Wikipedia:Reference desk/Archives/Science/2010 August 17

= August 17 =

HAARP Effects On Ionosphere
What are the serious repercussions when HAARP is used on the ionosphere? Is the HAARP destroying the ionosphere?174.114.236.41 (talk) 04:07, 17 August 2010 (UTC)
 * How could it possibly do that? It's 3.6MW of power - which is absolute peanuts compared to the energy the sun puts into the ionosphere. It does sound cool though, no? Playing with the ionosphere, it sounds very mysterious and strange. But 3.6MW is about the same as 20-40 cars running at full power. Ariel. (talk) 05:24, 17 August 2010 (UTC)
 * According to the article HAARP has been blamed for triggering catastrophes such as floods, droughts, hurricanes, thunderstorms, devastating earthquakes in Afghanistan and the Philippines, power outages, the downing of TWA Flight 800, Gulf War Syndrome and Chronic Fatigue Syndrome. Not to be outdone at recklessly irradiating the ionosphere, the Norway based EISCAT installation is capable of transmitting over 1 GW ERP. Wearing a Tin foil hat is a possible precaution. Cuddlyable3 (talk) 14:36, 17 August 2010 (UTC)


 * From the article:
 * According to HAARP's management, the project strives for openness and all activities are logged and publicly available. Scientists without security clearances, even foreign nationals, are routinely allowed on site. The HAARP facility regularly (once a year on most years according to the HAARP home page) hosts open houses, during which time any civilian may tour the entire facility. In addition, scientific results obtained with HAARP are routinely published in major research journals (such as Geophysical Research Letters, or Journal of Geophysical Research), written both by university scientists (American and foreign) or by US Department of Defense research lab scientists. Each summer, the HAARP holds a summer-school for visiting students, including foreign nationals, giving them an opportunity to do research with one of the world's foremost research instruments.
 * What that means is that even if you don't personally have the scientific knowledge to evaluate what they're doing, you could. If you're really concerned about it, you don't have to take it on faith that it's safe.  Just learn the relevant science and look at their data for yourself.  --Sean 14:34, 17 August 2010 (UTC)


 * The radio is basically a giant HAM antenna that puts out as much power as a reasonably large television station. Its effects on the ionosphere are measured by numerous independent scientists, to several decimal places; and these effects rarely persist more than a few seconds after the heater is turned off.  Despite the conspiracy theories, the radio is not significantly affecting the ionosphere, or the atmosphere, or the weather, or even operating at a band where it would interfere with FM radio or television signals.  When aircraft fly within a very conservatively estimated radius, the transmitter shuts down to make sure that it doesn't interfere with any of their communications or navigation equipment (though most flights in that region of Alaska are VFR anyway).  Surprisingly, despite all the static HAARP gets for mucking with "mysterious radio waves", there are very few legitimate critiques of its massive carbon footprint: the 3.6 megawatts of diesel-generators spew noxious fumes into the otherwise pristine Alaskan air.  The HAARP electric plant burns through a truckload or two worth of fuel during any hour of any given experimental run.  Nimur (talk) 18:34, 17 August 2010 (UTC)

Sex in Mount Everest
No kidding, I was just thinking about the possibility of having sex in Mount Everest. The problem in having sex in Mt Everest is 1. low temperature, 2. lack of oxygen. The first will probably cause frostbite in the exposed part of the body, while sex in Everest without carrying an oxygen cylinder is difficult. So is it possible to build some type of tent over the peak where the temperature can be regulated for the purpose of sex? If possible, how the tent should be built? Using helicopters? --Galactic Traveller (talk) 06:08, 17 August 2010 (UTC)


 * First of all, please do not use "in Mount Everest" as it is grammatically (if not logically, or even scientifically) illogical. Please say "upon Mount Everest" or at least "on Mount Everest". Question of frostbite is of no consequence as there is no such rule that both partners should be wholly naked ( that's a Hollywood stereotype ). As far sexual organs are concerned, the penis will be inside the cunt ! How convenient. Now for something serious - Indian yogis have been known to do such things up there. They spent decades up there, it would be highly unlikely that they didn't do it. No ?   Jon Ascton    (talk)  12:46, 17 August 2010 (UTC)
 * Can I please ask that you keep to the vocabulary of civilised discourse, and use the scientific name "vagina" rather than the vulgar name "cunt"? 76.229.199.177 (talk) 15:56, 17 August 2010 (UTC)
 * maybe he was referring to the woman. 92.230.233.158 (talk) 21:17, 17 August 2010 (UTC)
 * PS I found a discussion on this issue in Yahoo Answers, but I don't think the discussion there is scientific. --Galactic Traveller (talk) 06:12, 17 August 2010 (UTC)


 * Of course it is possible to build a tent on a mountain. It is possible to build a tent anywhere!  This is not a scientific question.  I suggest this question be deleted in the interests of maintaining this Reference Desk as a serious source of scientific debate.  Dolphin  ( t ) 09:03, 17 August 2010 (UTC)
 * Euophrys omnisuperstes seems to manage without a tent.  Sean.hoyland  - talk 09:36, 17 August 2010 (UTC)
 * This question is indeed misfiled. But we should make a present of it to some other reference desk, but which?  Humanities - entertainment - miscellaneous?  As for the sex, it's best to wait until the Bihar-Kathmandu-Shigatse freeway is tunneled, then pull off at the Everest exit and take the elevator to the hotel.  Ask for one of the honeymoon suites with the windows looking out of the mountain.  Don't miss the Suicide Mountain tour, where you rent out a pressure suit and look at the corpses and primitive tools, but skip "Ghosts of Everest", which is just lame (aren't they always)? Wnt (talk) 12:53, 17 August 2010 (UTC)


 * Humans could create a normal environment on the moon or on Mars or on the peak of Everest, by having a pressurized and heated dome. Then they could do whatever they might do anywhere on Earth. "Inside Mount Everest" it would be far simpler, once the excavation was done. Dig a tunnel, insulate and seal it, then it is home sweet home, and you might as well be in a Super 8 Motel in Sidney, Montana. Now go to it. A little sweet talk and a bottle of wine might facilitate things. Edison (talk) 23:16, 17 August 2010 (UTC)


 * A little levity may be expected, since Everest is roughly 6 miles above the usual 4000-mile radius of Earth; squaring this ratio one might have nearly a 0.3% reduction in body weight. For a buxom bride that might be most of a pound!  But that neglects the little detail that Everest is underneath a person, exerting the largest portion of the planet's gravity - so I suspect the weight reduction would actually not be so large.  But has any luckless Sherpa ever dragged up the experimental apparatus to find out? Wnt (talk) 20:23, 18 August 2010 (UTC)
 * In Into Thin Air, Jon Krakauer mentions in passing two people having sex on Mt. Everest (in a tent). It wasn't near the top of the mountain, I don't recall if they were in base camp or what.  I think it can be safely assumed that at a place where as many people congregate as at Everest during climbing season, sexual intercourse is going to occur. Buddy431 (talk) 02:22, 19 August 2010 (UTC)

how can ?
I am a mech enng student from India. i want to know how we can convert the by products during combustion of fuel into a useful form? i means that how we can convert by products to a new energy source? then how we can reduce the pollution due to the exhaustion of unwanted gases. if u can help me my email id is xxx jibin abraham

(OP's email id and phone number deleted, following Ref Desk policy)  Jon Ascton    (talk)  12:59, 17 August 2010 (UTC)


 * I have removed your personal contact information to protect it from third parties; all reference desk questions are answered here. Unfortunately, I don't know that you're likely to get much of an answer to your question from people on the internet.  Discovering how to take internal combustion engine byproducts and turn them into useful fuel while reducing pollution is a guaranteed doctorate and all but certainly a Nobel prize -- it's also an open question. &mdash; Lomn 13:06, 17 August 2010 (UTC)
 * Lomn - that's a truly terrible answer. This is not remotely "an open question" - it's exceedingly well understood and it's flat out impossible.  What comes out of a correctly tuned, modern internal combustion engine is almost entirely water, CO2, nitrogen and a few nitrogen compounds.  None of these will produce energy for you because their constituent atoms already gave up their free energy inside the cylinders of the engine.  So, no - the laws of thermodynamics prohibit any possibility of doing this.  It is true, however, that a poorly set up engine will produce some carbon monoxide - which could (in principle) be persuaded to release a little more energy by reacting it with oxygen (which is what happens in the catalytic converter to eliminate CO - which is poisonous to humans).  But as internal combustion engines have improved over the last 20 years, the amount of carbon monoxide they produce has become so small as to be essentially zero - and if any carbon monoxide is available, you would be better off engineering the car to run more efficiently and thereby not produce any carbon monoxide in the first place rather than trying to exploit it later.  Encouraging our OP to waste time on trying to do this (in the hope of winning that Doctorate/Nobel Prize that you promised him) is downright irresponsible.  This is a dead end subject - I strongly advise our OP to look for something more productive to work on. SteveBaker (talk) 15:43, 17 August 2010 (UTC)
 * Well, actually if you burn hydrogen, your exhaust is water (something useful, I'd say), and if you add enough energy (say in electrolysis), you can go back to fuel. --Stephan Schulz (talk) 17:53, 17 August 2010 (UTC)
 * If our OP was talking about hydrogen fuelled cars, then you'd certainly expect to see mostly water and nitrogen in the exhaust. But we know he's not talking about that because he's concerned about reducing pollution (which is notably absent in hydrogen cars).  But in any case, using electrolysis to convert the water back into hydrogen and oxygen isn't going to create energy (as the OP specifies) - to the contrary, it'll consume significantly more energy than it produces.  So that's still a dead end engineering-wise.  If you have enough electricity on board your car to convert the water back into hydrogen, you'd do MUCH better by tossing out the hydrogen, the water and the internal combustion engine - and just making an electric car!  So this too is a terrible answer. SteveBaker (talk) 19:56, 17 August 2010 (UTC)
 * Fuels work by converting one collection of chemicals to another that has a lower energy level. Organic fuels (fossil fuels, biomass, etc.) get converted to carbon dioxide and water, which are already very lower energy. There isn't really anything you can convert them to to extract more energy. You might be able to use them for some other purpose, but not as fuel. You may find carbon capture and storage interesting. --Tango (talk) 13:07, 17 August 2010 (UTC)
 * Yes, combustion releases energy from fossil fuels, turning them into low energy chemicals. About the only way to use the low energy chemicals as fuel is to add more energy to them, which won't be saving anything. --Chemicalinterest (talk) 13:11, 17 August 2010 (UTC)
 * A Catalytic converter (see article) converts fuel combustion products into nitrogen, oxygen, carbon dioxide and water. Cuddlyable3 (talk) 14:10, 17 August 2010 (UTC)
 * It doesn't produce energy, though, it just speeds up the breakdown of the products of impurities in the fuel. --Tango (talk) 15:32, 17 August 2010 (UTC)
 * I'd be very surprised if it did not produce energy. Of course, that energy goes away as useless heat. --Stephan Schulz (talk) 17:53, 17 August 2010 (UTC)
 * A catalytic converter simply burns partially burned fuel. It does nothing to fully burned exhaust. Ariel. (talk) 18:33, 17 August 2010 (UTC)


 * Modern "3-way" catalytic converters also convert NO and NO2 back into nitrogen & oxygen. As it's name implies, the catalytic converter uses a catalyst to drive the reaction - there is no actual combustion (in the sense of flames & burning).  The additional heat from those reactions is very small though - completely negligable compared to the waste heat produced by the engine itself.  In the drive for more fuel economy, the amount of unburned fuel and carbon monoxide has gone WAY down over the last 10 to 20 years.  If you wanted to reclaim energy from waste heat then you'd be better off doing something with the hot water in the radiator or with the heat of the exhaust gasses themselves.  However, efforts to do that have been pretty ineffective to date...I've seen people try to use stirling engines to extract energy from those sources - but the results have been less than impressive.  Probably the best use of waste energy from the exhaust is in cars with turbochargers where the pressure of the exhaust gasses are made to drive a turbine that pumps air into the cylinders at higher pressure and thereby allow more fuel to be burned in each cycle.  The result is a more powerful engine - and this allows us to use smaller engines without sacrificing horsepower.  That saves weight and therefore energy.
 * SteveBaker (talk) 19:56, 17 August 2010 (UTC)


 * I'm not sure if this actually works, but could CH4 be burned in the absence of oxygen in such a way that it forms C2 + 4H2? The hydrogen in this case would be useful as hydrogen fuel. ~ A H  1 (TCU) 23:40, 17 August 2010 (UTC)


 * We've running away here, but see - the heat of formation of methane ΔHfo(CH4) from carbon and hydrogen is -17.8 kcal/mol, which is to say, it liberates heat to do the opposite reaction.  That page doesn't discuss entropy directly (though it looks like a nice web site which might somewhere else) but I doubt that the separate carbon and hydrogen are entropically favored.  Also of course "C2" doesn't exist per se, though it could be added to a mass of bulk carbon. Wnt (talk) 19:57, 18 August 2010 (UTC)

Leopard frogs
What's the difference between this and this? --Chemicalinterest (talk) 13:09, 17 August 2010 (UTC)


 * According to this, the Southern Leopard Frog has a "light spot in the center of its tympanum, a longer pointed head, and only a few dark spots on the side of the body" compared to the Northern Leopard Frog. Mikenorton (talk) 13:29, 17 August 2010 (UTC)

marine mammal biology
Tailfins of marine mammals such as whales are horizontal--tailfins of fish are vertical. Is a horizontal tailfin a unique characteristic of marine mammals? —Preceding unsigned comment added by 189.93.156.125 (talk) 14:09, 17 August 2010 (UTC)
 * More or less. It comes about because the tails of marine mammals are basically modified feet - where fish tails have always been tails.  Some bottom-feeding fish appear to have horizontal tails - but this comes about because flat fish (like flounders) are essentially normal fish that have evolved to swim on their sides - so what looks like a horizontal tail is "really" a vertical tail laid sideways.  However, this means that there are fish with horizontal tails - so you can't use that fact to determine whether a marine animal is really a mammal or a fish. SteveBaker (talk) 15:22, 17 August 2010 (UTC)
 * Have to disagree with you in one detail, Steve: most aquatic mammals' tails have nothing directly to do with their former rear limbs, which are (usually) vestigially present but buried in the body far forward of the tail region. Their tails are merely developments of the conventional tails their terrestrial ancestors had.
 * The reason that they are horizontal as opposed to the vertical tails of fish (and reptiles) is as follows. The spines and general anatomy of fish is such that they generally move by passing lateral (side-to-side) waves down their bodies (themselves often laterally flattened) from front to back: vertical tails are obviously most efficient in this context. When some fish developed limbs and colonised the land, giving rise to the common ancestors of reptiles and mammals, some retained their sideways-sprawling limbs and continued to flex their spines from side to side while walking, giving rise to the characteristic movement of, for example, most lizards, but others, including the ancestors of mammals, eventually evolved more vertical limbs and switched to the more efficient mode of flexing their spines vertically, enabling gaits such as galloping and bounding.
 * When some mammals later returned to the water, they retained this now built-in vertical spine flexing mode (see Marine mammal), and since a horizontally flattened tail is most efficient with this mode, that's how their tails developed. (I've just finished reading Richard Dawkins' The Greatest Show on Earth, which goes into this question explicitly.) 87.81.230.195 (talk) 17:45, 17 August 2010 (UTC)
 * Concur with 87.81. Note that the third character in the classic convergent evolution example of marlin, dolphin, ichthyosaur also has the vertical tailfin, though structurally completely different from that of the marlin. As a reptile, it still had the stereotypical sideways gait seen today in snakes and lizards and so benefited from the vertical tailfin, even though it had to essentially remake it from scratch. Matt Deres (talk) 19:32, 17 August 2010 (UTC)
 * Dolphins? All cetaceans and sirenians have horizontal tail-fins (or at least all the photos we have of them have). CS Miller (talk) 20:37, 17 August 2010 (UTC)
 * There is also a fish called dolphin. I think it is also called Mahi Mahi.  Googlemeister (talk) 21:12, 17 August 2010 (UTC)
 * I don't think Matt meant that a (mammalian) dolphin has a vertical tail (which, of course, it doesn't). Rather that, of the three animals he mentioned - respectively a fish, a mammal, and a reptile - which have all converged on a very similar overall body shape, the fish has always retained its original sideways spine flexing and hence a vertical tail, the reptile has after returning to the water re-evolved a vertical tail because it had retained the sideways spine flexing during its land phase, but the mammal redeveloped its tail horizontally on becoming once more aquatic because it had developed vertical spine flexing while on land. 87.81.230.195 (talk) 22:03, 17 August 2010 (UTC)
 * Indeed. I can see how I was a little unclear, but but when I said "third", I made sure ichthyosaur was the third thing on the list I gave. :-) Matt Deres (talk) 00:25, 18 August 2010 (UTC)


 * I don't know if it's helpful to mention that some marine mammals, especially seals like the harbor seal, do use their fins oriented vertically in a side-to-side motion like fish do. These seals do have their rear fins derived from hind limb structures, whereas cetaceans have rear fins derived from the tail of the spine rather than rear limbs (note the location of the undeveloped hind limbs (C) in this skeletal image: http://en.wikipedia.org/wiki/File:Whale_skeleton.png forward of the fluke.) —Preceding unsigned comment added by Wevets (talk • contribs) 05:25, 18 August 2010 (UTC)
 * Just so, hence partly the 'most' in my earlier post. These rear fins aren't strictly 'tailfins' which the OP asked about, but some might confuse the two, so your clarification is timely. 87.81.230.195 (talk) 09:08, 18 August 2010 (UTC)

Small-scale carbon sequestration using phytoplankton?
Hi. I'm investigating common-sense and small-scale approaches to carbon offsetting, and have been asked to look into the potential of micro sequestration as a carbon offset. One approach that has come up in discussion is the growing of cultures of phytoplankton. I've found information intended for aquarists that shows it is relatively easy to grow a culture of phytoplankton, particularly for people on the coast. However, I'm finding it very difficult to obtain any information as to how effective these plankton are at sequestrating carbon in small quantities: a figure for mass or volume of plankton per tonne CO2e, for example. I recognise that this is unlikely to be cost effective and may require totally massive amounts of plankton, but I have no frame of reference at all, so it can't hurt to ask! Whether it's a good idea or not, for the sake of completeness I'd like it in my report, so it would be very helpful if anyone knows anything that might point me in the right direction.

Thanks much! Dan Hartas (talk) 14:33, 17 August 2010 (UTC)


 * It is going to heavily depend on what happens to the plankton. In the wild, studies suggest that only a small fraction of plankton biomass is sequestered, while most is eaten and recycled by other organisms.  If you intend to collect the plankton and bury them (or something) you could trap more carbon, but that would depend on specific human intervention.  Plankton are about 0.3 grams carbon per 1 gram dry weight, so 1 tonne CO2 could make about 900 kg of plankton (dry weight) assuming all other conditions were favorable.  In practice though, I would suspect that plankton growth is nearly always limited by other nutrients (e.g. Fe, P) and not by CO2, so you'd have to supply such nutrients to get them to grow in abundance.  Dragons flight (talk) 17:54, 17 August 2010 (UTC)


 * The real problem with plankton (although you didn't ask) is that they are decomposed by bacteria. Furthermore, those bacteria take up oxygen in the process of decomposing the plankton.  If the quantity of plankton is high enough to overcome the amount of decomposition, then the water becomes almost completely anoxic, killing most if not all animal life. Looie496 (talk) 23:52, 17 August 2010 (UTC)


 * Dragons flight, that weight stuff is for zooplankton, not phyloplankton, unless I've misunderstood. The nutrients aren't a problem, apparently ordinary plant food has everything they need. And on Looie496's point, would that happen in small-scale circumstances? It sounds like you can grow a culture of these things in about two weeks, though I haven't yet tried it myself. Would that be enough time for the decomposition to have a significant effect? Dan Hartas (talk) 08:51, 18 August 2010 (UTC)


 * It's not the bacteria you need to worry about, but viruses - they manage to kill off algal blooms and so if they got into your culture you'd be screwed. You might be better off seaweed farming as it would be a lot easier to harvest than microalgae and kelp can be extremely productive. Smartse (talk) 16:22, 18 August 2010 (UTC)

Gene copy number: human genes that are rarely deleted or duplicated?
I haven't been able to find anything definitive in the primary literature, so I thought I would pick the brains of the RDD (reference desk denizens). I'm planning an experiment in which I use real-time PCR to estimate the viral copy number of HPV infected tissues by comparing the viral DNA to reference one or more host genes. Many of these tissues, however, exhibit considerable chromosomal instability, so it's important that I'm comparing the HPV numbers to human gene that are unlikely to change in copy number (either up or down). It is safe to exclude any considerations of a Y-chromosome here. Does anybody know of any genes that are especially unlikely to be either deleted or duplicated (i.e., not have a copy number other than 2)? Thanks! – ClockworkSoul 15:14, 17 August 2010 (UTC)
 * This doesn't really answer your question, but is there a reason that you want the HPV copy number to be relative to the host copy number? Why not just generate a standard curve of HPV copy numbers and then determine the absolute copy number (or copies per microgram of input DNA) in your sample? --- Medical geneticist (talk) 18:22, 17 August 2010 (UTC)
 * Normally, that's what I would do since what I really want is the average virus count per cell, but there are two problems. First, I don't necessarily know how many cells I'll have, largely because of the difficulty in resolving cell numbers from microdissected FFPE (formalin-fixed, paraffin-embedded) tissue. Second, many of my higher grade samples have large-scale chromosomal anomalies (deletions, duplications) that make "copies per microgram of DNA" unreliable. The qPCR alternative works well enough, though, assuming there are really as many "baseline" copies of the human genes as you think. – ClockworkSoul 19:32, 17 August 2010 (UTC)
 * It's a little hard to answer your question without a detailed understanding of the system you're using (for example, how dramatic is the chromosomal instability) but it would be hard to imagine any single site being absolutely stable if there is enough instability to significantly affect the average amount of DNA per cell. How about using a selection of sites across multiple chromosomes and averaging them?  You could choose pre-made real-time PCR primer pairs or probes for various "sequence tagged sites," which already have well-established primer pairs. --- Medical geneticist (talk) 02:30, 18 August 2010 (UTC)
 * The try-a-few-and-see approach seems most straightforward; all I can add is that the cytology for most tumor types has been well studied (e.g. cervical cancer is known to have amplifications at 3q26 and 8q24, so you could try to avoid trouble spots. You could also use a standard curve.   Another approach might be to use a sequence you know is present in many copies (Alu, for example , though unless the virus is present in very large abundance it might be better to compare to a less common repeat. Wnt (talk) 14:24, 18 August 2010 (UTC)

House revisited
Hey, it's me from a few days up. How accurate medically is House M.D., overall. I've read Dr Scott's Polite Dissent blog and it seems to focus more on minor things from individual episodes rather than the 'big picture'. The impression I get is that sometimes the directors/writers will take some artistic license and sacrifice afew technical details for entertainment, eg the characters sometimes don't wear eye or face protection in surgery because it would obscure their facial expressions and thus their emotions, or the effect of a medicine is exaggerated to bring closure to an episode, or they run a culture and it comes back 2 hours later inconclusive so they move on to keep the plot moving, rather than the more realistic they run a culture it grows for 2 weeks and comes back inconclusive, they do it again, and then they move on, you get my point. But I saw an episode where a patient with a brain-dead right hemisphere couldn't see in his right eye but was fine in his left, a basic mistake, thus, here were are. --Anon. 18:25, 17 August 2010 (UTC) —Preceding unsigned comment added by 76.229.199.177 (talk) 18:25, 17 August 2010


 * Old discussion may be slightly relevant, though it doesn't answer your question directly. 90.195.179.60 (talk) 19:16, 17 August 2010 (UTC)
 * I can't speak to the accuracy of their medical facts, but in terms of basic procedure I think the show is pretty awful. The doctors there just don't behave the way that people trying to solve a difficult problem really behave.  They never seem to concentrate on what they're doing, they just come out with ideas, one after another without pausing.  You could say it's just drama, but the old ER show was far better (in the early years at least), and more dramatic too. Looie496 (talk) 23:40, 17 August 2010 (UTC)


 * There are enough fragments of accurate medical information to classify House as a "medical drama" but the writers take significant liberties with the process of medical diagnosis and treatment, with the result that the show ends up being not much more than a caricature of the medical profession. It's really just a soap opera.  I heard a lecture by an M.D. who serves as an adviser to the show, and he described the writing process as something like this: 1) the writers have an idea for a thread to develop some aspect of a character, 2) they consult with the medical advisers to identify a medical condition that could present in an unusual way and allow for a number of different diagnostic possibilities, 3) the writers take the idea and run, and 4) shortly before they start filming the episode the medical advisers check to make sure that there aren't any egregious errors (keeping in mind that it's ok for any aspect of the diagnostic process and/or treatment to be far-fetched or temporally inaccurate for the sake of the thread of drama).  Basically, the medical aspect of the show is merely a vehicle for the actors to portray the characters, and should not be taken as anything much more than that. --- Medical geneticist (talk) 02:49, 18 August 2010 (UTC)


 * One should give them credit for having advisers. Compare CSI - I've watched two episodes of that, and in one a killer was harvesting drug addicts for the heroin in their brains, and in the other someone was electrocuted because current from a cable buried in the sand arced up to his heart because someone wrote something on his chest in conductive ink.  What's next, a killer who breaks into high-rises by climbing the beam of his partner's flashlight? (oh no, I just gave them an idea... Wnt (talk) 14:29, 18 August 2010 (UTC)


 * I think you'll find most of these shows do have advisers of some sort. CSI:LV definitely does http://www.mightystudents .com/essay/Four.%284.%29.different.119952 (blacklisted site),, . It doesn't mean they listen to them Nil Einne (talk) 07:44, 19 August 2010 (UTC)

Genes and Genomes
How is a gene different to a genome? --T.M.M. Dowd (talk) 19:18, 17 August 2010 (UTC).
 * Our gene and genome articles are pretty thorough. – ClockworkSoul 19:22, 17 August 2010 (UTC)


 * Put simply, a Gene is a small piece of genetic information that codes for a specific trait. I have a gene that makes my eyes blue, my wife has a different gene that makes hers brown.  A Genome is all of the genetic information that makes up an organism - thousands to hundreds of thousands of genes.   It's a little more subtle than that - but that's the "Big Picture" explanation.  If you need more - look up the articles. SteveBaker (talk) 19:32, 17 August 2010 (UTC)


 * Put even more simply: An organism's genome is made up of genes. The Human Genome Project, then, was an attempt to map all of the genes in a human genome. (Well, a number of humans, but that's a bit beyond the point.) --Mr.98 (talk) 21:49, 17 August 2010 (UTC)


 * NO! You have many genes controlling eye colour - Eye colour (this has some examples where you could say you and your wife have different genes). Smartse (talk) 16:31, 18 August 2010 (UTC)
 * Steve and his wife could differ in only a single gene and still have different eye colors as he described. While a single gene is not solely responsible for determining eye color in humans, it's not incorrect to say that it would govern the determination in their particular case &mdash; a single genetic difference could be sufficient to alter the observed phenotype.  Heck, cut him a bit of slack &mdash; he noted that he was giving a high-level explanation.  TenOfAllTrades(talk) 16:59, 18 August 2010 (UTC)
 * I did say "It's a little more subtle than that"...but yes, eye color is a multi-gene thing. SteveBaker (talk) 03:13, 19 August 2010 (UTC)


 * A gene is a single instruction. A genome is the entire instruction manual.  -- Jayron  32  04:37, 18 August 2010 (UTC)


 * A gene is a bit like a recipe for making a particular protein, a genome is like a recipe book that holds all the recipes together and allows your cells to use the recipes. Smartse (talk) 16:31, 18 August 2010 (UTC)

Bouncing orbit
I'm trying and failing to locate an article. Maybe it doesn't exist. List of orbits didn't help.

Many years ago, I read a novel of hard science fiction, written by a scientist (I recall), in which a megalomaniac religious leader devised a hammer-of-god-like threat to the world that involved something the novel referred to as a "bouncing orbit".

In this scheme, a two halves of large mass are positioned above a pole of the Earth and allowed to fall straight down. If the religious leader chooses to allow it, at a predetermined time powerful electromagnets push apart the two halves with sufficient force for them to pass by the planet and meet again over the other pole. The electromagnets recharge themselves from the two half-masses coming together. When they meet, the combined mass continues upward away from the pole until it begins falling again.

This "orbit" has the center of mass bouncing up and down through the planet's center. I thought it was an interesting idea when I read it. The sources I can find, however, seem to be use this term in the context of subatomic particle interactions.

Thinking about this caused me to wonder if the acceleration experienced by the center of mass, orbiting this way, is the same as if the mass fell through a small hole bored straight through the Earth. ~Amatulić (talk) 20:26, 17 August 2010 (UTC)


 * Well, it isn't really an orbit if it requires powerful electromagnets. Orbits are what objects in free fall follow. I doubt you'll find an article on the subject, since it probably only exists in that one story. Someone might recognise the plot and be able to find an article on the book, but that's the best you'll get. The centre of mass will be exactly the same if the mass fell through the Earth rather than going around it, since the vertical components are the same and the horizontal components of the two halves cancel out. --Tango (talk) 21:33, 17 August 2010 (UTC)


 * That's what I thought. Thanks. ~Amatulić (talk) 21:53, 17 August 2010 (UTC)


 * But that answer is wrong. When the line between the two halves does not pass through the Earth, the force on the two halves is less than if they were united, for two reasons.  First, they're farther from the Earth's center.  Second, the force on each one is angled toward the Earth's center.  For example, say that the objects' center of mass is 6,000 miles from the Earth's center and they are 9,000 miles apart, or each 4,500 miles from their center of mass, conveniently making a pair of 3:4:5 triangles.  Then each object is 7,500 miles from the center, so the force on it is (60/75)&sup2; of what it would be if they were united at their center of mass.  And if we resolve the force into "vertical" (parallel to the Earth's axis) and "horizontal" (toward the other half) components, only 60/75 of the force is vertical.  So the center of mass, at that instant, is accelerating by just (60/75)&sup3; = 0.512 times as much as it would be if the objects were united.


 * When the line between the two halves does pass through the Earth, the calculation is more complicated because now the two halves are attracted by the full Earth whereas if they were united they would be attracted only by the inner part of the Earth (the part closer to the center). Since the question was only "is the acceleration the same", I am not going to determine by what amount it's different; but it will in general be different.--Anonymous, 22:58 UTC, August 17, 2010.


 * I haven't gone through your maths, but it seems unnecessarily complicated. The centre of gravity of the two halves is the same in both cases and the centre of gravity of the Earth and the two halves must be constant, since there are no external forces, therefore the centre of gravity of the Earth must be the same in both cases. That means its acceleration must be the same. --Tango (talk) 23:05, 17 August 2010 (UTC)


 * Tango, please do "go through the maths" before making wrong statements. Only for a spherically symmetric mass is it true that the force of gravity is equivalent to what it would be for a point mass on its center of gravity.  --Anon, 11:35 UTC, August 18, 2010.


 * The orbital period depends only on the semimajor axis - an object that almost brushes past the Earth will have the same period as one that orbits in a circle. That said, separating two halves of a mass with electromagnets does change the orbit...  to give an extreme example, if they are given near-escape velocity they would move out to a large distance and could take as long as you wish for them to fall back. Wnt (talk) 00:49, 18 August 2010 (UTC)

is this (arch of books) real?
is this real? (arch of books). why don't the books at the top fall down? The one in the middle of the top is vertical and can fall straight down if not glued - why doesn't it? 92.230.233.158 (talk) 20:51, 17 August 2010 (UTC)


 * The keystone book you refer to would not fall down due to fricton from the books on each side. The weight of each side of the arch is pushing on each side of that book.
 * There's no reason why it can't be real. I have built free-standing arches like that out of wooden blocks. ~Amatulić (talk) 21:13, 17 August 2010 (UTC)


 * so if you take that book out because that's the one you need, the whole thing would crash down? Doesn't sound as useful as it looks anymore. 92.230.233.158 (talk) 21:15, 17 August 2010 (UTC)


 * More likely, because that book is so thin, removing that center book may cause each side of the arch to fall toward each other a little bit, leaving another book in the center. Generally a keystone is a significant piece of an arch, the key that keeps it together. No, an arch of books isn't useful if you happen to need any of the books, not just the top center book.


 * Our article on keystone is incorrectly referenced; the keystone is no more important structurally than any other piece of the arch. It's only the "key" stone because it's the last piece to be put in place. Frankly, it's probably less important than the other pieces; if you were to remove it, the two sides would collapse into a semi-stable arch-like shape. If you removed a piece at the bottom... I'm looking for a proper reference, but the word keystone seems to have been completely co-opted by the ecology folks. Will keep looking. Matt Deres (talk) 00:32, 18 August 2010 (UTC)


 * In the building of bridges and other arches, the keystone is usually specially shaped and the material is chosen very carefully to ensure that it can withstand the forces. I agree, however, that other components of the arch are also important to stability.


 * The Arch article goes into some detail about different constructions of an arch. ~Amatulić (talk) 21:31, 17 August 2010 (UTC)


 * While some such arch might work in theory, I'm skeptical of some features of the photo. It seems like some of the books are separated by wedges - I don't think it's purely made out of books.  The center book seems to spread out toward the back of the arch rather than upward as one would expect of a keystone.  And the sides of the arch are perfectly level - you'd think that the pressures involved in an arch would bow those stacks outward; they're not masonry blocks.  My guess is that it's a typical artistic assemblage with many compromises in execution. Wnt (talk) 00:53, 18 August 2010 (UTC)
 * Furthermore, if you compare the book arch with the first illustration in Arch, the most obvious things missing are the abutments, which would stop the vertical stacks being pushed outwards. The book arch must have hidden reinforcement to stop this from happening. --Heron (talk) 08:08, 18 August 2010 (UTC)

Afterburners
Hello. Our article on afterburners says that extra fuel is injected after the turbine (which is most of the engine). Can someone tell me exactly where the extra fuel is injected? --The High Fin Sperm Whale 21:09, 17 August 2010 (UTC)


 * For the General Electric J79 they're shown as item #17 on this diagram "afterburner spray bars". -- Finlay McWalter • Talk 21:15, 17 August 2010 (UTC)


 * The fuel is injected after the turbine. :)
 * "Turbine" in this instance refers the turbine fan assembly. Behind that there's a hollow chamber with a nozzle at the very back end. Afterburner fuel is injected behind the aft fan of a turbine jet engine, but before the nozzle. ~Amatulić (talk) 21:16, 17 August 2010 (UTC)


 * In the combustion chamber? --The High Fin Sperm Whale 21:31, 17 August 2010 (UTC)


 * No, the combustion chamber is forward of the aft fan. The afterburner is between the aft fan and the nozzle. The combustion chamber is where fuel normally combusts and expands, being forced out the nozzle in back. The exhaust gases pass over the aft turbine fans to drive them, which in turn drive the forward compressor fans for sucking in more air. That's why jet engines are known as "continuous combustion" engines, as opposed to intermittent combustion as in a piston-powered internal combustion engine. ~Amatulić (talk) 21:51, 17 August 2010 (UTC)


 * High Fin Sperm Whale has written after the turbine (which is most of the engine).  This is incorrect.  Most of the engine is forward of the turbine.  The only component aft of the turbine is the nozzle.  A jet engine consists of diffuser, compressor, combustion chamber, turbine and nozzle, in that order.  Dolphin  ( t ) 11:20, 18 August 2010 (UTC)
 * I think you're misreading what was intended - the afterburner is after the turbine - which means that the afterburner is after most of the engine (we know that the turbine isn't "most of the engine"). It could have been clearer - but the intent was correct. SteveBaker (talk) 03:08, 19 August 2010 (UTC)

Mutation in genetic algorihms
It is not mentioned in the Wikipedia article where the mutation operation is used in the genetic algorithm. Let's say there are N chromosomes in the last step. (I say them old N chromosomes) I think that there are three different choises.

1) N new chromosomes are generated by three operations: a) Some are directly copied from initial population b) Some are generated by crossover c) Some are generated by mutation.

2) N old chromosomes enter crossover and after mating and crossover N new chromosomes are generated. Only N new chromosomes enter mutation, not new N chromosomes.

3) N old chromosomes enter crossover and after mating and crossover N new chromosomes are generated. Both N old and N new chromosomes enter mutation.

Can all three methods work? Or which one is true? Kavas (talk) 21:18, 17 August 2010 (UTC)
 * Any of these will work just fine, and there's no standard timing for mutation in a genetic algorithm. My own choice would be to copy/mutate, and then cross over since that could generate the most novel combinations, but it's entirely a design decision. Good luck! – ClockworkSoul 21:35, 17 August 2010 (UTC)


 * Thank you. But, what's copy/mutate? Kavas (talk) 21:46, 17 August 2010 (UTC)


 * It's important to limit the rate of mutations, or you get mutational meltdown. When you take that into account, I don't think it matters which technique you use. Looie496 (talk) 23:25, 17 August 2010 (UTC)


 * By copy/mutate, I just meant that if I were writing this, I would choose to generate mutant chromosomes and group them with the "old" chromosomes as a single population prior to sending them to the crossover routine. Just my personal preference, though. Again, though, all of these approaches are perfectly adequate and will all give you results. Looie496 is right though: mind your mutation rate! – ClockworkSoul 18:34, 18 August 2010 (UTC)

What is this tree?
Photographed in Hampshire, England. Kittybrewster  &#9742;  21:58, 17 August 2010 (UTC)
 * Unsure, but could it be a type of Ailanthus? ---Sluzzelin  talk  22:52, 17 August 2010 (UTC)
 * Maybe also a Fraxinus (Ash) species? While not the only tree family with compound pinnate leaves, its usually highly associated with the Ash family.  You'd have to check to see if the leaves are simple pinnate (i.e. each leaf is an individual leaf, with its own anchor point) or compoundly pinnate (i.e. the central "stem" of the cluster of leaves is really the main vein of the leaf, and each seperate "leaflet" isn't a seperate leaf, but part of the compoundly-pinnate structure).  The latter compoundly-pinnate structure is usually most closely associated with Ash trees.  -- Jayron  32  04:34, 18 August 2010 (UTC)
 * I think it has too many leaflets per leaf for it to be an Ash (at least based on the pictures in our articles), the new shoot also doesn't look like those of ash that I can find either. Whereabouts was the photo taken? Do you know anything else about it, like height, colour of flowers etc.? User:Smartse
 * Photo taken in a garden at late dusk. It is as high as a three-storey house. Colour of flowers not known. Kittybrewster  &#9742;  16:46, 18 August 2010 (UTC)
 * Then I still think it might a tree of heaven Compare google pics for Ailanthus + gardens + England. ---Sluzzelin talk  16:50, 18 August 2010 (UTC)
 * Agreed Sluzzelin - you win the cigar - the odius Tree of Heaven it is. It's set to take-over England if the papers are to be believed. Alansplodge (talk) 17:23, 18 August 2010 (UTC)

Optics: 35mm focal length equivalent
Hobbyist filmer here. I'd like to make mind-blowing ultra wide-angle images like Terry Gilliam, but in the more economical format of Super 8 mm film. What I do know is that I'm not even remotely looking like Gilliam with any focal length above 18mm...but that's my desired upper length in 35mm only. The focal length to achieve a particular angle of view (which is the thing that makes for the mind-blowing images with wide-angle images) is different with any format and sensor size you use, hence there's articles such as 35 mm equivalent focal length and crop factor. In other words, if you change the format (i. e. size of your film or sensor) but wanna have the same angle of view, you need a different focal length.

Now, I have a chance of acquiring a lens (for a Super8 camera made by the Austrian Eumig brand) which is labeled as ultra wide-angle, according to trade press this lens is guaranteed to be entirely rectilinear (no barrel aka fish-eye distortion, as I don't want this), and its focal length in Super8 is 4mm.

So what I'd like to know is, what's the 35mm equivalent of these 4mm in Super8, according to crop factor? Or in other words: If my desired upper limit is an 18mm focal length in 35mm, what equivalent focal length would that be in Super8?

I guess what might help are the dimensions of the Super8 frame area: 5.97mm horizontal x 4.01mm vertical, compared to 22mm horizontal x 16mm vertical in 35mm.

My second choice would be a 3CCD miniDV with a 1" chip size. What's the equivalent to 18mm there? --79.193.41.61 (talk) 22:39, 17 August 2010 (UTC)


 * Your 4mm Super8 lens would be approximately equivalent to a 15mm lens in 35mm format. When you halve the linear measurements on the sensor size, you double the effective focal length of the lens in terms of angle of view. Chip sizes are generally expressed in diagonal, so for a standard 3:2 aspect ratio, your 1" chip has dimensions of approximately 21mm x 14mm. That's almost the same as 35mm; the 18mm-equivalent would be around 17mm, maybe a little less depending on the aspect ratio. Thegreenj 22:41, 18 August 2010 (UTC)


 * Thank you, at least now I know about 4mm = 15mm. But how can it be that my 1" is largely identical to 35mm? Depth of field is largely dependent upon the crop factor too, and all video cameras have a very, very large DOF compared to 35mm, especially 1" CCD cams do, unless they're used with a 35mm adapter or are specifically equipped with CCDs as large as 35mm. It's why video is said to be "flat" compared to 35mm and above. --79.193.58.197 (talk) 00:30, 19 August 2010 (UTC)


 * My bad. Now I see I got 1" wrong with what's actually 1/3". Sorry. --79.193.58.197 (talk) 00:38, 19 August 2010 (UTC)


 * That makes sense; I was wondering about the 1" sensor, which isn't a size I've run across before. So your equivalent lens would be ~6mm (=(1/3)*17) for 1/3". If you're interested in comparing focal length, DOF, noise, etc. across different sensor types, you might check out this website: . It's a fairly straightforward&mdash;if very lenthy&mdash;guide to such things. Thegreenj 02:41, 19 August 2010 (UTC)


 * Thanks for that link, even though it seems to mainly limit itself to noise, sharpness, and DOF rather than focal length and angle of view. It uses the term "equivalent lens", but again seems mainly interested in noise, sharpness, and DOF. After clicking some of the links at the bottom though, I came upon this neat focal length calculator which helps me a lot. --79.193.41.249 (talk) 19:35, 19 August 2010 (UTC)


 * Oh, on second thought, the statement I've found on eBay of this ultra wide-anlge converter to be 4mm appears rather silly, as this is just a converter and the resulting focal length depends upon what optical system I'll attach it to. Going back to this trade press article, the angle of view is "three times as large" with this converter, and the Eumig cameras compatible with it that I've found so far all have zoom lenses with the shortest focal length of 7 to 8mm.


 * Thanks to the focal length calculator above, I can now freely convert my focal lengths to the 35mm standard, but how does an angle of view "three times as large" translate into focal length? Does that mean 8/3 = 2.66mm, with a 35mm equivalent of 10mm? Or do we have to go by the image circle produced by the lens and work out something based on Pi (i. e., a disk with an area "three times as large") which is then computed through an angle factor somehow? --79.193.41.249 (talk) 04:08, 20 August 2010 (UTC)


 * I think you're right. Angle of view is roughly proportional to (1/focal length), so an angle of view 3 times as large would indicate a focal length approximately 1/3 the original. If it were referring to the area of the imaging circle, it would be different (focal length would be multiplied by approximately 1/sqrt(3) ≈ 0.577), but I doubt that's the case; usually converters are marketed based on approximate effect on focal length (e.g., 10x teleconverter, 0.7x wide angle converter) and not the area. Thegreenj 01:36, 21 August 2010 (UTC)

Identify this snake
Hi. I saw a snake today in Southern Ontario, on a road near a canal, about 20 inches long with black and bright yellow stripes. What snake is this? I don't have any pictures. Thanks. ~ A H  1 (TCU) 23:29, 17 August 2010 (UTC)
 * Was it striped laterally? In that case it could have been Butler's Garter Snake. ---Sluzzelin talk  23:33, 17 August 2010 (UTC)
 * The stripes on the snake in that picture I would describe as wheat-coloured and yellowish-brown. The snake I saw had about as much yellow as black but the striping pattern was basically the same, and it was more of a neon-yellow than a yellowish-brown. The Butler's Garter Snake was the result I got from looking at a snakes of Michigan webpage, but so far I don't think that was it. ~ A H  1 (TCU) 02:13, 18 August 2010 (UTC)
 * The article does describe a range: "three yellow to orange stripes along the length of the body. The background color can range from brown, black or olive". Google has blacker and brighter examples. . ---Sluzzelin  talk  03:25, 18 August 2010 (UTC)
 * I guess it could also have been a different species from the garter snake genus (Thamnophis). The Common Garter Snake, for example, comes in different varieties too. Not all seem to have red markings, and some are blacker than others. Not sure about the "about as much yellow as black" part. The yellow stripes look thinner than the dark ones on virtually all the snakes I googled. ---Sluzzelin talk  11:49, 18 August 2010 (UTC)
 * This Common Garter Snake was photographed in Ontario. ---Sluzzelin talk  11:52, 18 August 2010 (UTC)
 * And here's one more garter snake candidate: A ribbon snake. If so, most likely Thamnophis sauritus septentrionalis (Northern Ribbon Snake). ---Sluzzelin talk  16:35, 18 August 2010 (UTC)