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March 15

How did people thousands of years ago know that fruits and vegetables are healthy?

Most of the foods that we eat today that are known to be healthy using the methods of modern science, have existed for many centuries. How did people know that e.g. carrots are healthy (the name for carrot in certain Asian languages translated literally into English is "strong body")? Count Iblis (talk) 00:15, 15 March 2013 (UTC)

Not really a proper answer, but... I'm not sure where the carrot example traces back to, but for example Dioscorides collated data about "normal" fruits and vegetables as well as more medicinal herbs. Ancient herbal knowledge was extensive, but shows certain limitations - especially, they don't seem to have had any conception of how to cure cancer or even whether their treatments caused it. For example, Dioscorides knew about yew, but he didn't know about taxol, and aristolochia, alas, continues to cause trouble to this day. From this limitation, I would suspect that the knowledge must have come from fairly short term trial and error testing and/or a lot of very careful observation. Wnt (talk) 00:31, 15 March 2013 (UTC)

Chimpanzees and rats and many other mammals eat fruits and vegetables. Do you really think it required a human cortex to start eating them? alteripse (talk) 01:01, 15 March 2013 (UTC)

By taking a little nibble on unfamiliar foods. Poisonous foods generally wouldn't kill them from just that. However, if they tasted horrible or made them sick, then they'd avoid those foods. If the nibble turned out okay, then next time they might try a bite. If that worked out they might try several bites. If there was no problem then, they might eat the whole thing. StuRat (talk) 03:24, 15 March 2013 (UTC)

The Count can correct me if I'm wrong, but I suspect the question wasn't "how did ancient humans know that certain foods weren't poisonous" or "at what point did humans begin eating certain foods." What I read into it was, e.g., how did ancient humans begin to associate certain foods with certain health benefits? As an example, how did they determine that apples were good for dental health or that carrots improved eyesight? I'm just spitballing, obviously I have no idea how old either of those beliefs are, but that's an example of what I think the Count was asking. Evanh2008 ^{(talk|contribs)} 03:31, 15 March 2013 (UTC)

Quite often, they didn't. Until the mid-18th century, people in Britain believed that tomatoes were poisonous, so they didn't "just know". People in Japan eat fugu, which most certainly is poisonous (even the supposedly "safe" parts of this fish are somewhat poisonous). We eat almonds - which in their "natural state" are full of cyanide. We worry about the side-effects of "chemicals" such as food colorings - yet we agree that cherries are good (but their pips produce prussic acid if even slightly damaged or swallowed). Apple seeds have cyanide too. Potatoes are OK...but green potatoes have enough toxins to kill people who ate too many of them. So I'm not sure that the wisdom of the ancient people was that good. We know that there are foods that won't immediately kill you - but may induce horrible diseases in later life. No amount of taking little nibbles, checking that you don't get sick over the following 24 hours, etc will tell you that eating cinnamon, nutmeg, black pepper and herbs such as basil (all of which contain safrole) will increase your lifetime risk of several different cancers. SteveBaker (talk) 04:06, 15 March 2013 (UTC)

Thousands of years ago carcinogens weren't much of a concern, as people were unlikely to survive to an age where cancer was much of a risk. Starvation was a far more likely cause of death. StuRat (talk) 04:19, 15 March 2013 (UTC)

There was some hit and miss to ancient recommendations. For example, night blindness is mentioned in Dioscorides' section on goat liver: "The watery fluid that drips from the liver of a goat whilst it is a roasting is good rubbed on for those troubled with night blindness. If anyone receives the smoke of it with open eyes whilst it is boiling he receives benefit from this. Eaten roasted it is good for the same purpose. They say that epilepsy may be discerned by eating the liver (especially) of the buck goat." Now, I'm pretty sure the smoke isn't going to be of much help, but liver (food) is about as good a source of vitamin A is to be found. Rubbing the juice on the eyes? I don't know. Topical retinoic acid is used for acne... maybe you could reach the retina if you got enough in there ... but I'm skeptical. The ancients seemed to have as much of an irrational preference for topical treatments as we do for pills taken internally. (For example, they frequently used opium topically; for us it was not even appreciated until fairly recently that peripheral opioid receptors exist) Wnt (talk) 05:33, 15 March 2013 (UTC)

An "irrational preference"? If you have a better method of getting penicillin or Tylenol into the bloodstream, one that preferably doesn't involve sticking sharp objects into the patient, why don't you tell all the doctors how stupid they are for not using it? You'll be famous and your name will be remembered for the rest of human history. --140.180.249.27 (talk) 06:17, 15 March 2013 (UTC)

When you start with the preconception that any medication must enter the bloodstream to be effective, then you're obviously not going to endorse topical applications. Your two examples are an antibiotic and a painkiller, both of which have topical equivalents. Of course, those are most appropriate where the infection and/or pain are near the surface. This allows a higher concentration where needed, and a lower concentration in the rest of the body, thus reducing the risk of side effects like liver damage and killing off beneficial bacteria in the digestive system. StuRat (talk) 06:34, 15 March 2013 (UTC)

It's well known in the pharmaceuticals industry that, for example, in the UK you pretty much have to deliver your medication in pill form, if you want most people to actually take it, no matter what delivery method would be most sensible. A liquid, suppository, injection, nasal spray, inhaler, patch, or topical application will simply not be as popular. Caplets are a work-around for liquids. Beyond that, it forces a lot of research into tablet technology, to try to make tablets effective at delivering medication that beter suits other routes. 86.161.209.78 (talk) 10:15, 15 March 2013 (UTC)

Another interesting example is Scurvy. As our own article says "The knowledge that consuming foods containing vitamin C is a cure for scurvy has been repeatedly rediscovered and reforgotten into the early 20th century" and as I guess most people interested in this sort of thing may know scurvy was a frequent problem for sailors and the like until fairly recently in relative terms. Nil Einne (talk) 06:53, 15 March 2013 (UTC)

On the other hand, the entire developed world has discovered how to get obese and stay that way, but seems completely beyond the knack of getting back to square 1. There's a million books, websites, diets, plans, schemes and TV shows, but the problem just gets worse. The rest of the world doesn't seem to have this problem. They're doing something right. -- Jack of Oz ^[Talk] 07:57, 15 March 2013 (UTC)

Thanks for all the replies so far. To clarify my question a bit more, it seems to me that centuries ago, people could still stuff themselves with unhealthy foods. While Europe didn't have access to sugar until only a few centuries ago, in Asia they did for many centuries, so you can easily imagine that people would stop eating vegetables, and only eat sugary desserts. But people still kept on eating healthy stuff. So, it's not about very specific knowledge they may have had that eating X will prevent disease Y, but more something like what a mother often says to her child: "If you don't eat your vegetables, you won't become as strong as your father". Count Iblis (talk) 12:36, 15 March 2013 (UTC)

Another factor is price and purity (just like drugs). A century ago, sugar was available, but was expensive, especially white sugar. So, you had people using less total sugar, and more of it was dark brown sugar or molasses, which aren't quite as bad as white sugar. StuRat (talk) 12:46, 15 March 2013 (UTC)

A most interesting discussion. I think a simple premise applies as much today as it did during the days of yore: people listen to what their bodies tell them. So if you get stomach aches eating the wrong food, you will gravitate towards what doesn't affect you, unless you want to carry on getting stomach aches. I think we've always known what was good for our bodies. Although there wasn't as much junk food those days, I'm sure people knew the benefits of a balanced meal as opposed to eating too much starch (for example) and then learning from observing the results in other people with bad diets. Sandman30s (talk) 13:00, 15 March 2013 (UTC)

We should also realize that our concept of what is "good for us" is based on what is deficient in our diet. In the modern world, this tends to be various vitamins, minerals, phytonutrients, and fiber. Thousands of years ago, on the other hand, salt and sugar were hard to come by, as were animal products for all but the rich, and many didn't get enough calories. They probably got too much fiber, due to sand in their food, for example, and plenty of most vitamins and minerals, from having nothing to eat but whole grains and vegetables. We see evidence for some of this, like too much fiber, from them having worn-down teeth.

So, what they would have been deficient in then would be salt, sugar, fat, etc., precisely what we get too much of. There's a reason for this, of course. Being deficient in those things for many generations led us to evolve to prefer those items, when we could find them, as people who gorged themselves when they did manage to get some meat, for example, or find some honey, were more likely to survive to pass on their genes. StuRat (talk) 13:11, 15 March 2013 (UTC)

“So I started asking soldiers how frequently they would like to eat this or that, trying to figure out which products they would find boring,” Moskowitz said. The answers he got were inconsistent. “They liked flavorful foods like turkey tetrazzini, but only at first; they quickly grew tired of them. On the other hand, mundane foods like white bread would never get them too excited, but they could eat lots and lots of it without feeling they’d had enough.”

This contradiction is known as “sensory-specific satiety.” In lay terms, it is the tendency for big, distinct flavors to overwhelm the brain, which responds by depressing your desire to have more. Sensory-specific satiety also became a guiding principle for the processed-food industry. The biggest hits — be they Coca-Cola or Doritos — owe their success to complex formulas that pique the taste buds enough to be alluring but don’t have a distinct, overriding single flavor that tells the brain to stop eating. [1]

Seems relevant, although I'm too tired to try to make the case. Gzuckier (talk) 16:26, 15 March 2013 (UTC)

If you've ever tried to subsist on just one type of food, you quickly either a) get bored with it, or b) start having funny symptoms. What most regional cuisines have in common is not that they somehow intuit healthy outcomes, but that they are blends of many different types of food around some sort of common bulk carbohydrate which delivers the necessary calories.

We should also take care to distinguish between "thousands of years ago" (which is fairly long by civilization's standards) and hundreds of years ago (which is what most people above are referring to). They are really quite different food situations. Anything post-Columbian (15th century onward) means you have much more worldwide availability of many different types of staples (corn and potatoes being especially important for population growth in Europe and Asia). Most of what we think of as "traditional cuisines" today in Eurasia are post-Colombian. --Mr.98 (talk) 18:30, 15 March 2013 (UTC)

Quite true on the post-Columbian thing. Traditional Italian dishes depend heavily on maize (Polenta) or the tomato (various tomato based sauces) which are new-world crops. All chili peppers are from the New World, so any "traditional" cuisine that depends on them owes itself to the Columbian exchange. Actually, the notion that the post-Columbian world has become more diverse in terms of diet and nutrition, even in "traditional" cuisines, is severely challenged in the recent work 1493: Uncovering the New World Columbus Created which asserts that there has been a massive homogenization of world crops and diets in the post-Columbian world. Certain new-world crops, like maize and potatoes, have become ubiquitous world-wide, often crowding out various local stables and completely replacing them, even old-world crops have become less diverse as basic efforts to increase productivity over preserving local food culture has led to less and less diversity as a few high-yield crops are replacing older varieties across the world. A particular strain of wheat may have been farmed in a locality for centuries, but it may have only been known for a few hundred square miles; crops like this have in many cases been replaced by higher-yield crops, homogenizing the world wide food system, and forever altering food cultures around the world. At least, that's the argument that the 1493 book makes, and it does a pretty convincing job of it. --Jayron32 05:25, 17 March 2013 (UTC)

While I agree that monocultures are a problem, I see no reason to attribute them to discovering new foods in the Americas. They are the result of modern agricultural practices. Without those, we'd have all the variety of the Old World and New World. StuRat (talk) 05:36, 17 March 2013 (UTC)

Except that many such monocultures are new world crops. 3 of the top 5 world staple crops are new world in origin (maize, potatoes, and cassava), and maize is far and away the worlds most produced staple. Also, the issue with the Columbian exchange isn't merely the one-way introduction of crops from the new world, that's not what the exchange is about. It's the world-wide shuffling of crops between old and new, and within the whole world. It's about the movement of many things from local culture to a world-wide culture. It isn't the introduction of new world crops per se that leads to the monoculture issue. It's the kind of world that creates the Columbian exchange that leads to the monoculture issue. --Jayron32 05:46, 17 March 2013 (UTC)

OK, I can agree with that. Both are caused by "modernization". StuRat (talk) 06:34, 17 March 2013 (UTC)

Section break

A relevant question. In nature, different species follow different diets though which they gain all necessary nutrients. What determines their diet? How do a specific species maintain a specific diet? Say for example, the diet of a lion is different from the diet of a deer. A lion will never eat grass. Why? What factors, including which genes, control their diet? --PlanetEditor (talk) 05:57, 17 March 2013 (UTC)

Well, the digestive systems of carnivores are different from omnivores, and both are different from those of herbivores. Ruminants, for example, need multiple stomachs to digest grasses. Beyond that, carnivores need the tools to catch their prey, like speed and sharp teeth and claws. A huge number of genes control all of this. StuRat (talk) 06:32, 17 March 2013 (UTC)

Actually most cats do eat grass, probably as a way of provoking vomiting or as a way of getting trace nutrients, and there is no reason to suspect that lions won't be any different. --TammyMoet (talk) 18:25, 18 March 2013 (UTC)

Dense ceramics

Are there any really dense ceramics that are comparable to lead or tungsten? ScienceApe (talk) 04:02, 15 March 2013 (UTC)

Ceramic armor might be of interest. StuRat (talk) 06:29, 15 March 2013 (UTC)

Tungsten carbide is a ceramic. It's heavy, but I'm not sure how it compares to pure Tungsten. ~Adjwilley (talk) 18:11, 16 March 2013 (UTC)

From the Tungsten carbide article the density is 15.63 g/cm³. But tungsten has density 19.25 g/cm³. Lead is much lighter at 10.66 g/cm³. Graeme Bartlett (talk) 11:14, 17 March 2013 (UTC)

Tungsten nitride W₂N has density 17.8.[2] Graeme Bartlett (talk) 11:09, 17 March 2013 (UTC)

CPAPs and habituation

CPAP machines strike me as weird; they blow air continuously into the patient's nose at a low pressure during sleep as a treatment for obstructive sleep apnea (among other things, I guess). Wouldn't this habituate the patient to exert their breathing muscles (the diaphragm, I suppose) less while sleeping, resulting in the patient breathing less deeply while asleep but not hooked up to the CPAP? Querentor (talk) 06:44, 15 March 2013 (UTC)

Not really. It forces you to fight it, and thus develop your diaphragm muscles. StuRat (talk) 07:07, 15 March 2013 (UTC)

CPAP makes your lungs work a bit harder on the exhale and makes inhaling a bit easier, but neither effect is anywhere close to being as large as the effort needed just getting air in and out though those branching airways, so the effect is minor. Stopping the Apnea before it ruins your heart is far more important.

Some modern CPAP machines do all sorts of cool things, like turning the back pressure way down during exhale, or reseating the mask by turning off for a second when excessive air leakage is detected. Some even auto-adjust the pressure in response to how many apnea events are detected. --Guy Macon (talk) 07:35, 15 March 2013 (UTC)

CPAP works in multiple ways, but reviews indicate that it works primarily as a pneumatic splint for the upper airway (PMID 1470809). This may reduce strain on respiratory muscles, because it reduces strain against a closed upper airway. As I said, it's complex, because central (CNS) issues are also at work in sleep apnea. I don't disagree with Guy Macon's answer (it sounds well-informed); in contrast, I am not sure where StuRat's answer above came from (no source was cited) - I suspect that it's not evidence-based. -- Scray (talk) 12:20, 15 March 2013 (UTC)

That's odd, since we agreed. Specifically, Guy's statement that "CPAP makes your lungs work a bit harder on the exhale". StuRat (talk) 12:53, 15 March 2013 (UTC)

Let us know if you find a reference for strengthening of "diaphragm muscles" by CPAP in persons with sleep apnea. -- Scray (talk) 14:18, 15 March 2013 (UTC)

I wasn't disagreeing with StuRat. I was expanding upon his answer. You don't need a reference to establish that, during exhale, a muscle which encounters slightly more resistance gets slightly stronger or that, during inhale, a muscle which encounters slightly less resistance gets slightly weaker.

If you need proof about it being a small increase in resistance change and thus a small strengthening/weakening effect, I can dig up a ref for that. As for the claim that "This may reduce strain on respiratory muscles, because it reduces strain against a closed upper airway", once again you have to consider the difference between inhaling and exhaling.

On the inhale, the CPAP pressure takes up a small amount of the load off the chest and diaphragm muscles, and it keeps the airway open, which is a huge difference in the load on those muscles (no longer trying as hard as they can to suck air down a closed airway). Alas, this happens at the exact time when your blood oxygen levels are dropping and your heart muscle is being damaged -- and you aren't doing the rest of your muscles any favors. I don't know whether the extra exercise helps the diaphragm more than the lower O2 hurts it.

On the exhale, the CPAP pressure adds a small amount of load to the chest and diaphragm muscles. Airway closure during exhale is not typical of obstructive sleep apnea (Instead of sucking a closed airway closed tighter, exhaling tend to inflate it). It can be a problem with central sleep apnea, which is why some CSA patients are on BIPAP instead of CPAP. --Guy Macon (talk) 17:14, 15 March 2013 (UTC)

What perplexes me most about this is that there's talk of exercise here, and just a little bit in the literature [3] [4], sometimes explained by ... counterintuitive hypotheses. Why isn't it the first-line treatment? (I know this isn't proof of anything, but I remember that five years ago I briefly encountered some incidents of sore throats/breathing issues. Realizing that it was very hard to keep my throat in the semi-closed position that matched the soreness, I "asked my sleeping mind about it" while semi-conscious, getting back the "answer" that it was more comfortable that way - because the diaphragm had the feeling that it "needed to be stretched", just like stretching your legs. Once I realized this I started doing an exercise every now and then where I breathe in as far as I possibly can and hold it, with an open airway for some time - which very rapidly became a spontaneous habit, since when the diaphragm (and ribs or something) feel that way the stretching is as pleasant a sensation when awake as when asleep, and accomplishes the task much better. I haven't noticed such trouble since - knock on wood! But I never found anything about this kind of thing in NCBI! Wnt (talk) 04:49, 16 March 2013 (UTC)

Invention?

Here is an idea...

Is it possible to replace rebar in concrete, with super large open-cell foamed metal? Plasmic Physics (talk) 12:31, 15 March 2013 (UTC)

Yes. Is it cost effective though?217.158.236.14 (talk) 12:35, 15 March 2013 (UTC)

The biggest problem with rebar is that it's made of steel. This means that if water infiltrates (especially saltwater), it can rust away, leaving the concrete unsupported. So, using some metal other than iron or steel would be a good idea, but, of course, would be more expensive. StuRat (talk) 12:50, 15 March 2013 (UTC)

It's not just that it leaves the concrete unsupported. It's also the fact that rust takes up more space than the equivalent amount of steel, resulting in cracking as the rebar expands. There's unreinforced concrete still around from the Roman age, but steel-reinforced concrete only lasts 100 years or so. They're looking at other ways of reinforcing that don't result in the same issues, either by using other metals (aluminum alloys, if I remember correctly) and things like fiberglass and carbon fiber instead. As indicated previously, the main issue is that they're currently more expensive than standard steel rebar. -- 71.35.100.68 (talk) 16:30, 15 March 2013 (UTC)

The rebar holds the concrete in compression, I don't think foamed metal would be as good that way. And by the way a little rust helps it hold on to the concrete though of course one doesn't want any more. Dmcq (talk) 13:02, 15 March 2013 (UTC)

Waida minute. Isn't rebar mostly for tension and shear? I know the article says "compression", but... Wnt (talk) 15:12, 15 March 2013 (UTC)

Yes, the concrete is excellent in compression, but bad at resisting just about any other force. The rebar is used to improve those properties. StuRat (talk) 15:17, 15 March 2013 (UTC)

Open-cell foamed metal explains why we won't see this idea implemented into real buildings. If cost were not an issue, we could also make a net of platinum and fill it with concrete. But that's not how things work. OsmanRF34 (talk) 15:29, 15 March 2013 (UTC)

Well I was assuming that someone could bring the cost down, it seems possible to me, however I can't see it being stronger in tension for a given weight than straight rod. See prestressed concrete for where one might first be thinking of doing anything new, straightforward rebars are basically a cheap and simplified version of that. Dmcq (talk) 16:19, 15 March 2013 (UTC)

If the cost is high for an item solely because it's not produced in scale, then producing it in larger batches should, indeed, bring the price down. However, if the price is high because the materials are rare, then making more of it will actually increase the price, as the materials just become more rare. Iron is common, while many other metals are relatively rare, at least in accessible locations. StuRat (talk) 20:36, 15 March 2013 (UTC)

I forgot to mention: the SLO-CMF would extend over the whole crossection. As the concrete permeates the foam, and tension would cause deformation of the cavities, would that not have an effect on the tensile strength? Plasmic Physics (talk) 03:25, 16 March 2013 (UTC)

I don't see why it would affect the tensile strength appreciably, and also it is quite difficult enough just to expel ordinary air bubbles in the concrete, that's why you see those vibrators always being used on sites. Perhaps you could explain why you think there is some merit in the idea, what kind of situation can you see it having some advantage? What particular property of the foamed metal would help? Dmcq (talk) 11:48, 16 March 2013 (UTC)

For one, the whole section would be reinforced, not just the core. Plasmic Physics (talk) 12:02, 16 March 2013 (UTC)

Rebar is formed into an open structure that goes near the edge, you're might be thinking of prestressed concrete but even in that case the cable or whatever follows the edge where there will be tension. You might be interested in Fibre-reinforced concrete which offers a bit of extra toughness to stop cracks but you still need rebar to strengthen in tension. I just had a look at the article on reinforced concrete and it describes things quite well. Dmcq (talk) 19:14, 16 March 2013 (UTC)

Extremely curious about boats, buoyancy, metacentres, etc..

I took a year of physics in undergrad but now I'm extremely curious & enthusiastic to learn more about the physics of buoyancy of a ship & especially the relationship between choosing between a narrow & deep ship verses a wide & shallow ship. Most fascinating to me was this piece:

Ignoring the ballast, wide and shallow or narrow and deep means the ship is very quick to roll and very hard to overturn and is stiff. And log shaped round bottomed means slow rolls and easy to overturn and tender. (from the Righting moment article)

I'm guessing that a cruise ship may have a different rolling/overturning priority than a battleship such as this. I assume (and correct me if I'm wrong) that the cruise ship is wide & shallow whereas the battleship is narrow & deep? (at least the part which is below the water's surface, which must be massive!)

The reason I'm so interested is because fluid dynamics was my favorite thing I ever learned in physics. I loved skimming the article you guys have called Free surface effect and also the article on Heeling (sailing) is very informative. I'm eager to find a hobbyist's resource where I can learn more about the fascinating physics of how/why shipbuilders choose the various shapes of vessels in order to optimize certain systemic properties (such as center of buoyancy, metacentre, shape, everything mathematical). Is there a good book I can procure through my local library or a good navel engineering episode on Discovery or NatGeo I can try to save on my DVR? (or even a few keywords I can try searching for on youtube which has so far been unsuccessful) Thanks in advance to anyone who can direct my curiosities to enlightening materials! Tomato expert1 (talk) 15:40, 15 March 2013 (UTC)

One thing you might find of interest is Pharaoh Khufu's ship, which was preserved, intact, over 4500 years: [5]. I saw a documentary where a clone of the ship was constructed and sailed. The hull had a rather rounded bottom, compared with most modern ships. This made it unsteady when still, but would allow the ability to make tighter turns, using oars. When under full sail, it stabilized considerably. StuRat (talk) 16:15, 15 March 2013 (UTC)

Also see hull design. StuRat (talk) 21:19, 15 March 2013 (UTC)

It's been a long time, but I am fairly certain there are chat rooms for people who are buoy curious. μηδείς (talk) 03:39, 16 March 2013 (UTC)

Uoy! ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:49, 16 March 2013 (UTC)

Hey, whatever floats your boat, right ? StuRat (talk) 06:09, 16 March 2013 (UTC)

Sure, even if it's navel engineering. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:01, 16 March 2013 (UTC)

I'm no boat expert, but I think that's why sailboats have keels... to help prevent them from rolling. ~Adjwilley (talk) 18:14, 16 March 2013 (UTC)

The keel converts sideways force into a forward force

The reason that sailing boats have such big keels (or a retractable one called a centreboard), is mainly that it stops the boat from skidding sideways when the wind is blowing from the side, and makes the boat move forwards instead. It also reduces the tendency of the boat to capsize under the pressure of the wind on the sails. Bigger ships do sometimes have stabilizers to reduce rolling. Alansplodge (talk) 22:57, 16 March 2013 (UTC)

Fascinating stuff about keels. I've checked out a couple books from the library which are way too advanced for me on engineering equations but I'm slowly gaining some qualitative understanding of how all this stuff works. A lot of it is so counter-intuitive which is what intrigues me and piques my curiosity so much. I really wished there was a show like Modern Marvels on this topic but maybe it's for the best. Thanks guys! Tomato expert1 (talk) 03:07, 17 March 2013 (UTC)

You might be interested in a Google Books preview about the debate over whether frigate-sized warships should have "short fat" or "long thin" hulls, in The Future of Sea Power By Eric Grove (p.115). I hope you are able to see it. Alansplodge (talk) 15:53, 17 March 2013 (UTC)

Allergic donated organs

I was reading this article and thought this question: will his donated organs still be affected by the alergy and subsequently affect the donees?165.212.189.187 (talk) 15:49, 15 March 2013 (UTC)

Allergy is in your immune system. It overreacts to things that are not dangerous. Your heart and lungs are not allergic. OsmanRF34 (talk) 15:57, 15 March 2013 (UTC)

• Are you asking whether someone can acquire an allergy he didn't previously have because an organ he has received was from someone who was allergic to something to which the recipient wasn't? μηδείς (talk) 20:19, 15 March 2013 (UTC)

Interesting question. I'd assume a bone marrow transplant would do it (haven't checked though). Liver transplant I wasn't so sure about, because the liver's role in producing blood cells decreases rapidly. Nonetheless [6] says there are two documented cases of passive transfer of food allergy this way. Very rare. Wnt (talk) 01:41, 16 March 2013 (UTC)

Better an allergy than rabies.[7] ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:21, 16 March 2013 (UTC)

As Wnt assumes, allergy can be transmitted by bone marrow transplantation, here's a reference: PMID 3059190. When it comes to solid organ transplantation, so called passenger leukocytes, possibly donor B lymphocytes that are contained in the transplanted organ, may develop into IgE-producing plasma cells in the host, and cause a transient allergy, potentially dangerous. Another proposed mechanism is that mast cells in the transplanted organ may already be loaded with specific IgE towards the allergen at the time of transplantation. Here's a case report about severe but transient peanut allergy developing after a lung transplantation from a peanut-allergic donor: PMID 21766079. --NorwegianBlue ^talk 11:13, 16 March 2013 (UTC)

March 16

Jet streams

My geography textbook says- "The movement of the westerly jest stream to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian peninsula during summer affects the monsoons." How? --Yashowardhani (talk) 05:55, 16 March 2013 (UTC)

Read Jet stream, for starters. In general, the jet streams affect weather because they aren't stationary, they shift around and help direct varying weather patterns. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:04, 16 March 2013 (UTC)

I still don't get it. — Preceding unsigned comment added by Yashowardhani (talk • contribs) 06:18, 16 March 2013 (UTC)

I'm more familiar with hurricanes, but presumably the same applies to monsoons. Jet streams serve somewhat like gutter guards in bowling, to corral the big storms between them. A powerful enough hurricane can "win" a fight with a jet stream, though. StuRat (talk) 06:03, 16 March 2013 (UTC)

The Nose Knows?

As a cynophile with a serious interest in criminology, I've read more than a little about cadaver dogs. My understanding is that they are specially trained to detect and respond to extremely minute quantities of cadaverine and/or putrescine. Of cadaverine in particular, I have read that it is nearly impossible to clean up every trace of it from something that has had contact with it, and that it is naturally present in semen and urine (in small quantities, but sufficient to contribute to the way they smell *to humans*). If these two facts are true, wouldn't every bathroom in the world and quite a few bedrooms smell at least as pungent as a well-scrubbed crime scene to one of the canine elite? Perhaps more significantly, I've read that cadaver dogs are trained to respond only to the smell of HUMAN decomposition, but cadaverine and putrescine are chemical compounds with fixed molecular structures, found in all decaying animal tissue. There's no such thing as distinctly "human" cadaverine, so how is the dog able to distinguish a place where a human body lay from a place where there was a dead rat, even after the passage of months or years? I don't doubt the reliability of cadaver dogs; I know they've only been proven wrong in about one percent of cases. I just wonder how it is exactly that they're able to do this, because the way I've read about it seems a little simplistic. — Preceding unsigned comment added by 172.3.129.135 (talk) 05:56, 16 March 2013 (UTC)

I suspect they use the cadaverine and/or putrescine to find the site, then, once close enough, they can detect the other, more subtle chemical odors which distinguish human decomp from other types. I would suspect that chimps would smell the closest to humans, so I wonder if a dead chimp can fool them. StuRat (talk) 06:07, 16 March 2013 (UTC)

They can distinguish a complex array of molecules, analogous to a signature. Some of the chemicals communicate "dead", while others communicate "human". ~:74.60.29.141 (talk):~ —Preceding undated comment added 07:13, 16 March 2013 (UTC)

Double-fuselage aircraft

I think an article about double-fuselage aircraft would be useful, although I have no knowledge of the field. Historical instances could be described along with the recent double-fuselage Airbus patent. Your thoughts? I was searching for this but found that the topic is not covered in Wikipedia.--Anixx1 (talk) 10:17, 16 March 2013 (UTC)

It's interesting we have no such article. But we do have Category:Twin fuselage aircraft for your reading pleasure. Someguy1221 (talk) 10:26, 16 March 2013 (UTC)

Radioactive sound

close request for medical advice
The following discussion has been closed. Please do not modify it.
Hi, I am from Japan, and I used to live in Fukushima Prefecture and moved south to Miyazaki Prefecture out of fears for radiation. I live with my mother and before moving I was wearing a mask and had a thing to detect radiation which I don't know how it's in English and before moving it made lots of sounds, loud sounds meaning that there was huge radiation. My question is whether that radiation stayed with me and If I run any health risk. — Preceding unsigned comment added by Hyerotaku (talk • contribs) 12:41, 16 March 2013 (UTC) Presumably the radiation detector was a Geiger counter of some kind. --Mr.98 (talk) 14:02, 16 March 2013 (UTC) This question is a request for medical advice. Only a medical doctor can determine if you are having health problems due to radiation exposure. Nimur (talk) 15:37, 16 March 2013 (UTC) The map in Fukushima Daiichi nuclear disaster and accompanying map should give a sense of the level of exposure, and Radiation-induced cancer gives some notion of the probability, though the article isn't very good. Wnt (talk) 16:36, 16 March 2013 (UTC)

If you can read and write Japanese, you can ask at the Japanese reference desk: ja:Wikipedia:調べもの案内.

—Wavelength (talk) 16:51, 16 March 2013 (UTC)

different sexual responses in women

This is kinda intimate question, but I mean it seriously and not as any kind of joke let alone being smutty or anything. But my boyfriend is interested in psychology, and knows some stuff about Freud, as do I. We both thought that his early material on how clitoral responses to sex are immature forms. But when my boyfriend began fondling me after we became a couple, some really interesting things happened. When it was foreplay and he was feeling my vagina with his fingers, I would become very wet after a while, which is normal of course, and then we would have sex.

But we had another kind of fantasy, which did not really have sex as its end result. You see, we are both very turned on by spanking fantasies. When he fondles me as he tells me how I am going to be turned over his knee and punished, I hardly get wet at all, even though it really makes me hot. On the other hand, my clitoris engorges with blood, and becomes like a stiff little ball, a bit like a penis. They are very different responses, and both of us can feel and attest that this is really happening, but we don't have any idea as to what is going on. It's like TWO different sexual responses based on different fantasies. We haven't asked anybody about it because it is so intimate, but we thought that here in Wikipedia, under the cover of anonymity, there might be some experts who could throw some light on this. Once again, this is real and I hope that no one thinks it is just a dirty joke. It's not. It's our own bodies and feelings, and we are just wondering as to what is going on. Sallysays (talk) 15:11, 16 March 2013 (UTC)

You're not going to get a great deal of 'help' here because many people will regard this as medical advice which we are not allowed to offer. What I would say in a general way is that what you are experiencing is, just as you surmise, different responses from different scenarios. This is widespread among the population and as long as you enjoy what you are doing and are not harming or affronting anyone else enjoy it. Sometimes with sex it is not always helpful to try and analyze everything that is going on. Freud knew little about physical (and probably emotional) sex but he had some theories about how guilty or otherwise some people feel about sex. Don't get hung up on the theory, just enjoy the practical. Caesar's Daddy (talk) 15:52, 16 March 2013 (UTC)

If this is a medical question, then so is a question about how best to roast a duck. :) Unfortunately, I have no idea how to answer it. I strongly suspect that erectile response, though commonly portrayed as all-or-nothing, must be somehow distributed throughout the body, a sort of general sensation/response that is only more prominent in certain familiar places. For example, nipples can become erect - sometimes - and I would suggest that so can the nose, in extreme cases in the form of honeymoon rhinitis. It seems like lots of other parts of the body can become arousable under some circumstances - the feet for example - and I recall reading of a paralyzed person transferring much of his former penile response to his thumb somehow. I personally think that each of these parts is potentially arousable independently of any other. Wnt (talk) 16:16, 16 March 2013 (UTC)

A doctor may have a 'hard' time with this question as I suspect it's not something covered in medical school! Sounds like something for the realm of a sexologist who I'm sure you can find online and anonymously. Sandman30s (talk) 08:10, 17 March 2013 (UTC)

There's nothing particularly surprising in the disparity between your differing responses, really. One scenario involves direct stimulation of the genital region and is more likely to involve parasympathetic nervous pathways which could stimulate lubrication more readily than purely mental/emotional triggers, regardless of overall level of arousal - we are talking about two different types of physical stimuli here, afterall, and it's not surprising that your body would react differently to them, , even though both would borrow upon many of the same physiological mechanisms. Remember also that not every nervous response involves information being passed directly back and forth between the brain (or even the CNS) and the stimulated region of the body; many are partially or completely locally reflexive and some of the former are processes involved in sexual response. In any event, consider that autonomic responses of this nature, including lubrication, sometimes occur during rape, compounding the emotional trauma of victims already struggling with a misplaced sense of shame, and we can make some safe assumptions about how much they enjoyed the stimulation. But even putting those extreme situations aside and looking at arousal in healthy interactions, it's clear that arousal is not one big spectrum of response (zero to a hundred), but a rather a complex composite of interconnected physiological and mental factors (more "a little paprika, a little thyme", and never exactly the same recipe). In fact, you hit upon this a bit in your own question when you noted that sex was not the end result of your fantasy; the fact of the matter is that humans are very lousy at distinguishing between various types of physical arousal (consider for example, the now well-replicated experiment in which men who were asked to meet a female grad student in a dangerous environment later rated her as more attractive than those who met her in a more neutral location; their acute stress response became mingled with their sexual appraisal) let alone distinguishing between different types of specifically sexual arousal. So, yes, not only is it possible to have two very different types of sexual response depending upon stimuli and context, it's a near certainty that you will have many different forms in your life but will be (hopefully blissfully) unaware of the subtleties between them. Snow (talk) 10:45, 17 March 2013 (UTC)

Of course the responses will be different, just as the stimuli are different. In the first instance, your boyfriend was directly stimulating the Bartholin's glands which produce the lubricating fluid. In the second instance, this direct stimulation is absent and, as Snow says, you were getting physically aroused by something different. Don't worry about it, get a copy of The Joy of Sex, and enjoy yourselves! --TammyMoet (talk) 18:21, 18 March 2013 (UTC)

Headphone socket problem

I've got a 3.5mm headphone plug going into (as one might expect) a 3.5mm headphone jack on my hi-fi - but I'm only getting the sound through the left channel. However, I can get stereo again if I only push the plug 3/4 of the way in.

There's nothing wrong with the headphones - I've tried them on a couple of other pieces of equipment and they work fine.

Any suggestions as to how I might be able fix this at home without opening up the stereo (or taking it to someone to fix it for me)? Or is it just the case that the socket needs replacing? I've had this sort of thing happen before on crappy equipment that I was never really bothered about fixing, but this is my main stereo now... --Kurt Shaped Box (talk) 15:22, 16 March 2013 (UTC)

Have you also tried other headphones on the stereo? μηδείς (talk) 16:23, 16 March 2013 (UTC)

Yes. Also with an extension cable. Same thing. --Kurt Shaped Box (talk) 18:26, 16 March 2013 (UTC)

The obvious work-around is to jam something into the jack to prevent the plug from going further than 3/4 in. Perhaps tiny balls of aluminum foil ? Be sure to add them slowly, and test after each one, so you don't go past the desired point. StuRat (talk) 16:30, 16 March 2013 (UTC)

When you push the jack in partway are you sure you're really getting stereo sound? Or are you just getting the one working channel in both speakers?

It would be weird it you actually got true stereo with an improperly plugged plug, but getting one channel from both speakers is what normally happens in that situation.

(bearing in mind that this is the final reply I wrote after I went back to check this out) Interestingly, it seems to have started working again now - but I'm aware that electronic equipment rarely fixes itself and it was definitely exhibiting the symptoms I described a few hours ago. Any thoughts... --Kurt Shaped Box (talk) 18:26, 16 March 2013 (UTC)

I suspect that your hifi is either broken or misconfigured (Is the balance knob cranked all the way over?) APL (talk) 17:07, 16 March 2013 (UTC)

The balance is fine - that was the first thing that I thought was wrong. --Kurt Shaped Box (talk) 18:26, 16 March 2013 (UTC)

My guess is that the hifi jack is either broken, or it isn't made for stereo sound. (They used to have mono headphones at one point, if I remember correctly.) If this is the case, then you only have 2 contacts in the jack, and 3 contacts on the headphones. Perhaps pushing it in 3/4 of the way makes it so the one contact in the jack touches both contacts on the plug. ~Adjwilley (talk) 18:20, 16 March 2013 (UTC)

It's definitely a stereo jack, FWIW. --Kurt Shaped Box (talk) 18:26, 16 March 2013 (UTC)

I'd say you have an intermittent open circuit somewhere between the amplifier and the headphone, most likely in the plug or the jack. FWIW 24.23.196.85 (talk) 05:37, 17 March 2013 (UTC)

I have some headphones which include a microphone. The microphone is just a little bulge in one of the wires from the earphone. Because of this, the little plug has one more ring on it than a plain stereo headphone, and if I push it all the way in, I only hear one channel. 99.140.253.109 (talk) 20:31, 16 March 2013 (UTC)

This is a common problem with wear and corrosion in the jack socket. If you are able to take your hi-fi apart (having unplugged it first, of course) to gain access to the socket, just gently clean the spring contacts with emery paper and very gently bend them in slightly towards the centre, but not too far or your headphone plug will not go in. If you plug in your headphones with the hi-fi opened up, then you will be able to see where there is a bad contact. Dbfirs 09:00, 17 March 2013 (UTC)

Alternatively, the contacts may be aligned properly but the slot itself malformed, such that the plug is skewed or leveraged at an inappropriate angle, forcing only one contact. I once had a device with a hard plastic o-ring on the outer surface of the socket of the jack, which was meant to grip the plug at its thickest point and hold it in place such that it made firm connection with the contacts inside. When the o-ring cracked, it released tension on the plug, allowing the weight of the cord to skew the angle of the plug such that only the one contact was made and it produced exactly the type of issue the OP is describing as a result. 108.248.176.172 (talk) 14:04, 17 March 2013 (UTC)

One thing I've seen on more than one piece of equipment is cracks in the solder joint between the jack and the circuit board, where there is typically not a great physical connection. The joint is typically subject to a lot of stress due to the cord leaning on the lever arm of the piece of the plug which protrudes, and one or more of the contacts breaks or gets loose and intermittent. Gzuckier (talk) 01:32, 18 March 2013 (UTC)

Runny nose / stuffy nose

When people get sick, they often experience either a runny nose or a stuffy nose. While we have article on both, neither seems to address the issue I am wondering about. When we get a runny nose or a stuffy nose in association with an illness is that because A) the illness / infection is directly causing problems with the nose, or B) the body is intentionally adjusting mucous production in an attempt to fight the illness / infection (i.e. its a natural response to infection)? I would assume that changes in nasal mucous composition might offer some protective benefit against certain nasal infections / irritants, so it seems plausible that it might be part of the body's natural response. However, I haven't seen anything that provides a detailed explanation of how and why people develop runny / stuffy noses. Dragons flight (talk) 16:56, 16 March 2013 (UTC)

It's actually both. Mucus production is a physiological response to agents that infect cells in the mucous membranes. Its function is to flush the agent out of the membranes. For viruses, for example, they infect cells, replicate massively, and then burst the cells and diffuse away to infect other cells. Flushing the membranes reduces the density of virus there. Looie496 (talk) 17:45, 16 March 2013 (UTC)

(ec) I believe it is an immune response designed to wash bacteria and viruses out of the nasal cavities. It might seem like this immune response is too late, but, once you are infected, that leaves you even more open to reinfection or additional infections, so keeping out additional microorganisms is important. Unfortunately, this is also a method to spread the disease to others, and some of the diseases may specifically trigger our immune response, in order to achieve this goal. StuRat (talk) 17:47, 16 March 2013 (UTC)

Hmmm, according to [8] it looks like the people getting placebo medications after laboratory infection with rhinovirus type 39 had the lower virus titer, but the difference wasn't significant. They had substantially fewer symptoms, however. Of course, this doesn't measure many things, including longer term effects, secondary infections, or antibody titer years later... I'm still not going to call the response worthless without more data than this. But it should be clear enough that if the virus is doing it "intentionally", it's doing it to spread, not to replicate. Wnt (talk) 18:10, 16 March 2013 (UTC)

Thinking back to AP biology (ugh, over a decade ago), a lot of the stuffy runny nose problems are actually caused by the immune system's response. That's why you still get stuffy when you have allergic reactions (i.e. when the immune system mistakes something harmless like pollen for a virus.) Unfortunately I don't remember any of the names of the cells that do the fighting (other than antibodies). ~Adjwilley (talk) 18:24, 16 March 2013 (UTC)

Histamine#Effects on nasal mucous membrane has a little bit, as does mast cell. --Jayron32 03:13, 17 March 2013 (UTC)

Thick rotor blades

Could the rotor of a helicopter be thicker, more resembling of aircraft wings? OsmanRF34 (talk) 19:53, 16 March 2013 (UTC)

Just over a week ago, I wrote a response to a similar question, comparing wings and rotors.

“ ...the thing to remember is that helicopter blades, fan blades, propeller blades, and fixed wings are all just airfoils. ...A helicopter rotor is different from (fixed-wing) airfoils; it is designed to provide lift and remain stable while the helicopter is operating in its normal flight envelope. ”

For good measure, here's The Helicopter Flying Handbook from the FAA, with all you need to know to start learning to fly helicopters. Nimur (talk) 20:21, 16 March 2013 (UTC)

And here's an easily-digestible quick read from NASA's technical archive, Desgn and Analytical Study of a Rotor Airfoil, and it's sibling-report, ...for an Advanced Rotor Airfoil (both produced for NASA out of Lockheed from 1980). As I summarized previously, and as both these reports clearly state, the primary design objectives (item number one, in fact) are limited by practical concerns like weight, manufacturability, and safety/reliability/durability. Table III in the first report lists dozens of airfoils tested and analyzed (including several NACA airfoils with various cambre). It even has a cartoon "design decisions flow-chart" on Page 64, indicating a few conditions that would encourage engineers to choose a thicker or thinner airfoil - with particular emphasis on the relationship between thickness and the drag divergence parameter. Nimur (talk) 20:46, 16 March 2013 (UTC)

See Sikorsky S-72 ScienceApe (talk) 22:13, 16 March 2013 (UTC)

Helicopter rotors and aircraft wings already resemble each other - but the chosen airfoils differ because the speed and AoA differs. It is also considered beneficial for a rotor blade to have a symmetrical airfoil, since it reduces the movement of the centre of pressure, whereas for fixed wing aircraft an asymmetrical airfoil is often preferred since it can provide more lift for less dreag. As a sidenote, the thickness of an airfoil is usually expressed as a percentage of the chord. Thus a wing for a passenger jet can be said to be just as thick as the rotorblade for a helicopter - but since the chord of the jet is longer, the measured thickness of the wing is several inches - or even feet - more. WegianWarrior (talk) 08:30, 17 March 2013 (UTC)

Aircraft wings are hollow! Rotor blades are usual not because they not only have to take up with much more than typical wing-forces (like vibration from switching airspeeds) but also with significant centrifugal force. So every extension of blade surface will get you a heavy extra weight for the hole rotor construction likely outweighing most or all gain in lift. --Kharon (talk) 12:09, 17 March 2013 (UTC)

One big problem is that when the helicopter is pitching or rolling, the swash plate is tilted and each rotor blade will change pitch twice in each revolution of the rotors. If the blades were wider, the rotational inertia about their long axis would be higher and it would be harder to get them to change pitch like that. This would, in turn, result in the helicopter being harder to control. This is enough of a problem in fixed wing aircraft so we (mostly) have ailerons, flaps and elevators rather than altering the pitch of the entire wing. Getting controls and actuators to do that inside a helicopter rotor would be really tough! Also, if the rotors are heavier, then the tendency of the body of the craft to rotate in the opposite direction of the rotors would be far greater - and since that force is controlled by the tail rotor, you'd need that to be MUCH bigger too. SteveBaker (talk) 19:28, 19 March 2013 (UTC)

Line of sight to the sun

Let's say you're naked in outerspace, and for some reason you don't die (just for the purposes of this question). If you have a direct line of sight to the sun (without anything else in the way), how hot will the side of your body facing the sun be compared to the side that isn't? ScienceApe (talk) 23:54, 16 March 2013 (UTC)

The answer depends on how far from the sun you are. Spectral_flux_density might be interesting. SemanticMantis (talk) 00:04, 17 March 2013 (UTC)

This third question from the last may be helpful. --PlanetEditor (talk) 01:20, 17 March 2013 (UTC)

After reading the NASA link above, I'd say that you would be pretty hot overall (over 100 C), but that there wouldn't be a huge temperature difference between the two sides of your body. I say this because I believe the rate of heat flowing from one side of your body to the other would be fairly large, especially if you're alive and your circulatory system is still going. But then you'd dehydrate pretty fast, being above the boiling point of water and in a vacuum. As a side note, I hope you're wearing sun screen, especially if you plan on performing this experiment naked. ~Adjwilley (talk) 01:32, 17 March 2013 (UTC)

What sunscreen is going to do when his body temperature is above 100 C? --PlanetEditor (talk) 02:05, 17 March 2013 (UTC)

If you were as far away as the Earth and rotating wouldn't you be about the same average temperature as the Earth? μηδείς (talk) 02:44, 17 March 2013 (UTC)

Approximately, yes; although some models also account for albedo or use a "gray-body" instead of black-body Stefan-Boltzmann law. This question is a typical homework problem in an astronomy class; apply your favorite variation of the equation for planetary surface temperature, accounting for as many non-idealities as necessary. Unlike planets and cows, a person might not be well-modeled as a sphere... If the question really is asking about the difference in temperature between illuminated and dark sides of an object, we must stop approximating the object as a sphere, and apply Fourier's law with an appropriate choice for heat capacity and thermal conductivity. Nimur (talk) 02:48, 17 March 2013 (UTC)

A bit hotter, since you don't have clouds to reflect some of the sunlight before it hits you. Sunlight can still reflect directly off you, but that's similar to it reflecting off the surface of the Earth. StuRat (talk) 02:50, 17 March 2013 (UTC)

Great thanks, that's exactly what I was looking for. I recall there being a huge disparity between something in the shade vs. in direct sunlight in space. That leads to my second question, why is it that night time (the side of the planet not facing the sun) doesn't freeze to those cold temperatures? Obviously nighttime is colder but if it's summer time, or near the equator, you can have a very very hot night, but that part of the planet is in the shade. Is it because of the retention of heat in the atmosphere? ScienceApe (talk) 08:09, 17 March 2013 (UTC)

Clouds in the atmosphere help to retain heat, so rapid cooling and frost is more likely with a clear sky, but the main effect preventing frost in summer is the thermal retention of the earth and oceans. Dbfirs 08:52, 17 March 2013 (UTC)

Agreed. Places without bodies of water or clouds (that is, deserts) do have temperatures drop dramatically at night. StuRat (talk) 08:56, 17 March 2013 (UTC)

Larry Niven's first story "The Coldest Place" (spoiler alert) Gzuckier (talk) 01:45, 18 March 2013 (UTC)

Your skin color might make a rather noticeable difference in how hot you get. Of course, once we turn into jerky, we'll probably all have similar coloration. StuRat (talk) 02:50, 17 March 2013 (UTC)

Here, Ice on the Moon... one of the greatest unresolved questions about lunar geology is exactly what thermal capacity and conductivity does the lunar substrata have? Though Apollo brought back lots and lots of surface material for study, we have never been able to directly study the geological properties of the subsurface. NASA's academic research consortium called this among the highest-priority unresolved scientific facts about the moon. Why does it matter? Because we're looking for icy permafrost in permanently shadowed areas of the moon, hoping these areas are cold enough to keep ice frozen - but that assumes that the thermal input comes from the sun - and we know that there is some thermal flux through the substrata. (Even shady regions will get some solar energy input that flows through the ground!) So, if we want to estimate how much ice there can possibly be, we need better thermal models for heat flow in the subsurface. In other words, how cold are the shadowed areas of the lunar polar regions? Are they cold enough for ice? To some extent, the LCROSS water vapor plume provided some new information. As we look for more water ice in more places around the solar system, we need all the information we can get to complete the picture - particularly when it comes to setting bounds on possible temperatures. Moral of the story: learn Fourier's law early, learn it well, apply it frequently; simulate your coffee thermal performance every morning,... because you never know when NASA will need to call you up to exercise those skills. Nimur (talk) 03:08, 17 March 2013 (UTC)

March 17

Holograms

I have read quite a bit on holography inc. bought books and here at Wikipedia but I cant find answers to these questions?

Here are my questions:

1. In addition to being required to interfere with the object beam, is the reference beams inclusion in the production stage simply a way of weaving a light source for viewing, into the production stage. It is a clever way of allowing a light source to illuminate the hologram for viewing without introducing new data which would destroy any hope of seeing the image? The reference beam being the purest form of light (monochromatic, coherent, collimated and with plane wavefronts) means it is the most reliably reproducible light source for viewing at a later date and venue?

2. Would the object beams' wavefronts expose the emulsion if the lasers' output was doubled (equalling the intensity of the peaks recorded with both an object and reference beam)?

3. I understand the speckles on the hologram are what have been recorded of the scene, so what are the swirling patterns we see in the emulsion?

Thanks in advance. — Preceding unsigned comment added by Eagle eyes 000 (talk • contribs) 14:32, 17 March 2013 (UTC)

The objective in holography is to recreate a three-dimensional light-field. The hologram itself is exposed on a single plane - which is a two-dimensional sample of the light-field from the original scene. To recreate a three-dimensional field, some additional light must be present. This is why a reference beam is used. The fact that we require monochromatic light, or laser light, is a practical limitation of the way we capture holograms in visible light. If we take the deep-dive into theoretical realms - or even if we consider acoustic tomography or holography, which operate on the same principle of reconstructing a full wavefield, we can see that the monochromatic reference beam is not a strict requirement, as long as we have the ability to reconstruct the reference with accurate phase. That process is possible - and easy - for, say, an ultrasonic scanner, but not easy for a visible light source, so we use a laser as a suitable source.

When you see wavy lines, you are seeing moire patterns. The actual "image" on the hologram's emulsion is a projection of the unfocused wavefield onto a plane. That projection is expected to have lots of periodicity for normal scenes, so it is expected to see moire patterns for the same reason they appear in other materials with similar patterns. Nimur (talk) 16:06, 17 March 2013 (UTC)

Moiré pattern   ←[correct link -74.60.29.141 (talk) 16:46, 17 March 2013 (UTC)]

Redirect created. Nil Einne (talk) 20:50, 17 March 2013 (UTC)

Usually redirects aren't created for article titles pluralized by appending letters—instead you write [[moire pattern]]s. But it doesn't matter since redirects are cheap. -- BenRG (talk) 02:13, 18 March 2013 (UTC)

While putting the pluralisation outside the wikilink may arguably be the preferred option in writing articles, this doesn't mean redirects from plurals shouldn't be created. In fact for frequent cases they should be because there is no expectation that wikilinks in the other way should be mass corrected particularly in comments, even Category:Redirects from plurals notes this ('do not replace these redirected links with a simpler link unless the page is updated for another reason'). There are also other advantages with the redirects existing, like in searching. While our search engine would generally end up suggesting the singular article as an option, a redirect will mean people automatically go to the article. Another advantage is external sites making linking errors will still find a target. In fact, Wikipedia:Naming conventions (plurals) notes this, 'Creating a redirect in cases like crayons is advisable as well, since third-party websites started adding automatic links to Wikipedia from their topics, and many of them follow the opposite convention, i.e., pluralization'. So from my experience redirects from plurals are very, very commonly created e.g. cats, humans, bananas, computers (all just random examples I didn't even both to test). Nil Einne (talk) 06:39, 18 March 2013 (UTC)

What do you mean by "To recreate a three-dimensional field, some additional light must be present"? -- BenRG (talk) 02:13, 18 March 2013 (UTC)

I was of course describing the reference illuminator, using somewhat coarse terminology.

When viewed, a hologram is not a static image. It is a light field, and it can be viewed from many different angles. It is a reconstruction of the original light field at all points in 3 dimensions, albeit it is an imperfect reconstruction, due to the limits of sampling and projection.

The exposed plane (the emulsion) is itself not three-dimensional. It is a 2-dimensional sample of the light-field at the plane of the exposure. To reconstruct the full light-field at all points, a source of illumination must be provided. Conventionally, that source is the "reference beam," a monochromatic source of the same type originally used to perform the exposure. The illumination scatters off the holographic emulsion, and the resulting light-field is a close approximation to the light-field of the original scene. This is how we can view the "scene" in three dimensions. The viewing-angles that are reconstructed - rather, the set of viewpoints where the reconstructed field is similar to the original field - are limited by the sampling aperture.

If we were modeling the wavefield, instead of synthesizing it in the real world, we could completely eliminate the reference illuminator. We could replace it with the "exploding reflector model" to cause the wavefield to "start emitting" with the sampling-plane as a boundary condition. In the real world, passive materials like photographic emulsions do not spontaneously "start emitting" wavefields - we must illuminate them. This numerical technique is used extensively in computed tomography to synthesize 3D imagery in a computer model, but we have no material that can synthesize such a wavefield, subject to the exposure-emulsion as a boundary condition, at optical frequencies, in the real world. Here is a reference on synthesizing an (acoustic) wavefield without re-injecting the source illuminator: the Exploding Reflectors model. BenRG, you may appreciate this approach, because it considers every possible wave interference interaction - including ordinary propagation in free space - as just a special case of Born scattering. I have seen this numerical technique (the "holography trick") applied to seismic imaging; positron tomography for medical imaging; ground-penetrating radar; imaging radar; and of course, wavefield optics modeling for computer-graphics. If you're incredibly interested, I can dig up papers for each one of these applications; but suffice to say, the wave physics and the math are all the same, even if the wave type is very different. Nimur (talk) 03:48, 18 March 2013 (UTC)

I'm not sure if I understand your questions. Are you asking if the reference beam is really necessary? The answer to that is yes. There's no such thing as a film that records the phase of light; all film records only the intensity. The way you fake recording the phase is by combining the light reflected off the object with a reference beam from the same laser. If the reference beam has intensity A² and the object beam has intensity B² at a particular point on the film, then the combined intensity of the two is (by the law of cosines) A² + B² + 2 A B cos φ, where φ is the relative phase of the two beams at that point. (The absolute phase of both beams varies with time, but the relative phase doesn't, as long as the light is monochromatic and the scene isn't changing.) The reference beam intensity is constant across the whole film, and you can treat the object beam intensity as roughly constant also, so roughly speaking the intensity captured on the film depends only on φ. -- BenRG (talk) 02:13, 18 March 2013 (UTC)

Would methane hydrate extraction spill significant amounts of methane into the atmosphere?

Methane hydrates have recently been in the news as possibly a main fuel source of the future. However, environmentalist friends of mine are very negative about this development, mainly because they believe that the process would spill too much methane into the atmosphere. Is this likely to be true? B^e——C_ritical 17:17, 17 March 2013 (UTC)

Not sure, but note that, even if none spills and you get 100% combustion, you'd still produce carbon dioxide, which is also a greenhouse gas. StuRat (talk) 17:32, 17 March 2013 (UTC)

Methane would produce much less carbon dioxide as a fuel than other hydrocarbon sources. It's not carbon neutral unless carbon dioxide sequestration is used as part of the extraction process, but it give off much less CO2. Because it creates much less atmospheric CO2, the only question is whether methane emissions are a significant danger. B^e——C_ritical 17:40, 17 March 2013 (UTC)

Not more so than for "conventional" gas drilling (the techniques used in clathrate recovery are similar to those already widely practiced in conventional gas drilling and in enhanced oil recovery), and less so than for fracking of shale gas deposits. 24.23.196.85 (talk) 00:11, 18 March 2013 (UTC)

So the calculation would at least have to:

• Make some assumption of how much methane would be released during extraction.
• Take into consideration the amount of time that methane exists in the atmosphere (8-12 years?)
• Take into consideration the amount of CO2 which would not be released as a result of using methane instead of other soruces.

The guesses require knowledge of, for example, how much natural gas is lost from fracking in the ocean. And other knowledge. B^e——C_ritical 17:57, 17 March 2013 (UTC)

At the ocean bottom depths it may also be possible to form Carbon dioxide clathrate at pressures between 12 and 44 bars. (120 and 440 meters deep). So there could be a way to store this CO₂. Graeme Bartlett (talk) 10:35, 18 March 2013 (UTC)

Russian M4 Parka

Are there any wiki articles about Russian military clothing? I'm particularly interested in their winter clothing like the Russian M4 Parka--Tommythehook (talk) 17:24, 17 March 2013 (UTC)

I don't think we have much. However, you could start from, let's say, Afghanka, and see what you can find... By the way, it would be easier to answer if you gave a little more details: are you interested in military clothing of Russian Federation only? Or would Gymnasterka of Russian Empire and USSR count too? --Martynas Patasius (talk) 17:50, 17 March 2013 (UTC)

Or the Telogreika of World War 2 vintage? 24.23.196.85 (talk) 00:02, 18 March 2013 (UTC)

The god particle

From CBS news today "The Higgs boson is often called 'the God particle' because it's said to be what caused the 'Big Bang' that created our universe many years ago." That isn't the reason it is called that, is it? Bubba73 ^{You talkin' to me?} 17:50, 17 March 2013 (UTC)

No, that isn't the reason, see this NPR interview ([9], several other good links within) with Dick Teresi, who is reported to have coined the term. He discusses it at length, but the title of the piece is

“ The Man Who Coined 'The God Particle' Explains: It Was A Joke! ”

That's pretty clear to me. SemanticMantis (talk) 18:01, 17 March 2013 (UTC)

Thank you,

Resolved

. Bubba73 ^{You talkin' to me?} 18:17, 17 March 2013 (UTC)

I don't know... The Higgs Boson sure does look like the FSM... More evidence here. --Guy Macon (talk)

That's a picture of the long-lived products of one or more collisions in one of the LHC detectors. They all look like that. Even if that one is a Higgs candidate, the Higgs isn't visible in it, since (a) its lifetime is too short and (b) the same decays can happen without the Higgs, so the existence of the Higgs is inferred from an increase in the rate, not from any particular event. -- BenRG (talk) 21:49, 17 March 2013 (UTC)

According to the book itself, the name was invented by Lederman, not Teresi, and he originally called it "the goddamn particle" because it's been so hard to find. However it was Teresi who decided to use it in the title of the book, thus ensuring that idiot journalists would repeat it forever after. -- BenRG (talk) 21:49, 17 March 2013 (UTC)

I guess the thing you should always remember is that the Higgs boson is a proposed, and experimentally-testable incarnation of the Higgs mechanism. And, the Higgs mechanism is just a really really high-resolution explanation of mass. We already know that mass exists, and we already know that mass interacts gravitationally. The Higgs mechanism only arises because we want to be very precise when we say "mass," and when we say "exist," and so forth. By using incredibly high energy, we set up the scale lengths and scale time intervals in such a way that we can probe the interaction that causes gravitation.

This is much the same way that - prior to the discovery of the electon - we knew that there was electric charge in an atom. By carefully setting up experiments, we were able to clarify how electric charge is distributed in the atom. We were able to localize the position of that charge to a point particle, albeit subject to certain constraints on this localization. And, perhaps most importantly, we were able to use this knowledge to more thoroughly predict the way that charge interacts wih matter by correctly describing the role of the electron in atomic interactions: what we today call electrochemistry. From the macroscopic point of view, nothing changed because of this discovery: scientists had known for millenia that charge exists, and that atomic interactions are somehow mediated by electric charge carriers - but by completing the picture at a higher resolution, we improved our understanding and very probably expedited the experimental discovery of many new material properties, chemical reactions, semiconductivity, nuclear physics, and so on. So, discovering the Higgs boson probably won't cause the ground to fissure open; but these investigations help physicists make better predictions and design new experiments to further our understanding of fundamental interactions.

All these questions come down to a very existentialist question: why isn't the universe simple? If the universe were simple, we'd all be one giant isotropic homogeneous soup of uniform goop. There would be no electric charge; no mass; nothing that interacted with anything else; nothing would ever change; the universe would have always existed and would exist into perpetuity, without ever deviating from itsmsteady-state equilibrium; and yet we instead observe a universe full of different types of particles, with different charges and masses, that interact to form nucleons and atoms and molecules and sentient mammals. If we can only figure out the mechanism that caused that very first fundamental symmetry breaking, then all the electric charge and nuclear forces and ribosomes and koalas all follow from first principles, given enough time to evolve, and the universe makes a lot more sense. This is why theistic philosophers like to equate symmetry-breaking with what is effectively a dialect of Creationism. Actual physicists tend to be predictive and descriptive, rather than epistemological, so physicists don't usually care for that equation. Nimur (talk) 21:43, 17 March 2013 (UTC)

isn't your definition of simple subjective and or presumptuous? I mean relative to the cosmos? Maybe it is simple and we just dont know it yet.68.36.148.100 (talk) 01:10, 19 March 2013 (UTC)

Fair point; substitute the term "simple" with the term "symmetric," as that is the term that physicists actually use. Particle physicists have the tendency to assume symmetry is the "natural" state over a particular variable, until they discover otherwise, by experimentally showing a specific type of symmetry-breaking. Nimur (talk) 02:13, 19 March 2013 (UTC)

Charge Selectivity of Glomerular Barrier in Nephritis

Hello. Why can anionic proteins pass through the glomerular barrier more easily than neutral particles if both are not repelled by the basement membrane? A link to a journal article would be appreciated. Thanks a lot in advance. --Mayfare (talk) 22:00, 17 March 2013 (UTC)

A quick search for "Charge Selectivity of Glomerular Barrier in Nephritis" on Google Scholar:[10] yields "About 2,710 results".

This one looks promising:  The glomerular filtration barrier function: new concepts

~Good luck on your exam!  ;)  ~:74.60.29.141 (talk) 04:51, 18 March 2013 (UTC):~

March 18

Positive charge on flying insects?

I was just reading the article in New Scientist 2 march called "Electric plant auras guide foraging bees", and it states "As bees fly through the air, they-like all insects- acquire a positive charge". I can't find any references that discuss this further, is it a well known fact? and what causes it to happen? — Preceding unsigned comment added by 122.108.189.192 (talk) 07:04, 18 March 2013 (UTC)

This link would suggest that it's true for bees and the cause is given as "frictional electricity" as they fly, and here's another on the subject. Mikenorton (talk) 08:08, 18 March 2013 (UTC)

Thanks Mike, that last link is fascinating.122.108.189.192 (talk) 07:35, 19 March 2013 (UTC)

interstellar Bomb

Even if this is not trolling there is nothing going to be solved by this. CambridgeBayWeather (talk) 06:40, 19 March 2013 (UTC)
The following discussion has been closed. Please do not modify it.
Hello, I want to know, if it is possible to send an atomic Bomb (or any other Device that destroys more than 1 km²) so that it reaches a Star within a distance of about 100 Lightyears not later than in the mid 42th Century in operational conditions. Additionaly the exact orbit properties of the target are unknown, so it is necessary for the Device to determine the exact course within this star system while on flight. Please take this question seriosly, there is more on stake than you can imagine. (excuse my bad english, it's not my usual language.)--AlaneOrenProst (talk) 08:08, 18 March 2013 (UTC) The technology needed for interstellar travel is not available. And the energy needed for interstellar travel cannot be obtained from Earth. So keep your fantasy in the pages of science fiction books. --PlanetEditor (talk) 08:50, 18 March 2013 (UTC) just because the necessary technology isn't available now, did not mean it is impossible. The article you linkend already gives some possible ways to acomplish what is necessary.--AlaneOrenProst (talk) 08:58, 18 March 2013 (UTC) PS: and, no, this is not a science fiction book. This is reality.--AlaneOrenProst (talk) 08:59, 18 March 2013 (UTC) Well I think it is just about possible, at the moment there's no good reason to spend the enormous amounts that would be involved on such an undertaking, but I'd guess in another hundred years it might actually become practical to think about sending off a fast interstellar ship. By the way you don't need a bomb, just don't slow it and aything going at that speed will destroy a wide area. As far a I know there are no current threats from bug eyed aliens that need to be countered so I don't see the point of the 'this is reality' business. Dmcq (talk) 09:24, 18 March 2013 (UTC) currently there is no problem, but if we do not act now, the Prophecy will fullfil, and the terrible Event I want to avert will happen. --AlaneOrenProst (talk) 09:30, 18 March 2013 (UTC) PS: more exactly spoken: the Event will happen with a probality between 37,5% and 62,5%, acording to the prophecy.--AlaneOrenProst (talk) 09:33, 18 March 2013 (UTC) Sure, there doesn't seem to be any scientific limitations on such an idea. Any technology required is not impossible, as noted, it's just not something that humanity currently capable of doing. Plasmic Physics (talk) 09:27, 18 March 2013 (UTC) then we have to hurry to get the technology to be capable.--AlaneOrenProst (talk) 09:38, 18 March 2013 (UTC) Why the rush? Plasmic Physics (talk) 09:40, 18 March 2013 (UTC) Well Plamsa Physics, could you explain where would you get the energy required for interstellar travel? --PlanetEditor (talk) 09:42, 18 March 2013 (UTC) @Plasmic Physics: because of the Blackbird-Molotow-Reich-Effect. As more we wait, as harder it gets to escape the prophecy.--AlaneOrenProst (talk) 09:44, 18 March 2013 (UTC) Oh the BMRE! I don't see the urgency. Isn't that not for at least a couple millennia? We have plenty of time. Especially since in 3127 we can harness time dilation technology and postpone that event almost indefinitely or at least until 1234567. No worrys. Lets revisit this in a coupe hundred years just in case. Or just tomorrow when you come down.68.36.148.100 (talk) 03:27, 19 March 2013 (UTC) If you - or anyone else - can figure out a way to send a probe to a star 100LY distance then I think that guidance should be a simple matter to sort out... You wouldn't need a nuclear warhead btw - just keep accelerating the whole way and impact the probe into the target. Refer to kinetic bombardment, impact depth and relativistic kill vehicle for more information relating to the power of kinetic energy. If you could manage an acceleration of just 0.0001G - that is just shy of one mm/s^2 - then the probe would arrive in just under 2000 years with enough speed to punch a sizable hole in a planet. WegianWarrior (talk) 09:46, 18 March 2013 (UTC) well, that sounds like something we can work with. But a sizable punch is not needed. I do not want to kill a whole world, the "1 km²" is more or less all the damage needed.--AlaneOrenProst (talk) 09:51, 18 March 2013 (UTC) To everyone providing their opinion, the energy required for interstellar travel is not available on Earth. This makes interstellar travel impossible. --PlanetEditor (talk) 09:48, 18 March 2013 (UTC) For now. Someguy1221 (talk) 09:57, 18 March 2013 (UTC) It most certainly is available on earth as nuclear fuel. Plus they're not trying to send people. I think I'd much prefer a cleaner way than Project Orion though, ion drive has lots of room for improvement and also in the future it should be possible to assemble stuff automatically on say the moon instead so pollution might not be such a worry. Dmcq (talk) 10:46, 18 March 2013 (UTC) Yeah, sending a tiny Voyager-like probe to the interstellar space may be possible. It will take more than 80,000 years to reach the nearest star Proxima Centauri. Nearly 3000 human generations. So manned interstellar travel is impossible. --PlanetEditor (talk) 10:52, 18 March 2013 (UTC) The qualifier for that statement in the article is a bit ambiguous, it doesn't say how long a reasonable time lasts. Plasmic Physics (talk) 10:57, 18 March 2013 (UTC) Actually, sending "a tiny Voyager-like probe to the interstellar space" is certainly possible, because we have already done that (you might quibble if the Voyagers have reached "interstellar space", but there is no reasonable doubt that they will reach it). And I see no hard physical reason why it should not be possible to send e.g. an 0.01c mission out to other stars. If it's economically and politically feasible is another question, but scientifically and technically it shouldn't be that hard. See Project Orion (nuclear propulsion). --Stephan Schulz (talk) 13:31, 18 March 2013 (UTC) If we're not worried about 100g type acceleration or stopping at the far end it should be possible to do considerably better than 0.01c.. Dmcq (talk) 16:07, 18 March 2013 (UTC) Yeah, what the previous guy said... it isn't named Voyager Interstellar Mission for nothing. If you think about it, once you have attained escape velocity, which we could even manage with a manned capsule, decades ago, you are on an interstellar trip, as long as you have plotted your course so as not to get trapped in the gravity well of another solar system body. If Voyager could do it with flybys through the ecliptic, it shouldn't be very hard if you aim out of the ecliptic. The only additional requirement for your plan is getting there on time, and as everybody knows, in space without drag you can just add acceleration until you get to the speed you need. I'm too lazy to do the math right now, but aside from standard rocket engines, you have the choice of not very advanced technological stuff like nuclear powered ion-drive thrusters, because over a couple of millenia even a tiny fraction of a G of constant acceleration tends to add up. And then there are always the way-out-there drive concepts, like solar sails, possibly with a boost from terrestrial-based lasers, interstellar ramjets, etc. which could be developed into operation in part of the 2000 years you have to spare. Certainly, there is no guarantee that any of these will get you there on time and functional, but there is no hard and fast reason that makes it impossible. And, you could certainly try all of the above, in the hopes that at least one will succeed. You're probably more at risk of failure regarding the control and guidance systems being functional after 2000 years to aim the thing, as you require. Also note that in addition to the plain old impact at that speed being destructive enough to eliminate the need for an explosive payload, as previously mentioned, in fact if you get up to a high enough velocity and you have enough control to steer the thing, all you have to do is flip it over 180 degrees just before you get there as though you were trying to slow down, and the relativistic blue shift of the energy of your engine will do some really serious damage to whatever you're moving towards. Gzuckier (talk) 16:26, 18 March 2013 (UTC) ok, that sound's like something basical. Who schould I contact to make this real?--AlaneOrenProst (talk) 17:01, 18 March 2013 (UTC) If you really want to go up to 100 lightyears in only 2100 years, then at constant acceleration you'd need to reach nearly 0.1c. You could do it with as little as 0.05c if you mostly front-load your acceleration. A mere 100 kg of projectile going 0.05 c would require no less than 10 petajoules (1×1016 J) of energy to achieve this (and likely a great deal more due to inefficiencies). Setting aside the fact that a rocket that small could never store that much energy, the amount of energy is "only" about the equivalent of a 3 megaton nuclear bomb, which means it is on the range scale of things humans have achieved. If instead of 10 petajoules, we imagine the inefficient (or larger) rocket actually requires 10 exajoules (1×1019 J) then that's still only about 20% of global annual electricity production. Finding a way to channel that much energy into a rocket would be extremely challenging, but given one or a few centuries to figure it out and a united global effort to accomplish it, then I don't see any reason it shouldn't be possible in principle. I certainly wouldn't expect to see such an effort in my lifetime though. Dragons flight (talk) 16:42, 18 March 2013 (UTC) it should better happen within the next few years. The Blackbird-Molotow-Reich-Effect is already dragging hefty.--AlaneOrenProst (talk) 17:01, 18 March 2013 (UTC) Okay, I'll bite. What is this Blackbird-Molotow-Reich-Effect ? Just a pointer to a source or web page will do (maybe one that doesn't use block capitals or flashing neon fonts). Gandalf61 (talk) 17:16, 18 March 2013 (UTC) the Blackbird-Molotow-Reich-Effect basicly means, that, on the long run, to change anything in history via timetravel (and the only way I can imagine the Prophecy can be here is that it was send back in time) is impossible. The changes you can acomplish will ever follow a a*t^k*e^-n*t²) formula, so on short you have an exponentionally efect, but on the long run in converges against 0. This efect was discoverd by prof. phy. Molotow, one of the small pack of refuges who made it to the TMSC Hope, and who discoverd the timegate and how it works, dr. hist. Reich, another refuge and as historical advisor member of the time travel commando and cmdr. Kathrin Blackbird, second in command of the TMSC Hope and leader of the time Travel commando, which tried to avert the foundation of the Cygnian empire throgh travveling from 31th Century to 21th Century earth. --AlaneOrenProst (talk) 17:32, 18 March 2013 (UTC) I can imagine another way this alleged prophecy could "be here": Someone made it up. Created the idea in their imagination. It happens, you know. ←Baseball Bugs What's up, Doc? carrots→ 03:46, 19 March 2013 (UTC) Fine, there is nothing wrong imaging a fantasy future. But from a scientific point of view, let me clarify some points. Predictions sometimes ignore reality and science. For example, A. C. Clarke predicted that dinosaurs will be cloned by 2023, but his prediction was not based on science. There are multiple obstacles to manned interstellar travel which cannot be averted unless you alter biological and physical laws. 1. Microgravity: Humans can stay in microgravity in the ISS for months, but a lifelong stay in microgravity defies human biology. 2. A lifelong stay outside the protection of Earth's magnetic field and exposure to cosmic rays will be disastrous. 3. If humans plan to make a trip to another star, they will need resources (oxygen, food reserve for decades to centuries), health care, repair and maintenance crew. Any possible damage to the starship need to be repaired, necessitating the burden of a repair crew and machinery on board. All these are just impractical and can exist only on Star Trek. 4. At 0.01c, even a tiny atom can do incalculable damage to the spacecraft. Chances of collision with a Small Solar System Body is very high when you are traveling at 0.01c in a gigantic starship through the Oort cloud. 5. Humans can survive short-duration stay in space. But lifelong space journey needs a self-sufficient ecosystem to produce human needs. And an ecosystem can't exist beyond the habitable zone. So far, humans have been able to visit space with active support from Earth, and with the protection of Earth's magnetic field. Self-sufficiency in space without any contact with Earth is impossible. It is economically infeasible, biologically impossible. --PlanetEditor (talk) 17:03, 18 March 2013 (UTC) PS, I think we have been trolled. --PlanetEditor (talk) 17:03, 18 March 2013 (UTC) Well, you might be right about that one, but most of the rest is, quite simply, wrong. Microgravity would not be a problem - on the size of an interstellar space ship, you can use centrifugal force as an adequate replacement for gravity. Cosmic rays are a problem, but not an unsurmountable one. For one, we already know how to generate magnetic fields quite well. And the damage done by an atom at 0.01 c is very much calculable - an H atom (the most frequent kind by far) will have about 6.6e-15 J (i.e. not very much). For WIM, the most common kind if interstellar medium, there are about 0.01 ions per cubic centimeter. Going 3000 km/s, the total energy deposited per second per square meter is about 2.2 J, i.e. measurable, but not a problem (for comparison, at 20 degrees centigrade, black body radiation of that square meter is about 400 W). And chances of collision with any solar system body is actually quite low (and, for a given distance, independent of speed). If there were that much stuff out there, we wouldn't see the stars). --Stephan Schulz (talk) 19:37, 18 March 2013 (UTC) you seem to ignore the fact, nobody here is speaking about manned interstellar flight except you. And, no, I'm not a troll, I try to avert a catastrophy. --AlaneOrenProst (talk) 17:09, 18 March 2013 (UTC) My proposal would be to send a microscopic self-replicating machine to either a solar system that's nearby to the destination or to some planet of that same solar system. The machine will then grow all by itself using solar energy into a nuclear bomb factory and missile factories within a year. It would take only a small amount of energy to send such a factory to the desired destination at a speed close to c. Count Iblis (talk) 17:22, 18 March 2013 (UTC) Ok, I've got to ask - what is this catastrophe you're trying to avert? Richerman (talk) 17:41, 18 March 2013 (UTC) the multiverse-War, from 4169 onwards, cost 210 billion human lives (217 Billion gross) and ended a milenia long period of peace and prosperity. --AlaneOrenProst (talk) 17:44, 18 March 2013 (UTC) Why worry about something 2,000 years in the future, when there's so much stuff to worry about in the here and now? ←Baseball Bugs What's up, Doc? carrots→ 03:48, 19 March 2013 (UTC) WP:DENY. μηδείς (talk) 17:46, 18 March 2013 (UTC) Putting aside the dull issue of the questioner's motivation, how about the interesting part: is it impossible to power an interstellar manned mission with all the Earth's energy? According to Apollo 13 you can go to the Moon and back in 143 hours - so 72 hours (3 days) to send 43,000 kg including 3 men for something like 380,000 km (10^5). By comparison, Alpha Centauri is 4.36 ly = about 41200000000000 km (10^13). That leaves us with 10^8 times the distance to go. The article doesn't say how long we have, so let's take the OP's figure of 2000 years = 240000 the time to do it in. So the interstellar mission has to have an average speed that is about 400 times faster than that of the space probe, which does indeed suggest the need for 160000 times the fuel (to speed up that much faster and burn that much longer). If I suppose that the giant first stage of a Saturn V was mostly to escape the Earth's pull, and count therefore only something like 600,000 kg of fuel used to get to the Moon, that gets me about 1 trillion kilograms of fuel. Compared to 88 million barrels of oil used daily = roughly 12 billion kilograms? that should be what, 80 days worth, times some factor for the extra energy in rocket fuel. Hmmm. Now let's just go for raw kinetic energy. We want 43,000 kg travelling at an average 4.12E16 m/6.3E10 s = 6.5E5 m/s. That gives kinetic energy (4.3E4 kg) (6.5E5 m/s) (6.5E5 m/s) = 1.82 E16 kg m^2/s^2 = 18 petajoules. Load up 18 Tsar Bombas and you're set. (Well, 19, let's not forget the one to spread the message of civilization to the stars!) Compare to what joule says, 9.4 E 19 joules used in the U.S. per year. Either way, we have this huge advantage that we've considered 1/25 the OP's distance - so should pay 625 times more, or 136 years of oil production (if we had it) to go to his destination in his time frame - or we should get to Alpha Centauri in, oh, I dunno, article doesn't say, but let's say 80 years, which happens to be 1/25 of 2000... ditto. That sallot of energy. But it's still 18*625 Tsar Bombas = 11250 of them. Our article says there are 17,000 nuclear weapons in the world ... what a splendid use for them! Pity it would be impossible to get them all on a 50,000 kg mission, though I wonder how many factors shy it need really be. Wnt (talk) 22:25, 18 March 2013 (UTC) Wnt, feed the birds, not the trolls! 24.23.196.85 (talk) 00:14, 19 March 2013 (UTC)

suicide by hanging

whether there is any kind of noise from the mouth of a person who hanged herself or himself. 120.59.132.210 (talk) 08:33, 18 March 2013 (UTC) Saurabh pandey,— Preceding unsigned comment added by 120.59.132.210 (talk) 08:28, 18 March 2013 (UTC)

How often does it happen with someone else observing? I would think not very often. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:06, 18 March 2013 (UTC)

Public hangings were once a popular spectacle, so there were plenty of observers. If the hanging is done properly, death is instantaneous and the airway is swiftly closed, so not much chance of a noise from the mouth. But if a suicide is botched and the victim slowly dies of strangulation, they might well make some noise during the process.--Shantavira|^{feed me} 12:30, 18 March 2013 (UTC)

Some one who commits suicide by hanging is unlikely to use a long drop, so they will die by slow strangulation. There might be some noise from the mouth, but as there would be very little airflow through the constricted throat probably not very much. AndrewWTaylor (talk) 12:42, 18 March 2013 (UTC)

For more info on noise made by strangulation victims, see Strangers on a Train. 24.23.196.85 (talk) 00:00, 19 March 2013 (UTC)

Heat flow

If you have two bodies of different temperatures next to each other, what is the rate of heat flow between them? Is it just proportional to the difference between the temperatures? Is there an exact relationship?

150.203.115.98 (talk) 11:02, 18 March 2013 (UTC)

What you are looking for is Newton's law of cooling, which says that "the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings". Note that this is an empirical law, not a theoretical derivation or definition - however, it is useful because it is approximately true in a wide range of circumstances. Gandalf61 (talk) 12:09, 18 March 2013 (UTC)

Its dependent on materials and conditions because heat flows different already in single bodies of different materials. Its all exactly described in Thermodynamics. --Kharon (talk) 15:15, 18 March 2013 (UTC)

If the bodies are in contact (with good thermal conductivity at the contact area), and there is not much heat lost or gained to the surroundings, then Thermal conduction is the main factor in heat flow between them, and this is usually proportional to temperature difference in good conductors. ( I say "usually" because someone will point out exceptions, though I can't think of any.) If the bodies are not in contact, and the main transfer of heat is by Thermal radiation, then this is proportional to the fourth power of absolute temperature, making the rate of heat transfer more complicated because there is radiative transfer with the surroundings. Dbfirs 16:33, 18 March 2013 (UTC)

I would be remiss, after my elaborate rant above on Fourier's law, if I didn't point out an exception! The infamous Peltier effect, wherein electrical energy is expended to make the heat flow in the wrong direction (against the thermal gradient), is a great exception. Though, if you want to get really really into technicalities, heat is still flowing from hot to cold; but because the material is subject to an electric field and unique material properties, the electron gas has a different temperature than the substrate. All the necessary mathematics work out, anyway; per my standard reference, oh, probably Chapter 4 of Bittencourt for physics of dealing with multiple temperatures in an ionized plasma (though I don't specifically recall any discussion about solid-state "electron gas" plasmas in Bittencourt's textbook). Nimur (talk) 17:15, 18 March 2013 (UTC)

Thanks, I knew there would be an exception! Dbfirs 17:54, 18 March 2013 (UTC)

Drug Interaction

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

--Jayron32 18:54, 18 March 2013 (UTC)

A few questions regarding atomic energy levels (1&2) and orbitals (1)

I'm currently working on a paper dealing with aspects of Franck-Hertz experiment, and encountered some puzzling descriptions and symbols in an article published in the past, as follows:

1. The article includes a simplified energy level scheme of mercury. This scheme includes also a 7th & 8th levels, despite the fact that the outermost level in Hg is n=6. Any reason or explanation to this 'odd' diagram ?

2. It's claimed in this article that when a triplet appears it means that the electronic configuration consists of 2 electrons in 6s6p orbitals "giving a total P state where the spins are coupled to a total spin with quantum number S=1". How this 6s6p configuration came to be so ? what's the meaning of the quoted phrase ? - I'm familiar with spin physics, but the quoted phrase is seemingly unclear. It'll great to elaborate on these.

3. d orbital is distributed equally in space: x, y & z axes. However, as it's shown in various textbooks, and Wikipedia isn't excluded, there is a kind of a spatial preference: x & y are populated first, and the 'leftovers' go to z. What's the reason for this spatial asymmetry ? BentzyCo (talk) 14:01, 18 March 2013 (UTC)

Try these answers on for size

1. Energy levels exist regardless of whether there are electrons that fill them. Remember that energy levels are merely geometric descriptions of the solutions to the Schrödinger equation, and you can arbitrarily feed any set of quantum numbers into said equation to get the data for any energy level or orbital you wish, those orbitals "exist" in the sense that an electron given enough energy will "promote" to that energy level, even if it isn't the ground state for that atom. There are an infinite number of energy levels, but we generally stop describing them when it isn't useful to use them. For the purposes of the Bohr model (which only strictly works on a "one electron atom", but qualitiatively the principles behind it still hold for all atoms) one will still need to know what the energies of the n=7 and n=8 energy levels are for an atom, because energy imparted to electrons will still cause electrons to jump from the ground state to those higher states, and when they relax back down to the ground state from those higher energy levels, you can use the emissions data to calculate what energy those levels were at.
2. Triplet state describes the situation. For a two-electron system, if the electrons are in separate orbitals, they exist in a triplet state: Four total spin states, with two degenerate with each other: basically they would be up-up, up-down, down-up, and down-down, with the middle two being degenerate. If the two particular electrons are in the same orbital, their spins MUST be opposed (per the Pauli exclusion principle, so the only possibilities are the degenerate up-down and down-up states; since these are identical in energy this is called the singlet state. What your sentence sounds like is that there is some state of mercury (not familiar enough to know if this is the ground state or an excited state) which has a 6s¹6p¹ configuration, which gives rise to the triplet (the expected 6s² state would be a singlet state).
3. All the d orbitals are distributed evenly in space, in the sense that all 5 d orbitals, if overlaid and added together, will make a perfect sphere (this is strictly true of all orbitals of the same n and ℓ values). For any geometry higher than ℓ = 1, the complete set of orbitals will not be geometrically identical. As you note, there's one d orbital whose shape does not match the other four; likewise for f orbitals, there will be four of one shape, two of another, and a single of yet a different shape. I'm not completely familiar with how or why this works out that way, or what this means for the "order" that d orbitals fill in; however as far as I know it is completely arbitrary as all 5 d orbitals should be identical in energy. But at this point someone else will need to answer more authoritatively, as I can't quite find the answer in any of my searches, and I've either not known (or more likely forgotten) this little bit of chemistry. --Jayron32 17:38, 18 March 2013 (UTC)

Re #2, the triplet state is three total spin states, not four. The fourth is the singlet state. $\left|\uparrow \downarrow \right\rangle -\left|\downarrow \uparrow \right\rangle$ is the singlet state (ignoring normalization). It has that value regardless of the spin axis you choose, even though the choice of axis determines the meaning of the up and down arrows. $\left|\uparrow \downarrow \right\rangle +\left|\downarrow \uparrow \right\rangle$ is one component of the triplet state (note + instead of −). If you rotate the spin axis you will not get that, but rather some combination (superposition) of it with $\left|\uparrow \uparrow \right\rangle$ and $\left|\downarrow \downarrow \right\rangle$, which are the other components of the triplet (in one basis, anyway).

Re #3, the orbitals that you see in pictures are just a somewhat arbitrary basis set. As an analogy, try to find an orthogonal basis for the plane x+y+z=0. One possibility is (1, −1, 0) and (1, 1, −2): they both satisfy x+y+z=0 and their dot product is zero. They don't seem very symmetric, though, compared to the plane itself which is symmetric under arbitrary permutations of the x, y, z coordinates (not to mention the much larger group of continuous rotations). That's okay, because no particular vector (except (0, 0, 0)) has that symmetry; it's just the whole collection of vectors that's symmetric, and (1, −1, 0) and (1, 1, −2) is a perfectly good basis for that collection of vectors. Likewise, with the orbitals, the pictures you often see in books are just basis vectors for a space of solutions. The sum of those basis orbitals is still not rotationally symmetric, just like (1, −1, 0) + (1, 1, −2) = (2, 0, −2) is not rotationally symmetric. It's the space of orbitals spanned by the basis orbitals that's symmetric. To put it another way, if you rotate an orbital in this space, you always get another orbital that can be expressed as a sum of orbitals from the same (small, finite) basis set. -- BenRG (talk) 18:27, 18 March 2013 (UTC)

Dr Anna L

Hello, I had recently saw on Facebook, under the page Abandoned Asylums, a mansion that was owned by a Dr. Anna L. The pictures are amazing and the contents of this mansion is very dated ie: glass medicine bottles and the containers organs are preserved in etc. It is said that he was killed in a car crash about 20+ years ago. It also states that his family didn't care about the inheritance, this is also odd. There is something most intriguing about this person and would like to know more but I cannot find much except a video footage on youtube under Mansion of Dr Anna L. I don't think he is English but I'm not sure where he is from either. Is it possible that you could find out more about this person? Thanks Michelle Gecas 24.102.51.143 (talk) 14:39, 18 March 2013 (UTC)

Googling shows that the mansion is in Europe, probably the Netherlands, but it's hard to find search terms that give anything more than that. Looie496 (talk) 16:48, 18 March 2013 (UTC)

As far as I can see, all text in the Youtube video and the pictures is in German, so it is probably in Germany, Austria or the German-speaking parts of Switzerland, Belgium or Luxembourg. - Lindert (talk) 17:05, 18 March 2013 (UTC)

A little further research shows that it's in a spa town in the vicinity of Berlin, but the exact location is a secret passed around by word of mouth, no doubt because the place has already been looted to some degree. Looie496 (talk) 17:44, 18 March 2013 (UTC)

Amount of dissolved salts in a solution

I want to find out the amount of salts and other elements like nitrates, sulphates, chlorides, ammonium, phosphorous, potassium, magnesium, sodium etc in a solution. I guess that I should resort to titration but I am not sure which standard solutions and indicators to use, to find out the concentration of different elements and salts. Is there a web site (or a book) which gives the detailed procedures for finding out the concentration of these? My requirement is very much similar to Water chemistry analysis but that page doesn't give much info. I could pay some labs to do these tests for me but I want to do it at home, as I am likely to repeat the tests many times - WikiCheng | Talk 17:01, 18 March 2013 (UTC)

Could you please give a complete list of the substances you're testing for? 24.23.196.85 (talk) 00:19, 19 March 2013 (UTC)

A manual from a university lab course on quantitative analysis might be a good start.--Wikimedes (talk) 00:49, 19 March 2013 (UTC)

Dollar bills and a reflecting telescope.

I was trying the other night to recall an anecdote about someone who placed a surprising amount of dollar bills on a large reflecting telescope to show ??how occluding part of the mirror does not affect the image. Maybe I have the reason back to front, but does anyone recall this story and hopefully provide a link. Richard Avery (talk) 19:21, 18 March 2013 (UTC)

Neutron instability - magnetic field effect

Are there some data (from measurements) concerning the effect of magnetic field to the mean lifetime of a neutron?--5.15.215.42 (talk) 21:37, 18 March 2013 (UTC)

Data on the number of books published annually in the world, 1950 and 2012

I have heard that data exists to identify the massive growth in books publihed in the last 50 to 60 years. I have found some UNESCO references to Scientific Publications but I was looking more broadly than just this. Is there any data I can readily access? — Preceding unsigned comment added by 124.187.78.18 (talk) 22:43, 18 March 2013 (UTC)

Some data are in the article "Books published per country per year".

—Wavelength (talk) 23:00, 18 March 2013 (UTC)

Can the energy needed for interstellar travel be obtained from Earth?

A message for those in the "Interstellar Bomb" section above who claim that "the energy needed for interstellar travel cannot be obtained from Earth":

This is a classic example of misquoting Wikipedia. It is instructive to examine how a good article was twisted into pseudoscience:

The original question asked about the feasibility of sending a few pounds (say, a nuclear artillery shell) on a one-way trip of 100 light-years with a flight time of roughly 2000 years. But of course the false claim isn't just that that trip is impossible, but rather that no trip is possible.

The Wikipedia page that supposedly supports this claim is at Interstellar travel#Required energy. To get the bogus claim, you have to:

• Change "trip" to "round trip"
• Change "arriving" to "decelerating on arrival".
• Change "a few pounds" to "big enough to support a crew."
• Change "no time limit" to "a few decades".
• Change "available energy" to "actual energy historically produced"

This may be a new record for misusing a Wikipedia page.

Not only is interstellar travel possible, but it has already been done, at least as far as starting the trip goes. It left in 1972. We will have to wait for a while before it reaches another star, but it will do so. --Guy Macon (talk) 23:51, 18 March 2013 (UTC)

"If deceleration on arrival is desired and cannot be achieved by any means other than the engines of the ship"

Uh, isn't the ship headed into a stellar wind at a considerable clip? Doesn't that count as a nifty power source for planetary encounters? Hcobb (talk) 23:59, 18 March 2013 (UTC)

Yes, stellar wind and a big sail can give you a considerable amount of braking. There is a limit, though; come in too fast and the sail won't have enough time to bring you to a stop before you blow past the star or hit something. --Guy Macon (talk) 05:50, 19 March 2013 (UTC)

If you converted the whole mass of the Starship Enterprise into energy (E=mc² etc) it would not go far anytime soon. Look at the math. Bit like saying that Neanderthal cavemen could achieve oceanic voyages by tossing a log into the sea, which washes up (eventually) on some distant shore. [11]--Aspro (talk) 00:02, 19 March 2013 (UTC)

Actually, it's like saying that no land-based species on earth could achieve oceanic voyages, while ignoring the fact that coconuts do it all the time. --Guy Macon (talk) 05:50, 19 March 2013 (UTC)

Sounds interesting. What's the Starship Enterprise's total displacement? 24.23.196.85 (talk) 00:29, 19 March 2013 (UTC)

And what's the question? I just saw statements and no question, not even an implied one. Dmcq (talk) 00:52, 19 March 2013 (UTC)

The (slightly ungrammatical) question is in the section header. I don't have a horse in this race (or a good answer), but I can see why the OP is asking for further references/clarification, even if he is sounding a bit pointy. SemanticMantis (talk) 01:02, 19 March 2013 (UTC)

So completely misrepresenting what a Wikipedia article says isn't disrupting Wikipedia to make a point but talking about the misrepresentation is disrupting Wikipedia to make a point? You learn something every day... --Guy Macon (talk) 05:50, 19 March 2013 (UTC)

Oops! Left in an extra word. Fixed now. (Note to self: next time, smoke crack after editing Wikipedia...) The question is, "Can the energy needed for interstellar travel be obtained from Earth?". It was raised in the the "Interstellar Bomb" question, and I thought it best to discuss it outside of the material about time travel commandos trying to avert the foundation of the Cygnian empire through traveling from 31th Century to 21th Century earth. --Guy Macon (talk) 02:43, 19 March 2013 (UTC)

Here are some sources:

• [12]
• [13]
• [14] see the energy section --PlanetEditor (talk) 03:10, 19 March 2013 (UTC)

...which nicely shows that humans reaching the stars is unfeasible using today's technology or any projected future technology. Robots are another story. We have already launched several with enough velocity to escape the solar system and reach the stars -- but it will take a very, very long time to get there. --Guy Macon (talk) 05:50, 19 March 2013 (UTC)

March 19

Why will tidal interaction destroy planet's orbits

is Tidal interaction Roche limit? Base on what I've learnt latter scientist believe Earth will be swallowed up because of tidal interaction but I don't know how it works. Yahoo answers said it is because the way sun rotates like if the day is longer than its year it can be tidally interact. Do sun currently have orbital period, sun is a star I wonder if it even orbits. Is Sun and Earth currently interact right now? I hear Moon eventually will get eaten up by Earth [15] before if it even gets toast by sun but I am not sure how it works. Mercury and Venus don't have an moon is it because it is too close to sun or is it possible it may once have moon and got eaten up by the planets. Do being too close to sun have anything to do if planets have a moon or not?--69.233.254.87 (talk) 00:53, 19 March 2013 (UTC)

I don't know about the rest of your question, but the Moon will definitely not be "eaten" by the Earth. In fact, it is actually moving away from Earth at a rate, if I remember correctly, of 5 cm per annum. Being able to retain a moon does not depend on how close to the Sun the planet is. Plasmic Physics (talk) 01:18, 19 March 2013 (UTC)

I am trying to figure out why will Earth get swallowed up by sun due to tidal interaction. Is it because of sun's rotation? Is Earth and Sun currently tidally interacted?--69.233.254.87 (talk) 01:34, 19 March 2013 (UTC)

Presumably because tidal heating saps the kinetic energy of an orbiting body. However, orbital dynamics are quite complicated, so I'm not going to fathom a guess as to if or when the Earth will be eaten (even ignoring the whole Sun-ballooning-up in 5 billion years). Someguy1221 (talk) 02:48, 19 March 2013 (UTC)

So tidal interaction comes in different definitions. Is there different types of tidal interactions. I just learnt there is two factors why earth will get eaten up by sun. 1.Weaker solar gases increase frictions 2. Tidal decay (I don't know what is that all about)--69.233.254.87 (talk) 05:04, 19 March 2013 (UTC)

If Mercury had a substantial atmosphere

If Mercury had a atmosphere like Earth will the planets temperature been alot cooler? When I was younger I would think Mercury is hot because it is close to sun. Is the reason mercury gets 850 F at daytime because there is no atmosphere to protect the extreme temperatures. If Mercury had an atmosphere like Earth how will its surface temperature be like? Daytime temperatures will be alot cooler like equator stay under 500 F, and the poles stay around 200 F? Will nighttime get be much milder with an atmosphere? --69.233.254.87 (talk) 00:59, 19 March 2013 (UTC)

It depends on what's in that atmosphere. Venus, similar to the earth in size, has an atmosphere, but much of it is acidic gas, and is extremely hot; as Carl Sagan once said, "A thoroughly nasty place." ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:04, 19 March 2013 (UTC)

There are more qualified people to answer this question than I, but in my limited understanding, the distance to the sun matters a lot, atmosphere or no. As Baseball Bugs said, the atmosphere's composition does matter, and one reason Venus is so hot is because it has a lot of CO2 in the atmosphere so it suffers from a pretty dramatic greenhouse effect. Also, I think the atmosphere would insulate against the huge day/night temperature swings. But the non-satisfying answer is that it depends on the atmosphere composition. I'll be interested to see what others have to say. ~Adjwilley (talk) 01:39, 19 March 2013 (UTC)

I mean if Mercury had a clear atmosphere like Earth does.-Earthlike atmosphere.--69.233.254.87 (talk) 01:35, 19 March 2013 (UTC)

My gut says the temperature would be more stable, but slightly warmer on average. That's just a guess. (I'm basing this partly on the fact that the moon is the same distance from the sun as the earth, but has a colder temperature on average, with much greater swings...+123C to -153C, I think.) ~Adjwilley (talk) 01:41, 19 March 2013 (UTC)

• A key factor here is that Mercury rotates very slowly, and the dark side becomes extremely cold -- our article says around 100K. That isn't cold enough to liquefy nitrogen, but it's easily cold enough to liquefy carbon dioxide. So you would get some heat transfer from the day side to the night side, but working out the parameters would be quite difficult and would depend on the composition of the atmosphere. Looie496 (talk) 01:58, 19 March 2013 (UTC)

V-22 Osprey

Is there a civilian version of the V-22 Osprey in any stage of development? 24.23.196.85 (talk) 01:10, 19 March 2013 (UTC)

Well, the AgustaWestland AW609 already exists, so... yes? Evanh2008 ^{(talk|contribs)} 05:11, 19 March 2013 (UTC)

Well, technically this would be a civilian version of the XV-15 rather than the V-22, but this is close enough for my purposes. Really, I was just thinking whether it would be plausible for Mackinac Lines (a fictional charter freight/air-taxi company that I made up for my book series dealing with air rescue) to acquire a couple of those.  :-) 24.23.196.85 (talk) 06:25, 19 March 2013 (UTC)

Fever

Is increased temperature a byproduct of the immune system working overtime or a reaction to infection that helps the immune system eliminate it?68.36.148.100 (talk) 03:17, 19 March 2013 (UTC)

See Fever#Pathophysiology which discusses the various internal and external things that can cause a fever. --Jayron32 03:24, 19 March 2013 (UTC)

Ok, I mean a fever from the flu. Not from hyperthermia. 68.36.148.100 (talk) 03:37, 19 March 2013 (UTC)

In this case, yes. 24.23.196.85 (talk) 04:47, 19 March 2013 (UTC)

Bomb shelters

What kinds of structures (other than the Paris Metro) were used as bomb shelters in occupied France during World War 2? Thanks in advance! 24.23.196.85 (talk) 06:32, 19 March 2013 (UTC)

Force field implementation

How does Dreiding FF compare with Merck Molecular FF (94) for small molecules? Plasmic Physics (talk) 06:37, 19 March 2013 (UTC)