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OK, if human gametes always acquired their chromosomes intact, then I'd have, on average, 11.5 from each of my grandparents, 5.75 from each great-grandparent, etc. Thus if I went back in my pedigree 7 generations—and with the further simplifying assumption that all of my ancestors were unique—then since there are 128 people back there and only 46 opportunities, the expected contribution from any one of them to my genome would be zilch. And seen the other way round, any one of my descendants 7 generations hence could expect to inherit nothing from me.
But, of course, meiosis doesn't work so tidily. So my question is, in practice how far off is the above reasoning? To state it more rigorously, how likely is it that any particular human gamete is free of crossovers, that each of its 23 chromosomes is simply a complete copy of one from the homologous pair?—PaulTanenbaum (talk) 03:41, 25 August 2008 (UTC)
The crossover rate varies by chromosome, but one would expect in general one crossover per chromosome. So one would have to go back more than seven generations to be reasonably certain that at least one ancestor in that generation had no genetic contribution to your makeup. - Nunh-huh03:52, 25 August 2008 (UTC)
Yes. And, in general, though not invariably, your son's autosomal chromosomes will likely contain some scraps from all four grandparents. The bigger the chromosome, the more likely there was a crossover event. - Nunh-huh04:22, 25 August 2008 (UTC)
The number of crossover events per chromosome is higher than Nunh-huh suggests. According to this book, "On average, between two and three crossover events occur on each pair of human chromosomes during meiotic division I." I was surprised by the confirmatory answer to the question about the likelihood of crossovers between the X and Y chromosomes, but Nunh-huh is right on this one - there are indeed tiny regions in the Y chromosome which do cross over with their X chromosome counterparts, see this figure from this article. --NorwegianBlue18:17, 25 August 2008 (UTC)
While it's true that there is a small area of the Y & X chromosomes that are homologous, and so permit crossover, it's not pertinent to the question asked about Paul's son's X chromosome, which came from Paul's wife (the crossover here occurred between the two X chromosomes of the mother, each of which contain portions of an X chromosome from her mother, and an X chromosome from her father, again due to crossover). - Nunh-huh03:13, 26 August 2008 (UTC)
Nun-huh is right about the point of my question. But I do appreciate NorwegianBlue's info about crossovers between X and Y, and the pointer to the NIH article is extremely helpful. Muchos gracias to both of you!—PaulTanenbaum (talk) 03:25, 26 August 2008 (UTC)
Take two slices of cookedham. Put one slice in an open-air container, and put the other slice in a container with a lid. Now put both ham-containing containers inside the refrigerator, and leave the two containers in there for two days. At the end of those two days, the ham in the open-air container will have become hard (in texture), while the ham in the closed container will still be soft. Why? —Lowellian (reply) 08:11, 25 August 2008 (UTC)
Because a refrigerator efficiently removes moisture from the air, and the dry air efficiently removes moisture from the meat. Franamax (talk) 08:28, 25 August 2008 (UTC)
In the film Better Luck Tomorrow, there is a scene where a character consumes a lot of alcohol, and another character jokingly warns him not to light a cigarette in his mouth because he "might explode". Is it actually possible to drink enough alcohol to combust by lighting a cigarette in one's mouth? —Lowellian (reply) 08:30, 25 August 2008 (UTC)
Does a lighter explode when you light it just because it is full of ethanol and there is a flame at the top? The simple answer is 'no'. You would have to drink pure alcohol (not a dilute like whiskey or vodka), and LOTS of it, because by the time it got into your body it would be diluted by whatever is in there. You would die long before you could drink enough pure alcohol for your body to be over the 'inflammable mark' of 100% proof. Alcohol fumes in the breath may be a very unlikely source of a flame, but certainly no explosion. Like setting your farts on fire.--ChokinBako (talk) 10:06, 25 August 2008 (UTC)
Flammable materials don't always explode. There needs to be just the right mixture of material and air/oxygen. This is why grain silos can explode. I doubt you would ever be in a situation where your body was in danger of exploding due to alcohol consumption. Combustion does not always imply explosions, but more often burning. It is entirely possible to ignite alcohol that is in your mouth, similar to what fire-eaters do, but unlikely that you would be able to ignite the alcohol in your body. --Russoc4 (talk) 14:50, 25 August 2008 (UTC)
According to alcohol poisoning, drinking enough to make alcohol compose 0.55% of one's blood will kill about half the people who try it, so let's use double that (1.1%) as the maximum amount of alcohol you can reasonably have in your blood. Now pour a 1.5 ozshot glass of pure alcohol into a gallon bucket of water, which by RefDesk serendipity comes out to give the mixture a 1.17% alcohol level, and consider trying to light that bucket of water. --Sean15:53, 25 August 2008 (UTC)
I agree with Russoc4 that it's impossible to render a human body flammable by consuming alcohol – we've got too much water in our bodies – but I think we might be choosing the wrong interpretation of the question. Instead of the entire body exploding, could we conceive of a case where there was sufficient high-proof alcohol (and alcohol vapor) remaining in the drinker's mouth to result in a fire or small explosion when triggered with a lit cigarette?
There are a quite a number of alcoholic drinks which are flammable, some which are deliberately set alight, and a few which are even deliberately ignited in the drinker's mouth (e.g. the Sambuca volcano—Attempt at your own risk). In any event, it's certainly possible to ignite some hard liquors in a person's mouth. Can you do it with a cigarette? That's a tougher question. Is is possible to retain enough alcohol and fumes in the mouth after swallowing? Also tough to answer (though high alcohol content would help—think Bacardi 151, or straight grain alcohol...). In principle, if one had the right mix of ethanol and air in one's mouth and lungs, it could ignite violently enough to be described as an explosion. If it also ignited liquid alcohol in the mouth, it could cause serious burns. TenOfAllTrades(talk) 19:11, 25 August 2008 (UTC)
According to our flash point article, ethanol has an autoignition temperature of 365°C. According to this site, a cigarette has a temperature of 400°C. I'd say that if you held a shot of grain alcohol in your mouth and stuck a lit cigarette in there, you could create the local conditions for autoignition and the ethanol flashpoint of 12.8°C would be more than enough to burn you badly. Just to be sure, have someone else draw on the cigarette when they put it in your mouth - that way you will have a friend in the hospital bed beside you. Franamax (talk) 23:22, 25 August 2008 (UTC)
I would say that the most dangerous part of this is not that the body literally "explodes", but rather that you can get fairly severely burnt. If you drink alot of alcohol, you might pass out to the degree where if the cigarette where to fall out of your mouth and set your clothes on fire, you might not wake up. This could prove fatal, or at the very least leave you with some nasty burns. Be careful with your booze, people! 90.235.4.253 (talk) 02:06, 26 August 2008 (UTC)
Please write more clearly - it's impossible to understand what the heck your question is! Something about disk insulators on 220 kvolt overhead lines....but what is "15 nos." ? SteveBaker (talk) 13:59, 25 August 2008 (UTC)
Guys, there is no need to be so snotty with someone who is asking a good faith question and is just having trouble expressing himself. My interpretation of the question is that it is regarding the stack of insulators used on overhead power transmission lines and why there are that number of them. The insulators are made of glass or ceramic or a modern composite depending on age of the installation. Each disc is able to insulate around 15kV without arcing over. Consequently for the high voltages used in power transmission a stack of them needs to be used. Our article here shows a 275kV pylon with a stack of 18 discs. For 220kV, 15 discs, as Manir states, would be about right, but there are no examples I can go and look at locally as 220kV is not a standard voltage used in the UK. The number of discs required depends also on other factors such as the material and the local climate (damp countries need more than dry deserts). SpinningSpark18:17, 25 August 2008 (UTC)
And that also accounts for the "crackly" sound you often hear on rainy days when walking near high-voltage lines - current leakage over the surface of the insulators. Franamax (talk) 22:59, 25 August 2008 (UTC)
I read in some medical publication of a woman who instead of flight, chose to fight in all emergency situations. There was an example where she was alone in her house and an intruder broke in. Instead of fleeing and getting help, she says that the impulse takes over immediately and she went after the intruder with a wooden spoon. She managed to chase away this intruder but afterwards she realized that she could have put herself in extreme danger. Then this publication named her condition as some medical condition and states than so many percent of Americans have this "disorder". I don't remember the name of this condition. Please help. --Anilmanohar (talk) 13:20, 25 August 2008 (UTC)
The OP sounds like the article stated that she actually lacks the fight-or-flight response and only possesses a will to fight. -- MacAddct 198414:49, 25 August 2008 (UTC)
The decision of whether to run or stand and fight is often made in a fraction of a second based on all kinds of things. If you're in your house, you may well not have anywhere to run - presumably the intruder came through the door, so is between you and the door. Deciding to stand and fight when others would most likely run would be an example of courage (possibly combined with stupidity!), I've never heard of it being considered a medical disorder. --Tango (talk) 19:09, 25 August 2008 (UTC)
Ok, I just thought about it more. Is there a medical condition in which a person creates more adrenaline than a normal person would? I mean if you have high amounts than normal of adrenaline coursing through your body, it could lead to unusual aggression? I was also thinking of the Geronimo Syndrome, but that is just an unusual desire to jump, I think. --Anilmanohar (talk) 13:12, 26 August 2008 (UTC)
Hi Tetsuya! You should check out our ion and copper articles, then get a healthy snack, then go finish your homework. Let us know if you still have questions after reading those articles. --Sean16:02, 25 August 2008 (UTC)
Something to do with its electron configuration. Look for all the usual things: spin multiplicity, filled or half-filled shells, etc. DMacks (talk) 14:44, 27 August 2008 (UTC)
Useful life of commerically packed grated ginger
I've occasionally purchased chopped garlic packed in oil. I'm pretty sure that this product is safe to open, use a little, and store the remainder in the fridge, using it as needed over an extended period of time. Recently, I've purchase grated ginger in a very similar looking package. It is not packed in oil. The ingredient list includes a preservative, the name of which I can't remember. Do you think this product will be stable in the fridge once opened, over a period of months? The labeling doesn't give any indication. ike9898 (talk) 16:54, 25 August 2008 (UTC)
Check the label again, is really should have storage instructions on it. If there is no "use within X weeks of opening", then it should be fine until the best before date. I'm not sure there's any need to refrigerate ginger, but the packet should say. --Tango (talk) 19:13, 25 August 2008 (UTC)
I'm more concerned about the garlic in oil, I thought that was a good place for botulism to develop. Per Saintrain, grated anything will likely oxidize pretty fast and lose its flavour. It will still be "good" in a month, but you won't taste anything. Franamax (talk) 22:55, 25 August 2008 (UTC)
Not strictly answering the question but I can't see why anybody would ever need t buy grated ginger, surely it is always better to simply buy some ginger and grate it yourself? It will be fresher, have more flavour and probably have a much much longer shelf life. Jdrewitt (talk) 10:14, 26 August 2008 (UTC)
The same reason people buy ready grated cheese: convenience. (Admittedly, I don't believe I've ever bought ready grated cheese, but I've seen it in shops, so there must be someone buying it.) --Tango (talk) 20:25, 26 August 2008 (UTC)
Maybe they don't own a grater and are under 18 in the UK, thus unable to buy any knives to chop it instead (although they can join the army and get access to their cutlery and graters)? 79.66.44.182 (talk) 00:27, 27 August 2008 (UTC)
I'm not convinced (unprocessed) ginger would necessarily have a longer shelf life then packed grated/minced/crushed ginger with preservatives. Cost wise, it doesn't make much difference (as opposed to cheese) particularly if you're only using a small amount. Of course convinience as Tango alluded to is the biggest reason. And from my experience it does still have a fair amount of flavour after a month (kept in the fridge of course) Nil Einne (talk) 23:44, 27 August 2008 (UTC)
If you mean the section of the diagram that is in yellow, it is labelled for "open plan office", thus would be filled with cubicles or something similar. That is the actual "occupiable space" the central core held elevators, lavatory facilities and such. --LarryMac | Talk19:51, 25 August 2008 (UTC)
The yellow area might even have walls that look like 'real' walls, but are not structural and can be reconfigured to match the needs of the renter of the space. ike9898 (talk) 19:53, 25 August 2008 (UTC)
A company I worked for had a branch office in one of the twin towers, long before their destruction. On my only visit, I don't know what I had been expecting, but it was not the poky little suite I found. As noted above, on that floor (mid-80s, as I recall), floor-to-ceiling walls had been erected to form offices and suites. The walls served mainly to divide space between tenants, provide privacy, hold up pictures. I'm sure some large organizations had very impressive offices, all built within the framework of the space labeled "open" in the diagram. Cantor-Fitzgerald alone occupied five floors of One World Trade Center. — OtherDave (talk) 01:16, 26 August 2008 (UTC)
Yeah, I didn't find that funny. Someone just getting hurt isn't generally funny, someone getting hurt in an unusual way (particularly if it's through their own stupidity) can be funny. Schadenfreude will give you some more info. --Tango (talk) 21:42, 25 August 2008 (UTC)
Most people that post to the comments section of youtube found it funny - hardly a representative sample. --Tango (talk) 22:08, 25 August 2008 (UTC)
Indeed. Comment-posters on youtube aren't considered the sharpest tools in the box. This onion article hits the nail on the head, in my opinion. Fribbler (talk) 23:16, 25 August 2008 (UTC)
If you ever watched America's Funniest Home Videos, most of the videos which are considered funny are accidents where someone appears to get hurt. And adults, many of whom are probably considered mature, laugh at it. Tango, I guess it depends on what you consider to be "most people" of a representative sample. After all, what is representative? In fact by saying "Comment-posters on youtube aren't considered the sharpest tools in the box." could easily be argued that you are drawing an unverified assumption about comment-posters on YouTube. ScienceApe (talk) 00:46, 26 August 2008 (UTC)
Home video shows usually show people getting hurt in interesting or dramatic ways (at least, the ones in the UK do), not just falling off a bike (they might fall off the bike into a swimming pool, or something). "Representative" is a perfectly well defined word, and youtube commenters are not representative of humanity as a whole. Humanity as a whole can spell better, for a start! --Tango (talk) 02:17, 26 August 2008 (UTC)
Nope, they don't. At least not more dramatically than the video I linked. Nope. It isn't. You have to qualify representative. Representative of what demographic? Humanity as a whole? So according to you, a representative sample would be individuals from every single country in the world, which is absurd. Also, you were the one to make the "humanity as a whole" qualifier, not me. I used "most people" in the casual sense, not the literal sense, so really you are nitpicking words which isn't very helpful. With that logic, you made a broad claim that people getting hurt generally isn't funny, while based on what I've observed from other people's behavior, it is. However you don't have a representative demographic to support your viewpoint, other than your own opinion that you thought it wasn't funny. Actually most of humanity can't write in English, so that disproves your last point. ScienceApe (talk) 06:32, 26 August 2008 (UTC)
To me anyway most people does in fact imply humanity as a whole. You don't have to sample people from every single country but I would expect a sample from the major cultures. I don't for example, see how you can say most people do something if few Chinese, Indians and Africans (or perhaps South Americans/Muslims) do it. Thats why I personally avoid saying "most people" unless it's something I don't expect to not have a strong cultural bias. And I often challenge those who say "most people" to question whether they have considered other cultures. IMHO people should be more specific, and not group everyone together without knowing much about them. You could say; most Americans, most English first language speakers, most people from the Western world or whatever. Of course, again you should make sure what you're saying is indeed true. For example, if you're saying most people from the Western world, does it apply to the French, Germans, Spanish or Italians? P.S. And you're right, most people don't speak English P.P.S. I agree we have no way of knowing whether most people find getting hurt funny. P.P.P.S. In this specific case, "a lot of people" or "many people" find this funny would have worked without sandboxing people of large variety of cultures into one box. Nil Einne (talk) 23:32, 27 August 2008 (UTC)
Well that's nitpicking semantics then. Most people on YouTube did find it funny, and I was going off that. If you prefer, you can take the original statement to be based off of that instead of nitpicking semantics, which isn't very helpful. I've noticed some people here taking certain statements too literally, and then dissecting it. That sort of thing should be avoided, it just bogs down discussion into a meaningless debate on semantics. ScienceApe (talk) 02:02, 28 August 2008 (UTC)
I think that people sometimes find it amusing to see someone of a particular group they happen to dislike injuring themselves due to their own stupidity. Suppose that you dislike skateboarder/biker kids doing their stuff on your property (not my view - just an example) - there may be certain pleasure to be taken in seeing a kid, just like the ones who were rude and antisocial to you when you told them to move on getting injured performing a particularly dangerous, ill-thought-out, possibly drunken Jackass-style stunt in a public place... --Kurt Shaped Box (talk) 01:48, 26 August 2008 (UTC)
I would imagine that, for the U.S. immature teenagers who post comments on that video, the "humour" comes from the fact that the kid is described as "fat". There appear (from the side bar recommending other videos) to be a lot of YouTube videos of large children being hurt. Bart13301:40, 26 August 2008 (UTC)
Sometimes
Re: above; It does seem to be universal, when old farts watch kids (or puppies, fawns etc.) "growing up", the reaction is "Awwww. Hahaha." Toddlers sitting down suddenly, or Bambi on ice or watching a kid cook onions for the first time. When there's actual danger involved, climbing a bookshelf or playing with drano it's an entirely different reaction. Certainly there's empathy but there's something else too. Whatsit? Saintrain (talk) 21:55, 25 August 2008 (UTC)
Sometimes the more excessive or ridiculous the fall the funnier it can be perceived, up to a point. Most people would agree watching a bad car crash is not funny, but watching one of the Marx brothers take a frying pan to the face can be hilarious. Of course the latter is not "real" but the effect is related. Perhaps Slapstick is an article worth citing for that reason. Vespine (talk) 06:37, 26 August 2008 (UTC)
why do I look worse in photographs than in mirrors?
I'm not a very good looking chap but when I look in the mirror do I think that I look okay, and then when I look at photographs of me I think I look bad? I'm the same me, right? So why? —Preceding unsigned comment added by 86.128.219.33 (talk) 21:39, 25 August 2008 (UTC)
It's not the same you. The one in the mirror is flipped left to right. Since that's the one you're used to, it can make actual pictures of you look somewhat strange. I don't know how much of the effect is caused by that as opposed to the explanations listed in the photogenic article. — DanielLC00:38, 26 August 2008 (UTC)
You can experiment by using a photo editor such as the GIMP or photoshop to flip your photos of yorself. -Arch dude (talk)
My theory is that when person A looks at person B, (in general, not in an intimate situation) they usually look less carefully and for a shorter time than is polite or possible if A is looking at a photograph of B. Also, in the first case, B is likely to be moving, whereas a photographic image is fixed and more susceptible to detailed study. Because of these factors, A is less likely to notice "imperfections" of various types in B. Similarly, if A is looking at his or her self in a mirror, they are less likely to notice "imperfections" of which to be critical than when looking at their photo.
But considering that A's image is also fixed when A is looking in the mirror, and A probably is applying detailed study to himself or herself, why would A be less likely to notice imperfections of which to be critical when looking in a mirror rather than in a photo? —Lowellian (reply) 11:49, 26 August 2008 (UTC)
Don't have much time now, but a common saying for the phenomenon 86.128.219.33 is describing is "the camera adds ten pounds". This blog thread has a discussion; I particularly like "your not supposed to eat the camera..." The thread links to this more credible webpage, which has a serious one-page explanation. --Bowlhover (talk) 08:22, 26 August 2008 (UTC)
Also have a look at: Perspective distortion (photography) - the lens itself provides a 'perspective' of reality. Sometimes that distortion is beneficial, sometimes it is not. As also noted a mirror is a constant changing image so doesn't capture 1/100th or 1/500th of a second of your face - at which point any number of problems could be evident such as your pose, lighting etc. I've heard that the 90-110mm range is consider a 'sweet spot' for portrait for photography. I have to agree that I also find most photos of me don't capture me as well as I think I look in real-life! 194.221.133.226 (talk) 13:08, 26 August 2008 (UTC)
It can depend a lot on lighting. Even in natural lighting a camera will perceive light and shadow differently than the naked eye. If care isn't taken with the lighting, Shadows can appear darker and "deeper" on film and change your perception of the shape of a face. Worse is if you're thinking of photographs taken with a flash that is only a couple inches away from the lens, that can cause all sorts of weird effects. APL (talk) 14:47, 26 August 2008 (UTC)
I wonder if the perspective has much to do with it. Most of our visual experience comes to us through binocular vision; someone in front of us (even the mirrored "us") is really composed to two half images (left and right) that our brain interprets as a whole in a complicated way that combines perspective, eye dominance, and other factors. A photo is both static and from a single perspective, which removes the true depth we're used to seeing. Matt Deres (talk) 21:38, 30 August 2008 (UTC)
According to this (from Google), women have one or two million at birth (another, unsourced, Ghit claims they have as many as seven million while still in the womb), are down to four hundred thousand or so by puberty, and are lost at about a thousand a month after that. Menopause occurs when the supply runs out entirely. Algebraist23:07, 25 August 2008 (UTC)
An ovum would probably have a density close to that of water (it's just a specialized cell - and cells are mostly water) - so we can make a rough estimate - an 0.1 to 0.2mm object will have a volume somewhere around 0.001 to 0.008 cubic millimeters - which is 0.000001 to 0.000008 grams. A million of them would weigh between one and eight grams and take up between one and eight cubic centimeters. For comparison, a US 1 cent coin weighs 2.5 grams. That seems perfectly reasonable.
Spacetime itself, possibly (it's unknown if it's infinite, and I don't know if you would count it as an entity). Other than that, I don't think so. There are some things in physics that end up with infinities in the maths, but that usually means we don't properly understand it (the density of a singularity in a black hole, for example). Negative temperature can, apparently, be thought of as infinite (or even more than infinite) temperature, but I've never understood that myself. The ranges of electromagnetism and gravity are infinite, but they both move at finite speed and the universe is a finite age, so no EM or gravitational field is actually infinite. That's about all I can think of that even comes close. --Tango (talk) 23:48, 25 August 2008 (UTC)
It a little tough to draw the line with "physical entity". The basic "measurements" of physical entities are the fundamental units: Mass, Length, Time, Current, Temperature, Amount of substance and Brightness. But clearly there can't be infinite lengths or times because the universe isn't old enough. Infinite amounts of the other things imply infinite mass/energy and therefore infinite gravity - and we couldn't stand that.
So - what's left? We pretty much have to resort to measurements that boil down to ratios of things where one of the things is literally zero.
We can say (for example) that the singularity at the heart of a black hole is infinitely dense. But that comes about from a boringly finite mass and a literally zero size - so the infinity really comes about because density is mass divided by size.
So anytime you can find something that has a property that is zero you can probably find a ratio that'll pop up an infinity. The ratio of mass of a photon to it's rest mass is infinite for example.
Although a physical measurable property cannot literally be infinite, mathematical models of reality may in some circumstances give an infinite answer, and it may sometimes be possible to assign a physical meaning to these "infinities". There is a story of a mathematician, a physicist and an engineer who were each asked by a firm of architects to calculate the strength of an especially complex structure. All three got the answer "infinity". The mathematician recommended that one of his graduate students should research better mathematical models for solving the relevant non-linear differential equations. The physicist recommended that the architects should design a simpler structure. The engineer wrote a report which concluded "There appears to be an adequate factor of safety for almost all feasible scenarios". Gandalf61 (talk) 09:10, 26 August 2008 (UTC)
Renormalization is one example of that - if you "do the math" relating to things like quantum electrodynamics, then all sorts of ikky infinities keep popping up - but the mathematical "trick" of renormalization fixes that problem and gives you nice, finite results. That's not really an example of a physical infinity though - the infinity appears in the math - but NOT in reality. SteveBaker (talk) 21:39, 26 August 2008 (UTC)
It was supposed to indicate that yes, you will eventually die. Breathing something almost identical to the earth's natural (dry) atmosphere isn't going to be very relevant though. Algebraist01:00, 26 August 2008 (UTC)
I think your friend is having a bit of fun with you. Regular old air (like the one you are currently breathing) is about 80% nitrogen and 20 oxygen (with some argon, water and CO2 thrown in for good measure). However, eventually, we will all die (it's like that line from Fight Club, "on a long enough timescale, the mortality rate of everyone drops to 0"). If the question is "Will breathing 80% nitrogen and 20% oxygen kill you?", then no. But if the question is "If you only breathe 80% nitrogen and 20% oxygen, will you eventually die?", then of course, yes you will. But the cause of your death wont be the air you breathe. 90.235.4.253 (talk) 01:56, 26 August 2008 (UTC)
Actually, the air could be what kills you - oxidation is one of the major contributors to ageing (just take a look at how many adverts stress the anti-oxidants in their products). --Tango (talk) 02:19, 26 August 2008 (UTC)
Heh, wasn't there a strange craze for huffing pure oxygen a few years back as a supposed cure-all for various ailments and medical conditions? --Kurt Shaped Box (talk) 02:25, 26 August 2008 (UTC)
Yes, it's true. A surprisingly large percentage of the population did this in the seventeenth century, and they all eventually died. (Note: they snorted the mixture because they called it "breathing", and they must have eventually died since they are not still alive.) -Arch dude (talk) 11:01, 26 August 2008 (UTC)
QUOTING FROM previous post: "on a long enough timescale, the mortality rate of everyone drops to 0" Or is it that the rate rises to 100%? Wanderer57 (talk) 16:20, 26 August 2008 (UTC)
Yeah, you're right, I got that wrong :) The real quote is "On a long enough timeline, the survival rate for everyone drops to zero." 90.235.4.253 (talk) 18:04, 26 August 2008 (UTC)
We can provide no medical advice on Ref Desk, but I am concerned about the absence of carbon dioxide in the posited breathing mixture. Wouldn't the absence of CO2 suppress respiration? Edison2 (talk) 04:23, 27 August 2008 (UTC)
No - you breathe in a couple of lungfuls of N2 + O2, some of the O2 is absorbed and some CO2 is excreted. It's THAT CO2 that triggers the next breath - not the trace amounts of CO2 brought into the lungs from outside. SteveBaker (talk) 04:39, 27 August 2008 (UTC)
Any way to discourage my parrot from washing her head in her water pot?
It's just a minor annoyance but it's worth asking. She gets a shower with me every morning if she wants one, but she still feels the need to stick her head in her drinking water, splah around and make a mess. I've tried replacing her water pot with a tube feeder but she didn't like that at all.
Is it even worth trying to discourage her? You know what parrots can be like when they've been doing the same thing every day for years. This is a hyacinth macaw by the way, I've posted here before about her. Thank you. —Preceding unsigned comment added by 84.70.186.194 (talk) 00:43, 26 August 2008 (UTC)
A suggestion, not to stop the head dunking but to try to reduce the mess. Get a large open-top plastic container, such as is sold for storing clothes etc. Perhaps 30" long, 18" wide, 12" deep, just as an example. Put the water pot in the container. (Never having lived with a parrot, this suggestion may be completely useless.) Wanderer57 (talk) 05:37, 26 August 2008 (UTC)
Beautiful animals the hyacinths. I would never discourage my parrot doing things. Maybe she wants to tell you that she wants another shower? Try immediately spraying her after she splashes around. If she complains splashing was for another reason. Maybe then she has an itch? They get ticks so that could be the problem. --Ayacop (talk) 08:48, 26 August 2008 (UTC)
Cheap, small, low-power technology for detecting a short-range distance?
I was thinking today about how one could make a cheap, small, low-power technology for detecting whether the detector in question is within, say, an inch of a wall or other object, without touching it.
One obvious idea I had was to use laser diode and a detector like an optical mouse. I thought about just using a light detector but that wouldn't work at night (or under various lighting conditions). I thought about a laser inferometer but those seem fairly large and probably take a lot of power.
I imagine there must also be a way to use just high frequency radio waves but I imagine the power requirements would be rather high.
Anyway... just thinking about this. Any ideas? I'm no engineer. This is not homework, just something I was trying to think over. --98.217.8.46 (talk) 01:25, 26 August 2008 (UTC)
In playing with LEGO robotics, I've used both sonar (with a regular speaker and microphone!) and an LED/light detector approach. The former works pretty good - sound is slow enough that you can reasonably measure the time-of-flight so long as you use a really high frequency sound 'blip' and have a small, responsive, speaker & microphone. The latter is highly dependent on the color and shininess of the surface. Since the speed of light is so high - you can't use the time-of-flight of the light at such short ranges (an inch out and an inch back is about 1/6th of a nanosecond - and it's incredibly hard to measure that short an interval effectively. So you're down to measuring the reflected intensity - for that, a laser is a sucky solution because the orientation of the surface to the light makes a DRASTIC difference to the intensity...compared to a more omni-directional LED. I got better results with an IR LED than a red one - I didn't try other colors. But such a solution really gives very variable results depending on the orientation, shininess and color of the surface. Sonar seems to work best. Best of all is a fine whisker - but that requires touching the surface (albeit a VERY gentle touch). I can't imagine radio working better than light - you still can't use time-of-flight - and the reflectivity issues are much more problematic because radio waves go right through most surfaces without much reflection. You could maybe get away with millimeter-band stuff - but that sounds difficult. None of these approaches are going to be very accurate though.
I wonder if you could do something like using the guts of a "stud finder" - those use a change in dialectric constant - they are certainly cheap and at the one I have produces a handy digital output that ought to be easy enough to read with a microcontroller. I don't know how good they are on all kinds of surfaces though...they clearly can detect wood through sheetrock - but that probably means they don't detect sheetrock so well.
I think an awful lot depends on what you know about the kinds of surfaces you are trying to detect.
Sonar-based distance finders (as Steve mentioned) are very cheap. The parts are very simple to remove and use for whatever purpose you like. -- kainaw™02:21, 26 August 2008 (UTC)
Would it work to project a diffraction pattern and "read" the resulting projection to determine distance? One might use a square aperture to detect a tilted surface, and vary the size of the aperture to improve accuracy for a variety of distances. I've not seen anything like this, so maybe it's just a bad idea. Scray (talk) 02:40, 26 August 2008 (UTC)
Assuming we're thinking of the same method, it's only possible to calculate the angle between a certain interference band and the central antinode in an interference pattern. Without measuring the distance along the wall from the antinode and the band, it's not possible to find the wall-to-sensor distance. --Bowlhover (talk) 08:13, 26 August 2008 (UTC)
If you know the orientation of the wall (say, you have a compass and know the general layout), you could bounce a laser off the wall at an angle and see which of a row of detectors it struck; a lit source farther from the laser means the whole array is farther from the wall. If you don't know the orientation, but do know that the wall is flat (on the scale of your detector), you could use two lasers at different angles and see how far apart their reflections onto your detector array are. You could minimize the power consumption by only pulsing the device for a few microseconds several times per second. --Tardis (talk) 15:23, 26 August 2008 (UTC)
You could use a laser to project a spot onto the surface - then use a pair of cameras to image that spot - the resulting stereographic information would yield a distance pretty readily. You could use very crude cameras - such as the one the Wii Remote uses. If lasers are cheaper than cameras - then you could use two lasers firing off parallel rays to project two laser dots onto the surface - then one camera could look at the distance between the two dots in "image space" and let perspective give you the range. With two InfraRed lasers, you might even be able to use an unomodified Wii Remote (it uses bluetooth to talk to the Wii and the protocol it uses is well-documented). In a robotic application, you'll find the accelerometers in the Wii Remote handy too!
More lateral thinking: What about using the mechanism in an optical mouse? Those are amazingly cheap. They contain a cheap, very low-res camera that measures the shift in 'texture' of your desktop over time to determine the speed and direction that your mouse is moving - but if you lift the mouse off the desk, the image becomes very blurry - no "texture" is detected and the mouse ceases to detect motion. That seems to happen at about one inch from the desktop. You could stick a mouse-mechanism onto the front of your machine and make it slowly vibrate somehow. So long as it reports no motion, there is nothing nearby - as soon as it "sees" motion, you're too close. It might fail if the surfaces you are measuring distance too are super-smooth and plain...but maybe you don't care about that?
You have a better optical mouse than I do, Steve! It's hard to hold it steady enough to tell definitively, but mine seems to stop working at about 5mm off the (plastic) desk. (But that's still better than the ball mouse I also have, which doesn't seem to work at all when I pick it up…) --Tardis (talk) 15:48, 26 August 2008 (UTC)
I actually studied optical mice when I was looking for cheap navigation systems for LEGO robots. The chip that they all seem to use comes with a plastic lens that focusses the light at the plane of the desktop. Theoretically, every optical mouse on the planet ought to have the focal plane of the camera at the exact same height above the desk. However, I've found (as you just have) that there is some variability going on between one mouse and another. Perhaps they don't all use the plastic lens that comes with the chip - maybe to save money or allow some different internal arrangement for the mouse guts or...something...who knows?! Anyway - by replacing the super-short focal length lens that comes with the mouse for a longer len would allow the OP to choose the range at which it would accurately focus. You'd probably need a brighter light source too.
The distance at which it 'gets motion' may also depend on the nature of your desktop. I have an old beat-up leather-topped writing desk - so there is probably more "texture" for the mouse to latch onto than a relatively pristine plastic desktop. What do you get if you hold the mouse over the printed page of a book or something? I can get more "altitude" by aiming a desk lamp under the mouse - so light falloff might also be an issue if your mouse had a dimmer LED than mine.
Anyway - it's clear that it's possible. Whether it's good or easy in practice is a harder call.
Cats and rats use their vibrissae (whiskers) as highly reliable short range proximity sensors. Cars of the 1950's had curb feelers which served the same function. Electro-optical curb feelers are discussed in that article. In the movie Dam Busters, bombing planes had to release the bombs at an exact height above lakes. A pair of spotlights and predetermined angles converged on the water surface when the plane was at the exact altitude. It would be a simple electronic process to use a pair of light beams to determine distance, or a light beam and a directional sensor or lens plus optical sensor. Bats and dolphins and some blind people use a form of sonar to echolocate and determine distance from objects. Edison2 (talk) 04:16, 27 August 2008 (UTC)
Whiskers would indeed be the simplest solution (Biology usually gets it right!) - but the OP specifically rules out touching the surface. SteveBaker (talk) 15:06, 27 August 2008 (UTC)
Using printed pages doesn't seem to change anything; one problem is that the mouse's light is directed at a shallow angle and thus misses the area under the sensor entirely with only a little vertical displacement. Running the mouse over the monitor (which is an odd concept) doesn't seem to give it any increased range, so perhaps it's the focusing issue. --Tardis (talk) 16:28, 27 August 2008 (UTC)
Testing your mouse on your monitor doesn't really prove much - the monitor flickers at 60Hz - which is probably similar to the update rate of the camera in the mouse - so the mouse is looking at a blank screen most of the time - it's going to be horribly confused! But the angle that the light source is aimed could easily be the real explanation of the problem. Maybe mine aims more vertically down? Anyway - what we know is that not all optical mice would do as range sensors without modification to (at least) the light source - and possibly also to the camera lens. For a one-off project, that's not going to fit the "cheap" criteria - but if you're planning on making a billion of them and taking over the world in a bloody robot revolution - then the cost of a different lens/LED setup would be almost zero. SteveBaker (talk) 04:31, 28 August 2008 (UTC)
General relativity analogy thoughts.
I have only a rudimentary understanding of general relativity, but I've always had a problem when someone tries to use the bowling ball / trampoline analogy. You need gravity to make the bowling ball / trampoline analogy work. I realise this is used as a simple analogy, but using gravity in an analogy to explain gravity is, well, not much of an analogy if you ask me! It's a bit like saying: The night was so dark, it was as black as night! So I was thinking about this and came up with what I think is a better analogy, which admittedly is not quite as simple, but it goes something like this: imagine space-time has a uniform "pressure" or "density", of course these terms are usually applied to things which have mass already, but imagine space-time has a quality which is analogous to "density". Any mass existing in space-time creates an area of low space time density, less dense the closer you get to the mass. So just like a balloon in air, any mass is drawn towards areas of least density, or pushed away from areas of higher density, which ever way you want to look at it. So that when two objects interact, the are drawn towards their "low density zones", the bigger will obviously have a larger zone. However unlike a balloon, the pressure areas are not defined by a membrane, but actually exist as a gradual pressure gradient, dropping off the further away you get, just like how we currently observe gravity. So inverse of the high pressure atmosphere created by our gravity, the atmosphere it self is stuck to our planet by the low pressure time-space near our planet. If you take the analogy one step further, could matter it self be condensed space-time? The area of low "space-time pressure" is in fact the "gap" left in space time by the mass it self coalesced in the middle? I'd be happy to hear what anyone more familiar with general relativity would have to say. Vespine (talk) 02:32, 26 August 2008 (UTC)
I'd just like to say I like the fact that you pointed out that problem. Clever. I didn't read the rest of it, sorry =P --mboverload@03:06, 26 August 2008 (UTC)
I don't think your analogy really works. Things move towards areas of low pressure in order to equalise the pressure and remove the gradient, but when things move towards a massive object they actually make the object more massive and increase the gradient. I'd stick with the trampoline analogy, while the reasons behind why it works don't make much sense, the outcome is a very good approximation of the real thing - you can even get marbles to orbit the bowling ball in realistic orbits (although they decay rapidly due to friction). I'm not sure your analogy would be as good at something like that, and it's also much more difficult to understand - people know exactly what happens with bowling balls on trampolines. To be honest, I think you just have to accept that GR is difficult to understand and there's not a lot you can do to make it easier! --Tango (talk) 03:07, 26 August 2008 (UTC)
It doesn't matter whether I'm familiar with GR or not because GR is not about analogies or allegorical heuristics - these are just little things to understand some general concepts that don't even matter that much. Gravity is, as far as we know, a field of interaction just like electromagnetism (using gravitons instead of photons). The "rubber sheet" analogy is useful because gravity, unlike EM, is a one-way force in most applications - it can only attract. But the mathematics is general enough that similar tensor equations can be used to solve both GR and EM problems. Mass occurs by the Higgs mechanism, as far as we know, which is really not anything like you described. Mass is also concentrated space-time pretty much by definition of gravity until we get quantum gravity worked out. The pressure analogy sort of works, because that's sort of how an interaction field works, but not really. SamuelRiv (talk) 13:05, 26 August 2008 (UTC)
The bowling ball / trampoline analogy is actually a good model of Newtonian gravity, even though, as you say, it looks like it's begging the question. The gravity well article explains the math behind it. It's not a model of general relativity. A lot of people confuse the curved trampoline with curved spacetime, but they're very different. So don't try to understand general relativity that way, you never will.
It might be possible to model general relativity as a local variation in the "density" of spacetime, but the simplest version of that idea won't work. Newtonian gravity is a scalar field theory, meaning that the field can be described by a single real number at each point in space(time). In the trampoline analogy, that number is the height of the trampoline at each point. Density is also a scalar. But general relativity is a tensor field theory: the field at each point is described by a symmetric 4×4 matrix. So you need more than just a density. You could do it if you allowed the "density" to be different in different directions (making it more like strain), and included time as one of those directions. But I think that model would be harder to visualize than the usual one (curved spacetime).
Could matter be condensed spacetime? Sure. A black hole of mass m and charge q interacts gravitationally and electromagnetically just like any other object with the same mass and charge, even though there's no "real" mass or charge anywhere to be seen. People often say that the mass and charge exist inside the event horizon (where they can't be seen), but we don't know that. Nothing behind the event horizon has any effect on the outside; spacetime could just end unceremoniously right inside the event horizon, and the part outside would still behave like it has mass m and charge q. So the universe doesn't need real charge; you can fake it with black holes. Applying Occam's razor, it's tempting to suppose that it doesn't have real charge. I'm a big fan of this everything's-a-black-hole viewpoint, but whether it has any merit remains to be seen. Nobody's yet concocted a working quantum theory along those lines, and not for lack of trying. -- BenRG (talk) 14:56, 26 August 2008 (UTC)
Given the same amount of sleep
Would you choose more or less REM sleep? I'm asking because a news article says people sleeping east-west may have fewer dreams than those north-south. Thanks. 67.243.6.204 (talk) 02:28, 26 August 2008 (UTC)
Quite a few people seem to believe in the 'sleep alignment' thing. I have no idea what it's actually called - but I think it's one of those new age-type beliefs... --Kurt Shaped Box (talk) 02:40, 26 August 2008 (UTC)
They believe it because <personal opinion> When you change position on your bed there are different pressure points/air flows/light intensities. I constantly switch my sleeping alignment and sleep better in different directions depending on the season/weather/my crazyness.</personal opinion>--mboverload@02:45, 26 August 2008 (UTC)
I think just about everyone does *that*. I think what the OP was getting at is the practice of intentionally aligning your bed (i.e. physically moving it) in the direction of the compass/chi flow/ley lines/earth's magnetic field/whatever. --Kurt Shaped Box (talk) 02:52, 26 August 2008 (UTC)
I'm not convinced of that. Based on purely anecdotal evidence, it seems to work in sleep (I'd look for studies, but I'm behind a corporate content filter). ie. after reading about lucid dreams and out-of-body experiences and all that nonsense, I had a couple "lucid" dreams. Of course again, that's anecdotal, but I'm sure there's at least one study that has employed placebo controls and sleep. -- Consumed Crustacean (talk) 03:14, 26 August 2008 (UTC)
As far as I know, lucid dreams are a purely psychological thing anyway, so I'm not sure there's a meaningful distinction between a "real" effect and a placebo, any effect is going to psychological in nature. --Tango (talk) 03:43, 26 August 2008 (UTC)
says "some studies suggest humans who sleep in an East-West position have far shorter" REM sleep. No sources cited. The article is about another study involving deer and cattle. This is an August 25 article, probably where the OP got the idea from. -- Consumed Crustacean (talk)
"Some studies suggest" Ah, the greatest cop out phrase in the history of fake and misleading news. Thanks for the detective work Consumed! --mboverload@03:18, 26 August 2008 (UTC)
I don't know about east-west versus north-south, but I sleep much better if I am facing the door. I always assumed that it is a basic instinct that I need to face the entrance so as to be more easily alerted to a predator. My girlfriend teases me but if we are set upon by wolves I'll be the first to know. Plasticup/C13:23, 26 August 2008 (UTC)
There was a recent study that showed cows and deer on Google Earth tended to sleep facing magnetic north-south, but they didn't go so far as to say why (or whether it would apply to humans too, although they had originally planned to look at campers). Confusing Manifestation(Say hi!) 01:56, 27 August 2008 (UTC)
Yes, I read that news article. No, I don't believe in new-age voodoo. Yes, I understand that "some studies" is a copout. No, I don't have a baseline for my question. I know so little about the subject anyway. Thanks a lot for the interesting discussion though. 67.243.6.204 (talk) 04:26, 28 August 2008 (UTC)
This food recall is a little scary because of the 30% death rate and reconfirms for me how much better it is to avoid processed foods when I can just make it myself. My question here is, the news agencies are saying that the people at risk are the elderly, immune-compromised individuals, and pregnant women. Why pregnant women? Is it the woman who is at risk, or is there a likelikood that the bacteria can migrate to the fetus? Franamax (talk) 03:10, 26 August 2008 (UTC)
Please note that the vast majority of food poisonings occur because of UNprocessed foods, such as fresh fruit. I would much prefer my food made in a controlled factory environment with all ingredients irradiated and put through large amounts of sterilization first =) --mboverload@03:13, 26 August 2008 (UTC)
Yeah, I know where you're coming from there. The point though is that poisoning from unprocessed food generally comes from surface contamination - and I'm willing to take responsibility for washing my food. With processed food though, the bacteria/virus is more often right there in the inside of the food, especially with meat. Franamax (talk) 03:48, 26 August 2008 (UTC)
As for Listeriosis, it's both that the woman is at risk, and that an infection can complicate pregnancy. Specifically, most infections occur in the third trimester of pregnancy, because that's when Th1-mediated immunity is most severely suppressed. Pregnant women are 20 times more likely than non-pregnant persons to catch the infection. Listeriosis can cause miscarriages and premature delivery. About 22% of cases of perinatal listeriosis result in the death of the fetus. Listeriosis can be caused, as noted, by uncooked foods, but also by cooked or pasteurized food that have been contaminated between the pasteurization/cooking and the consumption. Pregnant women are usually counselled to avoid unpasterurized milk, soft cheeses, and cold luncheon or deli meats. - Nunh-huh03:22, 26 August 2008 (UTC)
Hmmm - thanx. TH1 suppression during pregnancy, I wasn't aware of that. I'd be guessing (off-topic) that it is actually the fetus generating the immune-supression? Franamax (talk) 03:48, 26 August 2008 (UTC)
I think it's actually an estrogen effect - but possibly a literature search would turn up other factors as well. - Nunh-huh04:27, 26 August 2008 (UTC)
Well yes, babies have passive immunity using their mother's antibodies (from the pregnancy and milk) for a while after birth. Third trimester is nowt to that :) 79.66.44.182 (talk) 00:10, 27 August 2008 (UTC)
My understanding is that the fetus itself produces hormones which affect the mother. For instance (though I'd he hard pressed to find the reference), the fetus produces substances which modulate maternal weight gain in early pregnancy. It seems not unreasonable to consider that the fetus also modulates maternal immune response. After all, the fetus is 50% foreign material, so to speak. Franamax (talk) 08:44, 27 August 2008 (UTC)
Curling a ribbon by scraping it?
When you run one side of scissors along a ribbon, it tends to curl up. I've seen this technique used when wrapping
Xmas presents.
Is there an English word or Misplaced Pages article that describes this simple physics process, or this physical phenomenon? I've noticed it happen to hairs too when they are brushed with knots in them. And I'm sure it may be used in other aspects of engineering or fabrication.
--206.248.172.247 (talk) 03:35, 26 August 2008 (UTC)
(Note: I moved this question down from the original date because I added a third question four days after the original posting that seems to be getting overlooked.) —Lowellian (reply) 11:45, 26 August 2008 (UTC)
The lift motor also generates thrust - since every car requires lift, every car produces thrust. So I believe they pretty much have to be multiple unit trains. But in another sense, the "motor" is the track - so in a weird way, none of the train is the power unit. SteveBaker (talk) 02:56, 21 August 2008 (UTC)
The locomotive article has a section on maglev (that heading entitled "Magnetic levitation") that gives some information about maglev but does not in the least relate that information to the locomotive or explain what any of it has to do with a locomotive. Perhaps that section should be removed? —Lowellian (reply) 18:45, 21 August 2008 (UTC)
So, suppose a maglev train was running along at, say, 300 mph. Could it just almost instantaneously reverse direction and go in the other way, still at 300 mph? —Lowellian (reply) 01:28, 24 August 2008 (UTC)
Could you instantaneously reverse? Of course not! But neither can a traditional wheeled train. What you could do, of course, is reverse the direction of the driving force and begin decelerating at (approximately) the same G-force with which the maglev originally accelerated. In fact, for a maglev (as compared to a wheeled train) that's really your only means of braking unless you dump the maglev system and let the train slide along the guideway in what's probably an amazing shower of sparks. (Wheeled trains have friction brakes on the wheels, axles, or directly engaging the steel track.)
Are maglev trains the trains of the future, or is there some other competing advanced technology with the same potential? Fifty or one hundred years from now, is it likely that most trains will be maglev? (Yes, I know Misplaced Pages is not a crystal ball, but we're not in the main article space.) —Lowellian (reply) 08:19, 25 August 2008 (UTC)
From reading our Maglev (transport) article and this survey article, it seems that the answer is "probably not". The lower operating costs, greater people-carrying efficiencies and environmental benefits of maglev trains are only realised over long distances. However, the high costs of constructing a new permanent way (from $100 million/km to $500 million/km) mean that a long-distance maglev network will require a huge initial investment, and will take a long time to break even. Short-distance point-to-point systems may be cheaper, but they don't seem to be economical. Just because something is technologically feasible doesn't necessarily mean it will become commercially viable - to coin a phrase, we could call this the Concorde syndrome. Gandalf61 (talk) 12:41, 26 August 2008 (UTC)
This is still the reference desk though and not the place for idle speculation. Gandald has some good points. Also, the high speeds maglev trains are capable of achieving is likely to be pointless for urban trains, the short distance between stations means you don't have enough time to accelerate (presuming you don't want to kill all your passengers). But more generally, we simply don't know. It will depend on what sort of new technologies we achieve and a whole lot of o ther stuff (e.g. how much energy ends up costing). E.g. room temperature superconductors will help a lot but I'm not convinced they are possible. IIRC last time I read the article, there is also some techs using more permanent magnets but they're still in initial development. Nil Einne (talk) 14:27, 26 August 2008 (UTC)
There is a general trade-off between Speed and Cost:
Maglev's produce an almost frictionless surface - speeds are high - but costs are astronomical.
Conventional steel wheels on steel rail is still fairly low friction - speeds can still be reasonable (150mph to 200mph is no problem) - and it's cheaper. Monorails are pretty much a similar deal.
Rubber on concrete is higher friction - speeds over 70mph start to become problematic - but it's very cheap.
Dirt tracks and draft animals...?!
Getting rid of friction costs money but it gains you speed. But over a short run, you don't need the speed (and you can't get it without high accelerations - which are uncomfortable for the passengers). So you end up with this uncomfortable problem that high speed is only useful over long runs when the track costs kill you. Over short runs, you can maybe afford the high cost of the track - but you don't need (and can't use) the speed - so why pay extra?
So you find that steel rail works best over most of the speed/distance envelope - with rubber-on-concrete being used for really short runs like the trains that run around between airport terminals and such. Monorails tend to be used mostly for reasons of novelty (eg at Disneyland). Under-slung monorails may offer advantages in tight urban areas where they have to be added as an afterthought into existing infrastructure.
Hence, no maglev trains. It's a solution in search of a problem.
SteveBaker, are you saying that the lower-friction of steel-on-steel results in higher speed capability? I think this cannot be correct. See traction - if you want high speeds, you want high static friction between the wheel and the "road", and low friction between the wheel and the axle. Some other factor must be the limiter here. Nimur (talk) 21:27, 27 August 2008 (UTC)
"Friction" might not be the correct term, but it's a reasonably accurate description of the effect. The difference between rubber-on-concrete and steel-on-steel is the amount of deformation: a rubber wheel flattens on the bottom as it rotates, converting forward motion into heat in a very friction-like way. A steel wheel doesn't deform anywhere near as much, so there's very little energy loss. --Carnildo (talk) 23:12, 27 August 2008 (UTC)
Okay, thanks for the answers, though let me ask for a little bit more clarification: if maglev trains won't be predominant, what type of trains will be dominant then in the near (50-100 yr) future? Still the same steel-wheels-on-steel-rail trains as today? There's no other competing new technology besides maglev? —Lowellian (reply) 18:38, 27 August 2008 (UTC)
No, there isn't. There is no reason to expect anything but steel-on-steel to become dominant for the foreseeable future. (I would say that the foreseeable future in this context is more like 20-30 years than 50-100.) Trains using conventional steel-on-steel now run at up to almost 200 mph in regular service, with good energy-efficiency, and have been tested at over 350 mph. The same cost and political considerations for obtaining a route suitable to build a high-speed line apply no matter what the technology, but conventional trains can run onto conventional tracks, so the high-speed routes can stop at the city limits and trains can run through onto other parts of the network. It seems to me that the most likely thing to change this picture is a global war or energy shortage, and that would simply lead to the discontinuation of all high-speed trains, not the introduction of new technology. --Anonymous, 19:43 UTC, August 27, 2008.
Why is 3d10 configuration so stable??
Why is 3d10 configuration so stable?? According to Hund's rule, pairing decrease stability ..So why is 3d1 where every electron is paired so stable?? —Preceding unsigned comment added by Tetsuya26 (talk • contribs) 11:54, 26 August 2008 (UTC)
Hund's rule is saying that, once you have decided to place electrons in the same set of orbitals (like 3d taken as a whole), placing them in different orbitals gives a lower energy (better) state than placing them in the same orbital. However, you don't even see this in the spectroscopic notation: we just write 3d without bothering to say that this should be one electron in each orbital rather than, say, 2 full orbitals and a half-full. 3d is just fine because the only alternatives after you get to the obviously desirable 3d are to go to 4p or higher, which is worse. There are some near-degeneracies, though, where Hund's rule trumps the Aufbau principle; for example, copper is 3d4s even though 4s is "lower" than 3d. --Tardis (talk) 15:36, 26 August 2008 (UTC)
Geomagnetic reversal and the End of the World
I was watching a program about the End of the World (predicted to occur in 2012). In it, there was reference to Geomagnetic reversal and catastrophic (environmental, geologic, etc.)results when this occurs. I read the wiki artical but it is unclear if such a reversal would be "catastrophic" or if it would really make much difference in the grand scheme of things (other than wreaking havoc on our electronics!). Can anyone shed any light on this? —Preceding unsigned comment added by 216.154.16.106 (talk) 21:12, 26 August 2008 (UTC)
We talked about this just a few days ago. As I understand it, the problem is not that the field is reversed (ok - so your compass points the wrong way - I think we can deal with that!) It's that the reversal doesn't happen overnight. It might take years to decades for it to happen. During that interval, there might be either no magnetic field at all - or a wildly oscillating field. If the field were to "go away" for any amount of time, there is a risk that the mechanisms like the Van Allen belt might collapse and cease to protect us from hard solar radiation. A rapidly moving or oscillating field would induce electrical currents into large metal objects - and might do very bad things to electronics and such like. Since this kind of field reversal has happened MANY times in the past - certainly within the period since humans have evolved, it's not an "end of the world" event. Our species - and most others on the earth would survive. However, the number of deaths and associated problems with electronics and such might make it seem like a really major catastrophy to individual humans. But it's really hard to tell what all the ramifications of such an event would be on a technologically advanced civilisation. SteveBaker (talk) 21:30, 26 August 2008 (UTC)
Not really, we don't know exactly what would happen. The world has undergone plenty of reversals in the past and it's still here, so won't result in the end of the world, it might possibly result in the end of civilisation, but I doubt it (proto-humans survived the last reversal, so why can't we survive the next? We can protect ourselves with technology if we need to). Also, it's not going to happen in 2012 - it's a pretty quick thing by geological standards, but I don't think it's that quick, we would have detected changes by now if anything major was going to happen in 2012 (the changes we have measured suggest we've got another thousand years or two to go, at least). --Tango (talk) 21:32, 26 August 2008 (UTC)
Linear extrapolation from current trends suggest that a reversal could occur one or two thousand years in the future—there merest eyeblink on geological timescales, but a long, long time after 2012. (See geomagnetic reversal). Any effect on human society is purely speculative; penetration of the solar wind into the upper atmosphere may result in damage to electronic and electrical systems, and there may be an elevation in ambient radiation levels as more cosmic rays reach the Earth's surface. TenOfAllTrades(talk) 22:36, 26 August 2008 (UTC)
The year 2012 has become a popular choice by doomsayers based on interpretations of, among other things, the Mayan calendar. These doomsayers then tend to latch onto any possible explanation they can find for their predicted apocalypse, particularly things like planetary alignments and magnetic pole reversal, even if scientists know that these events are either not going to have the effect the doomsayers think they will (the gravitational effects of a perfect planetary alignment could be counteracted with a jumbo jet) or are almost certainly not going to happen as soon as 2012 (as TOAT points out, we suspect there will be a pole reversal in the next few thousand years, but thats three orders of magnitude bigger than the 4 years until 2012). Confusing Manifestation(Say hi!) 01:35, 27 August 2008 (UTC)
I have searched the internet and read the article on magnets and magnetic fields, but there are still questions I feel unanswered.
Would it be possible for a sphere shaped "hard magnet" to float above another "hard magnet" or flawlessly being repelled whenever the magnet would touch or get close to the other magnets surface? I do know that monopole magnets are just hypothetic, so I wonder rather if there is a possibility to "wrap" a pole inside another or possibly balance the poles, so it's 100% controllable?
To help illustrate my point, you could imagine a series of slides standing in a row on a flat ground. I would like to drop a ball on the first slide, make it "bounce" on to the next, slide down, and bounce up to the next one again - all by just using regular magnets. Is this plausible?
You mentioned a "spherical magnet." It would still have a north and a south pole, and if suspended over a north pole would flip so he south pole was down and crash into the magnet below. We know of no way to have a spherical magnet with the horth pole, say on the outside and the south pole on the inside, and no one has ever found a magnetic monopole, even though I don't think anyone has proved such to be impossible. Edison2 (talk) 04:02, 27 August 2008 (UTC)
He's referring to having north in the middle of the magnet and south on the outside, or vice versa. If this is done, the north and south will cancel each other out, and there will be no magnetism outside of the magnet. Besides using a diamagnet, you can spin the magnet, and use the gyroscopic effect to keep it balanced. These will both allow you to levitate the magnets, but the example you mentioned would be impossible because if the force is strong enough to push the magnet up to the next slide, it will be strong enough to keep the magnet from going down the slide. Get it? In general, if you think you found a perpetual motion machine, and you're not using general relativity, you messed up somewhere. — DanielLC15:48, 27 August 2008 (UTC)
I don't know about this specific case, but it's not unusual for pets to live longer than the same animal would in the wild due to having a reliable source of food, protection from predators, etc. Perhaps your father was basing it on the life span of these toads in the wild. --Tango (talk) 03:12, 26 August 2008 (UTC)
Somehow, my asking of this question seems to have correlated with my first real problem with the frogs.
Yesterday, I found that the frog case had been swarmed by ants. I rescued the three frogs, and relocated them temporarily to a large tupperware container filled almost to the top with sand. I placed a lid on the container, but not tight, since I wanted air to get in. Last night, the frogs were able to pop the top and escape into the house. This morning, I found the female and one male in the basement. I'm still searching for the other one. The family has made sure to keep all doors shut, so there's no way the frog can escape the house. My questions:
1) Is the final frog probably in the basement? Should I concentrate my search there?
2) Is the fact that two were in the basement relevant? Do spadefoot toads, who are burrowers, have some sort of inner sense helping them find the lowest place in the house?
3) After seven years of captivity, is the frog still capable of finding itelf food and staying alive until I locate it?
4) Will the frog move around? Or will it probably sit in the same place until nighttime? All they ever seemed to do is sit around while in the case.
5) Is there any way to set a trap for the frog? Maybe some type of cage with a cricket that the frog can enter but not exit (remember they can jump as well as burrow; I've seen it).
6) Anything else I should be aware of or take into consideration?
It will probably try and find somewhere damp, the basement may well qualify. You could try putting large tubs of damp sand (with food in, if possible) around the house that it can choose to burrow into (include one or two in the basement) and check on them every few hours until you find it. I doubt food will be an issue for a while, water will be more of a problem, but you've probably got some time to find it, especially if is succeeds in finding somewhere damp to stay. --Tango (talk) 01:42, 27 August 2008 (UTC)
I talked it over with my dad, and he's considering the idea, but he hasn't okayed it yet. We've decided towels would work better then tubs, to ensure that the frog can successfully get into the sand. Only problem is the frog eats live crickets. There's no concievable way to keep live crickets to stay on a pile of sand, is there? Oh, one last thing: any idea how frogs find their food/shelter? Visual? Olfactory? I just want to know if the only way the frog's gonna find our sand pile is by running into it. --Ye Olde Luke (talk) 01:59, 27 August 2008 (UTC)
I don't know, sorry! Hopefully someone else has some experience of catching frogs, I'm just guessing based on what little I know about them. --Tango (talk) 02:23, 27 August 2008 (UTC)
I once kept frogs. I put them in a terrarium with gravel on the botton and a terracotta dish filled with water. They burrowed under the dish and could not be seen. So a runaway frog might burrow under something damp and cool. Edison2 (talk) 04:00, 27 August 2008 (UTC)
August 27
Springs and simple harmonic motion
Okay, here's the thing. Physicists model the motion of a block attached to a spring using a sinusiodal function, or simple harmonic motion. I'm fine with this, but why can't the motion of the block be worked out from Newtonian mechanics? I've tried to do it, and haven't gotten very far, but it should be feasible.
Normally I wouldn't have a problem, but then my teacher showed that, if our guess of the motion of a spring was correct, the angular frequency ω must equal sqrt(k/m), and used this to show that the amplitude of the initial compression doesn't affect the the period. But isn't this bad physics? After all, it could be that our guess of the motion of the block on the spring was wrong. If I'm not explaining myself well, just let me know. Thanks! —Preceding unsigned comment added by 65.92.231.82 (talk) 00:55, 27 August 2008 (UTC)
It is done through Newtonian mechanics - you set up the differential equation, which comes from Newton's Second Law of Motion. You can then make the substitution and substitute that in to get an equation of simple harmonic motion. Confusing Manifestation(Say hi!) 01:28, 27 August 2008 (UTC)
The key equation of SHM is (which you'll have after the substitution suggested by ConMan - the a will be replaced by an appropriate constant of proportionality involving ks and ms), that is acceleration is proportional to displacement and in the opposite direction. You then simply observe that the sine (or cosine - which one you use depends on boundary conditions) function fits that equation, so you can use it as a solution. Just assume that (this is called an "ansatz"), substitute it in and solve for the constants, then you have your answer. --Tango (talk) 02:40, 27 August 2008 (UTC)
Firstly, calm down! There is no need to shout. Secondly, it's been a while since I learned how to separate variables and I'm probably just being blind, but how do you separate a 2nd derivative? What am I missing (unless you mean to use ConMan's substitution first, in which there really wasn't a need to shout since he'd already said it)? --Tango (talk) 21:56, 27 August 2008 (UTC)
It's possible to do using the substitution and a bunch of rearranging (and fiddling around with a plus-or-minus sign), but I agree the ansatz is much neater. More generally, you could use an exponential ansatz, as long as you're prepared to work with complex numbers (and know the relationship between the exponential and trigonometric functions). Confusing Manifestation(Say hi!) 05:10, 27 August 2008 (UTC)
There is a very good underlying question here. We know that or, more generally, gives a family of solutions to the equation of motion - but how do we know that this covers the whole solution space ? How do we know that there isn't some set of initial conditions that will result in an entirely different solution with very different behaviour ? Well, in this particular case we know that the differential equation is linear, which allows us to use the superposition principle to create a two dimensional family of solutions which we are sure covers the whole solution space. But if the equation of motion is non-linear (if, for example, we exceeded the spring's proportional limit) then it becomes much more difficult to know that we have a complete family of solutions (or even to find any exact solutions in the first place). This is why physicists and engineers will always attempt to linearise a problem if they possibly can.Gandalf61 (talk) 10:19, 27 August 2008 (UTC)
Is it obvious (I know it's true) that linearity immediately implies a 2d solution space? I might be being unusually stupid, but I don't see it. Algebraist22:04, 27 August 2008 (UTC)
It's not obvious to me, but that's not saying a lot - I avoid differential equations when I can help it! --Tango (talk) 22:17, 27 August 2008 (UTC)
Obviously we only have a 2 dimensional solution space if we have a 2 order linear d.e., not for all linear d.e.s. For the general case, if f(x) is a solution of a n order linear d.e. then the n derivative and above are expressible as a linear combination of f and its first n-1 derivatives. So iff is well-behaved enough to have a Taylor series expansion, doesn't it follow that the values of the first n coefficients in the Taylor series uniquely determine the rest of the coefficients, and hence uniquely determine f, and so we have an n dimensional solution space ? Gandalf61 (talk) 16:11, 28 August 2008 (UTC)
Yep - I'm pretty sure we know it's contageous. I believe there was a Science Friday piece on NPR that talked about this. What that show said was that yawning is nothing to directly do with tiredness - it's body-language that means something like "We all need to stop what we're doing and do something else now"...which could include going to bed. The reason it's contagious is because other people are subconsciously agreeing that there needs to be a change of group activity. SteveBaker (talk) 04:31, 27 August 2008 (UTC)
Okay I wrote out a response but lost it since it was blocked. Anyway I'm rather surprised about the article, it mentions yawning in non-human animals but mostly seems to treat these as seperate issues. To me that doesn't make much sense, I see no reason to presume humans are special here, whatever reasons for yawning hold for us likely hold for at least some other animals particularly those close related to us . There are quite a lot of theories of why animals yawn , one of them is to show off their teeth. This would also explain why yawning is contagious, if another animal is showing off it's teeth you'd want to as well. Incidentally I came across this paper of a Biology 103 student "We cannot be certain that humans have evolved from monkeys" do people really right that sort of thing in Biology papers? Nil Einne (talk) 08:03, 27 August 2008 (UTC)
I was under the impression that we can be certain that humans aren't descended from monkeys, but humans and monkeys are both descended from some proto-simian. Algebraist10:45, 27 August 2008 (UTC)
(Humans are a member of the Ape family - apes are not monkeys) Well, we aren't descended from any living species of ape. All apes are descended from a common antecedent - but that antecedent must in turn have been an animal that you would describe as an ape. That in turn must have descended from some kind of a simian (a "monkey") - but, again, probably not any living species. So the correct statement is: "Humans are descended from an animal that would be classified as an ape. Humans are not descended from any living species of ape." - I don't quite know why people fixate on "monkey" - the closest classification is "ape" and there are plenty of earlier species we descended via - so we're also descended from small furry mammals, fish-like things...bacteria. SteveBaker (talk) 13:38, 27 August 2008 (UTC)
I think the problem is most people don't understand that apes are usually not considered monkeys, particularly historically when the monkey thing first arose nor do they understand that monkeys (and apes) nowadays are not in fact the same as the ancesteral 'monkeys' (and apes) we all evolved from we so from their POV we are descended from historic modern day monkeys and we get silly questions like why did monkeys stop evolving (what?). (Of course it gets worse when they think humans are the end all of evolution and so ask why monkeys don't evolve into humans but that's another issue.) I'm still rather surprised the student thought it wise to demonstrate that ignorance in a biology paper but anyway... Nil Einne (talk) 20:04, 27 August 2008 (UTC)
I was told that we yawn because our brain lacksz oxygen.
Philosophia X Known(Philosophia X Known) 15:06, 27 August 2008 (UTC)--Earthan Philosopher
No - that would simply cause a slightly increased rate of respiration. Lack of oxygen in the brain is, however the cause of ridiculously large fonts in signatures. SteveBaker (talk) 03:54, 28 August 2008 (UTC)
hi, on channel 7 last night there was a story about a man (or kid?) with a strange growth on his face. Does anyone know if we have an article on this, and what is the condition called? 203.35.135.133 (talk) 07:38, 27 August 2008 (UTC)
And strangely enough, being Misplaced Pages, we do have a fair few articles on people known for little more than having an odd tumour. Jose Mestre was featured on a Discovery Channel program called The Man with No Face in which he underwent surgery to have an enormous abnormal growth removed from his face.Nanonic (talk) 15:12, 27 August 2008 (UTC)
Do cats have a second set of eyelids under their regular ones? A little while ago I was petting my cat, and his eyes opened a bit, and there was skin covering them, which opened when I woke him up. Black Carrot (talk) 08:05, 27 August 2008 (UTC)
It's worth noting that if you can still see the membrane on your cat, you should take it to see a veterinarian. It's usually a sign of illness in cats. —Cyclonenim (talk · contribs) 11:29, 27 August 2008 (UTC)
I think that's a bit hasty. It only happened once, and it fits the conditions mentioned in the article - he was asleep, and his eyelids slid open a bit. Thanks for the reference. Black Carrot (talk) 03:27, 28 August 2008 (UTC)
Can tapirs pick things up with their nose?
I asked this on the miscellaneous reference desk a while ago but no-one really knew - basically, can they use their nose anything like how an elephant uses his trunk? Can they pick up food and pop it into their mouths? Can they hold objects with their noses? Bradley10 (talk) 09:24, 27 August 2008 (UTC)
Is what they did in Jurassic Park possible if we did have any dinosaur blood? I know that the mosquito/amber technique wouldn't actually work, but could you, say, clone a dodo from the taxidermy dodos they have in Tring? Or could they make some new Yahzee River Dolphins? Bradley10 (talk) 09:27, 27 August 2008 (UTC)
DNA doesn't last forever - I don't think the mosquito/amber trick does work. While the shape and tissues of the mosquito are still there - the actual chemical composition of the DNA in the blood in it's stomach is completely wrecked. This is acknowledged in Jurassic Park too - they claim that they had to carefully reassemble the DNA - and fill in the missing bits with Frog DNA (this actually turns out to be the reason for the downfall of the park - most people miss that point in all of the action!)
A Dodo is much more do-able - the last viable DNA is only 350 or so years old, so perhaps it could be made to work. The Yangtze River dolphin is even easier because the DNA may still actually exist in the last few animals.
But using this technique to bring a species back is problematic. To get a viable breeding colony requires a sufficiently diverse gene pool. It's not enough to have one male and one female because all of their offspring would share genes from the same set of two archetypes - and the resulting in-breeding would soon produce all sorts of major health problems. Opinions vary on the minumum number of individuals needed - I heard the number 50 at one time - but a lot depends on how genetically diverse those 50 individuals are - and on how closely scientists could control their subsequent breeding to maximize diversity over the succeeding generations. We probably don't have DNA from 50 Dodo's - and we might not have it from 50 River Dolphins either.
With Jurassic Park, there are even bigger problems - the plants that the herbivores ate are probably all extinct - or perhaps have evolved chemical defenses that the dinosaurs would not be able to counteract (this too comes up in the movie - but very briefly). The idea that the T-Rex can survive on a diet of goat and lawyer is ridiculous - they'd need contemporary animals, which in a real Jurassic Park would be worth vastly too much money to feed them to carnivores. There might also be issues with them surviving modern diseases - but it's also possible that their great antiquity would mean that modern diseases were not able to infect them. It's hard to say. Worst of all - the amount of oxygen in our atmosphere is much less than it was in Jurassic times - the odds are good that these gigantic creatures wouldn't have sufficient lung capacity to survive at all in the modern world.
Another issue (which is carefully skirted in Jurassic Park - but which would affect the Dodo and River Dolphin too) is that having the DNA isn't enough. You also need to turn that DNA into a fertilised egg cell and implant it into the womb of a suitable donor species. In the case of a Yangtze River dolphin - you might be able to implant the egg into a Ganges River dolphin (or one of the other handful of river dolphin species) - but those are also under pressure. You probably can't use one of the more common oceanic dolphins as a surrogate because they live in salt water and river dolphins don't. Same problem with the Dodo - can you find a sufficiently close surrogate mother bird who can lay an egg containing the right nutrients, of sufficient size to contain the chick of a 50 pound bird? The nearest living relatives of the Dodo are pigeons...so no hope there. Perhaps some other large, flightless bird would be able to form a large enough egg - but there is no guarantee that it would have the right shell thickness with the right amount of oxygen transport and the right nutritional stuff.
With dinosaurs, you're in deep problems there. There are no relatives of the dinosaurs left to act as surrogates. This is quietly swept under the carpet in Jurassic Park.
There are some strong candidates for "bringing back" - I think the Mammoth is the most likely. Modern elephants are probably "close enough" to birth a mammoth calf - and we have freeze-dried meat with (perhaps) viable DNA from a significant number of individuals to make a breeding herd. Mammoths lived in sufficiently recent history that diet and such like wouldn't be a major issue.
It's an interesting matter - I think we'll see some of this kind of thing happening...but almost certainly not with Dinoasaurs.
I'm curious about your point that a T. rex could not survive on a delicious diet of modern goats and lawyers. Based on no knowledge of the matter at all, my impression was that an ancient carnivore such as a dinosaur could live on modern reptiles or mammals. What dietary requirements might be missing? Presumably the fat and protein in modern animals would provide the necessary energy supply and amino acids for growth (or am I wrong on that point as well?) Wanderer57 (talk) 13:59, 27 August 2008 (UTC)
No doubt the proteins and amino acids are there - but who knows what else too? Perhaps there are missing 'trace elements'? Look at modern animals: A lion can't live if fed only dog food (believe it or not - I know someone who tried that!)...and lions and dogs those are both modern carnivores. Chocolate is poisonous to dogs. Who knows what wierd stuff a dinosaur needs in it's diet? Who knows what stuff in modern foods would be poisonous to it?
Let's do a thought experiment. Consider even a human - cloned into an alien society a few million years in the future when humans and all of the apes and monkeys are long-extinct and giant super-intelligent cockroaches are now running the place. They find a mosquito trapped in amber with human blood in it's gut...they do the Jurassic Park thing and make a baby...so what happens?
The baby is brought into the world from an artificial placenta in an utterly sterile environment to avoid infection. They roach scientists have carefully researched all of the foods humans ate and they've even cloned tomatoes, corn, cows, etc. They somehow reproduce all of the nutrients present in human milk and make sure the baby gets all of that good stuff. But the scientists rapidly discover that the kid's blood won't clot. They have no clue why. They've double-checked the diet - cloned all the right foods - but eventually it dies. Well, maybe there was a cloning problem - maybe the DNA they got was from a haemophiliac. But no. They try this a dozen times with a dozen different clones from different DNA sources - always the exact same problem. They are totally at a loss.
What happened? Well, they cloned the human - but they didn't clone any "gut flora" - the 300 different species of bacteria that are specialised to live in the intestines of humans. A baby naturally gets those from it's mother - through all sorts of mechanisms. But a clone grown in a sterile lab a million years from now wouldn't pick them up. Our gut flora provide us with vitamin K2 - which is needed for blood clotting. No gut flora (or the wrong kind of gut flora or something that's poisoning the gut flora) - no K2 - the clone dies.
How would those future alien scientists figure that out with no living humans or human-descendants to study? Even if they do figure it out - perhaps no suitable bacteria exist in their future world that could substitute for the ones we get naturally. If there are 300 species of them living in our gut - then they would need an ungodly amount of research to figure out which ones they need to clone (and where the heck they'd get the DNA from is anyone's guess) in order to "fix" the poor clone's vitamin K2 deficiency.
We have no clue what subtle things like that we'd have to provide to a baby dinosaur...it's very likely we'd miss a whole bunch of things - even if we DID clone all of the right food plants and such. The problems of raising a creature from the Jurassic would be overwhelming...not just that some species of berry in the park happens to be poisonous - as chocolate is to a dog.
Also, what would happen if the aliens used DNA from one of the uneaten lawyers? They'd get their butts sued off for negligent cloning over the blood clotting issue. Litigious Park! Franamax (talk) 18:21, 27 August 2008 (UTC)
The only (partly) serious attempt I know of to clone an extinct animal is that of the Thylacine which survived until the 1930s. You may want to read the article for some of the challenges faced, and this is with an animal relatively recently extinct Nil Einne (talk) 19:45, 27 August 2008 (UTC)
P.S. Just remembered after reading SB's post there has ben some talking regarding the Woolly mammoth too and this is mentioned in the article although I don't think there is a specific effort yet Nil Einne (talk) 19:51, 27 August 2008 (UTC)
Is there any animal which lacks self-preservation instinct?
So that's the question: does any animal which lacks survival instinct, and survives just "by chance"? Maybe sea sponges? Leptictidium (mt) 11:31, 27 August 2008 (UTC)
Sea sponges don't have a nervous system - they certainly don't have a brain - so they lack pretty much ALL instinct. So you've certainly answered your own question there. In general, there are lots of animals that don't have brains - or whose brains are far to primitive - so we could probably form a long list that would meet your criterion. But you're probably thinking of higher animals - so let's look in that direction a bit. I'm not sure what you mean by "survival instinct". Survival isn't a single ability - it's a HUGE range of abilities - and "instinct" implies something we're born with - not learned behavior. Humans lack the instinctive ability to eat the right things and exercise properly - that certainly affects our ability to survive in SOME circumstances - yet even newborn babies have the instinct to hold on tightly to your fingers if you try to lift them up by their hands. So to find an animal that lacks some survival instincts is easy - probably all animals have some gaps - but to find one that has no instincts for surviving any set of circumstances probably does require finding one with almost no brain at all. SteveBaker (talk) 12:49, 27 August 2008 (UTC)
Your body doesn't crave certain food when it is missing essential nutrients? I most certainly do have instincts for nutrition and exercise. It is only through years of practice that we manage to suppress those instincts. Plasticup/C13:52, 27 August 2008 (UTC)
The problem is that we evolved in a time when certain high-energy foods (animal fats for example) were in exceedingly short supply. We have the "instincts" to eat large quantities of those foods whenever they are available - but they were so rare and hard to obtain without taking a lot of exercise - that it was impossible to overeat on a routine basis. Therefore we never evolved a mechanism to stop us from eating them when we start to get fat. In a world where you needed to put on a few pounds in the summer in order to survive a long, hard winter - having an instinct to NOT stuff our faces with egg, bacon and cheese McMuffins would have been pretty fatal - so it would be evolved away in no time flat. Worse still - it's pretty clear that we've evolved to crave foods that have high nutritional content - so we not only lack an instinct NOT to over eat - but we also HAVE an instinct to shovel down as much fatty food as we can find! Now we know (intellectually) how bad this instinct is - we can use our big-brain intellects to fight against it...but (for some people at least) it's tough.
It's a similar deal with exercise - we didn't need to evolve a mechanism for craving "pointless" exercise because we got plenty of exercise doing our daily food hunting and the issue of "Death by under-exercise" simply never needed a "survival instinct". Now we no longer do that by necessity - we pretty much lack any instinctive desire to leap on a treadmill a couple of times a week. SteveBaker (talk) 14:13, 27 August 2008 (UTC)
Glaucoma / abd pain
While reading Cope's "Early Diagnosis of the Acute Abdomen", a trusted reference on the surgical abdomen, I came across the following statement:
...the observer must remember that certain extra-abdominal conditions may cause deceptive pain within the abdomen; thus...even acute glaucoma may temporarily mislead the practitioner. Can anyone explain how glaucoma could possible be misinterpreted as an acute abdomen? Tuckerekcut (talk) 16:38, 27 August 2008 (UTC)
The short answer is referred pain—conditions which cause pain in one of the body to present as pain elsewhere. The mechanism of pain referral is not well-characterized, but our article addresses some possibilities. This article notes that referred pain in the abdomen can be caused by acute angle-closre glaucoma, and is symptomatic of a loss of blood supply to the eyeball. TenOfAllTrades(talk) 17:48, 27 August 2008 (UTC)
For anyone else interested in a more complete answer (though your short answer is appreciated Ten), this has a well thought out mechanism. In short, Noxious stimulation of trigeminal nerve afferents activates the paratrigeminal nuclei in the medulla with secondary stimulation of the vagus nerve.Tuckerekcut (talk) 18:23, 27 August 2008 (UTC)
Why ask if you know we can't answer? It could be a bruise, or it could be something entirely different. If you are seriously concerned about it, please seek the advice of a physician. --Russoc4 (talk) 18:25, 27 August 2008 (UTC)
On the contrary you can answer general medical questions so long as it isn't tantamount to medical advice. My question is: What happens when blood is injected (leaked) into tissue? Does it get absorbed? In what way would it get absorbed? Rfwoolf (talk) 18:29, 27 August 2008 (UTC)
The lesion you describe is known as a hematoma. The entrapped blood will slowly degrade by several mechanisms. Some blood cells will be broken down by natural and mechanically accelerated hemolysis. Macrophages and similar cells may consume and degrade some constituents. Some white blood cells are capable of migrating back to the intravascular space. The plasma will likely diffuse through the tissue and migrate in and out of spaces based on osmotic forces. Some cellular debris may stay in the hematoma site for a long time. Tuckerekcut (talk) 18:35, 27 August 2008 (UTC)
Thank-you! Hopefully this question will be indexed by google and your answer will be helpful to others will similar questions. Rfwoolf (talk) 18:48, 27 August 2008 (UTC)
Evolution and the "no new information" argument
I really just don't understand this one. What do creationists even mean when they say "no new information is ever created through mutations/evolution"? Do they mean more genetic code isn't being added? (gene duplication) Or are they ignoring the fact that ACC and CAC, while the same base amino acids, code for completely different proteins? -- MacAddct 198419:09, 27 August 2008 (UTC)
I've never heard this one before (I don't spend much time listening to creationists), so can you give us a link to somewhere the argument is presented? Algebraist19:13, 27 August 2008 (UTC)
My understanding is most creationists claim mutations are always deleterious and/or there is no evidence/it is impossible to form new, more complicated, structures from mutation. Nil Einne (talk) 19:32, 27 August 2008 (UTC)
See for example (does ) work? A mutation, being a random change in highly specified information contained in the nucleic acid base sequence, could almost never do anything but scramble the information; that is, reduce the information. Now sometimes such a loss of information results in a new trait—for example, purple or red flowers where there were only blue ones before (yes I know how dumb that is and how they're missing duplications etc but that's not the point) Nil Einne (talk) 19:36, 27 August 2008 (UTC)
The attempted argument is a bastardization of information theory. Objections to evolution#Evolution cannot create information discusses it, but here's the gist: in order to justify a necessisary "intelligent designer", some folks have decided to make the nonscientific (and clearly false claim) that only a intelligent agent can add information into a system because natural systems can, allegedly, only lose information. This natural-systems-can-only-lose-information paradigm stems from a mischaracterization of thermodynamics and incorrect assumptions about the nature of genetic mutation. The Specified complexity arguments of William Dembski are commonly cited (outlined in his "Law of conservation of information"). — Scientizzle19:47, 27 August 2008 (UTC)
Oh okay, that's pretty much what I suspected. Thanks for the links. (I was trying to find it listed in criticisms of evolution article maybe I'll redirect it) As always, just blatant and willful ignorance of facts. -- MacAddct 198419:59, 27 August 2008 (UTC)
Various experiments have shown to everyone's satisfaction that species do change over time, so the Creationists have been backed into saying those changes are going "downhill" by losing genetic information:
The rare ‘beneficial’ mutations to which evolutionists cling all appear to be like wingless animals, blind cave animals, and many examples of antibiotic resistance. They are downhill changes, losses of information which, though they may give a survival advantage, are headed in precisely the wrong direction for evolution. (source)
This rebuttal to the recent successes of the critters in the E. coli long-term evolution experiment concludes with "it is only possible to obtain truth about the past if we start with the only source of absolute truth in the present—the inerrant Word of God". So there you are. --Sean19:55, 27 August 2008 (UTC)
Oh, I don't know. It's actually much more honest than most Creationist groups in the respect that they recognize that some arguments which are incredibly common that Creationists have been using forever are wrong to the point of making the Creationists look stupid or dishonest (e.g. the Darwin eye misquote, which is always a useful way to spot totally ignorant Creationists). --98.217.8.46 (talk) 21:26, 27 August 2008 (UTC)
Creationists either don't understand - or refuse to acknowledge - the most basic science on this. The things they say are (without exception) ridiculously easy to demolish - but the people they are aiming these bogus arguments at are desperate to believe whatever crap is hurled in order that they can continue to cling to horribly outmoded beliefs. So there is guaranteed to be a breakdown in communication.
Here is the truth:
Evolutionary change comes about through at least THREE mechanisms:
Sexual reproduction - where two sets of similar (but not identical) genes are shuffled together.
Viral gene insertion where some virus comes along and inserts its DNA into that of the host species.
Mutation - where either a transcription error in the DNA or a zap from radiation or some nasty chemical agent in the environment (a carcinogen, for example) causes the insertion, deletion or corruption of a part of the genetic code - resulting in a brand new gene popping up.
Mutation is a genuine source of completely new genes - they come from absolutely nowhere in the environment - it's a truly random change.
The other two mechanisms are indeed nothing more than a reshuffling of existing genes. But even that can result in totally new "features" in the resulting organism because the consequences of two old, well-established proteins meeting in the same animal for the first time in history can easily result in some bizarre - but useful - side-effect.
So - sure, new 'features' can arise that have never been seen before - there is no problem with some limited pool of information being the only source of genetic material...that's obviously not true. Creationists who claim this are simply sticking their fingers in their ears and singing "La, la-la, la-laaaa. I can't hear you!" because they've been told this plenty of times and clearly enough.
The reason the entropy argument is bogus is because entropy only increases in closed systems - and it's a statistical increase - not an absolute cast-iron increase. So within a group of animals stuck in a "closed system" (on an island or something), the arrival of new mutations results in a very few, rare improvements that survive into the future and a much larger number of disasterously 'damaged' creatures that don't survive long enough to pass on their genes to the next generation. The total entropy of the island does exactly what the laws of physics predict - it increases.
Life on earth is evolving and improving - but at the cost of increasing the chaos on the planet at a much higher rate than would occur if there was no life (or life without evolution).
We can simulate this in a computer relatively easily. When we do this, we can actually measure the entropy of the system and watch it increase as predicted by physics while the synthetic "animals" befome more and more well-suited to their artificial environment.
I have seen the computer models before but it was awhile ago. Is this mostly university stuff or are there public resources on it? It would be most excellent if I could get a simplified version to just watch =P --mboverload@04:33, 28 August 2008 (UTC)
Artificial life and Evolutionary algorithm are the articles you need. I'd be surprised if there were no decent public-domain evolutionary demonstrations. However, it would be rash to assume there was anything to watch - firstly, even computer-based evolution can take a LONG time to develop anything interesting - and secondly, the systems involved are not necessarily graphical things you can watch. However, there are a few programs out there that run over a few days and produce brief graphical output - I have no idea whether any are in the public domain.
Some of these are pretty amusing - and they are rarely what you either want or expect. One guy built a system where each creature was made up of a set of cuboids hinged together with simulated "muscles" operated by an elementary neural network "brain". The size and shape of the cuboids, the positioning of the muscles and the connections within the brain were all determined by a set of "genes" that could be passed on from one critter to another with cross-breeding and mutation for variation. His first attempt was to try to evolve something that could walk - so he'd set up a bunch of randomly generated synthetic creatures and he'd have his software watch them move. Initially, some of them just 'twitched' - that nudged them SLOWLY in some direction. The one that moved furthest over some period of simulated time would go on to provide the genes that would be mutated to form the next generation. He ran the program for days and found from the readout that the winning creature could move amazingly fast - much faster than he expected. Viewing the "design" of the winning creature revealed that it had just one cuboid - no muscles and no brain whatever. It was very tall and very narrow and beat all the other creatures merely by falling over! Its center of gravity moved by half its height in just a few simulated seconds - so it met the criteria of moving the furthest in the allowed time - and it simply evolved to get taller and taller and narrower and narrower. Later, he fixed that problem by changing the fitness criteria - and found that his creatures would evolve to exploit bugs in his code - he fixed bugs and then found that many of his creatures merely consisted of two blocks, one muscle and a very simple brain. They simply vibrated at high frequencies and mysteriously slid across the ground - it turned out that they had evolved to exploit matematical roundoff error as a source of energy.
You might consider these as 'failures' - but in truth they are elegant demonstrations that creatures (even synthetic ones) will evolve to fit perfectly into their environment. If their environment inadvertently provides 'free energy' from roundoff errors - then for them, that's as important as sunlight is to plants out here in the real world. Making synthetic creatures evolve to look and behave like real creatures turns out to be virtually impossible. SteveBaker (talk) 06:08, 28 August 2008 (UTC)
Also : "it turned out that they had evolved to exploit mathematical roundoff error as a source of energy." It would be a great line in a science fiction short story. APL (talk) 16:20, 28 August 2008 (UTC)
It seems odd to me that at least three, probably four, groups of animals have developed highly complex and intelligent brains independently (corvids, parrots, cetaceans, and primates), during the Cenozoic era, while no known fossil from the Mesozoic has an encephalization quotient (EQ) much above that of an ostrich (the highest are troodontids). (I say "possibly four" because there were parrots in the Cretaceous, but I'm not sure about their intelligence.)
Is there any speculation as to why this is? (Is the Mesozoic fossil record poor enough that we could have missed an entire taxon as significant as, say, parrots or corvids?) —Preceding unsigned comment added by Vultur (talk • contribs) 23:33, 27 August 2008 (UTC)
One of the principles of evolution, articulated by Stephen Jay Gould among others, is that in any sufficiently large evolving population even a purely random exploration of all possible niches will lead to increasing diversity as one moves away from ancestral forms and tries new paths of life. Applied to the EQ in particular, this implies that since animals started with no brains (0 EQ), then even randomly directly evolution will lead to an expanding diversity of EQs. As a result, both the average and top performing EQ across any taxonomic group is likely to improve over time. If you look at the work of Jerison, for example, he generally concludes that the average EQ of birds and mammals has been increasing essentially since the inception of these groups, but that this random exploration of the "intelligence" space proceeds very slowly (perhaps max EQ doubles every 25 million years or so). If the average intelligence of birds and mammals has been improving gradually for a very long time, it is not too surprising that the intelligence of the brightest birds and mammals is also at or near a historical maximum today.
There is also a view that reptiles and fish, which still have low EQ even today, may be unable to evolve a high EQ due to the metabolic requirements of a large brain. In other words, high intelligence may be only possible in warm blooded organisms. However, if you believe that at least some dinosaurs were warm-bloodied then that still doesn't explain why 180 million years wasn't long enough for dinosaurs to develop interstellar travel. So ultimately I dont have a good answer for you. Dragons flight (talk) 07:03, 28 August 2008 (UTC)
Teleology would assume there is a plan or purpose beyond the evolution. Gould's point, somewhat oversimplified, is that given enough time random evolution will try nearly all possible stratagies for survival. Hence starting at any fixed taxa, the diversity of approachs is likely to increase across the range of species that are its descendants. That some descendants happen to become brainy requires only a sufficiently large pool of randomly evolving species and an assumption that increasing brain power is both physically possible and not so deleterious as to cause a species extinction. Dragons flight (talk) 18:49, 28 August 2008 (UTC)
A useful analogy is a simple random walk on the Euclidean plane. The expected position of the random walker (i.e. (expected x, expected y)) remains at the starting point no matter how long the walk has been going on, but the expected distance from the starting point increases with time (I think it goes as the square root of the number of steps). The reason is that x and y coordinates are equally likely to go up or down, but distance starts out at zero and can only go up. Evolution is also a kind of random walk, and any metric which starts at zero and can be positive and can't be negative will increase with time for the same reason. It won't increase forever—since there are also downward pressures which have no analogue in the simple random walk—but it will increase for a while from zero to some stable nonzero average. -- BenRG (talk) 19:33, 28 August 2008 (UTC)
Thank you. Perhaps the question was a bit poorly worded; I get that intelligence tends to increase over time I was wondering because we've only had 65 million years since the last big "reset" mass extinction, and the dinosaurs/pterosaurs/freaky mesozoic weirdnesses had much more. —Preceding unsigned comment added by Vultur (talk • contribs) 00:14, 29 August 2008 (UTC)
Objects rotating in space
I contend that it is impossible for an object to be rotating in more than one axis simultaneously without a continual force acting upon it, but there are others that disagree with me. Picture a pencil spinning along its axis, nudged so that it also spins end over end. Doesn't the gyroscope effect prevent an object that is rotating on one axis from also rotating on another axis such that after it has rotated 180° it is then rotating in the opposite direction on the original axis of rotation? Surely this periodic reversal of rotation (in an absolute, external observer sense) requires continuous application of force? How can I more clearly elucidate my point, or am I mistaken? — PhilHibbs | talk23:38, 27 August 2008 (UTC)
Any two rotations in 3D space around any two axes (that intersect - presumably at the object's centre of mass) combine to make a single rotation around a single axis, see Euler's rotation theorem. This means that if you try to make something rotate simultaneously around two axes you'll actually find that it's rotating about one, different, axis. --Tango (talk) 23:56, 27 August 2008 (UTC)
I don't see how what you've said below contradicts what I've said. I've just quoted a mathematical theorem, I'm pretty sure it's right, Euler knew his stuff! --Tango (talk) 20:15, 29 August 2008 (UTC)
Certainly you can combine any number of rotations in to a single rotation about some other axis. Whether you can change the rotation without an external force is a little tricky. The classic example of the spinning ice-skater who - with arms outstretched - can change the SPEED of her rotation by pulling her arms inwards. That's a change in speed - but not of the axis of rotation. However if she pulls in just one arm, she'll start spinning around an axis that DOESN'T run through her head and her feet. But she's still spinning about the same axis from a point of view of conservation of rotational momentum because her head/body moved one way as the arm moved the other way - the axis of rotation for the entire system is still vertical with respect to the ice - but from the perspective of the skater, it changed.
This principle is important for spacecraft. Using thrusters to change your axis of rotation consumes reaction mass - rocket fuel - which is valuable stuff...but instead you can have a big flywheel inside and use solar power to spin it up and to keep it spinning against friction. When the spacecraft needs to rotate, it applies forces to the flywheel - the flywheel spins one way - the remainder of the spacecraft rotates the other way in order to conserve rotational momentum. The spacecraft APPEARS to rotate without any external force being applied - where in physical terms, it's total rotational momentum didn't change. This mechanism is how the Hubble Space telescope turns to point where it needs to point without ever running out of fuel.
Gyroscopes are not magical - they use the same principles. When you see a kid's toy gyro spinning on a table - you do indeed see it "precessing" (it's axis of rotation changes) - but that's because there IS an external force - friction with the table (or whatever mounting points it uses) and gravity.
I'll bet you could skate around the inside of a cylinder. Starting and stopping would be problematic though. APL (talk) 20:28, 29 August 2008 (UTC)
OK here's a follow-up. What does torque-free precession mean in this context? It looks to me like it's referring purely to the precession of an axis of symmetry, not the precession of an axis of rotation. — PhilHibbs | talk13:28, 28 August 2008 (UTC)
Angular velocity (ω) can change without a torque. Angular momentum (L) is constant in the absence of torque, but L is not a scalar times ω, it's Iω where I (the moment of inertia) is a symmetric 3×3 tensor. Any real symmetric matrix is orthogonally diagonalizable, so you can think of the tensor as three orthogonal axes (the principal axes) with a scalar moment of inertia associated with each one. You can convert between L and ω by individually scaling their components along the three principal axes (thus L and ω do not generally point in the same direction). The trick is that as the object rotates, its principal axes rotate with it. If L is aligned with a principal axis (say x) then it doesn't matter; L = Ixω and that doesn't change as the y and z axes rotate into each other. If L is not aligned with a principal axis (or any combination of axes with the same scalar moment of inertia) then the angular velocity, hence the physical axis and speed of rotation, changes with time even though there's no torque. If the object is not solid then the moment of inertia may change in more complicated ways; objects tend to deform such that one of their principal axes aligns with L. -- BenRG (talk) 14:46, 28 August 2008 (UTC)
That's what free rotation looks like when L isn't aligned with a principal axis. See Poinsot's construction, which is summarized by the delightful phrase "the polhode rolls without slipping on the herpolhode lying in the invariable plane". The angular velocity is tracing out a herpolhode. The angular momentum, if it were plotted on the frame, would point toward the lower left. To directly answer your question, an isolated pencil in outer space can't spin around its long axis while also spinning end over end (tracing out a disc), but it can spin around its long axis while also tracing out a double cone, sort of like that asteroid is doing. -- BenRG (talk) 23:25, 28 August 2008 (UTC)
If Spaceman Biff sets his #2 yellow pencil spinning around it longitudinal axis, then he flips it to make it rotate around an axis perpendicular to the initial axis of rotation, it will precess. Edison2 (talk) 05:14, 29 August 2008 (UTC)
You can try the effects of rotations yourself using Orbiter_(sim). The physics model is very elaborate. It takes some time to get a grasp of the controls, but it is really worth the effort. —Preceding unsigned comment added by 84.187.95.86 (talk) 20:34, 29 August 2008 (UTC)
August 28
Spider silk
After watching a spider lower itself from the ceiling, I got to wondering. What happens to such a strand after the critter is done with it? Does it hang there until it disintegrates or somebody comes by? Or does the spider have some way to reel it in and recycle it? Spider silk answereth not. Clarityfiend (talk) 02:10, 28 August 2008 (UTC)
It says "It is not uncommon for spiders to eat their own web daily...", but how would a spider do that with a single strand when there's no other strands to move about on, unlike a web? Clarityfiend (talk) 03:41, 28 August 2008 (UTC)
This is original research but I find that any time I do something dusty (like sand wallboard or saw wood in the garage), a lot of "left-over" spider silk gets revealed by the dust that it traps. So my assumption is that spider silk hangs around until disturbed by external forces (like the wind or your vacuum cleaner). Once on the ground, doubtless some biological process breaks it down.
Gull. They're difficult to swallow whole (Google images has some wonderful pics if you plug in 'gull starfish') but they are definitely considered food if they happen to be there at the same time as the hunger. --Kurt Shaped Box (talk) 05:57, 28 August 2008 (UTC)
Having dissected a starfish in biology lab, I'sd about as soon eat a Dobie pad: "A white nylon/polyester mesh wrapped around a yellow urethane ...". Edison2 (talk) 05:10, 29 August 2008 (UTC)
My mom just told me that back in the days, yellow (I think!) clothing ripped most easily because yellow dye weakened the fabric. Is that true? Is it still true? What about other colors? Thanks. 67.243.6.204 (talk) 04:31, 28 August 2008 (UTC)
Most of the damage that I am aware of is not from the dyes themselves but from the mordants and other chemicals used to make the dye strike and color evenly. Yellow can be made from a number of different dyes (partly depending on if you are dyeing plants like cotton or animal fibres like wool) so it is hard to imagine a blanket statement could be correct. Rmhermen (talk) 00:58, 29 August 2008 (UTC)
It's unlikely that such information exists - at least publically - which means you probably won't get a decent answer here. Presumably these kits come with a "use by" date - and the manufacturers must have used some technique to estimate that date. If the lifespan of the kits is short then it's possible they didn't need to do accellerated aging - they may have simply been able to use the kits to test samples with known properties and see how good the test is after aging naturally. If they know that the lifespan is at least long enough to be acceptable to their customers then the manufacturer may just put an arbitary cutoff date on them. It's true for many drugs that the manufacturer knows they last at least (say) three years - and puts three years on the label just to be safe. There are cases when the US Military has tested drugs that are much older than the "use by" date and found them to be perfectly usable. It's therefore far from certain that anyone has ever even thought of using accelerated aging techniques to estimate the lifetime of these test kits. (For others who might know about accelerated aging, an "ELISA kit" is an "Enzyme-Linked Immunosorbent Assay" (ELISA). They measure antibody counts.) SteveBaker (talk) 15:34, 28 August 2008 (UTC)
No, you're right Steve, I was talking about the kit's lifespan. An industry expert said that they require at least have a verifiable 1-year shelf life. This gave us a "no go" signal for a university- invented ELISA kit as we don't have data regarding its shelf life. I was thinking of doing an accelerated aging test to this kit so they can be convinced to manufacture it. But judging from Steve's post, I think it's better to do a 1-year waiting game (my pity goes to the undergrad who unluckily gets this thesis).--Lenticel09:55, 29 August 2008 (UTC)
Sliding filament theory
How many ATP molecules are consumed per cycle of "sliding"? I believe it to be one, but would like a confirmation.
When I'd learnt about it (around 6 years back), it was believed that the ATP molecule was required to detach the "flexed" myosin head from actin. But, the the 20th (2001) edition of Ganong's Review of Medical Physiology said that there was a controversy surrounding the exact stage at which the ATP bound to the myosin head, and the 22nd edition says that ATP bindng is required for the actual flexion of myosin head as well as for detachment. The advantage of the previous theory was that it so beautifully accounted for rigor mortis (flexed myosin heads required ATP to detach, which gets depleted, so the muscle remains contracted). Now, rigor mortis is believed to be due to accumulation of calcium ions in the cytosol as its sequestration back into the sarcoplasmic reticulum also requires ATP.
So, it would be nice if some one could comment on this confusion, and I'd appreciate it further if some updated source is cited, too.
At the end of metaphase, are there 46 or 23 pairs of sister chromatids at the equator (in humans)? I feel it should be 46 pairs (homologous chromosomes will not be attached to each other), but am not sure of this assumption. My idea is that in the new daughter cells, there have to be 46 chrmosomes in all, so at metaphase, there should be 46 pairs of ("to-be-chromosomes") chromatids. The doubt is if the homologous chromosomes (of respecitve paternal and maternal origin) are also attached to each other by the kinetochore/centromere, or if they (pairs of homologous chromatids) remain widely separated?
If I'm sounding confusing (as am myself confused), let me give an example. Let's say, chromosome 7. A diploid cell is suppose to have a maternal and a paternal copy each of chromosome 7. Now, no doubt during metaphase two copies each of a maternal and paternal chromosomes would be present, which can be for convenience called maternal chromatids 7 (2 copies attached to each other) and paternal chromatids 7 (2 copies attached to each other), 4 copies of chromosome 7 in all. Now there are two possibilities—situation 1: the two pairs of chromatids remain attached to each other, in which case we'll get 23 copies of "chromatid-complexes" at the equator, and the other possibility—situation 2: the two pairs remain detached, meaning the two copies of maternal chromatids (which are attached to each other), remain separate from two copies of paternal chromatids (which are also attached to each other), in which case we'll get 46 "chromatid-complexes" at the equator. So, my doubt is which situation, 1 or 2, describes the event correctly?
Thanks. Well, I understood your answer that the homologous chromosomes are not attached to each other. It'd be nice if you could cite some source to support this. If you're finding the doubt too bothersome to understand, could you please go through specifically the second paragraph in which I've ginen an example to explain my doubt? —KetanPanchal09:57, 28 August 2008 (UTC)
In reference desk answers, it is considered sufficient to refer you to Misplaced Pages articles rather than to supply hard references. If you click through to the articles that User:Dragons flight linked to - you'll find references to the facts therein. SteveBaker (talk) 15:20, 28 August 2008 (UTC)
That's assuming the condition is real and not a hoax, of course. Perhaps I'm too suspicious, but considering that the only person named in the article is some cat owner "only identified as Feng" and she wasn't talking to the Telegraph, but to a local paper (meaning that the reporter who wrote this up is very unlikely to have personally confirmed the existence of these cats), and the research into this has allegedly been conducted by unnamed scientists and equally unnamed "veterinary experts", and that even the place this happened in is only identified as "Sichuan province", an area roughly the size of Spain, my first thought certainly isn't "gee, that that winged cat story sounds really, really believable". The picture's lack of detail doesn't help things any. Not that I'd be shocked to hear that it's true, but you don't exactly get a plethora of reliable sources and convincing details from the article. -- Captain Disdain (talk) 18:13, 28 August 2008 (UTC)
IF we believe the report (and maybe we don't) - the claim is that this only happens to male cats. That pretty much ensures it's a genetic thing. But these "wings" develop later in life - they aren't born with them - and we're told that a whole bunch of male cats started growing them at more or less the same time. That somewhat suggests it's not genetic. SteveBaker (talk) 19:42, 28 August 2008 (UTC)
Another problem is that the picture clearly shows a calico, which is nearly always female (a male calico would have to be XXY). --Joelmills (talk) 22:25, 28 August 2008 (UTC)
That winged cat article of ours is pretty interesting in that it claims that this whole thing with this Feng and her cat actually happened in 2007, in another province. That doesn't improve the original poster's news item's credibility (but of course, that may merely be a case of bad journalism by the Telegraph). The citations in the article are pretty vague, so they don't help us a whole lot on this particular case -- or, actually, at all, because the latest reference listed appears to be from 2003... But wait! The External links section includes a link to this unfortunately undated article, which also includes a little better picture, the same one as in the Fortean Times (always the most credible of sources!) article -- though unfortunately that one's pretty much worthless as proof; the bits she's holding up could be glued on, or even completely unattached; there's just no way to tell from the picture. That link was added on May 26, 2007, well over a year ago. All in all, this strikes me as a case where it's kind of hard to know whether there's any truth to the story at all, let alone what the cause of these "wings" in this instance is. -- Captain Disdain (talk) 21:28, 28 August 2008 (UTC)
Who would win?
OK, I know this may seem like a soapbox question or a joke, but I am serious and would like to keep the debate with scientific arguments: Who would win a fight to death, a fit adult man or a fit adult Velociraptor?.
Velociraptor is perceived by the general public as one of the most lethal dinosaurs ever. Yet, the fact that it is only turkey-sized, and the fact that The Truth About Killer Dinosaurs says that the dino's infamous claw was more a grappling device than a killer weapon, make me doubt. A human could break a Velociraptor's neck, or could sent it reeling with powerful kicks to vital organs... But the dino would still have its sharp teeth.
So... More or less, what are the scientific arguments for and against a human beating a Velociraptor in a fight to death? Leptictidium (mt) 16:15, 28 August 2008 (UTC)
I don't know much about dinosaurs, but I think it's reasonable to assume that they couldn't be more deadly than anything currently alive of about the same size, after allowing for the hunting-out we've done of large predators. That wouldn't apply to something the size of a turkey. So, it'd probably be comparable to a wildcat or small wolf, or maybe one of the more dangerous reptiles like the komodo dragon. A fit human could, with some damage, take out any of those, so probably could beat a small dinosaur. Black Carrot (talk) 19:53, 28 August 2008 (UTC)
Actual Velociraptor...not "Jurassic Park thing"
With the aid of a firearm, I'd assume that human's could essentially kill any dinosaur that previously existed. Without firearms, I don't know. Velociraptors were fast and had incredibly sharp claws. It's essentially like a dog running up, jumping at you, knocking you down and then slashing you to pieces. Who would win that? —Cyclonenim (talk · contribs · email) 20:05, 28 August 2008 (UTC)
If it helps modern humans sleep better to belittle dinosaurs equipped with formidable claws and fangs, so be it. I'd bet on the raptor. He also might not come to the fight alone. He might choose his battles so as to have numeric advantage. Edison2 (talk) 05:06, 29 August 2008 (UTC)
The thing only just barely reached up to you knees...it's like a small dog. Please! Jurrassic Park has a lot to answer for! SteveBaker (talk) 20:39, 31 August 2008 (UTC)
More along the lines of what Michael Crichton was thinking...
I've always had an interest in cryptozoology and the interesting creatures that come up. Recently, I was watching a program about some "researchers" who were looking for a new species of giant octopus (octopus gigantius with a tentacle span of 200 feet) in the Pugent Sound, Washington area. Their rationale was that since the Sound is so deep, it could easily hide one of these creatures. No surprise: thery found absolutely no evidence!
My question is this: from a biological point of view, is it POSSIBLE for such a creature to exist and what would the parameters be (i.e food supply, effects of the water pressure at depths of 700 feet or so, longevity, etc.)? —Preceding unsigned comment added by 216.154.16.106 (talk) 16:30, 28 August 2008 (UTC)
The problem is that it's not enough for the Puget Sound to have room to hide one of these creatures. There doesn't appear to be any means for the creatures to sneak into and out of the sound without being noticed - a 200' creature in water that's 175 feet deep in such a busy shipping area is going to get noticed. If they aren't sneaking in and out then there would have to be room for an entire breeding colony with sufficient genetic diversity to suvive...maybe a hundred octupi that size...plus a food supply large enough to support such a vast colony. So, I'd say no. SteveBaker (talk) 23:59, 28 August 2008 (UTC)
humidification operation
air at atmospheric pressure has a wet bulb temperature of 80 degree Fahrenheit and a dry bulb temperature of 150 degree Fahrenheit. 1.estimate the humidity,molal humidity, relative humidity and dew point of the air.
2.calculate the weight of water in 100 cubic feet of entering air.
3.the air is heated to 150 degree Fahrenheit and cooled adiabatically to 115 degree Fahrenheit.estimate the humidity,percentage saturation and dew point of the air41.205.166.241 (talk) 16:53, 28 August 2008 (UTC)
Welcome to the Misplaced Pages Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Thank you. -- kainaw™16:55, 28 August 2008 (UTC)
Please refer the questioner to the relevant articles, rather than merely scolding him for asking you to answer his homework, That is what a Real Life Reference Librarian would do. That is what Ref Desk volunteers should do. So to the questioner, this is an encyclopedia. Please read the Wikipdeia articles Relative humidity , Psychrometrics , Dry-bulb temperature , Wet-bulb temperature and Dew point. Feel free to ask a further question if needed. Thanks. Edison2 (talk) 04:57, 29 August 2008 (UTC)
Sure, although it should be noted that virtually anything is possible within the realm of imagination. Should both prove to be real, however, it's entirely reasonable to expect them to be related. — Lomn17:13, 28 August 2008 (UTC)
Hi. Well, that depends on what you mean by "similar". A book on primate cryptids notes categorises bigfoot into "neo-giants" (human-like footprints) and yeti into "unknown pongids" (big toe out at an angle). This suggests that if they exist then yeti might be more closely related to the skunk ape. Thanks. ~AH117:38, 28 August 2008 (UTC)
So how many 9 ft tall humans do you know who go prancing about in gorilla suits in the forest of North America or the frozen heights of Tibet? —Preceding unsigned comment added by 79.76.200.98 (talk) 01:26, 29 August 2008 (UTC)
They both appear to be Primates, so if they're both real they're going to be pretty similar. How similar are you looking for (Do you consider a Chimp similar to a Gorilla?). There are arguments either way. They have some pretty different territories though, the most recently they could have possibly interbred would be the last Ice Age. Still, that's not that long ago for a primate, and they both seem to share the startling evolutionary adaptation of being completely impossible to prove the existence of, so perhaps they're even the same species separated from each other for thousands of years. The only real way to know for sure is in-detail genetic tests or seeing if they're capable of interbreeding. When you catch one of each let us know. APL (talk) 02:49, 29 August 2008 (UTC)
The Yeti article states that “The Yeti can be considered a Himalayan parallel to Bigfoot (Sasquatch).” The article is even more specific: it says “Believers in its existence contend that such an animal, or close relatives of it, may be found around the world under different regional names, such as the Yeti of Tibet and Nepal, …” So yes, they are similar species. – b_jonas20:02, 30 August 2008 (UTC)
spider web sacs in trees?
Hi. Recently I came upon some spider-web like sacs in trees. The trees were all decidous, and I live in Southern Ontario. The material was likely spider webbing, but it also resembled thisn plastic bags or fine mesh nets. There were roughly 2 - 30 cubic ft in volume, and roughly 2 - 10 m off the ground. There was also some dark plant like material in the "webs", which were roughly elliptoidical, which might have been leaves, bark, dirt, etc. I didn't see any spiders present, but they reminded me of birds' nests, except larger and nearly transparent. I also came upon spider silk on another low-lying tree close to another one which had one of these web sacs. Any idea what it might be? Is there such thing as a "tree spider" (no article), and if there is, do they exist in Ontario and how large are they? Or, could this have been made by something else? Thanks. ~AH117:33, 28 August 2008 (UTC)
If you are able to check those trees again, you may find some or all of the leaves eaten, or perhaps find caterpillars busy eating the leaves. Wanderer57 (talk) 18:44, 28 August 2008 (UTC)
"Animal" is also a clue given in the quiz game Twenty Questions. In that game, "animal" generally means an animal or something created from some part of an animal. Eg, a leather saddle is "animal", a shark's tooth is "animal", a ivory carving is "animal", a wooden carving is "vegetable", and a meershaum carving is "mineral". Wanderer57 (talk) 19:00, 28 August 2008 (UTC)
PLEASE I WILL LIKE TO GET MORE INFORMATION ABOUT (THE ROLE OF MICROORGANISMS IN THE PRODUCTION OF ANTIBIOTICS). FOR MY PROJECT.
THANKS —Preceding unsigned comment added by 80.250.32.5 (talk) 19:35, 28 August 2008 (UTC)
First, STOP SHOUTING (using capital letters), it's considered rude on the internet.
Ages ago, there were these little cotton wool like things (about the size of the cotton on a cotton bud, only more spherical) in about groups of four and just about smaller than a pea, outside in a little crack by the front communal door. I assumed them to be spiders eggs, only they were a little big. Any idea what they are? I'm in the UK. Thanks, 86.148.47.145 (talk) 21:29, 28 August 2008 (UTC)
At a certain point of its development, if you carefully slit it open, you might see tiny spiders running around. At a later stage of development, spiders of some species can extrude strands of web which act like kites to carry them to remote locations, where by virtue of their small size they can enter a dwelling through the most minute cracks. Edison2 (talk) 04:53, 29 August 2008 (UTC)
There was no problem, because the paper was still readable once it was extracted from the infant's mouth, dried out a bit and sorted back to the pages it had been torn from. Edison2 (talk) 20:57, 29 August 2008 (UTC)
When my wife was in vet school, her cat ate the budget for the Animal Behavior Club. That was a tough one to explain. -- Coneslayer (talk) 11:43, 29 August 2008 (UTC)
My Peach-faced Lovebird once shredded my homework. She worked from the top of the paper down, chewing it into little strips. Luckily, there was enough of it left to show the teacher the next day, so I was given the benefit of the doubt... --Kurt Shaped Box (talk) 23:09, 29 August 2008 (UTC)
has our buddy broke his leg?????
This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.
This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~ Algebraist22:02, 28 August 2008 (UTC)
Conflicting information on effects of neutering dogs
There is a conflict of info on the effects of neutering of dogs with respect to the likelihood of contracting prostrate cancer. The article on castration directly contradicts the article on neutering. —Preceding unsigned comment added by 202.59.164.121 (talk) 23:30, 28 August 2008 (UTC)
I guarantee that neutering has no effect whatsoever on prostrate cancer. Prostate cancer is another matter, and I have no information about its incidence in dogs. — OtherDave (talk) 23:41, 28 August 2008 (UTC)
Common misconception. Neutering a dog does about double the risk of prostate cancer. I didn't know the castration article was covering this, but I'll fix it. --Joelmills (talk) 02:11, 30 August 2008 (UTC)
Just checked the castration article - it actually said it reduces the incidence of prostate disease. This is true, since benign prostatic hypertrophy is much more common in dogs than prostate cancer, and neutering does eliminate the risk of it. I did clarify the point about cancer in the article. --Joelmills (talk) 02:19, 30 August 2008 (UTC)
I have seen motorcycles turn, not by turning their steering wheel, but by leaning their bikes towards the ground. Why does this work. I've draw a free-body diagram, but I can't find the centripetal force. —Preceding unsigned comment added by 65.92.231.82 (talk) 00:27, 29 August 2008 (UTC)
I think it's because motorcycles are fast enough that you need to lean significantly even with a wide turning radius. In short, the amount you lean the bike is noticeable, but the amount you turn the front wheel isn't. In addition, do the the way bikes are built, leaning causes the front wheel to turn. — DanielLC00:52, 29 August 2008 (UTC)
In response to DanielLC, I'm sure it's a centripetal force causing the acceleration, and I'm also sure it's firction. I checked the article Bicycle and motorcycle dynamics, specifically turning, but they didn't why the friction force appears, or the derivation of the formula. —Preceding unsigned comment added by 65.92.231.82 (talk) 01:24, 29 August 2008 (UTC)
Friction provides centripetal force on a flat corner. On a banked corner, centripetal force is a combination of horizontal components of friction and normal force. Gandalf61 (talk) 10:22, 29 August 2008 (UTC)
Regardless of safety, can clorox (or similar) bleach effectively lighten hair? As an oxidizer, I would think that it would be mightily effective. Please also describe potential side effects of this procedure. Thank you. Kenjibeast (talk) 01:05, 29 August 2008 (UTC)
(from accidental experience) Yes, it will alter the color of hair. No, it will not make it blond. Yes, it will turn it a weird copper-green color. No, it will not look healthy. Yes, it will become thin and stiff and break when you try to brush it. No, it will not feel good. Yes, it will burn and leave a permanent thinning-hair spot on the back of your head that is still visible after 20 years. -- kainaw™01:35, 29 August 2008 (UTC)
Concur from the memory of the appearance of a friend's hair and the state of his scalp after he tried to bleach his hair using toilet bleach. It started falling out in clumps the day after - and the sores, they did weep. Not the best idea. --Kurt Shaped Box (talk) 19:27, 29 August 2008 (UTC)
Under Limits of Perception, http://en.wikipedia.org/Psychoacoustics it says, "The human ear can nominally hear sounds in the range 20 Hz to 20,000 Hz (20 kHz). This upper limit tends to decrease with age, most adults being unable to hear above 16 kHz." In fact, hearing ability in the entire upper audio range typically tends to decrease as a person ages. I cannot find an authoritative source for that statement, but I am sure there are authoritative sources. Andme2 (talk) 04:32, 29 August 2008 (UTC)
I don't think that was exactly the question. Yes, the upper audible limit deteriorates markedly with age but the questioner is instead asking is the human ability to reproduce an exact frequency age related. For instance, when an orchestra is tuning up before the start of a concert, the lead violin will play a note A 440Hz for the rest of the violins to reference to. There are no frets on a violin - the note is placed at the correct frequency entirely by ear. It is essential that the lead violin has perfect pitch to accurately reproduce the required note. 440Hz is a relatively low frequency, well below the normal age related deterioration. If the player has lost the ability to hear this frequency then he/she has substantially gone deaf. I don't know the answer to the original question but my guess is that perfect pitch is not related to the physiology of the ear and that deterioration in the function of the ear (provided it has not gone too far) does not affect this ability. I think that this rather wonderful skill is more likely an ability of the brain. SpinningSpark06:16, 29 August 2008 (UTC)
It's almost always the oboe that sets the orchestra's pitch, and not a violin, precisely because the oboe's pitch is more or less unalterable by the player once it's established, while the same is not true, as you point out, for the strings. - Nunh-huh06:59, 29 August 2008 (UTC)
The Mosquito, as well as the ringtone derived from it, were based on this assumption. As for references, I found this webpage from Hypertextbook.com, which claims:
"The range of hearing for a healthy young person is 20 to 20,000 hertz. The hearing range of humans gets worse with age. People lose the ability to hear sounds of high frequency as they get older. The highest frequency that a normal middle-aged adult can hear is only 12-14 kilohertz."
and
"The normal range of hearing for a healthy young person is 20 to 20,000 Hz; hearing deteriorates with age "
I once used Frequency Generator to test whether the maximum frequency decreases with age, and found the correlation was startlingly strong; a sound that one person considered unbearably loud was inaudible to a person only several years older. --Bowlhover (talk) 06:29, 29 August 2008 (UTC)
I don't have a source at hand at the moment, but I think that statistically speaking, on average the upper limit of hearing decreasing with age. As for whether the ability to perceive pitch changes at any frequency, including the mid-range, decreasing with age, I haven't seen anything to suggest that. It could be, but there are plenty of elderly musicians who play instruments such as the violin that require sensitive pitch perception. In any case it would have something to do with the inner ear's hair cells. It wouldn't surprise me if over time there is some kind of loss there. Pfly (talk) 07:22, 30 August 2008 (UTC)
I remember reading somewhere that Benjamin Britten had complained of standard pitch seeming to grow sharper as he aged. Google throws up an article about an NPR program which bears that out: "Our results clearly show that as people get older, they are perceiving things sharper than when they are younger," William Avery (talk) 15:07, 30 August 2008 (UTC)
I don't know how this relates to perceived musical sharpness, but the perceived sound of musical instruments becomes somewhat different as a person ages. All musical instruments produce complex (non-sine wave) tones. The sensitivity to higher pitches typically decreases as a person ages. Therefore an older person hears a less complex tone, somewhat closer to a sine wave. This would occur even at low fundamental frequencies. Also, of course, the perceived loudness of pitches with a high fundamental frequency decreases - that is a second effect. Andme2 (talk) 06:34, 31 August 2008 (UTC)
Clearly they propagate nicely along the interface between water and the air above it. It seems that to propagate within a body of liquid, there would have to be an interface within the liquid, such as a layer of fresh water above a layer of salt water where a river flows into the ocean, or the interface between oil and water. Longitudinal waves propagate nicely within a homogeneous liquid. Edison2 (talk) 04:46, 29 August 2008 (UTC)
The liquid has no strength or stiffness. It does not resist movement like a solid, so there is no restoring force to make a wave. However the liquid does resist compression, so you can get a compression wave. Graeme Bartlett (talk) 05:55, 29 August 2008 (UTC)
Why would it work in gasses but not liquids? The only difference is that gasses compress when under pressure. — DanielLC17:22, 30 August 2008 (UTC)
I heard of on- and off-pills used by the military so the pilots are guaranteed awake for combat and have a sound sleep afterwards. Can't find any reference on the net right now, though. Does anybody know about that and why it's allowed? If it is allowed, can I have access even if I'm not at war with anybody? 93.132.129.229 (talk) 19:53, 29 August 2008 (UTC)
The USAF (and probably other air forces) prescribe amphetamines to some of their pilots (e.g. B2 and B52 operations to Iraq based in the US and the UK respectively) where the pilots had to stay awake for long periods of time (reference). They do this under the control of a flight surgeon (a doctor), who is supposed to make sure their use is appropriate and the side effects managed. You may wish to consider whether you're comfortable with someone taking a drug which has side effects including nervousness, irritability, over stimulation, restlessness, euphoria, and feelings of suspicion and paranoia (reference) is a fit person to be in charge of weapons and aircraft. Lots of things are legal for the military to have (machine guns, tanks, nuclear armed submarines) which are nevertheless illegal for ordinary people. -- Finlay McWalter | Talk20:03, 29 August 2008 (UTC)
I see, so this is because they have machine guns, tanks, nuclear armed submarines and so on, so no one can effectively deny those rights to them.93.132.129.229 (talk) 20:32, 29 August 2008 (UTC)
No! That's completely untrue - and I'm very sure you know that. They have the right to use these drugs AND they have the right to use tanks, etc because the law/constitution of the country (rightly or wrongly) permits it. Your take on it would suggest that they demand the drugs and get them because they're heavily armed...that's a totally ridiculous point of view. Correlation does not imply causation. SteveBaker (talk) 22:06, 29 August 2008 (UTC)
SteveBaker: yes, I know that it is totally ridiculous, but I really wonder why. Why does a government deny psychoactive substances to their subjects (probably because they could do dangerous things while druged, like drunken driving) and at the same time allow it to those in charge of have machine guns, tanks, nuclear armed submarines? 93.132.129.229 (talk) 23:02, 29 August 2008 (UTC)
The stimulants given to military members are available to the US public by prescription. You just have to convince a doctor that you have a need for them. Combat pilots are given then on the theory that they need to stay alert or else they might die. Presumably if you had an equally compelling need (like combating certain sleep disorders), then you could use them too. In neither case are they simply given out for experimentation though. Dragons flight (talk) 23:10, 29 August 2008 (UTC)
These things are given to people rarely and under medical supervision. The people involved are generally pretty fit (mentally and physically) - and it's done for reasons of "national security". That's nothing like a typically unfit drug addict taking them unsupervised - getting them in probably impure form from who-knows-what source - and taking them far too often - for reasons that are deleterious to society in general - not beneficial. SteveBaker (talk) 00:47, 30 August 2008 (UTC)
Your argument is quite good. Actually, I would be more interested in off-pills as I have a longer than circadian rhythm. Do you think I would get a prescription in your country? 93.132.129.229 (talk) 23:19, 29 August 2008 (UTC)
Then there's nodoze tablets, which are available at most drug stores. They are taken voluntarily and without prescription. Andme2 (talk) —Preceding undated comment was added at 22:46, 30 August 2008 (UTC)
...yes - but active ingradient in NoDoz is caffeine which is not exactly a controlled drug! As I recall, they have about the same amount of the stuff as two cups of good, strong coffee! SteveBaker (talk) 15:32, 31 August 2008 (UTC)
Emit Visible Light by Radio Transmitter
According to article Electromagnetic spectrum, radio waves and visible lights are both electromagnetic waves. The only difference I can see between them is they have different frequencies. So is it possible for a radio transmitter to emit visible light if the radio transmitter can emit radio wave of extremely high frequency? - Justin545 (talk) 09:35, 29 August 2008 (UTC)
In principle, yes. In practice, the required frequencies are unobtainable in any system that would resemble a normal radio transmitter. Dragons flight (talk) 10:10, 29 August 2008 (UTC)
Yes, if you use the right equipment. Electromagnetic radiation in radio transmitters is an oscillating field caused by an oscillating current of electrons. That is, we accelerate the electrons back and forth. It's the acceleration in itself that is the trick and another word for electromagnetic radiation caused by the acceleration of a charged particle is Bremsstrahlung. File:Synchrotron radiation.jpgInvisible X-rays produced by a synchrotron emerges, ionizing the air and producing blue light as a result. With a current in a wire we only manage radio waves, but when sending the particles round in circles in a vacuum it's a different matter. This is called Synchrotron radiation and you can indeed achieve frequencies from radio waves, into and past the visible spectrum and into ultraviolet and x-rays. EverGreg (talk) 18:31, 29 August 2008 (UTC)
It's a matter of frequency, certainly - but it's easier to think in terms of wavelengths. (Frequency and wavelengths are opposite sides of the same coin here). So let's look at how long the actual waves are:
TV and FM radio waves are around a meter long...AM radio is out at 300 meters maybe.
Radar systems and microwave ovens operate at - between 10cm and 1cm wavelengths (there is an elegant experiment involving chocolate chips that lets you measure that in your microwave oven!)
Waves smaller than a centimeter are called "millimeter band" and are used for short, precise, distance measurements - short range radar - such as the 'reversing sensors' that some cars have.
Millimeter waves at 1mm are right next to the "far" infrared part of the spectrum - which extends down to "near" infrared at a millionth of a meter. For some reason, we call infrared "light" - not "radio" or "radar" - but it's all the same stuff - it's just a matter of wavelength.
Infrared light is right next to visible red light in the spectrum. Visible light waves are around half of a millionth of a meter long.
So "radio" waves are about a million times bigger than "light" waves - but they are EXACTLY the same phenomenon - it's just a matter of frequency and wavelength.
To answer the question then: To operate efficiently, Radio antennae need to be about a wavelength long. The antenna on your car is about a meter long - so it can pick up radio waves. The little stubby antenna on your cellphone reflects the fact that it's operating at wavelengths of a few centimeters. So the "antenna" for visible light would be less than a millionth of a meter long! But the systems that make radio transmitters work efficiently simply aren't designed to put out waves that small. The other side of the coin - the "frequency" is to do with how fast the electronics have to oscillate to make waves of the appropriate length. To make radio waves, you only have to oscillate a few million times a second. This is easy to engineer - there are crystals that oscillate at those rates - also you can build all sorts of circuits that'll do that. But as the frequencies get higher, it gets harder and harder to make systems that'll vibrate fast enough. We have computers that run at frequencies as high as 3 to 4 GHz - that's barely as fast as microwaves. Making electronics oscillate faster than that starts to get tough because the size of the electronics has to be small enough to let the electrons get across the circuit in a small enough amount of time. By the time you get into the infrared region, you need to have atoms oscillating - not big things like crystals. So we can't make a 'crystal radio' oscillate anywhere near fast enough to make light. We make infrared by stimulating atoms to vibrate - similarly with visible light. So while light and radio are "the same thing", in practice, it's not just a matter of retuning the transmitter and reducing the size of the antenna to convert a radio into a lightbulb. SteveBaker (talk) 19:10, 29 August 2008 (UTC)
That would be the distinction between a Marconi antenna (archaic nomenclature) and a half-wave dipole antenna; but in modern antenna theory, there are ten million variations on the theme, so "optimal efficiency" may be traded for directionality, bandwidth, narrow-band frequency-specific coupling effects, active control, etc. Nimur (talk) 21:32, 29 August 2008 (UTC)
Yes - and in any case, it's a pretty rough requirement. For the purposes of answering this question we don't need to get into horrible details of the 'black art' of antenna design! You can pick up a perfectly good signal over a wide range of radio or TV channels with a fixed size antenna of roughly a wavelength...but ten times the wavelength or a tenth the wavelength doesn't work nearly as well. The point is that a radio transmitter that's set up with an antenna suitable for AM radio won't make light (which would require an antenna a MILLIONTH of that length). SteveBaker (talk) 21:54, 29 August 2008 (UTC)
Two images of the sky over the HAARPGakona Facility using the NRL-cooled CCD imager at 557.7 nm. The field of view is approximately 38°. The left-hand image shows the background star field with the HF transmitter off. The right-hand image was taken 63 seconds later with the HF transmitter on. Structure is evident in the emission region.
There have been some experiments in radio-induced airglow or (artificial) aurora, such as this IEEE publication on work performed at the HAARP facility. This is an indirect effect and requires certain ionospheric conditions. The beam is a "High Frequency" radiowave, meaning ~5 MHz, and it is through ionspheric interactions that this energy can be converted in to optically observable light. Nimur (talk) 21:30, 29 August 2008 (UTC)
Here's a link to the Navy's description of optical emissions: . "The exciting result was that by pointing the HF beam directly along a geomagnetic field line, artificial emissions of greater than 200 Rayleighs (R) at 630.0 nm and greater than 50 R at 557.7 nm could be produced. This intensity was nearly an order of magnitude larger than that produced by heating directly overhead." Nimur (talk) 21:40, 29 August 2008 (UTC)
Let's not confuse the OP though. HAARP and the Navy work are NOT a matter of retuning a radio transmitter to broadcast up in the PetaHz (10Hz) range! We have no idea how to make a "radio transmitter" that works at such spectacularly high frequencies. The things you are discussing are systems causing secondary effects in the atmosphere. That's not at all what the OP is asking - so let's not muddy the waters! SteveBaker (talk) 22:01, 29 August 2008 (UTC)
I only half-agree. The generation of optical frequencies is a special class of frequency mixing, where the frequency mixer just happens to be a particular natural phenomena / atomic property. Though this effect occurs at high altitude, it's not so very different from using a diode mixer on a circuit board, where a different other atomic effect is responsible for signal conditioning suitable for changing frequency. Nimur (talk) 22:10, 29 August 2008 (UTC)
As you increase in frequency the techniques of producing the oscillations produces less and less power, and amplifiers produce less and less gain until you reach the technology limit around one terahertz. Your antennas will have to be on the same scale as light waves, much bigger than atoms and molecules, and potentially on the same scale as silicon chip technology. But really the problem is generating the arbitrary waveform at the required frequency. As you get to light frequencies the quantization in to photons also takes effect, raising your noise floor. Graeme Bartlett (talk) 08:54, 30 August 2008 (UTC)
Bat vs bird populations
White nose syndrome has had a crippling effect on bats here in the Northeast US. Add to that the heavy rainfall in June and July. It looks like these factors have caused a huge increase in the number of mosquitos in my yard. I normally don't use bug dope but while mowing the lawn just now, I was getting eaten alive! So, how long will it take for the bug-eating bird population to kind of fill the gap that the bats have left? Can I expect a change this year or do I have to wait till next year? Dismas|17:45, 29 August 2008 (UTC)
Wow... It's so quiet, you can hear them buzzing in your ears... Seriously, there aren't any ornithologists in the house? Dismas|00:23, 31 August 2008 (UTC)
The leaf you see here is covered with round green nodules that look rather like tiny apples. Does it normally look like that? Or is it evidence of some sort of parasite or leaf disease or something else?
Not be exactly with this leaf but quite similar with some mango leaves in my garden. There are some kind of insects implant their eggs in the leaves, making leaf tissue to swell up and the larvae live inside....Ninjaw —Preceding unsigned comment added by 124.120.215.21 (talk) 14:57, 31 August 2008 (UTC)
Freaks
I knew a girl with an additional vertebra in her neck. I knew someone whose uncle had three kidneys. My own mother grew a third tooth in her early 50th. I heard of people who have the heart not only in the right place but also on the right side, instead of the left. All those people are healthy and without examination undistinguishable from those people the anatomy books write about. How common are those uncommon features the like described above? What else can there be? 93.132.129.229 (talk) 19:15, 29 August 2008 (UTC)
It's possible to have an extra one (or an extra set) of many body parts, but often the extra parts are not fully formed. The supernumerary nipple article says the incidence for nipples is 1 in 18 people, but an extra one is often mistaken for a mole. The article on polydactyly (extra fingers and toes) gives an incidence of 1 in 500, but again, most of these are not fully developed. --Anonymous, 19:50, August 29, 2008.
I'm intrigued...are you left or right handed? And do you think you conform to the stereotype for whichever handed you are? (Wondering whether your brain is also left/right flipped). SteveBaker (talk) 21:40, 29 August 2008 (UTC)
There's a vast range of asymptomatic variation from the 'normal' human body. Perhaps the biggest culprit is the circulatory system, where just about any variation on a theme is possible. Check out the entry in Gray's Anatomy on the aortic arch. Normally three blood vessels (the innominate, the left common carotid, and the left subclavian) branch off the aortic arch. However, variations have been observed with but a single branch and with as many as six branches. (If you go through the 1918 Gray's, you'll find that a large number of sections contain information about 'Peculiarities'.)
This much more recent article notes that external landmarks are unreliable in locating the internal jugular vein in about a quarter of all patients. Moving away from the circulatory system, here's an article about a patient who was missing the upper lobe of his right lung (the rest of the lung just expands to fill the space; he showed no symptoms). In somewhere from 0.1 to 0.7% of people, the gallbladder is beneath the left liver: . TenOfAllTrades(talk) 01:41, 30 August 2008 (UTC)
Standard Units for Quantities of Lumber
Can someone please tell me what is the "standard unit" used for quantities of lumber?
My question was triggered by a note taken from Misplaced Pages:Manual of Style.
"if the text contains an obscure use of units (e.g., five million board feet of lumber), annotate it with a footnote that provides standard modern units, rather than changing the text of the quotation."
"Board feet" estimates the recoverable sawn lumber based on the size of the smaller end of the log, and "log rules" based on old growth timber with 1/4 inch saw kerfs do not accurately estimate the board feet of dimensional lumber recovered with modern thin kerf saws and computerized sawing. The delivered dimensions of nominal 2 x 4 , 2 x 10 inch etc lumber was made smaller in the 1960s, further changing the board feet contained in a tree. A modern 2x4 is 1.5 inches by 3.5 inches, or .656 actual board foot per nominal board foot. The "board feet" in a log changes with definition of a 2x4 and with sawing technology. The cubic meters includes the "total volume of sound wood" including dimensional lumber, chips and sawdust . It is not at all as direct as converting feet to meters. The 1950 conversion was 4.53 m per thousand board feet, but conversion factors up to 6.7 m have been found to apply. Edison2 (talk) 21:12, 29 August 2008 (UTC)
Protons will be taken up by bases. In fact a loose proton will react with almost any other substance, (even including helium to make helium hydride or hydrogen to make H3+) so a proton is not hard to add to something, it is extremely reactive! Neutrons are easily absorbed in many nuclei. Electrons are very light, but yet not many negative ions are stable. Graeme Bartlett (talk) 09:00, 30 August 2008 (UTC)
Ayacop, that isn't equivalent. They're held by different forces. The protons are actually repulsed by the force that holds the electrons in.
Graeme, You're talking about adding and removing protons from a molecule. 122 is talking about adding it to an atom. If you added a proton atomically to a hydrogen atom, you'd get Helium-2, which would immediately decay into Deuterium, and emit a beta particle. This is nuclear fusion, and is very different, and far more difficult, than if you just added a proton molecularly and made H2+. — DanielLC15:58, 30 August 2008 (UTC)
In the case of the s orbitals, it's because the nucleus is so tiny. The waveform of the electron can collapse anywhere in the s orbital, and is more likely to do so closer to the nucleus, but it's still not likely enough to make the electrons hit such a small target. The Pauli Exclusion Principle just explains why not all of the electrons are in the smallest orbital, and doesn't have much to do with the question. — DanielLC16:12, 31 August 2008 (UTC)
yes, the blood has its circulation rate reduced in the cold skin so that it does not lose heat. When the blood has oxygen consumed it changes colour from bright red to a dull red or purple. Combined with the bluish colour of empty skin it can look purple. Graeme Bartlett (talk) 09:04, 30 August 2008 (UTC)
I was just wondering how do you determine if a moleucle is optically active and why (or explaining why it is/isn't optically active). I know if a molecule has symmetry (i.e. it is achiral) it is not optically active, also, if a molecule does not have a chiral carbon it too is not optically active. But how do i determine if something like 2-bromopentane or 2-bromo-3-methylpentane (both formed from an addition reaction) is optically active?
If a molecule is not symmetric, it is optically active. So 2-bromopropane is optically active (and you can look up its specific rotation in the usual literature sources, maybe even on wikipedia). Now whether a particular sample of the compound has optical activity, that takes a physical measurement in a polarimeter. If you have a 50/50 mixture of both enantiomers of a compound, the effect of each will cancel the other and the net rotation will be zero. DMacks (talk) 06:35, 30 August 2008 (UTC)
So does optical activity only depend on the symmetry of a molecule? what if I know that there was a satureated molecule (alkene) and it under went an addition reaction to give me 2-bromopentane ? does the addition reaction tell me anything? Also, does a chiral carbon tell me anything about the optical activity of a molecule? —Preceding unsigned comment added by 122.108.169.75 (talk) 07:04, 30 August 2008 (UTC)
Optical activity does not depend on symmetry, nor on chirality, i.e. asymmetric molecules need not have a specific activity. That's why you see compounds with (+) and (-) labeled in addition to D- and L- specification. See also cryptochirality. Optical activity has to be measured. --Ayacop (talk) 07:17, 30 August 2008 (UTC)
Knowing the optical activity of a sample of a compound that is not symmetric can tell you whether the sample is just a single isomer or is a mixture of stereochemistries. But you would need some (potentially difficult) experiment or (very easy) literature search to figure out which isomer you have based on its optical activity. If you know whether your sample is "optically pure" (i.e., a single enantiomer) vs a racemic mixture, you can know something about the reaction mechanism. DMacks (talk) 07:36, 30 August 2008 (UTC)
My homework question asks to explain why 2-chloropentane is not optically active after it is formed via the addition reaction of pent-1-ene and HCl. the molecule is not chiral, so i thought would be optically active, however, how do i explain it is not? —Preceding unsigned comment added by 122.108.169.75 (talk) 08:22, 30 August 2008 (UTC)
one molecule of 2-chloropentane is chiral, with the number 2 carbon being substituted with hydrogen chlorine methyl and propyl. However which side would the chlorine add on? There is nothing to determine a left or right hand chirality, so both are made. Graeme Bartlett (talk) 09:11, 30 August 2008 (UTC)
Sorry i had meant to say that i know the molecule (2-chloropentane) is not achiral, so being that it is not symmetrical, shouldn't it be optically active? so why isn't it? —Preceding unsigned comment added by 122.108.169.75 (talk) 10:19, 30 August 2008 (UTC)
Because it chops off half the wave, so the output does not resemble the input. This is if you are not using it as an amplitude modulation demodulator. Distortion could arise in demodulcation, because after rectification you filter with a capacitor to remove RF, and this could reduce high frequencies. Graeme Bartlett (talk) 10:13, 30 August 2008 (UTC)
I wonder if there might be more distortion at high frequency because of the time of the rectifier to turn on, and the bias level for turn on, and if this might cause part of the waveform to be clipped off. What is "high frequency" depends on the response of the rectifier, its capacitance and other factors. Edison2 (talk) 19:30, 30 August 2008 (UTC)
According to the section Problems of the article Quantum computer, there are number of practical difficulties in building a quantum computer. One of the major difficulties is keeping the components of the computer in a coherent state. But I still get no sense of what interaction will cause the system to decohere... Is it environmental temperature? some form of noise? CMB? movement of planets, stars? cosmic inflation? Any ideas? Thanks - Justin545 (talk) 11:45, 30 August 2008 (UTC)
What I've usually heard is thermal noise. With say a silicon chip with a quantum dot on it, the chip emits a photon which hits the dot and ruins its superposition. Or the dot could emit a photon that hits the chip. Because of this, proper cooling is a preequisite of many quantum computer blueprints. EverGreg (talk) 15:43, 30 August 2008 (UTC)
Inventing VS Engineering
What exactly is the difference between an inventor and an engineer?
Inventor and engineer should help you differenciate the two. "Engineers are concerned with developing economical and safe solutions to practical problems, by applying mathematics and scientific knowledge while considering technical constraints." and "An inventor is a person who creates or discovers a new method, form, device or other useful means." are the key sentences. —Cyclonenim (talk · contribs · email) 15:46, 30 August 2008 (UTC)
An inventor is someone who had the idea for a device and usually also built it. This someone dosn't have to be an engineer by education. An engineer plan, develop, improve and build devices among other things, but can do their job fine without coming up with a new, original device. There's of course a grey area between an improved and a new device, but you can generally say that the person is an inventor of a new device if he/she can get a patent on it. Also see the term inventor in patent lawEverGreg (talk) 15:53, 30 August 2008 (UTC)
There's no reason an inventor has to be an amateur. And there are plenty of inventors that are not engineers. Consider how many patents are filed each year by physicists, biologists, etc. --98.217.8.46 (talk) 17:22, 30 August 2008 (UTC)
"engineer" is more of a job title. "Inventor" is just a description of something you've already done. APL (talk) 19:09, 30 August 2008 (UTC)
In modern times to call yourself an "engineeer" you need to be a graduate of an accredited college in an engineering curriculum. Experience and the passing of tests are required to be a "Professional engineer" entitled to do consulting for others. Some famous inventors of 19th century electrical gadgets, like Samuel Morse and Alexander Graham Bell knew virtually nothing about electricity and had assistants who understood electricity actually develop and build the invention, based on their idea. Others like Thomas Edison , Nikola Tesla and the Wright Brothers were knowledgable of the intricacies of most of their "inventions" and many qualified as engineers by the standards of the time. An invention is often an improvement on someone's earlier idea that did not quite work in a usable sense, perhaps incorporating other improved technologies. (edited)Edison2 (talk) 19:27, 30 August 2008 (UTC)
When asking this kind of question it's important to tell us what part of the world you live in. Australia, Scotland and Mexico have very different bugs. --Sean19:35, 30 August 2008 (UTC)
I have re-arranged your photo so that it doesn't go into the next section. Right-floating is better for left-to-right languages like English.--antilived00:18, 31 August 2008 (UTC)
Here is an interesting question found on this talk page of this article Udachnaya pipe
"should there be something noted about helicopters unable to fly above the pit? from what has been said or what ive heard, flight above the area causes damage to the helicopter, for example being completely destroyed. i am unsure of the research required, and would appreciate help in this area as with being unable to relocate the source of information, however use of the search query in google may provide sufficient sources of information. thanks."
It seems really impossible that flight over such a thing would result in some mysterious damage to the helicopter. THe person who posted that doesn't seem to have any references or proof of any kind. I'd ignore it until/unless proof is produced. If that person attempts to add that information into the article without some pretty decent references - just revert it. Extraordinary claims require extraordinary evidence. SteveBaker (talk) 21:19, 30 August 2008 (UTC)
I'm thinking something along the lines of very strong, unpredictable updraughts coming up from the pit walls - or perhaps some odd wind vortex effect due to the particular shape of the excavation... --Kurt Shaped Box (talk) 22:05, 30 August 2008 (UTC)
Given the north latitude and the depth, it seems plausible that heat release from the relatively deeper earth might cause turbulent updrafting over the pit. Wind effects are also an interesting possibility. Franamax (talk) 22:25, 30 August 2008 (UTC)
I've heard many, many times before that you can't fly over it with a helicopter, precisely because air currents -- but downdrafts rather than updrafts. I don't know whether that's true or just a story, but in any case, the idea of something that big affecting air currents certainly doesn't sound implausible to me. That said, though, they certainly wouldn't damage the helicopter by themselves, but they would make flying over the pit dangerous and could cause a chopper to crash. An example of these stories can be found at here. -- Captain Disdain (talk) 01:24, 31 August 2008 (UTC)
A halfway decent pilot can cope with updrafts and downdrafts if he/she knows they are likely. Unexpected vertical air motion is kinda dangerous - but if you were flying over a big hole in the ground, you'd be expecting it. Look at the number of helicopter flights they take into an out of the Grand Canyon for example. Any steep slope or cliff-face can be the source of an updraft (if the wind is blowing up the slope) or a downdraft (if it's blowing the other way). Helicopters can operate reasonably close to cliff faces and large buildings without problems. So this can't be true. I wouldn't find it hard to believe that helicopters have crashed there - perhaps even due to some careless piloting and that might be the source of some kind of an urban legend - but I used to make flight simulators for helicopters and we'd simulate all kinds of vertical air motion (both expected and unexpected) that pilots would train for. This pit might make it harder to fly a helicopter over/into - but there is no way it's some kind of magical helicopter crusher that mangles anything that comes nearby - that's just ridiculous. SteveBaker (talk) 15:26, 31 August 2008 (UTC)
I think (well, I've always assumed, anyway) that this has involved situations where the chopper is coming in low and actually going into the pit rather than flying a safe distance above it. That's got no basis on anything other than my imagination, though. -- Captain Disdain (talk) 17:59, 31 August 2008 (UTC)
But even that should be no worse than landing on a helipad on top of a tall building. The up/down-drafts around those things are phenomenal but pilots seem to have no problem sticking landings on them all the time. SteveBaker (talk) 20:15, 31 August 2008 (UTC)
I personally blame the Russian army's experimental EMP howitzer firing range just down the road. The one they haven't told us about yet. --Kurt Shaped Box (talk) 19:27, 31 August 2008 (UTC)
bipolar transistor
Is there a replacement or substitute for the old (1980) bipolar 100mhz, 115 volt, 10 amp, 100 watt complementary PNP/NPN transistors? —Preceding unsigned comment added by 71.100.4.91 (talk) 20:57, 30 August 2008 (UTC)
Are you sure about the 100MHz? Finding a 100W Pdiss, 115v Vcb, 10A Ic transistor with that fT is going to be difficult if not impossible.--79.76.176.172 (talk) 02:15, 31 August 2008 (UTC)
Butterfly Bee Insect (Unknown)
Hello,
I have a question about an insect that keeps returning to my Butterfly Bush here in lower Delaware. The insect aforementioned is about the size of a large Bumble-Bee, it consists of a black and yellow striped pattern, wings like a bee, mouth and feelers of a butterfly, and an odd fan shaped tail. It does not seem aggresive as I have been studying it for the last two months, and mingles with the other insects feeding on the bush without incident. I could not find it or any reference in any insect books I have, or google. Any help you could give me would be outstanding.
Side note: I planted a few Butterfly Bush plants near the end of my sojourn in my ex-Ontario home with the hard-fought backyard naturalized (wilderness) area. This was for the express purpose of atrracting more butterflies, which they did. Much to my chagrin, given my "naturist" mindset, when I looked up the plant species, they both turned out to be of Asian origin and listed as potential invasive species in temperate North America. Luckily, I didn't water them enough at the start, so I didn't have to actually kill a living thing, my problem was solved after two months. But beware! - Butterfly Bush is not a native-adapted plant. Franamax (talk) 00:37, 31 August 2008 (UTC)
August 31
Magnetic "field lines"
Reflecting my utter confusion on some parts of physics, what are magnetic field lines? The classic grade-school experiment with iron filings on a piece of paper with a magnet below shows field lines; the aurorae are produced by "recombination of field lines in the magnetopause"; and every diagram concerning the magnetic force has those dashed lines from N to S. So is the magnetic force expressed along physically real lines through space? Why isn't the magnetic force expressed on a uniform gradient, why does it have to go through certain "lines"? Which of Maxwell's equations result in a field line where the magnetic field is especially concentrated? And how do we predict that "here be a magnetic field line"? Is this a conceptual tool or a real phenomenon? Confusedly yours, Franamax (talk) 01:04, 31 August 2008 (UTC)
The field lines indicate the direction a tiny compass needle would point if placed at that spot. It not the case that magnetic fields are present along certain lines, with points between the lines where the magnet would have no effect on a compass needle. As for iron filings, they tend to clump together and establish a pattern of lines or curves. If the magnet were left and the filings were removed and new filings shaken over the piece of cardboard, the clumpy curves woould be similar but in slightly different places. The closeness of the spacing of the "lines" is a helpful approximation the the flux density variation. Edison2 (talk) 06:23, 31 August 2008 (UTC)
I guess that each small splinter attains a N / S-pole. As they are linear in shape, the N-pole of one then "sticks" to the S-pole of the next one, thus forming curves / field lines. --Cookatoo.ergo.ZooM (talk) 10:03, 31 August 2008 (UTC)
The ontological status of field lines can get a little complicated. I have read discussions on this very point by physicist/historian/philosophers. Sometimes they are treated as a mathematical construction, sometimes as a real physical entity. As far as I can tell, at least by conversations with plasma physicists, it's not totally straightforward. --98.217.8.46 (talk) 17:15, 31 August 2008 (UTC)
This is the SCIENCE desk - and science is all about experiments. Here is an easy experiment: Take your fridge magnet, a sheet of paper and some iron filings. Mark the location of the magnet under the sheet of paper, sprinkle your iron filings and trace along the lines that appear with a pencil. Now remove the magnet, shake all the iron filings off of the paper and do the exact same experiment again (making sure you replace the magnet in the exact same spot. If the field lines from the second experiment consistently line up with those from the first experiment no matter how many times you try - then you have good evidence that field "lines" exist because they are a reproducible phenomenon. If they don't line up - if the lines appear in different places each time you do it - then they are a side-effect of the way iron filing rotate to align with the direction of the field and clump together to make "lines". It's my belief that the lines are not real - magnetic fields are continuous functions just like any other field. But hey...go ahead and prove me wrong! SteveBaker (talk) 19:47, 31 August 2008 (UTC)
I get confused when I read in Nature a summary of a paper in Science about "a realignment of Earth's magnetic field lines...lead to luminous polar auroras". It does go on to say the "field snaps back into place". On reflection, I can however buy into the idea that the iron filings clump due to N-S attraction between the individually ferromagnetized particles, presumably the clumping mechanism is stochastic. I'm interested though in 98.217's comment - the geo(/space?)-physicists do tend to talk explicitly about "a" field line reconnecting. Franamax (talk) 22:58, 31 August 2008 (UTC)
Nobody is going to make 'bearings' out of lead - the point of a bearing is to remain perfectly spherical under load - and lead would deform and be an utterly useless material - it's far too soft. However, you can buy spherical BB-gun pellets in lead. As '79 says, you could look for musket balls. Quite a few antique gun enthusiasts must need large diameter lead projectiles. However, I think a lot of them make their own by pouring liquid lead into suitable molds. You could do that too. SteveBaker (talk) 03:02, 31 August 2008 (UTC)
Are you looking for ball mill grinding media? United Nuclear sells grinding media made of lead and antimony which are 12.7 mm in diameter. I'm sure other retailers sell grinding media closer to 20 mm if you search on the internet. Coolotter88 (talk) 20:01, 31 August 2008 (UTC)
NASA have looked at a range of possibilities - but so far, none of them have been brought to the point where we could actually deploy them. Further testing is needed because there is a severe risk of simply breaking up an asteroid into smaller chunks - which would be just as dangerous and have a larger probability of splattering something important on impact. There are also concerns that errors in calculating the precise orbit of the body might result in us inadvertently turning a one in one ten chance of a problem into a certainty. The best chance we have to do this cleanly is to detect the problematic body many years before impact. The smallest nudge at that time will avoid a problem - but if you leave it until the body is merely months away, it's vastly harder. Right now, we can't detect mountain-sized bodies until they are weeks away. Before we do anything about deflection or destruction - we first need to put serious funding into detection - and that's really not happening. The short answer is that we currently have absolutely zero protection - and at present rate of progress, we probably won't have such protection for decades into the future. SteveBaker (talk) 03:09, 31 August 2008 (UTC)
Oh shit! Well wouldn't it be a good idea if both Russia and America and anyone else were to get together to form a plan to detect and divert these objects which would probably terminate most of the life on earth rather than have petty squabbles about whose got more missiles in the others back yard?--79.76.176.172 (talk) 03:18, 31 August 2008 (UTC)
Why? That is nothing more than opinion. This is a reference desk, not a place to try and get a debate going about how important it is to drop everything and try to fix a problem that will likely never happen while humans are still alive on our tiny little speck of a planet. -- kainaw™03:21, 31 August 2008 (UTC)
Actually it was a question (as indicated by the ? at the end) not opinion, but thats a remarkably cool attitude you have there! Just how sure are you that its probably not going to happen sometime soon?--79.76.176.172 (talk) 03:36, 31 August 2008 (UTC)
See opinion and fact. Any question beginning with "Well wouldn't it be a good idea if..." is asking for opinion, not fact. This is not a discussion forum. There are thousands of discussion forums on the Internet. Use one of them if you feel such a desire to discuss opinions. -- kainaw™03:40, 31 August 2008 (UTC)
He did follow up with a legitimate question regarding the probability of an impact event during which humans inhabit the Earth. ScienceApe (talk) 04:38, 31 August 2008 (UTC)
What is your source for that statement that we can't detect mountain-sized objects until they are weeks away? My understanding was that our detection programs were pretty good. --Tango (talk) 03:46, 31 August 2008 (UTC)
We detect and follow a great many objects that are only tens or hundreds of meters in size . Most known objects are followed many years in advance. Yes there are unknown asteroids, and yes some could be very large, but the idea that we only see mountains right before they show up is simply not true. Dragons flight (talk) 05:16, 31 August 2008 (UTC)
I think there is a big difference between detecting a NEO for the first time and tracking it once it has been detected - tracking is much easier than detection. If you look at this NASA list of recent and upcoming close approaches, you can see that some of the objects have been tracked over several years. But if you drill down to the (rather cool) Java interactive orbital simulation for each object, you can see that most of them (especially in the sub-1km diameter range) were very close to the Earth when then were first detected. 1998 UP1, for example, has been tracked for 10 years, but it makes a close approach once a year (because its orbital period is almost exactly 1 year) and when it was discovered in October 1998 it was a few days past that year's close approach. NEO tracking programs seem to concentrate on detecting objects that repeatedly cross the Earth's orbit and make close approaches every few years, so that we can track them and get an accurate enough fix on their orbits to determine whether they will be a danger in, say, 50 or 100 year's time. Gandalf61 (talk) 13:32, 31 August 2008 (UTC)
That was, as you say, detected 10 years ago. Our detection programs have come on a long way since then - I would hope we would have spotted it sooner had it made the same close approach now. Also, I wouldn't consider sub-1km to be mountain sized. --Tango (talk) 14:22, 31 August 2008 (UTC)
I don't know - a cubic kilometer of rock would look a lot like a mountain if you put it in your back yard! But let's consult (say) an encyclopedia: Mountain#Definitions says that in the US, a mountain has to be more than 610m tall and in the UK, over 914m. Something that's 1000m tall qualifies as a mountain. SteveBaker (talk) 16:09, 31 August 2008 (UTC)
Yeah, I looked at those definitions and decided 1km was a good cutoff, so sub-1km wouldn't be mountain sized. Remember, these aren't going to be nice regular shapes, so the 1km presumably refers to the longest axis, the other will probably be significantly smaller. --Tango (talk) 19:30, 31 August 2008 (UTC)
The object that caused the Tunguska event and the object that created Meteor Crater in Arizona were both about 50 m in diameter - tiddlers, but large enough to cause explosions in the 1-10 megatons range. NASA's minimum size threshold for counting an object as a potentially hazardous asteroid is 150 m diameter - see "What Is A Potentially Hazardous Asteroid (PHA)?" at this FAQ. An impact event from a sub-1 km object can still cause massive damage. Gandalf61 (talk) 17:49, 31 August 2008 (UTC)
Sure, they'll hurt, but they're not end-of-world type events. Deaths would probably be comparable to other fairly frequent natural disasters. --Tango (talk) 19:30, 31 August 2008 (UTC)
Here is some data for the not-so-worried:
Tunguska_event#Similar_events shows that megaton-range events happened in 1908 and 1930 and many multi-kiloton (bigger-than-Hiroshima) sized events have happened in the last 50 years or so.
50m rocks hit us about every thousand years and can level 800 square miles of land (such as in the Tunguska event in 1908) - an explosion with minimum 5 megatons.
1km rocks hit us about every half million years.
5km rocks hit us about every ten million years and produce a 100km crater and perhaps 50 megatons of explosive power - the debris would blot out the sun and to terrible things to our crops...billions of people could die of starvation within a year.
The dinosaurs were likely wiped out by a 10km rock - some of humanity might survive it - but probably 99% of humans would die.
So - there is a 1 in 1000 chance per year of a random 800 square mile chunk of the planet getting wiped out with the force of a very large nuclear weapon - from a rock that's WAY smaller than we're able to detect even at the very last minute. Every decade or so we get hit with rocks that could kill a million people in the very unlikely event they might hit a city. Previous replies suggest that a 1km rock may or may not be detectable soon enough to do something - but it could take out an enormous amount of people and/or cause massive tsunamis.
Once every half million years for a really big rock may sound like a pretty remote chance - but the consequences would be extreme.
The problem with this kind of thing is to balance the probability of it happening versus the scale of the consequences. We spend an immense amount of money to protect ourselves from very probably events (car crashes, house fires, medical mishaps) that are very likely - but which don't affect many people at a time. We have a blind-spot to very infrequent/unlikely events that would take out half the planet. That's an odd thing. It really doesn't matter (on the grand scheme of things) how many people get killed in car crashes - but if a mountain of rock were to wipe out almost all of humanity - then that's something we need to pay attention to.
If there is a one in 500,000 chance of a meteor killing (say) 5 billion people each year (that's only considering the really big rocks) - that's an average of 10 out of every 100,000 people per year. OK - now let's examine: List of causes of death by rate. 20 people per 100,000 get killed in car crashes worldwide (it's more likely in places like the USA - but less likely in (say) India) - so you are twice as likely to die in a car crash than by the consequences of a 10km meteor. The probability of dying in a killer meteor collision is comparable to the chances of dying from one of the more common cancers or a random act of violence (eg a crime, a mass murderer or a domestic dispute). So, from an individual person's perspective - we should be spending at least as much on looking for and deflecting 1km meteors as we do on trying to eliminate street violence. Death by meteor is quite a bit more probable than death by Altzheimer's disease. You are maybe twice as likely to die from a meteor than from your house burning down.
From a purely statistical perspective, we should spend more on meteor protection than on (say) airbags in cars, Altzheimer's research or smoke detectors because no matter how much you spend, you'll never eliminate those things - where there is every chance that would could provide 100% protection against 1km+ meteor strikes. As a species, we should place more 'weight' on a potential species-obliterating-event than on more probable events that (while killing the same number of people on average) are no risk whatever to the survival of our species. You can go one further by saying that we'd also be protecting most other species on earth from obliteration too.
That's only considering the very infrequent planet killers - I guarantee that the first time a once-a-decade sub-50m rock hits a major city, delivering a few hundred Hiroshima-sized bombs worth of damage and perhaps killing a million people, we'll suddenly become VERY focussed on those smaller rocks.
You need to take into account cost:benefit ratios. You can almost completely protect a family with one smoke detector for a couple of quid. The cost per family of protecting against small asteroids is probably far far greater (I don't have any figures). Remember, even if we detect them, the cost of actually doing anything about it is probably going to be prohibitive if it's "only" going to save a million people. Using Deep_Impact_(space_mission) as a benchmark (a deflection mission seems roughly similar in parameters), we're talking about $330 million, probably more due to the need to do it quickly. $330 per person sounds pretty reasonable at first glance, but when you consider what else that $330 could be spent on (smoke detectors for 100 families, say), it may not be the best use of limited funds (and funds are always limited). --Tango (talk) 19:30, 31 August 2008 (UTC)
You have the math totally wrong. You can only spread the cost of $330 million over a million people once you know which million people will be affected. Before you know which million you're going to have to save, you get to spread the cost over the entire planet. If $330 million were all it would take to protect six billion people from a one in a thousand chance of death-by-meteor per year, it would be a total bargin! You'd have to put $3 smoke detectors into a lot more than 110 million homes to save a million lives. Remember - death from house fires is 5 per 100,000 people per year. To save a million people over maybe the ten year life of your smoke detectors in a year you'd have to put them 1,000,000x100,000/(5x10) homes...that's two BILLION homes...which would cost six billion dollars - not $330 million...and (furthermore) they'd have to be 100% effective in preventing death from fires - which they obviously are not.
If you are thinking about an after-detection calculation - then look at it like this: We spent considerably more than $330 per person on fixing up New Orleans AFTER Katrina - forget the deaths - the cost of reconstruction alone would more than pay for the mission to deflect a small rock. If a big rock was to hit New York and you asked the million people within the strike zone to pay $330 each to save their homes - I'm pretty sure they (or their insurance companies) would be more than happy to pay up! $330 million is NOTHING compared to the cost of a million lives. The government could justify it in terms of lost taxation revenue alone!
Linked earlier in this discussion, The Sentry Risk Table is an interesting read. It's fascinating how many serious impact events have better odds than a lottery ticket.
So asking people to pay $3,398 each for meteor insurance should be a no-brainer since dying is a much worse event than winning a lottery is a good event. SteveBaker (talk) 20:09, 31 August 2008 (UTC)
Steve, I've got you covered, where should I send my PayPal account information? Special this month only, $3,000 even if you act now! I'll insure you against winning Powerball too. However I won't cover you for the much more liekly chance of getting hit by lightning or contracting the flesh-eating virus (which amazingly I'm not able to find a wikilink for). Franamax (talk) 22:44, 31 August 2008 (UTC)
Poisonous things that taste good
I want to compile a list of notoriously carcinogenic/poisonous chemicals that also have a palatable flavor/scent. For example Lead(II) acetate, cyanide (I've heard it smells like bitter almonds), etc.. I would be eternally thankful if you could help me on my way, thank you.
Kenjibeast (talk) 06:20, 31 August 2008 (UTC)
Most kinds of ant poison taste good because it contains sugar to attract the ants. But most kinds also contain strychnine. (Refer to "strychnine" in Misplaced Pages.) Because of the sugar content, ant poison should be strictly kept away from children. Dogs like sugar too. The safest kind of ant poison comes in a little sealed can that has small holes for the ants to enter. Andme2 (talk) 15:32, 31 August 2008 (UTC)
The ability to smell hydrogen cyanide is genetic, though I assume non-detection is a side-effect of some more useful trait:) Phosgene smells nice. Lots of molecules are made of various sugars (as a class of compounds, not the specific "table sugar" and other sweeteners usually seen in foods. Some saccharaides are wickedly toxic, but don't know how they smell. Even some simple acetals smell nice but have toxic effects (first-hand experience here). DMacks (talk) 19:58, 31 August 2008 (UTC)
I'll nominate ethylene oxide which apparently has a "faintly sweet" odour which I've thankfully never detected - they have honkin' big signs around the EO facilities in refineries and gas plants. And of course, there's benzene, which gave the name to the whole class of aromatic compounds, because it smells sweet while it kills you. Franamax (talk) 22:29, 31 August 2008 (UTC)
Breakdown via anti-hydrogen
Could several anti-hydrogen atoms be used to take one proton, one by one, from a neculeus of a normal atom, stepping it through alot of different elements? Or would the normal atom usually decay into two seperate atoms if hit by a antiproton etc? —Preceding unsigned comment added by 58.108.249.161 (talk) 10:09, 31 August 2008 (UTC)
The energy released by a proton-antiproton annihilation event is on the order of 2 billionelectronvolts (2 GeV). The binding energy of an atomic nucleus is – for most nuclei – somewhere around 8 million electronvolts (8 MeV) per nucleon (proton and neutron in the nucleus). See our article on Binding energy#Nuclear binding energy curve for specific numbers there. The energy available from the annihilation is more than a hundred times the energy required to blow an extra proton or neutron out of the nucleus.
To be fair, the actual efficiency of transfer of annihilation energy to the nucleus is actually nowhere near 100% efficient. The first publicly available study I found was this one (warning, 7.0 MB PDF). They found that 120 MeV (on average) is transferred to a carbon nucleus, and about 450 MeV is transferred to a uranium nucleus. (That pretty much covers the gamut of atomic weights.) In any event, those energies are quite sufficient to drive fission events, so 'stepping' through elements one by one isn't likely to occur. TenOfAllTrades(talk) 14:59, 31 August 2008 (UTC)
Also, the probability of exactly one anti-hydrogen actually hitting your one atom is essentially zero. Even if this worked - you'd have to fire a lot of anti-hydrogen at a lot of your chosen material. Then you'll have no control of how many anti-hydrogens hit each atom in your material. So even if you could somehow evade the problems that TenOfAllTrades brings up - you'd still be doomed. SteveBaker (talk) 15:14, 31 August 2008 (UTC)
Do we have an article that explains why inbreeding/incest etc. causes DNA defects and why its eveolutionarily beneficial for genes too not 'mate' with genes that are similair to themselves?--58.108.249.161 (talk) 10:41, 31 August 2008 (UTC)
I've been eating a bunch of nectarines and peaches lately and I've saved all the pits so I can plant them (mostly nectarines, but a few peaches too). I'd just like to know when would be a good time to plant them and any tips on growing the trees. In case you're wondering, I live in Northeast Kansas.
Also, I just noticed that some of the pits are getting tiny little spots of mold and I'd like to know how to safely store the pits until they can be planted. should I discard the pits that have mold?
One more thing. We have lots of little wild plums around here (I cannot identify the specific species since I'm not a botanist :P), but I know that plums are in the same genus as peaches and nectarines (prunus) and I'd like to know if they would accidentally cross-polinate. If so, would this negatively affect the quality of the fruit?
For growing you will have to crack the pit open as the actual seed is inside, but after that there are not really any special preparations needed, just put the seed straight into some ordinary soil and keep it damp. It will take a long time to germinate though. Also try planting several seeds to increase the chances as in nature it is very rare for all offspring to survive. Remember that if you are growing them to eat, fruit grown from a seed almost never tastes the same as the fruit the seed came from. This is because the fruit you buy in the shops is bred asexually (basically clones the plant) and may have been crossed thousands of times to get it just right, but when you grow a seed it has had its genes all mixed up in independent assortment so you could get just about anything, though most of the time they just taste really bitter. Then again you could get a better fruit than the original, it's a lottery. JessicaThunderbolt14:47, 31 August 2008 (UTC)
I've found that too. If you have a friend with a good tree - get the pit from that, then you'll have a vastly better chance - also, you'll know that that variety of tree will grow in your local climate. SteveBaker (talk) 15:11, 31 August 2008 (UTC)
I would like to know a few methods using which one could track the movement of a lipid in a liposome. In the sense, suppose I want to keep observing a lipid molecule for say, 5 minutes, then how do I do that? —Preceding unsigned comment added by Psruthi16 (talk • contribs) 14:29, 31 August 2008 (UTC)
An admitted wild guess here (which I'm not supposed to do), but our article on fluorescent proteins indicates that they can be palmitoylated to mGFP. Palmitoyl is a fatty acid so possibly the GFP-palmitoyl complex could be incorporated into a lipid molecule? However, getting that complex through the liposome membrane would be a different story. Other than that, I got nothin'. Franamax (talk) 22:21, 31 August 2008 (UTC)
Found a insect that was thought to be an armored snail, it has slimy feet of a snail, but the head of a catapiller, and the shell of a pill bug(rolly polly bug). Cannot find any information on this insect?216.236.163.183 (talk) 15:23, 31 August 2008 (UTC)
It seems unlikely to be an insect. Adult insects all have six legs and a three-part segmented body (head, thorax, abdomen). SteveBaker (talk) 16:00, 31 August 2008 (UTC)
This sounds like a joke question, but I'll assume good faith. You should provide the location and a photograph of the creature to help people here make an indentification. Jdrewitt (talk) 16:05, 31 August 2008 (UTC)
There is a story that's been all over the news media over the last few days about researchers looking at Google Maps and finding that cows (and other herd animals like deer) have a preference for aligning themselves North/South. I'm trying to find out whether they mean that the cows all face with their noses to the north - or whether 50% of them are facing north and 50% south. I've been thinking that a possible reason for doing this (None of these reports seem to be suggesting reasons) is that it might be a way for the cows to arrange for the herd to get good all-round vision for predators. They have eyes out on the sides of their heads to improve their field of view - but they must have a blind-spot behind their thick, juicy, tender rear ends. If the cows pointed in utterly random directions, they'd have pretty good 360 coverage - but if they all pointed North - that would mean that they deliberately evolved a blind spot! However, if 50% faced north and 50% south that would guarantee no blind-spots and they could be using the earth's magnetic field to dramatically reduce the probability of a blind-spot. Has anyone heard a theory for this? SteveBaker (talk) 15:55, 31 August 2008 (UTC)
Am I the only one who has an image of a cow suspended on a piece of string slowly rotating to point north? Seriously, the first thing that crosses my mind is that they are putting the sun to their backs to avoid the glare. Is there any information on cows in Australia or South America? If they face South rather than North that would indicate that it is not magnetic field related. SpinningSpark16:22, 31 August 2008 (UTC)
Here is the study. It's not clear in the abstract, but I believe they were unable to determine from satellite images which way round cows were standing. The deer tend to be head-north though. To Spinningspark: they tested the magnetic hypothesis by looking at areas where magnetic north is significantly different from true north. It turned out magnetic north wins. Algebraist16:34, 31 August 2008 (UTC)
(ec) This report from the BBC says that the deer (all observed in Czech Rebublic) were 2:1 in favour of North over South and as Algebraist said, the satellite images of cattle could not resolve head from rear. It does say though, that cattle in Africa and S America are more NE/SW than N/S and speculate that this is because the field is weaker in these locations. SpinningSpark17:16, 31 August 2008 (UTC)
This sounds to me like what comes out of the back end of the cow. Cows point the way the boss cow is looking, because there might be something interesting there, and point the other way because they are a hierarchy and standing tranversely is inviting a fight. They orient to maximize warmth on cool days and into the breeze on hot days to keep the zillions of flies away from their eyes. However, if anyone has a copy of the full study, please email me, I'd love to read the whole thing. Franamax (talk) 22:05, 31 August 2008 (UTC)
Anyone here who thinks to understand that article? It all looks like technobabble to me. The formula below the heading Time-slicing definition looks as if it's integrating over just one path, not over all possible paths. 93.132.155.98 (talk) 16:13, 31 August 2008 (UTC)
Well, it's about quantum mechanics, what kind of babble did you expect? :) And it's about an idea developed by Richard Feynman, who had an extra several brains packed in his skull. Quantum theory is one of those areas where it becomes very difficult to meet the Misplaced Pages standard of "anyone should be able to read and understand the article". That can be done, but you'd need a box at the top saying "read these six hundred other articles first". Franamax (talk) 21:51, 31 August 2008 (UTC)
Pollution kills off lichens and bryophytes leaving algae. I can't help you with the toughest flowering plant. However there are different plants that can tolerate differing kinds of pollution. Some can tolerate high copper, others high phosphate, and yet others high acid. Is your pollution smoke, fluoride, acid rain, contaminated water or what? Graeme Bartlett (talk) 21:42, 31 August 2008 (UTC)
Physics Degree
I just met this grad student studying Physics and was wondering what exactly people with advanced degrees in Physics do, job-wise, after they graduate. Do they mostly become scientists? Professors? Or what? 128.239.177.28 (talk) 20:23, 31 August 2008 (UTC)Curious
Apart from your suggestions, I know planetarium operator, semiconductor factory developer, microwave nonlinear materials developer, geophysicist working for mining or oil companies, science teacher. Graeme Bartlett (talk) 21:47, 31 August 2008 (UTC)
There's actually quite a lot of them on Wall Street as well. Mathematical abilities + major smarts = ideal candidate for a lot of big business. --98.217.8.46 (talk) 22:40, 31 August 2008 (UTC)
The American Institute of Physics keeps track of this sort of thing. Just skimming over a report from a year ago (report here), 43% of people with MSc in Physics end up in the Private Sector, 21% end up at a university, 13% end up working for the government, 12% teach in high school, 8% go into the military, 3% do something else. The report omits this sort of discussion for PhDs but indicates that most of them aim for employment at universities, but only about 25% end up with jobs relating to directly to physics. Most end up doing engineering jobs of some sort. (p. 16 of the report)--98.217.8.46 (talk) 22:52, 31 August 2008 (UTC)
Red jelly growing in fridge
I have something unpleasant growing in my fridge. It is the colour and consistency of raspberry jam. It does not grow in the fridge compartment itself, but inside the small bore synthetic rubber tube that drains the condenstion from the fridge. Every few months the drain becomes blocked and the bottom shelf of the fridge gets wet which is how I know it is time to clean it out again. I have flushed the drain tube countless times, often with neat disinfectant but this alien substance always grows back after a few months. But strangely, it never seems to go anywhere outside the dark inside of the pipe. What is it? Is it dangerous? As it is only ever in the pipe and I don't seem able to kill it, I am wondering if it is a chemical reaction of the synthetic rubber rather than something biological. SpinningSpark20:37, 31 August 2008 (UTC)
This sounds to me like a slime mould (breaking the rules by guessing, again!). The rubber tube would provide a semi-porous substrate where the organisms could hide from your cleaning attempts. Also I think slime molds can form a biofilm which is resistant to disinfectants, although our articles seem to contradict me on this. The solution seems to be to buy yourself a new tube, or perhaps soak it in an acid or alkali solution for several days? I doubt it is a chemical reaction with the tube since presumably the tube would be gradually consumed in the reaction - unless the sulphur is acting as a catalyst, which I don't think would be the case. (On the subject of slime moulds, check out Dictyo for a really fascinating example of unicellular organisms turning into an animal when necessary - very Wikipedish!) Franamax (talk) 23:26, 31 August 2008 (UTC)
Why do we find some animals attractive?
Why do humans(at least some humans) think that animals like big cats, wolves, birds, and even certain reptiles, as well as some invertebrates such as insects, are beautiful? Because some of these creatures might be dangerous, standing around gazing at, say, a tiger could be quite an evolutionary disadvantage. 68.123.238.140 (talk) 21:51, 31 August 2008 (UTC)
Just to be sure, are you really asking: "Why do humans(at least some humans) think that animals like big cats, wolves, birds, and even certain reptiles, as well as some invertebrates such as insects, are beautiful?" --hydnjotalk22:37, 31 August 2008 (UTC)
Bilateral symmetry, anthropomorphic features (like the big eyes of a seal pup or panda bear), flowing "elegant" features would be some of the factors. Also, many sexual adaptations such as the "eyes" on a peacock's tail feathers and the brilliant colouration of male birds would weigh in. Of course, the concept of beauty is like your gas mileage - it varies. I personally find a preying mantis quite beautiful, but others might freak out. Then there's spiders - both beautiful and repellent. Franamax (talk) 23:34, 31 August 2008 (UTC)
Human lungs
Can human lungs grow in response to intense use, like human muscles can? I mean, can they function better because one does a lot of physical exercise? Divers can learn to hold their breath for minutes, what happens to their lungs? Can the VO2 max of adult lungs increase? I realize that the question isn't worded accurately, but I hope I'm clear enough to get an answer. —Preceding unsigned comment added by 24.7.54.224 (talk) 22:20, 31 August 2008 (UTC)
Yes, humans can train themselves to more efficiently take oxygen out of the air. I think Lance Armstrong has some kind of deformity that causes him to get more oxygen, but I could be wrong. --mboverload@22:41, 31 August 2008 (UTC)
Also, people that dwell in high elevations produce more red blood cells in order to transport more oxygen. I realize this borders on irrelevant.130.127.99.168 (talk) 23:32, 31 August 2008 (UTC)
Sweet smell from blown up capacitors?
I've blown up various capacitors through various mishaps and I've noticed one thing: the electrolytic ones pop like pop corn and gives out a fairly sweet smell. Does anyone know what compound causes that smell? --antilived23:12, 31 August 2008 (UTC)
which comes from Newton's Second Law of Motion. You can then make the substitution 
and substitute that in to get an equation of simple harmonic motion. 
(which you'll have after the substitution suggested by ConMan - the a will be replaced by an appropriate constant of proportionality involving ks and ms), that is acceleration is proportional to displacement and in the opposite direction. You then simply observe that the sine (or cosine - which one you use depends on boundary conditions) function fits that equation, so you can use it as a solution. Just assume that 
(this is called an "
and a bunch of rearranging (and fiddling around with a plus-or-minus sign), but I agree the ansatz is much neater. More generally, you could use an exponential ansatz, as long as you're prepared to work with complex numbers (and know the relationship between the exponential and trigonometric functions). 
gives a family of solutions to the equation of motion - but how do we know that this covers the whole solution space ? How do we know that there isn't some set of initial conditions that will result in an entirely different solution with very different behaviour ? Well, in this particular case we know that the differential equation is 
Done
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