The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
How long can you thrive/survive on water and calories?
My understanding is:
Without water you can survive a day or two.
With water but no food you can survive maybe a month or two.
With water, calories, and protein, you can thrive for about a month before symptoms of scurvy. It's not clear from the article how long you could survive (in ill health).
So I wonder:
What about the intermediate case of water and calories but no protein, e.g. sugar water but nothing else?
This depends on the initial body mass index. Fat will be converted to calories. Protiens (e.g. muscle) will be recycled (to e.g. bile ducts) but lost over time without replenishment. The correct answer depends on the body mass index distribution and fat proportion of the population. 71.212.249.178 (talk) 01:11, 16 July 2012 (UTC)[reply]
Well, what I meant was, that there would be no caloric deficit. Or are you saying protein deficit would still trigger depletion of fat? --174.118.1.24 (talk) 01:24, 16 July 2012 (UTC)[reply]
I see! Thanks for pointing that out. I should also then wonder if there is any other deficiency that I haven't considered that manifests before protein? --174.118.1.24 (talk) 03:43, 16 July 2012 (UTC)[reply]
The list of deficiencies that you will suffer from in a very short time would be very long. Since I can't find any examples of people who have tried to live on that diet, I can't say how all of those issues interact, but I agree with Tango that the most serious is Hyponatremia. Sodium (and also potassium) are very important in your nervous system and are constantly flushed from the body as they're highly water soluble. They're almost never in short supply, but with the constraints you've placed, your neuron function would be impaired very quickly. 203.27.72.5 (talk) 04:03, 16 July 2012 (UTC)[reply]
Sands and the other hunger strikers ingested water and salt. They were young men in good health until their hunger strike, so probably able to live as long as anyone could from the general population. They generally died in the tenth week of the strike; the seventh week was the worst. They certainly would have lasted shorter periods, and had a more unpleasant time, but for the salt. John M Baker (talk) 18:35, 16 July 2012 (UTC)[reply]
This also implies that, if he is a young man in good health, someone ingesting only sugar water and salt could survive for more than 10 weeks, maybe quite a bit more, although presumably he would start to suffer health effects from the lack of essential nutrients prior to that time (maybe in that difficult seventh week). I don't know how long someone ingesting only sugar water without salt could last, but I suspect less than 10 weeks, and it sucks to be that person. John M Baker (talk) 19:29, 16 July 2012 (UTC)[reply]
Water, salt, sugar
So my question was based on several mistaken assumptions. Water and salt is what gets you a couple of months. Salt is actually a limiting factor even before sugar, let alone protein! So what about water, salt, and sugar then? For that matter is it even correct to put sugar immediately after water and salt, or is there a more immediate concern? --OP 174.118.1.24 (talk) 04:46, 17 July 2012 (UTC)[reply]
Well, oxygen comes first but that goes without saying. I think water, salt, and sugar would get an average person several months. There could be some other water soluble minerals or vitamins which come before protein. 71.212.249.178 (talk) 05:23, 17 July 2012 (UTC)[reply]
You may find the article Kwashiorkor to be informative. It is a syndrome caused by inadequate nutrient intake (especially protein) among people who get adequate calorie intake. That pretty much describes your water-salt-sugar diet to a T. People live for years with the syndrome, but can suffer serious physical and mental health and other quality of life issues, which can be life-long and debilitating even if their diet is eventually corrected. The issue is especially acute in children, who can suffer developmental disorders as a result. The condition does not appear to be itself directly fatal, but it does result in many sorts of oportunistic causes of death (i.e. weakened imune system leading to more infectious disease). There are also articles on other malnutrition issues, such as marasmus (which is calorie deficiency) and Cachexia, which is a general "wasting away", but is more a symptom of other diseases than a disease unto itself. For micronutrient (vitamin and mineral deficiencies) you'll want to research those individually; things like scurvy or goiter or rickets, but many of those are chronic conditions not known to reliably cause death on their own, excepting perhaps scurvy. --Jayron3205:39, 17 July 2012 (UTC)[reply]
I expect, however, that people suffering from kwashiorkor do receive at least some micronutrients, which people on a water-sugar-salt diet would not (unless you consider salt a micronutrient), and I don't think it would be possible to live for years without micronutrients. In particular, I would expect that the lack of potassium would lead to a fatal case of hypokalemia at some point. I don't know to what extent other micronutrient deficiencies would be fatal. John M Baker (talk) 14:21, 17 July 2012 (UTC)[reply]
We can interpret "salt" pretty broadly. If you drink oral rehydration solution (which is water, sugar and various different salts) then things like potassium aren't a problem. I'm not sure if vitamins and minerals would get you first or if it would be essential amino acids. Can anyone find a source for that? If it's the vitamins and minerals, then it wouldn't be much of a stretch to add a one-a-day multivitamin to the water-salt-sugar diet. After that, I'm pretty sure it would be essential amino acids that would get you. You do need some fat in your diet as well, but I think you could go a long time without that. (This is all assuming you're an adult - children need different nutrients because they are still growing and babies need quite a lot of fat to support brain development.) --Tango (talk) 20:33, 17 July 2012 (UTC)[reply]
I don't know where the IRA hunger strikers got their salt, but it seems most likely that it was table salt, which does not include potassium. John M Baker (talk) 22:56, 17 July 2012 (UTC)[reply]
Also note this 1998 article in which a more recent hunger striker, 61 days into his strike, was expected to die soon due to his low potassium levels. In the event, Barry Horne ended his strike a few days later; his death three years afterward, from liver failure, is thought to have derived from his multiple hunger strikes. John M Baker (talk) 23:11, 17 July 2012 (UTC)[reply]
Well, smoking tobacco is itself unhealthy enough that you should discourage him from doing that in the first place. Also note that the phrase "smoking tea" is slang for smoking cannabis/marijuana, so it is unclear when you say "smoke tea" if your friend is smoking earl grey or is toking the refer, as the kids today say. --Jayron3206:34, 16 July 2012 (UTC)[reply]
Smoking camellia sinensis is not unheard of. I don't see any kind of harm it could cause, but I'm also not a chemist. Regardless, I'd be willing to wager that the tobacco smoke is doing far more damage to your friend than the tea ever could. Evanh2008(talk|contribs)06:36, 16 July 2012 (UTC)[reply]
I don't see why inhaling the product of the incomplete combustion of one clump of plant matter is any better than another, additives from the production process not withstanding. 203.27.72.5 (talk) 06:55, 16 July 2012 (UTC)[reply]
Nicotine, in the very small doses that you get in tobacco smoke, has a vanishingly small effect on your health. It's a stimulant, and that's about all. That's why nicotine inhalers, gums, patches, etc. are used to wean people off smoking cigarettes. The long term effects of smoking cigarettes has been widely studied. The effects of smoking tea leaves has not. They are going to contain a huge number of essential oils and other complex organic molecules for which the long term effects of volatilising and inhaling are unknown. At least with cigarettes you have some idea what you're doing to yourself. 203.27.72.5 (talk) 07:31, 16 July 2012 (UTC)[reply]
Just to clarify, the nicotine makes tobacco addictive, and the tar makes it harmful. I've never understood why cigarette companies don't go to nicotine inhalers as a permanent replacement for cigarettes, rather than just to wean people off tobacco. That way, the customers could get their nicotine fix without the tar, and the tobacco companies would still make their profit, by selling the nicotine they extract from the tobacco, in inhaler form. StuRat (talk) 07:54, 16 July 2012 (UTC)[reply]
Yeah, that way they would also have a surer income source, since their customer base wouldn't keep dying. I think the major hurdle to that is the fact that nicotine inhalers and what not are dealt with as medications from a legal perspective, whereas cigarettes, cigars, pipe tobacco, etc. are dealt with as tobacco procucts. I've heard smokers complain that they would like to try those methods for getting off the cigarettes, but they all cost so much more even with the high sin taxes on cigarettes, and some have the added inconvenience of needing a doctor's prescription. 203.27.72.5 (talk) 08:03, 16 July 2012 (UTC)[reply]
What Stu said. The tar is the primary harmful ingredient in cigarette smoke, sure, but the nicotine is what makes it addictive. The addictive properties of nicotine are what encourage people to smoke, and very often to smoke in larger and larger quantities. Even if tea smoke produces as much tar and/or other harmful substances as cigarettes do, there isn't going to be the same level of physiological dependence that comes with nicotine. If you roll yourself a tea cigarette, the most addictive thing you're likely to get is... caffeine, maybe? Evanh2008 (talk|contribs) 08:05, 16 July 2012 (UTC)[reply]
It sounds like we could save millions of lives just by changing the regulatory and tax structure of nicotine inhalers. You'd think this would be a major campaign issue, in a US Presidential election year. StuRat (talk) 08:11, 16 July 2012 (UTC)[reply]
Between a sitting President who smokes and generally believes in taxation, and an opposing candidate who generally doesn't believe in taxation but also has a moral proscription against smoking, it's not likely to come up. ←Baseball BugsWhat's up, Doc?carrots→ 13:46, 17 July 2012 (UTC)[reply]
Also, generally speaking, as per Cigarette taxes in the United States, most of the tobacco taxation is at the state level, which is beyond the reach of the Presidential candidates. In fact, it's a pretty low-level issue, as it's considered a "sin tax" by some, and from the libertarian standpoint it's a "voluntary" tax, in that tobacco is strictly recreational. ←Baseball BugsWhat's up, Doc?carrots→ 13:55, 17 July 2012 (UTC)[reply]
There's nothing "voluntary" about that; voluntary status has nothing to do with why you want the good being taxed. The notion of a "voluntary tax" is usually applied to things that considered are user fees in disguise, like the tax on gasoline, provided it's genuinely earmarked for highway improvement — you pay it to use the public highways, and if you don't want to pay it you can find a way not to use them. Of course it's not a perfect example, because maybe you want the gasoline for other purposes and you'd still have to pay the tax, but it's as close as the concept gets to making actual sense. --Trovatore (talk) 08:06, 18 July 2012 (UTC)[reply]
Right, but high taxes on cigarettes and low taxes on nicotine inhalers is exactly what we need to improve the health of millions. So what makes the inhalers cost more ? It seems to be a result of them requiring a prescription, so why do we require that ? I think I will break this off as a new Q. StuRat (talk) 19:23, 17 July 2012 (UTC)[reply]
If you listen really carefully you can already hear the screams of "School kids will think it's candy!" and other assorted nonsense red herrings. 203.27.72.5 (talk) 08:26, 16 July 2012 (UTC)[reply]
Smoking anything is harmful, as the small particles inhaled when you smoke ("tar") are a lung irritant, and can cause inflammation or more serious problems. StuRat (talk) 06:47, 16 July 2012 (UTC)[reply]
Why do nicotine inhalers cost more than cigarettes ?
This was discussed briefly above, but I'm still not quite understanding what causes the high prices on nicotine inhalers. Also, are there places where they cost less ? StuRat (talk) 19:27, 17 July 2012 (UTC)[reply]
Well, Health Canada Advises Canadians Not to Use Electronic Cigarettes. I can't speak for your countries, but here the solution would seem to be addressing Health Canada's issues with the technology. At the very least, that would require studies and lobbying in direct opposition to tobacco companies' interests. It may also require more R&D, should independent studies find serious side-effects to the use of those technologies (though it seems unlikely). BigNate37(T)19:32, 17 July 2012 (UTC)[reply]
See supply and demand. Concepts like value and the cost you pay for something are only very tentatively connected. In our minds, we have a sense of "price justice"; that the cost you pay for an item should be somehow connected to the cost necessary to produce that item. This is so far from economic reality to be laughably wrong, and yet most people believe that if item A costs twice what item B does, it must have cost twice as much to produce, etc. etc. That isn't how it works, in any way. If it was, it wouldn't explain why I can buy a 16 ounce bottle of soda at the front of a grocery story for $1.69 and get a 2 liter bottle of the same brand of soda at the back of the store for $0.99. The only contributing factor to what you pay for an item is what the market will bear. You have to pay high prices on the inhalers because that's what people will pay for them. --Jayron3219:49, 17 July 2012 (UTC)[reply]
So long as competition exists, then the price for which an item is sold should be closely related to all of the costs of producing and selling that item. That is, if it costs $1 to make, market, and sell an item, then you won't be able to sell it for long at $10, as a competitor will come along and undercut you on price and steal your customers. There are, of course, various ways that competition can be prevented, such as price fixing (illegal) or patents (legal). StuRat (talk) 20:57, 18 July 2012 (UTC)[reply]
Where are 2 liter bottles of Coke/Pepsi produced sodas $0.99? We're only slightly gentrified and it's $1.99, rarely $1.25 on sale. And we still have to pay bottle deposit and 8.875% tax. Though I remember a wholesaler let you buy single 2 liters for $0.69 in '97. 12.196.0.56 (talk) 00:43, 18 July 2012 (UTC)[reply]
I can regularly get one brand or the other (Usually Pepsi, owing to where I live, but sometimes Coke) at $1.25 per 2 liter on any given day, and about once a month I can find it discounted at $0.99. That's American dollars. --Jayron3202:22, 18 July 2012 (UTC)[reply]
Jayron, you ought to click that link you just suggested yourself. The reason for the price discrepency between small and large bottles of soda is production costs, but you have to take into account all production costs inluding transport, labour stocking the shelves, refrigerated space being consumed in the retail outlet and the inconvenience imposed on the customer by having the product further away (i.e. The most visible locations in a store are themselves a scarce resource that must be expended on the shelving of different products) and so on so forth. Market information as a scarce resource also comes into play. The theory of marginal utility and the resulting supply and demand curves shows that in normal market conditions the amount supplied approaches the point of breaking even for both of these products. You just have to factor in all of the costs. 112.215.36.171 (talk) 23:29, 17 July 2012 (UTC)[reply]
You know what is strange, is when you agree with me, but take a tone that indicates you would be disagreeing with me. Every statement you made is illustrative of the exact point I was trying to make (that the real price and cost of an item is complex, and can't be estimated simply by comparing relative amounts) and yet you phrased it as though you were disagreeing with me. I thank you greatly for providing additional evidence and support for my point, but am perplexed by the tone of the post that indicates you wouldn't be doing that. Odd. --Jayron3200:27, 18 July 2012 (UTC)[reply]
Well in that case, I think you're just missing the point of StuRat's question; why don't the tobacco companies lobby for a change in the regulatory structure so they can cheaply sell mass produced nicotine inhalers that don't have the same health effects as cigarette smoke? Do they like killing people? 112.215.36.171 (talk) 04:21, 18 July 2012 (UTC)[reply]
There's a huge supply infrastructure to producing cigarettes, beyond simply the companys that make and market the final product. A complicated (and arcane) system of tobacco growers and warehouses and auction systems still exist to this day, and have a vested interest in not upsetting the applecart, as it were. Living in a state where tobacco is king myself (North Carolina), the tobacco industry still has a huge political clout, and tends to be resistant to easy change. For various political reasons, tobacco has been one of the few crops to resist corporitized farming; large amounts of tobacco are still grown on small family farms, and for many small farmers tobacco is the most lucrative thing they can grow. That's what needs to be overcome in order to cause any revolutioary change in the nicotine consumption industry. And that's probably not going anywhere, as that lobby is still huge where it counts, especially on the state level. --Jayron3204:37, 18 July 2012 (UTC)[reply]
But why would any of that change ? The tobacco companies would still need to grow, buy, and warehouse tobacco, from which they would then extract the nicotine to put in the nicotine inhalers. Unless there's some cheaper way to obtain nicotine I'm unaware of ? StuRat (talk) 04:51, 18 July 2012 (UTC)[reply]
I realize that "other factors" contribute to the final cost, beyond the raw materials. I'm asking which other factors those are, in the case of nicotine inhalers. Dramatically lowering the cost and eliminating the prescription requirement would seem to help the cigarette companies, who could then sell more nicotine, and stop killing off their customer base. And, since customers can use them just about anywhere, they might consume more nicotine that way. Cigarettes seem like a bad business model, to me, between of the terrible PR and lawsuits and shrinking customer base, at least in the US. StuRat (talk) 04:15, 18 July 2012 (UTC)[reply]
But Stu, your reasoning implies that the existing cigarette companies would be able to control the market on nicotine inhalers. If the companies themselves don't believe that, they will absolutely resist changing the system. And even if they could, there is no rule that the executives of a company have anything approximating functioning brains. At least here in the US, corporations are notorious for resisting even wildly profitable changes to their business models. Someguy1221 (talk) 04:32, 18 July 2012 (UTC)[reply]
Unless there's some other cheaper way to obtain nicotine than from tobacco, the tobacco companies would seem to have an advantage there. StuRat (talk) 04:53, 18 July 2012 (UTC)[reply]
So you are correct! Synthetic nicotine is more expensive than plant-derived nicotine [1]. Is it possible that e-cigarettes are less addictive than the real thing? Someguy1221 (talk) 05:27, 18 July 2012 (UTC)[reply]
Well, since nicotine isn't itself detectable by smokers, they do tend to associate the nicotine high with the tar in a ciggy, which can be a problem when trying to get smokers to switch to nicotine inhalers. They just don't seem "right". But, if a new generation of nicotine addicts were started out on nicotine inhalers, this wouldn't be an issue. However, to do this, the whole concept of only prescribing nicotine inhalers to cigarette smokers trying to quit has got to go. StuRat (talk) 05:52, 18 July 2012 (UTC)[reply]
UPDATE: I'd still like to see some type of breakdown of the cost of nicotine inhalers, say by raw materials, manufacturing costs, regulatory costs, lawsuit insurance, taxes, profit, etc. StuRat (talk) 20:53, 18 July 2012 (UTC)[reply]
Searching for any such claim, I found a handful of forum posters claiming tobacco contains "other addictive alkaloids", namely, tobacco-specific nitrosamines. It is a curious idea, since these are produced from nicotine by opening the ring and some other fairly small alterations. (oddly, I found [2] that describes the methyl group as being the source of the mutations, yet the n-nitrosonornicotine article claims it's a carcinogen. Hmmm...) Getting closer to the goodies, I found [3] which says that nornicotine is as potent as nicotine at some receptors, and it has a longer half-life in the brain. Now, nornicotine is a "minor metabolite" of nicotine in the body, but it is also present in the source tobacco. It would be damned convenient if you could genetically engineer a tobacco plant that contains solely nornicotine, and it turned out to give smokers their high without so much cancer (on account of the missing methyl that reportedly is what mutates the DNA) but I don't know it's true. Wnt (talk) 11:28, 20 July 2012 (UTC)[reply]
Experience of submariners ascending from USS Tang?
According to the article, USS Tang was hit by its own torpedo and ended up heavily damaged in 55m of water. 13 seamen evacuated the forward compartment and swam to the surface, 9 actually making it, and only 5 of those managing to survive until pick-up the next day. My question is, what did these guys experience from the moment they left the submarine until surfacing? Were they wearing any sort of survival gear? Did they just take the biggest breaths they could and then slip through a hatch and swim like mad for the surface? Were they wearing buoyant gear that pulled them upwards faster than someone could swim? How quickly can a human swim 55m under water? I assume they suffered horribly from decompression sickness? The Masked Booby (talk) 08:35, 16 July 2012 (UTC)[reply]
(ec) I'd normally expect them each to have a Mae West (life preserver), but, from the description, it doesn't sound like they had them. Decompression sickness only applies if you are exposed to depths for enough time for your body to adjust, then decompressed rapidly. I would expect more rapid pressurization damage, like burst eardrums, in their case. StuRat (talk) 08:47, 16 July 2012 (UTC)[reply]
Recent examination of the wreck of the Royal Navy submarine HMS M1 suggests that at least some of the crew attempted to swim to the surface from a depth of 73 metres, but none survived. The pioneering Davis Submerged Escape Apparatus was introduced to RN subs four years later in 1929. Alansplodge (talk) 18:30, 16 July 2012 (UTC)[reply]
I've read somewhere that it is not possible to sneeze when you get hot. Am I living proof that this statement is wrong? Why do I sneeze when I become hot? Difficultly north (talk) 09:58, 16 July 2012 (UTC)[reply]
What do you mean by "hot"? One person's hot is another's cold. It has been in the news later that the USA has had a heat wave and people died. With a temperature that in Australia would cause us to put a coat on. 45 C can kill an Englishman, but a Saudi Arab would think nothing of it. Do you mean just hot enough to sweat noticeably? Or hot enough to cause distress and/or risk to your safety? I sneeze at the height of our summer here in Western Australia, where daily max temperatures run at around 42 C (average for hottest month about 39 C). Not because I'm hot though. Ratbone121.221.41.113 (talk) 10:53, 16 July 2012 (UTC)[reply]
Those U.S. temperatures causing deaths have actually been 40 - 43 C. And in our desert, where most of us don't live, it hit over 49 C. While the low in the mountains was -4 C the same week (24 F to 121 F in the continental U.S., July 4-10).[4]. Rmhermen (talk) 13:20, 16 July 2012 (UTC)[reply]
Our article Sneeze says (without a source) that a sneeze can sometimes be caused by a cold draught or a drop in temperature, but says nothing about sneezing being suppressed when you're hot. As I've seen many people with hay fever sneezing at the height of summer, I doubt that's the case. Rojomoke (talk) 16:57, 16 July 2012 (UTC)[reply]
Hahaha! Missed this. My father once microwaved some jalapeños and almost killed himself, my mom, and her mother. That story is retold every year on cinco de mayo.μηδείς (talk) 04:53, 18 July 2012 (UTC)[reply]
I was referring to when you suddenly warm up. After stress or on a hot British day (sat 20s-30s) or doing activity or have a hot flush. I can't comment on the first one. Difficultly north (talk) 11:16, 18 July 2012 (UTC)[reply]
I think one of the main problems is the roots not handling frost. You could try heat trace on them or some other method to monitor the temperature and then heat them above the survival temperatures. Anything above ground would effect the plants as well but not as badly as root damage I would think. You could 'bag' the tops and somehow keep those warm as well. They would probably still grow slower and produce less in cooler climates.--Canoe1967 (talk) 15:43, 16 July 2012 (UTC)[reply]
In Britain, where the OP geolocates, you really need a greenhouse. The San Francisco bay area, where I live, is a cool damp climate, but it rarely freezes and almost never snows, and a few tropical fruits, such as lemons and some other citrus, manage to grow okay. Looie496 (talk) 16:35, 16 July 2012 (UTC)[reply]
Not all "tropical" fruits have the same hardiness, let alone all varieties. For instance, this kiwi could almost certainly be grown in Britain with little special care (it was developed for Michigan) [5]. Other plants can grow outside their natural zones with special care. Historically, espalier technique was used to improve fruit yield in Europe. I've heard of some crazy people who manage to "lay down" entire fruit trees for the winter, so that they can be mulched and protected, but I wouldn't recommend it. Lastly, many passiflora species are hardy to cold climates, and even the tropical ones can bear fruit if brought in to the house over winter. SemanticMantis (talk) 20:16, 16 July 2012 (UTC)[reply]
I'm sure it is possible in the sense that one could describe a mathematics which would explain it. Tripartate symmetries like this are known in our own universe, though not in magnetism specifically (i.e. the three color charges from Quantum chromodynamics. Not being a mathematician, a phycist, nor particularly imaginitive, I'm not sure I can conceive of what a magnetic tripole would look like, but I suspect that the geometry of a magnetic tripole mapped onto a universe with four spatial dimensions would obey similar mathematical rules as our current universe, which has a magnetic dipole mapped onto a universe with three spatial dimensions. --Jayron3218:36, 16 July 2012 (UTC)[reply]
Given that opposite poles attract and like poles repel, I was trying to think how it could work if there were 3 poles instead of 2. The closest I can imagine is some electromagnetic equivalent of "rock-paper-scissors". ←Baseball BugsWhat's up, Doc?carrots→ 13:49, 17 July 2012 (UTC)[reply]
You may find the mathematics of multipole expansion enlightening. It is not possible to construct a field whose multipole expansion contains nonzero odd terms, and that is also consistent with the experimentally-observed behavior of magnetic fields. But, it's certainly possible to define a hypothetical field - in the mathematical sense - with arbitrary properties. Strictly, there's a very significant qualitative difference between having three "poles" and having three valid values for the magnitude (or "charge") of a pole; so the above comments about color charge should be interpreted very carefully. Nimur (talk) 18:24, 17 July 2012 (UTC)[reply]
The large sugar crystals dissolve more slowly than those of standard granulated sugar and do not settle in the bottom of the pot or rise up as froth to the surface. This reduces the risk of burning and the consequent need for stirring. It also allows impurities to rise for easier skimming. Because it minimises scum, it helps to make jams (UK) / jellies (USA) clearer.
This strikes me as odd. Larger crystals do settle more easily than small ones (I speak as someone who has grown innumerable crystals in a professional capacity over the years). And, surely it's the fact that they do settle that allows impurities (rather than sugar crystals) to float to the surface. But, conversely, if they do settle then the risk of burning increases, as does the need for stirring. Thoughts, anybody? Chris (talk) 19:08, 16 July 2012 (UTC)[reply]
It's a relatively short article stub, with an uncontroversial history. It's been years since any information was added to the article. It sounds as though you have some insight that could be helpful to other readers, so this is a case where being bold is the best course of action. BigNate37(T)19:51, 16 July 2012 (UTC)[reply]
OK so what you've observed applies to the crystals you've worked with. But does it apply to preserving sugar crystals in a fruit/sugar/water solution? If so, amend the article. If you don't know, maybe someone who does can confirm or deny it. --TammyMoet (talk) 20:35, 16 July 2012 (UTC)[reply]
For what it's worth the words "The large sugar crystals … clearer" may be from my increasingly dodgy memory a verbatim copyvio from the back of a sugar packet. Whitworths, I think. I'll have a look down the supermarket tomorrow. I happen to remember it because I remember thinking "What?" when I read it (on the sugar packet) – "surely if they settle more rapidly they'd increase the risk of burning and need more stirring". My practical experience (as an occasional amateur maker of jam) is that preserving sugar behaves in exactly the same way as bog-standard granulated sugar for high pectin fruit, for instance gooseberries. For low-pectin fruit such as strawberries jam sugar does the job. TonywaltonTalk23:35, 16 July 2012 (UTC)[reply]
"The large sugar crystals dissolve more slowly than those of standard granulated sugar and do not settle in the bottom of the pot or rise up as froth to the surface"
The first part of this sentence suggests that dissolving more slowly is an advantage. If so, it should be explained why it is. I suspect it is nonsense. (I realize that I'm going out on a limb suggesting it is nonsense. I may be way off base.) Wanderer57 (talk) 14:29, 17 July 2012 (UTC)[reply]
Shock wave faster than the speed of sound?
Can someone clarify this passage from me about a nuclear explosion effects:
At this point a shock wave forms at the surface of the fireball as the kinetic energy of the fast moving ions starts transferring energy to the surrounding air. This phenomenon, known as "hydrodynamic separation", occurs for a 20 kt explosion about 100 microseconds after the explosion, when the fireball is some 13 meters across. A shock wave internal to the fireball caused by the rapidly expanding bomb debris may overtake and reinforce the fireball surface shock wave a few hundred microseconds later. The shock wave initially moves at some 30 km/sec, a hundred times the speed of sound in normal air.
I get that shock waves from, say, a supersonic jet are caused by the jet moving faster than the speed of sound. I get that the expansion of an atomic fireball might be moving faster than the speed of sound, thus creating a shock wave.
But can the shock wave itself actually move faster than the speed of sound? This seems contradictory to me, but I am not a physicist. How does that work, if it does? I thought the shock wave was more or less a sound wave, and would be thus limited to the speed of sound? --Mr.98 (talk) 20:34, 16 July 2012 (UTC)[reply]
There may be a vague definition of a shock wave here. Your definition, a compression wave which does not actually move the air, and what they might be talking about, perhaps more properly called a "blast wave", where the air itself is blown away, potentially at much higher speeds. One complication is that the blast wave also generates sound along it's front, so, in that sense, the sound is moving faster than the speed of sound. StuRat (talk) 20:42, 16 July 2012 (UTC)[reply]
There's a bit of a trick in the way that the quote is worded; it's given away when they talk about the speed of sound in normal air. The air around a nuclear detonation is far from anything we'd call 'normal'. In an ideal gas under equilibrium conditions, the speed of sound is roughly proportional to the square root of the absolute temperature; at hundreds of thousands or millions of degrees, the speed of sound is quite a bit higher, as the individual molecules in the gas are on average moving at much higher speeds. In reality, the system isn't ideal, nor is it under equilibrium conditions, but you get the idea—the air heated by a nuclear detonation is going to be a lot hotter – and therefore faster – than 'normal'. The RMS velocity of an oxygen molecule at room temperature is about 500 m/s; the RMS velocity at 300,000 K is about 15,000 m/s: thirty-fold higher. TenOfAllTrades(talk) 21:27, 16 July 2012 (UTC)[reply]
related question: in this photo (from shock wave), does the leading edge of the shock wave (near the nose) not propagate with a speed nearly equal to that of the plane (e.g. mach 2)? I know the propagation of the wave must quickly slow down as distance from the plane increases, but this seems like it could be an obvious example of a shock wave traveling faster than the speed of sound. SemanticMantis (talk) 21:37, 16 July 2012 (UTC)[reply]
There is – perhaps appropriately – something of a semantic issue. The nose of the aircraft is certainly travelling at mach 2, therefore the tip of the shockwave would travel at the same speed. On the other hand, from one moment to the next, it isn't the same air molecules next to the nose of the aircraft; as far as the air is concerned, the shock wave really is only moving at the speed of sound. The leading edge of the shock wave at the aircraft's nose isn't a physical 'thing'. TenOfAllTrades(talk) 21:57, 16 July 2012 (UTC)[reply]
If you do the computations you find what TenOfAllTrades explained above. In case of a shock wave moving throug a medium, it is conventional to define the speed of sound to be that in the ambient state of the medium. The shock wave then moves "faster than sound", and the ratio of the speed of the shock wave and the speed of sound is called the mach number of the shock wave.
The reason why a shock wave can form at all is precisely because in a hot medium the speed of sound is larger than in a colder medium. So, if you start with a strong pressure wave, then in the compression phase the wave moves a bit faster than in the decompression phase. So, the compression phase will start to overtake the decompression phase and that eventually leads to the formation of a discontinuity in the pressure and density, which is precisely what an ideal shock wave is. In reality, there are also dissipative effects which smooths out the discontinuity. Also this will prevent small pressure from developing into shock waves. Count Iblis (talk) 22:10, 16 July 2012 (UTC)[reply]
Huh? Isn't there a missing angle in the above? A shock wave which is constant strength travels along its normal line which is not the direction of the plane. The shock wave has to be travelling faster than the plane to have a component equal to the plane in that direction... --BozMotalk19:26, 17 July 2012 (UTC)[reply]
A secondary question (on shock waves)
Thanks for the above, it has clarified it a bit, though I am still a little confused. Here's a question that might get me out of my confusion: in the situation above, would the blast pressure wave hit you before the formal "sound" of the explosion hit you? Or at they one and the same (as I had assumed before reading about the shock wave being faster than the speed of sound)? --Mr.98 (talk) 01:46, 17 July 2012 (UTC)[reply]
Arrange in increasing order of slackerdom: "students who post Q's online, expecting others to do their homework for them", "students who don't do their homework at all", "students who do their homework themselves, as intended". StuRat (talk) 22:35, 16 July 2012 (UTC)[reply]
Actually, checking the articles, I'm not sure we give enough information to actually answer the question (or at least not for someone like me, who was never much good at chemistry, and has forgotten what little he learned), though one would assume that if this is a homework question, the student should have already been given sufficient information to answer it. AndyTheGrump (talk) 23:20, 16 July 2012 (UTC)[reply]
You're comparing different types of values that you shouldn't- the furan and thiophene values are for deprotonating the neutral compound, while the pyridine number is for the acidity of the conjugate acid (the number that you actually want to determine basicity of the neutral species). Buddy431 (talk) 10:38, 17 July 2012 (UTC)[reply]
Is there a "how long you've been asleep"/awake calculator?
Or a graph by age? I can't seem to find one on Google. Shouldn't be too hard with sleep giving hours per night at certain ages, a curve fitting and an integration.
Are you going to share it? Proportion of age asleep does vary by age, but why would you need anything more accurate than dividing age by three? 71.212.249.178 (talk) 05:17, 17 July 2012 (UTC)[reply]
They're many calculators that ask health questions and spit out how many minutes, months, years, seconds and Plutonian years you'll live and even one that just says "You will die!", so why not one that takes your birthdate and gives how long you've been awake? Maybe I want to know how many "8 year old me" lives I've had? Though I don't know how much to cut off for early-life amnesia so I'll just cut off realistic minimum/maximum amounts and get bounds. 12.196.0.56 (talk) 00:59, 18 July 2012 (UTC)[reply]
Could they DNA test athletes and their pee so they don't try to cheat by giving other peoples' urine?
A saliva swab should be enough for the first part, right? Is there enough DNA in urine? Maybe they'll give their own urine from a clean year instead. So they'll test for signs of chemical degradation/aging in the pee, unless very well preserved urine is required for/would be detected in the normal course of drug testing. But then athletes will cryogenically freeze their urine in liquid nitrogen, and reconstitute it later for giving while they're doping. Uh, we could take their blood, right?, but that's apparently too invasive of their rights as they don't do so now. And I guess they need all the blood they can take to beat 9.58 seconds. How long after the athletic performance can they test and it still works? Maybe if they test for the last event on the athlete's calendar to save him all of his blood he could've doped on the earlier races? Allow the drug tester to take the blood sampling amount out before the Olympics and put it back in after they take the drug testing sample out?
Radioactive dating of the urine with a fast-decaying isotope? And also, would Usain Bolt run 9.59 seconds or more if he didn't pee before the race, avoid chains over circa 0.1% of his body weight, or evacuate his bowels? Will they eventually wear suits with golf ball-like dimples designed in supercomputers and the bib information printed on? Amputate their ears to save weight while racing and use stem cell-grown pinnae when not? Sagittarian Milky Way (talk) 23:38, 16 July 2012 (UTC)[reply]
I don't think there really is any DNA in urine. There are lots of things you could do to make drug screening more effective, but you have to balance a lot of factors, efficiency, practicality, cost, etc.. In situations like this, I default to the team of experts that has been paid to work this stuff out, instead of assuming my uninformed musings might come up with a method significantly better then what they have in place now. Vespine (talk) 00:46, 17 July 2012 (UTC)[reply]
Often you're right Vespine. But they managed to avoid NFL (USA's #1 sports league) drug testing till last year didn't they? 12.196.0.56 (talk) 01:52, 17 July 2012 (UTC) I'm OP on public computer.[reply]
Apparently 20% of the population can't pee when people are watching them. They could use a camera I guess but if I were a girl I would not want videos of urine coming out of my pee hole anywhere. They have Whizzinators so testers would actually have to view the pee coming out of the urethra. And which gender watches them if they're bisexual? Would the female Muslim athletes like any of this nonsense? Or, the final word, Good grief, some sort of near future airport scanner style very quick spectroscopy scan I saw in a science magazine that only detects explosives but can be set to see urea molecules ensuring that there are no supernumary urine reservoirs. They'll use this one day. 2040 Olympics. Unless they stop using urine testing. 12.196.0.56 (talk) 01:52, 17 July 2012 (UTC)[reply]
I think sexual orientation is mostly irrelavant in a case like this. Some people feel more comfortable going to a male or female doctor, so I don't see why an athelete couldn't choose the gender of the preson doing the "watching". But i don't think people chose the gender of their doctor because they think the doctor is going to get a sexual thrill out of the experience. If anything it might be because they're worried they'll get a sexual thrill when it's innapropriate. Or I wouldn't be surprised if some people, like exhibitionists make their choice based on the fact that they LIKE showing their private parts to people of their preffered gender. Vespine (talk) 04:07, 17 July 2012 (UTC)[reply]
urine needs some serious work. There is DNA in urine. Cell-free DNA in urine has been the subject of modern research as well as how to best preserve that DNA. See:
There are a number of confusing claims above. While urine tests are more commonly used particularly in out of season testing, and generally preferred because they're less invasive, blood tests (in addition to urine tests) are used in the olympics. See [6], Use of performance-enhancing drugs in the Olympic Games, [7]. I'm doubt it will be possible to detect autlogous blood doping via transfusion using urine (not that it's easy with blood). (Generally blood in the urine is taken as a bad sign, but I won't if enough normally end up in the blood that technically it may be possible to detect homologous blood doping via urine online.) A blood passport as recently in the media in relation to the Tour de France obviously requires blood. I don't think it's uncommon that it's easier or considered more reliable to detect certain things in the blood (or in the blood in addition ot urine), according to [8], it was done with EPO in the past although as our blood doping article and the source mentions, urine alone is now considered sufficient albeit somewhat controversially (but I'm not sure that blood helps the controversy since it appears to be about the ability to distinguish natural EPO from recombinant EPO). People mentioned Paruresis, but it's worth noting AFAIK there is no real provision for this in the olympics, see World Anti-Doping Agency. Urine collection is monitored, I've heard to the extent they athelete doesn't even hold their own penis (if male). I seem to recall there was a recent case I think at the olympics or just before (but not this olympics) where a participant failed to provide urine and it was suggest paruresis may be a factor, the WADA or someone said it's wasn't something they'd even encountered before. (Can't seem to find the case.) Some people were surprised by this since it isn't an uncommon condition, but others pointed out anyone with the condition would generally have failed to advance to the olympics because urine testing is widely used at earlier levels. Also while providing fake urine is a concern, I even seem to recall there was someone disqualified from the olympics for allegedly doing this a few years back, I don't think it's really that much of a concern compared to many of the other possibilities of cheating using drugs without detection given the level of observation done, see for example [9]. I mean if someone started physically implanting something to provide fake urine, it wouldn't surprise me if ultrasounds started being used to detect that. The whizzinator may work in some contexts but perhaps not the olympics. (Edit: Forgot to mention I'm primarily thinking of male atheletes, there may be avenues for a female athelete whike under strict observation although I haven't looked in to it.) Nil Einne (talk) 06:47, 17 July 2012 (UTC)[reply]
According to [10], DNA tests on urine have been used to confirm who the urine belong to, but this appears to be primarily when officials are complicit in the cheating. It wouldn't surprise me if they're now a regular part of test since it probably doesn't add much to the cost, but I still suspect it isn't really that important in terms of in-olympics testing for the reasons mentioned above. Nil Einne(talk) 07:57, 17 July 2012 (UTC)[reply]
Found [11] which describes collection observation in some US sports, I presume the olympics is the same or stricter. It also mentions ways atheletes have attempted to cheat in the olympics on urine collection including the method that is probably used in the case I mentioned remembering above. It sounds to me like only those who have perhaps never gone thru a normal olympics style observed testing would think they have a chance of using them. More sophisticated cheats know they won't work. I guess the catherisation method mentioned in the source above and [12] can't be detected via observation, but this would be difficult if you can suddenly called up for drug testing at any moment and aren't given any time alone once you're called up. And rejecting the first sample of urine as the earlier source mentioned also sort of kills the catherisation idea. In other words, DNA testing may have its merits, but the low tech solutions are likely the best methods to ensure you get what you want, a recent urine sample from the athlete.
DNA testing also opens up other complications, e.g. for a female finding foreign DNA in their urine stream may suggest they are careless, but perhaps not that surprising [13]. The ClinChem link above also mentions other ways foreign DNA can end up in the urine stream. And of course adding your own DNA to some other sample of urine can't be that hard. You could seperate these out, but relying on them adds complications. Then there is the problem of the athelete using a clean sample of their own urine and trying to test if they're doing that. All in all, best to rely primarily on low tech. (To be fair, it sounds like I was correct above that foreign DNA can be used to detect the possibility of autologous blood doping so it may be something important to look in to.)
Ive tried to calculate and got an answer for a seemingly simple problem yet I don't think it's correct. I have a cylindrical container with a radius of 0.05m which has a vertical frictionless piston of mass 10kg. Air is trapped inside. I want to know what the change in internal energy is when 300J of heat is transferred to the air causing te piston to move upwards by 0.2m. As this is a closed system, I'm assuming there's no mass flow and I'm quite confident that the change in heat energy is 300J so that leaves the change in work done. My initial guess was that this is 10kg x 0.2m but I don't think this is correct. Where an I going wrong? I'm sure that once I have the correct change in work done, I need too add this to the change in heat energy to get the change in internal energy. 82.132.249.136 (talk) 12:25, 17 July 2012 (UTC)[reply]
Because the air is doing work on the piston, the resulting change in its internal energy (without the heat) is negative. Meanwhile, check your units: mass times distance isn't energy. --Tardis (talk) 12:42, 17 July 2012 (UTC)[reply]
Thanks according to how I've interpreted what you've said, the answer should be -[(10x9.81)x0.1]+ 300. However, I still don't think this is correct. I think it may be to do with pressure but I'm not sure how to apply this. Thanks. 82.132.249.125 (talk) 15:18, 17 July 2012 (UTC)[reply]
I don't quite understand the question. Are you asking how much energy you need to add to the system in order to increase the heat energy of the air by 300J (which will be greater than 300J, due to some of the energy going to lifting the piston)? In which case, you were almost there, it's 300J+10kg*9.81m/s*0.2m. --Tango (talk) 20:40, 17 July 2012 (UTC)[reply]
Damselfly identification
I photographed a damselfly this morning in Liaoning Province, NE China Imgur Link. If someone can help me identify it, I will gladly add it to Commons and the related article (if one exists). I figure the white leggings should make for easy identification? Those are pretty unusual... The Masked Booby (talk) 15:28, 17 July 2012 (UTC)[reply]
Wow, based on the description that's definitely it! That article already has a few good photos but they might appreciate a clearer look at the namesake legs... Great job, Richard! The Masked Booby (talk) 21:51, 17 July 2012 (UTC)[reply]
You need to check the dimensions of energy. Holding a mass does not expend any energy. If you lifted the mass thru a certain height, you will have then added some potential energy to the mass. If this does not make it clear, imagine youself holding that 9kg for 1 hour. Your arms might then feel sore from having to maintain the force required, but force is not energy, and you'll still be breathing normally. Now, imagine yourself lifting 9 kg weights from the floor to a table top every second for an hour. Bet you can imagine yourself getting puffed out - heck you won't last an hour. That's because your muscles had to release some chemical energy, consuming oxygen to do so, and converting that chemical energy into mechanical energy to transfer as potential energy in the weights. Wickwack58.167.241.156 (talk) 15:47, 17 July 2012 (UTC)[reply]
Muscle usage is a strange duck, and analysis of it more rightly belongs with biology than "assume-a-spherical-cow" physics. While you're correct in that there is no additional energy imparted to the 9 kg mass by holding it in a fixed location, (and certainly a table or a mannequin will not expend any energy doing so), you're incorrect that holding something in your flexed arms doesn't expend any energy. If your muscles are in tension, you're expending energy to keep them that way, even if by a rough, entry-level-physics calculation you wouldn't be. The reason for this is that on a microscopic level your muscles have little bits that are constantly grabbing and releasing to maintain that tension, constantly burning chemical energy to do so. (Much like if you start and end with a mass at the same place on a table you don't impart any net energy to the mass, even if you expend much energy raising and lowering the mass repeatedly while the mass is temporarily hidden behind a curtain.) This is why it's often misleading to use muscle-based intuition to judge how much energy or force is required to do something. -- 71.217.5.199 (talk) 16:02, 17 July 2012 (UTC)[reply]
Clue: the concept in question is isometric exercise. If you Google "isometric exercise calories" then you will find various numbers, but not much information on how they were obtained. I expect they were obtained empirically by measuring CO2 and H2O output from human subjects, since physics won't tell you the answer. As Wickwack said, step 2 is wrong and there's no way to make it right, since the two sides of the equation are related by an unknown function that describes how muscles work. --Heron (talk) 19:03, 17 July 2012 (UTC)[reply]
When googling as suggested by Heron, I found that the top sites returned are hardly definitive, but most confirm that isometics burn very little calories. While 71.217.5.199 is certainly correct in what he said, there's the matter of scale. Certainly just holding 9 kg, although making you muscles sore if you hold it long enough, will not alter your breathing rate one iota (try it and see!)- confirming that the additional energy consumed is just about negligible compared to the calories you burn anyway just by being alive, warm, and awake. Wickwack124.178.145.103 (talk) 02:46, 18 July 2012 (UTC)[reply]
The way the OP set out his question strongly suggests he's seeking to understand the physics and needs to understand the difference between force, power, and energy - round cow physics if you like, rather than trying to undertstand muscle efficiency and physiology. It's up to Leptictidium to come back to us and let us know which it is - then if he still needs some help, we can tailor it accordingly. Wickwack124.178.145.103 (talk) 02:46, 18 July 2012 (UTC)[reply]
Um the OP already came back and said "Well, yes, my original aim was to find out how many calories you burn by holding 9 kg for 1 minute" which suggests he's much more interested in the biological answer (not necessarily how the answer is derived) rather then trying to understand the physics. Nil Einne (talk) 14:31, 18 July 2012 (UTC)[reply]
If you say so. It's virtually identical to his original question - no new points in it. I think it neither confirms nor denies he has no understanding of the physics. It neither confirm nor denies he understands that muscles, being an imperfect machine, actually burn calories to exert a force, but those calories are very small in quantity and he wants to estimate them neverthless. Wickwack58.170.181.203 (talk) 15:32, 18 July 2012 (UTC)[reply]
In a stable orbit, acceleration remains tangent to velocity
If they are in orbit around Earth and are subject to its gravitational pull, why aren't they continuously accelerating at 9.81m/s2? Is there drag or a terminal velocity for satellites? Ankh.Morpork21:09, 17 July 2012 (UTC)[reply]
Because in a stable orbit, the acceleration is always tangent to the velocity vector, so the magnitude of the velocity does not change. BigNate37(T)21:41, 17 July 2012 (UTC)[reply]
They accelerate at slightly less than 9.81m/s2 because they are further away from the Earth, but they are constantly accelerating towards the Earth. They are moving sideways as well, though, which means they keep missing the Earth (the direction that is towards the Earth changes as they move, so gravity causes them to go in a circle). It's just like when you have a weight on a string and swing it around your head really fast. You're constantly pulling on the string, pulling the weight towards you, but if never hits you (until you stop spinning!). --Tango (talk) 21:51, 17 July 2012 (UTC)[reply]
Presumably the larger the diameter of the orbit, the faster a satellite travels if they all have similar orbital periods. Is this the case or can two satellites at different heights travel at the same speed, just the lower one has a quicker time of orbit? Ankh.Morpork22:06, 17 July 2012 (UTC)[reply]
Intuitively, the further a satellite is from the mass it orbits, the weaker the force exerted by gravity. A weaker centrifugal force implies less centrifugal acceleration, so I would assert that velocity must also be lower to maintain the orbit. If I understood Kepler's Third Law better, I would explain the exact relationship between radius and speed of an orbit, but I don't and I can't. BigNate37(T)22:22, 17 July 2012 (UTC)[reply]
You are correct, objects in higher orbits move slower. Kepler's Third Law says that the square of the period is proportional to the cube of the semi-major axis, ie. where is the orbital period of the planet and is the semi-major axis of the orbit (for a circular orbit, that's just the radius). You might find it easier to think of it as . Put another way, if you double the size of the orbit, you multiply the period by . --Tango (talk) 23:47, 17 July 2012 (UTC)[reply]
I recently read a study saying that 70% of all hospitals use quaternary ammonium compounds to clean the hospital beds. Personal experience in a hospital by myself has proven this to be correct. They use a dilute bleach solution to clean Most items in the Room except for the bed which they use a quandary ammonium compounds such as Lysol to clean. Why is this? My understanding is that quaternary ammonium compounds do not kill spores, such as Clostridium difficille or ringworm spores. Wouldn't it make sense to clean the bed with a product that kills such spores?--64.38.226.90 (talk) 21:16, 17 July 2012 (UTC)[reply]
Many disinfectants can cause skin irritation and are therefore not used when they are likely to come in contact with the patient's skin. Ankh.Morpork21:32, 17 July 2012 (UTC)[reply]
The Candida article is rather incomplete though. I understand that Candida growing inside the eyeball in otherwise healthy people is almost always from "cutting their junk" with lemon juice before injecting. Closet addicts are always shocked when their ophthalmologist diagnoses the condition... --BozMotalk06:50, 18 July 2012 (UTC)[reply]
The first half dozen turned up by google scholar [14] all look reasonable. "Candida endophthalmitis after intravenous drug abuse" is notable enough to be worth its own article if anyone can take time out from Linux articles to write it. --BozMotalk17:07, 18 July 2012 (UTC)[reply]
Certainly some aspects of the Apollo missions were classified, but that's not the only reason why any particular aspect of the missions, like the designs, might not be made available to the public. Another reason might simply be that it isn't in their interet. Why would they make the designs available to the public? Vespine (talk) 01:38, 18 July 2012 (UTC)[reply]
There is an urban legend that the plans for the Saturn V rocket no longer exist. The paper copies were destroyed when they were no longer needed but they still exist on microfilm. As far as the other Apollo hardware, I don't know what happened to the blueprints. They might have been destroyed when they were no longer needed. Bubba73You talkin' to me?01:56, 18 July 2012 (UTC)[reply]
"Because it's the law"? The article linked seems to refer to copyright. Even if NASA was covered under this (which is by no means self-evident from the linked article), all it would amount to saying would be that if anyone got hold of the relevant details, it wouldn't be a breach of copyright to publish them - or presumably to use them to build your own Saturn rocket. How would this non-copyright status amount to an obligation to actually provide the details to anyone in the first place - assuming that they still have them? AndyTheGrump (talk) 02:14, 18 July 2012 (UTC)[reply]
Works by NASA are in the public domain, but that doesn't mean they need to go out of their way to make everything publicly available on the internet. No one has those kind of resources. -RunningOnBrains(talk)15:43, 18 July 2012 (UTC)[reply]
I don't know anything about the mechanical aspects, but I do know something about the electronics that have been used in the space program, and if they are typical, then there wouldn't be anything worth open-sourcing. NASA has been so conservative in its engineering that components were generally ten years out of date by the time a mission flew. Given how long it's been since the Saturn V missions, I shudder to think what you would see there. It would be like open-sourcing stone tools from the Neolithic. Looie496 (talk) 02:25, 18 July 2012 (UTC)[reply]
And following on from that, much of the hardware might simply no longer be available. Certainly the electronics, but I'd suspect much else besides. I don't think that there is much that is actually 'non-public-domain' in terms of the information you'd need to build a new 'Saturn equivalent' design from scratch - and it would probably be simpler than trying to reproduce the original technology exactly. I suspect that more modern technology would make a better system anyway: lighter/more powerful electronics, composite materials, and all the advances in CAD/CAM manufacturing would surely improve performance a little - though perhaps not a great deal, since basically a Saturn rocket before launch is mostly fuel and oxidiser by mass, and that won't change. AndyTheGrump (talk) 02:43, 18 July 2012 (UTC)[reply]
Not saying directly whether or not the designs are or are not classified, but if they were, one could certainly understand why they would be, and why they would still be, and it has nothing to do with covering up a moon hoax. The Saturn family of rockets were designed for putting people into orbit, but it would take much modification to make them into a perfectly functional ICBM, capable of reaching any place on Earth. The U.S. government has a vested interest in keeping such information on the QT. --Jayron3203:31, 18 July 2012 (UTC)[reply]
Are you saying the Apollo/Saturn plans are not open-sourced? Just my opinion, but I tend to believe if you sought out plans, you could obtain them. Plenty of people have built working replicas of the Apollo CM guidance computer, possibly the most sophisticated piece of equipment on the spacecraft. The computer plans are easily found online. (see here) The rest of the technology used on the spacecraft is far less advanced, and in the 21st century almost all of it is obsolete. → Michael JⓉⒸⓂ03:44, 18 July 2012 (UTC)[reply]
It was impossible to obtain some specifications of the Saturn V and related guidance systems at the time, and a few of those are probably still classified, but pretty much everything else was out in the open. You can certainly obtain blueprints which are very accurate but omit avionics -- that was one of NASA's most popular FOIA requests for years. You can obtain the Moon landing computer design and program, but not the launch avionics computer programs (digital and analog) for the Saturn V Instrument Unit's computers. The astronauts were often consulted as to how much of their private lives (i.e., medical and duty condition) would be shared with the press, and of course they all wanted pretty much everything out in the open, too. 75.166.200.250 (talk) 04:03, 18 July 2012 (UTC)[reply]
ITAR will make it complicated to gain access to the technical stuff which is not already available. Every drawing or schematic for hardware used in space is now ITAR restricted. Even giving the name and the type of plug used to connect Mars Science Laboratory parts is only allowed after checking with if it violates ITAR. The WWW is international and therefore putting the drawings onto the net will make you a target for homeland security.--Stone (talk) 10:09, 18 July 2012 (UTC)[reply]
ITAR is a list of things. Dual use items are on that list too. The classification of all material used in space as significant military equipment is written in the documents. It does not make sense but it is fact. Talk with people from Mars Science Laboratory is very annoying because at that time no TAA (Technical Assistance Agreement) was in place and therefore the only things presented were things already published or general knowledge. The point is different for US Citizens, but the rest of the world is not allowed to get access. --Stone (talk) 12:53, 18 July 2012 (UTC)[reply]
Was the technology classified? Yes, but not to a very high grade. A brief perusal of NASA Apollo documents shows that many of them have classification stamps on them: a CONFIDENTIAL description of the spacecraft from 1963; CONFIDENTIAL mission description from 1961; CONFIDENTIAL report of some kind from 1961; CONFIDENTIAL mission directive from 1961; CONFIDENTIAL study of moon landing modes from 1962; and so on. I haven't seen anything higher than CONFIDENTIAL, which is the lowest official ranking of classification you can have (it goes CONFIDENTIAL, SECRET, TOP SECRET, more or less; OFFICIAL USE ONLY is a rung below CONFIDENTIAL but is not really a legal classification category).
So that's pretty weak classification for mission-related things. The rocket technology itself was no doubt classified higher than that, because, as others have mentioned, it was (and is) dual-use technology, and because the US was, you know, engaged in a big Space Race with the ol' USSR. Mission details were likely CONFIDENTIAL just to avoid the possibility of sabotage, or giving away programmatic information on the US space effort. The low level of classification is meant to signal that even if they got out, it wouldn't be that big a deal; it also meant that the information could be widely shared within the NASA organization.
As for open-sourcing at the time, the reason you wouldn't do that is because the Cold War US model was "buy all the experts and give them gobs of resources," which gets rid of the need for open-sourcing. (Plus, this is rocket science. It's actually hard. Even when you do the "throw everything at it with the most brilliant people at your disposal" approach, your rockets still blow up on the launch pads half the time.) As to whether you could do it today, sure! In theory. But it takes a lot more to build a moon shot in theory than a bunch of people editing a Wiki. It's a Big Project, much harder in terms of technical accomplishment than, say, designing an atomic bomb or something like that. --Mr.98 (talk) 13:42, 18 July 2012 (UTC)[reply]
They all appear to orbit it's barycenter. I don't think it would be possible to orbit just one or the other, and have it be a stable orbit, unless, perhaps, the orbit was in a Lagrange point (and, even then, it's technically orbiting both). StuRat (talk) 07:38, 18 July 2012 (UTC)[reply]
I can't see how this question would be any different for the orbit of all the planets about the Sun. It too is affected by the other planets, and wobbles for each one. The wobbles must all be added up and come to one rather complex wobble. Myles325a (talk) 07:47, 18 July 2012 (UTC)[reply]
True, but then every object in the universe could also be said to be wobbling due to in orbit about every other object. The difference is, in the case of Pluto and Charon, it's visually obvious that they are orbiting the barycenter. StuRat (talk) 07:50, 18 July 2012 (UTC)[reply]
The Big Bang occurred everywhere. And Stu's statement is not usefully true, but only trivially. So yes, any galaxy is 'in orbit' around any other - but most of the orbits are wildly unstable! AlexTiefling (talk) 11:34, 18 July 2012 (UTC)[reply]
The three body problem is notoriously complicated. To give a simple example, suppose Pluto had the Earth's Moon revolving around it in the opposite direction, and one of those little satellites tried to sneak past five meters from its surface. Would the rock still be orbiting the barycenter? Nope - it'd go ass over teakettle in some odd direction and probably never be heard from again. It can't be modelled simply, except in roughest approximation. Wnt (talk) 17:25, 18 July 2012 (UTC)[reply]
Note that Pluto and Charon don't have any close-in satellites orbiting the pair. I suspect this is because any such orbit would be unstable, again with the possible exception of an orbit at a Lagrange point. StuRat (talk) 20:47, 18 July 2012 (UTC)[reply]
The Pluto-Charon system doesn't have any stable Lagrange points. L1, L2 and L3 are always unstable and L4 and L5 are stable only when one object is more than about 25 times the mass of the other (see Lagrangian point#Stability). Pluto is only about 9 times the mass of Charon, so L4 and L5 aren't stable. (There might be some quasi-periodic orbits, but they would only be stable in the short-term.) --Tango (talk) 02:20, 19 July 2012 (UTC)[reply]
Creationist time line refuted by Neandertal DNA
Scientists figure that the last Neanderthals were about 26000 years ago. Creationists reckon that must have been less than 6000 because the world was created on 4004 BC. And they argue that the presence of Junk DNA in the human chromosome is the result of man's degeneracy over the interim time, as his sinful nature corrupts what was originally a perfect system in the Garden of Eden.
But they DO agree that there are no Neanderthals now, and that they must have died out thousands of years ago. I would thus argue that in that scenario, the DNA of preserved human bodies thousands of years old, Neanderthal or some other variant, should then show much less "corruption" by embedded viruses and so on. If the world is only 6000 years old, and our current DNA has been progressively corrupted over that time, then DNA from even two thousand years ago should show a much smaller degree of such corruption.
But I gather they don't. I am interested to see if there is any difference at all in such junk DNA effects between us and them, and if that difference can lead to a callibration of how different they were to us, and how long ago they died out. Myles325a (talk) 07:42, 18 July 2012 (UTC)[reply]
But radiocarbon dating seems like a much easier and more accurate way to accurately date those fossils. Of course, creationists will ignore that, but they can also ignore DNA evidence and all of geology, astrophysics, and every other branch of science that disproves their world view. StuRat (talk) 07:54, 18 July 2012 (UTC)[reply]
It's a simplification to say that all creationists, or even all young-earth creationists, believe the world began in 4004 BC. That's just the Ussher chronology. But StuRat is right: some beliefs can be reinforced by science (such as the intuition that humans and apes have something in common), some are intrinsically unprovable (such as Deism's model of God - which can arguably ignored as irrelevant, but not specifically disproved), and some (like Creationism) are held by their believers directly in the teeth of overwhelming scientific evidence to the contrary. Something as sophisticated as junk DNA analysis isn't on the radar for these people, because they treat rigorous scientific methods as intrinsically suspect. AlexTiefling (talk) 08:07, 18 July 2012 (UTC)[reply]
The creationists are not very good at expressing themselves, so they get too little credit. Their typical retort to such things is to say "Were you there?". When we apply the tools of natural science, we assume that the consistent timeline we see in our experiments, which seems consistent with our own, is the only timeline. That if we go back generation after generation, the clock on the wall matches the time people experienced, and the circumstances we live under are those which our examination of historical sites supports. It is, however, definitely true that human experience can misperceive the world, that the timeline as we recall it is not what the facts indicate. Can we rule out, with certainty, that over time there is not some systematic bias - that indeed, our past, as sentient consciousness, is in what we could call one parallel universe, and our future in another? Creationism involves a very deep rejection of the materialistic certainties (faith?) of the secular perspective, and it may not be one that is satisfactorily redressed merely by more facts showing the consistency of the natural science timeline. We can argue to the consistency, clear immediate usefulness, and tremendous beauty of the natural science perspective; but to argue that our perception of the world is truly, absolutely real and not at all a matter of imagination or misperception? That is beyond our kingdom. Wnt (talk) 12:22, 18 July 2012 (UTC)[reply]
Wnt's words seem to be a long way of stating that the rate of time could have changed without our knowing it because we don't know everything and cannot be certain there isn't some aspect of physics that we've missed or not yet discovered. As such, it is true in logic, but does not seem very likely, given the weight of evidence in all manner of science fields of study, from geology, study of dinosaurs, radio isotope dating, you name it. I have actually had Christian creationists and Islamic people state this same argument to me. Wickwack124.178.177.30 (talk) 13:30, 18 July 2012 (UTC)[reply]
Actually, that's not what I meant. What I mean is more that you could be sitting there, typing away at the computer, and the next moment you look up and out at an audience around some futuristic zoo enclosure neatly labelled: "Day In the Life of an Earthling: Reconstructing the Century of the Anthropocene Extinction". Or many, many other things, some, one can hope, guided by a perfect hand, and possessing a greater level of reality. Wnt (talk) 16:34, 18 July 2012 (UTC)[reply]
The logical argument that we cannot know that the world/universe, etc, is real orginated with ancient Greek philosophers, but is it anything more than a perceptive exercise in logic? Wickwack124.178.177.30 (talk) 13:30, 18 July 2012 (UTC)[reply]
Although I think creationists are foolish in being such, I don't see that neandertals having a goodly amount of junk DNA proves anything. A Creationist might argue that they were an abombination, extremely degenerate. Further, evidence is coming to light that so called junk DNA is not so much junk after all - recent issues of the magazine Scientific American have elucidated research into this aspect. Wickwack124.178.177.30 (talk) 13:39, 18 July 2012 (UTC)[reply]
Even with such evidence, I doubt it will change anything. When faced with the harsh reality that the natural world does not resemble the world described in the Bible, literal creationists will always rather assert that the world is wrong because the Bible is always right. They can not see what is because they're too caught up with what should be. Good luck with making them see that.-- OBSIDIAN†SOUL17:40, 18 July 2012 (UTC)[reply]
Another line I've heard from creationists is that their god deliberately made the world with evidence that seemingly contradicts the Bible simply to test their faith. Once they take that position, no evidence will prove anything to them. HiLo48 (talk) 19:48, 18 July 2012 (UTC)[reply]
I want everyone to memorize this aphorism. Right now. Commit this to memory: "You cannot reason someone out of a position they did not arrive at via reason." Learn it. Know it. Live it. It doesn't matter what evidence you present to the YEC crowd: They evaluate the evidence through the filter of their predetermined conclusion, so there's no sense in trying to talk them out of it. Its a lost cause. --Jayron3220:07, 18 July 2012 (UTC)[reply]
Because the evidence is hardly hidden or arcane. If reality punched you in the face every day, and you refused to acknowledge it, what good is one more punch... --Jayron3223:24, 18 July 2012 (UTC)[reply]
From their perspective, it is more hidden and arcane than scripture, because of peer pressure, the promise of life after death for believers, and similar. 75.166.200.250 (talk) 20:40, 19 July 2012 (UTC)[reply]
airlifting a diver to hospital
So i was in vanuatu scuba diving the other day, a group of islands only one of which has a hyperbaric chamber to treat sombody with the bends. How might a diver with the bends be moved with haste to the chamber, is airlifting possible since increased altitude would worsen his problem. Can the cabin pressure of conventional planes be maintained at 1 atmosphere, or perhaps airlift by helicopter where the helicopter stays close to sea level? 110.175.191.101 (talk) 12:37, 18 July 2012 (UTC)[reply]
For airframe cost reasons, aircraft are presurised to the equivalent of 2000 m (or a little above for older aircraft), ie 80% of sea level pressure (ref http://en.wikipedia.org/wiki/Cabin_pressurization#cite_note-1), this is beacuse it is a good safety margin below the altitude (~2500 - 3000 m) where some pasengers may experience discomfort with certain medical conditions. A helicopter is not necessary for low level flight - all types of powered aircraft are required to be above the same minimum height when not actually landing or taking off - typically 1000 feet, and may be higher in built-up areas. Perhaps pilots undergoing rescue can get authorisation to fly lower, but 1000 Ft /300 m altitude has 95% of sea level pressure and should have negligible additional medical risk. Airfarme structural safety means you will not find an aircraft that can maintain sea level presure. Wickwack124.178.177.30 (talk) 13:15, 18 July 2012 (UTC)[reply]
It's more like 98% at 1000 feet. And try flying at 1000 feet in Dubai. Or Shanghai or Manhattan. There's at least 18 things at 1000 feet to fly into in Dubai. Sagittarian Milky Way (talk) 21:47, 18 July 2012 (UTC)[reply]
I believe that the helicopters typically used to transport people to a hospital aren't normally pressurized at all. Thus, they can't fly very high. However, I seem to recall hearing about one rigged for mountain rescue, where low air pressure might cause the pilots to pass out, having a pressurized compartment for the crew, and 2 separate rescue nacelles which were independently pressurized, so the patient(s) in them can be slowly returned to sea level pressure. I'd think the same strategy could work, in reverse, for divers. However, this is likely to be cost prohibitive except in areas with lots of divers. Also, one disadvantage to this system is that medical personnel can't tend to the patient during the flight, but, if they are likely to die without it, it's worth that risk. StuRat (talk) 20:22, 18 July 2012 (UTC)[reply]
I grew up a short distance from Whipps Cross Hospital in London, which at the time had one of only two hyperbaric chambers in the country. There were fairly regular visits from RAF and RN air-sea rescue helicopters carrying customers for it. I'm fairly sure the Westland Whirlwind didn't have a pressurised cabin. Alansplodge (talk) 22:21, 18 July 2012 (UTC)[reply]
Circles, flares around sun in photography.
I'm not sure this is the right section for asking about it
In photography sometimes when the sun is around the corner, strange circles appear in the photography. Something like this you can see the bright behind the tree.
Those are lens flares, caused by internal reflections within the camera lens. You can photograph them by taking pictures with very bright objects in or near the frame. That process is easier if you a camera where you look through the lens (such as an SLR camera or, I suppose, any digital camera with a viewscreen on the back) rather than through an independent viewfinder. Various lens filters can further enhance the effect. — Lomn14:51, 18 July 2012 (UTC)[reply]
Bokeh is not related to this. Lens flares are internal reflections of light which cause light to appear in front of foreground objects, bokeh is just differences in focal length; foreground objects will not be impacted. -RunningOnBrains(talk)15:34, 18 July 2012 (UTC)[reply]
Camera on a timer in 1850?
Coaz and the Tscharner brothers on the summit of Piz Bernina during the first ascent, 13 September 1850
I'm writing an article on Johann Coaz and am a little suspicious of a photo I've put in the article. This photo (right) purports to show Coaz and two others on the first ascent of Piz Bernina (according to its description in the Commons). Given that there was no one else around, could this photo have been taken on a timer with the technology available at the time (I'm hoping it could have been), or is it a shot from a different ascent that has been mislabelled? The rockiness of the summit could certainly be Piz Bernina. The source (naturfreunde-maiengruen.ch) is not very helpful at all... Ericoides (talk) 16:02, 18 July 2012 (UTC)[reply]
Here's a little history of the camera shutter for some background. This suggests that in 1850 the photographer would not have been using a shutter as we would recognise it, so also wouldn't be able to use a release timer. It seems that they would have come in about 1880. Having said that, I think that if the camera did have a shutter, the technology existed (Clockwork) to enable a delayed shutter release. However, looking at camera technology, this page tells us that Wet plate photography didn't come in until 1851. This photo (if it was taken in 1850) must, therefore, be a Daguerreotype. Here you can see the process involved in taking such a photo, with exposure times from 10 seconds to 30 minutes(!). A reasonably long exposure (maybe over 30 seconds or so) might be enough for the photographer to quickly skip round in front of the camera and arrange himself in an 'I've been here all along' pose. What do you think? - Cucumber Mike (talk) 16:15, 18 July 2012 (UTC)[reply]
At low sensibility film, there wouldn't be any traces. The sensitive material just register up a certain threshold. If the exposure time is several minutes, then things in the ball park of some seconds won't show up. Apparently, it was not unusual for photographers in the XIX century to portrait themselves: [[16]]. OsmanRF34 (talk) 16:36, 18 July 2012 (UTC)[reply]
OK, that sounds sensible, thanks. Two further questions: which one is Coaz, and which one took the photo? My hunch is that Coaz is on the right, looking at the camera, and the fleet-footed photographer is the man standing on the left (who might well also be Coaz). Ericoides (talk) 17:19, 18 July 2012 (UTC)[reply]
Looking more closely at the photo, the standing man and the man sitting on our left are holding things that look a little like posing stands. Could it be, therefore, that the man sitting on the right looking directly at the camera is the photographer? Also, you labelled the photo 'Coaz and the Tscharner brothers'; the two men who look most like brothers are the one standing and the one on the right (the potential photographer) - they seem to have similar facial features. If I've got that right, my bet for Coaz would be the man sitting on the left. Admittedly, I'm getting into rather serious guessing now! - Cucumber Mike (talk) 21:37, 18 July 2012 (UTC)[reply]
It's an optical illusion. The camera is probably on a standard 5-foot-tall tripod, sitting on a nearly-level ridgeline, aimed slightly downward. --Carnildo (talk) 22:47, 18 July 2012 (UTC)[reply]
I have taken pinhole camera photos of myself and others, with exposures of over a minute, and it was quite possible to start the exposure, run to my place in the photo, then run back and stop the exposure. I would not care to run across the ice and rocks evident in the photo. How sure are you there was no 4th person present? If I carried a view camera on a tripod up a mountain, I would not think it much of an additional burden to also bring a remotely operated shutter, even though in those days exposure control was usually by removing the lenscap, counting or timing the exposure with a watch, then replacing the lenscap. A "Bulb" shutter exposure was done by squeezing a rubber bulb attached to a long, thin rubber hose, with a shutter which opened when the bulb was squeezed and closed when it was released. Such bulb-hose-shutter arrangements were in use by 1853: "The Photographic journal: Volume 83, books.google.com Royal Photographic Society of Great Britain, Photographic Society of London - 1853 - Snippet view: "The camera ran on castors, and its height was adjusted by attachment to a pair of tall steel rods, up and down which it slid, and could be fixed at any desired position. Fxposure was made by means of a rubber tube and bulb. The shutter ..."
The adding of a remotely operated shutter would have been a pretty obvious alternative to running back and forth on a slippery mountaintop. The photo as presented is too low res to look for evidence of a remote operated shutter. Photos by 1850 were made on paper negatives, and not just Daguerrotypes. Edison (talk) 19:51, 19 July 2012 (UTC)[reply]
I think we can be certain that if this is a photo of 13 September 1850 then no one else was present. All records of Piz Bernina's first ascent say it was by Coaz and the two Tscharner brothers. On such a prestigious first ascent we'd definitely know if there was a fourth person in the party. Ericoides (talk) 07:37, 20 July 2012 (UTC)[reply]
I think that the strange quality of the light on the rocks and the completely indistinct background of the sky point toward a very long exposure. Wnt (talk) 11:08, 20 July 2012 (UTC)[reply]
Noise reduction
Given a mainstream PC (with a mainstream microphone and mainstream loud speakers/headphones), can a program running on it actively cancel noise? I don't mean any noise reduction filter, that can be applied on a file on the computer, just reducing the environmental noise for the user. OsmanRF34 (talk) 17:48, 18 July 2012 (UTC)[reply]
Read carefully: I said with mainstream headphones, not with noise-cancelling headphones. I want to know if a PC (with a mainstream microphone and mainstream loud speakers/headphones) can cancel noise, not if there are noise cancelling headphones at Amazon for a few quid. OsmanRF34 (talk) 18:06, 18 July 2012 (UTC)[reply]
Ok/ What software are you proposing to use? It is technically okay if you fix the distance between the microphone and headphones and resign yourself to it only working for wavelengths a lot longer than that (so say two octaves below middle C) but it would be a real faf to program versus the buy a cheap set of phones with a microphone inbuilt which does it better. I think the answer is probably "not with mainstream software". --BozMotalk18:40, 18 July 2012 (UTC)[reply]
Wouldn't latency be a problem (amongst other things)? Even with ASIO, I'm just not sure PCs can achieve the latencies required for such purposes compared to dedicated hardware although I guess with highly predictable noise it may still work slightly. Note that both our article and [17] mention it only really works for low frequencies and placement of the mics are important. Nil Einne (talk) 19:08, 18 July 2012 (UTC)[reply]
This depends on the characteristics of the noise and the signal channel. If you are talking about reducing non-speech noise, try running the signal through a vocodec like Speex and see if that makes it more ineligible. If you can characterize the noise spectrally and the channel in more detail, then I can give you a better answer. 75.166.200.250 (talk) 20:22, 18 July 2012 (UTC)[reply]
I used to work on Lotus' ANC system for cars. At the time, late 80s, PCs were 286s and the like, and could not process in real time. For real time 6x4 cancellation we used a TMS chip, and could cancel up to about 200 Hz. The chances are you need a higher frequency limit than that but only a single channel system, with the same cancellation signal to each ear. As such I think that current PC probably has the grunt, but getting timely access to the audio circuitry might be tricky in a multitasking environment. If this is a research project, go for it, but my noise cancelling headphones cost about an hours pay, and they are GREAT. Greglocock (talk) 08:47, 19 July 2012 (UTC)[reply]
It's a DIY project. So far, maybe it needs a dedicated chip, to deal with the problems cited above, something like an arduino chip. OsmanRF34 (talk) 16:22, 19 July 2012 (UTC)[reply]
Obviously. Details, man! How'd you know it was a bird? Did you see it? Was the sound angry-cat-like, angry-Ferrari-like, angry-boy-pretending-to-be-an-airplane-like? Fast? Loud? Soft? Repeated how many times? It could be anything from Yellow-headed Blackbirds (sounds like rusty hinges interspersed with plaintive nggrrraooows), any birds-of-prey (which though distinctive, can sound like an angry cat at lower pitches), other mimics like magpies (which like mockingbirds and catbirds can sound like anything they want to sound like), or even squirrels (which do meow like cats apparently, here's an angrier mrrao-ing one).-- OBSIDIAN†SOUL04:25, 19 July 2012 (UTC)[reply]
Radio comedy live audience
I was in the audience of the recording of a BBC radio comedy the other day. Musing about it since I was wondering whether the left channel of audience noise was the audience's left or stage left (actor's left, audience's right)? 10.64.0.169 (talk) 18:55, 18 July 2012 (UTC)[reply]
Call the show's producer's office and ask for the sound stage technician. It might not be something they try to keep constant all the time. 75.166.200.250 (talk) 20:24, 18 July 2012 (UTC)[reply]
Ideally, since when you view it at home, you "become" the audience, then they should have the left channel be audience left. That way, if an actor looked to the left (or on radio, said "Hey, you on the left in the funny hat...") and asked somebody on the left side of the audience a question, the answer would seem to come from the correct place. However, in shows where there's no interaction with the audience, it wouldn't much matter. StuRat (talk) 20:39, 18 July 2012 (UTC)[reply]
The host often introduces people saying where they are seated ("On my left, we have XYZ, and on my right, we have ABC."). I would expect the stereo to be set up in such a way as those directions make sense (with the listener in the audience's position, I agree). --Tango (talk) 03:48, 19 July 2012 (UTC)[reply]
London Weather
My friend said she heard on the radio that the UK was doing something to the atmosphere, like sending dry ice up on weather balloons, to force the jet stream to move so there would be "good" weather for the London Olympics. Is this true? 5.48.60.180 (talk) 23:07, 18 July 2012 (UTC)[reply]
Dry ice wouldn't move the jet stream, but, what it could do is seed clouds to make it rain. Obviously they don't want rain at the Olympics, therefore they would do this some distance away, so that clouds headed for the Olympic venues would be all "rained out" by the time they arrived. StuRat (talk) 23:10, 18 July 2012 (UTC)[reply]
Is "the UK was doing something to the atmosphere, like sending dry ice up on weather balloons, to force the jet stream to move"? No. As for the link to our weather modification article, the section in question relates to attempts to weaken tropical cyclones - and we don't get many of them in London. AndyTheGrump (talk) 23:21, 18 July 2012 (UTC)[reply]
Note that as our article and the source it links to mentions, China claimed to be doing that during the last Olympics. However they have extensive involvement in the field of weather modification, including a Beijing Weather Modification Office and according to various sources something like '$100 million a year and employs 50,000 for rainmaking; 6,781 artillery guns and 4,110 rocket launchers; 30 aircraft'. While they normally try Cloud seeding to encourage rain over areas of drought etc, the method they tried to use during the olympics was fairly similar but as StuRat suggested the attempt was to get it to rain in areas away from the olympics [22][23]. Our cloud seeding article and the earlier linked source also suggests they tried or were going to try to get it to rain before the olympics to help clear pollution.
As our article implies, whether their effors actually did anything useful is in much debate, as I understand it the field of weather modification is a controversial one with limited science backing up the claims of success (given our current limited ability to predict the weather, you can't know what would have happened if you didn't do anything so the only real way you can test your claims is by randomly choosing when to attempt modification and then carrying out statistical analysis to see if there's any evidence of a change but given how variable the weather is, you really need quite a long term project). Note that in one of the sources, even one of the key players from China said it wouldn't help much with big rain clouds, only small ones.
I somewhat doubt the UK will be attempting the same thing, not just because AFAIK they lack any real infrastructure (I mean they could easily adapt what they have but they'd still need to do more work then a country which already does it a lot), but as I understand it in most developed Western countries weather modification attempts are only generally done for research purposes (although not surprisingly I think a lot of research comes from China although some may question the quality of some of the journals it's published in which I believe includes ones from China) given the perceived lack of any scientific evidence of success (although our article suggests there may be some done for non research purposes in the US and Austria). As our article suggests weather modification attempts are also sometimes carried out in other parts of Asia where they either don't agree with the lack of evidence or don't care so much.
But for a simple answer, it happens when the image is made of tiny dots, and the dot spacing for the image does not match the dot spacing for the scanner. Looie496 (talk) 17:37, 19 July 2012 (UTC)[reply]
To what extent are astronomical observations automated ?
For example, if one of our large telescopes is pointed at some spot in space, and there's a point of light there not in any previous observations, does a human have to spot it, or would it be spotted by software comparing with previous observations ? StuRat (talk) 03:47, 19 July 2012 (UTC)[reply]
It depends on what the goal of the observations is. There are projects that look for transient or variable objects (e.g. Supernova Cosmology Project, OGLE), and those apply automatic algorithms to their data to detect variability or "new" objects. In general, survey telescopes such as Large Synoptic Survey Telescope, that revisit the same part of the sky repeatedly, state the search for transient objects as one of their scientific goals and will run those algorithms on their data. On the other hand, data from "visitor telescopes" (like the Very Large Telescope) where astronomers propose observations for a specific scientific purpose are not routinely screened for transient objects (most of the time there will be no other observations of the same field of comparable quality), and it will be luck if an astronomer spots something they haven't looked for. --Wrongfilter (talk) 08:57, 19 July 2012 (UTC)[reply]
(ec) Astronomers usually agree to share their observations with the observatory where they make them. Many of the large observatories have standardized processing steps that they perform when they add new observations to their archive libraries. However, a new point of light isn't typically going to flag an image for review unless spectral characteristics are being measured and it doesn't look like something common such as a asteroid or artificial satellite. A missing object or significantly changed brightness in an expected point of light is another matter entirely, and is more likely to flag the observation for review. 75.166.200.250 (talk) 09:03, 19 July 2012 (UTC)[reply]
Considering that those new points of light could be a meteor headed for Earth or something else important, it's a shame they can be tracked from 1st discovery. You'd think they could be compared against an artificial satellite database to eliminate that possibility. StuRat (talk) 09:35, 19 July 2012 (UTC)[reply]
There areautomated, specialized meteor-scanning telescopes plugged into computers. But not every telescope result is checked for meteors — the odds are super low and the number of false-positives would make such a system prohibitive, and many of them are not looking at the sky in ways that would even spot a meteor. I think you are underestimating the amount of astronomical data that is generated, as well. --Mr.98 (talk) 11:49, 19 July 2012 (UTC)[reply]
Is the amount of data collected from large telescopes just too large for all our computers to process ? If so, it sounds like we need to build up our computing capacity, maybe in the same way as SETI@home does (using volunteers' home computers). StuRat (talk) 18:34, 19 July 2012 (UTC)[reply]
Gluconeogenesis image review
Could someone please check commons:image:Gluconeogenesis_pathway.png please? The final product (top) purports to be glucose (in its pyran form), but is missing the methylol(?) group. This make me question if there are other mistakes in it. One of the previous steps is a furan ring with two methylol groups, so its unlikely the target is a pentose. TIA, CS Miller (talk) 05:39, 19 July 2012 (UTC)[reply]
Another interesting aspect is the so-called "wind-up problem" of the spiral arms. If the inner parts of the arms rotate faster than the outer part, then the galaxy will wind up so much that the spiral structure will be thinned out. But this is not what is observed in spiral galaxies; instead, astronomers propose that the spiral pattern is a density wave emanating from the Galactic Center. This can be likened to a moving traffic jam on a highway—the cars are all moving, but there is always a region of slow-moving cars. This model also agrees with enhanced star formation in or near spiral arms; the compressional waves increase the density of molecular hydrogen and protostars form as a result.
So, how do these density waves manifest themselves ?
1) Do some arms fade away while other arms appear ?
2) Or is it that when they give the variable rotation speed of the inside and outside of the arms, what they really mean is the stars within the arms, but that, as new stars are created and old stars die, the actual location of the arms move relative to the stars, so that the arms really have constant rotation ?
The stars move at (roughly) constant speed (in km/s), the waves move at constant angular speed; their motion is essentially independent. Individual stars pass through the waves in the same way that water molecules pass through water waves (or the other way round - water molecules oscillate around a fixed position while the wave passes through). Unfortunately, we can only measure the motion of stars and gas clouds in galaxies, not the motion of the arms/density waves. --Wrongfilter (talk) 08:47, 19 July 2012 (UTC)[reply]
But the part I don't understand is how the stars and waves can move independently, if the waves are composed of stars. Are the stars inside a "crest" just pushed closer together as the wave passes ? Are the stars brighter while it passes ? StuRat (talk) 09:30, 19 July 2012 (UTC)[reply]
That's not specific to stars and galaxies at all, and a partial explanation is contained in Wrongfilter's reference to water waves. Generally speaking, when a wave propagates through a medium, it does not do so by moving all the medium with it, but by vibrating the medium. To take a more obvious example: vibrations move through the strings of a stringed instrument without the entire string moving. If I grab a loose garden hose and waggle one end, the entire hose can adopt a wave-shape without the end running away from me. So with water, the body of water doesn't move as a whole when the waves move - or the tide would come in vastly faster than it does. And with stars - although the forces holding them together are gravitational rather than electrostatic - the same principle applies.
So, in that case, the wave must slow the stars at the leading edge and speed up the stars at the trailing edge, to force them closer together ? StuRat (talk) 09:38, 19 July 2012 (UTC)[reply]
FOLLOW_UP Q'S:
1) Why aren't pressure waves originating from the galactic core manifested as circular waves moving out from the core ? What gives them their spiral form ?
I really need to read up on this (it's not trivial), but I just point out that the waves in galactic discs are density waves, not pressure waves. The spiral pattern, i.e. the density pattern arises from the superposition of the stars' orbits, although the gravitational attraction also plays a role. It's a collective phenomenon in a non-collisional self-graviatating system, as is the bar. --Wrongfilter (talk) 10:55, 19 July 2012 (UTC)[reply]
Here's my casual explanation, no doubt wrong:
Galaxies have a core, which contains sites where stars are formed, at least some of which for some reason then travel away from the core.
They travel at different speeds, causing clusters. The clusters still move away from the core. This is like a series of small, non-stationary traffic jams.
Galaxies rotate.
Consider a long straight single-lane north-south road, with clusters of traffic on it. The traffic all emanates from a building in the middle point of the road, half going north, half going south. Rotate the entire road around this building, and the cars will form a spiral pattern (as the slower moving ones, and the ones stuck behind them, are left behind, falling off the rotating road, to form trails).
Yeah, I'm pretty sure that is wrong. Stars orbit the centre - they tend to stay at a roughly constant distance. There will be some stars moving outwards or inwards (mostly due to close interactions with other stars), but I doubt there are enough of those for it to be a significant effect. I'm almost certain it won't be a large enough effect to cause the spiral arms. --Tango (talk) 16:36, 19 July 2012 (UTC)[reply]
Yes, that makes some sense, but can those spirals create more than 2 arms ? I'd like to create some animations of this illustration and one with multiple arms, if I can figure out how the multiple arms case works in this model. StuRat (talk) 18:29, 19 July 2012 (UTC)[reply]
There is little discrepancy between theory and observations as far as galaxy rotation curve is concerned as long as that theory includes dark matter (which it should). Dauto (talk) 02:46, 20 July 2012 (UTC)[reply]
But dark matter fits solidly within the category of "not as well understood as one might expect". Without a clear-cut understanding of what exactly dark matter is, direct (as opposed to gravitational) evidence for its existence, or experimental evidence that would clearly rule out the alternative theories that compete with dark matter, dark matter currently isn't much more than a fudge factor that describes the discrepancy between observation and what the theoretical results would be without dark matter thrown in. That may well change if some good experimental evidence about dark matter starts coming in over the next decades, but at the moment, dark matter isn't a very satisfying explanation. Red Act (talk) 04:21, 20 July 2012 (UTC)[reply]
StuRat, perhaps you have figured it out already from the various links, but the density wave is principally a property of the galactic gas. We think of the interstellar medium as empty, but it is filled everywhere with diffuse gas. Though almost empty, waves can propagate through that gas provided that the waves are large enough (in this case on the scale of a whole galaxy). As the wave compresses the gas, that perturbation provides just enough impulse to trigger star formation in gas clouds that were already on the brink of collapsing. This means that the passage of the density wave is marked by a surge of young stars. It is those new stars, many bright and large, that make the spiral arms stand out visually. The stars, once formed, follow elliptical paths and are hardly affected by the density wave at all. However, many of the brightest stars are so big that they live short lives (only ten million years, for example), so they die out quickly compared to the travel time of the density wave. Hence the spaces far from the front of star formation appear darker. So yes, the arm positions (really a front of star formation) is moving relative to the actual stars. Dragons flight (talk) 19:23, 20 July 2012 (UTC)[reply]
I was wondering how much rechargeable li-ion battery cost per kWh. To grab very rough estimate I gone ebay and searched for different types of li-ion batteries there. To my huge surprise, it seems that 18650 form factor cells are most cost effective... And 10 batteries 3800mAh each 3.7V cost $14.94 with free shipping...
My question, if advertised characteristics reflect real performance, that translates for 140.6 Wh for $14.95, or ~$107 per kWh. My calculations correct? Or have I made a mistake?
And second question, how likely that such lots(not only on ebay, but alibaba etc) reflect the cost of production of 1 kWh rechargeable li-ion battery selling for around $100 and still making profits? Or such batteries are left overs from bigger orders or even flawed cells that haven't passed quality control, and thus price of them do not really reflect cost of kWh...
Um, don't ever trust mAh ratings from eBay. Given the price, you'd probably be lucky if the cells even have half the capacity [24]. I believe the real high end 18650 cells from Panasonic etc tend to be around 3100mAh [25][26][27]. From what I've read, cells with Xfire labels can vary from reclaimed battery pack cells to those that didn't make the grade for a battery pack. (You can get okay ones but you need to do a bit of research and ensure it's a supplier you can trust.) In any case, I wouldn't read too much in to the price, but it sounds like you should be more interested in the wholesale price anyway not the price from random eBay sellers who stick random labels on them. P.S. I'm pretty sure your calculation can at best be called simplified since you didn't take in to account the actual discharge curve for your cell which will depend on discharge current and to a smaller extent what voltage you stop at. Nil Einne (talk) 17:48, 19 July 2012 (UTC)[reply]
''it sounds like you should be more interested in the wholesale price anyway'' Yes, this is what I'm really interested to figure out. But not GM/Nissan/Ford claimed price of li-ion battery packs, but cheap modern li-ion chemistries produced out there(in China?) and wholesale price per kWh they are selling for... 70.49.169.86 (talk) 18:09, 19 July 2012 (UTC)[reply]
My point is the correlation between the price you pay retail for individual cells and the wholesale price is weak at best. Particularly in a case like this where the cheap retail options are of unknown heritage with random labels and the wholesale price will depend greatly on things like what sort of supplier you're willing to trust (given the way things can go wrong with li-ion cells, although of course one cheapish seller may give you total crap which blow up regularly, another selling at the same price may give you decent quality cells most of the time) and capacity (choosing the highest capacity cells is probably not the cheapest option), not to mention the typical stuff like quantity. Your best bet is probably looking at something like Alibaba or one of the other China B2B sites out there for the sort of quantity ranges you're thinking out, but you'd also have to have some idea of what you're looking at which to be honest it sounds like you don't. You can also try asking suppliers since they don't always bother to properly specify. Of course it does depend somewhat on what level you're actually looking at, I would guess at a low level range like 10000 cells a year you may get an okay idea from such sites, but if you're thinking of 100k a month, probably not. It's not that this info is super secret, it's just that it's not out there on some internet site because that's not how people who actually make the decisions are going to look for it. And navigating the China market can be difficult, if you don't much experience, given the variety of problems there is like unreliable suppliers. I don't really get the relevence of GM/Nissan/Ford as I didn't mention them, despite the recent interest in electric cars and the fact some of them now use li-ion cells, I'm pretty sure they still only make up a tiny percentage of the market. Nil Einne (talk) 04:44, 20 July 2012 (UTC)[reply]
First of all thank you Nil for pointing out that 3700 mAh was totally unrealistic to expect from 18650 cell. That helped me a lot:) Yes, correlation between retail and wholesale prices is hard to estimate precisely. But it still better then nothing and lowerest retail price would give some idea about wholesale price level... I have mentioned GM/Nissan cuz price of battery packs of Leaf and Volt has been published ($375 and $550 per kWh 'IIRC'). And that theoretically should help estimate wholesale price of batteries... But automotive packs are something different then what I'm looking for(at least the way GM define it). I have got a two question for you, Nil.
1) Wouldn't you think that LiFePO4 chemistry should be cheaper then bunch of 18650 cells with similar capacity?
2) Could you make an educated guess for me about a price of average capacity (2200 mAh?) 18650 cell. What would you consider cheap, but realistic and a good price for ~100k cells? Would you say that $1.50-$1.80 price range per cell is achievable? I know Tesla Motors was using hundred thirty one 18650 cells per kWh in their battery packs. So that translates into 7.6Wh per 18650 cell, should be a good estimate for price effective cell capacity I guess....
Thank you in advance, 70.49.169.86 (talk) 05:59, 20 July 2012 (UTC)PS. I have tried to use Alibaba even before I have asked question here, with very little luck. And really do not feel like approaching companies to get quotes...[reply]
To provide a quick source of food energy, which comes from the sugar
To rehydrate someone, due to sweating during exercise, this comes from the water
Sweating also contains a lot of salt, which needs to be replaced. If you drink too much water and not enough salt, you can get Hyponatremia, so the salt is there to keep the electrolytes in the body at the right concentration.
Water intoxication and hyponatremia are basically two sides to the same coin. Not exactly, but they are very closely related conditions: if you have too much water, it also means you don't have enough sodium. If the two are in correct relative balance, your kidneys should be working efficiently enough to keep things working well; that is for a properly balanced solution with the right amount of salt, it is hard to over-consume it: you'll just tend to piss a lot more. If you don't get enough salt, you'll experience the symptoms of water intoxication/hyponatremia. Too much salt or not enough water leads to dehydration and Hypernatremia. --Jayron3217:39, 19 July 2012 (UTC)[reply]
That's all correct, but my understanding is that there is also another factor: it is easier for the body to absorb fluids if they are approximately in osmotic balance with the bloodstream -- meaning that they have a comparable level of dissolved molecules, of whatever sort. Looie496 (talk) 18:00, 19 July 2012 (UTC)[reply]
The answers above are correct if you're talking about liquids consumed by professional athletes during strenuous training sessions. If you're talking about supermarket "energy drinks" consumed by non-athletes, the sugar and salt are there to make them taste good. -- BenRG (talk) 22:06, 19 July 2012 (UTC)[reply]
Yes, the answers above are for sports drinks, rather than energy drinks. Sports drinks are used by amateurs for the same reasons as professionals. Energy drinks are a completely separate market (do they usually contain salt? They're mostly caffeine and sugar, I think). --Tango (talk) 00:37, 20 July 2012 (UTC)[reply]
This may be an ultra-dumb question even for me, but one thing about Gatorade is that it tastes a lot better when you've been exercising strenuously than if you just take it like you would soda pop. So, does that have to do with a stressed body "craving" what Gatorade contains? ←Baseball BugsWhat's up, Doc?carrots→ 04:08, 20 July 2012 (UTC)[reply]
I don't know what is in Gatorade, but I do know you lose the ability to taste salt when severely dehydrated, which makes oral rehydration solution taste a lot better (it tastes like sugar water, rather than sugar and salt water). If Gatorade contains quite a lot of salt, then it could be the same effect. --Tango (talk) 06:04, 20 July 2012 (UTC)[reply]
That's exactly it: the salt. But it isn't that severe dehydration makes you unable to taste salt, it's that moderate loss of salt via sweating makes salt taste better than it usually does. Looie496 (talk) 06:39, 20 July 2012 (UTC)[reply]
See Gravitational binding energy. If the kinetic energy of a body exceeds the gravitational energy holding it to another, it will be able to escape. If the kinetic energy of the object is less than the gravitational energy, it will eventually be "sucked in" to the other object. To answer your question meaningfully, which I take it to mean "how close must an Earth-sized object be to a Jupiter-sized object before it will be gravitationally bound to it" the answer is "it depends"; mostly on the relative motion of the two objects. The dynamics are very complex, and can't be answered without more information regarding the specific orientation and relative velocities of all objects involved. However, I wouldn't worry about it happening any day soon. The distance would be a LOT closer than they are now; Jupiter is 5 times as far from the Earth as the sun is at the closest it ever gets to the Earth, and it is only 0.001 times the mass of the Sun. Roughly speaking, that means that Jupiter should exert a gravitational influence over objects only 0.001 times as well as the Sun does, and the Earth falls well outside of that sphere. The earth does experience a tiny effect from Jupiter's gravity, but it isn't going to send us crashing into Jupiter. --Jayron3217:35, 19 July 2012 (UTC)[reply]
Hello. Two-cell (comprised of P1 and AB) embryos were incubated either in a translation inhibitor or in a transcription inhibitor. The AB cells were then isolated, washed, and grown in culture. AB cells of embryos treated with the translation inhibitor produced only neurons and skin, while AB cells of embryos treated with the transcription inhibitor also produced muscle–their normal fate. The direction of signalling is from P1 to AB. Why would the signalling interaction at the two-cell stage most likely involve proteins? If proteins are the product of transcription and translation, wouldn't the P1 cells of embryos treated with transcription inhibitor not produce mRNA and, as a result, proteins? This would block the signalling pathway, right? Thanks in advance. --Mayfare (talk) 19:56, 19 July 2012 (UTC)[reply]
Because the two cells are adjacent. Low molecular weight hormonal signaling paths are unnecessary under those conditions. Yes to your second and third questions. 75.166.200.250 (talk) 20:46, 19 July 2012 (UTC)[reply]
In most organisms, transcription is marginal or completely absent for the first several rounds of cell division after fertilization. In Drosophila melanogaster, for instance, this stage lasts for ~2 hours and 12-14 rounds of cell division. Virtually every mRNA found in very early embryos has actually been produced maternally. And so the transcription inhibitors would have no effect because transcription isn't even on, or is nearly irrelevant if it is. Translation, on the other hand, is quite active, working from the maternally provided mRNA. Someguy1221 (talk) 22:14, 19 July 2012 (UTC)[reply]
Equivalent Animal Processing Power of Modern Computers
Out of some recent boredom, I have been reading up on the computer vs. human brain speed dealie. Though I knew that there is no easy way to measure and compare the two, I was interested in some of the (questionable?) methods used to approximate the processing speed of human brains and that they were considered to be vastly superior to current technologies. I was wondering, then: what animal's mental "processing power" is closest to the fastest computer processor available to consumers today? Have we even gotten past ant? Thanks, Sazea (talk) 19:57, 19 July 2012 (UTC)[reply]
Well, my opinion is somewhat heretical here, but since I have a Ph.D. in neuroscience I can present myself as enough of an expert to express it: I believe that the computational power of brains is way overstated, and that at a practical level a human brain has capabilities comparable to a powerful modern desktop PC -- except in terms of memory access bandwidth, where the brain really stands out. The thing that really makes brains superior, I believe, is the vast amount of information about the world they take in during the process of development. Looie496 (talk) 20:17, 19 July 2012 (UTC)[reply]
I'm not sure why you ask that, but there is no doubt that digital computers differ from brains in a variety of important ways. They differ so much that it is hard to find a basis for comparison. In my view, the only proper way to do it is to ask how powerful a computer would be needed to do the same tasks that the human brain can do -- for example, to pass the Total Turing test. I think it is likely that modern PCs, augmented by a few special chips, are powerful enough to do it -- that the real difficulty is in programming them, not in making computers that are strong enough. Looie496 (talk) 20:40, 19 July 2012 (UTC)[reply]
I just heard somewhere that they are thinking of biological memory to get some of the advantages of animal brain material and the configuration was one of them. I also remember that if we can make a wire small enough to connect we may try programming animal neuron groups.--Canoe1967 (talk) 21:22, 19 July 2012 (UTC)[reply]
It's been quite some time since I worked through the calculation (calculating the rate at which information in the synaptic weight distribution generates information in the population firing pattern), but my recollection is that I could get a value on the order of 1 terabyte per second without making any assumptions that seemed unreasonable. Looie496 (talk) 03:04, 20 July 2012 (UTC)[reply]
I dunno, I see 264 GB/s and 2 x 192.256 GB/s for the desktop in those lists. What's the Moore's law for GPU bandwidth? That's only 2.6 times to 1 TB/s (wow, a TB/s, that's fast). Some people put 2 or 3 (4?) graphics cards in the same PC, right? We've already matched it on some PCs. With coolers for each card that can play top games at max settings on a 26, 36 inch or something screen that's like 4 HDTVs worth of pixels. There are supercomputers with 20 TB of RAM, they probably blow away human brains in terabytes/s. Sagittarian Milky Way (talk) 18:07, 20 July 2012 (UTC)[reply]
Looie, what are your views on whether brains can even be considered computable. I have read penrose's thoughts on this, but for some reason have completely forgotten the gist of his argument. Perhaps it unsettled me. EggCentric17:55, 20 July 2012 (UTC)[reply]
Well I rather (personally) hope quantum mechanics explains my self-evident consciousness (as I define it) although I can't possibly see how it could. Free will I see no reason to belive in tbh. EggCentric21:35, 20 July 2012 (UTC)[reply]
"Mr. De Villiers says if CANDESAL can produce water for less than $1 a cubic metre, the technology has great potential. "If their business plan is right, then they're onto something really big," he says." --Canoe1967 (talk) 23:49, 19 July 2012 (UTC)[reply]
You can easily compute this from first principles. It follows from the change in the Gibbs energy. Suppose you have seawater with a concentration of n ions per unit volume in it. You take a volume V from this seawater, which will contain N = V n ions. The Gibbs energy of N ions in a volume V of water is approximately given as
g = N k T Log[N/(V Z)] where Z is the single ion partition function. Then the initial state is the water of volume V with ions at concentration n, and the sea which has some huge volume V' with ions at concentration n. The Gibbs energy of the initial state is then
g1 = N k T Log[N/(V Z)] + M k T Log[M/(V'Z)]
We then remove all the ions from the water by dumping into the sea. The limit of N to zero of the first term is zero. The Gibbs energy is thus given by:
g2 = (M + N) k T Log{[M + N]/(V'Z)}
The maximum amount of work that can be extracted from this process is the drop in the Gibbs energy, g1 - g2. This will be negative, so it will require a minimum amount of work of g2 - g1 to get to the final state. We have:
g2 - g1 = (M + N) k T Log{[M + N]/(V'Z)} - N k T Log[N/(V Z)]
- M k T Log[M/(V'Z)]
We then want to take the limit of V' and M to infinity such that M/V' = n. We can simplify the first term:
(M + N) k T Log{[M + N]/(V'Z)} =
(M + N) k T Log(n/Z) + (M + N) k T Log(1 + N/M)
The first term of this cancels against the last two terms in the expression for g2-g1, we thus have:
g2 - g1 = (M + N) k T Log(1 + N/M)
For small x we have Log(1+x) = x - x^2/2 + ..., so the limit for M to infinity becomes:
g2 - g1 = N k T
Seawater contains 35 grams per liter of salt. Sodium chloride has a molecular weight of about 58.45 u, so 35 grams of salt contains 3.606*10^23 ions of sodium and 3.606*10^23 ions of chlorine. One liter of seawater thus contains 7.21*10^23 ions, 10^4 cubic metres contains 7.21*10^30 ions. If the temperature of seawater is 15°C, then g2-g1 = 2.87*10^10 Joules. Count Iblis (talk) 03:58, 20 July 2012 (UTC)[reply]
Looie probably forgot a factor of ten somewhere, the source he uses says "0.66 kcal / liter is the minimum energy required to desalination of one liter of seawater, regardless of the technology applied to the process.". If you use this then you get almost the same figure as I obtained (they use 33 g/L for the salt concentration and I took 35 g/L, if you correct for that, then the agreement become even better). Count Iblis (talk) 15:35, 20 July 2012 (UTC)[reply]
Hi. Recently, I became interested in the concept that some animals other than humans can "understand" music and appropriately respond to it. We all know that humans have a range of musical perception, interest and appreciation, and that other animals use music or music-like sounds as a form of communication. Also, there are videos on Internet of dog and cat dancing to music. Birds, on the other hand, use song that humans interpret as musical. Meanwhile, in the Chinese language there is a proverb that states "playing piano to an ox", suggesting perhaps that oxen do not understand music. In the extreme case, insect buzzing can also be music-like, but their brains are small. Finally, the clade of dinosauria may have used music[citation needed]. Dolphins and other cetaceans use human-understandble music, have the second-largest encephalization quotient in all of Animalia, and some evidence of human-cetacean communication is potentially documented. All of these are examples of anecdotal evidence. However, could there be an overlap between human and non-human music? More specifically:
What brain structures and patterns allow for the comprehension of music?
Which lead to a more interesting question:
Is there any corresponding resonance pattern between the types of music that a certain species "understands" and the more subconscious brainwave patterns such as delta, mu and theta?
Furthermore, this leads to an even more interesting question:
I recently came across the above-linked articles, and they may be relevant in answering the question, as I knew nothing about this topic beforehand. Thanks. ~AH1(discuss!)22:40, 19 July 2012 (UTC)[reply]
It is largely a collection of case histories, not a theoretical book. But yes, almost everything he writes is excellent, even his account of falling down a mountain. μηδείς (talk) 04:34, 20 July 2012 (UTC)[reply]
"Undertanding" music and enjoying it requires at fundamental level 3 things (1) a sense of timing, (2) a sense of pitch (ie frequency as it is called scientifically), and (3) able to sense and enjoy repetition. The are a number of subtleties, such as what pop music composers have called "ear grabber" notes (notes that are harmonically slightly out of place, or melody lines that sound exciting), but that's what it comes down to. A quite good explanation of music in terms of expliting these 3 aspects was published in a book on how to write pop songs by, of all people, Rolf Harris, about 40 years ago. You may be able to obtain a copy via your local library. Aspect (3) is of course short term memory. Aspect (2) is of general use to animals as it helps to recognise the sounds of prey and predators, and is vital to communication. Aspect (1) is of general use in communication and in understanding the behavior of prey and predators. The brain structures responsible for aspects 2 & 3 have not been pinned down precisely, but a multitude of texts have been published on it. Aspect 1 has until recently been pretty mysterious, however special "clock" neurons have been discovered through the brain. Scientific American and Scientific AmericanMind has carried articles about it in the last year or so. Given that enjoyment of music is based on such fundamental requirements of intelligence, it should not be a surprise that animals have some sense of music. Having said that, my experience in owning several dogs, from dumb breeds like spaniels, to highly intelligent breeds like german sheherds, is that our music is just noise to them. Wickwack124.178.34.188 (talk) 02:21, 20 July 2012 (UTC)[reply]
Do different languages have different IUPAC names?
Well, sorry for asking this silly question, but I would like to know it. I mean are they comparable to scientific binomial nomenclature of living organisms. Vanischenu mTalk16:58, 20 July 2012 (UTC)[reply]
Evaporating a liquid it is absorbing heat, but if you have just one liquid can you use it, evaporating a part of it, at a dissipator and freeze the same type of liquid in another closed chamber? Both parts are at the same temperature. OsmanRF34 (talk) 18:00, 20 July 2012 (UTC)[reply]
That's essentially how dry ice is made - they compress the CO2, so it becomes liquid, then release the pressure and some of it evaporates cooling the rest until it freezes (they aren't in separate chambers, though). --Tango (talk) 19:10, 20 July 2012 (UTC)[reply]
Yes. The difficulty is that, for most materials, the vapor pressure of the solid is very, very low, and the vapor pressure of the liquid falls quickly as you approach the freezing point. This means that evaporative cooling becomes less effective as you get close to freezing. 75.166 points out that you can get around this by manipulating the pressures in the two reservoirs, and Tango's example of dry ice works well because CO2 has substantial vapor pressure in the solid phase. This online Q&A [28] says that you can also freeze water in a single reservoir with a vacuum pump, and here's a video that does it: [29]. I believe it's not terribly efficient because of the low vapor pressure, but it's interesting to see that it can be done. --Amble (talk) 20:27, 20 July 2012 (UTC)[reply]
What would happen if a whale hit a deepwater petroleum pipe?
Maybe this could be figured out with the whale's mass, speed of swimming, tensile properties of the pipe and whale head compressive strength etc.? Generally mechanics and materials science. And what's the biggest species of whale in oil producing regions? (i.e. North Gulf of Mexico, North Sea, Persian Gulf etc.) Sagittarian Milky Way (talk) 18:22, 20 July 2012 (UTC)[reply]
If you have access, you can check out this article "Hydrodynamics of a ship/whale collision" [30]. Which covers a lot of the physics involved. "whale collision" returns many hits on google scholar. But none on the first few pages have anything to do with stationary objects. The paper linked above seems to say that ships pose a special challenge for whales, which are normally rather good at avoiding smashing into things. A more realistic risk to pipelines might be large schools of fish, squid, or jellies. SemanticMantis (talk) 18:32, 20 July 2012 (UTC)[reply]
Thermoelectric materials
I was wondering what the best thermoelectric materials (not for measuring temperature, but rather for generating electricity) are that one would find in a normal household, or could easily and fairly inexpensively obtain at local stores? I know that there are far better out there, but I am not so optimistic about finding Bismuth chalcogenides laying around in the back room. The only other thing that I am concerned about is that they can be safely handled by an inexperienced experimenter. Thanks! Falconusptc19:32, 20 July 2012 (UTC)[reply]
Solid state heat pumps are made from semiconductors. They are usually in modern CCD cameras, laser diodes, microprocessors, and the like, but I think you probably want to take the diodes out of something like a USB beverage cooler. 75.166.200.250 (talk) 22:10, 20 July 2012 (UTC)[reply]
Assuming you don't mean specifically manufacturered thermoelectric devices, such as the beer cooler mentioned by 75.166.200.250 (you did say materials), I don't think you will find anything much. A good thermolectric material combines a high barrier voltage with very low thermal conductivity. The Russians in the 1940's and 1950' made an extensive search for such a material - the best they could come up with is Bismuth Telluride, and even that isn't very good. Bismuth Telluride is what is used in beer coolers, but not because it is efficient, but because it means no moving parts and convenient to make in a size really too small for a compressor. There are two possibilities I can think of: Copper oxide (once used to make diodes), which you can easily make at home, and Russian "radio lamp" materials. I think copper oxide will be so poor you will only be able to measure temperature with it, and not generate usefull power. I will post the instructions for making a radio-lamp generator later, when I find the reference. Wickwack120.145.176.214 (talk) 01:43, 21 July 2012 (UTC)[reply]
What components of cigarettes keep weight down ?
First, I suppose I should ask if cigarette smokers weigh less, on average, than nonsmokers. If so, do we know why ? Is it the nicotine or the tar ? And what's the mechanism ? Is it that it retards the sense of smell, and thus the appetite ? StuRat (talk) 20:44, 20 July 2012 (UTC)[reply]
Nicotine is an appetite suppressant, probably because it's a stimulant.
I doubt it. There are plenty of other appetite suppressants you could use that don't have the same nasty side effects as nicotine. Appetite suppressants aren't usually prescribed at all, though - they just aren't that effective a way of losing weight (and they all have some kind of nasty side effects). I saw something in the news recently about the FDA approving a new appetite suppressant - it was newsworthy because its so rare. --Tango (talk) 21:20, 20 July 2012 (UTC)[reply]
What side effects does nicotine have other than addictiveness ? How are they worse than other appetite suppressant side effects ? StuRat (talk) 22:09, 20 July 2012 (UTC)[reply]
Is is possible to be a sociopath in a narrow area?
I am certainly not a sociopath in any classical sense, indeed if anything I am fairly sure for various reasons that I have considerably more empathy than most people. However, what I just can't do is get offended by anything. I intellectually understand what offends other people (learned, I think, from trial and error) but have no visceral response at all. What's up with that? EggCentric00:41, 21 July 2012 (UTC)[reply]
Addition: Sometimes I pretend to be offended just cause I have the sense I should be claiming to be, even though I'm not, and I still can't help but think that that is what everyone else is doing. Also sometimes I get angry with twats and express it as being offended, but only cause that seems to be socially acceptable thing to do, not cause I'm actually offended. EggCentric00:47, 21 July 2012 (UTC)[reply]
Nah, you're probably just INFP. Some day, someone will cross a line that you didn't know was there, and you'll be surprised by your own reaction. --Amble (talk) 00:59, 21 July 2012 (UTC)[reply]
Apart possibly from introversion, where I am probably an introvert in terms of intrinsic preference (in that I loves me some nerd time) but an extrovert by usual behaviour, I am basically the opposite on that scale, so I doubt it EggCentric01:35, 21 July 2012 (UTC)[reply]
Three unrelated points: A) As far as psychologists are concerned, there is only "sociopath" and "not a sociopath". While indeed you can fit some of the criteria and not others, there is no defined thing as "sociopath for some things but not others". B) That said, I have only known one other person who so adamantly insisted they never could not be offended. I later realized this insistence was a coping mechanism and they actually took offense quite easily, but hid it well; C) Are you sure that nothing offends you, or are you just talking about insults? Being able to be unbothered by someone's attempts to get a rise out of you makes you more enlightened than the average human being, in my opinion. What if it is something more extreme, like being formally and publicly accused of a wrongdoing you are not guilty of? Or something really extreme, like watching someone kill a baby? Truth be told, even if you could honestly say "not offended" to all of those, I would scream that you're a sociopath. Though if you want a formal diagnosis, you'll need to see a psychologist. Someguy1221 (talk) 01:00, 21 July 2012 (UTC)[reply]
It may be that we are using different definitions of offended. Of course I would not want to watch someone kill, or even torment a baby. There would certainly be a visceral response. But I couldn't characterise that response as offence, it would be more like horror. I am not unable to be insulted either in principle, but it would just make me angry or irritated. I am talking more about say sexism, racism, or whatever. EggCentric01:28, 21 July 2012 (UTC)[reply]
