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November 17

Water

Is toilet water poisonous? JCI (talk) 00:11, 17 November 2008 (UTC)

Yes and No.

If by toilet water, you meant sewage then yes.

If by toilet water, you meant clean pipe water used to flush the toilet then no. 122.107.203.230 (talk) 00:38, 17 November 2008 (UTC)

Before or after you flush? The water comes from the exact same place as the water that comes out of your kitchen - so initially, it's clean and perfectly drinkable (assuming you live in a place where the mains water supply is clean and perfectly drinkable!) The toilet bowl itself is a lot cleaner than some people suspect because it's a hard surface that's not porous and there isn't much in the way of nutrients or sunlight for bugs to live on - and we typically expend an entirely disproportionate effort into sanitizing it. So this boils down to the issues with human waste - not the toilet itself. If it's your own waste that you're ingesting then whatever you're picking up was in your body before - so in small quantities it's not likely to be radically nasty. If the waste came from someone else - it's a different matter. Obviously, this isn't something you'd want to try if you didn't have to - and (of course) you'd have to be aware of any chemicals such as bleaches and toilet cleansers you might have tossed into the toilet or the cystern in advance - which might be extremely hazardous. I think that in an emergency - if there was no other source of clean water - I'd weigh up the pro's and con's and probably risk it. SteveBaker (talk) 00:43, 17 November 2008 (UTC)

Assuming you have access to the cistern, it contains a tap, just drink the water directly out of the tap and it's exactly like water out of any other tap. --Tango (talk) 01:00, 17 November 2008 (UTC)

And if you mean toilet water, then yes, some of it is fairly poisonous. -Arch dude (talk) 00:52, 17 November 2008 (UTC)

(EC)Depending on the type of toilet water, the high alcohol content and perfume and other ingredients such as liquid waxes or cocoanut oil might be harmful, especially if it were any alcohol but [Ethanol]. Edison (talk) 00:54, 17 November 2008 (UTC)

Ooh! I'd forgotten that meaning of 'toilet water' - yes, that stuff would be horribly bad for you. However, it's been a very long time since I last heard anyone describe perfume as 'toilet water'...for reasons that are fairly obvious! SteveBaker (talk) 01:35, 17 November 2008 (UTC)

Hah! Caught Steve in an area he knows nothing about. Strictly speaking (imagine the French accent, please), Perfume (as in eau de Parfum) is not really the same as eau de toilette - it's much more concentrated. --Stephan Schulz (talk) 07:57, 17 November 2008 (UTC)

People almost never translate "eau de toilette" into English, though. They just use the French. --Tango (talk) 11:36, 17 November 2008 (UTC)

"Both dogs and people occasionally splash toilet water on their faces, but dogs seem to enjoy the scent more." StuRat (talk) 03:09, 17 November 2008 (UTC)

"I've got a headache. I was dabbing some of that fancy toilet water behind my ears just before the show, and the lid came down and hit me on the back of the head." [Little Jimmy Dickens, Grand Old Opry] Edison (talk) 19:52, 17 November 2008 (UTC)

@SteveBaker - Dude, if you ever really do get that desperate, please at least consider going for the water in the tank rather than the water in the bowl... Matt Deres (talk) 00:26, 18 November 2008 (UTC)

Geology

What are the three types of stress force —Preceding unsigned comment added by 65.12.161.166 (talk) 01:01, 17 November 2008 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.

May I suggest Structural geology - I believe the answer you seek is in one of the articles linked from it. Better still - I'm 100% sure that if you crack open the textbook for your course, you'll find the answer listed neatly in the chapter you've just been working on in class. SteveBaker (talk) 01:33, 17 November 2008 (UTC)

Can't we just start giving them wrong answers? The three types of stress are work stress, family stress, and Microsoft-related stress which is the worst stress of all. 216.239.234.196 (talk) 16:41, 17 November 2008 (UTC)

There is an unreferenced article on Stress field, and Shear (geology) is probably useful. Graeme Bartlett (talk) 20:47, 18 November 2008 (UTC)

Home battery recycling

Is there any way to recycle or revive sealed lead acid or lithium batteries at home, for an electric bicycle for example? And are there any batteries that are self-recycling? And what chemical or thermal process would be involved after I wash the chemical out of the battery? Trevor Loughlin (talk) 05:30, 17 November 2008 (UTC)

There is nothing chemical or thermal that a non-specialist can do to fix a battery. "Deep cycling", i.e. charging a rechargeable battery followed by mostly discharging it under steady load and then recharging it again, is an electrical process that can help some rechargeable batteries under some conditions. Though with lithium rechargeables it is important that they never be completely discharged as this will almost certainly tend to shorten their life. Opening a lead acid battery is dangerous. The acid is corrosive and the lead toxic. Lithium batteries are only a little better as lithium will burn skin and the dust should not be inhaled. If the batteries are really dead send then to a professional recycler, don't mess with them yourself. Dragons flight (talk) 07:05, 17 November 2008 (UTC)

What killed the airship?

You know, dirigibles, zeppelins, etc... How did they come to be surpassed by contemporary jumbo jets? Kenjibeast (talk) 06:58, 17 November 2008 (UTC)

The Hindenberg disaster killed public opinion. Plus they are generally impractical. Dirigibles are huge, slow, and hard to operate compared to jumbo jets of the same cargo capacity. They are probably a reasonable solution to aerial surveillance of a fixed location (e.g. Goodyear blimps above sporting events), but they are not competitive as a means of transportation. Dragons flight (talk) 07:14, 17 November 2008 (UTC)

See also Airship#Practical_comparison_with_heavier-than-air_aircraft for a rather lengthy discussion of why airships were abandoned. SDY (talk) 07:48, 17 November 2008 (UTC)

Airships were not "surpassed by contemporary jumbo jets", though. They were abandoned about the time World War II started, and jet aircraft didn't even exist then, let alone jumbo jets, which came along 25 years after the war. But propeller aircraft did, and the war stimulated their development in a big way... and a bomber and an airliner can have many similarities in design. --Anonymous, 06:22 UTC, November 18, 2008.

A bomber and an airliner have some things in common, but the only difference between an airliner and a military cargo airplane is the paint scheme. --Carnildo (talk) 22:43, 18 November 2008 (UTC)

Airships again

What was the operating altitude for the USS Akron and the Hindenberg and other airships from that era? What are the practical considerations for a high-altitude airship (i.e. how much does the lifting power drop as atmospheric pressure decreases)? SDY (talk) 07:48, 17 November 2008 (UTC)

In the airships link above, it states: "The highest flight made by a hydrogen filled passenger airship was 5,500 feet (1,700 m) on the Graf Zeppelin’s around the world flight. The practical limit for rigid airships was about 3,000 feet (900 m), and for pressure airships around 8,000 feet (2,400 m)." And a rigid airship in 1917 "was forced to 24,000 feet", but it crashed as a result. -- MacAddct1984 ^{(talk • contribs)} 18:31, 17 November 2008 (UTC)

The practical operating altitude was "as low as possible": the Graf Zeppelin typically flew within 500 feet of the ground. Since hydrogen airships were typically operated with their lift cells as full as possible, gaining altitude meant venting off hydrogen to keep the lift cells from rupturing from overpressure -- and venting hydrogen means you also need to drop ballast to keep the airship aloft. When you run out of ballast, you either need to start dropping cargo, or you need to land where you are, neither of which is a desirable situation.

Staying low has other benefits, as well. Turbulence is minimized, which is important when you're flying something larger than the typical turbulence cell, and downdrafts are mostly converted into horizontal winds. It also gives the passengers a great view of whatever you're flying over. --Carnildo (talk) 01:04, 18 November 2008 (UTC)

Explain this optical illusion?

I was reading the Wikipedia article on The Fall of the House of Usher. In the "Analysis" section there is an image of a copy of the magazine in which the story was first printed. I had this image at the bottom right of the browser window and was reading the end of the preceding section when I noticed something odd: when, in reading, my eyes move left to the beginning of the next line, the image appears to momentarily take on a distinctly green tinge. Why is this? - 79.79.176.53 (talk) 08:59, 17 November 2008 (UTC)

This can happen particularly if red green and blue images are shown in sequence and one moves ones eyes. Some projector systems in particular suffered from it. I would have thought there wouldn't be too much problem with LCD monitors though. Dmcq (talk) 09:48, 17 November 2008 (UTC)

Seems you could be experiencing the after image phenomenon, due to the red cast of the image in question. Does that fit what you are seeing? --Scray (talk) 11:28, 17 November 2008 (UTC)

Jupiter causes an additional parallax

Stellar distances are measured most directly by parallax, using the fact that Earth's position changes by 3*10⁸ km within 1/2 years. Now of course when planets move around the sun, the sun itself also moves (but of course slower and in a smaller ellipse), and Jupiter causes the Sun's position to change by about 1.5 million km within 6 years. Earth orbits Sun in a close orbit compared to Jupiter, so it can be expected to follow this movement of the Sun (in addition to orbiting it). This should produce an additional parallax of about 7 milliarcseconds at α Centauri - this should be measurable e. g. with Hipparcos. Does this additional parallax have a special name? Maybe Wikipedia's article should mention it.

Additionally, Jupiter causes the velocity of the Sun to change by an amount of more than 20 m/s within 6 years, and the resulting Doppler effect should also be measurable when observing other stars.

Icek (talk) 09:57, 17 November 2008 (UTC)

Smoking and breast milk

Maternal smoking results in exposure to nicotine in breast-fed infants. Smoking mother's breast milk contains nicotine - when this fact was first discovered and who discovered it? Otolemur crassicaudatus (talk) 10:06, 17 November 2008 (UTC)

Who the heck smokes breast milk? Isn't too wet to ignite? I mean, I suppose you could get it into a bong, so that would eliminate the soggy paper problem, but wouldn't you still have problem lighting it? I suppose you could freeze-dry the breast milk, and smoke that, but it seems like a lot of trouble to go through... --Jayron32.talk.contribs 15:32, 17 November 2008 (UTC)

I have asked the breast milk of the mothers who (who denotes mother) smoke cigarette contain nicotine. It not the breast milk which the mother smoke, it is the cigarette which the mother smoke. Now if a mother smokes cigarette during her maternal period, it is observed that her breast milk may contain nicotine. I want to know who first discovered this and when (i.e. relation between maternal cigarette smoking and consequential nicotine concentration in breast milk)? Otolemur crassicaudatus (talk) 16:07, 17 November 2008 (UTC)

No shit, sherlock... I was being funny. You used the phrase "Smoking mother's breast milk" which is an example of a Dangling modifier since it is impossible to determine from the phrase which word "smoking" is intending to modify. Is the mother, the mother's breast, or the mother's breast milk the thing which is smoking. Such imprecise language is often the source of humour; phrases like "Eats, Shoots & Leaves" or "man eating cabbage" or "British Left waffles on Falklands" are other famous examples of imprecise language. Damn it, jokes are not as funny when you have to explain them... --Jayron32.talk.contribs 17:07, 17 November 2008 (UTC)

See also Amphibology. --Jayron32.talk.contribs 17:14, 17 November 2008 (UTC)

To be honest, it wasn't all that funny to start with... ;) If you're going to mock someone's imperfect but completely unambiguous (in context) grammar, it helps to answer the question as well. If you don't know the answer, keep quiet. --Tango (talk) 17:22, 17 November 2008 (UTC)

Alright smarty-pants. I did a google scholar search where the earliest reference I can find is this study done in 1933 by someone named WB Thompson, and appearing in American Journal of Obstetrics and Gynecology. Several other studies cite a 1942 JAMA paper as being fairly authoritative on the subject. Looking through the first 3-4 pages of the Google Scholar search turns up nothing earlier than 1933, but that doesn't necessarily mean there wasn't anything earlier. The online version of the 1933 paper is only an abstract; if you got the original you would probably find at least a cursory literature review, and you could see if there was anything earlier. Going backwards through the papers, you could probably find the seminal study. --Jayron32.talk.contribs 18:33, 17 November 2008 (UTC)

This study: [1] seems to cite the 1933 Thompson study, and its title "The Excretion of Drugs in Human Milk—A Review" would seem to indicate that it would be a great place to start if looking for that first study... --Jayron32.talk.contribs 18:35, 17 November 2008 (UTC)

Here's one from 1927: [2], and IT cites studies from as early as 1908. Again, I would start somewhere like this one, and work backwards until I got to the earliest study to mention it. It may take time; however access to a university library would make it possible to work it out. here's one from 1911 that talks a bit about the mechanisms of milk secretion, and the action of certain drugs thereupon. --Jayron32.talk.contribs 18:44, 17 November 2008 (UTC)

toilet seats

Assuming it is used normally, is it actually possible to catch any disease from a toilet seat? Reading transmission (medicine) suggests that it is not.--Shantavira|^{feed me} 10:11, 17 November 2008 (UTC)

Per this, toilet seats are relatively germ-free; an average toilet seat contains approximately 49 microbes per square inch compared with a keyboard, which may contain 25,127 microbes per square inch. Toilet seats are not common transmission channels of infectious diseases. To infect someone, the bacteria must have to enter his body through mouth, anus or urethra. But the bacteria cannot jump from the toilet, so someone using the toilet in usual manner is basically safe. But, yes there are possibility of skin diseases like scabies, herpes. Regarding Gonorrhea, a study in 1979 titled The gonococcus and the toilet seat claimed "nonsexual transmission from toilet seats is not impossible, just very unlikely". Here is an interesting reference which will help you a lot. Otolemur crassicaudatus (talk) 10:47, 17 November 2008 (UTC)

You really ought to be more worried about door-handles than toilet seats, especially in public bathrooms. Think about it, thousands of people touch those things, and many probably don't was their hands properly (if at all). You get it on your hand, and then you eat a popcorn or something, and bam!, you're infected. Much bigger hazard than toilet-seats. 83.250.202.208 (talk) 11:53, 17 November 2008 (UTC)

I wonder if there's a greater transmission problem with the widespread use of auto-flush toilets? I find they tend to perform quite a few, er, premature evacuations. On the one hand, the extra flushing presumably helps whisk away any residual nasties in the water; on the other hand, it tends to deposit a fine coating of "toilet dew" on one's nether regions, thus overcoming the bacterial obstacle of migrating from bowl to anus. Matt Deres (talk) 00:34, 18 November 2008 (UTC)

Keep in mind also that germs can't magically go through the skin, at least the vast majority can't. In order for any surface to be a vector of infection, you need a cut, abrasion, ect. In my opinion, the vast majority of concerns about germs from toilet seats are hysteria induced by overprotective parents, typical in women. The theoretical transmission of some skin-contact viruses supposes they got there in the first place, which would require blood contact (or mucus membrane) in the first place. Now an airborne virus might get deposited, as might microbes from, say, vomit, but even then the microbe would have to A) get on the sear B) survive long enough to be around when you get there, some germs will be dead in 15 minutes (IE HIV) some might last a week or more (IE Hepatitis), but it will reduce numbers C) you'd have to have an means for the virus to get into your bloodstream, such as a cut. In general I think that it could be said that your risk of exposure is the same as from any skin/surface contact that isn't your hands, hands being a greater vector because you often expose them to your internals by touching your eyes, mouth, food, ect. 69.210.56.62 (talk) 09:25, 22 November 2008 (UTC)

Red / Blue Shift

Apparently astronomers can determine the distance to a star or galaxy by its red shift or blue shift. Do we have any concrete proof, such as from experiments that can be replicated in a laboratory, that we are correctly measuring the distance to these celestial bodies, ie the red / blue shift measurement is accurate? Or is it all based upon theories and resulting formulae? —Preceding unsigned comment added by 75.67.217.220 (talk) 10:41, 17 November 2008 (UTC)

Ummm, well all science is based on a combination of evidence, experimentation, and theories, so I'm not sure what you are really asking. However, as discussed at cosmic distance ladder, a wide variety of techniques are used to validate measurements of cosmological distances and the agreements between different types of measurements can be seen as evidence that astronomers know what they are doing. Dragons flight (talk) 11:20, 17 November 2008 (UTC)

You don't measure distance with redshifting or blueshifting, you measure if something is moving towards you (blueshifting) or moving away from you (redshifting). As for concrete proof or a laboratory experiment confirming this effect, we absolutely have it! In fact, you can observe it for yourself! The principle behind it is something called the Doppler effect, and it happens with all sorts of waves, including sound-waves. Next time you're stuck in traffic, and hear an ambulance or a police-car rushing at great speed near you, think about how the pitch of the siren changes as the ambulance (or police) passes by you. It will be at a much higher pitch when approching you, and then as it passes you, it will suddenly have a much lower pitch. This is exactly what happens to light when they are emmited from stars that are travelling away from you. Instead of having a lower pitch, it will be slightly shifted to red side of the color-spectrum. 83.250.202.208 (talk) 11:50, 17 November 2008 (UTC)

"You don't measure distance with redshifting"? Doesn't Hubble's Law say that "the redshift in light coming from distant galaxies is proportional to their distance"?--Shantavira|^{feed me}

Yes, for sufficiently distant galaxies, redshift gives you an pretty good approximation of their distance, but only by comparing them to closer galaxies that you can measure the distance to via different methods (see the article Dragons flight linked to). --Tango (talk) 13:29, 17 November 2008 (UTC)

Yes, I should've been clearer about that point. I just meant that that wasn't what you were measuring directly, and without a reference it doesn't work. 195.58.125.52 (talk) 13:55, 17 November 2008 (UTC)

Thanks - put simply, the question was, when a distance is provided to another star or galaxy, how do we know the distance is accurate? If we are using a set of assumptions, means or formulae, can we use the same to measure a distance on earth and therefore prove that the assumptions, means or formulae produce correct results, thus giving creedence that the distance to the star or galaxy is accurate (or at least in the ballpark)? Sorry if I am not sufficently clear . . . I think the cosmic distance ladder probably answers the question, but I was wondering if you could explain it in a simple manner for us "common folk"? Thanks again

Tricks by Nikola Tesla in the movie "The Prestige"

I just rewatched the brilliant film The Prestige, and had some questions regarding some of the science-tricks that Nikola Tesla performed.

1. In one scene, Andy Serkis (Tesla's Igor, basically) takes Hugh Jackman out to a huge snowy field, with hundreds of lamps that are just sitting in the snow. Hugh Jackman asks "But where are the wires?". Andy Serkis replies "Exactly." (this particular scene is illustrated in the article, under the production heading). What is going on here? Has Tesla somhow electrified the snow? If so, why would the electricity pass through the light-bulbs, instead of going straight into the ground? The only plausible thing I can think of is that he has an enourmous electro-magnet nearby that generates a fluctuating magnetic field and there are some sort of generator in every one of the lamps (I haven't studied these things since high school, so I'm completely just guessing here). But Hugh Jackman lifts one of the lamps off the snow and then it turns off, but when he puts it back, the lamp turns on again. If anyone could explain that scene to me, I'd be mighty grateful.
2. In another scene (also helpfully illustrated in the article, wikipedians are apparently obsessed with Tesla) the great engineer walks underneath a Tesla Coil that's shooting bolts like crazy, apparently completely unharmed (the man knows how to make an entrance). I understand the principle here, that Tesla is wearing insulating shoes and so the electricity doesn't pass through him, but this is still got to be hugely dangerous, right? I mean, the air in that chamber where he walks has to be extremely hot from all the electricity, and what if a bolt passes through him and jumps through the air from his ankles down to the floor (the floor is definitely conductive, you see sparks hitting it all the time). I mean, this is not something a sane person would do, right?
3. After he has made his glorious entrance through the storm of lightning-bolts, he walks up to Hugh Jackman and grabs his hand, and hands him a lightbulb. Still clasping hands, Jackman picks it up with his other hand, and lo!, the bulb lights up (seriously, now he's just showing off). Asking where the electricity comes from, David Bowie in his best Serbian accent says "Ze body is a most excellent conductor!". Again, what's going on here? Has Tesla become so charged by walking through the lightning-bolts that he can keep a lightbulb on for several seconds, even after the electricity has passed through two bodies? And wouldn't the charge pass through Jackman's body straight into the ground (wouldn't that be the path of least resistance?), completely skipping the light-bulb?

I realize that this is a film with science-fiction elements in it, but I would expect the scenes introducing Tesla to be somwhat grounded in reality (as he was a really cool guy who could do really cool tricks with electricity, so why would you go the sci-fi route?). Can anyone explain this to me? 83.250.202.208 (talk) 11:41, 17 November 2008 (UTC)

Let me try to answer these the best I can...

1. He used a Tesla coil to power them. (wonder where THAT name comes from... hm...) A Tesla coil generates a strong electric field around it. Basically, a Tesla coil is a really freaking powerful broad spectrum radio antenna. Radio works by inducing an electric current in your reciever, but the current is small; it needs to be "amplified" by an external current in order to have enough energy to drive the speakers. If you drive enough static charge into the atmosphere, you can induce a current in the same way in just about any metal availible.

   You can do the experiment yourself relatively simply. If you have an AM radio tower anywhere nearby, take a simple hand-held transistor radio and get right underneath the radio tower. You will hear the broadcast from the tower without any batteries in your radio at all. At this distance, the power of the antenna is strong enough to power the circuit without amplification.

   The same principle works in a tesla coil; it will provide enough electrical potential in the air itself to power lightbulbs just inside the field, without any wires. Tesla had some pretty wild ideas about using these for civilian power generation. Basically, you'd build on in the town square, and everyone in town got free electricity. The downside is that these things have a nasty habit of discharging into anyone that gets too close, so it basically acted like a giant bug zapper that takes down birds, pets, wandering drunks, etc. etc.

2. Is likely bullshit, but only slightly. He could wear a "conductive suit" like linemen wear when working on high-tension wires, they act like a personal faraday cage, directing current away from themselves into the ground.
3. Is more likely total bullshit. I can't imagine that his body would act as a good enough capacitor to hold a charge long enough to do that. --Jayron32.talk.contribs 14:02, 17 November 2008 (UTC)

But here's my question about 1. Hugh Jackman picked up the lightbulb from the snow, and it turned off. Then he put it down again, and it turned on. I.e. it didn't work when it was in the air, it only worked when it sat in the snow. Wouldn't your Tesla coil electric field also work when the lightbulb was in the air? Or is the electric field somehow confined to the ground? 195.58.125.52 (talk) 15:37, 17 November 2008 (UTC)

Ah, I see the problem. No, then, that part is bullshit too... --Jayron32.talk.contribs 18:22, 17 November 2008 (UTC)

2) There is a very famous photograph of Tesla sitting under the coils in his laboratory. It's fake (double exposure), but most people don't realize that. (or don't care.) Virtually every portrayal or parody of Tesla recreates this photo somehow. 72.10.110.109 (talk) 14:27, 17 November 2008 (UTC)

Tesla demonstrated in the 1890's that if you set up a strong enough AC field in a room, specially built light bulbs would light without wires connected. This works for glow tubes like neon lights or Geissler discharge tubes, and even for fluorescent tubes. This was back before they worried about the effects of EMF on living things. Back then, they did not even know that X-Rays were harmful. Edison (talk) 19:47, 17 November 2008 (UTC)

Of course User:Edison would play up the danger of Tesla's research. 72.10.110.109 (talk) 20:23, 17 November 2008 (UTC)

Note that User:Tesla has made no contributions.Edison (talk) 00:57, 18 November 2008 (UTC)

There was an art installation in the UK by artist Richard Box back in 2004. The installation, called Field, placed more than a thousand fluorescent tubes on end under some long-distance high-voltage transmission lines. The electric field (and electric field gradient) below the wires was sufficient to light the tubes. Have a look: [3]. TenOfAllTrades(talk) 20:50, 17 November 2008 (UTC)

Box "discovered" this in 2004? It was demonstrated by opponents of overhead high voltage lines back in the 1970's, and had been demonstrated by Tesla and others back in the 1890's. There is a danger if the tubes are raised too high in the air, since they conduct electricity and if brought too near an energized conductor they could electrocute the person holding them. The conductors are elevated for a reason. Edison (talk) 00:51, 18 November 2008 (UTC)

Earth-like planet forming in the absence of life

In 2006, someone asked an interesting question on the talk page for the terraforming article:

http://en.wikipedia.org/wiki/Talk:Terraforming#Earth-like_planet

The question hasn't gotten much attention there and I'm very interested in it, so I'm asking it here: is there a way for a planet with conditions that could support human life (oxygen/nitrogen atmosphere, liquid water, appropriate gravity and atmospheric pressure etc) to form in the absence of life? It might be really unlikely, far-fetched and rare, but it's a huge galaxy and an even huger universe, so surely it's happened somewhere.

The critical thing here would be the generation of oxygen. Oxygen has to be constantly replenished on Earth because it reacts so well with many other elements and so gets locked up in rocks, but perhaps there could be some complex geological process that generates large amounts of oxygen. If the oxygen is too far fetched, what about a planet with otherwise Earth like temperature and pressure conditions but no oxygen so that it would be possible to go outside with only a tank of oxygen? Sure, it'd be limiting, but it's a start. 63.245.144.68 (talk) 13:11, 17 November 2008 (UTC)

I agree, oxygen is the critical thing. Without the oxygen requirement, it's easy - the Earth during the Archean period fits your description quite well (there was some primitive life, but I don't think it had had time to change the planet much - I may be wrong). --Tango (talk) 13:36, 17 November 2008 (UTC)

Only if you aren't too picky about pressure, speculation generally puts Archean atmospheric pressure at 3-10 times modern. Though one could almost certainly come up with inorganic ways to make a pressure closer to modern, so that probably isn't an impediment to the question being asked. Dragons flight (talk) 14:11, 17 November 2008 (UTC)

I've moved your edit conflict message to your own comment - I didn't conflict with myself! ;) A human could survive in 3 atm pressure with no problem, and probably 10 atm too (moving between that and 1 atm requires some care, of course). I think the OP is just looking for habitable planets for colonisation, so that qualifies. --Tango (talk) 14:36, 17 November 2008 (UTC)

That's not my EC note. It was already there before I got here. Dragons flight (talk) 15:07, 17 November 2008 (UTC)

Ah, it was Jayron's, my bad! I'll move it again! --Tango (talk) 15:45, 17 November 2008 (UTC)

(EC with tango) From a purely chemical/thermodynamic perspective the presense of free oxygen is an impossibility in any system which does not compensate in some way. If you look at almost any system with the following equilibrium:

$X+O_{2}<->XO$

The numbers skew SO FAR to the right for most elements that it is an impossibility for any element to exist in the presence of oxygen WITHOUT producing its oxide. The half-dozen or so elements it doesn't work for (copper, silver, gold, platinum, maybe one or two more) are not going to exist in significant amounts in any plantary system. The reaction is always spontaneous and highly exothermic. There's usually a high activation energy to this reaction, but that really only effects the rate of reaction. Given earth-like temperatures, and given a substantially long-enough time frame (say measured in the thousands of years) free oxygen will just stop existing. In fact, I can't come up with any spontaneous chemical process that will generate free oxygen from something that does NOT involve life in some way... --Jayron32.talk.contribs 13:41, 17 November 2008 (UTC)

It may actually be possible to have abiotic free oxygen production; this is a major issue for extra-solar planet spectroscopy missions like TPF and Darwin. For example, in (Selsis, F, Despois, D & Parisot, JP 2002, "Signature of life on exoplanets: Can Darwin produce false positive detections?", Astronomy & Astrophysics, vol. 388, no. 3, pp. 985-1003), it is estimated that a maximum equilibrium concentration of about 5% of $O_{2}$ can be maintained through photochemical processes. The actual photochemical equations (mainly revolving around photo-disassociation of $CO_{2}$ and $H_{2}O$) are apparently quite complicated (the source listed above includes about 150 in their model). I don't think they considered surface processes since these are potentially very variable; there are huge differences between a water-rich planet covered entirely by ocean and a water-poor planet with lots of geological activity (recycling the surface often). 58.96.70.254 (talk) 15:59, 17 November 2008 (UTC)

So if we were to find a planet with otherwise habitable conditions but with no oxygen, how difficult would it be to add the amount of oxygen necessary to support animal life? Industry on Earth is putting out massive amounts of gases into the atmosphere and is demonstrably changing the composition of it, so wouldn't it be possible to do the same on another planet by perhaps separating oxygen from oxide compounds in the crust and releasing it into the atmosphere? 63.245.144.68 (talk) 20:30, 17 November 2008 (UTC)

No, the amount of energy required to generate an oxygen atmosphere directly is ridiculously large. Completely unapproachable by technological means. The global microbial biosphere powered by the sun was able to do it, and any terraforming project is likely to have to rely on the same kind of process. Dragons flight (talk) 22:04, 17 November 2008 (UTC)

If a society has access to trans-stellar travel would likely have access to virtually unlimited energy, the amount it would require to put a workable colony into another star system is ridiculous in and of itself (talking, say, 500 colonists, microfactories, survival gear, trans-stellar communications gear, shelter, ect.) I agree that microbes (or even larger plants) are probably the way to go, but if you have access to that much energy you might be able to crack CO2 or water into usable oxygen. Cracking water has the benefit of producing useful hydrogen gas and the fact you can tap off some of the O2 production into stored LOX for use in a metal/oxygen rocket or fuel cells. As to getting that much energy. Solar satellites beaming power to the surface? Fusion? Geothermal? 69.210.56.62 (talk) 09:39, 22 November 2008 (UTC)

I think there are two separate issues here:

1. Do all planets with the right chemical and thermodynamic environment to produce life necessarily do so in a reasonable time-frame?
2. Do all planets which DO produce life inevitably see it evolve to produce intelligent civilisations?

Neither question is very well understood.

Sadly, science hasn't quite figured out the precise step that lead from "lifeless" chemicals to replicating and evolving lifeforms. Personally - I feel that the oceans are so enormous - and the amount of time involved is so immense that sheer statistics means that sooner or later a replicating molecule would appear - and from that point onwards, evolution takes hold and you have lots of life forms. But the precise chemistry of the situation might mean that this spontaneous formation of a small replicating molecule could take (on average) a trillion years of random chemistry - in which case we are an amazing flook that may have happened only once in the observable universe...or perhaps the statistics works out such that these molecules form within a matter of months - and absolutely every planet that's remotely capable of supporting life must therefore be crawling with the stuff. Which of these things is the truth is hard to know because we don't really know how simple life can be and still cause evolutionary change. The folks who are working on creating completely synthetic life-forms may well have an answer to that within a very few years...and they we'll have a better answer for this one.

If life is everywhere and evolution is in top gear - will there necessarily be intelligent civilisations? I kinda doubt it. The dinosaurs were around for a vastly longer time than the mammals have ruled the place - and they didn't manage to evolve this ability...presumably because there was no advantage to them in having it. So again - it might take a highly unlikely set of environmental pressures to make intelligence worth the price you have to pay for it in reproductive terms.

So I've gotta conclude that a planet with the perfect conditions for forming life might not ever do so - and even if it did, it's not obvious that it wouldn't be locked into a particular evolutionary path that does not favor intelligence. It's not certain that this is a true statement - but there is currently zero evidence that it's not true.

SteveBaker (talk) 22:18, 17 November 2008 (UTC)

While those are two interesting questions, I don't think either of them are what the OP is asking. I think the OP is talking about finding planets suitable for colonisation, not finding extraterrestrial life. --Tango (talk) 00:55, 18 November 2008 (UTC)

It's worth considering IMHO that whatever the case given the long travel distances, you're probably better off just terraforming planets that don't have the conditions suitable for life but could if you terraform them. Yes terraforming them may take thousands of years but I would say there's a good chance so would finding and reaching an already habitable planet without life. Indeed I would go so far to say that there's a fair chance we will terraform some planet or moon in this solar system even those the challenges are numerous before we reach an already habitable extra-solar planet. Nil Einne (talk) 08:11, 19 November 2008 (UTC)

information on the temperature and precipitation in the BOREAL SHEILD ecozone

information on the temperature and precipitation in the BOREAL SHIELD ecozone doesn't exist can someone add this info soon? —Preceding unsigned comment added by Shadow56121 (talk • contribs) 14:27, 17 November 2008 (UTC)

Neolithic period and a Young Earth

Without wanting this to turn into a religious debate, do those who adopt a Young Earth ignore the wealth of archeological evidence from the Neolithic period? While I know YECs are hesitant to accept radiometric dating, surely there must be enough archeological evidence to construct a fairly accurate timeline? -- MacAddct1984 ^{(talk &#149; contribs)} 17:27, 17 November 2008 (UTC)

You might have more luck on the Humanities page, as the beliefs of creationists have no basis in science. StuRat (talk) 18:08, 17 November 2008 (UTC)

On the contrary, there is no desire of adherants to any form of creationism to attempt to construct a coherant theory from evidence. Evidence is either modified or discarded as needed to fit the pre-existing theory; its a "cart-before-the-horse" method of "science" which is why no one with any real understanding of how science works takes it seriously. They don't derive the age of the earth from availible evidence, and modify that age as new evidence arises; they START with the date in mind, and bend the interpretations of the evidence to fit that date. --Jayron32.talk.contribs 18:20, 17 November 2008 (UTC)

I guess what I'm actually asking is: is there significant archeological evidence of the Neolithic period where a timeline can be formulated without having to resort to radiometric (carbon) dating? Which, as StuRat said, may be more of a question for the humanities page. -- MacAddct1984 ^{(talk &#149; contribs)} 18:28, 17 November 2008 (UTC)

I'd imagine that some evidence from dendrochronology could be used for events that are that recent (i.e. <10kya), though preserved wood construction from the neolithic is either very limited or virtually nonexistent. SDY (talk) 18:37, 17 November 2008 (UTC)

Proponents of the Young Earth theory like to ignore radiocarbon dating evidence not because of anything inherently wrong with the methodology of radiocarbon dating, but because it provides evidence that is in conflict with their pre-conceived date as to the birth of the Earth. If you were to present to them any other method which arrived at the same results as radiocarbon dating, they would dismiss it as a flawed method because it arrives at a different date than the exact one that they have in mind. You cannot use reason to talk someone out of a conclusion they did not use reason to arrive at in the first place! --Jayron32.talk.contribs 18:51, 17 November 2008 (UTC)

Indeed. While YECs come up with all kinds of complicated explanations for why carbon dating, etc. get the "wrong" results, those explanations are purely intended for us non-believers, they aren't the reasons the YECs believe what they do. The believe what they do because that's what they believe (probably because that's what they were told to believe by their parents and they never questioned it until it was too late and it was already so deeply ingrained in their psyche that they can't believe anything else), not because they have been convinced by the arguments they try to convince us with. --Tango (talk) 19:41, 17 November 2008 (UTC)

They seem to blame any archeological evidence that doesn't mesh with YEC as an artifact of (or 'proof' of) the Great Flood. They often don't call it the great flood, though. They come up with adorably pseudo-scientific ways of describing a giant, world-covering 40 day flood without actually sounding like they're talking about a biblical event. 72.10.110.109 (talk) 20:20, 17 November 2008 (UTC)

How much water would it take to flood the entire Earth? Assuming all the clouds rained until there were no clouds, would that be enough water? 216.239.234.196 (talk) 21:13, 17 November 2008 (UTC)

Not even remotely. To flood the earth, you would need about 8500 meters of water. 10 meters of water is about one atmosphere of pressure. Hence, for that much water to be suspended in the air, whether as clouds or as vapor, would cause about 850 atmospheres worth of extra pressure. In other words, it would require a major miracle... --Stephan Schulz (talk) 21:20, 17 November 2008 (UTC)

At any one time, the atmosphere collectively only holds enough water to raise sea level a few centimeters. You would need some totally different source of water to flood the Earth. Dragons flight (talk) 21:21, 17 November 2008 (UTC)

Out of curiosity, how much depth of water is currently on the earth that is not in liquid form? In short, if you melted all of the ice caps and glaciers and took the atmoshpere as well, could you get the 8500 meters necessary to cover Everest? SDY (talk) 21:53, 17 November 2008 (UTC)

According to freshwater, about 2% of the earth's water is ice. According to ocean, that means melting all the ice would give you about 25 million cubic kilometres. That's enough to raise the sea level by about 70m; a pretty significant increase, but a long, long, way from the top of Everest. The atmosphere gives you almost nothing. Algebraist 22:01, 17 November 2008 (UTC)

Well - let's be a little bit careful. Sure, there isn't enough water vapor in the air to do that. But we believe that if all of the ice and snow in the world melts - the oceans could rise 20 meters. Because water gets less dense as it gets warmer, if the climate heated up a lot - the water would expand and get quite a bit deeper than that. As the continents get inundated, the downward force of all of that water pushes the continents downwards - and that makes for still less visible land. It's not THAT unreasonable to assume that so much of the land would be underwater that a family with a fricking ENORMOUS boat and a lot of very fractious animals might imagine there was no land left anywhere! But that's OK - every other aspect of that story is ridiculous. SteveBaker (talk) 21:57, 17 November 2008 (UTC)

Ah, ah, ah! Your calculations are based on the earth being a spheroid. I think you'll find things work out just fine when you correct it to the proper shape. Look at all that extra water there; just imagine where it must end up. Matt Deres (talk) 00:45, 18 November 2008 (UTC)

It ends up...on....the.....back......of......the turtle! OH OF COURSE! Now it's all so clear. SteveBaker (talk) 05:17, 18 November 2008 (UTC)

The problem with creationists is that they know full well that if they spell out their beliefs carefully enough - they'll become testable and falsifiable. That's something they don't like to risk - so they have to keep it vague or science will crush their puny belief system under a large pile of rock-solid reasoning. So long as you keep saying "God did it" - then it's hard for science to pin it down. The conversation generally goes something like: "Why are there fossils of damned great dinosaurs - but no sign of any actual dinosaurs on earth right now?"..."God did it". "How come we can trace a clear history of human and proto-human ancestry back through the fossil record and back to the common ancestor of chimpanzees and man?"..."God did it". "Why does the cosmic background radiation appear so smooth - indicating a common point of origin for all of the universe?"..."God did that too". "Why the heck did God do such bizarre and unnecessarily annoying things?"..."To test our faith in him". QED. Where it gets tricky for them is when they want to get this doctrine taught in US schools in defiance of the constitutional separation of church and state - so instead we get "creationism-lite" - or "intelligent design" - where they say all the exact same things - but instead of "God" they say "some intelligent designer" (except when they slip up and say "God" by mistake). Sadly, this eliminates the "to test our faith in him" defense - so there have to start being some actual reasons - and that's where things start to get messy. SteveBaker (talk) 21:57, 17 November 2008 (UTC)

I've always wondered about those Young Earth Creationists you see occasionally who have real degrees from respectable schools. What do those people really believe? Assuming they're sincere, they must experience enormous mental dissonance every time some new fact comes out from the various fields they believe to be arrayed against them (biology, geology, astronomy, paleontology, archaeology, etc.). How do they reconcile that almost all natural evidence seems to point them away from something they believe? --Sean 13:19, 18 November 2008 (UTC)

I know of one case of a quite senior scientist from a very different field of science. He looks at very narrow bits of evidence and picks them apart until he can find a torturous interpretation that is in principle compatible with YEC. He ignores all the other evidence and the interconnections that make a mature field of science so resilient. If you read his texts on the topic, you get the feeling that he consciously and painfully avoids thinking one step beyond his immediate goal of dissecting just one single bit of evidence. --Stephan Schulz (talk) 13:40, 18 November 2008 (UTC)

On the other hand, people like that are quite rare. Most scientists, even the evangelical christian ones, have little problem working both thought systems into their world view. I know that I don't... --Jayron32.talk.contribs 17:13, 18 November 2008 (UTC)

The Laws of proportioning aggregates for concrete

Could anybody hep me find article by Fuller, W.B. and S.E. Thompson. The Laws of Proportioning Concrete. Journal of Transportation Division, American Society of Civil Engineers, Vol. 59, 1907. Thank you. —Preceding unsigned comment added by 202.70.74.132 (talk) 17:45, 17 November 2008 (UTC)

It sounds like you've found it! An article written in 1907 is not likely to be online - you'll probably have to take a trip to the library and get a copy on interlibrary loan. SteveBaker (talk) 21:37, 17 November 2008 (UTC)

comparative world livestock populations

Do we have a world list of livestock by quantity? i.e. how many domesticated pigs, goats, sheep, cattle, Bactrian camels, Arabian camels, donkeys, yak, horses, llamas, etc. are alive in the world today?--206.248.172.247 (talk) 17:57, 17 November 2008 (UTC)

This list provides information on cattle population by country, however it is not complete list. Otolemur crassicaudatus (talk) 18:06, 17 November 2008 (UTC)

Here is a good reference [4]. Click the arrow button to navigate to the other pages for information on other animals. Otolemur crassicaudatus (talk) 18:14, 17 November 2008 (UTC)

Compost pile

What happens if you put diseased plants into a compost pile? —Preceding unsigned comment added by 189.58.24.177 (talk) 20:27, 17 November 2008 (UTC)

That would depend on the disease. Some diseases might be specific to that type of plant or might be destroyed by the decomposition process, while others could possibly infect other plants which have the resulting compost spread around them. StuRat (talk) 20:34, 17 November 2008 (UTC)

If the compost gets "hot enough" during the decomposition process, it can kill disease organisms. However it is hard to be sure if your compost gets "hot enough". The cautious approach is not to put diseased plants into your compost system. CBHA (talk) 21:08, 17 November 2008 (UTC)

Math and physics podcasts

I've already found Mathgrad, Math mutation, Math factor, and Discrete Mathematics, but I'm having a harder time finding good physics podcasts. Could anyone please recommend podcasts about Math and Physics, not necessarily aimed at experts or professionals but maybe enlightened amateurs. Thank you. 190.220.104.35 (talk) 20:44, 17 November 2008 (UTC)

Well, Physics podcasts I don't know of, but usberkeley on youtube has physics lectures from 2007. I hope that helps 66.216.163.92 (talk) 23:39, 17 November 2008 (UTC)

type of screen

Does anyone know what technology is used for these station displays [5], [6]? They don't look like the traditional LED or plasma displays. And if possible can a link also be provided to the wikipedia article which explains the technology. Thanks in advance. Clover345 (talk) 20:54, 17 November 2008 (UTC)

I would guess they are digital rear projection screens utilizing DLP technology. They are large and bright and relatively cheap, but do have the disadvantages of being energy hogs, getting hot, and burning through bulbs. StuRat (talk) 03:50, 18 November 2008 (UTC)

Buoyancy

What causes the buoyancy force? The article doesn't really explain the origin of the force, just the equations used. —Preceding unsigned comment added by 76.69.241.185 (talk) 23:32, 17 November 2008 (UTC)

The medium (usually liquid) pushes on the object from all sides, but presses slightly less on the top than on the bottom because the bottom in this case is at higher pressure. If you push less on the top than on the bottom, the net force is up. SDY (talk) 00:11, 18 November 2008 (UTC)

Our buoyancy article does explain this in more or less those exact words. Because pressure increases with depth - the upward pressure on the underside of the object must be more than the pressure pushing down on the upper side because of the thickness of the object. Since the total upward facing area must equal the total downward facing area (measured at right angles to the gravitational field) - there must be a net upward force. The math falls out pretty simply from there. I suppose if you want the ULTIMATE source of the force - it's pressure - which is molecules in the fluid bouncing off of the object, imparting little bits of kinetic energy. But they bounce because of the electromagnetic repulsion between the outer electrons of the molecules - so that's a layer of explanation below that. SteveBaker (talk) 00:32, 18 November 2008 (UTC)

The explanations above do not explain why a stone doesn't float. And if an object does float in water, why doesn't it go on rising above the water, up into the air to the stratosphere, for the reasons given. (Air pressure on the bottom of the object is greater than air pressure on the top.) In fact, a submerged object that floats to the surface would leap into the air when the top of it leaves the water. (Directly below the surface, water pressure will not be greatly more than air pressure on the surface. But parts of the object that are deeper down will experience a rapidly increasing pressure with increasing depth because of the weight of the water around it. The pressure on the bottom of the object will be very much greater than the pressure on the top of the object, so it will leap out of the water, then continue to rise.) Actually, there will be an upward surge when the object breaks the surface, but it will not continue to rise into the stratosphere. Not many people can say "gotcha" to SteveBaker. —Preceding unsigned comment added by 98.16.67.220 (talk) 02:11, 18 November 2008 (UTC)

Well, that's because the difference in pressure in air is smaller than the difference in pressure in water, because water is denser than air...but I agree that the explanation doesn't make sense (in my mind, at least :)). See, wouldn't your explanation require that the shape of the object be significant. If the object was a sheet of something slightly denser than water with the same dimentions as a piece of paper, then in one orientation (long side perpendicular to the surface of the water) it might float because the bottom is much deeper than the bottom, while if rotated 90 degrees (so the long side is parallel to the surface) then it might sink for exactly the opposite reason. —Preceding unsigned comment added by 76.69.241.185 (talk) 02:21, 18 November 2008 (UTC)

Well, technically you have to think of it as billions of little molecules bouncing off the object. A sloped surface will transfer some down and some "right." In a cone, for example, all the "right" would be canceled by "left" and you'd get a net force that's either up or down. With an irregular object, it'll tumble as it rises or sinks. If you add up all of the vectors, though, you get a "down" force that's less than the "up" force. The main "enemy" is gravity (always "down" more or less by definition): if the net "up" force doesn't exceed that, the object sinks. Much easier to explain with a drawing, really. SDY (talk) 02:53, 18 November 2008 (UTC)

The reason a stone doesn't float - and most things don't float in air (although some clearly do) - is because the difference in pressure between the top and bottom doesn't exceed the weight of the object...so it still sinks (albeit a bit slower than it otherwise would have). My explanation makes it sound like a cone or something might behave wierdly - but you do have to read EXACTLY what I wrote. I said "Since the total upward facing area must equal the total downward facing area (measured at right angles to the gravitational field) - there must be a net upward force." - note the boldface here. A cone has the same area on the pointy end as the flat end when you measure the area at right angles to the gravitational field. As for your concern about a flat object and a flat object on its side: The surface area (at right angles to the gravitational field) of (say) a thin, flat, HORIZONTAL sheet of metal is large - but the pressure differential over it's skinny thickness is small. That small pressure differential multiplied by the large surface area (at right angles to the gravitational field) gives you the value for the buoyancy force. Turn the plate on it's side and the cross-sectional area (at right angles to the gravitational field) becomes very small indeed - but now it's much greater "height" increases the pressure differential between the 'top' and the 'bottom' edges of the plate. Crunch the math and you discover that the buoyancy of the plate remains the same no matter how you turn it around. In fact - it depends on the volume of the object - which is why we can neglect all of the complicated shape stuff and concentrate on the density of the object alone. Why an object breaking the surface doesn't leap up into the air is because the pressure on the bottom of the object depends on the depth of the water - which is now less than the thickness of the object - so even though the downward pressure has gone to more or less zero - the upward pressure is less than it was when the object was completely submerged - so as a floating object breaks the surface, the upward force gradually drops in strength until it exactly supports the weight of the object. SteveBaker (talk) 05:13, 18 November 2008 (UTC)

Ah, thank you for clearing that up. But I have another question: why does pressure increase with depth? I can understand why it would happen for a gas (the weight of the atmosphere above compresses the gas, increasing pressure), but why would the same happen for a non-compressable liquid? Thanks for your patience btw :) —Preceding unsigned comment added by 76.69.241.185 (talk) 23:50, 18 November 2008 (UTC)

The pressure is due to the weight of all the water above you...nothing complicated about that! Steel doesn't compress much either - but if I drop a one ton safe on you (OK - if I very gently LOWER a one ton safe onto you) - the pressure is still pretty significant!

Would you mind going into more detail? I see why there would be a greater force pushing down, but why would this force be distributed everywhere. —Preceding unsigned comment added by 76.69.241.185 (talk) 03:39, 20 November 2008 (UTC)

If you take a cube of jello and push down on the top of it hard with your thumb - what happens? It squishes out sideways - right? So the downward pressure of your thumb was translated into lateral pressure of the jello moving sideways. It's the same deal with the water. This has nothing to do with compressibility or incompressibility though. SteveBaker (talk) 20:14, 20 November 2008 (UTC)

I see why this would produce downward and lateral pressure, but how would upward pressure exist? —Preceding unsigned comment added by 76.69.241.185 (talk) 23:42, 20 November 2008 (UTC)

Here's another way to look at it. For simplicity, assume a flat-topped object is rising upward in water due to buoyancy. When the flat top is just a tiny bit below the water surface, the pressure on the top of the object is just a tiny bit less than pressure due to air pressure on the water surface. So when the object breaks the surface, there is no sudden decrease of pressure on top of it, so there will be no upward surge due to any sudden decrease of pressure on top. Of course, momentum will cause a surge, and breaking through the surface tension of the water will slightly slow the rate of upward motion. —Preceding unsigned comment added by 98.16.67.220 (talk) 15:35, 18 November 2008 (UTC)

Another factor is the viscosity of water. When the flat topped object breaks through the water surface, a little time will be needed for water to roll off the top of it. After the roll off, a film of water will remain, weighing the object down until the film of water evaporates. —Preceding unsigned comment added by 98.16.67.220 (talk) 22:52, 18 November 2008 (UTC)

November 18

CMBR

The article on cosmic microwave background radiation says that the radiation is isotropic except for a small blueshift because we're moving relative to the surface of last scattering. But shouldn't the side of the surface closer to the center of the universe be much warmer because there are more photons per cubic meter on the less-expanded side than on the more-expanded outer side? 71.176.180.12 (talk) 02:03, 18 November 2008 (UTC)

I think the universe is supposed to be expanding uniformly everywhere. StuRat (talk) 03:44, 18 November 2008 (UTC)

This is precisely the reason why measuring the background microwave radiation was so important. The mistake you're making is the all-too-common one of assuming that the big bang happened over 'there' and we're currently over 'here'. In fact, at the moment of the big bang, all of space was scrunched up in a teeny-tiny dot - which expanded rapidly in all directions. So there is no one particular direction you can point to and say "the big bang was over there". The big bang filled all of space at the time it happened - but space itself was very tiny. So the big bang is in every direction around us - which is why the cosmic background looks the same temperature in all directions. That discovery is the single thing that proves that the universe started with a big bang and not in some other manner. SteveBaker (talk) 04:56, 18 November 2008 (UTC)

The classic analogy to the big bang, for layman's understanding, is that of the inflating balloon. Take a balloon, and draw dots all over it. Picture yourself standing on any one dot, and blow the balloon up. All of the other dots are moving away from you. If you stand on any other dot, you observe the same thing; and yet NONE of the dots can be said to be the center of the expansion; if you run the expansion backwards beyond the empty balloon, and assume you can make the balloon infinitely small, ALL of the dots you drew are at that point; so ALL points are at the center... The universe works the same way, except in 3 dimensions instead of 2... --Jayron32.talk.contribs 18:53, 18 November 2008 (UTC)

To clarify, in that example you are a two dimensional creature living on the surface of the balloon, and can only see things along the surface. You have no ability to look inside or outside the surface. Also in that example, if you could look far enough in any direction, you would eventually see yourself. I wonder if that's true in our universe as well. StuRat (talk) 19:47, 18 November 2008 (UTC)

You're not the only one to wonder that. See Shape of the universe#Global geometry. --Tango (talk) 19:50, 18 November 2008 (UTC)

The problem is that even though the universe might have the 4-dimensional topology of a sphere or torus - it's certainly too big to be able to see all the way around it. We know that the observable part universe does not wrap back upon itself - we don't see identical copies of the same galaxies repeating off into the distance. So if it is sphere-like in topology then it's got to be too large for anyone to be able to directly observe that fact. SteveBaker (talk) 20:11, 20 November 2008 (UTC)

Or maybe we just need a larger telescope. Perhaps we can see our own galaxy now, but only as a distant, fuzzy point of light which we don't yet recognize. StuRat (talk) 02:16, 21 November 2008 (UTC)

Theremin range?

What exactly is the playing range of the theremin? I've heard it stated as just slightly higher and lower than the cello, is this true? Kenjibeast (talk) 02:23, 18 November 2008 (UTC)

The Theremin can play a range from subsonic into supersonic if it is designed to do so. In fact, even a Theremin designed for only the audio range will probably extend beyond the audio range, unknown to the designer of it, if the electrical values of the components used allow that. Basically, it's just an audio oscillator. —Preceding unsigned comment added by 98.16.67.220 (talk) 02:35, 18 November 2008 (UTC)

Alright, let's talk the Moog etherwave model in particular. That one. What's that one's range. Kenjibeast (talk) 02:40, 18 November 2008 (UTC)

That would take some complicated figuring, taking into account every component in the Theremin including its speaker. An easier way is it to have a very good microphone pick up the sound and supply it to an oscilloscope. The oscilloscope will show the basic frequency of the sounds. The microphone would have to respond to subsonic and supersonic audio, if you are interested in that and if the Theremin will go that low and that high. Or a good musician can match the lowest and highest frequencies of the Theremin on a musical instrument and name the pitch he is playing. —Preceding unsigned comment added by 98.16.67.220 (talk) 03:25, 18 November 2008 (UTC)

The Etherwave's tone is produced in a circuit configuration called a beat frequency oscillator. It consists of two high-frequency oscillators, plus a detector circuit which extracts the difference frequency, or beat frequency. One of the highfrequency oscillators (called the fixed pitch oscillator) operates at about 285 kHz, while the other high-frequency oscillator (called the variable pitch oscillator) operates over a range of about 282 - 285 kHz. The difference frequency ranges from zero to about 3 kHz, which is three and a half octaves above middle C. The pitch antenna circuit is connected to the variable pitch oscillator in such a way that increases in hand capacitance will decrease the variable pitch frequency as much as 3 kHz. This is how the pitch antenna circuit, in conjunction with the beat frequency oscillator circuit, enables the player to cover a usable pitch range of some five octaves (two octaves below to three octaves above middle C) simply by moving her right hand through a distance of two feet or so.

From here : UNDERSTANDING, CUSTOMIZING, AND HOT-RODDING YOUR ETHERWAVE ® THEREMIN. Hope this helps. APL (talk) 03:55, 18 November 2008 (UTC)

How can air barriers be permeable to vapor?

Resolved

I just read the following:

The water vapor molecule is smaller than airs other molecules - nitrogen and oxygen. Therefore, water vapor can squeeze through smaller microscopic spaces than air.

How can this be true? It certainly isn't true in a space-filling model: If H-O-H fits through an opening, so will O-O, because the former has to be at least as wide as an O atom, and the latter can't be wider than that.

It is conceivable that the picture looks different when we regard the orbital model. However, I don't think the effect is favorable for water, which has big lobes sticking out of the O on the opposite side of the two H. Moreover, it has high van der Waals forces, which should, if anything, rather contribute to the water getting stuck in narrow openings. — Sebastian 04:03, 18 November 2008 (UTC)

I'm no chemist - but hydrogen atoms are very, very tiny compared to oxygen or nitrogen. Certainly the weight of H2O is a LOT less than O2 or N2. SteveBaker (talk) 04:50, 18 November 2008 (UTC)

Water creates strong hydrogen bonds. As such, I'd expect it would be harder to squeeze through. — DanielLC 04:58, 18 November 2008 (UTC)

Yup, that's what I meant by van der Waals forces. — Sebastian 10:00, 18 November 2008 (UTC)

EC:The size of atoms isn't necessarily simply additive in molecules, as they can overlap when they share electrons or they can have empty spaces inside the molecules as in a benzene ring, buckyball, or carbon nanotube. Also, it's not as simple as the size of the molecule and the size of the holes. The molecules of the gas and container may have various attractions for each other which make passage difficult or impossible. StuRat (talk) 05:06, 18 November 2008 (UTC)

In reply to both of you: The holes could of course be hydrophobic, but that wouldn't be the same argument as the one I quoted. So, can we conclude that that argument is humbug? — Sebastian 10:00, 18 November 2008 (UTC)

On second thought, hydrophobicity should not play a role, as it is, according to our pertinent article, only a consequence of the bonds among water molecules being stronger than those with the surface - which is not the case for vapor. So, the question is: How can air barriers be permeable to vapor? — Sebastian 10:11, 18 November 2008 (UTC)

For atoms and molecules, they aren't all going to line up, they are constantly tumbling and twisting, so its not the SMALLEST dimension that matters, its the LARGEST dimension. In the case of dioxygen, the longest dimension is larger than that of water vapor. Doing a quick search, the O-H bond length in water vapor is expected to be about 95 picometers, and in dioxygen its 121 picometers. Likewise, the atomic radius of hydrogen is 25 picometers and the atomic radius of oxygen is 60 pm. I know that these are not truly additive, but doing a fermi calculation or spherical cow type aproximation should at least show that the O=O size in dioxygen (60+121+60 = 241) is much larger than the O-H size in water (25+95+60 = 180). It turns out that at these scales, molar mass is as good of a first approximation to molecular volume as any; one generally only considers that when judging the "size" of a molecule; and under that test, dioxygen (32) is much larger than water (18). --Jayron32.talk.contribs 13:09, 18 November 2008 (UTC)

Great explanation - thanks a lot! I will see if I can add that to air barrier somehow. — Sebastian 18:40, 18 November 2008 (UTC)

Advice for developing young scientists?

I am a recent graduate of microbiology at University of Texas at Austin. I want to plan a career in a relatively emerging and promising frontier of science, such as molecular genetics or cancer biology. However, the answer to these questions can be useful to any recent graduate.

What new and emerging field of science do you find have the biggest opportunity for future employment prospects i.e. what industry that is based on the science will always be in high demand? I personally had molecular genetics, cancer and developmental biology in mind.70.112.163.212 (talk) 05:15, 18 November 2008 (UTC)

Those all seem like jobs that will be in high demand, but there's another dimension you should consider. Even though such jobs may be in high demand, if they can be outsourced to someone for less pay in India, they will be, eventually (or you will need to take a drastic pay cut to compete with them). You need to find a job that can't possibly be outsourced, if you want a career for life. One that comes to mind is biowarfare, as defense related jobs can't be outsourced for security reasons. You might also be able to get some government job at the Atlanta Centers for Disease Control that would be somewhat secure. StuRat (talk) 05:35, 18 November 2008 (UTC)

What method of study besides job experience do you recommend for getting as up-to-date with that field as humanly possibly?70.112.163.212 (talk) 05:15, 18 November 2008 (UTC)

Reading trade magazines might help. If you can't find a mag specific to microbiology, you could go with some general science mags like Scientific American and Nature. Medical publications like the New England Journal of Medicine and JAMA might also be good (but beware that pharma companies routinely "plant" fake articles in those pubs to promote their products). StuRat (talk) 05:43, 18 November 2008 (UTC)

To reemphasize what StuRat said, the best way of being up-to-date in a field is to read the articles in the journals relevant to that field. This will be quite difficult to all but the most advanced undergraduates, but with time you will find yourself going through them with increasing ease. Magazines like Science and Nature are good, but they are general so a microbiology article may be beside an article on geology (there's no need worrying about things outside of your intended specialty). If you don't know the ranking of journals in your field then feel free to ask a professor or two which ones are the premier journals, they'll definitely know. There's no point paying too much attention (and spending too much time struggling through) journal articles in a journal that people do not respect. With time you'll be able to figure out which journals are rigorous and reliable, but as an undergrad you're probably going to have to rely on professors or grad-students.--droptone (talk) 19:04, 18 November 2008 (UTC)

What books do you recommend for obtaining a deep "philosophical" and practical grasping of basic tenants of science, what is its role in our modern world, what customs exist in the profession, and how researchers carry out their methodology. For instance, what percentage of experiments are novel, and what percentage are simply an extrapolation and testing of ideas that were advanced by a single or select group of researchers? What makes a good scientist a good scientist?70.112.163.212 (talk) 05:15, 18 November 2008 (UTC)

Sidestepping for a moment, you could talk to your ex-professor or one in another university and ask what the gaps for research in your area are at the moment. E.O. Wilson the ant expert invented the word "sociobiology" afaik, and said if he had his life over, he would be a microbiologist. He's a cool role model as scientists go. I would start with him and anything he's written for iinspiration. Julia Rossi (talk) 05:49, 18 November 2008 (UTC)

@StuRat: You failed to take into account the government grants that go into R&D. Whenever the govt. needs to diversify (for GDP growth etc. or like the current credit crunch) it will spend more on R&D. --Movieideas (talk) 12:33, 18 November 2008 (UTC)

I'm not sure how that counters what I said about outsourcing. Are you saying that all government grants will prohibit outsourcing ? That's clearly not the case, as many in the past have permitted this. The most ironic example is using illegal immigrants to build the wall with Mexico to prevent illegal immigration. I'd suspect that in the future, as less and less money is available for government programs and outsourcing becomes more acceptable, a larger portion of government contracts will allow outsourcing. The one exception is an actual jobs program (with the goal of giving out jobs). However, I'd expect those to provide minimal "safety net" jobs to prevent people from going onto welfare, not high-end careers. StuRat (talk) 19:38, 18 November 2008 (UTC)

Well atleast they won't be outsourcing Doctors anytime soon. So to the OP I would suggest get an MD degree. --Movieideas (talk) 00:40, 19 November 2008 (UTC)

I wouldn't be so sure about that. Test results can certainly be sent to a doc in India for him to examine and come up with a diagnosis and treatment plan. Digital photos/CAT scan images of areas of interest can be sent, too. There is even the possibility of performing surgery remotely using robotic technology. This has already been done a few times. StuRat (talk) 18:35, 19 November 2008 (UTC)

@OP: I would suggest you read this business article: Pharma struggles to adapt as patents expire http://www.reuters.com/article/Health08/idUSTRE4AF1QS20081117 --Movieideas (talk) 12:38, 18 November 2008 (UTC)

Not quite sure whether the CDC is such a great idea. Right now many researchers have abandoned ship because the work environment there has been getting steadily worse, with the tips of the icebergs scandals infrequently making it into the local paper (ajc). What does it help if your job is secure, but you'd rather do anything than go to work? This may however be about to change in the current political winds. Similarly military spending is highly dependent on political decisions. Defense contracts may not be subject to outsourcing, they can however be canceled due to budget cuts. Given that the US is currently financially over-extended I'd expect previously cushy government backed positions to be on a lot more shaky ground now. (OR example: Several communities in Germany found their economic rug pulled from underneath them when the US started closing their bases.) Droptone's assurance that reading anything outside of your immediate field would be a waste of time I can't second either. That works fine if your aim is to work at refining existing results. OP stated that he wanted to work at the frontiers of his field. Radically new ideas are usually the result of cross-pollination from other fields. I forgot whose quote it is, but some researcher said that once a sub-category in science had been given a name, all the most interesting and excitingly new science was done and what was left was filling in the gaps and fleshing out the details. On the other hand if you are looking for a secure career path the frontier is not really the place to go. For every shining star-scientist featured in magazines with their new multi million $$ IPO there are troves that slave in underfunded labs always one step away from a major breakthrough, which then comes to someone else or years after they've given up. You may be lucky and get both to do exiting new science and step onto a road to financial success, or not. Most people end up having to chose either or at some point (or more likely several times during their lives). I would not get scared out of my choice by the fact that someone else might be able to do it cheaper. No one has a crystal ball and can say what the future may hold. Today's sure thing can be tomorrow's dud. (OR: One of my relatives was convinced to choose baker as a profession because people would always need bread - shortly before factory bakeries became commonplace. Many of his peers changed fields. He specialized and made a mint with a small specialty bakery.) Given that, where would I look for advances in microbiology? The following are areas where I see a need for advances which is usually a good indicator: Bio-fuels: The EC is funding algae /sewage based projects. Maybe something similar, or novel to get from solar to gas without going via food plants and using arable land? Materials science: we are running out of resources in other things but fuel. Breeding microorganisms to reclaim waste, or build new materials with similar or better properties than what we used to have sounds interesting. Water: both turning water from various sources into drinking/potable water and removing pollutants from wastewater are fields with lots of opportunities Human-machine interfaces: Prosthetics and TBI [7] make this an area where even small advances have a a large impact. (- or you'll end up building the foundations for the next game console ;-) If you find cancer research overpopulated you might have better luck with diabetes. Human gut bacteria are not well understood from what I've read. Maybe one of those could be re-programmed to produce insulin? And totally off the wall: you could design a couple of bugs that eat/digest the explosives in the many unexploded land-mines that make farmland unusable in countless places. Also, have a peek at economics and political pages. See what companies (still) have money and what they are interested in and what projects political leaders put their weight behind. Then see if there is an angle where you could provide some advances in related sciences that they might fund. Don't worry if you don't get it right on the first try. I don't have comparative numbers, but many people go through several careers in their lives. Good luck. 76.97.245.5 (talk) 00:59, 22 November 2008 (UTC)

Resistance in space.

Does anyone know the resistance of outer space? Preferably as a function of distance from the Sun? I asked this as part of another question earlier. So far, the only answer I got was:

The resistance in space is pretty frigging huge. You need a series of actual atoms to transfer electrons along; and atoms are few and far between in space, so the resistance is likely, um, excuse the pun, "astronomically high". --Jayron32.talk.contribs 15:36, 17 November 2008 (UTC)

Let me continue from there. IIRC, space contains large numbers of ions and free electrons. This would cause the Earth's charge to slowly leak. This is quite different than how electricity normally works, so I don't know if the electrical conductance in space can be modeled the same, but I'm doing it on a planetary scale, so if there's anything slowing the charge down at all, it seems like the normal model might work. In addition, I'm dealing with a huge time-frame (5.5 billion years). Put simply, making a charge of 8e17 C once, and making it once every million years to keep it from going away, make the resulting difficulty in destroying the Earth differ by over three orders of magnitude. — DanielLC 05:26, 18 November 2008 (UTC)

Is the Earth also being constantly charged by the solar wind ? StuRat (talk) 06:42, 18 November 2008 (UTC)

Electromagnetic forces are vastly more powerful than gravity - if there was even a fraction of a volt difference in the charge on any of the planets or the sun, the solar system would be a very different place! If there is a 'charging' mechanism - then there must be a corresponding discharge mechanism...I kinda doubt that either are significant. SteveBaker (talk) 13:38, 18 November 2008 (UTC)

Steve, your intuition fails you. Yes, the electrostatic force between two protons is 10³⁶ times greater than the gravitational attraction between them, but the Earth is massive, having 10⁵¹ nucleons. So to put electrostatic forces on a similar scale to gravity you need an excess charge of say 1 electron for every 10¹⁸ nucleons, or a total of 10¹⁴ Coulombs of charge. That would give the Earth a potential of approximately 10¹⁷ V. A few volts is nothing on planetary scales. Dragons flight (talk) 17:20, 18 November 2008 (UTC)

I just noticed I didn't explain very well why I think space would conduct electricity. I mean that the ions of opposite charge would move towards the earth, and the ions of the same charge would move away, thus slightly increasing the amount of oppositely aligned ions entering the atmosphere, and decreasing the amount of similarly aligned ions. If there's nothing slowing the ions down, they'd just keep accelerating and causing the charge to go away faster and faster, but if they are slowed down, it would act the same as the atoms slowing down electrons in a conductor, just on a larger scale, making the normal models still work. — DanielLC 16:16, 18 November 2008 (UTC)

Your intuition is correct, and the solar wind is a ready-made conductor. But the problem is that neither it nor a true vacuum are ohmic conductors (only the intro of that article is relevant here); they don't have a single, well-defined "resistance" but rather a more general I-V curve. See also breakdown voltage. --Tardis (talk) 17:39, 18 November 2008 (UTC)

"Space" is a hard vacuum. A Vacuum tube usually has a hard vacuum. Both have immeasurably high resistance when there are no electrons or ions present in the space between electrodes. In some early (1930's) science fiction a plot gimmick was that the bad guy had broken the glass on the vacuum tubes, so the spaceman could not broadcast a warning message from his spaceship. The spaceman just donned his space suit and opened the hatch, making the interior of the ship a hard vacuum like outside, and the tubes worked fine. My point is that if you tested resistance of space by having metal surfaces some distance apart and applying a voltage between them while measuring the current, no current would be detected unless there were ionized gas atoms introduced between them, or unless electrons were emitted from the one with the negative charge.The Photoelectric effect describes how a metal piece will emit an electron when it absorbs electromagnetic radiation. As noted, there are some ions in space and there are some electrons, and these could carry a small current. The resistivity of space would depend on what ions and electrons were in it. Hot metal will emit electron via Thermionic emission. Edison (talk) 17:48, 18 November 2008 (UTC)

Tardis, do you know what the equation for this I-V curve is, or where I could find out? — DanielLC 06:03, 19 November 2008 (UTC)

(Sorry for the delayed response.) There isn't going to be a single curve because there isn't a single vacuum (or a single solar wind); it depends critically on the size and arrangement of your contacts, and even what material they're made of and what temperature they are. (If the current heats them, then the I-V curve changes over time and depends on the history of your voltage!) What I do konw is that for a true vacuum, there will be no current at all below the breakdown voltage (barring insignificant quantum effects like quantum tunnelling), and that above it there will be a current limited by the geometry of the system. --Tardis (talk) 22:53, 22 November 2008 (UTC)

Tankers and aircraft carriers

In this morning's reports of the hijacking of the oil tanker Sirius Star, an American Navy official is quoted as saying that the tanker, "(is) three times the size of an aircraft carrier." The Sirius Star is 330 metres long, or 1082 feet. After some googling around, I can't find any type of aircraft carrier that is shorter than about 800 feet. It isn't too easy to compare the 'weights', as there seem to be deadweight tons, shortweight tons, metric tons, and displacement. In any case, is there any measure by which this supertanker can be fairly described as 'three times the size of an aircraft carrier'? Audacious pirates anyway... —Preceding unsigned comment added by 80.101.134.43 (talk) 09:28, 18 November 2008 (UTC)

The Sirius Star has a displacement of over 300,000 tons. A Nimitz class aircraft carrier (the largest aircraft carrier ever) displaces just over 100,000 fully loaded, according to its infobox. Clarityfiend (talk) 10:07, 18 November 2008 (UTC)

See Tonnage for a bunch of ways to measure ship sizes. PrimeHunter (talk) 18:13, 18 November 2008 (UTC)

The term "size" is incredibly vague, and thus can be molded to whichever direction the writer wants. If they wanted to convince you the aircraft carrier was larger, they would likely compare the masses when unloaded and call that the "size". StuRat (talk) 19:26, 18 November 2008 (UTC)

Selective breeding pros/cons

What are the pros and cons of selective breeding? is it ethical/unethical? Discuss —Preceding unsigned comment added by Fas327 (talk • contribs) 09:57, 18 November 2008 (UTC)

That little word 'discuss' signfies...homework. As noted at the top of the page we're not here to do your homework. If you want to consider the ethics of breeding etc. perhaps search for any pro or anti organisations mentioned in your text-books with regards to it. Also read through Selective breeding and the subsequent links that page will likely contain. 194.221.133.226 (talk) 10:42, 18 November 2008 (UTC)

Not to mention the rules agreed to when posting to the ref desks: "The reference desk does not answer requests for opinions or predictions about future events. Do not start a debate; please seek an internet forum instead." -- Aeluwas (talk) 12:35, 18 November 2008 (UTC)

Rhode Island is neither a road, nor an island. Discuss. --Shaggorama (talk) 00:12, 19 November 2008 (UTC)

Brain Tumor Cells vs. Normal Brain Cells

• What is the difference between Brain Tumor Cells and Normal Brain Cells?

• The article Brain tumor states: A brain tumor is any intracranial tumor created by abnormal and uncontrolled cell division, normally either in the brain itself (neurons, glial cells (astrocytes, oligodendrocytes, ependymal cells), lymphatic tissue, blood vessels), in the cranial nerves (myelin-producing Schwann cells), in the brain envelopes (meninges), skull, pituitary and pineal gland.

• So can the body to use the tumor cells for Thinking? --Movieideas (talk) 12:24, 18 November 2008 (UTC)

No, you can not use the tumor cells for thinking, as illustrated in this fascinating article about an awake craniotomy. --Sean 13:34, 18 November 2008 (UTC)

I once read a creepy science fiction short story about a college lecturer who quoted "I think, therefore I am" and the thought took shape as a cancerous brain cell which became a tumor which grew and took over his thought processes, basically arguing with him, before he died from the effects of the rapidly growing tumor. Edison (talk) 20:27, 18 November 2008 (UTC)

Your fascinating article doesn't state why we cannot think using the tumor cells? Or what is the difference? I mean if it is uncontrolled cell division, so there would be more neurons, and then there would be neurotransmitters, to facilitate thinking? --Movieideas (talk) 00:28, 19 November 2008 (UTC)

The problem with "thinking" is that it is far more than an issue of the number of cells or the amount of neurotransmitters. What we perceive as "thinking" is the result of exceedingly complex brain architecture and neurophysiology that requires coordinated electrical and chemical signals between various parts of the brain (unfortunately, neuroanatomy and nervous system don't really do this topic justice). Even those functions of the nervous system that operate autonomously (i.e. you're not aware of them happening, like control of your breathing, heart rate and blood pressure) require an exquisite circuitry that is simply not present in a tumor mass. While the cells involved in that tumor may derive from a cell type that was once a functional neuron, or had the potential to become a functioning neuron, the uncontrolled cell division means that these cancer cells never extend functional neuronal processes that would enable cell-cell communication in any kind of coordinated fashion. In fact, a brain tumor might cause a structural or electrical distortion that impairs your function in one way or another, perhaps resulting in seizures or other neurological impairment. The simple answer to your question, as stated above, is no. Medical geneticist (talk) 15:53, 19 November 2008 (UTC)

Where does the Earth's heat go?

This has puzzled me since I was a kid. The Earth is a closed system (more or less). The Sun constantly heats the Earth. So shouldn't the Earth be constantly getting hotter and hotter? Heat is the vibration of atoms and space is a vacuum. So where does all the heat go? 67.184.14.87 (talk) 14:08, 18 November 2008 (UTC)

It emits it into space as infra-red radiation. See thermal radiation. --Tango (talk) 14:20, 18 November 2008 (UTC)

The Earth is not a closed system. If it were, it would not absorb heat from the Sun. --—— Gadget850 (Ed) ^talk - 14:31, 18 November 2008 (UTC)

By the way, Earth is also heated by radioactive decay. Omission of that factor caused a bad estimate mentioned in Age of the Earth#Early calculations: physicists, geologists and biologists. PrimeHunter (talk) 16:55, 18 November 2008 (UTC)

Most of it bounces is sent back into space as mentioned above, but some of it gets captured as chemical energy by plants. --Sean 17:07, 18 November 2008 (UTC)

There is a difference between the radiation from the sun reflecting back into space and it being absorbed and re-emitted - both happen. --Tango (talk) 17:55, 18 November 2008 (UTC)

I know, and was using "bounce" loosely. In my pedantic defense, even reflection consists of absorption and re-emission. --Sean 18:45, 18 November 2008 (UTC)

The basic error in your assumptions was that all forms of heat transfer require a medium. While this is true of convection (fluid required) and conduction (fluid or solid required), this is not true of thermal radiation, which can happen across a vacuum. Radiation is actually more effective in a vacuum, as no portion of the radiation is absorbed or reflected by the medium. StuRat (talk) 19:13, 18 November 2008 (UTC)

Yes - the confusion is that heat (the kinetic energy due to the motion of molecules) can be converted to electromagnetic radiation (like infra-red light) - which IS NOT HEAT (which is kinetic energy) but instead electromagnetic energy. The infra-red light subsequently hits some molecules and sets them off moving - thereby giving them kinetic energy (which manifests itself as heat). Hence, one way for the earth to cool off (to slow down it's molecules) is by radiating infra-red light. This is only one of three traditional ways to describe the shedding of heat (Radiation, Conduction, Convection) - the latter two don't work in a vacuum - but the first does. It's convenient to think of the heat 'flowing' from one place to another - but in the case of radiative loss/gain, it's really not. The heat is "going away" and being replaced by IR light - then (eventually) the light hits something and (typically) creates heat as a result. However, the IR light could instead hit an electron and cause an electric current to flow or cause some other kind of energy to be created. SteveBaker (talk) 19:39, 18 November 2008 (UTC)

is Jesus's 100% man/100% God dualty like quantum wave/particle dualty?

So Christians think that Jesus is completely, 100% a normal human being, he can die, everything about him is normal, he's just like you and me. At the SAME time, he's 100% God Himself. He's completely God. It's not that he's 20% Human and 80% God. He's completely a mortal human and completely immortal God. Obviously, this is ridiculously illogical and anyone who would believe that is off their rockers....I was thinking.

But wait: I remembered that reality itself has such a dualty! Light is 100% a wave, it interacts in wave patterns, by any standard you could measure it's completely a wave. But it's also a particle, it comes in photons, by any standard you could measure it completely comes in particles. So it seems you don't have to be ridiculously illogical to believe that, since our physical universe ACTUALLY has such a manifestation! But I'm not a quantum physicist so, could I ask:

Is my conclusion right? If Christians believe what I said about Jesus, is it comparable to what quantum physicists believe about light? Thank you! —Preceding unsigned comment added by 79.122.75.250 (talk) 14:28, 18 November 2008 (UTC)

You're really speaking in metaphors here all the way through so I'm not sure whether the comparison is bad or good. Light it isn't a wave or a particle—it's light, and we understand that macroscopically as being something of dual nature (we understand it in the terms in which we know how to think). You could, I suppose, make the argument that indeed, the dual humanity/Godness of Jesus is something similar, that he would be, in fact, just "Jesus", and that we abstract that in terms we understanding (either all man or all God, depending on the context). But it's not a real one-to-one scientific comparison at all, though I suppose both appeal to realms of non-standard logic, logic in spheres outside of our mere mortal comprehensions. --98.217.8.46 (talk) 14:32, 18 November 2008 (UTC)

Your first fallacy is thinking that all Christians have the same beliefs about Jesus; see Christian views of Jesus. --—— Gadget850 (Ed) ^talk - 14:40, 18 November 2008 (UTC)

Put simply, we don't say light is a wave and a particle, we say it behaves as a wave and a particle in different contexts. Whether that is similar in any way to Christian understanding of Jesus is something for another ref desk. --Tango (talk) 15:42, 18 November 2008 (UTC)

I have a magical coin in my pocket that is both perfectly round and perfectly square at the same time. The difference between the respective dual natures of light and my coin is that one of them will stand up to centuries of well-funded and intellectually rigorous scientific inquiry by the smartest people on Earth, and one of them won't. I'll let you guess which is which, and which might be more akin to Jesus's dual nature in that regard. --Sean 17:06, 18 November 2008 (UTC)

This is the science desk - not the guessing-wildly-about-the-supernatural desk. The scientific answer is that we have been given no opportunity to perform any experiments on either Jesus or God - and we actually have no evidence that either ever existed. So it's unreasonable to expect us to have an answer for you. An analogy is not a way to reason about the universe...it's a way to explain something that you already understand. SteveBaker (talk) 19:31, 18 November 2008 (UTC)

Well, that's not completely true. AFAIK, most historians believe that a Jewish religious leader named Jesus did exist 2 thousand years ago. 67.184.14.87 (talk)

Some, certainly. I don't know about most. It's far from all. We have an article, historical Jesus, but it's been a while since I've read it. --Tango (talk) 22:48, 18 November 2008 (UTC)

Then read Historicity of Jesus - which asks what actual EVIDENCE there is - as opposed to what may be inferred from the dangerous assumption that the bible is basically correct (which is what Historical Jesus discusses). The former says that aside from the (somewhat biassed) reports in the Bible - the first independent account was around 100 years after Jesus supposedly died when the whole religious thing was beginning to get off the ground. This can only be a second or third-hand account. So there really is no independent, reliable evidence. Certainly not enough to base an answer to this question on! SteveBaker (talk) 20:06, 20 November 2008 (UTC)

Anatomy

Can someone link me to some information on the evolution of the ear, or make a wikipedia page on it? Evolution of the nose wanted, too :) I'm curious... Also, any information on the evolution of blood (not individual blood types like A and B but the substance of blood) would be cool. Could someone compare and make a cross-section on the differences between different species' blood? Or at least groups of species (insects, mammals, fish etc.), please. Also, how do the immune systems of smaller organisms like insects work? Can someone further explain the system through which lymph is conveyed through the body, and also compare that to other organisms' lymph transportation? Some more questions about blood - I know that Red blood cells live about 120 days, and they go to the Liver to be "cleaned" (this is correct, right?), but how often do they go? How are they cleaned? Also, how does Hemoglobin work? I know that arteries move RBCs through peristalsis - does this mean that arteries are smooth muscle? How do veins keep that momentum of the blood up, especially far away from the heart? veins use valves, don't they? Are the valves cells of their own, or inanimate proteins or what? Oh, and evolution proponents say that one human chromosome is the fusion of 2 chimp ones or something like that. Without getting into a pro/anti-evolution debate, how could these have fused gradually/quickly?

Thanks for all your time. Answer as much as you can :) I really like learning and am curious about this stuff... —Preceding unsigned comment added by 216.102.78.170 (talk) 16:45, 18 November 2008 (UTC)

That's too many questions for a humble refdesker like me to answer, but I'll point out that arteries do not move red blood cells through peristalsis! See heart. --Sean 18:51, 18 November 2008 (UTC)

True, of course. However, the questioner is correct in asserting that the arteries have smooth muscle. Its function is vasoconstriction, which is used for the regulation of blood pressure, conservation of heat (directing blood away from the skin when it's cold) etc. --NorwegianBlue ^talk 21:17, 18 November 2008 (UTC)

Just a comment on the valve question. Those aren't valves that the body controls, they are simple valves, just a flap over an opening, such that the flap is closed when movement occurs in the opposite from normal direction, and open when flow is in the correct direction:

_____________________
           /|
 Flow  -> /   Flow
 Dir     /    Dir
 Closes /     Opens
 Valve /  <-  Valve
      /
            |        

StuRat (talk) 19:09, 18 November 2008 (UTC)

And the valves are MUCH larger than individual cells, they are macroscopic, and composed of both cells and extracellular proteins. The proteins are mostly collagen, many of the cells are fibroblasts, and the valve is covered by endothelial cells. --NorwegianBlue ^talk 20:31, 18 November 2008 (UTC)

• The lymph question is answered in the articles Lymph and Lymphatic system. Basically, what is to become lymph is part of the plasma of the blood as it leaves the heart. In the capillary network, some of the plasma leaves the blood and becomes interstitial fluid. Most of it goes back into the venous blood in the venules. The surplus enters lymphatic capillaries. Note that the lymph vessels start as "blind alleys" into which this liquid enters, before moving towards the great veins in the neck, where it enters the bloodstream. Lymph vessels have valves, and the transport of the lymph against gravity is in part caused by pressure from nearby pulsating arteries, in part by contraction of striated muscles (e.g. in your legs -- same thing as for the veins). According to our article, lymph vessels also have peristalsis. (I didn't know that, and am a bit sceptical -- could someone confirm? (User:Nunh-huh, are you reading this?))

• Well, I hadn't been, but now you've gone and invoked the name of the devil, and so I am. Small lymph vessels are thin-walled channels, typically just tubes consisting of endothelium, so they can have no peristalsis. Only the larger vessels have any muscular layer, and there is some sequential contraction in these that aid lymph flow. However, like you, I recognize that pretty much the only thing ever actually referred to as having peristalsis is the GI tract. I think the jury is out on which method of lymph propulsion is predominant: skeletal muscle compressing the lymphatics (with the one-way valves assuring that propulsion occurs in the proper direction), vs. propulsion intrinsic to the lymphatic vessel, and my money's on the importance of the former. But both have been observed, and described, and so both occur, regardless of which is more important. - Nunh-huh 03:13, 21 November 2008 (UTC)

• The liver/"blood cleaning" question: I have no idea what "cleaning" of red blood cells would mean. It is correct that the Kupffer cells of the liver may phagocytose aging red blood cells, but that is far from the most important function of the liver, and a task which is believed to be primarily performed by the spleen. See Liver. The key point in understanding its function, is realizing that it receives all the blood from the gut, with all the nutrients, and also all the nasty stuff, toxins etc. (For the exception, see Chyle - the lymph from the gut, which contains fat, and which bypasses the liver). So two of its most important tasks are buffering glucose as glycogen, to keep the blood glucose level stable between meals, and detoxifying otherwise toxic substances that are absorbed from the gut. In doing so, it also often modifies drugs that are taken orally. In addition to this, the liver has many other functions which are described in the article.
• The chimp question: see Chimpanzee genome project for a comparison of the genomes (human chromosome 2 is a fusion of two chimp chromosomes), and here for an explanation of the mechanics of how such a chromosomal rearrangement could happen. A single chromosomal rearrangement does not necessarily prevent meiosis from occurring, but heterozygotes tend to be less fertile and may have an evolutionary disadvantage. --NorwegianBlue ^talk 21:06, 18 November 2008 (UTC)

gama rays

is gama rays can break the atomic structure of water? because cosmic radiation break the water molecules in the air,bat in nuclear power station the water molecules in the steam tank dosent break down--אזרח תמים (talk) 17:41, 18 November 2008 (UTC)

Water is self-ionizing. The bonds will break (and quickly reform) if you just use harsh language towards it. -- kainaw™ 17:44, 18 November 2008 (UTC)

To clarify - water exists naturally as a mixture of H2O atoms, H+ ions and OH- ions, constantly splitting and recombining. Gamma rays may increase the rate at which that takes place, I'm not sure, but it won't make a great deal of difference (if they are splitting more often, they will recombine more often too, the proportions may shift slightly, but that's about it). --Tango (talk) 18:00, 18 November 2008 (UTC)

Plus, the number of actual gamma ray particles compared to the number of water molecules is vanishingly small. Grab a geiger counter sometime and listen to the clicks. In a normal room, they go click...pause...pause...click...pause...pause...click. Each click is a gamma ray - so just imagine how few of the 100,000,000,000,000,000,000,000 or so water molecules in that bucket over there gets hit every second! Even in the presence of low level radioactive waste, the counter doesn't go completely nuts. So the extra ionisation caused by gamma rays through the water is really pretty negligable - even when the radioactivity is off-the-chart.

Another way to think about that (although my explanation is going to be a bit superficial and will probably be poked to death by the experts here) is that each gamma ray comes about because one unstable atom of the radioactive stuff decayed to something more stable. That one gamma ray then goes on to ionize one water molecule. So in order for (say) a kilogram of water to be ionized, an equivalent number of atoms of plutonium (or whatever) would have had to decay into something less nasty. But since plutonium atoms are super-heavy compared to water molecules, it would take VASTLY more than a kilogram of plutonium decaying completely to ionize one kilogram of water. But they put a few kilos of plutonium fuel rods in thousands of gallons of water - so the fraction of the water that'll get ionised is negligable. But in any case, all of that plutonium doesn't decay immediately - that's the entire problem! It sits there S-L-O-W-L-Y decaying for thousands of years.

SteveBaker (talk) 19:26, 18 November 2008 (UTC)

When the gamma ray hits a water molecule it could cause some unusual ionization. It is more likely to run into electons in an oxygen atom, because there are more of them there, and then eject a high energy electron and make a H₂O⁺, the moving electron then goes on knocking out many more electrons, and causing more ionization. I am guessing that you may get hydrogen peroxide and hydrogen molecules formed. But as SteveBaker says above, there will actually be very few molecules involved. Graeme Bartlett (talk) 20:36, 18 November 2008 (UTC)

In a normal environment, far from unusual radioactive sources, most of the clicks you hear from a Geiger counter are caused by cosmic ray produced muons not gamma rays. Dragons flight (talk) 00:15, 19 November 2008 (UTC)

The color of Dunkleosteus

I recall reading at one point that the actual color of Dunkleosteus had been determined due to some kind of chemical analysis of the fossil (bear with me--I read this a few years ago so my memory's a bit sketchy). This was an amazing announcement, but I'm not sure if I'm willing to believe it, because this information was packaged along with the "Arsinoitherium had hollow horns" assertment, which we know now is incorrect. So I am not sure if the claim about Dunkleosteus is valid or not. I can't seem to find any verification online, but I'm not sure if this is because there really isn't any such evidence, because I somehow missed the optimal keywords that would have brought me the results I wanted, or if it's just due to the material being unavailable online or in my particular language (there are a few paleocritters I can't find anything on, but I don't doubt that they exist). So what's the deal with Dunkleosteus? Do we know what color it was, or is this just another baseless "fact" that shouldn't be taken seriously? 70.213.5.52 (talk) 19:48, 18 November 2008 (UTC)

I can think of two ways to determine the color of the skin, fur or scales of a fossil:

1) Preservation of that skin, fur or scales. It might have been damaged, though, in which case a chemical or microscopic examination might still be able to find a few traces of pigment. However, fossils over a few thousand years old aren't likely to have any of the original skin, fur or scales remaining.

2) DNA analysis. DNA in teeth and bones can last a bit longer, but usually not millions of years. However, when it does last, it could theoretically be analyzed for pigmentation genes. However, this is a very complex process, and I'm not sure if it can be done at a reasonable cost and time-frame, yet. Give us a few years, though, and we will know everything there is to know about a dino, just from it's DNA.

Since the Dunkleosteus is some 360 million years old, I'd think it unlikely that either of those methods could work. StuRat (talk) 20:52, 18 November 2008 (UTC)

Yep the DNA will not work any time in the near future, the DNA is too degraded after 360 million years. It's pretty hard getting DNA from something 1000 years old. And we don't know enough about Dunkies to interpret any sequence data we might get. Aaadddaaammm (talk) 19:17, 20 November 2008 (UTC)

hubble telescope

How far into space can the hubble telescope see? —Preceding unsigned comment added by 208.100.237.47 (talk) 20:48, 18 November 2008 (UTC)

You might need to clarify the question. The Hubble telescope, or your eyeball, can each see an infinite distance if that distance contains a pure vacuum and the object on the other side is bright enough. However, the image it sees may just be a point of light, which isn't as useful as seeing, say, the spiral arms of a galaxy like ours, or, better yet, the individual stars within the galaxy. StuRat (talk) 20:55, 18 November 2008 (UTC)

The Hubble Ultra Deep Field is an image captured by a very long exposure. It captures images said to be "13 billion years" old. The obvious answer is to say that the objects in the picture (galaxies, mostly) must be 13 billion years old. But I'm not sure that that is correct. That's a big enough distance that you might have to take the expansion of the universe into account. I'm sure if you wait a bit someone knowledgeable about astronomy will clarify.

The HUDF was taken over a couple of weeks. 'Snapshots' with the telescope will obviously be less sensitive. APL (talk) 21:31, 18 November 2008 (UTC)

The light from them was, indeed, emitted 13 billion years ago, in the usual sense. They are (now), however, more than 13 billion light years away, due to expansion. --Tango (talk) 23:15, 18 November 2008 (UTC)

To complicate the answer there's also gravitational lensing to consider.76.97.245.5 (talk) 06:24, 21 November 2008 (UTC)

It's not really a fair question to ask how "far" a telescope can see. It all depends on its limiting magnitude, and in the case of Hubble, it can see all the way to the edge of the visible universe, assuming that the objects are bright enough. For comparison, the farthest object the human unaided eye can usually see would be the Andromeda Galaxy. ~AH1^(TCU) 16:17, 22 November 2008 (UTC)

However, with the "provided the object is bright enough" qualification, the human eye could also see to the edge of the universe. (But, of course, there aren't any objects that bright in the universe.) StuRat (talk) 21:02, 24 November 2008 (UTC)

Finding the amount of moles

Suppose that I had a 60% ethanol solution (40% water). How would I go about finding the moles of ethanol boiled off if I were to boil it for a certain period of time?

Basically what I am trying to do is boil the ethanol vapors for an experiment I am doing. I need to measure the amount of moles of ethanol in the vapors. I have access to lab equipment, so do not need to be hesitant with any suggestions if they include laboratory apparatus. Thanks. This is probably really simple but for some reason I can't think of the proper method to measure.

--proficient (talk) 21:32, 18 November 2008 (UTC)

The easiest method probably involves measuring the density of the solution after a given point in time. Since the density of the solution will tell you the relative concentration of the ethanol, once you know the final and initial masses of the solution, and final and initial densities, you can determine exactly how much of the loss of mass is water vapor and how much of the loss is ethanol vapor, and just convert these masses to moles. This page: [8] contains ALL SORTS of useful calculators and tables for figuring this stuff out. --Jayron32.talk.contribs 21:57, 18 November 2008 (UTC)

Titrate it with KMnO4 before and after to find he concentration of the ethanol.124.169.74.251 (talk) 23:07, 18 November 2008 (UTC)

That'd work too... though using a hydrometer would likely save a few steps and be a bit quicker... --Jayron32.talk.contribs 00:53, 19 November 2008 (UTC)

How many human habitable planets can there be in a solar system?

I'm watching Battlestar Galactica and a thought occurred to me. In the show, their solar system has 12 planets that are inhabited by mankind. It seems to me that it would be extremely unlikely, if not impossible, for a single solar system to have 12 planets that could be inhabited by humans. In fact, I'm wondering if how possible it is to have 2 planets within a solar system's habitable zone. So, theoretically speaking, how many planets can there be within a single solar system that could be habitable by man? By 'habitable' I mean that the people could live on it naturally without the need for a space suit or 'moon base' like enclosure. 67.184.14.87 (talk) 21:39, 18 November 2008 (UTC)

It depends on the type of star, hotter stars have wider habitable zones. Greenhouse effects and similar can expand the zone as well. I can't see a problem with two or maybe three planets being in the habitable zone. If there were more, they would have to be quite close together, which would probably only be stable if they were in resonant orbits (but there's no reason why they couldn't be in resonant orbits). If you allow habitable moons (or double planets), then the number of possible habitable places increases quite significantly. I haven't seen BSG, do they do any terraforming? If so, then that could increase the number significantly (depending on the effectiveness of their technology). --Tango (talk) 22:46, 18 November 2008 (UTC)

(after edit conflict)I suppose it would depend on how closely packed together the planets' orbits are. I don't suppose that there's any reason why you couldn't have several earth-type planets orbiting within a star's habitable zone.

• How about a binary/trinary/quadruple/quintuple star system with habitable planets orbiting each star?
• Do you include terraformed planets?
• Gas giants in the HZ with several habitable earth-sized moons?
• I think it's possible for more than one planet to share the same orbit too.

--Kurt Shaped Box (talk) 22:49, 18 November 2008 (UTC)

If you were to swap Mars and Venus, the solar system could have three reasonably-habitable planets. If you start doing fancy stuff like putting Earth-like planets in each other's L4 and L5 Lagrangian points, or put Earth-like moons in orbit around a superjovian planet, the numbers can get even higher. --Carnildo (talk) 23:06, 18 November 2008 (UTC)

And to discuss the premise that prompts this, I don't think BSG (at least not the new one) claims that all 12 planets are in a single system. Now Serenity, on the other hand.... — Lomn 00:00, 19 November 2008 (UTC)

According to Twelve Colonies (yeah, Wiki has everything!): The original series had them as twelve planets in a binary star system with some orbiting one star and some the other. The new series has not stated anything on screen about their relative location, but the series creator has indicated that they are again part of a single star system (without any discussion of how they are arranged). Dragons flight (talk) 00:06, 19 November 2008 (UTC)

Serenity/Firefly has a reasonable number of planets and moons (on the high side of reasonable, maybe), it's just terraformed them all into habitable ones. --Tango (talk) 00:13, 19 November 2008 (UTC)

There's no terraforming in the new BSG, at it's least not mentioned in the show. But after they leave their solar system, they travel a substantial distance (2-3 years almost 2 years worth of episodes) before they find another habitable planet, a dreary, shabby planet. I would have preferred to stay on the ships. 67.184.14.87 (talk) 00:43, 19 November 2008 (UTC)

And the next planet they find is also dreary and shabby. Possibly for a different reason, though. (Dun dun dun...) zafiroblue05 | Talk 08:43, 19 November 2008 (UTC)

God damn you all to hell! ;) It will be interesting to see what sort of twist they put on this. 67.184.14.87 (talk) 12:55, 19 November 2008 (UTC)

How hot would Venus be if it was in Mar's orbit?

67.184.14.87 (talk) 21:39, 18 November 2008 (UTC)

Just a guess, but perhaps as hot as Mars? But maybe that's too simple an answer. —Cyclonenim (talk · contribs · email) 22:17, 18 November 2008 (UTC)

No, because Venus has a green-house effect that dramatically raises temperature. 67.184.14.87 (talk) 22:33, 18 November 2008 (UTC)

As with any of "what if" question like this, it depends on exactly what you intend to change and what you want to keep the same. If a planet of Venus' size formed in place of Mars in its orbit, then it would probably be warmer than Mars, but colder than Earth (it would still have a significant atmosphere, which would keep it warmer than Mars, but due to its distance from the Sun it wouldn't be very warm). If Venus as it is now were to move to Mars' orbit, keeping its greenhouse effect, then it would still be pretty warm, although not as hot as it is now, I'm not sure how it would compare to Earth. --Tango (talk) 22:38, 18 November 2008 (UTC)

A very crude estimate is to note that transplanting Venus into Mars' orbit doubles the distance from the sun, hence reducing the received sunlight by a factor of 4. To reduce radiant energy by 4, you have to decrease the effective temperature of thermal radiation (roughly the cloud-top temperature) by 4^1/4. If we crudely imagine that the surface temperature scales proportionally to the cloud-top temperature then it might go from the 735 K at present to around 520 K (250 C). Of course that assumes that it's atmosphere stays intact and nothing else changes. Dragons flight (talk) 23:00, 18 November 2008 (UTC)

One of the factors involved would be the "heat albedo" of Venus -- its ability to reflect incoming heat radiation from the sun. —Preceding unsigned comment added by 98.16.67.220 (talk) 22:59, 18 November 2008 (UTC)

Another issue for this imaginary waste of time is the magnetic field. If Mars was in Venus' orbit, would it get a nice gooey core and start up a magnetic field again? If so, it could rebuild an atmosphere. If Venus was in Mars' orbit, would it get a nice hard nuget center, which would inhibit the magnetic field and, as a result, leave the atmosphere unprotected as it slowly wisps away into the void of space? Without an atmosphere, there's no greenhouse effect. -- kainaw™ 02:26, 19 November 2008 (UTC)

While a magnetic field certainly helps protect the atmosphere, is it strictly required? Also, being closer to the Sun, the solar wind is stronger so it would require a greater magnetic field to protect from it. --Tango (talk) 13:48, 19 November 2008 (UTC)

But being closer to the sun ALSO increases tidal forces on the solid part, increasing temperature of the solid bits itself. A good portion of Earth's warmth, for example, is from its internal heat. --Jayron32.talk.contribs 13:58, 19 November 2008 (UTC)

Without a magnetic field, I do not see how it is possible to maintain an atmosphere for any length of time. Solar winds will keep pushing away the outer atmosphere. The planet can try to replenish it, but the planet will eventually run out of gas to fill the atmosphere and you will end up with a planet like Mars, which likely had a magnetic field when it was full of internal heat, but the magnetic field died out and now the atmosphere is thin and getting thinner. Any attempt to pump in an atmosphere will be a waste of time since solar winds will keep stripping away anything that is pumped in. It is like trying keep a balloon inflated when it has a small hole in it. You can't fill it up and quit. You have to keep adding more and more air. -- kainaw™ 14:04, 19 November 2008 (UTC)

Why would Venus have trouble maintaining its atmoshere? It has an atmosphere now. 216.239.234.196 (talk) 14:43, 19 November 2008 (UTC)

Hmmm... this was probably mentioned just a few lines above... let me see... oh yes. It helps to read first and ask second...

Quoted from above: "If Venus was in Mars' orbit, would it get a nice hard nuget center, which would inhibit the magnetic field and, as a result, leave the atmosphere unprotected as it slowly wisps away into the void of space?" -- kainaw™ 14:50, 19 November 2008 (UTC)

Your rudeness aside, thank you for your answer. 216.239.234.196 (talk) 15:24, 19 November 2008 (UTC)

No, the core dynamo is not appreciably impacted by the orbit location. Also Venus has no appreciable dynamo, so your assumptions are false. Despite lacking a magnetic dynamo Venus has the largest atmosphere of any rocky planet. The solar wind probably robbed Venus of most of it's original water, but carbon dioxide and nitrogen are too heavy to easy ablate even without a field. Dragons flight (talk) 19:44, 19 November 2008 (UTC)

I looked it up and Venus is actually hotter than Mercury even though Mercury's much closer to the Sun. 216.239.234.196 (talk) 15:04, 20 November 2008 (UTC)

Indeed, that's due to the greenhouse effect. Mercury doesn't have an atmosphere (due to a combination of it being much smaller, so having weaker gravity, and it being closer to the Sun, so the heat and solar wind erodes the atmosphere more). --Tango (talk) 23:35, 20 November 2008 (UTC)

Newton's Second Law (F=ma)

I was wondering specifically one thing about Newton's Second Law.

Giving the basic summary, Issac Newton was an English physicist among many other things. He came up with the principle of Force = mass * acceleration.

The current system used in physics, even included in Newton's equation, is in the metric system. Mass is measured in kilograms, and acceleration is also measured in meters per second squared. The metric system didn't exist in Newton's time and first used the meter in 1793. This date is way after the proposed date of death of 1727 for Issac Newton, and you should even assume he published his book before his death. My main question?

When Issac Newton first wrote his book, what did he use in place of these metric units? —Preceding unsigned comment added by 68.83.4.99 (talk) 23:39, 18 November 2008 (UTC)

If you check Newton's_Second_Law#Newton.27s_second_law:_law_of_acceleration, you will see that Newton originally wrote Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur, i.e. a textual representation of the relationship in Latin (published in 1687). Formulas like F=ma do not depend on the units used. If you use pounds for mass and furlongs per decade squared for acceleration, your force will be in very weird units, but it will still be right. --Stephan Schulz (talk) 23:46, 18 November 2008 (UTC)

(ec)Newton's statement of his second law was unit-free. From Wikisource: The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the straight line in which that force is impressed. I don't know what units he used for force or momentum when he used units at all. Algebraist 23:47, 18 November 2008 (UTC)

The metric system is just a series of standardized units. Before the metric system, people had all sorts of other units. The metric system was just an attempt to totally standardize them. There's no big mystery or innovation to it other than that. --98.217.8.46 (talk) 23:48, 18 November 2008 (UTC)

But as to what units Newton actually used when measuring something, they would have been the traditional British units. Inches and feet and yards and chains and miles for distance, seconds and minutes and hours for time, and so on. (Yes, the same seconds that are in the metric system.) --Anonymous, 23:56 UTC, November 18, 2008.

Wrong. He, probably because of his day job as Master of the Mint he could borrow some of the government's scales, liked to measure his "weights" in troy ounces--which are, of course, always units of mass, and are not and never have been units of force--rather than the avoirdupois units we now think of as normal. But for length, especially when he wanted to be precise, he was partial to using the toises and pieds and pouces of the French system. For force, he never actually expressed that in any units specific to the purpose, as far as I can tell--it would just be the mass units times the acceleration units. Gene Nygaard (talk) 20:04, 19 November 2008 (UTC)

Ah, interesting. Can you cite an example of him using French units? --Anon, 20:48 UTC, November 19, 2008.

Plan for establishing uniformity in the Coinage, Weights, and Measures of the United States, 1790, http://avalon.law.yale.edu/18th_century/jeffplan.asp footnote 2:

"Sir Isaac Newton computes the pendulum for 45 degrees to be 36 pouces 8.428 lignes. Picard made the English foot 11 pouces 2.6 lignes, and Dr. Maskelyne 11 pouces 3.11 lignes. D'Alembert states it at 11 pouces 3 lignes, which has been used in these calculations as a middle term, and gives us 36 pouces 8.428 lignes = 39.1491 inches. This length for the pendulum of 45 degrees had been adopted in this report before the Bishop of Autun's proposition was known here. He relies on Mairan's ratio for the length of the pendulum in the latitude of Paris, to wit: 504:257::72 pouces to a 4th proportional, which will be 36.71428 pouces = 39.1619 inches, the length of the pendulum for latitude 48 degrees 50'. The difference between this and the pendulum for 45 degrees is .0113 of an inch; so that the pendulum for 45 degrees would be estimated, according to Mairan, at 39.1619 - .0113 = 39.1506 inches, almost precisely the same with Newton's computation herein adopted."

Gene Nygaard (talk) 23:15, 19 November 2008 (UTC)

Thanks. --Anon, 06:33 UTC, November 20/08.

November 19

Heroes

In what ways is the science in the show Heroes (for instance, the way they discuss evolution or utilize the genome project) bad? And I'm not just talking typical super-power suspension of disbelief here: I mean, when they try to use real science on the show, how often are they on/off the mark? --64.26.98.90 (talk) 00:22, 19 November 2008 (UTC)

There's a lot of online discussion about this, e.g. [9] [10]. You could check out Heroes forums/boards, e.g. the IMDb[11]. —Preceding unsigned comment added by Maltelauridsbrigge (talk • contribs) 12:22, 19 November 2008 (UTC)

The "real science" on Heroes is almost entirely science fiction. There is no resemblance between our current understanding of the mechanisms of evolution and what the dear Dr. Suresh loves to pontificate on. While it is true that the genome projects have given us huge insights into many areas of biology, there is no reality to the science of Heroes. Don't let it stop you from suspending your disbelief, though. I love the show, even if the pseudoscience is sometimes a bit appalling. By the way, this probably applies to almost all pop TV shows that involve some form of "science" or "medicine" in their plot lines. Most of them are vast distortions of the real world. Medical geneticist (talk) 15:32, 19 November 2008 (UTC)

One of the ways I suspend disbelief when watching this brilliant show is that since their fictional powers emanate from their brains, perhaps they are able to produce quantum effects on a massive scale by altering probability using unusual neural processes, even to the point of overcoming conservation of energy (definitely required if you are going to fly into space) but in the far future transhuman technology based on a new unknown physics could make such powers commonplace. The probability of such powers developing naturally is a bit far fetched because if genetics did have the potential for this, every living creature would have evolved to exploit such an enormous advantage. The way I suspend disbelief on this issue is that nature only does just enough to get us to feed, reproduce and avoid predators, and has no use for us after we have served this function-hence we do not regenerate badly damaged organs and limbs or have eternal youth. Of course a new plot line has some of the heroes altered by genetic scientists which is a bit more plausible, albeit a hundred years from now. In real life evolution, what was to other creatures was a monstrous superpower has evolved twice. Sight in prehistoric times and later, human intelligence. There were very large gaps between the two so who is to rule out the next step in evolution, but the biggest likelihood is that it will be created by human science rather than genetics. Another method to suspend disbelief on the issue of why such powers would not have develped earlier or be widespread is that perhaps the solution space had so many bridges and false maxima and minima that even the power of evolution could hardly ever reach such perfection. Of course the Superman films simply get round that by saying he comes from a part of the universe with an entirely different physics-in which case he would havecome from a parallel universe. And as for conservation of energy, apparantly he is fueled by solar neutrinos which somehow interact with his dense matter. —Preceding unsigned comment added by 80.0.106.90 (talk) 03:22, 20 November 2008 (UTC)Trevor Loughlin (talk) 02:36, 23 November 2008 (UTC) 80.0.106.90 (talk) 03:27, 20 November 2008 (UTC)

My main complaint about the "science" in Heroes is when they refer to the Human Genome Project. In reality only a handful of individuals contributed their DNA to the project(s), but in the show they treat it like a database of the genomes of every human being on the planet. Aaadddaaammm (talk) 18:59, 20 November 2008 (UTC)

OK, and the idea that a simple mutation can cause such fricking cool (and diverse) phenotypes is ridiculous. And also genetics (Darwin even got this right) does not allow major, disruptive mutations to effect a population, the only way evolution occurs is by TINY, stepwise changes. Aaadddaaammm (talk) 19:03, 20 November 2008 (UTC)

Me again, I just read the first link supplied up there ^, and it says exactly what I said (just more eloquently). Go science! Aaadddaaammm (talk) 19:12, 20 November 2008 (UTC)

Plasma

How would moving through Plasma feel aside from it burning/hurting you?--76.28.73.16 (talk) 00:59, 19 November 2008 (UTC)

Obviously, that depends a great deal on the plasma temperature (or, in general, electron energy distribution), density, and composition :) . In a very cold and dilute interstellar plasma you would freeze to death rather than burn (unless suffocation or very rapid loss of fluids kills you first, of course). In a rather hot plasma (and radiation field) of a stellar atmosphere you would evaporate rather fast. However, in a weakly-ionized air at sea level you will probably last very much longer. St. Elmo's fire plasma is harmless, unless you get struck by lightning eventually. --Dr Dima (talk) 02:16, 19 November 2008 (UTC)

Ahem... Space Does Not Work That Way. If the plasma is dilute, you would explode way before you would freeze to death because there aren't enough plasma particles coming into contact with you to transfer heat away from your body. « Aaron Rotenberg « Talk « 04:34, 19 November 2008 (UTC)

AhemHEM... You wouldn't explode; your body is far too resiliant. If you're mouth were open, the air would merely be rapidly sucked out of your lungs (or if not, likely, through your nose). If you closed your eyes, mouth, and plugged your nose, your body would probably "spring a leak" somewhere, but once your lungs were emptied of their contents (which wouldn't take too long) the integrity of the rest of your corpse would be quite fine. After a time, the moisture in your body would likely evaporate, leaving a nice, dessicated mummy floating around in orbit. Sleep well! --Jayron32.talk.contribs 04:43, 19 November 2008 (UTC)

The release of some of those would be fairly abrupt (especially if you had your mouth open), so it could still sort of be described as an explosion, or perhaps a series of explosions. And it's definitely not freezing. « Aaron Rotenberg « Talk « 00:37, 20 November 2008 (UTC)

Parts of your body may rupture (i.e. tear through) but you will definately NOT "explode" in the sense that you won't spray little bits of yourself all through outer space. You will likely not escape injury in the event of exposure to a hard vacuum, but your body will be intact. Look, there's just not enough pressure in your lungs to do any damage to your trunk. At earth-pressures, you can expect about 760 torr (15 pounds per square inch, or 1 atmosphere) of pressure in your lungs. Your body can and does survive those pressures quite easily. Think about scuba divers. They can go down to well over 2 atms of pressure without their bodies crushing in on themselves. The pressure in your lungs cannot exceed 1 atm of pressure pusing out; your ribcage and the rest of your chest is quite able to withstand such pressures without any trouble. Now, the air will likely cause ruptures in particularly weak places as it escapes (sinuses, ear drums) but there's just not enough force inside your lungs to make your body spray little bits everywhere. But we are in agreement that you certainly won't ice up. As I said, you'll mummify long before your temperature drops enough to freeze. --Jayron32.talk.contribs 02:24, 20 November 2008 (UTC)

Very well. It's just as disgusting (and probably more disturbing) that way. « Aaron Rotenberg « Talk « 06:24, 20 November 2008 (UTC)

And, of course, weakly-ionized air smells of ozone, but feels like a regular air as far as the "moving through" is concerned. --Dr Dima (talk) 02:21, 19 November 2008 (UTC)

The very first victim of a weapon

Of course it's impossible to tell who was the first victim (in any species) of a malicious stabbing, or what human was the first victim of a gunshot, or who first paid the ghastly price of being cannon fodder. But is it safe to assume that the most exquisite Madame Curie was the first victim of the horrific weapon of high-level radiation? Sappysap (talk) 01:01, 19 November 2008 (UTC)

Girls who used luminous paint to paint numbers on clock and watch dials suffered from radioactive poisoning. They put the tip of their artists' brush in their mouth to get a sharp point. I don't know the dates on this, but it must have been before the danger was realized. —Preceding unsigned comment added by 98.16.67.220 (talk) 01:24, 19 November 2008 (UTC)

I suspect that some of our much more distant ancestors may have succumbed to cancer caused by exposure to naturally-occuring radon in their caves.

In the modern era, Marie Curie wasn't the first to be killed by radiation. Long before her death in 1934, a number of patent medicines began to include radium for various not-clearly-elucidated reasons. Eben Byers was one of the most famous victims of Radithor (sold from 1918-1928); he died in 1932. (See also radioactive quackery.)

Occupational exposure was also a problem. Unshielded x-ray tubes were widely used from World War I onward; many early radiologists likely died before Curie. As noted by the anon, radium jaw was widely recognized by 1925; I expect that at least some of those individuals died from their radiation exposure before Curie did. TenOfAllTrades(talk) 01:28, 19 November 2008 (UTC)

Madame Curie wasn't killed by a weapon. Also, in addition to all the other examples, I expect it wasn't very healthy to be around a natural nuclear fission reactor. Clarityfiend (talk) 01:35, 19 November 2008 (UTC)

I think the OP was talking about people. Not the bacteria that were around when natural nuclear reactors were active 2 billion years ago. — DanielLC 05:57, 19 November 2008 (UTC)

Hmmm...I thought they were a bit more recent. So what's a few billion years more or less? Clarityfiend (talk) 07:30, 19 November 2008 (UTC)

Clarence Madison Dally died in 1904 from the cancers caused by prolonged exposure to X-rays while an assistant to Thomas Edison. He started working with X-rays in 1895 and had serious radiation damage by 1900. In the early days, no one knew that radiation was harmful. Perhaps the first known victim of radiation? In the 1950's shoe stores still had X-ray fluroscopes to show how well shoes fit little children. They were basically World War 1 surplus X-ray machines. Kids would put their feet in the machine and push the button at every visit to the shoe store. Reportedly it harmed more shoe salesmen than it did children. They were shut down before 1960. Archie Frederick Collins, early 20th century science popularizer, wrote in "The Boy Scientist" (1925) detailed descriptions of how a child could build an x-ray machine and do lots of fun experiments with it. Edison (talk) 06:35, 19 November 2008 (UTC)

My 2c, correlation does not prove causation... Aaadddaaammm (talk) 18:56, 20 November 2008 (UTC)

As others have pointed out the Marie Curie example is flawed. But I guess the other question is, what is a weapon? It's clear the work of Marie Cure, as well as others mentioned above wasn't in any way related to weapons so I question whether you could call them the first deaths from the weapon of radiation poisoning. It's possible someone used some radioactive material as a poison beforehand but if not, the first deaths would surely either have been during the Manhattan project or Hiroshima. I presume there were deaths during the Manhattan project. One I found was Louis Slotkin [12] but I would say even in his case it's questionable if it was a weapon since what he was working on was subsiary to the main project and not really part of developing a weapon Nil Einne (talk) 13:17, 23 November 2008 (UTC)

What if we cut a hole through Earth?

On the Science Channel, they were saying that if we cut a hole all the way through the Earth such that it is a straight line, goes through the center of the Earth and comes out the other side, that if we dropped an object in the hole it would pass all the way though the Earth to the other side of the Earth, fall back down again and keep going forever. Even if we ignored friction/air resistance, this seems wrong to me. I'm wondering that once the object starts falling below the Earth's surface, the matter that is above the object would exert a gravitational pull and thus would slow down the object. Eventually the object would come to a standstill at the center of the Earth. Am I correct or am I incorrect? 67.184.14.87 (talk) 05:16, 19 November 2008 (UTC)

See Shell theorem. But briefly : The object would not become weightless until it hit the exact center. (Logically, that's the only point where the forces would balance out.) By that time it's going to be going about a zillion miles per hour.

So you're right that gravity would get weaker and weaker, But even weak gravity is going to make you speed up, not slow down. Without friction, nothing would slow you down until after you pass the center point. APL (talk) 05:33, 19 November 2008 (UTC)

You're right. I didn't say that properly. Whan I meant is that the gravitational pull of the matter above the object would decrease the rate of acceleration and after numerous passes through the Earth's core, the object would eventually slow down such that it comes at a complete rest at the center of the Earth. Or to put it another way, treating the Earth as if it's gravitational pull was concentrated at a point at its center is an oversimplification, that once it passes beneath the Earth's surface there is now matter above it that also exerts a gravitional pull in the opposite direction, and that the Science Channel's explanation ignores this graviational pull. (I'm the OP on a different computer.) 216.239.234.196 (talk) 13:56, 19 November 2008 (UTC)

Point 3 of shell theorem addresses this concern. Ues Image:Shell-diag-4.png for illustration. The mass "above" the object (that is, all grey area to the right of point m) exerts a retarding pull, yes. This is offset by the mass of similar altitude but towards the center (that is, all grey area left of point m), which exerts an accelerating pull. The latter has more mass but is further away, and calculus demonstrates that they balance precisely. More to the point, though, is that the process is symmetric. Regardless of actual values, you have no acceleration at the center point. 1 meter beyond the center point, you are decelerating at the same value with which you accelerated while 1 meter before the center point. 5000km out, the deceleration remains the same magnitude as the falling acceleration. Once you establish that you reach the antipode (and stop there, for some infinitesimal period), you're effectively back at your starting point with no degradation. Without outside influence (i.e. friction), then, your object never slows to stop at the center of mass. — Lomn 14:49, 19 November 2008 (UTC)

I would expect air resistance to slow it down and prevent it reaching the antipodal location. Also, I would expect it to rub against the side of the borehole due to conservation of angular momentum. At the surface, it was moving East at about 1000 miles per hour, if it started near the equator, but halfway to the center the hole would only be moving east half that fast, etc, resulting in extreme friction. But I was sometimes wrong in physics class. Edison (talk) 06:23, 19 November 2008 (UTC)

If you're going to talk about practical matters, it would be impossible to construct such a hole in the first place. The pressure in the center of the Earth is far in excess of anything that any known material could resist. But if friction is ignored, and the Earth is treated as a homogeneous sphere, and the hole was possible, then it's correct that the object would oscillate in a sort of linear orbit within the hole. Incidentally, this is also true for a straight hole through the Earth connecting any two points at the same elevation on the surface, no matter whether it comes near the center of the planet or not -- and the period of oscillation is the same for any such hole. I bet Wikipedia has an article on this, but I don't know what it would be called. --Anonymous, 11:24 UTC, November 19, 2008.

Edison is correct; unlesss the hole were cut directly down the Earth's rotational axis (north pole to south pole) any object dropped down would eventually smack into the side of the tunnel. Air resistance can be neglected through the simple expedient of capping both ends of the tunnel and pumping out the air. (If we're assuming the magical ability to construct this tunnel at all, surely we can assume sufficient magic to make it airtight.)

As an aside, I'm quite certain that this notion formed the core of a science fiction short story I once read. It involved an astronaut falling from space directly through the core of a planet. (Some sort of force field was being used to maintain the opening. I don't recall why the tunnel was there; I'm guessing mining.) Might have been Asimov who wrote it, but it could have been Niven. TenOfAllTrades(talk) 14:34, 19 November 2008 (UTC)

But wouldn't the falling object start with the same rotation as the Earth ? What would later cause it's rotation to vary from that of the Earth ? StuRat (talk) 18:02, 19 November 2008 (UTC)

An object on the equator travels 40000km/(sidereal) day parallel to the surface of the earth. But a point in 3000km down the tunnel (1/4 of the Earth radius) is only traveling 20000km/(sidereal) day parallel to the surface of the earth. So a free-falling object will always hit the leading edge of the tunnel on the way down. --Stephan Schulz (talk) 20:26, 19 November 2008 (UTC)

Something doesn't seem quite right about that logic. That would also mean that any vertical pipe would have the same effect, but to a lesser extent, resulting in one side of the pipe wearing out more quickly because the fluid keeps ramming into that side of the pipe to increase or decrease it's rotational speed (depending on if the fluid is going up or down). Has any such effect ever been noted ? StuRat (talk) 01:17, 20 November 2008 (UTC)

There's nothing wrong with the logic; this is simply a form of the Coriolis effect. Remember, it applies to all motion that is in a rotating reference frame, and not along the actual axis of rotation. (So for a shaft between the North and South Poles, this would not be an issue.) It applies in a vertical pipe, a horizontal pipe, or any other direction -- but in any situation in the ordinary world, the magnitude of the force is so tiny as to be insignificant. See also Steve Baker's reply below. --Anonymous, 04:41 UTC, November 20/08.

While not practical on Earth due to the magma, would drilling a hole through the Moon or a smaller body actually be possible ? StuRat (talk) 18:01, 19 November 2008 (UTC)

"Magma" isn't really relevant; the point is the immense pressure at the center of a planet. For the Moon it would be less, but I'm sure still plenty enough to collapse any tunnel in the rock. That said, I'm not sure exactly how you compute it -- anyone know the formula or where to find it? Of course with a small enough body, like a small asteroid, the gravity is so light that it would be practical. --Anon, 04:45 UTC, November 20/08.

Magma is indeed relevant, as such liquid rock is due to high temperatures which would melt the lining of any tunnel. StuRat (talk) 07:00, 22 November 2008 (UTC)

Oh, and again, if you're thinking of actually trying this, be sure to consult the local building code on the asteroid. :-) --Anon, 04:47 UTC, November 20/08.

A lot of asteroids are believed to be piles of loose rubble, so you would need to build a retaining wall around your tunnel. The asteroid itself would just collapse in on itself, even at the surface. --Tango (talk) 23:32, 20 November 2008 (UTC)

We talked about this a couple of times before - and someone calculated that the air pressure in the center of the tunnel would be so high that the air would liquify. So the tunnel has to be pumped down to a nice, hard vacuum for you to be able to fall through it. Unless the tunnel is dug through from pole to pole, the coriolis forces also prevent you from falling cleanly down through the tunnel without hitting the sides. SteveBaker (talk) 19:11, 19 November 2008 (UTC)

To what does 'bi' refer in 'bicarbonate'?

To what does 'bi' refer in 'bicarbonate'? ----Seans Potato Business 12:31, 19 November 2008 (UTC)

It refers to the fact that the ion takes half of the positive ions that sodium carbonate did. They were named before the actual structure of the ions were known; but what was known was that with roughly equivalent masses of carbonate and bicarbonate, the carbonate took twice the mass of, say, sodium to form sodium carbonate as it did to form sodium bicarbonate. Once the actual structures of the ions was later discovered, it turned out the same was entirely inaccurate, but it stuck. --Jayron32.talk.contribs 12:47, 19 November 2008 (UTC)

So what's the correct name for sodium bicarbonate? --70.167.58.6 (talk) 15:32, 19 November 2008 (UTC)

sodium hydrogencarbonate? Sjschen (talk) 15:51, 19 November 2008 (UTC)

Generally "sodium hydrogen carbonate" is the formal, IUPAC name, but as with most common compounds, even chemists find the formal names somewhat pedantic, and will commonly use the older, more common names, such as "sodium bicarbonate". For example, no chemist would use the more formal "ethanoic acid" where "acetic acid" is the more accepted, common name; or would use "2-propanol" (IUPAC name) where "isopropanol" or "isopropyl alcohol" is more common. --Jayron32.talk.contribs 17:52, 19 November 2008 (UTC)

Does WP have a list of such "wrong but stuck" scientific terms? —Tamfang (talk) 09:12, 20 November 2008 (UTC)

They aren't "wrong" any more than any part of a workable language is "wrong". There are formalized versions of English, for example, but that does not make the non-formal versions of English "wrong" in the way that the answer to a mathematics problem can be "wrong". As long as everyone in the audience of the speaker has an unambiguous understanding of the content of their speach, it is perfectly valid language; regardless of its adherance to a set of formalized rules. The IUPAC rules actually work very well for medium-sized compounds. Very large compounds start to take on confusing and cumbersome names; while smaller compounds which were well known before their implementation retained their names because it made sense; there was already thousands of pages of literature that referred to these compounds, so it made little sense to "change their names" as such a change (such as everyone all of a sudden starting to call acetic acid as "ethanoic acid") would likely lead to MORE confusion; and the IUPAC rules are all about causing LESS confusion by providing an unambiguous nomenclature system. Using terms like "sodium bicarbonate" or "acetic acid" is not wrong in any sense... --Jayron32.talk.contribs 14:17, 20 November 2008 (UTC)

Okay then, does WP have a list of scientific terms that, although not wrong, do not mean what an otherwise knowledgeable person would infer by the usual conventions of the field's terminology? —Tamfang (talk) 08:49, 21 November 2008 (UTC)

I was taught at school that the bi means hydrogen. No explanation was given.--GreenSpigot (talk) 01:24, 21 November 2008 (UTC)

The color of shower gel

I have noticed that while shower gels come in a wide variety of colors (the ones I usually use are red or brownish-yellow), the water when taking a bath always has a bluish-green tint, no matter what brand/color of shower gel I use. What exactly is happening here? -- Ferkelparade π 12:48, 19 November 2008 (UTC)

Shower gels are coloured with small amount of dyes. While it shows up in the bottle, the amount of dye in one use of the gel is likely not enough to change the colour of the large quantity of bathwater, which I think gets its greenish-blue colour due to the Tyndall effect or Rayleigh scattering. -Sjschen (talk) 15:50, 19 November 2008 (UTC)

Actually, blue-green bathwater is more likely due to oxidized copper in the water. The water source may have the copper, or it could be coming from corroding copper pipes. ~Amatulić (talk) 02:23, 22 November 2008 (UTC)

Restrictive NAT on DSL modem?

--moved to computer desk--- --71.158.221.237 (talk) 02:34, 20 November 2008 (UTC)

stupid question -- water filters filter flouride or no?

Sorry this is a dumb question, but ... water filters like Brita won't keep me from benefting from the medicamentous flouride with which the water supply is laced, will they?

According to Brita's FAQ: [13] "The BRITA Water Filter System does not remove fluoride from tap water. Fluoride is a negatively charged ion and does not react with the components of the BRITA Filter Cartridge." I don't know if other filters use the same process. Fribbler (talk) 16:00, 19 November 2008 (UTC)

See Water fluoridation. Flouride cannot be filtered out of water, but it is debated whether fluoridation is of any benefit to adults.--Shantavira|^{feed me} 18:34, 19 November 2008 (UTC)

But fluoridation still seems like a good idea, whether it assists us only in childhood, adultery, or both. StuRat (talk) 01:11, 20 November 2008 (UTC)

StuRat must value teeth free of caries in extramatrimonial affairs...XP 152.16.15.23 (talk) —Preceding undated comment was added at 02:10, 20 November 2008 (UTC).

Yes, an adulterous woman already is looking to have one cavity filled, what does she need with another ? StuRat (talk) 23:34, 20 November 2008 (UTC)

It's not her hydroxyappetite that is the problem. DMacks (talk) 01:43, 21 November 2008 (UTC)

We're hearing lots of news about the adverse effects of fluoridation these days. Besides, the flouride barely even touches your teeth, it just goes down into your stomach and through your body. Reports are that fluoridation may be correlated to mental retardation, if I remember correctly. Also, don't be afraid to ask questions, there are no "stupid" questions. I also have a similar question: if water is boiled, does it remove fluoride? ~AH1^(TCU) 16:08, 22 November 2008 (UTC)

It can still get into the teeth from the roots, via the bloodstream. As for boiling, I would expect it to stay in the pan after the water is boiled, as part of the mineral crust. So, what's boiled off and recondensed (distilled water), would indeed have the fluoride filtered out. StuRat (talk) 16:35, 22 November 2008 (UTC)

Apple trees

How many years does it take an apple tree to bear fruit, counted from the time the apple seed was planted? —Preceding unsigned comment added by 207.210.129.15 (talk) 19:40, 19 November 2008 (UTC)

Apple trees aren't really grown from seeds. You can probably plant an apple and get a tree out of it, but you will probably not get any fruit resembling the apple you planted. All commercially planted apple trees, even ornamental crabapples and the like, are propagated by grafting. --Jayron32.talk.contribs 20:08, 19 November 2008 (UTC)

If you get apples at all, why wouldn't they resemble the "parent" apple? What does the rootstock contribute to the quality of the fruit? —Tamfang (talk) 09:10, 20 November 2008 (UTC)

This issue is with apples' ease of mutation, which is one of the reasons why there are so many varieties of apples (several thousand, iirc). You get an apple tree when you plant an apple seed, but you wouldn't get a granny smith apple tree by planting a granny smith apple seed. That's fine if you're just growing something for the backyard, but a pain in the ass if you're trying to sell a recognizable brand. Matt Deres (talk) 16:07, 20 November 2008 (UTC)

Uhh I believe that's due to pollination and the ease of recombination. It's not that apples mutate easily -- it's the fact that so many apple traits (that were bred through husbandry) are caused by relatively few genes. A lot of apples can mate with wild flowers from other trees that are actually quite genetically close to apples, though morphologically they look much different. John Riemann Soong (talk) 07:27, 25 September 2010 (UTC)

Jayron's correct, but I'll answer anyway: 2 to 5 years (source). --Sean 20:12, 19 November 2008 (UTC)

So why wasn't he called Johnny Grafter? Deor (talk) 23:15, 19 November 2008 (UTC)

Because graft is left to the politicians. StuRat (talk) 01:07, 20 November 2008 (UTC)

Johnny Appleseed really did spread seeds and not grafts; however none of his apple orchards were for eating. People didn't really eat apples (well, maybe a few), but just like most grapes went into wine production; apples were primarily used to make hard cider and apple brandy. You could make far more money per tree producing liquor than fruit; and when you are just after the fermented products, then producing a consistant tasting fruit isn't probably high on your list of important traits... --Jayron32.talk.contribs 02:15, 20 November 2008 (UTC)

People always ate apples [14]. They could be dried and eaten during the winter in fried pies or other confections long after the last apple in the barrel had been eaten or had rotted [15]. Cider, hard or otherwise was a fall use of apples, but dried apples kept over the winter without refrigeration or canning. (Edit) I agree that good tasting eating apples come and mostly came even in Chapman's day from the grafting of the tasty mutant apple limbs onto less tasty root stock, but that the root-stock aples coming from the seeds Chapman picked out (for free) from the pulp at a cider mill would still make good cider. The genetic reason why seeds from a tasty apple woulkd not ever produce trees yielding tasty apples is very unclear. Why wouldn't seeds from, say a Paula Red or a Granny Smith produce offspring trees of varying tastiness, with some tasting like the source apple? Crops like potatoes were improved by using the eyes from the best to produce the next crop. Same for corn (maize), or tomatoes before modern hybrids, with seed from the ones with the most desirable characteristics used for the next crop. Edison (talk) 06:05, 20 November 2008 (UTC)

Are there more extreme temperatures (way above or below average?) than years ago?

In discussing our weird wether, and how it's been weirder than normal the last few years, a friend and I deduced that the main thing is the number of days with temperatures way above or below average.

I was wondering if there was a rather easy way to determine whether there have been, in fact, more highs at least 10 degree Fahrenheit above or 10 degrees below average in the last 5 years than in a similar stretch, say, 30 years ago. Have any studies been done about this?

This may seem arbirtary, but considering the normal temperatures in the Great Lakes region of the United States, this sounds like a reasonable level. Of course, there will always be times when temperatures are unusual, but it seems that 10 degrees above or below is unusual enough that, when weather functions normally, it would be at least somewhere rare, whereas in his words, "now it seems like you go right from summer to winter and back again without a fall or spring."Somebody or his brother (talk) 20:54, 19 November 2008 (UTC)

Even if this were true, it doesn't necessarily mean much. What I mean by that is that we have probably less than 200 years of reliable daily temperature data to work with. That's not really enough to wash out the "noise" of random results and really determine if such statistics were causal or random. Let me give you another example. Lets say I threw a die 200 times. Now, I should get each face of the die about 1/6th of the time; but if I look at a small, localized subset of the 200 times I throw the dice, say the last 20 throws, and see that 6 came up like 7 or 8 times, it wouldn't mean that the dice was "loaded". Random chance says that during substantially small subsets of data, there will be "streaks" that aren't causal at all; in fact the laws of probability say that any random set of numbers is far MORE likely to feature such streaks than to lack them (for example, having 100 rolls of the dice with NO consecutive repeats is FAR less likely than having 100 rolls of the dice and having say, 6 come up 3 or 4 times in a row). Now, given all of this, it does not mean that global warming or climate change is NOT happening. Daily temperatures are part of the weather, and daily weather is so variable it is impossible to predict trends with any certainty. Global warming is about climate, which can be predicted quite well. Lets go back to the 200-throw-of-the-dice analogy. If 8 of my last 20 throws came up 6, it probably wouldn't mean much, but if say the average number, if I say added all 200 throws and divided by 200, turned out to be like 4.7, then we would CERTAINLY say that something fishy was up. That's what we have with climate change; while local places on earth may or may not have seen any "weird" weather in any given year, when averaged over the last few centuries, there is definite evidence of playing with "loaded dice"...

Also, it should be noted that the Great Lakes region is probably a bad example to use; areas near the centers of continents always feature much more dramatic temperature swings than areas near the coast. It is not uncommon for high temperatures from day to day in Illinois to swing more than 20-30 degrees, or to see the temperature drop 40 degrees in a matter of hours. Finding the same swings in, say, Boston is much more unusual. --Jayron32.talk.contribs 21:24, 19 November 2008 (UTC)

Thanks; that makes sense now. Yeah, i tend to forget just how little reliable data we actually have. And, I hadn't thought about the difference between the coasts and inland; I don't know if I'm just not catching it or they're not explaining it well on the news (probably a bit of each, little blurbs can't include everything) but it always seems like they're implying, "This stuff is happening everywhere at the same time" to me.Somebody or his brother (talk) 22:55, 19 November 2008 (UTC)

It may be, but it may or may not mean much. The local TV news doesn't even understand basic logic, such as the fallacy post hoc ergo propter hoc, and does not understand the difference between "correlation" and "causality"; much less understand the complexity of the science of climate change. I have no doubt that climate change is occuring personally, however I also don't expect to be able to correlate such changes to actual single weather events. --Jayron32.talk.contribs 23:04, 19 November 2008 (UTC)

And worse still, they ALWAYS confuse 'weather' with 'climate'. One random hot day that breaks all records doesn't prove that global climate change is true - and one random cold day doesn't disprove it. Even an entire year of record temperatures wouldn't do that. Weather is the short-term and very localised change - climate is the reactions of large chunks of the planet over many years. I think it's likely that dramatic climate change may indeed result in more wild weather swings - and therefore more records broken - but that's very much a secondary thing compared to the relentless grind of steadily increasing global average. SteveBaker (talk) 02:50, 20 November 2008 (UTC)

If you are talking about global warming here, there are many factors that influence temperature range. Nowadays, there are urban heat islands that cause hotter weather during summer daytimes, and effects associated with global warming such as the shrinking of inland lakes and the possible slowing or shutdown of the thermohaline system may cause more drastic temperature differences between hot and cold. However, since global warming itself tends to reduce the temperature contrasts, such as that it produces more warming at the poles than in the tropics, more at higher altitudes than lower ones, more warming at night than during the day, and more warming in winter than in summer, it may reduce this effect. ~AH1^(TCU) 16:01, 22 November 2008 (UTC)

Levoglucosan

what are ' Levoglucosan'? —Preceding unsigned comment added by Balukri4 (talk • contribs) 22:20, 19 November 2008 (UTC)

The search function is wonderful. I typed the above word in the search box to the left, and came up with the following, from the article Smoke: "Levoglucosan is a pyrolysis product of cellulose." Then I typed the same word in google, and came up with the following page: [16] which says "Levoglucosan (1,6-anhydro-β-d-glucopyranose), a major constituent of smoke from biomass burning,". So, there you go. Its basically a sugar. --Jayron32.talk.contribs 23:01, 19 November 2008 (UTC)

Do not, under any circumstances, trust that Wikipedia's search engine will find the results you desire. I love Wikipedia, as does everyone reading this, but its search engine lacks much to be desired unless you articulate things absolutely precisely, or you're feeling lucky. If you need to search this ungodly compendium for X, go to google and type "X site:wikipedia.org" For all you reading: is this heresy? I'm not a zealot in anything I ever have to say. Just a pragmatist. Show me a more rigorous way of searching this Hitchhiker's Guide to the Galaxy, and I will be so grateful. I only ask that you start the guide with the words: Don't Panic Sappysap (talk) 02:11, 20 November 2008 (UTC)

Except that, in this case, it did. The deal is, one should at least type the word into the Wikipedia search engine and into google BEFORE asking the question here. It took me longer to type my response than it did to find the information I posted above. C'mon, at least put forth an effort! --Jayron32.talk.contribs 04:03, 20 November 2008 (UTC)

It should also be noted that now the wikipedia search has the suggest function enabled things may be somewhat better then before. Having said that, a search for Levoglucoson suggests Levlawson with the wikipedia search (on Google it's Levoglucosan) Nil Einne (talk) 01:24, 21 November 2008 (UTC)

Nuclear Science

Why does the binding energy per nucleon even matter? The binding energy is the amount of energy that must be put into the nucleus to break it apart, so why do we need to figure the energy per nucleon? TIA, Ζρς ι'β' ^¡hábleme! 22:53, 19 November 2008 (UTC)

Three reasons I can think of: the binding energy of the entire nucleus is the energy required to separate each nucleon from every other nucleon (ie. disintegrate the entire nucleus), which rarely happens (except for heavy-ion collisions such as those done in RHIC). Much more common is that "a few" (probably four, in the form of an alpha particle) nucleons are ejected. The second reason is that when viewing a plot of total binding energy vs. atomic mass, there will be a linear factor involved that will obscure other features; normalising the plot to binding energy per nucleon allows us to see certain trends like "closed shells". The final reason is that binding energy per nucleon roughly corresponds to stability; if I have some set number of nucleons the most stable configuration would be to arrange those nucleons into nuclei of the largest binding energy per nucleon (I think it's Iron-56). 58.96.70.254 (talk) 23:12, 19 November 2008 (UTC)

Actually it is Nickel-62, although Iron-56 does have the lowest mass per nucleon. --130.88.47.42 (talk) 13:36, 21 November 2008 (UTC)

When you have a nuclear reaction, you don't generally conserve nuclei, but you do (usually) conserve nucleons. So if, as is common with normal fission and fusion reactions, all the products have energies per nucleon that are higher (lower) than all the reactants, you can immediately say that the reaction is endothermic (exothermic) without further analysis and without having to consider each particle separately. --Tardis (talk) 23:48, 22 November 2008 (UTC)

November 20

Rotating spherical shells and gravity

The shell theorem says there is no gravity inside a hollow sphere. If that sphere is rotating, is there an acceleration which would be perceived as gravity by someone on the inner wall of the shell? —Preceding unsigned comment added by 128.194.103.45 (talk) 01:13, 20 November 2008 (UTC)

If you are rotating with the shell, then yes, you would feel a centrifugal force (and yes, there is such a thing). Its strength would vary depending on latitude (highest at the equator, zero at the poles). You could probably tell it apart from gravity, especially if the shell is fairly small, because of the Coriolis effect. --Tango (talk) 01:59, 20 November 2008 (UTC)

Although - if you're thinking of a Dyson sphere - that's not a problem. However, very large spheres have severe stability problems. SteveBaker (talk) 02:39, 20 November 2008 (UTC)

Actually, I was thinking of Pellucidar and why everything doesn't just fall into the central sun (and what IS that central sun burning, anyway?). I imagine one rotation per 24 hours wouldn't provide significant g-force, though. 128.194.103.45 (talk) 04:13, 20 November 2008 (UTC)

Since we on Earth don't go flying off from centrifugal force, you could reasonably say that. As I recall, centrifugal force accounts for about a 1% variation in the apparent force of gravity between the equator and the poles. Someone on the inside would notice a tendancy for things to move towards the surface, but it wouldn't be significant. --Carnildo (talk) 22:36, 20 November 2008 (UTC)

It's important to note that this perceived outward force would only be perpendicular to the 'floor' at the equator. The sphere can only spin about one axis at a time, so anybody standing along the equator would feel like they were standing on level ground, but as you move toward the poles, the "gravity" force (actually centripetal force) would decrease but at the same time the perceived slope of the walls would increase. The slope would reach vertical at precisely the same time as the centripetal force disappeared - that's when you reach the pole. Maelin (Talk | Contribs) 02:03, 22 November 2008 (UTC)

The Universe is Red and Purple

I look at the electromagnetic spectrum and I see a band of red on the left, and a band of purple on the right, with the tiniest sliver between them that fluctuates colour dramatically. I'm sure we evolved to see only that magical sliver for a reason. My question is: would we function as well, would we have been as succesful, if our eyes lived deep in the red or deep in the purple?

(Ignore this: I was thinking about the subject b/c I'm designing a spacesuit for my pet bat, Franky. When Franky and I go to the moon, he could never "see" beyond the plate of his helmet's visor. I feel so sorry for those species that evolved on sonar.) Sappysap (talk) 01:32, 20 November 2008 (UTC)

Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light.

Rather conveniently and probably not coincidentally, the visible spectrum falls at a point where water and the atmosphere in general are relatively transparent. Some birds see a little more in the UV spectrum than humans do. Interestingly enough, according to infrared, that drop in opacity at 10 micrometers corresponds with infrared wavelengths radiated by humans and presumably other organisms emitting heat. 152.16.15.23 (talk) 01:56, 20 November 2008 (UTC)

It also coincides quite closely with the frequencies that are emitted most strongly by the Sun. --Tango (talk) 02:07, 20 November 2008 (UTC)

Indeed - when you consider what we need our vision to do - that little slot is perfect. If the wavelengths are too long, you can't resolve small objects like the branches that a small furry mammal needs to climb on or not walk into. You need to be able to see small things like ants so you don't get bitten by them. On the other end of the spectrum - energetic short-wavelength waves make things transparent - and that's no use either. Mostly, what we need is to be able to see the relatively subtle difference in color between an unripe fruit, a perfectly ripe fruit and one that's gone off. For (say) an apple - that's a very narrow range of frequencies - green to red to brown. Evolution didn't need us to be able to see everything - just the things that allow us to survive and reproduce. Other animals do see over wider spectrums - but that's because they need to - and we don't. SteveBaker (talk) 02:34, 20 November 2008 (UTC)

Maybe you realize this, but those long bands of red and purple in the picture you linked shouldn't be there. Most of those frequencies are outside the visible range and we don't see them at all. The whole picture is pretty sloppily drawn. I can't make sense of the frequency scale on the spectrum (it's kind of logarithmic, but not really), and the visible range is actually far narrower than shown there (assuming a roughly logarithmic scale, it should cover about a tenth of the 10¹²–10¹⁵ Hz range, not half). I'm surprised the image got featured in that state. -- BenRG (talk) 02:51, 20 November 2008 (UTC)

I think the purple and red swaths were supposed to artistically illustrate the infrared and ultraviolet part of the spectrum extending off to the sides of the visible. 152.16.15.23 (talk) 03:46, 20 November 2008 (UTC)

@BenRG It is featured on Commons, where accuracy is not so much of an issue. A version of this picture failed to become a feature picture on EN in large part due to the colouring issues. I didn't like it then either! Matt Deres (talk) 16:14, 20 November 2008 (UTC)

Perhaps organic material cannot refract frequencies that are much lower than red light light, so there cannot be eyes for these lower frequencies. Higher frequencies than blue light are blocked by the atmosphere, so eyes would be useless and would not evolve, even if possible for organic material. —Preceding unsigned comment added by 98.16.67.220 (talk) 02:59, 20 November 2008 (UTC)

Infrared can be refracted by plants and other such larger objects because the wavelength is small enough. That's not too much of an issue. A bigger potential biological obstacle might be coming up with a photoreceptor that is sensitive enough to be triggered by an infrared photon (which is lower energy than visible photons) yet will not be falsely triggered by routine thermal temperatures and the infrared light being generated by the organism itself. 152.16.15.23 (talk) 03:43, 20 November 2008 (UTC)

The graph shows that electromegnetic radiation with a wavelength of more than 11 meters is blocked by the atmosphere. A note on the diagram also says that. Yet radio waves of much longer wavelength actually are propagated through the atmosphere, as everyone knows.

I can't respond with certainty but the reason why the graph shows the atmosphere as opaque is that long radio waves get reflected/interfered with by the ionosphere. 152.16.15.23 (talk) 03:35, 20 November 2008 (UTC)

True but the image may count the ionosphere as the atmosphere. You should sign your posts by typing four tildes "~" in a row by the way 152.16.15.23 (talk) 04:04, 20 November 2008 (UTC)

Radio waves have to pass through the atmosphere to get to the ionosphere.

The ionosphere is part of the atmosphere, specifically the "thermosphere." I think the main point of the image is to show that low frequency radio waves generated from distant space may not penetrate the atmosphere all that well. Regardless, there is probably a of lot noise from solar events and random x-ray bursts colliding with the upper atmosphere and whatnot. The image may be wrong too, but I'm not an expert on the subject... 152.16.15.23 (talk) 04:22, 20 November 2008 (UTC)

Talking about the visible spectrum and eyes, there is a MUST READ book called Wonderful Life, by Stephen Jay Gould. It describes small fossils found in the Burgess shale (in the Burgess Pass, Canada). These fossils were the earliest creatures to develop eyes, and the author reaches the fascinating conclusion that the ability to see was the cause of the Cambrian explosion, in which evolution proceeded with great rapidity and in many directions. With eyes, predators could see their prey from a distance, and they developed many ways of catching and holding their prey. The prey creatures also had eyes, and developed many ways to evade the predators. Be sure to read this book.

One more potential evolutionary issue is that the eye does not contain anything like an achromatic doublet that would prevent chromatic aberration. At least, that's true for human eyes and I haven't heard of any species where it isn't true. With the narrow range of wavelengths of visible light, this is not much of an issue; you don't normally notice that your eyes focus red light a little differently than they focus blue light. If our eyes had evolved to see a much wider spectrum of wavelengths, they would need some other sort of improvement in order to see as sharply as we do. Whether this has actually been a factor in evolution I can't say, but it makes sense. --Anonymous, 04:57 UTC, November 20/08.

The yellowness of the lens blocks shorter wavelengths which the retina would otherwise be able to see, but which would make the chromatic aberration worse. People who have had the lens removed to correct cataracts can see near UV wavelengths the rest of us can't, unless they get a lens implant which blocks the shorter waves. An evolutionary compromise in favor of resolution over sensitivity. Edison (talk) 06:03, 20 November 2008 (UTC)

In order to prove that some "design feature" (pardon the term) is the result of "evolutionary compromise", you not only need to demonstrate that it has an advantage over some alternative that might exist, you also need to demonstrate that the alternative has existed and found wanting. In other words, you don't just need to show that the lens has this property; you also need to show evidence that an earlier form of the species, or a less successful related species, had lenses that did not block those shorter wavelengths. Otherwise you're guessing: the alternative hypothesis would be that the lens is that color because the yellowish material was the first one that evolution produced that was good enough for a lens such as we have. I don't have any information like that, and that's why I said I don't know. --Anonymous, 09:53 UTC, November 20/08.

A little earlier in this discusion of electromagnetic radiation, I wrote "Perhaps organic material cannot refract frequencies that are much lower than red light light". What I meant was that perhaps all organic material is opaque to frequencies lower than red light, and perhaps it is not possible for living things to develop an organic material of that type. —Preceding unsigned comment added by 98.16.67.220 (talk) 13:36, 20 November 2008 (UTC)

I said that it may be impossible for living things to develop an organic material that is transparent to electromagnetic radiation lower in frequency than red. However, pit vipers have an organ on each side of their head that is sensitive to heat. By this means they can detect their prey, even in darkness. There is apparently no lens so there is no refraction, but the organ is quite complex. Could there be some other form of focussing, refractive or otherwise? The organ is extremely sensitive to slight differences from the background heat. I wonder what the resolution is. See "pit viper" in Wikipedia. —Preceding unsigned comment added by 98.16.67.220 (talk) 13:58, 20 November 2008 (UTC)

The pit organ is essentially a low-resolution pinhole camera, which works by limiting how much of the world can illuminate any given part of the pit. --Carnildo (talk) 22:56, 20 November 2008 (UTC)

Carnildo, thanks for that word "limiting". It made me realize for the first time how a pinhole camera really works. —Preceding unsigned comment added by 98.16.67.220 (talk) 06:21, 21 November 2008 (UTC)

The diagram for this topic shows a vertical band of purple. Purple is a combination of red and blue, which are at opposite ends of the visible spectrum. Where did that crazy diagram come from? —Preceding unsigned comment added by 98.16.67.220 (talk) 06:17, 21 November 2008 (UTC)

There are actually two forms of the color purple: the red+blue that you refer to, and actual purple light: wavelengths shorter than blue but not so short they can't be seen. Because the red sensors in the human eye are also slightly sensitive to blue, the two forms look the same, giving us the color wheel you're familiar with. --Carnildo (talk) 23:43, 21 November 2008 (UTC)

The color band in the diagram is violet. It leads into the invisible ultraviolet. If I correctly understand the description of violet in Wikipedia, it is the color at the high-frequency end of the visible spectrum. The word "violet" can also refer to the mixture of red and blue - not a spectral color. The word "Purple" refers always and only the mixture of red and blue. I think the title of this thread should be "The Universe is Red and Violet". —Preceding unsigned comment added by 98.16.67.220 (talk) 00:39, 22 November 2008 (UTC)

Restarting the Earths spin.

Apparently the Earth will slow down to a stop after a long time, which will be hard on the nations facing away from the sun. Would a large gyroscope on a big enough motor planted in the North pole be able to slowly spin the Earth back up? Trevor Loughlin —Preceding unsigned comment added by 80.0.106.90 (talk) 03:34, 20 November 2008 (UTC)

Assuming, of course, such a stop will happen before the sun engulfs the earth as a Red Giant. According to our article on the subject: [17] the earth is slowing down at a rate such that 2.3 milliseconds are added to the day every century. At this rate, the day will reach 25 hours (as measured on our scale) 828,000,000 years in the future, and the day will be twice as long as it is now (i.e. 48 hour day) 19,872,000,000 years in the future. By comparison, the Sun will reach "red giant" phase, at which point it will likely engulf the earth, in a mere 5,000,000,000 years. The earth is not going to stop before it is destroyed... --Jayron32.talk.contribs 04:00, 20 November 2008 (UTC)

And even if it did - the amount of energy required to spin it back up again would be immense - more than we could possibly obtain by any means I could imagine. Worse still - because of conservation of momentum - in order to spin the enormous mass of the earth up to a 24 hour rotation period would require spinning something else just as heavy in the opposite direction with a 24 hour rotation period...or something half as massive to a 12 hour rotation - or a quarter as massive to a 6 hour rotation. What you'd find (and it's too late in the evening for me to crunch the numbers - so this is a guess) would be that for a sensibly massive, buildable gyroscope to provide enough inertia to equal that of the earth would require it to spin so fast that it would fly apart no matter how strong the material it was made from. So I don't think it's a practical engineering possibility so spin a planet up to any kind of useful speed. But as Jayron correctly points out - it's not going to be a practical problem. SteveBaker (talk) 04:28, 20 November 2008 (UTC)

Honestly, I wouldn't mind a couple extra hours of sleep at night. That's one of the reasons I look forward to Mars colinization. ;) 216.239.234.196 (talk) 13:26, 20 November 2008 (UTC)

The folks a million years ago probably could not imagine the levels of energy we posses now, so logivcally, we cannot forsee the technology of a million years in the future (assuming there are still any people around). Maybe Earth's aliens, robots, or Uber cockroaches will have figured out ways to exert force on a planet-spinning level. Edison (talk) 06:00, 20 November 2008 (UTC)

According to the Kardashev scale we will get there a lot faster than in a million years. We are already 72% on the way to a Type 1 civilization, which is the minimum power we would need to get our planet spinning again. Sandman30s (talk) 11:18, 20 November 2008 (UTC)

Rather than "stopping" with one side permanently facing the Sun, Earth is much more likely to become tide-locked to the Moon. —Tamfang (talk) 09:06, 20 November 2008 (UTC)

Not to worry, the Sun is gradually getting warmer. In about a billion years, it will be too warm for liquid water to exist on Earth, wiping out all life on the planet. 216.239.234.196 (talk) 13:24, 20 November 2008 (UTC)

OH MY GOD! What a shock! I misread the previous post, and for a minute I thought that "all life on the planet" only had a million years to live! Edison (talk) 00:33, 21 November 2008 (UTC)

Thing that bothers me is the the speed of the path leading to that end, and what conditions for existence is that life existing under until the point of annihilation (if not all life, then species by species being wiped out every week). Perish the thought, but...there it is – the slanty bit to doomsday. Julia Rossi (talk) 00:40, 21 November 2008 (UTC)

I calculated in a recent answer to a similar question that it would take over 5 TRILLION years for the earth to cease rotating at the current rate of decrease (1.7ms per century) - so not exactly an urgent issue. Exxolon (talk) 03:16, 22 November 2008 (UTC)

Compounds:both ionic and covalent

Which compounds are ionic in solid state AND covalent in vapour state? --Siddhant (talk) 10:13, 20 November 2008 (UTC)

Strong acids are a class of compounds which are covalently bonded, but are also strongelectrolytes; i.e. they are ionic in the "aqueous" state. At room conditions, all strong acids are either gases or highly volatile liquids; they may form ionic solids in the solid state; I am not sure on that one. What you are probably looking for is a compound with highly polarized covalent bonds, such that the lattice energy of the solid form of the compound is greater than the bonding energy of at least one of the covalent bonds in the gasseous phase. It make take some research to find them; but your best guess is to look for compounds with bonds between elements with an electronegativity difference very close to 1.5 . That number is generally taken as the "boundary" between a "polar covalent bond" and an "ionic bond". Compounds that lie RIGHT on the line are likely to display some hybrid behaviors between the two. As one real example, ZnCl₂ has an electronegativity difference of 3.16-1.65 = 1.51 . Zinc Chloride is definately an ionic solid, but also has a low melting and boiling point, and displays some molecular character at higher temperatures. I know for a fact that SnCl₄, aka Tin(IV) chloride is in fact a molecular substance (despite being a metal-nonmetal compound) as it is a liquid at room conditions. --Jayron32.talk.contribs 14:05, 20 November 2008 (UTC)

What about PCl₅?--Siddhant (talk) 06:20, 22 November 2008 (UTC)

Yeah that one looks like it fits. See Phosphorus pentachloride. --Jayron32.talk.contribs 06:31, 22 November 2008 (UTC)

PCl₅ is definitely yes. Also AlCl₃? See this link the period three chlorides. Has some nice information (which wikipedia can use). Are there more than two such compounds? --Siddhant (talk) 08:53, 22 November 2008 (UTC)

genius of firefox

hello wikipedia,

i've recently downloaded firefox 3.0 and am just wondering how the 'ominibar' works. if you type a phrase/word (i.e. not a complete web address) it either directs you to the wikipedia entry, the google search results or the actual specific website. what amazes me is that it so accurately reflects what i want- 90% of the time its like its reading my mind! What i'd like to know is how, when i type 'gmail' (for example) does it know i'm looking for the website and not the wikipedia entry on gmail, or indeed, the search results for gmail? What's the algorithm involved does anyone know? thanks, 82.22.4.63 (talk) 14:02, 20 November 2008 (UTC)

Here's one of Mozilla's blog posts about the subject. In short, the bar runs a search on your history and bookmarks, both against the URL text and against plain-text titles. If no option is selected (that is, you type text and press enter), it throws that string to a search engine -- though that functionality isn't anything revolutionary. — Lomn 14:10, 20 November 2008 (UTC)

While we're up: when I type something in (for example) WP's search box, where does the list of suggestions come from? They're clearly not from my history. —Tamfang (talk) 19:52, 20 November 2008 (UTC)

It's from the list of all Wikipedia page titles starting with your string. Algebraist 20:02, 20 November 2008 (UTC)

So does Firefox keep a list of these? How often does it update? —Tamfang (talk) 08:50, 21 November 2008 (UTC)

It's done by Wikipedia, not by Firefox. It should be documented somewhere, but I can't find it. AFAIK it updates as soon as a new page is created. Algebraist 09:30, 21 November 2008 (UTC)

Maybe my question wasn't concrete enough. If I enter a keystroke in the search box, a popup menu appears, very quickly. Does Firefox get that list from Wikipedia (or perhaps some other cache) before or after I start typing? Before seems wasteful; after seems impossible. —Tamfang (talk) 20:38, 21 November 2008 (UTC)

I'm almost sure it's after you start typing. It only grabs a dozen or so articles at most, so if you just type in an "s", it just grabs the first 10-12 articles that start with "s" and keeps moving from there. Since it's all sequential anyway, I doubt it's much of a hassle to grab that quickly. Matt Deres (talk) 21:10, 21 November 2008 (UTC)

Okay. —Tamfang (talk) 04:08, 22 November 2008 (UTC)

The browser (Internet Explorer for me, but I suspect Firefox is no different) does keep a cache of the lists, as shown by the fact that lists I've already seen still appear after I disable the Internet connection. --Bowlhover (talk) 07:01, 23 November 2008 (UTC)

Evolutionary Mammal Anatomy Blunders

A while ago, my biology teacher recited a list of evolutionary mammal anatomy blunders such as our trachea is too close to our esophagus. Thus one can easily die from choking. What are the other evolutionary mammal anatomy blunders? Please note that this is not a homework question. I am curious and just trying to remember. --Emyn ned (talk) 14:26, 20 November 2008 (UTC)

The human knee has always struck me as proof of Idiotic Design. DuncanHill (talk) 14:28, 20 November 2008 (UTC)

Why so, Duncan? --Emyn ned (talk) 14:35, 20 November 2008 (UTC)

Have you ever tried using a pair? They are too loose for walking or running efficiently, not loose enough to be able to sit on the ground comfortably, and if you kneel on them they complain. DuncanHill (talk) 14:43, 20 November 2008 (UTC)

Just go through a list of common ailments and causes of death - a significant number could probably be avoided by a slight modification to our anatomy (although doing so would undoubtedly introduce different problems). --Tango (talk) 14:38, 20 November 2008 (UTC)

Just so everyone is clear, Evolution cannot make blunders, because it is not a directed, thoughtful process. Though the trachea is too close to our esophagus, it is hardly a blunder, it is actually quite efficient to use one orifice to perform two functions. In fact, it may be "safer" for a vertebrate to have one location for both intake of oxygen and consumption of food, because there is a decrease in infection rates with fewer openings to the environment. Also, and this is critical, evolution cannot create parts, it has to make do with what you have. For example, a facial nerve in a shark shifts position in humans to control the diaphragm and breathing. Evolution is incredibly efficient in utilizing whatever we have available. But in the end

evolution is driven my random mutations, genetic drift and natural selection, none of them very intelligent. And of course, in a few million years, after a certain group of humans dies out because it keeps choking on it's food, maybe some flap in the trachea keeps this from happening. Oh yea, we've already evolved epiglottis, which prevents that from happening. So, if I were a student in your teacher's class, I'd tell him he needs to return to college and refresh his training in biology, because he's completely and utterly wrong. OrangeMarlin ^{Talk• Contributions} 14:58, 20 November 2008 (UTC)

Further, given how important the sense of smell is to the ability to sense food as well as simply sensing things in the air we breathe (two survival advantages), it makes a lot of sense that the smelling organ can be positioned at a shared region of "breathing" and "eating". DMacks (talk) 15:37, 20 November 2008 (UTC)

The word "blunder" was used in a rhetorical sense. Could it be said that God has blundered? No, God has allowed evolution to proceed without divine interference, just as God has given men free will to do good or evil. —Preceding unsigned comment added by 98.16.67.220 (talk) 15:24, 20 November 2008 (UTC)

Evolution does not involve the existence of any supernatural being. OrangeMarlin ^{Talk• Contributions} 00:18, 21 November 2008 (UTC)

That's what I said. God does not get involved.

The uneven occurrence of human intelligence is an evolutionary "blunder". Most humans are still cave men; they can learn (remember) but they cannot create. All they are basically suited for is a hunter, gatherer, fighter, existence. Less than one percent of humans - the intelligent minority - has created civilization. The rest simply copy what the intelligent ones have shown them. The primitive ones nearly always have control of government, and as a result of their cave man instincts they often take their country into war, using advanced weapons placed in their hands by the intelligent ones. Eventually the human race will destroy itself - through industrial pollution, if not through nuclear war. The intelligent ones will be responsible - the cave men didn't know any better. The intelligent ones weren't moral enough - they put their brains at the service of cave men. From the standpoint of evolutionary history, civilized mankind will have lasted only a very short time indeed. There was a very patchy development in IQ without an accompanying development in MQ (moral quotient) in all humans. —Preceding unsigned comment added by 98.16.67.220 (talk) 15:40, 20 November 2008 (UTC)

There is an article on maladaptation, which might be related to what you had in mind, though it doesn't quite answer your question either. ---Sluzzelin talk 16:29, 20 November 2008 (UTC)

Kurt Vonnegut still has Internet access, apparently. --Sean 18:32, 20 November 2008 (UTC)

A couple of non-optimal designs spring to mind:

1) The blood vessels for the retina are on top of it, not behind it, causing a blind spot.

2) Having the spinal cord inside the spine may make sense for quadrupeds, but not for bipedal humans. Something more like a notochord would make more sense for the nerves, and could run parallel to the spine but more toward the front of the body. The spine, on the other hand, could contain a rubbery chord in the center without any nerves. This design would hopefully eliminate pinched nerve injuries and paralysis when the spine is broken, and strengthen the spine, as well. StuRat (talk) 23:25, 20 November 2008 (UTC)

Sexual selection has played all sorts of havoc over the evolution of morphological or anatomic characteristics, that on the face of it, may appear to be unfavorable. For example, after too many pints how many men (or indeed women) have rued the day our baculum was selected against? And all those pale, freckled gingers from the Celtic nations? Not so great when you spend the Glasgow Fair largin' it in sunny Ibiza. Rockpocket 23:41, 20 November 2008 (UTC)

Chromosomal shortening at the telomeres as a results of replication seems inefficient.CalamusFortis 00:07, 21 November 2008 (UTC)

Actually, that may well provide an evolutionary advantage by killing off older people and allowing their resources to be used to raise their descendants. Shorter lifespans allow for faster adaptations to changing conditions and hence increase the chance that those genes will survive. StuRat (talk) 03:45, 21 November 2008 (UTC)

Response to StuRat. Again, since eye evolution is not "designed" by anyone, the blood vessels must exit the eye someplace, causing the blind spot. Given what was available genetically and morphologically, as evolution of the eye progressed, the construction of the eye as it is must have some advantage to the organism over other possibilities. As for bipedal humans, the spine works perfectly as a protective shield to the spinal cord. Who knows what will be there 20 million years from now. By using the word "design" you imply that there was conscious choice in how evolution proceeded. There isn't any, so the eye and spine we have, must have had some advantage over alternative evolutionary pathways. OrangeMarlin ^{Talk• Contributions} 00:17, 21 November 2008 (UTC)

We all realize that evolution has no "designer", but our language often fails us when we try to talk about the results of evolution. I tried to get past this problem by saying "sub-optimal designs". I don't necessarily think that a design implies a designer, as you could say "those freckles on your face make a nice design", even though nobody planned them that way. But, much as we say "the Sun has risen" when the Earth has really rotated so that the Sun has come into view over the horizon, I think it's fine to use words like "blunders" when talking about evolution.

I also don't buy your argument that "the eye and spine we have must have had some advantage over alternative evolutionary pathways". That would only be the case if all evolutionary pathways had been tried. Only a small portion of them have been. Then there is the issue of gene-linkage. Perhaps there were better evolutionary pathways tried but they were on the same chromosome as a gene which caused more harm than that advantage, so died out. StuRat (talk) 03:35, 21 November 2008 (UTC)

Blind spot is actually a good example of an evolutionary blunder. Note that cephalopods have the blood vessels existing behind the retina and have similarly good arrangement with the nerve endings so they have no blind spot. The issue here is a bit more subtle; blind spots aren't a big deal and once the mammalian eye was set up the way it is it is difficult to evolve away from that and there's little incentive to do so. Keep in mind that evolution generally only makes moves that are either neutral to local fitness or improve local fitness. Thus, one something has evolved in a more or less suboptimal way if there's no simple mutational fix or then evolution won't move to fix it. One helpful analogy might be to think of evolution as an ant that is taking a semi-random walk trying to find high points on a bumpy surface. The ant cannot see points that are far away even if they might be much higher. JoshuaZ (talk) 01:08, 21 November 2008 (UTC)

No offense, but this is a singularly silly subject. Basically we are assuming that "x" is a blunder because it is not "y" .... or "z" or any other letter you wish to choose. As we can only but guess what a creature's existence would be like if x were y (seemingly better) we can but hypothesise re that alleged "improvement". Ah, but if x were y, would c be c or would it have been d? Then given that change would n still be n ot would it be p? Think it through, woud these changes represent an improvement, or would they so signifcantly change life aswe know it that we'd not be having this discussion? &#0149;Jim62sch&#0149;^dissera! 01:42, 21 November 2008 (UTC)

Not really. We can ask "if a given organism X has fitness f(X), and we put in organism X' in that situation would we have f(X')> f(X)". This is well-defined both biologically and mathematically and biologists talk about it all the time. The most relevant Wikipedia article is fitness landscape. JoshuaZ (talk) 01:47, 21 November 2008 (UTC)

OK, it's not silly, agreed. I was being pissy. &#0149;Jim62sch&#0149;^dissera! 01:52, 21 November 2008 (UTC)

Also, one of the misconceptions about evolution is that it will only preserve those traits which are "best" and that, through evolution, all life is somehow "improving". That's not the case at all. Evolution preserves any trait which does not kill the carrier of the trait before it had the chance to breed. Basically, a trait will be passed on not because its the best, but merely because it didn't kill you. Also, life isn't "improving", its merely constantly changing in response to environmental changes. Life isn't always getting better, its merely getting different. --Jayron32.talk.contribs 03:41, 21 November 2008 (UTC)

Sure, but life as a whole is "improving" because the traits that happen to be preserved just because they're not lethal don't become widespread. Only traits offering an advantage to a species become more common in that species' population.

Some blunders could be/include Vestigial organs, for instance wisdom teeth. [18] EverGreg (talk) 12:23, 21 November 2008 (UTC)

It has been postulated that wisdom teeth were useful to our evolutionary forbears, who were herbivorous. These molars helped them grind their vegetable food. The human race has become omnivorous and fewer molars are now needed. Also in the course of evolution, the human jaw seems to have become smaller, causing crowding of teeth at the rear of the jaw. Hence, impacted wisdom teeth. (See wisdom teeth in Wikipedia.) I wonder what the advantage of a smaller jaw has been. Could it be random change with no use? Evolutionary change has been thought to be advantageous (survival of the fittest). Could some evolutionary change be meaningless - neither good nor bad, just change? Actually, as far as wisdom teeth are concerned, a smaller jaw is a disadvantage. Could there be an offsetting advantage? —Preceding unsigned comment added by 98.16.67.220 (talk) 14:45, 21 November 2008 (UTC)

Wisdom teeth may be a case of seeing an evolutionary change that's only halfway complete. If your diet is high in vegetable matter, a large grinding surface is an advantage. As you increase the amount of meat in the diet, a smaller jaw with better leverage for cutting and tearing becomes advantageous. Jaw size and number of teeth are controlled by different genes, though, so after you've got the smaller jaw, you need a second evolutionary step (and a corresponding selective pressure) to get rid of the wisdom teeth. --Carnildo (talk) 23:59, 21 November 2008 (UTC)

Perhaps wisdom teeth should be called stupidity teeth. They no longer have a use and sometimes cause trouble. —Preceding unsigned comment added by 98.16.67.220 (talk) 03:14, 22 November 2008 (UTC)

This issue often pops up in watchmaker analogy-type evolution debates, and in that context, I've read a detailed "design review" of the eye a few years back. This article covers most of the points, but I also remember reading that the lens is controlled by six muscles; only three are needed. This Talk.Origins archive] gives a much more comprehensive list of less-than-optimal design.

As for whether the word "design" is appropriate, I don't see why not. Evolution, as a process, can be considered a conscious designer in the same way that the brain is conscious even though its cells are not. --Bowlhover (talk) 06:45, 23 November 2008 (UTC)

Egg nutrition

Aside the size, does the chicken eggs and quail eggs have the same nutritional value? The article on Egg (food) only mention nutrition value of mostly eaten chicken eggs. Does nutrition vary on eggs size? --202.168.229.245 (talk) 14:59, 20 November 2008 (UTC)

Take a look here and here (set them both to "100 grams" for a fair comparison). The biggest difference seems to that quail eggs have about twice the cholesterol of chicken eggs. --Sean 18:38, 20 November 2008 (UTC)

BACON...cholesterol

I'm trembling to ask, but does bacon contain the 'good' kind of cholesterol??

My heart says no, but my head says yes, yes, yes!!! —Preceding unsigned comment added by 94.27.160.199 (talk) 19:21, 20 November 2008 (UTC)

Kosher bacon has no cholesterol. In fact, it is nonexistent. —Preceding unsigned comment added by 98.16.67.220 (talk) 19:29, 20 November 2008 (UTC)

In fact, many approximations of kosher bacon exist. They're just not pork bacon. Depending on the variety (and how far you're willing to stretch your definition of "bacon"), they may be cholesterol-free -- tofu bacon would certainly seem to qualify. — Lomn 19:48, 20 November 2008 (UTC)

Or lean chicken breast. —Preceding unsigned comment added by 94.27.160.199 (talk) 20:52, 20 November 2008 (UTC)

Actually, the focus on dietary cholesterol is probably a red herring, nutritionally speaking. The way that your body processes the foods it intakes, there is little correlation between macronutrients you eat (such as lipids, carbohydrates, and proteins) and how your body makes its own lipids, carbohydrates, and proteins. For a long time, the adage "you are what you eat" has really produced some starkly bad nutritional advice; its also entirely not true. Eating higher cholesterol foods does not raise cholesterol; eating higher fat foods does not raise your body fat in any direct way.

When doctors tell you that you need to lower your cholesterol its not because cholesterol is itself harmful; cholesterol is a symptom of an underlying problem. Its like having a runny nose. The runny nose is not itself a disease, but is an indicator of infection. Likewise, your cholesterol numbers (and all 3 are important, your total cholesterol, your LDL cholesterol, and your HDL cholesterol) can tell doctors that there is an underlying problem, but the cholesterol itself is no more than an indicator of that problem.

Now understanding the function of cholesterol is important to understand why these numbers are so important. Cholesterol is an important structural component to every cell in your body. When your body needs to make extra tissue, the liver produces the cholesterol from availible lipids (and its important to note that your liver does this even if you ingest no cholesterol in your diet. Your liver can even make cholesterol from just about anything, even if you take no lipids in at all.). Also, as your body breaks tissues down, the cholesterol is sent back into the blood stream, where the liver can take it and break it down to make other stuff as needed. Now here's where it gets really important: your body needs to be able to distinguish between these two cholesterols; that is the cholesterol destined for your tissues to make stuff, and the cholesterol destined for your liver to be recycled. However, its just all cholesterol, so you need some "marker" to determine where the cholesterol is headed. Its sort of like a train ticket. Some of the cholesterol bears an "outbound" train ticket, and some bears an "inbound" train ticket. Those tickets take the form of lipoproteins, which tag the cholesterol molecules for their destination. Cholesterol heading from the liver to the rest of your body is tagged with LDL (or low density lipoprotein) markers, while that headed towards your liver is tagged with HDL (or high density lipoprotein) markers.

If you haven't seen where this is going, and some of you may, here's the most important bit. Having high LDL levels means that your body is making lots of new cells. An adult body should probably not be making lots of new cells, aside from general maintenance, so elevated LDL levels means that your body is probably busy making lots of fat cells, which is the primary way in which an adult can "grow". If you have elevated HDL levels, this is an indication that your body is primarily breaking down these fat cells, and transporting the products back to the liver, which is generally pretty healthy thing to be doing.

Now back to the nutritional aspect of this. The body makes all of these compounds on its own, irrespective of what you are eating. It is going to do this cycle regardless of whether you eat a high fat diet, a low fat diet, lots of carbs, little carbs, etc. etc. Your body doesn't wait for cholesterol and fats and decide what to do with them when they arrive, it is going to make them or break them down as conditions dictate. The most important factor in deciding how your body is going to operate in this manner (i.e. will it be involved primarily in making fat tissue or breaking it down) is what is known as blood glucose level. Elevated blood glucose levels tell your body that you have eaten more calories than you are using, and your body, not being wasteful, starts to put this energy away in long-term storage, which is, you guessed it, fat. Elevated glucose levels are caused whenever you eat too many calories for your level of activity, so the way to signal your body to produce the good cholesterol is to keep this glucose level low; i.e. either eat less food or exercise more.

What is the upshot of all of this? Well, don't feel bad about eating bacon. Go ahead, because eating bacon in-and-of-itself isn't going to raise your cholesterol level. However, knowing that you ate that bacon, you should probably eat less of something else (like say, have 1 waffle instead of 2) or go run an extra mile. --Jayron32.talk.contribs 20:51, 20 November 2008 (UTC)

That seems to be entirely too rosy of a picture. Bad cholesterol in the circulatory system is actually the cause (or at least a contributing factor) of plaque formations, which can ultimately cause heart attacks, strokes, and other problems. And bacon does indeed include bad cholesterol, whereas vegetable fats, like avocado and most salad dressings, tend to contain good cholesterol fats. StuRat (talk) 22:55, 20 November 2008 (UTC)

That is entirely true, however the blood cholesterol level has really very little to do with ingested cholesterol. Metabolism just doesn't work that way. The bad cholesterol IS in fact the source of many things such as artierial plaques, which are quite dangerous. However, this cholesterol is made by the liver and sent to other parts of your body. Any cholesterol that you eat is digested before being processed. The LDL-cholesterol in your blood is not there because you ate it. Just as a runny nose if left untreated may lead to a sinus infection, high LDL-cholesterol levels if left untreated can do nasty stuff to the body; however cholesterol is still not the primary cause of the problem. The primary cause of the problem is elevated blood-glucose levels, caused by an imbalance between diet and activity level. And to correct StuRat, only animal-derived cells contain cholesterol. Plants do not make any cholesterol. Bacon contains lots of saturated fats; which given their difficulty in digesting do lead to all sorts of health problems. Vegetable fats tend to be unsaturated fats, which are easier for your body to digest, and so are generally seen as "healthier". But vegetables contain no cholesterol at all. Once again, there is a confusion here between cholesterol and fatty acids. Both are classified lipids, but the production, disgestion, metabolism, and use of them in the body is not at all the same! --Jayron32.talk.contribs 03:28, 21 November 2008 (UTC)

Yes, I confused good and bad fats with good and bad cholesterol. I'd still like to see some proof that dietary cholesterol has no effect on our health, however. Do you have any sources ? StuRat (talk) 03:56, 21 November 2008 (UTC)

Oh, you are probably right. I may have overstated the case some. Certainly dietary intake of cholesterol DOES matter some. However, the single-minded focus on the cholesterol molecule has placed a out-of-proportion focus on intake of cholesterol. The greater problem for overall health is persistant elevated blood glucose levels, brought on by an out-of-balance diet and activity regimen. There is no real adverse health problems associated with eating an occasional piece of bacon, so long as a) your diet is balanced (i.e. you don't subsist SOLELY on bacon) and b) your overall caloric intake is low and your activity level is high. That basic relationship is probably the most important for determining overall heart and vascular health more than anything. Eat some bacon once in a while, just be sure to also keep your diet balanced and apporpriate. --Jayron32.talk.contribs 06:32, 21 November 2008 (UTC)

I hate to ask this, but, could you tell us whether you have or ever had anything that might be construed as a financial or family interest in anything related to bacon?94.27.160.199 (talk) 20:57, 20 November 2008 (UTC)

I am a semi-retired chemistry teacher, and current "stay at home" parent of a 2 year old. My parents are a retired hospital receptionist, and a service technician for a computer printing equipment firm. My grandparents were a) a nurse b) a machinist c) a homemaker and d) a shoe store manager and salesman. I have no connection to any food service industry at all. But I do get annoyed when gross misunderstandings of physiology lead to poor nutrition advise... --Jayron32.talk.contribs 22:45, 20 November 2008 (UTC)

The world is filled with urban myths and such. I'm sure if I had a reasonable diet of Big Macs and fries in reasonable amounts, with lots of exercise, no smoking, etc., I could live a long time. Or not. Because so much depends on genetics, bad luck, and many other things. OrangeMarlin ^{Talk• Contributions} 00:22, 21 November 2008 (UTC)

I don't think it's possible to be healthy on a diet of just Big Macs and fries, as you would be missing some important nutrients we get from veggies, etc. However, a small portion of your diet could be BMs and fries, as long as the rest of your diet was healthy. StuRat (talk) 04:01, 21 November 2008 (UTC)

Here's the nutrition data for an ounce of pan-fried bacon, but it doesn't distinguish between good and bad cholesterol: [19]. StuRat (talk) 23:08, 20 November 2008 (UTC)

Thanks Jayron32 for your concise and thorough explanation - better than any Doc (who was allowed to give medical advice) ever did for me :) - I'm sure you'll take some hits for your candor. -hydnjo talk 00:27, 21 November 2008 (UTC)

If you'd really like to start worrying about your breakfast consider this: frying or grilling your bacon produces Nitrosamine which is known to cause cancer. This goes for some "heart healthy" varieties like turkey bacon, too. see liquid smoke There is a way to inhibit nitrosamine formation by adding ascorbic acid. If you then add a diet soda, however, you might end up with benzene in your test tube (=body). You can compound the problem by adding cheese and a pickle. In our best efforts to feed the ever growing masses foods that taste better than the sawdust a lot of it is made from and neither kills them off nor makes them ill in unacceptable numbers we often identify culprits to be avoided and end up being led up the garden path. Remember we ended up with trans fats because butter was deemed unhealthy. Simple truths like eat less and exercise more no one wants to hear because they don't fit the way we live. "Life is dangerous to your health." - Just a thought. 76.97.245.5 (talk) 04:44, 21 November 2008 (UTC)

:: Nitrosamine is known to cause cancer in rodents. It has never been shown to cause cancer in humans. One telling difference between humans and the animals in which nitrosamine has been shown to cause cancer is that humans have a long history of eating scorched animal flesh. Hamsters... not so much. Of course we are exposed to a lot of nasty chemicals in this modern world in which we live, but you can't take something that has been shown in an animal model (even if the model in question is a primate, but especially if it's a rodent) and say that it happens in humans. For that, you need research in humans. --121.127.209.126 (talk) 00:44, 22 November 2008 (UTC)

And then I read the reference that the "nitrosamine causes cancer" statement in our nitrosamine article points to. It's a toxicological evaluation of nitrosamine in condoms. Its evaluation: Safe. --121.127.209.126 (talk) 00:52, 22 November 2008 (UTC)

And then I read the other reference on the page and it was a useful epidemiological study. That makes it more likely to be relevant. --121.127.209.126 (talk) 00:57, 22 November 2008 (UTC)

I also have to argue with your assertion that animal studies are useless. If a given chemical causes cancer in animals, it's quite likely to also cause cancer in humans. It would be unethical to intentionally expose people to a chemical that is a suspected carcinogen in order to perform such a test. Also, animals are frequently exposed to much higher levels than humans in the test. If it only causes cancer in one in a million subjects at the usual exposure level, this would be difficult to detect in animal testing, requiring tens or hundreds of millions of subjects. However, by increasing the exposure level you can also increase the cancer incidence, if it is indeed a carcinogen, to a level which can be detected in animal tests. So, in conclusion, if animal tests show a chemical is a carcinogen, we should play it safe and avoid the chemical wherever possible. StuRat (talk) 06:54, 22 November 2008 (UTC)

The other issue is that while it's true that humans have long been eating scorched flesh, the selective pressure for many times of cancer is not great since very frequently they may have died long before any cancer would take hold. Nil Einne (talk) 09:03, 22 November 2008 (UTC)

It doesn't take very much pressure to change the genes, I would have thought it is pretty certain that we have some adaptations for eating scorched food and for protecting against any cancers from it by now. Older members of the community can help bring up the children. Dmcq (talk) 11:07, 22 November 2008 (UTC)

Let's say that eating scorched food will only kill one in a million people before they can pass on their genes and that 1% of the people are somehow immune to this effect. Then, after one generation, one part in a million of the 99% will have been eliminated from the gene pool. By my calcs, somewhere in the neighborhood of 1.000001% would be immune in the next generation. You can see that the entire human population won't be immune anytime soon, at that rate. You might argue that a one in a million chance of getting cancer is insignificant, but, in the US that would mean 300 people would die from cancer before they can pass on their genes and likely far more after. That's significant enough to ban a chemical (if there are non-carcinogenic alternatives), or just put out an advisory, if no substitute is available. In the case of scorched food, just telling people not to eat food that's burnt to a cinder is likely to work. Incidentally, this might be exactly how people develop an immunity to dying from eating burnt foods, by developing an aversion to eating such foods. StuRat (talk) 16:27, 22 November 2008 (UTC)

It's not just having the children that matters, it's that the children grow up on an equitable basis with others. That's what I was saying about older people mattering. And yes it would have to affect at least 1 in 100000 rather than a million and probably more like 1 in 10000, which if it is detectable in animals it probably would. Dmcq (talk) 17:57, 22 November 2008 (UTC)

November 21

Question for all the people in the medical profession here...

Just how common are 'strangest/most impressive foreign body retrieved from an orifice' contests amongst emergency room doctors? My aunt used to be a nurse and she told me that it went on to some extent in all the (UK) hospitals she ever worked in. Generally, they'd throw in a few quid each and at the end of each month, the doc deemed by an impartial third party to have the most impressive 'find' would receive a bottle of expensive malt whiskey, or some expensive cigars. If not the doctors doing it, it was the nurses. This was in the 70s/80s, so the culture may have changed now, I dunno. --Kurt Shaped Box (talk) 00:21, 21 November 2008 (UTC)

Would a seagull be considered a "foreign" body? -hydnjo talk 00:33, 21 November 2008 (UTC)

I dunno. Can you make it fit up there? ;) --Kurt Shaped Box (talk) 00:34, 21 November 2008 (UTC)

I read that an expensive cigar was removed from the oval orifice. Edison (talk) 00:37, 21 November 2008 (UTC)

Perfect Edison, perfect! hydnjo talk

How about these? (Oops, disclaimer - I'm not amongst ...all the people in the medical profession here...) -hydnjo talk 00:47, 21 November 2008 (UTC)

I'd seen that list before - but not recently. Still makes me giggle slightly. My aunt once told me of a man who presented in A+E with a magazine from a semi-automatic pistol (with a condom over it) jammed up his rectum. That was probably the craziest one I've ever heard (I assume that his doctor won the prize that month). There was a guy who'd slipped a AA battery into/down his urethra and lost it too. --Kurt Shaped Box (talk) 00:59, 21 November 2008 (UTC)

Shocking! -hydnjo talk 01:06, 21 November 2008 (UTC)

I hope the battery was flat (makes it easier to insert)--GreenSpigot (talk) 01:28, 21 November 2008 (UTC)

Ouch ! even just thinking about it :( -hydnjo talk 01:38, 21 November 2008 (UTC)

There sure are a lot of anal-retentive people in this world, aren't there ? StuRat (talk) 03:19, 21 November 2008 (UTC)

More receptive than retentive. —Tamfang (talk) 20:42, 21 November 2008 (UTC)

Isn't the retention the issue which causes them to seek medical assistance ? Or do they just go there to show off ? StuRat (talk) 22:39, 21 November 2008 (UTC)

Per the list cited by Hydno, the 100 watt light bulb would likely be the A19 size, 2 3/8 inches (6 cm) across at the broadest point. Such a bulb would easily shatter, complicating the removal. A spiral compact fluorescent bulb would seem even more likely to break, and in addition would release a bit of mercury. The development of small LED replacement bulbs would seem to offer advantages beyond efficiency, service life and absence of mercury. Edison (talk) 04:34, 21 November 2008 (UTC)

Thanks Edison, your bright comments are sure to illuminate the darkest recesses of our minds. (Or any dark recess, really.) StuRat (talk) 05:40, 21 November 2008 (UTC)

Yeah - but that's a little bit like packing match-heads into a tin can, isn't it? --Kurt Shaped Box (talk) 22:57, 21 November 2008 (UTC)

By tradition, if they remove an expensive bottle of malt whiskey from an orifice, the patient gets to keep the cash. --Sean 15:34, 21 November 2008 (UTC)

Where do they put the cash, exactly ? And do they wait for the receipt ? StuRat (talk) 15:43, 21 November 2008 (UTC)

Just swipe an ATM card. Though only for male patients...for ladies, no way to enter what the PINis. Okay, that was a bit of a stretch. DMacks (talk) 17:34, 22 November 2008 (UTC)

You should be ashamed of yourself... that was terrible! :) --Tango (talk) 21:53, 22 November 2008 (UTC)

Quantum dots

While doing a project involving the fluorescence of quantum dots, I noticed that only the radius of the quantum dot effected the wavelength of the light it fluoresced. The larger ones fluoresced red and the smaller ones fluoresced green. I was using an almost UV source for excitation. While doing this experiment, I did not feel the solution containing the dots changing temperature, but the energy was obviously not conserved in the form of light. So my question is, where is the extra energy going? There is quite a bit of energy between the almost UV and the almost IR. What type of energy did this become. TIA, Ζρς ι'β' ^¡hábleme! 03:55, 21 November 2008 (UTC)

It almost certainly did end up as heat. It takes quite a bit of absorbed light to generate an amount of heat perceptible to the touch. Try repeating the experiment under identical conditions, but fill the cuvette (or whatever your sample container was) with a solution of black ink or some other strongly absorbing substance. Under those circumstances, virtually all of the absorbed light gets converted to heat, but I'd wager that you won't notice a change in temperature as long as you're using your hand as a measuring device. The smll amount of excess heat gets dumped into the ambient room air just about as fast as it gets put in to your sample. TenOfAllTrades(talk) 05:14, 21 November 2008 (UTC)

Potassium bicarbonate question

Potassium chloride can be used as a substitute for sodium chloride (table salt), for those who wish to limit their sodium intake. So, can potassium bicarbonate be used as an antacid, in place of sodium bicarbonate, for those with upset stomaches who also want to limit their sodium intake ? StuRat (talk) 04:11, 21 November 2008 (UTC)

I would think that it would make a decent substitute, since it is the bicarbonate anion that functions as the antacid.CalamusFortis 04:42, 21 November 2008 (UTC)

As with potassium chloride, you would need to take care and consult a medical professional before using lots of potassium in your diet. Your body is MUCH more sensitive to fluctuations in potassium levels than to sodium levels; you can literally overdose on potassium quite easily... --Jayron32.talk.contribs 05:48, 21 November 2008 (UTC)

It is available to buy for eating and cooking purposes from some health food shops. It does not taste quite the same as the sodium salt, but has a potassium ion flavour, similar to the potassium sulfate and potassium chloride. Graeme Bartlett (talk) 11:24, 21 November 2008 (UTC)

Thanks. Which health food stores ? Does this include GNC ? StuRat (talk) 15:37, 21 November 2008 (UTC)

The last one I bought was branded Salt Skip, and from Health Spectrum. Also Healthy Life have it. I don't think we have GNC in Canberra. The price is five to ten times higher than the sodium salt, because so few want to buy it. Graeme Bartlett (talk) 20:59, 21 November 2008 (UTC)

I'm asking about potassium bicarbonate. It sounds like you might be talking about potassium chloride. StuRat (talk) 22:31, 21 November 2008 (UTC)

The product is definitely potassium bicarbonate. The same company produces both kinds of product. Graeme Bartlett (talk) 20:56, 22 November 2008 (UTC)

Double Gravitational Acceleration Paradox

If you calculate the gravitational acceleration of two objects with mass M and m, the gravitational acceleration will be GM/r^2 and Gm/r^2 respectively. So which acceleration should I use and what did I get wrong? ----The Successor of Physics 15:03, 21 November 2008 (UTC) —Preceding unsigned comment added by Superwj5 (talk • contribs)

The object of mass m accelerates at a rate GM/r^2, and the object of mass M accelerates at Gm/r^2. Where's the problem? Algebraist 15:07, 21 November 2008 (UTC)

Both gravitational accelerations are measured with respect to the center of mass of the system — not the other object. TenOfAllTrades(talk) 15:09, 21 November 2008 (UTC)

Or with respect to any other inertial frame, since acceleration is frame-independent (as long as you stick to inertial frames). -- BenRG (talk) 17:15, 21 November 2008 (UTC)

The acceleration of the two objects toward each other is the sum of the two. For one large object (like a planet) and one small object (like you), the acceleration of the large object is insignificant. StuRat (talk) 15:33, 21 November 2008 (UTC)

Er, actually it's GMm/r². Does that answer your question? --Heron (talk) 21:04, 21 November 2008 (UTC)

That's the force between M and m, not the acceleration!(To Heron only) ----The Successor of Physics 04:02, 22 November 2008 (UTC)

Pipe bursting temperature

A friend of mine said he was told that if you turn your house's thermostat temperature below 55ºF you run the risk of pipes bursting. This seems rather high to me (also considering we had our house at 54ºF all winter last year when we were out of the house and had no problems). What's the real risk here? For context I live in the Boston area (where it does get quite cold in the winter, from a water-freezing point of view), in a multi-story house with a basement. Our house heating is maintained through radiators in the individual rooms (fairly old house). We keep it at 54ºF at night and when we are away from the house because heating oil is incredibly expensive. --98.217.8.46 (talk) 16:31, 21 November 2008 (UTC)

The pipes will only burst if the water actually freezes, 54F is quite a bit above freezing point (although that's the temperature of the air inside your house, the pipes may be a little colder), so I would expect you'll be fine. I've only ever heard of people having problems with pipes bursting when they've not been living in the house over winter - if you are there and it's warm enough for you to be reasonable comfortable, then the pipes should be fine.--Tango (talk) 17:01, 21 November 2008 (UTC)

I had a pipe burst once, even though the house temp was set at 50ºF. It was on an exterior wall leading to an outside tap. After fixing the pipe, I installed a cutoff valve before the pipe gets to the exterior wall, so I can now turn off the water, open the outside faucet to drain the contents, and make it through the winter without a flood. StuRat (talk) 17:17, 21 November 2008 (UTC)

Yeah, we cut the water to outside taps for this reason. --98.217.8.46 (talk) 18:41, 21 November 2008 (UTC)

As long as you use your water every day, and keep water flowing through the pipes, there is little danger of your pipes freezing. I grew up in New Hampshire, where the weather regularly stays permanently below freezing for weeks at a time, and we took no special precautions as long as we were occupying the house. There can be problems if you leave the house unoccupied for several days, in that case it is recommended that you turn off the water in your house and drain all of the pipes. Also, if you live somewhere where the temperature stays above freezing for significant portions of the day (say average January highs in the 40's), and where the temperature does not drop below freezing except occasionally at night, then you are probably safe regardless of whether or not the house is occupied. I say probably, because strange and unpredictable things do always happen; if you are away on vacation from a normally mild climate, and a strange cold spell comes along while you are away, unexpectedly, all bets are off... --Jayron32.talk.contribs 17:38, 21 November 2008 (UTC)

Where I have lived, occasionally the pipes freeze up in winter, but they never burst. Are there better quality pipes that can withstand the pressure? Graeme Bartlett (talk) 20:42, 21 November 2008 (UTC)

It has to do with the way they freeze. Normal freezing only increases the size by about 10%, and most pipes can stretch that much. The problem is when the pipe freezes from both ends, pushing the water in front of it from both sides. This results in a bulge where the two ice formations meet, which can be enough to burst most pipes. Repeated freezing can also stretch a pipe beyond it's fracture limit. StuRat (talk) 22:25, 21 November 2008 (UTC)

I recently bought a home that has copper water pipes. The tees and elbows are joined to the pipes with solder (sweated). Some of the tees and elbows had become detatched from the pipes. I theorize that the water in the pipes froze and the expanding cylinder of ice pushed off the tees and elbows. The copper pipes must also have bulged a bit. The home had been empty for 3 years and unheated. It is in western Pennsylvania, where we just had 10" of snow. I am going to replace all the pipes with PEX pipe and fittings. PEX plumbing pipe, which is new, is easy to work with. There is no soldering. (A torch is a fire hazard in close places, like inside walls). PEX pipe can be easily cut without a hacksaw, and unlike iron pipe it needs no threading. PEX is also easier to cut than ordinary plastic water pipe, and it can be given a bend around a corner by hand (if the turn is not too sharp). PEX elbows are available for sharp turns. —Preceding unsigned comment added by 98.16.67.220 (talk) 00:21, 22 November 2008 (UTC)

What is glabrata?

In relation to Women's health? --Emyn ned (talk) 18:18, 21 November 2008 (UTC)

Candida glabrata. Fribbler (talk) 18:23, 21 November 2008 (UTC)

Mystery objects

Can anyone help identify these objects? They were found in the shed of a dead relative (a mechanic who was also into woodworking). Hut 8.5 20:24, 21 November 2008 (UTC)

The serrated disks are blades for a circular saw. I would guess that the rest are other components for the same device. StuRat (talk) 20:39, 21 November 2008 (UTC)

Yep, you might like to see spindle as well. Very much the woodworker... (those articles could use a pic like this). Julia Rossi (talk) 21:58, 21 November 2008 (UTC)

One of the blades is inscribed with the name Dormer, a manufacturer for precision tools in Nottinghamshire with stacks of outlets in many countries. [20] gets you to their website. --Cookatoo.ergo.ZooM (talk) 22:01, 21 November 2008 (UTC)

Thanks very much. Hut 8.5 22:28, 21 November 2008 (UTC)

Nottingham... my home town! We're apparently good for something other than violent crime! —Cyclonenim (talk · contribs · email) 23:13, 21 November 2008 (UTC)

Surely the Sheriff of Nottingham can deal with the disruptive behaviours of a few outlaws? Edison (talk) 23:17, 21 November 2008 (UTC)

You'd be right, if he wasn't dead for several hundred years. I've heard decomposed bodies left only with a skeleton find it hard to fight crime these days. Damn life cycle. —Cyclonenim (talk · contribs · email) 00:32, 22 November 2008 (UTC)

Well I'll be damned, apparently there is still such thing as the Sheriff of Nottingham, although it's appointed to the mayor and no gangs will look at him and shiver about anything but his looks. —Cyclonenim (talk · contribs · email) 00:34, 22 November 2008 (UTC)

Scientific term and research on the topic

For this question, just assume the following is true: A human is shown a pattern "abbb" and asked if it best matches "accc" or "cbbb". The human answers "cbbb" because the a is insignificant to the three b's. So, the human is biased towards whatever is mostly visible.

For a paper I'm writing, I'm discussing the tendency for AI pattern matching algorithms to be biased in the same way. However, I don't know what the scientific term for this bias is. Does anyone here know it? Also, if anyone has links to research on it that I can cite, that would be overly helpful. -- kainaw™ 22:37, 21 November 2008 (UTC)

Sounds like you might be interested in Hamming distance. --Carnildo (talk) 00:09, 22 November 2008 (UTC)

The human and/or the AI is biased by its choice of similarity measure [21] of which the hamming distance is one. Speaking of bias in general, every AI need to have some kind of bias to be able to generalize to unseen examples. This is called bias-variance tradeoff or the bias-variance theorem and is covered in most introductory books on AI and pattern classification, though I can't guarantee you'll grasp it quickly or intuitively. (I certainly didn't :-)

Thanks. I almost had it. I was looking for psychological distance. Now, I can reference that little section of this paper and wrap this thing up for review next week. -- kainaw™ 13:21, 22 November 2008 (UTC)

Would humans really favor "cbbb"? I think I'd favor "accc," it'd feel like it was "next" in the order. zafiroblue05 | Talk 01:52, 23 November 2008 (UTC)

November 22

equatorial water:direction

dear peoples i believe that water goes down a drain in different direction north and south of the equator,ie, clockwise and anti clockwise,and i would like to know if there is a permanant geographical location where north and south meets. if so,does the water go straight down the drain without clockwise or anti clockwise direction? and,given that the earth wobbles on its rotational axis,could any such location remain static? —Preceding unsigned comment added by 58.84.211.251 (talk) 00:37, 22 November 2008 (UTC)

It's a myth. Water spirals down the drain in a direction that is not in any way related to the rotation of the earth. So the water will spiral (either clockwise or anti-clockwise) whether you're north, south or in the middle - or even on the moon. --121.127.209.126 (talk) 01:20, 22 November 2008 (UTC)

And some references:

• Snopes
• Yahoo answers
• Straight Dope
• Australian Broadcasting Commission Self Serve Science
• Youtube

--121.127.209.126 (talk) 01:26, 22 November 2008 (UTC)

Beat me to it they did, here's one more to top things off [22] - 76.97.245.5 (talk) 01:31, 22 November 2008 (UTC)

I suspect that the OP really wants to know what the coriolis effect does at the equator. Ignoring water in a drain, the fact remains that a fluid flowing over a long distance to a region of lower pressure (or lower elevation in the case of flowing water) on the rotating earth will experience a force not in its line of direction. If the low pressure area is centered right on the equator, then yes, the fluid won't rotate around that point. ~Amatulić (talk) 02:02, 22 November 2008 (UTC)

I suggest someone find some satellite photos of storm systems around the equator. They're of the right scale to be affected by coriolis (cyclonic = clockwise in the south, anticlockwise in the north). --121.127.209.126 (talk) 02:14, 22 November 2008 (UTC)

The coriolis effect is far too tiny to affect water going down a drain. It does affect large storm systems - but even then, once they are spun up to speed, the coriolis force is dominated by the momentum the storm already has - so even if a clockwise-spinning storm crosses the equator, it's going to keep spinning clockwise for quite a while. So I wouldn't expect to see any especially remarkable at the equator - except, perhaps, the consequences of a clockwise storm hitting a counterclockwise one. SteveBaker (talk) 03:31, 22 November 2008 (UTC)

I believe the lack of coriolis efffect at the equator is precisely why we rarely get hurricanes forming there. StuRat (talk) 06:36, 22 November 2008 (UTC)

Yeah, we've debunked the idea that toilets are effected by the earth;s rotation. As to the effect of the Coriolis Effect at the equator, see Doldrums... --Jayron32.talk.contribs 04:14, 22 November 2008 (UTC)

This is more interesting than useful now, but there have been related discussions on the Reference Desk; see [23] and [24]. To respond to StuRat, tropical cyclogenesis says "a minimum distance of 500 km (300 miles) from the equator is normally needed for tropical cyclogenesis".

"if there is a permanant geographical location where north and south meets.[...] given that the earth wobbles on its rotational axis,could any such location remain static?"

I'm not sure what this is asking. Isn't the "geographical location" the equator? As for Earth's wobble, that would be precession, which does not change the orientation of Earth's axis with respect to the planet's surface. What is now the equator will always be the equator. --Bowlhover (talk) 05:14, 23 November 2008 (UTC)

Fate of the universe

Assuming that our present knowledge of quantum mechanics and relativity are both roughly correct and that any discrepancies will be worked out and leave the existing knowledge of those fields intact, is it possible that our far-distant descendents will be able to stop the inevitable doom of the universe? It seems that this would require a reversal of the 2nd law of thermodynamics, and I vaguely remember reading something about a possible microscale violation of it (basically, small beads dragged through a liquid lower the temperature in their trail), but can't remember many details. 69.177.191.60 (talk) 01:17, 22 November 2008 (UTC)

I don't think the decline of the universe is in any way preventable - but that doesn't mean that they can't survive. The amount of available energy can never go completely to zero. The trick will be to live more slowly as the energy declines. You have to imagine some kind of technology that's way beyond where we are now - one perhaps where our intelligences are stored on computers of some kind rather than biological brains. Then - as the energy available declines by half, you simply perform your calculations half as fast. Gradually our future selves would 'think' more and more slowly - using less and less energy until it might take a million years to accumulate enough energy to have a thought. But if the universe never COMPLETELY runs out of energy - and if it will indeed last forever - then this is a viable strategy. SteveBaker (talk) 03:23, 22 November 2008 (UTC)

SteveBaker has roughly the right idea. Heat death is an asymptotic condition, not a finish line. Though the question remains what happens once the ammount of usable energy in the universe reaches levels below the Planck constant... (oh, and the universe is not running out of energy. The energy will always be there. The universe is gaining entropy, which is a slightly different idea. </pedanticrant>.) --Jayron32.talk.contribs 04:07, 22 November 2008 (UTC)

Sure - I was (loosely) talking about available energy. As entropy does its thing and most of the energy has diffused out into forms that make it impossible to collect - the amount of available energy will asymptote towards zero. But surely only the average energy will fall below the plank constant - the number of particles with enough energy for our future selves to collect and use will asymptote toward zero also. So we sit there with our battery charger and our "just greater than plank-constant" energy/particle collector and we sit there - just above absolute zero charging our tiny batteries. When we have scraped enough energy together - our super-low-power brain/computer runs one clock cycle - then, with the battery once more drained, we wait for enough more particles to come along to do it again. It will eventually take an exceedingly long time for this to happen - particles with enough energy to kick some into our battery would start to come along less and less often - so our brains would run more and more slowly.

From our perspective it would be like time started to run faster and faster - but with the universe being such an amazingly boring and slow-moving place - that would hardly matter. Indeed, that would presumably be a benefit because it would attune our minds to the pace at which interesting events are happening.

We might have to think more slowly anyway because such a high-entropy device as a chunk of carefully doped silicon or nanotechnological push-rod memory would become hard to maintain with the stretching of space becoming noticable on the timescales of our thoughts. So perhaps we'd be using the spin on a single electron as a 1 bit storage element and super-low energy photons to pass information between them. As space stretches and our minds become physically larger - the time it would take for information to pass through it could become ridiculously large anyway - so a slower pace of thought would likely become inevitable. But infinity is a very large number - we aren't in any hurry. SteveBaker (talk) 14:04, 22 November 2008 (UTC)

Depending on how quickly our thoughts slow down, we may only be able to have a finite number of thoughts in an infinite amount of time. In that case, infinity, while very large, wouldn't be large enough. (This is the exact opposite of Tipler's Omega Point.) --Tango (talk) 15:09, 22 November 2008 (UTC)

Classically you never reach absolute zero, but quantum mechanically you can and do—there are only finitely many energy levels between the current state and the ground state. Maybe you can avoid that in a system that grows without bound, but in ΛCDM no system (with a density much lower than the dark energy density) can grow beyond ${\tfrac {2c}{H_{o}{\sqrt {\Omega _{v}}}}}$ ≈ 30 billion light years in diameter while still remaining in mutual contact. I'm pretty sure QM plus GR with a positive cosmological constant leads to an unambiguous "no" on this one. Of course, my assumptions might be wrong (especially the one about there being a cosmological constant.) -- BenRG (talk) 23:26, 22 November 2008 (UTC)

Might it be the case that by the time that by the time the heat death of the universe becomes a problem, humanity (or whatever humanity has evolved into by then) will have figured out a way to crack open a gateway in the fabric of reality and go 'elsewhere', where conditions are more hospitable? Or does it not work like that? --Kurt Shaped Box (talk) 09:25, 22 November 2008 (UTC)

Yes. --Stephan Schulz (talk) 09:37, 22 November 2008 (UTC)

It's impossible to speculate. With what we know now - categorically, no. But who knows what peculiar stuff will show up at the margins in the future. I read yesterday that a pocket of dark matter has been located 'only' 2000 light years from us. It's likely that being able to study that would reveal all sorts of aspects of the universe that we don't currently understand. But we don't know what we don't know - so speculation about radical new physics is impossible. However, what I said above about slowing the pace of thought in order to make use of declining amounts of energy doesn't violate any physics that we're currently aware of - so it's possible that this could be the way to survive the entropy death of the universe - and we can reasonably speculate about that using only what we currently believe to be true. SteveBaker (talk) 14:04, 22 November 2008 (UTC)

"It's impossible to speculate." You must be joking! :o) - CBHA (talk) 17:16, 22 November 2008 (UTC)

I believe the Doomsday argument may apply. If people are going to be around forever, than we would almost surely be living so far from when the universe, human race, etc. started that we wouldn't be able to comprehend how long ago it was. — DanielLC 18:15, 22 November 2008 (UTC)

However if human thought is going to slow down in the future that could compensate - in terms of percieved time, we may not be that near the beginning. --Tango (talk) 18:41, 22 November 2008 (UTC)

One idea is to look at The Last Question, which is too good and too short to spoil here. And (not to assign homework or anything), His Master's Voice by Stanislaw Lem ends with very interesting thoughts along these lines. zafiroblue05 | Talk 01:50, 23 November 2008 (UTC)

Stanisław, please. The slash makes the l into a w. Algebraist 01:55, 23 November 2008 (UTC)

Flower Identification

What is the name of the plant in this picture?--Abhishek Jacob (talk) 09:47, 22 November 2008 (UTC)

What a beautiful flower. It is a Heliconia rostrata. Richard Avery (talk) 12:20, 22 November 2008 (UTC)

Psst Richard A, do you mean Heliconia bihai? [No, you're right, the bihai is erect instead.] Julia Rossi (talk) 12:30, 22 November 2008 (UTC)

Yes, well, if you're looking from Oz it would be up the other way! ;-)) Richard Avery (talk) 15:35, 22 November 2008 (UTC)

Air conditioning plant sizing

Hi there, I regularly build 3D models of buildings (for fun/creative fulfilment whatever you want to call it) and being a perfectionist, I like to make things accurate. One thing I am never sure about is how much space in the building I should allow for mechanical services (ventilation plant, boilers etc). I have read quite a bit about the subject in so much as how these things work and I like to think I have a reasonable knowledge of that side of things but I have no idea at all about sizing - how much space I need to allow in the building to accomodate plant rooms etc.

I am currently sketching out floor plans for a large building I plan to construct a virtual model of and need some guidance on plant sizing. I have several large spaces that are 250 sq m by 9 m high (ie 2250 cu m if my calculations are correct.) that will need cooling, I would estimate 20 air changes per hour. How large (phyically) would the air handling unit for each of these spaces need to be? There is no need for refrigeration locally in these plant rooms as the site will be supplied with chilled water from a central plant. Does the plant room need to be more than one floor high?

As well as the aforementioned large production areas requiring local air handling units, other areas of the building used for storage and smaller production areas require air conditioning to a lesser degree, say 5 air changes per hour. The total space reuiring this is 30,000 cubic metres. I plan to put air handling plants on the roof to serve this but again, how large would they need to be? I plan to have three units so each one would need to serve 10,000 cubic metres. Again, these would served with centralised chilled water.

The next question concerns the chilled water plant itself. I currently have a double hight space of 234 sq m allocated for the chiller plant; is this large enough, bearing in mind the above requirements?

Finally, how much space do I need to allow for the cooling towers to serve the chiller plant?

Any suggestions/ideas would be much appreciated. I have read the article here on Air Handler and Googled the subject but I have not found any useful information on plant sizing.

Ta,

Arthur —Preceding unsigned comment added by 62.249.220.179 (talk) 10:51, 22 November 2008 (UTC)

I can't give a numeric answer, but do have some factors to consider:

1) What's the initial source of energy for the A/C ? More space (and ventilation) is required for a natural gas fired A/C unit than an electric one.

2) When will the water-chilling portion of the A/C be operated ? If operated "on demand", the storage tank would be smaller, but, if operated at night only, you could take advantage of lower rates and avoid losing A/C during summer brown-outs/black-outs.

3) Consider that it may be necessary to change the cooling technology used over the life of the building, as petroleum prices skyrocket and new technologies become available. Thus, make your design as flexible as possible. For example, you could make the rooms larger than needed and use the extra space for storage. This storage space could be re-purposed in the future, though, if a new technology is put in place for the A/C which requires more space. StuRat (talk) 15:43, 22 November 2008 (UTC)

Name of old mechanical airport/rail schedule signs?

I am trying to locate information about the old type of signs in airports and railway stations that consisted of small static signs rotated around a horizontal axis in the middle like a rolodex. The problem is I do not know what they were called and all current equipment is digital, does anybody know what this technology was called? —Preceding unsigned comment added by Caisys (talk • contribs) 17:21, 22 November 2008 (UTC)

Split-flap display, like the Solari departure board? DMacks (talk) 17:28, 22 November 2008 (UTC)

Thats right thanks a lot —Preceding unsigned comment added by Caisys (talk • contribs) 19:53, 22 November 2008 (UTC)

states of matter

how many states of matter are there? and what are they? which conditions facilitate their existence? —Preceding unsigned comment added by 122.252.249.42 (talk) 17:42, 22 November 2008 (UTC)

Try State of matter. --Tango (talk) 17:44, 22 November 2008 (UTC)

Or read the textbook your teacher gave you. --Shaggorama (talk) 20:02, 22 November 2008 (UTC)

In the view of some of these people, there are only 50 states that matter. Clarityfiend (talk) 04:30, 23 November 2008 (UTC)

false positive in blood test

I am 61 yrs old, female, and was recently hospitalized with a mild heart attack. One of the physicians said that marijuana showed up in the blood tests. I explained that I had taken one capsule of boswellia serrata that day for inflammation in my hands and had taken senna, but certainly had no exposure to marijuana. When I asked if there could have been a false positive, the doctor said no. As boswellia is from the resinous plant frankincense, could the chemical composition have similarities to marijuana, which is also resinous, that could trigger a false positive in the type of testing which is done to detect marijuana in the bloodstream? There is no way I came in contact with marijuana and would like an explanation for the false results. I am uncomfortable with the doctor's definitive assertion of no possibility of error and of that result appearing on my medical records. —Preceding unsigned comment added by 206.74.114.213 (talk) 19:06, 22 November 2008 (UTC)

No test is perfect so there is always a chance of a false positive. I don't know how they test for marijuana so I have no idea what could cause a false positive, but there will be things that will (mixing up your blood sample with that of a marijuana user, for example - assuming it's a half decent hospital, the chances of that are very remote, but they aren't zero). --Tango (talk) 19:12, 22 November 2008 (UTC)

The test is usually for 11-nor-9-Carboxy-THC which can show a positive days after consumption. This site says Ibuprofen will show a false positive for cannabis. SpinningSpark 19:37, 22 November 2008 (UTC)

And this site has a more comprehensive list of pills for false positives. SpinningSpark 19:47, 22 November 2008 (UTC)

Not only do all tests have false positives, but one of the most common reasons for a false positive is a lab screw-up. It's more likely that the lab mixed up samples than it is that you had a false positive for a biochemical reason, so it's probably someone else's positive result. It's certainly not worth worrying about; an isolated result in a big thick chart won't get anyone's attention. It's a little odd, though, to do a blood test for marijuana; most such tests are done on urine - maybe you just got that part confused. Otherwise it would be a rather wasteful way for your doctor to be spending your money - urine toxicology screens are cheap, blood toxicology screens expensive. - Nunh-huh 03:41, 23 November 2008 (UTC)

The Rydberg Constant in Balmer's Formula

Okay so in my optics class, we were doing experiments to determine the characteristic wavelengths of hydrogen (using diffraction grating) and then comparing them to the known values. Before the lab, in the theory section in our lab manual, there is a little problem which we cannot figure out. The author states the four postulates of the Bohr theory and then says that using these postulates, it is possible to derive an expression for the energy of the stationary states as given by

$E_{n}=-{\frac {me^{4}}{8\epsilon _{0}^{2}h^{2}}}{\frac {1}{n^{2}}}$

where n=1,2,3,4,...

And then the frequency of those transition is given by

$f={\frac {me^{4}}{8\epsilon _{0}^{2}h^{2}}}\left({\frac {1}{2^{2}}}-{\frac {1}{n^{2}}}\right)$

where n=3,4,5,6,... Then on the next line he says that using $c=f\lambda$, which we know is true for all waves, gives that

${\frac {1}{\lambda }}={\frac {me^{4}}{8\epsilon _{0}^{3}h^{3}}}\left({\frac {1}{2^{2}}}-{\frac {1}{n^{2}}}\right)$

On the wiki page, the Rydberg constant has both a c and h cubed in the denominator. So does that mean the expression for f is wrong? Or is it the expression for energy? Which one is wrong and what are the correct expressions? We were trying to go from frequency to wavelength by just substituting f=c/lambda and then dividing by c but we don't get the same thing.

Another question is, when electron jumps from one stationary state to another, they don't have to jump to a consecutive state, right? Can they skip three stationary states and then jump to the fourth one?----A Real Kaiser...NOT! (talk) 22:47, 22 November 2008 (UTC)

The expression for f is wrong. It's equal to $E_{n}-E_{2}$, which is an energy. To get the frequency you need to use E = hf. Then you can substitute f = c/λ and you should get Wikipedia's formula.

It looks like the author also forgot to divide by c on the right side and added an extra e0 to the denominator. --Bowlhover (talk) 02:40, 23 November 2008 (UTC)

Electrons can jump between non-consecutive energy levels. You're calculating the energies/frequencies/wavelengths of transitions from level n > 2 to level 2 (the Balmer series), and those transitions skip at least one energy level when n > 3. -- BenRG (talk) 23:14, 22 November 2008 (UTC)

(after ec) : OK let's start from the last question. No, electrons do not have to "jump" to consecutive "states". (Actually, n is not a "state", it is a configuration that is made up of 2n² distinct states; and electron does not "jump", it makes a transition; but that does not matter now). When electron makes a radiative transition in which its principal quantum number changes from n=3 to n=2, it emits a photon in Balmer alpha line. Transitions from n=4 to n=2 give Balmer beta, n=5 to n=2 give Balmer gamma, and so on. Now, for the first part of your question, the best reference is the NRL Plasma Formulary here. This being homework, I am officially precluded from checking your math; but everything you need is in the NRL Formulary. Just make sure you stick with the SI units and don't mix SI units with cgs units. All the best, --Dr Dima (talk) 23:24, 22 November 2008 (UTC)

Actually, this was not homework. This was a lab (which we already did by the way) and this theory was just something we read before we did the lab but we didn't go into much detail because our teacher keeps deferring everything and tells that you will do more in upper division and grad school. My class is actually a lower division undergrad physics. It is the first calculus based physics class we can take. It is just that the author of the lab manual gave us these formulas and we all knew that there is a typo so we were trying to figure it out. That is it! Thanks both of you. We got it now. It makes much more sense. That formulary looks pretty handy.----A Real Kaiser...NOT! (talk) 23:32, 22 November 2008 (UTC)

Plaster Glue?

What's the best way to repair a broken plaster statue? I have all the pieces, but I'm not sure what to stick them together with. I don't want them falling apart again, but I also want to leave as little visible seam as possible. Black Carrot (talk) 23:27, 22 November 2008 (UTC)

I would go for a two-part epoxy myself, although I did find this what kind of glue do I use to repair a plaster statue (not you is it?) which says that there is a concrete and plaster glue at all hardware stores (never seen it myself). You will need to sand the joints after, not a problem if your statue is painted as the touch-up will cover any marks but would need to be done with great care if it is bare as colour of the glue will get rubbed in to the surrounding plaster. If you want maximum strength bear in mind that generally fast setting epoxies have lower final strength than the regular ones. That means you want to work out how to clamp the pieces before you start spreading glue. If this is the Venus de Milo you are repairing strike all the above and go see an expert. SpinningSpark 00:08, 23 November 2008 (UTC)

I don't see any mention of plaster glue on the Home Depot or Hobby Lobby websites, but maybe I'm searching wrong. I'll try out the epoxy. What would you recommend to hold the pieces while they dry? It's a big hollow statue, about three feet high, and the plaster is a quarter-inch thick shell painted mostly black. Black Carrot (talk) 01:10, 23 November 2008 (UTC)

How about duct tape? —Preceding unsigned comment added by 98.16.67.220 (talk) 02:01, 23 November 2008 (UTC)

The handyman's secret weapon? I don't think I'm that desperate yet. Black Carrot (talk) 03:48, 23 November 2008 (UTC)

The oracle of all things sticky [25] says superglue. Personally, I'd probably go with slow epoxy - but it's not runny so the two halves won't fit perfectly back together because of the layer of glue. It'll also ooze out everywhere and you'll have to wipe it off while it's still wet. So maybe superglue (which is very runny) is a better choice. My concern with superglue is that it's not as strong as epoxy. If you do go with superglue - pick a slow one...the ones that dry in seconds are a pain. I like Zap. SteveBaker (talk) 03:59, 23 November 2008 (UTC)

Fresh plaster to make the repairs could make sense. I'd use the harder plaster to join the pieces, then fill the joins with a softer finishing plaster. It depends on the relationship of the pieces when you're talking about holding them together – they could be supported in place with packing or sand, taped in place (masking tape is good, the right kind doesn't leave sticky residue), or strapping – much the same as if you're gluing wood/furniture pieces together. Whatever keeps them from shifting. Julia Rossi (talk) 06:59, 23 November 2008 (UTC)

November 23

i need a help please in organic chemistry

important question I am a student at first year of medicine in italy and i searched for material in organic chemistry for the difference between the d/l structure and the r/s structure and i didn't fine info about this specific material and i need this in 2 days so first what D/L and R/S and what are the difference please answer fast and send me the answer to my e-mail because i don't have account my e-mail: [email address removed] and i am sireas about this thank u anyway .

—Preceding unsigned comment added by 151.60.86.123 (talk)  

Any answers will be given here, we don't respond by email. Therefore, I've removed your email address to protect you from spam. --Tango (talk) 01:47, 23 November 2008 (UTC)

You might want to look at Chirality (chemistry) or Wikibook's Organic Chemistry. -- JSBillings 01:52, 23 November 2008 (UTC)

There are three ways to consider the chirality of a molecule, and you will find all 3 systems in use:

• the d/l or +/- system: A polarized light source, when shined through a pure chiral compound, will rotate the light some number of degrees one direction or the other. If the light rotates right, this is called "dextrorotary" and if it rotates left its called "levorotary". In a pair of stereoisomers, one molecule will always rotate the light to the right, and this is indicated as either "+" or "d" (always lowercase d); while the other which rotates light to the left is called either "-" or "l".
• The R/S system (aka the Cahn–Ingold–Prelog priority rules): When looking at the stereocenter in a chiral molecule, assign the 4 groups attached to this atom a priority number based on molecular mass. Thus, the smallest attached atom is assigned "1" on up to "4" for the heaviest attached atom. Arrange the molecule so #1 is away from you and #4 is straight down. Look at 2 and 3. If the order increases to the right 2 --> 3 then the molecule is called the "R" stereoisomer. If the order increases to the left 3 <-- 2 then the molecule is the "S" stereoisomer. This system has no correlation to the d/l system above. Sometimes the R is the d isomer, and sometimes the R is the l isomer.
• The D/L system (which usually applies ONLY TO SUGARS). Note that this system uses capital D and L, not lowercase as above. The two systems have no connection to each other. In the D/L system, the molecule is compared to glyceraldehyde which has two enantiomers, labeled D and L. In this molecule, D=R=+ and L=S=- to compare to the other systems. If you look at the Fischer projection of glyceraldehyde, the middle carbon has one of two configurations. The D is the one with the H-C-OH fischer configuration, while the L has the HO-C-H fischer configuration. In all other sugars, such as glucose, look at the analogous carbon (the second one down on the Fischer projection). D-glucose has the same configuration at this carbon as D-glyceraldehyde, while L-glucose has the same configuration as L-glyceraldehyde. For sugars, which have MANY stereocenters (glucose has 4 for example, meaning it has 16 possible configurations) the R-S system makes little sense... --Jayron32.talk.contribs 02:50, 23 November 2008 (UTC)

Television Logo Removal

Is there any device or software that can not merely blur, but interpolate shapes in television pictures to restore the spoiled scene behind the opaque Digital On Screen graphic, as broadcast by ITV 2 and also can any device get rid of the non-opaque DOG on BBC HD, preferably in real time? Are there any programmable custom devices for doing this sort of video processing? Also what technology would be required to re-broadcast the logo so that it covered the entire screen on everyones television? Trevor Loughlin (talk) 02:29, 23 November 2008 (UTC)

Since the information 'behind' the logo has never been transmitted, it's impossible to restore the missing stuff. The old-style translucent logos could be somewhat removed - but an opaque one is a really hard problem. Silicon Graphics had a software solution that did a reasonable job of removing translucent logos - but I don't think they sold it commercially. Detecting the logo is mostly fairly easy (it's the one thing on the screen that doesn't move) - but with the animated logos we're starting to see on some channels - we're really screwed.

Rebroadcasting is also not reasonable - you'd have to rebroadcast on the same frequency - so your transmission would interfere with the original and result in a mess - the amount of transmitter power you'd need to put out to override the original channel would demand massive transmitter towers and so forth. Also, if you are jamming that channel - how can you receive that channel yourself in order to rebroadcast it?

The best way to get rid of logos is to pursuade everyone who is annoyed by them to turn off the TV. Only when ratings for logo-besmirched channels plummet - will the broadcasters realise what insanely annoying things these are. Better still - watch DVD's instead.

SteveBaker (talk) 03:33, 23 November 2008 (UTC)

Boycotting logo-covered channels is unlikely to work, because such channels will of course not realize WHY their ratings have dropped, and have no reason to suspect it is because of the silly logo. They are just as likely to replace the venerable old news anchor on the 6:00 news with some chick with big bazooms as they are to remove the logo... --Jayron32.talk.contribs 04:15, 23 November 2008 (UTC)

DScaler comes with a "Logo Killer Filter" intended to get rid of the translucent logos. I haven't used DScaler recently, but if I recall it was primitive and it didn't really work all that well. APL (talk) 05:17, 23 November 2008 (UTC)

Spacetime

Can spacetime be created and/or destroyed, unlike matter/energy?