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March 5

Do all mammals have pair of kidneys like human being has?

(I know for example about the prevailing opinion which claims that all mammals have 7 cervical vertebra, but in fact it's not true and there are at least 3 mammals which don't have 7 cervical vertebra. That's why I'm asking here about the kidneys to see if there is an exception like in the issue of the cervical vertebra) 93.126.95.68 (talk) 01:01, 5 March 2016 (UTC)

I don't know for sure, but bilateral symmetry would seem to mean an organism would typically have an even number, unless they are located on the sagittal plane. StuRat (talk) 01:17, 5 March 2016 (UTC)

Some humans have one kidney, an extra large horseshoe shaped kidney across the back. Graeme Bartlett (talk) 01:32, 5 March 2016 (UTC)

And some have three! DuncanHill (talk) 01:35, 5 March 2016 (UTC)

Does the OP mean "Do all mammals normally' have a pair of kidneys? DrChrissy ^(talk) 01:43, 5 March 2016 (UTC)

That's right. My question is about the normal cases rather than about abnormals.93.126.95.68 (talk) 02:33, 5 March 2016 (UTC)

In Mammals, and many other Vertebrates there is also the Mesonephros, which for humans is around from the sixth to tenth week of the gestation. A Pronephros also forms in mammals, but since it is non-functional as a kidney, I don't think you can call it that. So you may wish to confine you scope to adults. Graeme Bartlett (talk) 03:57, 5 March 2016 (UTC)

That's technically true but bordering on the needlessly pedantic. (You could say that not all humans have any kidneys because a 3-day-old embryo only has 8 undifferentiated cells. Or that not all mammals have a four-chambered heart because a 3-week-old human embryo just has a primitive heart tube.) TenOfAllTrades(talk) 19:55, 7 March 2016 (UTC)

Falcon 9 full thrust

Falcon 9 Full Thrust launch on March 4, 2016. The discarded first stage is in the lower right. The second stage is in the upper left, with the jettisoned payload fairing.

I was photographing the launch of the Falcon 9 full thrust today and a while after it dropped the first stage, it dropped something else. Does it drop the payload shroud while the second stage is still burning? Bubba73 ^{You talkin' to me?} 03:24, 5 March 2016 (UTC)

Yes, it jettisons the payload fairings early in the second stage flight. The timeline from spaceflightnow gives:

T+0:02:47: First Ignition of Second Stage

T+0:03:42: Fairing Jettison

which is just under a minute into the second stage burn. I too saw what I now assume were the fairings, but I didn't realize what they were until you asked. I hope you got some good shots. I tried a long duration exposure (from a long distance away), but it didn't come out that well. I think the later (1846 vs 1835) launch time they had planned last week (as well as the slightly earlier sunset then) would have helped me, but I see that some people (a lot closer to the Cape) got some very good shots despite the light. -- ToE 05:01, 5 March 2016 (UTC)

I'm 180 miles from the cape, and longer after the rocket gets up a bit. The launch was 8 minutes after sunset so I knew that the sky would be too bright for a time exposure (which I often do). I got several shots after the first stage was dropped, showing both, but then I was looking at the photos, and at least one showed something else being dropped off, well after the first stage. It must be the fairing. And also there are two small points (1 pixel each) near the fairing that might be some sort of associated debris. Bubba73 ^{You talkin' to me?} 07:52, 5 March 2016 (UTC)

Does this rocket use explosive bolts to jettison the fairing? That might be your 2 pixels. --DHeyward (talk) 10:48, 8 March 2016 (UTC)

I added a photo. You can see the two parts of the fairing, plus the first stage. Bubba73 ^{You talkin' to me?} 21:00, 5 March 2016 (UTC)

Nice. Here is some amateur video shot from Wilmington, NC (400 mi to the north) starting at second stage ignition, running through fairing separation, and showing plumes from the second stage at the start and end of its reentry burn. -- ToE 13:43, 7 March 2016 (UTC)

"chemical castration" for racehorses

My earlier question about (not) castrating a cat got me thinking: Male racehorses are pretty routinely gelded in the hope of improving their performance on the racecourse. The very obvious disadvantage is that they are rendered permanently infertile, and if they turn out to be a star winner, you can't breed with them.

Wouldn't an equine form of Chemical castration (administering androgen-suppressing drugs) be a possible alternative in terms of getting the horse to perform on the racecourse as if it was a gelding, whilst still being able to be used as a stud horse once its' racing career was over? (Obviously, at that point, you would simply stop administering the androgen-suppressing drugs, and the horse's sex drive and sperm production would in time return, wouldn't it?). If it was that simple, surely someone would have thought of this idea? Or is it actually being done? Are there veterinary medical difficulties in "chemically castrating" a horse? Cost issues? Or is there some rule of racing in most or all jurisdictions which forbids such treatments being administered to racehorses, even if they would give the horse no competitive advantage over the standard "surgical gelding"? What am I missing? Eliyohub (talk) 11:53, 5 March 2016 (UTC)

See Equine drug testing. I don't know if these drugs would actually work, but if they did they would almost definitely fall in the category of performaance modifying drugs. Nil Einne (talk) 16:34, 5 March 2016 (UTC)

BTW a simple search for 'racehorse chemical castration' finds [1] Nil Einne (talk) 16:38, 5 March 2016 (UTC)

Also [2], [3], [4] (while it doesn't mention what was discussed, consider what the meeting was for), [5] (not about race horses but your question seemed to also be about the general idea of equine chemical castration). Note that not all of these refer to reversible chemical castration, quite a few refer to immunuchemical castration that may not be reversable. However there's no suggestion that will affect the legality of such techniques in racehorses. Nil Einne (talk) 16:46, 5 March 2016 (UTC)

I have a related question. Why does castration improve the speed of racehorses? What is the reason why geldings are faster than stallions? I hadn't known that geldings were faster until this discussion. I had thought that horses were gelded to make them easier to handle, not faster. Robert McClenon (talk) 17:27, 5 March 2016 (UTC)

To be honest, I'm not sure it does directly. Most sources I saw when researching this seem to agree it's mostly about handling but also perhaps longevity. See also [6], [7], Gelding (see the paragraph that starts with In horse racing and two paragraphs down), [8], [9], [10] (although this claims as a rule of thumb for an older horse it may make it race as if it were one year older). In fact the discussion about muscle mass or musculature wonders if it may reduce performance of younger horses. However if you are having trouble training the horse or if it gets distraced during races or whatever, it may effectively help performance (a few of the sources suggest that). Nil Einne (talk) 18:33, 5 March 2016 (UTC)

If they are anything like people, the timing can affect all sorts of features including limb length and lung capacity. See Castrati which was done to preserve pre-pubescent voice range. The effects weren't at all intuitive (at least to me).--DHeyward (talk) 10:38, 8 March 2016 (UTC)

Subject of image File:Jj6.png

While clearing out shadowed files, I have come across this image. I cannot find out what glacier it is of. Does someone here know? Jo-Jo Eumerus (talk, contributions) 16:41, 5 March 2016 (UTC)

The unknown glacier

The Mendenhall Glacier

That photo looks a lot like THIS image of the Mendenhall Glacier in Alaska. That photo shows an expanse of open water at the foot of the glacier (where the people are standing in Jj6.png) - but the photo at right here (which is from our Mendenhall Glacier article) shows the lake freezes and is snowed over in winter. SteveBaker (talk) 18:00, 5 March 2016 (UTC)

I added the unknown glacier for comparison. I agree that this looks like the same glacier, but photographed from a slightly different location. Specifically, the location from which the unknown photo was taken may be more to the right and farther out. StuRat (talk) 19:29, 5 March 2016 (UTC)

Yeah, a comparison of the geographical features on the photographies clinches it for me - file moved to File:Mendenhall Glacier.png.Jo-Jo Eumerus (talk, contributions) 19:40, 5 March 2016 (UTC)

I updated the pic here accordingly, and will mark this Q resolved. StuRat (talk) 22:15, 5 March 2016 (UTC)

Resolved

List of possible things that could be gained from the Sun

• Carbon/emission footprint-less:
• Free energy:
• &:

Apostle (talk) 20:46, 5 March 2016 (UTC)

Most forms of energy we use ultimately come from the Sun. Solar, of course, and wind due to uneven heating of the atmosphere by the Sun, and wave energy from the wind, and hydro from precipitation caused by evaporation of water in the sunlight. Photosynthesis changes sunlight into plant and then animal energy, including all our food, and any wood we burn. Long ago many of those plants and animals died and produced all the fossil fuels. Tidal and geothermal energy are partially from the Sun, with the Moon and radioactive decay playing larger roles. Nuclear energy isn't from the Sun at all.

In space, a solar sail can also make use of the Sun to accelerate.

The gravity of the Sun moves the Earth in it's orbit far enough so that 6 months apart we can take measurements to the nearest stars and determine their distance by parallax. StuRat (talk) 01:30, 6 March 2016 (UTC)

See free energy. It will note that free energy may be either thermodynamic free energy, which is probably not what is meant here, or perpetual motion in pseudoscience. Obviously the bullet really means economically free, but, as noted above, there is a cost in collecting or harnessing the energy from the Sun. The only form of usable energy that does not come from the Sun either in the present or in the past is nuclear power. Uranium is a primordial radioactive element that comes from a star that no longer exists, from supernova nucleosynthesis. One theory is that the expanding shell from a supernova was one of the causes of the collapse of the protostellar cloud into a main-sequence star with planets. Robert McClenon (talk) 01:41, 6 March 2016 (UTC)

I'll read through. Thanks. -- Apostle (talk) 18:46, 6 March 2016 (UTC)

March 6

white substance in the kidney in picture on wikipedia

what is the name of the white matter inside the kidney which is found in the article (kidney) on Wikipedia (here). There is no information about it there. There is an image which describes the parts of the kidney and I can not see it there. 93.126.95.68 (talk) 01:12, 6 March 2016 (UTC)

Do you mean the pic of the pig's kidney, here: Kidney#In_other_animals ? StuRat (talk) 01:25, 6 March 2016 (UTC)

Yes. 93.126.95.68 (talk) 02:24, 6 March 2016 (UTC)

In the image you and StuRat link the white material is the ureter. The tube of the ureter fans out inside the body of the kidney to collect the urine produced by the nephrons, this is clearly seen in the diagram of the kidney in the same article. Richard Avery (talk)

Renal pelvis. --TammyMoet (talk) 09:16, 6 March 2016 (UTC)

I think in general the kidney starts off with a rich blood supply to be filtered at the outside, and gets lighter as you go further in to tissue that is more structural, with little functional demand for blood flow and more extracellular matrix. So the renal pyramid, for example, is redder at the base, whiter at the tip, as it gets more and more large tubules packed together, with a loose interstitial material. But I think the white shade you're looking for begins at the minor renal calyx and continues on from there. There is also renal sinus space. In these regions fat makes up a portion of the tissue - you can see at [11] how white a region with fat can be. I think the urothelium is not really that dark either. Fat and collagen (to form tough ducts) are both just accumulations of stored material, essentially, with relatively low metabolic needs. Wnt (talk) 18:24, 6 March 2016 (UTC)

Questions instead of hypotheses

Can an experiment be carried out in the same way that Mythbusters do it: by asking a question and then performing the experiment? Since middle school I've had to come up with hypotheses for lab assignments that tasked me with finding what happens for various things. Strikes me as superfluous. — Melab±1 ☎ 02:45, 6 March 2016 (UTC)

They're trying to teach you how to think like a scientist. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:55, 6 March 2016 (UTC)

Mythbusters does seem rather unscientific. One error they make repeatedly is assuming that since they can't do X, then it isn't possible, without considering that they might not have had the right set up. StuRat (talk) 03:08, 6 March 2016 (UTC)

Yes you could, but usually experiments are made to check a theory, rather than the "what happens if I electrolyse water and then spark the resulting gas" type experiment. Quick answer in that case involves a cross parent. Greglocock (talk) 03:33, 6 March 2016 (UTC)

On the other hand, most of the work on catalysts has been by massive numbers of experiments as the theories about how catalysts work were sketchy at best. Pharma work has also been heavily dependent on massive numbers of experiments. In short - this is a very complex question. Collect (talk) 03:45, 6 March 2016 (UTC)

It's pretty easy to extend "asking a question" to "forming a hypothesis"...just try predict the outcome of the experiment before you do it based on some kind of pre-known set of facts and rational thought process. For Greglocock's example, one could say "I heard that the formula for water is H2O, so I think that electrolysis will give me hydrogen and oxygen gases...if so, they'll burn when I spark them". If they don't, I'm probably making some other gas instead. For Collect's example, one doesn't need to know how something works to perform experiments that probe the the cases where it works. "This catalyst works on compound X, and compound Y is similar to X, so I think it will work on Y also." If it doesn't work, there's something about Y as compared to X that prevents the catalyst from working. Both cases one has a basis for thinking something will work a certain way rather than going in blindly. And if it doesn't, one learns something about one's underlying assumptions and an obvious route of what to study next to figure out more ("future work", in the scientific-method parlance). DMacks (talk) 04:09, 6 March 2016 (UTC)

But that seems unnecessary. On one episode they had to determine if a plow could slice a car in half. If that was one of my labs, I'd be asked to form a hypothesis as to what would happen when the plow slams into the car. While that may be interesting, it contributes nothing to the conclusion aside from making it more awkward to write. — Melab±1 ☎ 21:25, 9 March 2016 (UTC)

• Any question can be framed as an hypothesis, and vice versa. The way you frame it is irrelevant, the way you investigate it isn't. Although Mythbusters are far from thorough most of the time, they're at least teaching people to question and think. Never a bad thing. Fgf10 (talk) 10:20, 6 March 2016 (UTC)

Not every question can be transformed into a scientific hypothesis. The latter has to be falsifiable. Something has to happen to be able to settle it. That's why questions about God's existence is not a hypothesis. Scicurious (talk) 18:15, 6 March 2016 (UTC)

True to some extend, although I would say that "Does God exist?" is essentially equally nonsensical as "I hypothesise that God exists". My statement assumed falsifiable questions/statements, as we are on the Science Ref Desk. Fgf10 (talk) 08:07, 7 March 2016 (UTC)

It's not inherently nonsensical, it's merely incomplete: The hypothesis does not define "God". So there's nowhere to go with it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:09, 7 March 2016 (UTC)

Well...the deeper problem is that there is a claim that God is "omnipotent" and "omniscient" - and any being or entity for which those claims are made is immunized against the scientific method. If (hypothetically) there were some experiment I could perform to prove the existence of God - then he can just use his omniscience to know that I'm going to do it - and his omnipotence to change the result from "true" to "false"...presumably to "test my faith" or some such excuse. So even if I were to be able to do such an experiment, a "false" result wouldn't convince any religious OR scientific people because of the "omniscient"/"omnipotent"/"wishes-to-test-our-faith" triangle. That makes the "god-hypothesis" unfalsifiable. Religious people then take this as some kind of proof that they're right - when in fact, there are any number of equally unfalsifiable hypotheses (such as that we should believe in Odin and Valhalla and die as bloodthirsty killers in order to get into an afterlife full of quaffing and orgying). So, here is a tip for anyone who wants to make something that people will believe in and which science will be unable to disprove: Make it unfalsifiable - use infinities in your argument. So the only part of the description of "God" that matters is "omnipotent" and "omniscient". Take away those, and we might stand a chance of proving/disproving this hypothetical being's existence. SteveBaker (talk) 16:27, 8 March 2016 (UTC)

The difference is rooted in the philosophy of science. The classical positivist science approach poses falsifiable hypotheses about the relationship between two or more variables that can be tested. The falsifibility, statement of relationship, presence of variables, and testability are all key. Not all questions have those elements. But more importantly is that science never finds answers to questions. It simply fails to find evidence disproving the hypothesis. In other words we find enough evidence to reject the null hypothesis (the version of the hypothesis which claims no relationship between the variables). Fail to find evidence disproving it enough times and we start to assume it is likely a correct statement. But we can never be sure. It is possible we just keep having fluke experiments over and over (see quantum suicide). EvergreenFir (talk) Please {{re}} 18:45, 6 March 2016 (UTC)

This is all good and correct, but I'll add that WP:OR any practicing scientist will tell OP that what we teach about scientific method can be very different from how we practice scientific method, especially in interdisciplinary sciences. For example, hypotheses are often crafted ex post facto for purposes of writing a clean manuscript, and publication bias skews our available evidence of negative results. 14:24, 7 March 2016 (UTC)

Very true. I think everyone admits to at least tweaking the "front end" of a paper to better match (or perhaps to better facilitate discussion in) the "back end". Some do go quite a bit further though. EvergreenFir (talk) Please {{re}} 06:10, 9 March 2016 (UTC)

• A hypothesis is equivalent to a yes/no question. Questions that are open ended, or allow for a range of answers, are not equivalent to hypotheses. Looie496 (talk) 15:53, 7 March 2016 (UTC)

Having a specific hypothesis rather than just a question is very useful: it helps you to focus not just on what you want to know, but on how to construct the experiment such that you actually learn something from it. Asking a question and doing an experiment to look for "an answer" can mislead you, because there may be multiple reasons why the experiment comes out the way it does, and you may not have thought of all of them. Forming a hypothesis and trying to disprove it encourages you to think through the problem in a way that leads to a well-designed experiment.--Srleffler (talk) 03:33, 8 March 2016 (UTC)

Some people (notably Albert Einstein) argue that because we cannot measure both the position and the velocity of a particle quantum theory is incomplete. In the case of God, we have a complete theory, as expounded by Jesus Christ. All it takes for enlightenment is to read the Bible. 94.192.182.71 (talk) 13:06, 8 March 2016 (UTC)

This is something often said by people who have never opened the Bible at page 1 and read it through to the last page. I've actually done that - it's an utter mess of confusing, contradictory - frequently horrifying and quite disconnected stories. Far from being enlightened - it convinced me that atheism is the only reasonable response! So no, you're wrong. If you truly believe what you say, then stop cherry-picking the 'good bits' that your local priest tells you to read - and start at page 1 and read through to the end. Trust me, you'll learn something - and it won't be "Jesus tells you all about God"!

You don't have a complete theory of God - you can't answer basic questions like "How was God created?" or "Why does God make diseases that kill innocent little babies?" or "Can God make a rock so heavy that he can't lift it?" or "Why the heck does he insist on not providing concrete evidence of his existence?" or "Why did he confuse everyone by burying all of those fake dinosaur bones?". You can't tell me why your 'theory' of God is the correct one when the other few hundred religions or the world insist that theirs is the correct one. There are a million simple questions that your "theory" can't answer. Can you tell me why the nerve that controls one side of your larynx goes all the way down your neck into your chest cavity, wraps around an artery, then comes all the way back up your neck again - while the one on the other side goes directly to the brain by the straightest route? I can...using the science of evolution. In the end, religions answer these questions with pathetic answers like "God wants it like that" or "It's to test our faith" or "God works in mysterious ways". All kinds of really transparent bullshit. Copouts. In science, there are no copouts. If there is something we don't understand, we come right out and say it. "We don't understand dark energy" or "String theory looks good - but we can't prove it". Nothing gets pushed under the rug. We work tirelessly to try to provide answers where we don't have them. (Religions work hard to bury things that aren't explained). On the other hand, when we DO know something (like why that larynx nerve goes that crazy route), we don't only explain it - we provide explanations for the explanations - all the way back to actual experiments that you can (in principle) do for yourself to convince yourself of those things. SteveBaker (talk) 16:15, 8 March 2016 (UTC)

One of these days we ought to just get a room already and have the great religion debate to end all religion debates. But there are different formulations of religion, not all of which assign divine truth to every last syllable in the Old Testament, for example; while you perhaps rightly oppose a certain conventional form of religion you certainly can't dispute other versions so easily. In general, the "cop-out" of religion should be balanced by the cop-out of science, which is to say, a complete unwillingness to go beyond what the data can tell us - including whether there are billions of copies of us being made every nanosecond, for example, which is just an "interpretation" of the math and unworthy of speculation. Religion goes in and thinks, or should think, about all the matters outside this one lonely universe we can study - including the provenance of that universe. I could give responses for some of the old questions you cite (whether they're true or not is another question....) Wnt (talk) 23:31, 8 March 2016 (UTC)

I think the OP is partly right. I have had the scientific method preached at me, but I haven't seen clear proof that any particular formulation is "genuinely right", and in fact, I see various formulations that don't agree. I think the idea that there was a huge jump between "dark ages" and "age of reason" is exaggerated. Yes, there are specific tricks that improve scientific method, like blind trials and double-blind trials and statistical significance calculations (though the commonly used 5% threshold there is more ad hoc magic, and the source of endless ponderous philosophizing lately as people realize that publishing 5% of all the random things people choose to look at in studies is a lot). But "why don't we try it and see what happens" is a fair approach in science - it played a huge role in early chemistry, for example.

That said, having a hypothesis is an elegant thing that can pay off, and counts as one of the useful tricks. The notion is that experiments take some kind of planning. I mean, you can put a cockroach shell between a pair of diamond anvils and see what happens, sure, but ... see what what happens? I mean, are you going to be looking at it through a microscope? Then you're hypothesizing that its appearance in visual light will change. Why? What chemicals are going to change form to make that happen? Are you going to pick it out afterward and run chemical tests? Then you're hypothesizing some kind of reaction that occurs only under high pressure. Why? Are you measuring the charge between two points? Why, you think it's piezoelectric? Etcetera. Note that this kind of "hypothesizing" is often less a question of what you think ought to happen than what you think is easiest to look at. A lot of genetics experiments are like this - people look for changes in mRNA level because it's easier to do than, say, looking at what happens to the chromatin on the DNA. Doesn't matter that the effect on the chromatin is more directly and logically expected from many treatments - your "hypothesis" is formed by convenience, not prediction. Wnt (talk) 23:21, 8 March 2016 (UTC)

File:WH3.JPG

Another question about the identity of a location: Does someone know what this file is a skyline of? Jo-Jo Eumerus (talk, contributions) 11:28, 6 March 2016 (UTC)

Given the title, and looking at the original uploader's short list of contributions, it's a good bet that it's Winter Haven, Florida. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:00, 6 March 2016 (UTC)

Yes. Compare with this. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:04, 6 March 2016 (UTC)

Thanks, moved it to a better name (after first moving it to Winter by mistake...) Jo-Jo Eumerus (talk, contributions) 19:43, 6 March 2016 (UTC)

Winter Haven is correct. Anything that has "Witner" is a typo. --Amble (talk) 18:11, 7 March 2016 (UTC)

Ha, that explains why I couldn't find it in the search box - I insisted on spelling it correctly. It's File:Skyline of Witner Haven, FL.JPG. Presumably there's a way to get that error fixed? (It's only been wrong since 2010.) ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:51, 7 March 2016 (UTC)

I have added a rename request template to both images. --Amble (talk) 21:53, 7 March 2016 (UTC)

Thanks to Widr for performing the moves. --Amble (talk) 16:40, 8 March 2016 (UTC)

• What happens when you click on the section title? My result is weird. —Tamfang (talk) 02:19, 8 March 2016 (UTC)

That confused me too at first. It's because the Winter Haven images were uploaded directly to English Wikipedia. One of those was named WH3.JPG. But since that file has been renamed, there is no longer a WH3.JPG on English Wikipedia, but there does happen to be an unrelated file with the same name on Wikimedia commons. So now when you click on the link, you get that one instead. --Amble (talk) 06:22, 8 March 2016 (UTC)

Skin cancer from smoking

This 1956 article raised the issue of smoking causing lung cancer. One of the author's lesser topics regarded tar and condensed smoke causing skin cancer when they were, essentially, "painted" on the skin of various other mammals. Today, nobody seriously disputes the idea that smoking raises the risk of lung cancer, and secondhand smoke is sometimes an issue, but we virtually never hear about secondhand smoke causing skin cancer. Has such an idea been disproven, or is it merely minor enough that it just doesn't get much attention? Nyttend (talk) 17:29, 6 March 2016 (UTC)

I had never heard that before, so I googled "cigarettes and skin cancer". A number of items came up, including this from 2012, which says smoking significantly increases the risk of skin cancer. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:51, 6 March 2016 (UTC)

There are several unrelated cancers that are called "skin cancer". So, the answer to this question depends on exactly what cancer you mean. Ruslik_Zero 19:48, 6 March 2016 (UTC)

I'm actually interested in a slightly different thing: the effects of smoke (not smoking) on the skin. In the experiment addressed in the article, cigarette tar and "condensed" smoke were pasted onto mice; three-fifths developed papillomae, and almost half developed what the article calls "true cancer". Obviously, tobacco smoke is the only cigarette byproduct regularly in contact with the human skin, and I suppose secondhand smoke would be the best mechanism for testing this issue; the article Bugs found says that smoking weakens the immune system, so that's another variable you'd have to consider when studying the effects of cigarette byproducts on the skin of smokers, but not for nonsmokers. Nyttend (talk) 20:19, 6 March 2016 (UTC)

I don't think it was ever suggested that cigarette smoke would cause skin cancer. It would appear from the article that painting the tar on the skin was just to see what effect it would have on living cells in high concentrations. As it says, inhalation experiments weren't producing lung cancer in animals so the next step would be to see what effect higher concentrations had. They couldn't get the rodents to inhale the tar so it was easier to paint it onto the skin. it's the same principle as when they test something like artificial sweeteners by giving them to rats in concentrations that are higher then anyone could achieve by ingesting them in food and drink. Hopefully any problems will show up much quicker that way. Richerman (talk) 22:24, 6 March 2016 (UTC)

I think it falls under the "minor" category. Public health messaging probably doesn't focus on it because by far the leading cause of skin cancer is UV exposure. So for reducing skin cancer, it's much more important to promote limiting sunlight exposure and use of sunscreen. As for messaging about secondhand smoke, its effects on the respiratory system are more well-studied, so it's just easier to cite that. --71.119.131.184 (talk) 22:29, 6 March 2016 (UTC)

Maybe we need to convince everyone to smoke so much that the smoke clouds block the sunlight. :-) StuRat (talk) 14:48, 7 March 2016 (UTC)

Need to drill inverted cone into top of LED

I have an LED lighting project where I need low power RGB LEDs to provide as much light to the side as possible. I'm unable to find any lower power LEDs with an [inverted cone lens] so I'm going to try drilling/cutting an inverted cone shape into the plastic of regular RGB LEDs with my small rotary tool. Is this idea clearly flawed? --92.6.114.99 (talk) 21:38, 6 March 2016 (UTC)

Not at all! Using a small lathe might be an idea. Use a file (tool) before. Mayme a treatmend with sand by abrasive blasting or a P80 / P100 Sandpaper might fulfill Your need. --Hans Haase (有问题吗) 22:15, 6 March 2016 (UTC)

If You want to restore a clear surface, You need to use a P2000 or higher fine sandpaper, used to prepare car paint coating, used with water as a release agent tu use the paper for more applications and better results. Using the lathe, mount the drill fixed and rotate the LED. Using a sharp drill will crash the LED and other platic. See how to prepare a drill for metal and how to apply it on plastic. --Hans Haase (有问题吗) 23:39, 6 March 2016 (UTC)

Actually, coating with metallic paint or tinfoil to reflect the light will work better.--TMCk (talk) 23:45, 6 March 2016 (UTC)

I'm wondering if a curved mirror behind the LEDs might be a better option, to redirect light headed in the wrong direction to the direction you have in mind. This is how LED flashlights tend to work, so you might use parts from those. Can you describe your application ? Specifically, how closely are the LEDs to be packed ? StuRat (talk) 14:41, 7 March 2016 (UTC)

I don't think your read the question closely enough! The OP wants MORE light at the sides - which is the entire point of inverted-cone lenses that reflect the light that would normally exit from the center of the lens to shine out at the sides. A convex mirror positioned in front of the LED might work - but it's a pain to manage physically. Drilling a conical hole in the front of the LED is by far the best solution - but you need the right kind of drill bit, some means for holding the LED in place, and a reasonably accurate control of the depth of the hole. The sides of the hole need to be fairly smooth, so a higher RPM drill might be preferable. SteveBaker (talk) 20:25, 7 March 2016 (UTC)

Where I said to put the mirror "behind" the LED, read that as "in the location where you don't want the light to go". So, if the goal is to have a single LED spread light to the sides instead of straight forward, then the mirror should be in front of the LED. The cone shape sounds good, except for the noted problems below. The use of the word "lens" instead of "mirror" for something that reflects rather than refracts light just didn't seem right to me. StuRat (talk) 05:14, 9 March 2016 (UTC)

I see a potential problem which may explain why nobody makes RGB inverted cone (also known as concave cylindrical) LEDs. If you look at http://www.quickar.com/wic6.jpg (from the http://www.moreleds.com/whiteinverted.htm webpage) you will see the banding that is typical of inverted cone LEDs. and RGB LED has the three dies next to each other, so each color will have the bands shifted. This will cause a rainbow effect instead of the desired even color mixing.

Have you considered making a small cover out of white translucent plastic? --Guy Macon (talk) 09:20, 8 March 2016 (UTC)

Here is somebody selling them on the Italian ebay: [12] perhaps you can figure out where they are sourcing them? Also, note the color problems I mentioned above. --Guy Macon (talk) 09:37, 8 March 2016 (UTC)

The avail sample might be a question of the price. The need to modify the LED is in changing its light emitting characteristics. Such LEDs usually were designed as a spotlight, emitting most of the light in an angle of 10 to 30 gedrees. Philips came up with such inverted but diffuse cones, to giving the LED a 360 light emitting characteristic. Another idea depending on the applications mght be to look for socalled "filament LEDs". --Hans Haase (有问题吗) 14:49, 8 March 2016 (UTC)

I suppose I should ask the obvious question: "Have you considered using multiple LEDs, pointing to the side, to get the desired effect ?". Considering the low cost of LEDs, this seems feasible, to me. StuRat (talk) 05:19, 9 March 2016 (UTC)

March 7

Reverse Correlation Method

Hey Guys, I have a psychology assignment that I am doing, and I was reading a study, titled Seeing Jesus in toast: Neural and behavioral correlates of face pareidolia. In the text, it contained a passage: We, for the first time, directly compare the neural responses of face pareidolia to that of non-face object (letter) pareidolia. Specifically, we explore the specific role that the FFA plays in face pareidolia. In the present study, participants were instructed to detect faces from pure-noise images in the face condition, and letters from the same pure-noise images in the letter condition. To ensure that face or letter pareidolia really occurred, we used a reverse correlation method similar to that used by Hansen et al. (2010) to obtain classification images based on behavioral responses (face or no face response in the face condition and letter or no letter response in the letter condition).  I do not know what reverse correlation method is. I tried going on the Wikipedia page for it, (Spike-triggered average) but found it was a lot of jargon. If anybody knows anything about what it is, I would be very thankful. JoshMuirWikipedia (talk) 08:28, 7 March 2016 (UTC)

You haven't adressed the most obvious line to take: Did you look up Hansen et al (2010)? If not why not? If yes, give us the compplete harvard reference and tell us why it didn't help you. 60.228.17.3 (talk) 10:43, 7 March 2016 (UTC)

The article Fusiform Face Area (FFA) describes the part of the brain involved in face recognition. Correlation is a mathematical measure of the consistent relationship between two sets of data. Although correlation does not always imply causation, we do suppose that neurons emit spikes as a response to preceeding stimuli. So-called "reverse correlation" is the collection and averaging of historical data that preceeded every spike. The procedure to obtain a Spike-triggered average is to record all the stimuli as a continuous time record, then detect each spike time and finally look backwards in time at the stimuli that were recorded prior to the spike. This diagram demonstrates study of a neuron that is sensistive to a bright spot in the visual field, but whole face recognition and facial illusion (paraidolia) are more complex psychological phenomena. AllBestFaith (talk) 13:31, 7 March 2016 (UTC)

• Let me try to describe the method as simply as I can.

1. Start with a set of completely random images. Participants look at them and claim to see faces in some of them but not in the others.
2. Average together all the images in which participants claim to see faces, and separately average together all the images in which they claim not to see faces.
3. Subtract the averaged no-face image from the averaged face-image. The result is called the Classification Image.
4. The claim is that this Classification Image has a structure that more or less resembles a picture of a face.

Looie496 (talk) 19:03, 7 March 2016 (UTC)

This paper has a fairly accessible description of the method. Tevildo (talk) 00:09, 8 March 2016 (UTC)

Wi-fi

Can an operating microwave oven interfere with a wi-fi connection? 2601:646:8E01:515D:FC5A:F45A:C719:3885 (talk) 10:32, 7 March 2016 (UTC)

Yes, potentially quite a bit. As our article says, Wi-Fi b and g use the same range of frequencies that microwave ovens do. One technique to mitigate this is to switch between Wi-Fi "channels" (frequency bands). A lot of Wi-Fi equipment includes features to automatically switch channels if needed (often referred to by names like "Auto channel select"). --71.119.131.184 (talk) 11:25, 7 March 2016 (UTC)

YES - along with quite a few other things. Apple gives a list of the main sources of interference here: https://support.apple.com/en-gb/HT201542 109.150.174.93 (talk) 11:49, 7 March 2016 (UTC)

Microwave ovens are supposed to be shielded, with a Faraday cage. That's the fine wire mesh you see in the door. It's also behind the plastic on the sides, top, and bottom. StuRat (talk) 14:36, 7 March 2016 (UTC)

Microwave ovens operate at ~10,000 times the power output as wifi. A microwave can be legally compliant if it "only" blocks ~99.8% of the power output, which would mean it still emits 20 times higher than what a wifi router is allowed to emit. It is easy to see how microwave oven could interfere with wifi. Whether or not they actually will interfere generally depends on the quality and integrity of the shielding. Dragons flight (talk) 16:48, 7 March 2016 (UTC)

Why metering devices are based on different standards and different etalons?

If economics are always based on standardization and certification (based on standards and etalons), so why metering devices are based on different standards and different etalons (based on different standardization and different certification)?

Did the USSR-Russia are used international standards and international etalons in their standardization and certification of metering devices on which been based their economy?--83.237.197.222 (talk) 13:00, 7 March 2016 (UTC)

Therefore, did the economy as also and metering devices should be objective or subjective?--83.237.197.222 (talk) 13:15, 7 March 2016 (UTC)

In the USSR only electricity meters had been compulsory for all, so that in the USSR were no been gas meters and water meters in households because gas and water were always paid according to fixed state tariffs, and in Russia it is mandatory for all added water meters but not gas meters.--83.237.198.253 (talk) 14:27, 7 March 2016 (UTC)

According to wikt:etalon, it's a device for delaying a laser beam. Is this really what you meant ? StuRat (talk) 14:32, 7 March 2016 (UTC)

Sorry - but your question is very hard to understand - particularly, the word "etalon" that you use four times means: "An optical device containing parallel mirrors, used in laser design to delay light"...which probably isn't what you mean here. I assume you are using automatic translation from Russian into English - but it's not working well enough. Can you find someone who speaks English to ask the question for you? SteveBaker (talk) 14:34, 7 March 2016 (UTC)

Etalon is French for a measuring gauge or a measuring standard - so the standard meter or the standard kilogram is an etalon. I suspect this is the meaning here - but the question still isn't clear enough to know what is actually being asked. 109.150.174.93 (talk) 14:41, 7 March 2016 (UTC)

Ah - OK, so maybe we can have a shot at answering it... SteveBaker (talk) 16:51, 7 March 2016 (UTC)

• If economics are always based on standardization and certification (based on standards and etalons) -- I don't think economics are based on standard measurement methods. Clearly, when you're talking about the value of goods, you have to know how much goods are involved - but it doesn't seem to be an important part of economics.
• so why metering devices are based on different standards -- Are you asking about why (for example) some markets measure using the metric system and others on imperial units? It's usually very clear what goods are sold using which units of measurement (gallons versus liters, feet versus meters, pounds versus kilograms, etc)...and there are standards for converting between them - so it's really not much of a problem. That's not always true - if you cut wood or paper into sizes that are standard in one country - but not in another, then there will be problems. If you sell A4 sized sheets of paper, you're not going to sell much in the USA, where people normally use "Letter" sized sheets...but if you sell gasoline by the liter, you'll have no problems selling it in US gallons. Everything depends on what the item you're selling is.
• Did the USSR-Russia are used international standards and international etalons in their standardization and certification of metering devices on which been based their economy? -- Most places in the world choose the standards they use for historical reasons rather than for economic reasons. But if you trade all around the world, choosing the metric system is generally easier.

I hope I answered the right question! SteveBaker (talk) 16:51, 7 March 2016 (UTC)

Some other examples where unit conversion doesn't work come up with food, which is sometimes measured by weight, sometimes by volume and sometimes per item. It's not that easy to compare a pound of apples with a peck or with a dozen. You need to know the average volume, mass, and how tightly they are packed (and, due to edge effects, large quantities may be packed more densely). In the case of things like brown sugar, the volume to weight (or mass) also depends on the water content. Of course, none of this relates directly to the Q. StuRat (talk) 17:48, 7 March 2016 (UTC)

I interesting, did it make sense to install meters (metering devices) if their readings are not standard and etalon (measuring gauge) according to the international standardization and international certification of their?--83.237.195.181 (talk) 17:34, 7 March 2016 (UTC)

I believe we already answered. To repeat, it doesn't matter what units are used, as long as those units can easily be converted into any other units. StuRat (talk) 17:43, 7 March 2016 (UTC)

And as for the why any country would not chose an international standard, in short old habits die hard --Lgriot (talk) 17:56, 7 March 2016 (UTC)

There are up-front expenses with switching standards, and politicians tend to be incredibly short sighted, so the long term benefits may be irrelevant to them, compared to the short terms costs. StuRat (talk) 18:03, 7 March 2016 (UTC)

And in Russia, IP addresses jump around even more than in the United States or the United Kingdom. Robert McClenon (talk) 18:16, 7 March 2016 (UTC)

Thanks StuRat. However, did it make sense to install meters (metering devices) if the word economies already have a depreciated cost (residual value – liquidation value) due to the depletion of natural resources, in my country USSR-Russia it had been due to the depletion of natural gas resources?--83.237.195.181 (talk) 18:58, 7 March 2016 (UTC)

I don't quite understand. Are you saying the cost is too low to worry about metering it ? The cost of something has to be extremely low for that argument to be true. Even water is typically metered when delivered by pipe to homes. It could be delivered for free, and just use taxes to pay for it, but then peole would tend to waste water, since it won't affect their bill. StuRat (talk) 19:36, 7 March 2016 (UTC)

StuRat, I mean that the profit is extremely low due to the residual value – liquidation value which already presents in the world economics, so that I think that there is not sense to install meters (metering devices).--83.237.200.134 (talk) 20:01, 7 March 2016 (UTC)

StuRat, low profit did not make chance to successfully develop economies of the world.--85.141.239.105 (talk) 21:10, 7 March 2016 (UTC)

It may be that we aren't answering the original poster's question because we don't understand it. Does the Russian Wikipedia have a Reference Desk? Robert McClenon (talk) 21:14, 7 March 2016 (UTC)

ru:Википедия:Форум/Вопросы. Nimur (talk) 21:18, 7 March 2016 (UTC)

Thank you for answering that question. Original poster: We have difficulty in understanding your question, largely because it isn't in clear English. If Russian is your first language, as we would guess from your IPs geolocating to Russia, why not ask the question in Russian at the Russian Wikipedia? Robert McClenon (talk) 21:21, 7 March 2016 (UTC)

"Вопросы, не относящиеся к работе над Википедией, будут удалены." I suspect they will not tolerate this type of question on the Russian Wikipedia reference desk. Nimur (talk) 23:43, 7 March 2016 (UTC)

There may be it sense a residual value - liquidation value of the national currencies of the economies of the world.--83.237.207.66 (talk) 07:13, 8 March 2016 (UTC)

My country USSR-Russia did make the stupidest thing to becoming saving an electricity at the beginning of its development, installed an electricity meters and to becoming saving a natural gas at the end of its development, beginning to install a water and natural gas meters.--83.237.207.66 (talk) 07:29, 8 March 2016 (UTC)

In the end it will be possible to learn from my country USSR-Russia has justified its banking on natural gas or not.--83.237.197.166 (talk) 10:23, 8 March 2016 (UTC)

Dependence on any one industry will eventually lead to economic collapse when that industry declines. I am in Detroit, which has suffered from economic collapse as a result of over-dependence on the automobile manufacturing industry. Theoretically, you could have taken all the profits from natural gas and used them to develop other industries for when that industry declines. However, actually doing so require extreme discipline which is lacking just about everywhere. We didn't do it in Detroit, Russia doesn't appear to have done so with gas, and Saudi Arabia doesn't seem to have done so with oil. For an example of where it has been more successful, maybe look at the economy of Hawaii, which at one time was dependent on tropical crops, like pineapples (and before that, whaling). They have been able to diversity into other industries, like tourism. StuRat (talk) 15:38, 8 March 2016 (UTC)

Thank you StuRat. The main age-old quests problem of my country USSR-Russia is that, did a natural gas turned out more cheap than electricity for it or not.--83.237.205.112 (talk) 16:39, 8 March 2016 (UTC)

As for me, it is be often interesting why my country USSR-Russia choose their banking on natural gas against to electricity.--83.237.207.147 (talk) 18:45, 8 March 2016 (UTC)

Having large reserves of natural gas makes that look promising, while electricity has to come from somewhere, like nuclear power plants, and Chernobyl makes those look like a bad idea there, while transmission of electricity over vast distances causes losses due to resistance. StuRat (talk) 19:05, 8 March 2016 (UTC)

Since my country USSR-Russia from the very beginning of its development already was saving electricity, it did forced to use electricity combined with natural gas at the end saving natural gas, I think it been cheaper for its development than using only electricity.--83.237.201.20 (talk) 07:58, 9 March 2016 (UTC)

Of course, I think that more simple combinations of electricity with natural gas are always been more effective – more cheap than more complex combinations of electricity with natural gas. — Preceding unsigned comment added by 83.237.201.20 (talk) 09:12, 9 March 2016 (UTC)

StuRat, agree, that than cheaper be the energy source so that been the more quickly pays for itself regardless of the technique which is be simple or complex. (Of course, for quickly pays for itself of more expensive technique is always been required a more cheap energy source.)--83.237.203.184 (talk) 13:53, 9 March 2016 (UTC)

It's not always best to use the cheapest energy source. Since fossil fuels like natural gas are not renewable, it may make sense to save them for later, when hopefully the global supply will be lower and the price will be much higher, even if that means using a more expensive energy source now. This means saving a valuable resource for later generations rather than exploiting it today, though, which is rarely popular with politicians. StuRat (talk) 17:36, 9 March 2016 (UTC)

StuRat, Is it meaning that in terms of cheapest and most cheapest energy sources the level of complexity of technique never did not matter for pays for itself, because it did so fasters?--83.237.206.41 (talk) 19:54, 9 March 2016 (UTC)

(StuRat, is it be possible that natural gas development was turned out more cheap to my country USSR-Russia than electrical development?)--83.237.206.41 (talk) 20:28, 9 March 2016 (UTC)

At last, should be economy as also and accounting systems been objective or subjective?--83.237.205.112 (talk) 13:58, 8 March 2016 (UTC)

Wherever possible, everything should use objective measures. But, it's not always possible, therefore subjective (opinion) measures are sometimes all that we have. For example, a school teacher can objectively evaluate a student's math answers, but must subjectively evaluate an essay. StuRat (talk) 15:22, 8 March 2016 (UTC)

StuRat, Did it according to metering devices (meters)?--83.237.205.112 (talk) 15:33, 8 March 2016 (UTC)

A metering device should always be objective. I don't see how it's even possible for a meter to be subjective (some places did at one time have the customers mail in the readings, so maybe that's what you mean ?) . StuRat (talk) 15:42, 8 March 2016 (UTC)

StuRat, If economics are always been based on know-hows, so that did these know-hows are been standardized and certificated according to international standards, if they been a meters?--83.237.205.112 (talk) 15:49, 8 March 2016 (UTC)

I don't understand this question. StuRat (talk) 19:05, 8 March 2016 (UTC)

StuRat, If economics are always using know-how, some of them are been technical know-how, so that did these use's know-how are been standardized and certificated according to international standards, if they been a meters or been using in meters?--83.237.203.184 (talk) 14:30, 9 March 2016 (UTC)

Muscle memory

I don't want to be led astray too much by a mere choice of words for a concept, but could it be that muscle memory implies memories stored in muscles too? If you train a movement, could a muscle codify information about it in itself, that's posteriorly triggered by the brain?--Llaanngg (talk) 13:51, 7 March 2016 (UTC)

No. You should read muscle memory for more details if you are interest. The term is colloquial, and does not mean that the muscles themselves store memories like your central nervous system does. --Jayron32 14:08, 7 March 2016 (UTC)

(EC)Sure, that is a conceptually reasonable implication to look in to. But it happens to be not true. See Muscle_memory. It's not clear to me whether your interest is more in the logic of the matter or the actual science. Lots of things have logical possibility yet are not true, however most things that are logically impossible are not true. While it's not true that human muscle stores memory, memory can be stored in odd ways. Memory in general is a bit nebulous, and here [13] is some research that made a splash a few years back discussing how certain behaviors of slime molds seem to indicate they have memory. SemanticMantis (talk) 14:13, 7 March 2016 (UTC)

I get from the corresponding article that the mainstream view is that muscles do not store information. I suppose that includes that the synapses in the muscles (that is they do not store information either). However, how can we scientifically test whether memory is stored outside the brain too? The spinal cord has neurons whose axons project into the muscles. Could it be at least that a signal does not have to travel all the way to the brain, but be dealt with locally by the neurons of the spinal cord? --Llaanngg (talk) 14:59, 7 March 2016 (UTC)

There is compelling evidence for plasticity in the spinal cord; see for example PMID 11520919. Note though that most neuroscientists tend to think of the brain and spinal cord as parts of the same entity, the central nervous system. In any case there is no clear boundary separating the brain from the spinal cord; they merge continuously into one another. A more interesting question is whether there is plasticity in the peripheral nervous system -- I don't know the answer. And there is at least one part of the body other than the nervous system that shows a substantial learning capacity: the adaptive immune system. Looie496 (talk) 15:16, 7 March 2016 (UTC)

You might also be interested in the reflex arc and peristalsis, two cases where muscles are controlled, at least in part, locally. The beating of the heart may also fall into this category. However, there is no "memory" in these cases, as these forms of muscle movement are present at birth. The movement of long thin animals, like snakes, worms, centipedes, and millipedes, also seems to work in a manner similar to peristalsis. That is, the brain of the animal starts the front segment moving, but each following segment moves in turn right after the segment in front does, based on inputs from the previous segment. StuRat (talk) 14:29, 7 March 2016 (UTC)

A large part of the autonomic nervous system can operate independently of the brain and spinal cord and form memories, in particular the stomach can independently remember your pattern of eating and does not depend on the brain to prepare for a meal at the right time. In general though what is called muscle memory refers to learnt actions which are controlled by the cerebellum and need not go anywhere near conscious awareness. Dmcq (talk) 17:00, 7 March 2016 (UTC)

The section Muscle memory#Music memory says "Memorizing is done by muscles....[22]" with a citation to an 1896 paper in the American Journal of Psychology. Clicking to this link gets you to a free copy of the article, which says on page 454: "It was not, then, a reproduction of the word as heard or as associated with something seen, but of a muscular movement, which, latent for five years, was recalled by the suggestion of a similar movement. This incident suggests that possibly, under normal conditions, the muscles play a greater part in our memories than we are accustomed to assign to them". Loraof (talk) 14:57, 7 March 2016 (UTC)

I'd be more than a little skeptical of a 120 year old study involving memory, as they knew almost nothing about how memories were stored, at that time. StuRat (talk) 15:23, 7 March 2016 (UTC)

I have removed that source from the article, as well as the statements based on it. Looie496 (talk) 15:38, 7 March 2016 (UTC)

It might be good for the history section. StuRat (talk) 18:04, 7 March 2016 (UTC)

One aspect of memory that has always intrigued me is that memory can apparently survive metamorphosis in some animals e.g. [14] I always thought that during metamorphosis of the caterpillar, it temporarily became a "soup". Perhaps I am thinking of this too simplistically. DrChrissy ^(talk) 19:29, 7 March 2016 (UTC)

Much of it does, but some key organs seem to stay intact as they relocate to their new position. A fascinating process, isn't it ? StuRat (talk) 19:32, 7 March 2016 (UTC)

You mean imaginal discs, but they are not organs (yet) and they do not stay intact through pupation. It is by no means logically necessary that some physical organ must persist for learned behavior to persist, as shown by the unicellular slime mold I mentioned above, PNAS paper is here [15]. Anyway, we've now stumbled in to highly contentious cutting-edge research in entomology, wherein the "Hopkins host selection principle" and the "chemical legacy hypothesis" still vie for prominence and acceptance and nobody knows for sure what's going on [16] [17], [18]. This is indeed a fascinating direction for a thread on memory to go, but I'd be hesitant to take the one PLoS paper above as evidence of anything other than the latest punch in science fight that has lasted about a century. SemanticMantis (talk) 19:52, 7 March 2016 (UTC)

Ecdysozoans and even holometabolous insects don't really become a "soup" during metamorphosis. Their regeneration is something like an extreme specialization of how our own works: small diploid cells go from stem cell to rapidly dividing population, then become polyploid, larger, terminally differentiated, and eventually get worn out and thrown away. The difference is just (in ecdysozoa) the growth evolved to be phased to minimize the periods when the skin is unprotected by cuticle (but it's not as straightforward as growth during the molting period, more the opposite - see [19]), and in holometabolans their differentiated cells get discarded all at once as the imaginal discs rapidly spread out and replace them across the entire exterior of the body. But there's always a zone where tissue comes from and a zone where old tissue is gotten rid of, whether we're speaking of a butterfly or our own skin. Wnt (talk) 20:28, 7 March 2016 (UTC)

More on the innervation [20][21][22]. There's still a bit I don't understand about the geometry of the process, but it should be clear that the rewiring is relatively local. Wnt (talk) 20:37, 7 March 2016 (UTC)

I have just read the slime mold paper cited by SemanticMantis. It is absolutely fascinating! As someone who has worked in vertebrate animal behaviour my entire career, "We challenged our slime mold..." as a quote will stay in mind forever! DrChrissy ^(talk) 21:17, 7 March 2016 (UTC)

The time to start worrying is when it challenges you back! Have I mentioned my conjecture that the Loch Ness Monster is a giant grex? {The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 21:36, 7 March 2016 (UTC)

No, you haven't! And I'm sure I speak for most ref desk regulars when I thank you profoundly for your omission. SteveBaker (talk) 21:47, 7 March 2016 (UTC)

Physarum can also learn to anticipate periodic events, as this paper shows [23], and though they don't have a biomechanical model (yet), they have a nice conceptual differential equation model for how they think memory might be working. (And yes, I think this is still relevant to the notion of "muscle memory" loosely considered, and the biological study of where memory resides :) SemanticMantis (talk) 22:15, 7 March 2016 (UTC)

Probably not stored like memory but muscles grow and train through repetitive use. In that sense, there is a muscle memory as certain groups are trained more and differently than others and the repetitive nature makes that action less fatiguing than doing the same or similar task with different groups. If your a carpenter that uses a hammer in your right hand for years and then switch, not only is your brain unfamiliar, your muscles cannot perform at the same efficiency. --DHeyward (talk) 00:17, 9 March 2016 (UTC)

March 8

Can we read minds with science ?

Not precise thoughts, exactly, but just whether something makes them happy or sad, for example. The idea would be to show disturbing videos, say of the Holocaust, to refugees from the Middle East, and put some electrodes on their heads to detect if the video makes them happy or disturbs them. Those that are made happy or at least undisturbed by scenes of mass death would be denied admission and returned to their nation of origin. Is this technically possible ? (Note that I am explicitly NOT asking about the ethics of doing so.) StuRat (talk) 03:41, 8 March 2016 (UTC)

Passing over the basic stupidity & repugnance of the idea, Functional magnetic resonance imaging says "Some companies have developed commercial products such as lie detectors based on fMRI techniques, but the research is not believed to be ripe enough for widespread commercialization". Polygraph says "In 2001, a significant fraction of the scientific community considered polygraphy to be pseudoscience". So. Mainly no, then. --Tagishsimon (talk) 04:15, 8 March 2016 (UTC)

Your suggestion is reprehensible and technically impossible in equal measures. Fgf10 (talk) 07:58, 8 March 2016 (UTC)

Note that for purposes of security theater, a device can be completely bogus and still see wide use as a reassuring "security precaution". Terrorists frequently report being disturbed by civilian casualties caused by the non-terrorist bombs that non-terrorist organizations detonate at public events, so I'm not sure which end of your spectrum would actually contain more terrorists. Still, it's possible that a generalized psychometric approach that excludes anyone who is too smart, too dumb, too shy, too outgoing, too suggestible, too resistant etc. will deliver a subset of "near clones" who all think and act alike; provided most are not terrorists perhaps all will not be terrorists. But I don't know if there's any proof for that assertion and somewhat doubt it, since there is probably more 'entropy' in the middle values, more ways for a set of random personal factors to tot up to seemingly average characteristics. The question seems rather fundamental to concepts of psychopath in psychology, so maybe there's something along that line to be found.

Note however that what you're asking is about predicting minds with science. It is much easier to merely read minds with science. For example, the would be entrant can be shown the cover of the current Inspire magazine and his P300 measured, and you can exclude him if he recognizes it. This is, obviously, a test that only works once; better yet, some wag might spam the (H-1B, typically) employees of Microsoft with some kind of email campaign to make them be excluded by the test... then threaten Apple they'll do the same to theirs if they don't fork over a couple of million bucks, which kind of defeats the purpose of hiring H-1Bs in the first place. ;) Wnt (talk) 11:56, 8 March 2016 (UTC)

The answer to your question "Can we read minds with science ? Not precise thoughts, exactly, but just whether something makes them happy or sad, for example." is simply yes for we already have done this [24] with fMRI and machine learning. --Modocc (talk) 14:31, 8 March 2016 (UTC)

• This is a large topic, with many approaches of varying degrees of sophistication -- the history goes back at least to the Thematic Apperception Test developed in the 1930s. Looie496 (talk) 16:35, 8 March 2016 (UTC)

You can do a lot more than what you've wished for/explained with/using science/technology, but, I guess, something[s] are just hypothesis... -- Apostle (talk) 18:12, 8 March 2016 (UTC)

A 1993 newspaper article (and many journal articles) said that a psychologist named Emmanuel Donchin proved that we can read minds with brain waves, specifically the P300 evoked potential: [25]. Computers are way faster now than in 1993 when it comes to analyzing brain waves. See also Brain-reading, Brain–computer interface and Brain fingerprinting which mention Donchin's work.Edison (talk) 06:45, 9 March 2016 (UTC)

conjoined twins are usually born with two hearts or one?

I read this article on BBC about the existence of two hearts in woman and I found the following sentence: "Aside from conjoined twins, no human is born with two hearts". But I can not conclude from it if it's usually or not. 93.126.95.68 (talk) 04:57, 8 March 2016 (UTC)

Our article Conjoined twins lists the various types of conjunction that occur, and the percentage each contributes to the total. The first (28% of cases) usually involves the heart, while the second (18.5%) always does. Rojomoke (talk) 06:26, 8 March 2016 (UTC)

Wi-Fi part 2

Can heavy rain and/or thunderstorms interfere with wi-fi (other than by causing physical damage to the network)? 2601:646:8E01:515D:D1E0:6CC9:A57C:4C96 (talk) 05:57, 8 March 2016 (UTC)

If your wi-fi transmits across an outdoor space then heavy rain will affect it by reducing the signal strength. Lightning can affect the internal electronics, as with any electronic equipment. Dbfirs 09:28, 8 March 2016 (UTC)

But can lightning interfere with the signal without actually damaging the router? 2601:646:8E01:515D:D1E0:6CC9:A57C:4C96 (talk) 11:19, 8 March 2016 (UTC)

My intuition would be "yes" because electromagnetic fields can change the bits on a bus and in memory, but perhaps someone else with more experience and expertise can cite some research on this? Distant lightning would not generate a sufficiently strong field to cause a problem, but could cause a spike on the electricity supply, and this, in turn, could affect the router. Dbfirs 12:30, 8 March 2016 (UTC)

Lightning creates a broad-band burst of EM radiation, part of it in the wifi band. This adds noise to the wifi signal, reducing the signal-to-noise ratio and degrading the signal for a few deciseconds. This could affect you if the signal is already weak. The short wavelength of wifi radiation is easily absorbed by water in the air, so the lightning has to be quite close to have any effect. PiusImpavidus (talk) 13:05, 8 March 2016 (UTC)

To some extent it also depends on what you mean by "interfere with the signal" and "damage". While I never had a wifi router, after renovations my childhood home in Malaysia had a fuse box which was quite sensitive to lightning. Possibly there were some design problems or maybe it was because it was connected to all 3 phases which is a bit of an unusual config. I think there was a good true earth connected ground so having MOVs at the meter likely would have helped. But anyway this would rarely cause any damage, it would just fuse sometimes a few times during lighting storms (which are quite common in KL).

When there was damage, I'm pretty sure it was from the phone line. (Phone line connections also lack a MOV or any sort of protection at the entrance in Malaysia unlike the US. Or at least that's what someone on usenet said was the case in the US time after time.) We did have a lightning arrestor but one time that failed to protect and so the dialup modem died. (The arrestor also died but that was fairly common. Stupid me forgot to connect to disconnect the arrestor and so for a time I thought the phone line was dead until after 3 sets of telephone line technicians one of them diagnosed it as the arrestor.) We then largely relied on just disconnecting the phone line until one time this wasn't done and a lighting strike took out not just the ADSL router but most of the computer. (Definitely the mobo, can't remember about the PSU or monitor. Not sure if the CPU was even properly tested.)

While we never actually had an AP in the house AFAIK obviously if we did and without a UPS by cutting off the power to the AP it would interfere with the wifi signal rather badly until the fuse was manually reset. And without damaging the AP or anything else. (Possibly there was some very minor damage to something but this went on for many years without any clear problems other than with the lightning/phone line issue.)

Nil Einne (talk) 16:37, 8 March 2016 (UTC)

We actually had a brief power outage last night, although my equipment didn't "notice" it, as it all is plugged into an online UPS. Operatively here, what was theorized above about lightning EMF interference was what occurred at the time. A nearby lightning strike dropped the power for about ten seconds, at the same time, my wireless signal lost lock and had to reconnect. Water also can absorb RF energy, rain is obviously water and the shorter the wavelength, the more impacted the radio signal would be. For commercial applications, where a loss of signal or significantly degraded signal may occur, various methods were utilized to mitigate against signal loss, ranging from signal compression, directional antenna, high gain receivers, etc. After all, at the physical layer of WIFI in the OSI model, it's just a radio.Wzrd1 (talk) 19:57, 9 March 2016 (UTC)

source for the sentence that humans have 7 subdivisions in renal medulla

I've read on the article renal pyramid that "The renal medulla is made up of 7 to 18 of these conical subdivisions (usually 7 in humans)." I would like to ensure that by a professional source, do you have? (I tried to search on google books but maybe because I'm not native English speaker I couldn't find) 93.126.95.68 (talk) 06:17, 8 March 2016 (UTC)

Type in to google "The renal medulla is made up of 7 to 18 conical subdivisions" and see what you get. This one from The University of Ottawa says 8 to 18, but the difference is fairly insignificant. The sentence in the article seems to have come from the Cram101 study guides one of which is here Richerman (talk) 10:07, 8 March 2016 (UTC)

Here's a cute variation: a "desert gerbil" with a single renal pyramid so long that it extends down the ureter. The system is so efficient at recovering water that it doesn't need to drink. :) On the other hand this source says that the morphology doesn't have to be so extreme for water to be recovered. It might be worth trying to figure out what species have what morphology and how well they conserve water at some point... Wnt (talk) 11:36, 8 March 2016 (UTC)

To be honest, in the books Gray's anatomy and Moore anatomy, the kidney is with seven pyramids, eve though I didn't it's written in words but the pictures says it. 93.126.95.68 (talk) 14:56, 8 March 2016 (UTC)

How much power do field lights use?

Specifically, I'm interested in finding out how much it costs to run field lights for a typical American high school stadium - something equivalent to what's in the picture at right. How much electricity do they consume and at an average American electricity price, how much would it cost to light a field per hour. I'm only looking for a ballpark (pardon the pun) figure within, say, an order of magnitude. Edgeweyes (talk) 13:34, 8 March 2016 (UTC)

Here is the cost analysis for installing and maintaining (including electricity costs) field lights at Wilde Field at Lisle High School in Lisle, Illinois. --Jayron32 14:17, 8 March 2016 (UTC)

Keep in mind that the values can swing a great deal depending on the type of lighting used. LEDs in particular are often promoted as having fairly short payback periods due to their reduced power consumption in comparison to halogen bulbs. The amount of illumination required (probably a function of the size of the field) would also be a key variable. Matt Deres (talk) 14:54, 8 March 2016 (UTC)

In my neighborhood, road lighting and other large outdoor lighting installations have switched to using LEDs as part of a Department of Energy project. Here's LED Lighting Facts - Outdoor Area Lighting, a brochure from Department of Energy's Office of Energy Efficiency and Renewable Energy.

All this is part of the CALiPER program, "to address a need for unbiased, trusted product performance information in the early years of [solid state lighting]." As SteveBaker and others have mentioned, it is hard to compare long-term economics of LEDs because the technology is so new; the data collection is still ongoing to see how LEDs compare to other technologies when used in large, bright, high-intensity outdoor settings over decades. The DoE websites I linked contain loads of quantitative data. Nimur (talk) 16:22, 8 March 2016 (UTC)

That short "payback period" would be for replacing incandescent bulbs. That won't apply at all for new installations, while for replacing CFL bulbs the payback period will be much longer, since LEDs cost more but are only slightly more efficient than CFLs. StuRat (talk) 15:15, 8 March 2016 (UTC)

Sure, in the home or office, LED lamps are substantially the most efficient, and the longest lasting, and not as harmful to the environment as CFL's. In the last couple of months, their prices have dropped to almost the same level as CFL's and incandescents (From Walmart, 60W-equivalent: $0.99 for incandescent, $1.47 for CFL and $2.17 for LED...HomeDepot has 60W-eqiv LED's at $3.55 for a pack of two - 40W-equiv candelabra bulbs are even cheaper). I recently moved to a new home - and I've more or less replaced every bulb in the house with LED's. CFL's should be obsoleted now - they were a great stop-gap measure while LED bulbs cost $30 or more - but now that LED's are affordable, they need to go away. The reasons for sticking with incandescents versus CFL (unnatural color, slow start, poor brightness in cold conditions, mercury in the environment) don't apply to LED. You can get LED lamps in four shades of white now! They turn on instantly, and they don't care about the temperature and they last for so long that the manufacturers can't get a sufficiently high failure rate to measure it. There is no longer any excuse to stick with incandescents.

But we're talking about lamps bright enough to light a football field from some towers at the corners, operating well in extremes of cold and hot weather. It's difficult and expensive to replace them. That requires extremely specialized lamps - and I'd be very surprised if CFL's are even considered in that kind of application, or that sufficiently bright LED clusters are yet available. Either way, knowledge of what works in the home and office yeilds zero information about the OP's question. SteveBaker (talk) 15:49, 8 March 2016 (UTC)

Indeed, a quick review of the Department of Energy's detailed reports for the Outdoor Flood lamp category show that SSL (LED) lamps are often more power efficient, but sometimes they are less power efficient, compared to a metal halide lamp. So, LEDs have a lot of promise as a better technology for this application, but it still requires a careful long-term look at the practical engineering and economic details! Nimur (talk) 16:29, 8 March 2016 (UTC)

I get my CFLs for 50 cents each. Many of those disadvantages have now been fixed, as CFLs come in a range of color temperatures and brightnesses, instant start is available, and some work in cold weather. I actually like slow start for some applications, like when turning on a lamp first thing in the morning, when I'd rather not have it flash a blinding light in my face immediately. As for mercury, that may still be an issue, but throwing out all your CFLs early certainly won't help to prevent mercury contamination. StuRat (talk) 16:04, 8 March 2016 (UTC)

Six NHL arenas light their playing surfaces with LED light clusters. The referenced vendor lists an outdoor arena product with a -40° C to +55° C temperature operating range. So the tech exists, and is affordable at the professional sport level, but I don't know how far it's filtering down. I suspect new construction is going to be pretty much exclusively LED from here out, though. — Lomn 16:30, 8 March 2016 (UTC)

At the SAP Center (the Shark Tank), they also have a fascinating technology in which a professional photographer can connect to the arena lighting. Synchronous to each photograph capture, the arena lights strobe up to an illuminant level something like (WP:OR) four times brighter, for a net gain of something like 2 f-stops. I can't find any official documentation, except this brief mention from the Ice Hockey Officials of Northern California website warning not to let the strobes distract or annoy participants.

As an avid physicist and strobe enthusiast, I would love to read more technical information about what type of light can repeatedly boost the illumination of an entire hockey arena by some 4x, on command, with a response time and synchronicity on the order of tens of milliseconds! That's some serious technology, the sort of spooky stuff that The Government straps to the bottom of a B-17 to help the war effort!

Nimur (talk) 16:47, 8 March 2016 (UTC)

Running field lights for a typical American high school stadium might very well have a net negative energy cost. It is quite likely that the power saved by a large number of people going to the game instead of staying home with the lights, TV, computer and/or appliances running is a lot larger than the energy used by the stadium lights. This, of course, assumes that what you care about is total energy use. If you only care about how much energy the school has to pay for those other savings don't matter. --Guy Macon (talk) 16:51, 8 March 2016 (UTC)

It isn't "quite likely", though it's an interesting argument and worthy of some calculation. I suspect the gasoline used to drive to the venue - and I presume USians will tend to drive - on its own will outweigh any savings from the telly & lights being turned off at home. --Tagishsimon (talk) 16:58, 8 March 2016 (UTC)

Let's do some back-of-the-envelope calculations.

Amon G. Carter Stadium has 30,500 seats. The ten largest high school football stadiums in Texas range from 16,500 to 23,000 seats.[26] Smaller stadiums would of course cost less to light but would also have lower savings from fewer people not being at home. It costs $100 per night to light Amon G. Carter Stadium.[27] If this unreliable source[28] is correct, an average house uses about $2.40 in electricity a day. Mine is about $60/month, so that number is in the ballpark. BTW, our Domestic energy consumption article badly need expanding. If we assume 16.5 cents per person per day energy saving, that's $5,000 saved. You can plug in different assumptions, but you won't overcome a 50:1 difference in costs.

Gasoline costs are harder to figure. According to Miles per gallon gasoline equivalent 33.7 kilowatts kilowatt hours per gallon is about right. I am guessing three persons per car (two parents and one child), so perhaps 10,000 cars in the parking lot of our imaginary 30,000 seat stadium. I am also guessing that it takes about a gallon to get to the local high school and back, and $2 per gallon gasoline. So that's $20,000 spent on gas. Maybe $40,000. Now comes the hard part. How many of those people would have driven somewhere else that is farther away with fewer people in the car if they weren't at the game? --Guy Macon (talk) 18:20, 8 March 2016 (UTC)

Most of them weren't driving somewhere else because the premise of the comparison is that they stayed home to watch the game on TV versus driving to the stadium. Having said that, I accept that a few might drive to a friend's place or to a bar to watch it over a few beers. Akld guy (talk) 23:06, 8 March 2016 (UTC)

In that scenario, the stadium lights are on either way, an according to my back-of-the-envelope calculation above the energy used to drive the cars would almost certainly far outweigh the energy used by running the TV, cooking the snacks, etc. I am glad you brought up cars, because I was originally only thinking electricity. --Guy Macon (talk) 07:16, 9 March 2016 (UTC)

How do you convert "gallon of gas" (a energy number, Joule) to "kilowatts?" ( a Joule/sec power number)? --DHeyward (talk) 00:29, 9 March 2016 (UTC)

By making a dumb typo. It is, of course, kilowatt-hours. --Guy Macon (talk) 07:16, 9 March 2016 (UTC)

Thanks, Jayron, that's exactly the kind of thing I was looking for, and matches the type of field lighting I'm interested in. The key phrase, "cost to operate the lights would be approximately $6/hour", answers my question nicely. Edgeweyes (talk) 16:56, 8 March 2016 (UTC)

A factor we should consider when considering low cost but inefficient lighting versus expensive but highly efficient lighting is the duty cycle, or hours used per week. In an office or manufacturing plant which is used perhaps 50 hours per week, a small increase in efficiency can justify a much higher installation cost. In a high school football stadium where the lights are used, say, 4 hours per week, a lower efficiency but cheaper lighting system might be more cost effective. How many years is the payback time for a higher purchase price system which uses less energy, in a given application? This is engineering economics. Edison (talk) 06:27, 9 March 2016 (UTC)

When running is there an Vasodilation or Vasoconstriction in the blood vessels?

I think that in case of hot climate there is vasodilation because the body wants to cold the blood by the blood vessels in the surface of the body and the it makes them wider and in the most of the cases a lot of them even can be visible. Am I right? 93.126.95.68 (talk) 15:00, 8 March 2016 (UTC)

I can only attest to my personal experience. When I exercise in the cold, such as shoveling snow, my limbs get quite cold, while my core overheats. There is apparently a reaction to limit blood flow to the limbs, in order to conserve heat, but this reaction, at least in my case, ignores the temperature of my core, and seems to be solely based on the outside temperature. To try to compensate, I wear warm gloves but take my coat off. StuRat (talk) 15:11, 8 March 2016 (UTC)

It's a mix. Blood vessels that feed into muscles dilate, but blood vessels that feed into the guts constrict. The blood flow to the skin is determined more by temperature regulation needs than by activity per se: when you are too hot the skin vessels dilate; when you are too cool they constrict. The blood flow to the hands and feet can also be reduced if they are losing too much heat, but if they cool to the point where there is danger of tissue damage the flow will increase. In short -- it's complicated. Looie496 (talk) 15:18, 8 March 2016 (UTC)

Yes, it is complicated. It will differ if you are out for a training run or being chased by a tiger. If you are out for a training run, you will thermoregulate to effect homeostasis and blood will be moved around your body according to those needs. If you are running from a tiger, thermoregulation is temporarily dispensed with. In a typical Fight-or-flight response, blood is directed to the major locomotor muscles and essential organs such as the heart and brain. After you have escaped the tiger, your body will return to thermoregulatory processes. DrChrissy ^(talk) 19:13, 8 March 2016 (UTC)

Yep, *really* complicated. Even when running in a hot climate, homeostasis must be maintained, both in blood supply to muscles and to the skin for cooling. If one fully vasodilates, one would go into shock, as happens in anaphylactic shock. Meanwhile, various parts of the body can be vasodilated or vasoconstricted while running just to maintain homeostatis, as was mentioned in two responses above. The body maintains homeostatis by using sympathetic and parasympathetic nervous systems in opposition to one another to maintain a greater degree of control with only one operating at a time.Wzrd1 (talk) 19:48, 9 March 2016 (UTC)

Oort cloud

I assume the Oort cloud is so far only theoretical, no one knows for sure whether it really exists. However, I read that Voyager 1 will enter the inner extent of the Oort cloud in 300 years. Does this mean that after that time, we will receive definite confirmation about whether the Oort cloud really exists? JIP | Talk 20:15, 8 March 2016 (UTC)

The article states that by 2025, Voyager 1 will have effectively shut down. So it appears that the only way we can receive information about the Oort cloud is to launch another such spacecraft. Is this true? JIP | Talk 20:20, 8 March 2016 (UTC)

As with many things particularly those relating to astronomy or physics, I'm pretty sure it depends what you mean by "information" but the answer is probably no. See [29] [30] or if you're interested in the nitty-gritty perhaps read [31] [32] as an example of how we can get information without actually flying a spacecraft into or near to the Oort cloud and receiving information back. Nil Einne (talk) 21:01, 8 March 2016 (UTC)

Which question are you replying to? Is it "No, we won't get information once Voyager 1 enters the Oort cloud" or "No, launching another spacecraft is not the only way we can ever possibly get information about the Oort cloud"? JIP | Talk 21:24, 8 March 2016 (UTC)

If that isn't obvious from the refs (none of which refer to Voyager 1) and my actual answer (which also only refers to how we can get info without sending a spacecraft and never refers to Voyager or receiving info from a spacecraft) then I guess my answer isn't helpful to you. Nil Einne (talk) 21:37, 8 March 2016 (UTC)

Sorry, I didn't read through all the information you provided. I guess that's it has to do with the same problem as with the asteroid belt, that contrary to popular image, the Oort cloud, if it exists, is way too sparse to just get near it and notice a bunch of comets flying around all over the place. JIP | Talk 21:53, 8 March 2016 (UTC)

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is." Rmhermen (talk) 01:24, 9 March 2016 (UTC)

There may be other ways to detect it. Perhaps it can be observed by emissions of infrared radiation or perhaps by eclipses of stars. Perhaps neutral molecules can make through the vacuum from a cloud object to the vicinity of the Earth. So far it is observed by the large objects that appear to come from it, so more detailed observations and missions to long period comets may reveal more. I suspect Earth based radar and lidar do not have the range to reach it. Graeme Bartlett (talk) 00:44, 9 March 2016 (UTC)

I would expect that we would have lots of ships, still communicating with Earth, in the Oort cloud within 300 years. Just look at how many ships we have flying around the inner solar system now, and how impossible that would have seemed 300 years ago. However, as JIP noted above, just being in the Oort cloud wouldn't make it all that apparent, any more than being in the ocean makes it obvious that there are coelacanths there. StuRat (talk) 01:01, 9 March 2016 (UTC)

It's not like the Oort cloud is some kind of unicorn dream. We have observed ~5000 long-period comets [33] bound to the sun. The Oort cloud is simply the name given to the parent population of those objects. Because many of the observed comets have recurrence times in the thousands, tens of thousands, or even hundreds of thousands of years, it follows that most long-period comets are far enough away from us right now that they have never been observed. Thus we extrapolate a population of billions of comets from an observed sample of thousands. The properties of that population are going to be sketchy. Is it really a uniform cloud in all directions? What is its inner and outer limit? How many objects are out there? Etc. However, the argument for a large population of comets at the edge of the solar system far beyond the known planets is already on pretty good empirical observational grounds. Dragons flight (talk) 08:22, 9 March 2016 (UTC)

It seems fitting that the otherwise-unrelated word "ort" suggests what the Oort cloud would be - the "bread crumbs" of the solar system. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:54, 9 March 2016 (UTC)

Wikt:Ort means "leftovers", to me, which is even better, since they are the leftovers from the formation of the solar system, perhaps with some captures from outside the solar system (the neighbor's leftovers ?). StuRat (talk) 15:42, 9 March 2016 (UTC)

Bingo. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:36, 9 March 2016 (UTC)

Provenance of image

Greetings, another image along my theme: Does someone here know what File:Wanderlust.jpg is an image of? Jo-Jo Eumerus (talk, contributions) 21:28, 8 March 2016 (UTC)

Any or all of the following:

1) A family vacation photo stolen from the Internet, original here: [34]

2) Somewhere along the coast of Oregon (according to Grant Chambless photo album)

3) "I went to this location and took a photo. Therefore this picture is mine."

It should probably be deleted as likely copyright violation. --Amble (talk) 23:50, 8 March 2016 (UTC)

Now listed at Wikipedia:Possibly_unfree_files/2016_March_8. --Amble (talk) 00:00, 9 March 2016 (UTC)

Does the ovum is made of many cells?

I've read that the one of the part of the spheres of the ovum has follicular (corona) cells and I was shocked because I always thought that the ovum is a uni-cell. Now I'm confused and I'd like to get an explanation.93.126.95.68 (talk) 22:38, 8 March 2016 (UTC)

Just click on Ovum. You see the ovum is in the middle, with the corona radiata (and more generally the cumulus oophorus) around it. This is a common state of affairs - for example, flies have nurse cells to do this task. The reason is that the egg is a huge cell, and it's the sort of exception that proves the rule: to be this big, it needs other cells pumping their resources into it. Nonetheless, technically the ovum remains a single cell inside its membrane - though at least in Drosophila there are actually cytoplasmic connections, and a stickler might call it a syncytium that only happens to have the majority of cytoplasm around one nucleus. Wnt (talk) 23:43, 8 March 2016 (UTC)

Thank you for your comment. But I still don't understand what is this complex of the ovum with all the cells that belongs to it - is called. Is there a name for all this complex? because I made google and of course I clicked on the article but I always see that it's called ovum includes all these accompanying cells. 93.126.95.68 (talk) 01:15, 9 March 2016 (UTC)

It's called the ovum. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:35, 9 March 2016 (UTC)

The ovum is a single cell - the haploid female gamete. It is surrounded by a cluster of smaller cells both in the ovary and in the uterus after ovulation - the ensemble being the Cumulus oophorus and forms one more hazard for the poor little sperm to get through. 109.150.174.93 (talk) 09:24, 9 March 2016 (UTC)

Thanks, I took the liberty of wikilinking more words in you text. SemanticMantis (talk) 15:37, 9 March 2016 (UTC)

March 9

Some structures on a ship's deck

This and this are tiny screenshots from the film Titanic. Specifically, they are from the scene early in the film wherein the sailors are on the ship's deck, running toward Jack and Rose after hearing her screams when she slips off the railing and nearly falls into the ocean. Questions:

1. What is the large white cylindrical structure, with what looks like a door with six handles, to the left of and behind the sailors?
2. If that is a door, why does it need six handles instead of just one?
3. What is the white column, curled forward at its top end so that it is sort of shaped like an upright bowl pipe for smoking, to the left of the large cylinder?
4. What are the two black barrels/posts to the right of the sailors?

—SeekingAnswers (reply) 05:44, 9 March 2016 (UTC)

The bowl-pipe thing is a cowl on a ventilation duct to get fresh air to some lower deck area. DMacks (talk) 05:57, 9 March 2016 (UTC)

Dover gun turret.

2) The big white cylinder looks like a gun turret (compare with the pic I've added here). Did they by any chance use a decommissioned military ship for that scene ? If so, the guns (cannons) would have been removed from the top, but the turret left in place. As for the door, perhaps shells would be loaded that way, and the massive armored door would need several latches to hold it in place under enemy fire (more sophisticated designs had elevators to lift shells into position from below deck). Here's a diagram of a Dreadnought class battleship, with turrets and guns in place: [35] (you can only see the top of the turrets in the side view, since most is below the rails). StuRat (talk) 06:03, 9 March 2016 (UTC)

My guess: the base of an electric crane, towards the front of c-deck. See http://www.encyclopedia-titanica.org/titanic-deckplans/c-deck.html --Tagishsimon (talk) 06:49, 9 March 2016 (UTC)

Or ditto, towards the rear of b-deck. http://www.encyclopedia-titanica.org/titanic-deckplans/b-deck.html ... seems to tie in better with the ventilation doodab and the, err, grey rope thingies. See also figure 129 on this page - http://www.copperas.com/titanic/dynamo.htm --Tagishsimon (talk) 06:51, 9 March 2016 (UTC)

Yup, crane. [36] has a ton of photographs and descriptions of the various structures on this class of ship. DMacks (talk) 06:59, 9 March 2016 (UTC)

As to the 6 handles. They are securing a curved watertight door to a curved structure & protecting an otherwise exposed electrical motor ... I suspect 6 were necessary to ensure watertightness ... one on each corner & two in the middle. By the looks, the crane was operated from above the circular platform we see - see the photo in this discussion - [37] - and so I guess the door provided access for maintenance purposes (i.e. quite rare) rather than for operation. All speculation, of course. --Tagishsimon (talk) 07:12, 9 March 2016 (UTC)

I'm surprised that Wikipedia does not have a watertight door article. The closest we seem to come is Compartment (ship)#Doors. Multiple dogs (see Dog (engineering)#Hatch dogs) are necessary to fully secure a watertight door whether it is sealing against a curved surface or a flat one. It is possible to connect the dogs together with lever mechanisms so that they are all activated simultaneously via a single wheel or lever, but this adds complexity which increases the cost of the door and its required maintenance. I don't know if such quick acting watertight doors were in use back in 1910, but individually acting watertight doors are still used extensively today where there isn't sufficient traffic to justify a quick acting one. Ships will often have small deck houses solely for providing access to a companionway (steps) to a lower deck (the alternative being a deck hatch and ladder), but they are typically smaller than the "white cylinder" in your images and often sloped on the side opposite the door. I think that DMacks and Tagishsimon are right on target and it is the base of a 2-1/2 ton electric crane. See this photo. I also concur with them regarding ventilator cowl for #3 and bitts for #4. -- ToE 14:28, 9 March 2016 (UTC)

Quick acting watertight doors were provided on the Titanic, designed and built around 1910. They were controlled electrically from the bridge. Akld guy (talk) 17:55, 9 March 2016 (UTC)

"What are the two black barrels/posts to the right of the sailors?" I think they're called bollards. Rope used to tie up the ship is passed between them, and they're designed to be strong enough to resist movement fore or aft. Ah. Also called bitts, mooring bitts, double bitt bollards, &c. --Tagishsimon (talk) 09:34, 9 March 2016 (UTC)

What is this US Navy electronic thing?

A friend found this at a ham radio club flea market - https://farm2.staticflickr.com/1502/25650380485_f00cde1ba4_o.jpg What is it? Roger (Dodger67) (talk) 19:29, 9 March 2016 (UTC)

It might help if we could read the top line of labels. Can you add that info ? StuRat (talk) 19:47, 9 March 2016 (UTC)

I see it was made by General Mills. Some sort of electric pastry warmer ? :-) StuRat (talk) 19:50, 9 March 2016 (UTC)

The main selector switch appears to be "OFF","W/H SAFE","W/H ARMED" and the red label says it came from the Bureau of Ordnance's Naval Ordnance Laboratory. So "W/H" is probably "warhead", and this is either a controller or some sort of dummy simulator for a weapon system of some sort. DMacks (talk) 19:58, 9 March 2016 (UTC)

Much better than what (talk) suggested and accurate as well. As for General Mills, I've personally fired a M2 Browning made by IBM and another made by the Singer Sewing Machine Company. Who has the equipment at a specific era makes the device for the government.Wzrd1 (talk) 20:16, 9 March 2016 (UTC)

The markings I could decipher are:

USN = United States Navy

BUORD = Buro of Ordnance - 1862 to 1959 when it became the Buro of Naval Weapons (BUNAVWEPS)

NAVORDLAB = Naval Ordnance Laboratory

White Oak = a part of Silver Spring, Maryland. In 1993 the site was transferred to the Food and Drug Administration when many of the naval facilities around and near Washington DC were consolidated in the Washington Navy Yard.

General Mills established its Electronics division in 1946 so that sets the earliest date, the latest is 1959, when the label would have changed from BUORD to BUNAVWEPS.

Sorry, this photo is all I have currently. Roger (Dodger67) (talk) 20:19, 9 March 2016 (UTC)

I'm really going to have to start going to flea markets, especially since we've relocated to just outside of Barksdale AFB.  ;)Wzrd1 (talk) 20:22, 9 March 2016 (UTC)

This [38] covers a lot of "test set" equipment the navy uses to test missiles and such. They list diagrams for many similar sized gizmos with TS-XXXX numbers. Your example has T-3026 and says "test set". So I think it's a test set for testing ordnance, basically per DMacks. Here [39] is a very nice page listing the manuals for many bits of testing equipment the Navy used in that era, but it only covers radio test equipment. I suspect the owner of the website could be contacted for further assistance, as he has a lot of knowledge and interest in US Navy electronics of the era. SemanticMantis (talk) 21:11, 9 March 2016 (UTC)

Why during a total solar eclipse one can't see stars?

On almost all photos of a total solar eclipse stars are not visible. Thanks.--93.174.25.12 (talk) 20:58, 9 March 2016 (UTC)

Even during a total eclipse, there still is sunlight from the corona to light things brighter than the stars.Wzrd1 (talk) 21:14, 9 March 2016 (UTC)

They are not visible without any eclipse either. Light pollution. --AboutFace 22 (talk) 21:18, 9 March 2016 (UTC)

In fact, at totality it is possible to see stars in the sky - but only if you look well away from the sun. As the photos of an eclipse are all looking right at the sun, there is too much light from the corona for the stars to be visible in the area of sky close to the sun.109.150.174.93 (talk) 21:20, 9 March 2016 (UTC)

I can report from personal experience in France in 1999 that it's possible to see the corona during a total solar eclipse even if there is a thin layer of cloud. I would not expect to see stars in that situation. This shows how bright the corona is, and supports what 109.150 says.--69.159.61.172 (talk) 21:26, 9 March 2016 (UTC)

http://www.enchantedlearning.com/subjects/astronomy/sun/solareclipses.shtml says "During totality the sky is dark enough to see stars in the sky". Loraof (talk) 21:28, 9 March 2016 (UTC)

And varoius other sites say the same thing--google "seeing stars during total eclipse". Loraof (talk) 21:31, 9 March 2016 (UTC)

There's a detail here worth noting. The original poster asks specifically about photos of a solar eclipse. The thing is, you can't photographically capture both stars and a much brighter object like the Sun (as mentioned above, there's still light from the Sun's corona even during a total solar eclipse) at the same time. This is an issue of optics. This is also an issue in space photographs, and is sometimes brought up by uninformed people as "proof" that photographs from the Apollo missions are fake because you can't see stars in them. Here's an article about this and other aspects of the Apollo pictures. --71.119.131.184 (talk) 21:46, 9 March 2016 (UTC)