Wikipedia:Reference desk/Archives/Science/2007 April 18

= April 18 =

Hurricane names
Who gets the job of naming hurricanes? Do they have someone standing around with a book of baby names and write down random ones?  bibliomaniac 1  5  00:29, 18 April 2007 (UTC)
 * Tropical cyclone naming tells all. Rockpock  e  t  01:01, 18 April 2007 (UTC)

Change in velocities of orbits
"In the elliptical orbit, the center of mass of the orbiting-orbited system will sit at one focus of both orbits, with nothing present at the other focus. As a planet approaches periapsis, the planet will increase in velocity. As a planet approaches apoapsis, the planet will decrease in velocity."

The above is taken directly from the Wikipedia article on orbits. I was wondering why the planet increases in velocity as it approaches periapsis and why it decreases in velocity as it approaces apoapsis. Thanks a lot 208.96.96.207 00:41, 18 April 2007 (UTC)


 * In a circular orbit, the force of gravity on a planet is always facing perpendicular to the direction of motion of the planet, and thus gravity cannot do work on the planet, and cannot change its velocity speed. In an elliptical orbit, however, on the approach to periapsis the force of gravity has a component in the direction of the planet's motion, and thus the planet speeds up.  And on the way to apoasis, the force has a component opposite the planet's direction of motion, so it slows down.  You could also interperet the change in velocity as a change in kinetic energy to exactly cancel the change in gravitational potential energy as the planet's distance from its star changes.  You could also interperet it the correct way, with general relativity, but that would be nasty and unnecessary.  Someguy1221 00:53, 18 April 2007 (UTC)


 * In a circular orbit, the force of gravity on a planet is always facing perpendicular to the direction of motion of the planet, and thus gravity cannot do work on the planet, and cannot change its velocity.
 * This is bullshit! Velocity is a vector and if gravity cannot change the velocity of the planet then the planet would move in a straight line and the planet would not be in a circular orbit. Obviously gravity can change the velocity of the planet. 202.168.50.40 01:11, 18 April 2007 (UTC)
 * Calm down, corrected now. Someguy1221 01:13, 18 April 2007 (UTC)
 * Goodness - that was a bit uncourteous. --bmk
 * Goodness - that was a bit uncourteous. --bmk


 * Although the distinction between "speed" (a scalar) and "velocity" (a vector) is always made in physics and is a useful one when talking about these concepts, it mostly isn't made in other fields. In particular, people involved with space travel tend to say "velocity" even when they mean speed: for example, they speak of escape velocity rather than "escape speed", even though escaping depends only on kinetic energy and therefore only on speed.  (Okay, speed and not being on a collision course.) --Anonymous, April 18, 2007, 08:40 (UTC).


 * Another good way to think about it is that the satellite's angular momentum is constant, so a shorter radius implies a faster velocity and vice versa. anonymous6494 16:17, 18 April 2007 (UTC)

which paper towel are strongest?
68.96.105.152 02:09, 18 April 2007 (UTC)

I would guess Bounty as they seem to be obsessed with proving this, but it is probably the only good thing about them. I think this might count as advertising though. You should test it yourself to make sure.
 * Self-testing is good, because that will let you narrow down the possibilities for what constitutes strongest. Does that mean "most weight supported" or "most scrubs before ripping"?  Tearing in the plane or against it?  Wet or dry?  And so forth.... &mdash; Lomn 15:41, 18 April 2007 (UTC)


 * Blue 'shop towels'...by far. My son did a study of this for an 8th grade science fair.  He dropped a steel ball bearing down a vertical tube onto sheets of paper towels affixed with rubber bands to the bottom of the tube.  He tested every brand we could get our hands on (over a dozen brands) by dropping the ball from different heights onto both wet and dry paper towels in a rig he built.  He recorded the height from which the ball had to be dropped to go right through the towel - converted that to a velocity and recorded the mean from a dozen drops.  It took all day to do it...(he even did it 'double-blind' for extra bonus points!)...and if only we still had the data file lying around someplace, I could tell you the answers in detail.  Sadly, it's gone the way of so many such things!  One thing was very obvious - more expensive towels were indeed stronger - except for one brand that were heavily advertised as being 'super-soft' which were by far the weakest (I think it was Scot's or something).  There was a wide variation between wet and dry towels - some types that were strong when dry just fell apart when wet - others were no different wet or dry.  Anyway - what sticks in my mind is that the strongest towels by far - both wet and dry - were those blue "shop towels" you can buy in car parts stores. SteveBaker 04:04, 20 April 2007 (UTC)

Chinese to English Geology Dictionary
Dear Wikipedians:

Does anyone know where I might find a good online Chinese to English geology dictionary or translator?

Thanks,

70.53.61.246 04:10, 18 April 2007 (UTC)

"Perfect" insulation
Let's say I have a big hollow ball made of some magnetic material or other. The shell of this ball is quite thick, and is completely airtight. Inside the ball is just plain old room temperature air from my garage. Now lets say I enclose this ball inside another ball in such a way that the inner ball is suspended by magnets, and I've completely evacuated the air from the outer ball. (I now have a ball floating inside a vacuum.) Just for good measure, I cover the outer ball with a mirror surface. Next, having nothing better to do with my money, I ship my ball down to Antarctica and drop it (gently) on the ice. Will the temperature of the inside ball ever drop? — Jonathan Kovaciny (talk|contribs) 05:45, 18 April 2007 (UTC)


 * Yes, because:


 * 1) You can never completely remove all the air, so some conduction and convection will occur.


 * 2) No mirror reflects all radiation, so some heat will be transferred by radiation, as well.


 * StuRat 05:54, 18 April 2007 (UTC)


 * This is just a variant of the perpetual motion machine. Perfect machines only exist in *expletive deleted* minds. Vranak


 * Even if you assume that you have a perfect vacuum, heat can still be lost through radiation instead of the normal heat transfer. And when you have two metal spheres like that, I can't help but think there's some sort of surface charge effect that would occur that might change the temperature over a long period of time, but I'm not sure if that'd happen. --Wirbelwind ヴィルヴェルヴィント (talk) 06:18, 18 April 2007 (UTC)


 * I protest - this has nothing to do with perpetual motion whatsoever. This is a thermodynamic question, really.  See blackbody radiation - if your outer shell is at a different temperature than the inner shell, the two will inevitably communicate energy via the radiation field between the shells, which will always exist.  Entropy will increase, and your system will equilibrate!   --bmk
 * It's related to the perpetual motion machine in that the idea is to create conditions that are unchanging. Which is a pipe dream. Vranak
 * I see that I just repeated most of Wirbelwind's comments - sorry! --bmk


 * No problem. I wanted a confirmation that I didn't make something up anyways =P --Wirbelwind ヴィルヴェルヴィント (talk) 01:40, 19 April 2007 (UTC)


 * It's obviously not a perpetual motion machine per-se because nothing moves - however it suffers from the same issues of violation of the laws of thermodynamics. The theoretical answer is yes - with a perfect vacuum and a perfect mirror and no sources of radioactive materials and no tidal gravitational forces and no...(lots of other things I can't think of offhand)....the inner sphere would stay at the same temperature forever.  This is the principle behind the thermos flask - and in a practical implementation a thermos will keep your coffee hot or your chilled mocha cold for a good long time - but not perfectly.  The problem is that there are lots of practical deviations from the purity of your thought experiment - some of which are quite literally unsurmountable.  Some of the deviations from perfection are obvious: a perfect vaccuum is impossible to achieve because all materials will out-gas or permit gasses to slowly diffuse through them or will slowly evaporate - and a perfect mirror would have to be a 100% perfect reflector at all wavelengths - which is a thing that most certainly doesn't exist anywhere in nature.  But some of the practical objections are really tricky - as the moon orbits the earth, it exerts a microscopic tidal force across the width of the inner sphere - that will produce an utterly miniscule gain in heat over geological time.  Since all practical materials emit tiny amounts of background radiation - that's another source of microscopic heat gain.   So truly stable temperatures are utterly impossible in any non-thought-experiment.  It's impossible in the same sense that you can't make a practical perpetual motion by building a wheel with a perfectly frictionless axle and spin it in a perfect vacuum and put it somewhere infinitely far from gravitational  sources to make a wheel that would (theoretically) spin forever - there are just too many teeny-tiny fringe effects that you could never eliminate them all.  SteveBaker 03:43, 20 April 2007 (UTC)

What planet is this?
I took this image in southern Uganda, looking west, north-west just after sunset (~8:00pm local time). I think that the cluster of stars just below the planet are the Seven Sisters (of Subaru fame). Also, Orion is just out of frame in the far upper left. I was a degree or two south of the equator. Thanks. --Cody.Pope 07:01, 18 April 2007 (UTC)


 * By using this neat online sky simulator and entering approximate Ugandan coordinates (0 N 33 E) and your specified time (17:00 UTC) and direction (azimuth 280), I determined that your planet is Venus. --bmk
 * BTW I doublechecked, and Orion is indeed up and to the left in the sky. --bmk
 * Genius! I knew there were tones of programs and scripts out there for this, but I has having trouble finding one.  Also, this too confirms that my star cluster is indeed  Pleiades.  --Cody.Pope 08:07, 18 April 2007 (UTC)


 * Whenever you see a bright planet in the western sky shortly after sunset (or in the eastern sky around dawn), it's almost certainly Venus, which is the brightest object in the sky (after the moon) and never very far from the sun.--Shantavira 08:16, 18 April 2007 (UTC)

Genetic Tests
You sometimes hear of surveys about the genetic make-up of an area (like proving there's lots of Celtic genes in England for example), how would you get one of these tests for yourself to trace your ancestry? And what exactly can they test, is it only the direct male or female line?137.138.46.155 07:18, 18 April 2007 (UTC)
 * National Geographic offers a home kit through their website. They track only your paternal (if you're a male) or maternal line (via Y-chromosome micro-satellites or mitochondrial DNA, respectively).  Your lineage would then go into their database, though.  You could find out from whereabouts your line came.  I believe the kit cost 100USD.  Do a search for "genealogy project" on their website. --Cody.Pope 07:27, 18 April 2007 (UTC)
 * You should take a look at Genealogical DNA test. National Geographic tracks fewer markers than most commercial tests. To find actual links to commercial labs, see Genetic_genealogy. If you want advice or a personal recommendation on testing, drop me a note on my talk page. - Nunh-huh 02:18, 19 April 2007 (UTC)
 * Thanks, I was curious really, don't think it's worth paying out till I'm a bit richer, or the tests get better, as I already know my ancestry is North European.137.138.46.155 07:19, 19 April 2007 (UTC)

Is there a lot of vegetation in the South of China?
I saw in a satellite map a representation of methane emissions, most of the "methane clouds" were caused by zones with heavy vegetation, such as in equatorial areas. Despite that, the biggest one was allocated in southern China, in a circle-like area. My question is: Is there such a huge amount of vegetation or are the Chinese just producing a "special" kind of pollution there? Thanks. --Taraborn 10:06, 18 April 2007 (UTC) Please show us the map,'South China'is too genernal.I can't give a nice prediction without enough info.Anyway,as I know,South China is one of the relatively developed area of China.The presence of heavy vegetation is less likely to appear in such area.--lowerlowerhk 21:06, 18 April 2007 (UTC)
 * Was it this one ? -Haikon 17:43, 18 April 2007 (UTC)
 * Yes, that's exactly the map I saw :P --Taraborn 19:06, 18 April 2007 (UTC)
 * And it's mountainous!Josh Holloway  17:47, 18 April 2007 (UTC)
 * This map shows "natural primary vegetation cover".  It might also help to look at List of countries by population density. -Haikon 17:53, 18 April 2007 (UTC)

There were a lot of trees around that area a while ago, and mst of them are likely to still be there. I think I read somewhere that a lot of methane is produced by farm animals, especially cows. Which is why there is so much over India.


 * Also, aren't a billion people going to produce a fair amount of methane ? Perhaps to save the planet we should supply free Beano to the Chinese. :-) StuRat 23:15, 18 April 2007 (UTC)


 * Looks like it corresponds with population density pretty well,, with the strongest methane area over the Yellow River plain, China's "breadbasket", if I'm not mistaken. Pfly 02:31, 19 April 2007 (UTC)

Vitamin B - Thiamin as a mosquito repellant
Hi

I'm writing to you from South Africa and currently in hospital with malaria. My question however deals with thiamin as a bug repellent.

I recently saw an advert for a bugpatch that claims to allow small amounts of thiamin (vitamin B1) into the skin which apparently keeps mosquito's at bay? Wikipedia explains what Thiamin is, its chemical constitution, etc, but no mention is made of its mosquito or bug repelling qualities. Could anyone perhaps tell me:

1. If Thiamin is an effective repellant; 2. If yes, why this is so?; 3. if one cannot get hold of a patch etc, would simply ingesting thiamin (e.g. vitamin B) syrup be effective?; 4. how much would a person have to ingest for it to be effective?

regards —The preceding unsigned comment was added by Andrerabe (talk • contribs) 12:03, 18 April 2007 (UTC).


 * I remember that was big 20 years ago. Most of the 'alternatives' have been tested and found ineffective.  --Zeizmic 12:18, 18 April 2007 (UTC)

There's no evidence that thiamine is effective as a mosquito repellent:



Interestingly, acute thiamine deficiency can mimic and complicate malaria infection, which is especially important in Southeast Asian populations. I'm not sure how relevant that is to malaria patients in South Africa, but my understanding is that it's a major reason that patients are commonly supplemented with thiamine in Southeast Asia. --David Iberri (talk) 14:04, 18 April 2007 (UTC)


 * I would guess that's how the idea came about that thiamine worked as a mosquito repellent, from observations that people wearing thiamine patches came down with less severe cases of malaria. StuRat 18:41, 18 April 2007 (UTC)

Baset trailer
Is there such thing as a baset trailer? James S. 14:30, 18 April 2007 (UTC)


 * I doubt it; the discussion page has details. Why in the world would somebody use a gasoline electric generator to drive a car?  This is adding an extremely lossy stage of energy transfer; if the same engine were used to directly power the car, the fuel efficiency would be immensely better. Nimur 17:25, 18 April 2007 (UTC)


 * There are many advantages to gasoline-electric hybrids:


 * 1) They can have smaller engines, meaning less weight, since power for acceleration is provided by the batteries.


 * 2) The engine can be run at the most efficient speed to charge the batteries, as opposed to the variable speeds needed for a gasoline only vehicle.


 * 3) Gasoline is quick and easy to replace on the road, due to the existing infrastructure, while recharging an electric-only vehicle is not.


 * 4) Gasoline-electric hybrids provide a longer range than electricity alone.


 * 5) A well designed hybrid will have redundancy in that the vehicle can run on either gasoline or electricity alone, if need be, in case of a failure in either system. StuRat 17:52, 18 April 2007 (UTC)


 * 6) All wheel drive is easier to accomplish with an electrically driven vehicle than gasoline (I'm not positive on this one). StuRat 17:50, 18 April 2007 (UTC)


 * In support of your last point, the Toyota/Lexus AWD hybrid SUV has no driveshaft to the rear differential ; there's just an electric motor located where the driveshaft would connect to the rear differential case. That arrangement saves the weight of the driveshaft, the U-joins, and the center differential.


 * Atlant 19:40, 18 April 2007 (UTC)

Heavy questions
Where did the heavy elements on Earth come from ? I am aware that heavy elements (over the mass of iron, I believe) come from supernovae. What I'm asking about is if we know which specific supernova(e) contributed to the Earth's supply. There are many sub-questions related to this:

1) I assume the supernova(e) in question must have been within our Milky Way galaxy. Is this correct ?

2) I'm assuming that heavy elements existed on Earth, in roughly the same ratio (except for those lost due to radioactive decay), since the Earth was formed some 4.3 billion years ago. Do we know this to be correct ?

3) Are heavy elements relatively evenly dispersed throughout the galaxy, by solar system, or is it uneven ? (I realize that planets, especially terrestrial planets, are heavily weighted towards the heavy elements.)  If evenly distributed, this would lead me to believe that so many supernovae contributed that it would be difficult to track specific sources.

4) Can we date the age of heavy isotopes with long half-lives (say billions of years), by comparing the ratio of the original isotopes with the stable products, much like carbon dating ? If so, and if there is only one supernova source, or perhaps a small number, we might be able to match up supernovae remnants with those ages.  Has this been done ?

5) I am assuming a supernova would need to be relatively close to our solar system to contribute a significant amount of heavy elements to Earth. Either that or many supernovae would be needed far away.  Is this correct ?

6) Are there any candidate supernova remnants (like black holes or neutron stars), relatively near our solar system and over 4 billion years old ?

StuRat 17:41, 18 April 2007 (UTC)


 * Those are heavy duty questions. I think the presence of heavy elements is pretty sparse; combined with difficult detection due to low quantities (relative to say, Hydrogen).  Our best detection tool is emission spectroscopy, but "new-age" astronomers/astrophysicists like to use long-time-interval image processing to detect wobbles and gravitational perturbations; and make inferences about mass and distribution, etc.


 * As far as the original source, I think the theory holds that our solar-system is a second-generation (or nth generation) of material from an originally larger star. I doubt that significant amounts of the material (especially heavy metals) came from outside the near solar vicinity.  I don't know of any large 'candidate supernova' objects within a reasonable range; but if the time-scale is billions of years, a lot of speculation is naturally part of the theory, and you can start looking at extremely distant (millions of light-years) objects.  As a bit of precaution, it is not a good assumption that stellar material (especially large quantities) could move even a significant fraction of the speed of light; so an element that formed 10,000 light years away might take millions (billions?) of years to "travel" to us.


 * In summary, I think the best estimate for where the material came from is "here" - i.e., this solar system; which has undergone a very significant time-evolution since its original creation. Nimur 17:53, 18 April 2007 (UTC)


 * But, if there was a supernova right in our own solar system, shouldn't there be a black hole or neutron star left over from it ? StuRat 17:58, 18 April 2007 (UTC)


 * If there were a supernova in the solar system, the Earth wouldn't be here. Speaking of which, what is a safe minimum distance to be from a supernova? From a regular run-of-the-mill nova? Clarityfiend 18:02, 18 April 2007 (UTC)


 * StuRat isn't suggesting that said supernova occured after the solar system formed. That said, see Supernova.  Novae would probably have less impact, but their even more variable scale means that a lower limit can't really be imposed. &mdash; Lomn 18:10, 18 April 2007 (UTC)
 * It's worth noting (backing up to StuRat's question about a black hole in the vicinity) that a star could go supernova in the general region of the sun 5 billion years ago and not be anywhere nearby now. For example, Barnard's Star is presently ~6 light years away, but will have closed to 4 ly within 10,000 years.  Scale that out to a few billion years and you're talking about the star being up to around one million light years distant when the solar system was formed.  &mdash; Lomn 18:19, 18 April 2007 (UTC)


 * I think metallicity is the general concept you're looking for. As Nimur notes, it's more the case that the solar system (even the galaxy) is of generally later population.  While particular supernovae may have contributed to the collapse of whatever dust cloud the solar system coagulated from, it simply isn't practical to assign individual supernovae to the distribution of metals.  Rather, entire classes of older population stars exploded to form not just metal-rich individual stars/planets but entire metal-rich galaxies and galaxy clusters. &mdash; Lomn 17:59, 18 April 2007 (UTC)


 * Do other galaxies and clusters have roughly the same ratio of heavy elements ? StuRat 21:00, 18 April 2007 (UTC)
 * Of Hydrogen/Helium to metals? No.  As noted in metallicity, the Milky Way has from 2 to 5 times the relative metal content of the Magellanic Clouds.  Within the metals (say, Iron to Uranium)?  I'm speculating, but I would expect that it's relatively constant, since (I think) any supernova produces stuff all the way up the periodic table.  Theory suggests that this holds for even the oldest, originally metal-free Population III stars. &mdash; Lomn 21:11, 18 April 2007 (UTC)

To answer question 4, there are a number of radioactive isotopes with half-lives of hundreds of millions to billions of years. Check out Uranium-lead dating. Someguy1221 18:55, 18 April 2007 (UTC)

To answer #5: The sun is traveling with about 17 km/s through its stellar neighborhood. In 5 billion years, this leads to a distance of 2.8E+5 light years - so anything that was close back then isn't necessarily close to the sun now. Icek 01:29, 19 April 2007 (UTC)

Determining energy cost of household
Hi, I am wondering if anybody can help me calculate the energy cost of my household. I know how to do so for simple devices, like lightbulbs with clearly marked wattages, but how do I do such a thing for other devices? I'm particularly interested in how much energy it takes my washer and dryer run, but I don't see any useful info as to how to do such a thing anywhere on them

Update: thanks to everybody for replying, I found this site http://www.tribaluk.com/laundry.htm which lists Energy Consumption in kWh (60ø C) for various machines. What exactly does that mean? Does it refer to per cycle? What does the 60ø C mean? 4/19/07

Robin


 * Well, if all you want is the total energy, you can obviously just check your electric (and also maybe gas or fuel oil) bill! Or you could find and learn how to read your electric meter, to get more fine-grained answers. --Steve Summit (talk) 20:36, 18 April 2007 (UTC)


 * You could turn everything in the house off (the breaker board might help with that), record what your electric meter says, do a load of laundry, and then record again what the meter says. The difference in those numbers is how much juice it took to do the laundry.  You could do it a few times and take the average if you wanted more accuracy.  --TotoBaggins 21:01, 18 April 2007 (UTC)


 * If you really want to get per-device numbers, you need only a multimeter and a pocket calculator. I think there are also "user friendly" meters designed especially for this if you don't want to muck around with wires. -- mattb 21:02, 18 April 2007 (UTC)


 * Actually, no (to the first bit, that is): determining the power/energy used by a device requires measuring both the voltage and the current. Measuring the voltage is easy, of course (and to first order you don't even have to measure it, because it is what it should be), but measuring the current requires interrupting the circuit, and requires a high-current scale (amps or tens of amps) on your multimeter, which most small/inexpensive meters don't have.  All of that is why a more convenient, clip-on ammeter is a splendid idea, except that I get the impression they're all inaccurate, or expensive, or both.  (But I could be wrong.) —Steve Summit (talk) 02:56, 19 April 2007 (UTC)


 * My cheapest multimeter is rated for 10 amperes. That should handle most household devices save for your space heater, microwave oven, electrical stove, water heater, etc. -- mattb 03:06, 19 April 2007 (UTC)


 * See also clamp meter, but the problem is that you don't much care about the instantaneous reading but rather the time-integral of the reading. Some of the fanciest clamp meters can do this. There are also gadgets you can buy that you plug your appliance into; they then calculate this.


 * Atlant 12:18, 19 April 2007 (UTC)


 * The voltage and current ratings are marked on a lot of devices, but beware that those values are probably maximums and the actual usage will differ from that. anonymous6494 21:57, 18 April 2007 (UTC)


 * They also often don't account for all of the energy that's wasted as heat, either in the wires leading to the device or in the power supply for the device (if it has one). Someguy1221 22:08, 18 April 2007 (UTC)


 * Doesn't matter. Unless there's something very wrong with the wires (whether leading to the device or within it), substantial energy won't be dissipated in them.  And the nameplate rating of a device normally reflects the current it actually draws, regardless of the use it'll get put to.  For example, a 100 watt light bulb does indeed draw 100 watts, although it converts most of those watts into heat, not light.  But my point is that the nameplate reading (to the extent that it's at all accurate in the first place) does reflect the amount of energy that is wasted (as heat or otherwise) in the rated device. —Steve Summit (talk) 02:56, 19 April 2007 (UTC)


 * The "nameplate" on a lightbulb or an electric heating device such as a range, toaster, space heater or hairdryer may accurately reflect the energy consumption, but on computers and motor appliance such as washing machines, the nameplate may overstate the average power consumption during operation. A utility electric meter has marked on it a "kh" factor which allows it to be used as a watt-meter to measure instantaneous power. Per Electricity meter, "The amount of energy represented by one revolution of the disc is denoted by the symbol Kh which is given in units of watt-hours per revolution. The value 7.2 is commonly seen. Using the value of Kh, one can determine their power consumption at any given time by timing the disc with a stopwatch. If the time in seconds taken by the disc to complete one revolution is t, then the power in watts is P = 3600×Kh/t. For example, if Kh = 7.2, as above, and one revolution took place in 14.4 seconds, the power is 1800 watts. This method can be used to determine the power consumption of household devices by switching them on one by one." Measuring amps, even with a high quality RMS clamp meter, is not an accurate way to determine energy consumption in AC circuits with motor load or electronic load. Volts times amps will generally overestimate the watts, due to the less than unity Power factor.Edison 15:26, 19 April 2007 (UTC)

Mercury
How much tuna would I have to eat to get my daily recomended value of mercury? What other foods are a good source of mercury?


 * Cute question. Some would call it a troll, not me though.


 * Anyway, methyl mercury comes from coal power plants. If you don't live around coal power plants, the local tuna won't have much mercury, so try to get it from the Eastern seaboard of the United States. There's a rather large number of coal-fired plants over there. Also, as the recommended daily intake of mercury is 0.0mg for men, 0.0mg for women, you may actually want to avoid tuna caught along the Eastern seaboard altogether. Unless of course you do have a deathwish. Vranak
 * The man's got a deathwish! adam the atom T E C  20:07, 18 April 2007 (UTC)


 * Sharks can contain even more mercury (as they are higher up the food chain; they eat the tuna which themselves contain mercury). Therefore, shark fin soup may be right up your street. Of course, sharks are endangered and the process for removing the fins is usually rather cruel (cutting off the fins while the shark is still alive often takes place) and assuming you live in the USA, importing shark fin or catching it in US waters is illegal unless you can import an entire shark carcass, which just happens to have its fins still attached. Laïka  21:21, 18 April 2007 (UTC)


 * Sadly, not even vegetarians are necessarily safe from mercury poisoning; in the 1960s and 1970s, methylmercury was a popular fungicide for treating wheat, especially in Iraq. People then made this wheat into bread and suffered from mercury poisoning, while the Chinese emperor Qin Shi Huang was killed because he believed that eating mercury would make him immortal; unsurprisingly, it didn't. Laïka  21:28, 18 April 2007 (UTC)

I think the proper way to interpret this question is "how much tuna fish can I eat per week without being in danger of mercury poisoning". I seem to recall a fairly low recommendation, something like 2 cans per week. StuRat 23:07, 18 April 2007 (UTC)


 * StuRat, that sounds outrageously low! I recall eating tuna fairly often as a kid, and I turned out alright... Nimur 00:05, 19 April 2007 (UTC)


 * Well again, it's going to greatly depend on where the tuna came from. East coast bad, far out in the Atlantic, or Pacific, good. Vranak


 * Also, it depends on the length of exposure. Mercury was used in hat making.  After many (many)  years of working with mercury, the mercury poisoning would take effect (baldness and insanity), hence the term "mad hatter".  Those who wore mercury-laden hats all their life had very little effect.  A single dose of mercury has no long term effects.  I drank mercury once as a baby.  It only resulted in a silver splotch in my diaper. --Kainaw (talk) 13:06, 19 April 2007 (UTC)

See here for some figures from the FDA. And here for toxicity information of methylmercury, the relevant compound, from the EPA. Icek 00:53, 19 April 2007 (UTC)

Hey i survived mercury exposure once. from thermomiters i acctually broke them to play with the chemical as they formed tiny little balls on the floor that rolled. its i mean it was quite fun =) and look at me no problems what so ever no insanity or nothing of the sort. and im still clearly alive =). User:Maverick423 If It Looks Good Nuke It 15:16, 19 April 2007 (UTC)


 * Yeah, but you edit Wikipedia so how sane can you be ;-)?


 * Atlant 15:02, 20 April 2007 (UTC)


 * Mercury as the metal is much less toxic than when as an organometallic compound. Xrays showing people with lots of bright spots of metal inside are quite interesting but the victims can recover, unlike Karen Wetterhahn. See our Mercury poisoning article for more info about these distinctions. DMacks 15:26, 19 April 2007 (UTC)

ah so there is a diffrence! all this time people kept telling me there wasnt but now i can prove them wrong! User:Maverick423 If It Looks Good Nuke It 17:08, 19 April 2007 (UTC)


 * See also Environmental toxins and fetal development where we mention Minamata Disease. And then, of course, there's the ever-popular Thiomersal-in-vaccines controversy. Also, even with metallic mercury, be aware of the possibility of poisoning from mercury vapor.


 * Atlant 15:02, 20 April 2007 (UTC)

The skull
Is the skull a single bone or a group of bones? Heegoop, 18 April 2007 (UTC)


 * 22 bones. Check out human skull.  Someguy1221 20:38, 18 April 2007 (UTC)

"Perfect" Black Hole insulation
Jonathan Kovaciny saids ''Let's say I have a big hollow ball made of some magnetic material or other. The shell of this ball is quite thick, and is completely airtight. Inside the ball is just plain old room temperature air from my garage. Now lets say I enclose this ball inside another ball in such a way that the inner ball is suspended by magnets, and I've completely evacuated the air from the outer ball. (I now have a ball floating inside a vacuum.) Just for good measure, I cover the outer ball with a mirror surface. Next, having nothing better to do with my money, I ship my ball down to Antarctica and drop it (gently) on the ice. Will the temperature of the inside ball ever drop?''

'''Now suppose I increase the mass density of the inner ball until it becomes a blackhole. Now even the radiation cannot escape from the inner ball. Will the temperature of the inside ball ever drop?'''

202.168.50.40 22:45, 18 April 2007 (UTC)


 * Maybe --> Hawking radiation. Someguy1221 22:52, 18 April 2007 (UTC)


 * So many hypotheticals... I think the ("safe") practical answer is to call bluff on the "perfect insulation" which could clearly never be built in practice. (Perhaps the easy-way-out, but it's realistic).  As for turning the problem into a black hole, it suddenly ceases to matter whether the system is insulated, because the insulation would be inside the event horizon.  I think this is a gedankenexperiment that I want no part of.  Nimur 00:09, 19 April 2007 (UTC)

Doesn't the temperature rise when the inner ball is collapsed? But the real object of the question is does temperature have meaning if it can't be measured? If no one is in the forest, does the falling tree make a sound? --Tbeatty 07:38, 19 April 2007 (UTC)


 * To first part, yes the inner ball cools down. Whilst there may be a vaccuum between the inner and outer balls, this only eliminates transfer of heat by convection (of course in practice no man-made large-scale volume vaccuum is perfert and a tiny heat transfer by convection will occur). Having a vaccuum layer does not prevent radiative loss of infra-red heat from the inner ball outwards. Your question also ingnores the strength of magnets needed to levitate the inner room - if they are electromagnets then heat will be generated. So yes the inner ball will heat up allbeit extremely slowly.
 * If you collapse the inner ball into a black hole, then Gay-Lussac's law would suggest its temperature reaches infinite, although this applies to an infinitely small volume, so no overall change in temperature in the wider orginal volume of space. However how are you going to suspend the black hole within the outer ball ? - Its going to take huge amount to power - (nolonger question few centimeters between inner & outer shell wall but outer wall to centre of the space). Crushing the inner ball into a black hole will take a fantastic amount of power (no black holes ever been created from just an atomic bomb explosion, and supanova are somewhat hot over an area rather larger than the earth!). Lastly, tiny black holes probably radiate off their mass as Hawking radiation and eventually explode! David Ruben Talk 13:41, 19 April 2007 (UTC)

Didnt they mention a particle accelerator that acctually creates tiny black holes? come out on a show think it was naked science. where they smash atoms at great speeds that they form tiny black holes. it was quite intresting.


 * There was talk about it, but no evidence of any formation of black holes exists so far. One of the risks could be black holes form and then swallow up the equipment, followed shortly by the rest of the earth.  However a very tiny black hole may be too small to even fit one particle in during any reasonable time period! GB 07:48, 20 April 2007 (UTC)