Wikipedia:Reference desk/Archives/Science/2010 February 23

= February 23 =

Material in Servo Motor Winding?
Sir/Ma'am

I am looking for the material used in servo motor coil winding. Thanks
 * Copper? Noodle snacks (talk) 07:16, 23 February 2010 (UTC)


 * And insulator (electrical). Icek (talk) 11:01, 23 February 2010 (UTC)


 * All these: enameled copper wire, Solder, Insulator (electrical), see Electric motor Cuddlyable3 (talk) 14:54, 23 February 2010 (UTC)

Making tea with zingless water
If I boil water in order to make some tea, then get sidetracked for 30 minutes before I've poured it, I have 2 choices:
 * reboil the by now tepid water and then use it
 * start again with a fresh batch of cold water.

But I've always been told NOT to reboil the water, as it's lost its "zing" through the initial boiling. Always start from scratch with new water, is what I've been told to do.

For starters, how true is it about the "zing" thing? If it's true, doesn't that mean that no cup of tea ever has any "zing", because all tea uses boiled water, and boiled water is, according to this theory, zingless?

Assuming that it's true: Does it ever regain its "zing" by somehow reabsorbing oxygen from the atmosphere, and if so, how long does it take? --  Jack of Oz    ... speak! ...   10:49, 23 February 2010 (UTC)


 * Personally I doubt all this very much. I'm in the habit of filling a kettle first thing in the morning, boiling it, and reboiling it for the subsequent cups of the day, and never notice any difference in the flavour of the tea whatever. Old wives tale if you ask me. --TammyMoet (talk) 11:36, 23 February 2010 (UTC)
 * Not that it's pertinent to my question, Tammy, but doesn't your practice mean that you're always boiling more water than you need (until you get down to the last cup/potful in the kettle), and thus wasting both time and electricity? and money?  --   Jack of Oz    ... speak! ...   20:24, 23 February 2010 (UTC)

Might be something to do with boiling away impurities? We have quite hard water here with lots of lime in it, and other things, and boiled then cooled water does taste different than water straight out of the tap. Gunrun (talk) 11:59, 23 February 2010 (UTC)
 * Lime and other minerals don't get boiled away. They are what's left after the water boils away. Possibly you could boil away the chlorine and byproducts if your water is treated with such. But the usually mentioned difference is oxygen (not that I know if there is any truth to oxygen changing the taste.) Rmhermen (talk) 14:29, 23 February 2010 (UTC)

Interesting. Health advice for parents of young children drinking baby formula in the UK commonly includes the advice to boil the water once only before using it to make up formula. I've often wondered what it is that they're worried about in reboiling. --Dweller (talk) 12:31, 23 February 2010 (UTC)


 * I was told that the more the water boils, the more oxygen it loses, and the flavour of the tea depends on interaction with that oxygen. However, I haven't been able to find a reliable source for that.--Shantavira|feed me 13:47, 23 February 2010 (UTC)


 * @Dweller - I think there's either some miscommunication or a bit of social engineering going on. The worry with formula is that parents will boil the formula, which breaks down some of the nutrients. Liquid formula should be heated by placing it in an indirect heat source like a pot of heated water rather than in a microwave or on a stove top. With dried formula, I think the concern is that parents will do up a large batch (properly) and then directly reheat the formula as needed through the day, causing the same problem. If you were to essentially do the operation "in parallel" (mix formula and multiple-times re-heated water in a cup as needed, rather than re-using a pot of re-hydrated formula "in series") there would be no problem. Matt Deres (talk) 15:30, 23 February 2010 (UTC)
 * We had these permanent, continuous boiling water urns at our office which just automatically topped the water up as you used it and kept it relatively close to boiling all the time. Never heard anyone complain about lack of zing. They were never turned off, so in the morning you'd be drinking water that has been boiled several times over night. As far as I have seen those kind of urns are not uncommon. If that means anything.. Vespine (talk) 01:11, 24 February 2010 (UTC)

As far as I know, there are two things one might worry about regarding reboiling of water for drinking. Both has to do with potentially harmful trace amounts of pollutants: One such cup of tea will not kill you, but some people find it to be worth the effort, in the long run, to make it a habbit not to reboil water for consumption.For many people, this above explanation is far to tiring. The "Zing"-explanation is much quicker and since many people actually do keep on doing what their knowledgeable (great great) grandmother once stated was the right thing to do, then the zing explanation may be the best one after all. --Seren-dipper (talk) 04:43, 24 February 2010 (UTC)
 * 1) Plain tap water is far from chemically pure. Many of the pollutants in it, have a boiling point higher than the H2O (pure water). Therefore: The longer total time you boil polluted tap water, and the longer total time you keep it steaming hot, then the higher concentration of pollutants you get. (Because some of the water evaporates while pollutants remains in your boiling pot).
 * 2) Hot water dissolves pollutants far more easily than cold water does, and the longer time hot or boiling water stays in direct contact with a material the more of the material will be dissolved. Something from the plastic or metal (alloy) in your boiling pot is quite likely to give off trace amounts to your water. And that may bee something that you would be better off not swallowing to much of in the long run.
 * That makes a fair amount of sense, Seren-dipper. --   Jack of Oz    ... speak! ...   12:52, 24 February 2010 (UTC)

I don't have specific scientific evidence but I buy into the theory that brewing good tasting tea requires oxidation, and if the water sits stagnant for too long (such as during successive boilings) it will lose it's oxygen content and the resulting tea will not have as much flavor. Other brewed beverages such as coffee rely on similar processes, however it is up to the raw material (The tea or coffee used) to be susceptible to oxidation during brewing in the first place, so not all teas/coffees will show a change in flavor by changing the oxygen content of the water. --144.191.148.3 (talk) 14:38, 24 February 2010 (UTC)

I've been unable to find the solubility of oxygen in water at temperatures above 50 degrees C. But I feel that since oxygen redissolves quite quickly in water; and convection currents mixing the surface layes would make equilibrium happen even faster. If someone thinks there is a difference in tea flavour due to oxygen concentration they can put a lid on the cup or put immediately after pouring and see what changes. Polypipe Wrangler (talk) 12:51, 28 February 2010 (UTC)

Ice on car Windscreens.
Its cold in the UK and I find ice forming on my car windscreen but not on any other windows of my car. I looked at other cars as I was driving to work and this seems to be the case on most of them. Why is the ice only forming on the windscreen and not on the other windows? --Cipher-xs (talk) 11:33, 23 February 2010 (UTC)


 * The windscreen usually is the window facing more empty sky than the other windows. The sky serves as an infrared radiation sink. The other windows's loss of heat by radiation is compensated by reception of infrared from the surroundings. Note that this only happens on cloudless, still nights, as clouds radiate back, and wind tends to enhance the heat loss compensation by convection. DVdm (talk) 11:39, 23 February 2010 (UTC)
 * Is there not also a precipitation of water from the air, which tends to fall and thus coats glass in proportion to the surface it presents when seen in plan view? --Tagishsimon (talk) 12:26, 23 February 2010 (UTC)
 * Probably, yes. Hadn't thought of that one. DVdm (talk) 12:59, 23 February 2010 (UTC)
 * There are at least two types of ice commonly called frost. The first is the kind described in the frost article (which itself is two types - convective and radiative), the second is (sadly a redlink) what I have heard called frozen dew. The first is where a surface gets cold enough to freeze water out of the air, the second is where a dew forms and then the temperature drops enough to freeze it. In the first case your windscreen cops the worst of it because it faces the cold sky (as DVdm said). In the second your windscreen cops the worst of it, but rooves, boots (trunks) and bonnets (hoods) also get a pretty white coat --Polysylabic Pseudonym (talk) 08:07, 26 February 2010 (UTC).

Orbits
I know that most of (Pluto isn't a planet anymore I forgot) the planets in our solar system orbit on the same plain, and orbit in the same direction, because of how our solarsystem was formed or something? Anyway not my question. My question is would this happen naturally anyway? My friend says that if we were to introduce a new planet to the system it would eventually level into the same plane as the other planets, regardless of where you placed it (Obviously giving it enough velocity to orbit the sun), whereas I can't see why it would. Why couldn't a planet orbit the sun at a 90 degree angle to everything else. Also is there any reason why a planet couldn't orbit in the opposite direction of the other planets? Gunrun (talk) 11:57, 23 February 2010 (UTC)


 * He might be thinking of Accretion disc where a circular cloud form into a pancake-flat disk by conservation of angular momentum when some material fall into the center and become the star. This explains why all "original" planets orbit in the same direction, they were formed from the same pancake.
 * I can't see how what your friend proposes could happen for a new planet at a steep angle to the rest. But the conservation of angular momentum means that if the new planet gradually "falls into place", it aquires angular momentum in the solar system and therefore other planets must loose it. At the same time, the total kinetic energy must be conserved too. I can't see how this should happen, so I'm guessing your friend is wrong. :-/ —Preceding unsigned comment added by EverGreg (talk • contribs) 12:50, 23 February 2010 (UTC)


 * Yeah - I think it would happen, although it would take a very long time - and Pluto has not yet done that...further evidence that it was not formed like the other large bodies in the solar system.  Let's imagine an object orbiting in a plane that's (say) 30 degrees from the ecliptic - for half of each orbit it's on one side of the ecliptic, for the other half, it's on the other side.  The gravitational fields of every single other body in the solar system are exerting a force on that object.  The vector sum of all of those forces is overwhelmingly towards the sun (which is why the object is orbitting) - but the other planets are each creating an additional very tiny pull - which can be resolved into a net force parallel to the ecliptic and another at right angles to the ecliptic.  The 'parallel' force will vary as the various planets, moons and other debris go around their orbits and seem more or less random (although dominated by wherever Jupiter happens to be).  But the force at right angles to the ecliptic is ALWAYS in the direction of the ecliptic.  When the object is below the ecliptic, this net force is always in the upwards direction, when it's above the ecliptic, the force is down.  This means that the orbit is going to gradually be pulled around until it's in the same plane as everything else.   You can see this kind of effect happening in (for example) Saturns rings.  When two house-sized chunks of ice smack into each other, the fragments will scatter off in all directions - if it were not for this kind of effect, the rings would quickly break up and turn into a random spherical shell of chaotic colliding debris - but their relative gravitation forces them all into an almost perfectly flat, insanely thin disk.  That's likely why galaxies are pretty flat too.  SteveBaker (talk) 13:50, 23 February 2010 (UTC)
 * When the planet is attracted to the ecliptic, it seems that the planet would oscillate around the ecliptic, not settling into it. The sum of kinetic and potential energy for the new planet would have to be conserved after all. EverGreg (talk) 14:08, 23 February 2010 (UTC)
 * Well, conservation is managed because the other planets (etc) get pulled slightly towards the plane of this rogue body - so the entire plane of the ecliptic tilts slightly in reaction to this new body. However, unless the new body is utterly gigantic, that effect would probably be too small to measure. SteveBaker (talk) 21:21, 23 February 2010 (UTC)

Thanks steve,think that answers my first question pretty well. Does this mean if you had a planet orbiting in the other direction to the others (say they go clockwise this one goes counterclockwise) it would eventually get slowed down and thus move closer to the sun (Like how a space station de-orbits) presumably bringing it onto a collision course with a planet coming the other direction, or would such a planet be impossible?) Gunrun (talk) 13:57, 23 February 2010 (UTC)


 * Yes to this new hypothetical question that doesn't explain where the rogue planet came from. Eventually all the established planets would orbit very slightly slower but we can't predict whether the rogue planet collides with a planet before it crashes and burns in the Sun. Cuddlyable3 (talk) 14:40, 23 February 2010 (UTC)


 * Didn't you mean "would orbit very slightly more slowly", Cuddly? (Sorry, couldn't resist).  :)  --   Jack of Oz    ... speak! ...   20:35, 23 February 2010 (UTC)


 * So in an act of pure malice after being downgraded to a mere dwarf planet, Pluto wreaks revenge by smacking into the Earth in a few billion years? SteveBaker (talk) 21:24, 23 February 2010 (UTC)
 * hey, wouldn't you? heaven hath no fury like a planet scorned...-- Ludwigs 2  21:29, 23 February 2010 (UTC)
 * ...a dwarf planet scorned... :-) SteveBaker (talk) 04:05, 25 February 2010 (UTC)
 * If it would just ditch Charon, It would be back to planet status. Googlemeister (talk) 21:42, 23 February 2010 (UTC)

freezing point
What is the freezing point of 80 proof alcoholic beverages?

Thank you.

Ken Carter —Preceding unsigned comment added by 97.91.189.14 (talk) 15:28, 23 February 2010 (UTC) Sorry I can't help but I removed your email, in accordance with our guidelines and to avoid you getting spam. --TammyMoet (talk) 15:39, 23 February 2010 (UTC)


 * This site suggests -23 &deg;C (-10 &deg;F) for a 40% ethanol solution (which equals 80 proof); however this site suggests -33C for 84 proof. Vodka is essentially diluted ethanol, so it should freeze at that temperature, as will most other spirits. Other alcoholic beverages (like Southern Comfort) may contain significant amount of sugars that may affect the freezing temperature. Regardless, it won't freeze in a household freezer. -- Flyguy649 talk 16:53, 23 February 2010 (UTC)
 * One thing I have heard (and this is unsourced), is that if you start to freeze vodka, small ice crystals will begin to form. These crystals are mostly water, so if you remove them, you increase the proof.  Googlemeister (talk) 17:43, 23 February 2010 (UTC)
 * See Fractional freezing. -- Flyguy649 talk 18:04, 23 February 2010 (UTC)

liver
pls can you help me to answer this question how can diesel affect the liver of a male wistar pls this is a project work —Preceding unsigned comment added by 41.204.224.39 (talk) 15:48, 23 February 2010 (UTC)
 * First have a look at the effects of diesel on wistar rats in general. Then as a followup, take a look at this research report, for example, which discusses other systemic effects, including the liver.  You might be interested to know that Google Scholar is available to help you find specific scientific publications.  I just searched for "wistar diesel liver" and found a huge quantity of interesting results.  If you know what you're looking for specifically, you can narrow down the search.  Nimur (talk) 16:43, 23 February 2010 (UTC)

Octanediol
What is it and what are its uses? --Reticuli88 (talk) 16:04, 23 February 2010 (UTC)

oh, is the same thing as Octane-1,8-diol? --Reticuli88 (talk) 16:05, 23 February 2010 (UTC)
 * "Octanediol" is a somewhat generic name. It probably has an implied meaning of one specific chemical (or group of them) in some contexts. The "1,8" is one specific chemical of this type ("diol" is "two OH groups", the "1,8" says there is one of them on each end of the chain rather than scattered along the middle). DMacks (talk) 16:34, 23 February 2010 (UTC)

Do you know which brands contain Octane-1,8-diol as descibed in the article? --Reticuli88 (talk) 16:38, 23 February 2010 (UTC)
 * Fisher Scientific sells many types, each specified with a full IUPAC name. They do carry 1,8-octanediol.  Nimur (talk) 16:47, 23 February 2010 (UTC)

LOGIC GATES
Q1 Explain factors to be considered when constructing logic gates? Q2 Explain the positive as well as negative logic? Q3 Explain Digital Families and their characteristics? —Preceding unsigned comment added by Jyoti.prakash1507 (talk • contribs) 17:46, 23 February 2010 (UTC)
 * Read the article Logic gate. I have a feeling that you will also find Binary numeral system interesting. However we shall not do your homework for you. Cuddlyable3 (talk) 18:19, 23 February 2010 (UTC)

Agni III
Why does not the Agni III burn when it reenter in the atmoshphere. —Preceding unsigned comment added by 58.68.8.189 (talk) 17:49, 23 February 2010 (UTC)


 * I'm not sure about the Agni III in particular, but our atmospheric reentry article discusses a variety of techniques for engineering vehicles to survive reentry. -- Coneslayer (talk) 17:54, 23 February 2010 (UTC)

time dilation?
Does time really move fast near to gravitational field and slow when at far from gravitational field? I feel that though time is considered as the fourth dimension but still it is virtual in concept. So when we say that time moves fast or slow i think we take into account relative time (with respect to something) and not the absolute time. Though near Black hole time change is certain but still the absolute time(Universal Clock) has the same time. —Preceding unsigned comment added by Itsrohit (talk • contribs) 18:12, 23 February 2010 (UTC)


 * Yes. Time dilation is a real effect.
 * It has been verified with atomic clocks. See Time_dilation.
 * See also Effects_of_relativity_on_GPS
 * APL (talk) 18:58, 23 February 2010 (UTC)
 * Oh. To answer your second question : No, as far as we know there is no "universal time". Time itself runs differently for observers in different reference frames. There can be no "universal time" without an absolute reference frame, but there isn't one. See Special_relativity.
 * APL (talk) 19:02, 23 February 2010 (UTC)
 * (ec)Yes, the effect can be measured with real clocks, which of course don't care about theories or dimensions. Also note that there nothing virtual about time. Time is just what we read on clocks, which is the reason why a concept like absolute time is as meaningless as a concept like, say, blue time. DVdm (talk) 19:06, 23 February 2010 (UTC)


 * Time is a completely variable thing. Because it's affected by both the speed you're moving and the force of gravity, as I type this email, the tips of my fingers are experiencing a very slightly different rate of time flow than the rest of my body because they are moving relative to it.  Time can be running at different rates at every point in the universe.  It's even more weird than that.  The entire concept of two events "happening at the same time" is utterly meaningless unless they are at the exact same point in space - and so is the concept of "Event A happened before Event B".  We can only use those relationships because we are all moving at very close to the same speed and in roughly the same gravitational field - and the differences in the rate of flow of time on "human scales" is so microscopically small that we can't tell that we have this rather deep misunderstanding of the way that the universe operates.  Even when we understand this intellectually - the "gut feel" that time stays very firmly nailed down is hard to shake. SteveBaker (talk) 20:51, 23 February 2010 (UTC)


 * "The future is already here - it is just unevenly distributed" - William Gibson -- Finlay McWalter • Talk 21:00, 23 February 2010 (UTC)


 * Don't go too far with the weirdness! "A before B" (or the reverse, as appropriate) is a perfectly valid, invariant relation for all events with timelike separation, which is quite the superset of "at the exact same point in space".  You get that some observers will say (in their coordinates) "A was before B" and others "B was before A" when the separation is spacelike.  --Tardis (talk) 21:21, 23 February 2010 (UTC)


 * Yeah - you're right that in a lot of cases it's OK to say that two events happened in a particular order - but not in all cases. Basically if the two events happen so close together time - but so far in space that light from one event has not yet had time to reach the place where the other event happens before it happens - then some observers may disagree about the order they happened in.  If there is time for light to travel between them then their order is well-determined for all observers. SteveBaker (talk) 21:39, 23 February 2010 (UTC)


 * One of Einstein's great observations—and most controversial statements, even in his own time—was that there is no way to possibly measure absolute time and thus it doesn't actually exist. (Or, put another way, it must thus be an inherently metaphysical concept, and not part of science.) He believed in local time—as did many other people at the time—but he was really the only one who threw out the concept of absolute or universal time as being superfluous and unwarranted. Over time scientists have come to go with Einstein's approach—simply because his definition of time does seem to work out, does produce the weird experimental effects he predicted it would, and does not seem to require an idea of absolute time to work. --Mr.98 (talk) 22:11, 23 February 2010 (UTC)

Do most people get enough vitamins and nutrients from their regular diet?
I've always been slightly suspicious of dietary supplements like multivitamins (I believe Sheldon from The Big Bang Theory once described them as things that "make your urine very expensive", which I thought was apt), so I figured that once and for all I'd read the damn wikipedia article and the arguments for and against it. The arguments against them in the article are a lot stronger than the arguments for them unless you're a post-menopausal woman or suffering from malnutrition (in which case you have bigger problems, I suppose). The pro-side is basically one paper, one editorial and one doctor, while the con-side is the NHS, HHS and the UK Food Standards Agency.

However, there was one argument that wasn't addressed that I'm very interested in: doesn't most people living in affluent countries pretty much get everything they need (in terms of vitamins and minerals and such) just from a regular diet, even a pretty unhealthy one? I mean, comparatively speaking, isn't a western diet is hugely diverse by historical standards? Look at a Big Mac: not the healthiest of meals, but it has salad, tomatoes, beef, bread, cheese and pickles in it. I mean, that's like an explosion in different varieties of nutrients! Compare that to a stone-age meal consisting of badly cooked mammoth and a few berries, and it's hard to see the case for modern people needing additional nutritional supplements.

Is my intuition correct? Surely there has to have been studies that look at the average persons diet and checked whether it matches up with the Recommended Daily Intake? Belisarius (talk) 18:28, 23 February 2010 (UTC)


 * I've heard the same thing, and I'd love to have a definitive understanding of how often people do or don't have aspects of malnutrition while on a typically Western diet. I certainly know of anecdotal cases of people in the modern world where supplements were important, but those generally involve restricted diets that wouldn't necessarily be called typical.  For examples, vegans often take supplements to deal with nutrient that can be hard to obtain from an all plant diet.  My mother does similar things to deal with restrictions caused by her food allergies.  And I once knew a grad student that was diagnosed with scurvy (lack of vitamin C).  It is very rare to see that kind of basic malnutrition in the USA, but it is still evidently possible to make such poor diet choices that one unwittingly misses out on basic nutrients.  So, I guess my point is that supplements do have uses, but I don't know how useful or not they are for the typical Westerner.  Dragons flight (talk) 19:00, 23 February 2010 (UTC)


 * Short answer: yes they do get enough vitamins. If they didn't they would be dead. But since 100% of people are alive, then by logical analysis, everyone gets enough vitamins. Maybe not -ideal-, but they seem to get by alright. Besides, a severe deficiency in any important materiel will result in particular cravings. Vranak (talk) 19:04, 23 February 2010 (UTC)
 * A lot of things have their effects over long periods of time and shorten your life. By your logic, smoking is perfectly safe. 92.29.57.43 (talk) 23:52, 23 February 2010 (UTC)
 * What a ridiculous answer. They aren't dead yet, so obviously everyone is in good health. That's just stupid. Also, the body may be smart about some things, but it isn't magic. It can only give you cravings for things it is internally set up to measure and understand, which isn't everything. Most Westerners do fine, but don't mistake that for saying proper nutrition isn't relevant to good quality of life. Worldwide, malnutrition still contributes to ~60% all deaths every year, mostly in the impoverished third world countries. Dragons flight (talk) 20:13, 23 February 2010 (UTC)


 * It's not the least bit stupid. Dead is dead is dead. But yes, your point is well-taken. I generally reserve my consideration for countries that don't suffer widespread famine. In fact I would submit that any nation where people starve to death is no nation at all. Vranak (talk) 20:40, 23 February 2010 (UTC)
 * Sure! Like Ireland in the mid-19th Century, or China during the Great Leap Forward.  Ireland and China weren't nations!  They were, um, these things ... where people of similar ethnic groups governed by the same people, um ... just happened to live ...  But definitely not "nations."63.17.65.39 (talk) 02:20, 24 February 2010 (UTC)
 * It is kind of stupid. Malnutrition is not the same thing as starvation. Plenty of people are malnourished in all nations. It is not an issue of "widespread famine"—there are plenty of places where a poor diet is common amongst huge sectors of the population, and the results of that are medically palpable (lowered IQs, shorter statures, etc.). Heck, even if you are extremely well-fed you can easily run afoul of malnutrition if you don't eat the right thing. I know of a guy who ate nothing but hot dogs and soda for an entire summer and got scurvy as a result. (Which was itself pretty stupid, but it illustrates the point well!) --Mr.98 (talk) 22:14, 23 February 2010 (UTC)
 * I know some purists will object, but you can prevent scurvy while on the hot dog diet simply by adding ketchup. Googlemeister (talk) 14:06, 24 February 2010 (UTC)
 * Alright, I see we are not on the same wavelength here. Vranak (talk) 01:03, 24 February 2010 (UTC)
 * Bluntly, Mr.98 is on the right one, and you're on the wrong one. "Not getting enough nutrients" is not remotely close to the same thing as "dead".
 * Just as an example, if I recall correctly, having inadequate serum levels of vitamin D means you're more likely to get cancer, or at least some kinds of cancer. Does everyone who doesn't get enough D, get cancer?  Certainly not.  But that doesn't mean you can be sanguine about D deficiency, even if you haven't yet gotten cancer.
 * Of course you don't want too much D either; it's a complicated question. --Trovatore (talk) 01:09, 24 February 2010 (UTC)
 * The only proof that someone did not definitively get enough nutrition is if they die. Otherwise they can make a recovery. So there is no absolute way of calling someone 'malnourished' because they may just pull through, and their deficiency was never really that critical, if it did not quite finish them off. Still, your objection is noted and respected. Vranak (talk) 02:01, 25 February 2010 (UTC)
 * So you're saying you don't mind getting cancer, heart disease, or high blood pressure from incorrect nutrition, provided there's no actual proof that that was the cause? --Trovatore (talk) 02:07, 25 February 2010 (UTC)
 * It has become abundantly clear to me that you lads are not interested in the truth, so I take my leave from this debate. Vranak (talk) 03:58, 25 February 2010 (UTC)
 * It's become abundantly clear that you're ignoring good answers. If someone has a deficiency of a certain vitamin, they become diseased. Disease does not equal death, it means that you're not at optimum efficiency and if you continue to degrade in health, you could die. Furthermore, there are not just two levels of well-being when it comes to vitamins. For example, someone who has a lack of vitamin C will get scurvy, but it doesn't mean they'll die from it. It means they'll become ill, and if they continually lack the vitamin in sufficient quantities over time, they'll die. However, if they get treatment, they'll live. If they get just under the bare minimum quantity of vitamin C, they can present with some symptoms of scurvy but not die. There's the proof that your theory is flawed. I can prove that the last person mentioned didn't get enough vitamin C because they presented with the symptoms, but they didn't die. Therefore, you can prove someone has a lack of nutrients even if they're not dead. Regards, --— Cyclonenim | Chat 18:14, 25 February 2010 (UTC)


 * You can see what percentage of the most commonly needed stuff is in your food because it's right there on the mandatory labelling - so you don't have to take our word for it...you can figure it out for yourself. But even the most dull and non-nutritious seeming breakfast cereal has something close to the recommended amount of just about everything (and that's not counting the milk you pour onto it - which, remember is sufficiently "well rounded" in nutrients to grow a tiny calf into a modest sized cow with no supplementation).  Since that's only the first meal of the day - it's pretty clear that you'd have to go out of your way to pick a sufficiently poor diet.  The exceptions (and they are important ones) are pregnant women (who will reduce the risk to the baby by taking some specialised supplements), nursing mothers, older people, people with dark skins who live in the extreme north or south of the planet, sick people, malnourished people and so forth.   But if you are in your prime and eating "normally" - you should be just fine without any kinds of special supplements whatever.  Like I said...check the product labelling and then you'll know for sure. SteveBaker (talk) 20:26, 23 February 2010 (UTC)
 * Well, the labeling is only for a fairly restricted group of nutrients &mdash; by no means everything that you might want more of (or, sometimes, less of). Most phytochemicals that aren't actual recognized vitamins, for example, don't get called out on the label, but your health is at more risk if you don't get enough of them.  I'm talking about things like soluble fiber, polyphenols, many many more.  Omega-3 fatty acids are another group of nutrients that many Westerners don't get enough of.  You don't have to be poor to be in this boat; it might be that you just don't particularly enjoy the foods that provide these nutrients.  The best solution to that is to recalibrate your food preferences, which is possible to some extent.  But if you absolutely can't, or refuse to, then supplementation may be an option.  --Trovatore (talk) 22:34, 23 February 2010 (UTC)


 * "Westerners"? If that means you consider Europe, Aus, NZ, etc to be homogenous with the USA then that is a mistake - we tend to eat different foods and have a different culture and conventions. 92.29.57.43 (talk) 23:47, 23 February 2010 (UTC)


 * You're right, it was a careless choice of words. I meant people in affluent countries, in countries where access to food isn't really a problem. Belisarius (talk) 00:42, 24 February 2010 (UTC)


 * I read a detailed academic study online a while ago that said that taking a multivitamin everyday was worse for you than not taking one. Because of that, I stopped taking them and concentrated on eating more vegetables, fruit, and oily fish. Have not been able to find a link to that article unfortunately. 92.29.57.43 (talk) 23:51, 23 February 2010 (UTC)


 * Vitamin B12 deficiency can be a real problem for vegans.--Shantavira|feed me 06:53, 24 February 2010 (UTC)


 * Despite deciding to stop taking a daily multivitamin after reading a scientific paper about this, I do take Vitamin D during the winter, after reading a Scientific American article about this that I think was published in November 2008. The modern diet has a lot of saturated fat and salt, both of which I am trying to avoid by avoiding processed food, and also red meat and dairy products. 92.29.32.229 (talk) 20:57, 26 February 2010 (UTC)

Linus Pauling
In the reference to Linus Pauling it states that he died in 1994 and that he taught at Oregon State University in 1996. Must have been interesting classes. I don't know if he actually taught at OSU but I think he didn't do it in 1996.

Regards all,

Stephen Wilson —Preceding unsigned comment added by Zashiban (talk • contribs) 19:01, 23 February 2010 (UTC)


 * I don't see where it says that he taught at OSU. It says that the Linus Pauling Institute moved there in 1996, but that's a different thing. Looie496 (talk) 20:16, 23 February 2010 (UTC)


 * Err, yeah, read a little closer. It does not say what you think it does. --Mr.98 (talk) 21:33, 23 February 2010 (UTC)
 * Mr 98 it really would be way more helpful if you could say exactly where the problem is. If you have spotted the discrepancy, (and well done for that) let's get it sorted and move on. Caesar&#39;s Daddy (talk) 08:43, 24 February 2010 (UTC)


 * This is best handled on the belonging talk page. However, my curiousity was spiked, and I felt the need to quote what has been written (and not edited, by the look of the history): In 1996, the Linus Pauling Institute moved from Palo Alto, California, to Corvallis, Oregon, to become part of Oregon State University, where it continues... Bolding is mine. All other searches for "1996" yield results outside this context. However, he studied at OSU (first line in #Career). I can conclusively say that Mr 98 is wrong. 77.18.74.19 (talk) 10:06, 24 February 2010 (UTC)


 * Ummm...I don't think Mr98 said anything wrong...perhaps you were confusing him with the OP? It looks like Mr98 made basically the same response as the rest of you.PhySusie (talk) 17:28, 24 February 2010 (UTC)
 * Ah, I thought Mr98 was replying to Looie496. :) My bad. 77.18.12.14 (talk) 16:55, 25 February 2010 (UTC)


 * In theory, posts that are indented are responding to the post which is of lesser indent to the one above it. If I were responding to Looie496, I would have indented it one more time. (I'm seriously surprised that this is any real confusion.) --Mr.98 (talk) 14:19, 26 February 2010 (UTC)

Sodium
How can I extract pure sodium from baking soda (sodium bicarbonate)? --J4\/4 &lt;talk&gt; 20:11, 23 February 2010 (UTC)
 * Basically you can't. See Downs cell for the simplest method of producing pure sodium. Looie496 (talk) 20:21, 23 February 2010 (UTC)
 * Why not? Baking soda has sodium in it, after all. --J4\/4 &lt;talk&gt; 20:27, 23 February 2010 (UTC)
 * I didn't mean that it's impossible in principle, just that it's impossible without very serious equipment. The article I pointed to should give you an idea of why.  I don't actually know how to do it with sodium bicarbonate, but it must be harder than the Downs cell process. Looie496 (talk) 20:31, 23 February 2010 (UTC)
 * In layman's terms: Sodium (as I'm sure you know) is highly reactive. When it reacts with things it puts out a LOT of energy.  Hence, to get it separated back out again, you have to somehow replace all of that energy and fight Sodium's tendency to react with whatever happens to be nearby.  It follows that getting pure sodium out of its compounds is difficult.  (You can't get it out of common table salt either!) SteveBaker (talk) 21:31, 23 February 2010 (UTC)
 * (e/c) put simply, sodium is very reactive, you can ionize it in solution fairly easily (plop plop fizz fizz) but getting it out of solution without it recombining with the other solutes (or other materials) is a bear and a half. -- Ludwigs 2  21:34, 23 February 2010 (UTC)
 * IMHO, if you want detailed advice on how to make sodium, you'll be better off using table salt as your starting material. The best method is to melt it (it melts at ~800 C) and then electrolyse it using a graphite anode and a steel cathode with some kind of hood over it to catch the molten sodium as it rises and thus prevent it from reacting with air.  Warning: chlorine gas given off at the anode is highly toxic, avoid inhalation.  Also, all solid/liquid materials will be red hot, don't burn yourself.  As for the other, common-sense advice: Don't try this at home, at least unless you really know what you're doing.  Clear skies to you 24.23.197.43 (talk) 01:27, 24 February 2010 (UTC)


 * Let's try also to explain this in a different manner. Sodium comes in two forms: Sodium metal, where each atom has 11 electrons, and ionic sodium, where each atom has 10 electrons.  The nucleus of sodium contains 11 protons, so that makes sodium metal neutral, and sodium ions have a charge of +1.  Energetically, it turns out that sodium ions are MUCH MUCH MUCH more stable than neutral sodium.  That's why when you add sodium to water, it releases so much energy; in giving an electron to the water, the sodium becomes more stable, and in the process releases the pent-up energy that was making it unstable (which explains the big boom).  You can look at it this way:
 * Na0 --> Na+1 + 1 electron + a shitload of energy
 * Well, what the OP is proposing is to reverse the reaction; take the IONIC form of sodium (which is the form in sodium bicarbonate) and turn it into the METALIC form of sodium (the neutral one). So if you run the reaction backwards; you would get
 * Na+1 + 1 electron + a shitload of energy --> Na0
 * So the first thing you need is a shitload of energy; basically you need exactly as much (or more) as you release if you were to add the pure sodium metal to water. As the OP is aware, that's quite a bit.  The second problem is that you need to do it in such a way as to keep the sodium metal away from anything that would give it a pathway to give away that electron again.  Any environment that contains any water, for example, will just lead to your newly-made sodium metal instantly reverting back to its ionic form, and you'll never get a measureable amount of the pure metal.  The Downs cell noted above is the only really practical method of creating metallic sodium, and it is a complex process that requires some exotic equipment and a lot of energy to work.  -- Jayron  32  16:40, 24 February 2010 (UTC)
 * Water is partly ionic, so it has free H+, and OH- ions. Table salt is Na+ Cl-. When you electrolyse a solution, the ions with with least electrode potential with be released. H+ is less than Na+. This is why electrolysis of sodium salts is normally done with molten salt, as is stated above. CS Miller (talk) 18:57, 25 February 2010 (UTC)

acid
once spilled strong acid has dried is it inert or is it still caustic —Preceding unsigned comment added by 67.246.254.35 (talk) 22:15, 23 February 2010 (UTC)
 * AFAIK it depends on the volatility of the respective acid anhydride. Hydrochloric or nitric acid may volatilize completely, leaving no caustic residue (unless it had soaked into the surface instead of evaporating); sulfuric or hydrofluoric acid, on the other hand, will remain caustic after having dried up.  However, even with fairly volatile acids, there's no way to really be sure that it has really dried up and not just soaked into the surface.  Always clean up acid spills promptly and follow safety guidelines. 24.23.197.43 (talk) 01:35, 24 February 2010 (UTC)
 * "Acids" are usually solutions of acidic chemical dissolved in a solvent. So you have to figure out what you mean...is the solvent evaporating, leaving an extremely concentrated acidic residue, or is the acid chemical itself evaporating. Most of the common strong acids, and many of the common weaker ones (that still might be very corrosive) are volatile enough to evaporate completely with their solvent: if you are in a situation where the water is evaporating, the acid will also. To put another way, acids are acidic--evaporating them merely changes the physical state of them, so whereever that physical acid chemical goes, in whatever form it is, that's where the acidic properties exist. DMacks (talk) 02:52, 24 February 2010 (UTC)

im talking about car battery acid ( i think sulfuric ) —Preceding unsigned comment added by 67.246.254.35 (talk) 03:21, 24 February 2010 (UTC)


 * Yes, car battery acid is sulfuric acid. Also, what kind of surface did you spill it on? If you spilled it on dirt, grass, or sand, it probably would have soaked in and would not leave any caustic residue. If you spill it on concrete, tile, or wood, I think the acid would evaporate with the water. So in any case, I think it would be safe, depending on how long ago you spilled it. --The High Fin Sperm Whale 04:12, 24 February 2010 (UTC)


 * You can neutralise it with sodium bicarbonate which will fizz as it reacts. There may be some bisulfates left after sulfuric acid reacts with concrete, and these can be neutralised. Graeme Bartlett (talk) 11:25, 24 February 2010 (UTC)

the battery exploded in my car hood the acid is all over the engine parts ect under the hood  —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 15:25, 24 February 2010 (UTC)
 * In that case, you should take your car to a mechanic to check for acid corrosion to engine parts and bodywork -- most car parts are made of carbon steel, and sulfuric acid will corrode it readily and could cause serious damage. (BTW, why don't you sign your posts?) 24.23.197.43 (talk) 05:50, 28 February 2010 (UTC)

"local hour angle" in astronomy
I'm trying to do some astronomical calculations based on the "Astronomical Formulae..." book by Jean Meeus. I almost have it, but I have a question about "local hour angle". On page 44 (chapter 8) he defines (along with the observer's latitude) "H = the local hour angle, measured westward from the South". Is the local hour angle simply the observer's degrees of longtitude? Bubba73 (You talkin' to me?), 22:42, 23 February 2010 (UTC)

I'm not certain of this, but I think it refers (in the context of your probable interest) to the angle in right ascension between the meridian and the horizon, measured from south to west. If RA is in degrees, divide by 15 to put it into hour:minute format. This is also called the western diurnal semi-arc. More broadly (outside your context), it is "the angle between the great circle that passes through the poles, and that which bisects a specific point in the heavens" ("Encyclopedia of Astrology" by Nicholas Devore). 63.17.65.39 (talk) 02:35, 24 February 2010 (UTC)


 * The local hour angle is the angle measured westward from the meridian (that is, the projection of the line of longitude the observer is standing on onto the celestial sphere) to the hour circle of the celestial object, measured westward along the celestial equator. See "hour angle" in the Glossary of the Astronomical Almanac. I don't really see how thinking about "south" helps understand this. Jc3s5h (talk) 02:53, 24 February 2010 (UTC)


 * Yes, the mention of "south" confuses me. I think it may be an error in the book, since the same phrase is used for azimuth (where it does make sense).  Bubba73 (You talkin' to me?), 03:45, 24 February 2010 (UTC)

Perhaps I need to back up some. I am writing a program to calculate the altitude and azimuth of the Moon, given (my) latitude, longitude, and the time. Chapter 30 of the book by Meeus give how to calculate the geocentric latitude and longitude (lambda and beta). The program is doing that - it agrees with the example in the book. (The Moon's motion is complex.) But I'm stuck on getting from there to altitude/azimuth.

Chapter 8 of the book shows how to calculate alt/az from my latitude, the declination, and the local hour angle. The description of the local hour angle isn't clear to me. It shows two ways to calculate the hour angle, based on the local sidereal time and the right ascension (alpha). But I don't know if these r.a. and dec correspond to the geocentric lat and long.

Just before that it shows how to calculate right ascension and declination from lambda, beta, and the tilt of the Earth's axis. I suppose I need to do that to get the declination to use in the alt/azimuth calculation, but I'm not sure.

So my problem is how to get from geocentric lat/long to alt/azimuth, given my latitude, longitude, and the time. How is that done? (I'm confused.) Bubba73 (You talkin' to me?), 05:01, 24 February 2010 (UTC)


 * Forget that "south" business. It is conflating hour angle with something else . If someone was considering a point on the celestial sphere, say the position of a star, and you wished to instruct him how to find another point, you would have to tell him in what direction to look from there. Due South is 0°, Southwest is 45°, East is 270°, and so forth. Also supply the distance, and you've done it. B00P (talk) 06:39, 24 February 2010 (UTC)


 * Don't forget the south, it's correct and belongs in the explanation (assuming you're in the northern hemisphere). If you stand facing south, an object on the meridian, in front of you, has an hour angle of 0h.  Now turn around and face north.  An object directly in front of you has an hour angle of 0h if it's above the north star, but an hour angle of 12h if it's below the north star.  To put it another way, each day and night a circumpolar star will cross the meridian twice, but it's the meridian to the south that it crosses at 0h hour angle.  -- Coneslayer (talk) 12:28, 24 February 2010 (UTC)
 * That said, the formulas should "just work" for your calculation, and you don't need to worry that HA is measured from the south. You do, of course, need to worry about whether azimuth is measured from the north or south.  -- Coneslayer (talk) 13:10, 24 February 2010 (UTC)


 * OK, I have Astronomical Algorithms, which I think is an older edition of the book, but unfortunately the chapter/equation numbers don't match up. I think you've basically got it figured out.  You have geocentric latitude and longitude (lambda and beta).  Convert those to RA & dec (alpha and delta) using the relations you've found.  Then get the hour angle based on RA and local sidereal time (or RA, observer's longitude, and Greenwich sidereal time), and use the relations you've found to convert HA & dec to altitude and azimuth.  All good?  -- Coneslayer (talk) 13:03, 24 February 2010 (UTC)


 * Astronomical Algorithms is actually a newer book (also by Jean Meeus) than the one I have. I'll try to finish it up, based on what seems right.  Unfortunately, there is no complete example of getting the Moon's position in alt/azimuth in the book, so I'll have to check it some other way.  Bubba73 (You talkin' to me?), 01:40, 25 February 2010 (UTC)


 * Bubba, I have the correct answer (and my answer above from "63.17.65.39" was correct, but I thought you wanted it relative to the horizon -- but I see you're referring to the moon). It's very simple:  subtract the right ascension of the moon from the right ascension of the meridian (RAMC).  RAMC is the same as local sidereal time.  If the RAMC is less than the RA of the moon, add 360 degrees (or 24 hours) to the RAMC.  So it's just subtraction! 63.17.57.56 (talk) 02:21, 25 February 2010 (UTC)
 * Another way to think of "local hour angle" -- in this case, the LHA of the sun -- is "At my latitude on earth, how many 'time zones' away is the sun at 'high noon'?" So if you're in New York and it's 3 PM, it's noon on the west coast -- so the "hour angle" of the sun in NY is approximately 3:00, because LA is 3 time zones from NY.  (A better example would be two cities at the same latitude, but you get the point.)  The same goes for the moon or anything else, except it's "the moon's noon," i.e. high point.  Along the same line of geographical latitude, the hour angle is simply how far away in geographical longitude (equivalent to right ascension) a point in the sky has reached its maximum height ("due south").  If the moon is due south (at its high point) in LA (longitude 120ish), the moon's hour angle in NY (longitude 75ish) will be appproximately 45 degress, or 3 hours.  (Again, literally speaking, it has to be along the same line of latitude on earth, and time would be measured as on a sundial, not a regularized clock.  I just say this to avoid the usual pedantic corrections.) 63.17.57.56 (talk) 04:09, 25 February 2010 (UTC)


 * It is my bedtime - I'll read that tomorrow. But in the meantime there are two things I don't understand. The final step is calculating the altitude and azimuth.  Meeus shows how to do that in equations 8.5 and 8.6.  But these equations depend only on the observer's latitude, hour angle, and delta (the declination).  Why doesn't the R.A. enter into it?  Secondly, is that declination the parameter calculated for the Moon in geocentric coordinates?  Bubba73 (You talkin' to me?), 06:16, 25 February 2010 (UTC)


 * You needed the RA to get the hour angle, so that's how RA enters into it. The declination (along with the RA) is calculated from the geocentric coordinates (you originally wrote: Just before that it shows how to calculate right ascension and declination from lambda, beta, and the tilt of the Earth's axis.  That's where the declination comes from.)  -- Coneslayer (talk) 12:20, 25 February 2010 (UTC)