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Contents 1 February 21 1.1 Aids 1.2 List of Animal Name's Help 1.3 biography william cullen brown 1.4 Internal energy 1.5 Genetic tendancy towards AIDS amongst Black people? 1.6 the most distant place in the earth from another place in the eath 1.7 Another antipodal question 1.8 Herpes 1.9 nose bump 1.10 Megaphone 1.11 Eyeball Transplant 1.12 Is It Sinus Infections Untreated? 1.13 Water vs. Polaroid 1.14 Dwarves, midgets and penises? 1.15 Cholera 1.16 Voltage Conversion 1.17 In the Middle of It 1.18 Electromagnetic sheilding 2 February 22 2.1 Chemoluminescence again 2.2 Denatonium 2.3 Nose grease: is this article for real? 2.4 Extraction of Upper Incisors 2.5 Smelly retainers 2.6 Outermost electron shells 2.7 Physics/collisons 2.8 optics 2.9 microorganisms 2.10 Juvabional 2.11 Acetaminophen 2.12 Questions? 2.13 Balancing a bicycle 3 February 23 3.1 Operators acting on an enitys wavefunction. 3.2 steroids 3.3 LPG TRANSPORTATION 3.4 Turning tv off in lightning 3.5 pH of Copper Sulphate 3.6 Budgie body language 3.7 Budgie question 2 3.8 Jealousy 3.9 Budgie question 3 4 February 24 4.1 How much is one pound of US$20 worth? 4.2 Tapeworm 4.3 valence and ground state 4.4 contact lenses 4.5 Decarboxylation 4.6 chemistry problem 4.7 Tapeworm 4.8 Ten years after cloning of Dolly the Sheep: What prevents primate somatic cell cloning? 4.9 i need assistance 4.10 How much Fertilizer do crops require? 4.11 Hydrogen in the table 4.12 Liposuction and Fat 4.13 Homemade nuclear reactors 4.14 American Wire Gauge 4.15 valence and ground state 4.16 Supercontinents 4.17 contact lenses 4.18 Chicken 4.19 Decarboxylation 4.20 Jogging 4.21 Solids 4.22 Population center of the Earth 4.23 Setting cheese with orange juice 4.24 Venus 5 February 25 5.1 Voices 5.2 Good and Evil 5.3 Killing 5.4 chemistry problem 5.5 A genetically modified organisms question folks 5.6 solar system models 5.7 rainbows in mirrors 5.8 Hydroxyapatite 5.9 Nuclear Fission For Space Propulsion 5.10 The Theory of Evolution and falsifiability 5.11 My budgie questions 5.12 aspirin and food poisoning 5.13 Sprained Ankle Question 5.13.1 Wikipedia:Medical disclaimer 5.14 Aviation 5.15 Interesting question 5.16 Earth Days 5.17 Most efficient brain drug delivery route? 6 February 26 6.1 Evolution 6.2 Hepatitis A and B Vaccines 6.3 Recombinant protein production 6.4 EMF 6.5 Icefish 6.6 Chemistry: Ionic strength (μ) and rate constant (k) 6.7 Someone recommended a gull book to me a while back... 6.8 Melting point of Cheddar 6.9 Peculiar and elusive disease/illness, please help 6.10 Digital TV and Freeview 6.11 “Gira” bird 6.12 Feeding boiled eggs to the gulls... 6.13 chromotagraphy 6.14 Non classical light 6.15 glycerol burning 6.16 Black models 7 February 27 7.1 Lithium in oil 7.2 Wastewater Treatment and Ammonium Alum 7.3 Calcium Chloride and Sodium Carbonate 7.4 GPS 7.5 A measure of non-concentricity - a unit or discriptor 7.6 Stickers that luminate on mobile phones 7.7 Adverse effects of darkness 7.8 drugs 7.9 Swallowing stuff 7.10 rivotril 7.11 Insects cheat? (tongue-in-cheek question) 7.12 drugs 7.13 What is the exact mechanism that causes global warming? 7.14 % of water in humans 7.15 Hydrogen exhaust 7.16 lacquer 7.17 pregnacy 7.18 Steering a tram 7.19 How difficult would it be...? 7.20 Obseving mutation in our own time 8 February 28 8.1 Diffusion and the human body 8.2 Urine Examination 8.3 Macaws with flushed pink cheeks 8.4 human growth 8.5 Theoretical contraption for capturing light/photons 8.6 Raw milk and the menstrual cycle 8.7 Autism 8.8 Super Volcano 8.9 Super Disasters 8.10 So is gravity currently a theory or a law? 8.11 Hypothetical question here... 8.12 Eye contact during sex 8.13 Elliptical Machine 8.14 Foamy human urine 8.15 Space exploration 8.16 Algae Research... Pyrrophyta, the Dinoflagellates 8.17 Elliptical Part 2

[edit] February 21

[edit] Aids

Are you able to cathch aids through mosquito's? —The preceding unsigned comment was added by 60.234.64.178 (talk)

Visit our HIV and AIDS misconceptions page, where that is answered in item #4: "HIV is transmitted by mosquitoes". DMacks 02:51, 21 February 2007 (UTC)

Or the Mosquito#Mosquitoes_and_health section. --Wirbelwindヴィルヴェルヴィント (talk) 03:19, 21 February 2007 (UTC)

Kudos DMacks, that's a great page that I probably would have never found or stumbled upon otherwise. --Cody.Pope 04:21, 21 February 2007 (UTC)

[edit] List of Animal Name's Help

Recently, the article List of animal names has been tagged a hoax, because at least some of the names appear to be made up.

Does anyone know any good, detailed resources to use for the article? and second, if anyone here who thinks they may know something could go look it over that would be great.

Feel free to move this if this is not the correct location to be asking for this sort of help.

Thanks--Honeymane_{Heghlu meH QaQ jajvam} 04:58, 21 February 2007 (UTC)

Whomever placed that tag should use the {{fact}} citation request for any specific issues they have. I can only find a few that appear questionable, (eusuchian for alligators? I had never heard this, but Google seems to agree at first glance[1]), most of the others seem fairly common. Nimur 05:42, 21 February 2007 (UTC)

[edit] biography william cullen brown

Hi, I tried searching the web for the birthdate and date of death of William Cullen Brown, son of John Brown (doctor), the only thing I found is a probable birthdate in 1776 or 1777. does anyone here have some reference for looking it up? would be great, thanks, 134.76.144.35 15:01, 21 February 2007 (UTC)

[edit] Internal energy

Which has the greater amount of internal energy, an iceberg of a cup of hot coffee?

That depends on what you mean by "Internal energy". If you mean of the relatavistic mass/energy (the 'E=mc²' kind) - then the iceberg wins (assuming it has a mass of several hundred tons versus maybe a tenth of a kilo for the coffee). But you probably mean 'thermal energy' - which is in the formal sense of Internal energy. Then there is a problem because internal energy is normally talked about as a relative thing - you can talk about adding such-and-such internal energy or subtracting such-and-such - but the idea of an absolute amount is fairly meaningless (the article on Internal energy explains this quite well). It's just not a terribly meaningful question. If forced to come up with an answer, we might talk about the internal energy as the amount of energy you'd have to add to raise the temperature of the object from absolute zero to it's present temperature. This means that we need to consider our temperatures relative to absolute zero. Let's do this in degrees Kelvin rather than Centigrade: The iceberg (at about zero C) is at 273K and the coffee (at maybe 100C) is at 373K. The amount of heat required to raise one kilogram of water through one degree kelvin is 4186 joules (the specific heat capacity of water) - so we're looking at 4186 x 273 x m_iceberg versus 4186 x 373 x m_coffee (assuming the specific heat capacity of coffee is pretty similar to plain water). We have to add a little to the coffee's energy to allow for the energy to put it through a 'phase change' from ice to water: That's 0.334 Joules/Kg - which isn't going to make much of a difference to the total. So if we pick a smallish iceberg (1000kg maybe) and a large cup of coffee (1kg!) we're going to end up with internal energies of 1142megajoules for the iceberg and 1.56megajoules for the coffee. For a more 'typical' iceberg the numbers could easily be 100,000,000kg - and for a more typical coffee cup, 0.1kg. But it should already be very clear that the huge mass of the iceberg is going to dominate this equation no matter what. SteveBaker 15:46, 21 February 2007 (UTC)

This person could also be referring to bond energy, which means if you were to take your cup of coffee and your iceberg and break all of the bonds and break the compounds in to elements, how much energy would be released. Assuming that the coffee is mostly water, then the iceberg would have significantly more energy because it contains more bonds. In addition, a quantitative measure of particle energy is called temperature- Temperature is actually a measure of the speed and therefore energy of the particles in a substance (and absolute zero would be when movement stops). This question could be answered with the fact that the individual molecules of coffee (which is hotter) contain more energy than the particles of ice (colder). —Preceding unsigned comment added by 72.240.212.185 (talk • contribs) 20:25, 22 February 2007

[edit] Genetic tendancy towards AIDS amongst Black people?

I copied this question from AIDS myths talk page because I am also interested to see an answer for this. It seems all statistics show that black (negroid) people have a greater chance (up to 15 times!) more to get AIDs then a white person of European (Caucasian) decent. Is this a genetic tendancy or some other reason? Has there been any scientific studies? Question copied by 193.167.109.145 14:42, 21 February 2007 (UTC)

While there is some indication that a very few people have an innate, genetic immunity to HIV, there isn't – as far as I know – any study which links susceptibility to HIV to race. The chief reasons why HIV and AIDS are so common in Sub-Saharan Africa (see AIDS pandemic for statistics) are social, cultural, and economic; the fact that most of the residents of these countries are black is not a factor and does not increase their susceptibility to the disease.

Instead, HIV is transmitted rapidly through the population because

• general access to health care and health education is often poor in developing nations;
• access to and use of condoms is limited, women may be unable to require their partners to wear condoms;
• availability of antiretroviral drugs is limited, tending to result in a more rapid progression to full-blown AIDS, and allowing a much higher rate of mother-to-child transmission of HIV at birth;
• there are a number of myths circulating (such as the idea that sex with a virgin will cure AIDS) which can encourage risky behaviour.

This may in turn lead to a perception that black people are innately more likly to develop AIDS. TenOfAllTrades(talk) 15:01, 21 February 2007 (UTC)

We have to tread very carefully here - are you saying that a black person who is exposed to the disease under the same circumstances as a white person has a 15 times greater chance of catching the disease? This seems very unlikely to me. But if you are saying that across the population of the earth, 15 times as many black people as white have AIDS - then that's a totally different thing. The problem is that AIDS is more widespread where educational standards are lower - where people are poorer - where treatment is less available - where diagnosis comes much later - where condoms are an expensive item relative to income. For purely historical reasons, that is predominantly in places where black people are the majority of the population - so inevitably, they have many more opportunities to get infected and will catch the disease at vastly higher rates. This would mean that even if there was no genetic predisposition in blacks relative to whites, black people would still suffer from it to a much greater extent. So the raw statistics tell you nothing meaningful about genetic predisposition. SteveBaker 16:05, 21 February 2007 (UTC)

Surfers have a much higher chance of suffering from a shark bite than people who live in the middle of a desert. They also have a much higher chance of drowning than people who never go near water. Genetics is not the answer in this case either. --24.147.86.187 04:50, 22 February 2007 (UTC)

[edit] the most distant place in the earth from another place in the eath

What you have to do, to find the most distant place in the earth from another place in the earth?? An example to find the distance place from 19 west and 40 south (talking about cordinates) you have only to add + 190 to the 19 and 90 to the 40???

Here's how:

If the numbers are expressed in degrees, minutes and (possibly) seconds, first convert them to decimals (being careful about the sign of the seconds and minutes!), So -10 deg, 30 min, 12 sec becomes -(10+(30/60)+(12/3600)) or -10.50333 degrees.

...then...

• If you have latitudes and longitudes expressed as signed numbers, then you have to change the sign of the latitude from positive to negative (or from negative to positive) and if the longitude is negative, add 180 degrees - or if it's positive, subtract 180 degrees.
• If you have them expressed as positive numbers with North/South and East/West letters then simply switch the latitude from S to N (or from N to S), switch the longitude from E to W (or W to E) and replace the number with 180 minus the number. Hence (10.-104) becomes (-10,76) and 40S 19W becomes 40N (180-19)E or 40N 161E.

SteveBaker 16:31, 21 February 2007 (UTC)

See also: antipodes, antipodal point. TenOfAllTrades(talk) 16:34, 21 February 2007 (UTC)

...but...we weren't asked about the antipodes - we were asked about the most distant point. We ought to think a bit carefully about this. Is the point furthest from the South pole really the North pole? Remember that the earth isn't a perfect sphere - it's a bit squashed at the poles - so I guess it's possible that the furthest distance (measured in a straight line through the middle of the planet) from the South pole might actually be a bit off to the side of the North pole. Think what it would be like if the earth was squashed much more than it really is - suppose it was squashed so much that it's major axis was ten times as big as it's minor axis (from pole to pole)? Then, it would be obvious that the furthest point from the South pole would be a long way from the North pole...but with a lesser degree of squash, the same principles apply. Hmmm - that hurts my head. I think you already have the answer you actually wanted - but many of us on the science desk refuse to let you walk away with merely the answer you wanted. Sometimes we have to come up with the 'other' answers too! :-) SteveBaker 16:45, 21 February 2007 (UTC)

We might also define the distance in many ways: through the planet, or on the surface, or perhaps even some other way (such as along the magnetic field lines). Nimur 04:09, 22 February 2007 (UTC)

Steve's point is valid, but mostly nullified by the fact that the Earth's shape is very close to an ellipsoid of revolution whose polar axis is the same one that our latitude and longitude coordinates are based on. This means it has enough symmetry that the simple calculation above does produce the right answer or something very close to it. As I recall, the discrepancies between the geoid and a true ellipsoid are on the order of 50 feet, so the error in using the calculated position isn't going to be a lot more than that.

If we're talking about points on the Earth's surface, of course, the shape of the geoid isn't the only consideration; you may want to take their altitude into account. In which case you now have to decide how you want to measure distance. Any discrepancy from the calculated latitude/longitude position will still be pretty small, though; even Mt. Everest is only about 5 miles high.

--Anonymous, February 22, 2007, 04:44 (UTC).

Coincidentally, I was reading an article today in the current (March) issue of Discover, and it turns out that "50 feet" was off by one order of magnitude. "Measurements reveal that some parts of the ocean are 390 feet lower than average, and others are 300 feet higher." (page 47, article "GRACE in Space" by Sam Flamsteed). It's still a small matter when you're talking about the distance between points halfway around the world. --Anon, Feb. 23, 23:50 (UTC).

[edit] Another antipodal question

OK - here's a good one. Take a look at this map from antipodes - it shows (in red) the continents and (in yellow) the antipode of each point:

I'd never seen it drawn like that. Is there some good scientific reason why there is so little overlap between continents and antipodes? It's remarkable (especially when you subtract off the ice-shelves in the antarctic so they don't get labelled as 'land' - the antipode of almost every place on dry land is ocean! SteveBaker 16:54, 21 February 2007 (UTC)

Fascinating! I wonder why the planet does not "bounce" like a car wheel that is not balanced properly?--JLdesAlpins 18:01, 21 February 2007 (UTC)

Just thinking about the statistics - *is it* that remarkable? Currently 71% of the world surface is covered by water. Therfore 29% is land. Assuming that the probabilities are uncorrelated then one would only expect 0.29^2 % of the surface to be covered by land and have it antipode covered by land - that is 8.41 % of the world surface or only 20% of the land sruface. To me the map seems to have something of the order of 8% of the world coloured orange.

Oh, and there is land under most of the antartic IIRC. --Neo 18:04, 21 February 2007 (UTC)

Bearing in mind the small content of land, as noted above, it's also worth pointing out that the distribution between northern/southern hemispheres is far from even - most of the land mass is in the northern hemisphere. And once you allow for Antartica mapping to the north pole, where - barring Greenland - there's no land, that value gets even smaller. So it's hardly a surprise, really.

What's really interesting (well, I think so) is how much it has varied over the millenia. Today's value might be quite high, by comparison. If you buy the model of pangaea, the value then was probably very close to zero. Spiral Wave 18:35, 21 February 2007 (UTC)

Hmmm. I thought about it like this: If land and sea were randomly distributed then the probability of the antipode of where I'm standing being land would be 29%. This same fact is true for every point on the land - so 29% of the land on that map should be orange. OK. But I don't see anything close to a third of the land being orange. Remember that this map projection makes greenland and antarctica look huge - when in fact, antarctica is about the same size as Australia...so forget that huge-looking orange patch in antarctica/greenland...it's tiny. So the only signigicant area of overlap is where the tail of South America overlaps China...aside from Borneo, that's really the only overlap of any significance! That looks more like 5% than 29% SteveBaker 19:07, 21 February 2007 (UTC)

Just for completeness, and to come back to JLdesAlpins' point, the uneven distribution does cause a slight wobble, simply by conservation of angular momentum. In the first instance, the Earth's rotation rate is affected (narrower objects spinning faster; if all the continents formed a band round the equator, for example, the day would be slightly longer). Indirectly, the effect is magnified by continents pushing against each other, raising mountain ranges or tearing deep rifts. Secondly, for similar reasons, our axial tilt is affected. The reason it's never mentioned is because the effects are pitiful, far smaller than we can measure. Take this BBC article and this Phsorg one (about the same event), for example. The effects caused by the continents sloooooowly sliding around are orders of magnitude smaller, of course (apart from those sudden jumps called earthquakes), so there's no 'wobble' to notice because what there is is taken as normal. Spiral Wave 21:23, 21 February 2007 (UTC)

Studies of Mars indicate that the planet is asymmetric about its equator. Planetary scientists still don't have a complete answer as to why this is. Nimur 04:13, 22 February 2007 (UTC)

[edit] Herpes

Where is research for a cure?129.112.109.250 17:37, 21 February 2007 (UTC)

Herpes#Future vaccines contains a couple of pointers - some of the external references in that article look promising. SteveBaker 19:38, 21 February 2007 (UTC)

[edit] nose bump

Hi...

Was wondering why some people have bumps on the nose. Is it genetic or a result of how your treat your nose? :) the Human nose article didn't seem to have any info on it.

thanks. --Spundun 17:51, 21 February 2007 (UTC)

It is mostly genetic. If your parents have bump then you have more propably bump. Jews and arabs have most usually bump at their nose. But it exists in Europe too. There is urban legend that if you pick your nose it will be bigger or have bump, but I dont believe in it. 193.65.112.51 20:26, 21 February 2007 (UTC)

You mean Blackheads? Abidh786 19:58, 21 February 2007 (UTC)

[edit] Megaphone

I am currently looking to buy a megaphone, i have come across the notation '25w' and '10w', i am presuming that the w stands for watts. This may be incorrect, so i would like some clarification on the matter, how loud exactly is 'a watt' or '10 watts' (some real life examples would be useful) and what would be an acceptable price for a megaphone, thanks in advance for any answers, Dave--88.111.82.185 20:13, 21 February 2007 (UTC)

A watt is a measure of electrical power, not sound level (that would be measured in decibels), and there is no simple mapping between the two beyond expecting a 25w megaphone to be louder, or perhaps more clear at high volume, than a 10w megaphone. Perhaps there is a local hardware store that would allow you to test some for yourself? — Lomn 21:50, 21 February 2007 (UTC)

Yes w stands for watts, but like with pretty much all electrical equipment, watts just means how much energy it uses, NOT how efficiently it turns that energy into the WORK the device is supposed to do. I've had a lot of experience with power tools and the same thing applies there, one well made tool can be a lot more powerful then a crappy made tool of the same kind with the same wattage rating. Also, the manufacturer is free to measure the wattage rating of their device however they like, meaning frequently what it says in big letters on the box is unrealistic and only applies to very certain conditions the manufacturer has managed to achieve in a laboratory. In fact, I would go so far as to say in a lot of cases, wattage should be completely ignored as it is mostly just misleading. Price and reputation are much better indicators of a products actual quality.Vespine 21:58, 21 February 2007 (UTC)

Thank you, both, for clearing this up. I think it is very misleading of the companies selling products such a this to use watts a sign of prestige, if the general public (ie me, albeit being only 16) cannot understand the significance of the numbers and presume,like i did, that a higher number will lead to a higher output something is terribly wrong. Any further information is still very much appreciated, thank you again for your time and effort in response as it has undoubtedly saved me a few pennies. Dave 88.111.82.185 22:15, 21 February 2007 (UTC)

Well.. true an efficient low-wattage device can be louder than an ineficient high-wattage device. but if you are comparing 2 megaphones of the same brand, that utilize the same technology, i think its a pretty darn safe assumption that the 25 watt one would be louder than the 10 what one. adam the atomTEC

Yes I don't disagree with the above. from the same brand you can assume that the 25w will be louder then the 10w, If you are however looking at two different brands of megaphone, then don't rely purely on the wattage, the only way to be sure is to actually hear it in action. Vespine 02:58, 22 February 2007 (UTC)

I work with audio amplifiers reasonably often. It's valid to say that loudness is a combination of physical intensity (accounting for distance to the source), psychological perception, and other factors. But, almost invariably, 25 Watt amplifiers are louder than 10 Watt amplifiers. Though the above comments voice legitimate concerns about manufacturers tolerance, variability, test conditions... that might matter if you were to compare a 25 and a 28 watt system... but it is unrealistic to assume that there could be such blatant order-of-magnitude errors. A 10 watt system will not realistically have so much variability that it could be louder than a 25 watt one. I mean, be fair; an engineer actually did design it to USE its extra wattage! Nimur 04:21, 22 February 2007 (UTC)

[edit] Eyeball Transplant

Is it possible to have eyeball transplants? Is it surgically possible to change iris color?

I don't think so, although there are a number of parts that can be transplanted. Notably, the cornea is often transplanted. I think the lens, too, but I'm less sure of that. I would imagine the 'wireing' needing to make the optic nerve function again is beyond current technology. As for the color, I would tend to doubt it. Take a look at Iris (anatomy), though. --Mdwyer 23:09, 21 February 2007 (UTC)

A surgeon would probably prefer colored contacts to change iris color; they are simpler and safer. When possible, invasive surgery is usually avoided. But cosmetic surgery has always pushed the envelope of common sense...Nimur 04:23, 22 February 2007 (UTC)

Sadly, optic nerve of a human (or any mammal) does not regenerate. I do not think a vision in a transplanted eye can be restored; however, I am a physicist, not a physician, so I am not 100% sure on that. I do know, however, that it is possible to develop artificial (electro-optic) light receptors that hook up directly to the (intact) optic nerve. Googling for 'artificial retina' returns plenty of hits. As for your second question, googling for 'iris transplant' returns some links that suggest that artificial iris transplants are now in clinical trials, so yes, it can be done; at least as an eyesight-saving surgery (and probably not as a cosmetic one). Cheers, Dr_Dima.

[edit] Is It Sinus Infections Untreated?

Can the above cause deformaties of the face? I can't remeber what insult does it. I'm pretty sure it's an infection, but I'm just going by my memory; if any of you can know better please let me know; as always, reponses on my talk page will be greatly appreciated. Thanks!100110100 22:09, 21 February 2007 (UTC)

Look at Sinusitis. We would give you our standard answer that you better go see a doctor! --Zeizmic 22:59, 21 February 2007 (UTC)

[edit] Water vs. Polaroid

This question is related to the one above. again, im comparing the qualities of water (with plenty ions) and other conductors. polarizing lenses have tiny conductive strands alligned in one direction. the electric feild induces currents in that direction, there by producing tiny amounts of heat and wasting the energy of the light, so only the light rays the perpendicular direction can get through.

Now consider this: salt water conducts in all directions! why does a hallow lense filled with saltwater (or a lens made of ice for that matter) let any light through at all? shouldn't the feild induce those currents and diminish the energy of the light?

Lets go back to the flashlight example from the question above. now thats two phenomena that should prevent a beem from being shone from inside the water onto something outside the water. why doesnt it do so in practice? -- Mr. Anony Mous

Conduction is more complicated than simply "conducting" or "insulating." You are already aware that some materials can be anisotropic - meaning different conductivity in each direction. There is also dispersion, which means that the transparency varies with frequency. (Or you could say the [[attenuation, the phase-velocity, or the index of refraction vary with frequency, however you want to think of it). Salt water is transparent to light wavelengths; in short, because it has no chemical or atomic components which interact strongly at those frequencies. Nimur 04:28, 22 February 2007 (UTC)

[edit] Dwarves, midgets and penises?

Do male dwarves and midgets have penises in proportion to the rest of their bodies, or are they roughly the same size as those of regular-sized humans? --90.241.43.72 23:36, 21 February 2007 (UTC)

I have no experience about this but I would quess they have normal size because dwarfness is a growth problem in bones and not in soft tissue like penis. Dwarfs often have normal sized nose, eyes and ears 193.65.112.51 23:52, 21 February 2007 (UTC)

It's no coincidence that male porn stars tend to be shorter than average -- it makes their equipment seem bigger. —Steve Summit (talk) 03:28, 22 February 2007 (UTC)

[edit] Cholera

WikiProject Reference Desk Article Collaboration This question inspired an article to be created or enhanced: Cholera toxin Please consider contributing

What is known about choleras stucture?

A good bit, actually. Cholera is caused by the bacterium Vibrio cholerae; it's a curved rod shape, with a flagellum for movement. These bacteria secrete an enterotoxin called (rather uncreatively) cholera toxin. This link has some more detailed information about the molecular structure and function of cholera toxin. TenOfAllTrades(talk) 00:59, 22 February 2007 (UTC)

Just a note—I've created the article cholera toxin, if anyone wants to add to it or clean it up. TenOfAllTrades(talk) 04:07, 22 February 2007 (UTC)

And now we have an article on the more general topics of AB₅ toxins, too. Feel free to contribute. :D TenOfAllTrades(talk) 05:36, 22 February 2007 (UTC)

[edit] Voltage Conversion

In the telephone exchanges,a voltage of -48v DC is used to prevent corrosion.Any idea how is that converted to positive voltage for use in the electronic circuits???

I don't think the voltage was chosen "to prevent corrosion" so much as it was just a handy voltage, high enough to allow a reasonably-long subscriber loop while still being low enough to be reasonably safe and easy to store on lead-acid batteries.

In any case, to answer your question, lots of telephone equipment operates directly on -48V. And modern electronic equipment simply uses DC to DC converters to convert the 48V to any voltage that is needed. because of its widespread use in the telephone industry, you can get all sorts of electronic equipment that runs directly from 48V or converts 48V to other voltages.

Atlant 12:13, 21 February 2007 (UTC)

Voltage is simply electronic potential. Like all measures of potential energy, it is only meaningful in terms of some reference value (except in certain quantum applications). -48 V simply means that the line is 48 V below the reference point (probably ground). It is equivalent to say that the reference has a potential 48 V higher than the line. Sometimes people will refer to ground as having "zero volts" potential, but this is a little bit misleading since ground itself has a voltage with reference to some other point. The sign on voltage has no special meaning; it only indicates which point has the higher potential. -- mattb @ 2007-02-21T17:29Z

In other words, if you want to get 48 VDC from -48 VDC, just switch the positive and negative leads. -- mattb @ 2007-02-21T17:42Z

Unless you are connecting the things to wall-socket power - or allowing people to come into contact with metal parts of the appliance. But in the case of telephones, there are two wires that form a loop from the telephone exchange, through the phone (when the handset is 'on hook') and back to the exchange. This is a 'current loop' interface. With old fashioned phones with mechanical bell, the high voltage was actually used to drive the solenoid that made the bell ring. Since you could be many, many miles from the exchange, they needed to deliver enough voltage to ring the bell despite the voltage drop due to the resistance in those long wires. Worse still, when telephones were first invented, the joins in the wires between the exchange and your phone weren't soldered together - they were just twisted together. Since the wires are frequently run underground - there is a lot of scope for water to get into the wiring. A really robust amount of power is needed to punch through all that nastiness. SteveBaker 19:49, 21 February 2007 (UTC)

The current which rings the telephone is alternating current, not the stated 48 volts of DC. Since it is a current loop, the phone company has a high enough resistance in series with the 48 volt battery to limit the current to a small fraction of an amp. (I have measured around 39 milliamps from a 52 volt phone line). My voltage with the receiver off-hook rises to 79 V DC. A typical U.S. phone may receive a 20 Hz AC signal at 60 volts RMS while ringing. If water gets into the undergroung cable, the voltage is likely to short to ground or between conductors, so higher voltage is not a cure for poor insulation, but it does help the signal to get through the long run of small wire. Early (19th century) phone wires were single pole, with earth return, like telegraph wires, but they soon found that twisted pairs greatly decreased the inductive noise pickup and crosstalk between calls. Paper insulated cables inside a lead sheath were used widely well until late in the 20th century (may still be for all I know). Edison 21:24, 21 February 2007 (UTC)

It's not the voltage itself which prevents corrosion, it's the polarity. Using a positive potential relative to the ground would cause faster corrosion of the terminals; the negative potential prevents that (IIRC, that was more of a problem when a single wire was used instead of the current twisted pair). --cesarb 23:39, 21 February 2007 (UTC)

In any case, the polarity of the phone loop actually reverses at several points during the progress of a call. —Steve Summit (talk) 03:33, 22 February 2007 (UTC)

Not generally, athough that was the principle used to control some payphone (coinboxes); the solenoids that "collected" or "returned" the coins were polarity sensitive.

Atlant 13:27, 22 February 2007 (UTC)

It may have changed over the years, but once upon a time, the tip/ring polarity reversed once when the call was connected, and again when it was disconnected. This was used by, for example, 1A2 "key system" phones (the classic old 5-line "kachunk-kachunk" phones, with the mechanical-seeming hold button) to detect when the calling party waiting on hold had gotten tired and hung up, so that the hold circuit could release. I've seen these polarity reversals myself, and designed my own circuits that depended on them. (You're right about payphone coinboxes, though, and there are some fascinating stories about those...) —Steve Summit (talk) 23:56, 22 February 2007 (UTC)

[edit] In the Middle of It

What would it be like to live in the dead center of a neutron star? [While totally disregarding, of course, how one gets there in the first place.]--JLdesAlpins 17:56, 21 February 2007 (UTC)

Assuming it were hollow, you'd be weightless. — Lomn 18:08, 21 February 2007 (UTC)

If it's not hollow, however, you'd be crushed by matter heavier than any matter on Earth. Think of it this way. Matter on Earth contains vast expanses of vaccuum. Even the most solid objects on Earth have large gaps between individual atoms, and atoms are almost entirely empty space, with extremely dense electrons and nuclei. Now think about a neutron star. There's almost no space between atoms, and the usually empty space between atoms would be all crammed into an area the size of a nucleus. In fact, it would be so dense that individual neutrons would make up the matter, and there would be almost no space between them. That's a star heavier than the sun, but as small as a city. A small stone dropped on it would release as much energy as an atom bomb. Hope this helps. AstroHurricane001^{(Talk+Contribs+Ubx)} 18:43, 21 February 2007 (UTC)

If you are interested in the freakish nature of neutron stars, I'd actually make the unusual step of suggesting that you read a SciFi book: Dragon's Egg by Robert L. Forward (who was a physicist) - and if you enjoy it, it has a sequel: Starquake. The author described the book as "A textbook on neutron star physics disguised as a novel". The story is about teeny-tiny fast-living creatures who live on the surface of a Neutron star - and the slow-moving humans who come to study them. Sure, it's SciFi - and some liberties are taken with viable fact - but it's a great way to come to grips with the whole weirdness of these things. SteveBaker 19:33, 21 February 2007 (UTC)

But right in the centre gravity will be much less than on the surface:)

I'm afraid Lomn got there first, my nameless friend: assuming you could make such a cavity, you'd not just weigh less, but be completely weightless at the centre. Spiral Wave 23:59, 21 February 2007 (UTC)

Neutron stars are 'liquid' inside...well, a freakish neutronium analog of a liquid anyway. But supposing you were in a little chamber at the center - I think the tidal forces would be pretty serious. With all the mass of a typical star crammed into 12 miles, the gravitational forces would increase dramatically within just a few feet from the exact center - so I think you'd still be squished. SteveBaker 04:43, 22 February 2007 (UTC)

It depends upon the particular neutron star. If it's a slow rotator, then as long as you're within a hollow spherical chamber, you're fine; there can be no net gravitational force at any point in the chamber, and so no tidal forces. Newton's shell theorem saves you, neutron stars being about as close to spherically symmetric as anything in the universe. If it's significantly unspherical you might run into trouble, but it'd need to be a pulsar, probably even a millisecond pulsar, to have any significant oblateness, the typical deviation being less than a tenth of a millimetre even then. Spiral Wave 10:49, 22 February 2007 (UTC)

Surely the rotation only helps the forces in the direction of the star's equator - you're still getting tidal forces from the north and south poles of the star. I don't think rotation helps you much. SteveBaker 10:58, 22 February 2007 (UTC)

I don't get you, sorry. Have I explained myself poorly? I meant that rotation is bad for our intrepid explorer, so I'm not sure what you mean about it not helping much. If it's spherical, it doesn't really matter what or where you call the poles. It's the deviations that kill you, be it directly from oblateness or indirectly through starquakes. Spiral Wave 11:21, 22 February 2007 (UTC)

Yeah - you've confused me no end! If it's rotating then we can define the terms "pole" and "equator" by analogy to the way we use the term on Earth. I wasn't thinking about oblateness (which might indeed be utterly negligable) - I was thinking of the effects of centrifugal forces on (a) the pressure of the liquid code and (b) the centrifugal force on our poor neutron-star-engulfed victim (which would tend to reduce the gravitational forces in the parts of his/her body that are further from the axis of rotation of the star. But it's all pretty silly - you can't survive the tidal gravitational forces in something 12 miles across that weighs as much as an entire star...period! SteveBaker 18:34, 22 February 2007 (UTC)

Hi Steve, Please read up on the shell theorem that Spiral Wave provided a link to. Or maybe it is easier to understand the electrostatic equivalent: a spherical shell of electric charge produces zero electric field in its entire interior cavity. This follows immediately from spherical symmetry (any field would have to be radial) and Gauss's law (the total electrical flux out through a closed surface is proportional to the charge inside). Because there is no charge inside any imagined surface in the cavity, there cannot be any electric field at any point there. Since gravity follows the same distance-squared law as electrostatics, the same is true there: a spherical symmetric hollow shell, of any thickness and density, produces exactly zero gravitational field inside the cavity. Thus there would be no tidal forces at all. Spiral Wave referred to rotation not because of centrifugal force on you (which would only matter if you rotated inside the star), but because it would cause the star to become oblate, and thereby break the perfect spherical symmetry assumed by the theorem. --mglg_(talk) 22:49, 22 February 2007 (UTC)

Bingo. I see what happened now - I made it messy by saying "slow rotation". I was simply assuming there would be some rotation - there always is - so it was a case of slow vs fast, rather than non-rotating vs rotating, which would be the ideal. I didn't mean to imply that slow rotation was better than none. Sorry for the confusion. Spiral Wave 00:04, 23 February 2007 (UTC)

[edit] Electromagnetic sheilding

OK, if you put a radio inside a fine wire mesh cage or a metal box, it doesnt work. From what I learned in university physics, this is because the "electro" part of the electromagnetic feild causes charge movements in the wire mesh that create an opposite electric feild, which makes them cancel out, so it essentially sheilds the radio. obviously, this wouldnt work with a plastic wire mesh: it only works because its a conductor.

Now consider this: a waterproof flash light is submerged in saltwater. it can shine on something outside the water. similarly, a submerged camera can film something outside the saltwater. WHY? would a radio be able to transmit/recieve from under saline water? does sheilding not occur because its light in stead of radio waves (which only differe by wavelength and frequency) or because its saltwater instead of metal (which are both good condctors..so that would be kinda wierd) ? --Mr. Anony Mous

Look at Faraday cage --Mdwyer 23:09, 21 February 2007 (UTC)

Maybe Transparency (optics) is more what you want? I think you might be close to the answer though. The difference between light and radio seems to be just wavelength and frequency, but I think you start getting into the range of quantum mechanics if you look too closely. Radio generally acts like a wave. But light acts as if it is a particle.

Finally, you might also look at color. Salt is a bad example, but the reason that many dyes appears to be a certain color is because they tend to absorb only specific frequencies of light. --Mdwyer 23:35, 21 February 2007 (UTC)

Also, the bottom of the article on electromagnetic shielding touches on differences in frequency. It takes time for the "cancelling out", and at higher frequency (light is much higher frequency than radio waves) there isn't enough time so most of the radiation gets through. adam the atomTEC 23:40, 21 February 2007 (UTC)

See also plasma frequency; the fewer ions present, the slower they react and the less capable they are of rejecting EM radiation (that is, they reject only lower and lower frequencies). Water is not exactly a plasma, but the same sorts of considerations apply; the mere ability of charge to flow at all does not imply that it will flow in a manner that destroys incident EM oscillations. Yet more: radio waves are larger than the spaces between the wires; microwaves are larger than the spaces in the grill of most microwave ovens; visible light is quite tiny indeed and may very well simply pass between ions for quite some distance, at which point they're entirely irrelevant. (I don't actually know the mean time between "close" approaches to an ion in normal salt water, but it's at least illustrative even if the other reasons are more important.) --Tardis 00:29, 22 February 2007 (UTC)

The word you are looking for is attenuation. Visible light and radio waves are the same thing. They differ only in the degree of attenuation in a particular medium. 202.168.50.40 00:15, 22 February 2007 (UTC)

Regarding the Faraday cage, you need only consider Gauss's law, one of Maxwell's equations (remember, practically any problem in classical electromagnetics can be described with Maxwell's equations). Basically, since a conductor tends to equally distribute charge on its surface, there is no net electrical field within a closed conductive surface. With respect to your second question, you're talking about a totally different situation since the water doesn't actually take the form of a closed, hollow, conducting surface that is the defining trait of the Faraday cage. -- mattb @ 2007-02-22T00:54Z

Also, salt water isn't really that great of a conductor, at least not compared to metals. Check out the chart at Electrical conductivity - the conductivity of various metals is on the order of ten million times greater than that of seawater. Chuck 21:37, 22 February 2007 (UTC)

Answer 1: The material property you are asking about is the attenuation length, or skin depth. It depends (in a complicated but decreasing manner) on the ratio of electrical conductivity to the frequency of the electromagnetic wave, see Eq. 3 of skin depth. Sea water has much lower electrical conductivity than metals, and light has much higher frequency than radio waves. Thus the water-light combination yields a quite long attenuation length (i.e. water is more or less transparent to visible light), whereas the copper-radio combination produces an extremely short attenuation length (i.e. copper does not transmit radio waves very far at all, but reflects (and partially absorbs) them almost immediately).

Answer 2: The parameters that go into the expression for the skin depth (which, in addition to electrical conductivity, also include the dielectric constant and the magnetic permeability) actually themselves depend on frequency, and therefore make the skin depth depend in a much more complicated way on frequency than Answer 1 would have you believe. But in the radio regime answer 1 works, so water is more transparent to low-frequency than to high-frequency radio waves. For this reason, ultra-low-frequency radio has been considered for communicating with submarines. --mglg_(talk) 21:56, 22 February 2007 (UTC)

[edit] February 22

[edit] Chemoluminescence again

You know these stars and stuff that glows in dark after being exposed to light? Is such material possible to be boosted somehow so that light gets more powerful? Is it possible to make them glow without first exposing them to light, for example with heat or electricity? Sorry about stupid question 193.65.112.51 00:02, 22 February 2007 (UTC)

• There's no such thing as a stupid question! Impossible without first exposing it, because that would be creating energy from nothing... unless ofcourse there's an alternate source of energy (discussed later bellow). As far as boosting it, again you can't get more energy out than you put in, so the only way would be if a material could store it over a long period of time then release it with one big glow (ie a flash), and there is no glow-in-the-dark material that does that. As far as alternate way to charge up, sure there is. Some high-end watches contain small amounts of radioactive material in the paint used on the hands, and dots at 12/3/6/9 hours. The decay of this material fuels the glowing, so you don't have to expose it to light first. It will eventually stop glowing when all the radioactive material decays, but that's usually longer than the life expectancy of the watch itself. You also asked about heat--Yes! thats called a light bulb. The heat makes the metal filament glow. Ofcourse, you need very high temperatures... so its not suitable for glow in the dark stickers and what not :-P With electricity, well again, that's basically a light bulb. Electricity flows through metal, causing it to heat up, causing it to glow. I hope that answers your question adam the atomTEC 00:29, 22 February 2007 (UTC)
  • (edit conflict) Because types of electromagnetic radiation with shorter wavelengths (e.g. UV, X-ray) deliver more energy in the same amount of time as other types (e.g. infrared, radio), you can charge a glow-in-the-dark object faster under a UV lamp, although this is not "without exposing them to light", as visible light is another wavelength. My science teacher once taught my class this by exposing two glow-in-the-dark stars to blue and red lights, and the blue one glowed brighter. - AMP'd 00:32, 22 February 2007 (UTC)
    • Good point AMP'd... its not exposure to light, but still exposure to electromagnetic radiation. The bottom line is, you need some source of energy, and the light energy produced can't be more than the energy absorbed in charging it. adam the atomTEC 00:41, 22 February 2007 (UTC)

Above, it was discussed that electricity can heat a filament. Electricity can also cause a light emitting diode to operate. The operation is more complicated; but essentially, electricity is converted directly into light (without heating anything to blackbody radiation). This is because the semiconductor material is constructed to have an energy transition exactly equal to the radiated light. Above all, energy must be conserved; secondarily, a practical way to convert energy must exist; but otherwise, any form of energy (kinetic, chemical, springs...) can theoretically be converted to light. Nimur 04:31, 22 February 2007 (UTC)

Thanks for answers! What happens if I put glow-in-dark stars to microwave oven? Is microwave close enough to light wave to make same effect or are they different? 193.65.112.51 07:49, 22 February 2007 (UTC)

A microwave is much too low-frequency. As a general rule, lumenescence requires that the material be exposed to a light of the same or higher frequency as the light it emits. A heat lamp, which glows mostly in the infrared, might work. An ordinary flashlight will work well. An ultraviolet light will work extremely well. --Carnildo 20:54, 22 February 2007 (UTC)

You might also melt the star if it's not microwave safe...in fact, that's all that the waves in the lower part of the electromagnetic spectrum (infrared, microwave, radio) do - heat things up - AMP'd 21:48, 22 February 2007 (UTC)

[edit] Denatonium

What structural feature of denatonium makes it an unbearably bitter compound? Also, if it is swallowed or taken up by the body (which admittedly is unlikely), what dangers will it pose? Superfly2005 19:58, 22 February 2007 (UTC)

Bitterness is sensed by a type of taste chemoreceptors on your tongue. Receptors are molecules that act like a lock that only fits a certain type of key: if it encounters that precise kind of key (the receptor's target molecule, or ligand), the receptor signals its cell (which then signals the brain) that a target has been found. Thus you feel a bitter taste if there are molecules in your mouth that bind to bitterness receptors. Presumably denatonium fits these receptors very well, and binds to them strongly. Ditto for saccharin and sweetness receptors, etc. --mglg_(talk) 22:05, 22 February 2007 (UTC)

Our denatonium page mentions the lack of health risks. It appears to bind to a G protein-coupled receptor, a type of protein that can be hard to analyze structurally. Would probably be more productive to try QSAR to explain the bitterness. There's active current research to try to understand the receptor specificity and biochemical signalling (for example, PMID 17253962 and PMID 16195580) but not sure about the ligand itself. DMacks 06:38, 23 February 2007 (UTC)

[edit] Nose grease: is this article for real?

Hi.... I bumped into this article... and doesn't sound like a wikipedia article at all... Is that a hoax?

Thanks .. --Spundun 00:09, 22 February 2007 (UTC)

It survived an AfD. Check out the sources linked to in the footnotes / references section. -- Consumed Crustacean (talk) 00:11, 22 February 2007 (UTC)

No sir, valid article. The uses certainly seem bazzaire but hey, it's well-documented.adam the atomTEC 00:36, 22 February 2007 (UTC)

My grandfather taught me to use it to lubricate the ribbon holder on a manual typewriter, an application which I concede has seen rather dwindling use over the years since I learned it... —Steve Summit (talk) 03:20, 22 February 2007 (UTC)

I wonder if there is any possible practical use for gooch grease? :) --Kurt Shaped Box 01:05, 22 February 2007 (UTC)

How does nose grease differ from cheek grease or forehead grease? Isn't it the same grease? 193.65.112.51 07:50, 22 February 2007 (UTC)

The article confirms that nose grease is different, in that it contains more squalene than oil from other parts of the skin. This is even verified from a reliable source! --Charlene 15:53, 22 February 2007 (UTC)

[edit] Extraction of Upper Incisors

Both my upper incisors fall behind the lower incisors and to say the least they're pretty wonky. This is due to extra teeth coming through when i was younger. Now the upper right incisor is long and almost looks normal, but the upper left incisor shorter and placed higher up in the gum, which makes it look like i've chipped the tooth. I also have a underbite.

I've been to the dentist who referred me to the NHS who said I can have treatment, but told me I would have to wear a brace and have an operation on lower jaw, but they say it could take up to 3 years. The dentist at NHS said it would even be difficult for me to have dentures because the bottom set of teeth slanted backwards to compensate for the underbite. Are they just being funny?

Do you think if i was blunt with a dentist and asked them to extract the upper incisors would they do it?

No one here can tell you that extracting your upper incisors is a good idea if your dentist has recommended against it. If you are unsatisfied, seek a second opinion. . Vespine 02:44, 22 February 2007 (UTC)

• Why would you want teeth extracted if their position can be corrected? If dentures are gonna be a problem for you, removing them would leave a hole in your teeth. They're the experts, so I doubt they're being funny, but you can always ask for a second opinion. Personally, I'd be glad it can be solved without extraction. - Mgm|^(talk) 08:42, 22 February 2007 (UTC)

There could be a reason you would want to extract a superficial tooth. It would make spaces between teeth and your mouth less crowded; bacteria would have less opportunity to build a living room. I know every dentist cringes when she has to extract a healthy tooth, but I was in a similar situation, and now I'm glad I did it. A year afterwards, the free space was near completely filled from left and right by neighbouring teeth, and now it's as if there was nothing. --Rwst 15:18, 22 February 2007 (UTC)

[edit] Smelly retainers

Ok, so I wear upper and lower retainers, and have since my orthodontic braces were taken off. When I take them off they smell funny. Not funny. They smell like semen. I perceive this as a possible problem, with the possibility of my breath smelling that way, and the smell is very strong if I leave them out. Only while they are wet. What is going on? And, no, I haven't been swishing around semen in my mouth :) [Mαc Δαvιs] X (How's my driving?) ❖ 05:08, 22 February 2007 (UTC)

Gross.Nimur

Some website [2] actually suggests using denture cleaner tablets. -- Consumed Crustacean (talk) 05:14, 22 February 2007 (UTC)

I've heard you should leave them overnight in lemon juice. zafiroblue05 | Talk 07:37, 22 February 2007 (UTC)

I like that idea! I love to eat lemons :) [Mαc Δαvιs] X (How's my driving?) ❖ 20:36, 22 February 2007 (UTC)

You can buy retainer cleaning tablets. Fill a glass with water, pop one in and put your retainers in. The tablet fizzes up like Alka-Seltzer. — Matt Eason ^{(Talk • Contribs)} 10:40, 22 February 2007 (UTC)

My orthodontist recommended soaking them in mouthwash once a week. --Carnildo 21:05, 22 February 2007 (UTC)

And, no, I haven't been swishing around semen in my mouth — at least, you're not aware of it if you have been. ;-) ... :-P --24.147.86.187 00:00, 23 February 2007 (UTC)

[edit] Outermost electron shells

What proof is there, that the outermost electron shells directly affect their properties?

By "their", I think you mean chemical properties. For this, you can look at the periodic table, which groups chemicals based on the number of outermost electrons (each row is a new group of outer electrons). The "proof" is probably better stated as 'evidence of trends' - metals appear in columns; similar chemical reactions occur in columns; color, shininess, density, appear to follow trends in columns. Hopefully this helps. Nimur 05:58, 22 February 2007 (UTC)

It's the other way round - by studying the properties of elements it's possible to infer that the outer electron shells have certain properties. There is no proof. The structure of the atom an electron shell rules etc are all infered based on observations...87.102.9.28 15:36, 22 February 2007 (UTC)

[edit] Physics/collisons

What articles can I read here that will tell me more about softer collisions/ones that supply less force over an occupant (eg air bags in a car)? Cuban Cigar 07:33, 22 February 2007 (UTC)

Pressure? Momentum? Force? 213.48.15.234 09:41, 22 February 2007 (UTC)

I can't think of anything specific - but the thing to remember is that F = m.a - Force equals mass times accelleration. If your mass is constant (which it must be) then the only thing you can do to reduce the force in a collision is to lessen the accelleration. When something hard like your head hits something solid like the dashboard of your car, you have to decelerate from whatever speed you were going to zero in whatever distance the dashboard deforms over. If v is your initial velocity, a is your accelleration and s is the distance over which you are stopping then a = v²/(2s) ... So if it has a centimeter of padding and your head hits it at say 10 meters/second (20mph or so)- your accelleration is (10x10)/(2x0.01) which is 5000 meters/sec² - which is over 500 g's! But if the airbag deploys in time - then you are slowing down over a distance of perhaps 10 centimeters instead of 1 centimeter. The accelleration is ten times lower - about 50g's - and the force is ten times lower too. So the first thing to look at is whether the material can collapse over a sufficiently large distance to slow down the impacting object with less accelleration. Of course it also has to be strong enough to resist the force being applied to it. A kid's balloon might be the same size as an airbag - but it's fairly weak - so if you hit that instead of an airbag, it would theoretically be able to decelerate you safely - but not if it can't withstand the impact forces and pops instead of absorbing the collision. In modern cars, they aim to use the forward structure of the car to absorb the impact too - hence all of those 'crumple zones' - which increase the distance over which you are slowing down by using the structure of the car itself to absorb the energy. People like the idea of driving big, solid tank-like cars with lots of metal...but if those don't crumple intelligently, they are more dangerous than a car that collapses nicely. So if the bumper and the crumple zones can collapse by 10 centimeters and the airbag can slow you down over a further 10 centimeters - then you've halved the forces on the passenger's head compared to the airbag alone. SteveBaker 10:50, 22 February 2007 (UTC)

Well Baker's comments are actually quite helpful (because they're writtn in plain english). Thanks to all who helped.Cuban Cigar 11:02, 24 February 2007 (UTC)

[edit] optics

i waant to knowabout proof of magnetic character of light ifany..

Short answer: Light isn't affected by magnetism at all.

Longer answer: Light is made of photons - and photons have no electric charge. Magnetism exerts a force on particles given by:

F = q v B

where

q is the electric charge of the particle,

v is the velocity of the particle, and

B is the magnetic field.

But the charge on the photon ('q') is zero - so the force ('F') is also zero no matter the size of the magnetic field or the speed of the particle. In other words, photons are not affected by magnetic fields - light isn't bent or otherwise distorted by magnets.

SteveBaker 11:32, 22 February 2007 (UTC)

What SteveBaker says is true; however, in case you're asking a different question, see electromagnetic radiation. The "magnetic" is there for a reason: light is a system of oscillating electric and magnetic fields that regenerate each other in the direction that the light is travelling. In that sense light is quite magnetic. --Tardis 14:46, 22 February 2007 (UTC)

The plane of polarization of light is affected by magnetism, as found by Michael Faraday in 1845. See Faraday effect. Faraday did a long series of experiments attempting to demonstrate relationships between different forces, following his findings that related magnetism and electricity. He also attempted to find interactions of these fields with gravity, unsuccessfully. Edison 15:22, 22 February 2007 (UTC)

1. If your question was 'how can I convince myself that light, as we know it, is actually an electromagnetic radiation?', see light and diffraction. 2. If your question is 'does light interact with magnetic field in vacuum?', the answer is 'theoretically, yes, but that is very hard to observe'. I can think of two ways photon can interact with magnetized vacuum. The first one is a conversion of photon to an axion in presence of a strong magnetic field (note that there is no proof axions exist; they may just as well not exist at all). The second way that can happen is by a virtual electron-positron pair production in presence of a very strong magnetic field (this was proposed theoretically but I am unaware of any experimental observarion of vacuum lensing or birefringence in presence of a very strong magnetic field). 3. Finally, if your question is 'does light interact with magnetic field in matter?', the answer is 'yes, indirectly'. See Zeeman effect and Faraday effect for starters. Hope this helps. Dr_Dima.

Okay, I am out of my league in this one, but my guess is that polarization can be affected by magnetic fields. This is simply an extension of the effect on lower frequency microwave radiation via a circulator. Ooh and the article confirms it. Ferromagnetic garnet crystals. Cool! --Tbeatty 05:09, 23 February 2007 (UTC)

[edit] microorganisms

Explain how humans can harbor many microorganisms on and inside their bodies without experiencing symptoms of infection?

You may want to look at our article on gut flora as one aspect of this concept. TenOfAllTrades(talk) 15:10, 22 February 2007 (UTC)

The relationship of any two organisms can be symbiotic, commensal, or parasitic; the relationship of bowel flora to humans is an example of symbiosis; of skin flora to humans is an example of commensalism; infecting organisms are an example of parasitism. You may want to have a look at our article, bacteria in the human body. - Nunh-huh 23:16, 22 February 2007 (UTC)

Imagine you are a bacterium - what you want to do is spread - make as many more bacterium just like you as you can. If you kill off your host - or make them so sick that they can't function - then you and all of your progeny are probably going to die along with your host. From the perspective of a bacterium - your best strategy is to spread as much as you can without harming the host too much - and hope that you can eventually spread to another human. This strategy is the way most bacteria have evolved - so they live inside us quite happily - moderating their growth rates and their demands on our bodies so that they don't do terrible damage. Our gut flora have gone a stage further - actively helping us out to allow their host to do better. This isn't true of all microorganisms - but a good fraction of them do that. It is notable that many diseases that initially cause a high rate of fatality soon evolve to be less nasty to their hosts. One of the huge concerns about new flu strains like 'bird flu' that are on the point of jumping species to become human diseases is that they have not yet evolved to lower their fatality rates. This is why new and rare diseases are often so very serious. SteveBaker 13:01, 23 February 2007 (UTC)

[edit] Juvabional

Hello, Google gives 50 hits but doesn't explain what's a juvabional chemical substance. Where does it come from? Dr. Duke's Phytochemical Database spits out this term for a bunch of substances. Is it some activity on the body, or is it something like 'antifungal'? Even better would be the exact meaning. Thanks --Rwst 15:01, 22 February 2007 (UTC)

Juvabional seem to mean "having the effect of juvabione". Juvabione is apparently an insect hormone, presumably (from the name) affecting some aspect of physical maturation. I dont know what effect (accelerating or inhibiting) or what aspect (transition from larva, or growth, or lifespan, or whatever), but maybe this will help you know what to look for). alteripse 17:15, 22 February 2007 (UTC)

Juvabione is one of the juvenile hormones. DMacks 17:24, 22 February 2007 (UTC)

From reading around the subject, it seems like it's an ingredient of some insecticides - it works by preventing the insects from developing past the larval stage - which stops them from breeding. Our article on juvenile hormones suggests that this stuff can be added to drinking water - so one would assume that it either has no effect on humans - or the effects are not too serious. SteveBaker 18:39, 22 February 2007 (UTC)

[edit] Acetaminophen

Copied from the Villiage Pump ~ ONUnicorn 19:37, 22 February 2007 (UTC)

Does amoxicillin have a reaction with acetaminophen? --myselfalso 00:24, 22 February 2007 (UTC)

Nothing can be seen at Beta-lactam antibiotic, but keep in mind that Wikipedia does not give medical advice. --Mdwyer 20:44, 22 February 2007 (UTC)

The question asked for information, not advice. There is no significant interaction between acetaminophen and amoxicillin; the two drugs are used together routinely. - Nunh-huh 23:09, 22 February 2007 (UTC)

[edit] Questions?

Does anyone know "the current state of health cARE in the US"?

tHANKS

Guess what? There is an article called Health care in the United States. So the short answer is yes, and the longer answer is in Health care in the United States. GB 23:10, 22 February 2007 (UTC)

Actually, the short answer is "Great if you have money, appalling if you don't". --169.230.94.28 23:55, 22 February 2007 (UTC)

It's pretty desperate. I'd say: "Great if you have money - or health insurance as a part of your job - appalling if you don't". There are 'safety nets' (Medicare (United States) and Medicaid) of sorts to provide health care if you are elderly, disabled or live below the poverty line and have children - but that means that if you are moderately well off but without health insurance then if you do get some serious problem you'll be paying for it until you ARE below the poverty line! As a case in point, I knew a married couple (no kids) - the wife was a school teacher, the husband a house painter. Neither had health insurance as a part of their jobs - and it would have eaten about half of their income to purchase it - so that was out of the question. But they had a reasonably 'average' income - a rented house, two cars. The wife developed some kind of inner-ear condition that made her dizzy and nauseous. She was soon unable to work - ran out of sick leave and lost her job. They were too well off for any of the 'safety nets' and testing to discover what was wrong ended up costing them $6,000 - which was pretty much their entire savings. With her no longer able to work, they were now trying to live on half of their former single income and had to move out of their nice neighbourhood into somewhere much nastier and cheaper. Furthermore, the treatment for her condition involved lots of drugs and an operation - total cost estimated at $8,000. Since they couldn't afford that - and nobody would lend them it - they had no choice but for her to remain desperately sick and to slide gradually downhill into poverty - selling whatever of their posessions they could until they were so badly off that they could get some kind of basic coverage from charity organisations (their church). It's been ten years now and they still aren't able to get back to where they were from a relatively simple inner ear problem! It literally ruined their lives. I'm British (living in the USA) - and whilst we Brits complain about our national health system - it's huge merit is that it doesn't allow this kind of disaster to happen to people. SteveBaker 12:48, 23 February 2007 (UTC)

A couple of minor quibbles: most two-"average" income couples can afford basic health insurance if they wish to-- they just would rather spend the money on something else, especially if in their twenties and feeling like health problems happen to someone else. One of the main arguments for universal coverage is that it would prevent people from choosing not to have coverage to preserve more money for what most of the world would consider luxuries. Second, no one else would describe a condition that prevented employment and required surgery and lots of drugs costing $8000 as a "relatively simple inner ear problem". alteripse 13:38, 23 February 2007 (UTC)

Not wanting to put words in people's mouths, but I believe "relatively simple" meant a doctor could solve it without too much fuss, if someone paid. Skittle 14:44, 23 February 2007 (UTC)

I would sum up US healthcare as (1) expensive, compared to rest of the world, (2) highly uneven, in quality, accessibility, and cost-effectivenss, and (3) oriented toward individual people with problems rather than public health. The unevenness includes some of the best care in the world for conditions not even treatable in much of the world but also some failures to make some more fundamental services universally available. alteripse 13:48, 23 February 2007 (UTC)

[edit] Balancing a bicycle

Why is it (relatively)easy to 'balance' on a moving bicycle and the same, impossible on a standing cycle?

We all know this.... i just want to know the physics behind this everyday action

How can we easily balance ourselves (stay upright) on a moving bicycle (or bike) but the same thing is impossible when a try on a stationary two-wheeler? _________________

i did some re-searching and it looks like its not entirely 'angular momentum' as in the case of a top and also not entirely the gyro effect either... http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

all the facts are here... i can almost see the answer forming but not quite there... help me out - somebody pls put this phenomenon in nice understandable sentences

Thanks a lot

Seethahere 21:21, 22 February 2007 (UTC)

Contrary to a common belief, angular momentum (the gyroscope effect) has (almost) nothing to do with it. The main point is that you have an effective means of controlling your balance when moving, but not when standing still. It works like this: suppose your bike is starting to lean over slightly to the left (i.e. your center of mass is to the left of the line between the wheels' contact points with the ground, which is the axis you would pivot around if you were to fall over). Thus you are (your center of mass is) starting to fall over towards the left. When you notice this, your learned bicycling skill makes you make a nearly unconscious correction, by turning the handle bar slightly to the left. This causes your front wheel to move to the left under you, until the line between the wheels' contact points is once again vertically under your center of mass. In other words, you have regained balance. This correction doesn't work if you are standing still, because turning the handlebar doesn't then cause the front wheel to move sideways. --mglg_(talk) 21:36, 22 February 2007 (UTC)

Ok, that is one of the most complex articles ever, for something so simple. Bikes have self-stability. That means if you just hold a bike still, you can make it steer left or right by leaning it. You can ride a bike without hands, and steer just by leaning. It's a bit like a skateboard. --Zeizmic 23:27, 22 February 2007 (UTC)

Sorry I don't believe it, a well "ghostied" bicycle will go forward without a rider for a long time without falling over, which obviously has nothing to do with slight, almost unconscious steering inputs from the rider. I've ridden both bicycles and motorcycles a lot in the past and definitely there is more to it then 'corrections' made by the rider especially on a motorcycle that's going at speed, so much so in fact that when you TRY to turn the motorcycle and then release the pressure the motorbike will return on its own to travelling in a straight line. Can you source your assumption of gyroscope effects not having much to do with it? Vespine 23:48, 22 February 2007 (UTC)

http://www2.eng.cam.ac.uk/~hemh/gyrobike.htm Skittle 10:43, 23 February 2007 (UTC)

Ah, ah. No complaining, unless you made a pretext of reading that long, long, article! :) (which covers this particular turning thing somewhere..) --Zeizmic 01:01, 23 February 2007 (UTC)

The principle is correct, but there's no unconscious inputs involved - the stability comes from the bike turning itself. The horizontal "trail" (as pictured) is the key. Explaining the details of it is beyond me, but the gist of it is that when the bike starts to lean, the trail causes the wheel to steer into the turn, straightening it up and preventing the fall. It only works above a certain minimum speed, but it's why you can let go of the handlebars and not fall over. There's no special skill involved; the bike is genuinely driving itself.

Apparently a lot of time and money goes into getting the trail right, to ensure stability. I saw a really good explanation of this very recently, but I can't for the life of me remember where. If it springs to mind, I'll post the link. Spiral Wave 01:08, 23 February 2007 (UTC)

Might it have been in New Scientist, in the "The Last Word" section? I've linked to a bit of it, although I don't know how well this will work for those without a subscription. It also provides an answer for those who don't believe how little effect the gyroscopic effect has: a bike designed to cancel out all gyroscopic effects which people could ride with ease. Skittle 10:42, 23 February 2007 (UTC)

Turns out there is also a (very) brief mention of the effect in the trail article linked in the caption. I do remember that it's why bikes are built with trail. If the steering column was vertical, the result would be highly unstable. Spiral Wave 01:31, 23 February 2007 (UTC)

You can see from the diagram that if the bike is stationary - and leans to one side, there is a gravitational force acting through the frame of the bike and a ground reaction from the point where the front wheel touches the ground. This causes a rotational moment through the steering tube that causes the front wheel to try to turn 'into' the direction the bike is leaning. If you stand next to a bicycle and just lean it to one side, you can see that happening. But when you are moving rapidly, you have forward momentum and it takes a significant amount of force to cause the bike to change direction. The reaction to that force is pushing the wheel back into a straight line - so there is a net upward force countering gravity and making the bike stand up straight. It's hard to explain without a white-board and some force vector diagrams! SteveBaker 13:50, 23 February 2007 (UTC)

All of this is true, but please realize that the self-correction induced by the rake is only there to help you make roughly the right correction. The rider still does the fine tweaking to perfect the balance (and yes, this tweaking can be done either without hands, by leaning the frame so that the rake induces the front wheel to turn, or more simply by turning the handlebar by hand). The bike is NOT fully self-balanced, as you can establish by letting your rider-less bike roll down a hill by itself and seeing what happens (I don't recommend that test with an expensive bike...). --mglg_(talk) 18:31, 23 February 2007 (UTC)

[edit] February 23

[edit] Operators acting on an enitys wavefunction.

When a physicsit applies an operator to the wavefuntion are the solving the wavefunction for a specific observable (and thus predicting the value of that observable)? If so, what does a creation/anhilation operator do exactly? 68.95.116.222 05:00, 23 February 2007 (UTC)

I'm not up to answering these questions at the moment, but someone who is may find it useful to refer to our articles Operator (physics) and Creation and annihilation operators. TenOfAllTrades(talk) 05:47, 23 February 2007 (UTC)

"Operator" is a pretty general term in quantum mechanics - an operator transforms the wavefunction in some way. Some operators (specifically, self-adjoint linear operators) correspond to physical observables. Applying such an operator to a wavefunction can give you information about the corresponding observable - if a given wavefunction represents a particle with a well-defined momentum, for example, applying the momentum operator will end up multiplying the function by this momentum value. There are plenty of operators which don't satisfy these constraints, however, and these have nothing to do with observable quantities. Some of them are still useful, however. Creation and annihilation operators, for example, are not self-adjoint but they do correspond to changes in particle number in multi-particle states. I recommend the articles pointed to by the previous poster, as well as introductory books on quantum mechanics. JPFlip 02:07, 24 February 2007 (UTC)

[edit] steroids

Could you give me the history of steroids and why it was createdDmpaw 07:52, 23 February 2007 (UTC)

Have you checked out our article on steroids? You can get there by clicking the word 'steroids' in blue in my first sentence, or by typing 'steroids' in the search box on the left. That article gives you more information about steroids, and might help you to work out what kind of steroids you're asking about. For example, there are naturally occuring steroids and artificial, synthesised steroids. There are sex steroids and anabolic steroids and many others. Skittle 10:34, 23 February 2007 (UTC)

[edit] LPG TRANSPORTATION

Any idea how LPG and other fuels when cooled retains its liquid state in the cylinder(or cigarette lighter) until its used and then it forms a vapour to flow out of the burner?08:07, 23 February 2007 (UTC)

See our article on LPG, in short it is kept at a very high pressure to keep it liquid. --antilived^{T | C | G} 10:01, 23 February 2007 (UTC)

The temperature at which a gas condenses to become a liquid depends on the pressure. If the pressure is higher, the gas will liquify at a higher temperature. That's why you can keep bottled propane at room temperature as cooking gas. It only gets cold when you release the pressure so that the liquid boils. So LPG can be transported without needing to cool it just so long as the pressure stays high enough. SteveBaker 17:13, 23 February 2007 (UTC)

[edit] Turning tv off in lightning

Hi all. There's currently some lightning near my house. And it started us debating as to whether turning your tv off in a lightning storm will decrease the chance of your house getting hit. Is that the case? Thanks. - Akamad 10:54, 23 February 2007 (UTC)

Our own lightning article doesn't mention tv, but if you do a Google search on "lightning safety television" you will find advice such as:

Turn off the television and any other electrical appliances. Electricians suggest unplugging televisions and other valuable appliances because lightning can strike or cause electrical surges that can destroy these appliances.[3]

Do not handle any electrical equipment or telephones because lightning could follow the wire. Television sets are particularly dangerous at this time.[4]

So, not sure if you can do anything to decrease the chance of a hit, but you can certainly take steps to reduce the damage that will be caused if your house is hit. Gandalf61 11:58, 23 February 2007 (UTC)

Italic text the questions on electricity generation. —Preceding unsigned comment added by 210.212.210.166 (talk • contribs)

I'd guess TVs are at risk because lightning would strike the aerial and travel down. Lightning follows the line of least resistance, so it would probably like to flow through the TV and to the earth connection (and possibly live/neutral too?), so having the TV switched on (which may help it travel through the TV) and having it plugged into the mains will have an impact. Lightning can also cause power fluctuations which could harm other electrical devices, for example your PC. I'd suggest unplugging these from the wall socket during a lightning storm. Don't get too paranoid though, the risks involved are fairly low. --h2g2bob 17:35, 23 February 2007 (UTC)

Yeah we didn't unplug anything anyway, because the lightning was pretty far. But I did know that it's a good idea to do that, simply to save the devices incase of a hit, but I wasn't sure whether or not that changes the cnances of getting hit. Thanks. - Akamad 21:39, 23 February 2007 (UTC)

[edit] pH of Copper Sulphate

What is it? Any ideas? 213.48.15.234 12:42, 23 February 2007 (UTC)

The pH of Copper Sulphate can change, and is relative to surrounding chemicals. This page seems to suggest this, and a quick look at Google Answers talks about the effects of "low pH of copper sulphate", as well as of a high pH. I'm sorry I can't give you a more definitive answer. JoshHolloway 13:06, 23 February 2007 (UTC)

I can't find an answer from looking either :/ 213.48.15.234 13:10, 23 February 2007 (UTC)

(Darn! Edit collisions!) pH is a measure of the concentration of active hydrogen ions - since CuSO₄ contains copper, suphur and oxygen - but no hydrogen whatever, the pH is kinda meaningless. I suspect that you are actually asking about the pH of a solution of Copper Sulphate in water or the pH of those pretty blue 'hydrated' copper sulphate crystals (which contain water). That being the case, (and I'm not a chemist) I think it's neutral (ie a pH of 7) but if it's not then the answer will be entirely dependent on the concentration of the solution, so there is still no good answer. SteveBaker 13:15, 23 February 2007 (UTC)

No pH is more complicated than that. When you dissove a salt in water there are H⁺ and OH^- ions infrom dissacitated water molecules and adding the salt will change the balance. Generally a stong acid and a stong base Like sodium chloride will be neutral, and strong base with a weak acid like calcium carbonate will be alkali and a weak base with a strong acid will be acid. Theresa Knott | Taste the Korn 13:24, 23 February 2007 (UTC)

I had a bottle of solution sitting on the shelf so I tested it with universal indicator paper. it came out as 4. Theresa Knott | Taste the Korn 13:20, 23 February 2007 (UTC)

Excellent! Actual scientific research happening right here on the help desk in realtime! Wow! :-) But that's got to be dependent on concentration. If I took a hundred thousand liter tank of pure water and added one copper sulphate crystal to it - the pH would be 7. So we're not really measuring the pH of Copper Sulphate - but the pH of a solution copper sulphate in water at some concentration that our questioner has not specified. SteveBaker 13:26, 23 February 2007 (UTC)

It sounds like the actual question concerns the pKa of copper sulphate. If the pKa is known, the Henderson-Hasselbalch equation could prove useful in determining a pH of a solution. -- Scientizzle 19:35, 23 February 2007 (UTC)

I thought that would be the answer. Let me see if i can specify a concentration. (I'm asking on behalf of someone else) 213.48.15.234 13:34, 23 February 2007 (UTC)

From here http://www.chemguide.co.uk/inorganic/complexions/acidity.html pKa ~ 7.5 so the equilibrium constant is 10^-7.5 for equation 1 (see below) approximately.

[Cu(H2O)5OH-(aq)] [H+(aq)]
-----------------------  =~ 10-7.5
[Cu(H2O)62+(aq)]

So given that your pH was 4 means [H⁺_(aq)] ~ 10^-4 giving a copper concentration of approximately 10^-0.5 ~ 0.3M ? Note for 1M CuSO₄ the pH would be about 3.75.87.102.77.117 20:58, 23 February 2007 (UTC)

You're measuring this:

Cu(H₂O)₆²⁺_(aq) > Cu(H₂O)₅OH^-_(aq) +H⁺_(aq) (Equation 1)

Further ionisations can also occur but are less likely eg

Cu(H₂O)₅OH⁺_(aq) > Cu(H₂O)₄(OH)_2(solid?) +H⁺_(aq)

Additionally sulphate can act as a base - but it is so weakly basic that under normal aqueous conditions it will not have much effect:

SO₄^2-_(aq) + H⁺_(aq) > HSO₄^-_(aq)

So copper (II) ion in water is acidic - your pH measurement is effectively measuring the equilibrium in equation 1

By the way most metal ions in water are weakly acidic.87.102.6.2 13:42, 23 February 2007 (UTC)

Thanks, it's been a long time since i've studied chemistry 213.48.15.234 14:34, 23 February 2007 (UTC)

See here http://www.creative-chemistry.org.uk/alevel/module5/documents/N-ch5-10.pdf87.102.77.117 20:58, 23 February 2007 (UTC)

[edit] Budgie body language

What does it mean when a budgie stands on his perch with his wings held out from his body (the ends of them crossed across his back) and the rest of his feathers pulled flat? --81.76.42.135 18:41, 23 February 2007 (UTC)

[edit] Budgie question 2

Is it true that you can determine a budgie's mood by the warmth of his feet? Someone once told me that. Supposedly, a happy, contented bird will have warm feet. --81.76.42.135 18:44, 23 February 2007 (UTC)

[edit] Jealousy

Do you think that jealousy is closely related more to anger or fear?

I would say neither. Jealousy seems to me more closely related to desire, and can fall into both of the anger and fear camps. You can have a jealousy based in fear (someone is dancing with your wife) or a jealousy based in anger (the guy dancing with your wife just slept with her). -Wooty Woot? contribs 00:49, 24 February 2007 (UTC)

[edit] Budgie question 3

Is it possible to buy captive bred wild-type budgerigars? I'm looking for one that hasn't been selectively bred/inbred to change the colour, feathers and size, just a basic small, plain green and yellow bird that's no different to the ones you'd see if you went to Australia. Thanks in advance. --81.76.42.135 18:51, 23 February 2007 (UTC)

[edit] February 24

[edit] How much is one pound of US$20 worth?

Just curious how much value one pound (16 ounces) of USD $20 bills would be worth. --24.249.108.133 00:44, 24 February 2007 (UTC)

There are 490 notes in a pound [5]. So one pound of $20s would be $9800. - Nunh-huh 01:09, 24 February 2007 (UTC)

[edit] Tapeworm

In the most recent episode of House, he discovered a 25-foot-long tapeworm in a girl's intestines. He said that she hadn't collapsed from pain because she suffered from CIPA, then he said that the record for the longest tapeworm was 60 feet. Unless the person who had that tapeworm also suffered from the rare CIPA, why didn't they collapse in pain, as well? Corvus cornix 00:26, 21 February 2007 (UTC)

Didn't see it, but he was probably just saying something silly. Pain, and its effects, are not readily quantifiable, and some people bear pain far better than others, even in the absence of congenital insensistivity. Yes, tapeworms can cause abdominal pain, but longer length doesn't mean more pain, and shorter length doesn't mean less pain (though greater length might increase the likelihood of intestinal blockage, which would certainly be painful). Pain isn't usually the predominant problem (which could be malnutrition or allergic reaction, weight loss and diarrhea). Certainly one can have a long tapeworm and not have pain. (The longest human tapeworm was apparently Diphyllobothrium latum at 18m (59 feet); average for this species is about 10m.) - Nunh-huh 00:55, 21 February 2007 (UTC)

59 feet not 60? Whoa, you mean House was wrong? [Mαc Δαvιs] X (How's my driving?) ❖ 23:02, 21 February 2007 (UTC)

Sounds like dramatic license to me. Nimur 02:28, 21 February 2007 (UTC)

You mean everything on television isn't true? ;) Corvus cornix 20:04, 21 February 2007 (UTC)

I think the most disturbing line of the article about the 10m worm is that it uses the phrase "The preferred treatment...causes the worm to detach and be passed whole"! Laïka 22:36, 22 February 2007 (UTC)

You would prefer passing smaller bits of it over a period of a week??? - Nunh-huh 01:50, 25 February 2007 (UTC)

[edit] valence and ground state

Are the valence shell and the ground state basically the same thing? Part of my instructions include "ground state electron configuration" and all I can deduce from that and research is that it means the valence shell. Thank you in advance. 75.84.49.209 03:32, 24 February 2007 (UTC)

It specifies "ground state," since there always seems to be room for variations in chemistry. Ground is taken as the "right answer." Sorry, I realized I can't really explain this. [Mαc Δαvιs] X (How's my driving?) ❖ 04:07, 24 February 2007 (UTC)

Can someone define ground state please? 75.84.49.209 04:42, 24 February 2007 (UTC)

Ground state. Basically the lowest allowed energy state in a quantum system. No, it is not the same thing as the valence atomic shell. -- mattb @ 2007-02-24T04:46Z

What is exactly mean by lowest energy? is this the one before the valence or the very first level? 75.84.49.209 06:02, 24 February 2007 (UTC)

State in which a particle is at the lowest possible energy for a given quantum system. I don't know how else to describe it. I think you're grasping for a one-liner reconciliation of some QM concepts with the classical "orbital" model of a free atom, and I don't know if such an easy thing exists. You have to understand that the ground state of a system is highly dependent on the parameters of said system; the electron ground state in a crystalline lattice of atoms will not be the same as the ground state associated with a single isolated atom. I had better not say much more, I'm not particularly good with solid-state physics, so my answers may confuse you more than help. -- mattb @ 2007-02-24T06:34Z

The ground state as people have said above is the lowest energy state - higher energy states are called 'excited states'. The ground state for an atom will include the electrons in their typical positions in the valence shell. It also means that electrons in (lower energy) inner shells (those shells that have been filled) will be normal ie filled.

For instance sodium has electron structure 1s²2s²2p⁶3s¹ - this means that the first and second 'shells' are filled and the third shell has one electron. (hence sodiums tendancy to form Na⁺) - the valence shell in this case is the '3s'.

Discussions about valence shells will always assume that the electron is in the ground state. So in simplistic terms you were not wrong. Hope this helps87.102.67.190 15:57, 24 February 2007 (UTC)

[edit] contact lenses

are contact lenses safe?

There are risks associated with everything. Most people use contact lenses with no problems, but injuries can and do sometimes result from their use. - Nunh-huh 09:08, 24 February 2007 (UTC)

If used correctly, the risk of adverse effects is small. See Contact lense#Complications and there references therein. Rockpocket 09:11, 24 February 2007 (UTC)

All risks are relative, so you must weigh the dangers of contact lenses against those of wearing spectacles (breakage, etc.) or leaving vision uncorrected (walking into walls, etc.). --TotoBaggins 14:46, 24 February 2007 (UTC)

Yes they are safe. Glasses are more likely to injure your eyes in an accident.

I weak contacts so I will give u some pointers.

1. If they hurt you, take them out.
2. Don't leave them in overnight.
3. Clean them carefully before each use to prevent infection.
4. If your contact lenses are old, throw them out.
5. When you first get them, they tend to bother your eyes a lot. Get some eyedrops. I like the Renu brand.

Some companies such as electric utilities banned the wearing of contacts on the job because of anecdotal and possibly bogus reports of the lens being "welded" to the cornea by electric arcing in the vicinity. Practically, it is bad to get dust or grit stuck behind the lens when your hands are dirty and there is no sink to clean them. Edison 22:43, 24 February 2007 (UTC)

[edit] Decarboxylation

Does decarboxylation reaction only occur in the Kreb cycle or glycogenolysis?

Nor sure exactly what you mean but I can say that decarboxylation occurs in many other reactions outside the two you have mentioned.87.102.67.190 16:02, 24 February 2007 (UTC)

[edit] chemistry problem

if you have the equation : NaHCO3 + CH3COOH --> H2O + CO2 + NaCH3OO,

how many moles of NaHCO3 and CH3COONa are necessary to make 425 mL of CO2?

You first need to calculate how many moles of CO₂ 425 mL is.

425 ml is 0.425 L

1 mole of a gas occupies 22.4 L at STP

0.425 L x 1 mole/22.4 L = .01897 moles or (rounding) 0.019 moles

Since both NaHCO₃ and CH₃COONa are in equal ratio to CO₂ on the other side of the equation, you need the same amount of each of them.

So you need 0.019 moles of NaHCO₃ and 0.019 moles of CH₃COONa to produce 0.019 moles of H₂O and 0.019 moles of CO₂ and 0.019 moles of Na CH₂OOH.

- Nunh-huh 04:22, 25 February 2007 (UTC)

[edit] Tapeworm

In the most recent episode of House, he discovered a 25-foot-long tapeworm in a girl's intestines. He said that she hadn't collapsed from pain because she suffered from CIPA, then he said that the record for the longest tapeworm was 60 feet. Unless the person who had that tapeworm also suffered from the rare CIPA, why didn't they collapse in pain, as well? Corvus cornix 00:26, 21 February 2007 (UTC)

Didn't see it, but he was probably just saying something silly. Pain, and its effects, are not readily quantifiable, and some people bear pain far better than others, even in the absence of congenital insensistivity. Yes, tapeworms can cause abdominal pain, but longer length doesn't mean more pain, and shorter length doesn't mean less pain (though greater length might increase the likelihood of intestinal blockage, which would certainly be painful). Pain isn't usually the predominant problem (which could be malnutrition or allergic reaction, weight loss and diarrhea). Certainly one can have a long tapeworm and not have pain. (The longest human tapeworm was apparently Diphyllobothrium latum at 18m (59 feet); average for this species is about 10m.) - Nunh-huh 00:55, 21 February 2007 (UTC)

59 feet not 60? Whoa, you mean House was wrong? [Mαc Δαvιs] X (How's my driving?) ❖ 23:02, 21 February 2007 (UTC)

Sounds like dramatic license to me. Nimur 02:28, 21 February 2007 (UTC)

You mean everything on television isn't true? ;) Corvus cornix 20:04, 21 February 2007 (UTC)

I think the most disturbing line of the article about the 10m worm is that it uses the phrase "The preferred treatment...causes the worm to detach and be passed whole"! Laïka 22:36, 22 February 2007 (UTC)

You would prefer passing smaller bits of it over a period of a week??? - Nunh-huh 01:50, 25 February 2007 (UTC)

[edit] Ten years after cloning of Dolly the Sheep: What prevents primate somatic cell cloning?

An MSNBC article [6] says it is 10 years after the announcement of the successful cloning of a sheep, Dolly the sheep , from the breast cell of an adult sheep. The article goes on to say that human cloning efforts are "on the back burner" partly because of the high incidence of dead or deformed clone offspring of other mammals. The article says no primate has ever been cloned using the Somatic cell nuclear transfer technique used for Dolly, and that it may be impossible to clone primates that way. My question is, what makes it possible per List of animals that have been cloned to clone from adult somatic cells mice, rats, cats, dogs, rabbits, sheep, deer, mules, cattle, and oxen, but not primates? This smacks of 1950's sci fi movies where bad things happened to the scientists who got too big for their britches and tried to do experiments "humans were not meant to do." It reportedly takes 80 to 300 attempts to produce a healthy live clone of a mammal, but aside from that, what mechanism in the genetic or reproductive structure prevents primate cloning? Edison 19:10, 22 February 2007 (UTC)

Primates have a mechanical support structure in the cell nucleus that does not appear to be present in any other group of species. The current hypothesis as to why cloning of primates has alway failed is that this structure gets damaged during the nuclear transfer process. --Carnildo 21:10, 22 February 2007 (UTC)

Is there a references or source for this special "mechanical support structure?" Are primates the only creatures blessed with such a feature? Does this reflect evolutionalry pressure resulting from walking upright and having a big brain, or might it be seen as "God's will that humans and their little simian cousins not be cloned?" How did we get so lucky or unlucky?Edison 14:31, 26 February 2007 (UTC)

I don't know any of the details. I just remember it from something I read. (I believe it was an article in Scientific American on the history of cloning.) --Carnildo 00:45, 27 February 2007 (UTC)

[edit] i need assistance

Hi, I'm an engineering student and want assistance in building a DC to AC inverter and i want u to please help me to come up with some information that will help me. Thank u very much.

Start here: Inverter (electrical) --Mdwyer 20:45, 22 February 2007 (UTC)

As I recall there's a nice discussion of this topic, with some sample circuits, in Horowitz and Hill's classic (and highly recommended) The Art of Electronics. —Steve Summit (talk) 01:55, 23 February 2007 (UTC)

(I haven't actually looked at the H&H discussion of inverters, but I'll note that) modern, high-efficiency inverters don't tend to use mains-frequency transformers any more. Instead, they use a DC to DC converter to switch the battery voltage up to 170 volts (for 120 VAC countries) or 340 volts (for "230" VAC countries). They then use a MOSFET H-bridge to switch that DC voltage to the load, usually with a sequence that goes: 0V, +V, 0V, -V to approximate a sine wave. Better inverters pulse-width modulate the voltage to better-approximate a sine wave. In this way, they can put out hundreds of watts of AC while still dissipating only a few tens of watts. Our inverter article also discusses this new approach.

Atlant 14:01, 23 February 2007 (UTC)

"0V, +V, 0V, -V" does not approximate a sine wave. It is a square wave and many electronic or electromechanical devices will not work correctly on it.Edison 14:33, 26 February 2007 (UTC)

No, a square wave strictly alternates between +V and -V. This (inverter output) has 90-ish° steps in between at 0V. Do the Fourier transform on it; it's lot close to a sine wave than is a square wave.

Atlant 00:14, 27 February 2007 (UTC)

[edit] How much Fertilizer do crops require?

I am interested to know how much land human waste can fertilize. I wanted to start with the question of how much fertilizer does the average farmer use per acre? For different crops? In different parts of the world? Then I wanted to look at it more fundmentally. e.g. How much fertilizer (Nitrogen, etc.) is required to replace what is taken out in harvested crops?

thanks for any help. 24.7.84.147 05:46, 23 February 2007 (UTC)

You will have to do some research on your own to get the big picture. As always, any facts, figures, or inferences presented here are for discussion only and we accept no liability whatsoever for inaccuracies errors or omissions or for the consequences of accepting the information or acting on it. Consult a soil scientist, a sanitation expert or agricultural expert for advice to be acted on. Here are some article to look at: Agriculture, Organic farming , and Fertilizer. One of the references at Fertilizer is The Fertilizer Institute]. There is no "average farmer." In the U.S. a farmer may grow corn (maize) or soybeans, in rows in the midwest. Or he may grow highly irrigated tomatoes or other human food in other areas. Or he may grow cotton, sugar cane, sugar beets, peanuts, hay, etc. Different crops need different amounts of Nitrogen, Phosphorus, and Potassium. The fertilizer requirements are vastly different for each crop. The U.S. grows lots of corn, so Googling "corn production" you will find detailed directions from various state agriculture departments, including fertilizer reciommendations. Iowa corn production is probably a good source for information. Other countries also have agriculture departments which compile usage statistics and recommendations for their own countries. Especially see Manure, which is the term for animal feces.(Compared to "green manure" which is crops grown to be plowed under to improve the soil). The farmer may spray pig manure on the field from the "honey wagon" producing a rude awakening for city folks who have moved to the country to live the peaceful rural life next to a working farm. Manure is expecially rich in nitrogen. Fresh manure is reputed to "burn" plants. Composted or "rotted" manure has very little smell and is said to have less potential to "burn" the plants. Manure is not a complete fertilizer for many crops. In traditional farming, the plowhorse fertilized the field a bit as he plowed it, then the barn manure of horse, sheep or cattle dung mixed with straw fertilized the garden. Chemical fertilizers, introduced in the 1930s, more than tripled the corn (maize) yield in the U.S. In the 19th and early 20th century, farmers sometimes used up the soil by harvesting crops without fertilizing the field until the productivity dropped to an unecomomic level, at which time the farm was abandoned. More enlightened farmers used manure or green manure and rotated crops to maintain fertility in the long term. Human feces and much animal feces may spread disease unless it is somehow sterilized. Mad cow disease might be spread by the feces of animals which have consumed the remains of other animals, as when sheep tissues were fed to cattle in Britain and other countries in past years. Normal sterilizing methods, such as in rendering plants, do not destroy the prions which spread mad cow disease. There is a highly regarded book called "Five Acres and Independence" by M. G. Kains available at Amazon.com and elsewhere. Amazon can also recommend other similar books which treat organic farming. The 1940 revision of that book says (p155) that a 2-horse load of manure is a "liberal amount" for a 2500 square foot garden. Half that amount would give fair results and twice as much would be best for foliage or stem crops such as "celery, spinach, cabbage, cauliflower, etc." An adult Horse weighs 850 to 2000 pounds depending on the breed. The average of these is about 1425 pounds. Human weight says adult males in the U.S. average 191 pounds (86.8 kg) while females average 164.3 pounds (74.5 kg), for an overall average of about 179 pounds (80.7 kg). The point of this is that a horse equals about 8 present day Americans in weight, so by that standard an average American could fertilize about 160 square feet liberally if not sanitarily. So it would take about 268 American humans to fertilize an acre of farmland. Kains says fresh or rotted animal manure should be applied before working the soil, and dried processed manure (such as you buy in bags at the garden store) should be applied after plowing and raked into the top inch of soil. Of dried (sterilized) manures he recommends 100 pounds of sheep manure to 1000 square feet, 75 pounds of poultry manure, 100 to 150 pounds of horse manure, or 150 to 200 pounds of cow manure. On p157 he cites research by the state of Maryland agriculture department, bulletin 309 , where a 13 year experiment had found equivalence between 4 tons of manure and 500 pounds of fertilizer, and some benefits of applying certain amounts of fertilizer plus certain amounts of manure. Newer books on farming may have newer data. Human feces lists some of the deseases found in human excrement, and says "feces contribute to spreading of diseases and intestinal parasites." This is a clear problem for fertilizing with "night soil" as is done in some developing countries. The article gives no figures for what the annual yield of dried, sterilized feces would be per human, or how it compares to the manure from various animals cited above. Ecological sanitation says a human produces 50 liters of feces per year, and Human feces says it is 75% water, implying 12.5 liters of dried feces per human per year. I believe some produce far more. There are no figures for converting this to pounds. If it had approximately the density of water, (I would expect it to be denser) it would amount to about 25 pounds, and if comparable to horse or cattle manure (big ifs) it would fertilize 50 to 100 square feet per the above figures and assumptions. This would would then imply an input of 435 to 750 humans to fertilize an acre, which would unfortunately be able to produce sufficient food for only a small fraction of that many. The range of estimates shows the imprecision in the source data and the approximate nature of the assumptions as well as the "back of the envelope" quality of the calculations. Edison 15:25, 26 February 2007 (UTC)

[edit] Hydrogen in the table

Where is Hydrogen meant to go on the periodic table and why? My dad learnt it above Lithium, and thus it is shown on the article, but a printed version I've seen has it floating in the space between periods 2-13 groups 1-3. I am confused. Please reply to my talk page. Thanks! Jake95_(talk!) 19:54, 23 February 2007 (UTC)

Hydrogen has one electron available for bonding therefor usually goes above the alkali metals (Li, Na etc), however it also only requires 1 electron to fill it's 'shell' and so could go above the halogens (F,Cl etc) - in fact hydrogen shows behaviour of both these groups - eg forms a positive ion (in water) like Li, but bonds to only one atom eg (H-Cl) like fluorine - it's really up to you where you want to put it - I put above both the alkali metals and the halogens.87.102.77.117 20:13, 23 February 2007 (UTC)

The two-dimensional version of the periodic table is very unsatisfying because the left end of each row really needs to be joined onto the right end of the preceeding row - as in this circular version. But if you do this in three dimensions you get a long spiralling ribbon where consecutive loops of the spiral stack on top of each other. That gives you a much better idea of what's going on. It's just not terribly useful for printing on flat bits of paper or computer screens! It's hard to explain in words. SteveBaker 05:44, 24 February 2007 (UTC)

Here's a good picture of exactly that. [7] anonymous6494 07:51, 25 February 2007 (UTC)

The periodic table really looks like this (sorry about any errors, I drew this up in a hurry):

                                                                                            H  He
                                                                                            Li Be
                                                                          B  C  N  O  F  Ne Na Mg
                                                                          Al Si P  S  Cl Ar K  Ca
                                            Sc Ti V  Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr
                                            Y  Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I  Xe Cs Ba
  La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W  Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra
  Ac Th Pa U  Np Pu ...

But the way we usually draw it is better in that the elements with similar properties get in the same columns, especially that helium goes with the noble gases, not in the alkali earth metals. So, I belive hidrogen is quite a good place above the alkali metals' column, but that's just my opinion. – b_jonas 08:33, 26 February 2007 (UTC)

Not quite sure how your columns are chosen, but "elements with similar properties get in the same columns" is the pretty much the essence of the thing being a "periodic table" instead of a list of elements in order of atomic number. DMacks 08:42, 26 February 2007 (UTC)

If you consider helium as a special case, this is almost the same as a normal wide periodic table. The difference is that the two leftmost columns are moved to the right instead. I drew it this way to show how it has a nice regular shape (with a straight right edge and a parabolic left edge). That shape follows from how electron configurations work. I did that to show why I think hidrogen should be above lithium, which was the original question. – b_jonas 17:34, 26 February 2007 (UTC)

But it's not really how electron configurations do work. The noble gases have full valence levels, the "next" element after each goes into the next level, not more into the same. He and Be aren't alike except in "have 2 valence 2 electrons", and even then, that fact is precisely what makes them so different chemically. DMacks 17:47, 26 February 2007 (UTC)

[edit] Liposuction and Fat

Alright, so fat is stored in special cells that are scattered about the body. Especially high concentrations exist in the stomach, buttocks, thighs, etc. As far as I know, as a person gets fatter in these areas the number of fat cells stays static, they just acquire and store more fat because it's available.

So my question is, if you have liposuction in a certain part of your body that removes a considerable number of fat cells, do they get repalced? Can you get really fat in that part of your body in the future? The article on liposuction doesn't appear to talk about this.

Thanks, – Lantoka (talk) 00:40, 24 February 2007 (UTC)

If I recall correctly (I am in no way expert on this), once it gets past a certain stage of 'fatness' the body makes more fat cells, meaning that once you get past a certain level of fatness, it's easier to get back up to that level. But the idea with liposuction is that you will never get that fat again in that area, because you have fewer fat cells. It can mean (according to my mother) that people can end up looking very weird, as they start storing more fat in the areas where they didn't have liposuction. Skittle 19:54, 25 February 2007 (UTC)

[edit] Homemade nuclear reactors

How many amateurs have constructed their own reactors? David Hahn tried and failed, while Thiago Olson actually succeeded in 2006. Both were 17. Are there any others? Clarityfiend 01:14, 24 February 2007 (UTC)

The University of Chicago Scavenger Hunt listed a nuclear fission reactor a few years ago, and that was made for the contest. Hm, maybe I should do one, that would be a good project next year! [Mαc Δαvιs] X (How's my driving?) ❖ 04:05, 24 February 2007 (UTC)

It's not a reactor, but you used to be able to buy a toy called the Gilbert Atomic Energy Lab, which had some uranium, a geiger counter, and I think a scintillation screen. The good old days of toxic fun (like how my mom let me play with mercury as a kid).  :) --TotoBaggins 14:42, 24 February 2007 (UTC)

(Offtopic) That whole 'playing with mercury' thing is very interesting. When I was in high school in UK back in the '60s, we were given blobs of mercury to play with during chemistry classes. Two years later, when it's toxic effects had been noted, someone broke a mercury thermometer in the same classroom and half the school had to be evacuated! The number of people in the world who have experienced the extreme weirdness of holding mercury in their hands is going to decrease markedly in about 40 to 50 years because nobody is allowed to do that anymore. The stuff is insanely heavy - it's reverse-meniscus makes for some very strange effects when you splash the stuff (it breaks up into little balls) and it's just generally very pretty. The experience was well worth the long-term brain damage I got as a result!  :-) SteveBaker 00:08, 25 February 2007 (UTC)

www.fusor.net is for the backyard fusion researcher. Thiago Olson was working with fusion rather than the more traditional fission reactor. Detroit free press claims that he was the 18th ameteur to achieve fusion. I guess that there are no systems actually producing net power yet. GB 03:32, 26 February 2007 (UTC)

[edit] American Wire Gauge

I was looking for the minimum gauge wire to carry 30 amps of DC current over a circuit that could be a maximum of 15 feet or so. I looked at the wiki article on this subject but after looking at a few sources, it looks like there is a rating for both power transmission and chassis wiring and even a few more sources have different gauges for the length of wire. Can you sort this out? Is there a book or something that I can use as a good source for wire gauges? Thank you.

You did not give any details of the application so the answer must be general. Just like any other question, the answers here are presented as general information and assistance in finding where information is in the Wikipdeia, and we do not accept any liability for anyone's reliance on the information. You could consult an electrical engineer who is a registered Professional Engineer specializing in the type of construction you contemplate. American wire gauge says that number 10 copper wire with insulation rated at 60 degrees C is rated to carry 30 amperes. The National Electrical Code (US) code is another source, which gives rating factors for wires packed into a conduit, and says how full the conduit can be. There are also guides which explain what the code book states in legalistic technical jargon, since it was written by a committee of technical people. Wire wound into a solenoid or a motor winding or packed tightly into a conduit will heat up more than wire in open air. Electrical power conductors are sometimes dynamically rated by utilities based on ambient temperature, previous loading history and wind. These are a couple of factors which can complicate the selection of wire size. Larger wire (smaller numerical gauge) would also carry 30 amperes, with less voltage drop. You can work out the voltage drop from the stated resistance by Ohm's law. Remember to double the length of the wire in the calculation since presumably current will go from the battery or generator to the load and back. It looks the voltage drop would be (15feet*2)/(1000 feet)*(.9989 ohms per thousand feet)*(30 amps) = 0.899 volts. See also Electrical insulation, since the wire must be insulated per safety and electrical codes to withstand the voltage between conductors and to ground that willl be applied, and suitable for whatever environment it is exposed to, and adequately strong mechanically to support itself and any wind or ice load if used for an overhead run. Edison 22:38, 24 February 2007 (UTC)

Edison's information is all accurate. In general, two factors contribute to the required wire size: (1) how much voltage drop you can tolerate, and (2) how much of a temperature rise you can tolerate. The voltage drop is easy to calculate, based on the resistivity of copper. Determining the temperature rise is much more complicated. How hot a current-carrying wire gets is obviously dependent not only on the I²R power being dissipated, but also on the thermal resistance of the environment (insulation and/or wiring enclosure). How much heat you can tolerate depends on the properties of the insulation. For example, the electrical code says that (if you really want to) you can run 50 amps through a 14 gauge wire, if the wire is uninsulated and in air (i.e. strung between insulators on a pole). This is a real shock -- er, surprise -- to those of us who (thought we'd) learned that 15 amps was the max for 14 gauge.

If you're not doing anything exotic, and if you're not trying to absolutely minimize the wire size, you don't have to worry about any of this or do any calculations: just go with the general-purpose rules and use 10 gauge, and you'll be fine. —Steve Summit (talk) 23:49, 25 February 2007 (UTC)

P.S. Whatever you're doing, make sure you've got a fuse or circuit breaker in the circuit. —s

[edit] valence and ground state

Are the valence shell and the ground state basically the same thing? Part of my instructions include "ground state electron configuration" and all I can deduce from that and research is that it means the valence shell. Thank you in advance. 75.84.49.209 03:32, 24 February 2007 (UTC)

It specifies "ground state," since there always seems to be room for variations in chemistry. Ground is taken as the "right answer." Sorry, I realized I can't really explain this. [Mαc Δαvιs] X (How's my driving?) ❖ 04:07, 24 February 2007 (UTC)

Can someone define ground state please? 75.84.49.209 04:42, 24 February 2007 (UTC)

Ground state. Basically the lowest allowed energy state in a quantum system. No, it is not the same thing as the valence atomic shell. -- mattb @ 2007-02-24T04:46Z

What is exactly mean by lowest energy? is this the one before the valence or the very first level? 75.84.49.209 06:02, 24 February 2007 (UTC)

State in which a particle is at the lowest possible energy for a given quantum system. I don't know how else to describe it. I think you're grasping for a one-liner reconciliation of some QM concepts with the classical "orbital" model of a free atom, and I don't know if such an easy thing exists. You have to understand that the ground state of a system is highly dependent on the parameters of said system; the electron ground state in a crystalline lattice of atoms will not be the same as the ground state associated with a single isolated atom. I had better not say much more, I'm not particularly good with solid-state physics, so my answers may confuse you more than help. -- mattb @ 2007-02-24T06:34Z

The ground state as people have said above is the lowest energy state - higher energy states are called 'excited states'. The ground state for an atom will include the electrons in their typical positions in the valence shell. It also means that electrons in (lower energy) inner shells (those shells that have been filled) will be normal ie filled.

For instance sodium has electron structure 1s²2s²2p⁶3s¹ - this means that the first and second 'shells' are filled and the third shell has one electron. (hence sodiums tendancy to form Na⁺) - the valence shell in this case is the '3s'.

Discussions about valence shells will always assume that the electron is in the ground state. So in simplistic terms you were not wrong. Hope this helps87.102.67.190 15:57, 24 February 2007 (UTC)

[edit] Supercontinents

So at various times in the Earth's history, most of the landmass was in a single continent. My question is: how do they figure out the shape they were in? The articles on Laurasia, Gondwana, Pangaea, and Rodinia all have maps of the continent, giving rough outlines of their shapes and locations of present-day continents. How does one work something like that out? --210.246.30.59 05:24, 24 February 2007 (UTC)

Some of this can be deduced just by looking at how the continents fit together. It's really blindingly obvious that the east coast of South America fits beautifully into the west coast of Africa. We also know the directions and speeds at which the continents are currenly moving because we can measure that (continents move by inches per year and we have ways to measure that accurately). Motion in the past can be estimated by examining the ridges that form down the middles of oceans as they spread apart - if two continents are moving in opposite directions, the ocean floor between them will tear apart and the gap fills in with lava to form new rocks. By measuring the age of rocks either side of one of those fault lines, we can see how fast the ocean floor spread - and thus estimate the speed of the continental drift. Yet further evidence comes from looking at the direction of magnetic fields in ancient rocks. When a rock is formed, in a liquid state, it's magnetic field lines up with the earths magnetic field. Once it hardens, that magnetic field direction is 'frozen' into the rocks. If the continent that the rock is a part of moves - then the magnetism in the rocks will no longer line up with the earth's field. So, if you take a bunch of rocks in different continents that are of the same age, you can deduce that their magnetic fields were once all lined up in the same direction. If those fields aren't lined up now then you can tell how one continent has rotated compared to the other. This is an inexact matter because the Earth's magnetic field has an annoying habit of reversing periodically. But a combination of these three things gives us a pretty good idea of how things were. SteveBaker 05:58, 24 February 2007 (UTC)

You can also look at the rocks that date to various times - for example, there are some 1.1- to 1.4-bilion-year-old rocks in the NW US and SW Canada that are remarkably similar in composition, texture, thickness, etc., to rocks of the same age in Siberia. Careful study can reveal the directions from which some of the sediment that made those rocks came, indicating relative positions of lands, seas, and even other smaller-scale environments like rivers and large lakes. If we find bits or minerals in Siberia that have chemical signatures indicating they were derived from North America, it helps a lot in the quest to show that they were once connected. This particular connection (western N. Am. and Siberia about 1.4 billion years ago) is quite well documented nowadays. Cheers Geologyguy 21:25, 24 February 2007 (UTC)

You can also look at fossils, and see the areas that an organism is found over. If you find it in one area on the west coast of Africa, and another on the east coast of South America (for example), you can guess that those areas were probably once connected. Skittle 19:47, 25 February 2007 (UTC)

[edit] contact lenses

are contact lenses safe?

There are risks associated with everything. Most people use contact lenses with no problems, but injuries can and do sometimes result from their use. - Nunh-huh 09:08, 24 February 2007 (UTC)

If used correctly, the risk of adverse effects is small. See Contact lense#Complications and there references therein. Rockpocket 09:11, 24 February 2007 (UTC)

All risks are relative, so you must weigh the dangers of contact lenses against those of wearing spectacles (breakage, etc.) or leaving vision uncorrected (walking into walls, etc.). --TotoBaggins 14:46, 24 February 2007 (UTC)

Yes they are safe. Glasses are more likely to injure your eyes in an accident.

I weak contacts so I will give u some pointers.

1. If they hurt you, take them out.
2. Don't leave them in overnight.
3. Clean them carefully before each use to prevent infection.
4. If your contact lenses are old, throw them out.
5. When you first get them, they tend to bother your eyes a lot. Get some eyedrops. I like the Renu brand.

Some companies such as electric utilities banned the wearing of contacts on the job because of anecdotal and possibly bogus reports of the lens being "welded" to the cornea by electric arcing in the vicinity. Practically, it is bad to get dust or grit stuck behind the lens when your hands are dirty and there is no sink to clean them. Edison 22:43, 24 February 2007 (UTC)

[edit] Chicken

you know people use hormones to make chickens grow faster and bigger. does the hormone effect transfer to humans when eaten. i'm asking this because my dad says i'm tall and have a moustache at an early age through eating too much chicken.

Your IP localizes to New Zealand. According to [8], "growth hormones never have been and never will be used in New Zealand's poultry industry". See also [9]: "The perception that hormones are routinely included in poultry diets has been fueled by inaccurate statements made by The World Health Organization who apparently issued a plea to stop giving growth hormones to chickens grown for human consumption". Being taller than, and maturing faster than, your father is more likely the result of good nutrition than it is chicken hormones. -Nunh-huh 09:07, 24 February 2007 (UTC)

Unless she's a girl?

 :)

The USA also disallows hormones. Chickens are made so grotesquely enormous now by applying the optimization methods of the factory to their lives, which might leave some ethical residues, but not hormonal ones. --TotoBaggins 14:54, 24 February 2007 (UTC)

That's not necessarily the case. If one were to (hypothetically) measure the amount of growth hormone produced naturally within each chicken - and allow only those with greater than average amounts to breed, then over generations of careful selection, you'd have super-chickens that were much larger than normal and which contained worryingly large amounts of residual growth hormone. This would not be illegal (as I understand it) - but the results would be exactly the same. It might be too costly to do blood tests on every chicken and measure the natural hormone level - but you might (and I stress might) be able to achieve the exact same results by simply breeding only the largest birds from each generation since (perhaps) size of chicken correlates well with amount of naturally occurring growth hormone. SteveBaker 15:18, 24 February 2007 (UTC)

It is a big stretch to claim that selective breeding is the equivalent of artificially boosting the chickens with growth hormones. Humans have been selectively breeding animals (and plants) for thousands of years. If they hadn't done so, we wouldn't have chickens (or cows, horses, dogs, cats, corn, seedless grapes and oranges...) --Kainaw ^(talk) 16:10, 24 February 2007 (UTC)

But it's only relatively recently that humans discovered hormones. Breeding for growth hormone would require extensive blood testing, but I imagine it would produce very different results than conventional breeding. Bhumiya (said/done) 21:03, 24 February 2007 (UTC)

It's also something that a wikipedian just made up, instead of something based in fact, or something that actually happens. - Nunh-huh 01:54, 25 February 2007 (UTC)

Sure - I did say hypothetically. It's possible that breeding for size could be producing the exact same hormone concentrations as artificial hormone injections. It bothers me that people work so hard to separate selective breeding methods from chemical interventions, cloning, gene modification, etc. The artificial direction of an animal's evolution by selective breeding is perfectly capable of producing undesirable levels of growth hormone in chickens. I'm not saying it definitely happens - just that it's perfectly plausible. SteveBaker 03:58, 25 February 2007 (UTC)

In general, answers to questions on the Reference Desk really ought to be based in fact rather than wild conjecture. - Nunh-huh 04:05, 25 February 2007 (UTC)

I agree entirely. TotoBaggins asserted that it was not possible for todays 'grotesquely enormous' chickens to have excess growth hormones. That (IMHO) is pure conjecture. I explained that. I was correcting conjecture by saying that we don't know that this is true. SteveBaker 18:15, 25 February 2007 (UTC)

Not only do we not know it to be true, we have absolutely no reason to suspect that it is, and absolutely no data that supports the idea. - Nunh-huh 04:05, 26 February 2007 (UTC)

It's worth bearing in mind that, although you live in New Zealand, I would imagine that not all the meat you eat comes from New Zealand. Unless your parents have consciously chosen to only buy New Zealand meat, chances are that (particularly in processed food) you've eaten food from all over the world. So the chicken farming conditions in those countries are relevant as well. 86.139.237.132 19:38, 25 February 2007 (UTC)

[edit] Decarboxylation

Does decarboxylation reaction only occur in the Kreb cycle or glycogenolysis?

Nor sure exactly what you mean but I can say that decarboxylation occurs in many other reactions outside the two you have mentioned.87.102.67.190 16:02, 24 February 2007 (UTC)

[edit] Jogging

Hi. I am trying to get fit by jogging. I'm not too out of shape or anything (tall light weight male), I'm just trying to increase my endurance. The problem is, I can't get a good work out out of it because my lungs/heart don't tire out before my lower legs. After less than 1 km my shins start to hurt. Sometimes it feels like the muscle(s) opposite to the calf are fatigued (which is weird because the calf and upper legs do more work), while at other times it feels like the shin bone itself is hurting. I'm forced to stop before I feel I've realy worked myself. Is this normal? Shouldn't your chest tire out before your legs? What can I do to eliminate/reduce this problem? Thanks in advance for any advice.

Most people I see jog really badly. Try to get a Personal trainer for at least a session or two. If you don't do this, some bad things are going to happen. --Zeizmic 19:53, 24 February 2007 (UTC)

Run faster, it affects your lungs and heart more

The trainer might be able to show you proper [Stretching]] to do before and after exercise, and a proper conditionind routine to build up to your desired distance. Edison 22:45, 24 February 2007 (UTC)

Shin splints are very common for beginning runners. Here is an article about beginning running. The standard advice is the same as for other beginners: run slowly, use good form, don't increase your distance by more than 10% per week. That website has other good tips, and training programs for beginners. Runner's World and the like's sites do, too. Have fun! --TotoBaggins 23:18, 24 February 2007 (UTC)

I'm not a jogger, but you can clearly continue to stress the rest of your system while resting your calves by shifting to a different excersize. A simple example: lie down and do leg lifts. When your stomach muscles give out, roll over and do push-ups. If you want to equalize the stress, buy a rowing machine. My only experience with this is from Tae Kwon Do, where we also shifted to a bunch of different stances that stresed other muscles. -Arch dude 23:39, 24 February 2007 (UTC)

It also makes a big difference what kind of surface you run on, and what kind of shoes you use. A resilient surface like grass or an artificial track is much easier on your legs than asphalt or concrete. (Dirt is somewhere in between.) A running or training shoe is usually designed with a fair amount of its own padding -- although if it's too squishy, it can affect your maneuverability and comfort, and can make a twisted ankle more likely, especially if you're running outdoors on uneven surfaces. But if you're unsure of your equipment or technique, definitely ask an experienced runner or a personal trainer for advice. There are lots of variables, and running can be painless and enjoyable (besides great exercise!) if you do it right, so definitely make sure you're doing it right. —Steve Summit (talk) 23:59, 25 February 2007 (UTC)

[edit] Solids

I read the article on solids, but I couldn't find one vitle piece of information. Why do solids hold together? What makes the atoms attract each other and why does this fail to work after the solid has been torn in half? Same question for liquids.

Different kinds of solids are held together by different forces. Ionic solids like salt are made of positive and negative ions which attract each other. Macromolecular solids like diamond are held together by covalent bonds. Metals can be thought of as positive ions surrounded by a fluid of electrons (see Metallic bond). When you break a solid in half, the surfaces are microscopically rough and adsorb gases on their surface that prevent them from bonding when brought back into contact. If you cut a piece of metal with a sharp blade in a vacuum, the two pieces will fuse back together in a cold weld. —Keenan Pepper 20:39, 24 February 2007 (UTC)

Dang, we need some articles on these things. —Keenan Pepper 20:41, 24 February 2007 (UTC)

Start with the basics. Solids are either homogeneous or composite. A composite is composed of a set of homogeneous pieces that are held together by inter-molecular interactions at their surfaces and/or by physical interlocking at scales above the molecular scale. Depending on the scale, we are in the realm of metallurgy, structural engineering, materials science, or civil engineering. Within each homogeneous piece, the piece is held together by attractions between the molecules that comprise that piece: we are now in the realm of chemistry, and the other answers apply.

As to your secondary question: after splitting a solid into two pieces and then sticking the two pieces back together: It depends. For some solids, the split causes the molecules on the new surfaces to rearrange to join with each other, so energy would need to be added to cause them to re-connect to their old positions after you stick the two surfaces back together. In other cases, the new surfaces are chemically active and when you create the new surfaces by tearing the original solid, the new surfaces immediately combine with atmospheric molecules (usually oxygen) to reach chemical equilibrium. In a vacuum, if you split a homogeneous piece of iron into two pieces and then put the two new surfaces back together, they will rejoin in a process called "vacuum welding." If you could realign the surfaces perfectly at the atomic level, the weld would be (in theory) as strong as the original piece.

for your third question: In my experience, when I split a liquid and then rejoin it, there is no difference: that is, the rejoining does not fail to work.For the other half of you r liquid question, im my experience. nothing holds a liquid together: when I spill my martini, I cannot get it back into the glass. there is a second-order attraction called "surface tension" but this will not put my martini back together again, alas. -Arch dude 23:27, 24 February 2007 (UTC)

There are two measures of how well a liquid "holds together". One is the strength of the cohesion between molecules of the liquid, as measured by its surface tension. The other is the resistance of the liquid to shear stress, as measured by its viscosity. Taking water as an example, water molecules are highly polar, so each water molecule is linked to surrounding molecules by multiple hydrogen bonds. This gives water a relatively high surface tension and also has a high latent heat of vaporisation. However, these hydrogen bonds are constantly being broken and reformed, so water has a relatively low viscosity i.e. it can flow easily. Gandalf61 11:34, 25 February 2007 (UTC)

Keep in mind that at the quantum level, there is no such thing as a chemical bond. Rather, electrons have higher probabilities of having their motions controlled by particular nuclei through the exchange of photons between nuclei and electrons. This exchange of photons is explained by Quantum Electrodynamics. Having said that, my impression is that when you tear apart a solid, you can't put it back together again because it's impossible to establish the same degree of photon coupling between nuclei and electrons after that break. You would have to go in and rearrange each nucles and electron at the atomic level (which may be impossible due to Heisenberg Uncertainty?). If it is some sort of homogeneous crystal, the other option is to heat the solid into liquid or gaseous phase and then let it cool back into solid form, allowing the substance to achieve a cohesive, consistent state as a liquid and gas and recrystalize or solidify when the temperature is brought down. Not sure if this is accurate, any physicists in the room? Wikipedia brown 20:22, 25 February 2007 (UTC)

[edit] Population center of the Earth

If you average the position vectors of all human beings, you get a point inside the Earth. Where does the line from the center of the Earth through that point intersect the Earth's surface? —Keenan Pepper 20:46, 24 February 2007 (UTC)

My guess would be the border between China and India. No clue though. --Tbeatty 21:05, 24 February 2007 (UTC)

I looked at a lot of Google results for "population center" earth and did not see any really precise result. For a state or a small country you can treat it as a flat surface and the result is easy. For the globe, various sites say it would be near the center of the earth but perhaps below the India China border as Tbeatty said. There should be a way to do it mathematically but force it to be on the surface, as if you wanted to put a pizza restaurant where the average delivery trip would be shortest. Edison 23:01, 24 February 2007 (UTC)

A decent first approximation that would be very easy to teach a computer to calculate would be grab the population of each city from List of cities by population, snarf out the coords tag from that city's page (or improve wikipedia by adding it!), and then adding a vector for each city coordinate, weighted by population. Version 2 could have an improvement where you allow for the diffusely-located part of the citizenry by taking each country's population, less the population of its cities included in that first list, and add a vector for the country's geographic center, weighted with that population. By increasing the length of the list of towns/villages/burgs in the first part until you're down to the level of Enkhbayar's yurt encampment, you'll eventually get something very accurate. On the India/China border. :) --TotoBaggins 23:39, 24 February 2007 (UTC)

There is a type of graph which is a geographical map that adjusts the size of a region depending on a single factor in the region, such as population, GDP, or life-expectancy. If you wanted to find the population center of the Earth, all you'd have to do is construct that type of graph and you select the biggest region. The more individual regions you can have, the more accurate your answer will be. I just made that up off the top of my head, is that a correct answer? [Mαc Δαvιs] X (How's my driving?) ❖ 07:32, 25 February 2007 (UTC)

Start with the image at right; it's coloured by population density. Your 'center' is going to be near the point that's at the minimum distance from those bright red hotspots of density. I wouldn't be surprised if it fell somewhere in northeast India, Bangladesh, Myanmar, or China. TenOfAllTrades(talk) 19:07, 25 February 2007 (UTC)

Some further thoughts: someone more adept at math noted that solutions in the interior of the earth are not very meaningful, since basically we live on a surface and not in a volume. They suggested that a computer program could be written to produce a "flattening function" for each unit of population (in the extreme each person but for starters each country or region of a country) in relation to the others. A similar program could calculate a solution or set of solutions for surface population centroids for any topology such as a sphere, an oblate spheroid such as the earth, a cube, a tetrahedron, a donut, or what have you which is a continuous closed surface. Think of "great circle" routes on the globe. If people lived only on the equator of a sphere and were equidistant, there would be 2 solutions, the north and south poles, not the center of the sphere. If they lived only in the northern hemisphere and were equidistant, the solution would be the north pole. If half lived on the north pole and half on the south pole, there would be an infinite number of solutions lying on the equator. For the surface population centroid of the Earth, any reference to a Mercator projection or other flat map is arbitrary and absolutely meaningless, since it depends not only on the distortions resulting from the projection but also the question of where the map is centered. I just came up with a thought experiment: Take an inflatable globe. Glue a weight, equivalent to the population of each country, at the location of that country on the globe. Small coins could be used with each representing so many million people. Place the inflated, weighted, globe in a container of water. Would the lowermost point be a sort of population centroid (it might actually be a lightly populated area like the Himilayas)? And if you were "living on top of the world" would you be in a fairly lonesome area (maybe between Easter Island and Robinson Crusoe Island)? This would make an interesting science project in analog computation, but it could also be implemented in a program such as Mathcad. Edison 15:55, 26 February 2007 (UTC)

I would say Pakistan, starting between india and china, but skewed off a lot more by europe ans africa that by america

[edit] Setting cheese with orange juice

I want to make a small amount of paneer, but don't have access to lemon juice at the moment. Could I substitute orange juice, perhaps in a different proportion, and end up with a similar product? Or is orange juice simply not acidic enough? Thanks! Bhumiya (said/done) 20:59, 24 February 2007 (UTC)

Orange juice should be acidic. Do you have vinegar? That works too. --Kainaw ^(talk) 22:02, 24 February 2007 (UTC)

No, I had thought of using vinegar, but I don't have any of that (I'm on a college campus with a very small convenience store). I'm going to do a small-scale test with some orange juice. Bhumiya (said/done) 22:49, 24 February 2007 (UTC)

An idea that may not work at all: Freeze the orange juice. When it half-melts again, I believe most of the non-acidic water will be in the ice, leaving juice with more acid outside the ice. Of course, I could be very wrong about that. The acid may be trapped in the water (ice) and you may get a weaker juice from the process. --Kainaw ^(talk) 00:08, 25 February 2007 (UTC)

For what it's worth:

The pH of lemon juice is about 2.00 to 2.60.

The pH of vinegar is about 2.40 to 3.40.

The pH of orange juice is about 3.30 to 4.15.

OJ will probably work, just give it enough time. The only way to be sure is to try. - Nunh-huh 02:00, 25 February 2007 (UTC)

Though when calculating the amount to use, remember that pH is a logarithmic scale, so to get the same acidity, you'd need 10-100 times the usual amount. ST47Talk 19:23, 25 February 2007 (UTC)

Though, acidity is about concentration, not volume; so adding more orange juice will not yield more acidity. Kainaw's suggestion to concentrate the juice by freezing might actually work. Nimur 11:14, 26 February 2007 (UTC)

[edit] Venus

Hi. I usually answer questions, but now I am asking one. Recently I have observed Venus through a small, cheap telescope, usually through a window. I have been able to observe, from two different windows, with a telescope, the small finderscope, and a small pair of binoculars, a strange star close to Venus. If it helps, I live in Canada and I observed early in the evening about an hour after sunset. In the binocs and finder, I see a faint star, about mag. 4-8, beside venus. In my binoculars, it probably appears to the left of venus, and in the finder and telescope, it appears to the right of the planet. This is because the orientation of the binoculars is correct, but in the finderscope, the view is inverted, and through the telescope, its horizontal view is inverted. Sometimes, I have been able to see it as a comet-like thin streak of light beside venus, another time I couldn't see it at all, and another time I saw it and it looked like a chain of three stars. I tried an online star chart, and none of the stars right beside venus in that area seemed to perfectly resemble the object, in placement, brightness, and type. If anyone has a telescope and a clear night, or if you know a site where the info for it is avalible, can someone try to figure out what it is? Thanks. AstroHurricane001^{(Talk+Contribs+Ubx)} 19:27, 24 February 2007 (UTC)

Well, nobody answers, so I guess I'll answer it myself. After some recent observations, I've made a theory that can explain most of my observations. It's rather dissapointing, but It's a phenomena that puzzled scientists for centuries. Here's my theory. The windows, lenses, and eyepiece might play a role. People have sometimes described it as a moon of venus, but my telescope lacks the resolution to resolve a cresent. My theory is that the light from venus is so bright that it reflects off the eyepiece, to the aperture lens, and back to the eyepiece again. This is because I have noticed that the star, or streak, seems to move when I move the binoculars, and can also be in different places when viewed with the telescope or finderscope, especially as angle or position changes. Is this possible, and if so, any thoughts? Thanks. AstroHurricane001^{(Talk+Contribs+Ubx)} 00:10, 25 February 2007 (UTC)

Sounds feasible, especially if it's moving with your eyepiece (and so is clearly not a physical object). I'm guessing your binoculars and telescope don't have an anti-reflective coating, or at least not a very effective one; if that's the case, this can happen quite a lot when viewing bright sources. See if you can snag a pair with a good coating from somewhere, and you should find the extra lights disappear. Failing that, Venus is pretty bright at the moment, so watch to see how the light changes as the planet changes in magnitude. Once it starts to grow dim again, the extra light should vanish. You would have to observe it regularly up to that point though, to prove to yourself it hadn't disappeared earlier and so was not related to magnitude. Spiral Wave 01:10, 25 February 2007 (UTC)

The phrase that struck me was "usually through a window". Unless you're looking normal to the pane (exactly 90 degrees), you will get some internal reflections in the window. (Darn, I wish I could sketch a diagram). What's probably happening is that the light coming from Venus first hits the outside surface of the window. About 2% of this is reflected, and no longer has anything to do with this conversation. The remaining 98% continues through the glass until it hits the interior surface on the inner surface (does that make sense). Again, about 2% of this light is reflected, but the reflected light will then hit the inner surface of the exterior surface of the window (nuts! I'm in too deep but even I'm getting confused). Once again, about 2% of this light will bounce back, and if you've been keeping track, you'll see that it's heading for the 'scope. Now since you're not looking straight through the glass (see above, er... somewhere), this light will be offset from the light coming at you directly from Venus. If the window were infinitesimally thin, you wouldn't notice the difference. But since there is some real thickness to the glass, this twice-reflected light will be offset by an amount that depends on the thickness of the window, and the angle through which you're looking through it. Since the light is much dimmer, it doesn't look like the original object, but appears as a small source of light near the brighter original. (whew!) Bunthorne 04:32, 25 February 2007 (UTC)

But if your estimates for the reflectivity of the glass are right, then the 'ghost' image would be 2% of 2% or 0.04% of the brightness of the main image! Venus has a magnitude of -4.7 - and 0.04% of that puts you about 10 magnitude steps down from that or around +7 - that's pretty dim for a cheap telescope or binoculars. Well, I guess our questioner can step outside or open the window and see if the ghost image goes away - then we'd know for sure. SteveBaker 06:11, 25 February 2007 (UTC)

According to [[10]], my estimates "were" off a bit. It's closer to 4%/surface. However, even if it "did" appear to be magnitude 7, I don't think that that's so dim. Even the cheapest 'scope should be able to see that with no problem. But I agree opening the window and trying it is a capital idea. Bunthorne 06:30, 25 February 2007 (UTC)

You're thinking about it too much. A small scope might not pick up a mag 7 object, but it doesn't need to here if it's just a reflection anyway. Matt Deres 21:48, 27 February 2007 (UTC)

::::Ok, I have too much time on my hands. Here (it is to be hoped) is my first attempt to upload a sketch to show what I was taking about. Be gentle, it's my first time. Bunthorne 07:21, 25 February 2007 (UTC)

Hi everyone. Thank you for answering my question. Like I mentioned above, sometimes I have not been able to see the ghost image, and that's usually when I'm outside. It was often too windy to observe anything carefully, and I initially thought that was why. I think my telescope can handle magnitude 7, because I mentioned that I estimated mag. 4-6. I calculate that even my finderscope, which is the worst light gatherer, should be able to see to about mag. 8, which makes sense because I was able to see it under a semidark sky. Thanks again. You have once again proved wikipedia worthy of being one of the most easly accessible places for wanted information. PS. Wouldn't it be about 98% of 2% of 2% of 98%, which is close to 2% of 2%, which means you're mostly right, about less than 0.04%, so is that about mag. *calculating* (2500 times less than mag. -4, mag. "-4 + 5 + 3.5") about mag. 4.5? Does that make sense or not? Thanks. AstroHurricane001^{(Talk+Contribs+Ubx)} 00:47, 27 February 2007 (UTC)

Yes, it should be magnitude 4.5 --Bowlhover 17:13, 1 March 2007 (UTC)

Much of this also assumes that he's looking through a single pane of glass. That's not likely in Canada in the winter. Most modern windows are double-pane; some are triple-pane. --Charlene 04:12, 1 March 2007 (UTC)

[edit] February 25

[edit] Voices

Why is it that deep voices are more pleasing to hear than high-pitched ones? PitchBlack 00:38, 25 February 2007 (UTC)

It is a matter of opinion. Some people may prefer high-pitched ones. --Kainaw ^(talk) 03:16, 25 February 2007 (UTC)

I think he's asking more about narrators? Deeper-voiced narrators are amazing! They're just fun to hear! Listen! [Mαc Δαvιs] X (How's my driving?) ❖ 07:34, 25 February 2007 (UTC)

But the opinion is indeed popular. --Proficient 16:25, 25 February 2007 (UTC)

[edit] Good and Evil

Moved to humanities reference desk.

Wikipedia:Reference_desk/Humanities#Good_and_Evil87.102.2.242 15:35, 25 February 2007 (UTC)

[edit] Killing

Is there a possibility that a serial killer, a person who is pleased with killing, not having some psychological disorder? Is there some chance that it is somehow "right". Think of "method to my madness." PitchBlack 00:38, 25 February 2007 (UTC)

Right and wrong are not absolute truths to every human. Consider deer. For some, it is right to thin the herds by killing them. For others, it is not. What about a tiger in India that goes into a village and kills people? Some say it is right to kill it, others say no. What about a serial killer who has murdered a dozen or more people? Some say it is absolutely necessary to kill them. Others say that it is never ever right to kill a human. What about average criminals that will never, under any circumstances, obey the law? Some say it is OK to kill them, others say they should just be locked up for life. What about a city full of rude, mean, uncaring, selfish, generally nasty people? Some feel it is right to thin the herd. Others call those people a serial killer. I didn't even begin to step into the area of right and wrong in relation to religion. More people have been killed in God's name than for any other reason. --Kainaw ^(talk) 03:15, 25 February 2007 (UTC)

From a more pragmatic than philosophical point of view, I think the number of serial killers who are not mentally ill is probably near zero, more or less by definition. The complete lack of empathy that would be necessary to kill innocent people (outside of a socially-acceptable context such as war) would in itself be considered a mental illness. --TotoBaggins 03:44, 25 February 2007 (UTC)

A serial killer who enjoys killing could, in the right circumstances, be a military hero. --Duk 04:25, 25 February 2007 (UTC)

Roland Dechain, at times, does enjoy it, although he is a hero. Enjoying killing other persons, and doing it, alone is the psychological disorder. It is a psychological disorder to enjoy and perform murders on persons, there is no doubt about it. [Mαc Δαvιs] X (How's my driving?) ❖ 06:31, 25 February 2007 (UTC)

I'm sure everyone disagrees, but I believe there is a difference between "enjoying killing people" and "being pleased with killing people because it is somehow right". I believe that a person who is killing for a greater purpose, be it country, religion, or because the neighbor's dog said so, feels pleasure in doing what they believe to be right. --Kainaw ^(talk) 22:52, 25 February 2007 (UTC)

[edit] chemistry problem

if you have the equation : NaHCO3 + CH3COOH --> H2O + CO2 + NaCH3OO,

how many moles of NaHCO3 and CH3COONa are necessary to make 425 mL of CO2?

You first need to calculate how many moles of CO₂ 425 mL is.

425 ml is 0.425 L

1 mole of a gas occupies 22.4 L at STP

0.425 L x 1 mole/22.4 L = .01897 moles or (rounding) 0.019 moles

Since both NaHCO₃ and CH₃COONa are in equal ratio to CO₂ on the other side of the equation, you need the same amount of each of them.

So you need 0.019 moles of NaHCO₃ and 0.019 moles of CH₃COONa to produce 0.019 moles of H₂O and 0.019 moles of CO₂ and 0.019 moles of Na CH₂OOH.

- Nunh-huh 04:22, 25 February 2007 (UTC)

[edit] A genetically modified organisms question folks

The danger of genetically modified organisms are the restriction enzymes used to cut the strand which could have a series of events in the species and produce cancers right? But if the GMO reproduces does the offspring still have the alien restriction enzymes in his genome? —The preceding unsigned comment was added by 213.217.212.29 (talk) 11:22, 25 February 2007 (UTC).

The danger that most people fear is less specific than cancer or anything like that. It's that the GMO could have unforeseen negative consequences in the natural environment and be impossible to get back in the bottle. --TotoBaggins 13:16, 25 February 2007 (UTC)

There is more to it than that though

""which could have a series of events in the species and produce cancers right" - this is a hell of a non-sequitur. But yes, successive generations might have a chance of inheriting it. -Wooty Woot? contribs 18:55, 25 February 2007 (UTC)

You mean inheriting the trait which has been introduced, or inheriting the restriction enzymes which where used to insert it? (I'm curious about the enzymes)

P.S. With series of events I meant subsequent chemical reactions in the organism which may lead to alteration in the genome mac

Oh, I understand what you mean now. I thought you were simply talking about the trait. I'm no expert when it comes to this subject, so perhaps this is incorrect, but I don't understand why an enzyme introduced in the lab would have any effect on successive generations and actually lead them to produce the restriction enzymes. You're simply using the enzymes to snip out parts of DNA as a one time event. While the snipped DNA will (of course!) be present in the offspring, it probably has a less-than-infinitesimal chance of somehow inadvertently creating a sequence that produces the enzymes in cells. Asking if the offspring has the enzymes used as a tool to genetically modify the parent is like asking if someone's born with a scalpel in their appendix if their mother had an appendectomy. -Wooty Woot? contribs 21:05, 25 February 2007 (UTC)

The thing is that these enzymes are the only reason I heard why GMO can cause cancer, and I think that scientists are bright enough to remove a scalpel if it was that simple.

I very much doubt that GMOs have a strong correlation to cancer, and the only danger I could think of is if the restriction enzyme accidentally removed things it shouldn't, which seems to be nearly impossible. Perhaps someone with better qualifications can answer this better, but it seems that what you've heard doesn't make much sense from the standpoint of heredity. -Wooty Woot? contribs 00:41, 26 February 2007 (UTC)

When restriction enzymes are used to make a genetically modified organism the genes for the restriction enzymes are not introduced into the genetically modified organism. The restriction enzymes are used to cut DNA in test tubes. The DNA is then introduced into cells. I suspect that the reason you heard that restriction enzymes can cause cancer is because there have been claims that food from animals exposed to a genetically engineered hormone causes cancer. The story goes like this: farmers boost milk production by injecting dairy cows with growth hormone. The growth hormone use changes the milk. People drink the milk and the altered milk causes something "bad" to get into the blood stream and then it causes human cells to grow out of control and produce cancer. See Bovine somatotropin. --JWSchmidt 04:14, 26 February 2007 (UTC)

On a slightly related note, genetically engineered humans have already been born. Strange. I guess we have yet to see the effect of intentionally and directly altering the human genome. − Twas Now ( talk • contribs • e-mail ) 04:17, 26 February 2007 (UTC)

So the enzymes aren't left in the cells as they grow and reproduce?

Correct. Try reading Restriction digest and DNA ligase. These enzymes are tools used in laboratories to produce recombinant DNA. The recombinant DNA is what gets inserted back into a living cell. --JWSchmidt 20:22, 26 February 2007 (UTC)

No, they aren't. Restriction enzymes are used to snip out particular pieces of DNA of interest; at a later step, but still before the DNA was introduced into the cells, the DNA is typically attached to other DNA using other enzymes. If you left in the restriction enzymes, you'd potentially be snipping out that bit of DNA which you worked so hard to attach in the second step! Chuck 20:03, 26 February 2007 (UTC)

[edit] solar system models

Hi, just doing some research on the development of models throughout history of models of the solar system. could someone please tell me the main differences between Kepler's model of the solar system and that of Copernicus. Any help would be much appreciated asap.

Thank you very much

alex —The preceding unsigned comment was added by Quantumchemistryfan (talk • contribs) 14:15, 25 February 2007 (UTC).

The articles on kepler (see Harmonice Mundi, Astronomia nova and Mysterium Cosmographicum) and copernicus (see Copernican heliocentrism) will have this infomation.87.102.2.242 15:29, 25 February 2007 (UTC)

[edit] rainbows in mirrors

We have a mirror that for whatever reason has its edges cut off, so that it has five sides, four of which are at an angle to the wall. Whenever I look at a light reflected in one of these sides it is a different colour to what it should be. And the colour changes if I move. It looks blue near one edge, then as I move sideways it changes to green, white, yellow and then orange. After that the light passes the edge of the mirror, but i assume it would be red next. What causes this effect? And is it really a rainbow?Hidden secret 7 18:36, 25 February 2007 (UTC)

The broken bit is acting as a prism. That article will give you all the details. While you're right that it would be red next (at least in Western cultures), it's not a rainbow, since that requires --- wait for it --- rain! It's actually the other way around: water droplets in a rainbow act like the prism in your bathroom, both yielding the color spectrum of visible light. --TotoBaggins 19:39, 25 February 2007 (UTC)

Are you suggesting that prisms produce different colours in different cultures? That's a new one on me! —The preceding unsigned comment was added by 137.138.46.155 (talk) 08:45, 27 February 2007 (UTC).

Yes! Same wavelengths, same chemical reactions in the photoreceptors of the eye, but different colors: in Western culture, the colors of the rainbow are Red, Orange, Yellow, Green, Blue, Indigo, and Violet, but those divisions are totally arbitrary. I personally would not be offended if Newton or whoever had chosen to roll Indigo into one (or both!) of its neighbors. In Japan, green is thought of as a shade of blue. If my wife had named the colors of the spectrum, there would probably be at least two dozen distinct colors in the rainbow. :) I don't know where HiddenSecret's doing his bathroom experiments, but perhaps his culture has something between Orange and Red. There's more on this topic at Color#Color_naming. --TotoBaggins 02:14, 28 February 2007 (UTC)

[edit] Hydroxyapatite

Is hydroxyapatite the same as hydrated calcium phosphate?

Strictly speaking, hydroxylapatite, Ca5(PO4)3(OH), is a mineral with hydroxyl (OH) bound into its crystal structure. Hydrated calcium phosphate would have water (H2O) somehow attached to the calcium phosphate. It’s probably pretty likely that someone is using the terms interchangeably, but not quite accurately. Cheers Geologyguy 22:20, 25 February 2007 (UTC)

[edit] Nuclear Fission For Space Propulsion

If a nuclear reactor such as the one in the USS Enterprise (CVN-65), was used in a spacecraft already in Earth orbit, would the reactor be able to supply enough power to both the ship and its engines? I am curious if the reactor would produce enough power to run a VASIMR type propulsion? Thank you for any ideas.67.122.139.34 21:22, 25 February 2007 (UTC)

The USS Enterprise reactor should be quite powerful. However how would it be cooled in space? - it would have to radiate heat by thermal radiation as the nuclear generator is a heat engine. Nethertheless there could be enough power to run an ion drive as well as run the equipment on the ship. If you could run the reactor extremely hot, perhaps you could heat the plasma directly from the core, (if you don't mind venting radioactive waste to space)! GB 03:06, 26 February 2007 (UTC)

Thank You, heating the plasma from the core wouldn't be a bad idea! Who cares about radiation anyways...

[edit] The Theory of Evolution and falsifiability

Hello. I know that creationists and ID proponents frequently object that evolution is unfalsifiable. I know that, thanks to Karl Popper, unfalsifiability is generally thought of as a major strike against any scientific theory that goes further than pure definitions. So my question is, how would you falsify evolution? If a fossil were found in the wrong geological stratum, couldn't it be argued that it was a case of convergent evolution? If a natural evolutionary explanation cannot be found for the origin of a biological organism or system, couldn't it be argued that eventually we will find one? Much appreciated. 69.223.135.80 22:53, 25 February 2007 (UTC)

It's a fair question, but easy to answer: if you were to prove false any of the core assumptions of evolution (that the Earth is old, that traits are passed to offspring, etc.), you would have falsified evolution as well. It's not necessary to prove that the earth is 6,000 years old in order to falsify evolution, but it would certainly be sufficient. --TotoBaggins 00:29, 26 February 2007 (UTC)

Good question! Expanding on TotoBaggins's answer:

Evolution says (in a nutshell) that species evolve under natural selection to optimize their fitness in the environment. Darwin's original research found differences in the beaks of finches based on details of their diet and habitat. If we observed random beak differences without any cause, that might be evidence which would tend to disprove evolution. If we observed differences in diet or environment without any unique adaptations in the finches, that would be evidence which would tend to disprove evolution. Later work (I can't remember the details) has shown changes in the beak length of certain birds in response to the depths of the flower bulbs they eat out of (depths which were varying due to changes in weather patterns). If we couldn't find any examples of that happening, we wouldn't have any evidence in favor of evolution, and it would be effectively falsified.

And of course there are more complicated counterarguments. If we observe an organism with an especially surprising optimization, and if we cannot propose a valid evolutionary pathway which would/could lead to it, this too would be evidence which would tend to disprove evolution. For example, the argument is often put forth that "half a wing" (which, in some form, is a necessary point along the evolutionary path from no wings to fully-functional wings) would be useless for flying and would also be a detriment (a useless appendage) in a non-flying organism. If this observation were valid (if half a wing were truly a disadvantage), evolution would be in real trouble -- but if you think about it more carefully, having half a wing isn't necessarily useless, after all. If you can glide a little, or even if you can just run a little faster than your wingless (or even less-wingful) contemporaries, this might prove to be a selection advantage -- however slight -- in the battle for scarce prey, or the battle to escape your predators. And we've learned that even the tiniest of selection advantages can have profound effects when applied over thousands of generations.

Finally, evidence in favor of a competing theory could tend to falsify evolution. If we broke the legs or cut the hair or stretched the ears of an organism, and if these environmentally-induced traits were passed on to the organism's offspring, this would not directly disprove Darwinian evolution, but it would tend to prove the (discredited) Lamarckian theory of evolution, and would throw our understanding of evolution into such disarray that a major reanalysis of all of it (and almost certainly abandonment of at least some of it) would be necessary. And if we observed miraculous adaptations within a single generation -- for example, the sudden decrease in the rib count of one species, and the concomitant appearance of a hitherto-unseen but closely-related species, we might have to admit that everything we know is wrong.

—Steve Summit (talk) 00:42, 26 February 2007 (UTC)

It's easy to do an experiment that would falsify evolution if it came out 'false'. Take a bunch of petri dishes containing some nice simple bacteria colonies. Treat them all with a mild dose of some common antibiotic - not enough to kill them all - but enough to kill (let's say) 99% of them. Allow the surviving bacteria to grow and recolonise. Repeat this step hundreds of times. If evolution works then after a reasonable number of "generations" we'll find that this same dose of antibiotic - instead of killing 99% of them will kill much, much fewer. The bacteria will have been found to have evolved a resistance to the antibiotic agent. If this experiment fails - then you have a reasonable falsification of evolution. Sadly, this "experiment" has been proven to work many, many times over in hospitals around the world where an abundance of antibiotics in the environment has caused the evolution of drug-resistant strains of TB, AIDS and a variety of other diseases. The issue of falsifiability is long gone for evolution. It's been proved, conclusively in an experiment that could have come out false that is really easy to reproduce.

The problem is that the people who dislike that evolution is at odds with their religious views don't "get" that evolution is happening right here and now and that it's really easy to demonstrate in the laboratory. The only possible scientific question is whether evolution is in fact the cause of the diversity of creatures we see around us. That's a completely separate question than the one asked here - and it's arguably harder to prove. SteveBaker 02:20, 26 February 2007 (UTC)

Okay, thanks...I know, though, that most creationists would counter the example of evolving bacteria by saying that that's "microevolution," but "macroevolution" and common descent between distinct organisms has to be proved (or falsified) using the fossil record. So while we're at it, how would you test (falsify, verify, whatever) the claim that "evolution is in fact the cause of the diversity of creatures we see around us?" 69.223.135.80 05:01, 26 February 2007 (UTC)

First, "Macro-evolution" and "micro-evolution" are terms used by creationists and their kin to create an artificial distinction where in fact there is none. "Microevolution" and "macroevolution" are the same thing -- the change in allele frequency over time. This is the definition of Evolution.

Evolution is not the cause of diversity, per se. New traits are introduced by means of random mutation. Evolution, through natural selection, determines which of these are good and flourish, and which are bad and die out. Raul654 05:14, 26 February 2007 (UTC)

I agree that the distinction between the macro- and micro- scale is highly artificial to science - but we do have concrete examples of creatures such as birds and fish evolving on human timescales where some major ecological change has hit a small ecosystem. Warfarin resistant rats, Mixamatosis resistant rabbits...examples abound. One recent evolutionary change has been in Central America where Marajuana plants have evolved to be immune to the defoliants that US DEA folks spray onto them from the air (these crops now thrive because the defoliants kill weeds and many harmful insects). But perhaps the evolution sceptics would regard these as merely meso-scale evolution.

It's tricky to come up with a possible falsification for a theory that's essentially been proven to be true. A total lack of fossils or any other evidence of past creatures that clearly show a line of descent to modern animals would pretty much prove evolution was false - of course if that evidence didn't exist then a determined evolutionist could fly in the face of that evidence by saying "just because we havn't found a fossil yet - doesn't mean we won't one day find one"...and then you'd be able to complain that evolution was unfalsifiable by that means. But since we actually have that evidence, it's not really something you could say was falsifying evolution.

The whole concept of falsification really only relates to theories that we do not have solid evidence for - it doesn't have much meaning for a scientific theory for which there is abundant evidence.

The contrary viewpoint to evolution isn't falsifiable though. If you claim that there is a supernatural being who is completely omnipotent who created all of those animals - then that being also has the power to fake evidence, change the results of our experiments and even 'edit' our thoughts. So that theory is utterly and forever unfalsifiable. SteveBaker 06:07, 26 February 2007 (UTC)

"It's tricky to come up with a possible falsification for a theory that's essentially been proven to be true."

But if you look at it another way, it's trivial! Simply take all the hypotheses and experiments and examples and arguments which have already been used to essentially prove that theory true. That's a dandy list of experiments which, had they failed, would at the very least not have proved and would quite likely have disproved the evolutionary hypothesis. --Steve Summit (talk) 14:42, 26 February 2007 (UTC)

OK - I've got it. Evolution would be proven false if a bunch of creatures bearing no resemblance whatever to any existing life form started to appear spontaneously around the earth and were surviving despite being less well suited to their environment than other creatures in those ecosystems - ideally they would share no common DNA with any known creature. An intelligent designer could do that - but evolution could not. SteveBaker 06:15, 26 February 2007 (UTC)

The only way you could disprove that "evolution is the cause of the diversity of creatures we see around us" would be to find evidence that does not fit in with the assumptions/postulates that the evolution makes. As an example, some would argue that the Cambrian explosion is something that is difficult to explain from an evolutionary perspective. (I don't need people to go getting all excited and explain to me how this can be explained from an evolutionary perspective - there is plenty of information in the article. I'm giving an example, OK?) You also need to take into consideration things external to the theory that it does not explain. I frequently say that miracles and Biblical prophecy are both difficult to explain from an evolutionary perspective. I also consider the origin of the universe and abiogenesis to be problems for evolution. (Again, I don't need people presenting me with emotionally charged counterpoints to these things; I am familiar with the arguments and am not interested in turning this post into a creation vs. evolution debate.) BenC7 06:37, 26 February 2007 (UTC)

Theories about the origin of the universer, or about the origin of life are not theories of evolution: abiogenesis is unrelated to evolution, a theory about the origin of species. And miracles and Bible "prophesies" (i.e., reinterpretations of Bible verses shorn of their contexts in order to make them seem prophetic) are also unrelated to evolution. - Nunh-huh 06:57, 26 February 2007 (UTC)

Okay, thanks again everyone...but this has gotten back to one of the points on my mind when I first posted this. I've noticed a pattern in creation-evolution literature, that when creationists point out a gap in the fossil record or a biological system for which we have no current evolutionary explanation, mainstream biologists answer that this is an argument from ignorance. After all, absence of evidence is not evidence of absence. But if we can always say, "there is a natural evolutionary explanation, we just haven't found it yet," how can we falsify evolution? Again much appreciated. 69.223.135.80 14:53, 26 February 2007 (UTC)

So let's forget about evolution for a moment - suppose you're an Archeologist who studies Roman road-building (the Romans built beautiful straight roads that ran for hundreds of miles and lasted for hundreds of years after their empire fell). So you have a hypothesis that they built a road from (say) Rome to Turin or someplace. So you find the beginning of the road and the end of the road and you see that they line up - then you dig along the line where you think the road ought to be - and you find paving slabs and bits of roman footware and broken wagon wheels and mile stones marked "<== Rome 120 miles, Turin 67 miles ==>" and all sorts of evidence for the road along it's entire length - except for one section one mile long where there is no evidence that you can find. Is it reasonable to say that the road never existed? No - of course not. Is it reasonable to say that because we are missing a 'link' that the road must have been unfinished? Well, no - there is just a statistical distribution of paving stones and bits of debris that's inevitably going to have the odd gap - so this is no disproof of the 'continuous road' hypothesis. So whilst you can't say with scientific rigor that the road definitely ran from Rome to Turin - you can say that:

1. Romans definitely did build roads in general.
2. It's overwhelmingly likely that this particular road ran from Rome to Turin without a break.
3. Because all other evidence is that roman roads were very straight then it's pretty likely that the missing mile was a dead straight line with a bridge over the intervening river at such-and-such location...but maybe not...it's possible there was a big detour here...we really don't know.
4. Can we say that because of this gap it must be that the Romans used flying carpets to get from Rome to Turin? ... Eh? What??? WHAT???

OK - so back to evolution. We know for sure that things evolve. We've seen it happen to Wolfarin resistant rats - and we can make it happen reliably in the lab by creating drug resistant bacteria. That's like understanding that the Romans could indeed build roads - we know for sure from direct evidence. We also have fossil records to show that evolution more or less leads from the primitive archeobacteria to humans. We do have the odd break in the record. Should these breaks be proof that evolution isn't a true theory? Certainly not. Should the breaks cast doubt that men are evolved from archeobacteria - well, not really - the evidence is still pretty amazingly solid. But do they mean that we don't precisely understand the step from this particular fish with this particular gill setup to this other fish with the rather different gill setup - yes...for sure. There are steps along the way that we are missing that have to be filled in by conjecture until/unless we find that missing link. But the existance of that little gap that can't possibly be taken to destroy the entire theory because every single piece of evidence we do have - and every single experiment we can do - fits exactly with the hypothesis. Just as you can't use a small break in a Roman road as evidence that all Roman roads were magically constructed by Merlin the Wizard. The intellectual leap is just that huge. SteveBaker 18:39, 26 February 2007 (UTC)

I saw this today. Lactose (in)tolerance: A good example of evolution acting to change modern humans: http://www.sciscoop.com/story/2007/2/27/5820/14064 SteveBaker 16:58, 27 February 2007 (UTC)

You could disprove the theory of evolution if you proved that a)organisms did not inherit characteristics from their parents (eg, it is just coincidence that you appear to have many of the same features as your parents and other family members) b)these characteristics were passed down in such a way that they could not change (eg, all descendants of white rats with pink tails 10cm long are white rats with pink tails 10cm long, forever) or c)there are no factors which favour one characteristic surviving over another (so the genes which create deer that run faster are as likely to be found in the next generation as the genes for deer that run slower). Naturally, any of these findings would mean that we'd had some amazing coincidences over the years... Skittle 23:19, 27 February 2007 (UTC)

That's OK though - falsifiable means 'falsifiable in principle' - theories that happen to be true are never falsifiable in actual practice because if something is definitely true, you can never find evidence to disprove it. I have a theory that 2+2=4 - I have evidence to prove it and we can't find evidence that it's not true...so it's not literally falsifiable. But in principle it is - you could take two apples and put them next to two apples and count how many apples there were - and one day the answer might come up '3' - and we'd have falsified the theory. So 2+2=4 is falsifiable - but it also happens to be true. However, you can never disprove the existance of The Invisible Pink Unicorn, because she can arbitarily alter any of your experiments - change your brain patterns to cause you to believe you just did a convincing experiment to prove her pinkness's existance (when in reality you didn't)...she is utterly non-falsifyable. SteveBaker 06:19, 28 February 2007 (UTC)

[edit] My budgie questions

I asked some questions a couple of days ago - does anyone have any answers? Thanks very much. :) --84.65.181.93 23:09, 25 February 2007 (UTC)

According to this, this is your very first edit (question, comment or whatever). So, are you sure that you posted your inquiry on WP? --hydnjo talk 01:53, 26 February 2007 (UTC)

There were a couple of budgie questions on the 23rd, but apparently there is no resident expert. Clarityfiend 02:38, 26 February 2007 (UTC)

Ok an expert I'm not but I've raised many cage birds over the years and have a degree in Wildlife Bio so here goes: 1)The wings over the head is often a defence or threat posture. The little guy is trying to look bigger than he is. That being said I've often seen it in cage birds with no apparent cause and it may just be boredom or stretching. 2)Warm feet indicating mood, that's a new one tho it makes sense somewhat. The legs & feet of small birds are often considerably cooler than the body. If they are warm it probably means that the little guy is well fed & content. 3)You're looking for what breeders call the F1 or wildstock. If allowed to breed randomly Budgies will often revert to the wild colouration over a couple of generations but true wildstock is no longer availible since Australia no longer allows exportations of thier critters. Hope I've helped Canis sylvaticus

Thanks for your answers, mate. FYI, I have a dynamic IP, so the questions I asked probably came from a different address. My budgie doesn't really put his wings over his head - he sort of splays them out to the side whilst keeping them folded behind his back. Fom the front, it gives him a sort of heart shape (sorry, it's quite hard to explain), like an eagle in a painting. He often does it after I've had to pick him up to trim his toenails or put him back in his cage when he won't go in by himself (though that's not the only times he does it). --84.64.101.26 13:08, 26 February 2007 (UTC)

[edit] aspirin and food poisoning

Given aspirin's ability to drop the stomach pH... Could it be used as a prophylaxis against food poisoning? 65.94.222.105 23:16, 25 February 2007 (UTC)

No. pH isn't going to protect against food poisoning. - Nunh-huh 01:37, 26 February 2007 (UTC)

However, the Food poisoning article does state that Salmonella which is a common cause of food poisoning (but by far not the only cause) is very acid sensitive. Quote: An artificially higher stomach pH level greatly reduces the number of bacteria required to cause symptoms (by 10- to a 100-fold). That does NOT necessarily mean that a lower pH will have an opposite effect, but it does seem to suggest it. Commonly, interactions between drugs are more complex for us mere mortals to hypothesize about. Could in fact be that aspirin in some other way does something else which increases some other avenue of food poisoning, a doctor is really the only person who could give any kind of advice. Vespine 04:09, 26 February 2007 (UTC)

Once again: no matter how many wikipedians make up some imagined mechanism that makes it seem feasible, aspirin has no use as prophylaxis against food poisoning. - Nunh-huh 05:18, 26 February 2007 (UTC)

It might treat some peripheral symptoms (headaches?) but it probably will not prevent food poisoning. Nimur 10:26, 26 February 2007 (UTC)

[edit] Sprained Ankle Question

I know, I should "see a doctor". Nevetheless, I come to my trusted wikipedians: I sprained my ankle a few hours ago playing basketball. I felt to distinct "pops"/"snaps" when I landed, which I believe were the tendons/ligaments being extended. It is not so bad that I cannot walk on it, but when I do it hurts and I am forced into a limp. I was told to tie my basketball shoes tightly in order to inhibit the swelling, and when I got to my room I wrapped it tightly with athletic tape. Now I received conflicting information, however, saying I should Ice it...seeing as it is not a horribly sprained ankle, what is the best course of action? Keep it warm and tight? Iced and open? Thanks, 140.180.8.28 00:01, 25 February 2007 (UTC)

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[edit] Wikipedia:Medical disclaimer

One More Time: We are not allowed to offer medical advice on this reference desk. See a doctor. SteveBaker 00:10, 25 February 2007 (UTC)

I don't think anybody "permits" or "forbids" us from giving medical advice. It's just a community-enforced bit of common sense that WE ARE NOT TRAINED EXPERTS and MEDICAL ADVICE HAS CONSEQUENCES. Go see a doctor. Nimur 11:12, 26 February 2007 (UTC)

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I would ice it and take an anti-inflammatory.... before seeing the wikipedia-mandated doctor. --138.29.51.251 02:35, 25 February 2007 (UTC)

Sprains should be x-rayed. If something heals badly, you're going to have to get it broken all over again! Ouch! --Zeizmic 15:40, 25 February 2007 (UTC)

We should be allowed to say "I have known people with complaints such as your who had a broken ankle or serious injury needing medical attention, so if I were in your shoes ;<) I would see a doctor." Edison 16:02, 26 February 2007 (UTC)

In my personal experience, ice immediately and save the warm treatments for after 24-48 hours. Follow the advice here http://sportsmedicine.about.com/cs/rehab/a/rice.htm But definately see a doctor asap. It may be major. Rawbanana 02:10, 1 March 2007 (UTC)

[edit] Aviation

1. can a bird strike take place on an upper surface of a wing?sumit 06:52, 25 February 2007 (UTC)--sumit 06:52, 25 February 2007 (UTC)

2. What is riggers angle of incidence? What is its relevance vis a vis stability, range cruise flying, passenger comfort?sumit 06:52, 25 February 2007 (UTC)--sumit 06:52, 25 February 2007 (UTC)

Check out angle of incidence. --TotoBaggins 13:16, 25 February 2007 (UTC)

For question 1, I don't see any reason why not, unless it was very high up:)Hidden secret 7 18:53, 25 February 2007 (UTC)

The real danger of bird strikes is if it clogs the engine. They do consider this when testing new engine designs, by firing chickens into it. --h2g2bob 22:07, 25 February 2007 (UTC)

Birds can also damage or obscure the windshield, which can make the airplane perform poorly. anonymous6494 01:43, 26 February 2007 (UTC)

And clog the pitot tubes, which puts the airspeed indicator out of service. In one accident - Eastern Air Lines Flight 375 - birdstrikes damaged three engines, blocked the windscreen, and damaged all the pitot tubes. 62 died. --Charlene 04:26, 1 March 2007 (UTC)

[edit] Interesting question

Does anyone know of a medical condition that there is/has never been any known case of?

I know that diseases/pathologic states are defined based on presentation etc...

You mean like a 'hypothetical' disease/pathologic state? I suppose it isn't impossible but I would have thought by now, every single known biological process probably has a failure that has been observed and recorded. Umm, that's not to say no new diseases will ever be found, I suppose, but, doesn't the discovery, by definition, preclude the classification? Vespine 23:29, 25 February 2007 (UTC)

How about supercalifragilisticexpialidocious-itis, in which the patient (usually a British nanny) will begin to fly upon picking up her umbrella. Also, these patients enjoy singing. − Twas Now ( talk • contribs • e-mail ) 04:11, 26 February 2007 (UTC)

Has there ever been an scientifically validated case of phenomenon of retrocranial inversion? Countless people have been claimed by others to be suffering from it, but actual cases do not appear in the medical literature anywhere that I could find. Edison 16:38, 26 February 2007 (UTC)

Have you checked with the Walter Reed Medical Centre?

Seriously, here's one: oxygen anaphylaxis. Another: water anaphylaxis. --Charlene 04:29, 1 March 2007 (UTC)

No therianthropy has ever been proved to have happened

[edit] Earth Days

I've read in numeroues places that an earth day is 23 hours and 56 minutes long (one place: http://www.space.com/scienceastronomy/101_earth_facts_030722-2.html see #13). However, a day is commonly defined to have 24 hours (exactly). My clocks certainly don't skip a few minutes, so what's going on here? —The preceding unsigned comment was added by 70.122.69.27 (talk) 21:59, 25 February 2007 (UTC).

See leap year and leap second --Russoc4 22:02, 25 February 2007 (UTC)

Sidereal day explains 23:56:4.091. Weregerbil 22:13, 25 February 2007 (UTC)

Just wondering if anyone ever comes back for the answer. So, if the original poster (70.122.69.27) sees this then "ping" back to us just to let us know that someone is listening. Thanks, --hydnjo talk 02:18, 26 February 2007 (UTC)

The earth does indeed spin about it's axis once every 23 hrs 56 minutes - but our 24 hour "day" is the time between one sunrise and the next. Since the earth moves around the sun as well as spinning on it's axis, the sun would rise and set once per year even if the earth wasn't spinning at all. So we have to add the time for one 365th of a day to the rotation period. When you do that, it works out neatly to 24 hours. SteveBaker 02:40, 26 February 2007 (UTC)

[restored from accidental revert] It's one (solar) noon and the next; sunrises and sunsets have additional complications because of day length variations. --Tardis 04:01, 26 February 2007 (UTC)

Of course it works out neatly to 24 hours, that's the definition of 24 hours :p Capubadger 10:56, 26 February 2007 (UTC)

Don't be silly, 24 hours is defined to be 794243384928000 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of Caesium-133 at rest in zero magnetic field at 0K. (pauses for breath) It's a complete coincidence that this comes out as one solar day :p Algebraist 15:51, 26 February 2007 (UTC)

How much energy would be required to speed it up to one revolution per 24 hours exactly? How much power if it were done over a one year period? Edison 16:42, 26 February 2007 (UTC)

A lot. anonymous6494 17:32, 26 February 2007 (UTC)

Yes! The energy required would be 1/2 I w² where w is the amount you want to speed it up by in radians/second I is the rotational inertia of the earth - which we could approximate as a homogeneous sphere (although in reality it has a liquid core and variable density...but let's go with an approximation for now). I = 2 m r²/5 ...so um...I=6x10³¹ or so. We need to add 2 pi radians per year of rotational velocity - which is about 2x10^-7...so we're looking at 10¹⁸ Joules. No problem! SteveBaker 19:03, 26 February 2007 (UTC)

That's not a prohibitively large amount of energy, it is much more difficult to provide a force to rotate the entire earth. anonymous6494 00:40, 27 February 2007 (UTC)

Solar sails? Capubadger 08:25, 27 February 2007 (UTC)

It's worse than you think. What we need to calculate is , which is not at all the same as but is rather . For small changes in rotation (like this one), we can ignore the squared term: the result is that your energy needs to be multiplied by . [in reply to Capubadger] As for solar sails, even if the entire Earth were a perfectly reflective sail (which it couldn't very well be), with all the force somehow applied at and tangent to the surface (which it couldn't very well be), we'd expect an angular acceleration of , which would take more than 82 million years to produce the desired change in the day. Admittedly, this is not long in geologic time, but in "tolerating the Sun being blotted out by solar sails everywhere" time, it's quite a lot — and it's a conservative estimate. --Tardis 14:54, 28 February 2007 (UTC)

Ack! You're right! My profuse apologies. So much for 'back of envelope' calculations. In future I'll use the front of the envelope too (that way I can incorporate the stamp into the math). SteveBaker 20:30, 28 February 2007 (UTC)

[edit] Most efficient brain drug delivery route?

Hi all! Simple question first: What is the most efficient route of administration of drugs (or any other substances) to the brain? By efficient, of course, I mean: fastest, with least side effects, and with best drug absorption possible. If the dosage form of these substances was the most simple and effective one (I'm assuming that would be solutions, or even gases), and those substances were able to cross the blood-brain barrier with no complication, what would be the easiest way for those substances to get there?

Now, if I assumed that oral delivery is one of the most effective paths to the brain (and excuse me if I'm way off here), what is the most effective route of administration in the mouth? (My guess would be sublingual delivery... I dunno!)

Speaking of which, before searching for an answer, I'd heard of a special route of delivery, of which there is little to no info on Wikipedia: gingival delivery. Last and hardest question: How effective, if at all, is gingival delivery compared to other delivery routes (to the brain or not)?

Hope it's not too much... Thanks in advance RD'ers!! Kreachure 22:41, 25 February 2007 (UTC)

Yeah, I am not a doctor and I only have limited experience with brain and drugs but I think you are way off with the oral thing. Administering drugs to the brain is made difficult by what is known as the Blood-brain barrier, reading that article might give you more insight. Vespine 00:46, 26 February 2007 (UTC)

Delivery to neural tissue necessitates a crossing of the blood-brain barrier, as you said. Here's how one would accomplish that, from the beginning. First, get the medication into the blood. The easiest way to do this is to put the chemical into solution and inject it into the bloodstream. Oral administration is appropriate for chemicals that adsorb through the gastrointestinal tract. Sublingual, transdermal, insufflated, and inhaled drugs exist. Intramuscular, intrameningeal and intraosseous delivery methods are also available. Once the chemical is in the blood, it has to get across the neurovascular endothelium, which insulates the blood from the brain. There are two common ways to do this, one is to use a drug that can cross the lipid bilayer easily, an aliphatic drug (though that also means that it will be difficult to dissolve in the blood and may need a carrier). The other method is to use another drug which temporarily causes the epithelium of the neural vasculature to become leaky or fenestrated. Administration of one of these endothelially-active drugs along with IV administration of your chosen drug is usually your best bet for rapid infiltration of neural tissue, so intrameningeal drugs are usually reserved for plan-b scenarios. Some hormones, for some ridiculous reason, are only available (at reasonable prices) via gingival delivery, but it is only really called for in certain conditions where patient-directed delivery has to be just right, and the patient refuses to use intramuscular injection methods (that is, for needle-phobic individuals outside a hospital setting). ^tucker/_rekcut 02:58, 26 February 2007 (UTC)

The question might be about this BBC report. --Charlene 04:34, 1 March 2007 (UTC)

I have no good references for this at the moment, but most people agree that the most efficient way for the average person to administer a psychoactive drug is intravenous injection. Opioids are edible, smokable, intramuscularly injectable, etc., but all junkies choose to inject intravenously.

When you talk about sub-lingual administration, you must be talking about LSD (I can't think of any other drug that can be administered in this way.) LSD is so powerful and potent that sub-lingual administration is very efficient; however, some users claim that the tear ducts absorb LSD more readily and efficiently (using liquid LSD like eyedrops).

Ketamine is a good example of a drug that can be administered in numerous different ways, either by ingesting, insufflating, injecting intravenously and intramuscularly, etc. Erowid has a good chart on the efficiency of each route of administration. [11] That chart shows that for ketamine, injection (either intramuscularly or intravenously) is the most efficient, and insufflating is substantially less efficient (requires three halves the amount). Oral administration (ingestion) and rectal administration are far less efficient (requiring six times the amount.)

You can always do research through WP:PDD! Jolb 23:05, 1 March 2007 (UTC)

[edit] February 26

[edit] Evolution

Evolutionary theory posits " randomness ". What is the ultimate source of this randomness? QM ? 206.74.74.42 01:00, 26 February 2007 (UTC) Willie

Evolution requires inheritable variation, which may arise through random mutation, but may not — other sources of new variation are gene flow between populations and the reshuffling of genes during sexual reproduction. Our article on evolution gives a good summary of the causes of mutations. -- Avenue 01:27, 26 February 2007 (UTC)

Also see Randomness#In_biology. -Wooty Woot? contribs 01:27, 26 February 2007 (UTC)

Randomness is at the heart of all things - Quantum theory basically says that all of existance is just a matter of statistics - even in the absence of quantum effects, Chaos theory gives plenty of randomness to drive evolution. SteveBaker 01:52, 26 February 2007 (UTC)

Chaos != randomness. — BRIAN0918 • 2007-02-26 19:19Z

Evolutionary theory does not posits "randomness", it posits "Changes to the environment". The changes to the environment need not be random. For example: Human have been "overfishing" the seas, this has lead to the evolution of the fishes in the seas/oceans. I would not call human fishing an act of randomness. 202.168.50.40 03:51, 26 February 2007 (UTC)

I think the questioner is talking about the changes that happen to DNA. There are two parts to evolution - a new DNA configuration creates a slightly different creature - then 'survival of the fittest' selects the configurations that work the best. Sure - changes to the environment change the definition of "the fittest" - but some mechanism to scramble up the DNA periodically is also needed. This implies some kind of randomization either by random cross-breeding or transcription errors in DNA replication - or whatever. SteveBaker 04:39, 26 February 2007 (UTC)

Maybe the questioner is instantiating a philosophical query about determinism into the specific example of biology. A lot of theology and secular philosophy deals with randomness. A lot of computer science and number theory also deals with randomness. Evolution may or may not be 'random' depending on how you want to define 'random.' Nimur 10:23, 26 February 2007 (UTC)

If the question asker wants more concrete sources of gene mutation, they can be caused by viruses, chemicals, radiation, and other mutagenic agents. Others appear to be truly random DNA replication errors. StuRat 18:13, 26 February 2007 (UTC)

To the question poster: imagine flipping a coin. Will the result really be random? No, because if you flip the coin in exactly the same way every single time, it will end up on the same side every single time. But the result of the coin flip changes due to the tiniest variations in how and where you flip, so we can consider the result to be random.

Gene mutations are not random, but we can consider them to be because small changes in the radiation level, chemical concentration, etc. will cause very large changes in the actual mutation. --Bowlhover 01:16, 27 February 2007 (UTC)

Coin flipping is fairly reproducible - but it's a bad example of a classical system that exhibits randomness. Lets pick an easier system to talk about. Take a free-swinging pendulum with a magnet on the end with it's North pole pointing downwards - and position beneath it two other magnets a reasonable distance apart with their South poles pointing upwards so as to attract the pendulum. Depending on where you start the pendulum swinging, it'll eventually end up stationary over one or the other of the two magnets - although it might loop around them a few times in a fairly complicated way. Suppose you get a piece of paper and mark on it every possible starting point for the pendulum and colour that point in Red if the pendulum ends up over the magnet to your left and Green if it ends up over the magnet to your right. The resulting 'map' is very interesting. It's a fractal - kinda like a mandelbrot set. You can theoretically use it to say "If I start the pendulum here - where will it end up?". As you might expect, there are some regions (near the left magnet for example) that are solidly red - and other areas (near the other magnet for example) that are solidly green - and yet other areas that have swirls and stripes of red and green. But there are other places on this map where the red and green marks are mixed up together very densely so that it would seem to be almost impossible to position the pendulum accurately enough to reliably get a red or green result - some microscopic change in air currents or in the shake of your hand would prevent you ever getting the exact result you'd expect. But even if you control those things - keep the system in a vacuum - use a robot to position it - put it into a deep cave where no vibrations could affect the system), there are places on that map where the red and green regions are smaller than an atom - smaller even than an electron - smaller than the smallest quantum of distance. At that point, no matter how accurately you started off the pendulum, you could never - even in theory - predict where it would end up. Quantum distance limits and Heisenburgs uncertainty principle would forever prevent you from getting a reproducible result and the result is truly random. This is Chaos Theory - and it controls a surprising amount of what we know about the world - random cosmic radiation striking the DNA and messing it up is certainly a chaotic effect with quantum-level complexity. You can't (even in principle) predict it. There is true randomness at the heart of all things. SteveBaker 16:56, 27 February 2007 (UTC)

Strong agree with Steve Baker. But of course, this is only one of many philosophical interpretations of scientific theory and mathematical fact. People will believe what they want to believe. Nimur 06:28, 28 February 2007 (UTC)

[edit] Hepatitis A and B Vaccines

Are the vaccines for Hepatitis A and B live viruses or not? —The preceding unsigned comment was added by 67.176.206.159 (talk) 04:01, 26 February 2007 (UTC).

No. Hepatitis A vaccine (VAQTA or HAVRIX) contains inactivated virus. Hepatitis B vaccine (Heptavax-B) is made from recombinant viral proteins and thus contains no actual virus, killed or otherwise. - Nunh-huh 04:11, 26 February 2007 (UTC)

[edit] Recombinant protein production

Why do inclusion body are generally formed at the very end of cell and not in the middle? —The preceding unsigned comment was added by 203.200.225.163 (talk) 04:45, 26 February 2007 (UTC).

[edit] EMF

If you had a really long circuit, say a switch, joined in a circuit by 3x10^8m of wire to a lamp. What would happen when you turned the switch on, then turn the switch off before a second has passed (before the light has turned on)? Would the light blink? I'm thinking that although the EMF is off, there is still the "shockwave" of current moving around the circuit, so it would blink for as long as you kept the switch on.

What do you think? Capubadger 07:43, 26 February 2007 (UTC)

Yes, the light would definitely blink. See transmission line. In fact, an entire sub-set of electrical engineering deals with the practical and theoretical analysis of this sort of phenomenon. You don't even need a particularly long circuit to observe this effect; smaller lengths of wire cause shorter delays but are relevant to AC signal phase. Also, you can have delays caused by other things such as active devices, transistors, or simply the material properties of your transmission medium. Nimur 10:18, 26 February 2007 (UTC)

I suppose it is analogous to a pipe full of water? If you turned a tap on at one end, if the pipe was really long, then you would have to wait for the water shockwave to travel down at the speed of sound, but it would still flow out the other end after a time? Thanks for the second opinion :) Capubadger 10:26, 26 February 2007 (UTC)

Sure. Water in a pipe is a compression wave or shock wave; but electromagnetic phenomena actually propagate as electromagnetic waves, so your analogy is conceptually similar but not exactly equivalent. Also, the electromagnetic waves can travel at various speeds based on the type of medium it is traveling through. This article helps explain the various details of the speed effect. This effect is a very real one that engineers must worry about. Utility power companies work with a power factor that determines how much power is burned up in the line because of this delay (and other effects). Computer engineers must carefully route integrated circuit wires to make sure signals get where they are going at the right instant. Radar engineers build phased array antennas by carefully controlling the delay, allowing for beam steering. As you can see, you've stumbled across a very important effect of electromagnetic theory! Nimur 11:30, 26 February 2007 (UTC)

The internet isn't a big truck, it's a series of tubes, right?213.48.15.234 15:46, 26 February 2007 (UTC)

Keep in mind though the resistance of the wire. According to American Wire Gauge, 12 gauge wire (common in your home) has a resistance of 3.3 ohms per kilometer, giving you a total resistance (including return path) of almost 2 gigaohms. There will be nearly zero current in the wire, thus the light will not go on. anonymous6494 17:29, 26 February 2007 (UTC)

Damping is a second-order effect. In the ideal wire approximation, the signal is not attenuated or distorted. But yes, if the wire were actually ~10^8 meters long, significantly more complicated analysis would be needed even beyond simple resistive damping. Nimur 17:45, 26 February 2007 (UTC)

Sure if you send a short pulse of electricity, the pulse continues to travel along the wire even if you've stopped sending it. This is not only noticable - but most high speed electronic circuits rely on it. Computers operate at speeds where a few nanoseconds matter - and since a nanosecond is about a foot of wire, these things become vitally important long before you have a light-second worth of cable! SteveBaker 18:10, 26 February 2007 (UTC)

See Time domain reflectometry for a practical application. A pulse is initiated down the transmission line and it has a delay to the impedance mismatch. Since the generator doesn't have any idea what the load is, it transmits all it's power into the line and some of it is reflected when the impedance changes. --Tbeatty 05:01, 27 February 2007 (UTC)

[edit] Icefish

I just read about these things that live in Antarctic waters; because of the low temperature and the high oxygen content in their environment, they don't need hemoglobin and can basically suck in oxygen by direct osmosis. According to FishBase, their "gill membranes fused." So... do they have gills, or not? If not, does that make them unique among fish? Nimur 10:15, 26 February 2007 (UTC)

They do have gills, according to this. --TotoBaggins 11:32, 26 February 2007 (UTC)

Wow! I looks like space alien Jormix 21:15, 26 February 2007 (UTC)

[edit] Chemistry: Ionic strength (μ) and rate constant (k)

The article on rate coefficient explains that a rate coefficient is affected by "temperature […], ionic strength, [and] surface area".

I understand how temperature would affect the rate coefficient (explained by the Arrhenius equation), but it is not clear to me why ionic strength has an affect. Why is it necessary to show the ionic strength when stating a rate coefficient? − Twas Now ( talk • contribs • e-mail ) 13:09, 26 February 2007 (UTC)

Okay, I figured that out. However, I'm not sure what effect it would have to double a reactant's concentration but keep ionic strength constant. I would think the rate constant would stay the same but the rate of reaction would increase? − Twas Now ( talk • contribs • e-mail ) 15:54, 26 February 2007 (UTC)

Yes that sounds right (provided the rate of reaction depends on the concetration of reactant - it doesn't always).87.102.3.88 17:50, 26 February 2007 (UTC)

[edit] Someone recommended a gull book to me a while back...

It was a few months ago now and I can't seem to find the topic in question. It was a book specifically about 'gull > gull', 'human > gull' and 'gull > human' communication if I remember correctly. Now I have enough money to buy books again, I'd be interested in chasing it up ;). Could the kind person in question possibly refresh my memory as to title and author? Thanks very much... ;) --Kurt Shaped Box 13:27, 26 February 2007 (UTC)

Have you had a look in the reference desk archives?, or go for your contributions. You have been posting to the science reference dsk quite a lot. This will give you the date, and then you can see which archive to look in.

GB 00:22, 27 February 2007 (UTC)

It's a ruse to make us dig through gull question archives! 128.12.131.191 02:48, 27 February 2007 (UTC)

Yes there are a lot of gull questions, and they seem to be connected with Kurt Shaped Box, but I was hoping that user could take a look! - - - GB 03:27, 28 February 2007 (UTC)

[edit] Melting point of Cheddar

What's the melting point of Cheddar cheese? --Ppk01 14:35, 26 February 2007 (UTC)

I don't think it exactly melts. Many things with a high fat content just get thinner as they warm up, but are never really completely liquid. I know it's hot enough to burn when "liquid", so maybe around 200 F, if I had to pick a temp. StuRat 17:51, 26 February 2007 (UTC)

Cheddar cheese becomes a runny dipping sauce at water's boiling point, which is why a double-boiler is used to keep the cheese from burning. --Kainaw ^(talk) 17:58, 26 February 2007 (UTC)

Yes - I doesn't melt (like ice) - see melting point " Amorphous materials as well as some polymers do not have a true melting point as there is no abrupt phase change at any specific temperature. Instead, there is a gradual change in their viscoelastic properties over a range of temperatures." - cheddar cheese is a complex mixture of different substances - some of these compounds start to melt before others - meaning the cheese gets softer and softer as the temperature increases - I've managed to melt cheddar in a microwave to a thickish orange liquid.87.102.37.39 20:47, 26 February 2007 (UTC)

[edit] Peculiar and elusive disease/illness, please help

Hey everybody, I have some sort of neurological impairment which has perplexed my doctor, and neruologist, and NHS consultant, I was wondering if anybody on here might have any suggestions as to what could be up with me. My symptoms are similar to epilepsy, I have seizures, although i have them in my sleep, i apparently become quite aggressive, throwing myself of my bed, and have apparently pulled off a trained paramedic and my father and I am only sixteen, and not very muscular. I also begin to swallow my tongue, until my father put me in the recovery position. My local health authority has run a battery of tests, including a Magnetic Resonance Imagine scan (MRI), and an electroencephalogram scan (EEG). We have, after applying some pressure to my doctors, received the results of the scan, and have been told that there is no sign of a growth, and no sign of any abnormal brain activity which could indicate epilepsy. So now, both me and my doctors are frankly, baffled about what is wrong with me, the seizures are becoming increasingly more frequent, and irritating. Does anybody have any suggestions as to what could be wrong with me? Thanks in advance Ahadland 15:53, 26 February 2007 (UTC)

Wikipedia cannot provide medical advice. Consult a second opinion if you have to. Splintercellguy 16:06, 26 February 2007 (UTC)

I have, many times, they're as confused as i am —The preceding unsigned comment was added by 82.36.182.217 (talk) 16:29, 26 February 2007 (UTC).

Not medical advice, but Wikipedia articles which might be of interest include Sleep disorder , Parasomnia , Somnology , and Polysomnography and possibly Restless legs syndrome as well as Seizure and Seizure types . Best wishes for getting diagnosis and treatment. Edison 16:59, 26 February 2007 (UTC)

I don't know if this helps, I'm not a doctor. Some seizures are triggered by light flickering, if you close your eyes you can still see light flicker, maybe make sure you have all lights turned off around the area you sleep, if that doesn't work try more light, maybe your body reacts to certain frequencies that light (especially florescent) produces. Try staying in a different room, then maybe a different house etc. We are looking for a "trigger" remember. If all that has been done the next step would be sound. Sound would be the next "frequency" of things I would try to look for. Hope this helps. Good luck.

Clearly if you are having seizures while you sleep, someone has to record your brainwaves while you sleep in order to know what's going on. You don't mention having had sleep studies, and it rather sounds like you should insist that someone perform them - Nunh-huh 06:23, 28 February 2007 (UTC)

[edit] Digital TV and Freeview

Hello,

I am going to buy a Freeview box to get digital tv but i need to know some stuff:

• Firstly i need to know if i can recieve it. I live slap bang in the middle of Lincolnshire, UK; will i get it? (the Belmont Mast is close by!)

• Secondly I'm confused as to what to buy. I had a look on www.amazon.co.uk and places like Argos and Currys and i found lots of Freeview boxes, which is what I want, for around £20-30. The problem is that I'm not sure which ones are actually the ones that "I plug into my tv and i can get the freeview channels". Are any of these what im looking for: 1/2/3? —The preceding unsigned comment was added by 84.64.158.119 (talk) 17:22, 26 February 2007 (UTC).

http://www.amazon.co.uk/Goodmans-GDB3-Freeview-Box-Interactivity/dp/B0007LYJ68/sr=1-4/qid=1172508692/ref=sr_1_4/203-9129227-6237561?ie=UTF8&s=electronics 1

http://www.amazon.co.uk/DIGIHOME-FREEVIEW-Digital-Terrestrial-Receiver/dp/B000BISKUS/sr=1-1/qid=1172508692/ref=sr_1_1/203-9129227-6237561?ie=UTF8&s=electronics 2

The two above are both what you want - the third link you supplied is for a PC not a TV.

Note that your TV will need to have a scart input (or similar eg composite or component) - that's an input 'at the back' that isn't an aerial socket - if you have a very old TV there might not be a scart input - otherwise you will be fine - many freeview boxes also output a RF signal that can be tuned into like a standard channel.

Most of the UK is now covered by Freeview - I'm sure Lincs as well (you can check coverage by inputing your post code at this site http://www.freeview.co.uk/home)- note when we got freeview we needed a new aerial - I'm not sure that that is always the case - given that the belmont mast is so near you probably will have a very strong signal and reception should be easy. By the way I live in hull and often wondered where the TV signals where transmitted from - now I know!.

I recommend this site http://www.freeview.co.uk/home for general info - boxes with a 7/8 guide tell you what will be on for the next week - I recommend those.87.102.3.88 17:46, 26 February 2007 (UTC)

You need good reception (check here) and a good-ish areal for digital. A better option is to ask your neighbours what sort of signal they get. As for the box, just buy a £30 Digibox from Tesco or something, it really doesn't matter. You do not need a TV which supports SCART, which 87.102.3.88 suggested above, as the digital TV is added as an extra channel as the TV signal passes "through" the digibox. If you don't have SCART, you will need to tune a channel on your TV to the Digibox channel (just like when adding Channel Five). --h2g2bob 19:43, 26 February 2007 (UTC)

[edit] “Gira” bird

Sorry, this is a hard one (at least for me): I am trying to find the scientific name of a bird I saw at the Montreal Biodome, the guide called it a “gira” (“jeera” but not “djeera”). He also mentioned it looks like a roadrunner and that it’s a recent addition to the ecosystem. Since the part of the ecosystem it was in is the tropical rainforest of America (mostly South America but also Central America) it comes from there. I’d personally describe the bird as very similar to a Great Lizard-Cuckoo (Saurothera merlini) but with a more brown appearance and a pale brown crest. It also has a big black tail with white spots. If it helps there were three birds that stayed together and looked curious. Hoping you can help me. Thanks in advance. Pro bug catcher (talk • contribs). 05:11, 17 February 2007 (UTC)

A search using the Biodome search form suggests colaptes auratus. --Shantavira 13:24, 17 February 2007 (UTC)

Colaptes auratus is not a tropical bird of South or Central America, does not look like a Great Lizard-Cuckoo (Saurothera merlini) and certainly doesn't have a crest. But thanks for the try. Pro bug catcher (talk • contribs). 02:52, 18 February 2007 (UTC)

Did you try asking them? --NorwegianBlue ^talk 22:51, 26 February 2007 (UTC)

[edit] Feeding boiled eggs to the gulls...

Someone suggested to me today that gulls enjoy eating boiled eggs. I have some that're just past the use-by date, so I'll cook them up tomorrow for my feathered associates. One question - shell on, or shell off? Which do you think would be preferable to them? --Kurt Shaped Box 23:04, 26 February 2007 (UTC)

What is it with you and seagulls anyway? Vitriol 23:39, 26 February 2007 (UTC)

I enjoy feeding them and watching them in my garden. I like gulls in general. --Kurt Shaped Box 23:42, 26 February 2007 (UTC)

Good evening. Is The Birds your favorite movie, by any chance? Clarityfiend 00:01, 27 February 2007 (UTC)

I love the ending. Those gulls are so tame.... ;) --Kurt Shaped Box 00:14, 27 February 2007 (UTC)

Clearly it is time for a science experiment.  ;-) Set out some with shell on and some without and see what they go for most readily. Dragons flight 00:32, 27 February 2007 (UTC)

I'd be a little concerned as to what that much egg shell could do to the innards of my precious gulls. I suppose my original question should've been "can gulls digest egg shell?". I know that gulls can and do eat eggs in the wild but I don't know if that includes the shell or not... --Kurt Shaped Box 00:46, 27 February 2007 (UTC)

Well, I doubt they find very many peeled ones out in the wild. That implies to me that they either eat the shells or they are capable of removing the shells. Of course, their is a possible flaw with this logic. The eggs they may encounter in the wild are not boiled. That may make a difference. For instance, with a raw egg, they could smash it in their beak and let the yolk and egg white run into their throat then spit out the shell. With a boiled egg, the shell may not be as easy to seperate. I don't think the egg shell is going to hurt them. Even if they normally shell their eggs, I would think they edd up swallowing some shell anyway. I would try to science experiment per Dragons flight. Johntex\^talk 02:45, 27 February 2007 (UTC)

Well, anyway - I gave them three with shell, three without. They scarfed down the peeled eggs and ignored the others (after poking them a bit). Then they started begging for more food. So I shelled the rest for them... ;) AFAIK, in the wild they thoroughly smash the eggs of other birds and lap up the yolk from the ground/floor of the nest. --Kurt Shaped Box 13:21, 27 February 2007 (UTC)

I guess that pretty well settles it. Thanks for reporting back. Johntex\^talk 14:19, 27 February 2007 (UTC)

Chickens and parakeets I have known eat grit and gravel which they supposedly used in their crop or gizzard or some such to grind up food. Are gulls different in this respect? Would eggshell be harder on them than the other grit?Edison 14:33, 27 February 2007 (UTC)

I would only expect birds which eat hard things like seeds to need stones in their crop. StuRat 16:12, 27 February 2007 (UTC)

And now we have all learned something. Ain't science grand. Of course, one has to wonder if it was because that can't deal with shells, or if it is because they have already learned that they can always get you to make things easier for them  ;-). Dragons flight 18:34, 27 February 2007 (UTC)

It used to be the case that if I gave them anything other than freshly cooked meat (I made a deal with my local butcher for offcuts), they'd reject it outright and stand there begging and wailing. It was really getting out of hand - and the gulls were getting fat. Seriously. I was being too nice to them and I guess they figured out how to play me. --Kurt Shaped Box 18:50, 27 February 2007 (UTC)

Do they limp around with a pretend broken wing to generate extra sympathy and handouts ? (I hope they aren't reading this, I may be giving them ideas; you'd better make sure they can't see the computer monitor from the window.) StuRat 21:13, 27 February 2007 (UTC)

The gull I raised as a baby still makes the baby noises and head-bobbing/flicking movements to get my sympathy, despite being ten years old now. The sad thing is that it works every time. I'm sure that she consciously knows this. With a pet parrot, I know it can be the case that the bird trains the human to respond to its vocal commands... --Kurt Shaped Box 22:40, 27 February 2007 (UTC)

(The colons are getting silly :p) My mother claims that once she was duped into giving more bread to a certain seagull that hopped around on one leg. She thought that its leg was broken. Do gulls often hop around on a single limb? Vitriol 03:51, 28 February 2007 (UTC)

(Thanks for the colonectomy.) I wonder if we will eventually end up with the evolution of seagulls that all hop around with fake broken legs and wings ? StuRat 05:09, 28 February 2007 (UTC)

All birds like to stand on one leg from time to time whilst resting, though I've never seen one 'resting' like that whilst in the typical gull feeding frenzy. There are plenty of gulls with broken-and-badly-healed/missing legs around though. There was a particular one-legged herring gull that used to hang around here on-and-off for many years - it was the most ferocious individual I've ever seen and it would never back down in a squabble (I guess that it needed to compensate for its disability). If there was food there, it would sit down over it and fight, refusing to be moved, no matter how much the others pecked it. Its head was covered in scars and it eventually lost an eye. --Kurt Shaped Box 09:35, 28 February 2007 (UTC)

[edit] chromotagraphy

How is chromatography similar to gel electrophoreisis? —The preceding [[Wikipedia:Sign your posts on talk pages 24.90.187.56 23:28, 26 February 2007 (UTC)Rebecca|comment was added by 24.90.187.56 (talk) 23:26, 26 February 2007 (UTC).

Sounds like homework! You don't say which kind of chromatography, but our article explains the most common types, compare and contrast with gel electrophoresis. Rockpocket 03:00, 27 February 2007 (UTC)

Gel electrophoresis is one of dozens of types of chromatography. (4crates 05:55, 27 February 2007 (UTC))

[edit] Non classical light

One article whose name I have forgotten and which I cant find anymore told that very small bubbles in water makes light if exposed to big noise.

It said it is unknown why this light exists and amongst different theories presented were one that that said that the light is non-classical light. There was no article about non-classical light and the word did not link anywhere. What is non-classical light? 193.65.112.51 23:35, 26 February 2007 (UTC)

The article is Sonoluminescence if that helps (or even if it doesn't). Clarityfiend 23:53, 26 February 2007 (UTC)

No such thing as "non-classical" light. Perhaps they meant... I'm not sure what they could have meant. Also, we know where the light comes from. [Mαc Δαvιs] X (How's my driving?) ❖ 07:13, 27 February 2007 (UTC)

Well, could you please edit the article then? Preferably with references. I'd be interested to read your edits, and you clearly know something about the subject :-) Skittle 22:55, 27 February 2007 (UTC)

The talk page refers to "quantum vacuum radiation" (turning virtual photons into real ones) as a possible source, which would definitely be non-classical, but according to the discussion, that theory has been debunked. If so, the reference in the article should be removed, but I'm way beyond my depth here. Undergrad physics doesn't cover this. Clarityfiend 05:49, 28 February 2007 (UTC)

[edit] glycerol burning

I need an engine that is powered externally. An example is a Sterling engine or steam engine. We have the external burner that would attach to such an engine. Additionally, an electric generator would be attached to the engine so the engine could produce electricity.

The material we would be bufning to power the engine is glycerol, a waste/by-product when making biodiesel. Biodiesel is made from soybeens, jatropha beans and many other types of feedstock and all produce about 15% to 20% of waste glycerol.

The engine requested does not have to be in production - we can tool up to build it.

Thanks for your help!

68.107.124.221 21:53, 26 February 2007 (UTC)

Dear anonymous user, a bit more detail would be of assistance in answering your question.

If your biodiesel plant is big and produces a lot of glycerol, maybe you should be chatting to GE Energy or Siemens, both of whom make steam turbines from about 1 megawatt up. If you want something smaller, try a google search for "small scale steam turbine". For the Sterling engine alternative, you might try some of the links from the Wikipedia article, but it doesn't look too promising - these guys seem to be about the only ones with anything remotely close to your needs. --Robert Merkel 05:46, 1 March 2007 (UTC)

[edit] Black models

moved to humanities desk Black models

[edit] February 27

[edit] Lithium in oil

Why does lithium still oxidize in vegetable oil? --Bowlhover 00:58, 27 February 2007 (UTC)

I would guess because the vegetable oil contains substantial quantities of water, either mixed with or lightly bound to its constituent compounds. You might try heating the vegetable oil for a while to drive the water off. (But be careful when doing this, as the hot oil may generate lots of smoke and stink up your kitchen/lab, and of course could also be a fire hazard.) —Steve Summit (talk) 01:42, 27 February 2007 (UTC)

Vegetable oils are not the same as the hydrocarbon oils that one usually uses for storing reactive metals. You could be having things related to Bouveault-Blanc reduction and other reactions happening. You could also have dissolved gases in your oil. Lithium metal reacts with damn near everything in the atmosphere, including nitrogen...only argon is suitable among the usual "inert" gases. DMacks 04:43, 27 February 2007 (UTC)

Thanks. I tried boiling the water out of oil, but it refuses to boil even at 180 degrees Celsius, suggesting that something other than water is reacting with the lithium. I guess I'll have to buy some hydrocarbon oils; anyone know where to get kerosene?

By the way, lithium reacts with vegetable oil to produce a gas and a black, powdery substance. Anyone know which specific chemical the lithium is reacting with? --Bowlhover 03:47, 28 February 2007 (UTC)

According to our mineral oil article, it's one of the oils of choice for storing alkali metals, and you can get it in any drugstore.

(But, inquiring minds want to know: where'd you get this lithium you want to store, if not supplied in an appropriate oil already? :-) )

I'm with you on the kerosene (that's what I thought Lithium and Sodium always came in), and I think it's readily available, although I can't honestly say where. (But it's obviously needed for kerosene lamps, and it's the lubricant of choice for glass cutters.)

Can't help you on your second question, other than to wonder if DMacks's speculation about Bouveault-Blanc reduction is apropos. —Steve Summit (talk) 04:31, 28 February 2007 (UTC)

Get Kerosene from a supermarket, a hardware store or petrol/gas station. Is quite common. You can get lithium from a lithium cell - if you are very careful! Otherwise you can start a litium fire. (extinguish this with sand) GB 05:50, 28 February 2007 (UTC)

[edit] Wastewater Treatment and Ammonium Alum

Hi! I am working on a project for my chemistry class (yes I have done my own homework; read on!) in which we have to filter artificial wastewater (not actual sewer water, thankfully) to make it as clean as possible. We have to remove a great variety of things, including odour and colour, but also heavy metal ions and soap suds. We also have to balance the pH. We are relying mainly on activated carbon filters and a pH balancer/buffer we found in a pet store, both for use in fish tanks. I am aware that alum is often used in wastewater treatment, to aid in flocculation. Here, then, is my question. What I have before me is ammonium alum purchased at a local drug store. It is marked as a "hemostatic astringent for relief of minor cuts". If I put this stuff (it is a white powder) in to the waste water prior to putting it in the filter, would this work, and how much should I put in? I estimate we will be given about half a litre of water. Also, any general tips on things you would include in a filter would be useful, keeping in mind that the filter is in a open-top 2 litre pop bottle. We can get access to relatively common chemicals at our fairly-well-stocked school lab. Thanks ever-so much! Goyston talk, contribs, play 01:21, 27 February 2007 (UTC)

I just realized that I should, perhaps, mention that the end-result does not have to be drinkable, just significantly cleaner than it was on entry. Nobody will be attempting to drink anything. Goyston talk, contribs, play 01:23, 27 February 2007 (UTC)

• There are some examples on the www such as water treatment for rafters , here they suggest a 25ppm, but also treat with lime afterwards to balance the Ph. water treatment FAQ suggests 10 to 30 ppm. The amount required will depend on how much clay is suspended in the water.

GB 05:57, 27 February 2007 (UTC)

[edit] Calcium Chloride and Sodium Carbonate

When Calcium Chloride and Sodium Carbonate react, what do they form? Thanks.

--Freiberg, Let's talk!, contribs 03:41, 27 February 2007 (UTC)

Sounds like a double replacement reaction. Nimur 04:17, 27 February 2007 (UTC)

Thank You!--Freiberg, Let's talk!, contribs 12:57, 27 February 2007 (UTC)

Chalk one up for the old salts at the Science Desk. StuRat 16:07, 27 February 2007 (UTC)

[edit] GPS

It seems that GPS for the civilian use is sort of slow.But the gps in use for the military has fast readout of co-ordinates.Any idea how can it be almost instantaneous for the weapons moving so fast but slow for civilian devices???210.212.194.209 04:29, 27 February 2007 (UTC)

• The article on GPS states that the military has the capability to lower the positional accuracy of the signal for civilian use (this is called "selective availability"), but I don't see anything about speed. What makes you say it is slow for civilian use? The answer may be in the detector, not in the satelite signal. In other words, the problem may be that your particular unit is slow. Johntex\^talk 04:35, 27 February 2007 (UTC)

• • It depends on the acquisition algorythm of the receiver. If it kind of knows what time it is, and about where it is, it can pick up and identify satellites very quickly. IF it has to correlate it's results and determine where it is, it's slow. Selective availablity is a time error that is encoded onto certain satellites randomly. Since time is what is used as the synchronizer, time error correlates to position error. --Tbeatty 05:11, 27 February 2007 (UTC)

• According to a GPS FAQ: there is no law of nature that limits the velocity at which a GPS receiver works. However, there is a legal limitation in the US that receivers must not work above 900 knots and at an altitude of 60,000 feet. The software in the receiver will detect if the limits are exceeded and will refuse to display correct data. Presumably the rationale is that the US would prefer people not to build their own GPS-enabed supersonic cruise missiles and such, at least without prior permission. Note: The above-mentioned FAQ is pretty old. There have been changes in selective availability since then. I suggest googling if you want to research further if speed limitations have been lifted. Weregerbil 09:37, 27 February 2007 (UTC)

The simple explanation is that most commercial civilian GPS units use standard components (pre-configured electronics and software), which are designed at lowest-cost and fastest-development time. These systems do not take full advantage of the available GPS signal. Furthermore, the military uses additional signal reception to increase accuracy. See GPS modernization to learn about the different bands used by civilian and military, and planned upgrades. Nimur 06:37, 28 February 2007 (UTC)

[edit] A measure of non-concentricity - a unit or discriptor

I'm trying to find out how to describe circular objects that are supposed to be concentric, but are not quite. How does one describe non-concentricity? What would the unit of measure be? Thanks, (4crates 05:49, 27 February 2007 (UTC))

A quick way is to measure the distance between the centers of the two (supposedly-)concentric circles. But there are more technical definitions of concentricity if you need to be more technical. DMacks 06:11, 27 February 2007 (UTC)

[edit] Stickers that luminate on mobile phones

What is the English name of the stickers that are put on mobile phones, and when the phone calls, they make light pulses in different colours? Hod do they work? Do they turn radio waves to light? Is there any other way to make them make light? For example if attached to radio mast? Or if put in microwave oven? 193.167.45.242 12:51, 27 February 2007 (UTC)

Probably either electroluminescence or organic light-emitting diodes.

Atlant 13:38, 27 February 2007 (UTC)

As an interesting aside, radio waves are themselves a form of light, just at a much lower energy than visible light. Anyway, as Atlant indicated, I'd bank on LEDs or OLEDs, which produce light by a quantum process called radiative recombination (spontaneous emission). -- mattb @ 2007-02-27T22:24Z

[edit] Adverse effects of darkness

Would a long time spent in complete darkness have any permanent effects on the eyes? I know after removing an eyepatch that's been worn for a couple of weeks, bright light is painful and causes the eyes to tear up. Would wearing an eyepatch for several months permanently weaken the eye? 4.79.17.248 15:02, 27 February 2007 (UTC)

I am the darkness. nah well in my case i can acctually see a bit better then most people when it comes to darkness. you talk about adverse effects. one such effect is the loss of pigmentation from the skin. Eye sensitivity is also one such effect but prolonged darkness shouldnt cause pain in it. when a person removes a eye patch i guess the pain might come from the sudden electrical impulses from the eye to the brain that are common in making you able to see. hope that helps a bit. Maverick423 15:25, 27 February 2007 (UTC)

People also use sunlight to synthesize vitamin D, so you would need to be sure to get that vitamin from other sources. Seasonal affective disorder would also be a risk, as would messing up your circadian rhythm StuRat 15:47, 27 February 2007 (UTC)

What about xeroderma pigmentosum patients? I guess they take supplements? [Mαc Δαvιs] X (How's my driving?) ❖ 16:33, 27 February 2007 (UTC)

Just to clarify, the concerns about vitamin D mentioned by the two previous editors would not be an issue if you generated "darkness" by eye-patches (as the mechanisms involved are extra-ocular.) And vitamin D supplements are not required by XP sufferes if they have a healthy diet, as you can get sufficient qualities from food sources. Its a interesting point about whether having two eye patches would disrupt your circadian rhythm or increase risk of SAD, though. The fact that blind people live in perpetual darkness would be the perfect study group for this question, indeed these studies suggest blind people do have circadian rhythm abnormalities. Studies of the blind and SAD are rarer but a paper by Rosenthal et al (Seasonal affective disorder and visual impairment: Two case studies." Journal of Clinical Psychiatry 50(12): 469-472, 1989.) explains how, "the second patient, fully blind since she was 1 year old, nonetheless suffered as an adult from winter depressions, which responded to bright -- but not to dim -- light treatment. This suggests to me that SAD may also be mediated through extra-ocular mechanisms and therefore complete darkness from wearing eye-patches need not automatically increase your risk of development. If StuRat has sources suggesting otherwise, I'd be interested to see them. Rockpocket 18:46, 27 February 2007 (UTC)

No, that sounds reasonable to me. The circadian rhythm could also be set by non-visual cues, like warmth on the skin. Other cues, like always going to bed after a certain TV show, might also work. Similarly, SAD, being a psychological reaction, would likely respond to the perceived lack of daylight, not the actual lack. If you know it's day (due to warmth on your skin from the Sun) or even just think it's day (due to bright lights, for example), you are likely to avoid the effects of SAD. StuRat 21:07, 27 February 2007 (UTC)

The circadian rhythm is set by bright light on any exposed surface of the body. In one well-known experiement, researchers altered subjects' rhythms by exposing the backs of their knees to simulated sunlight. --Carnildo 22:32, 27 February 2007 (UTC)

[edit] drugs

affects on having relationships with woman while on the drug rivotril

If you need it, and it is not for recreational use, I'd have to say it would be undoubtedly good, since it is used to treat epilepsy, anxiety disorders, manias, Tourette's, schizophrenia, and more. [Mαc Δαvιs] X (How's my driving?) ❖ 16:26, 27 February 2007 (UTC)

[edit] Swallowing stuff

Hey i have heard a rumor alot that if you swallow gum that you will not digest it until the next 7 years have passed. i know this is kinda dumb to be asking but is this true? or is it just a way for parents telling their kids to not swallow the gum? Maverick423 16:11, 27 February 2007 (UTC)

Yes and no. You won't digest it, but it won't stick around in your body seven years either. It'll get passed out with the rest of the solid waste. 4.79.17.248 16:19, 27 February 2007 (UTC)

so then it doesnt get digested it just leaves the body as a whole?. cool its good to finally know. Maverick423 16:34, 27 February 2007 (UTC)

I'm sure it can't be too good for you either way, but it's probably no worse than swallowing a coin, and a good deal less painful to pass. 4.79.17.248 16:47, 27 February 2007 (UTC)

Ouch now that you brought that issue up how do people that swallow glass and stuff like that survive? i would figure the class would cut you up real bad from the insideMaverick423 16:55, 27 February 2007 (UTC)

As for that, I don't know. I had a friend who was convinced that by disolving powdered glass in someone's drink you could kill them without leaving any evidence. I think she probably got that from historical fiction tho. Seems like a modern autopsy would detect that. 4.79.17.248 17:02, 27 February 2007 (UTC)

Powdered glass generally won't "dissolve" in any liquid that a human is likely to successfully drink. Perhaps your friend was simply going to attempt to "hide" the glass in the drink and hope the prospective victim didn't notice the hard grains in the drink? Paging Horatio Caine...

Atlant 17:24, 27 February 2007 (UTC)

I always check trusty old Snopes for questions of this nature. − Twas Now ( talk • contribs • e-mail ) 07:45, 28 February 2007 (UTC)

changed the title to suit the conversation. anyways what about all those guys we see on tv that pourpusly eat glass and plates and stuff like that how do they survive all that? Maverick423 17:29, 27 February 2007 (UTC) eh neat info then thanks much 47917248 Maverick423 17:07, 27 February 2007 (UTC)

I saw a program about a guy eating lightbulbs. He trained both to toughen himself as well as learning how to actually break down the glass in his mouth so it's not as dangerous. Other than that, I have no idea. --Wirbelwindヴィルヴェルヴィント (talk) 19:09, 27 February 2007 (UTC)

You can't always believe what you see. Remember - fake 'breakaway glass' as used in the movies when someone smashes a bottle over someone elses head is made of sugar. Not only does this not form sharp edges like real glass - but it also dissolves! Now - are you SURE you saw him eat a real lightbulb - and not a 'breakaway glass' bulb? Remember - these guys are doing a stage act - what makes you think they are any more 'real' than the magician who can make playing cards vanish and saw ladies in half. SteveBaker 06:01, 28 February 2007 (UTC)

You hear about people eating entire planes over the course of several years, I'll see if I can find a link - here we go: Michel_Lotito -- Capubadger 07:47, 28 February 2007 (UTC)

That guy sounds almost as cool as the Goatse Man! --Kurt Shaped Box 09:17, 28 February 2007 (UTC)

Almost. Capubadger 09:55, 28 February 2007 (UTC)

I have to admit that the Goatse Man is one of my heroes. Icon of freedom of expression! --Kurt Shaped Box 10:10, 28 February 2007 (UTC)

And Tubgirl? Capubadger 13:56, 28 February 2007 (UTC)

[edit] rivotril

what affects the rivotril to not to have a plesure with a woman. I use it for diffrent reasons, but should i quite using it to have the plessure i need, is their a limit on taking so many that later you will have a problem having relations in the future.

If you're looking for medical advice, ask your doctor. Friday (talk) 16:53, 27 February 2007 (UTC)

im sure we got a article on rivotril. im not implying anything but if you take this drug with out perscription, i dont see how a doctor will be able to help you. maybe someone here can post something about the sideffects just incase that is the situation. once again im not accusing or anything im just stating for the record Maverick423 17:05, 27 February 2007 (UTC)

That article lists side effects, but impotence isn't among them. Can you be any more specific as to how it affects you ? Perhaps something else is the cause of the problem. StuRat 20:57, 27 February 2007 (UTC)

[edit] Insects cheat? (tongue-in-cheek question)

I always read that insects are "the most diverse group of animals on the Earth, with over a million described species — more than all other animal groups combined"; but I believe they are cheating somehow. How comes that all these: [12], [13], [14], [15] belong to different species, while these: [16], [17], [18], [19] all belong to the same subspecies of wolf (not even a species itself)?--cloviz 17:00, 27 February 2007 (UTC)

I'm no expert, but my guess is that those insects aren't capable of interbreeding, although they look very similar. All kinds of dogs, wolves, dingos, and so on can interbreed and produce fertile offspring. Some similar species can produce sterile offspring, like horses and donkeys producing mules, and lions and tigers producing ligers, but there's no way you can breed a dog with a cat. —The preceding unsigned comment was added by 4.79.17.248 (talk) 17:08, 27 February 2007 (UTC).

darn beat me to the punch =) but yea basicly what he said. most insects can only breed with a insect from the same species and cant breed with others. lets say a moth and a monarch= motharch? anyways its just not possable they are too diffrent even though they may look the same at times Maverick423 17:12, 27 February 2007 (UTC)

The butterfly version of The Onion is probably filled with articles analogous to "New Toothbrush Slightly Different From Already Existing, Perfectly Good Toothbrushes". :) --TotoBaggins 02:25, 28 February 2007 (UTC)

As a human and a mammal, your perception of differences is tuned towards the selection of photographs of canines you linked. A trained entomologist could point out subtle differences among the various insect photos. An insect might be able to distinguish even more details that are imperceptible to our senses and psychological interpretation. Nimur 07:15, 28 February 2007 (UTC)

[edit] drugs

how long does drugs last in our system does it matter if your fat or skinny how can you get the drug out before you can get tested. It deppends on the drug your using "right".

yes it does depend on what drugs you use. some last mear minuets. others last hours. some even last days weeks and even months and yearsMaverick423 17:59, 27 February 2007 (UTC)

See our article on drug tests for some more information. TomTheHand 18:35, 27 February 2007 (UTC)

[edit] What is the exact mechanism that causes global warming?

I'm interested in how gases, such as carbon dioxide and methane can cause global warming. I understand that the earth emmits radiation in the infra red spectrum, and that some of this is trapped in the atmosphere by gases. I want to understand on the quantum level, what it is about the structure of these molecules that scatters or absorbs and remits the radiation.

I have tried to look into this, but there seems to be some disagreement about what is happening. Does remittance of photons from greenhouse gases always involve an increase in kinetic energy? Thank you for any assistance you can offer. —The preceding unsigned comment was added by 81.155.239.194 (talk) 19:14, 27 February 2007 (UTC).MerKaBa 20:26, 27 February 2007 (UTC)

This site gives some detail, but doesn't get into the actual math: [20]. StuRat 20:28, 27 February 2007 (UTC)

I think that the Greenhouse_effect article should probably answer most of your questions, but there is also some stuff at Infrared spectroscopy#Theory which may help. — Alan^✉ 21:15, 27 February 2007 (UTC)

Global warming#Causes. − Twas Now ( talk • contribs • e-mail ) 07:36, 28 February 2007 (UTC)

[edit]  % of water in humans

ok guys can someone tell me how much of the human body has water? thanks Maverick423 20:48, 27 February 2007 (UTC)

In men about 72% of the body mass is water. This value is about 68% in women due to a higher proportion of body fat. -- Body water Raul654 20:49, 27 February 2007 (UTC)

thanks much now i can continue my article =) Maverick423 20:54, 27 February 2007 (UTC)

That's why we are all "ugly bags of mostly water". :-) StuRat 21:21, 27 February 2007 (UTC)

hey im a cute bag of water my mama said so =) Maverick423 22:03, 27 February 2007 (UTC)

[edit] Hydrogen exhaust

If all motor vehicles used hydrogen fuel, what would be the environmental effect of their H₂O exhaust? --Lazar Taxon 07:03, 27 February 2007 (UTC)

You do know what H2O is, right? What's the environmental effect of cars dripping water? The pollution effect would be zero, I believe, since water is just water. However, it might have some ecological effects from extra evaporation, etc. But that's just coming from me. --Wirbelwindヴィルヴェルヴィント (talk) 07:10, 27 February 2007 (UTC)

Yes, I know what H₂O is. ;-) Of course there wouldn't be "pollution", but I was wondering what the environmental consequences would be, if any, of hundreds of millions of vehicles emitting water vapor into the atmosphere. This article summary mentions stuff like stratospheric cooling and ozone depletion. --Lazar Taxon 07:16, 27 February 2007 (UTC)

Don't we already have all cars (modulo the electrics:) pumping out tons of water vapor? It's a major product of hydrocarbon combustion. From a quick read of that abstract, it sounds like it's not talking about water from the exhaust (combustion product), but rather water created as a result of some other exhaust component. Now hold on though, you've already got a refereed article in a major scentific journal that appears to answer your question for you...are you asking us to second-guess it? DMacks 07:32, 27 February 2007 (UTC)

Just wondering if anyone had some more info. In fact I also just found this paper, which says that the other paper is wrong and that there really wouldn't be significant negative effects. --Lazar Taxon 07:35, 27 February 2007 (UTC)

I can think of a negative effect (no I didn't take the time to read all the supporting docs). What do you do with water when the air temp is below freezing? It's hard to get rid of when you have to heat it up just to pump it out. Gasoline engines are nice since they waste all that hot air and hence have no problem keeping water in a vapor until well after its out of the vehicle. What about those of us that live above the 40th parallel where winter is taken seriously? --66.195.232.121 14:48, 27 February 2007 (UTC)

A hydrogen engine would still get hot - and presuming it's still using air as it's source of oxygen, there will still be lots of hot unburned nitrogen (80% of air is nitrogen remember) coming out of the tailpipe along with the water. It's also not entirely true to say that the exhaust would be 100% clean - if the hydrogen is burned in a conventional piston engine, there will still be burned oil from old worn out engines - and high temperatures inside the engine could still cause NOx emissions in some engine designs. When hydrogen comes from a high pressure cylinder, heat is needed to boil the liquid hydrogen and prevent the car from icing up - it is likely that the hot exhaust would be used to do that - so what comes out of the tailpipe would be the left-over air, the odd pollutant and water as a liguid. The hydrogen fuel cell gets rid of some of those problems - but that's a very non-traditional kind of vehicle. SteveBaker 17:20, 27 February 2007 (UTC)

Won't we all die from dihydrogen monoxide poisoning ? :-) StuRat 15:58, 27 February 2007 (UTC)

But seriously, the pollution is produced not when the hydrogen is burnt, but when it is produced, by burning coal, for example, so you should look there for the source of air pollution. StuRat 15:58, 27 February 2007 (UTC)

I live above the 50th paralel and winter is pathetic up here, but I isn't going to matter soon, with all this global warming

Water vapor is a greenhouse gas much more so than CO2. --Tbeatty 04:44, 28 February 2007 (UTC)

But there is so much water vapor in the air already that tailpipe emissions won't make a significant impact on global warming, by this route. StuRat 05:04, 28 February 2007 (UTC)

You could make the same argument for CO2. --Tbeatty 13:32, 28 February 2007 (UTC)

There is evidence we have increased the CO2 in the air over time, but not the water vapor. If you add CO2 to the air, it stays there, if you add water, it comes out as precipitation. StuRat 17:11, 28 February 2007 (UTC)

Not if the air gets warmer. Water stays there. Vicious cycle. But it is a good point that there are also negative feedback cycles such as plants, dissolved CO2 in ocean water (negative feedback of CO2 vs temperature). This is what makes it so hard to correlate man made CO2 sources to the increase in CO2 in the atmoshphere and also determining weather temperature/CO2 are correlated observables or cause/effect. --Tbeatty 04:52, 1 March 2007 (UTC)

There is a serious concern some people have raised that fits the literal title of this thread. The water vapor from hydrogen cars is not a concern, but the hydrogen itself is; if enough of it leaks, it could reduce ozone in the upper atmosphere and contribute to ozone depletion. As far as I know there's no hard evidence yet, or firm agreement among experts, as to how big a threat this could actually be. --Trovatore 05:00, 28 February 2007 (UTC)

Wouldn't free hydrogen either (a) drift off into space because it's lighter than the rest of the atmosphere or (b) react spontaneously with oxygen and therefore not be long-lived in the atmosphere? Seems hard to believe it would hangs around up there for very long. The problem with CO2 is that it's persistant stuff - it doesn't easily react with other things in the atmosphere or break down into anything else - so it just keeps building up. I doubt that could possibly happen with hydrogen. SteveBaker 06:10, 28 February 2007 (UTC)

I don't know what would actually happen -- what I'm telling you is this is a genuine concern of some experts. No, it wouldn't "build up", of course; that's not the point. What it could do is reduce the ozone, thereby, ahem, reducing the ozone. In the process the hydrogen would be consumed, but there would be more of it on the way, if we genuinely moved to a hydrogen economy and couldn't keep it from escaping. So the concern is that we would therefore have less ozone in the upper atmosphere, all the time. --Trovatore 06:58, 28 February 2007 (UTC)

[edit] lacquer

how is a metal is lacquered and what are the benefits and what are the types —The preceding unsigned comment was added by 59.92.61.26 (talk) 17:23, 27 February 2007 (UTC).

Lacquering just means applying liquid to a surface and waiting for the liquid to dry, making the surface shiny and reflective. I guess the benefit is that some people like shiny surfaces, although I'm not sure why you'd want to lacquer a metal. As for types of lacquer, the article lists a few. --Bowlhover 04:40, 28 February 2007 (UTC)

Lacquering certain metals (such as brass) helps prevent corrosion. Nowadays, there are high-tech (e.g., chemical vapor deposition) finishes that mimic the appearance of brass but don't require lacquering or any routine maintainance.

Atlant 13:13, 28 February 2007 (UTC)

When I have successfully lacquered brass in the past, I cgot it clean, then polished it to the desired brightness, then cleaned it again, then warmed it a bit to drive off moisture, then sprayed on lacquer using a good technique to get an even coat without drips or runs. If the metal were unprepared and had a fingerprint (even if not visible), or dirt, or moisture, the lacquer would look bad or come off. I used cotton gloves when handling the cleaned polished metal. Lacquer is not a durable surface, since it dissolves in alcohol and is made cloudy by water. Edison 16:10, 28 February 2007 (UTC)

[edit] pregnacy

my girl is pregnant and she says a sertain month that she has 4 months left i was locked up and it imposssble to be that way so my question is, how long does it take to know that your pregnant

my cousin knew after a few weeks

Most women know within a few weeks, when they miss their first period, but there can be some light bleeding during early pregnancy, which women with light or irregular cycles can mistake for a period. In that case, they wouldn't have reason to suspect pregnancy until other symptoms developed. — Laura Scudder ☎ 19:43, 27 February 2007 (UTC)

But there have been many, many cases [21] [22] [23] of babies brought all the way to term without the mother knowing. Having watched my wife's pregnancy over nine complicated and often difficult months - this seems quite utterly amazing to me - but it happens - and it happens many times each year. SteveBaker 05:52, 28 February 2007 (UTC)

As they say, denial ain't just a river in Eqypt. "I can't be pregnant, I only let him sleep with me once!"

Atlant 13:15, 28 February 2007 (UTC)

That has to be a part of it...but having put my hand on my wife's stomach in her third trimester and clearly felt the heel of my son's foot kicking - then taking my hand away and being able to see the little 'bump' on the skin every time he did it (it looked like that scene from Alien (movie)!)...it's really hard to imagine someone being able to simply deny that! But it happens. So when the questioner asks whether it's possible for his girl to have been pregnant for 4 months without knowing it - well, yes - it's definitely possible. It might be that she has been in denial - or it might be that the signs were simply not clear enough - but yes, it's very possible that she didn't know it (or didn't accept it) until recently. SteveBaker 16:26, 28 February 2007 (UTC)

Larger women often have polycystic ovarian syndrome and don't have regular periods in the first place, plus they may not notice the size gain as anything out of the normal. (And of course there is the odd woman who is thin, has irregular periods, and carries strangely enough so that at 8 months she looks a little bloated with gas.) --Charlene 04:46, 1 March 2007 (UTC)

Congrats!! ^.^ all i can say is be sure your ready Maverick423 16:31, 28 February 2007 (UTC)

[edit] Steering a tram

How does a tram driver control the points? At Railroad switch#Tram and monorail systems, it just says "the switch points of tram lines are often operated remotely by the driver" but gives no further detail about how this is done. Many thanks. — Alan^✉ 21:03, 27 February 2007 (UTC)

This information is undoubtedly out of date. So pretend that's it's about 1968. And further pretend that we're talking about the MTA trolley system in Boston, Massachusetts.

A further disclaimer is that L and R in the following discussion might be reversed.

The trolley wire about 50 feet from the switch (points), while capable of delivering sufficient current to run the motor, is insulated from the rest of the system. There are sensors in this section which detect the amount of current being drawn by the trolley car (tram). The output of the sensors is binary. Let's call the output either L or R (For left or right). If the current being drawn is less than a certain amount, the output will be L., which is the default situation. If it's above that amount of current, the output will be R. The point of switching is chosen such that the trolley car will draw less than that amount with all lights on, but the motor not drawing current.

Thus, if the driver intends to turn left, it's necessary to enter this block with the motor off but with sufficient speed to coast through the switch. If he intends to turn right, he will stop in the block, then toggle an electrical switch which draws sufficient current through the system to trigger the switch mechanism to change to R. It's possible to draw enough current with just the motor, but the timing must be perfect, and it's not generally done that way.

By the way, L and R refer to comparative direction. For instance, if one track goes left, and the other straight, the straight direction is considered R. Bunthorne 22:31, 27 February 2007 (UTC)

The trouble with the power on/off sensing system is that traffic on the road may prevent the driver from doing the right thing. In Toronto, that method was abandoned following an accident. In the system that replaced it starting in 1945, at the critical position some contact wires were mounted beside the trolley wire; these were touched by contacts mounted to the top of the trolley pole as it passed by. A sign next to the wire would call attention to the position of the sensor. The driver had a pushbutton on the dashboard and would hold it down to go one way, leave it alone to go the other way. Later this system was replaced by some sort of radio transponder, presumably using coded pulses, still controlled by the driver's button.

Incidentally, a similar issue arises with trolleybuses, which don't run on tracks but do need switches to send the trolley poles onto the right wires. They also use the power on/off system in many cases. Another method is sensors that detect whether the head of one pole is ahead of the other: if the driver is in the left lane, the right-hand pole will be leading, and the switch will be set to turn left. It seems quite possible that some places today use radio control, but I don't know.

--Anonymous, February 28, 2007, 05:22 (UTC).

I vaguely recollect something about a VHF transmitter (wireless radio, so to speak). It's not that different from a garage door opener. It's also probably more modern than the current sensor described above... —The preceding unsigned comment was added by Nimur (talk • contribs) 23:59, 28 February 2007 (UTC).

[edit] How difficult would it be...?

How difficult would it be to poison someone, especially a famous person such as Anna Nicole Smith, with heavy water if you can make heavy water simply by boiling [tap, river, rain or sea] water down over a period of time? (Also don't do this at home folks. Its against the law. Killing someone that is...) 71.100.171.80 21:16, 27 February 2007 (UTC)

Anna probably died from drugs as she was always seen stoned or something on her interviews. anyways thats besides the point. check out water intoxication for more info on the adverse effects of water

If you are asking about the difficulty in administering a large quantity of D₂O to a human over a period of about one week without allowing them to consume any natural water (H₂O) over the same time period, you might want to check out Heavy water#Toxicity in humans. If you are asking about the difficulty in distilling D₂O from regular water, then you should be aware that only 1 in 6400 molecules of naturally occurring water is actually heavy water. Thus, in a 100% efficient process, you would need to distill somewhere between 100,000 and 250,000 liters of water to achieve the 25-50% deuteration of a 70kg human necessary to kill. There are much more efficient methods of heavy water production than distillation, but they are very expensive and impractical as a murder weapon. -- C. S. Joiner (talk) 22:10, 27 February 2007 (UTC)

The difficulty I'm most concerned about is in detection although this follows making or stealing (below) heavy water for use as a lethal weapon. Of course it would probably remain even for a long time in the grave although creamation would probably eliminate its post mortum detection but unless it was suspected how easily would it escape being detected by non-specific tests? 71.100.171.80 00:26, 28 February 2007 (UTC)

Of course a lot of labs have D2O on stock, so you wouldn't really need to distill it, just get an internship with a decent lab (-; VectorPotetial^Talk 23:43, 27 February 2007 (UTC)

Just for fun using this source for heavy water, it would cost you about 8,575.00USD-17,150USD to purchase 12.25kg-24.5kg of heavy water. This would be enough to kill a 70kg (~154lbs) human (replacing 25%-50% of body water (70% of total weight) @ 70USD/.1kg). But eh, it would be pretty easy to detect if someone looked for it; moreover, I'd bet a purchase of that much heavy water would get you a FBI file. --Cody.Pope 01:20, 28 February 2007 (UTC)

And if you purchase by phone, you'll get an NSA file to go with it. :) --TotoBaggins 02:44, 28 February 2007 (UTC)

Distilling D₂O isn't that simple - whilst one in 6400 hydrogen atoms is deuterium - that means that in normal water, one in 3200 water molecules has one deuterium atom and one regular hydrogen atom in it. That means there is a reasonable amount of HDO - but the probability of a naturally occurring D₂O molecule would be vastly less - one in 6400x6400 if it's down to chance alone. Rarer still is the third isotope of hydrogen - tritium. SteveBaker 05:44, 28 February 2007 (UTC)

But the atoms in water are constantly exchanging, so separation would give you more D2O that started in the sample of water. Consider carefully distilling to remove all H2O, leaving only HDO and D2O...as two HDO ionize and recombine to form one H2O and one D2O, that H2O distills off, leaving more D2O. DMacks 06:14, 28 February 2007 (UTC)

Are you sure that water molecules are "constantly exchanging" hydrogen atoms ? To exchange one of its hydrogen atoms, I think a water molecule would first have to be ionised to a hydronium or hydroxide ion, and then the ion would need to react with another water molecule. But our article on Self-ionization of water says that only a very small proportion of water molecules in pure water exist as hydronium or hydroxide ions, and the lifetime of a random water molecule is about 10 hours. Not saying there is no exchange of hydrogen atoms at all - just saying it seems to be a very slow process. Gandalf61 14:18, 28 February 2007 (UTC)

Note that much of the water we consume in a given day is not taken as liquid water. A significant fraction of our water intake is from water that's incorporated into the food we eat. (See this PDF for more information about the water content of various fruits and veggies, and here for water in meats.) Most salad ingredients are about 95% water; potatoes are about 80% water; cooked meats are about 60% water. Depending on a person's diet, you might not be able to ever push them to a fatal concentration of heavy water just by tampering with what they drink—there's enough light water in the rest of their diet to keep them going. TenOfAllTrades(talk) 17:26, 28 February 2007 (UTC)

I don't think there's enough information available to know if that's a reasonable assumption. The test quoted didn't say what the food diet for the subjects was. If they were on a normal diet, that we can assume that they took in a lot of water through their food diet. The only control (if I understand it correctly) was the liquid water intake. Thus, if we assume that they got 50% of water through their food, and if they call 25% (for example) heavy water dangerous, than, in effect, if the subjects only water intake were through liquid, that the danger point would really be about 12.5%. Bunthorne 18:47, 1 March 2007 (UTC)

[edit] Obseving mutation in our own time

I've heard that evolution has been observed occurring in recent times, as with bacteria, fruit flies, moths, turtles, even humans adapting to drinking milk. But the common descent of organisms requires random mutation to introduce new genes into a population. It might be argued that those experiments merely prove natural selection of genes that were already in the population. Is there an experiment that clearly demonstrates evolution, by natural selection and mutation, occurring in our own time? Thanks. 69.223.135.80 22:37, 27 February 2007 (UTC)

Treating a colony of bacteria with an antibiotic over time? Splintercellguy 23:27, 27 February 2007 (UTC)

See the mutation article to understand the different kinds of mutations possible. Any kind of mutation has the potential to either create new genes or make existing genes lose their function. Frame shift mutation is one type of mutation that has great impact on the entire DNA, because in it an entire sequence of nucleotides are shifted. Remember that mutations don't always result in the gaining of beneficial traits. Also, there has been experiments on bacteria and antibiotics, like the other person mentioned. Different colonies of a specific bacteria are put in separate plates with an antibiotic. Normally, the bacteria won't have resistance, but those w/ mutation will survive. I'll get back to you about who conducted this experiment; it won the Nobel prize, I think, because it shows that mutations are random and doesn't rise from the organism being exposed to the substance. I'll get back to you when I get the name of the scientists who did this experiment. Such mutations happen all the time, especially in terms of diseases. Many species of harmful bacteria that we've thought we're able to kill have developed resistance through such mutations. 128.163.116.59 00:57, 28 February 2007 (UTC)

HIV, the virus that causes AIDS, mutates so rapidly that it can essentially evolve during the progression of the disease within a single individual. Under ordinary conditions ~10-100 billion virus particles are produced per day. Coupled with a relatively high error rate per copy, this is sufficient for the virus to spontaneously generate new characteristics on timescales that are accessible to humans. Anti-HIV drugs provide a strong selection effect, so that in the presence of such drugs the appearance of a random mutation that conveys drug resistance will quickly come to dominate within the individual. This is one of the factors that make HIV so hard to treat as many patients develop spontaneous drug resistance within 5-10 years of treatment. The "triple cocktail" as a treatment for HIV attempts to combat this by providing multiple drugs that make it substantially more unlikely that drug resistance will spontaneously appear for all of them at once. Dragons flight 01:23, 28 February 2007 (UTC)

Ha, I was just about to paste this HIV. --Cody.Pope 01:25, 28 February 2007 (UTC)

If I may attempt to interpret your question, I get the feeling you would like to know whether there is data regarding gene duplication (which produces a "new gene") followed by mutation, resulting in the new gene having a function different from that of the original. This is different from ("old") genes acquiring mutations leading to a new function, as it leads to the creation of a new "palette" for evolution to work with without disrupting the old one.

Susumu Ohno proposed this model in 1970 and it has gone on to be a cornerstone of molecular evolution. I, personally, can't think of an experimental manipulation that has demonstrated this in the lab, mainly because the forces of Darwinian selection are slow. Though there may be examples in bacteria aor viruses that I am not aware of. However, there is lots of evidence that it has occured through comparative genomics. Examples include the evolution of colour vision in new-world monkeys (PMID 10413401) and, in a slightly more complex duplication event, the evolution of antifreeze proteins in fish. [24]

A particular version of this type of evolutionary model is called the duplication-degeneration-complementation (DDC) model. Here a gene duplicates, then both genes are mutated so that the entire function of the original gene is divided up between both daughter paralogues, often in the context of temporal or spatial expression. This happens quite regularly in species that have undergone whole-genome (or very close to whole genome) duplication, such as zebrafish. An exquisite example of this in zebrafish is the microphthalmia-associated genes mitfa and mitfb which together fulfil the same role as a single Mitf gene is mammals (PMID 11543618). Rockpocket 01:56, 28 February 2007 (UTC)

Well, if you believe the evidence that genes already in the population can become common by the process of natural selection - and you believe that a creature with a specific gene stands a good chance of passing that gene on to it's offspring via inheritance - then the only remaining part of the puzzle is whether you believe that new and novel genes ever appear in one individual through mutation. If you can cope with that - then you shouldn't have trouble believing that a new gene can spontaneously appear - that this single individual can reproduce spreading the new gene into some part of the population - and then you shouldn't have trouble believing that natural selection can select for it (or more likely, against it since most mutations are not good news!). If you believe each of those three pieces to be true - then it's clear that all three happening in sequence must be true - and hence evolution is true. So why wouldn't you believe that genes mutate? It can happen just randomly due to transcription errors. Each DNA strand is copied billions of times over in each individual and has tens of thousands of genes in it. So there are tens of trillions of opportunities for errors to occour for that reason. This is such a common thing that higher animals have DNA repair mechanisms to fix up these problems when they are detected...bacteria actually NEED to mutate regularly in order to stay ahead of their hosts development of antibodies and such so they lack the error-correction mechanism - which is why they evolve so rapidly. Then there are also situations when bits of DNA get knocked out or changed or copied due to such environmental factors as radiation and certain chemicals - even ultraviolet light can cause this to happen. It is also possible for bits of genetic material from viruses to get mixed up with our DNA. Check out mutant for some actual examples of brand new bits of DNA appearing through these causes. So between mutation, inheritance and natural selection, evolution is just a shorthand way of explaining the way lifeforms change over time as a result of repeated application of those three mechanisms. SteveBaker

Nice answer. I would only add that there may be more to the virus-induced mixing phenomenon than you've alluded to -- there's evidence that genetic material from one species has occasionally ended up in completely different species, transferred there by viruses. Needless to say, this is usually at least as destructive as a random mutation, but every once in a while, the gene lands in exactly the right place to magically give the recipient organism some trait from the "donor". —Steve Summit (talk) 05:47, 28 February 2007 (UTC)

[Addendum: Sorry I can't cite my sources on this genetic transfer; "I read it somewhere". It might be, or be related to, genetic transduction or transformation. —s]

Quick & dirty answer: Tame Silver Fox − Twas Now ( talk • contribs • e-mail ) 07:28, 28 February 2007 (UTC)

On a side note a single human cannot evolve, as you may have suggested (i.e. adapting to drinking milk). For example, one cannot evolve tolerance to cold, but a species (or population thereof) can evolve such a tolerance. The Inuit are evolved to tolerate cold; the Zulu are not. A single Zulu may become accustomed to cold after living in Canada from childhood to adulthood, but this will not be passed on to their offspring. − Twas Now ( talk • contribs • e-mail ) 08:33, 28 February 2007 (UTC)

Agreed. Evolution can only operate by reproduction. If a genetic change makes an individual more likely to survive until breeding age, attract a mate and generate offspring - then that change will be more and more common in later generations. Nothing can happen in just one individual. This article about the evolution of lactose-tolerance in humans [25] explains that it has taken several thousands of years for us to evolve lactose-tolerance in adults. It's an interesting story actually. In primitive times, it was evolutionarily better for babies and young children to be tolerant of lactose (so they could drink their mothers milk) - but to lose that ability as they grew older in order that they not continue to drink their mothers milk and thereby deny that nutrition from their younger siblings. Hence adult lactose-INtolerance was advantageous because it helped to wean children off milk and onto solid foods at an advantageous time. So this was evolutionarily selected and pretty much everyone would have been lactose intolerant as adults. However, as we started to move into an agricultural lifestyle, milk from cows became an easy source of nutrition - and the occasional rare older child adult who (through a "faulty" gene) never developed lactose intolerance would have an advantage - this changed the conditions that evolution was selected for - and lo and behold, we (as a species) have gradually become more and more lactose tolerant. But there are still a lot of lactose intolerant adults around because two thousand years is simply not long enough for us long-lived creatures to completely evolve this new ability. In the western world, people are very unlikely to be unable to survive to breeding age or attract a mate because they can't drink milk - so it's likely that evolution will cease to push us any further towards lactose tolerance - so we'll probably just randomly get that gene into the future. In the developing world, where food is still in short supply, it might still be very serious to be lactose intolerant - so perhaps we should expect people living in those situations to continue to evolve lactose tolerance. It's an interesting thought. Mmmmm - frosty cold chocolate milk...thanks evolution! :-) SteveBaker 16:14, 28 February 2007 (UTC)

Richard Lenski's 20,000-generation (maybe 30,000 now) experiment with E. coli - since they have the ancestral organism, and the organism at various times along the way, they can compare the descendents directly with their ancestors. IIRC, the ancestral organism was unable to metabolise certain elements present in the medium, while the descendents could...the ability would have had to arise through mutation. Guettarda 02:51, 1 March 2007 (UTC)

Cool! That's an elegant experiment. Incidentally, our article on Experimental evolution says that he's past 40,000 generations now. SteveBaker 16:04, 1 March 2007 (UTC)

The inuit hav enot "evolved" to deal with the cold. they have certainly adapted, but without the prope clothing they will freeze as well as anyone else. Mongoloids do tend to be small and stockier, and this is clear evidence of natural selection, but it does not mean that there was a large amount of evolution. Human generation times are simply too long for us to easily observe the change in our genes. But as one poster noted, bacteria are wonderful for this. they can evolve antibacterial resistance rapidly where previously they had none. This can be very annoying when carrying out bacterial culture research. 137.122.187.87 23:27, 1 March 2007 (UTC)John

I'm not so sure. We're told that lactose tolerance in adults has evolved over just a few thousand years - 50 generations perhaps. That's a pretty impressive rate. Rats have evolved resistance to Warfarin since 1948 (when the stuff was first used as a rat poison) and I'd certainly heard of resistant rats becoming a major problem in the 1980's - so 40 years (which is perhaps 40 to 100 generations of rats) was sufficient in that case too. SteveBaker 03:09, 2 March 2007 (UTC)

[edit] February 28

[edit] Diffusion and the human body

What happens when a person is submerged in water for a long time without being able to drink (thereby replenishing their dehydrated cells)? What happens that the dehydration occurs? What is the difference between submerging in fresh water vs. salt water? -Mysekurity 05:10, 28 February 2007 (UTC)

I don't think dehydration while submerged in water is any different than dehydration while on dry land. Either way you feel thirsty, get headaches, faint, lose consciousness, and die (according to the dehydration article). As for the difference between fresh and salt water, the skin cells will gain water in a fresh-water environment and lose it in a salt-water environment, due to osmosis. This is just the skin cells though; I don't think it affects the rest of the body, although I could be wrong. --Bowlhover 05:24, 28 February 2007 (UTC)

How does this relate to endocytosis and exocytosis? - Mysekurity 05:57, 28 February 2007 (UTC)

If you were submerged in fresh water, you would certainly not be dehydrated. Have a look at this photograph of Omayra Sánchez, trapped in water for three days after the eruption of Nevado del Ruiz. See also this Google image search for other photographs of the unfortunate girl. If you were trapped in sea water, I don't know what would happen. Normal ocean water has the same sodium concentration as human blood (about 7%), but probably not the same concentration as the body as a whole. − Twas Now ( talk • contribs • e-mail ) 07:19, 28 February 2007 (UTC)

Your skin is very good at keeping moisture out - it is your intestines which absorb water into the body. --h2g2bob 07:42, 28 February 2007 (UTC)

[edit] Urine Examination

1- what is the chemical composition of normal urine? 2- what is the source of chloride, calcium and phosphate in normal urine?

Our urine article is in pretty bad shape, but human urine has some better information; see the Composition section. Unfortunately I'm not seeing any mention of where the chemicals you mentioned come from. Dave6 ^talk 10:13, 28 February 2007 (UTC)

I would guess that "what goes in must come out", most of the chemicals you mention are probably almost exclusively from food. Whether biological processes convert some components of food into the chemicals you mention, i don't know. Calcium comes from dairy products and other foods that are rich in calcium, and is probably excess calcium that your body cannot use at the moment. Chloride probably comes mostly from salt. Not sure about phosphate, it's a major component in biological systems, and is vital for ATP, DNA, RNA etc. I suggest you have a look at Chloride, Calcium and Phosphate for more details on their occurrence and roles in biological systems. Capubadger 11:18, 28 February 2007 (UTC)

[edit] Macaws with flushed pink cheeks

What does it mean when the skin on a macaw's face flushes pink? I've just been looking at some of the parrot pics on Commons. The skin is usually white but on some of the pics, it's bright pink, like the bird is blushing. --81.77.38.252 11:47, 28 February 2007 (UTC)

Like this guy:

--81.77.38.252 11:50, 28 February 2007 (UTC)

[edit] human growth

what vitamins, minerals (and even exercise or everyday actions) have an affect on growth or stimualtes HGH production?

Wouldn't that be pretty much all of them ? Your body can't grow without the necessary building blocks, after all. StuRat 13:24, 28 February 2007 (UTC)

[edit] Theoretical contraption for capturing light/photons

This may be a silly idea, but I think it's worth asking so I can know more about the nature of light. Is it possible to create a "light container"? So, say we make a container with some special mirror lining in the interior surface. So, when light is shined through it, the container then will be completely shut so the light remains trapped. The photon particles then keep bouncing around the mirror, right? Assuming that such perfect mirror and containing mechanism are possible, will the light keep bouncing around forever? Will the photons lose energy and somehow disappear? What will really happen? 128.163.116.59 00:42, 28 February 2007 (UTC)

The tricky part here is this notion of an interface that would cause perfect reflection, which simply doesn't exist. Assuming one did, what would happen would depend on how far apart the mirrors were (that is, whether we are considering classical or quantum effects) and what was in between mirrors. -- mattb @ 2007-02-28T00:57Z

Let's assume that such perfect mirror exists. I'd like to know what happens to light if it keeps bouncing around indefinitely. And for the contraption, I was thinking that the inside space is a sphere (coated w/ the mirror). —The preceding unsigned comment was added by 128.163.116.59 (talk) 01:00, 28 February 2007 (UTC).

Well, the light would attenuate and disappear, its energy being absorbed by whatever media is inside the sphere. Maybe (and I'm not 100% sure), if you had a perfect vacuum and a perfect mirror sphere, light could bounce around practically forever inside it. However, I really don't think that possibility is worth considering since it can only exist on paper. -- mattb @ 2007-02-28T01:05Z

That's called an Optical cavity - and it's somewhat how some lasers work. But in any real-world setup, the reflections will be imperfect and some percentage of the light will be lost in each reflection. Light moves very, very quickly indeed - so in any reasonable size of object, there are going to be an awful lot of reflection. If your light trap was a meter across - and we know that light moves at 299,792,458 meters per second - there are going to be at least 300 million 'bounces' within the first second alone. If the mirrors were imperfect to the tune of one part in a MILLION (which would be an unbelivably clean, polished mirror!) then within a couple of milliseconds all of your light will have been absorbed. A typical glass mirror absorbs something like 4% of the light...so all of the light will be gone within maybe a millionth of a second. Of course if your light trap were HUGE - a light-year across say - then the number of reflections would be very small indeed and you'd be able to keep the light inside for thousands of years. So as a thought experiment - yes, it's a theoretical possibility - but as a practical matter - no, not by a very long way! SteveBaker 01:11, 28 February 2007 (UTC)

A small nit: optical cavities are designed with dimensions based on multiples of optical wavelengths with the specific intention of utilizing some sort of interference... I wouldn't call any just kind of mirror setup an optical cavity. Sorry for being so anal... :) -- mattb @ 2007-02-28T01:21Z

A fun thing to think about with a pair of perfect mirrors facing each other across a perfect vacuum is that a horizontal laser beam ping-ponging back and forth between them would fall to the earth at the same rate as any stone. --TotoBaggins 02:54, 28 February 2007 (UTC)

I'm intrigued. I assume this is somehow covered under GR since photons have no rest mass? Care to elaborate a little? -- mattb @ 2007-02-28T03:04Z

The photons are held in a mirrored ball, and the mirrored ball would fall like a stone. --h2g2bob 07:53, 28 February 2007 (UTC)

Well, light is affected by gravity just like everything else. The only reason we don't see segments of horizontally-fired laser beams falling like arrows is that they are all moving faster than the escape velocity of the local gravitational bigwig (assuming no Wikipedians are reading this from a black hole). So if you fire a laser horizontally, it will fall a little, having been accelerated downwards at 9.8 m/s², and when it gets bounced back it will be accelerated downwards a little more, and so on. This guy does the math (search for "parallel mirrors"). Caveat: I've never actually tried this with the perfect mirror and vacuum chamber which I happen to own, but it seems right. --TotoBaggins 14:14, 28 February 2007 (UTC)

What would be the point of 'storing' light in something a lightyear across, wouldn't that be almost the same as just doing nothing

Yeah - no point at all. I was just illustrating the point that using a larger container would cut down on the number of reflections and let your light stay intact for much longer. There is no point to this entire discussion as a practical matter - it's all just a thought experiment. SteveBaker 15:51, 28 February 2007 (UTC)

I can't believe no one mentioned the recent developments in 'stopping' light. Why bother reflecting it when you can just freeze it in place and then start it up later when you need it? see this for more info. --66.195.232.121 16:02, 28 February 2007 (UTC)

Or without stopping it you could simply slow it to a point where its "practically" useful, see slow light 156.34.212.175 03:20, 1 March 2007 (UTC)

how can you see light that has stopped?

[edit] Raw milk and the menstrual cycle

Can drinking raw milk (non-pastuerized, straight from the cow) have an effect on a woman's menstrual cycle? According to what I've read [26] the milk would have a certain level of progesterone in it which regulates the cycle but progesterone is poorly absorbed orally. Dismas|^(talk) 02:47, 28 February 2007 (UTC)

But does progesterone "regulate the cycle" if taken regularly in small doses throughout the cycle? That's not how birth control pills work. BCPs contain hormones (often in varying amounts depending on the day) for only 21 out of 28 days. Most women take 21 pills a month then skip seven days, but some pills contain seven "dummy pills" for those who tend to forget when they're supposed to start the new pack. Also, if raw milk did regulate the cycle, ancient herbals wouldn't be packed with instructions on how to regulate the cycle - and IIRC none of those remedies contain milk at all. --Charlene 05:00, 1 March 2007 (UTC)

So your answer is no? Dismas|^(talk) 15:41, 1 March 2007 (UTC)

[edit] Autism

I remember looking at a website a while ago that was talking about facial features common to people with Autism. Now I cannot find it, for the life of me! Google has abandoned me. ;_; Where can I find some sauce that addresses this? V-Man737 05:51, 28 February 2007 (UTC)

This site mentions that people with both Angelman Syndrome and Fragile X Syndrome—which are somehow connected with autism—have certain facial features. And this site also mentions Fragile X in a similar manner. − Twas Now ( talk • contribs • e-mail ) 07:06, 28 February 2007 (UTC)

But this site claims that those with autism look no different to others, the behaviour is different such as a lack of eye contact, fixed concentration on one thing. GB 07:19, 28 February 2007 (UTC)

The problem here is that autism isn't so much of a disorder, as a syndrome, a collection of symptoms and signs, and it isn't a vigorously defined one. Thus the term "autistic" describes a number of different disease states and processes that create a spectrum. Diseases such as fragile X syndrome and Asberger's syndrome both can be considered autistim, even though only one, fragile x, is associated with obvious changes to physical traits. The autism article explains all of this, and puts it concisely by stating that an autistic is a child who exhibits "1. impaired social interaction, 2. impaired communication and 3. restricted and repetitive interests and activities." " 'before the age of three years' ". ^tucker/_rekcut 16:44, 28 February 2007 (UTC)

[edit] Super Volcano

They say that yellowstone is really a super volcano. if it erupts how long will it take to consume the planet? of course assuming its a powerful explosion capable of doing so. how long will we last before we die out (if we die out). =) i love natural disasters so please dont sugar coat.Maverick423 15:32, 28 February 2007 (UTC)

Well, you could read Supervolcano. I saw a Discovery Channel documentary (Supervolcano (docudrama)) about the Yellowstone thing a while back - there is certainly a good chance of this happening - and the results would be pretty devastating. Yellowstone erupted in this way 1.3 and 2.2 million years ago - so we know it's not going to "consume the planet" - but it would through enough dust and ash into the atmosphere to make drastic changes to weather patterns and the resulting loss of crops would certainly result in a lot of deaths. I doubt it would cause our species to die out though - there were humans on earth during the eruption 1.3 million years ago - and enough of us survived that to allow the planet to be repopulated - and that was without all of our modern technology. SteveBaker 15:46, 28 February 2007 (UTC)

Technically Homo erectus. Homo sapiens are only about 200,000 years old. Dragons flight 19:59, 28 February 2007 (UTC)

neat and yea i did read the artical =) so then i take it that life wouldnt just keel over after a eruption like that then. but what would it take?? i mean i know that a metor impact can wipe out the population on earth but is it possable for a volcano to ever create the same effects? I saw that supervolcano show on DSC too it was awsome. it even got me thinking about other natural disasters reaching a "super" status. i will ask about them in a bit =)Maverick423 15:53, 28 February 2007 (UTC)

There is some evidence that the eruption of Toba on Sumatra about 73,000 years ago may have reduced the human population of earth to a few thousands. Geologyguy 18:06, 28 February 2007 (UTC)

[edit] Super Disasters

with the world currently changing in quite a bit of ways, super disasters have been on my mind recently. what are the chances?

• that a thunderstorm will release enough lightning to destroy a small town?(got this from that movie the core)
• that a hail storm can drop car sized hail oneday (made this one up)
• that a tornado can one day reach 500 or 600 mph (made this one up)
• that a mud slide can involve an entire mountain falling ( dont know if this happend)
• that a earthquake can be strong enough to rip a contenaint apart ( got this from that movie 10.1)
• that the ice caps melting can cause a reverse effect on global warming causing instant freezing enviorments ( got this from that movie day after tommarow)
• that a hurrcaine can become so powerful to cover half the atlantic or pacific ocean. (made this one up)
• that a hurrcaine can form and never dispell ( as observed in the great strom on jupiter)
• that a tusnami (sorry cant spell that one) can reach as far inland as 300 miles or more ( dont know if this happened before)

well those are the basics. what would it take for some of these stuff to happen if they even have a chance to happen at all. thanks o and like always no sugar coating Maverick423 16:11, 28 February 2007 (UTC)

• Slim to none, especially if you mean all at once (: VectorPotential^Talk 16:46, 28 February 2007 (UTC)

• Of course with a few billion years left in the Earth's lifespan they'll probably all happen at some point in the distant future, even if they are highly improbable. The funny thing about probability is that if you give it enough time almost any improbable event will probably occur (: VectorPotential^Talk 16:49, 28 February 2007 (UTC)

of course not all at once but like you said over a period of time. =) like i said what would it take for them to even happen to begin with.it would be pretty cool to watch from far away though Maverick423 16:54, 28 February 2007 (UTC)

They all seem highly unlikely to me, with the tsunami going 300 miles inland being perhaps the most likely. Maybe the meteor 65 million years ago, off the Yucatan Peninsula, that killed off the dinos, might have done that. For a hurricane to last forever, I would expect there would need to be no land in it's way, and the Earth would need to lose it's tilt, since winter (caused by the Earth's tilt) ends the hurricane season, at present. StuRat 16:57, 28 February 2007 (UTC)

hmmm for the no land area would simple massive flooding make a no land senario for the hurricane to continue its path? in other words massive flooding in a single area to make it more water then land so that the storm can continue to move. and as far as the tilt would global warming cancel out the effect of the tilt one day? Maverick423 17:10, 28 February 2007 (UTC)

I imagine that due to continental drift the tropics have been, and will again sometime be, land-free, especially when there is a supercontinent on one of the poles. We could cancel out the Earth's tilt with a massive meteor at the proper vector. StuRat 19:19, 28 February 2007 (UTC)

For an earthquake to tear apart a continent, you'd probably need a close encounter with another planet or star (When Worlds Collide). But here's the real super disaster: another Rocky movie...starring Madonna. The carnage would be mind-boggling. Clarityfiend 17:51, 28 February 2007 (UTC)

thats more of a universal disaster no? lets keep it small =) Maverick423 18:30, 28 February 2007 (UTC)

The common problem with "ripping a continent apart" is that it is based on the concept that continents are little clumps of dirt and rock floating on the ocean. Of course, continents are actually extremely tall groups of mountains raising from the ocean floor. So, the idea of a continent being torn apart is equivalent to asking if some disaster could rip a mountain apart. It really depends on the size. You can rip small ones apart with a volcano. Large ones are a lot more difficult - and an earthquake won't do the job. You need a lot of explosive force, not just a line of bumping and grinding rocks. --Kainaw ^(talk) 19:11, 28 February 2007 (UTC)

You may be interested in the Risks to civilization, humans and planet Earth page. --h2g2bob 19:44, 28 February 2007 (UTC)

Hail has a critical size at which realistically it must fall back to earth. Hail must be upwelled by air currents in order to keep accumulating new ice. It would stop growing once it were heavy enough to overcome the wind. Surely some theoretical limitation exists on the maximum size; a meteorologist might know specific numbers. Nimur 00:05, 1 March 2007 (UTC)

The heavier the hail, the more powerful of an updraft is needed to keep it aloft. For large hail stones you would need a powerful updraft, such as that found in the funnel of a tornado. Hence the association between large hail stones and tornadoes. StuRat 01:14, 1 March 2007 (UTC)

[edit] So is gravity currently a theory or a law?

Simple question (I think), but after reading the Gravity article and the Law of Gravitation article, I'm not sure if gravity is now a law, due to Newton's Law of Gravitation, or if since it has been "swallowed" by the larger Theory of Relativity it is now a theory or a subdivision of a broader theory. --MattShepherd 16:51, 28 February 2007 (UTC)

Gravity is one of the four fundamental forces. See Fundamental interaction. Newton's theories and general relativity are both used to explain it, although in vastly different ways. A Scientific law is really just a very well-supported theory, so don't worry too much about the distinction between "theory" and "law" in science. Note that in science, "theory" has a different meaning than in general usage. Friday (talk) 16:57, 28 February 2007 (UTC)

Note that Newton's law of universal gravitation isn't correct in many situations (this is where GR comes in). So as Friday said, a the difference between a theory and law isn't worth agonizing over. -- mattb @ 2007-02-28T17:29Z

In the context of me and a colleague at work trying to remember "is it the law of gravity? Or the theory of gravity?", is gravity currently generally considered a law or a theory, though? I.E. "Wile E. Coyote falls off the cliff because he suddenly remembers that the _________ of gravity requires him to do so." Maybe it's just either/or. --MattShepherd 18:07, 28 February 2007 (UTC)

Wile E. Coyote falls from mid-air because he suddenly remembers that gravity exists. Outside of cartoon physics, gravity is simply a fact; laws of gravity describe its effects, and theories of gravity seek to explain the mechanism by which it occurs. If you really want a word for your blank space, it would be "law" rather than "theory", as it involves the effects of gravity, not its mechanisms. - Nunh-huh 19:02, 28 February 2007 (UTC)

Scientists used to use the word "Law" for any fairly convincing principle that they discovered - but the alarming number of those that proved to be just approximations has lead modern scientists to use the word "Theory" instead. So old scientific principles are "Laws" -- eg "The Laws of Thermodynamics", "Newtons Laws of Motion" -- but these may actually be only approximations (eg Newtons Laws are not 100% correct because of Einstein's Relativity). Modern principles are always Theories (eg "Chaos Theory", "String Theory", "Einsteins Theory of Relativity"). There is no difference whatever in our confidence levels for these things - it's just a customary thing. Newtons ideas on gravity were only an approximation. They work very well indeed at 'normal' speeds and in 'normal' gravity so we still use Newton for everything from working out how stiff the springs need to be in your car to what trajectory to give to a spacecraft to get it to Mars. But for extreme things - like how matter falls into a black hole or how light behaves as it passes by a star - we need to take into account that Newtons "Laws" are not actually 100% true - so we use Einstein's work instead. At extremely small distances (like inside an atom), Einsteins "Theory" also breaks down and we have to flip over to the theory of Quantum Mechanics. But don't read anything at all into the use of the word "Law" or "Theory" - it's just a historical thing. There are lots of laws that we don't 100% believe anymore (eg The Ideal Gas Laws) lots of laws we do believe (The Laws of Thermodynamics), lots of Theories we believe in (Relativity) and lots of Theories we strongly doubt (String Theory). There is nothing in the name. SteveBaker 20:13, 28 February 2007 (UTC)

Laws are things that can be broken, but gravity can't, so it shouldn't be a law

That is a simplification. Laws are rules which give definitie results. They can actually be broken. So for example, the equation f = G*m1*m2/(r^2) is Newton's Law of Gravity. That doesn't mean it is correct. In fact, in some unusual circumstances (such as accelerating frames; extremely dense mass) this law is totally inapplicable. Scientific laws are just explanations which prescribe a determinate answer. Theories are more general and give explanations, not results. Nimur 21:26, 1 March 2007 (UTC)

Gravitational theory predicts gravitational law. A theory is a conclusion reached from a general set of observations. A law is a mathematical expression of a theory.137.122.187.87John

[edit] Hypothetical question here...

Ok, so this may sound kind of odd, but the information will actually be useful to me. I'm attempting to imagine a unique, modern weapon that would allow it's weilder to have pretty much uncontested military might. The best idea I could derive from high-school level science is a plastic or crystal material that can be sprayed as a liquid, but when hardened, becomes nigh indestructible and as close to frictionless as is physically possible.

This material could have several applications: as a body or vehicular armor it could be applied in a faceted design that would make any conventional shells slide along it, ensuring the vast majority of the time the target would only get the most glancing of blows. Secondly, a very heavy load coated in the material fired from, say, a railgun mounted on a war-ship at a high enough velocity at a low enough angle could pretty much cut a swath of destruction for hundreds of miles before coming to a rest.

I'm an English major, so could anyone explain any glaring problems with my wonder-weapon in non-technical terms? Thanks, 156.34.212.175 18:56, 28 February 2007 (UTC)

For armor, hardness is not the end-all. If you were wearing your dragon-steel armor +7 (whatever the cool RPG armor is these days), and you were shot - it would hurt a lot. The entire energy of the round coming at you would be absorbed by the armor. Since it is hard, it won't absorb anything and pass it all right on to you. That means that you will be jerked in the direction of the round being fired at you.

What you want is a soft armor that absorbs and holds any incoming round, completely absorbing the energy before it reaches you. Then, you won't budge at all when you are shot. Of course, nothing like that exists. The closest thing would be a monstrous bowl of jello - big enough that firing a round into it would cause the round to stop before exiting the other side.

Another option all together is to disable enemy troops before they have any ability to act. Tesla is rumored to have created plans for lightning towers that obliterated anything metal that got near them. Just make a line of those on the border and all planes, tanks, jeeps, and even armored troops are stopped. --Kainaw ^(talk) 19:05, 28 February 2007 (UTC)

Tactical nuclear weapons were intended to do this. These small nuclear weapons would hypothetically be used for a single battle. In addition to a powerful blast, radioactive fallout (designed for local effect) would scatter over the battlefield. Tanks, planes, and metal bunkers might survive the blast but they would hold ionizing radiation for days or weeks. I f new enemy reinforcement crews re-manned the tanks, they would be killed. No such weapons have been deployed to the armed services, let alone used (most of our nuclear arsenal is pretty high yield). I'm not even certain if any were ever tested. Nimur 21:35, 1 March 2007 (UTC)

There isn't all that much energy in a bullet - the problem is that the energy it has is concentrated at one teeny-tiny spot - so the pressure is immense and the bullet makes a big hole. But don't buy the movie business of someone being hit by a bullet and knocked backwards ten feet - that's nonsense (did you see the Mythbusters episode where they debunked that one?). Remember that every action has an equal and opposite reaction? Think what happens when the bullet is fired - the force in the bullet is equal to the force of the recoil - and the force of the recoil when spread out over just the area of the butt of the rifle isn't enough to cause you any harm at all. So the idea is to spread that energy out over a larger area. So a very rigid armor plate would work just fine (and indeed - ceramic plate and kevlar do just exactly that). The problem is that hard substances also tend to be brittle - so after one hit, the plate shatters and the next hit is very bad news. Also, large stiff plates are very uncomfortable to wear and can't be used over joints because they don't bend. This is a major problem for people who have to wear this stuff for 12 hours at a stretch while running around. SteveBaker 20:01, 28 February 2007 (UTC)

Dragon Skin body armor is a very powerful armor that is being tested. the one i saw on a Future Weapons episode withstood a gernade explosion while the armor was acctually laying on the gernade. another armor i saw on DSC was a metalic goo that when fired at uses a magnetic charge to streghten the armor at the point where the bullet is ganna hit. i have also seen the develop ment of a plasma sheild on the DSC but the energy and size of the shield are uneffective although it does work. as far as weapons are concerned there is that sound blaster that imobolizes people but its non lethal. erally i need to check weapons though so i cant really say anything about weapons. basicly all i can say is check out Future Weapons on DSC it rocks Maverick423 19:14, 28 February 2007 (UTC)

This is what you are looking for.

http://analogik.com/mm_rev_tetra.asp

202.168.50.40 20:44, 28 February 2007 (UTC)

The main attribute to my substance was not the hardness, as I'm aware of the basic laws of physics --- the principally interesting function of my fictional material is its incredibly low coefficient of friction. That is to say projectiles would never communicate more than a minute fraction of their kinetic energy to the target because they would always hit the armor at an angle and slide along it, continuing on their way without imparting any appreciable force. I hope that clarifies what I meant. 156.34.212.175 01:00, 1 March 2007 (UTC)

Unless the impact was exactly perpendicular to the plating, in which case the force of the impact would still be absorbed --VectorPotential^Talk 01:03, 1 March 2007 (UTC)

There's also the material that turns rigid whenever it received a shock:

http://www.livescience.com/scienceoffiction/051204_ribcap.html The article calls it "shear thickening" Getting it to turn hard enough, fast enough would be the challenge with ballistics. --24.249.108.133 01:13, 1 March 2007 (UTC)

Silly putty does that. When you mould it and push it slowly with your hands, its soft - but if you drop it onto a hard floor, it bounces without changing shape hardly at all. I guess that a substance like that would work reasonably well because it could bend and flex as the wearer moves - but go really stiff when something that's moving fast hits it. SteveBaker 03:16, 1 March 2007 (UTC)

Kevlar operates on a similar principle. It doesn't stop the bullet, it melts it. Nimur 21:32, 1 March 2007 (UTC)

But with a low enough coefficient of friction, can't anything but a perfectly perpindicular projectile be deflected in this manner? I mean, especially if the armor was made up of many tiny facets a dead-on hit is pretty much statistically impossible, right? If all it took was a few hundredths of a degree to turn the bullet aside and have it "skate" along the armor wouldn't it be pretty much impregnable? 156.34.212.175 01:31, 1 March 2007 (UTC)

It doesn't matter how slippery the surface is, the bullet will still transfer energy to the surface as a function of the cosine of the impact angle. That won't work. SteveBaker 03:18, 1 March 2007 (UTC)

Could you please explain further? It was my impression from my rudimentary knowledge of physics that the longer the impact lasts the less violent the trauma is. Are you saying there is a kind of minimum force dictated? If so, would that force be particularly strong?156.34.212.175 03:34, 1 March 2007 (UTC)

Well, spreading the amount of energy in the bullet over a longer period of time would reduce the force it can apply which would be a big help. But having it hit a slippery surface doesn't do that. SteveBaker 04:39, 1 March 2007 (UTC)

you might want to try some sort of antigravity field, like UFO's have :) Hidden secret 7 18:39, 1 March 2007 (UTC)

Using a low coefficient of friction is much less functional than just having many oblique angles. Modern armored vehicles use "weird angles" to deflect projectiles; they use conventional armor materials because these have the strongest properties available. Nimur 21:30, 1 March 2007 (UTC)

[edit] Eye contact during sex

Why I cant have orgasm when I look in womans eyes and she looks at my eyes during sex? There is perioid of grow of exitement before I can reach orgasm. During that perioid if woman looks my eyes and I look her eyes this perioid is cancelled and it must start again Nitsimagoi 19:12, 28 February 2007 (UTC)

eye contact shouldnt effect sex unless you dont really love the girl.Maverick423 19:15, 28 February 2007 (UTC)

I dont understand this point Nitsimagoi 20:51, 28 February 2007 (UTC)

maybe because she is ugly

No she looks good and she have pretty big eyes. I feel somehow controlled or supervisioned when I am in eye contact with her. Normally that does not bother me but during sex it prevents orgasm. Nitsimagoi 20:49, 28 February 2007 (UTC)

Perhaps there is some personal psychological reason behind it. Looking a woman in the eyes generally enhances the pleasure for me. − Twas Now ( talk • contribs • e-mail ) 23:38, 28 February 2007 (UTC)

Some people are just not good at eye contact. I have Aspergers syndrome - it's very hard for me to make eye contact without it looking somehow creepy. Maintain eye contact during foreplay...that's critical. I don't think it's impolite to look away at that critical moment - but I'm definitely the wrong person to give that advice. I guess if all else fails you could try a different position!! SteveBaker 19:52, 28 February 2007 (UTC)

well as far as I heard when you make eye contact its supposed to be like love behide the eyes and it should help with the sex. but well really i cant explain it heh i heard this in class so my professor will have to be the one to tell you how it works Maverick423 21:47, 28 February 2007 (UTC)

I very much doubt there is a physiological reason for this, instead it sounds like it might be a quirk of your Psychosexual development. If it is somthing that concerns you about your sexual relationships, you could always speak to a psychiatrist. Rockpocket 18:36, 1 March 2007 (UTC)

[edit] Elliptical Machine

I noticed when I am on the elliptical machine, there is a "fat burning zone" at 65% of my max heart rate, and an aerobic zone at 75%. If I am trying to lose weight, how important is it for me to stay within the fat burning zone? Its just too slow for me. Am I burning something else other than fat (like muscle) if I am in the aerobic zone?

In the "fat-burning zone" you will get a higher proportion of your energy from fat, though you will burn the same total amount of fat in both the "fat-burning zone" and the "aerobic zone". In the "aerobic zone" you will burn an additional amount of calories, most likely stored carbohydrates (glycogen). Your body doesn't like to eat its own protein storage, and will only do this under extreme circumstances.

• "The body does burn a higher percentage of calories from fat in the 'fat burning zone' [but] at higher intensities, you burn a greater number of overall calories which is what you should be concerned about when trying to lose weight." (emphasis added) → [27]
• "at 50% VO2max, fat would provide about 50%, on average, of the energy you needed [and] at 75% VO2max, fat would provide 33% of the required calories. […] A moderately fit athlete exercising at 50% VO2max generally consumes about 220 calories during a 30 minute workout. If the same athlete works out at 75% VO2max, 330 calories are burned during the same period. Of course, 50% of 220 calories and 33% of 330 calories yield an identical number of calories coming from fat—110 calories. → [28]
• "while at rest, although a higher percentage of your calories is indeed coming from fat, you are ultimately burning a lower absolute number of calories" → [29]
• See also [30]

− Twas Now ( talk • contribs • e-mail ) 23:34, 28 February 2007 (UTC)

Another thing to consider is that if you are exercising at a high heart rate you might get exhausted sooner and stop your workout, which would ultimately mean burning fewer calories than if you had worked out longer at a slightly lower heart rate. 75.138.84.159 03:01, 1 March 2007 (UTC)

[edit] Foamy human urine

Are any medical conditions indicated by urine that is extremely foamy? Too much sugar or protein? Just curious... --Navstar 20:28, 28 February 2007 (UTC)

Foamy urine suggests that there is a high concentration of protein in the urine, and yes, lots of medical conditions can cause proteinuria, some benign, and some serious. Testing for protein in the urine is a standard part of every urinalysis, so anyone who notices foamy urine can have it evaluated simply by a a urinalysis ordered by their physician. There are additional tests that can be done if the foamyness is particularly impressive. - Nunh-huh 20:55, 28 February 2007 (UTC)

[edit] Space exploration

I have noticed that all the time we launch a probe into space to explore beyond our planet, we only launch it on a 2 dimensional plane. they go straight passing mars passing jupiter passing all those planets. but i never seen a probe go up not towards any planets but just plane up. now correct me if they have but as far as i have checked i cant find any probe that goes to explore that dark dust cloud that surrounds our Sol system. Maverick423 21:27, 28 February 2007 (UTC)

• You might want to read up on gravity assist --VectorPotential^Talk 21:30, 28 February 2007 (UTC)

yes i know the gravity helps the probe but it only gives us a 2d view of our sol system. what if we were to launch a probe from orbit with about the same fule it takes to lift it off the ground and into space would that accomidate for the extra speed? Maverick423 21:41, 28 February 2007 (UTC)

You'd need to come up with a fuel source that could function continuously for the entire time the probe was operational, considering only existing technologies that's halfway between impossible and prohibitively expensive. --VectorPotential^Talk 21:45, 28 February 2007 (UTC)

what about those foils that catch solar winds are those just plain to expensive? once the fule runs out the probe slows down right? cause of the sun.. Maverick423 21:52, 28 February 2007 (UTC)

Solar sails are "a proposed form of spacecraft propulsion" therefore they aren't an existing technology (: VectorPotential^Talk 21:54, 28 February 2007 (UTC)

ah i see. hmmm... nuclear reactors? thats really the only thing that i can think of that might work for a long time after launchMaverick423 21:59, 28 February 2007 (UTC)

I don't see where there would be much of a point to launching a probe in the direction you're asking about. We know that the planets rotate about the sun and that's about all that it would see. By launching "two dimensionally" we can get shots of the planets while on the way to whatever destination is the goal. Dismas|^(talk) 22:06, 28 February 2007 (UTC)

the dust clouds that i spoke about restrict our view of whats out there. sending a prob there might show a bigger discovery then if we just sent it straight. i have seen some diagrams of other systems and they suggest that planets can orbit in all 3 dimensions of space. Maverick423 22:09, 28 February 2007 (UTC)

There's also a pretty clear problem with the initial question -- what "dark dust cloud that surrounds our solar system"? There isn't one. Obviously, we can see well into the galaxy and beyond. That said, there are various things out there, some of which (such as the Oort cloud) might exist in density outside of the plane of the ecliptic -- I don't know. However, no extraplanetary solar system features are (meaningfully) closer to the sun's poles than its equator. Since propulsion is easier via gravity assist, and since probes can investigate non-primary features along the way (c.f. New Horizon's recent flyby of Jupiter), there's no reason to launch outside the ecliptic. Also, note that probes like the Voyagers, launched in the ecliptic, are thought to be approaching the heliopause and are still returning data. (after edit conflict) — Lomn 22:11, 28 February 2007 (UTC)

ah those are the clouds i was talking about i didnt know the name of them. so then i take it that its just more likely a waste of a good prob to launch in those directions. well you make a persuasive argument but i still have a feeling that there might be something more in those directions. guess we wont find out till a lot later though =)that is assuming that there is something out there =P Maverick423 22:18, 28 February 2007 (UTC)

i just read that heliopause article. man am i that behind on space? this shock wave and hydrogen wall they speak of can it destroy the ship or is it just a inconvenince?Maverick423 22:35, 28 February 2007 (UTC)

Simply that some astronomical object exists is almost invariably determined from Earth or a versatile near-Earth mission such as Hubble. If you don't know (or suspect) that something is there, and that you know precisely where there is (more accurately, where there will be years down the road), there's nothing to launch a probe at. In this specific case, there's also a massive problem of scale. The Voyagers are, after 30 years, maybe 100 AU away and are at the limits of their capabilities (and they're nuclear-powered -- "nuclear" solves electrical power, not thrust). The Oort cloud is theorized to be 50,000 AU away. Without that paradigm shift in propulsion VectorPotential alluded to above, you're talking about a probe that won't reach its destination for over 5000 years, needs the reliability to match, and needs communications equipment untold orders of magnitude superior to what we've got today -- all to encounter an area so sparsely populated that one-in-a-million is a charitable description of the odds of encountering anything there.

As for the heliopause, etc, the densities are far too low to concern conventional spacecraft. "Empty" space inside the orbit of Jupiter (as an arbitrary cutoff point) is far more dense than average interstellar space. — Lomn 22:40, 28 February 2007 (UTC)

The Oort Cloud is extremely sparse, so doesn't have any noticeable effect on our ability to see outside the solar system. It would take a spaceship decades to get there with current technology. Pluto and a few other objects have orbits noticeably outside the regular orbital plane. While it would be possible for planets to orbit at right angles to one another, the way our solar system formed, from a single rotating gas cloud, made this unlikely. StuRat 01:07, 1 March 2007 (UTC)

Going back a bit, Voyager 1 did actually leave the plane of the solar system "early", bending "upwards" at Saturn and so never going on to meet Uranus and Neptune. I can't find the good image of it that I remember from books anywhere on the web, but I believe that it left the plane at Jupiter too and swung out in an arc. I might be getting confused with the Pioneers, I don't know. All the diagrams I can find are resolutely planar, which is irritating. If anyone can find something that shows what I mean, I'd be grateful....

As for the heliopause, it's not that big a shock. Voyager 1 has possibly already passed it, and Voyager 2 should be there soon, as explained in their articles. In fact it's so weak, that no-one's really sure just where it is; the instruments those craft carry simply aren't good enough to nail it down precisely. So it's only an inconvenience in the sense that you can fly right through it without noticing! Which is why there's another mission in the works to find it once and for all. Check references 74 and 75 of the solar system article. Spiral Wave 01:24, 1 March 2007 (UTC)

Take a look at Ulysses probe for discussion of a mission, "out of the ecliptic plane by 80.2 degrees, in order to investigate the polar regions of the Sun." --JWSchmidt 02:54, 1 March 2007 (UTC)

The simplest explanation is that there isn't much to see outside the ecliptic (the plane of our solar system). Only a few very special sorts of space probes have any use for such trajectories (such as the above mentioned Ulysses probe. It's very difficult and expensive to send space probes, and sending them towards (essentially) nothing sounds awfully wasteful to most sponsors. Nimur 08:25, 1 March 2007 (UTC)

It's worth noting that the heliopause mission (Interstellar Boundary Explorer) will be making observations from Earth orbit to calculate the position of the heliopause, not actually travelling to it. — Lomn 14:44, 1 March 2007 (UTC)

There is that and I'm glad you remembered it (I didn't), but I was referring to a suggested mission to actually go there with proper instrumentation. It is still only a proposal, compared to the IBE, though. Spiral Wave 18:20, 1 March 2007 (UTC)

[edit] Algae Research... Pyrrophyta, the Dinoflagellates

I need a lot of info on "Pyrrophyta"!!!

~Thanks --12.74.210.0 22:37, 28 February 2007 (UTC)

We happen to have an article on the subject: Pyrrophyta (: VectorPotential^Talk 00:57, 1 March 2007 (UTC)

[edit] Elliptical Part 2

A lot of people have told me the calorie counter is incorrect on the elliptical machine, are they right? I usually do an hour at medium intensity (about 80rpm) with resistance level 14 (20 is max) and it says I burn about 1100 calories. Is that anywhere near correct? What would be the approximate correct number of calories burned?

The calorie counter on any exercise machine is bound to be highly approximate, based on guesses of things like your metabolic rate which the machine can't know for sure. I don't know of any reason to suspect an elliptical machine of being less accurate than any other. My guess is that one approximation is as "correct" as any other -- though this is speculation on my part, and someone with more knowledge of exercise machines and calorie counting might be able to give a better answer. —Steve Summit (talk) 01:28, 1 March 2007 (UTC)

A Calorie is a measure of the amount of energy you use when you perform an activity ("work"). On the elliptical machine, you work to move the pedals, overcome the resistance in the rotor, etc. That Work is measured by the elliptical machine (you can get it to display an instantaneous measure of that work with the Watts setting, on some machines. A Watt is a measure of work). Work over time is energy, so if you keep a constant Watt output over an hour (and multiply by a constant factor), that is the number of Calories of energy consumed during that hour. However, it's possible that those Watts and Calories are not being produced strictly by you - some of that work could be done by momentum in the mechanical components or other things (I don't really know how elliptical machines work) . This is where the uncertainty comes from. If you were really burning 1100 Calories every time you work out, you should be burning about a pound of fat every 3 days! (There are about 3500 Calories in a pound of fat). —The preceding unsigned comment was added by Sthomson06 (talk • contribs) 19:21, 1 March 2007 (UTC).