Wikipedia:Reference desk/Archives/Science/2015 April 7

= April 7 =

microwave
If you push your face against the door of a microwave to watch the food going around inside, how much dose of radiation do you get? — Preceding unsigned comment added by Coosquirt3 (talk • contribs) 00:53, 7 April 2015 (UTC)
 * Literally nothing, if you mean ionizing radiation, which is the stuff that causes real issues. Microwave ovens do not produce ionizing radiation, which is what causes cancer and radiation sickness and stuff like that.  Microwaves emit a high-energy form of radio waves, not much different from the signal that is picked up by your TV set if you receive an over-the-air broadcast.  According to this, the average microwave oven "leaks" about 2 milliwatts per square centimeter at a distance of 2 inches from the glass over the whole lifetime of the microwave total.  Assuming a microwave lasts ten years, 2 milliwatts per square centimeter per decade is basically next to nothing.  -- Jayron 32 01:09, 7 April 2015 (UTC)
 * Your response is susceptible to a misunderstanding. Milliwatts are units of energy flux, not total energy. The meaning of the FDA standard is that the flux (i.e., rate of energy leakage) can't increase beyond a certain limit (5 mW /cm2) as the oven gets older. This is not necessarily related to the accumulated flux over time, which would be measured in joules per unit area. Short Brigade Harvester Boris (talk) 01:31, 7 April 2015 (UTC)
 * Yes, microwaves are designed to be safe. The glass door has a mesh that prevents leakage of sufficient microwave radiation to cook your eyeballs, but I wouldn't recommend spending many minutes with your eyes pressed against the glass, just in case ...    D b f i r s   09:15, 7 April 2015 (UTC)
 * I suppose that in cases of microwaves all been depended on by ionizer (radiator) of microwaves.--85.141.239.195 (talk) 15:47, 7 April 2015 (UTC)
 * No. Again, ten times no.  Microwaves do not ionize anything.  Microwaves are not ionizing radiation.  Microwaves do not do to your cells what things like X-rays and gamma rays do.  -- Jayron 32 16:45, 7 April 2015 (UTC)
 * Thanks. I’m thought, that a configurations of ionizer (radiator) of microwaves are been determine.--83.237.194.163 (talk) 17:39, 7 April 2015 (UTC)
 * Are not been. But when you press your eyeballs against the glass, you really see light waves that aren't really there. No harm staring at water to see what are been later, but if microwaved first, you be not seen again. Like been atomic and hydrogen bomb, but not really leave shadows that aren't really there. InedibleHulk (talk) 18:21, 7 April 2015 (UTC)
 * Sitting in front of old TVs can also burn shadows, but only on TV. InedibleHulk (talk) 18:27, 7 April 2015 (UTC)
 * Did geometry is been determine too?--83.237.197.142 (talk) 18:57, 7 April 2015 (UTC)
 * Of course. If trajectory is been known, you drop rectangle at bisection point. If rectangle area is been greater than or equal to face and volume is been beating ballistic limit, harm is been undone. If not, face melt. InedibleHulk (talk) 19:26, 7 April 2015 (UTC)
 * Agree, that a radiator of microwaves is been a radio antenna of high microwave ionization.--83.237.214.220 (talk) 16:30, 8 April 2015 (UTC)
 * Still no. InedibleHulk (talk) 18:59, 8 April 2015 (UTC)
 * Thank you. I think that magnetical action is been a ionization.--83.237.203.56 (talk) 19:29, 8 April 2015 (UTC)
 * As for me, the question is in that, could magnetism change a structure of substances or not it didn’t.--83.237.202.245 (talk) 21:42, 8 April 2015 (UTC)

How long do LED, CFL, etc bulbs stay "on"?


LED and CFL bulbs cut on and off 60 times per second right (on US A/C). How long do they stay on in each cycle?

Yesterday I took three photos that included a street lamp. The exposure time was 1/400 second. In two of the photos, the street lamp was very dim but in the third it was brighter than I remember it being.

So how does the light output of modern bulbs vary across one cycle of A/C? Bubba73 You talkin' to me? 03:20, 7 April 2015 (UTC)


 * I don't know, but I do know that "60 times per second" is wrong unless the light is only on when the AC current is flowing one way and not the other way. Any such flicker should normally be at 120 times per second. --65.95.176.148 (talk) 03:27, 7 April 2015 (UTC)


 * You are right - if it flickers, it should be 120 times per second (US A/C). Bubba73 You talkin' to me? 03:51, 7 April 2015 (UTC)
 * An LED may not flicker in both directions. Current tends to only easily flow in one direction through a diode. I'd think that'd keep them at 60 Hz. --OuroborosCobra (talk) 03:57, 7 April 2015 (UTC)
 * Ah, that D does stand for "diode", doesn't it? Good point.  (But see Z-man's response just below.)--65.95.176.148 (talk) 18:27, 7 April 2015 (UTC)


 * Most modern fluorescent lights use an electronic ballast that changes the frequency to to something on the order of tens of kHz. LED bulbs don't turn off and on at all. They use a rectifier to supply the actual LED with DC. Any flicker is just a result of the driver circuitry not smoothing the output very well. Mr.Z-man 04:07, 7 April 2015 (UTC)
 * Bet me to it, even cheap LED bulbs will have a rectifier circuit in them, I have actually used them as a cheap source of 12v rectifiers for other projects. Vespine (talk) 04:22, 7 April 2015 (UTC)

I've added cropped versions of three photos that I took the other day within seconds of each other. I didn't notice any change in brightness. They were all taken in aperture priority, ISO 100, f/8. (the first one was at a focal length of 60mm, the next two were at 70mm.) The camera exposed the first and third for 1/320 second and the second one for 1/400 second. Yet, the second one is brighter, even though its exposure was shorter. Why? Bubba73 You talkin' to me? 05:14, 7 April 2015 (UTC)
 * The lamp in question could very well be flickering, that would explain the different brightness. We're making a lot of assumptions. MY guess is that it isn't an LED lamp, but have no good guess as to what it is. I suppose some sort of fluro makes the most sense. Could you take some more photos, maybe manually set the exposure to 1000th and see what it looks like? also take some photos of OTHER lamps in the area, in case the one you picked just happened to have a faulty driver perhaps flickering because it's "on the way out"? That's probably unlikely, but might be worth eliminating as a factor. Vespine (talk) 06:51, 7 April 2015 (UTC)
 * New photos, see the link below. Bubba73 You talkin' to me? 03:04, 9 April 2015 (UTC)


 * Flickering fluorescent lights are a fairly well known problem in photography. See here for example.  Modern DSLRs can include anti-flicker circuitry.  Check out the review of the Canon 7d Mk II at the same site for a description of it in action.--Phil Holmes (talk) 10:05, 7 April 2015 (UTC)


 * My camera (Nikon D7100) as the anti-flicker and I have it on. However, the lamp is only a small portion of the entire photograph, so it may not have picked it up.  Bubba73 You talkin' to me? 15:24, 7 April 2015 (UTC)


 * I would like more info on this. The OP asks about LED, CFL, etc. These photos look like one of the 'etc' bulbs. I.e.,  common incandescent. What color balance did you use (AWB?)(and there are sky clouds clearly visible  behind so me thinks AWB) ... its reddish, so not a LED  nor fluorescent. Its light flux is just varying 120 times per second. --Aspro (talk) 15:12, 7 April 2015 (UTC)


 * Yes, I did have auto white balance on, and it was set to normal. Bubba73 You talkin' to me? 15:24, 7 April 2015 (UTC)
 * In my WP:OR, it is rather hard to get two identical photos, even with a tripod, with a modern digital camera on "auto/normal" modes. The white balance, autofocus, and lots of other factors conspire such that even in controlled situations where you know the subject and light haven't changed, the photos can still look rather different. SemanticMantis (talk) 15:42, 7 April 2015 (UTC)
 * It wasn't in auto/normal mode. Bubba73 You talkin' to me? 17:55, 7 April 2015 (UTC)
 * Forgetting the specific terminology of your camera, I just meant this - "Yes, I did have auto white balance on, and it was set to normal" - that means the camera was making at least a few choices on your behalf, that may well change the apparent brightness in the photograph. SemanticMantis (talk) 18:06, 7 April 2015 (UTC)


 * Yellowish, street light? I would guess sodium-vapor lamp.  I think these can flicker with the power cycle, though I'm not entirely sure.  Dragons flight (talk) 17:42, 7 April 2015 (UTC)


 * I think sodium-vapor is most likely. Bubba73 You talkin' to me? 17:58, 7 April 2015 (UTC)


 * Sodium-vapor lights can flicker: flicker. Bubba73 You talkin' to me? 18:06, 7 April 2015 (UTC)

Here are 32 shots of the same lamp taken over the period of less than 1 minute. This was done in manual mode, 1/1000 second, f/2.8, so the camera isn't doing any fiddling with the exposure. They show that there are times when it is bright and times when it is dim. Bubba73 You talkin' to me? 01:26, 9 April 2015 (UTC)


 * CCFL use an inverter. LED a current regulated buck converter which is supplied by rectified and filtered AC input. The unfiltered 120 Hz would be a visible stroboscope, but some converters pulse a higher frequency instead of regulated current. -- Hans Haase (有问题吗) 18:46, 9 April 2015 (UTC)

Modern medicine / human evolution
To what extent does modern medicine undermine natural selection in humans, thereby hindering human evolution? ― Mandruss  &#9742;  11:48, 7 April 2015 (UTC)


 * This is a hard question. We can't really do controlled experiments, and there's no generally applicable method of quantifying the "strength" or "speed" of evolution. Here's an article that discusses the problems with studying human evolution, and points to newer methods in genome studies and haplotype structure as a way forward, and here's a more recent article by some of the same authors: . The point is, these are relatively recent papers in Science and Nature, and we are a long way from having robust and widely accepted methods and results. A few things to keep in mind: Selective pressure will usually act the fastest when it acts at a life stage prior to sexual maturity. Now, some medical treatments save children that would have otherwise died without, but many medical treatments are applied to people who have already reproduced, or may never, and these don't have as strong of an effect. Here's an article that briefly mentions human impacts on human evolution, but it's mostly about human impacts on evolution in general . Now, there are some ways that pressures after reproductive age can influence evolution - notably kin selection and group selection. This recent work on orcas points out some similarities with humans - we are some of the few species where females survive and hang around after menopause. Now, humans did that before modern medicine, but it hints at how culture and sociology can influence evolution via mechanisms different from classical Darwinian selection. Finally, this book  seems to have some discussion closely related to your question, but I have not read it. So - no real answers here, but lots of refs. SemanticMantis (talk) 15:02, 7 April 2015 (UTC)


 * There's also the false dichotomy between the natural and unnatural. Environmental pressures effects evolution.  Period.  Modern medicine is an environmental pressure which effects human evolution.  Nothing else needs to be understood by introducing spurious ideas like "natural" and "unnatural".  The question makes more sense if you merely asked "What sorts of evolutionary pressure is introduced to the human species by modern medicine?"  -- Jayron 32 16:42, 7 April 2015 (UTC)
 * I agree with Jay. Selection pressures are changing, but they are not going away. So evolution will continue to do its thing. Consider moles - by digging underground they stop being preyed on by birds of prey - that means that that evolutionary pressure is reduced, but others come into play (less vision, better sense of smell, better sensing of vibrations, better burrowing). It's similar with humans - we can now treat some conditions that would previously be deadly, but that does not mean that all people have the same reproductive success. It's hard to tell which features currently are selected for, but that does not mean that none are. Richard Dawkins's The Extended Phenotype has some interesting ideas on the interaction of populations and how they modify and interact with their environment. --Stephan Schulz (talk) 16:54, 7 April 2015 (UTC)


 * For a species with generation length as long as humans, selection pressure has to be sustained for thousands of years to have a significant impact. In far less time than that we will be able to engineer the human genome from top to bottom. So it really doesn't matter at all. Looie496 (talk) 17:21, 7 April 2015 (UTC)


 * I believe a better question would be: Is there any form of selection pressure in humans? Selection pressure would increase the likelihood that one set of humans would produce offspring while reducing the likelihood that another set of humans would produce offspring. Other than young death, I've only seen respectable studies linking lack of education and poverty to an increase in the number of offspring, but not to the likelihood of producing offspring. 209.149.113.89 (talk) 19:04, 7 April 2015 (UTC)

Sexual selection is a mechanism that evolved over hundreds of millions of years to keep evolution from going off the rails when for prolonged periods important selection mechanisms are absent. E.g. if prey animals live for many generations in an area where predators are absent, sexual attraction will still lead the fitter animals to contribute to the gene pool. Count Iblis (talk) 20:04, 7 April 2015 (UTC)
 * Sexual selection is of course a real thing, but for the rest of your claims, please. SemanticMantis (talk) 20:12, 7 April 2015 (UTC)
 * Well, it just seems logical to me that sexual attraction will, in general, have evolved to enhance the survival of the next generation. The article on sexual selection is a bit misleading because the evidence for sexual selection is most apparant in the rare cases where sexual preference leads to offspring with features that are of no benefit. This then leads to the evidence that sexual selection is a factor these cases, but of course, this is not how it works in general. Count Iblis (talk) 21:06, 7 April 2015 (UTC)
 * Sort of. But come on, you have some science training, right? You should know that your notion of logic applied to an area that you are not specifically trained in is not a reference. Sexual selection is in no way something that generally increases fitness in the absence of other pressures. Many aspects of sexual selection, and the interaction with other selective pressures are still very poorly understood, and very active areas of research, please don't fall in to this trap :) SemanticMantis (talk) 15:58, 8 April 2015 (UTC)


 * Infectious disease is believed to be the greatest evolutionary force in humans, from sickle-cell anemia to smallpox, to cholera causing the evolution of multiple sclerosis. It has also been suggested that shortsightedness among the Chinese is linked to their long history of agriculture (where one need not spot and sneak up on the prey from a distance) and modern medicine has removed much of the burden of things like type-I diabetes and problematic childbirth, which will lead to people who otherwise wouldn't have survived to reproduce passing on problematic genes. μηδείς (talk) 20:21, 7 April 2015 (UTC)

My question was prompted by an earlier thread at WP:RDM, in which the issue of infant cranial size vs birth canal size was mentioned. I don't think there's any disputing that this problem has resulted in the deaths of many mothers (and infant girls), but far fewer after the development of relatively safe C-sections and other things. It seems intuitive that, without the interference of modern medicine, the problem would eventually correct itself. Aside from Looie496's point, which would render this purely academic, is there any validity to this? Is the idea that with modern medicine this should cease to be viewed as a "problem"? ― Mandruss  &#9742;  02:20, 8 April 2015 (UTC)
 * I don't know, I don't think there's a simple answer. But you may enjoy reading Obstetrical_dilemma, and this nice blog post explaining some of the problems with that perspective, written by a physical anthropologist . SemanticMantis (talk) 19:50, 8 April 2015 (UTC)
 * Also recall that C-sections are not readily available to all. I have no idea what the access rates are, but I suspect rather low outside rich countries, and most of the human population is part of the global poor e.g. SemanticMantis (talk) 19:52, 8 April 2015 (UTC)
 * It has gotten to the point where certain domestic animals regularly require veterinary assistance to give birth. In the past, if a woman was genetically ill-suited to give birth due to small hips, she would not pass on those genes.  Nowadays it is not unheard of for women to have multiple c-sections.  Their genes are not being culled from the system.  I have a cousin whose whose wife could not conceive normally, but had two children with gynecological assistance, another cousin who bore a child with in vitro, and a sister in law with her own congenital problems who was advised pregnancy would be difficult to achieve and dangerous to  undergo.  She had two children, both with congenital issue, one of who may be mentally retarded and never walk.  I would never have argued on eugenic grounds that they should not have pursued children, but from an impartial biological perspective, the evolutionary implications are clear. μηδείς (talk) 20:10, 9 April 2015 (UTC)
 * Impartial is the key here. The issue is that the question (and many questions like this, historically speaking) place a normative value on concepts like "natural" or events which would occur without human intervention; except human intelligence is an evolutionary adaptation, and anything human intelligence produces is likewise an evolutionary adaptation which in turn feeds into the genetic distributions in real ways.  To say or imply that human action is somehow against "natural" processes like this implies that evolution has an intelligent purpose or ends, and that human action stands in the way of those ends.  Certainly, medicine has measurable effects on the human genome.  That is an undeniable, self-evident fact.  To then place normative values on those effects isn't valid, from a purely scientific standpoint.  Whether one wants to make moral arguments one way or the other is fine, but such arguments cannot be based on any scientific meaning of "good" or "bad", and one will have to look for their moral code independent of the science here.  -- Jayron 32 20:20, 9 April 2015 (UTC)
 * I'll assume that was a response to me. I am all for medical advances.  I'd likely have died in early childhood without modern medicine, and would with 100% certainty have before my 33rd birthday without extreme measures unavailable in the 70's.  But civilizations falter and fall, and there will be a great culling with something as simple as the failure of the electric grid. That's fact, not moralizing. μηδείς (talk) 04:44, 10 April 2015 (UTC)
 * Cooking food by our ancestors led us to lose a large part of our bowels. We can no longer digest raw food. Count Iblis (talk) 20:16, 9 April 2015 (UTC)
 * I'l remember that the next time I eat sushi, a raw egg, or steak tartare. μηδείς (talk) 04:44, 10 April 2015 (UTC)

Engineering and design - constructional systems of the USSR
Are engineering and design - constructional systems of the USSR, including the civil and military army systems of the USSR being promising advanced (perfected) systems? I saw, many people told that engineering and design - constructional systems of the USSR, including the civil and military army systems of the USSR are not being perfected, because the USSR had not a advanced (perfected) computer.--85.141.239.195 (talk) 15:25, 7 April 2015 (UTC)
 * Every one of those words is English, and yet I can't understand what you say. Perhaps if you asked the question at the Wikipedia of your native language, you could be better understood?  Just about every Wikipedia of any size has a place like the reference desk.  If you tell us your native language, we can direct you better to a place where you can be understood by those trying to help you.  -- Jayron 32 16:39, 7 April 2015 (UTC)
 * The USSR was losing in the Cold (nuclear) War, because the USSR had not a basis of applied programming. I’m sorry, but I had not got an education in applied programming, what’s why I was asking this question.--83.237.197.142 (talk) 18:19, 7 April 2015 (UTC)
 * Asking questions at a website where they understand your native language is more likely to get meaningful answers. AndyTheGrump (talk) 18:21, 7 April 2015 (UTC)
 * Thanks. I suppose that to become a winner in Cold (nuclear) War always must be had scientific skills, but not a finances or political reasons as biography of politics.--83.237.197.142 (talk) 18:53, 7 April 2015 (UTC)
 * I should edit, that I’m understood that Cold War was win the program linguistics of assembler, but what kind of symbiosis of assembler program linguistics did win, I’m don’t know.--83.237.197.142 (talk) 19:37, 7 April 2015 (UTC)
 * Is been lost USSR from dangerous ovens Cold (microwave) War? μηδείς (talk) 20:00, 7 April 2015 (UTC)


 * Nothing is ever perfected, I'd say; there are always compromises – between different requirements, or with the time available for the engineers to complete their task. The USSR had good computers, I believe, but they might not have been available to engineers on low-priority projects. —Tamfang (talk) 22:39, 7 April 2015 (UTC)
 * The new program linguistics are been mainfull.--83.237.207.57 (talk) 10:08, 8 April 2015 (UTC)
 * I wish to edit that, as I'm know, the USSR always been used the most simplest program linguistics of low levels program math languages.--85.141.232.244 (talk) 12:48, 8 April 2015 (UTC)
 * I was said to this, that the USSR had not got a complex mathematicals, because the USSR always been used the most simplest program linguistics of low levels program math languages. Of course, the USSR had not got a perfected control systems, because the mathematics of the USSR always been simplest.--83.237.203.56 (talk) 19:15, 8 April 2015 (UTC)
 * The USSR always had got a simplest mathematics which was free from applying new science methods, so the USSR always been used simplest math Basic and math Fortran.--83.237.203.56 (talk) 20:38, 8 April 2015 (UTC)
 * I can sort of see the point in talking like that, but the way you reply to yourself to end your sections doesn't do anything for anyone, on any level. Scale it down or go home. InedibleHulk (talk) 20:48, 8 April 2015 (UTC)
 * Thanks. I understood your massage attention, but I wish to say that the position of mathematics is always been the same for position of linguistics.--83.237.202.245 (talk) 21:58, 8 April 2015 (UTC)
 * I’m very sorry for myself replying discussion, but I must to said, that using low levels program math languages makes do it impossible to do complex calculations in mathematics and other sciences, because the math logic of this program linguistics is very (basically) simplest, that’s why the USSR had not got to do complex calculations and perfected computer. That's why always win a symbiosis program languages.--83.237.218.62 (talk) 08:51, 9 April 2015 (UTC)

Unless there is someone with a literal gun to your head forcing you to type on Wikipedia, you do not "must to said" anything. Your replies are going nowhere and you are not asking any questions nor listening to any answers or responses. --OuroborosCobra (talk) 10:48, 9 April 2015 (UTC)
 * I'm sorry!--83.237.207.119 (talk) 12:28, 9 April 2015 (UTC)

Flat loudspeakers
I would like to know something more about a series of big, flat loudspeakers manufactured by Yamaha Matsushita some twenty years ago. They were blue with a black frame and marketed as "digital" (whatever they mean with that word). Designed mainly for theatres and similar places.--Carnby (talk) 16:58, 7 April 2015 (UTC)


 * If you would like to know about how these planar speakers work we have two articles: Magnetostatic loudspeaker & Electrostatic loudspeaker.--Aspro (talk) 21:57, 7 April 2015 (UTC)


 * Thank you, I also discovered that they weren't made by Yamaha. The were manufactured by Matsushita and sold as Technics AFP series. I found this page with some techncal specs, but it's all in Japanese.--Carnby (talk) 11:56, 8 April 2015 (UTC)


 * Copy and paste it into Google Translate. It translates Japanese very well. 209.149.113.89 (talk) 12:11, 8 April 2015 (UTC)
 * Or. Abecedare (talk) 22:11, 8 April 2015 (UTC)


 * I tried to translate Japanese text; they seem to be big-sized conventional speakers rather than magnetostatic or electrostatic ones.--Carnby (talk) 22:27, 8 April 2015 (UTC)

Squeezing a very round head inside an oval helmet?
Is it safe to squeeze a very round head inside an oval helmet? Given an oval helmet on a very round head, will that protect the round-headed bicyclist from accidents? 140.254.136.149 (talk) 17:19, 7 April 2015 (UTC)


 * We have a pretty long article on Bicycle_helmets. I'm not sure what you are asking. There are a few different shapes and styles, but many of them are indeed just and oval shell that rides on top of the head. A good fit is important for a helmet to properly protect, see e.g. here . There shouldn't be any squeezing of heads required to wear a helmet. SemanticMantis (talk) 17:59, 7 April 2015 (UTC)


 * Some cyclists wear skateboard helmets like these, to give better protection to the sides of the head. But they are hotter and heavier, so each rider makes their own choices. Here are a few scientific studies on the effectiveness of using bicycle helmets to prevent injuries in crashes . From the first article " Risk of head injury in helmeted vs unhelmeted cyclists adjusted for age and motor vehicle involvement indicate a protective effect of 69% to 74%" -- short answer: helmets do help protect against head injuries.  SemanticMantis (talk) 18:02, 7 April 2015 (UTC)
 * There was a recent ESPN Outside the Lines about hockey helmets and such. Helmets largely protect against skull fracture. They are much less reliable for protecting against concussions. ←Baseball Bugs What's up, Doc? carrots→ 18:22, 7 April 2015 (UTC)
 * Please be aware that for a cyclist that knows what they are doing, and is just commuting and not racing, a helmet is completely unnecessary (cf the Netherlands and Denmark), and will only put people of cycling. 82.21.7.184 (talk) 20:19, 7 April 2015 (UTC)
 * Yes, the Danish and the Dutch have it great, with their protected cycle superhighways,, and all sorts of other cycling-friendly infrastructure. In the USA however, cyclists " face a higher risk of crash-related injury and deaths than occupants of motor vehicles do" . WP:OR: Last weekend I saw a car intentionally knock down some cyclists in TX. Even in non-race situations, skilled cyclists can crash and get severely injured. I would probably not wear a helmet if I cycled in the Netherlands :) SemanticMantis (talk) 20:51, 7 April 2015 (UTC)
 * "Knowing what you're doing" is insufficient. Wearing a helmet is essential. ←Baseball Bugs What's up, Doc? carrots→ 22:11, 7 April 2015 (UTC)
 * Nope, have cycled in the very aggressive British traffic for all my life, had several crashes, never worn a helmet, and never had any head injury (or any other major injury for that matter). As long as you know how to cycle and how to fall, there's no need for a helmet at all. Most cyclists are far too meek, they need to be far more aggressive to be safe. 82.21.7.184 (talk) 07:21, 8 April 2015 (UTC)
 * You've just been lucky so far. ←Baseball Bugs What's up, Doc? carrots→ 08:57, 8 April 2015 (UTC)
 * Citation needed. Also, it would be good if you could refrain from personal attacks on the cycling abilities of posters. I agree with the poster above, cycle helmets are entirely pointless if the cyclist knows what they're doing. 131.251.254.154 (talk) 13:45, 8 April 2015 (UTC)
 * Nope, not lucky, skilled. Big difference. 82.21.7.184 (talk) 16:19, 8 April 2015 (UTC)
 * That's why the Tour de France guys don't wear helmets, eh? ←Baseball Bugs What's up, Doc? carrots→ 01:08, 9 April 2015 (UTC)


 * Everyone who is still alive has been "lucky so far". The question is whether the benefits of wearing a cycle helmet outweigh the disadvantages, and there is little, if any, evidence that they do. See here for example. AndrewWTaylor (talk) 13:23, 8 April 2015 (UTC)
 * The far better solution is to avoid the need for helmets altogether by proper behaviour on the bike. 131.251.254.154 (talk) 13:45, 8 April 2015 (UTC)
 * I think you mean Nil Einne (talk) 15:28, 8 April 2015 (UTC)
 * Purely original research, but the VW Golf that overtook me, pulled in front and then performed an emergency stop, ended up with a helmet-shaped dent in his boot. I suspect that I wouldn't be writing this had it been head-shaped. Alansplodge (talk) 18:37, 8 April 2015 (UTC)


 * The IPs here have provided no references. This is not a forum. It should be obvious that in any operation of a vehicle, there are factors outside the operator's control. Even a perfectly trained and well-behaved cyclist can get hit by a drunk driver   . So, do what you want, IP users, we can't give you medical advice, or require you to wear a helmet. But please do not fill this space with un-scourced claims that helmets are useless or unnecessary. Note that in the USA, many states require the use of helmets under some conditions  SemanticMantis (talk) 15:53, 8 April 2015 (UTC)
 * The vast majority of car-bike accidents are through ignorance or stupidity of the cyclist and are very much avoidable. For the tiny minority of the rest, meh, karma. I'd rather actually be comfortable and safe on my bike than to obsessively worry and thus be unsafe. 82.21.7.184 (talk) 16:19, 8 April 2015 (UTC)
 * Um... - until I see evidence to the contrary, your claim is just your own opinion, and not very helpful on a reference desk. SemanticMantis (talk) 19:46, 8 April 2015 (UTC)


 * Well, let's get some facts straight here shall we, rather than slagging off 'some IPs', just because they are right. 1) Helmets offer some protection in certain crashes, but their effectiveness has been grossly overstated, mostly for commercial purposes. 2) The more skilled a cyclist is, the safer they are. 3) The best way to avoid head injuries is to avoid crashes and accidents altogether 4) The vast majority of accidents are avoidable by the cyclists, through assertive cycling, assuming all drivers are out to kill them (not that far from the truth), and making sure both you and your bike are up to scratch. 5) Some accidents are unavoidable, and some of those will be fatal. Deal with it. An asteroid could hit you in the head tomorrow. Now, having said that, I still maintain that making cyclists 'special' by making them wear helmets, high-vis, lycra and more such nonsense creates an illusion that cycling is weird and not normal, therefore creating a us-vs-them mentality on the roads and decreasing safety. Disclaimer: I grew up in the Netherlands, and have since emigrated and have been cycling British roads for many years now. Fgf10 (talk) 16:28, 8 April 2015 (UTC)
 * Fairly sure the risk of unavoidable accidents to even the most skilled cyclist is a few orders magnitudes higher than the risk of being hit in the head by an asteroid tomorrow. Anyway let's not forget the OP's question was whether a helmet would offer protection if their head was too round. The question of whether helments offer protection at all is relevant. The question of how much protection is relevant. While technically not relevant, we can perhaps accept some minor diversion in to whether or not the OP would be better served by improving their cycling skills, whether or not they choose to wear a helmet, but that would seem to be about the limit and even that seems to have a fair chance of being irrelevant to the OP. The question of whether or not mandatory helmet laws exists, or should exist, or do more harm than good, or whatever is not relevant. The question of whether the OP is worrying too much about something which is too low risk is not relevant. I'm not sure what the IP meant above about karma, but whether they meant when someone is injured or killed in an unavoidable accident they shouldn't bemoan it because they obviously did bad in their life, of whether they meant perhaps the person who injured or killed the cyclist will hopefully receive payback some time (which doesn't actually help the injured or dead cyclist, and also ignores the possibility that no one is really at fault in an accident) is most definitely not relevant. People are entitled to their person views about whether or not it's wearing a helmet is a good idea (and all the other stuff), but the RD, and in particular this question is not the place for them. Nil Einne (talk) 17:05, 8 April 2015 (UTC)
 * I'm not "slagging" anyone, and I don't care if they are IPs or registered like you. I mean to imply that assertions here should be supported by references. You also have provided no references to support your claims.  I'd be happy to read any references you have, especially that support points 1) and 4). I'm not unsympathetic to your points, in fact I agree with many of them. Indeed, I don't wear a helmet often, even though I cycle every day in a big city. However, I still believe helmets are useful at preventing injury, and that I am taking a calculated and informed risk. Really, we should just ban all non-commercial autos, and then we'd all be much safer :) SemanticMantis (talk) 19:44, 8 April 2015 (UTC)

colleges for message therapy
Is there any colleges have message therapy courses ? — Preceding unsigned comment added by 106.76.24.162 (talk) 17:40, 7 April 2015 (UTC)
 * I think you mean "massage therapy". There is a type of vocational school called "massage therapy school", where people come out as licensed/certified massage therapists. Legal massage therapists abide by the laws of the jurisdiction, which may or may not charge illegal services like erotic massages and prostitution. You may be interested in seeking a massage therapy school in your district. 140.254.136.149 (talk) 17:48, 7 April 2015 (UTC)


 * If you actually mean "message therapy", a course in business writing would be a good option. ←Baseball Bugs What's up, Doc? carrots→ 18:20, 7 April 2015 (UTC)

Discovering an asteroid
A century ago, how was it decided that one had discovered an asteroid? For example, when 284 Amalia was discovered, how did the discoverer know that it wasn't just another asteroid that had already been discovered by someone else? I understand that astronomical tables have been developed for planets and bigger objects, with precise orbits calculated and future locations accurately predicted, but was this routinely done for minor asteroids? Nyttend (talk) 17:59, 7 April 2015 (UTC)


 * The short answer is that yes they did plot the orbits of all the asteroids. The somewhat longer answer is that sometimes asteroids did get lost and rediscovered later.  See: Lost asteroids.  In general, if you know the orbit, you can calculate where something would have been in the past and then match early observations with modern ones, so sometimes people do rediscover previously lost asteroids.  Dragons flight (talk) 18:08, 7 April 2015 (UTC)


 * Also, an orbit is characterized by its orbital elements. These are just a set of numbers and are easily compared to confirm that two bodies are in different orbits, provided that there's enough data for the orbital elements to be well established.  (Different computations of the orbit for the same body may not produce exactly identical numbers, due to things like perturbations and minor observational errors, but the elements will be close enough to suggest when further investigation is required.  That'd be the only case where you'd actually have to compute where the thing was at some particular time.) --65.95.176.148 (talk) 18:38, 7 April 2015 (UTC)


 * You can probably find the original paper on the topic, this search for Auguste_Charlois between the years of 1888 and 1905 gets plenty of hits. The articles are even freely available. But they do seem to be in French... This address titled "Asteroids past present and future"  may also shed some light.  SemanticMantis (talk) 18:16, 7 April 2015 (UTC)

Who realised that whales and dolphins are not fish?
See title. It doesn't seem very obvious. --82.45.61.67 (talk) 18:31, 7 April 2015 (UTC)


 * Aristotle said so in the 4th century BC, according to this book preface (7th page of the PDF). --65.95.176.148 (talk) 18:45, 7 April 2015 (UTC)


 * It is sort of obvious, when you consider pre-scuba people typically only saw whales coming up for air. Fish don't do that. The first time they killed one and realized it was filled with blubber would've also been a hint. InedibleHulk (talk) 18:49, 7 April 2015 (UTC)


 * Aristotle had it right, but not necessarily for the right reasons. Moby Dick contains a long passage on the subject, and concludes that dolphins must be fish. Here is what you should read: When Whales Became Mammals: The Scientific Journey of Cetaceans From Fish to Mammals in the History of Science  -- it is a nice historical overview of cetacean taxonomy from a historical perspective: it starts with Aristotle, and continues through antiquity, Renaissance, and up to the modern day, detailing each new them in taxonomy and some of the morphological work that supports the claims. SemanticMantis (talk) 20:10, 7 April 2015 (UTC)


 * Amusingly, Wikipedia has an entire article on the cetology of Moby-Dick. Ishmael/Melville wasn't saying anything about cetacean biology when he said they ought to be fish. He was merely complaining about the over-narrow modern definition of "fish". -- BenRG (talk) 23:05, 7 April 2015 (UTC)


 * It seems obvious now, but not so much before animal anatomy became widely studied and known. In addition to needing to come up to breathe, whales and other marine mammals have flat tail "fins", which are really highly adapted feet. ←Baseball Bugs What's up, Doc? carrots→ 12:37, 8 April 2015 (UTC)
 * And their babies stick around nursing for about a year, depending on the species. Some kids drink 500 litres a day. Hard to imagine an early hunter cutting up a mother and not noticing that much milk, even if they'd missed the suckler. They wouldn't have called it a mammal yet, but must've thought it more cow than fish. InedibleHulk (talk) 19:19, 8 April 2015 (UTC)


 * Literally more cow than fish: Cetartiodactyla. μηδείς (talk) 04:34, 10 April 2015 (UTC)

Can a human body creates toxins by itself?
Can a human body cell creates toxin by itself, or it must be done by bacteria and other foreign things? by the way, CO2 can be called "toxin"? Thanks. 5.28.178.16 (talk) 18:37, 7 April 2015 (UTC)
 * The human body produces many toxic waste products through natural metabolic processes. These need to be filtered out by the kidneys and then excreted.  When the kidneys are not functioning properly, there can be serious health problems that result.  Deli nk (talk) 18:41, 7 April 2015 (UTC)


 * "Methanol (wood alcohol), for instance, is oxidized to formaldehyde and then to the poisonous formic acid in the liver by alcohol dehydrogenase and formaldehyde dehydrogenase enzymes, respectively; accumulation of formic acid can lead to blindness or death." (See Alcohol). StuRat (talk) 18:57, 7 April 2015 (UTC)


 * For a simple example, see creatinine. This is produced in muscle cells and has to be excreted from the body. It is a very common toxin to be checked to see if the liver and kidneys are functioning well because the rate of creatinine production is fairly consistent throughout the day. 209.149.113.89 (talk) 18:56, 7 April 2015 (UTC)


 * Whether CO2 is toxic depends on its concentration. It is present in in small quantities in ordinary air and that doesn't injure anyone.  But in high concentrations it is a dangerous toxin (not just an asphyxiant).  See this page from the CDC and this PDF appendix from a US BLM document produced under their National Environmental Policy Act. --65.95.176.148 (talk) 18:57, 7 April 2015 (UTC)


 * Relevant here is the adage the dose makes the poison. The idea is that almost anything is toxic (and almost anything is safe) depending on the amount present.  While not 100% true (there's probably some substances toxic in any measurable amount), as noted with something like CO2, it absolutely depends on the dose.  Also relevant is the quote The amount of times someone uses the word "Toxin" is inversely proportional to their actual knowledge of chemistry.  The word "toxin" is a marketing term created by charlatans who want to sell you magic crystals and other new-age hokum.  It really is a marker of a lack of science knowledge to use the term.  -- Jayron 32 19:29, 7 April 2015 (UTC)


 * I'm afraid it's Jay's lack of knowledge that's showing. If you consult the OED, you will find four citations of the word "toxin" being used, all of them in genuine scientific writing. (They are all from the period 1890–1905; that part of the dictionary was originally written in 1913 and hasn't been fully updated yet.) Jay is right that the word is often used in pseudo-scientific marketing, but it isn't by any means exclusive to that.


 * Having said that, the OED's definition of "toxin" is "A specific poison, usually of an albuminous nature, esp. one produced by a microbe, which causes a particular disease when present in the system of a human or animal body", and clearly CO2 does not fit either the "usually" or the "especially" part. But it is a "specific poison" in sufficient concentrations. --65.95.176.148 (talk) 09:56, 8 April 2015 (UTC)


 * See etymological fallacy; that the word was once used in a scientific context doesn't mean that is how it is being used. It would have perhaps been better to say that it has been hijacked by charlatans.  It has become a shiboleth for the scientifically illiterate, and as such, even if it once had a legitimately scientific reason, has become marked and isn't used much in that way anymore.  -- Jayron 32 12:37, 8 April 2015 (UTC)


 * That's better, thanks. Now, for evidence that the word is in fact still in scientific usage, try this Google search. --65.95.176.148 (talk) 16:35, 8 April 2015 (UTC)


 * The human body is not merely capable of "creating toxins" is is essential that it does, otherwise it would be a dead body. Roger (Dodger67) (talk) 07:45, 8 April 2015 (UTC)


 * I arrive a bit late here but I'll just mention rhabdomyolysis as an example. There are of course many toxic metabolites of exogenous substances, which may vary according to genetics (there was a spectacular case of a patient a decade or two ago who dosed himself with huge amounts of DMSO and converted it to DMSOO/dimethyl sulfone and sickened the emergency personnel...)  Wnt (talk) 00:57, 11 April 2015 (UTC)