|\psi\rangle_A|\psi\rangle_B$$ collapses to either $$|1\rangle_A|0\rangle_B$$ or $$|1\rangle_A|1\rangle_B$$. Besides, the probability of finding particle $$B$$ in state $$|1\rangle_B$$ is
 * $$P\left(|1\rangle_B\Big||1\rangle_A\right)=\frac{P(|1\rangle_A\cap|1\rangle_B)}{P(|1\rangle_A)}$$ (according to conditional probability $$P(B \mid A) = \frac{P(A \cap B)}{P(A)}$$)
 * where
 * $$P(|1\rangle_A\cap|1\rangle_B)=P(|1\rangle_A|1\rangle_B)=|\sqrt{0.56}|^2=0.56$$
 * $$P(|1\rangle_A)=|\sqrt{0.24}|^2+|\sqrt{0.56}|^2=0.8$$
 * therefore,
 * $$P\left(|1\rangle_B\Big||1\rangle_A\right)=\frac{0.56}{0.8}=0.7=|\sqrt{0.14}|^2+|\sqrt{0.56}|^2=P(|1\rangle_B)$$
 * Similarly, if we try to measure the state of particle $$A$$ of $$|\psi\rangle_A|\psi\rangle_B$$ and get state $$|0\rangle_A$$, it means $$|\psi\rangle_A|\psi\rangle_B$$ collapses to either $$|0\rangle_A|0\rangle_B$$ or $$|0\rangle_A|1\rangle_B$$. Besides, the probability of finding particle $$B$$ in state $$|1\rangle_B$$ is
 * $$P\left(|1\rangle_B\Big||0\rangle_A\right)=\frac{0.14}{0.06+0.14}=0.7=P(|1\rangle_B)$$
 * The above illustration shows that we are not able to distinguish whether the state of particle $$B$$ has collapsed or not, because no matter the state of particle $$A$$ we measured is $$|0\rangle_A$$ or $$|1\rangle_A$$, the state of particle $$B$$ always collapses to $$|1\rangle_B$$ with probability $$0.7$$. Therefore, we can say the particle $$B$$ DOSE collapse instantly (and so do all other particles in the universe) when we measure particle $$A$$, but we just have no way to emphasize that.


 * - Justin545 (talk) 06:06, 10 October 2008 (UTC)

what is the best way to structure a case study presentation on a medical patient ?
I have to present a case study to a large, mixed group of medical and allied-medical professionals. I have chosen my subject (the patient) and would like opinions on how best to structure and present the information and how to encourage discussion.Mollyisthedog1 (talk) 13:21, 9 October 2008 (UTC)


 * Are you planning to use Powerpoint? See "Medical history". Start with age & sex. Presenting complaint. History of presenting complaint. Past medical history. Drugs & allergies. Occupation. Social circumstances. Smoking & alcohol. Clinical examination findings. Relevant investigations. Treatment. Information about the specific disease. In smaller groups, I often invite individuals to comment on differential diagnosis and proposed management during the presentation. Axl  ¤  [Talk]  18:16, 9 October 2008 (UTC)


 * Have you seen House (TV series)?


 * Just a thought, it may be worthwhile to present a brief abstract and overview before you plunge into details. Much of your audience will likely be used to reading journal articles, so following that structure (summary->methods->data->interpretation) will make the talk easier to follow for those familiar with the format.  If the case study involves several cycles of "let's try this test, no that didn't work" it may make sense to have an overall summary, then do methods/data/discussion for each angle considered.  SDY (talk) 15:03, 10 October 2008 (UTC)

solar power roof installations and having to do roof maintenance
Hi,

When you install a solar panel on your roof, and then have to replace the roof shingles for routine maintenance, how do the solar panels get in the way? Do you have to take the solar panels off, replace the shingles, and then reinstall the solar panels? What's the deal?

I feel irritated that all the solar roof websites I've read don't discuss this issue.

Thanks

--InverseSubstance (talk) 18:31, 9 October 2008 (UTC)


 * Hm. I don't know much about this, but perhaps calling one of the companies directly may get you a live person, who could answer any specific questions that you have?  Its a start... --Jayron32. talk . contribs  19:20, 9 October 2008 (UTC)


 * Asphalt shingles are now available with rated lifetimes of forty years or more; steel roofing is often good for a hundred years. A properly designed and built roof that doesn't use low-quality shingles will almost certainly outlast the photovoltaic system on top.  Proper installation of the solar panels may even slightly increase the lifespan of the roof by providing a small amount of extra protection from the elements.  What type of 'routine maintenance' are you expecting to have to do that would require removal and replacement of shingles?
 * Interestingly, one can also purchase 'solar shingles'&mdash;photovoltaic panels which replace shingles altogether. TenOfAllTrades(talk) 19:33, 9 October 2008 (UTC)
 * The questioner could be asking about a solar water heater, and the removal of shingles might not be for maintenance of the shingles but maintenance of the roof structure. It's going to be hard to answer the question without knowing a lot more about the structure of the roof, how large the panel is, how and where it is located. It's good practice always to get at least three quotations for any kind of building work and the companies should be asked whether they have encountered a similar situation before and how they dealt with it. Itsmejudith (talk) 13:35, 10 October 2008 (UTC)

Ask your self something. How do they shingle around the various ventilation pipes protruding from the roof? The answer is you use flashing/and shingle around. So likewise, the supporting columns (for lack of a better word) for the solar panel would be shingled around.71.237.51.41 (talk) 19:59, 14 October 2008 (UTC)

Yes, and that's one disadvantage of a roof mounted photovoltaic solution. In lieu of the roof you could mount them on the side of the house or erect a pole in the yard and build a solar tracker. The roof mounted solutions block the sun so the roof will have less wear and tear.


 * I dont know shingles, but with ceramic tiles the solar electric panels are on an aluminium frame going through the roof. Then the tiles are cut just the same as the ones around the chimney etc. There is always an air gap between roof and panels, even if the roof angle is the same as the panels work less effeciently when hot. Working from the ceiling I suppose you could replace mostly from underneath.  I'm not exactly answering your question, but the panel frames on the installations I've seen can always be unbolted (thieves do it). Polypipe Wrangler (talk) 21:42, 15 October 2008 (UTC)

Watch question
When was the jump hour function invented for clocks and watches? I imagine it must be quite old (here's a watch from the 1890s with the ability), but was curious. --140.247.42.160 (talk) 20:10, 9 October 2008 (UTC)

Unit of Measures
Would UOM KOhm be the same as kOhm —Preceding unsigned comment added by A01534 (talk • contribs) 20:27, 9 October 2008 (UTC)


 * I would think so. A lowercase k is the correct abbreviation for the SI prefix, "kilo-", but "K" is fairly common. I don't know anything else it could mean (in computing it sometimes means 1024 times, but that's non-standard). --Tango (talk) 20:54, 9 October 2008 (UTC)


 * I always found that slightly confusing. I had thought capitals were for "bigger"  prefixes, and lower-case was for "smaller" prefixes.  That seems to be the pattern most of the time - mega vs. milli, peta vs. pico, etc.  But kilo, deca, and hecto don't.  I guess it would be asking too much to be completely logical.... But yes, K probably means k in your question - there is no (SI) prefix for a capital K.  --Bennybp (talk) 22:07, 9 October 2008 (UTC)


 * What you have to remember is that all the prefixes from milli- to kilo- are part of the original metric system while the ones from mega- upwards (and from micro- downwards) are later additions that have come in several batches over time. Presumably the forms "kg" and "km" were well established by the time that M- for mega- was introduced, and it wasn't until there were several more prefixes that the pattern of "higher prefixes get capitalized" was really established.  So it makes sense that there was no pressure to change kilo- to be represented with a capital K.  --Anonymous, 01:08 UTC, dekaOctober :-) 2008.


 * Along those same lines, the M- for mega- is also obviously influenced by the m- prefix already being in use. The next step there led to the use of μ- for micro-. Had more size prefixes started with k's, you'd likely see k-, K-, and κ- prefixes instead. Personally, I think using the Greek symbol was a dumb idea, but they no doubt didn't think of the hassle it was cause folks trying to use it on standard keyboards (and typewriters!). I would have gone with i- (for itsy-). ;-) Matt Deres (talk) 10:48, 10 October 2008 (UTC)


 * They probably rationalized it by assuming the letter 'u' could be used in place of the 'μ' without loss of clarity in typewritten documents. (No SI prefix uses upper- or lowercase 'u'.)  Heck, I still use that shortcut&mdash;I've got Word set to autocorrect any instance of um to μm for me as I type.


 * I'd still say it's a better solution than the one adopted by some (mostly electrical) engineers. They use mm as a prefix (millimilli-) in lieu of mu, which is just asking for trouble.  (Did you mean 1 mF or 1 mmF?  Or do you want me to use a capacitor 1 mm long?) TenOfAllTrades(talk) 13:50, 10 October 2008 (UTC)


 * In fact the use of "u" in place of µ was officially approved by the ISO in 1974, but later withdrawn as character sets including µ became more commonly available. --Anonymous, 18:57 UTC, October 10, 2008.


 * See, all this confusion could have been avoided if they had just asked me in the first place! That way, at least I would have understood. (Of course I was only born in 1985, but that's what time machines are for!) :) --Bennybp (talk) 19:47, 10 October 2008 (UTC)
 * Then you'll appreciate what King Alfonso X of Castile (known as "Alfonso the Wise") said: Had I been present at the creation, I would have given some useful hints for the better ordering of the universe. --  JackofOz (talk) 20:28, 10 October 2008 (UTC)
 * "Ohm" as a unit of measure is not capitalized: hence "kohm". Axl  ¤  [Talk]  18:57, 10 October 2008 (UTC)


 * Of course, if one were being pedantic, kohm is no more acceptable than kgram, kmeter, or kamp. It's either k&Omega; or kilohm.  TenOfAllTrades(talk) 19:05, 10 October 2008 (UTC)
 * It would seem your spelling is correct, but what happened to the other 'o'? --Tango (talk) 19:10, 10 October 2008 (UTC)


 * It seems to be an arbitrary decision by the powers-that-be (I presume the BIPM). For ease of use, the doubled vowel was removed from kilohm and megohm (instead of using kiloohm and megaohm).  A similar change was made with the are, giving us areas in hectares rather than hectaares.  Not all double vowels are forbidden, however&mdash;kiloamperes and megaampere are cool.  I imagine that there's a formal document spelling all this out somewhere, but I can't bring myself to hunt it down at the moment.  TenOfAllTrades(talk) 20:14, 10 October 2008 (UTC)


 * Googling bipm.org reveals 3 instances of "kiloohm" and none of "kilohm". The SI brochure itself says nothing about removing vowels. It seems to me that the shortened forms, although widespread, are not sanctioned by the CGPM, but some national bodies like the NIST choose to define their own variants. --Heron (talk) 10:40, 11 October 2008 (UTC)


 * The SI standard only defines the symbols, not the spelling of the units (thus "m" is standard but corresponds to "meter" or "metre" in English, "mètre" in French, "Meter" in German, "metro" in Spanish, the Cyrillic equivalent of "metr" in Russian, etc.). National standards bodies may standardize the spelling of units, though.  I don't know about the particular cases in question.  --Anon, 21:48 UTC, October 11, 2008.

trying to remember the name of a certain stone
hi I have been trying to remember the name of a certain stone that we used to see alot of when we were kids. its a flacky stone that is black and foung in abundance in caves. i believed it was called "mika" but a search of it came up empty. the best way to describe it is that it usually comes in small or large chunks but can easily be split into little flakes and crumbles verry easily. If you could please get back to me it would be verry much apreciated. My email is [Redacted] —Preceding unsigned comment added by 99.241.82.198 (talk) 20:51, 9 October 2008 (UTC)


 * (I've removed your email address to protect you from spam - people will reply here.) I don't know much about rocks, so you'll have to wait for someone else to come along, but you can look through List of rock types and see if anything jumps out at you, if you like. --Tango (talk) 20:57, 9 October 2008 (UTC)


 * Mica? Saintrain (talk) 20:59, 9 October 2008 (UTC)
 * And if the variety you were seeing was black, Biotite. Deor (talk) 02:58, 10 October 2008 (UTC)


 * Another possibility is flint - but I was also thinking mica when I first read the question. Flint can be flaked, but mica is more "crumbly". Franamax (talk) 06:38, 10 October 2008 (UTC)

Venus axial tilt
Which one is right? Is Venus upside-down tilt axis of 177 degs, or normal upright of 2.6 degs. Old books say 2.6 degs axial tilt, but ewer study say Venus is upside down of 177 degs.-- Freeway 9  1  22:28, 9 October 2008 (UTC)


 * Either, they're the same thing. You can think of it as being tilted 177 degrees and rotating in the usual direction ("prograde"), or tilted 3 degrees and rotating backwards ("retrograde"). It doesn't really make any difference which you go with. (Although, interesting, our article says 177 degrees and retrograde, which doesn't sound right to me...) --Tango (talk) 22:36, 9 October 2008 (UTC)


 * Another way to view it is that "retrograde" means the axial tilt is greater than 90°, so "177° and retrograde" is a perfectly legitimate choice and in fact is probably the one I see most often. I don't know how professional astronomers describe it, though.  --Anonymous, 01:11 UTC, October 10, 2008.


 * Then if Venus is rtro, then count it as 2.7 deg tilt. What about Pluto (which is no longer plnaet). If Pluto is rtro would it still be 120 deg. tilt?-- Freeway 9  1  22:51, 9 October 2008 (UTC)

Quantum Mechanics
Since quantum mechanics can't provide deterministic predictions, is it really falsifiable? And if it's not falsifiable, is it really a true science? 12.10.248.51 (talk) 19:02, 9 October 2008 (UTC)
 * The statistical predictions of QM are very much deterministic in the important ways, similar to Meteorology. In the place QM says things can not be determined (uncertainty principle) the theory puts a tight limit on the indeterminance(uncertainty) of its predictions. This aspect of the theory would easily be falsified by a theory being able to make a more accurate prediction.  It might interest you to know that the prediction of QM explain many aspects of observations we make with chemical instrumentation. If we saw something different than what we do with NMR, EPR, UV-Vis, FTIR, Electroanalytical chemistry we would have to work on QM.  This isn't to say QM is complete its just our best working theory.  I've moved this to the reference desk since its a more appropriate place for the question and will receives explanations that far surpass this one.--OMCV (talk) 23:32, 9 October 2008 (UTC)


 * You can certainly falsify all sorts of aspects of it, even the stuff that appears almost purely philosophical at first glance. See, for example, the Bell test experiments. And the non-deterministic nature doesn't preclude testing or even predictions. Simple example: we have no way of making a "deterministic prediction" about when a single unstable atom will decay. But we can make statistical predictions which are easily testable (and thus come up with things like half-lives which are pretty iron-clad on the aggregate, even if they tell us nothing about the individual atom).
 * Note of course that Quantum Mechanics is the name of a field, not the name of a specific theory. Asking "can you test Quantum Mechanics?" is like asking "can you test Biology?" or "can you test Anthropology?" You wouldn't say a field was untestable unless the field's very definition excluded the possibility of naturalistic explanations (like Creationism). You can falsify all sorts of aspects to the theories that make up QM—it's been done since the 1930s, and is why we have the version of QM we have today and not many of the other versions that have been floated. (It's why we have something more like Bohr's version of QM rather than Einstein's, for example.)
 * There are some aspects of QM which are at the moment not falsifiable, in the realm of the metaphysical/philosophical interpretations of them. Whether those interpretations count as "science" would depend on who you asked and how you interpreted the term "science" in this case. But even then, sometimes they actually turn out to be falsifiable, like the issue of the EPR paradox, which was thought to be just a philosophical debate with no real testable content when it occurred in the 1930s, but in the 1970s it was discovered that there were very complicated but clever experimental setups that should be able to distinguish between some of the possible answers of it (the Bell tests I linked to earlier). --98.217.8.46 (talk) 23:58, 9 October 2008 (UTC)