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March 4

Refusal to investigate the existance of God.

Billions of dollars are spent to investigate the existance of the God Particle(Higgs boson) but scientists refuse to investigate the existance of God even though millions of people including the Pope,Cardinals,Imams and most polititions have constant contact with Him/Her and would be available to prove it.This would be of great value to world peace to prevent the religious divide facing everyone. John Cowell124.179.205.11 (talk) 00:12, 4 March 2011 (UTC)

The scientific method deliberately excludes religious faith. One cannot investigate the existence of something supported only by faith. Scientific investigation of the existence of God would be no different from investigating the existence of any deity, such as the Invisible Pink Unicorn, the Flying Spaghetti Monster, or any member of the Twelve Olympians in the Greek Pantheon. ~Amatulić (talk) 00:17, 4 March 2011 (UTC)

Pretty much every premise in the OP statement is wrong. Lots of scientists undertake investigation into the existence of God and you are free to undertake or fund any such activity you please. You might want to start with an article like Relationship between religion and science and go from there. Vespine (talk) 00:22, 4 March 2011 (UTC)

The OP should also note that "God Particle" is short for "Goddam Particle" because it is so elusive, but Lederman's publisher would not accept that name for his book. -- 119.31.121.88 (talk) 00:40, 4 March 2011 (UTC)

There have been several experiments to analyse the efficacy of prayer. Praying for someone else, who does not know they are being prayed for, shows no measurable effect. Due to the placebo effect, it is hard to check for an effect when the patient prays for their own recovery. For further reading, see this Google search for "double blind prayer study. CS Miller (talk) 06:36, 4 March 2011 (UTC)

Harvard did a study on cardiac patients, who when told they were being prayed for showed a statistically significant rate of worse outcomes, probably due to stress factors. Imagine Reason (talk) 19:38, 5 March 2011 (UTC)

If anyone really could prove the existance of god(s) to the same standard that is usually expected in science, then scientists would listen. The truth is, they can't. Faith and proof really don't go together. --Tango (talk) 00:23, 4 March 2011 (UTC)

I also disagree with Amatulic. There are many scientists that study this issue, amongst others Victor Stenger and Sam Harris argue that as long as religion makes claims about physical reality, there is no reason why science can not be brought to bear about the validity of those claims. You could argue that a pure definition of religion doesn't make claims about the "natural" world, only the spiritual or supernatural, but no religion fits this description. As soon as the spiritual or supernatural affects or interacts with our physical reality, which in all religions it does, then science can have a valid say. That's one of the reasons we don't like religious questions here, because they are very divisive and tend to degenerate into forum like discussions, which this site is not the place for. Vespine (talk) 00:30, 4 March 2011 (UTC)

Belief in Invisible Pink Unicorns does not cause the slaughter of innocent people.J.Cowell124.179.205.11 (talk) 00:46, 4 March 2011 (UTC)

Show me the Pope, Cardinal, or Imam who would be willing to submit any claims to measurable, scientific existence of God to scrutiny by disinterested, objective, and critical scientists. I have not seen them. Show me the claims they are making that they would allow external, unfettered investigation into. I have not seen them. I think you fundamentally misunderstand the situation if you think that religious leaders are interested in having their claims put to rigorous scientific scrutiny. They are not interested in cowing to scientific authority, much less risking the possibility of being wrong. (And even if you believe that God does exist, and does want to help you, you can still imagine a God that doesn't want his existence objectively proven and would hide it when push came to shove, because that would obviate the need for faith.) --Mr.98 (talk) 00:48, 4 March 2011 (UTC)

BTW it's not just faith that would be obviated (I like that word :). It's also free will. A provably omniscient God would not be compatible with free will. Free will requires a person to at least believe that their actions are their own (it's immaterial if the actions really are or aren't). Ariel. (talk) 01:15, 4 March 2011 (UTC)

While scientists can investigate (and disprove) concrete religious claims, like that the Earth is only a few thousand years old, you can't investigate the existence of God, since God can always "retreat" deeper. If we prove that nothing since the Big Bang requires the existence of God, you could then argue that God caused the BB. If we later prove what caused the BB, then God could be said to have created that, etc. StuRat (talk) 02:37, 4 March 2011 (UTC)

...essentially God of the gaps in a(n) historical rather than deeper-detail perspective. DMacks (talk) 04:45, 4 March 2011 (UTC)

The basis of science is to witness the universe in every form and derive the most accurate acount describing its modus operandi, and use this accumulated knowledge to make accurate deductions and predictions for that which cannot be observed.

Since God is not from within this universe, science cannot test for his exsistance or non-existance, there is no testable premise. All submitted evidense is subject to personal interpretation. Plasmic Physics (talk) 03:08, 4 March 2011 (UTC)

What I imagine the OP is saying is you'd go to someone who supposedly talks to God on a regular basis, like the Pope, and say, "so, Pope. Is there anything we could do that would prove the existence of God? Why don't you ask God about it and come up with something that we can test, e.g., look this direction on this day at this time and you'll see a comet the flies by and says, 'hi guys!'" I mean, if such a thing happened, and you could really be sure that it wasn't some kind of colossal hoax, even atheisty me would find it pretty interesting, maybe even compelling. But nothing like that has ever happened and nothing like that will happen. The Pope would never agree to such a thing. Whether that's because he knows it is probably outside of his ability to provide results, or because, again, those kinds of results would have severely problematic theological implications, or however you want to interpret it, it just isn't ever going to occur. No way, no how. It's not a case that scientists would ignore the Pope — I am sure the Dawkinsy types at the least would be happy to set up monitoring stations on the (highly likely) chance that the Pope would look like a fool in the process. But the Pope would not be foolish enough to partake in such a game, and would have perfectly good theological reasons for not participating. Feel free to insert any other religious figure for "Pope" in this paragraph. Every once in awhile such figures do hazard concrete beliefs about when a miracle will happen (the Earth will end next Thursday, etc.), but so far none of them have panned out. --Mr.98 (talk) 03:13, 4 March 2011 (UTC)

God wouldn't likely agree to it either, since it would defeat the whole faith aspect of God-based religions anyways. Plasmic Physics (talk) 03:21, 4 March 2011 (UTC)

That gives me an idea! Has anyone written a book or movie about a world where God DOES exist and is readily verifiable? Answers devout believer's prayers, punishes the wicked and performs regular miracles for example. Maybe investigating the contrasts between THAT kind of world and the one we live in would be an interesting exercise.. Vespine (talk) 03:42, 4 March 2011 (UTC)

There's a book where the protagonists can travel to all sorts of parallel worlds, and one of the worlds has an "active" God. The main difference is that no one can disbelieve, and that sins are punished instantly. It's not explored much else though. I think it's The Number of the Beast by Robert A. Heinlein, but I'm not certain. Ariel. (talk) 04:00, 4 March 2011 (UTC)

The Number of the Beast (novel) is a direct link to the page on Heinleins' book - 220.101 talk^\Contribs 15:02, 4 March 2011 (UTC)

As far as I know, He only proved himself once before. In the Koran (Wikipedia excerpt), I've read that He lowered a table from the sky with a feast on it. Apparently, He wasn't very happy about having to do it, infact He sounded quite annoyed. Plasmic Physics (talk) 03:29, 4 March 2011 (UTC)

How does Plasmic physics know that God is not from within this universe? J.Cowell05:10, 4 March 2011 (UTC) —Preceding unsigned comment added by 124.179.205.11 (talk)

I don't know how PP knows it, but it seems to me an eternal entity could not be part of a universe (as we know it, according to science's current understanding) that has both a beginning and an end that does not allow for anything to exist outside of it. DMacks (talk) 05:30, 4 March 2011 (UTC)

Wow I so terribly do NOT want to start a debate but since when doesn't it allow for anything to exist "outside" of it? I've never heard that, for all we know, there might be an infinite amount of big bangs creating an infinite amount of universes completely separate to our own, in some other "dimensions" or something. Your view sounds "univercentric" to me ;) ... It might be impossible to know, but that's a log way from saying it is positively "excluded"? Vespine (talk) 05:54, 4 March 2011 (UTC)

The question specifically says "this universe", which I assumed meant the one we inhabit, rather than some other one or a superset/multiverse situation. DMacks (talk) 06:01, 4 March 2011 (UTC)

Our God-Bothering polititians will be most upset if you relegate God to another universe!.J.Cowell06:16, 4 March 2011 (UTC) —Preceding unsigned comment added by 124.179.205.11 (talk)

No, what I meant was, that He exists outside of everything, outside of time, space, reality. By "reality", I mean outside of our perspective. Think of it this way, all of the above is a very complex figment of His imagination. That's what I mean with outside. Plasmic Physics (talk) 06:33, 4 March 2011 (UTC)

Would you care to define in what way(s) that differs from non-existence as seen from an "in universe" POV? Roger (talk) 06:57, 4 March 2011 (UTC)

It is simply a matter of personal preference.

Are we getting of topic? Plasmic Physics (talk) 07:11, 4 March 2011 (UTC)

This whole thread is off topic for this desk and should have been boxed from the start. --Sean 14:30, 4 March 2011 (UTC)

If anyone is interested, in Contact_(novel), there is an excellent chapter where science's stand with respect to religion is explained. ManishEarth^{Talk • Stalk} 15:12, 4 March 2011 (UTC)

Rather surprised that in this supposedly enlightened age there are still those who wish to shut down discussions on the most fundamental of all scientific questions.Shades of Galileo,Scopes and book burning.J.Cowell124.185.229.128 (talk) 00:01, 5 March 2011 (UTC)

No, you miss the point. It is not a scientific question at all. Individual scientists no doubt have their own beliefs one way or the other about God, but science per se is not concerned with the matter. It is a question of personal faith, period. Nobody has ever proven that God exists, or that God doesn't exist - in a way that would satisfy science - and they never will. That's why it's not a relevant topic for the Science reference desk. -- Jack of Oz [your turn] 00:11, 5 March 2011 (UTC)

Im confused. Why does it matter if God exists or not? what will it change? If he does exist then we still wont be able to explain anything, we will still be trying just as hard to figure all this stuff out. Its not like if we prove he exists, he will come out from behind the clouds and say ok you got me here are the answers to all the questions you could ever ask. We will be in the same reality either way. —Preceding unsigned comment added by 98.221.254.154 (talk) 01:18, 5 March 2011 (UTC)

Now what if God was proven to exist? If so the conlusion would generate another question, who created God or where did he come from? Maybe God was created by an ancient story teller with a vivid imagination. Perhaps another supreme being created God. Then theres that fact that he just simply does not exist. In my opinion, searching for the existence of a supreme being is a waste of valuable time. We could be doing things more important for all of our benefits. Instead of just finding some proof to satisfy everyone for a short period of time. I do not mean to offend anyone but this is what I had to say. Matthew Goldsmith 19:23, 8 March 2011 (UTC)

Flower identification

Sitting on a coworker's desk in NE China. The plant is basically a 2 dimensional green hand shape. This flower appeared at the very tip of one of the "fingers". Can anybody tell me what plant this is? purple and white flower It's quite fragrant. The Masked Booby (talk) 01:44, 4 March 2011 (UTC)

Looks to me like Neomarica northiana, part of the Neomarica (Walking Iris) genus. Nanonic (talk) 02:04, 4 March 2011 (UTC)

I believe you've nailed it! Thank you. The Masked Booby (talk) 02:08, 4 March 2011 (UTC)

That's a beautiful picture too. If it's yours, would you upload it to Commons, now that you know the name of the plant? ~Amatulić (talk) 21:17, 4 March 2011 (UTC)

Einstein in the Manhattan Project

Why didn't Einstein get clearance for working in the Manhattan Project? It is true that he was left-leaning, but being the genius that he was, and the Einstein–Szilárd_letter, shouldn't anyone consider him more of an asset than a risk? Quest09 (talk) 01:48, 4 March 2011 (UTC)

By that time physics had moved on well beyond Einstein, who was more of a figurehead than a leading physicist. StuRat (talk) 02:29, 4 March 2011 (UTC)

They approached Einstein very early on with the possibility of getting help from him on the theory of gaseous diffusion. They found him to be kind of useless — the sort of work Einstein did well was fundamental and theoretical. The kind of work that was really required to make an atomic bomb was specific and literal and practical. It was in many respects more of an engineering task than a scientific one, albeit it was an engineering task so bleeding-edge that it required huge teams of scientists to work out the details. He was considered a security liability because of his strong political beliefs, as well. But mostly the people who ran the project couldn't see much use for him. Building a bomb required nuclear physicists, engineers, chemists, metallurgists, etc. It didn't require people who had clever ideas about the structure of space and time. It was really not Einstein's forte.

By contrast, Niels Bohr they did bring into the project, even though he also didn't do much of practical value. (He helped with the theory of the neutron initiator, but that's the only practical problem he was involved in, as far as anyone knows.) Bohr was more of a morale builder than anything else. It's also not the case that Einstein was really "beloved" by that generation of physicist in the way that Bohr was; it's not clear to me he would have helped morale. Einstein was also seen by the quantum theorists as kind of backwards for his long-standing debate with Bohr. He also had essentially no students, so it's not like people looked up to him fondly for that reason, the way that many did with Bohr. --Mr.98 (talk) 02:58, 4 March 2011 (UTC)

(ec) Some searching in Google Books turned up The Einstein File by Fred Jerome, which appears to be well researched and cites primary sources. Chapter 4, "Banned from the Bomb", is all about this question. The short version is that there's not enough evidence to be sure, but the author thinks that it's J. Edgar Hoover's fault. You have to remember that this is a bureaucracy—Roosevelt trusted Einstein, but it wasn't Roosevelt's job to make the decision. Incidentally, Einstein did not request clearance; Roosevelt requested it for 31 scientists including Einstein. I somehow doubt that Einstein would have agreed to work on the Manhattan Project in any case. What StuRat and Mr.98 said is also true (Jerome mentions this as well). -- BenRG (talk) 03:12, 4 March 2011 (UTC)

I'm not sure that FDR really trusted Einstein on that level of things. It's one thing to trust him when he says, "Germany's trying to get us, look into this," and even then, FDR didn't really put a lot of money behind that. That's not the same thing as saying, "please run my bomb project."

If Einstein had really been valuable to the project, they probably could have decided to let him in. They made a lot of security exceptions during the war — Oppenheimer was super lefty, practically Communistic, at points in the 1930s, as all well knew. Arthur Compton was a member of various "fellow traveler" organizations. There are other examples as well. Because these people were actually quite essential to the work, Vannevar Bush and later General Groves were willing to look the other way, so long as close tabs were kept on them. With Einstein, it wasn't worth the risk.

It's worth also qualifying what is meant by "risk" here — it isn't necessarily that he's a spy or a saboteur. It could also just be that he's not good at keeping a secret, which is a less vicious, but equally damning, concern.

It's of note that the period in which Vannevar Bush thought about trying to get in touch with Einstein on this, the Manhattan Project was still in the extremely exploratory stages. Maybe at that stage having someone like Einstein would have been useful. But once you get into 1942 or so, he would not have been useful at all. --Mr.98 (talk) 03:23, 4 March 2011 (UTC)

Einstein made his "practical technologist" bones early on in his career, back in the era when Edison and Tesla were inventing useful things. Didn't he work in a relative's electric motor factory? Didn't he invent some type of refrigerator? And finally, didn't he review myriad patents? He still had the same brain, despite the decades of theoretical physics, and he could have been of great use to the project in many practical areas, let alone theoretical physics. Edison (talk) 04:51, 4 March 2011 (UTC)

Sure, very early on he did that sort of thing, with a previous era's technology. But the guy was practically retired by the time of World War II. He spent his time hanging out on the beach and having coffee with Gödel and fruitlessly trying to come up with the Unified Field Theory. He was out of the game. (Oppenheimer certainly felt that he was, in any case. There is some snarky quote that Oppenheimer gave the magazines just after the war about how Einstein was a signpost of where physics had been, not a sign pointing to where it was going.) You really imagine him going to Los Alamos and breaking a sweat on how to design a diffusion plant, or going to Chicago and engineering the first reactors? If he had been some kind of great organizer, the type of guy who could run a big project, I'd agree with you. But he never really displayed a talent (or interest) for that kind of thing. In his work, the stuff he was great at was coming up with the big, grand theory. He was not great at doing millions of calculations, much less quickly. The kind of work that was required to build the bomb was millions of calculations, not big, grand theories. A few clever ideas, sure. But they had other idea people, once the program really got under way. --Mr.98 (talk) 12:43, 4 March 2011 (UTC)

Were it not for security worries, it would have made sense to use the far from ancient and doddering mind of Einstein in the defeat of the Axis, if he were willing to help. Einstein was only 63 in 1942. Richard Feynman was 68 when he played an important role in the Challenger shuttle disaster investigation, which was in an area of technology he had zero background in. Even if Einstein was squeamish about building bombs to drop on Hitler, there were many areas of war research he could have helped with, just as Thomas Edison worked on acoustic detection antisubmarine apparatus and synthetic phenol in WW1, 1914-1918, from age 67 to 71. At a mundane level, Einstein could have screened patent applications to pick out those which actually were physically practical and which could have use in war equipment or in any area useful to the war effort such as communication, electricity, transportation, food preservation, or refrigeration. Edison (talk) 16:30, 4 March 2011 (UTC)

Well, to me the real question is to ask whether he could have worked on other projects, and why he wasn't used more readily there. There were plenty of projects of far lesser security concern than the bomb — things that were graded only "secret" or "confidential" rather than "top secret." An indeed, Einstein did do some consulting with the Navy. But I just don't seem him packing up and going to a government lab, myself. (And, entirely separately, I would argue that Feynman's background — including his war work! — actually made him much more qualified for a Challenger-like investigation than Einstein would have been. Feynman had lots and lots of practical experience in debugging large systems; that's actually what he did during his work with Oak Ridge during the war on radiation safety, on the possibility of critical masses forming inadvertently, if I recall. I don't see any similar experience on Einstein's resume. Einstein and Feynman were both great theoretical physicists, but they had very different minds. Feynman's strikes me as the far more practically oriented.)

Incidentally, there was, I do recall, a physicist who screened said patent applications for the Office of Scientific Research and Development in the manner that you describe (but we lack an article on him). It probably would have been a job Einstein could have, in fact, done quite well if he had been asked to, and wanted to. --Mr.98 (talk) 16:51, 4 March 2011 (UTC)

Physicists at MIT dropped everything to work on radar(secretly). By contrast, it would have been a morale builder if some aging science superstars such as Einstein were shown in Life magazine in a lab somewhere "doing war research" even if it was not really the forefront. A mathematician or physicist is typically far over the hill in terms of major breakthroughs by his early 60's but they are the bedrock of review panels, with experience and perspective to decide what is promising, and what is a blind alley that has been gone down before. I knew women who drove over an hour each way to work a long shift building artillery shells and airplanes in WW2, and it seems unconscionable to have brilliant physicists "sit the war out" rather than making whatever contribution they were capable of to keep Hitler and Hirohito from dividing up the spoils after defeating the Allies. Edison (talk) 16:59, 4 March 2011 (UTC)

Mm, perhaps, but we're getting a bit far afield, now. We've gone from discussing whether Einstein would have been useful for the Manhattan Project, to whether he would have been useful as a bit of propaganda. If I were a government scientist-administrator like Vannevar Bush (who was on the cover of Time magazine for his war research), I wouldn't necessarily want to give Einstein such a soapbox. Einstein's political views were fairly out of the mainstream for the period (even if most of them are pretty tame by modern standards), and propping up someone as a centerpiece can backfire on you. (Would Einstein have followed the "party line" if it went against his convictions? I'm doubtful.) Anyway, I'm not saying that the past had to happen the way it did, but I do think their decisions were defensible along both practical and scientific grounds. Personally I think Einstein is pretty out of step from the kind of scientist who was really quite useful in World War II. He's not a Bush, Oppenheimer, Compton, Szilard, or a Teller. This in no way should be seen as disparaging of Einstein as a scientist, or as a person. --Mr.98 (talk) 20:24, 4 March 2011 (UTC)

There are women (and men) right now who drive more than an hour each way to work long shifts building artillery shells and airplanes. I don't see how this is relevant. --140.180.5.6 (talk) 17:29, 4 March 2011 (UTC)

Sorry for your lack of comprehension of what I was trying to say. You may be unfamiliar with the fact that people (our moms and grandmothers) abandoned their typical lives during WW2 to devote their full time to the war effort, travelling long distances (probably taking far longer than an hour in many cases) at the wartime 45 mph speedlimit on bald tires to do hazardous unfamiliar work. Einstein was basically left sitting on his butt, maybe scribbling unified field equations that could not work on a blackboard,and did not aid the war effort, if statements above are correct. He might have been able to do more to win the war than "Rosie," my ancestor who worked double shifts making antiaircraft rounds, and once setting one off by accident in the crimper, by working faster than the machine was set up for, while Albert sat on his butt, unused and ignored. A wasted Einstein seems criminal. Maybe he could have worked some double shifts and devised a proximity fuse for artillery shells which was less prone to explode over friendly troops on the way up when it should have exploded over enemy troops on the way down, as Audie Murphy reported in his war memoirs, or maybe he could have devised a magnetometer an airplane could have used to locate enemy subs, as the Japanese devised toward the end of the war, or night vision goggles as the Germans devised toward the end of the war, and saved thousands of Allied lives and shortened the war. Edison (talk) 05:11, 5 March 2011 (UTC)

In my web searches the one thing which people are most eager to credit Einstein for in the second World War is the "Philadelphia Experiment". Now I don't believe the crazy stories about that event, but I think it was typical of the military at that time to try to drown out accurate information with wild disinformation (such as covering up experimental aircraft or surveillance balloons with flying saucer alien stories). I reserve suspicion that even after all this time, there might still be some tech he was really working on, perhaps stealth technology for ships - something basic, e.g. "antisound" for radar, hmmm, or for subs... - which remains sensitive enough that Einstein still hasn't been given his due, except by fringe sources. Wnt (talk) 17:33, 4 March 2011 (UTC)

The problem is that there is literally zero reason to suspect this, other than "it'd be interesting if it were true." --Mr.98 (talk) 20:27, 4 March 2011 (UTC)

Oh, you're absolutely right. But there are many things from that war that remain absolutely secret, and thus many histories that seem a little implausible. Like Glenn T. Seaborg's discovery of so many elements after the war, as opposed to, hypothetically, while trying to build a better neutron initiator. We have to indulge our imaginations now and then in order to avoid believing systematic error is fact. Wnt (talk) 00:23, 5 March 2011 (UTC)

I'm not sure I gather your Seaborg analogy at all — Seaborg discovered all those elements because he had a total monopoly on the tools necessary to discover said elements. There's no real mystery there. It's also not like he wasn't working on the weapons program at the same time — he was, in various capacities. While it's always possible there are secret programs out there that have not yet been discovered, there is really no reason to assume any science fiction. It's also hard to imagine that programs of the scale of what you're describing would have existed with absolutely no evidence having surfaced thus far. --Mr.98 (talk) 02:24, 5 March 2011 (UTC)

We know that Seaborg worked on nuclear initiators.^[1] We know that early nuclear initiators are said to have used polonium-210. The question is only whether some improved formula might have been discovered and kept secret. I don't think it's implausible that something more sophisticated might have been thought up and kept quiet. Seaborg may have had great advantages finding elements after the war, but still, I think his output for that period is regarded as absolutely extraordinary. Yes, I know there's no evidence that he discovered any of those elements during the war; I just don't think that in the absence of evidence we have to assume, confidently, that nothing like that happened, when it seems just as plausible that it could have.

I suppose that what really appeals to me about the notion of Einstein hiding ships somehow is that it is the sort of thing that would have appealed to his pacifist ethics. What better war weapon for him to invent than a way to protect innocent ships from skulking U-boats? Wnt (talk) 01:13, 9 March 2011 (UTC)

Time-travel photography

Suppose one has an opportunity to travel to the past and take photos in, say, ancient Greece or Rome (assuming that his/her activity wouldn't affect the subsequent events). Is there any way to prove that the photos are genuine upon return to our times, making such activity worthy? —Preceding unsigned comment added by 89.76.224.253 (talk) 12:24, 4 March 2011 (UTC)

You could test for evidense of image manipulation eg, CGI Plasmic Physics (talk) 12:37, 4 March 2011 (UTC)

There are ancient structures (such as remains of houses) that have been found and identified, but not yet excavated. You could bring a list of such structures and scratch "89.76.224.253 WAS HERE!" on a few of them (to make sure at least one inscription survives) and take pictures. Sjö (talk) 14:11, 4 March 2011 (UTC)

They don't have to be structures that have yet been found—collecting photographs which successfully and accurately guide new present-day archaeological exploration would be an extremely potent evidence. If our hypothetical scenario allows the photographer to leave physical evidence and objects behind, the science-fiction-story-approved method is to bury a small artefact containing a known quantity of one or more radioisotopes in a suitably sealed, tamper-resistant, temper-evident container. TenOfAllTrades(talk) 14:36, 4 March 2011 (UTC)

BTW. Even if time-travel is impossible, can information be transmitted from one time to another? 212.169.188.228 (talk) 14:48, 4 March 2011 (UTC)

Sure, but only in one direction — past to future. Transmitting information from the future to the past is time-travel, just dressed up in different lingo ("information" must be transmitted by a carrier, and the carrier is a "thing" you are sending back in time). --Mr.98 (talk) 14:58, 4 March 2011 (UTC)

I'm not sure why it's so frequently stated on the science ref desk that backwards time travel is impossible. That's not what it says in the article. In answer to the question, I suspect the kind of physicists who think about time travel would make little distinction between information and matter, and tend to regard one as equivalent to the other, but IANAP. 213.122.8.112 (talk) 15:15, 4 March 2011 (UTC)

Photographing the stars will set the time period when you are talking about going back hundreds of years. Of course, any photo of anything is easy to fake now - and will surely be easier to fake in the distant future when time travel might become possible. -- kainaw™ 14:49, 4 March 2011 (UTC)

If some laaarge planet was made of, say, highly shiny metal, and you had an amazing telescope, you could use the reflection to photograph Earth (and possibly its inhabitants) a few million years ago. Finding such planets that show you the past ten thousand years are a bit hard though... Anyways, as of now, we can't even see planets, much less view your reflection on them.

Information can only be transferred forward in time. There are two ways of transferring information, one is with materials (a gold plaque, light, radio waves, paper, etc), and another is with quantum mechanics. Materials can't be sent back in time (because time machines destroy themselves 10^-43 seconds after they are created), and with quantum mechanics, though it can send data faster than light, you can't create a Tachyonic antitelephone with it, for various reasons. If you want some links for more information on sending information into the past, see: Tachyonic antitelephone, and Causality (physics). ManishEarth^{Talk • Stalk} 15:06, 4 March 2011 (UTC)

There are a number of fiction stories with plots very similar to this. Hero gets some sort of past viewer, takes some photographs, then can't sell them because his photographs contradict in some ways with modern archeological thought. Therefore everyone assumes they're expertly made, but poorly researched fakes.

I think your best bet would be to use your past-viewer to identify some archeological sites that have not yet been discovered, then very publicly predict where they will be. (So that, after the fact, there can be no doubt that you were the first to suggest their existence.) APL (talk) 15:54, 4 March 2011 (UTC)

... and here's one of me with a dodo. Tasted a bit like chicken ... Gandalf61 (talk) 16:37, 4 March 2011 (UTC)

Two ideas: (a) Photograph a familiar large natural object (I'm thinking about a mountain) that existed both then and now, and which has been changed by human development, preferably a thousand years ago, perhaps via a strip mine, something like mountaintop removal mining, or a lot of housing construction; (b) Take pictures of the night sky through a telescope (no light pollution!) and when you come back, have an astronomer friend verify that the different star and planet positions align with the date that you were visiting. For bonus points, take a look at list of novae before you go, and make sure to photograph areas of the sky that contain those stars. Neither of these ideas will provide irrefutable evidence that you did travel back in time, but you may be able to convince some Experts, on the grounds that a layman would not really be able to simulate those particular photos. While you're at it please bring back a photo of The Sphinx with its nose; I remain curious. Comet Tuttle (talk) 18:43, 4 March 2011 (UTC)

Naturally, but I presume that proving the portraits of people is impossible... —Preceding unsigned comment added by 89.76.224.253 (talk) 21:48, 4 March 2011 (UTC)

Would that be the sphinx in ancient Greece or Rome? Cuddlyable3 (talk) 05:43, 6 March 2011 (UTC)

Check this spin out. "ancient ... Rome" was an example the original poster gave of a target time. As you can see from our article Ancient Rome, this is a reference to the entire Roman civilization back then, not just the city of Rome; and for several hundred years, Ancient Rome included Egyptian territory including the Great Sphinx of Giza, which I had linked to. So, I choose "Ancient Rome". Saved! Comet Tuttle (talk) 19:14, 8 March 2011 (UTC)

Deepwater Horizon oil spill: Why the glacially slow testing of the blowout preventer?

The Deepwater Horizon oil spill article says that the blowout preventer, which failed to seal the pipe, was removed for analysis on September 4 2010, that the investigation by NASA began November 16, 2010, and that it was still ongoing December 23, when the U.S. Chemical Safety Board called for for the investigation to be taken over by others due to a perceived conflict of interest. NASA now been investigating this device (which has no apparent connection to aeronautics or outer space) for 3 1/2 months, with no expected date announced for a final report on how it malfunctioned, other than occasional "leaks" about a dead battery and leaky hydraulics. There is nothing like a deadline to sharpen the focus of an investigative team. When are the investigators expected to issue a report on the blowout preventer? The most recent news stories I found, from January 2011 said a "final report" on the oil spill was issued January 11, without the report on the preventer, which was expected in February 2011. I have seen no press coverage of the preventer analysis final report.Is this one of those cases where they wait until the press has lost interest, or has the government progressed from data collection and analysis to spin doctoring of the language in the findings? Edison (talk) 15:59, 4 March 2011 (UTC)

Here are some possible questions to ask as to why it hasn't already been done.

Should NASA drop everything else and divert their limited resources to this one issue?

Should NASA disrupt its current timetable, (which will have been planned sometime back and have other areas, departments, experts, etc., already committed to the current times and places)?

Should NASA just get on and pull apart the blow-out preventer before they have had time to come up with a comprehensive plan to avoid destroying any evidence due to oversights?

Should NASA just place the blow-out preventer in any of their unused lots and pull it apart there, or should they schedule it to be tested in a suitable or custom built test bed (pressurised tank or what ever) which might enable a better scientific analysis to be carried out -so that with the knowledge gained, the occurrence of future oil-spills at sea can be reduced? --Aspro (talk) 17:04, 4 March 2011 (UTC)

This is just me, but I think the OP was more interested in his other questions: namely, why NASA is investigating this in the first place, even though it has nothing to do with aerospace. --140.180.5.6 (talk) 17:16, 4 March 2011 (UTC)

I have over stated NASA's part in this. It hasn't been sent to NASA for their aerospace know-how, rather their project oversight skills and their ability to provided the basic facilities, site security, etc., were the work can be carried out by whoever is brought in to do it. NASA isn't doing the work themselves no more than they manufature rockets and things--Aspro (talk) 19:56, 4 March 2011 (UTC)

From your comments, it just sounds like NASA is Way Too Busy to do this crucial analysis, which bears on possible dangers lurking in countless other blowout preventers, which might be similarly unable to perform their only known function. Maybe the analysis should have been given to some university, or some other group with no knowledge of petroleum extraction, but with "project oversight skills and their ability to provided the basic facilities, site security, etc." like maybe the Federal Reserve, the FBI, the National Security Agency or the National Bureau of Standards. Edison (talk) 05:00, 5 March 2011 (UTC)

Here a news report on it: [2]:

'"The condition of the BOP, as well as additional unanticipated events, were the reasons for the delay," the joint investigation said in a statement.'

Somebody should have asked what the "unanticipated events" were. Perhaps the press has already lost interest. Some appear to suspect sabotage of the investigation:

'A lawmaker and the Chemical Safety Board have questioned whether the integrity of the BOP testing has been damaged by the involvement of a Transocean employee who served as the subsea supervisor on the rig that was drilling the Macondo well.'

StuRat (talk) 21:57, 4 March 2011 (UTC)

Thanks, Stu, that news report is exactly what I was looking for. Strange how much the phrase "unanticipated events" sounds like someone tap dancing while they whistle "Tea for Two" as they try to think up phrasing to make unacceptable blunders seem like acts of God. Edison (talk) 05:40, 5 March 2011 (UTC)

Edison, you may also be interested in reading the National Academy of Engineering's special committee report, commissioned by the President: Analysis of Causes of the Deepwater Horizon Explosion, Fire, and Oil Spill to Identify Measures to Prevent Similar Accidents in the Future. Interim Report on Causes of the Deepwater Horizon Oil Rig Blowout and Ways to Prevent Such Events is available for free to the public. This was a preliminary investigation; the report was published in November; in addition to preliminary technical analysis, one of the critical items they determined was that a suitable agency does not currently exist to evaluate deepwater drilling safety or to investigate accidents. Several preliminary policy-level suggestions were made. In fact, it was this November report that preceded all of the events (such as NASA involvement)that you are currently expressing frustration with! One of the reasons NASA has been doing technical analysis was its role as an uninvolved Government agency; it was pointed out that the Mineral Management Service, who oversaw deepwater drilling, had serious conflict of interest because the same agency collected revenue and enforced policy (a unique case in the Government - compare the IRS and, say, the FBI). MMS has since seen a major organizational overhaul, by presidential decree; NASA was an "independent" agency who would play the role of unbiased Government advocate; and minimize the risk of any crony-ism or direct conflict of interest. But this is also a reason why technical analysis has been going so slow. The engineering analysis of the accident is confounded by legal-ese, decision-by-committee, and government regulation. I had the (mis)fortune to hear a presentation by the NAE committee right before they released their November report - and what I gathered was that the scientific and technical results must all be revealed very strategically to avoid poisoning any legal process that is currently taking place. (And there is some heavy, multi-billion-dollar litigation taking place amongst all involved parties). Nimur (talk) 13:13, 5 March 2011 (UTC)

Where do very sticky stickers come from?

Someone put up an offensive picture on a utility pole near my home and it can't be peeled off. What to do besides calling the city? 12.199.96.253 (talk) 16:18, 4 March 2011 (UTC)

Is this a "science" question? Bus stop (talk) 16:20, 4 March 2011 (UTC)

At your local hardware store, ask them about solvents that remove stickers. I've a little bottle of very nasty stuff that dissolves basically anything sticky within a few seconds. Not very expensive. Very handy thing to have around in life more generally. I'm sure the stuff is toxic as all get-up, but every once in awhile you actually like to get things clean... --Mr.98 (talk) 16:33, 4 March 2011 (UTC)

Acetone might work. Not good to inhale, or otherwise ingest. Bus stop (talk) 16:37, 4 March 2011 (UTC)

Acetone's pretty darn safe to both inhale and ingest: [3]. Buddy431 (talk) 23:41, 4 March 2011 (UTC)

Look for a liquid called "Goo-Gone" at the hardware store (The dam spam filter prevented a link to a useful article at E-how). It is useful solvent for removing adhesive stickers. You might have better luck with the utility company than the city, since the city does not own the pole, although if the Mayor complained to the utility it might motivate them. Edison (talk) 16:47, 4 March 2011 (UTC)

Would it work on stickers that don't come off? YouTube videos primarily show adhesives being removed, but what if the sticker itself doesn't come off? Imagine Reason (talk) 22:33, 4 March 2011 (UTC)

Just because someone else has interfered with a utility pole, does that remove the duty of another citizen to report you to the authority's for committing further possible damage simply because you can't stop your sensitivities from being activated. Should we be encouraging individuals to take things into their own hands like this by answering such a question? Say the bottle of solvent broke and it ignited, other people could be left without a utility until its fixed. --Aspro (talk) 17:18, 4 March 2011 (UTC)

I'm pretty suspicious of the idea that you could really interfere with the utility pole with some solvent. We're not talking about bathing the pole in gasoline. Topical application. And yes, I think in today's day and age, encouraging people to take a little responsibility for their communities is not a bad thing, assuming it is not a really dangerous or hazardous recommendation. I certainly wouldn't expect MY city council or utilities company to do anything about it, with their track record. If citizens do not take some responsibility for public spaces it quickly becomes a tragedy of the commons situation. --Mr.98 (talk) 18:19, 4 March 2011 (UTC)

I suppose a black felt tip pen is out of the question. Richard Avery (talk) 19:34, 4 March 2011 (UTC)

For some reason my various permanent markers never seem to go really dark when I really need them to. Imagine Reason (talk) 20:53, 4 March 2011 (UTC)

Some other things that might work:

WD-40. Still smelly and messy, but not quite as toxic as acetone. Less likely to damage the paint (if any) on the pole than acetone.

Actually I believe WD-40 is more toxic than acetone. Acetone is not very toxic at all. Ariel. (talk) 22:24, 4 March 2011 (UTC)

Yeah, you can literally drink acetone (not without ill effects, but you aren't likely to die or have any long term impairment). One guy drank 200 mL (about a cup) and turned out fine (eventually) [4].

Peppermint oil (or clove oil, etc.). Smells pleasant and less toxic (although I don't suggest you drink a bottle). Can damage plastics, and might damage some paints. StuRat (talk) 21:30, 4 March 2011 (UTC)

Goo Gone and a scraper (such as a putty knife) should do the job.--Srleffler (talk) 18:16, 5 March 2011 (UTC)

Marshmallows in the microwave

What causes marshmallows to expand in size when microwaved? And why do they collapse when you take them out? Googlemeister (talk) 17:11, 4 March 2011 (UTC)

At a guess, I would say that as their made by having air whipped into them, then it is this air that is expanding!--Aspro (talk) 17:20, 4 March 2011 (UTC)

The air expands when it is heated by the warming marshmallow, the marshmallow cools when it comes out of the microwave and cools the air which shrinks. That combined with the very elastic substance of the marshmallow which allows the air to expand but retains it encapsulated inside the goo.Richard Avery (talk) 19:30, 4 March 2011 (UTC)

Air doesn't expand much when heated, but water expands dramatically when boiled. Since microwave ovens use a frequency designed to preferentially heat water, it may boil while the rest of the marshmallow is still well below the boiling temperature of water. Turning off the oven would allow the water vapor molecules to quickly cool and condense back into liquid water. StuRat (talk) 22:00, 4 March 2011 (UTC)

Ditto. (edit conflict) Plasmic Physics (talk) 22:06, 4 March 2011 (UTC)

Note that it isn't really true microwave ovens use a frequency designed to preferentially heat water. See Microwave oven#Principles. It's just that Dielectric heating works better on water then other substances commonly contained in food. According to the last post here [5], nitrobenzene and chloroform can also be efficiently heated, but most of us don't want either in our food... Nil Einne (talk) 22:44, 4 March 2011 (UTC)

An infestation of ladybugs

Okay, I read Coccinellidae#Infestations. It doesn't really explain what I'm seeing in my condo unit.

Nearly every day for the past year, I find a ladybug in our home, buzzing around our dining room chandelier at dinnertime or just crawling up a wall or window. I dutifully catch it and throw it outside. There certainly was never a "swarm" that flew in, as described in the article. We see just one at a time. We'd notice a swarm because they'd have no place to hide, no air ducts, no plants. I suppose the only inaccessible spaces in our home are the spaces behind the kick panels under our kitchen and bathroom cabinets, but I see no reason why a ladybug would want to go into such dry dusty places.

There are plenty of other bugs outside (flies, mosquitoes, moths, etc.), far more numerous than ladybugs, that could fly in or crawl in when we open the door. But we don't see those, except for an occasional crawler like a spider or silverfish. We just see a ladybug about once a day.

I'm skeptical that every day one ladybug waits outside to seize an opportunity to fly into our door on the brief occasions when it opens. And I'm pretty sure they aren't hitch-hiking in on our clothing. And I'm quite certain that I'm not throwing out the same ladybug every day!

I have wondered if they're breeding in our house, but I've never seen any larvae, and I don't know how they'd survive in our home with no plants and no aphids — unless they're eating dust mites or other critters too small for my vision.

Any thoughts about what might be going on? I don't mind the ladybugs, but I'm curious to know how they get in, when other more numerous bugs don't. ~Amatulić (talk) 21:11, 4 March 2011 (UTC)

How can you be certain they aren't on your clothing when you come home ? Do you fully check yourself in a mirror to be sure you don't have one on your back ? StuRat (talk) 21:17, 4 March 2011 (UTC)

These are persistent creatures, capable of finding small crevices, and they show up in the oddest places - between panes of double pane windows, for example. I have little doubt that they'd be coming in through some crack, but finding it may not be easy! Many references like [6] can be found using "asian ladybug cracks" for search terms. Wnt (talk) 00:16, 5 March 2011 (UTC)

Thanks for the responses.

StuRat: Actually, yes. I take my jacket off and check it. Even if they do come in on my clothing, I seriously doubt that one hitches a ride every day. It isn't the time of year for seeing ladybugs outside either.

Wnt: They may be coming through cracks, but as I said there are other more numerous crawly things around that can fit through cracks also, but don't. And why they seem to trickle in at a rate of one a day mystifies me. I think seeing them between panes of a double pane window may be the result of a larva crawling through a crack in the seal of the window pane and then metamorphosing between the panes, since those are rather flat soft creatures while the mature beetle is round and hard and unlikely to fit. ~Amatulić (talk) 01:22, 5 March 2011 (UTC)

Hello. I manage a hotel, and your very same question was a mystery to me for years. There would alsways be one or two lady bugs randomly crawling around somewhere in our lobby. In my experience to your question, there is, somewhere in your home, an infestatation of lady bugs...you just haven't found it yet. Ours was way up in the outside corner of an air duct in the ceiling. Not inside the duct, but rather in between the metal tubing and the wooden housing. Needless to say, they don't really hurt anything, so aside from fogging your house with professional grade chemicals, a lady bug or two crawling around is not so bad relatively speaking. Maybe you should get a houseplant and give them somewhere to hang out ;) Cheers! -- David Able 04:37, 5 March 2011 (UTC)

Pouring liquids

I'm not sure whether the question was already answered earlier, but anyway. When I start to pour juice for example, the pack shortly afterwards starts to "breathe" and "exhales" some quantities of juice, disrupting the normal flow. Why is that and how to avoid it? —Preceding unsigned comment added by 89.76.224.253 (talk) 21:58, 4 March 2011 (UTC)

It's because you are creating a partial vacuum in the container by removing part of the contents without replacing it. An air hole in the opposite side is a simple cure, allowing air to replace the missing contents. If that's not practical, pour slowly enough that the opening is not entirely blocked with liquid, and air will get sucked back in that way.

If you don't do either, the partial vacuum will build until it sucks the some juice and air back in, possibly going slightly over atmospheric pressure, and will then "spit some back out", to equalize the pressure. StuRat (talk) 22:02, 4 March 2011 (UTC)

To expand on that, making an air hole is very easy. Just get something sharp (knife, scissors, pin, whatever) and make a small hole in the top of the carton away from the opening. You'll find even a very small hole makes a really big difference. --Tango (talk) 23:22, 4 March 2011 (UTC)

Use a Churchkey, a device specifically designed for the job (with cans, anyway). Buddy431 (talk) 18:51, 5 March 2011 (UTC)

Apple pH

What would be the approximate pH of a common-or-garden eating apple? DuncanHill (talk) 23:35, 4 March 2011 (UTC)

Probably about the same as the juice, on the acidic side between 3.5 and 4.0. Not as acidic as citrus. There's a list of pH levels from the USDA for various fruit juices here. ~Amatulić (talk) 01:28, 5 March 2011 (UTC)

Thank you. DuncanHill (talk) 03:48, 5 March 2011 (UTC)

March 5

An attempted desription of Eternity,

Would someone identify the writer of this attempt to illustrate the idea of Eternity which I read decades ago and will now try to re-create. Try to imagine a block of granite 100 miles long by 100 miles wide by 100 miles high.Once every 10,000 years a small bird alights on it to sharpen it's beak.After the last bird has worn away the last granule of the block this will represent the first second of Eternity. J.Cowell00:27, 5 March 2011 (UTC) —Preceding unsigned comment added by 124.185.229.128 (talk)

I think it may be HG Wells in his book about the history of the world. 92.24.182.238 (talk) 00:44, 5 March 2011 (UTC)

It sounds like a bit of the sermon on Hell in A Portrait of the Artist as a Young Man by James Joyce. AndrewWTaylor (talk) 13:34, 5 March 2011 (UTC)

Yes, it is from Portrait:

Now imagine a mountain of that sand, a million miles high, reaching from the earth to the farthest heavens, and a million miles broad, extending to remotest space, and a million miles in thickness; and imagine such an enormous mass of countless particles of sand multiplied as often as there are leaves in the forest, drops of water in the mighty ocean, feathers on birds, scales on fish, hairs on animals, atoms in the vast expanse of the air: and imagine that at the end of every million years a little bird came to that mountain and carried away in its beak a tiny grain of that sand. How many millions upon millions of centuries would pass before that bird had carried away even a square foot of that mountain, how many eons upon eons of ages before it had carried away all? Yet at the end of that immense stretch of time not even one instant of eternity could be said to have ended. At the end of all those billions and trillions of years eternity would have scarcely begun.

. See here for the full text. AndrewWTaylor (talk) 13:38, 5 March 2011 (UTC)

The bird with the grain of sand illustration did not start with Joyce. The evangelist Charles Finney used it in 1855. See, "On Neglecting Salvation" from April 11, 1855 by Finney [7]. However, it may be older than Finney. The granite and the sand are variations of the same sort of illustration. I'm also interested to know the original source.

I'm not convinced that is it. I still recall something in one of the several history books by HG Wells. I think I remember an illustration that went with it. 92.15.18.16 (talk) 14:41, 6 March 2011 (UTC)

Since this found its way to the Science desk rather than Humanities, I should point out that such a vision of eternity does not have a basis in the world as we know it. When we look at physics with a particular set of laws, as for atoms and molecules, the universe seems to have a beginning in a Big Bang, and an ending in (probably) cold and endless space. When we look at the universe as an eternity (by considering the logarithm of time, or something similar) we encounter all sorts of different physics without beginning nor end, from quark-gluon plasmas to decaying protons. The stage of eternity is one on which bird and sand and observer and probably even space itself are fundamentally transformed, become unrecognizable, and transformed again, a continual ferment of raw creativity following a plan of supreme beauty, which is unknown to all those who lack infinite energy and infinite time for experiment. Wnt (talk) 21:10, 6 March 2011 (UTC)

What makes tape sticky

I find myself on this board, randomly contributing to answer a question, and figured I'd throw one out there that I came across today. So, I was doing my expense report and taping receipts to a piece of paper for photocopying, and I wondered: What makes tape sticky? I mean, I know it has something to do with an adhesive, and tacki-ness (sp), but more specifically what exactly is going on? Is it a chemical bond? What physical process is going on that makes it stick, but not bind permanently? Also, it seems when you peel scotch tape off paper, the tape is "less" sticky but the paper is not sticky at all. Is it absorbed? Deep thoughts, by David Able 04:51, 5 March 2011 (UTC)

Adhesion is the article, but it's unfortunately confusing. The most important thing is that adhesives flow into microscopic gaps in the surface, giving a much larger contact area. In the case of scotch tape that happens when you press the tape against the surface. When you pull something apart (i.e., put it under enough tension that it breaks), the weakest bonds break first. If you're lucky those will be the bonds that formed when you applied the adhesive, but that's not a foregone conclusion. No bond is really permanent. As for the actual bonding mechanism of scotch tape, I'm not really sure. It's some kind of van der Waals force. -- BenRG (talk) 11:07, 5 March 2011 (UTC)

I keep wondering if electrostatic attraction isn't involved in "stickyness" in some molecular/nanoscale fashion. Edison (talk) 03:10, 6 March 2011 (UTC)

energy

It is sometimes, but not always, possible to obtain "energy" via a differentiation of a spatial coordinate; (for example, kinetic energy is related velocity squared - which is a nonlinear operation on the first derivative of a spatial coordinate). So, "energy" is rarely a useful coordinate in most physical treatments. But you must know the mass to get the actual energy, right? — Preceding unsigned comment added by 98.221.254.154 (talk • contribs)

I would say that energy is very often a useful concept of most physical systems. Dauto (talk) 06:04, 5 March 2011 (UTC)

The OP is directly quoting my response to the question about "Dimensions" from March 2, 2011, but out of context. I was discussing whether "energy" would be a useful generalized coordinate, not whether it would be "useful." Nimur (talk) 13:32, 5 March 2011 (UTC)

Yes, you need to know the mass to get the (classical, kinetic) energy. 83.134.170.152 (talk) 06:32, 5 March 2011 (UTC)

Exactly - if you mean classical, kinetic energy, you must know the mass of the object - which is a constant. Nimur (talk) 13:35, 5 March 2011 (UTC)

Food spoilage rates

Why does meat spoil faster than fruits and vegetables? And why do flour, cookies, potato chips, and crackers just go stale instead of spoiling like the aforementioned meat, fruits, and vegetables? —SeekingAnswers (reply) 08:03, 5 March 2011 (UTC)

A few thoughts:

1) Moisture content is critical, and dryer things may not rot at all, like crackers and flour.

2) Trans fats are specifically used because they increase shelf life, in products like cookies, potato chips, and crackers. Apparently they are as unhealthy for microbes as they are for us.

3) Hi salt content also retards bacterial growth.

4) In other cases, some partially rotten products may still be considered edible. This is the case with fruit, for example. There are examples of fermented meat which people still eat, but most people find such things more distasteful than fermented fruit.

5) In the case of fruit, vegetables, and, in particular, potatoes, then may remain "alive" for some period after they are removed from the rest of the plant, and thus their own immune system may continue to fight bacterial growth. Since potatoes and onions can grow new sprouts, under the right conditions, this means that they must still be alive.

6) Fruit often has a skin designed to act as a barrier to bacteria, and that provides some period of protection. StuRat (talk) 18:21, 5 March 2011 (UTC)

Trans fats are not intentionally added, dude. They are a byproduct of catalytic hydrogenation of alkenes. John Riemann Soong (talk) 22:59, 5 March 2011 (UTC)

I'm not following you. If they aren't intentionally added, are you saying they are accidentally added ? StuRat (talk) 07:07, 6 March 2011 (UTC)

Thanks, but the answer to my two questions are still not entirely clear. I'm rather confused by the listing out of so many factors; which of them are most important? I don't think the question of why meats are so much more prone to spoilage than fruits and vegetables has been completely addressed; salted meat will still spoil faster than fruits and vegetables. Anyone else have anything to add? —SeekingAnswers (reply) 01:27, 6 March 2011 (UTC)

Beef jerk is salted and dried meat. I lats a long time. Dauto (talk) 01:47, 6 March 2011 (UTC)

Ethene and fermentation are articles of particular interest. ~AH1^(TCU) 03:11, 7 March 2011 (UTC)

The simple answer, and the one I would give to someone asking this for the first time, is that certain things are needed by the micro-organisms that decompose food, so an absence of those things can slow down or stop food spoilage.

First, there needs to be some micro-organisms or their spores (abtut like tiny eggs) present: when we sterilise something, we try to kill any micro-organisms and their spores. This is why sterilised food has to be sealed completely airtight, because micro-organisms and their spores are in the air around us everywhere. Canned food, and food you buy in a sealed jar, relies on this.

Secondly, there needs to be a source of food for the micro-organisms. Obviously, all things which are food to us also contain food for micro-organisms.

Thirdly, there needs to be enough available water for the micro-organisms. That's why drying food slows spoilage, because it's hard for micro-organisms to live in such dry conditions. Crackers are generally very dry, although they start to spoil as they absorb water from the air. It's also why food with a lot of sugar or salt lasts longer, because the high levels of sugar or salt dry the micro-organisms out! Think of how dry your mouth feels if you eat a lot of sugary or salty food without drinking anything.

Fourthly, it needs to be warm enough for the micro-organisms. At room temperature or warmer, micro-organisms tend to multiply very quickly, break food down quickly, produce toxins very quickly. At fridge temperatures, they do everything more slowly. At freezer temperatures, not only have they slowed right down but the water is frozen! And micro-organisms need water. And, of course, get them hot enough for long enough and they die.

These are the basics, and they are all important. We have an article on food preservation. 86.163.4.134 (talk) 12:58, 7 March 2011 (UTC)

Your answer addressed why wet things spoil faster and why sealed, salty, or frozen things spoil slower, but not why meat spoils faster than fruits and vegetables. —SeekingAnswers (reply) 14:51, 8 March 2011 (UTC)

Yes, these basics easily answer your second question. They also largely answer your first, although there are additional relevant details I excluded for simplicity's sake. One large part of the answer is that more dangerous micro-organisms or their spores are already present on the meat than the fruit, so meat spoils in the sense that it is unsafe to eat more quickly than fruit. Another is that the fruit and veg is often still sort-of alive, with functioning cells that continue their resistance to micro-organisms: some more so than others. Fruit is also typically sugary. Etc, etc. Check out the article I linked. 86.163.4.134 (talk) 16:46, 8 March 2011 (UTC)

Run Lola Run “sideways thru time” question

In the film Run Lola Run, and in many other sci fi films, the theme of “how would a small difference in the order of events affect long-term consequences as time moves on?” is explored. In this film’s case, (and it takes its philosophy pretty seriously) , Lola has to run somewhere in order to save her boyfriend. That run is shown three times, and each time there is some small difference, for example, she bumps into some people which slows her down a little. That difference ends up completely changing the results of her efforts at the end of the day. No one seems to think there is anything odd about this, and other films explore this theme with similar outcomes.

I have thought about it, and in my thought experiment, the whole platform on which Run Lola Run rests can be demonstrated to be false. Yes, it is true that a single, small event can change a whole life. For example, a young man attends a party that he had not intended to go to, meets a girl, and they end up getting married. But such life changing events that are the result of a small deviation in routine are rare. Run, Lola, Run implies that EACH such deviation has long-term consequences that radically alter one’s life.

I feel that can be refuted decisively by reflecting on one’s own life. In my case, for example, I lived in the same place for over 10 years. Each day, something unexpected would occur; I’d meet an old friend by accident and go and have a few drinks and so on. But at the end of each day, however many deviations from the norm occurred, I would end up back in my own little bed, safe and sound. If small deviations in the norm changed outcomes like they do in Run Lola Run, one’s life would be a huge storm of chaos, each day would be a major alteration of direction. It would be impossible to live like that. I feel surprised that no one seems to mention this when the scientific and philosophical themes of such films are discussed: that the structure of lives has a sturdiness that is not NORMALLY perturbed by chance meetings and intervening events. We are put off course briefly but we get back on course. We miss a train, so we catch the next one. If that means we miss a meeting, we discuss it with someone else. So our lives end up pretty much where they were before.

I’ve got no argument with Run Lola Run in the depiction of a small PARTICULAR event having a radical impact on the outcome of an entire enterprise, but it is only feasible that it happens once. The film puts forward the idea that EVERY such deviation from the norm has a radical effect, but the general ordinariness of our own lives provides ample refutation of that notion. I think this is a scientific question as well as a philosophical one, and I would be interested in the opinions of other WIkipedians. Myles325a (talk) 09:01, 5 March 2011 (UTC)

Have you checked out butterfly effect and perhaps Butterfly effect in popular culture? Nil Einne (talk) 09:24, 5 March 2011 (UTC)

You might also wish to consider the sum over histories theory of Richard Feynman. --TammyMoet (talk) 11:37, 5 March 2011 (UTC)

For an even more detailed (and in my opinion more delightful) "study" of this question, see Groundhog Day, where the same day is run through hundreds of times with only one variable (Bill Murray) changing. In any case, the idea that the little things in life get overwhelmed (most of the time) by the big trends is indeed a valid criticism, I think. I'm not sure it holds universally, though. In the context of history, this is discussed in some detail in Carr's What Is History?, where he talks about attributing too much to "accidents" of history (e.g. the entire fate of the Russian revolution to the fact that Trotsky got a cold on the wrong day). Carr says that these explanations miss out on the fact that huge forces have been previously put into motion anyway behind these "accidents" — that focusing on the tip misses you the rest of the iceberg. --Mr.98 (talk) 14:15, 5 March 2011 (UTC)

I think the answer is somewhat in between. That is, while not all seemingly insignificant events in your life have a dramatic effect on the outcome, many do. I think of it in terms of equilibrium, and will use a glass bowl analogy. Which events upset the equilibrium, like pushing a bowl off a table where it shatters, and which are self-correcting, like pushing a bowl, having it wobble a bit, then settle back down ? Your "missing a train" example could be self-correcting, if you get on the next train. However, what you do during that period or what you would have done, had you been on the earlier train, are also events which need to get back onto the original path. The longer it takes, and the more subsequent events occur, before you "catch the next train", the less likely it is that the time-line will be fully restored. StuRat (talk) 18:10, 5 March 2011 (UTC)

The real problematic part here is strictly speaking, as far as we know, time just doesn't work this way. Film gives us the impression that we can divide it into little indefinite segments, and possibly reloop "time lines" in different ways. But as far as science tells us (odd interpretations of quantum theory notwithstanding), the arrow of time is one way (although it can run at different rates depending on your reference frame, etc.). This is not a pedantic point; it was the foundation of a great deal of the philosophy of time, by people such as Henri Bergson, who explicitly criticized film as giving people very bad ideas about how to visualize "time" and "events". Bergson would say about your comment: "there is no time-line to be restored; there is just one time-line, and it plays out how it plays out, irrespective of how you imagine it in a more ideal form." Only in fiction do we get to have multiple "time-lines" in the sense you mean. To very much bastardize Bergson, he would say, when you try to make broad statements about the nature of time based on metaphors from film, you are making as big a category error as you would if you were trying to make broad statements about the nature of violence based on cartoons. --Mr.98 (talk) 19:47, 5 March 2011 (UTC)

The OP seems to assume that there exists a sequence of events, called the norm, from which various degrees of deviation occur i.e. 1) deviations that cause only a temporary disturbance to the sequence that is supposed to be in equilibrium to which it returns, and 2) deviations that have expanding repurcussions that irrevocably change everything that follows. The assumption is appealing because it allows unlimited speculation about Counterfactual history. However it is impossible to prove the speculation that any future sequence of events is more "normal" than any other, and the grading of "deviations" is an Anthropomorphism. Example: the corrosion of an electric contact may cause an innocuous click in a telephone conversation or prevent a nuclear bomb exploding, but the corrosions were equally inevitable in the given environments. Cuddlyable3 (talk) 23:12, 5 March 2011 (UTC)

All physical systems respond elastically to perturbations below some threshold and plastically to larger perturbations. It's universal. I see no way to avoid the conclusion that human history, considered as a physical system, behaves in this way also. You could treat Earth's weather as external to the system, or you could treat it as internal and have the external perturbations come from micrometeorites or something. In the end it doesn't matter much.

You can't escape this by arguing that it's impossible to define a notion of alternate history, because that's an argument against the scientific method. If you believe that experimental data is noisy, and that one must ignore the noise when looking for patterns, then you believe in counterfactuals. That's what a counterfactual is. For that matter, if you believe that there's such a thing as entropy then you believe in counterfactuals. It's the same thing.

I realize that it's disturbing to think that human history could have gone entirely differently, and it's tempting to argue against it for that reason alone, but this is the science desk and that's the science. If you can come to terms with trillions of other galaxies that probably harbor intelligent life, or with the eventual demise (by heat death or spacetime singularity) of everything the human race has ever created, then you can come to terms with this. -- BenRG (talk) 01:55, 6 March 2011 (UTC)

Suppose we consider two sets of spacetimes, with identical pasts, one where you turned right, and one where you turned left. You were able to turn right or left from the same past because physics is indeterminate. Likewise, it is possible that the worlds where you turned right or turned left have the same future, because of the same indeterminacy. So if you select out a set of parallel spacetimes and arrange to travel between them by the twisting of a knob on a machine, then whether you travel among worlds with the same pasts and different futures, or different futures and the same past, or same pasts and same futures, or, of course, different in every regard, depends solely on how this very hypothetical machine is contrived.

If it is not necessary to build a machine - notably, if one supposes a connection between such parallel spacetimes based on religious faith - then there is no physical law to prove or disprove that one's consciousness moves between these parallel worlds as the process of divine creation continues to unfold. Wnt (talk) 20:58, 6 March 2011 (UTC)

The whole question seems to reduce to whether potential outcomes in a walk of life are oscillatory or deviatory. The situation could branch into almost an infinity of possible outcomes or the outcome of a decision could have two or three possible outcomes. This is another issue involving whether humans have free will and how deterministic human interactions are (or whether our decisions cause quantum collapse) and the simple answer is: we don't know. ~AH1^(TCU) 03:09, 7 March 2011 (UTC)

I've always thought Terry Pratchett summarised this idea particularly well in the Discworld novel, Lords and Ladies:

The universe doesn't much care if you tread on a butterfly. There are plenty more butterflies. Gods might note the fall of a sparrow but they don't make any effort to catch them. Shoot the dictator and prevent the war? But the dictator is merely the tip of the whole festering boil of social pus from which dictators emerge; shoot one, and there'll be another one along in a minute. Shoot him too? Why not shoot everyone and invade Poland? In fifty years', thirty years' ten years' time the world will be very nearly back on its old course. History always has a great weight of inertia.

--Kateshortforbob _talk 15:57, 7 March 2011 (UTC)

Kolmogorov complexity

Hi. I'm pretty new to computer science, but am fascinated by the term Kolmogorov complexity. The article has an example that contains the letters "ab" repeated 32 times, and encodes it as "ab 32 times". However, what if the actual string given is "ab 32 times"? How could we differentiate that from an encoded version of the abab... string? 88.112.51.212 (talk) 12:13, 5 March 2011 (UTC)

The example we use in our article is a bit "invalid" (for the sake of simplicity) - it's missing a complete description of an escape character that would be required. Some piece of information (at least one single bit) is required to indicate whether the substring "32 times" should be interpreted literally or as a "modifier" to the preceding characters. This extra information can be included by using an escape-character that is always specially-interpretted; but then you can never print the escape character! So you need a little more sophistication in the scheme. This problem pops up a lot in the implementation of encoding-algorithms; the answer invariably is either "indicate the special interpretation using side-channel information" or "indicate the special interpretation by using in-band escape-characters." Naturally, trouble arises when trying to convey the literal value of the escape-character; but again, this can be done with either in-band or side-channel information.

You might find it helpful to consider actual implementations of run-length encoding or lossless data compression to see the practical implementations of these theoretical requirements.

I will also point out that a complete information-theoretical description of complexity of a data-stream should account for the complexity of both the data-stream and the algorithm or machine that must be used to decode it. Abstract machines (or decoding-algorithms) require some minimum number of bits to define them - and this is often the "forgotten" information-container when "infinite compression" schemes are proposed. You may find Turing completeness interesting, and the principle of the quine program concept. Nimur (talk) 13:45, 5 March 2011 (UTC)

It is not true that in constructing a data compression code one must invariably indicate the special interpretation by using in-band escape-characters. In LZW compression thst is used in GIF image files the coding algorithm starts by expanding all characters slightly rather than compressing them. The trick lies in the encoder then teaching (up to a limit) the decoder about every string of characters that might repeat, so that only one character suffices to convey each repetition. The resulting compression ratio can be very high. Cuddlyable3 (talk) 15:52, 5 March 2011 (UTC)

I think this talk about escape characters is a red herring. Escape characters are an irrelevant implementation detail, and they're not even commonly used in real compressed stream formats. The important thing is that compressed and uncompressed streams are kept separate. You don't have to distinguish your compressed stream from an identical uncompressed stream because your decompressor will never get an uncompressed stream. If you compress abababababababababababababababababababababababababababababababab to "ab" 32 times then you probably will compress "ab" 32 times to something like '"ab" 32 times' 1 time—or at any rate, to something other than a copy of the uncompressed string. Yes, the compressed string is longer than the uncompressed string; that's unavoidable in general (by the pigeonhole principle, aka the counting argument).

The other important thing is that the compressed formats used in discussions of algorithmic complexity have to be Turing-complete programming languages. Most (all?) real-world compressed formats aren't. The reason you need Turing completeness is that every compressed format must be "convertible" into any other by prepending a description of a decompressor for the other format to compressed data in that other format. This makes the optimum compression ratio format-independent in the limit of arbitrarily large files, which means that you can define algorithmic complexity (in the limit of arbitrarily large files) without tying it to any particular compressed format. -- BenRG (talk) 23:31, 5 March 2011 (UTC)

Are gays and lesbians fertile?

If a gay man had sex with a straight woman or a lesbian was raped by a straight man, would they produce viable children? —Preceding unsigned comment added by 93.29.254.150 (talk) 12:18, 5 March 2011 (UTC)

Most likely. Sexual orientation has no effect on fertility necessarily. See Clay Aiken (specific example) and artificial insemination (the method that he used). Finalius (Say what?) 13:09, 5 March 2011 (UTC)

Yes, of course they are. Many have had children. And the millions of those who were married but "in the closet" over the years had children as well. --Mr.98 (talk) 14:11, 5 March 2011 (UTC)

Residents of France, of whom the OP seems to be one, are not AFAIK famous for such ignorance about sexuality. The OP poses scenarios that are incompatible with consensual sex. A child conceived in such abnormal encounters is as likely to be biologically viable and grow as any other, but its mother will need to compensate somehow for the lack of a normal father figure. Cuddlyable3 (talk) 15:25, 5 March 2011 (UTC)

@Cuddlyable3: I don't know anything of mothers having to compensate for the lack of a normal(?) father. Actually, I don't even know what a normal father is.Quest09 (talk) 02:22, 6 March 2011 (UTC)

Also, the first case can perfectly well be consensual. Happens now and then. Aaronite (talk) 03:11, 6 March 2011 (UTC)

Although gay parents are not unknown, I don't know if they are equally fertile. If their hormonal levels are different, they certainly could be less fertile. Quest09 (talk) 02:23, 6 March 2011 (UTC)

@Quest09, on this ref. desk we try to provide sourced information and references to questioners. You have posted "I don't know..." 3 times[8] [9] which is unhelpful. Cuddlyable3 (talk) 04:36, 6 March 2011 (UTC)

@Cuddlyable3: Saying "i don't know" is a polite way of saying "I've never heard about this shit before."Quest09 (talk) 13:18, 6 March 2011 (UTC)

Yes CA3, we should provide sources and references, and not provide unasked for opinions (which of course can not have proper source or reference). For instance, the phrase "its mother will need to compensate somehow for the lack of a normal father figure." True, many editors opine here, but in this case the OP asked only about viability of offspring, and not about your feelings on family life. SemanticMantis (talk) 15:54, 6 March 2011 (UTC)

I think Cuddlyable3's point is that these desks are not conversations between one editor and the rest of the world. If an editor has something positive to contribute, they're welcome. If they don't know the answer to a question, nothing is gained, and space is wasted, by them coming here to tell the world that they don't know. The OP certainly couldn't give a tinker's cuss that some anonymous bloke on the internet does not know the answer to their question. -- Jack of Oz [your turn] 20:55, 6 March 2011 (UTC)

You would be right if my "I don't know" were simply expressing the fact that I don't know something. However, I was reacting to the assertion of Cuddlyable3 that: "its mother will need to compensate somehow for the lack of a normal father figure" (is that a sourced reference?) and also pointing out to the fact that homosexuals could have a different fertility level. I was actually saying: "THAT's fishy!"Quest09 (talk) 21:58, 6 March 2011 (UTC)

You could make an argument either way for possible differences in homosexual fertility. Some would say that homosexuality could potentially be associated with physically intersexed phenotypes, but for example, I think that all suggestions of a correlation with Klinefelter syndrome or Turner syndrome have been rebuffed. Though there's still a chance for a small unobserved effect. On the other hand, I remember seeing something in print a decade or two ago saying that female relatives of gay men actually had higher fertility, which was used in support of kin selection; however, the typical formulation neglects this effect and focuses on non-genetic benefits.^{[10]PMID 18810630} I wouldn't rule out that homosexuals themselves could have higher fertility rates for other reasons - for example, women who avoid men should not suffer allergic reactions to sperm. The problem is that getting data is difficult. If you look at this the way you'd look at a mouse experiment, then Utah has a far higher fertility rate than other states, ^[11] but of course this doesn't prove anything. What is clear is that many gays and lesbians who decide to have children are able to do so; to a zero-order approximation, there is no known difference. And there is a wide variety of difference among heterosexuals - for example, a steadily falling sperm count in the U.S. and western Europe. Eating specific foods like hemp seeds can cut sperm count by 50%. So you're looking for a tiny signal in a sea of noise, under circumstances that make even crude counts unreliable. Wnt (talk) 20:46, 6 March 2011 (UTC)

Skyscraper

Let's say, in strictly theoretical terms, that there is a skyscraper so tall it reaches all the way up into the higher atmosphere, space even. Would the building look like it was bending upwards from ground level according to the Coriolis effect, or would it still look perfectly straight? Thank you.--Editor510 ^{drop us a line, mate} 14:33, 5 March 2011 (UTC)

A viewer standing on the ground is in the same inertial frame of reference as the skyscraper and therefore observes its true straight shape, with minor modifications due to obscuration by clouds, and refraction due to the atmosphere's temperature gradiant. Cuddlyable3 (talk) 15:31, 5 March 2011 (UTC)

A viewer standing on the ground is in the same inertial frame of reference as the base of the skyscraper. Except at the poles, a skyscraper on the surface of the rotating Earth will be experiencing a slightly different acceleration at each height. TenOfAllTrades(talk) 16:02, 5 March 2011 (UTC)

So? Cuddlyable3 (talk) 21:51, 5 March 2011 (UTC)

As Coriolis effect says, the Coriolis effect is an apparent deflection of moving objects when they are viewed from a rotating reference frame. The skyscraper is not moving in the reference frame of somebody standing besides it, so there is no Coriolis effect. However, if somebody dropped an object from the top then, due to the Coriolis effect, it wouldn't fall straight down. This can be observed from far smaller heights. A gunner or sniper at the bottom aiming for the top would also see the projectile curving and would have to not aim straight at the goal even if gravity is ignored. PrimeHunter (talk) 17:47, 5 March 2011 (UTC)

Thank you.

Resolved

--Editor510 ^{drop us a line, mate} 22:29, 5 March 2011 (UTC)

Will the frame dragging effect of twisted spacetime cause a theoretical if not appreciable bend in a similarly tall object? —Preceding unsigned comment added by 129.67.37.227 (talk) 15:01, 6 March 2011 (UTC)

Looking for an electronic engineering journal

Hi there, hope this is the right place to ask! I was wondering if someone could recommend a good journal on electronic engineering, preferably one that can be subscribed to in paper form from the UK. Kind regards, Raywil (talk) 19:54, 5 March 2011 (UTC)

Are any of these any good to you? List of Institute of Electrical and Electronics Engineers publications--Aspro (talk) 20:19, 5 March 2011 (UTC)

Thanks for replying. There are definitely some interesting titles there and I didn't realise the IEEE published so many things. I'm still looking for a particular recommendation though if anyone has one. Raywil (talk) 21:11, 5 March 2011 (UTC)

Electronic Design Magazine is free and though Electronics (magazine) 1930 - 1995 is no longer published you may find copies in library collections. Cuddlyable3 (talk) 21:59, 5 March 2011 (UTC)

Any recommendation would really depend on what the OP is hoping to gain from it. If it is just for general interest, then pop along to a local WHS and paw through a copy of Electronics World. If it is to prepare for an electronics course then it would be best to ask the course lecturer or whoever for their recommendation. Local public reference libraries should have a subscription for one or two of the more popular publications. Or let your imagination rip! One of my student flat-mates, got his dear aunt to fork out for a Playboy subscription. After all - he was studying anatomy (an' 'e ended up with first class 'onours to boot!).--Aspro (talk) 22:57, 5 March 2011 (UTC)

Thank you very much for all of your suggestions so far. I've sent off for a copy of Electronic Design and will have to look out for Electronics World next time I'm in WHS as I've never noticed it there before. I'm considering studying the subject at uni so thought I'd better get myself some related reading material. Any more appropriate suggestions would definitely be much appreciated. Raywil (talk) 00:54, 6 March 2011 (UTC)

IEEE Spectrum is a good one too - it's not too technical or domain-specific, but provides a "generalist" viewpoint into the cutting edge of electronics. I would say Spectrum is the magazine you should read (IEEE calls it the "flagship publication"). You can read online versions at http://spectrum.ieee.org or order paper subscriptions. Nimur (talk) 15:33, 6 March 2011 (UTC)

In my recollection, it is very expensive to join IEEE and get their journals. Edison (talk) 00:48, 7 March 2011 (UTC)

adaptive features of fish

tell me about adaptive features of fish —Preceding unsigned comment added by 220.225.96.217 (talk) 20:35, 5 March 2011 (UTC)

Have you tried searching the web or searching for relevant articles on Wikipedia? We are somewhat unlikely to write an essay on the subject for you. Please ask us about specific issues when you have done your own research. 88.112.59.31 (talk) 21:03, 5 March 2011 (UTC)

It also helps to narrow down the question. Just one example is symbiosis of clown fish to the sea anemone. ~AH1^(TCU) 02:49, 7 March 2011 (UTC)

inverting integrators and time integral of voltage

When I take the time integral of voltage, what unit do I get? I'm trying to use an equation similar to that in Operational_amplifier_applications#Inverting_integrator and I want to know if I have an RC value of 1.06 milliseconds how much that would scale my output by. John Riemann Soong (talk) 21:54, 5 March 2011 (UTC)

You can get the Time constant you mention using R = 1060 ohm and C = 1 uF. If there is a step change of +v at the input then during the next 1.016ms (assuming the integrator output is not saturated) the output will change negatively by −0.632v. Cuddlyable3 (talk) 22:16, 5 March 2011 (UTC)

Can you walk me through that? I totally understand the RC part -- what I don't get is that is that if I take this integral of a sinusoidal function, I seem to get an output integral reported in V/s, not V. This is because the inverted integral of sin t dt is cos t -- thus I get cos(t2)/RC-cos(t1)/RC as my theoretical output.

Which of course I am puzzled by, because my output should be in V, not V/s. If I do a square wave I am fine -- the inverted integral of a constant +v is -v*t/RC, which gives me an output in volts. How do I calculate how to scale my output for sinusoidal functions? John Riemann Soong (talk) 22:36, 5 March 2011 (UTC)

The sinewave input is V_in = V_pk sin ( ω t ) where ω = 2 π f

You omitted the frequency f. The angular velocity ω is in radians sec^-1. Cuddlyable3 (talk) 00:09, 6 March 2011 (UTC)

Exactly. In fact sin t is not a physically meaningful statement because it is a non-polynomial function of a dimensional quantity which makes no sense. Dauto (talk) 02:04, 6 March 2011 (UTC)

This non-polynomial?

${\begin{aligned}\sin t&=t-{\frac {t^{3}}{3!}}+{\frac {t^{5}}{5!}}-{\frac {t^{7}}{7!}}+\cdots \\[8pt]\end{aligned}}$ Cuddlyable3 (talk) 05:06, 6 March 2011 (UTC)

Yes, it is non-polynomial. see the first sentence of polynomial. The problem is that every term in the expansion above has a different dimension (it is measured with different units) so they cannot be added in a physically meaningful way. Dauto (talk) 06:17, 6 March 2011 (UTC)

Huh? ω t is (radians / sec)* sec, i.e. radians. Which are handled as non-dimensional units in the sin expansion above. They can all add up. Doing sin of something in radians is quite ordinary. Wnt (talk) 07:16, 7 March 2011 (UTC)

Image of a moleclue

OK, how would the researchers this image? After all I've learned of quantum mechanics, I thought it wasn't possible to narrow down the location of an atom so closely. Magog the Ogre (talk) 23:02, 5 March 2011 (UTC)

That's an electron density map. You can theoretically predict it using calculators. It's important because we can now measure electron density empirically rather than merely theoretically. John Riemann Soong (talk) 23:11, 5 March 2011 (UTC)

As long ago as 1989, IBM used a scanning tunneling microscope to position 35 Xenon atoms to spell out IBM. SpinningSpark 01:04, 6 March 2011 (UTC)

Then what is all this quantum physics nonsense about not knowing an atom's state at any place and time? Magog the Ogre (talk) 02:51, 6 March 2011 (UTC)

See quantum uncertainty. Bear in mind that the scale of an atom is very different from the scale of a nucleon or an electron, and that while quantum uncertainty is quite real at all physical scales, it's only really relevant once you're subatomic. — Lomn 04:04, 6 March 2011 (UTC)

So that means a telescope that's 10000x as powerful as this one could probably not exist? Magog the Ogre (talk) 08:21, 6 March 2011 (UTC)

Microscope, not telescope. Unlikely, for different reasons. Plasmic Physics (talk) 08:36, 6 March 2011 (UTC)

It's also worth noting that you can't really tell the precision of those images very well from the image alone. At the level of an atom, uncertainty principle says there will be limits to your precision — not that you can't know anything. It's a ratio of how precise your understanding of both position and momentum can be. It is only when you get to the level of, say, a bare electron, that the ratio gets so extreme that you start being able to know only one or the other. It is a common entry-level physics problem to ask students to calculate how much precision in position/momentum you can have for visualizing things on that level, how "in focus" they can maximally be. --Mr.98 (talk) 14:36, 6 March 2011 (UTC)

That's a truly gorgeous image, but note that you see rings, not points. The uncertainty principle tells us that we can't follow individual electrons zipping around that racetrack, but it does not in any way prohibit us from calculating nor observing the shape of molecular orbitals in breathtaking detail. Wnt (talk) 20:01, 6 March 2011 (UTC)

March 6

Better quality rest giving better quality work

Your demanding day job makes you feel tired. Is there any scientific evidence (rather than speculation please) that better rest in the evening results in better work the following day? If you spend evenings feeling bored and physically uncomfortable, is there any significant difference work-wise from evenings when you are entertained and physically comfortable? Thanks 92.29.117.180 (talk) 00:27, 6 March 2011 (UTC)

The articles Sleep deprivation and Effects of sleep deprivation on cognitive performance provide reliable sources. Cuddlyable3 (talk) 01:32, 6 March 2011 (UTC)

I think the OP is talking about how well you relax in leisure time, not how well you sleep. 90.195.179.167 (talk) 02:25, 6 March 2011 (UTC)

It is tritely obvious that the OP is not interested in how I personally sleep. Sleep is the major remedy for feeling tired and its quantitative relation to work efficiency has been studied extensively, whereas subjective evening notions of boredom, entertainment and discomfort do not provide hard scientific evidence. Cuddlyable3 (talk) 04:58, 6 March 2011 (UTC)

I was not asking about sleep, thanks. Let's assume you are getting enough sleep. 92.15.18.16 (talk) 12:16, 6 March 2011 (UTC)

On the other hand, there is this potential cycle: stress → increased stress hormones → insomnia → fatigue → decreased productivity. Try stress and productivity on Google Scholar or try these articles from LiveScience: [12] [13] [14] [15] [16]. ~AH1^(TCU) 02:38, 7 March 2011 (UTC)

Where is water taken up in the digestive system?

Where is uptake of water in the human digestive system mainly taking place? The stomach, the small intestine or somewhere else?

From digestion: "Other small molecules such as alcohol are absorbed in the stomach, passing through the membrane of the stomach and entering the circulatory system directly." The water molecule is even smaller than alcohol, so I presume water is taken up by the stomach.

From small intestine: "Water and lipids are absorbed by passive diffusion throughout the small intestine."

--Mortense (talk) 00:58, 6 March 2011 (UTC)

The stomach and the small intestine will absorb some water but the large intestine is where the bulk of the water is absorbed. Dauto (talk) 02:16, 6 March 2011 (UTC)

Agreed. Otherwise the intestinal contents would be too thick to flow around the sharp bends of the small intestine. StuRat (talk) 06:55, 6 March 2011 (UTC)

See colon, the first line confirms Dauto's answer. Richard Avery (talk) 08:51, 6 March 2011 (UTC)

Ironically, the article specifically does NOT confirm that answer. The first line makes no statement of the proportion of water absorbed; moreover, the section on colon function specifically states that 90% of the water has been absorbed prior to entry into the colon. The article might be wrong, and a reliable source would be great here, of course, but I don't think the answers above (nor our article) settle the question. -- Scray (talk) 18:40, 6 March 2011 (UTC)

The question needs to be clarified somewhat: each segment of the digestive tract deals with what arrives into it. This is complicated substantially by secretion, i.e. the mouth produces about 1 liter of saliva per day. I would guess the OP is asking about net absorption of ingested water in the digestive tract. -- Scray (talk) 19:24, 6 March 2011 (UTC)

Still looking for a reliable source, but this page states: "An important function of both small intestine and colon is the absorption of water and electrolytes. Approximately 2000 ml of food and drink is ingested daily, and the volume of gastrointestinal secretions (salivary, gastric, biliary, pancreatic and intestinal) is about 8,000 ml daily; therefore, approximately 10 liters of fluid enters the intestine each day. Of the 8 liters secreted, about 1-1.5 liters enter as saliva, 2-3 liters are secreted by the stomach, about 2 liters enter as bile and pancreatic secretion (about 1 liter each), and about 2 liters are secreted by the small intestine. (Please note that these figures are approximate, not absolute. Volumes may vary, depending on experimental method and conditions.) Of the 10 liters which enters the gut each day, only about 1 liter passes into the colon, about 90% having been absorbed across the small intestinal epithelium. Only about 150 ml is lost in the feces daily, with the remainder being absorbed by the colon. It should be obvious that any derangement in intestinal fluid absorption would profoundly influence the balance of fluid and electrolytes in the body, and that the normal functioning of the intestines plays a significant role in regulating water and electrolyte balance." This strongly suggests that the small intestine is a better answer than the large intestine/colon, but is probably not the final word. -- Scray (talk) 19:34, 6 March 2011 (UTC)

I think the net absorption of water in each part of the digestive tract is the relevant info we need here. You listed 1 liter going into the large intestine, and 0.15 coming out, so that means 0.85 liter of net absorption. That, divided by the 1.85 liters that enters the mouth and doesn't leave the other end, gives us approximately 46% of water being absorbed by the large intestine. If we can come up with comparable figures for the stomach and small intestine, we will then have a way to determine where the net absorption of water is greatest. StuRat (talk) 20:34, 6 March 2011 (UTC)

Well, if we stick with stomach vs small intestine vs large intestine, the answer is pretty clear - the stomach secretes 2-3 liters and is well-known to absorb very little, so its net absorption will be nil. That leaves 54% to the small intestine. -- Scray (talk) 20:41, 6 March 2011 (UTC)

Absorption of nutrients often depends on whether they are water-soluble or fat soluble and this also applies to vitamins. ~AH1^(TCU) 02:19, 7 March 2011 (UTC)

Two questions about filters

(1) Why do filters for digital cameras exist? Can't you process the pictures after shooting them with a software filter?

(2) Is there a filter for glasses to make everything look black and white? Quest09 (talk) 02:26, 6 March 2011 (UTC)

1)You can process color images with Photoshop or other software and gain many of the advantages of using color filters, such as if the image is transformed to black and white, after a yellow filter effect is used to emphasize clouds in an outdoor color photo. Actual filters can achieve some effects which would be difficult or impossible with Photoshop, since a filter might have a very narrow bandwidth, while the three channels of color info in a digital image are very broadband. 2)Kodak produced a "viewing filter" which made it easier to visualize how a B & W image of a color scene would look. The name of it is a "Kodak Wratten 90 filter." If memory serves, it might have been brown or orange. The scene did not really look black and white through it; that is impossible. See also [17]. Edison (talk) 03:07, 6 March 2011 (UTC)

UV, infra-red and polarizer filters cannot be emulated in software. Cuddlyable3 (talk) 05:17, 6 March 2011 (UTC)

1) One other advantage would be to get the filtered results immediately, and thus know if another photo should be taken, while the subjects are present and the lighting is still the same. Here I'm assuming that the software filter is used later on. If you apply it as the picture is taken, then that's good, too. StuRat (talk) 06:43, 6 March 2011 (UTC)

As the preceding responses note, there are some filter effects that cannot be employed after the fact, because the camera doesn't record the information required to reconstruct the 'filtered' image. Typically, the camera will collect just three pieces of information about each pixel: the intensity of light in that spot as seen through a red, a green, and a blue filter (built into the camera's sensor). This is usually enough to reproduce the color and brightness of the pixel as our eyes would see it, but can still leave much to be desired. For instance, specular reflections of light will be polarized to some degree; a suitable polarizing filter allows the photographer to suppress (or enhance) the appearance of this reflected light. Here are some examples. Since your digital camera's sensor doesn't record polarization information, you cannot reconstruct the polarized-light image in software.

Similarly, with only three color channels recorded, a great deal of information about the spectrum of the light observed is lost. This is usually not particularly important, but it can have significance under unusual lighting conditions or with particularly novel subjects; astrophotographers can have a particularly complicated toolbox here. To take an extreme example, look at the sun. (Figuratively only — don't actually go out and stare at the sun, please.) If you photograph the Sun – with appropriate filters so that you don't cook the camera's optics – you'll get a yellow-white blob, which may have some discernibly-darker patches: sunspots. Photograph the sun through an H-alpha filter (which extracts just a narrow window of light around 656 nm wavelength) and you'll get a much more richly detailed image. TenOfAllTrades(talk) 16:41, 6 March 2011 (UTC)

A graduated neutral density filter can help digital cameras with a restricted dynamic range cope with a bright sky etc. If the sky gets burnt out, then no amount of post editing of the RAW file will bring it back. Yet if the sky is brought within range, the ground can become too dark and noisy. WP as ever, even has an article on filters in general.--Aspro (talk) 19:28, 6 March 2011 (UTC)

Alternatively, some digital cameras have settings to enhance colour contrast in a live photo or to make it appear B&W or sepia. ~AH1^(TCU) 02:06, 7 March 2011 (UTC)

If there's a heart defibrillator, why isn't there a brain defibrillator?

So a defib paddle can restart a flatlined heart; why isn't there a defib device that restarts a flatlined brain?

What would it take to invent a device that would restart a flatlined brain? What obstacles would it have to overcome and how would it overcome them? --70.179.169.115 (talk) 03:39, 6 March 2011 (UTC)

The heart has a beat to restart, the brain doesn't. Clarityfiend (talk) 04:31, 6 March 2011 (UTC)

CF, what does the brain have to restart then? It must have something to keep going. --70.179.169.115 (talk) 04:34, 6 March 2011 (UTC)

DISCLAIMER: I'm no expert, so take the following with a boulder of salt. Compared to the brain, the heart and its operation is a lot less complicated. It follows a repetitive, relatively simple cycle, which somebody has discovered that a jolt of electricity can restart. Various areas of the brain, on the other hand, fire off at different times, intensities and combinations depending of the stimulus. There is no set pattern AFAIK for you to kick start. Also, I'm guessing that neurons are a lot more fragile than heart muscle, and would not take kindly to being zapped. As a rough analogy, kicking a malfunctioning washing machine has a much better chance of working than (physically) booting your PC. Clarityfiend (talk) 05:16, 6 March 2011 (UTC)

Actually, this question isn't entirely off base. The heart doesn't usually stop beating entirely, but rather goes into an abnormal contraction pattern, called fibrillation, and the shock stops that and allows the normal beat to return. Similarly, the brain sometimes has abnormal electrical patterns, and some attempt has been made to stop those and allow the brain to "restart", via electroshock therapy. While this therapy has a bad reputation from being used improperly, it still has it's advocates, especially when compared with brain surgery. StuRat (talk) 06:37, 6 March 2011 (UTC)

It's an interesting question. I know little about it other than you would need to get the the neuronal ion pumps to start working again but the IP may be interested in having a read around the subject of cortical spreading depression in the visual cortex. It's kind of like part of the brain flatlining for a while (in the sense that neurons remain excessively inhibited) after a hyperexcitability phase (a spreading jolt of electricity). Sean.hoyland - talk 07:09, 6 March 2011 (UTC)

What does it mean to re-start a brain? We re-start heart because they are fibrillating and you could die. If the brain is not working properly there are other means to 're-start' it. If you mean re-starting a brain without activity, I have to say that you should have re-started the heart earlier. —Preceding unsigned comment added by 212.169.187.20 (talk) 13:08, 6 March 2011 (UTC)

I will note parenthetically that a defibrillator cannot restart a 'flatline' rhythm (asystole). This is a popular myth perpetuated by the lazy or inept writers of movies and televised medical dramas, where the flat EKG and beeeeeeeeep of the monitor are a convenient and widely-recognized device for plot advancement. TenOfAllTrades(talk) 16:08, 6 March 2011 (UTC)

This is one of the reasons why a brain dead person is often considered deceased even in cases when the heart continues to beat. The brain and heart are also co-dependant in some processes. ~AH1^(TCU) 02:03, 7 March 2011 (UTC)

weather

If we wanted to know everything about the weather to predict it w/ 100% accuracy, would it be better to ask all the inhabitants to hold their breath and stop moving or include those interactions in our analysis? by better i mean to predict the weather, not for the inhabitants. —Preceding unsigned comment added by 98.221.254.154 (talk) 04:42, 6 March 2011 (UTC)

What about the animals, continental plate movement, variable solar activity, the odd earthquake, even plant growth? Clarityfiend (talk) 05:21, 6 March 2011 (UTC)

How would you even model interactions between humans and the atmosphere? Titoxd^{(?!? - cool stuff)} 07:39, 6 March 2011 (UTC)

You could build a scalar field of global baked bean sales. That would be a start. Sean.hoyland - talk 07:56, 6 March 2011 (UTC)

To actually answer the question, no, because of the butterfly effect.--Shantavira|^{feed me} 08:18, 6 March 2011 (UTC)

Yes all those things also. how can you answer no to an "either or" question? Just b/c it might be totally impossible to do does nto change whether we would need it for the 100%. —Preceding unsigned comment added by 98.221.254.154 (talk) 17:33, 6 March 2011 (UTC)

I believe 98.221.254.154 is making a valid point if he/she is saying that all factors would need to be accounted for if we are to achieve 100% accuracy in a prediction. By the way, please "sign" your posts with 4 Tildes. See WP:SIGN. (Bus stop (talk) 17:41, 6 March 2011 (UTC)). Bus stop (talk) 17:37, 6 March 2011 (UTC)

If you wanted to lift Mount Everest, would it be better to remove the snow from the top or lift harder in order to take the snow into account? There is no sensible way to answer questions such as this. Looie496 (talk) 19:03, 6 March 2011 (UTC)

If by better you mean easier (less work), then most likely lifting harder, because it is extremely unlikely that the work needed to remove the snow before lifting it would be equal or less than the same work associated with the snow portion when lifting it with the snow in place.98.221.254.154 (talk) 04:02, 7 March 2011 (UTC)

If both methods are 100% accurate, then they are equally good at predicting the weather. Your question makes no sense. --Tango (talk) 22:17, 6 March 2011 (UTC)

I am asking if attempting to artificially isolate certain phenomena at the expense or exclusion of other valid ones in order to only understand the isolated ones is as fruitful (if at all) as attempting to identify and combine all possible phenomena as they exist entangled.98.221.254.154 (talk) 04:02, 7 March 2011 (UTC)

The effects of human breathing are typically considered negligible on global weather and thus are not included in numerical weather forecasting methods, even as it contributes to the butterfly effect. Human-made contrails, effects of greenhouse gas emissions, Arctic haze, dust from overgrazing, reduced evaporation from deforestation, the Asian brown cloud, soot in the atmosphere, the ozone hole and even wind farms likely have a much greater effect on weather than breathing, and those are usually not included either. It's not useful to consider any and all possible influences on weather, as that would amount to trillions of co-interacting and co-evolving factors even boiling down to the movement of every individual organism in microscopic gut flora in each of the nearly 7 billion humans on Earth having an effect on weather...so you get the idea. ~AH1^(TCU) 01:59, 7 March 2011 (UTC)

Just b/c those are not usually included doesn't mean they shouldnt be.

Just because they do not feature explicitly in the equations doesn't mean that human breath and a thousand other factors are not implicitly included in the mathematical model. All such factors contribute to the initial conditions that are used as a starting point for the forecast, and they are possibly included in the constants of the equations. Perhaps an expert in weather forecasting can confirm this? The forecast might be rendered inaccurate if the whole population of a large city decided to take vigorous exercise simultaneously for a few hours, but I expect that the effect would be more from the extra heat generated than from the breath, unless they all faced in the same direction and blew hard! Dbfirs 17:20, 7 March 2011 (UTC)

(ec) Reputable scientists are in agreement on this one: there is no practical benefit to over-parameterizing global models of climate. See, for example, our article on Global climate model. Here are several actual models in use. If you can extend any of those models, or the computer-code implementations of them, you can probably make a career for yourself as a climate scientist. But if your suggested model extension is totally infeasible and incompatible with today's theory and practice, (like your current suggestion to model microscopic effects due to human breath), you will have a hard time making a scientific case that you are modeling and predicting meaningful parameters. Being able to test your model against some parameter is a requirement for scientific research. Nimur (talk) 17:21, 7 March 2011 (UTC)

Testosterone as an anti-depressant in men

Has any research been done on using testosterone as an anti-depressant on men with or without low testosterone levels? —Preceding unsigned comment added by 76.169.33.234 (talk) 05:55, 6 March 2011 (UTC)

There's plenty of research showing a small but statistically significant decrease in bioavailable testosterone levels correlated with depression (such as [18]), but the only research I can find on treatment of depression with testosterone has actually been done on women to treat symptoms of menopause (such as [19], if you're allowed to access it). Someguy1221 (talk) 06:05, 6 March 2011 (UTC)

Chemicals that mimic testosterone are used in anabolic steroids. ~AH1^(TCU) 01:51, 7 March 2011 (UTC)

Period & Bloating

When a woman gets bloated during her period, is the bloating all blood or water? —Preceding unsigned comment added by 76.169.33.234 (talk) 05:57, 6 March 2011 (UTC)

It's water retention. Surprisingly little blood is lost during the menstrual period - about a teacup over the average 5 days. Most of what you see is endometrium, or the lining of the womb. --TammyMoet (talk) 09:13, 6 March 2011 (UTC) Edit: Sorry, I meant an eggcup. The Menstrual cycle article says 10 - 80 ml. (Note to self: wake up before you start posting!) --TammyMoet (talk) 11:32, 6 March 2011 (UTC)

Life on meteorites?

Hi. Could this be evidence of panspermia? Please refer to this unpublished article from the Journal of Cosmology (no Wikipedia article), as well as this older similar discovery from 2004. I'm not asking for opinions here, just an overall analysis of the articles presented here (is JoC a reliable source?), and comments on whether any information from these studies once peer-reviewed and published are to be included in Wikipedia articles. Thanks. ~AH1^(TCU) 15:58, 6 March 2011 (UTC)

If they are truly bacteria (a big if there) which really originated from outer space (another big if), and if they appear to be based on the same "code" as we are (e.g. they look more or less like life on our planet), I'd say that would be pretty suggestive towards panspermia, assuming that the probability of us finding similar designs on meteorites is low (which I think is a reasonable assumption at the moment, but it might be the case that our "template" for life is more common than we realize). If they don't look like they're on the same template as the rest of Earth, then probably not — could be independently developed somewhere else. I lack the technical ability to judge the article, but as a layman I would worry that humans are extremely good at looking for recognizable patterns, and are seeing bacteria where they might otherwise just see random structures. Lots of things look like bacteria at scales like that, when all you have access to are morphological structures and relatively clunky things like how much nitrogen or carbon are in them. But again, I'm no scientist — but these seem like the obvious things to be concerned about. The JoC looks legit as far as I can tell — peer-reviewed, non-nuts running it, etc. --Mr.98 (talk) 17:38, 6 March 2011 (UTC)

The Journal of Cosmology looks extremely non-legitimate to me. Did you look at the other articles it's published, such as these ones? The editorial board includes Subhash Kak, who also frequently publishes in the journal (as do other board members). The board also includes Roger Penrose as a "guest" editor, whatever that may mean. The "author guidelines" page contains the remarkable phrase "Do Not Use "Latex" Word Processing Programs". The "manuscript preparation" page says that authors should include with their submission a list of qualified reviewers. And they charge for submission and publication. This looks for all the world like a vanity journal for crackpots. -- BenRG (talk) 20:21, 6 March 2011 (UTC)

I can't speak to the crackpottery (not yet having investigated the journal), but charging authors for submission and publication has long been the norm in academic journals. Typically, charges are made per page, for preparation of illustrations, and so on, and are quite steep. 87.81.230.195 (talk) 15:30, 7 March 2011 (UTC)

Check out: Fox News Publishes Fake ‘Exclusive’ About Discovery of Alien Life for a bit more on this subject, this scientist and the journal. Rmhermen (talk) 19:10, 6 March 2011 (UTC)

That link doesn't take me to a specific story. It also seems to be a gossip mag. I think relying on a gossip mag to debunk Fox News is a sure route to madness! --Tango (talk) 19:21, 6 March 2011 (UTC)

Link takes me directly to the story. To summarize, he appears to have already announced this discovery on panspermia.org in 2004 and in 2007 in a paper at a conference for the Society of Professional Instrumentation Engineers. But necver in a top-line journal like Nature. He also appears to have claimed that the fossils are older than the solar system. Rmhermen (talk) 19:43, 6 March 2011 (UTC)

The only thing that gawker is saying is that Fox is ridiculous for calling this "new" or "exclusive." That the guy has been shopping this theory for years doesn't really count against him. JoC seems to have reviewed it rather thoroughly before publication, if one takes their editorial note as being accurate. That doesn't mean it is right, but it also means that it shouldn't just be dismissed out of hand because it is unusual. The gawker criticism of the JoC is entirely on the basis of their webpage design — I hate to inform them that most academic journals have pretty lousy web designers. They then back up their evidence by linking to another blogger (who is a biology professor, good for him) who says it is not true. All in all, fun commentary, but not science. --Mr.98 (talk) 20:10, 6 March 2011 (UTC)

The article can also be found here. -- BenRG (talk) 20:21, 6 March 2011 (UTC)

Some ways in which the bacteria may not be extra-terrestrial:

1) Fraud. They could have been placed there by the scientist who "found" them.

2) Accidental contamination. It's difficult to prevent Earth bacteria from getting onto a sample. Even with careful decontamination procedures, bits of bacteria may remain.

3) The meteorites may have come from Earth, as a result of an ancient meteor strike, similar to the one that may have hit to form the Moon, and only recently have fallen back to Earth. I'm unsure if the composition is consistent with a meteorite from Earth. StuRat (talk) 19:32, 6 March 2011 (UTC)

I say JoC looks about as genuine as a thirteen dollar bill. But don't take my word for it - read PZ Meyers at [20]. Note, however, that the scenario of finding life preserved in just the right meteorite is genuine - this was claimed before for a Martian meteorite - but this just isn't meeting the threshold. Wnt (talk) 05:54, 7 March 2011 (UTC)

Why take PZ Meyer's word on it? He seems to me as partisan as any blogger, and willing to make gigantic claims that he doesn't bother to support with evidence. His objections to JoC is "it's online", "it has stuff in it I don't like", and "it has an ugly website." That's not exactly a scientific critique. It might be fringe, but I don't think you can tell that from its webpage alone. --Mr.98 (talk) 01:14, 9 March 2011 (UTC)

weird question about evolution

Did Human being become more sophisticated and intelligent by becoming omnivores? —Preceding unsigned comment added by 1.23.4.211 (talk) 17:04, 6 March 2011 (UTC)

Do you have reason to believe that being omnivorous leads to intellectual attainment? You may be right—I don't know. But we have List of omnivores with a mix of creatures of various intellectual capacities. I'm curious to know how being omnivorous may have spurred on humans to evolve to have intellectual capacities at the upper end of the range. Bus stop (talk) 17:12, 6 March 2011 (UTC)

There's some discussion on the evolution of eating meat by humans here and here, without any reference to cranial capacity. Personally I kind of doubt it — it's not clear to me when you want to say that "humans" evolved to be omnivores anyway, and we have evidence from other great apes that being an omnivore or a vegetarian doesn't seem to push you into the human range at all. (Chimps are omnivores; gorillas are vegetarians. Bugs not included.) It's clear that evolving to eat meat was important for human evolution more generally, especially by allowing them to expand into different ecological niches, but I'm just not sure it can be called a main or prime motivator for our big brains. --Mr.98 (talk) 17:27, 6 March 2011 (UTC)

I'd rather say humans are omnivores (= opportunistic feeders) because they are intelligent. However, I don't see how diet can have an influence on your intelligence as a species. Proper diet is determined more by your intestinal track than by your brain. And along evolution, you tend to adapt to be able to digest the food available to you. Quest09 (talk) 17:43, 6 March 2011 (UTC)

Isn't there an argument that by eating meat, and/or by inventing fire and cooking, humans have been able to get more nutrition from a given quantity of food, and thus spend less time foraging for food, and more time in activities that would make use of their bigger brains? (not sure how that would impact the evolution of the brain, however). --rossb (talk) 17:55, 6 March 2011 (UTC)

Any change that requires an increase in the complexity of behavior and of decision-making ought to generate evolutionary pressure for an increase in the sophistication of brain structure. Since omnivorous behavior is more complex than consistently eating a single type of food, it ought to create a pressure for increased intelligence. Whether this pressure is significant in comparison to other factors, though, is far from clear. Looie496 (talk) 18:59, 6 March 2011 (UTC)

The point is that being omnivore, as I said above, is not exactly our nature. We are opportunistic feeders, so there is less pressure on us, since we can eat what's available. Quest09 (talk) 20:26, 6 March 2011 (UTC)

Animals that have always been herbivores (meaning no omnivores or carnivores in their evolutionary past) do tend to be less intelligent than omnivores and carnivores (or those species descendant from them), but there doesn't seem to be as much difference between omnivores and carnivores. I'd say that this is because hunting requires more skill than foraging. StuRat (talk) 19:21, 6 March 2011 (UTC)

Elephants are reputed to be herbivores, and are very clever animals, as apparently are many parrots. However, I should say that I am always skeptical of claims of absolute herbivory in any animal. An angry elephant can supplement its diet with more than a bit of meat,^[21] and as we know from the mad cow disease outbreak, even cattle feeding can involve substantial amounts of animal byproducts. Wnt (talk) 19:32, 6 March 2011 (UTC)

Elephants are not going to eat too much meat. They don't have the teeth or habits for it. I do think, though, that in general, hunting requires more brain power than running away, though there are some important exceptions where the impetus for more brain power seems to have come from elsewhere. (And comparing it with cows is a complete non sequitur. Cows are herbivores. That we feed them meat tells us only about us and nothing about them.) --Mr.98 (talk) 20:05, 6 March 2011 (UTC)

Regarding "hunting requires more brain power than running away"; that's an invalid comparison, as being a hunter does not exclude one from being hunted, and vice versa. I would also argue that being hunted is important to developing intelligence, and humans likely were considered prey for large predators for most of our evolution. Thus, being both hunter and hunted might lead to the most intelligence with being neither predator nor prey leading to the least, such as the infamous dodo. StuRat (talk) 18:17, 8 March 2011 (UTC)

There are some stupid hunters, like crocodiles, which would eat more intelligent animals like zebras. Quest09 (talk) 20:26, 6 March 2011 (UTC)

Some would take exception to your claim that crocodiles are stupid hunters. See here. Lsfreak (talk) 23:31, 6 March 2011 (UTC)

"Although we classify them as herbivores, hares occasionally eat meat." Bus stop (talk) 20:19, 6 March 2011 (UTC)

Some pretty vicious rabbits have been observed, too. --NorwegianBlue ^talk 21:38, 8 March 2011 (UTC)

Being intelligent also implies having a big brain, which implies lots of energy, which implies some calories rich diet, which contains at least some meat. Quest09 (talk) 20:34, 6 March 2011 (UTC)

The troodon was considered the smartest dinosaur prior to its extinction, and it was also omnivorous. Feral cats eat both meat and grass. ~AH1^(TCU) 01:49, 7 March 2011 (UTC)

I don't think that grass is part of the normal diet of cats. Both feral and domestic cats do eat grass, but probably only as a medicine? Can an expert comment on this? From observation, domestic cats eat grass only when they are about to be sick! Dbfirs 09:46, 7 March 2011 (UTC)

These cat experts give several theories as to why cats eat grass, of which one is that it induces vomiting which helps the cat bring up hairballs. Other sources including The new Encyclopedia of the Cat (Fogle) advise offering grass to indoor cats for this purpose. Cuddlyable3 (talk) 10:44, 7 March 2011 (UTC)

While a common claim, I think the 'sick' part is perhaps a little simplistic particularly if you're thinking they do it because they need to or are about to or already have thrown up. Plenty of cats seem to eat a blade of grass without outward signs of being sick and not all seem to vomit afterwards. A lot of claims are made of the reasons why, but as with many claims about pets, I think there isn't actually much evidence or research. See also [22]. More interesting is [23] which is also covered in [24] and while primarily about dogs they do mention cats, in particular an ongoing study is mentioned (I didn't find evidence has been published yet but didn't look that hard). The hypothesis presented would support a 'medicinal' function I guess. In any case while eating grass is apparently 'natural' and not that uncommon, I wouldn't call cats omnivores and would be careful about giving too much emphasis to them eating grass. Nil Einne (talk) 10:52, 7 March 2011 (UTC)

When talking about carnivores, perhaps a distinction should be made between predators, scavengers, and others, like filter feeders (or are they considered to be omnivores ?). Predators presumably would be more intelligent, as hunting requires more brain power than the others. Note, however, note that baleen whales are filter-feeders, which doesn't seem to require much brain power. I believe, however, that they evolved from fish-eating whales, and retained the brain structure developed for that. StuRat (talk) 18:06, 8 March 2011 (UTC)

lamps

what material are lamp shades made from? — Preceding unsigned comment added by Wdk789 (talk • contribs) 18:05, 6 March 2011 (UTC)

The variety would be very vast. Bus stop (talk) 18:06, 6 March 2011 (UTC)

We could roughly cover the entire spectrum of material science: fiber, polymers, glass, or metal. Almost all day-to-day materials fall into one of those categories. Nimur (talk) 20:30, 6 March 2011 (UTC)

... and bacon! --DI (talk) 22:00, 6 March 2011 (UTC)

Human skin (must be jewish). Cuddlyable3 (talk) 09:38, 7 March 2011 (UTC)

[25] confirms human skin but suggests it wasn't possible to determine the ethnicity of the human. Given the source, Jewish is probably more likely to be right then wrong, but we still can't be certain. Nil Einne (talk) 10:28, 7 March 2011 (UTC)

Human skin (goys OK). --Sean 15:23, 7 March 2011 (UTC)

florida homes

do florida homes have insulation in walls — Preceding unsigned comment added by Wdk789 (talk • contribs) 20:35, 6 March 2011 (UTC)

A quick google search for "Florida building code" + "insulation" provides several hits that suggest that insulation is required to meet the building codes. Such as: http://www.dca.state.fl.us/fbc/committees/energy/energy_forms/New_Energy_forms/600C_04Nrevised.pdf

--DI (talk) 21:56, 6 March 2011 (UTC)

Many Florida homes however do not seem to have basements. ~AH1^(TCU) 01:43, 7 March 2011 (UTC)

I live in Florida and I can attest that basements here are exceedingly uncommon. Dauto (talk) 03:42, 7 March 2011 (UTC)

Interesting I'm sure but I don't get the relevence. No one mentioned basements before you. Nil Einne (talk) 10:58, 7 March 2011 (UTC)

The presence or absence of insulation would depend on when the home was built, and that would apply anywhere - insulation did not come into general use until the 1920s, and wasn't required until the 1940s or 50s in most of North America. In Florida, I'd suspect it wasn't required until somewhat later. Acroterion _(talk) 05:16, 7 March 2011 (UTC)

Energy Densiy of Vacuum Quantum Fluctuations

How can I calculate the energy density of vacuum quantum fluctuations using quantum electrodynamics? Luthinya (talk) 22:31, 6 March 2011 (UTC)

First of all, understand that quantum electrodynamics is a very difficult and subtle subject. If you aren't familiar with it, it will be unwise to try to learn a small piece of it, and attempt to apply some textbook-equation to a particular problem where it might be invalid. Next, have a read at vacuum energy for a conceptual overview of the topic; and read the research publications and textbooks at the bottom of our article. The key is to apply physical constraints to calculate an upper bound on the energy density; our article suggests that modern researchers use the cosmological constant as the upper bound constraint on the vacuum energy. Finally, note that different approaches result in estimated values that differ by hundreds of orders of magnitude. As a general rule, when separate well-known physical theories disagree so significantly, it is a clue that our current theoretical understanding of the relevant process is incomplete - in other words, even the best and brightest physicists who specialize in this field don't know the answer to your question with a great deal of certainty.

As a consequence of this question, I am now reading The Structured Vacuum: Thinking About Nothing. This monograph was written by a professor of physics at University of Arizona, and seems to be an excellent resource for the advanced undergraduate physicist. Without solving the Dirac equation, the chapter on vacuum polarization describes the necessity of a virtual particle plasma of virtual electrons and positrons; these inherently have a statistically fluctuating vacuum polarization (and hence, embodied energy); I suppose to solve for the magnitude of that energy, you must solve the Dirac equation for the virtual particles, subject to physical constraints. Nimur (talk) 00:55, 7 March 2011 (UTC)

The vacuum energy of electrodynamics like the vacuum energy of most quantum field theories is formally divergent. That is not a serious problem for a theory that does not include gravity. That is one of the many theoretical reasons that make supersymmetry a popular subject. Supersymmetry allows theories with finite vacuum energy to be built through a careful cancellation of formally divergent terms with opposite signs. These cancellations depend on the existence of superpartner particles that are yet to be detected experimentally. Dauto (talk) 04:12, 7 March 2011 (UTC)

March 7

Reactions with super-heavy elements?

Hi there, just wondering if any reactions have been done with super-heavy elements that have long enough half-lives. (I'm guessing this would be done to see if they have similar properties to other elements in their respective groups.) If so, what reactions have been done and what been the outcomes? I'm also wondering if there is good reason for trying to create 'new' elements e.g. Element 119, i.e. are scientists looking for anything in particular, or is it just done in case these elements can be used in the future for something? If that is the case, what are the expected applications of these super-heavy elements? I've had a good search of Wikipedia but can't really find anything to help so any answers or thoughts would be much appreciated. Kind regards, Raywil (talk) 03:17, 7 March 2011 (UTC)

Island of stability. ~AH1^(TCU) 03:21, 7 March 2011 (UTC)

Many thanks for the reply: I know about the island of stability but didn't realise that the article described the potential applications of elements that make up the island. Now for the rest of my questions... Raywil (talk) 04:02, 7 March 2011 (UTC)

Thought I'd give this a sort of "bump" to see if anyone else has answers. Thanks. Raywil (talk) 22:49, 7 March 2011 (UTC)

I don't think practical (chemical) applications are likely, any time soon, since the cost of such lab-made chemical elements is likely to be prohibitively high. StuRat (talk) 17:48, 8 March 2011 (UTC)

Also it's too early to answer those questions. Till we make macroscopic amounts of those elements it's pretty hard to figure out applications for them. As for why they are making them, it's mainly curiosity, but also, maybe there will be some awesome application. No way to know till you (they) try. Ariel. (talk) 21:33, 8 March 2011 (UTC)

The highest temperature

Is there any point such as kelvin zero for highest temperature?a. mohammadzade iran--78.38.28.3 (talk) 04:10, 7 March 2011 (UTC)

No.--Srleffler (talk) 05:26, 7 March 2011 (UTC)

You could consider -0 (negative zero, or zero approached from the left) to be the highest temperature, which like absolute zero, is unachievable. See negative temperature. Although depending on the system, positive infinity could be the actual maximum (and unachievable) temperature. Someguy1221 (talk) 07:18, 7 March 2011 (UTC)

A rather poor article but perhaps Absolute hot may be of interest. Nil Einne (talk) 10:24, 7 March 2011 (UTC)

By the current theories, temperature is the measure of the average speed of the particles. An approximate formula is $T={\frac {v_{avg}^{2}\pi M}{8}}$. (M is molecular mass). By this definition, you can have absolute zero with molecules of avg speed zero. Now, your maximum speed is the speed of light, and you can maximize temperature by plugging it in, but, this is the maximum temperature for a molecule with given molecular mass. Take a bigger molecule, and your temperature increases. So there's no maximum temperature. ManishEarth^{Talk • Stalk} 12:16, 7 March 2011 (UTC)

It's almost never a good idea to 'plug in' the speed of light if you're not very sure of the assumptions underlying a formula. Temperature is a measure of the average thermal energy per particle, which for a gas under reasonable conditions is roughly proportional to the average kinetic energy per particle. In classical mechanics, the kinetic energy of an object is proportional to its mass, and increases with the square of its velocity; that's were the v² term comes from in the equation you've used. This falls apart when you get to temperatures high enough that special relativity rears its ugly head. As you put more kinetic energy into a particle in order to increase its velocity, there will be an associated increase in its relativistic mass. The effect is negligible at any reasonable velocities and temperatures, but the particle's mass (and its kinetic energy) will asymptotically approach infinity as you bring its velocity closer and closer to the speed of light. Any hypothetical molecule travelling (impossibly) at the speed of light would have an infinite kinetic energy and therefore an infinite temperature. TenOfAllTrades(talk) 13:59, 7 March 2011 (UTC)

Indeed not only that but the aforementioned equation is missing a Boltzmann constant, and if true, would imply and absolute hot, as there exists only a finite mass; but alas, it is all irrelevant.— Preceding unsigned comment added by 129.67.37.227 (talk • contribs) 23:50, 7 March 2011 (UTC)

More importantly, the basic statement is wrong. Temperature is not a measurement of the average speed of the particles.

This is something that needs to be emphasized every time it comes up. The direct relationship between temperature and kinetic energy works only in one very simple, idealized case — an ideal gas made of individual particles (at normal temperatures, this means a monatomic element like helium or neon). In all other cases, the relationship breaks.

What temperature really is is a statistical concept. It's not about kinetic energy per se. --Trovatore (talk) 00:03, 8 March 2011 (UTC)

Temperature, despite the fact that we use it every day, really IS a very hard concept to get at. Personally, I find the explanation afforded by the Zeroth law of thermodynamics to be most satisfying; the general concept that temperature is defined in terms of thermal energy transfer; two bodies are empirically defined as the same temperature insofar as they are in thermal equilibrium; the temperature at any equilibrium can then be defined as dH/dS, (or dq/dS if you prefer) the relationship between heat and entropy at a particular thermal state. --Jayron32 06:24, 8 March 2011 (UTC)

See a previous discussion at: Wikipedia:Reference desk/Archives/Science/2009 July 14#The Limit of heat?. Staecker (talk) 13:22, 7 March 2011 (UTC)

You might say "absolute zero". Minus absolute zero, that is! See negative temperature. But that is a specialized usage of the idea. Wnt (talk) 05:50, 8 March 2011 (UTC)

exploding of supernova

how dos explode a supernova and how will be the fragment of its inner matter i couldn't find perfect explanation of this in encyclopedia. akbar mohammad zade iran march 2011--78.38.28.3 (talk) 04:18, 7 March2011 (UTC)

In existing nebula if the star matter be powder and dust or it remain molten?a. mohammadzade--78.38.28.3 (talk) 04:23, 7 March 2011 (UTC)

A supernova explodes when the core of a star collapses, causing extremely high pressures. These pressures cause the star to "bounce" back, blowing it to bits.

Stars are made mostly of hydrogen and helium, and the core of a star gone supernova has some carbon, oxygen, silicon, magnesium, and iron. Many of these are gases at most temperatures and pressures, and in the vacuum of outer space, most of them will be gases. Does this answer your question? --T H F S W (T · C · E) 04:53, 7 March 2011 (UTC)

thanks i think that might have gathered pieces ,then this gathered pieces will be molten, because of its condensed early condition and first density what have been observed in crab nebula .if that be gas then in which density?and how can it have 11000 degrees temperature?a. mohammadzade --78.38.28.3 (talk) 05:23, 7 March 2011 (UTC)

The density is very low - the only reason we're able to observe it, is because the nebula is so big. The temperature of the nebule is a measure of the average thermal energy per particle. (molecule, atome, etc.) Since the nebula is so sparse, an observer located inside the nebula would not notice a difference in temperature compared to outside the nebula. Plasmic Physics (talk) 10:06, 7 March 2011 (UTC)

To help to explain this, think of putting your hand into an oven at full temperature. If you touch something dense inside, like a pot, your hand would burn instantly. If you only touch the less dense air, then your hand heats up more slowly, and you might be able to take a few seconds without getting burnt. Now imagine that the air is a trillion times less dense, and your had wouldn't get hot at all (except for radiation from the sides of the oven, but we'll ignore that). StuRat (talk) 17:38, 8 March 2011 (UTC)

Petrochemical Distallation

Is it possible to sort a mixture of waste plastics using fractional distallation under an anoxic atmosphere? Plasmic Physics (talk) 09:56, 7 March 2011 (UTC)

In general, no, because plastics tend to decompose when heated, producing hydrocarbons and other products. You may get useful fuel out, but not gaseous plastic that you can then condense and reuse.[26][27][28][29] --Colapeninsula (talk) 11:51, 7 March 2011 (UTC)

Would increasing the pressure to several times atmospheric pressure have any effect on the rate of pyrolysis? Plasmic Physics (talk) 22:21, 7 March 2011 (UTC)

Where are the batteries on this bike?

Where does the energy come from for this? http://www.bbc.co.uk/news/uk-england-10858682 I cannot see any batteries. Can anyone explain what this is supposed to be doing? Thanks. 92.29.124.221 (talk) 12:42, 7 March 2011 (UTC)

They're in the pedal. You can see them on the video - they're the two objects on either side of the pedal, wrapped in a black shrinkwrap. The pedal has had a motor and batteries added. Assuming the user resists the attempt of the pedal to turn, the pedal and foot combined will drive the crank. --Tagishsimon (talk) 12:48, 7 March 2011 (UTC)

Thanks. I expect batteries that small will last about two minutes, so they are practically useless. 92.29.124.221 (talk) 12:52, 7 March 2011 (UTC)

They probably didn't developed the bike to be run all the time with these tiny batteries, but only to give you an added push. 80.58.205.34 (talk) 16:36, 7 March 2011 (UTC)

Excavations at ancient battle sites

What are the odds of finding the helmets, shields etc and human remains at the sites of ancient battles (such as Thermopylae)? Also I'm curious what would be the depth of digging to reach the weaponry and human remains in case of Thermopylae? —Preceding unsigned comment added by 89.76.224.253 (talk) 14:42, 7 March 2011 (UTC)

Just to note here that the helmets, shields and such would have been recycled by the victors and so you wouldn't have much chance of finding them. In Repton, UK, a number of male skeletons were found near the parish church in the last century, and it is speculated that these were victims of a Dark Age skirmish.Repton Church --TammyMoet (talk) 15:21, 7 March 2011 (UTC)

Just to be clear, what you're referring to is looting and/or grave robbery (depending on the circumstances) and is considered unethical and/or illegal depending on the jurisdiction. Unfortunately, the illegal antiquities trade has been going on since the "antiquities" were brand new, meaning that many, if not most, archaeological sites have been pretty seriously plundered of what non-archaeologists would consider valuable (cool stuff like weapons are in almost a high demand as the shiny stuff). I don't know the depth of the soil at Thermopylae, but our article at least indicates that the water levels have dropped since the battle took place, so at least they won't be underwater. Matt Deres (talk) 17:51, 7 March 2011 (UTC)

I think many other people have thought about this in the past and the likelihood of finding any remains now is, well, slight, and that's being optimistic. 86.4.187.76 (talk) 20:42, 7 March 2011 (UTC)

Technically, it's not unethical to dig up ancient artifacts and treasure; it's only unethical for poor people to profit from them, rather than license-holders and established institutions. Wnt (talk) 00:58, 8 March 2011 (UTC)

I'm sorry, but that's just incorrect; the problem has nothing to do with who profits, it's with what happens to both the artifacts and the state of the site. The people who raid such sites just dig holes all over, grab whatever they figure they can sell, and make off with whatever they can carry away, paying no attention to recording provenience of the pieces, horribly contaminating the site and artifacts to render most dating techniques unreliable, and literally destroying whatever gets in their way of making a buck. The pots and jewellery and neat looking human remains get sold off and lost from the archaeological record, to the detriment of everyone. Matt Deres (talk) 04:20, 8 March 2011 (UTC)

Just like to point out, the person asking didn't say they were going to dig up battlefields, they just asked a hypothetical question about what might be found at old battlefields. There's no need to get on your soapboxes, people. Pretend he/she is an archaeologist. --Colapeninsula (talk) 10:35, 8 March 2011 (UTC)

I wonder; if helmets, armor, shields, and weapons were there, if they would be totally corroded by now. I believe the Battle of Thermopylae occurred during the Iron Age, so it may have all rusted away, by now. Perhaps some high ranking soldiers might have had some gold accents on their items, but then those would have been even more likely to have been stolen. StuRat (talk) 17:26, 8 March 2011 (UTC)

Budgerigar 'charming'?

How/why does this work? I think that this effect, or something like it has been discussed on here before in relation to other bird species. The guy in the video is a real veterinarian, who also has some 'mystic' beliefs which he draws on, alongside the traditional medicine (AFAIK) - but I'm personally sceptical that this is actually a 'mystic' phenomenon. Something is clearly happening here though, to render the budgie still and docile. Any ideas? --95.148.106.17 (talk) 15:10, 7 March 2011 (UTC)

He also does the same thing with a lovebird here while trimming its beak. --95.148.106.17 (talk) 15:16, 7 March 2011 (UTC)

Interesting.. Wonder if it is something similar to Chicken hypnotism.. That's what really annoys me about stuff like this, there's obviously something very cool and interesting going on and then he has to go and say that he's seen John of God do it to people who then have surgery standing up without anaesthetic, what a crock. Vespine (talk) 00:37, 8 March 2011 (UTC)

This one is even more extraordinary. It certainly seems woo-ish from the way he describes it - but he's obviously doing *something* that works. A parrot flipped on its back would normally bite (hard) and struggle to escape. --Kurt Shaped Box (talk) 02:23, 8 March 2011 (UTC)

Parrots peacefully scattered around in the landscape on their the backs (drunk) isn't an unusual sight in Queensland so they seem to have a "I'll just have a bit of a lie down for a while" mode. Sean.hoyland - talk 17:41, 8 March 2011 (UTC)

I can think of two triggers that might calm a bird:

1) The "time to sleep" trigger might occur when the light level goes down, such as covering the eyes (or entire cage) of a diurnal bird. This doesn't seem to have been used, in this case.

2) The "preening" trigger might occur in social birds, where they are preened by others. This might apply here, as stroking of the feathers may set this off. Thus, those birds which calmed down, when being preened by others, might have been more likely to survive and pass on their genes than those that became agitated. Do budgies preen each other ? StuRat (talk) 17:10, 8 March 2011 (UTC)

I'm actually not very impressed with this video. The bird tries to get away again and again and again, and he has to hold its wing awkwardly at one point to contain it. It's not obvious to me that a bird has to struggle to escape continuously, as opposed to once a minute as this one does, especially not when it's an old arthritic bird that has lived most of its life in a cage. It is apparent, of course, that the feel of a hand around its wings and/or being upside down has some effect, but this is scarcely magical. It reminds me of something from mouse work - supposedly, holding the mouse by the scruff of the neck keeps it from trying to get away when injected, but honestly, I suspect that any pain equivalent to such a pinch makes the mouse briefly play possum (or otherwise stop moving), and the specific technique is unimportant. Wnt (talk) 22:53, 8 March 2011 (UTC)

Acrylamide in commercial breads

I buy 100% Whole Wheat breads from supermarkets, and try to purchase as few sugars as I can, but I'm not sure if anything can be done about acrylamide. Is making my own bread by boiling the only way to avoid the substance? (And no, I don't believe epidemiological studies.) Imagine Reason (talk) 19:08, 7 March 2011 (UTC)

How does one boil a bread? Dauto (talk) 19:55, 7 March 2011 (UTC

A bread what? I think we usually call it a loaf or a roll (or bap) 86.4.187.76 (talk) 20:40, 7 March 2011 (UTC)

Bagels are boiled. Ariel. (talk) 20:49, 7 March 2011 (UTC)

The idea with boiling is the temperature, not the actual boiling. All you need to do is cook the bread till it's cooked, but not browned. So avoid a heavy crust, and take it out when it's still pale. You should also make smaller bread, so the inside is fully cooked without having to heat the outside very much. If you are really worried, then cut off the crust. The inside of bread doesn't really go much above boiling (if it did it would dry out and become crust). Ariel. (talk) 20:49, 7 March 2011 (UTC)

So maybe picky children (who want their PB&J with the crusts cut off) were right all along. StuRat (talk) 18:30, 8 March 2011 (UTC)

I've noticed various brands of crustless bread in the supermarket - some new process, I think. 81.131.26.97 (talk) 04:44, 8 March 2011 (UTC)

I assumed they just cut the crusts off and used it for other things, like bread crumbs or animal feed. StuRat (talk) 18:30, 8 March 2011 (UTC)

I tried two brands: one seemed to have the crusts cut off as you say, the other had a thin layer of dense but pale bread instead of crust. 213.122.24.251 (talk) 23:44, 8 March 2011 (UTC)

I investigated this myself in the past. There is such a thing as steamed bread, and there are steamed bread rolls which are a Chinese thing.

I've never seen either of them for sale anywhere, but if steamed bread was done at high pressure it may be no better than ordinary bread. Steamed bread redirects to Chinese steamed rolls. Frying them as the article shows would introduce acrylamide into them.

Wholemeal bread has more acrylamide in it than white bread. Soda-bread has less acrylamide in it. Since acrylamide is associated with browning (by heat, not enzymic browning) then pale un-browned bread such as some pitta bread is likely to be safer. Any manufacturer who can supply acrylamide-free bread will make a fortune. By the way, crispbreads have very very large amounts of acrylamide in them. Cooking food in a microwave also results in acrylamide.

I'd be very interested to learn of any practical recipies for home-steamed bread or even rolls. 92.29.127.85 (talk) 20:53, 7 March 2011 (UTC)

Boston brown bread or hobo bread. Rmhermen (talk) 00:19, 8 March 2011 (UTC)

Thanks. The three and a half hour cooking time is something to think about, although on the other hand my bread machine takes longer than that. 92.15.0.66 (talk) 16:25, 8 March 2011 (UTC)

As an aside, the acrylamide scare is the unwarrented-panic-du-jour. If it is present in baked starchy goods, then it has been there for thousands of years, or roughly as long as humans have been baking bread. Whether or not, and at what levels, it is carcinogenic isn't nearly as important as the measurable health outcomes of consuming acrylamides on baked goods such as breads. In other words, does the eating of bread have a measurable impact on your likelyhood of dying of cancer, solely from the acrylamide content? How many cancer cases per year can be traced to acrylamide consumption from ordinary baked goods? I think you'll find these numbers to be vanishingling small, close to zero. On the list of risks to your own life, in terms of both length and quality, eating whole grain bread falls somewhere near the bottom. --Jayron32 04:58, 8 March 2011 (UTC)

Our physiology has evolved for many millions of years since the beginning of life. We only started cooking bread very recently. Evolution is not very sensitive to early deaths after you've had kids. 92.15.0.66 (talk) 16:23, 8 March 2011 (UTC)

We've been drinking alcohol for a long time, too. Ok, so it's much safer than beer, but we've been ignorant for most of our history. 66.108.223.179 (talk) 14:31, 8 March 2011 (UTC)

The Romans did not live very long because they were unwittingly poisoning themselves from the lead in their pipes and drinking vessels. I think they may also have added it to wine, not sure. They did not detect it was poisonous because everyone was consuming it. Before acrylamide was found in food, it was clasified as a probable carcinogen. Now that its been discovered in food, then all of a sudden it becomes harmless? Can I remind you that a large proportion of people (do not recall exact proportion) die of cancer. So, carcinogen in food, and lots of people dying of cancer - surprised? 92.15.0.66 (talk) 16:12, 8 March 2011 (UTC)

Yes, it could be a problem, but we need more info to know if it really is a problem. That is, just how carcinogenic is it ? It would be impossible to avoid all carcinogens entirely, as you likely inhale several with every breath. So, then, since we can't avoid all carcinogens, the issue becomes avoiding the worst ones. StuRat (talk) 16:53, 8 March 2011 (UTC)

"Just how carcinogenic is it" you ask. "The European Chemical Agency added acrylamide to the list of substances of very high concern in March 2010.[5]". 92.15.20.212 (talk) 17:50, 8 March 2011 (UTC)

Your footnote didn't copy, do you have a link ? StuRat (talk) 18:26, 8 March 2011 (UTC)

Go to the Acrylamide article and find footnote number 5. 92.15.20.212 (talk) 20:56, 8 March 2011 (UTC)

OK, following the link I found a study that showed no evidence of it causing cancer in humans, but they did find it caused cancer in rats when given at the rate of 3 mg per kg of body mass per day. So, then, the question is whether the amount in bread comes close to that. I didn't find info for bread, but this site lists the level as 1.57 mg/kg for French fries ("chips" in British English): [30]. However, this is per kg of food, not per kg of body weight. So, you'd need to eat twice your weight in fries each day to have the same exposure level as rats had in the study. If bread has comparable levels, then the results should be similar. StuRat (talk) 22:41, 8 March 2011 (UTC)

There is "no evidence of it causing cancer in humans" because no one would do such an unethical experiment. The mice would have been fed acrylamide for a short time (they only live a year or two, maybe less) which is not the same as eating it over more than fifthy years for a human. The mice can show it is carcinogenic to mice and by inferance mammals, but the dose in relation to bodyweight cannot be extrapolated due to the different time-scales inolved. 92.24.191.116 (talk) 23:46, 8 March 2011 (UTC)

Note that it could still be highly carcinogenic if you have a bottle of it, and yet be completely insignificant as a food safety risk, if the quantity in bread is small enough. For example, ozone is also a health risk, but the amount in the air we breath is typically low enough that it's not a concern. Only when we have elevated levels, as in cities with a pollution problem, do we need to do something about it. StuRat (talk) 18:35, 8 March 2011 (UTC)

OK, tell us, how little is harmless? How many scientists do you have working at the StuRat Laboratories? You must have a secret underground headquarters like Dr. No in James Bond. 92.15.20.212 (talk) 20:56, 8 March 2011 (UTC)

I don't have time to respond to that...I'm too busy petting a cat with one hand and adjusting the calibration on my missile launcher with the other. StuRat (talk) 23:11, 8 March 2011 (UTC)

See also Post hoc ergo propter hoc. AndrewWTaylor (talk) 17:03, 8 March 2011 (UTC)

Cleaning bones

Hello. I have some friends who found a coyote skull, broken into four pieces. I was thinking of gluing them together and making a stand for a nice display, but I need it cleaned first, and I need some small, invertebrate help to do it. If I were to put it in a terrarium with either mealworms or crickets for a while, would they get it all nice and clean for me, similar to Dermestidae beetles? --T H F S W (T · C · E) 19:25, 7 March 2011 (UTC)

Amazingly, we have already answered this question on the Reference Desk. See "Help Cleaning a Dog Skull" from May 2008, and "Part Two" of the same. Nimur (talk) 19:32, 7 March 2011 (UTC)

This subject actually comes up a lot - Rabbit, February 2008 (discussion regarding the use of beetles)... Nimur (talk) 19:39, 7 March 2011 (UTC)

Thank you, the above links were helpful, but you still did not answer my question: could I use either mealworms or crickets to clean a skull without damaging it? --T H F S W (T · C · E) 23:20, 7 March 2011 (UTC)

Crickets are omnivores and will apparently eat decaying organic matter. Our mealworm article indicates that they prefer vegetarian fare, so I'm unsure if they will be useful for cleaning your specimen. Previous responses have suggested ants. Nimur (talk) 00:06, 8 March 2011 (UTC)

(Edit Conflict) The articles to which you have already linked both suggest that these insects are primarily herbivores that may eat insect remains if that's all that's available, but do not mention any propensity for eating mammalian organic remains, which seems to me unlikely as it's far from their normal diet. You could simply try them both out - the bones are not going to suffer if either or both don't perform, and you can then try one of the other methods.

You might find some useful information in this post. 87.81.230.195 (talk) 00:07, 8 March 2011 (UTC)

(EC)Hmm, i'm not an expert but I don't think so. crickets and mealworms mostly eat vegetable matter, not decaying meat.. I just use flies and ants. if you have any "yard", buy a cheap bucket, put some holes in it, cover the skull and put a brick on it so a cat or something can't drag it off. Vespine (talk) 00:08, 8 March 2011 (UTC)

Also, if it gets to the stage where you are gluing it back together, I read that bone collectors use regular PVA glue: It's transparent, doesn't damage the bones, bonds well enough and can be washed off if required. Vespine (talk) 00:10, 8 March 2011 (UTC)

Hmmm. Is there anything wrong with your standard housefly/bluebottle maggots? Or how about simply boiling the skull? --Kurt Shaped Box (talk) 00:09, 8 March 2011 (UTC)

Normal house flies would take too long and the place would stink while they did their work (If THFSW is in the northern hemispeher, there also might not be many flying around at this time of year). Boiling the skull would be quick, easy, and thorough, so long as you don't mind a little grossness. FYI, the bones might not fit back together as neatly as you might hope; in living animals, the bones can bend slightly before breaking - if this critter was hit by a car or something, you might end up with a skull that looks warped or deformed. Matt Deres (talk) 01:08, 8 March 2011 (UTC)

I haven't actually seen the skull, some friends of mine found it. i don't know about the condition, it might not even be worth it to try to piece it together again. Just one question: will boiling the skull (sounds barbaric!) get rid of all the flesh and dirt? I think that this skull may have been underground for a long time, so cleaning it may be the only issue. --T H F S W (T · C · E) 05:30, 8 March 2011 (UTC)

In my experience, boiling in water alone will remove dirt but not all the flesh. The flesh does become softer and easier to remove, after many hours of boiling, and the skin and muscles fall off, but other parts remain attached, including cartilage and especially the marrow insides bones. Perhaps boiling it in bleach might be more effective. This would have to be done outside, say on a fire pit or grill, as you don't want your home filled with bleach fumes. Also, avoid using an iron pot, as the bleach would cause it to rust. StuRat (talk) 16:39, 8 March 2011 (UTC)

Sad story: I recently shot an 800 lb boar hog. I couldn't make head cheese from it for boring reasons, so I just put it in the woods for critters to eat the flesh off and I'd have an epic skull with enormous tusks. I screwed an eye hook into the skull and wired it to a tree. When I went back a week later it was gone. The wire had been broken off. :( --Sean 14:45, 8 March 2011 (UTC)

A rotting boar skull covered with maggots and flies sound very Lord of the Flies to me. StuRat (talk) 16:42, 8 March 2011 (UTC)

If only you had the foresight to embed a transmitter with a GPS device in the brains! Comet Tuttle (talk) 18:04, 8 March 2011 (UTC)

Pistol shrimp & goby fish

The pistol shrimp often lives in symbiotic life with the goby fish. The pistol shrimp is almost blind, but is able to dig long galleries for their common home; the gobi does nothing, but watchs around with his big eyes, should a predator be approaching, in which case, he gives the alarm and quickly leads the shrimp back home. The shrimp also carries a kind of big and loud gun in one of his claw, that uses to shoot down his preys (the continuous gunshots of these guys even interfere with submarines' sonar system, they says). Apart the obvious side remark that God is apparently an addicted Marvel Comics reader, I wonder: how does the goby avoid being shot by his blind gunslinger friend? Thanks. --pma 22:04, 7 March 2011 (UTC)

I don't have an answer, but this has been sitting here a few hours now and I just have to say: this is the funniest, cutest and quirkiest subject / question I've seen here for a long time. I've probably read past it ten times and it still makes me smile, absolutely love it. :) Vespine (talk) 05:31, 8 March 2011 (UTC)

You mean DC Comics. According to the goby fish article, the symbiotic gobies are known as Watchmen. ;) (Sorry, no real answer yet - though I should say that the shrimp apparently knows how to target its prey) Wnt (talk) 05:47, 8 March 2011 (UTC)

I am shocked to learn that the pistol shrimp is blind, when that other famous slinger of shrimpoluminescence, the mantis shrimp, has the most complex eyes in nature. --Sean 15:18, 8 March 2011 (UTC)

doxycycline

What was the antibiotic doxycycline first isolated from? 82.132.248.19 (talk) 23:22, 7 March 2011 (UTC)

Tetracycline_antibiotics#History has some background. While doxycycline is not directly covered, it seems that the tetracyclines in general seem to derive from various strains of Streptomyces bacteria. --Jayron32 23:38, 7 March 2011 (UTC)

Doxycycline is a semi-synthetic antibiotic: it can't be isolated from any organism because it doesn't naturally occur in any. I believe but can't find a reference, that's it's produced by chemically altering the naturally occurring tetracycline (obtained by fermentation with Streptomyces species). You may be interested in the history section of this article- Nunh-huh 03:09, 8 March 2011 (UTC)

Blood erythritol

The polyol erythritol is used as a sugar substitute. Although it is absorbed by the body and passed through the kidneys, it is not metabolized. It does not increase "blood sugar", i.e. blood glucose, it is a sugar alcohol. Even so, it actually has anti-oxidant effect.^[31] Even so, I have to ask: is erythritol also a kind of "blood sugar" -- i.e., does erythritol have any properties that duplicate those of an equal amount of glucose? For example, does it increase blood viscosity, cross-link proteins, or add to strain on the kidneys? Wnt (talk) 01:37, 8 March 2011 (UTC)

Gear trains

actually i have solved a gear train questions which is giving negetive value for number of tooth for one of the gears.what could i interpret from that. should i take absolute value of the number of tooth. 59.93.130.41 (talk) —Preceding undated comment added 06:42, 8 March 2011 (UTC).

We would need more information about what great train question you solved (i.e. what the math was). A negative number could mean you have an error, or perhaps it means the gear is rotating in reverse. It's impossible to say without knowing what formula you used. Ariel. (talk) 11:01, 8 March 2011 (UTC)

Q.

The annulus A in the gear shown in the figure rotates at 400 rpm about the axis of the fixed wheel S which has 80 theeth.The four armed spider is driven at 180 rpm.Determine the number of teeth required on wheel p. —Preceding unsigned comment added by 59.93.134.20 (talk) 12:46, 8 March 2011 (UTC)

I've tweaked the image to make it viewable. --Tagishsimon (talk) 12:49, 8 March 2011 (UTC)

Thanx for tweaking, Here when we solve we get number on tooth on annulus gear(red one ) to be -24.82.to solve remaining problem should we take modulus value of number of gears.Or it is having any significance. —Preceding unsigned comment added by 59.93.134.20 (talk) 13:07, 8 March 2011 (UTC)

Don't you worry about the fractional number of teeth as well? Dauto (talk) 15:26, 8 March 2011 (UTC)

Which gear is S and which one is p ? Gandalf61 (talk) 15:29, 8 March 2011 (UTC)

Typically "S" is the "Sun" (center) and "P" is the "Planet" gear (by analogy to orbits). See Sun and planet gear. In this case, we have one sun, four identical planets, and an outer-ring that the OP is calling the "Annulus" (A). Nimur (talk) 17:15, 8 March 2011 (UTC)

And can you show us your math ? StuRat (talk) 15:58, 8 March 2011 (UTC)

Ariel seems to be right. Epicyclic_gearing#Gear_ratio says that a negative result means rotation in the opposite direction. --Heron (talk) 19:17, 8 March 2011 (UTC)

Autotrophic respiration

We don't seem to have an article on root respiration (autotrophic respiration), although it seems to be a fairly mainstream topic. I am curious about the interaction between scion and rootstock on tolerance to waterlogging and couldn't even find the relevant mechanisms defined here. DId I miss it or could someone who has a clue (unlike me) start one? --BozMo talk 09:59, 8 March 2011 (UTC)

Perhaps the articles Autotroph or Photoheterotroph may help? - 220.101 talk^\Contribs 15:08, 8 March 2011 (UTC)

Flight angle

An accident occured in which the vehicle was twisted at flight angle. What does the term "flight angle" mean technically and also how is it used on day to day basis? aniketnik 16:26, 8 March 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

Probably, "flight angle" refers to either the angle of attack (the angle of elevation of the wing surface, relative to horizon, as a rotation along the pitch-axis); or to the pitch angle (the angle of the aircraft airframe, measured relative to the horizon, along the axis designated as the "pitch axis"). In the case of a catastrophic accident, those two angles might not be identical! See our diagram for the conventional layout; and on most fixed-wing aircraft, note that pitch and angle-of-attack of the wing surface are fixed relative to each other. Other important "angles" are described in our aircraft flight dynamics article, with animations. Your exact quote, "twisted at flight angle", sounds very ambiguous - it is possible that the intended meaning is that the aircraft was within its normal operating orientation limits and should not have stalled. If you provide a source for your exact quote, we may be able to interpret the intended meaning a little better. Nimur (talk) 17:00, 8 March 2011 (UTC)

spin

How can they force the spin axes into a horizontal alignment by imposing an electric field that alternates at radio frequencies like it says in this article http://findarticles.com/p/articles/mi_m1200/is_n11_v133/ai_6507705/ — Preceding unsigned comment added by Lufc88 (talk • contribs) 17:55, 8 March 2011 (UTC)

I have a question.

Elements which make life possible

Which element or elements makes life possible? I am also wondering if life can be inorganic instead of organic? Matthew Goldsmith 19:08, 8 March 2011 (UTC) — Preceding unsigned comment added by Lightylight (talk • contribs)

This is covered in some detail in the article Hypothetical types of biochemistry. Short answer: there may be all sorts of different chemical configurations that can make life happen, but we haven't observed them yet. (Except maybe GFAJ-1, but that's a small modification of the general template, if it is real.) --Mr.98 (talk) 19:58, 8 March 2011 (UTC)

I added a better (sub)title; please try to make your title more useful in the future. Also, a question: Do you mean chemical elements, or "elements" like light, heat, water, and gravity ? StuRat (talk) 22:15, 8 March 2011 (UTC)

Carbon, hydrogen, oxygen, nitrogen, (phosphorus or arsenic), and sulfur are all necessary. --75.15.161.185 (talk) 01:10, 9 March 2011 (UTC)

efficiency

how efficient are steam power plants like coal in converting heat to electricity in percentage? how efficient are antennas in converting em waves to electricity in percentage? — Preceding unsigned comment added by Lufc88 (talk • contribs) 19:39, 8 March 2011 (UTC)

The answer is, of course, "it depends." Practically, a coal power station is about 40% efficient, per carnot efficiency and engineering practicality. Antennas can be very close to 100% "efficient," if your amplifier and signal path are impedance-matched to free space (377 Ω), if you count all power out in any direction. Read thermal power station efficiency, and antenna gain. Do you need help understanding those articles? Nimur (talk) 21:28, 8 March 2011 (UTC)

Standardization in Redox Titrations

Hello. Is standardization of KIO₃ necessary before titrating against ascorbic acid if I am preparing KIO_3(aq) from its solid? Thanks in advance. --Mayfare (talk) 21:42, 8 March 2011 (UTC)

Hi Mayfare. I think you have to ask yourself what reasons might mean that weighing solid KIO₃ might not accurately tell you the molarity of the solution. Here are a few to consider...

• Purity of solute (KIO₃) as sold. Was the solute intended for use as a primary standard or is it just a ground-up radiation pill, etc?
• Storage. Has the solute been kept in an airtight container so that it can't react with atmospheric gases around the lab? Would that be an issue?
• Humidity. Is the solute totally dry? If not, how might you dry it before use?
• Purity of solvent (H₂O). You might get an extra mark for mentioning this!
• Accuracy of weighing. How much solute are you weighing out? What is the precision of the weighing device?
• Accuracy of dilution. What errors might you expect here?

Hope this helps. Try estimating the cumulative effect of the last two (Accuracy) points. - Pointillist (talk) 22:31, 8 March 2011 (UTC)

Inheritance traits and DNA

Is it possible to determine the skin tone, hair/eye color and blood group after studying the inheritance traits during DNA analysis? --89.76.224.253 (talk) 22:33, 8 March 2011 (UTC)

It certainly is in the DNA somewhere (barring the use of hair dye, colored contacts, and such), but I'm not sure if we know exactly where. It's sometimes vastly more complex than just one chunk of DNA which sets each trait. There might also be certain diseases or environmental factors which might have an effect (like sun-bleached hair). StuRat (talk) 23:06, 8 March 2011 (UTC)

(ec)There are some claiming to do this.[32][33] This is fairly embryonic, and I would keep an eye out for chicanery. Genetic testing to determine the blood type shouldn't be difficult, but I can't think of many situations in which it would actually be useful. After all, if you have blood, might as well go for a DNA match. Wnt (talk) 23:07, 8 March 2011 (UTC)

The Daily Mail article is (no surprise) extremely misleading. It says that theoretically in the future you could reconstruct certain details about a person's face from DNA. (Granted in theory you could do this to some degree — but we're a long way away in practice, and it's unclear if those details you could extrapolate would actually be useful in identification.) Then it says something like this was already done... because they used DNA to determine that a suspect was Black rather than white. That's not the same thing at all; it's relatively easy to guess what ethnicity/racial category someone would fall in based on their DNA (it's probabilistic, but you can say things like, "you carry genes are extremely prevalent in people from this part of the world as opposed to this part of the world" — which, in some situations, is probably enough to say, "this guy is probably pretty white looking or Asian looking or Black looking" — which is not terribly precise, but could be useful in identifying a suspect). It's totally different — one is modeling development (which is hard), the other is tracing origins (which is not as hard). --Mr.98 (talk) 23:21, 8 March 2011 (UTC)

It's not easy to say exactly where this line is crossed, because any statistical fact is meaningful. We shouldn't expect that one day the genetic information is worthless and the next you can draw the suspect's face - rather, there is a period when it can rule out some possible suspects and provide "most likely" values for some features. Wnt (talk) 23:38, 8 March 2011 (UTC)

Note that even ruling out suspects (or matching DNA) is (under currently used practices) still probabilistic. They do not currently sequence entire DNA sequences (though someday they may do this, once it gets really cheap), just a finite series of markers within them. The odds of two different sets of DNA being seen as identical under these procedures is small but not impossible. (And calculating those odds depends on what assumptions you make about the target populations.) It is to my understanding still quite rare to use DNA testing to say something about what your suspect should look like — usually DNA analysis is useful after you already have samples to compare against. --Mr.98 (talk) 00:36, 9 March 2011 (UTC)

Speed of back-and-forth motion

How to measure the speed of continous back-and-forth motion? One b&f move per second? -) —Preceding unsigned comment added by 89.76.224.253 (talk) 22:56, 8 March 2011 (UTC)

How about dividing the total distance traveled per cycle by the time for each cycle ? This will give you the average speed. However, if you want the instantaneous speed, which would be expected to be zero at the furthest extensions and (normally) at maximum in the center, that gets trickier. StuRat (talk) 23:03, 8 March 2011 (UTC)

If I continously make for example 0,5 m back and forth per 1 s, that would be 0,5 m/sec per cycle, I guess? But what about instances where speed is inequal? --89.76.224.253 (talk) 23:08, 8 March 2011 (UTC)

If it goes half a meter one way, then half a meter back, that's 1 meter total. If that happens in one second, then that's an average of 1 meter per second. However, the speed WILL be uneven. That is, it must stop and turn around at the end of it's motion at each end. This is what I was getting to with "instantaneous velocity", which is the speed at any given time. If we make some additional assumptions, like constant acceleration/deceleration and no rest time at each end, we might even be able to come up with a graph of the instantaneous velocity at each point in the cycle, from the data you supplied. StuRat (talk) 23:19, 8 March 2011 (UTC)

Do you mean Hertz? You could say that the motion has frequency v and then calculate the position = K sin (2 pi vt) and therefore velocity = 2 pi K v cos (2 pi vt) [the derivative]. (K is half the total distance moved; the 2 pi factor converts cycles per second to radians per second, which can be multiplied by seconds and input into the sin function) But only if it moves sinusoidally. It could just bounce back and forth at constant velocity, for example.

To elaborate, suppose you have a piston that is driven by something that circles 0.25 m away from a central pivot once per second. Therefore the piston moves 0.5 m back and forth once per second. (Depending on the linkage I don't think this is precisely sinusoidal, but it could be) Time zero is the piston half extended, moving outward. The position of the piston is simply 0.25 m (2 pi t). When t = 0.25 it is 0.25, 0.5 it is 0, 0.75 it is -0.25, 1 it is 0.25 again. The velocity of the piston is (2 pi radians/cycle) (0.25 m) (1 cycle/second) cos (2 pi radians/cycle * 1 cycle/second * t). At t=0 this is 0.5 pi "radians" m/s = about 1.57 m/s. The decision to use radians in the velocity is momentarily confusing (both radians and cycles are in a sense "dimensionless") but radians signify the actual distance traveled, whereas cycles are merely a count of events. Wnt (talk) 23:24, 8 March 2011 (UTC)

Only a massless object could do that. Any real world object takes some time to accelerate and decelerate. However, the instantaneous velocity profile isn't necessarily sinusoidal, that's only true under constant acceleration. In the case of a ball being batted back and forth by a cat, for example, this wouldn't be the case. StuRat (talk) 23:23, 8 March 2011 (UTC)

I just edited the above a little, but to address your point, yes, there is at least some period of acceleration. But if the impact is elastic at either end, it would be a very small amount of time. Wnt (talk) 23:26, 8 March 2011 (UTC)

So, we should ask, what's driving this object to move back and forth ? This may help us to determine what type of motion and acceleration we're dealing with. StuRat (talk) 23:28, 8 March 2011 (UTC)

We have an article on the simple harmonic oscillator. This is the simplest type of "back and forth" motion modeled in physical systems. More complicated models deal more accurately with other types of motion. Nimur (talk) 23:37, 8 March 2011 (UTC)

dust mite covers and bed bugs

Will a special mattress cover designed to keep out dust mites (for those who are allergic) also keep out bed bugs, so that if bed bugs appear in the apartment, the person who lived there wouldn't have to throw out the mattress after eliminating the bed bugs? I guess I want to find out if a dust mite mattress cover could be part of preventative measures. I'm not asking medical advice. Thanks, 74.14.13.241 (talk) 00:02, 9 March 2011 (UTC)

Well it might act as a partial barrier, but bed bugs are particularly resourceful in gaining access to the sleeping body. There are accounts of them climbing up the bedroom wall and jumping off onto the bed, having calculated the appropriate parabolic trajectory! (No, I don't believe that, but I do believe that they will find their way round most obstacles to gain access to their food.) Treatment with insecticide is much more effective, but even that is not guaranteed. Dbfirs 00:11, 9 March 2011 (UTC)

Are you actually asking if the cover will keep them in? i.e. the bed bugs will be locked under the cover and can't reinfect the room? Assuming you kill all the ones in the room? It seems unnecessary to me - killing the bugs in the mattress is pretty easy compared to killing the ones hiding in the room. Also they can live for a year without food, even under that cover. As a general answer, the cover will do nothing, since the bed bugs can live in the room and then walk over to the person on the mattress. (Unlike mites they don't live inside the mattress, they hide on the mattress in seams.) And they can also hide in cracks in the floor or walls, etc. Ariel. (talk) 00:58, 9 March 2011 (UTC)

Antimatter explosion

Is it possible to determine/make an educated guess as to what a (hypothetical) antimatter explosion in air would actually look like? Would it appear similar to a nuclear bomb going off - but larger for the given mass of 'explosive' material? Would there be a mushroom cloud? Would the explosion be the same colour? --Kurt Shaped Box (talk) 00:25, 9 March 2011 (UTC)

It should look more or less like a nuclear explosion, which itself (from a superficial point of view) is just the creation of a gigantic expanding ball of heated air. The mushroom cloud is caused by it being close to the ground, and is not unique to a nuclear explosion (any explosion of a sufficient size will cause one if it is close enough to the ground to suck up dirt). I don't know about the color — nuclear explosions generally just look like the standard black body spectrum (a ball of fire), but you do get weird cloud colors because of the radiation involved, ionization of the air, etc. I don't know what kinds of things you'd get from an antimatter explosion but I'd imagine they would mostly look pretty similar, since the essential thing responsible for the appearance of a nuclear explosion (lots of heat energy all at once) is essentially the same. (I would not expect all of the effects to be the same, mind you. But you can't see neutrons, for example, so the fact that nukes let out gobs of neutrons doesn't really change how they look.) --Mr.98 (talk) 00:31, 9 March 2011 (UTC)

As a point of clarification, while a nuclear mushroom cloud can contain particulate material pulled up (and/or vaporized) from the ground, this is not required to form the cloud. When warm, moisture-laden low-altitude air is rapidly lifted up by the fireball and then cools, fine droplets of water condense out, forming the cap of the mushroom. (Even in the absence of soil and dust from the ground, the vaporized remains of the bomb and its casing rapidly condense to provide a rich supply of condensation nuclei for water droplet formation.) While very-high-altitude bursts won't form explosions, it is because they are unable to draw up enough warm, humid, air from lower altitudes—not because they can't suck up dirt. TenOfAllTrades(talk) 01:12, 9 March 2011 (UTC)

If you are reacting exactly equal amounts of the same element (rather than anti-matter in air) it will make almost 100% gamma rays (assuming you can mix the two fast enough, which is NOT easy). That type of explosion will not look like a normal explosion. It will ionize air to a tremendous distance, and will look more like an aurora than a fire. If you just drop anti matter through the air it will look either like a meteor, or a series of explosions (probably depending on how fast it moves through the air). It won't explode all at once, since the initial explosion will push away all the matter, leaving nothing to react with the antimatter. The explosion will then stop, letting matter back in, and it will cycle. If it's moving fast, then the fresh air arriving at the front will constantly provide matter to react with, and it will leave a trail of light. (But because most of the energy is being released in the front, it will rapidly slow down.) I am assuming it will take the form of fire because the two elements being reacted are not the same, so you have residual particles to carry energy as heat. If things match up however (perhaps you pick anti-silicon which has twice the atomic number of nitrogen in air), then you'll get mostly gamma rays and bursts of auroras (aurorae?). Ariel. (talk) 01:08, 9 March 2011 (UTC)

Aftertaste

Why does chocolate have such an unpleasant aftertaste? Some other sweet foods have similar, but not quite as strong, aftertastes, as well. --75.15.161.185 (talk) 01:07, 9 March 2011 (UTC)

Try a different brand of chocolate. Also, personally, if I eat too much chocolate in a short period of time it starts tasting sour, so perhaps let your tongue rest first. Ariel. (talk) 01:13, 9 March 2011 (UTC)

But it's happened with other foods too, not just chocolate. Most foods with sugar or (to a lesser extent) starch also seem to have a bad aftertaste. --75.15.161.185 (talk) 01:18, 9 March 2011 (UTC)