Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

January 28

Artemisia absinthium

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

I'm not going to argue this one, because my feeling was that we couldn't have answered it anyway. For most uncommon herbal remedies too little research has been done to tell whether the herb itself is safe or effective, let alone in combination with specific pharmaceuticals. Wnt (talk) 06:27, 28 January 2011 (UTC)

Chemistry and Calculus

Hello. I am in intermediate chemistry at my high school right now. Unlike most of my peers, however, I have already got a solid grasp of calculus. What is a good book for understanding chemistry with the involved calculus (for example, in entropy or enthalpy)? I would like a book to cover chemistry from the very basics (down to Lewis theory even) up because I am only in intermediate chemistry right now. I have had some physics but also not from a calculus perspective. Thanks. 24.92.70.160 (talk) 02:35, 28 January 2011 (UTC)

Sounds like what you need is a thermodynamics textbook. The one I used in college for chemical engineering was by Smith, Van Ness, and Abbott. --shoy (reactions) 03:52, 28 January 2011 (UTC)

Any college-level physical chemistry book should be chock-full-o-calculus. Find the nearest used college book store, or look online for a used book; you can get one on the cheap. --Jayron32 04:16, 28 January 2011 (UTC)

Hadron collisions

Would the collisions be the same (or show the same information)if, instead of TWO atoms colliding AT each other linearly, there were four or eight atoms colliding in the same symmetrical way? —Preceding unsigned comment added by 98.221.254.154 (talk) 05:30, 28 January 2011 (UTC)

In theory it would be the same, as long as you had balanced collisions so there was no leftover momentum. But in practice the messier the collision the harder it is to extract good data from the experiment. Plus it would be nearly impossible to get the timing exactly right. Ariel. (talk) 06:58, 28 January 2011 (UTC)

Does having one linear collision as opposed to a "multi-atomic implosion" also limit the data you can gather? —Preceding unsigned comment added by 165.212.189.187 (talk) 14:41, 28 January 2011 (UTC)

I'm not sure I understand the difference between this and the original question. Essentially, the LHC is all about high energy and high luminosity (collision rate). They collect insane amounts of very noisy data and plug it into subtle statistical models to search for new phenomena. The type of collision doesn't matter too much, except that (as Ariel said) the more complicated it is, the noisier the data you collect. Proton-proton collisions are already complicated and a "multi-atomic implosion" would be worse. Also, in practice it's impossible to arrange collisions of three or more particles. The LHC doesn't aim particles at each other; it just crosses two particle beams and lets them collide as they may. If you crossed three or more beams, the overwhelming majority of collisions would still involve only two particles. -- BenRG (talk) 04:59, 30 January 2011 (UTC)

Firing a gun underwater

What factors determine whether a gun (pistol, assault rifle, whatever) can be successfully fired underwater, or will simply explode as soon as the trigger is pulled? --Kurt Shaped Box (talk) 10:04, 28 January 2011 (UTC)

Mythbusters episode 51 tested four modern firearms. "The entire gun had to be completely submerged in water—all pockets of air must be removed—in order to prevent a possible explosion when fired." No gulls were harmed in the testing of this myth. Clarityfiend (talk) 10:22, 28 January 2011 (UTC)

I have been told that a firearm will explode (burst the barrel or the breach, with danger to the shooter) if anything but air is in the barrel: a bullet which did not leave the barrel due to poor discharge of powder, snow, mud, someone's finger. Mythbusters "disproved" this for a shotgun they tested, but rifles and pistols are not modern shotguns, and older weapons may not have been made to the same standard. WW2 veterans have told me that keeping barrels clean was highly emphasized, to prevent the barrel bursting. Water is so much denser than air that when a bullet traveling 1000 feet per second strikes it it would seem to be as immoveable as concrete. So it is surprising that the bullet somehow instantly pushed the water out of the way without a pressure buildup which bursts the barrel, if the other plugs mentioned would cause the barrel to burst on some firearms. Rifles and pistils sometimes blow up for no known reason, so water filling the barrel would push a marginal barrel over the edge. Edison (talk) 17:07, 28 January 2011 (UTC)

From looking on YouTube (of course there are going to be videos of guys firing guns underwater on there!), various Glocks seem to manage just fine, as does the AR-15 and the Ruger LCP - though the bullet's range is something like 4 feet, or less. The Mythbusters ep (also on YouTube) proved that being shot underwater at this range would probably still be lethal (I guess that you'd have to go for a contact shot, or close to it to be certain). Heh, wonder if SpecOps ever do this? --Kurt Shaped Box (talk) 17:35, 28 January 2011 (UTC)

Naturally there is an article APS_amphibious_rifle --80.176.225.249 (talk) 18:27, 28 January 2011 (UTC)

It is perfectly possible (if not especially advisable) to fire a well-made gun underwater without an explosion, as is stated above. Firing a gun that is only PARTIALLY filled with water might be more of an issue. On the other hand, even the mythbusters tests didn't use frangible rounds: many (if not most) civillian bullets are meant to expand when they hit flesh. Flesh being very similar in density to water, I'd suspect a hollowpoint or JHP round might start to mushroom in the barrel underwater. 65.29.47.55 (talk) 00:55, 29 January 2011 (UTC)

When a gun or rifle of any kind is fired the propellant burns completely (or almost completely) before the projectile leaves the barrel. While the projectile is still in the barrel the barrel is being subjected to maximum pressure available from burning the propellant, and yet the barrel doesn't explode. Clearly, barrels are sufficiently strong to withstand maximum pressure available from burning the propellant. Inserting water, mud or any other solid object into the barrel does not somehow increase the energy available from burning the propellant so there is no reason to expect that doing so will cause the barrel to explode. Dolphin (t) 05:33, 30 January 2011 (UTC)

Full name for invertebrate zoologist "von Linstow" active late C19, early C20?

Resolved

Hi all,
Have I mentioned that my pet peeve is binomial authorities without corresponding biographies? OK. So, "von Linstow" is the binomial authority for Telosentis exiguus. He also appears to be the binomial authority for nematodes hosted in "Salties" Crocodylus johnstoni and Crocodylus porosus.
All that said, who is this "von Linstow" guy? --Shirt58 (talk) 11:57, 28 January 2011 (UTC)

According to this book, his initials are OFB. Hope it helps. --Albval (talk) 12:03, 28 January 2011 (UTC)

And after some more google-searching the guy should be this Otto Friedrich Bernhard Von Linstow (page in Finnish) --Albval (talk) 12:09, 28 January 2011 (UTC)

The above link is to a Finish book shop, for ISBN 9781103982332. Both the Finish bookshop and Amazon indicate that the book is in English, however, the title and front-cover are in a Germanic language. CS Miller (talk) 12:57, 28 January 2011 (UTC)

The book is about helminths, which would agree with Shirt58's original request. CS Miller (talk) 13:02, 28 January 2011 (UTC)

(EC)This gives his dates and the dates of publication of his main work Compendium Der Helminthologie: Ein Verzeichniss Der Bekannten Helminthen, Die Frei Oder in Thierisch. Mikenorton (talk) 13:06, 28 January 2011 (UTC)

His book is on Archive.org, oddly enough. He is listed as a "Stabsarzt," which I believe is an Army medical officer. Seems like an obscure guy who happened to write one of these obscure compendiums that named a few new species? --Mr.98 (talk) 13:43, 28 January 2011 (UTC)

I think so too; he was probably an army doctor with an interest in helminths. Here are some more publications of his; he wrote more than that one book. Ucucha 14:15, 28 January 2011 (UTC)

Wikispecies have what looks to be a very comprehensive list of taxon authorities and a tiny stub on him. (I wish I had known about this last time you asked!) SmartSE (talk) 18:51, 28 January 2011 (UTC)

A biography says that he was born 17. October 1842 in Itzehoe received his medical phD 1864 in Kiel and worked as military doctor in Hameln later in Göttingen he published his book Compendium der Helminthology in 1878 in Hannover and died 3. May 1816 in Göttingen.--Stone (talk) 21:16, 28 January 2011 (UTC)

Oh we have an article Otto Friedrich Bernhard Von Linstow.--Stone (talk) 22:06, 28 January 2011 (UTC)

Resolved. Now, if we can turn our attention to the species H. finlandicus, endemic to Albval's Finland... :-) --Shirt58 (talk) 12:19, 29 January 2011 (UTC)

Fuel efficiency

I know that natural gas and propane both burn cleaner than gasoline but are they as "fuel efficient" as gasoline (i.e. all things being equal, will one get the same "MPG" with NG and Propane as one would with gasoline)? 74.198.17.84 (talk) 14:34, 28 January 2011 (UTC)

There is no way for all things to be equal. Which is why we have MPGe. Rmhermen (talk) 15:41, 28 January 2011 (UTC)

The most similar fuel commonly used to power cars is Liquefied Petroleum Gas, which contains mostly butane or propane: efficiency is around 25% worse with LPG compared to gasoline.[1] --Colapeninsula (talk) 15:56, 28 January 2011 (UTC)

If we're strictly talking propane and natural gas, and comparing "miles per gallon" (really, "energy per volume"), then the comparison is a no-contest win for Gasoline. Have a look at energy density - there are many ways to measure energy "per ___": energy per mass, per volume, per dollar, and so on. This chart of energy density in materials can be sorted by mass- and volume- density. Nimur (talk) 18:14, 28 January 2011 (UTC)

LPG is as the poster above says around 25% less efficient, but in the UK it's compensated for (at least financially) by being about half the price of petrol (gasoline) so you still come out ahead in terms of cost per mile. Downside of course is the installation cost and the loss of space for a spare wheel or in the boot. Exxolon (talk) 16:42, 29 January 2011 (UTC)

Can vets determine the cause of death in a hamster?

Topic says it all. ScienceApe (talk) 15:27, 28 January 2011 (UTC)

In principle, a veterinarian can conduct or order virtually all of the same diagnostic tests during a hamster necrospy that a pathologist would perform as part of a human autopsy. With a certain number of caveats, there is a lot of common ground among most mammals from the level of biochemistry right up to tissue structure.

In practice, there are limitations caused by the smaller size of the animal (it is more difficult to examine and conclusively describe fractures of the smaller bones, less blood and other tissue is available for destructive tests, etc.); the vet may have less access to certain items of specialized equipment, and the resources available for conducting animal necropsies may be limited; and the body of literature and reference materials for diagnosing cause of death may be more limited in animal forensics than it is for humans. As with humans, some causes of death in animals are easier to conclusively diagnose than others. TenOfAllTrades(talk) 15:53, 28 January 2011 (UTC)

Pragmatically, hamsters are fairly disposable as pets. At the outside, they live maybe 3 years. A hamster that lived into his fifth year would be positively Methusalah-like on a Hamster scale. While that does nothing to lessen the emotional loss for someone that suffers the loss of a pet, it does explain why, even if technically feasible, it probably doesn't happen with any regularity that one would autopsy a dead pet which, if it was older than a year and a half, was already beating the average... --Jayron32 17:51, 28 January 2011 (UTC)

In vaguely the same ballpark, my dad had his dead rabbit necropsied. He was very close to her (nursed her back from cancer and an op that involved basically lifting all her innards out, cutting out/off the bad bits, then putting them back in - she lived for another three years after) and he wanted to know what had happened. He just asked the vet to do it. Heart attack, as it turned out. --Kurt Shaped Box (talk) 18:01, 28 January 2011 (UTC)

Yes, they can, if you want to pay a lot of money. Small mammals have been dissected and studied micropically for a long time. Robert Koch in the 1870's would give mice anthrax, then dissect them and examine the liver, lungs, etc microscopically to determine the cause of death. Today medical researchers use mice, hamsters, guinea pigs, etc to study all sorts of infections, cancer, and other ailments, and routinely dissect them postmortem and study sections microscopically and in comparable ways to what a human autopsy involves. It is just not done that often for dead pets, due to the cost. Edison (talk) 21:08, 28 January 2011 (UTC)

Though if you're a hamster breeder, or have a large collection of fancy hamsters, it may be worthwhile to order (and pay for) a necropsy if your beasties start dropping dead inexplicably at a young age. --Kurt Shaped Box (talk) 00:40, 29 January 2011 (UTC)

If the gas pressure decreases what happens with temperature?

What happens with the temperature when the pressure of a gas decreases? I'd like to know this for my job, but it doesn't make sense for me. For example if we have steam at 1.3 MPa and 192 Celsius (just above saturation), according to WolframAlpha, its enthalpy is 2788 kJ/kg (http://www.wolframalpha.com/input/?i=enthalpy+water+at+1.3+MPa+and+192+Celsius). If the pressure would decrease, and I assume the temperature is constant, to 1.0 MPa its enthalpy would be 2809 kJ/kg (http://www.wolframalpha.com/input/?i=enthalpy+water+at+1.0+MPa+and+192+Celsius). So the energy increases which seems strange to me. I thought the energy would decrease when the gas loses pressure. Will the gas temperature actually drop for the energy to be constant or decrease? In my example it is steam in a power plant that passes through a valve and there the pressure drops. Assuming no loss of heat to the surroundings. Wikifantast (talk) 15:36, 28 January 2011 (UTC)

See Ideal gas law. Looie496 (talk) 18:44, 28 January 2011 (UTC)

An assumption is wrong; unless the valve does work on the steam, the energy in the steam can't increase. So, either the steam is no longer at 192 celsius, or work was performed on it (in the form of heat transfer, or some other method). If exactly zero energy was transferred, and there was absolutely no change in volume, the temperature will change (per the pressure-temperature law; with that temperature, you should find an exactly equal enthalpy on both sides of the valve. In reality, energy should be lost: work was performed by the steam as it passes through the valve: some percentage of steam cavitated, liquified, condensed, changed volume, and lost heat to the walls of the valve and pipe. So energy was lost through that process. We should expect a temperature change to account for both the adiabatic- (ideal gas law) and non-conservative work (energy loss to surroundings). Why do you believe the temperature would be constant on both sides of the valve? Have you instrumented the steam-temperature on both sides? Nimur (talk) 19:27, 28 January 2011 (UTC)

Thank you. I think then that both the volume and temperature will change too. At 184 Celsius Wolfram Alpha says the energy is the same[2]. I have no data of the temperature on both sides. But intuitively it seemed to me that the temperature could stay constant although the pressure dropped through the valve; pV/T could still be constant if the volume increased (density decreased). Wolfram Alpha also calculates the density.

In reality of course there will always be heat loss to the ambient (non-conservative work) but I guess you can assume it is zero. Wikifantast (talk) 21:37, 28 January 2011 (UTC)

please explain binary stars in simpler language than the article

I am trying to understand how binary star systems work with planets. 1. how close are the two binary stars? would it be like the sun and jupiter, or the sun and pluto, or the sun and alpha centori? 2. would the planets orbit both stars or just one? 3. in stars wars on luke's planet there are two suns in the sky of the same size not too far from each other. does this mean the stars are very close or one is a lot bigger than the other? would luke's planet be orbiting one or both of them? 4. if you are on a planet orbiting just one of the stars, and the other one is far away, does it look like another star in the sky? is there a way you could tell it is your binary sun? for example, i know you can tell other planets from stars because they sometimes move backwards in the sky. would the sun you are not orbiting do the same? Many thanks. —Preceding unsigned comment added by 74.14.13.241 (talk) 15:43, 28 January 2011 (UTC)

Let's simplify the problem first. 1) Any two objects orbit the Barycenter of the two objects. The barycenter is the center of mass of the two object system. For the earth-sun system, the barycenter is NOT the center of the sun. It is inside the sun, but off-center by a small amount. So it is technically incorrect to say that any one object orbits another; the two objects oribit around a point on a line between their individual centers of mass, which is located relative to their relative masses. The effect is really obvious when the objects are close enough in mass so that the barycenter lies outside of either object; this happens in the Pluto - Charon system. This works exactly the same regardless of the composition of the two objects; so two chunks of rock (like Pluto-Charon or Earth-Moon), a planet-star system (like Earth-Sun) or a binary star system. The way the two objects move is the same. 2) The major problem with adding a planet to the system is that you create an n-body problem, which is not stable; that is there is no way to predict the relative motion of all three bodies in the long term, even given their initial locations and velocities. --Jayron32 16:14, 28 January 2011 (UTC)

(e/c) Binary systems vary a lot in terms of the size of stars and the distance between them. This page discusses a stable system similar to that around Tatooine where stars are on average 23 AU apart, which is slightly more than the distance from Earth to Uranus.

The Wikipedia page on binary stars says it is possible for a planet to either orbit a single sun or to orbit both, depending on how close the stars and planet are. The example I mention above assumes the planet orbits only one star, at a distance of less than 3 AU (a bit more than the distance between the sun and Mars). Orbitting a single star would probably be a bit more hospitable for human life.

The distance from the planet to the farther star would be far less than between the sun and the next nearest star (our sun is 250,000 AU from the next-nearest star), so assuming the farther-away star was a similar size to the sun, it would look much brighter than any star but much smaller and dimmer than our sun. --Colapeninsula (talk) 16:23, 28 January 2011 (UTC)

Thank you and thank you. that helps to visulize it. Jayron do you mean that a planet like tattoone is not possible because it would keep moving a different distance from the suns and get too hot or cold for life? Because colapeninsula says it can be stable? That is interesting you would always be able to tell you are in a binary system because there are two things brighter than the stars. --74.14.13.241 —Preceding unsigned comment added by 74.14.13.241 (talk) 17:39, 28 January 2011 (UTC)

You can carefully construct 3-body problems like Tatooine so that they can be stable over fairly long periods; so yes, it is technically possible to do so. It would be rare, but of course not impossible, that such an arrangement could arise naturally. --Jayron32 17:47, 28 January 2011 (UTC)

Sorry, I just read colapeninsula's link that says the planet like tattoine would have billions of years before it moved enough to make it unhabatable. thanks again for the help. (talk) —Preceding undated comment added 17:43, 28 January 2011 (UTC).

Can we keep Tatooine from getting too close to a star by putting it in a Lagrangian point? I guess if you want to see both suns in the sky at the same time it would have to be points L4 or L5, unless it's possible to orbit around the L2 point (the article implies that it's possible). —Preceding unsigned comment added by 205.193.96.10 (talk) 21:03, 28 January 2011 (UTC)

The "orbits" around L1-L3 are not completely stable. They require small amounts of station keeping, which is easy for a spacecraft like the Solar and Heliospheric Observatory, but impossible for a planet. The other problem is the relative masses of the objects. L4 and L5 are only stable if the larger of the two objects (in this case, the two stars) is 25 times more massive than the smaller. That can happen if you have a binary system of a blue supergiant and a red dwarf, but you aren't going to get two sun-like stars with that kind of difference in mass. The other problem is that the object at the L4 or L5 point has to have a very small mass - small enough not to have any noticeable effect on the other two bodies (the stars). I'm not sure quite sure how small the body must be, but I suspect a planet would be much too large, especially since one of the stars is, because of the 25 ratio thing, required to be very small. --Tango (talk) 20:56, 29 January 2011 (UTC)

You might find HD 188753 interesting. Astronaut (talk) 16:23, 29 January 2011 (UTC)

ear piercing

When you pierce your ears is anything dying or is it just being pushe to a new location?Accdude92 (talk) 16:35, 28 January 2011 (UTC)

Surely at least some cells are ruptured by the act of piercing, though that article doesn't discuss piercing trauma very much at all. Comet Tuttle (talk) 17:46, 28 January 2011 (UTC)

Agree. In addition to the many types of skin and subcutaneous tissue cells that would be directly crushed during piercing, trauma to blood vessels will result in some bleeding, and the cells leaking from the laceration will die quickly. -- Scray (talk) 19:25, 28 January 2011 (UTC)

Hmmm. Why is it that ear piercings done with a piercing gun don't tend to bleed (or if they do, in such a tiny volume as to be unnoticeable)? This is my experience, as well as that of others I've discussed it with. --Kurt Shaped Box (talk) 19:29, 28 January 2011 (UTC)

I would guess that they are designed to apply pressure on both sides of the puncture, in a standardized way. The challenge has been to do so with an instrument that can be cleaned properly between victimscustomers. -- Scray (talk) 23:50, 28 January 2011 (UTC)

Personally, I'd recommend that anyone who fancies a piercing goes to an *experienced*, *competent* (shop around, ask questions - they're pros, they don't mind) piercer who uses a needle and an autoclave. I know it's a highly politicized subject (some piercers basically consider those guns to be the devil's spunk and seem genuinely furious that they exist) - but I'm simply stating this from my own personal experience with ear and eyebrow piercings (been considering a bridge piercing on and off for a couple of years) - and the healing thereof. Plus, you're not restricted to a stud for your first piece of metal. --Kurt Shaped Box (talk) 00:58, 29 January 2011 (UTC)

Also, is the a time when closing of the piercing is impossible?Accdude92 (talk) 17:26, 31 January 2011 (UTC)

Physics, conservation of linear momentum-collisions

2 bodies make elastic head-on collision on smooth horizontal table kept in car. Do u expect change in result, if the car is accelerated on a horizontal road because of the non-inertial character of the frame? Does the equation " Velocity of separation = velocity of approach" remains valid in accelerating car? Does the equation " Final momentum = initial momentum " remain valid in the accelerating car?

.....with proper reasons.

—Preceding unsigned comment added by 122.169.145.208 (talk) 17:20, 28 January 2011 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. DMacks (talk) 17:29, 28 January 2011 (UTC)

No this isn't a home work question! I saw this question while I was going through the book "Concepts of physics 1" by H.C.Verma. I know that in inertial frame, momentum and kinetic energy are very much conserved in this case but I couldn't decide myself whether momentum is conserved or not. I think its not conserved as pseudo force acts. But just I need clarification whether my thinking is correct or not. I am not confident about my answer, so I put this question here, but not for the sake of completing the homework! Hope you answer this ....

Yes, you are right, the pseudo-force acts, but the collision takes a very short amount of time to happen and since the change in momentum is given by dP = F dt, unless the pseudo-force is very strong (very high acceleration), the change in momentum is likely small enough that it can be considered negligible in which case all the usual rules of thumb for solving collision problems still apply. 71.101.41.73 (talk) 16:30, 30 January 2011 (UTC)

Aside the obvious answer

How can I find out if a sheet of glass is toughened (without actually breaking it)? --BozMo talk 17:31, 28 January 2011 (UTC)

A polarizing filter will help you see if there are strains in the glass. Here's a reference, The Identification of Toughened Glass using Polarized Light (1973). You can also use a web-search for comparative images: here's a sample Google query. Nimur (talk) 18:00, 28 January 2011 (UTC)

(EC) As per Toughened glass#Properties, the strain pattern resulting from tempering can be observed with polarized light or by using a pair of polarizing sun glasses. Red Act (talk) 18:05, 28 January 2011 (UTC)

In case anyone doesn't have access to the article I linked, here's a summary of the "methods" section: place the glass-under-test between two crossed polarizer filters, and illuminate from behind with white light. Rotate the polarizer filters. If you see an iridescent color-behavior that has a periodicity with each 90-degree rotation of the polarizer-filter, you have toughened glass; if you simply see a variation in light intensity, you have annealed glass. A few caveats exist, related to whether your glass has any fracture surfaces, that are described in detail in the paper I just linked and elsewhere on the web. Nimur (talk) 18:08, 28 January 2011 (UTC)

I'd consider the obvious answer to be to contact the manufacturer. I doubt anyone would sell toughened glass without advertising it as such. What are the circumstances you're trying to figure it out under? — DanielLC 03:03, 30 January 2011 (UTC)

Obviously he's asking out of doing research for a breaking and entering robbery job. In this case, calling the building's owner and ask whether he had toughened windows installed is not exactly an option... 62.166.201.27 (talk) 13:31, 31 January 2011 (UTC)

A hydrogen bomb in an undersea volcano= add new land?

If a fusion bomb was placed in an undersea volcano, would it induce an eruption so massive that this volcano will spew out enough lava to permanently break the sea level and become an island?

Surtsey happened naturally, and Japan and Taiwan is in an epic land crunch for real estate so this would be an instantaneous way to reclaim more real-estate from the sea, wouldn't it?

By the way, I think the results might be better if the bomb was made to explode upside-down. Instead of a mushroom cloud, how about a mushroom laccolith under the volcano's base? Therefore, how can a bomb be made to explode a mushroom cloud into the earth instead of up in the sky? --129.130.32.220 (talk) 20:07, 28 January 2011 (UTC)

I'll add that to the list of crazy ideas I've seen on those pages over the years. BTW, there is no such thing as an upside down explosion. The mushroom goes up because hot air rises. 71.101.41.73 (talk) 20:37, 28 January 2011 (UTC)

Yes, the idea of an upside-down explosion is just confused. The explosion of a nuclear blast is just a sphere of fire and blast. It rises because it is hot.

You could shape the blast, probably, to fire more energy in one direction than another, though. These sorts of schemes were considered in developing Project Orion. It strikes me as probably doable, though whether that would hep or not, I don't know.

As for the geology of it, I have no clue. There were worries in the 1980s that sufficiently large underground nuclear tests could induce seismic and possibly volcanic activity (see, e.g. Amchitka). But this didn't happen. But it wasn't meant to happen, either — it's not clear to me that you couldn't do it on purpose. It should be noted, though, that Japan is probably the last place on Earth that would ever embrace Plowshares-like projects. Their disinclination to mess with nukes goes pretty deep!

There is nothing on this topic in The constructive uses of nuclear explosives (1968), which is sort of a catch-all book of proposals for "fun" and "peaceful" things you could do with nukes. --Mr.98 (talk) 20:55, 28 January 2011 (UTC)

How could one prevent the bomb from melting or being disrupted by the heat while placing it "in a volcano?" Place it in a shell of Unobtanium? Edison (talk) 21:01, 28 January 2011 (UTC)

Heh, heh, Edison, Tungsten has a higher melting point than the temperature of lava, IIRC. We just have to get it thrown in there deep enough (by a tungsten drill, maybe?) and have it detonate by a timer or a switch. --70.179.181.251 (talk) 06:03, 29 January 2011 (UTC)

Presumably you wouldn't put it in the lava itself, but near it. E.g. to the right of the label "3" in this diagram, or something like that. But I am not a geologist. --Mr.98 (talk) 21:05, 28 January 2011 (UTC)

For perspective, consider reading about human-induced seismicity. Most induced seismic response is the result of many years of continuous changes in the overburden or fluid-pressure, due to extraction of solid or liquid material during mining, water-well extraction, or fossil-fuel extraction. Nimur (talk) 21:04, 28 January 2011 (UTC)

Even if it could work (I am pretty sure it couldn't, but lets play a game and pretend that it could), what would be the point? I am pretty sure that the lava would become impregnated with lots of highly radioactive fallout from the bomb you just set off; great, so you have new land but its so radioactive to be unlivable. What good is that? That of course ignore the point that even the most powerful thermonuclear devices pale in comparison to the power of geologic events. A single volcanic eruption or earthquake packs many times the wallop of an H-bomb. I'm pretty sure if you put the entire world's nuclear arsenal in one place and set it off all at once, it wouldn't even be as big as the 1980 eruption of Mount St. Helens, which while impressive was not uncommonly so, at least on a geologic scale. The main blast which caused the collapse of the north face of the mountain moved about 1/20th of a cubic mile of earth, an unimaginably large chunk of solid rock to be pulverized to dust. I just can't see a bomb doing that kind of work. --Jayron32 21:14, 28 January 2011 (UTC)

To be fair, nobody is saying that the bomb would have the force of a volcano, just that it could be used to trigger one. I'm not sure that's not impossible. The trick about energy release is that it matters how much is released in how small a volume. An earthquake releases a huge amount of energy but over long distances. The sun releases an unfathomable amount of energy but it does so over such a diffuse distance and time scale that we perceive it as a warm bath, not a searing flame. I think there are probably geological situations where a properly placed, sufficiently large thermonuclear detonation could act as a catalyst for a much larger volcanic eruption. It's not necessarily the case that fallout would be mixed into the magma itself — there might be clever ways to make the eruption contain the bomb blast (e.g. bury it even while it erupts upwards). But I don't know much about volcanos, to be sure. --Mr.98 (talk) 21:27, 28 January 2011 (UTC)

Actually Mount St. Helens released "only" about 24 Megatons of energy which is somewhat less than the largest hydrogen bomb ever detonated. The Krakatoa eruption, one of the largest eruptions in recorded history, was about 200 Megatons of energy. So, volcanoes are somewhat larger than but on the same order as hydrogen bombs. Of course the energy is released in very different ways, which does make a significant difference with respect to the impacts it has. Dragons flight (talk) 21:36, 28 January 2011 (UTC)

It's worth noting that Krakatoa's explosion left less land above the sea than before. And Mt St Helens got smaller when it exploded. Guaranteeing more land would be a challenge. HiLo48 (talk) 21:58, 28 January 2011 (UTC)

True to a point, but keep in mind that the goal would be to take the internal parts of the mountain and spread them out in order to create a structure with more surface area and less height. Still, Mt. St. Helens is a good example in many ways. Even if it had been surrounded by water, and somehow did end up with water above sea level, mixed ash is not really an ideal building material. And it strikes me that for all of the effort, the amount of land is still not going to be that useful by human standards. (And again, I'm wary about comparing nukes to volcanos in terms of explosive force, anyway, because the time scales are usually quite different, and the effects that correspond are quite different.) --Mr.98 (talk) 20:12, 29 January 2011 (UTC)

I'm not certain that the demand for new land in Japan is any higher than it is in New York. Though they have enormously high population densities in the biggest cities, due to most of the land being unusably steep (Japan#Geography), they also have a falling population size, and 6,852 little islands that already exist. The most significant reason for the high population of cities is that a large number of people want to live close together. Is Izu Ōshima so crowded that they need a second one? Land reclamation does say that 20% of Tokyo Bay has been reclaimed, but land that's contiguous with Tokyo must be worth a lot more than land which is offshore and radioactive. 81.131.22.166 (talk) 23:25, 28 January 2011 (UTC)

January 29

Sweet crude oil

I was in class and my prof mentioned that there is a type of crude oil called Sweet crude oil, and he said that workers would actually taste the oil. Isn't oil toxic? Wouldn't tasting it be detrimental to their health? ScienceApe (talk) 02:34, 29 January 2011 (UTC)

According to this document from the Oil Spill Academic Task Force of the State of Florida, "In the 19th century, oil workers would taste and smell small amount [sic] of oil to determine its quality." Clarityfiend (talk) 02:56, 29 January 2011 (UTC)

Many geologists are rather partial to having the occasional lick of anything that looks (or smells) interesting. DuncanHill (talk) 03:07, 29 January 2011 (UTC)

It looks like geologists like to put dirt in their mouth for several purposes, also to evaluate a sample's texture. See, for example, siltstone or, regarding oil, old formation evaluation tools to detect oil and gas by grounding the well cuttings between their teeth. They "tasted to see if crude oil was present", according to that article, unreferenced. Other sources seem to suggest it was for detecting texture, not taste. ---Sluzzelin talk 05:06, 29 January 2011 (UTC)

And they're not the only ones. Ask an archaeologist some time about how to tell the difference between a bone fragment and a flake of stone in the field. (The bone sticks to your tongue, but stones don't). Matt Deres (talk) 14:42, 31 January 2011 (UTC)

Tasting this oil is not detrimental to the health? ScienceApe (talk) 16:25, 29 January 2011 (UTC)

No one is claiming that! This (commercial) site lists some figures and hazards, toxicity in case of ingestion or skin contact included. The data are referenced. They don't directly answer your question, but it's pretty clear this isn't something you want to try at home, and certainly not repeatedly. Some of the long-term hazards from doing this repeatedly, such as carcinogenicity, probably couldn't have been detected soon enough to make a connection, at the time. (I wanted to point you to an article on the history of occupational health and safety, but, judging from the few articles that link to Bernardino Ramazzini, we have no such article, nor is it well-covered in any of the history sections). ---Sluzzelin talk 16:53, 29 January 2011 (UTC)

The level of benzene in crude oil before cracking is not very large, and cancer is definitely not guaranteed - though no level of exposure is truly acceptable. But bear in mind that petroleum was taken as a "medicine" in Western countries at a time when its use for fuel was obscure if not forgotten. Wnt (talk) 21:39, 29 January 2011 (UTC)

giving m₂=0 for newton formula

what happens for field when we give m₂=0 for newton gravity formula.(G) a. mohammadzade —Preceding unsigned comment added by 78.38.28.3 (talk) 11:26, 29 January 2011 (UTC)

See the article about Newton's law of universal gravitation which is expressed by the equation

$F=G{\frac {m_{1}m_{2}}{r^{2}}}\$

Any real physical object has mass, but if a hypothetical object had zero mass it would have no gravitational attraction to any other object. Cuddlyable3 (talk) 15:23, 29 January 2011 (UTC)

Well, there would at least be zero gravitational force acting on the zero mass object. But from F=ma (Newton's second law), calculating what acceleration results when an object with zero mass is acted upon by a zero force results in the indeterminate form a=0/0, so you can't conclude that the zero-mass object experiences no acceleration. What works better in this case is to combine Newton's two equations to give

$a_{2}=G{\frac {m_{1}}{r^{2}}}\$,

where a₂ is the acceleration of the object you're calculating the acceleration of, and m₁ is the mass of the other object. That combined equation avoids the indeterminate form when m₂=0, and helps lead toward the more appropriate understanding of gravity as involving a coordinate acceleration as is produced by a fictitious force, rather than being a real force, as per Einstein's equivalence principle. As per that combined equation, a theoretical zero-mass object will still experience the same acceleration due to gravity as an object with nonzero mass, even though there is no force acting on it. Red Act (talk) 18:06, 29 January 2011 (UTC)

Yes, except that equation arises by dividing by zero. The best we can say in the Newtonian theory is that following the ordinary acceleration of gravity is the limiting behavior as the mass of a body goes towards zero. However, if there were any force acting on the body except for gravity, that force would completely dominate its behavior when its mass gets small enough. It could be a force that is so tiny that its effect is not observable for anything but massless bodies, and so the Newtonian theory cannot actually predict that massless objects move with the acceleration you quote (that is, "predict" in the sense that it would automatically falsify the theory to find a massless object that did not move so).

And actually, the massless objects we know (that is, photons) do not experimentally behave in gravity fields like Newton says they ought to. They are deflected by more than the Newtonian limit, thanks to GR and space curvature. –Henning Makholm (talk) 01:30, 30 January 2011 (UTC)

Perhaps I should have given more emphasis to the requirement that the above equation would only apply in the case of there being absolutely no (nongravitational) forces acting on the object, either forces that are now known or that might be discovered in the future (or perhaps even some physical phenomenon discovered in the future that results in a proper acceleration but can't be expressed as a force). But I did end the post with the phrase "even though there is no force acting on it", so that limitation should have at least been rather clearly apparent at that point, even if it hadn't been obvious enough before then.

Newtonian gravity as an approximation to general relativity falls apart at high relative speeds, regardless of whether or not the object in question has a nonzero mass. And the approximation falls apart at high speed for even geometrical considerations alone, so the approximation's breakdown can't just be fixed by special relativistic corrections to the mass. So I was treating the question as pertaining to a hypothetical zero-mass object moving at low speed, since behavior at low speed is the only condition under which any discussion of Newtonian gravity has any validity at all. So the behavior of photons is irrelevant to the hypothetical situation that I was considering.

The equation above is the correct equation for the (coordinate) acceleration due to gravity of low speed objects in the absence of any (real) forces in the weak-field approximation as predicted by general relativity, and the equation above can be derived using general relativity without ever taking the object's mass into account (assuming the mass isn't large enough to itself cause nonnegligible curvature of spacetime). The geodesic followed by a object experiencing no real forces is completely governed by the geometry of the spacetime on which the object is traveling; the object's mass has nothing to do with it. So there isn't a division by zero involved if you derive the equation using general relativity.

Indeed, any other behavior for even an object of zero mass would be nonsensical for even geometrical considerations alone. In the absence of any real forces, the object must have a zero proper acceleration, because the local isotropy of space would prevent the object from having any way to even choose a direction in which to accelerate. And if the object has no proper acceleration, the only other "acceleration" the object can have is the coordinate "acceleration" of the object's local inertial frame with respect to the chosen noninertial coordinate system. And the coordinate "acceleration" is a purely mathematical device that has nothing to do with actual physics, so any physical properties of an object like whether or not it has a mass is irrelevant to the expression of the magnitude of the coordinate acceleration as expressed in the equation above.

As with any fictitious force, the apparent acceleration of objects under the "influence" of gravity is most appropriately viewed as more fundamentally being a coordinate acceleration, that only looks like a "force" if you artificially multiply that acceleration by an object's mass. That's the general relativistic perspective, and that's actually the entire reason why I pointed out in my earlier post how gravity can be described as being an acceleration, with any notion of a "gravitational force" being removed. I wasn't trying to fully explore the acceleration of a hypothetical low speed massless particle that might actually be discovered in the future. So bringing up tiny additional forces that might be discovered in the future and what-not is really tangential to my intended point. Red Act (talk) 08:06, 30 January 2011 (UTC)

Anal orgasm

Is it possible for woman to have orgasm from anal stimulation alone, and how is it distinct from vaginal orgasm? --78.150.235.125 (talk) 11:43, 29 January 2011 (UTC)

Orgasm#Anal_stimulation provides some referenced information for this and this Slate article may also be useful. SmartSE (talk) 12:34, 29 January 2011 (UTC)

Balloons

How much force upward does a balloon exert? I recently saw Up, and I know getting a house airborne would be impossible, but I am curious as to how much helium would be needed to lift a person or a basket. And how about hydrogen balloons? What is hydrogen and helium's lifting power per square inch? --T H F S W (T · C · E) 18:15, 29 January 2011 (UTC)

Per square inch it's zero ;-). The molecular weight of Hydrogen (H₂) is 2 g/mol, the molecular weight of Helium (He) is 4 g/mol, and the average molecular weight of air is 80%*28+20%*32 (for Nitrogen and Oxygen, both diatomic gases), or just shy of 29g/mol. So one mol of Hydrogen can lift 27g, one mol of helium can lift 25g. One mol of gas under standard condition occupies 22.4l, so the lifting power of either gas is about 1g/l or 1 kg/m³. Of course, that is the gross lift - for the net lifting capacity, you need to subtract the weight of the balloon. If you need more exact numbers, apply a calculator ;-) --Stephan Schulz (talk) 18:27, 29 January 2011 (UTC)

There was the interesting case of Lawnchair Larry, who dared in 1982 to try this experiement "at home". He attached 45 helium-filled weather balloons to a lawn chair in his back yard and flew to an altitude of over 15,000 ft! (Asked why he did it, he replied, "[Because] a man can't just sit around.";) WikiDao ☯ 18:28, 29 January 2011 (UTC)

OK, thanks, I'll start collecting weather balloons! Joke - for now.--T H F S W (T · C · E) 18:48, 29 January 2011 (UTC)

N.B. his "honorable mention" at the Darwin Awards...;) WikiDao ☯ 19:36, 29 January 2011 (UTC)

Anyone know the area of a normal party balloon? And @Stephen, yeah, I meant a cubic inch. Heh heh. --T H F S W (T · C · E) 19:58, 29 January 2011 (UTC)

You're a quick study, right? ;-). Do you mean the surface area or the projection onto the ground? Or do you actually mean the volume? A 30 cm ballon has a volume of around 14 l. It weights maybe 1.5 g, so it can lift around 12 g. --Stephan Schulz (talk) 21:16, 29 January 2011 (UTC)

In real units. 1000 cubic foot of hydrogen at STP will lift 74 lb. So a cubic foot balloon is err.. I think 1.184 ounces of lift. Helium has a lift of 72 lb per 1000 cu ft.--Aspro (talk) 21:29, 29 January 2011 (UTC)

Fully saturated moist air weighs only 5/8 of dry air and is very much cheaper than H or He. You can create some by burning (say) propane or butane gas in a large bag. That will also heat it and increase the lift still further. Thinks.... If one were to leave said bag open at the bottom you could keep it hot by continuously burning more gas. Hey! I wonder if Microsoft has patented this idea yet? --Aspro (talk) 21:47, 29 January 2011 (UTC)

While water vapor (gaseous H₂O) is about 5/8 the mass of an equivalent volume of dry air at the same temperature and pressure, it's highly incorrect to say that moist air is 5/8 that of dry air. Humidity notes that at 30°C, saturated air contains 30 g per cubic meter of water, which equates to at most 18 g of lift per cubic meter. This compares to an air density of 1.164 kg/m³, so humid air would be at most 1.5% lighter than dry air. This compares to the ca. 80g/m³ lift you get by heating 15°C air to 35°C (cf. Density of air). It's true that if you had an equivalent volume of water vapor at the same temperature and pressure, you'd get 3/8ths lift from it, but at temperatures below 100°C, that's not possible, as all the water would condense, and you'd have a deflated container [3], or a partial vacuum. -- 174.21.236.191 (talk) 00:25, 30 January 2011 (UTC)

Quite right -the lift is pitiful. Maybe instead, a sealed balloon of pure water vapour, fabricated from aluminium foil backed bubble-wrap, with argon filled bubbles to reduce conductive heat loss. Then a small radioisotope heater unit to maintain the vapour at ≥100 deg C temperature. --Aspro (talk) 18:32, 30 January 2011 (UTC)

Of course, the weight of the balloon itself also has to be lifted. My intuition says that a single large balloon should require less gas to lift the same weight than a large number of small ones, although this is not 100% obvious, because the large balloon might need to be thicker. Anyway, balloonists normally do use a single large balloon, so it makes sense that that's best. (The great airships like the Hindenburg did use separate gasbags within an outer cover, but I think that was mainly in order to contain the effects of any damage.) --Anonymous, 00:05 UTC, January 30, 2011.

While not an WP:RS, this forum thread reckons 60lbs per square foot of living space, or 120lb per square foot of footprint for a house is the approx weight. Exxolon (talk) 16:55, 30 January 2011 (UTC)

Buckminster Fuller went as far as to propose airborne towns.--Aspro (talk) 18:21, 30 January 2011 (UTC)

Graphite

In graphite, are the layers stacked so that the carbon atoms in one layer are directly on top of the carbon atoms in the lower layer, or are they over the centers of the other layer's hexagonal holes? --75.15.161.185 (talk) 19:39, 29 January 2011 (UTC)

The latter. See: graphite. Dragons flight (talk) 19:41, 29 January 2011 (UTC)

Converting ohm to siemens

I'm doing a science project on the electrical conductivity of different materials. I have an ohmmeter and know how to convert ohms to siemens. The problem is, I'm testing piece of rubber and the reading just shows up as 1 on the 2M setting. How would I convert this value? Writing down 1 [S/m] doesn't seem correct. —Preceding unsigned comment added by 68.230.183.227 (talk) 19:49, 29 January 2011 (UTC)

A multimeter reading of "1" typically means the value is unmeasurable because it is beyond the range of that meter. Since you put the multimeter on 2 MΩ, you know that the resistance of the rubber is greater than that (R > 2 MΩ), so the conductance is less than (1÷(2 MΩ) = 500 nS), so G < 500 nS. --Link ^(t•c•m) 21:04, 29 January 2011 (UTC)

I talked with my dad and he basically said the same thing. Thank you so much though. —Preceding unsigned comment added by 68.230.183.227 (talk) 21:51, 29 January 2011 (UTC)

Central American Bat Identification

8.70780°N 83.49300°W / 8.70780; -83.49300

I recently photographed this individual roosting on a tree trunk, approx 8-10feet above ground level. Accompanied by one other individual, roosting a few feet above. Osa Peninsula, Costa Rica. Hopefully those lines of white pale fur are destinctive, thanks in advance Benjamint 22:36, 29 January 2011 (UTC)

Looks very like the bats shown in this query, which have been identified by a respondant as either Lesser Sac-winged bats (Saccopteryx leptura) or Greater Sac-winged bats (Saccopteryx bilineata). 87.81.230.195 (talk) 02:45, 30 January 2011 (UTC)

January 30

My Honda Accord will be 10 years old this year. Why no rust?

Some junked antique cars are coated with rust, and I've read that they've rusted rather quick.

Yet my 2001-model has almost 130,000 miles so how does it remain rust-free anyhow? --70.179.181.251 (talk) 00:12, 30 January 2011 (UTC)

There are lots of factors that cause different amounts of rusting. If you maintained your car very well, and didn't drive it on a lot of salted roads, I would not expect it to rust. All of our cars have been far older than that when we got rid of them, and other than a tiny spot, I can't remember any rust on any of them. Of course, it could be rusting in places that you don't see, but even that's not a guarantee. Basically: it depends on a lot of different things. I cannot tell you why your car specifically is not rusting, but I can surmise why a car might not rust after ten years. Falconus^{p t c} 03:14, 30 January 2011 (UTC)

At least in Germany, it's now standard for most new cars to have a fully zinc galvanized body, which makes rust a very rare occurrence. Toyota started the wide-spread use of galvanized steel in Europe in 1992, and seems to use it more or less universally since 2000. Car-makers now have the technology to nearly completely eliminate rust as a problem, although not all use it to the same degree (arguably, there is no reason for outstanding longevity if cars are retired for obsolescence reasons after 10 years anyways). --Stephan Schulz (talk) 09:19, 30 January 2011 (UTC)

Sorry, my mind misread Honda for Toyota. I don't know when exactly which Honda models started using galvanized steel, but from what I could find online it should be in a similar time frame.--Stephan Schulz (talk) 12:05, 30 January 2011 (UTC)

As above - modern cars rustproofing is a lot better than before. If you're driving in a dry climate without lots of rain, snow or ice the car's bodyshell will not degrade very much. Exxolon (talk) 16:38, 30 January 2011 (UTC)

Short answer: It's a Honda. :P Roger (talk) 17:38, 30 January 2011 (UTC)

How do I customize GPS navigation voices?

I think the voices that vehicles give through their embedded GPS navigation systems should reflect their ages and nationalities. At least the voices of the vehicles I plan to drive, anyway. Moreover, I'd also like some kind of subroutine that will "age"/deepen the voice of the navigation system as the vehicle ages.

For example, if I buy a used 2005 Volvo XC90 in 2013, how do I get the navigation program to voice out the directions sounding like a Swedish boy?

I think if I drive a Hyundai, the GPS voice should have a Korean accent. If I drive a Fiat, an Italian accent, etc. Moreover, their voices should reflect the date of the car's manufacture. (I won't have to worry too much about how silly they'd sound because I don't plan to buy vehicles newer than 5 years old anyway. It saves a bucketload of $$$ buying used.) --70.179.181.251 (talk) 00:12, 30 January 2011 (UTC)

I think most commercial GPS systems do not synthesize their voice phonemically; they simply play back a series of sampled words. So you would need to (1) pay a voice actor with your desired voice and accent to record a complete vocabulary for the navigation system, (2) rent a voice recording studio for him/her to do it in, (3) pay the manufacturer of the GPS system to help you get the new vocabulary into the box's firmware, as if it was a new language localization. The latter is not an off-the-shelf service; you could easily be looking at $10,000 or more here, and expect to pay in advance. Repeat everything whenever you think the voice ought to change due to the car aging.

Oh, and the GPS manufacturer may not even want to touch this unless you promise that they won't get sued if you let somebody borrow your car and they misunderstand the GPS directions and end up in a river and drown, and they may want you to back this promise with a bank guarantee or a fully paid up indemnity insurance policy, which isn't cheap either, and then you'll also want to pay a lawyer to go over the promise before you sign it, to make sure you're not accidentally signing away your firstborn.

It may be cheaper if you start out with an open-source navigation system running on off-the-shelf laptop or smartphone hardware, though in that case you'd need to hire a freelancer or consultant to do the heavy lifting (you can legally do it yourself, but if you had the skills to do so you wouldn't have to ask here), and that would still set you back at least several thousand dollars in addition to the actor's fee, and you'd risk getting a less stable and feature-rich system than a commercial GPS solution. –Henning Makholm (talk) 02:29, 30 January 2011 (UTC)

Henning is right about commercial sat nav systems, but there is an alternative: the free navigation app from Google, available on Android smartphones. It uses the Google text-to-speech (TTS) engine, which is customisable in principle since it's open source. How you would do it in practice, though, I have no idea. Also, it's currently only available in the USA and the UK. The British one sounds as you would expect the Bride of Frankenstein to sound. It tries to synthesise place names phonetically, often getting them wrong, but you can usually work out what it's trying to say. --Heron (talk)

Standalone GPS systems are easy to customise as long as you have voice samples in a compatible format and the master list that tells the system there's a voice there and which sample to play for each situation. If you could access the memory of an integrated system it should be possible to do the same. Exxolon (talk) 16:36, 30 January 2011 (UTC)

Vocal synthesizers, not voice actors.

Problem is, I'm not looking for actors' voice samples. I'm looking for vocal synthesis Aren't there vocal synthesizing programs that enable me to change any vocal recording to that of a desired age? Why can't I just convert the existing recordings to those instead?

(And if I do get a vocal synthesizer, how do I also change the accent to that of a desired country's?) --70.179.181.251 (talk) 17:08, 30 January 2011 (UTC)

This might be more of a question for the computer desk. Most SatNav vendors have a wide range of voices that can be downloaded from their website, some free, some purchased. The files are easy to install, simply copied to the SatNav flash drive. However, the data is not in a publicly published standard so it will not usually be possible to create your own without collaboration with the manufacturer. As Heron said, many devices use sampled voices rather than synthesis so there would be no way of programming in a variant synthesiser, there is just no facility. The best you could do would be to access the analogue audio going to the speaker (which will probably involve taking your satnav apart) and feeding it through a voice disguiser, suitably adjusted for the effect you are looking for. SpinningSpark 19:38, 30 January 2011 (UTC)

GPS satnav system are just not set up for this. If you connect one to your PC and browse it, you'll find a folder for the voices. Each subfolder contains all the samples needed to construct all the sentences ever needed and a file telling the satnav which sample to play when it needs to make that particular part of a sentence. Looking back at your original post it looks like you want the GPS to reflect the cars "personality" for want of a better term - an integrated SatNav with a voice that's appropiate for the car make, model and age - no manufacturer will bother doing this - it's a lot of expensive work for a demand that's just not there. It would be just about possible to do this manually assuming you could find or record samples in the relevant accent, timbre, elocution etc and access the satnav memory - you could then manually set the voice to match the car. However you'd have to do this manually for each make/model you wanted to do - there's no way to do it automatically. You'd also have to periodically replace the samples manually if you wanted to reflect the age of the car - there's no way for the satnav to switch samples based on the age of the car. This really isn't going anywhere. Exxolon (talk) 01:04, 31 January 2011 (UTC)

My sister's TomTom satnav has a range of different voices, accents and languages - I believe the feature was built in when she bought it. She prefers the Irish accent of "Sean" over the "posh English lady" :-) TomTom#Upgraded Voices suggests some of their products support the purchase(?) of celebrity voices. Astronaut (talk) 17:11, 31 January 2011 (UTC)

What's at the edge of a piece of diamond or graphite?

Or other lattice compounds, for that matter. Unlike molecular compounds, the atoms on the edge would have unpaired electrons, so what do they do? Do they just bond with random hydrogen or oxygen atoms from the air? --75.15.161.185 (talk) 03:17, 30 January 2011 (UTC)

Yes --Plasmic Physics (talk) 03:33, 30 January 2011 (UTC)

See in particular material properties of diamond, which contains some discussion of which terminators they typically end up with. Apparently we have nothing similar for graphite (I wonder whether it would be an acute problem there -- because the orbitals are hybridized throughout the graphite layer, the burden of lacking an electron could be shared among many more atoms than in a small radical. On the other hand, it appears that a phenyl anion is not considered aromatic, so perhaps the edge atoms are not allowed to just borrow their missing electron). –Henning Makholm (talk) 04:23, 30 January 2011 (UTC)

What if it's formed in a vacuum by vapor deposition? --75.15.161.185 (talk) 13:24, 30 January 2011 (UTC)

Then it would appear that the graphite has no choice but to grow with unpaired electrons at the edges, wouldn't it? As far as I can search, the most abundant molecules in carbon vapor are things like :C=C: and :C=C=C: which have more unpaired electrons than they have atoms, so it would still be a net win for them to join a growing graphite sheet, even if the sheet does not terminate nicely. –Henning Makholm (talk) 14:44, 30 January 2011 (UTC)

fruit

If a fruit falls from a tree and no animal eats it, will the fruit aid in the seed in growing? —Preceding unsigned comment added by 92.3.157.72 (talk) 03:35, 30 January 2011 (UTC)

If the fruit is not eaten by an animal, it's likely to rot before the growth season starts anyway. And even if it miraculously avoids rotting, the seedling would have to absorb the sugars from the fruit through its root, and it's far from clear that it would be up to that task -- the root epidermis would have to express specialized membrane transport proteins for this, and likely has no evolutionary reason to think trying that might be a good idea. It's even possible that the osmotic pressure of the sugar would make it difficult for the seedling to absorb enough water to grow. –Henning Makholm (talk) 04:55, 30 January 2011 (UTC)

Wait, surely the fruit rotting is a good thing, as now the seeds are sitting in a small amount of compost? I don't think any theory of fruits and seeds proposes that the seeds make use of the unrotted fruit. I'm sure many plants rely on animals eating the fruit to disperse the seeds, but that seems far from the only purpose of fruit in all non-cultivated plants: there are fruits with protective systems to prevent them being eaten, for example. And some apples, for instance, do rot where they sit without being eaten, and then the apple seed grows in the apple-enriched earth: there doesn't need to be only one benefit to something. 86.164.58.119 (talk) 10:33, 30 January 2011 (UTC)

This is a common misconception; the main purpose of fruits is not to provision seeds. Generally speaking, the purpose fruit serves a plant is to disperse the seeds via animals. This is a classic mutualistic interaction, because it benefits both the plant and the animal. SemanticMantis (talk) 05:33, 30 January 2011 (UTC)

And where fruits contain poison normally the poison is only present until the fruit is ripe or it is only in the nut or it is poisonous to some mammals rather than birds for instance so the seed gets widely dispersed. Dmcq (talk) 11:01, 30 January 2011 (UTC)

What is the point of the rough almost armoured coat on a lychee? This coat or rind seems "designed" to prevent animals from eating it. Thanks 92.29.125.152 (talk) 14:09, 30 January 2011 (UTC)

Plants often 'target' a certain animal to disperse their fruit. In the case of the lychee, the shell may keep out insects or mice, but allow a bird to eat the fruit and carry it farther. SemanticMantis (talk) 14:17, 30 January 2011 (UTC)

Dmcq mentioned something similar (before the OP's question) and there are also chillis and durians as other examples of targeting the right dispersal agent/animal. Nil Einne (talk) 15:14, 30 January 2011 (UTC)

Durians 'target' a handful of primates annually, resulting in several fatalities. -- 110.49.193.138 (talk) 17:22, 31 January 2011 (UTC)

the temperature of crab nebula

i had read any subject in scientific american that the temperature of nebula of such crab is 10⁴ degrees centigrade . i want to know if that is so or i have forgotten. --78.38.28.3 (talk) 06:22, 30 January 2011 (UTC)a.mohammadzade

I've fixed the formatting so that the question is more easily readable. Mitch Ames (talk) 06:27, 30 January 2011 (UTC)

According to our Crab Nebula article:

In visible light, the Crab Nebula consists of a broadly oval-shaped mass of filaments ... The filaments' temperatures are typically between 11,000 and 18,000 K ...

10⁴ degrees Centigrade is about 10,000 Kelvin, so the visible part of the nebula is about 10⁴ °C. Mitch Ames (talk) 06:35, 30 January 2011 (UTC)

ok thanks alot .then for recent observation the crab nebula is accelerating particles . is there any nucleic reaction in such clouds?--A.mohammadzade (talk) 06:57, 30 January 2011 (UTC) — Preceding unsigned comment added by A.mohammadzade (talk • contribs) 06:49, 30 January 2011 (UTC)</spanTemplate:Unsigned -->

Note that "temperature" is fairly misleading in this setting. The crab nebula is a high-quality vaccum by our standards. So while the average energy of molecules in the nebula is high (that defines "temperature"), the energy density is extremely low. You could sit inside the nebula in a space suit forever, and still loose more energy from your thermal radiation at ~300K than you would take in from the rare interaction with one of the "hot" particles. The nebula is a recent supernova remnant. Supernovae often generate a lot of (in absolute terms) very heavy radioactive elements. So I'm fairly certain that there still is a measurable amount of nuclear fission going on in the nebula. I don't think there is an appreciable amount of fusion, though. --Stephan Schulz (talk) 09:27, 30 January 2011 (UTC)

Tidal Locking Formula

Dear Wikipedia

I emailed Dr. Burns at Cornell University (e-mail address removed). He said that he had a quick look for formula 2 [which has 10 to the 10 years on the end of it] and it is not in the book cited on the wiki page. http://en.wikipedia.org/wiki/Tidal_locking#Timescale

Would Dr. Peale know? (e-mail address removed)

I have removed e-mail addresses in the above, as per the policy at the top of this page. Red Act (talk) 09:35, 30 January 2011 (UTC)

The formula you seem to be referring to is not cited to a book at all. Which book is it missing from? Do you contend that the formula is wrong? –Henning Makholm (talk) 11:34, 30 January 2011 (UTC)

Can anyone provide clear, simple answers to these Mandelbrot Set questions needed

1. I’ve heard that the Set is connected I gather this means it has no islands. Does that mean you could go from any point on it to any other point without lifting your pencil? But could you do it without crossing any other line?

2. I see great electric lightning type tendrils coming from the main body. Are these lines or do they have have some kind of width? With the tendrils, I have seen images where they extend many times further than the diameter of the main body. How far is the longest one/

3. Also on tendrils coming from the main body, I notice that they seem to be more violent and extensive at the poles of the three main bodies, and that more sub MD sets are clustered there. Is this true, or do I just imagine that there are areas more conducive for such activity?

4. On the tendrils, sometimes a sub-MD appears. How does this happen? Why does a tendril go on normally and then suddenly explode into a full MD. Is there some value in the code which, when it is encountered, explodes it into a whole new set?

5. It says in the article that the MD is self-similar, but unlike Koch’s snowflake and others, you can’t make a priori predictions as to what will be happening down levels deeper. I’m told that this means that the volume enclosed by the set can’t be calculated except within limits. Is this true?

6.There seems to be no shape or line in this set which looks like anything in Nature, expect superficially. There are no circles or lines. I noticed in images that the lance of the MD seems to have something like a straight line, or gradually curved one, and that the fractal activity there appears less complex. Are there areas of the Set where complexity is reduced compared to other areas? Can this complexity scale be measured? Myles325a (talk) 11:57, 30 January 2011 (UTC)

1: Yes, when we say it is connected, it means you could (in principle) draw a line from one point in the set to any other point in the set, without leaving the set or lifting your pencil. SemanticMantis (talk) 14:55, 30 January 2011 (UTC)

5: Basically, yes. Note that the Mandelbrot set is not self-similar in the same strong sense that the Koch curve is. There is at the moment no exact area known for the Mandelbrot set, but we can (in principle) calculate it as precisely as we choose. Related is the idea of the Coastline problem, which is often paraphrased as "The length you get when measuring a coastline depends on the length of your measuring stick". SemanticMantis (talk) 16:18, 30 January 2011 (UTC)

6: It is interesting you say no shapes that look like 'nature', and then mention circles and lines. It is true there are no perfect circles or lines in the (boundary of) the Mandelbrot set, but there are also very few circles or lines in nature (i.e. the physical world). In fact, many sources mention that things like clouds, mountains, or islands are better described by fractal geometry than Euclidean. SemanticMantis (talk) 14:14, 30 January 2011 (UTC)

4: There is no why. The set is what it is. There is no secret input value hidden in the code. In fact, the code is incredibly simple. 71.101.41.73 (talk) 16:34, 30 January 2011 (UTC)

2: These filaments do have width, a program such as fractint will let you zoom in to see more detail. Also note that all the pretty colors are 'outside of the set, and colored by 'escape speed'. For the questions you are asking, you want to focus on the second, black-and-white picture in our mandelbrot set article. SemanticMantis (talk) 21:11, 31 January 2011 (UTC)

Delivery

during the delivery of a child the child does not get harrased or injured while passing through the pelvic girdle? — Preceding unsigned comment added by Joshuki (talk • contribs) 12:15, 30 January 2011 (UTC)

See Birth trauma (physical) for some types of physical injury that the child can sustain during delivery. As for harassment, I think the risk is low. Staecker (talk) 13:56, 30 January 2011 (UTC)

What do nebulae look like in visible light?

What would a nebula look like if you were inside it on a spaceship? --75.15.161.185 (talk) 13:26, 30 January 2011 (UTC)

It depends on the nebula. For interstellar clouds, in most cases, it would be invisible. Matter is very diffuse in these nebulae. The Great Andromeda Nebula would presumably look a lot like the Milky Way from the inside. --Stephan Schulz (talk) 13:35, 30 January 2011 (UTC)

Would it ever look like the dense, glowing fog/clouds used in TV shows like Star Trek? --75.15.161.185 (talk) 15:11, 30 January 2011 (UTC)

Only if you use a positronic scan with reversed polarity. --Stephan Schulz (talk) 15:43, 30 January 2011 (UTC)

Make it so, Mr. Broccoli. --Anonymous, 03:52, January 31, 2011.

cell sonicator

is there any other cell distruption method, other than sonicator ? —Preceding unsigned comment added by 115.242.140.78 (talk) 15:24, 30 January 2011 (UTC)

Yes, there are a number of different options. The optimal method will depend a lot on your ultimate goal and what you want to do with your cell lysate. As it turns out, we have a very interesting article entitled cell disruption that would be a good place to start. --- Medical geneticist (talk) 15:38, 30 January 2011 (UTC)

A scientific test to determine if Blacks are dumber than Whites

If we wanted to design an thorough scientific experiment (and ignoring all ethical considerations) to determine if Blacks are dumber than Whites for purely GENETIC reasons alone, how would we design the experiment? I came up with the following experiment, please tell me if this is a good experiment (ignoring ethical considerations) with proper controls.

The sample size of each group is unclear to me at this point. Suggestions on minimum sample size would be helpful.

1 group of newborn Blacks with at least 90% of their DNA can be traced to Sub Saharan Africa. Divided into two subgroups, one half is intact, the other half has their skin bleached. Half of the intact newborns, and half of the bleached newborns are placed into adoptive parents that live in upper class society. The race of all the parents should be white. The other half of intact and bleached newborns should be placed into adoptive parents that live in lower class society in the inner city. The race of all the parents should be black.

1 group of newborn Whites with at least 90% of their DNA can be traced to Europe. Divided into two subgroups, one half is intact, the other half has their skin darkened (not sure how this can be accomplished, but lets assume that it can be). Half of the intact newborns, and half of the darkened newborns are placed into adoptive parents that live in upper class society in the suburbs. The race of all the parents should be white. The other half of intact and darkened newborns should be placed into adoptive parents that live in lower class society in the inner city. The race of all the parents should be black.

As they all grow up, they should be given IQ tests at different time intervals, and their academic performance should be measured. This experiment would last for several decades.

The bleached and darkened newborns are there as controls. If the bleached Black newborns performed as well as intact Whites in their respective socio-economic levels, it would prove that intelligence is determined from purely external factors, and not determined by genetics.

How is my experiment? Suggestions? Are there any unnecessary groups? What should be changed? Etc ScienceApe (talk) 16:53, 30 January 2011 (UTC)

Well (gritting my teeth and trying to ignore the offensive wording of parts of the question), to have a properly controlled experiment, the participants need to be blind to the status of the subjects. You can't make a person from sub-Saharan Africa look caucasian, or vice versa, merely by bleaching or darkening skin, so I don't see how that would be possible. Going beyond this, the fact that sub-Saharan Africa comprises more human genetic variability than the entire rest of the world put together makes experiments of this sort a bit silly, in my opinion. It's like asking whether mammals are smarter than dogs. Looie496 (talk) 17:58, 30 January 2011 (UTC)

(edit conflict) Here at the RD/S we routinely rebuff, for good reason, "scientific" questions built on speculative assumptions ("what if you traveled at 1.5 times c for 5 years in an elliptical path, returning to your starting point..."). This one is in that category for multiple reasons, aside from the patently offensive premise and wording on which it's built (the hypothesis, as stated, is clearly one-sided). We have insufficient scientific basis for (i) how representative these study groups would be of the overall population on which you build the premise, (ii) that the groups could be sufficiently blinded to the study assignments, (iii) that there are "bleaching"/"darkening" procedures that would eliminate racial characteristics giving rise to bias, (iv) that adoption itself does not fundamentally alter linkages among key variables - thus making the adoptive placements an invalid surrogate for race reversal, (v) IQ tests and current measures of "academic performance" are valid measures of intelligence. More importantly, we do not have a basis for believing that these children would not be harmed in the course of this research, so it's unethical as proposed. Bottom line, this proposal is offensive, unethical, and unscientific. -- Scray (talk) 18:06, 30 January 2011 (UTC)

I've put a hat on this, a better idea would be to propose something without the given variables, but the same idea. Tofutwitch11 ^(TALK) 18:11, 30 January 2011 (UTC)

What are "blacks"? What are "whites"? We need a much better definition of terminology before we can proceed. Bus stop (talk) 18:11, 30 January 2011 (UTC)

I have hatted it. Tofutwitch11 ^(TALK) 18:12, 30 January 2011 (UTC)

In the world of science, is there anything that is as taboo as this subject? 88.112.59.31 (talk) 18:45, 30 January 2011 (UTC)

I don't think the word "taboo" is perfectly applicable here. The fundamental problem, IMHO, is that "race" is a social construct, and "intelligence" as broadly defined is impossible to measure (currently). So, science is a very poor domain in which to address the intersection of race and intelligence, and the attempts to do so end up embroiled in meta-discussion. -- Scray (talk) 18:55, 30 January 2011 (UTC)

It's not "taboo". It requires definition. What are we trying to find out? "Blacks" and "whites" are meaningless terms. "Intelligence"—what is "intelligence"? Bus stop (talk) 18:56, 30 January 2011 (UTC)

Interracial cookie. Bus stop (talk) 19:00, 30 January 2011 (UTC)

See Race and intelligence. Further discussion in this realm is unlikely to be fruitful. --Jayron32 19:14, 30 January 2011 (UTC)

I'm unclear as to why this has been hatted, except for the idea that any discussion of the topic is verboten. The OP has clearly indicated that the experiment is fanciful — he is just asking whether it would actually be useful to ferreting out the answers, or if there are methodological problems. I think there are methodological problems (the entire thing is reliant on a 19th-century vision of both race and the nature/nurture debate). But I don't see why we can't talk about that. I suppose it could be viewed as troll food, but I'm wary about preemptively labeling topics that just because they are controversial. --Mr.98 (talk) 20:39, 30 January 2011 (UTC)

But the OP labelled it in the section title with the hypothesis of Blacks are dumber than Whites. That's not a good start. I'd like to see the objective reasoning behind that. And, as Looie496 said, we need this to be a double blind experiment. I would need to hear a lot more about how that was going to happen. HiLo48 (talk) 21:00, 30 January 2011 (UTC)

It's a HYPOTHESIS. A hypothesis isn't meant to be true; it's meant to be tested, and possibly refuted, by the experiment. If a hypothesis is known to be true, it wouldn't be a hypothesis, and there would be no point in performing the experiment. --99.237.234.245 (talk) 21:04, 30 January 2011 (UTC)

Have fun! --Jayron32 20:51, 30 January 2011 (UTC)

Yes, but he could have titled the question as "A scientific test to determine if Whites are dumber than Blacks" as well, but he didn't. Why not? Clearly there is some underlining bigotry here. I agree that instead of hatting it we should discuss it openly and show why such a study (even as a hypothetical study) is unlikely to prove anything useful. Dauto (talk) 21:10, 30 January 2011 (UTC)

What about if we reformulate the question into correlation between IQ and skin color? The second can be measured, and if someone manages to measure the first, we can plot the data... Quest09 (talk) 21:16, 30 January 2011 (UTC)

Take young children from their parents and have them raised by adoptive parents? It has been done before, many times, with tragic consequences for which the Australian parliament has apologised. See Stolen Generations#Australian federal parliament apology. Dolphin (t) 21:42, 30 January 2011 (UTC)

Just a reminder - Jayron32 provided a useful link to our article Race and intelligence, which provides a thoughtful treatment of many of the issues. That would be a great starting point, if this discussion is to be fruitful at all. I'm sure that article could be improved, as well, if someone has lots of energy. -- Scray (talk) 21:46, 30 January 2011 (UTC)

The answer is that no valid scientific experiments can be done on this, because neither race nor intelligence have useful operational definitions. You could perhaps perform a study to compare the performance on standardized tests of people with various amounts of certain skin pigments, and see if there is some correlation. However, this scientific dead-end was abandoned at the beginning of the 20th century, and I don't see why one would want to waste their time with it. I'm not sure why one would suspect that skin pigments would affect test performance. As people have suggested, you might want to take a look at Race and intelligence, where you can learn more about experiments that have been done, as well as allof the bad science that's been done by people trying to prove that "Blacks are dumber than whites". -- Mesoderm (talk) 21:56, 30 January 2011 (UTC)

BTW, A lot of the responses above have been predicated on the fact that race can not be found in DNA, or that race is a social construct. This is not true, see here: http://blogs.discovermagazine.com/gnxp/2010/12/to-classify-humanity-is-not-that-hard/ Ariel. (talk) 22:53, 30 January 2011 (UTC)

It is certainly possible to classify humans based on genetics, however those classifications would not correspond with the usual concept of "race". The article you link to mentioned this: "The various phenotypically “black” peoples of the world, Africans, Melanesians, and some South Asians, do not cluster together. Rather, all non-Africans are separated from Africans by the largest component of variance within the data set." --Tango (talk) 23:17, 30 January 2011 (UTC)

Why are you only using upper class white parents and poor black parents? If you want to eliminate the effect of wealth from your study (which you need to do), you need to have white and black parents with a wide range of wealths. --Tango (talk) 23:17, 30 January 2011 (UTC)

Yikes, I didn't think I would be accused of being a racist. If it makes any difference to anyone, I have dark skin myself and I was sick of racist bigots claiming that black people are dumber than whites. They kept saying how there isn't a black nation on the planet that is modern, that the bell curve for black's performance on IQ tests is worse, that Africa isn't as technologically advanced as white nations because they are inferior, etc, etc. Just awful things, and I was so sick of it, I wanted to at least conceive of a real scientific test that would at least provide some evidence that what they are saying simply is not true. But I want it to be as accurate as possible with proper controlls, so please try to indulge me for the sake of argument. How would I do this if we had no ethical considerations stopping us? ScienceApe (talk) 00:13, 31 January 2011 (UTC)

You would begin with an operational definition for both race and for intelligence. After that, the experiment would be trivial to conduct. The difficult part is creating an operational definition that other people agree on, because science is subject to peer review. As you have been informed many times, both concepts - race and intelligence - are poorly defined, and therefore difficult to use in straightforward experiment. Nimur (talk) 18:33, 31 January 2011 (UTC)

I want to expand on someone's concern above about IQ tests. They do not measure smartness and dumbness. They measure the ability to score well on IQ tests. HiLo48 (talk) 00:34, 31 January 2011 (UTC)

Then we can't use terms like race and intelligence since they aren't well defined. I'm having trouble phrasing a testable hypothesis with terms that have well defined definitions, but here's my attempt,

"Americans with at least 90% of their ancestry descended from Subsaharan Africans have comparable IQ and academic performance to Americans with at least 90% of their ancestry descended from Europeans based on genetics alone" ScienceApe (talk) 19:21, 31 January 2011 (UTC)

All humans descend from a common ancestor. So your definition fails to specify a meaning for "90% of their ancestry descended from (blank)." That leaves an enormous ambiguity subject to interpretation, meta-debate, and so on. As I said, meaningful and scientifically acceptable construction of definitions will be the hard part of your experiment. Nimur (talk) 19:51, 31 January 2011 (UTC)

Well I remember this American researcher coming to Nigeria saying he was researching to show blacks had the same IQ as whites and being asked was that American whites or European whites. Went off in a huff he did. :) Dmcq (talk) 20:37, 31 January 2011 (UTC)

Any suggestions would be helpful Nimur. ScienceApe (talk) 04:07, 1 February 2011 (UTC)

Personally, I don't believe there is any meaningful scientifically valid definition of human race. I think that emphasizing race in scientific and sociological literature solidifies the position of race as an established social norm, indirectly validating all of the social ills associated with racial discrimination. I believe race is just one of many weakly-defined social institutions that are constructed by the gentry with the intent to isolate, divide, and weaken the proletariat; and that when we all finally unite as a species, instead of quibbling over insignificant differences of language, gender, color-tone, and eye-shape, we will be unstoppable. But my opinion isn't at issue here. You can read all about other viewpoints at our article, Race (classification of humans); you can also read scientific racism for perspective. Regarding the definition of intelligence, I think IQ is a pretty darned good indicator of how smart you are, albeit with some well-known flaws; but again, my opinion isn't at issue here. You can read about intelligence, intelligence quotient, and standardized testing to see what professional psychologists and other researchers have previously concluded; and you can make up your own mind. If you really want my opinion, though, I will direct you to this archive from August 24 of last year where I posted several long paragraphs about intelligence in response to another IQ-related question. If you would like references for specific books on human intelligence, or various books expressing different viewpoints about the sociology of human racialism, I can recommend those too. Nimur (talk) 04:40, 1 February 2011 (UTC)

Well that's exactly what I want to prove here, that race is just a social construct. But just asserting that without evidence doesn't say much. There has to be a scientific test to back up that claim with evidence. ScienceApe (talk) 17:48, 1 February 2011 (UTC)

How to remove glue?

I was building a Heller Ariane 5 model rocket when, due to defective assembly instructions, I glued together the two halves of the fuel tank before I was supposed to. Now I need to unglue them without risking damage to the structure, so ideally I'd like to remove the glue without applying force on the model. Is it OK to submerge the model in hot water and wait for the glue to decompose?

I am using standard tube glue. Thanks everyone. Leptictidium (mt) 18:01, 30 January 2011 (UTC)

"standard tube glue" is not very specific, but in context I assume you're referring to the glue generally used for plastic models, i.e. butanone-based adhesive. There are de-bonding agents sold in hobby stores for this purpose; I'm not confident that hot water will achieve the results you want because butanone works by dissolving a bit of the polystyrene and allowing the two parts to fuse, but if it won't damage your model then you could try it. -- Scray (talk) 18:33, 30 January 2011 (UTC)

I am not sure what the best way to proceed would be. One thing that comes to mind is to allow the two glued halves to remain glued together, and then to cut them apart with a tool like a Dremel rotary tool. Of course this is a very expensive approach, so you will probably want to consider other alternatives. But I just thought I'd mention the possibility of this. I really don't know much about the exact situation. But I know sometimes glues can be difficult to reverse once they have set. Bus stop (talk) 18:40, 30 January 2011 (UTC)

You can possibly try to carefully pry them apart with an old style plain razor blade. Be careful with the remaining 9 fingers! --Stephan Schulz (talk) 19:27, 30 January 2011 (UTC)

Acetone (i.e. nail polish remover) is often useful for dissolving glues. Use a cotton swab to spread some (liberally) over the glued area, and then after it's had a few minutes to work, take a razorblade to it. It might only dissolve partway through the glue the first time -- if so, cut in as deep into the glue as you can, and then apply more acetone and repeat. -- Mesoderm (talk) 19:34, 30 January 2011 (UTC)

Note that if we're talking about a welding glue like butanone, which is really a solvent as I noted above, then any solvent that can dissolve the joint may damage, weaken, or at least deface the material with which you're working. Any "liberal" application might be tested on a throw-away piece of the same material to ensure you get the results you desire. -- Scray (talk) 21:20, 30 January 2011 (UTC)

To answer your question properly you're going to have to tell us what "standard tube glue" is. Ariel. (talk) 22:45, 30 January 2011 (UTC)

EEK! I would be especially careful of acetone as it could dissolve more then just the glue! Solvents can soak into the plastic and melt them or soften them to the point where they become impossible to set. I would try the very careful razor approach. Vespine (talk) 01:23, 31 January 2011 (UTC)

Thanks to all for pointing this out -- I've used acetone to remove glue in the past without problems, but I'll definitely be more careful in the future. What types of plastics specifically do you have to worry about? -- Mesoderm (talk) 02:23, 31 January 2011 (UTC)

Actually, I found the answer to that question. Here is a list of plastics that can/can't be used w/ acetone:

Acetone-Plastic Compatibility List

Acetone, pure - Ketone, Aliphatic

• LDPE at 20C ..... Little or no damage after 30 days of constant exposure.
• HDPE at 20C ..... Some effect after 7 days of constant exposure.
• PP at 20C ..... Some effect after 7 days of constant exposure.
• PPCO at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• PMP at 20C ..... No damage after 30 days of constant exposure.
• PETG at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• FEP at 20C ..... No damage after 30 days of constant exposure.
• TFE at 20C ..... No damage after 30 days of constant exposure.
• PFA at 20C ..... No damage after 30 days of constant exposure.
• ECTFE at 20C ..... No damage after 30 days of constant exposure.
• ETFE at 20C ..... No damage after 30 days of constant exposure.
• PC at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• RPVC at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• PVCT at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• PSF at 20C ..... Some effect after 7 days of constant exposure.
• PS at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• PVDF at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• PMX at 20C ..... No damage after 30 days of constant exposure.
• TMX at 20C ..... Some effect after 7 days of constant exposure.
• PET at 20C ..... Some effect after 7 days of constant exposure.
• PMMA at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• SAN at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• PK at 20C ..... Data not available.
• FLPE at 20C ..... No damage after 30 days of constant exposure.
• TPE at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• SILI at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• XLPE at 20C ..... Immediate damage may occur. Not recommended for continuous use.
• NYL at 20C ..... No damage after 30 days of constant exposure.
• LDPE at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• HDPE at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PP at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PPCO at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PMP at 50C ..... No damage after 30 days of constant exposure.
• PETG at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• FEP at 50C ..... No damage after 30 days of constant exposure.
• TFE at 50C ..... No damage after 30 days of constant exposure.
• PFA at 50C ..... No damage after 30 days of constant exposure.
• ECTFE at 50C ..... Little or no damage after 30 days of constant exposure.
• ETFE at 50C ..... Little or no damage after 30 days of constant exposure.
• PC at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• RPVC at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PVCT at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PSF at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PS at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PVDF at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PMX at 50C ..... No damage after 30 days of constant exposure.
• TMX at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PET at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PMMA at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• SAN at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• PK at 50C ..... Data not available.
• FLPE at 50C ..... Little or no damage after 30 days of constant exposure.
• TPE at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• SILI at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• XLPE at 50C ..... Immediate damage may occur. Not recommended for continuous use.
• NYL at 50C ..... No damage after 30 days of constant exposure.

So basically, if you know what type of plastic the model is, you could check this list and see if it's safe to use acetone.Mesoderm (talk) 18:12, 31 January 2011 (UTC)

I have rolled your list up for convenience. Can you provide a reference citation for that list? Nimur (talk) 21:00, 31 January 2011 (UTC)

Just to be on the safe side, you can always "patch test" the solvent first on the inconspicuous inside of a part or on the disposable frames that hold the pieces. Vespine (talk) 22:04, 31 January 2011 (UTC)

@Nimur: Thanks for collapsing the list -- sorry I didn't think about doing that. I got the information from here (Select "Acetone, pure" and "All materials/resins", and don't select anything from "chemical class"). -- Mesoderm (talk) 02:15, 1 February 2011 (UTC)

Codeine and its counterparts

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. If you have a question about drugs to take if you have an allergy, please ask a physician or pharmacist.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. If you have a question about drugs to take if you have an allergy, please ask a physician or pharmacist.--~~~~

I have taken this discussion to the Ref Desk talk page. Bielle (talk) 22:14, 30 January 2011 (UTC)

Highbeam's offer of scientific magazines

Does Highbeam have many top scientific magazines among its offer? Quest09 (talk) 21:04, 30 January 2011 (UTC)

Here's a list of the science magazines they have. Red Act (talk) 21:12, 30 January 2011 (UTC)

Well, I can't seem to find any which is really highly prestigious.Quest09 (talk) 21:18, 30 January 2011 (UTC)

Agree - no first-tier journals. The latter are a bit hard to define dogmatically, but ScienceWatch, Eigenfactor, and Science Gateway have lists that might be relevant. -- Scray (talk) 21:40, 30 January 2011 (UTC)

Big alignment

I heard that our solar system and all the planets and the sun will be aligned with the center of the milky way galaxy in next year if so will this be noticeable. --93.107.73.219 (talk) 21:11, 30 January 2011 (UTC)

• It's not the case, and it wouldn't be noticeable everyday effects even if it were. After the moon and the sun, the gravitational effect of heavenly bodies on the Earth is basically negligible. Jupiter is the next most significant, and you've never been affected by its gravity nor observed the effects of such, and we align with Jupiter roughly once a year. — Lomn 21:45, 30 January 2011 (UTC)
• This is just part of the 2012 Hoax. A large part of the sordid story is at 2012_phenomenon#Galactic_alignment. In short, there is no particularly exciting multiple conjunction in 2012. The Earth, the Sun, and the galactic center line up roughly once per year. --Stephan Schulz (talk) 21:52, 30 January 2011 (UTC)

If you use a telescope and check the position of the planets, you will notice where they are, but why would it matter? --Lgriot (talk) 13:27, 31 January 2011 (UTC)

It's much easier to photograph planets when they're nearby. Stunning and artistic photographs, such as this one, featured at NASA's Astronomy Photo of the Day in April 2000, are only possible during syzygy or near-syzygy. Here's a nice gallery of December 1, 2008 Moon Venus Jupiter alignment, photographed throughout the world. A few scientific observations are possible during planetary occultations; radio shadow, atmospheric refraction spectroscopy, and other scientific measurements are possible as a one object traverse across the limb of another object. Otherwise, planetary alignments have no special significance. Nimur (talk) 22:12, 31 January 2011 (UTC)

An approximate planetary alignment can also help make it possible to use the slingshot effect to have a spacecraft efficiently do a planetary flyby of multiple planets, as in the Planetary Grand Tour of Voyager 2. Red Act (talk) 23:14, 31 January 2011 (UTC)

Subterranean flows of water (contains spoiler of Philip Pullman's The Tiger in the Well)

Starting on page 265 of Philip Pullman's The Tiger in the Well is talk of subterranean rivers and springs and whatnot. Mentions of houses crumbling into such bodies of water (and sewage and other wastes) after storms seem to be based on historical fact. Where can I read more about this phenomenon, both as a matter of fact and of history. Thanks. 66.108.223.179 (talk) 23:06, 30 January 2011 (UTC)

See Underground river, Sinkhole, Cenote and be sure to follow the "See Also" links from those articles. Ariel. (talk) 02:03, 31 January 2011 (UTC)

January 31

Star formation

Is it right that stars can blow up and their remains recondense to form new stars? Is it also right that this cycle cannot continue forever but must gradually wind down? —Preceding unsigned comment added by 86.135.27.52 (talk) 00:03, 31 January 2011 (UTC)

In two words, yes and yes. in more words, i'm not sure where to start, perhaps with Stellar evolution and entropy.. feel free to come back if you have any more specific questions. Vespine (talk) 00:19, 31 January 2011 (UTC)

Also take a look at Metallicity. As stars age, they burn Hydrogen into heavier elements. When they "blow up" (into red giants, or even supernovae), some or all of the material of the star is ejected from the star. This can become part of a later population of stars. But not all of the ejected material is Hydrogen. The heavy elements have a number of interesting effects (they catalyse different fusion processes in the star), but, in particular, they cannot themselves fuse in the same way Hydrogen does. Eventually, a region of space will run out of Hydrogen to form stars from. --Stephan Schulz (talk) 00:32, 31 January 2011 (UTC)

(Edit Conflicts) Yes to both questions.

As is detailed in Star formation (surprise!), stars form from condensing clouds of interstellar gases and dust. Some of the gases are left over from the initial creation of the universe in the Big Bang, but this only made Hydrogen (H) and Helium (He) (and maybe a little Lithium (Li)): all other gases and (non H/He) dust have been created by nuclear fusion processes within stars (see Stellar nucleosynthesis) and then dispersed when they exploded as novae or supernovae; some of the H and He will also have been cycled through those stars without being consumed in nuclear fusion.

However, only a small proportion of stars explode. Most (see Stellar evolution) simply use up all their nuclear fuel and then gradually cool down (although the Universe has not yet existed long enough for any of the resultant white dwarfs to stop glowing from their fusion-created heat). Also, some of the material forms not stars but planets and associated materials, which do not get redispersed much. Even when a star does explode, some of its material usually remain concentrated as a white dwarf, neutron star or black hole.

Because these processes 'lock up' some of the universe's material, the amount available for forming new generations of stars is continually diminishing, and will (presumably) eventually run out. When that happens no new stars will form, no fusion will occur, and all the white dwarfs, planetary material, and so on will gradually cool down by radiation which will heat up the colder interstellar (and intergalactic) clouds until everything in the universe is at a uniform (very low) temperature - this is called the Heat death of the universe.

However, the Heat death scenario assumes that the universe eventually stops its expansion and becomes static. If it continues to expand indefinitely, the result may instead be what is called the 'Big Freeze', which may not look much different. If however the universe stops expanding and begins to contract, it may be able to restart star formation for a while before eventually coalescing into a Big Crunch, after which the prognosis is unclear. 87.81.230.195 (talk) 00:43, 31 January 2011 (UTC)

• Thanks for the great answers! I have one more question... does anyone have any clue about the maximum number of times that any material will be recycled through different stars? I'm not expecting an exact answer, but something more along the lines of whether the answer is 3 or one million... 86.135.27.52 (talk) 00:56, 31 January 2011 (UTC)

Depending on how you define "material", closer to 3 (I'd put it somewhere from 10 to 100). The percentage of hydrogen fused by a star varies based on the mass of a star. The sun will fuse, ballpark, 10-20% of its hydrogen, with larger stars fusing less and smaller ones fusing more (red dwarfs, being convective, fuse nearly all of their hydrogen, albeit on much longer time frames). As for the "depending" -- well, a good chunk of that fused hydrogen, now helium, will get fused later on, either in that star or reconstituted in another future star. Is it still the same material? Still, though, there is a finite number of fusion progressions available before net energy becomes negative. Much of those heavy elements end up as the starting mass for black holes. Now, granted, at the end of all this, you can still have the material out and about somewhere (Earth's heavy elements are basically all supernova ash), and so you can get outlier cases where a bit of material cycles as unburnable stellar ash over and over and over, but odds are that a black hole will vacuum it up sooner or later. — Lomn 02:15, 31 January 2011 (UTC)

Considering the age of the Universe and the time it takes for stars to form, live, and die, most stars are either first or second generation (i.e. either formed from the initial material from the Big Bang or from the direct result of those stars "dying"). Our sun is a second-generation star, IIRC. There are likely some third or fourth generation stars out there, but with each successive generation there are probably orders or magnitude fewer stars to be found. --Jayron32 15:38, 31 January 2011 (UTC)

No, this is something of a confusion. Our sun is a Population I (or "metal-rich") star, as are most stars in our vicinity. Population II stars are metal-poor stars that formed earlier. The hypothesized Population III stars would be the very first stars, formed before the interstellar medium had been enriched by an earlier generation of stars. Since "metals" (for astronomers, everything except for Hydrogen and Helium) catalyze certain fusion processes, population III stars could become extremely large before fusion became strong enough to generate enough light pressures to stop the further increase in size. Such large stars have a very short lifetime (compared to the universe, or our sun - Hypergiants like Eta Carinae live only a few million years), so the PI-PIII classification does not correspond directly to the number of generations. --Stephan Schulz (talk) 16:32, 31 January 2011 (UTC)

color changing mug

A Chemical Engineering org I worked with gave me this wonderful mug. It's black but when you pour hot coffee in it, it changes color and reveals the group's logo. Any idea how it works? --Lenticel ^(talk) 01:31, 31 January 2011 (UTC)

My guess is the mug uses thermochromic liquid crystals, making it a kind of liquid crystal thermometer, similar to a mood ring. Red Act (talk) 01:47, 31 January 2011 (UTC)

Thanks for the explanation--Lenticel ^(talk) 02:39, 31 January 2011 (UTC)

By the way, if it's like the ones my wife and I bought about 20 years ago, be careful how you wash it. We found that the thermochromic layer was not well bonded to the mug and was very easily damaged. Of course, the technology may have improved since then. Incidentally, on ours that layer was black at room temperature and turned clear with heat, revealing the pattern painted underneath. --Anonymous, 04:00 UTC, January 31, 2011.

Identify unknown mineral

Hi. I have a very small sample of a mineral, and need some help in identifying it. I have discerned the following properties:

• Type: Non-metallic
• Colour: Red to reddish-brown
• Crystal shape: Nearly amorphous, some flat sides, slightly irregular
• Morphology: Tar-like appearance, may have layers, smooth with creases
• Rock form: Igneous appearance, two 'parallelogram' sides (opposite at angle), two long nearly 'triangular' sides (opposite), one rhombus-like 'trapezoidial' side, one small 'triangle' side (opposite aforementioned)
• Angles: 50° to 130°
• Other minerals: At least two, one may be quartz, other mineral is greenish-brownish-black and earthy striated appearance
• Mohs hardness: >6.0 (scratches stainless steel and glass)
• Lustre: Waxy or resinous
• Diaphaneity: Translucent to opaque
• Specific gravity: ~3 - 5 (imprecise method)
• Reactions: No visible reaction w/ brown vinegar

Any idea what the mineral might be? Thanks. ~AH1^(TCU) 03:30, 31 January 2011 (UTC)

I have uploaded an image. For the other lower-quality images, see here and here. ~AH1^(TCU) 19:33, 31 January 2011 (UTC)

I would suggest Jasper from the colour and hardness, although the S.G. would be less than you measured, any idea where it came from? Mikenorton (talk) 19:46, 31 January 2011 (UTC)

First, u must know is streak, it is very important if it's not white.--Chris.urs-o (talk) 20:02, 31 January 2011 (UTC)

I found the mineral sample as a piece of gravel on a paved road surface near a river. When I measured the specific gravity, I used a floating container in water and compared the volume displaced by the "rock" to the water-volume-equivalent (mass) displaced by the rock, thus it is an extremely imprecise method. I am unable to test the streak as I do not have an "unglazed porcelain tile" handy, though attempting to crush the rock produced a white powdery surface and pinkish edges. ~AH1^(TCU) 20:11, 31 January 2011 (UTC)

Something must scratch the mineral, just tell me the colour of the streak. The characteristics of the streak (mineralogy) and of the cleavage (crystal) (angle n surface, if u could use a hammer), would be nice. --Chris.urs-o (talk) 20:33, 31 January 2011 (UTC)

I tried using tools such as a clamp and a hammer to create powder from the mineral, and it appears noticeably white, at least compared to the mineral itself. Any cleavage of the mineral is likely not distinct, but may come in roughly rhombus-shaped thin layers. However, I unfortunately lost the sample down the drain when attempting to wash it, so any further tests will at least momentarily be unlikely verifiable. By the way, the sample itself could have originated almost anywhere. The actual geographical location where I found it though, is Southern Ontario. ~AH1^(TCU) 19:42, 1 February 2011 (UTC)

Damiana

does Damiana lower testosterone like weed does — Preceding unsigned comment added by Tommy35750 (talk • contribs) 04:34, 31 January 2011 (UTC)

According to most of the sources here, many herbalists claim that it stimulates testosterone production, and acts as an aphrodisiac[4]. On the other hand, one author has stated that the claims of aphrodisiac qualities are an "herbal hoax"[5]. Either way, I'm certainly not seeing anything claiming that it reduces testosterone levels. -- Mesoderm (talk) 05:17, 31 January 2011 (UTC)

Paternity

Hello, i had sexual intercouse with a woman 10 months ago. I ejaculated in her oral cavity, not in her vagina. Now she has had a baby and claims i am the father, which i can't as i disposed no jizz in her vagina. Am i the father and what can i do?—Preceding unsigned comment added by 77.17.27.62 (talk) 10:22, 31 January 2011

It's easier to become a father than you might think. While it's not very likely in the individual case, sperm can get into the vagina from other ways of intercourse. You can request a paternity test (but try to be diplomatic about it). If its yours, you'd better cherish and support it. --Stephan Schulz (talk) 10:33, 31 January 2011 (UTC)

Even with perfect use, coitus interruptus has a failure rate of about 4% per year, i.e., out of 100 couples who use coitus interruptus correctly every time they have sex for a year, 4 women will become pregnant. It is thought that the primary cause of failure in the case of perfect use is preseminal fluid picking up some sperm from a previous ejaculation. So this is not necessarily a case of paternity fraud. Red Act (talk) 15:10, 31 January 2011 (UTC)

In her mouth? Kittybrewster ☎ 17:07, 31 January 2011 (UTC)

It is possible she either accidentaly or deliberately transferred it. SpinningSpark 17:39, 31 January 2011 (UTC)

I had thought something similar initially but a careful reading suggests the OP's described scenario is ambigious. He said 'i had sexual intercouse with a woman 10 months ago. I ejaculated in her oral cavity.' This may mean he solely had receptive oral sex and his penis never went anywhere near his partner's vagina, it may also mean he had vaginal intercourse (which is a common meaning for sexual intercourse) but withdrew before ejaculation (i.e. coitus interruptus) to ejaculate in his partner's mouth. In the later scenario, Red Act's reply is clearly relevant Nil Einne (talk) 18:13, 31 January 2011 (UTC)

Yes, my interpretation of the question is that vaginal sex occurred prior to the oral ejaculation. Red Act (talk) 02:42, 1 February 2011 (UTC)

You sound very much like Boris Becker after his intercourse with Ermakowa. He accused here that she stole his sperm and impregnated herself later. The whole thing was a big hype and was called the "Samenraub" Afair.--Stone (talk) 19:33, 31 January 2011 (UTC)

In theory, simple tooth brushing can cause bacteremia, so I suppose that human microorganisms might also penetrate to the bloodstream by this means. And bleeding occurs normally during ovulation, at least briefly within the ovary as it ruptures, and perhaps for a longer duration in unusual cases. This makes me think that it is theoretically possible to have a conception which, though not immaculate, is certainly unexpected. However, the odds of this probably rank up there with getting hit by a meteor - I'd need to look up the original bacteremia data to make even a wild guess. Of course in practice, I expect a paternity test is what is needed to find the truth. Wnt (talk) 00:12, 1 February 2011 (UTC)

Wnt, it seems like you are pushing way past the boundaries of "theoretically". That scenario is not even remotely possible; others have given much more plausible answers above. Let's stick with relevant references and not wild guesses. --- Medical geneticist (talk) 01:06, 1 February 2011 (UTC)

The OP's statement that the "Had sexual intercourse" with the paramour before "ejaculating in her mouth" provides ample possibility of introduction of his sperm in her vagina. Genetic testing might be informative. (This does not constitute medical advice, but I once watched the Jerry Springer Show). Edison (talk)

Monatomic elements?

Is there such a thing in nature? [6] <-- Is there any truth to this or is it all basically pseudo-science? -- œ^™ 10:52, 31 January 2011 (UTC)

The noble gases are monatomic gases, but the idea that there are macroscopic amounts of precious metals in a stable monatomic form at normal temperatures and pressures makes no sense. The article that you link to is definitely pseudo-science. Gandalf61 (talk) 11:27, 31 January 2011 (UTC)

This was discussed recently; see Wikipedia:Reference desk/Archives/Science/2011 January 27#ORME Orbitally Rearranged Monoatomic Elements. –Henning Makholm (talk)

Most of that site is pure balderdash, but nuclear isomers including superdeformation and hyperdeformation of nuclei are real. And I do think that this phenomenon one day will be the basis of some very important technology... Wnt (talk) 00:23, 1 February 2011 (UTC)

However, the idea that nuclear isomers would have a different enough electron structure be relevant for chemical bonding sounds firmly like balderdash. There's the isomeric shift, but that's rather more subtle. –Henning Makholm (talk) 02:02, 1 February 2011 (UTC)

WiFi laptop or home PC amateur radio packet network equivalent

I know that armature radio has a packet radio relay system which can serve as a network with each station becoming essentially a switch. Is there a way for home computers and laptops with WiFi to set up such a network as well? I ask because even in my neighborhood whenever I try to set up my WiFi I get a list of connections I might log onto. --Inning (talk) 13:04, 31 January 2011 (UTC)

Yes, the general term for such is a wireless ad hoc network, and WiFi supports such capability. Note, though, that those connections you're seeing (almost certainly) aren't configured for that purpose. — Lomn 14:15, 31 January 2011 (UTC)

How might one configure those connections for such a purpose in the event of an emergency? 19:43, 31 January 2011 (UTC) — Preceding unsigned comment added by Inning (talk • contribs)

You might be better asking these questions on the computing/IT ref des. CS Miller (talk) 19:59, 31 January 2011 (UTC)

With wifi, the short answer is "you won't". Wifi is a very short-range network type intended to transfer data between computers -- it's not capable of cross-linking into a ham radio system or other useful emergency response system. Additionally, the hardware to run a standard no-config-needed wifi network is dirt cheap and readily available -- just grab any $50 router off the shelf at a store and plug it in. Ad hoc wifi has very little real purpose or utility. — Lomn 21:05, 31 January 2011 (UTC)

That said, your search engine of choice (or your operating system help files) will readily tell you how to use ad hoc networking for your particular system. — Lomn 21:07, 31 January 2011 (UTC)

...so you are saying I can not log onto my neighbors WiFi and in turn have him log onto one down the street , etc until a link of WiFi's make up a network that reaches across town and eventually to the next town, county, state and country? --Inning (talk) 02:10, 1 February 2011 (UTC)

In principle, I see no reason that you couldn't, provided you've got enough suitably equipped computers to bridge the inevitable network gaps. The effort and cooperation needed, however, is unlikely to ever materialize, nor is there any compelling use case beyond "to see if it can be done" (a motivation which has a rich tradition on the internet, to be sure). But if you want wireless computer communication in the event of emergency, plan on some combination of data-rich mobile service or satellite internet -- protocols designed for the purpose at hand. — Lomn 04:21, 1 February 2011 (UTC)

Brace, brace

I've noticed that the advised position to brace for impact on cheap flights (e.g. Ryanair or Easyjet) would place my head hard against the seat in front, with tension in my neck. I'm just under six feet tall, which I suppose is about average height for a 26 year old male in the UK. Could the intention be that a quick cervical dislocation would reduce/prevent my suffering in the event of a collision? --129.215.47.59 (talk) 16:55, 31 January 2011 (UTC)

I think the idea is to protect you from injuries like whiplash in the case of light impacts. Of course, if your plane ploughs headlong into the side of a mountain, there is not much you can do. Also, it's not just cheap providers who offer this advice - it's standard across industry. I don't have any references for this, but I can tell you I have never flown on the providers you mention and I have seen this advice on pretty much every flight I have been on. --KägeTorä - (影虎) (TALK) 17:03, 31 January 2011 (UTC)

We do have an article about it: Brace for impact. --KägeTorä - (影虎) (TALK) 17:07, 31 January 2011 (UTC)

The general idea with a brace position is: you're going to end up in that position anyway in a hard deceleration. By pre-positioning yourself in that position, you reduce blunt head trauma and whiplash involved with getting your head into that position from the crash. Whatever then happens, was going to happen anyway. Arakunem^Talk 17:08, 31 January 2011 (UTC)

The brace position will soon be adapted to the air-bags used in some planes.--Stone (talk) 19:04, 31 January 2011 (UTC)

Incidentally, some people seem to believe that the brace position was designed to kill you (to lessen the insurance payout). Mythbusters did an episode on it, finding this not true, and that the position does really help reduce neck and head injury: [7]. Buddy431 (talk) 04:38, 1 February 2011 (UTC)

I understand that passengers would be better off if all the seats faced backwards, which I whjat I'd prefer. 92.28.247.121 (talk) 18:42, 1 February 2011 (UTC)

ear piercing (2)

A follow up to semi-archived discussion above: (copied text removed) –Henning Makholm (talk) 19:48, 31 January 2011 (UTC)

Also, is the a time when closing of the piercing is impossible?Accdude92 (talk) 11:26 am, Today (UTC−6)

Could you try asking your question with more detail? I don't understand. Comet Tuttle (talk) 18:43, 31 January 2011 (UTC)

Insulated windows

I am not sure if this question has been answered before, but here goes:

My parents built a new house last spring/summer. They had energy efficuent windows installed. Several times over the course of this winter (central Ontario, Canada), they have noted frost (sometimes significant amounts) on the insides of all of the windows. When they enquired about this, the builder told them that there was too much moisture in the air. Personally, I don't buy this. I have had new windows installed in my home (several years ago) and while there may be some condensation at times (eg. after a hot shower), there has never been any kind of frost. So, while there may, indeed, be excessive moisture in the air of my parent's home, there is no way that I can think of that frost would develop unless there was something wrong with the windows construction and/or installation. The cold air from outside needs to somehow get inside to freeze the condensed moisture; properly built and installed windows should not do this. What do others think? Physics is not my forte . . . 76.75.136.254 (talk) 17:40, 31 January 2011 (UTC)

Googling for "condenstation windows", I found this guy, who claims that the condensation might be a sign that they did a good job, because it means the house is properly sealed up and thus trapping all of the moisture inside. Drafty houses let in the dry winter air, which lowers the relative humidity, making condensation less of a problem. It sounds like they sealed up your windows properly, and your parents need to get a dehumidifier. -- Mesoderm (talk) 18:04, 31 January 2011 (UTC)

I think the OP is implying that the windows are sub-standard because they are letting heat out (hence the frost), not because of the condensation per se. But I have no idea whether or not this would be normal at Canadian temperatures. SpinningSpark 18:42, 31 January 2011 (UTC)

Oh, yes. I see that now. Sorry. -- Mesoderm (talk) 18:50, 31 January 2011 (UTC)

This is very odd. We had -26°C last winter and no more than -10°C during the day and the 20 year old double glass isolation windows showed a lot of condensation but no ice not even in the bedroom where the heating was very low at that time.--Stone (talk) 19:01, 31 January 2011 (UTC)

It really does depend on the temperature gradient between outside and inside. If you keep the room very cool, and it is extremely cold outside, then frost would be normal. I regularly get quite a thickness of internal frost in single-glazed unheated rooms, but frost on the inside shouldn't happen in a heated room with efficient double glazing except in really extreme conditions. Drawing curtains across at night might make frost more likely. Do you have a guarantee on the windows, or any specification on their insulation rating? Are they sealed units? It sounds as if there is some convection of freezing air somewhere. Dbfirs 19:53, 31 January 2011 (UTC)

Thanks for the feedback everyone. All of the rooms are well heated but there is frost formation whether or not the curtins are drawn. A dehumidifier was recommended but, as I note, nothing should be frosting over (in my opinion). Frost develops not only where the upper and lower window meet but also on the glass and sil itself. Is there a way to measure or determine if there is a problem with the window construction or installation? 76.75.136.254 (talk) 21:12, 31 January 2011 (UTC)

Just feel the temperature with your hand. Compare the temperature of various windows, and also compare it to some external walls. A double paned window should be somewhat colder than the walls if the walls are insulated, and about the same temperature as uninsulated walls. Feel also for drafts near the window, and feel the edges of the window (not the glass, the frame), because maybe they didn't insulate the edges. Make sure they actually used double paned glass (it's easy to tell, just look inside the window at the edge). Ariel. (talk) 03:08, 1 February 2011 (UTC)

If the frame and sills are frosting first, it sounds like they are the cheaper ones without the hollow cavities having been filled with polyurethane foam; See diagram. Between the frames and sill, where they meet the walls, lintels and so on, there should also be foam sealant (often bright yellow), to keep out moisture and draughts. Also, the optimum air gap is 16 mm and with two sheets of glass -that's 24 mm total. The paper work that your parents signed (contract), agreeing to have them installed, should give details as to who's frames (or Window System) they are. From that, you can find out from the manufacture, what specifications and standards they meet. They also need to know the manufacture, in case they need to order new parts for repairs.--Aspro (talk) 14:07, 1 February 2011 (UTC)

Often the coldest part of a window is the frame. Glass can be made relatively efficient in terms of thermal efficiency, although there are limits. The frames are harder to make energy-efficient do while retaining sufficient stiffness to support the glass and to seal, since stiff materials tend to also be conductive. Single-pane glass has a U-value of about 1.3 (lower is better). Plain double-pane glass, U= about 0.49, triple clear about 0.34 and double glazing with low-e coating and argon fill about 0.30. Super-efficiency windows might reach 0.15. This is in contrast with normal wall construction, which in Canada should have a U value of about 0.05, so even efficient windows are the cold spot. The temperature of a glass or frame surface is related to the temperature gradient through the assembly, and the right combination of temperature and relative humidity might produce condensation or frost, so the answer is: it depends. Frame construction, glazing options and construction details all play a part. Acroterion _(talk) 16:07, 1 February 2011 (UTC)

Handheld missile/rocket launchers with multiple missiles

Are there any handheld rocket/missile launchers that can carry multiple missiles/rockets? ScienceApe (talk) 18:38, 31 January 2011 (UTC)

The M202 FLASH fits that description. --Daniel 18:40, 31 January 2011 (UTC)

While not a missile/rocket launcher, there is also the M32 Multiple Grenade Launcher, as well as others. --KägeTorä - (影虎) (TALK) 18:47, 31 January 2011 (UTC)

Fliegerfaust qualifies if "effectiveness" isn't one of the requirements ;) . Vespine (talk) 21:34, 31 January 2011 (UTC)

what the species name?

hi. i found a funny pic of a baby monkey online. here is the link: http://www.superlaugh.com/pets/babymonkey.jpg please, could you tell what species that baby belong to? —Preceding unsigned comment added by 62.0.34.93 (talk) 20:38, 31 January 2011 (UTC)

It's a macaque. I'm not sure about the specific species, but possibly a Toque Macaque. CS Miller (talk) 22:41, 31 January 2011 (UTC)

Processing of metals: casting

When using a pattern for hot metal casting, which kind of pattern volatilizes when the metal is poured? —Preceding unsigned comment added by 208.54.5.54 (talk) 21:22, 31 January 2011 (UTC)

Usually a pattern is used to make one or more moulds, and the molten metal is then poured into the moulds and allowed to cool. In many applications, each mould is then destroyed to allow removal of the cast object. I have not heard of volatile moulds or patterns. You could investigate investment casting and the lost-wax casting process. Dolphin (t) 21:31, 31 January 2011 (UTC)

When I was at school we used expanded polystyrene to make a shape, then formed damp sand around this. We poured aluminium into the mould and the polystyrene vapourized, leaving an aluminium shape. Whether this is still considered safe, I'm not qualified to comment. --Phil Holmes (talk) 22:03, 31 January 2011 (UTC)

See also evaporative-pattern casting. Our entire article on casting (metalworking) has lots of interesting stuff, actually. TenOfAllTrades(talk) 03:59, 1 February 2011 (UTC)

Parachutes

Why do parachutes have holes in them? 74.15.137.130 (talk) 22:25, 31 January 2011 (UTC)

See Parachute#Round types. Basically, it reduces flapping around. I think it also increases drag by forcing the air to flow around the interior of the chute, rather than creating a high-pressure cell. --T H F S W (T · C · E) 22:33, 31 January 2011 (UTC)

How does it reduce oscillations? 74.15.137.130 (talk) 00:13, 1 February 2011 (UTC)

If you drop a piece of paper it slides back and forth as the air spills first from one side then the other. By putting a hole in the middle all the air spills from there instead of the sides, which stops it from doing that. Ariel. (talk) 03:02, 1 February 2011 (UTC)

To clarify a bit, the holes help the parachute keep its shape. It is simplest to explain with the round "WWII" style parachutes. If you just have a closed fabric "cup", inverted, the air rushing into the parachute from the bottom needs a way to get out. If you don't have a hole in the middle, it gets out by tipping the entire cup shape on its side, which does a pretty terrible job of actually slowing you down. By putting a hole in the middle, the inrushing air is "funneled" out the hole in the center, which prevents the chute from tipping over or collapsing. Now, with all of the inrushing air escaping out the top, the chute is able to maintain its inverted cup shape, and thus help to trap most of the air, and thus slow you down. The same principles apply to the rectangular shaped parachutes, but its just organized a bit differently. --Jayron32 05:37, 1 February 2011 (UTC)

And you can tug on a pair of handles just before you hit the ground which close the holes and slow you down. Alansplodge (talk) 09:24, 1 February 2011 (UTC)

Also, per the article, vents enable a certain amount of steering.--Shantavira|^{feed me} 10:25, 1 February 2011 (UTC)

February 1

Levitation material

Back in the mid 80's, I recall that a group (probably some university students) had mixed some compounds together which was then shaped into a disk. As I remember it, I believed that they needed to heat this compound in a kiln as part of the process. Later, they were then able to have this disk suspend over some sort of gas, perhaps liquid nitrogen or it could have possible have even been dry ice - I am not sure. It became an interesting science fair project and was repeated often (certainly at that time). Other than being able to get the compound to suspend or levitate - I can not recall what use it may have eventually became of it. Certainly, ideas of high speed trains utilizing this discovery were at the forefront. I do recall however that Omni magazine had a contest which was to determine the best practical use of this discovery and challenged its readers to submit idea/designs towards that end. Would anyone recall what I am referring to and how the Omni contest turned out?24.89.210.71 (talk) 02:24, 1 February 2011 (UTC)

The only thing that comes to mind for me is the Meissner effect. --Mr.98 (talk) 02:35, 1 February 2011 (UTC)

I agree, a levitating superconductor seems like the best explanation. Ariel. (talk) 03:00, 1 February 2011 (UTC)

That is exactly right. To be more specific, high-temperature superconductivity was discovered in the mid 80s. Low temperature surperconductors had been known for many decades previous to that time. Dauto (talk) 03:12, 1 February 2011 (UTC)

It was probably a demonstration of a YBCO (yttrium barium copper oxide) superconductor. It's sometimes called 123 or Y123, both because of the ratio of its metal ingredients (1:2:3 Y:Ba:Cu) and because it's a straightforward synthesis (as easy as 1-2-3...). The raw ingredients are sintered at around a thousand degrees to make the final product; that would be the kiln step you remember. I don't have a reference for the Omni contest, but mayhaps you'll have more luck given the material name. TenOfAllTrades(talk) 03:54, 1 February 2011 (UTC)

Lockout Hasps

what r Lockout Hasps used 4 — Preceding unsigned comment added by Tommy35750 (talk • contribs) 03:15, 1 February 2011 (UTC)

Sounds like Lockout-Tagout. Note that many readers here do not speak English fluently and are not teenagers, so text-message-abbreviations are not a great way to communicate. DMacks (talk) 03:49, 1 February 2011 (UTC)

They are used for teaching how to hack the man in the middle attack in a classroom demonstration. One student uses a lockout hasp and padlock to safely lock a message in a box. He leaves. Another student comes in and sees a padlock on the box and agrees to place his lock on the box. He leaves. The original student returns and sees two locks, so removes his lock. He leaves. The second student returns and removes his lock to get the message. Secure, right? No. -- kainaw™ 03:57, 1 February 2011 (UTC)

Something about igniting salt water with radio waves - our energy savior?

I heard or read long ago about an experimenter shooting radio waves at a beaker of salt water, therefore igniting it.

How come I haven't heard anything else? If igniting salt water produces more energy than what it takes to ignite it, then wouldn't that be our energy savior once and for all?

If it truly works as hoped, we could shut down all the dirty power plants and refit all motor vehicles to run on salt water instead. To expend salt water would be an EPIC civic duty because we might stem the tide of rising sea levels just from burning it off.

Moreover, the source of energy should be epically cheap. How much $ per gallon would salt water sell for?

Anyway, if the energy expenditure-to-energy generation ratio isn't efficient enough, why not improve the tools and methods to make the process more efficient?

^{PS: I wonder what the emissions would be, and if it'd be detrimental.} --70.179.181.251 (talk) 05:01, 1 February 2011 (UTC)

How do you get the energy to generate the radio waves? I'll give you a hint: It probably invoves burning something that is the compressed remains of dead algae... --Jayron32 05:05, 1 February 2011 (UTC)

(ec) That's a lot of wondering to do about something that is total nonsense. Looie496 (talk) 05:07, 1 February 2011 (UTC)

Could someone supply the chemical equation for the combustion of saltwater, or prove that it is utter nonsense? Edison (talk) 05:12, 1 February 2011 (UTC)

It isn't combustion. If you take wet salt (or molten salt, but wet salt is easier to obtain) not salt water, but rather slightly moisten salt, and blast the shit out of it with a powerful electric current, you will electrolyze it into sodium metal and chlorine gas. The deal is, their's more than enough ambient energy in the air to provide the activation energy to cause the sodium and chlorine to pretty much instantly re-react again, creating a rather impressive fireworks show. You get lots of brightly colored flames when you do it. If you have a carefully controlled set up, you can isolate the chlorine gas (it will form at the cathodic electrode) and prevent it from recombining with the sodium. But if you basicly just jam the leads from an stripped extension cord into a pile of wet salt, you get some pretty awesome flames. (note to kids: DO NOT DO THIS AT HOME). This isn't actually combustion per se, its just the tiny bit of sodium and chlorine gas you just formed via electrolysis reacting to reform the salt. --Jayron32 05:25, 1 February 2011 (UTC)

...and it should go without saying – though I'll say explicitly it here anyway – that the heat and light energy released by the recombination of the chlorine and sodium will never exceed the amount of electrical energy that you put in to separate them in the first place. (This will be true regardless of the energy source used, actually—there's nothing special about radio waves versus electric current.) If it were possible to extract additional energy from the process, it would be a perpetual motion machine of the first kind. If you prefer to think of it in terms of combustion, sodium chloride is just the 'ash' you get when you burn metallic sodium in a chlorine atmosphere; it's the waste product you get after you've extracted very nearly all the available chemical energy. TenOfAllTrades(talk) 14:04, 1 February 2011 (UTC)

See the video here. The relevant part starts about at about 1:20. But yes, as Jaron implies, it's bullcrap. Specifically, bullcrap that a bunch of ignorant reporters decided to pass off as news years ago. Someguy1221 (talk) 05:32, 1 February 2011 (UTC)

Getting arsenic out of water

How does one purify arsenic out of groundwater.--128.54.15.47 (talk) 06:07, 1 February 2011 (UTC)

With ion exchange. --T H F S W (T · C · E) 06:39, 1 February 2011 (UTC)

See Arsenic contamination of groundwater. The sourcing is terrible, but it will provide you some good terms to Google for. Also, see the books listed here. -- Mesoderm (talk) 07:01, 1 February 2011 (UTC)

OP here (probably a different IP though). Anyone know the cheapest option on filtering arsenic out? If so, know the cost? I'm trying to compile a budget for a project and it would be a great help.--128.54.224.231 (talk) 07:50, 1 February 2011 (UTC)

It really depends on the scale. For a small scale - for one or a few households - reverse osmosis would probably be the cheapest however disposal of the "filtrate" and used filter cartridges will be a serious concern. Roger (talk) 07:55, 1 February 2011 (UTC)

I'm trying to develop a proposal for rural Bangladesh so it can't be anything too complicated I imagine. Specifically I'm responsible for the budget. I'm thinking a community scale of sorts. Household can work too. I know this is an odd question.--128.54.224.231 (talk) 08:02, 1 February 2011 (UTC)

I'd consider asking an expert at a school of public health, like Allan Smith at Cal Berkeley. Researchers at schools of public health usually have their heart in the right place, and will certainly know the data and many of the options. Looks like Bangladesh is on his list, too. -- Scray (talk) 12:55, 1 February 2011 (UTC)

Study what already works localy. [8]--Aspro (talk) 13:12, 1 February 2011 (UTC)

Planetary Satellites Book

Dear Wikipedia I emailed Dr. Burns at Cornell University (email redacted) and he does not think that Tidal Locking [9] timescale formula number 2 is in the book "Planetary Satellites." It is not in the Gladman article http://audiophile.tam.cornell.edu/randpdf/gladman.pdf. Formula 2 has 10 to the 10 years at the end of it. Would Professor Peale at University of California Santa Barbara (email redacted) who wrote the chapter have the answer?PaulNethercott (talk) 09:28, 1 February 2011 (UTC)

The answer to what? And how should we know whether some particular person can answer whatever? This is an encyclopedia, not an oracle. –Henning Makholm (talk) 10:04, 1 February 2011 (UTC)

A discussion about the formulae quoted in the article Tidal locking was started here and should be continued on the article talk page. The OP seems to have investigated the reference sources (no. 4) quoted in the article. To investigate further, one can look through the article history to find who has edited the article and try contacting them on their talk pages. Cuddlyable3 (talk) 11:38, 1 February 2011 (UTC)

Using lasers to melt snow

Anything like this exist yet? ScienceApe (talk) 15:20, 1 February 2011 (UTC)

Why would you want to? A hair drier is likely to be more efficient than a laser would be for that purpose... --Jayron32 15:26, 1 February 2011 (UTC)

Possibly, unless it actually isn't very good at melting snow. Doesn't seem like it would require that much technological know how, so why don't we have these? Well I mean a device that blows hot air for the sole purpose of melting snow I mean. ScienceApe (talk) 15:36, 1 February 2011 (UTC)

Because melting snow requires a lot more energy than shoveling it out of the way. --Stephan Schulz (talk) 15:44, 1 February 2011 (UTC)

For roads maybe, but I had drive ways in mind mostly. ScienceApe (talk) 17:53, 1 February 2011 (UTC)

Why would there be a difference? --Stephan Schulz (talk) 17:56, 1 February 2011 (UTC)

Because on a driveway, you're breaking your back to shovel it! You're not using a truck. ScienceApe (talk) 18:10, 1 February 2011 (UTC)

This [10] doesn't use lasers, but it apparently uses a dragon. Acroterion _(talk) 15:50, 1 February 2011 (UTC)

As Acroterion say's. If you look at the Enthalpy of fusion you will see that it take about 333 kJ of energy. One only needs about 4KJ to then bring it to boiling. In other words, melting ice consumes a lot of energy , almost as much as boiling it. Might be cheaper to compress it, load it onto a bulk-carrier and sale it to Arabia. There exchange it for oil, which is costs less than bottled water.--Aspro (talk) 15:52, 1 February 2011 (UTC)

It's actually somewhat more efficient to collect the snow and melt it in a purpose-built device — just blowing hot air means wasting a lot of energy (not all of the heat is efficiently transferred to the snow; a lot of warm air would escape). See Winter service vehicle#Snow melter and Metromelt. In areas which receive sufficient snow, the only way to clear the roads can be to melt it in place and dispose of the runoff through the sewer system; there just isn't enough space available to store the snow locally, and carrying it long distances to the suburbs is cost-prohibitive. TenOfAllTrades(talk) 16:57, 1 February 2011 (UTC)

There is such a thing as a heated driveway, sidewalk, or roadway. Usually, it takes the form of a fluid heat-exchanger running through specially-constructed plumbing pipes underneath the pavement. This maximizes the energy-efficiency of the heat-transfer to the snow; heating from above with a "hair-dryer" or hot-air machine would result in huge losses to convection and warming the air. (Though, to call a heated driveway "energy-efficient" is being generous, at least). I have seen radiant heat lamps, but lasers, by their very nature, are extremely focused/collimated - so you'd be melting tiny millimeter-sized holes of snow at a time. If you had a special need, I imagine you could probably use a cutting laser, but there would be great potential risks of high-power reflections, in random directions, off the specular snow-surface. This would be an unpredictable and incredible safety hazard.Nimur (talk) 18:27, 1 February 2011 (UTC)

Well, the whole point is that, being a tightly focused beam of light, a laser is actually markedly worse for melting snow than just about anything, even the completely shitty hair-drier. The point wasn't that the hair drier would be a good idea, it was just that, as completely terrible a job as a hair drier would do, the laser would be even worse. --Jayron32 19:20, 1 February 2011 (UTC)

Laser dazzlers

The dazzler article has an unsourced mention of an "alleged use of a Soviet dazzler against a Space Shuttle in 1984". This seems very unlikely to me; how could this have been effected? And why? Googling the key terms turns up little more than Wikipedia forks and mirrors. Was this actually possible and where are these allegations?--Shantavira|^{feed me} 17:27, 1 February 2011 (UTC)

It was the Terra-3 complex that did it. The atmosphere straight up is very transparent - in other words, the laser power under goes little attenuation. More than enought to upset delicate sensors.--Aspro (talk) 18:12, 1 February 2011 (UTC)

Some discussion of this at Sary Shagan. Apparently the reason was just to bug the Americans, in response to Reagan's stubbornness on SDI. It's not the most brilliant thing to have done, but not out of character for the pre-Gorbachev USSR. Incidentally for years afterwards the US over-estimated the Soviet SDI work going on at Sary Shagan, which was in fact pretty primitive. Not sure if that's connected with this incident or not. --Mr.98 (talk) 18:34, 1 February 2011 (UTC)

Dreams

I saw this on a few blogs, but I can't find a source for it, is it true? "Fact: we only dream of what we know. Our dreams are frequently full of strangers who play out certain parts – did you know that your mind is not inventing those faces – they are real faces of real people that you have seen during your life but may not know or remember? The evil killer in your latest dream may be the guy who pumped petrol into your dad’s car when you were just a little kid. We have all seen hundreds of thousands of faces throughout our lives, so we have an endless supply of characters for our brain to utilize during our dreams." -112.213.219.56 (talk) 17:59, 1 February 2011 (UTC)

I can't confirm or refute, but I think the claim is untestable. Even careful experiments like the one mentioned here [11] wouldn't be able to determine whether a face was known to a dreamer prior to dreaming. SemanticMantis (talk) 18:20, 1 February 2011 (UTC)

Sounds unlikely to me. Why is it that we can imagine unique faces for fictional characters in the books we read or write but our brains wouldn't be able to generate new fictional faces while dreaming? Abyssal (talk) 18:22, 1 February 2011 (UTC)

You get faces in your dreams? For me I either "know" who the person is (by name), or I just get a general idea of them (gender, age) basically an archetype, but no distinct/recognizable face. Ariel. (talk) 19:43, 1 February 2011 (UTC)

water

where can i get a jug that has a valve like this http://www.youtube.com/watch?v=LimbOdetYeM