Wikipedia:Reference desk/Archives/Science/2006 October 7

Raising a baby bird in isolation
Suppose if I were to raise a baby bird from the egg to adulthood in complete isolation, with me as the only other living creature he had contact with. How would his behaviour differ from that of the rest of his kind? Would he ever learn to fly? Would he copy my mannerisms? Would he know that he was a bird or would he assume that he was the same species as me?


 * It would think that you were its mother and follow you around. Some chap hand reared some ducks or geese or something, and when he drove in his car, they followed him by taking to to the air!--Light current 01:02, 7 October 2006 (UTC)


 * To get a Budgerigar (parakeet) which will talk, it is thought best to choose a young male and raise it away from others of its kind, so that it will bond with the humans. Parakeets raised with parakeets are thought less likely to do much talking. This is lore and not empirical science. But does the bird think it is a human, or that we are big parakeets, or that it will grow up to be human, or we will someday change to be birds, or is he a victim of the Stockholm syndrome? Who can say. His behavior would probably be different from a parakeet raised in a cage full of parakeets or in the wild. If you raised him from the egg (i.e. hatched with an incubator) you would need to feed him tasty little worms or whatever the birds diet normally is. Baby whooping cranes are kept from seeing their human caretakers, and fed with puppet-gloves resembling the adult birds. Some baby birds imprint on the first creature they see and will learn to follow a human around.Edison 01:05, 7 October 2006 (UTC)


 * Some of this surely depends on the specific species. It's a pity that birds typically don't react to offers like "a penny for your thoughts", so that we can only guess what the bird knows and assumes. So we don't know whether Konrad Lorenz's imprinted geese thought Lorenz was a big goose, or assumed they themselves were little Lorenzes. --Lambiam Talk  01:13, 7 October 2006 (UTC)


 * I doubt if non-human animals ever ask the question "What am I ?". That level of self-awareness would lead to religions and complex burial rituals, which we don't observe in any animals other than humans. StuRat 17:41, 7 October 2006 (UTC)
 * Elephants have complex burial rituals (and, according to this article, also rape and kill rhinos)
 * When an elephant dies, its family members engage in intense mourning and burial rituals, conducting weeklong vigils over the body, carefully covering it with earth and brush, revisiting the bones for years afterward, caressing the bones with their trunks, often taking turns rubbing their trunks along the teeth of a skull’s lower jaw, the way living elephants do in greeting.
 * --JianLi 22:32, 14 October 2006 (UTC)

The frequency (oscillations) of his "speech" would be different from birds raised by other birds, for one. -THB

taking control of Opportunity and ROver
If one had the cash, how would you go about stealing control of the two Mars rovers from Earth?

How much do you suppose the radio equipment would cost?


 * During the Apollo program, Popular Electronics started to publish a series of articles on how an electronics hobbyist could build a receiver to receive the transmissions from the Apollo astronauts on the moon directly, rather than listening to the TV coverage of the moon landing. They stopped after about the first article in the series, because they said they had calculated that it would cost far more than a house was worth. Now consider that Mars is around 400 times as far away, and you would need not only a receiver but a transmitter, and it gets really pricy, even allowing for advances in electronics since 1969. Microwave links from studio to transmitter have been hijacked (it once happened to WGN in Chicago) and communications satellites have been hijacked. The most likeley scenario would be a foreign power (such as the U.K. China or Russia) with its own deep space network, with all the programs used by the Rover and all the communication profiles obtained from someone in the program, and for some reason not worried about pissing the U.S off. Then perhaps they could tell the Rover to take a long walk on a short cliff or some such. It would be hard to do it and not be detected.Edison 02:44, 7 October 2006 (UTC)


 * You forgot the mention the most important thing: motivation. Why spend so much time and effort just to throw a rover down a crater? There's hardly any reason to hijack a Mars rover. ☢  Ҡ i∊ ff   ⌇  ↯  03:11, 7 October 2006 (UTC)
 * id do it if i had the cash....


 * interesting!
 * Which is why you don't have the cash. People with cash tend to be better users of cash, and very frequently, use it to get more. — X [ Mac Davis ] ( SUPERDESK | Help me improve  )08:59, 7 October 2006 (UTC)


 * Really Mac Davis? How about the United States?  They're rich, but they use the money to murder innocent people in Iraq.  --Bowlhover 14:49, 8 October 2006 (UTC)


 * The people who are spending that money didn't earn it. &mdash;Tamfang 06:34, 11 October 2006 (UTC)


 * Actually, most of that money is borrowed from other countries. Nobody in the U.S. earned it. -THB 09:08, 16 October 2006 (UTC)

This reminds me of a story from the Vietnam war. I have been told that during the war, people at my university (in Sweden) intercepted the television transmissions from Vietnam to USA and so they were able to see all the material uncut. Quite cool, i think. —Bromskloss 13:33, 7 October 2006 (UTC)


 * Crash it? Why crash it? I fail to see the point. The question was about controlling it, obviously for the same reasons it was sent there in the first place, to explore. Of course, others could then pick up the results sent back, like those Swedes did. And people with money tend to use it to make more money for themselves, which could be endangered by others getting the info too. Which is why owners of money often don't do what is best for mankind (only for themselves) and are therefore not necessarily 'better users of cash'. Also, MacDavis assumes that people with cash earned by wise use of it, which is quite often not the case (most wealth is inherited). DirkvdM 08:25, 8 October 2006 (UTC)
 * can we all just agree that macdavis is a fool and call this question 'answered'?


 * The first bit, sure. :) The second bit, no. Neither question has been properly answered (just that it would be 'very expensive'). DirkvdM 08:27, 9 October 2006 (UTC)

Human eye resolution
What is the resolution of the human eye? 10000 X 10000.. or more than that?--Light current 01:56, 7 October 2006 (UTC)


 * According to Rod cell, the eye has about 100 million rods, so... yes! But the resolution within the fovea is better. Melchoir 02:18, 7 October 2006 (UTC)


 * Number of "pixels" is not the same as resolution. Let's agree that if you can just distinguish detail of 1 mm at a distance of 1 m, the resolution is 1/1000, so low means good. I saw some data that the diameter of cones in the fovea is about 2 micron, while the focal length of human eye is about 17 mm. That gives a limit of 1/8500, less if the cones are not tightly packed. Our article Eye, in the section "Acuity", presents some data that suggest 1/1380 (((8.7 mm)/12) / 1 m), but, taking a turn I can't follow, settles for 1/1075 (0.93 mm / 1 m). For practical use 1/1000 seems reasonable; in any case 1/10000 is not possible. --Lambiam Talk  02:22, 7 October 2006 (UTC)
 * This page cites (Ackerman, Eugene, Biophysical Science, Prentice-Hall, 1962) as reporting that the data show that the resolution limit for "most people" is 1/2000, while the most acute vision under optimum circumstances is 1/5000. --Lambiam Talk  02:55, 7 October 2006 (UTC)

Fovea?--Light current 02:56, 7 October 2006 (UTC)


 * The light has to pass through the cornea, an imperfect optical device which does most of the diopters of convergance, then through the aqueous humor, then through the lens, which adjusts focus and is an imperfect optical device, then through the vitreous humor, which may have crud floating in it, then hit the cones  to activate the detection. Resolution is lost at each step. A hawk or eagle has 5 to 10 times better acuity than a human. The high resolution is only in the very central part of vision, but we're usually not aware of it because a visual scene is analyzed in a series of fixations with quick saccadic jumps between them. We can achieve as good as 20/10 vision with corrective lenses,better than the "normal" 20/20, resolving a detail of about 1 minute of visual arc.Edison 03:00, 7 October 2006 (UTC)


 * Also, see http://www.clarkvision.com/imagedetail/eye-resolution.html (it has some interesting info). The typical human eye can distinguish between a pair of lines 0.6 arc-minutes apart. 0.6 arc-minutes is about the size of an object 1.7 mm large, seen from 10 metres away. --Bowlhover 03:05, 7 October 2006 (UTC)


 * Which corresponds to 1/5730 radians. That corresponds to being able to discern the individual pixels on a 1000-pixel high screen from a distance of 5.7 times the screen height. Apparently neither of my eyes is typical, because there is no way I can do that. --Lambiam Talk  06:14, 7 October 2006 (UTC)


 * Not really. The webpage I gave was trying to say that: if you draw two parallel lines, each 1000 pixels long, on your television screen, and you separate the two lines by 1 pixel, than you can distinguish between the two lines at a distance of 5.7 times the screen height.  Seeing the individual pixels requires significantly more resolution, since you need to see more than 1 dot per pixel to say that the pixel is not an infinitely-small dot.  --Bowlhover 04:28, 8 October 2006 (UTC)


 * I don't believe it has the same resolution once your brain has processed the image. StuRat 17:07, 7 October 2006 (UTC)


 * How do you mean?--Light current 18:01, 7 October 2006 (UTC)


 * No doubt there are many aberrations coming from the rods and cones, and your brain needs to average them out so you don't see "random pixels". Thus, it might take signals from 100 rods/cones and produce a single output signal. StuRat 21:52, 8 October 2006 (UTC)


 * So what the resolution of your brain then? 8-)--Light current 22:47, 8 October 2006 (UTC)


 * I can't tell, since mine is out of focus. StuRat 03:30, 9 October 2006 (UTC)


 * I thought so. 8-)--Light current 03:35, 9 October 2006 (UTC)

A confounding factor to all of this is that your eyes' resolution varies depending upon which part of the retina is doing the imaging, but your brain hides a lot of this from you as your eyes slew around, taking in various parts of the overall scene. That is to say, wherever you look, you're seeing with the high-resolution part of your retina.

At one point, when computer power used to be limited, people were actually discussingtaking advantage of this effect for flight simulators. The idea was that the computers that synthesized the images the "pilots" were seeing were rather limited in how much high-resolution imagery they produced, so the engineers were going to couple the computers with eye trackers that watched where the pilot-under-test was looking. Only at the pilot's point of regard would a high-resolution image be generated; the rest of the scenery would be generated using a quick-and-dirty, much lower resolution method. I don't know if this was ever actually implemented; nowadays, computers can crank out acres of high-res imagery without the use of such whiz-bangs.

Atlant 16:47, 9 October 2006 (UTC)

Eating Disorders
Do people in third world countries suffer from eating disorders such as anorexia ?--Jobame80054 04:19, 7 October 2006 (UTC) .... I have been asking this question, of healthcare professionals, nutritionist & epidemiologist, for five years. Nobody could answer this question (they didn't have a clue)nor could they refer me to journal/research articles that addressed this subject.


 * It may not directly answer your question, but Anorexia nervosa certainly has a section on 'social and environmental factors'. Did you look there before you asked? --ColinFine 08:25, 7 October 2006 (UTC)
 * I think in countries where you are not sure you have enough food to live, you would never contract this psychological disorder. No body could ever answer the question before they never checked? The demigod of Google Scholar can help too.. — X [  Mac Davis ] ( SUPERDESK | Help me improve  )09:04, 7 October 2006 (UTC)


 * I would probably say that the answer is no. Anorexia nervosa is a psychiatric illness, meaning it is regarded as a health problem; not what someone has when they are completely starved. Iola k ana • T  11:35, 7 October 2006 (UTC)


 * I don't think you understood the question. Yes, someone could develop anorexia during times when food is plentiful.  However, the condition would likely go undiagnosed in such a place, as being underweight is widespread due to many causes there and many diseases also cause a lack of appetite. StuRat 17:01, 7 October 2006 (UTC)


 * Being underweight is not widespread in third world countries. True, the worst famines hit them harder, but if I may make a wild guess, I'd say that some 99% of people in third world countries get enough to eat to prevent them from getting as skinny as anorexics. Stop watching too much CNN and go out there and see what the world is really like. :) DirkvdM 08:47, 8 October 2006 (UTC)


 * You're dead wrong; it's about 34% of children according to this site: . StuRat 21:38, 8 October 2006 (UTC)


 * Hmmm, I wonder what causes the huge discrepancy between that figure and my personal experience. First of all, it's about preschool children, although I don't know why they should be affected so much more. Also, there is the question of what one calls 'underweight' or 'falling behind the accepted weight standards'. I've been to many third world countries (including 11 in Africa, the worst hit continent in most respects) and I haven't seen many people that looked anorexic (which is what the question was about). Many may have been ill fed by western standards, but that is not the same. DirkvdM 08:38, 9 October 2006 (UTC)


 * Actually, being so skinny is probably more common in the US (and other western countries to a lesser extent), where there are many women who think that being skin and bones makes them look pretty. Hmmm, did I just answer the original question? DirkvdM 08:50, 8 October 2006 (UTC)


 * Someone once told me that many historians think that certain medieval saints show symptoms of anorexia nervosa. They had psychological symptoms in common: for one, the saints believed they were getting "closer to God" by starving themselves, and similarly, some contemporary anorexics have a belief that by not eating they become "pure". This would seem to suggest that it's not only the skinny models in Western fashion magazines that make people anorexic, so it probably does occur in the third world, sometimes. --Grace 05:33, 9 October 2006 (UTC)

Yes, people in the Third World get anorexia nervosa, too. Not everyone in Third World countries is poor, or starving. The rich are more like the rich in other countries than they are like the poor in their own. -THB 09:11, 16 October 2006 (UTC)

james harry keighly McCollum
James McCollum was a Canadian engineer, born, I believe, in Toronto. He is famous for his invention of the sleeve-valve in the early 1900s. This device was used in automobile and aircraft engines. The sleeve-valve was concurrently invented by Scottish engineer, Peter Burt and by agreement, applications of the device were known as Burt-McCollum sleeve-valves.

Strangely, I cannot find a single biographical detail on James McCollum - not even birth/death dates. Any help would be much appreciated.

Jerry Wells, Trentham, Australia.58.84.88.186


 * Looks like we're found wanting here! Ah but sleeve valve is here where it says :

The sleeve valve principle, was invented in 1903 by an American, Charles Yale Knight. --Light current 07:11, 7 October 2006 (UTC)

Where did you get the info you already have on him ? That would probably be the best place to start your research. Do they list their sources ? Perhaps he goes by a slightly different name. StuRat 16:53, 7 October 2006 (UTC)


 * LIke Charles Yale Knight for instance? 8-)--Light current 16:58, 7 October 2006 (UTC)

McCollum filed quite a number of PATENTS in his time; that's where I got his full name from. Jerry W.9 Oct.

human proteins
someone had asked a question on 5th october about human proteins being synthesised in plant cells.... can u explain it to me with an example?


 * Usually you want to produce human proteins for use as therapeutic drugs: insulin, growth hormone, etc. This is done by introducing the DNA encoding the gene for the protein into a cell, and letting the cell produce proteins from the DNA by its usual mechanism. Human proteins have been produced in bacteria, in mammalian cell cluture, in plant cell culture, and in transgenic plants. Each technique has advantages and disadvantages. - Nunh-huh 11:51, 7 October 2006 (UTC)


 * Here is an article that you may find helpful: Genetically modified organism

Gary 17:36, 7 October 2006 (UTC)

Acid to dissolve hard rock/stones
Hello,

I wish to know, if there are any acids(or mix of acids )available, which can dissolve or decimate a part of rock or a part of any hard stone within a short time, may be some hours ? Appreciate some informatation and help !

Regards Anton
 * What kind of rock? I'm sure throwing some fluoroantimonic acid, hydrofluoric acid, or hydrochloric acid would fix your problem. No, not at me, at the rock!!! — X [ Mac Davis ] ( SUPERDESK | Help me improve  )10:14, 7 October 2006 (UTC)

Whether it could dissolve rock would depend on the composition. Acid could easily dissolve limestone, no so easily dissolve basalt. As far as decimating a rock, why would you want to reduce it by a tenth? Just stop what dissolution process when it is only 10% along. alteripse 12:46, 7 October 2006 (UTC)


 * While the original meaning of decimate was to reduce by 1/10th, the modern meaning is to wipe out completely. StuRat 16:45, 7 October 2006 (UTC)


 * Ah but its not correct is it? Its Word meaning creep! (Not you). To wipe out completely is still to annihilate. Or maybe youre thinking of macerate? Catachresis--Light current 16:55, 7 October 2006 (UTC)


 * Ah! Another romantic who believes that because a word means one thing it cannot mean something else, and because one word means something another word can't do so. Too bad. --ColinFine 20:03, 7 October 2006 (UTC)


 * Agree with first part, disagree with second. The reason I agree that because a word means one thing it cannot mean something else is simply avoidance of confusion and clarity of meaning rather than obfuscation. Cleary we need to differentiate between:
 * Reduce to one tenth and
 * reduce by one tenth
 * for instance. 8-|--Light current 22:58, 8 October 2006 (UTC)


 * "I refuse to tithe to the church, because it would decimate my finances (and because the priest can damn well pay for his hookers with his own money)." StuRat 03:27, 9 October 2006 (UTC)


 * I do believe that the above sentence is grammatically correct and self consistent. 8-))--Light current 03:31, 9 October 2006 (UTC)

Holding it
What factors go into how long you can hold one's urine? If you reach your urinary bladder's capacity, does it just come out? — X [ Mac Davis ] ( SUPERDESK | Help me improve  )10:14, 7 October 2006 (UTC)


 * The bladder has three ways out, the urethra, and the two ureters. The urethra has a sphincter to keep urine in when you want it in, but the ureters do not. If you are able to hold in your urine for so long that your bladder fills completely, which would be painful and very uncomfortable in itself, the first pathological event to occur would be reflux of the urine into the ureters and eventually into the kidneys. This reflux would alter the delicate concentration gradients in the kidney and would damage (eventually permanently) the organ's ability to filter blood. This may also cause infection of the kidney if bacteria was present in the proximal urethra or bladder. Reflux from an overfull bladder occurs most often in children with psychological pathologies that prevevent them from voluntarily voiding their urine. Since the bladder is relatively thick and muscular, it usually will not fail just from being overfilled. However, even in a relatively mild trauma, such as a low speed automobile crash, a full bladder can rupture, leading to a surgical emergency: another reason to "go" before you go.Tuckerekcut 14:35, 7 October 2006 (UTC)


 * I've had the urine back up into my kidneys. The way I can tell is that, after urinating, just a few minutes later I have to urinate again.  That second time was urine which had backed up into the kidneys and then drained back down to the bladder.  My advice, don't drink a Big Gulp during a long car  trip ! StuRat 16:31, 7 October 2006 (UTC)


 * This was easily the most painful answer I've ever seen on the reference desk. Just reading it made my kidneys hurt :S Oskar 18:35, 7 October 2006 (UTC)


 * Yeah but did it make your eyes (or anything else) water? 8-)--Light current 22:53, 8 October 2006 (UTC)


 * Sphincter? Do you mean prostate in men. What is sphincter in woman? Do they not have more trouble holding it?--Light current 16:41, 7 October 2006 (UTC)


 * He means sphincter: specifically, the urethral sphincter. (A sphincter is any circular muscle (or group of muscles) that contracts to regulate the flow of material through an opening). TenOfAllTrades(talk) 18:14, 7 October 2006 (UTC)


 * Yes.. I did actually looked it up after posting that, and found the page you quote. Couldnt resist a quick few edits while I was there! 8-)--Light current 22:52, 8 October 2006 (UTC)

To add to the above answer, the bladder also ruptures in utero when boys have outflow tract obtructions as in posterior urethral valves. Because urine continues to be produced but cannot escape, the bladder ruptures and the urine fills the body cavities. InvictaHOG 20:24, 7 October 2006 (UTC)


 * "... how long you can hold one's urine"? Whose urine do you wish to hold? (yuk) DirkvdM 08:56, 8 October 2006 (UTC)
 * I was about to say that when I reread what I had written. — X [ Mac Davis ] ( SUPERDESK | Help me improve  )


 * Its sterile! (when fresh) 8-)--Light current 22:51, 8 October 2006 (UTC)


 * Such a long discussion, and nobody has mentioned yet Tycho Brahe and his unusual and painful death. Simon A. 21:20, 12 October 2006 (UTC)

I have a friend who held it for at least 24 hours (or he claimed to do so). Why didn't he need surgery for a ruptured bladder(why didn't his bladder rupture in the first place?)? Does he have an oversized bladder? Ilikefood 21:31, 12 October 2006 (UTC)

Bruhathkayosaurus vs. Amphicoelias
Someone asked a question about the largest dinosaurs. I looked it up on Wikipedia, and the Bruhathkayosaurus article gave a ridicoulously over exaggarated estimate of 220 tons for weight. The same went for Amphicoelias, which was given 170 tons. According to some sites, the theoretical limit for the weight of a land animal is 140 tons. If this is true, than the above estimates couldn't be possible. Which would be larger?


 * Bruhathkayosaurus cites http://www.gavinrymill.com/dinosaurs/largest-dinosaur-ever.html, which says "Based on the estimated mass Bruhathkayosaurus may have weighed 175-220 tons" and http://www.miketaylor.org.uk/dino/faq/s-size/records/ which says of 8. Bruhathkayaosaurus matleyi "44.1 meters, 175-220 tons". The real truth is, as http://www.miketaylor.org.uk/dino/faq/s-size/diff/index.html notes, the process for arriving at these numbers isn't very reliable. -- Finlay McWalter | Talk 11:25, 7 October 2006 (UTC)


 * Finlay McWalter is more or less correct. However, both Bruahthkayosaurus and Amphicoelias are known for very little evidence. It's easily possible that the above estimates are incorrect. According to http://dml.cmnh.org/2004Sep/msg00086.html, the weight of Bruhathkayosaurus has been reduced considerably from 175-220 tons to 157 tons. While still pretty heavy, 157 tons might be light enough for a land animal to support. As for Amphicoelias, it was probably lighter, at about 120-130 tons at the maximum. To summarise, Amphicoelias was probably much longer, and Bruhathkayosaurus much heavier. Hope this helps. -- Roger Davidson

Hard question on evolution
If all the non-plant creatures that can move around are automagically erased (by say a very powerful ET being). Can a pine tree (eventually) evolve into a kangaroo?


 * It could happen eventually, but since the two are very different it would take a very long time and there's no guarantee that it would happen. - Dammit 11:00, 7 October 2006 (UTC)


 * I don't think it would be possible, although they are both Eukaryote, one is an Animalia, the other a Plantae. And because Kangaroos already exsise, the rtee wouldn't evolve in to it, the teory says that it would evolve into something new, but I'm almost certain it would only ever be another Plantae Englishnerd 12:05, 7 October 2006 (UTC)


 * In theory, the kangaroo niche being up for grabs, convergent evolution might result in a species descending from pine trees taking up that niche. They should be a bit careful hopping around or the pine cones will come off too early. To be more precise, the whole ecosystem will be gone thanks to our ET friend, so actually there is no niche left. But a similar ecosystem could return. On a shorter term, many plant species (for example Whitebark Pine) crucially depend on (motile) animals for reproduction, and these animal-dependent species would die out long before any significant effects of natural evolution could kick in, and so would other plants depending on such moribund species. On the time scale we need, continental drift is important, and Australia might not remain a recognizable entity (see Austro-Eurafrasia). --Lambiam Talk  12:54, 7 October 2006 (UTC)


 * It is quite likely that the idea of an animal, i.e. a living being that can move around, is picked up again by evolution. However, just look how many different kinds of locomation there are: Vertebrates walking on four legs, walking on two legs, flying with two wings, swimming with various fins, snakes, then even more invertebrates, with many more legs, things which move completely differently such as starfish, even stranger stuff in the depths of the ocean etc etc. So, evolution would certainly produce moving beings again, and these would fill out all the elements and perfectionate locomotion in water, on the ground, in the air, on hard and soft ground, in soft earth, and so on. But these animals, being capable of the same feats of locomotion as today's animals, might do so by completely different means. After all, we see that there are many different ways to move, and hopping on two legs, using a muscular tail as additional leg (kangoroo) is only one of many possibilities. On the other hand, there are tasks for which there are only a few sensible devices capable of it, most importantly seeing: There seem to be only few possible designs of eyes, as witnessed by the fact that evolution reinvented them several times independently, and hence, would probably come up with them again. Simon A. 15:43, 7 October 2006 (UTC)

Note that plants are capable of movement, just at a very slow rate, like flowers which track the sun. There are also some rapid movements, like exploding seed pods. StuRat 16:21, 7 October 2006 (UTC)
 * Other examples of moving plants include Venus fly traps and bladderworts. None are as motile as kangaroos, though. Many plants have sperm that can swim, but that's about all I can think of offhand.
 * You really have to ask yourself how much like a kangaroo the descendant of a pine tree would have to be to be called a kangaroo. As a biologist, I would certainly classify the two as separate, even if the plant-descended one looked exactly like the original. See convergent evolution for more information of that concept. The pine tree-kangaroo would not be able to interbreed with the original kangaroo, if your alien were to bring them back.
 * It would probably be more likely for some other organism to take up the kangaroo niche, probably a descendant not of plants, but of some sort of microorganism. From the rules given in the first post, that is, nothing that can move gets to live, the phylum Apicomplexa might survive and spread out, perhaps eventually including organisms that can move and later end up evolving into a wide variety of organisms. Bacteria might also evolve into some kangaroo-like thing after many millions of years. Evolution isn't goal directed, it never had kangaroos as a goal in the first place, but it could certainly produce something similar to kangaroos again, if populations of organisms were exposed to the right circumstances. Gary 17:55, 7 October 2006 (UTC)

Jack Cohen has long distinguished between what he calls 'universals' and 'parochials' in Evolution (see Evolving the Alien for example). 'Universals' are structures or processes that have evolved more than once independently (for example wood, articulated limbs, flight, eyes, and intelligence), while 'parochials' are not known to have arisen more than once - knees, vertebrae, DNA. His suggestion is that in exobiological evolution one would expect to see universals arising again (though generally by different mechanisms) but not parochials.

So from this argument, one might well expect a large fast-moving herbivore to evolve, but it would be surprising if it moved by bounding, or if it was marsupial. --ColinFine 20:18, 7 October 2006 (UTC)

Note that if all non-plant life forms were erased, plant life forms would probably die fairly soon as well. The circle-of-life needs microorganisms to recycle the nutrients from dead plants back into the soil. And if these microorganisms are left around, I'll bet they would evolve locomotion before plants would. johnpseudo 01:38, 8 October 2006 (UTC)

Colin: Interesting stuff you point out by refering to this book on xenobilogy. Might be a good read. Gary: Seeds that swim with theit own propulsion: that sounds intriguing. Do you have an example at hand? You write it's common. Simon A. 10:02, 8 October 2006 (UTC)


 * A plant can't evolve into a mammal. Or could it in principle, given enough time, if we assume that the Sun and the Universe will never die and all other such ceteras remain paribus? DirkvdM 10:44, 8 October 2006 (UTC)


 * Sure a plant can evolve into an animal (and, given enough time, a mammal). After all, single-celled animals are believed to have evolved from single-celled plants. StuRat 21:29, 8 October 2006 (UTC)


 * I am not talking about seeds, such as the seeds that fall from a tree or other plant, I speak of the sperm which plants use in sexual reproduction. Some types of plants have flagellated sperm, including the Ginkgo and cycads. Others have ciliated sperm. Motile sperm seems to be a primitive characteristic in plants, left over from their aquatic beginnings. Gary 23:05, 8 October 2006 (UTC)

No, a pine tree cannot evolve into a kangaroo. It is already too evolved from a single cell; it would have had to branch off far too long ago into an animal. However, at one point, there was a "something" that could evolve into either a pine tree or a kangaroo. -THB 09:24, 16 October 2006 (UTC)

Are there obstacles to industrial-scale production of cultured animal tissues for food?
Some vegetarians avoid animal products in their diet on religious or philosophical grounds. It seems that at least to some of them their concerns or objections can be addressed by growing animal tissues in a lab environment (as opposed to getting the same tissues by raising and slaughtering animals). I wonder if industrial-scale culturing of animal tissues for food would become a reality in the next several decades. Can someone picture how this may happen, or are there difficult obstacles to making the idea work? --71.244.110.187 12:21, 7 October 2006 (UTC)


 * One of the big problems with tissue engineering is infection control; without all the multilayered immunological defense systems you get in a cow, a lump of cow muscle growing in a tank is susceptible to all kinds of infection. Maintaining sterility and controlling infection is expensive - that's worthwhile when you're growing someone a new organ (where they'll happily pay tens of thousands of dollars per pound), but it's going to make the cost of any meat you produce outlandishly expensive.  You've also got consumer acceptance issues and a pretty small market - lots of vegitarians don't want to eat meat, lots of others want to eat healthy natural food (not some weird lump of tissue that's been floating in a tank of antibiotics in some factory somewhere), vegitarian meat substitutes are pretty good (or at least good enough for vegitarians to not pine for meat very much).  I don't think you'll find that the religious objections to a given meat are going to go away with tissue engineered vatmeat - muslims and jews are as unkeen on anything made from pig as they are on pork, ham, and bacon, so your BeakerBacon isn't going to sell there. As to efficiency, with modern breeds and rearing methods, it'll be very hard to beat a cow as a means of producing meat. -- Finlay McWalter | Talk 12:36, 7 October 2006 (UTC)


 * I don't know what to make of this website, I can't really tell if it's more about science or art, but it seems relevant to your question (and appears to be affiliated with an educational establishment of some sort).Tuckerekcut 14:20, 7 October 2006 (UTC)


 * You made some good points. The issues that you raised point to an (admittedly freakish) idea: an artificial organism (or perhaps more accurately, assemblage of organs) optimized for meat production and nothing else. Such an organism, if one can call it that, would have no high-level neurological functions — only enough apparatuses to grow meat, sustain itself, and defend against microorganisms. That would bring "franken-food" to a whole new level of freakishness. --71.244.110.187 17:00, 7 October 2006 (UTC)


 * Setting aside how like what you describe a modern cow breed already is, you're quite right (but probably, really, hopefully, wrong). Margaret Atwood's novel Oryx and Crake (which I can't recommend highly enough - it's grimly hysterical) describes one such "animal", a genetically engineered chicken thing branded "chickie-nobs" which is mostly breast meat and a basic GI tract, with the minimum of brain, bone, beak, and other extraneous parts. This is certainly possible, and it's so much easier to do than tissue grown in abstract - but even then I've difficulty seeing the market for it.  For poor people, who just need protein, grain and legume sources (e.g. soy) are always going to be much cheaper (and, if you're pushed, it's easier to genetically engineer a more productive soy plant than a more muscular cow).  For richer people we've seen an ever increasing concentration on food quality, and an increasing concern about where food comes from and how it's made.  This is reflected in a great increase in the sales of organic food, free-range chicken, barn eggs, and enhanced restrictions (at least in Europe, I don't know about other places) on the conditions for animal transportation, slaughter, and veal production. Such people want happy, healthy food, and aren't going to put GMO-sarcomal in the same basket as their organic eggs and free range chicken.  I really can't think there's much of a middle market, people who want meat, can't afford real animal, and are willing to accept the flesh of some eyeless monstrosity.  Even the fast food chains, masters off passing of mystery meat as wholesome goodness, are going to have problems marketing the tissues of such horrors, even to the most foolish of teenager.   We will see ongoing enhancements of our food crops (plant and animal), but it'll be incremental and subtle, the way it has been for centuries - our current plant and animal foodstocks are so divorced (by generations of selective breeding) from their native cousins that the natives seem barely edible to us. -- Finlay McWalter | Talk 17:45, 7 October 2006 (UTC)


 * Margaret Atwood would appear to have taken that idea, at least, from 'Chicken Little' in The Space Merchants. --ColinFine 20:22, 7 October 2006 (UTC)

I would say, that in the long term, such engineered meat (and milk and eggs) could replace normal animal food. There is the potential for such food to be healthier and more efficiently use resources (since it doesn't have to do all the other things animals must do to survive, like move). However, this will likely take decades to perfect, so don't expect it to be cheap anytime soon. One side effect will be that the numbers of farm animals, like cows, will be greatly reduced. Some day you may have to go to a zoo to see one. StuRat 16:12, 7 October 2006 (UTC)


 * The Chicago Museum of Contemporary Art has an exhibition with a nose being grown in a jar of growth medium. Produce enough snouts and you could gring them up to make bologna.Edison 20:10, 7 October 2006 (UTC)


 * That type of art really gets up my nose. :-) StuRat 01:08, 11 October 2006 (UTC)


 * BTW, somewhat unrelated but in a microbiology course I once attended one of the lecturers mentions that someone had considered culturing some single-cell thing to produce enough protein to replace all the soybean in Europe (to feed cattle I believe). They even built the worlds largest fermenter (now unused). But they worked out out wouldn't work because of all the subsidies etc it was cheaper to grow the soybean. I couldn't remember the details but from a quick Google I found (and remembered) it was ICI . It's called "single cell protein" and they were going to use Fusarium fungus . Evidently it may also have partially been because the petroleum products they require cost most then they expected and the Soviet Union were also looking in to it . But I think this does all highlight one key issue. As long as subsidies remain it will be difficult for culture systems to compete (unless these are also subsidiesed which IMHO is unlikely until they start to suceeded). Even if the subsidies are removed, this will likely mean that third-world countries will be the primary agricultural areas and their lower wages etc may mean culture systems will still have difficulty competing. Plus people are likely to be reluctant to trust culture and the large companies that will probably be running them. Almost definitely, they will initially replace feedmeal and later used as ingredients for companies selling prepackaged complex food rather then something the ordinary consumer will be using until much later Nil Einne 14:32, 15 October 2006 (UTC)


 * Fusarium is the main ingredient of Quorn, which was indeed invented (jointly) by ICI. They don't use petroleum as a feedstock, however. -- Finlay McWalter | Talk 09:39, 16 October 2006 (UTC)

It is possible but it is highly unlikely to occur in the next few decades to a degree sufficient to appease vegetarians. The primary obstacle is financial--it would be very expensive compared to other sources of protein. Soylent Green is cheaper, anyway. -THB 09:28, 16 October 2006 (UTC)

proteins
why do proteins absorb at 280nm?do they absorb at 200nm?


 * Absorb what ? StuRat 15:52, 7 October 2006 (UTC)


 * UV light, I imagine. See (for example) DNA extraction. --jpgordon&#8711;&#8710;&#8711;&#8710; 16:25, 7 October 2006 (UTC)


 * Different proteins absorb light at different wavelengths. Have a look at spectroscopy and for a machine which uses infrared absorption have a look at pulse oximeter.Mmoneypenny 17:54, 7 October 2006 (UTC)

Fossils made from bone
Hi, I've been interested in buying a fossil for my girlfriend's birthday (a diprotodon tooth actually: possibly one of the silliest examples of megafauna ever)! I've had a look at C & J Fossils. On this page they mention that the tooth fossils that they sell are not replacement fossils, but the actual teeth themselves. Is this possible? The page at Fossil does not really seem to mention it, except for "Some fossils consist only of skeletal remains or teeth; other fossils contain traces of skin, feathers or even soft tissues. This is a form of diagenesis." This reads to me like actual teeth would not last over 65 million years, but be replaced by minerals. Thanks in advance... -postglock 15:07, 7 October 2006 (UTC)


 * It could last indefinitely in the right environment, like buried in a desert or encased in stone or amber. Of course, over that long of a time period, many desert areas will have changed climate dramatically, so encasing it might be the only way to protect it for so long.  Note that such methods will favor small fossils, as a T-Rex femur is unlikely to be entirely encased, and one small hole will allow replacement to occur. StuRat 15:47, 7 October 2006 (UTC)

Hmmm, well, I suppose for the price they are selling them at, they weren't encased in stone or amber. Wouldn't the other option, the desert, not really seal the fossil from the elements too well? I guess trapped in an icy cave might be another option, but I'd imagine also unlikely for 65+ million years...? -postglock 16:38, 7 October 2006 (UTC)


 * Teeth get replaced by minerals. The owners of that website may be mistaken, as some teeth, such as those from sharks, become fossilized and retain a smooth, shiny luster, despite having their minerals replaced by others from their surroundings. Diprotodon died out only around 50,000 years ago, so its fossils may actually retain some organic material. I've dug up 2 million year old megafauna fossils in Newberry, Florida, and they contained collagen. They were encased in clay, and were very brittle. Gary 18:08, 7 October 2006 (UTC)

Cheers, thanks for the replies! -postglock 00:45, 8 October 2006 (UTC)

diatomic elements
Why exactly do certain elements exist as usually encountered in their basic states within the periodic table diatomically? Is this simply yet another unexplained and unpatterened thought, or is there a particular reason in the explanation of certain elements- for instance, it being known that all halogens exist in diatoms? If the former answer is positive, then is there some sort of notable chemical result which might occur when one attempts to separate a diatom- by heating, for instance? And if not, why? Sorry- this is really a lot of 'firsts' but a complete answer would be appreciated to subjection in blind rote learning beneath a principle one does not care or cannot explore. Luthinya 15:28, 7 October 2006 (UTC)


 * You might know that chemical bonds occur whenever the energy of the bound molecules is lower than its constituents (because then you would have to put in energy to seperate them again). As explained at least roughly in the article on the covalent bond, pairing electrons usually lowers the energy. So, if you give each outer electron ( i.e., each electron which is not stowed away in a closed electron shell) a partner to pair up with, it will form a bond with this partner, losing energy and hence staying stuck. And where might a suitable partner for each electron of an atom come from? From a second atom of the same kind, of course. Hence, when two atoms of a gaseous element meet, their outer electros will pair up, the energy of the system is reduced, and a diatomic molecule is formed. This is, of course, only as easy with gases, because in solids, an atom is always equally close to several other atoms. And noble gases have no outer electrons and hence do not form diatoms. Simon A. 16:05, 7 October 2006 (UTC)


 * The above sounds good, but I also think that idea of diatomic elements arises from bonding and antibonding of MO theory. See the wikipedia article on antibonding where it gives an example with hydrogen. It basically is saying that bonds are likely to form if there is no antibond to counteract the bond, and if there is none, then it is more energy favourable to form a bond rather than exist as seperate atoms. I don't know your chemical background, so this explanation might be harder to understand versus the above. You could search google and look up simple versions of bonding and antibonding diagrams where you might be able to find one or two where it would show you why for instance fluorine exists as a diatom while something like argon does not. Perhaps someone can explain this better than me, but I think the theory is right. 72.56.169.205 16:17, 7 October 2006 (UTC)


 * The second poster might be right that I oversimplified things a bit too much. One thing I should add for the very least, as you specifically were referring to the example of halogens: There, a single sigma bond is formed (IIRC), such that the two atoms now share one electron pair. As they had before a nearly closed filled p orbital (5 instead of 6 electrons), the two paired electrons now sort of close off both orbitals. But the usual problem with covalent bonds is that all explanations are very hand-waving and insatisfying unless one really goes down to advanced quantum mechanical calculations which then justify then justify tings like the LCAO approximation. Simon A. 10:13, 8 October 2006 (UTC)

Additive Volumes and Mols
Hi, I'm going to be doing a lab in the coming weeks in my chemistry class. Basically I have a reaction and I aim to produce an amount of product based on it. This is not a problem, I can figure out the number of moles of the product I want since I know the concentration and volume desired. I can then use mole ratios based on the reaction coefficients to figure out how much I need of the reactants. There are 3 reactants producing what I want. If I want 250 mL of product, how does it work if I need to combine the 3 volumes? Using mole ratios and figuring number of moles of each reactant I can do, but then wouldn't that just be the ratio for using 250mL of each reactant and not say 80 mL I intend to use for each and adding them together to get a final volume? I asked my teacher, he said that it might not work if I do additive volumes but I'd have to see when I do it, and if so I'd have to change the lab design (I'm guessing he just wants me to see what happens and try to solve any problems myself.) I've also noticed that some problems in my textbook for example say that they neglect volume changes (I guess to make the calculations easier). Any Ideas? 72.56.169.205 16:02, 7 October 2006 (UTC)


 * You first need t tell us whether you are talking about gases, liquids, solutions, or solids. Simon A. 16:07, 7 October 2006 (UTC)

Well it'd be in solution, an acid and two other species. 72.56.169.205 16:14, 7 October 2006 (UTC)


 * If you are using aqueous solutions that are relatively dilute, it is usually a good approximation to add the volumes. You will usually run into problems when mixing solvents, since they might sort of dissolve each other and you would end up with LESS volume. If you really wanted a certain volume, you could certainly use more concentrated reactants to get the correct number of moles, then dilute :) --Bennybp 02:48, 8 October 2006 (UTC)

Antacids
Does anyone know of any common food-stuffs which function as Antacids? Englishnerd 16:46, 7 October 2006 (UTC)
 * Baking soda is perhaps the simplest. Your box of Arm & Hammer should have a Drug Facts label for an antacid. --Russoc4 16:48, 7 October 2006 (UTC)
 * Yes, baking soda is one of my favorite foods. — X [ Mac Davis ] ( SUPERDESK | Help me improve  )
 * The Common chemicals article may also be of interest.--Russoc4 16:56, 7 October 2006 (UTC)

Shrimp diagram request for comment
This is a rough draft of an anatomical diagram of a shrimp. I am looking for feedback on accuracy. I would like suggestions and criticism. What should I do to improve it, is there anything I should change, did I make any mistakes? I was planning on adding a little more detail such as hairlines along some of the limbs and tail, and perhaps add color/shading/detail. Of course, I would also add lables as well. So comments would be appreciated. Thanks for your consideration. Please leave comments at Image talk:Shrimp.svg.--Andrew c 17:32, 7 October 2006 (UTC)


 * Is it any particular species ? StuRat 21:11, 8 October 2006 (UTC)


 * No. I would like help in establishing distinguishing features in order to make the image more accurate. Right now it is a generic shrimp. My references are about 7-8 images and diagrams found on the commons, wiki images, and google. Because of this, I may have a Frankenstein of a shrimp, which is why I am asking for external review.--Andrew c 00:48, 10 October 2006 (UTC)

Homework question
I knew that would be eye-catching! It's a homework question that I am trying to mark - should I mark as correct pupils who have put helium in the s-block? By definition, it is, of course, but we can also see why it is often put at the top of the p-block in the periodic table. So is it in the s-block, or more realistically a quasi-p-block element? --G N Frykman 20:08, 7 October 2006 (UTC)
 * It says on p-block that "... minus helium (which is located in the s-block)". I would mark correct. Iola k ana • T  20:37, 7 October 2006 (UTC)
 * I think you should mark them correct, but when you hand the tests back to the class, explain to them that helium is grouped with the inert gases, on the right side of the periodic table, even though its only electrons are in an s orbital. Gary 22:39, 7 October 2006 (UTC)


 * The question is: What did you teach them about this? And what answer were you (or the text book) expecting? 8-)--Light current 09:13, 8 October 2006 (UTC)

If you are the teacher and you are having to ask here what you tested your students on, then you need to give credit either way, and give the explanation, as above. -THB 09:34, 16 October 2006 (UTC)

Masochism
Is there any kind of cure for it? One that works, I mean. --OGoncho 20:18, 7 October 2006 (UTC)
 * You could try aversion therapy. Vitriol 20:28, 7 October 2006 (UTC)
 * Due to the nature of the subject, aversion therapy sounds like it could add fuel to the fire. --OGoncho 08:26, 8 October 2006 (UTC)
 * It was a joke, dude. Vitriol 13:53, 8 October 2006 (UTC)
 * A psychiatrist? They eventually deter you from being interested in it. Iola k ana • T  20:39, 7 October 2006 (UTC)


 * This is the type of thing that you should talk to an expert about, rather than asking people on a website. A psychiatrist would have to ask for more information, but I would bet that the most important part of treatment is making the person want to stop causing themself pain. Are you looking to cure yourself of something self-destructive, or are you concerned about someone close to yourself?


 * You can respond by clicking the "edit" link to the right, but I would really suggest you talk to a medical professional if you or someone you know is hurting themself intentionally.Gary 22:32, 7 October 2006 (UTC)


 * I have the condition, but I am not here looking for professional advice. I'd like to know of the options, but I'm unlikely to act any time soon (if at all) given the taboo-ness of the subject. If there is a cure of some kind, I will speak to an expert about it if I ever choose to do such a thing. Masochism as I mean it is sexual response to certain scenarios, while you seem to be talking about self-harm or algolagnia. --OGoncho 08:26, 8 October 2006 (UTC)


 * Is it a disease? --Lambiam Talk  06:10, 8 October 2006 (UTC)


 * No, but it is not normal, and therfore it is a taboo. If it can be removed, it would be regarded a cure by many, even if this is not a proper term. --OGoncho 08:26, 8 October 2006 (UTC)
 * Look, you sound really hung up over it. Will you be shot if it is discovered you like this kind of thing? Vitriol 13:53, 8 October 2006 (UTC)


 * As you seem to be sure that you are not talking about self-harm but about masochism I wonder why you are looking for a cure. Remember that many non-mainstream sexual practices have first been considered as psychiatric illnesses and then no longer. Having learned its lessons from the history of homosexuality, psychiatry seems to have now understood that an aberation (i.e. a non-mainstream behavior) should only be considered an illness in need of therapy, if it causes suffering. So, do you suffer? Are you unhappy? Maybe you have found or will find a partner who allows you to live out your sexuality in a way that satisfies you both. If you doubt that you can find such a partner, if you fear that your masochistic tendencies may lead you to allow dangerous bodily harm to occur to you, if you cannot enjoy your sexuality due to feelings of guilt, or anything else of this kind, then you have a lot of stuff you might want to discuss with a therapist. I am no psychologist, but I imagine that it would be far from clear that your masochism turns out to be the actual root of your problems. And surf a bit on the web to reassure yourself, that there are plenty of people with quite bizarre sexual preference who actually live out their fantasies and seem happy with it. (No, i don't recommend reading porn sites, rather discussion sites about sex. They exist but require quite clever googling to stay clear of the porn.) Simon A. 19:14, 8 October 2006 (UTC)


 * Im surprised no ones mention the joke about the sadist and the masochist yet!--Light current 23:08, 8 October 2006 (UTC)
 * I made a joke already. Was it not good enough for you? Vitriol 01:11, 9 October 2006 (UTC)


 * Yes I laughed. Didnt you hear me? 8-)--Light current 01:29, 9 October 2006 (UTC)

No, there is no way to rid your self of masochistic feelings. You must learn to accept them and deal with them. Having thoughts and desires does not mean you have to act on them, and you can learn to control your behavior. -THB 09:37, 16 October 2006 (UTC)

Recent news regarding the treatment of Fetal Alcohol Syndrome
I'm trying to find an article I read a while ago (maybe a couple of months) which outlined success in inhibiting or even reversing a lot of the negative effects of the brain damage associated with FAS with early, intensive theraputic treatment. The article described the therapy as cognitive and emotional, and stated that the findings were preliminary because the kids were still very young. Ring any bells? Anchoress 20:44, 7 October 2006 (UTC)


 * One MeltBanana  21:19, 7 October 2006 (UTC)
 * That's the one!! Thanks a bunch, MB. I was sure it was on a Cdn news site, but I was so sure it was CBC I didn't bother looking on Canada.com. Cheers! Anchoress 21:45, 7 October 2006 (UTC)

Disproof of the theory that information cannot move faster than speed of light
You just get a really long pole, going from one place to the other. Then you push or pull it to make morse code, and the other place obtains the info instantly, faster than light. --216.164.197.56 22:47, 7 October 2006 (UTC)


 * Fraid not. If your pole was infinitely stiff (fnarr) then this would work, but it isn't - it'll be compressed and elongated as you push and pull it. In a short pole you won't notice, but in a pole long enough to meaningfully test its movement against light, you'll find the pole lengthenings and shortenings take a considerably longer time to propagate along the pole (at the speed of sound for whatever the pole is made of, I guess). -- Finlay McWalter | Finlay McWalter|Talk 22:53, 7 October 2006 (UTC)


 * It won't work. When you push an object you compress its internal structure, so basically its atoms push the others creating a wave of compression that travels along it, at the speed of sound for that particular material. The information will move at this speed, which will be much, much smaller than the speed of light for any real-world material. So like Finlay said, it would require an infinitely dense material in order to achieve speed of light, and by then the pole would just collapse into a black hole before you could have anything to push :) ☢  Ҡ i∊ ff   ⌇  ↯  07:42, 8 October 2006 (UTC)


 * worse yet! you cannot push or pull the pole fast enough. its impossible to get anything with mass (such as a pole) to move at the speed of light. in order to do the moarse code, you would be pushing and pulling the pole WAY slower than the speed of light no matter how much force you applied. you would be much faster off substituting the pole for a pulse of light itself.


 * A better way to "prove" this was mentioned a few months ago, by shining a flashlight on the moon and swishing it around so fast that the resultant beam on the moon appeared to move faster than the speed of light. It doesn't prove anything, though, because as mentioned above, you can't move your hand anywhere near the speed of light, so it's impossible for you to manipulate the shape in any way that would actually produce a useful fast message on the moon (i.e. you may be able to draw a line very fast, but you wouldn't be able to write a binary sequence that could be interpreted as information). Much more relevant is the fact that the photons are moving at an entirely predictable c, so there is still almost a considerable wait (1.3 seconds) before your super-fast moving flashlight beam reaches the surface in the first place. freshofftheufo  ΓΛĿЌ  03:41, 8 October 2006 (UTC)


 * 'Apparent' motion that is faster than light is easy: The spot of light on a distant object could move faster than light - No problem - but no actual matter is moving at that speed. If you could see the beam, it would show a nice curve, like a transverse wave in the beam of light (pretty!). There was a case of this noted a while ago: A star had gone supernova, and its shockwave was impinging on a gas cloud. The circular boundary between the shockwave and the cloud was expanding faster than light.
 * But, as to your rod: the information will travel at the speed of sound in the rod. You will create a pressure wave in it which will travel along it. Sorry. 124.148.6.57 08:31, 16 October 2006 (UTC)
 * The first answer is right, the second not, I afraid. Indeed, the long pole would allow for transmission faster than ,light if it were perfectly stiff. This example is the reason why one says that special relativity is where the idealization of the rigid body, abundant in classical physics, breaks down. It is also no wonder that it does not work. After all, forces such as the push are mediated within the pole due to the electromagnetic repulsion of the atoms (the same force that keeps the solid from being compressed arbitrarily). And changes in these force fields only travel with light speed.


 * Freshgavin, you miss a point in saying, a pulse of light were faster, If the pole were perfectly rigid, it would be sufficient to just push it slowly. The other end would start moving as slowly but immediatly, i.e. somebody at the other would notice without light speed delay when you start pushing, I also wonder why you brought up the flashlight to the moon. This example is usually used to illustrate that certain things still may travel faster than light if they neither contain mass nor transport information. If you swivel a flashlight, directed at the moon, quite leisurely, the spot on the moon (if the light were bright and collimated enough) would move quite fast from one pole of the moon to the other, possibly faster tha light. However, the movement of the refelction of the spot on the moon surface is not the movement of the light, and there is also no transport of information along the path of the spot, but only along the light beam. Hence, there is no problem. Simon A. 07:18, 8 October 2006 (UTC)


 * I put "prove" in quotations to show that I was being sarcastic. I guess you didn't notice. Sigh. Also, you seem to be confusing my comment with the one before it. freshofftheufo  ΓΛĿЌ  09:25, 8 October 2006 (UTC)


 * No, I didn't notice, sorry. Simon A. 09:54, 8 October 2006 (UTC)

Quantum tunneling is the best proof I've seen that info can move at superluminal speeds. StuRat 20:58, 8 October 2006 (UTC)


 * Being pedantic, it is possible for this to work, but your pole has to be in a dense medium, where the speed of light within the medium is slower than the speed of compression of the material of the pole. It's not faster than c, but it's faster than the light. Kind of. GeeJo (t)⁄(c) &bull; 22:16, 8 October 2006 (UTC)

Can a hard drive go through an X-Ray scanner?
Can a computer's hard drive go through an airport scanner (say it was in your luggage) without information loss, or would it be damaged? - Rainwarrior 23:40, 7 October 2006 (UTC)


 * It'll be fine. Millions of laptops and iPods go through airport scanners every day. -- Finlay McWalter | Talk 23:44, 7 October 2006 (UTC)


 * It's strong magnets that are the problem, and there's not really that much radiation coming from an X-ray scanner in the first place. (Disputed). freshofftheufo  ΓΛĿЌ  03:34, 8 October 2006 (UTC)


 * I don't know about that. X-rays are ionizing radiation. They could have an effect, but the casing of the HDD might protect the disks. ☢  Ҡ i∊ ff   ⌇  ↯  06:24, 8 October 2006 (UTC)


 * Yes, but the levels you're being exposed to in an X-ray scanner I wouldn't exactly call "strongly magnetic". freshofftheufo  ΓΛĿЌ  07:03, 8 October 2006 (UTC)


 * Finlay suspects that not the magnets are the problem (there are non in X-ray machines) but the ionizing capacity of X-rays. But Freshgavin is right, ionizig radiation is not so much a problem. First, X-rays will hardly penetrate the metal case of a harddisk. Second, you might be thinking of DRAM where ionizing radiation is an issue because it might make the capacitors temporarily leaky. But I am unsure whether a hard disk without metal casing might in fact get erased by X rays. Simon A. 07:22, 8 October 2006 (UTC)


 * I wasn't differentiating between ionization and the electromagnetic effects produced by it. My bad. freshofftheufo  ΓΛĿЌ  09:22, 8 October 2006 (UTC)


 * I believe the new scanners use THz frequencies.--Light current 09:09, 8 October 2006 (UTC)

Thanks for the replies! I think I've got enough of an answer. - Rainwarrior 03:40, 9 October 2006 (UTC)


 * I (guardedly) disagree. While there's no question that the magnetic information on the disks will be safe, at a sufficient intensity of X-rays, the Flash ROMs in the disk will be partially or completely erased, and without that data, your disk drive is just a lump of metal. (The flash contains not only the computer code that makes the disk's microprocessor work, it also contains disk-geometry information that is unique to your particular disk drive and couldn't be replaced or recovered if lost.) I have no idea what intensity of X-rays would be required, but if places still have warning signs (as used to be present in the old Hong Kong airport) that say "This X-Ray machine will fog your photographic film; ask for hand inspection!", I'd avoid running my disk drives through them as well.


 * Atlant 17:01, 9 October 2006 (UTC)

All carried-on laptops go through x-ray machines at every airport (at least in the U.S.) and none of them are damaged, hundreds of thousands of times a day. -THB 09:41, 16 October 2006 (UTC)