Wikipedia:Reference desk/Archives/Science/2007 January 2

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Science desk
< January 1 << Dec | January | Feb >> January 3 >
Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.


January 2[edit]

basis for our current time standards (sec, min and hr) dividing one day/night cycle also 360 degrees in a circle.[edit]

What originally contrived our current time standards of 60 sec in a min, 60 min in an hour and 24 hours in one day/night cycle? Was it related to early astronomy? navigation aboard a ship? keeping duty watches aboard ship? or some other scenario? Any book or research paper on this matter would be helpful. Also would like to find out who decided that a circle should be comprised of 360 degrees (why not 4OO? why not some other quantity). Thanks much Cmarcuson 01:02, 2 January 2007 (UTC)

There are 400 grads in a circle. We may gradually get round to using these.
See the article Babylonian numerals, and for some context also Babylonian mathematics. So this goes back some 3600 to perhaps 4000 years! It shows you how hard it is to change a tradition. The Babylonians are involved because of their astronomical calculations, which somehow were passed on to the ancient Greeks, and finally to us. Be glad that they did not use a base 61 system :)  --LambiamTalk 01:18, 2 January 2007 (UTC)
As for why they keep it that way, the only really official answer is "convention" though base 60 can be more convenient than, say, base 10 in some cases, I believe. Movements to introduce decimal time have universally failed, mostly because it doesn't increase the ease of time calculation in many cases, and because most of the import of time is that it is coordinated with others (my 5 o'clock is your 5 o'clock, so we show up to the meeting at the same, expected time) it is very hard to get people to change from an accepted system (you'd have to change all of it at once, which is a big job and would cost quite a bit of money, and in the end a base-10 system would be no less arbitrary). --24.147.86.187 01:21, 2 January 2007 (UTC)
There's also some info in the 'History' section of our article on degrees. -- SCZenz 01:22, 2 January 2007 (UTC)

As for why the Bablylonians chose 360 degrees in a circle, I think there are two main reasons:

  • There are close to 360 days in a year.
  • 360 is easily divided in many ways, making calculations simpler, than say using 365.25 degrees in a circle. The factors of 360 are: 1x360, 2x180, 3x120, 4x90, 5x72, 6x60, 8x45, 9x40, 10x36, 12x30, 15x24, 18x20. So, the lowest numbers which aren't factors of 360 are 7 and 13, and it's not often that one needs to divide a circle into 7 or 13 pieces. StuRat 12:54, 2 January 2007 (UTC)

As for why 24 and 60 were chosen as units of time measurement, I can think of two main reasons:

  • They are also both more easily divided than 10, with both being divisible by 3, 4, and 6, and 12. 24 is also divisible by 8, and 60 is also divisible by 5, 10, 15, 20 and 30.
  • You might notice that 6 is a factor of 24, 60, and 360. I don't believe this is an accident. That's about the most objects that most people (savants aside) can instantly recognized by number, without the need to count them individually. This made accounting a bit easier, eliminating much of the counting that would otherwise be needed to record the number of bundles of grain, etc. Ten is also a natural base to use, because we have 10 fingers. Alternating these bases gives sizes of 6, 60, 360, and 3600. Apparently they felt that 6 hours in a day was too few and 60 too many, so decided on 24 as a nice compromise which is still easy to divide up. So, we can now have 2 twelve hour shifts, 3 eight hour shifts, or 4 six hour shifts in a day. StuRat 13:17, 2 January 2007 (UTC)
The day and the night were each divided into 12 hours (which is why we have the :RD/Science]]|Science}}


January 1[edit]

...and drink plenty of fluids[edit]

The advice "get plenty of rest" when you are sick I can understand - this would allow the body to devote more of its resources to fighting the infection (and I imagine there are some other reasons too). But what is the purpose of saying "drink plenty of fluids"? BenC7 11:07, 1 January 2007 (UTC)

At the risk of giving medical advice, I would suggest that two of the reasons are (a) because if you get a fever you may sweat a lot and lose lots of fluids, causing your cells to become dehydrated and probably more vulnerable to attack from pathogens, and (b) because more water flowing through your body helps flush out toxins that may accumulate either as a result of infection or your own immune response. (a) seems more valid to me, but I'm not a doctor so I'm not 100% sure. Confusing Manifestation 12:42, 1 January 2007 (UTC)
Avoiding dehydration. See the article for more details. Carcharoth 16:44, 1 January 2007 (UTC)
And also, diarrhea may cause dehydration. StuRat 16:43, 1 January 2007 (UTC)

I've currently got a cold - and I need lots of liquid because of the amount of 'stuff' I'm coughing up/coming out of my nose.. Though I do seem to need to drink more than I'm apparently losing.87.102.14.212 18:45, 1 January 2007 (UTC)

Basically, it's something your doctor can tell you to do while you wait for your immune system to do its job. The likelihood that your thirst will stop working and you will get seriously dehydrated because of a cold is near zero if your brain works. Unless you have dysentery (severe diarrhea) you will have no problem maintaining hydration by drinking when thirsty. The toxin explanation is early 20th century American folk medicine: no one has ever demonstrated any such phenomenon as "flushing toxins" though plenty of alt med quacks make a living on the concept. alteripse 03:25, 2 January 2007 (UTC)

sulphur in eggs[edit]

I know that eggs contain lots of sulphur, and therefore smell of hydrogen sulphide, but I was wondering what form this sulphur was in inside the eggs, weather it was just sulphur, or hydrogen sulphide, or as amino acids. 172.142.71.239 11:33, 1 January 2007 (UTC)

  • I imagine some sort of iron sulfur protein, in which case it would be in the sulfide form, or specifically would probably come from a cys residue which contains a sulfide, an egg is after all, a biological system. I could be completely wrong of course, I'm not a chicken chemist--71.247.246.54 12:57, 1 January 2007 (UTC)
In a fresh egg the sulfur is bound in organic molecules (mainly proteins), and you shouldn't be able to smell it. It is only when the organic matter is broken down by bacteria that foul-smelling hydrogen sulfide is produced. The sulfur-containing amino acids used in the formation of proteins are cysteine and methionine. —The preceding unsigned comment was added by Lambiam (talkcontribs) 19:29, 1 January 2007 (UTC).
I think one should eggspect a fowl smell from chicken eggs! —The preceding unsigned comment was added by 88.109.92.168 (talk) 01:55, 2 January 2007 (UTC).

control &c.[edit]

Apparently some people can learn to control how fast their heart beats, even though this is supposed to be subconscious. Are there other things like this people could potentially control, and what would the limit of this sort of control be?—Preceding unsigned comment added by 172.142.71.239 (talkcontribs)

  • Meditation. I used to be able to control my pulse rate, haven't practiced in a while--71.247.246.54 13:40, 1 January 2007 (UTC)
You can also learn some control over brain waves and skin temperature. There is some info at biofeedback.--Shantavira 13:43, 1 January 2007 (UTC)
Also blood pressure. The limit of control over autonomic systems would probably be resting levels or slightly lower. I doubt that any amount of practice could enable someone to raise their skin temperature to 105 degrees, or slow their heart rate to zero, or lower their blood pressure to below healthy levels. *The article also mentions pupil dialation and sexual arousal.* Anchoress 03:33, 2 January 2007 (UTC)

magnets[edit]

Is there anything that can be put in front of or around a magnet, to stop things being attracted to it? Like plastic can be wrapped around a wire &c.172.142.71.239 13:28, 1 January 2007 (UTC)

  • Wrapping plastic around a wire with an active current doesn't have any effect on the magnetic field it produces, see also current--71.247.246.54 13:38, 1 January 2007 (UTC)
Superconductors have interesting magnetic properties, however I'm not sure if they would be usable in the way you suggest. TERdON 13:43, 1 January 2007 (UTC)

You may complete magnet to a ring with some magnetic material. Therefore, magnetic lines of the magnet will be gathered mostly inside the ring, and there "amount" in air would reduce. Magnetic suspectibility may amount to thousands, so it's the factor in which you can effectively reduce the attracting force, it seems.

What about a screen, cutting off constant magnitic field? Yes, a superconductor of 1st kind would help. But it needs temperature less than 20K. ellol 14:39, 1 January 2007 (UTC)

The best thing we have for magnetic shielding is Mu-metal. --Zeizmic 16:04, 1 January 2007 (UTC)

How about a diamagnetic material.87.102.14.212 18:18, 1 January 2007 (UTC)Such as glass or plastic.87.102.14.212 18:43, 1 January 2007 (UTC)

I thought about this a lot, I don't think there is such a thing becasuse if there was I can think way to make a perpetual motion machine. Vespine 21:59, 1 January 2007 (UTC)
Diamagnetic material wouldn't help, because usually its magnetic susceptibility is tiny fractions of 1. ellol 01:18, 2 January 2007 (UTC)

Does a Faraday cage stop magnetic waves? What if there's a current running through the cage? Would that be electromagnetic shielding? Will electromagnetic shielding block magneticism? magnetism?--Kjoonlee 15:49, 2 January 2007 (UTC)

A Faraday cage will only block the EM field down to some lowest frequency (which depends on its construction). A steady (~dc) magnetic field would not induce any current in the metal of the Faraday cage and so would not be "bucked" (cancelled).
Atlant

You can place more magnets on either side in a specific pattern which will almost cancel the magnetic field on one side, see Halbach array.EricR 17:27, 2 January 2007 (UTC)

Just like how a Faraday cage works for EM field, a cage made of a good magnetic (ferromagnetic ?) material should be able to act as a magnetic shield. I suppose that a magnet placed in such a cage will not attact things outside the cage -- WikiCheng | Talk 06:42, 3 January 2007 (UTC)

Catastrophal global warming through release of gaseous compounds from ocean floors[edit]

Read a newspaper article in 2006 which described a potentially catastrophic release of gaseaous compounds from the floor of the world's oceans. Stored (how?, when?) in the ocean floors, they are held there by a combination of pressure and cold temperature there. The prognosis was that when the oceans became warmer, through global warming, they would be released; causing a rapid rise in the greenhouse effect----and a rapid atmospheric temperature rise resulting in extinction of all life. This article was not referenced in any way (names, institutions, etc.); and its negative effect on me led to ´my not searching for more info at that time.

Question: Does anyone know more about this? Is it a real threat, or just someone's idea of how to have fun scaring people?—Preceding unsigned comment added by 81.229.41.91 (talkcontribs)

If you ever get extremely interested in it, I can have you talk to a friend of mine that is an expert in such area. These stored gaseous compounds are clathrate hydrates, mostly methane clathrate. See the Clathrate-gun hypothesis, for our closest article to what you are looking for. Happy new year! X [Mac Davis] (DESK|How's my driving?) 16:02, 1 January 2007 (UTC)

ITs the damn lakes u know, they release CO2 in toxic amounts stored in them. cuz there was no flow of water so it stayed underground, until the pressure pushed it up, and killed people. read it somewhere on Wikipedia Black Sea you will find it from that article. somewhere. --Judged 08:40, 6 January 2007 (UTC)

Polymaths needed![edit]

The lists listed at Lists of basic topics need to be proofread for ommissions. Please choose one or more that you are familiar with and browse them to see if any holes or gaps pop out at you. If they do, by all means, fill them in!  The Transhumanist17:37, 1 January 2007 (UTC)

Some basic topics don't have any subtopics! I'm adding them! X [Mac Davis] (DESK|How's my driving?) 20:35, 1 January 2007 (UTC)
What's the difference between "Physics Scholars" and "Leaders in Physics"? Clarityfiend 08:16, 2 January 2007 (UTC)
Those were just part of the template that was substituted in using the subst command. They work for some of the lists, but in those which they don't provide the best fit, simply replace with whatever does. Like "Famous physicists" or what not.  The Transhumanist14:49, 5 January 2007 (UTC)

coke[edit]

How come if I pour coke into a cup it goes really all fizzy whereas if i pour it into glass it is less fizzy? — Preceding unsigned comment added by 86.128.220.133 (talk)

It depends on how you define "cup". It probably has something to do with (possibly) nucleation sites on the cup's surface, which don't exist on smooth glasses. Just a guess, though. I could be totally wrong. PTO 19:02, 1 January 2007 (UTC)
I think that's fairly accurate. Vranak
Interesting. You could try pouring some into a squeaky clean glass and some into a dirty glass (eg fruit juice residue) to test this. Make sure both glasses are dry to start with.--Shantavira 20:16, 1 January 2007 (UTC)
Unlikely to give good results with fruit juice residue. There's likely to be leftover acids on the surface which will completely taint the result (put a slice of lemon into your coke to see the effect). --OliverH 10:08, 6 January 2007 (UTC)
Pour it slowly into a coffee mug, or pour it quickly into a plastic cup. Nucleation and agitation produce different effects. X [Mac Davis] (DESK|How's my driving?) 20:34, 1 January 2007 (UTC)
I'm not sure this is at all related but I've done some experiments before in a glass: basically, I think, the more organic matter in the water, the smaller the bubbles. Are you using the same bottle/can of coke in each cup/glass? And as a quick note, shake the coke first, to make sure that the concentration is even, rather than the liquid being more concentrated at the bottom of the bottle than the top. Cheers! Yuser31415 20:58, 1 January 2007 (UTC)

If you pour water in the cup then throw it away before pouring in the coke, you shouldnt get as much fizzing. Better still, try it with beer.

I read recently that nucleation caused by flaws in the surface of the container is, in fact negligible, and the main cause is particles on the surface. 80.169.64.22 19:29, 3 January 2007 (UTC)

You mean dirty glasses? —The preceding unsigned comment was added by Light current (talkcontribs) 20:49, 3 January 2007 (UTC).

January 2[edit]

basis for our current time standards (sec, min and hr) dividing one day/night cycle also 360 degrees in a circle.[edit]

What originally contrived our current time standards of 60 sec in a min, 60 min in an hour and 24 hours in one day/night cycle? Was it related to early astronomy? navigation aboard a ship? keeping duty watches aboard ship? or some other scenario? Any book or research paper on this matter would be helpful. Also would like to find out who decided that a circle should be comprised of 360 degrees (why not 4OO? why not some other quantity). Thanks much Cmarcuson 01:02, 2 January 2007 (UTC)

There are 400 grads in a circle. We may gradually get round to using these.
See the article Babylonian numerals, and for some context also Babylonian mathematics. So this goes back some 3600 to perhaps 4000 years! It shows you how hard it is to change a tradition. The Babylonians are involved because of their astronomical calculations, which somehow were passed on to the ancient Greeks, and finally to us. Be glad that they did not use a base 61 system :)  --LambiamTalk 01:18, 2 January 2007 (UTC)
As for why they keep it that way, the only really official answer is "convention" though base 60 can be more convenient than, say, base 10 in some cases, I believe. Movements to introduce decimal time have universally failed, mostly because it doesn't increase the ease of time calculation in many cases, and because most of the import of time is that it is coordinated with others (my 5 o'clock is your 5 o'clock, so we show up to the meeting at the same, expected time) it is very hard to get people to change from an accepted system (you'd have to change all of it at once, which is a big job and would cost quite a bit of money, and in the end a base-10 system would be no less arbitrary). --24.147.86.187 01:21, 2 January 2007 (UTC)
There's also some info in the 'History' section of our article on degrees. -- SCZenz 01:22, 2 January 2007 (UTC)

As for why the Bablylonians chose 360 degrees in a circle, I think there are two main reasons:

  • There are close to 360 days in a year.
  • 360 is easily divided in many ways, making calculations simpler, than say using 365.25 degrees in a circle. The factors of 360 are: 1x360, 2x180, 3x120, 4x90, 5x72, 6x60, 8x45, 9x40, 10x36, 12x30, 15x24, 18x20. So, the lowest numbers which aren't factors of 360 are 7 and 13, and it's not often that one needs to divide a circle into 7 or 13 pieces. StuRat 12:54, 2 January 2007 (UTC)

As for why 24 and 60 were chosen as units of time measurement, I can think of two main reasons:

  • They are also both more easily divided than 10, with both being divisible by 3, 4, and 6, and 12. 24 is also divisible by 8, and 60 is also divisible by 5, 10, 15, 20 and 30.
  • You might notice that 6 is a factor of 24, 60, and 360. I don't believe this is an accident. That's about the most objects that most people (savants aside) can instantly recognized by number, without the need to count them individually. This made accounting a bit easier, eliminating much of the counting that would otherwise be needed to record the number of bundles of grain, etc. Ten is also a natural base to use, because we have 10 fingers. Alternating these bases gives sizes of 6, 60, 360, and 3600. Apparently they felt that 6 hours in a day was too few and 60 too many, so decided on 24 as a nice compromise which is still easy to divide up. So, we can now have 2 twelve hour shifts, 3 eight hour shifts, or 4 six hour shifts in a day. StuRat 13:17, 2 January 2007 (UTC)
The day and the night were each divided into 12 hours (which is why we have the 12-hour clock), and 12+12 = 24. According to our article 12-hour clock, the 12-hour clock originated in Egypt. It is mum on the why of 12. Egyptian numerals were 10-based. The fact that 12 is a highly composite number may of course have played a role.  --LambiamTalk 14:22, 2 January 2007 (UTC)

Energy density of gunpowder?[edit]

What is the energy density of gunpowder? I checked both articles but couldn't find it. I don't need a precise value, something in the right order of magnitude would be fine. Thank you. --24.147.86.187 01:51, 2 January 2007 (UTC)

here's an answer - seems reasonably plausible. --Robert Merkel 06:12, 2 January 2007 (UTC)
That works fine, thanks. I didn't realize it would be so low, though the explanation given there seems to account for it. --24.147.86.187 19:32, 2 January 2007 (UTC)

Slave ships[edit]

On a recent TV program a black historian said that because of the insanitry conditions the slaves were kept in on the ships that people on land could smell the ship long before they could see it. Can you tell me is that possible? thanks —The preceding unsigned comment was added by 88.109.92.168 (talk) 03:39, 2 January 2007 (UTC).

Unless the people on land are blind, no way. Imagine trying to smell something from 20 km away; I don't think even a factory could release such strong odour. In any case, what would the captain do if his ship stinks that much? --Bowlhover 04:00, 2 January 2007 (UTC)
You are failing to consider both the effect of wind on carrying smells and the fact that you certainly wouldn't see a ship over a few miles at night, I imagine. According to CNN:

So barbaric was [the slaves] treatment that it was said you could smell a slave ship from ten-miles away, and it was estimated that of every 1000 slaves transported a minimum of 168 would die en route, usually a lot more.

"I was soon put down under the decks," wrote Olaudah Equiano, a former slave whose account of his experiences -- "The Interesting Narrative of the Life of Olaudah Equiano" -- caused a sensation when published in 1789.

"There I received such a salutation in my nostrils as I had never experienced in my life: so that, with the loathsomeness of the stench, and crying together, I became so sick and low that I was not able to eat, nor had I the least desire to taste anything.

"I now wished for the last friend, death, to relieve me; but soon, to my grief, two of the white men offered me eatables; and, on my refusing to eat, one of them held me fast by the hands, and laid me across I think the windlass, and tied my feet, while the other flogged me severely." [1]

Rockpocket 04:14, 2 January 2007 (UTC)

Of course if you can't see a ship no matter what, you'll smell it before you can see it. Also, the CNN source says: "...it was said you could smell a slave ship from ten-miles away". To me, this seems to suggest that ten miles was an exaggeration, used to express that the conditions were barbaric.
Wind does help carry the smell, but even with the wind any smell is quickly dispersed. Have you ever tried moving away from a smoker to avoid breathing their smoke? Even if you're downwind from the smoker, the smell rapidly weakens with distance. Additionaly, if the smell was really that bad, what would the captain do? --Bowlhover 04:30, 2 January 2007 (UTC)
I read that as simply that, since we no longer have slave ships, we must rely on the accounts at the time, hence "it was said". The phrase is pretty commonly used to describe the ships:
  • "The stench and squalor below was such that it was said that you could smell a slave ship long before you could see it." [2]
  • "Royal Navy sailors said that they could smell the stench of a ship carrying slaves anything up to 10 miles downwind." [3]
  • "Slave ships were so foul that some people claimed you could smell them before they could be seen" [4]
As for what the captain would do. Well apparently he would shower them with seawater occasionally. But olfactory accommodation is a remarkable things. An odor which might be an overpowering stench to a virgin nose can easily be tolerated, to the level or barely noticing it, to a well accustomed nose. Rockpocket 05:01, 2 January 2007 (UTC)
People do smell things from miles away sometimes -- forest fires, stinky factories, industrial spills, garbage dumps. The distance is greater if the wind is blowing steadily in the right direction, so the smelly substances form a narrow plume. I think we'd need an expert on smell to really evaluate this one, which I don't imagine any of us here is, but I think it has some plausibility. --Anonymous, January 2, 2007, 07:03 (UTC).

The quantity has a huge effect on how quickly it disperses. I used to regularly drive by a cattle fed lot and could smell the manure from many miles away. Sulfur from major volcano eruptions may even be smelled much further than 10 miles away. StuRat 12:39, 2 January 2007 (UTC)

I think sulfur from major volcanic eruptions can be more than hundreds or thousands of tons. Even if 100% of the weight of the people on board would dissipate away, it would need more then 10000 of them tho have the same effect. --V. Szabolcs 13:10, 2 January 2007 (UTC)
Remember, some chemical compounds have a very low threshold for detection by nose. To take an extreme example, you can detect ethyl mercaptan – the odorant added to natural gas so you can smell gas leaks – at about 0.2 parts per billion in air. That means that one kilogram of the stuff, as vapour, will scent about two trillion liters of air: about two cubic kilometers.
Now, a ship isn't going to be carrying drums of ethyl mercaptan, but there will be a lot of other fragrant organics on board. (Hydrogen sulfide, for instance, has a detection threshold of about 5 parts per billion.) If the scent is only detectable directly downwind, and if that scent comes and goes (assume that it comes in concentrated 'bubbles') then it's quite plausible that it could be detected at a ten-mile range. TenOfAllTrades(talk) 14:54, 2 January 2007 (UTC)

Blood question[edit]

I want to know if blood is flammable, if so, what makes it flammable? and why does it turns powdery black? i want to investigate about it...phb124.104.183.164 07:56, 2 January 2007 (UTC)

Blood is not flammable. According to our Blood article, it's 92% water. -- SCZenz 09:03, 2 January 2007 (UTC)
When does blood turn powdery black? When an animal is burned, the black ash is from the flesh and bone, not blood. The ash is carbon. --Bowlhover 09:53, 2 January 2007 (UTC)
I assume he means dried blood. Theresa Knott | Taste the Korn 10:29, 2 January 2007 (UTC)
Dried blood, and indeed any dried body parts, with the exception of bones and teeth, are flammable, yes. StuRat 12:32, 2 January 2007 (UTC)

I beg to respectfully disagree. Body parts, including blood, are not flammable (easily ignited and capable of burning rapidly). In common usage, flammable usually means that it will catch fire if touched with a flame, not that it can be oxidized to ash. Even milk can be reduced to ash in a bomb calorimeter, but to say milk is "flammable" stretches the definition beyond recognition. For questionable exception, see spontaneous human combustion. alteripse 14:27, 2 January 2007 (UTC)

My definition is "able or likely to burn", from the Kernerman English Multilingual Dictionary. Under this definition, wood is flammable, even though you can't generally get it to burn by holding a match to it, either. StuRat 01:13, 3 January 2007 (UTC)
Just out of interest why wouldn't you go with OSHA standards or follow standard MSDS definitions? Surely they are more relevant to this question? And according to them, as alterprise has already noted, you are stretching the definition beyond recognition. This type of word play is not really helpful when trying to have a sensible discussion. Common usage is more important than a technically correct answer. Wood is certainly combustable, and its oxidation is also spontaneous from a thjermodynamic perspective. Neither of these observations make it flammable under normal conditions. Wood dust blown in a flame would be flammable, but this would hardly be a normal situation. Likewise blood, under certain conditions, could be considered flammable but not under normal conditions. David D. (Talk) 05:08, 3 January 2007 (UTC)
Dry powdered milk, like most any dry powdered substance, when dispersed in air can burn with explosive force yet we do not normally consider powdered milk or most any burnable powder either flammable or explosive. 71.100.6.152 15:25, 2 January 2007 (UTC)
The reason dried blood turns powdery black is because red blood cells contain hemoglobin which contains iron. Iron oxides can be black. --Kjoonlee 15:41, 2 January 2007 (UTC)

Metallic taste[edit]

Why do stainless steel utensils sometimes pick up a 'metallic taste' after coming into contact with other metals, a taste that doesn't go away with washing, but disappears after a few days? Thanks - Fairness And Accuracy For All 10:57, 2 January 2007 (UTC)

Stainless steel is actually a perfectly normal metal (with metallic health effects), except that it produces a stable oxide film which seals it. According to this [5], there is a metallic taste when you disturb the oxide film by scouring, and some nickel is released. They actually have MSDS on things like stainless steel tubing (dangerous when dropped on your foot!) --Zeizmic 17:15, 2 January 2007 (UTC)
This sounds like the "Lasagna cell" effect, and it only occurs if the metal surfaces were in contact both with salty food, as well as contacting each other. Whenever we place two metal objects into salty (conductive) food, and they're made of two different metals, then we form an electrolytic cell (battery.) If the two metals then touch together, the battery is shorted out, an electric current appears, and chemical reactions begin running within a microscopically-thin layer on both metal surfaces. Remember that batteries are essentially powered by corrosion, and a shorted battery is a powerful surface-corroder. You're no doubt tasting the corrosion products: metal chlorides and oxides. Some of these are probably solids, so it would either require quite a bit of scrubbing to remove them, or they might over time react with water or foods and be removed or changed to something without strong flavor. --Wjbeaty 23:52, 3 January 2007 (UTC)

Men/women telephone bills[edit]

What do men compared to women spend on average for their phone bills? —The preceding unsigned comment was added by 216.194.22.39 (talkcontribs).

Also asked at the Miscellaneous Reference Desk; let's keep the conversation over there.
Atlant 17:18, 2 January 2007 (UTC)

Metal surfaces[edit]

What was the date and place of the first aiircraft in the US and in Europe to replace cloth fabric surfaces coverings with metal? 71.100.6.152 15:14, 2 January 2007 (UTC)

Can't find the exact year but it appears the first mass-produced one was a Junkers model during the First World War. Rmhermen 15:29, 2 January 2007 (UTC)
The first all-metal plane in the U.S. appears to be much later, the Pullman in 1924.[6] Rmhermen 15:30, 2 January 2007 (UTC)

Phytonutrient content[edit]

How much of each phytonutrient are we supposed to eat? Nutrition literature only says to eat a variety of fruit and vegetables and this and that many servings, but how much of the phytonutrients, lycopene for example, has been shown to have these health benefits we hear about all the time? 1 microgram? 1mg? 1g? Thanks in advance. Jack Daw 16:10, 2 January 2007 (UTC)

Most calculations of phytonutrients are based on what some nutritionist calculated would be found in an ideal varied diet with lots of fruits and vegetables. Exact RDAs have not been proposed for most of them, and would basically be consensus guesses. Humans can survive and reproduce on an amazing variety (and lack thereof) of diets, so there is an enormous difference between threshold-of-obvious-deficiency-effects and "optimal intake" even for the best-studied traditional vitamins. Optimal intake may also vary by the other components of the diet or by other environmental influences, as well as good old human variability. We seem to be in the process of revising the RDA for something as ostensibly well-studied as vitamin D, so any proposed "recommended intakes" for specific phytonutrients are speculative guesses at best. And Happy New Year to you, Jack. alteripse 16:57, 2 January 2007 (UTC)
I found the answer here http://www.whfoods.com/genpage.php?tname=foodspice&dbid=44 if someone else was wondering. Doctor L., did you get my last e-mail? :D Jack Daw 18:08, 2 January 2007 (UTC)
That's an interesting article, but it is some 6000 words, and in reading it twice I must have missed what it gives as the recommended intake for lycopene. Could you summarize?  --LambiamTalk 21:36, 2 January 2007 (UTC)
Oh sorry about that, what I meant was that the article indicates how much lycopene a tomato contains, making it possible to determine at least to some degree how much lycopene you "need" per day. Jack Daw 23:46, 2 January 2007 (UTC)
You didn't miss it. It is not in the article. Based on the following link (note no %DV shown for lycopene) it appears that the recommended intake for lycopene has not been established. David D. (Talk) 22:18, 2 January 2007 (UTC)

valves 3/2 or 3/2 valves?[edit]

Are the numbers of ports and positions positioned after or before the word valve(s)? For instance, should I write 'a 3/2 valve' or 'a valve 3/2'? --Raggiante 17:36, 2 January 2007 (UTC)

  • According to google, it should be "3/2 valve". — BRIAN0918 • 2007-01-02 19:06Z

Calorie consumption at low temperature[edit]

As we all know Arctic explorers and the like need several thousands of 'extra' calories a day to maintain body temperature. But I am wondering if it is possible to work out how many extra calories you burn at less extreme temperatures.

For example, if for a weight loss program (purely theoretical, I'm not overweight), I reduced my normal room temperature from 21C to 15C would I burn an extra 50kcals or 500kcals? I have never seen this advised as a weight loss program (though conversely sitting in a sauna is which almost certainly doesn't work), and I doubt it is because it would be unpleasant.

What exactly is a "temperature neutral environment" as described in Basal Metabolic Rate? Does this mean if one does not feel "cold" one is not actually expending any extra energy keeping warm? As in if I expend a certain amount of energy at 21C, raising it to 28C wouldn't expend any extra energy because my normal body functions already keep me warm (i.e. at 36C).

I'm sure the figures are not trivial to work out, extra fat of course would insulate you and people do have different metabolic rates. Probably could do something with assuming people are a big bag of water and calculate relative heat losses like that but it's been a while since I did calculations like that. (86.133.203.195 18:18, 2 January 2007 (UTC))

Well, you can turn that around. If you turned the temperature up to around 30-40 degrees, you could be sweatting your weight off. 81.93.102.185 19:34, 2 January 2007 (UTC)
Yes but that isn't really 'weight loss' in the same way if I go for a really long wee I may be 1kg lighter, but I've not lost weight. 86.133.203.195 19:39, 2 January 2007 (UTC)
Speaking from personal experience, spending significant amounts of time sitting in a 60F room does increase your calorie usage over that in a 70F room, but not by much. At a guess, you could lose maybe a pound a month from it. --Carnildo 20:51, 2 January 2007 (UTC)
A comfortable natural skin temperature is about 32 C (88 F) and thermal conduction is proportional to temperature gradient, so as a first guess I'd say that a naked person increases their energy consumption by nearly a full BMR for every 5 C (10 F) their skin temperature is reduced. However, that can't be entirely accurate since vasoconstriction and other strategies allow the body to conserve heat by drawing it deeper inside, which will partially counteract this and cause the trunk temperature to matter a lot more than the extremeties. So for ballpark, I would guess that you increase by 1 BMR for every 5-10 C (10-20 F) you reduce your skin temperature across the trunk of your body. Of course since most people wear clothes, which trap heat, you would probably have to reduce the ambient environment temperature by 2-4 times the change you wanted to see in your skin temperature (assuming you didn't put on heavier clothes). So, to get back to a practical question, if your BMR is 2000 kcal/day and you lower the room temperature from 21 C to 16 C, my guess is that you would requires somewhere between 300 and 700 kcal/day assuming you could will yourself not to do anything else to make yourself feel warmer. Dragons flight 21:32, 2 January 2007 (UTC)
If those figures are in the right ball park it seems at first glance like a reasonable suggestion for weight loss. 500kcals is a significant number, 25% of a normal persons intake, and the equivalent of a couple of hours of running.
So what are the potential dangers of this? 15C doesn't sound that cold to me, in winter it is often this temperature or lower in my house when the heating isn't on. But I read in Hypothermia "Children can die of hypothermia in as little as two hours in water as warm as 16°C" (Though of course water will carry the heat much faster than air).
And obviously people (in good health like Arctic explorers) can survive much colder temperatures. 86.133.203.195 22:44, 2 January 2007 (UTC)
Your clothing would also be critical. If you were naked at that temp, it would be quite uncomfortable but you would also burn more calories. If you were properly clothed, it would be comfortable but you wouldn't burn many more calories than at normal room temp. StuRat 00:56, 3 January 2007 (UTC)
Well I have seen the theory circulated that one of the (many) contribuary factors in people getting fatter in certain countries is the rise in temperature control, meaning we tend to stay at close to optimum temperatures and so burn the fewest calories possible. Hotter or colder temperatures would lead us to burn more. So someone thinks it makes a difference to weight loss. Skittle 02:03, 3 January 2007 (UTC)

When it is too hot I feel tired more and can't be botered to do anything, maybe this is connected. 172.159.156.28 14:50, 3 January 2007 (UTC)

I don't think you guys are really examining the practicality of this. I don't much like exercise, but I like freezing my ass off in cold air a lot less. If I were ever to consider doing such a thing, I'd just say to myself, "Wait, this is stupid," and then go on the treadmill for awhile where I can burn calories while not freezing my ass off. Being cold is miserable. --Cyde Weys 16:15, 3 January 2007 (UTC)

Water is about 25 times better at carrying heat than air - you can get hypothermia in 70 Fahrenheit water (which is a perfectly pleasant air temperature). A question - which would burn more calories, reducing the air temperature by 10 degrees all the time or exercising for an extra 30 minutes a day? Another practicality issue would be the air conditioning cost (although the heating cost reduction in winter might make up for it). Vultur 18:08, 3 January 2007 (UTC)

My initial feeling is that reducing the temperature 10 degrees would burn far more calories than 30 minutes of exercise. And in northern europe residential air conditioning is unheard of, it regularly gets to below 15 degrees for most of the year, and times like now when it's early morning the heating has been off for hours and it's quite chilly inside, it doesn't bother me much. Remember people in this part of the world probably spend their life at average temperatures quite a bit lower than in the US (probably an increasing number with the crazy cost of natural gas these days). 86.133.203.195 00:51, 4 January 2007 (UTC)

Calorific content of Ethanol[edit]

On reading the article on Calorie, I notice that "ethanol (alcohol)" has a high calorific value.

While I certainly understand that it's an efficient fuel, as in burning it in a calorimeter, but does it actually contribute to the energy available and if so how? And if not, what does that table mean and why are calorific values not simple produced by burning the food?

I was under the impression (though I've no real knowledge in the subject), that respiration in cells used glucose entirely, and fat, carbohydrates are converted/stored/converted into glucose by various complicated metabolic reactions. Does this mean the body converts ethanol to glucose/glycogen and then uses it in cells?

86.133.203.195 22:17, 2 January 2007 (UTC)

See article called Ethanol_metabolism and specifically the diagram in the section Ethanol_metabolism#Gene_Expression_and_Ethanol_Metabolism. Note it can be converted to Acetyl-CoA or pyruvate, depending on which enzymes are active. Consequently, it can be used to make ATP, or stored as fats, or glycogen, amongst many other possible fates. David D. (Talk) 22:29, 2 January 2007 (UTC)

Thank you, very speedy response. Sort of missed that, or at least the implication in your final sentence, which is what I think the author of Ethanol_metabolism was trying to point at by mentioning that it finally enters the Citric acid cycle (which answered any of my further questions). Didn't mention the pyruvate, but I see how that works too. 86.133.203.195 22:59, 2 January 2007 (UTC)

Ice[edit]

This is where we get our water from, more or less

Why is ice more flavored than liquid water?--cloviz 22:52, 2 January 2007 (UTC)

If you define cold as 'a flavour', then such makes sense. Vranak
Is it? Does your ice come in different flavours? Which ones?  --LambiamTalk 23:07, 2 January 2007 (UTC)
It may be because the ice picked up the flavours of other foods in the freezer; it may be because ice can lose air bubbles which makes it taste different, it may be because chlorinated water loses its chlorine as it freezes, for starters. Anchoress 23:12, 2 January 2007 (UTC)
Well I discard the first and third options because hail tastes stronger than rain water, at least for me. What about "cold stimulates taste buds"; does that make any sense? Maybe it's just me, hehe.--cloviz 23:19, 2 January 2007 (UTC)
OK well not being a science expert I'd think more airborne particulate would stick to hail than water (because of the multiple surfaces for it to stick to and also the hail being more attractive because of its temperature), so maybe it's that? Anchoress 23:25, 2 January 2007 (UTC)
I'd have to say that evaporated chlorine is the most likely reason. Unless your water source is not treated with chlorine (or ozone) to begin with. In which case you are fortunate. Vranak 23:36, 2 January 2007 (UTC)
You guys obviously don't understand what he means! Ice tastes different! I don't know if that could be answered, from the vagueness of the sensation. X [Mac Davis] (DESK|How's my driving?) 04:38, 3 January 2007 (UTC)
It's possible that the ordered structure of ice gives it a different taste.. The tongue seems receptive to OH groups - maybe the fixed positions of the OH's in ice activate taste sensors in a different way..87.102.4.89 15:42, 3 January 2007 (UTC)
Why would water or ice have a "taste?" Maybe it has more to do with mouthfeel than an gustary sensation. X [Mac Davis] (DESK|How's my driving?) 16:12, 3 January 2007 (UTC)
Ice has a distinct, slightly metallic flavor to me.--cloviz 17:38, 3 January 2007 (UTC)
I can taste the same flavor, and yes, I would say "metallic" is a good description, although sometimes it tastes a bit like nuts. Vultur 18:10, 3 January 2007 (UTC)
I notice that the outside of new ice cubes often has a distinct flavor. But half-melted ice cubes in my drink do not. (Try tasting the cubes which have been in a cup of water for a few minutes.) This suggests that the outside of newly-made ice cubes has some contamination, but this is removed if they're allowed to melt for awhile. --Wjbeaty 21:26, 3 January 2007 (UTC)
Mmmm, icicles!  ;-) --hydnjo talk 00:39, 4 January 2007 (UTC)