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September 7

port tuning frequency

I have a ported(bass reflex) sub and I'd like to know what its cabinet tuning frequecny is tuned at(not the resonance frequency of the driver itself though!). I mean is this for possible? If I only know the cabinet's dimensions and its ports sizes and don't have the t/s for the driver. i thougt may there was some web site where type in your cabs-ports dimensions and get the cabs tuning frequency. —Preceding unsigned comment added by 85.26.241.107 (talk) 02:03, 7 September 2010 (UTC)

The resonant frequency of a loudspeaker mounted in its cabinet can be measured as a peak in its electrical impedance. See Electrical characteristics of dynamic loudspeakers. Cuddlyable3 (talk) 19:46, 7 September 2010 (UTC)

Fine, but i was talking about the box tuning frequency not the drivers fs —Preceding unsigned comment added by 85.26.241.82 (talk) 04:17, 8 September 2010 (UTC)

Methane, oxygen, and the trapped Chilean miners

I need some help understanding some very basic chemistry: those Chilean miners trapped underground right now are not being served beans, and news outlets reporting this are saying, with the obligatory wink, that it's because beans produce gas and it's a confined space and well in sum, the less unpleasantness, the better. However, is there more to it? Since some percentage of expelled farts (30-40% maybe?) actually contain methane, would an increase in methane rob the existing air of some oxygen and increase carbon dioxide levels, or does this reaction (methane + oxygen → carbon dioxide) require some sort of kick-start? This is probably featured in Chemistry for Pre-Schoolers, but I don't know what is needed for such a reaction to take place, if anything, and I would appreciate your help.Wolfgangus (talk) 06:15, 7 September 2010 (UTC)

Flatulence#Composition_of_flatus would be an interesting read for you. Additionally, the volume of gas expelled in flatulence is too small to be of concern for the miners in this case. The buildup of carbon dioxide due to normal exhaling would be of exponentially greater concern than even the worst bean-brocolli-cabbage-Guinness farts ever recorded. --Jayron32 06:25, 7 September 2010 (UTC)

(ec)"methane + oxygen \u2192 carbon dioxide" (and also water as a product) is not spontaneous combustion except perhaps under extreme conditions of temperature, pressure, mixture ratio). The mixture requires a source of ignition (spark or existing flame, for example) kick-start just like a gas stove (methane is natural gas, the same stuff piped into many houses). Methane is a huge problem in mines because it's already usually present and possibly at easily-ignitable amounts in many mines. Lots of mine-explosion disasters are caused by that, so it's critical that mines are ventilated to avoid methane build-up (and monitored to know if the atmosphere is reaching a dangerous situation). Given the size of Chilean mine chamber, I don't think the addition of a few farts would matter much (wouldn't suddenly push a safe atmosphere into a dangerously flammable one), but I don't know the actual numbers off-hand. DMacks (talk) 06:28, 7 September 2010 (UTC)

Without bothering to look it up, I would assume that they're pumping fresh air down to the miners anyway, which would render the problem moot. Rojomoke (talk) 08:33, 7 September 2010 (UTC)

Excellent, it all makes good sense. I very much appreciate your time and input. Wolfgangus (talk) 12:10, 7 September 2010 (UTC)

I assume that they want to limit farts due to the smell (generally caused by small amounts of sulfur containing compounds), rather than because it's actually dangerous. Just a guess, though. Buddy431 (talk) 14:17, 7 September 2010 (UTC)

Energy Conservation and the Cosmological Redshift

In this paper by Alasdair Macleod at http://arxiv.org/ftp/physics/papers/0407/0407077.pdf, can anyone explain to me how his kinematic derivation of the equation for the Doppler shift shows that it conserves energy on a photon-by-photon basis? More importantly, can anyone explain how he derived equations 23, 24 and 25? With many thanks, Luthinya (talk) 11:04, 7 September 2010 (UTC)

Let me say first off that this is a 6-year-old preprint that proposes a new cosmological model and is apparently unpublished, which means it's 99.999...% likely to be wrong.

I've only glanced through the paper, but I don't even understand what he's doing in the special relativistic case (section 2). He apparently shows that if a radiating object changes velocity, the radiated power (measured with respect to the original frame) is unchanged. That may be true, but it has nothing to do with energy conservation. If a light bulb suddenly starts glowing at a different brightness, that doesn't mean energy isn't conserved. In fact, a moving battery-powered lamp will emit the same power as an equivalent stationary one, but the battery will last longer (time dilation), so the total emitted energy is actually larger, even though the power isn't. That doesn't violate energy conservation either because that's not what energy conservation means. Since the author's notion of energy conservation seems to make no sense even in the special relativistic case, I don't think it makes sense in section 5 either.

The problem in general relativity is not that energy conservation is violated as such. It's that you can't even define a total energy to plug into the conservation law. The reason is that energy is the time component of a four-momentum, and the four-momenta of different particles can't be added because they're defined on different tangent spaces. You can parallel transport the momenta to a common location and add them there, but the result depends on the path through which you transport them, and also on which point on each particle's worldline you choose to represent its "present" momentum. If you're willing to make arbitrary choices like that, then you can define a total energy that is conserved in the standard cosmological model. -- BenRG (talk) 20:08, 8 September 2010 (UTC)

Is soccer or other team sport more predictable than individual sports?

Since other players can compensate for each other, the probability of something unexpected happing is relatively lower.--Quest09 (talk) 11:36, 7 September 2010 (UTC)

See Shell Caribbean Cup 1994 Sean.hoyland - talk 12:46, 7 September 2010 (UTC)

tl:dr. Don't presume that whatever it is that is evident to you in that competition / page comes through to any of the rest of us. --Tagishsimon (talk) 14:05, 7 September 2010 (UTC)

He may be referring to the reference at the end: http://www.snopes.com/sports/soccer/barbados.asp 92.15.12.116 (talk) 14:45, 7 September 2010 (UTC)

(EC) How is that article tl:dr? There is only one part that even has any text. And for that part it's probably best if you read it all since it's all related. I'm not saying I agree there's much of a connection to the question. All it really tells you is sometimes teams do whatever it takes to win, even stuff you may not have thought of. In particular, it tells you nothing about relative probabilities Nil Einne (talk) 14:47, 7 September 2010 (UTC)

Okay, I grant you that if you do read the text, it makes some more sense. Bizarre happening. --Tagishsimon (talk) 16:16, 7 September 2010 (UTC)

Consider the anomaly section as data for the questioner rather than an answer. Since the questioner asked about soccer and the unexpected events in team sports I hoped they would enjoy it. Sean.hoyland - talk 16:47, 7 September 2010 (UTC)

You probably want to be looking at the relative ranking of the opponents and the odds that bookmakers assign to the matches. Soccer may complicate things since a draw is usually a possible outcome. Perhaps you can pick a team sport where one of the teams must emerge victorious and rankings are frequently updated. Then compare with, for example, singles tennis. For example, if the topped ranked baseball team is playing a team ranked about 10 below them, how do bookmakers' odds of winning compare with the top-ranked tennis player playing someone ranked about 10 places below them? I know little of baseball so I'm not sure if this is a good example but am confident that someone will be along shortly to advise :-)--Frumpo (talk) 18:39, 7 September 2010 (UTC)

Sorry, I'm talking nonsense. The bookmakers' odds reflect the rankings. So, you could compare the odds offered before the match against the actual outcome to assess the predictability.--Frumpo (talk) 19:15, 7 September 2010 (UTC)

Soccer is a bad example since it is a low-scoring game (0-0 and 1-0 being the most common scorelines), thus it only takes one moment of individual brilliance to turn a game. Sports such as basketball (I presume), American football (I presume) and rugby, where regular scoring takes place, would (probably) lead to more predictable results and upsets that are much rarer, although more noteworthy when they do happen. I'd be fascinated to read actual data or theories about this though. Zunaid 18:55, 7 September 2010 (UTC)

I'm not much of a soccer fan, but from what I have watched, my impression is that it's misleading to just look at the scores. A 1-0 match is not necessarily close. A lot of times it means that the winning team gets one goal and sits on it. They could score more, but they feel that their winning chances are better if they just play defense and permit no more goals for the rest of the match.

The least predictable major sport is probably baseball, with so much dependent on the home run. --Trovatore (talk) 19:26, 7 September 2010 (UTC)

I believe that the questioner is asking, "Is it more likely that an individual sport can be upset by a player purposely doing poorly compared to a team sport in which a single player doing poorly is overshadowed by other players?" It depends entirely on the game and the players. If a goalie in soccer decides that he doesn't feel like playing well, it will have a rather noticeable affect on the score. -- kainaw™ 19:23, 7 September 2010 (UTC)

For sports sessions that can be divided into two halves, you could see if the outcome forecast by the half-time score was less accurate for team sports compared with solo competative sports. 92.29.119.29 (talk) 16:16, 11 September 2010 (UTC)

charge

Does putting power into a battery charge it? —Preceding unsigned comment added by Half charged (talk • contribs) 13:47, 7 September 2010 (UTC)

If it is a secondary cell. Primary cells may explode or leak when they are charged. --Chemicalinterest (talk) 14:24, 7 September 2010 (UTC)

I have a question, hope it's ok to tag it onto this one; how do chargers which are sold specifically to charge non-rechargeable batteries work? 82.44.55.25 (talk) 14:50, 7 September 2010 (UTC)

Read this Recharging alkaline batteries first, and if you have any questions about it post them. Ariel. (talk) 18:29, 7 September 2010 (UTC)

Why aren't primary cells not prohibited on airplanes? Or how can they know that a laptop battery was not transformed into an explosive non-re-chargable battery?--Quest09 (talk) 13:08, 8 September 2010 (UTC)

They don't explode, they pop. I took apart an old 9Volt battery. I was holding one cell. It exploded. Little bits of chemical flew around the room. The end popped off and shot about 15 feet. The battery shot backwards about 5 feet. Loud pop. --Chemicalinterest (talk) 14:35, 9 September 2010 (UTC)

Hafnium controversy

I was reading this article and found it fascinating. Essentially they are trying to use x-rays to get a Hafnium isomer to release all its energy. Correct me if I'm wrong, but the nucleons are in an excited nuclear state. Excited electrons can also be in a higher electron state, and when returning to a lower state, releases a photon. If an electron absorbs a high energy photon, the electron moves to a higher electron state correct? My question is, what do we use to catalyze excited electrons to return to a lower state, and release energy? Why can't this also be used to on excited nucleons? ScienceApe (talk) 14:25, 7 September 2010 (UTC)

It might seem paradoxical, but what is used to get electrons to give up their energy and release a photon is... another photon. This is basically the principle of the laser, and the ^178m2Hf would, in effect, produce an X-ray laser. The problem is that the photon that stimulates the emission has to have exactly the right frequency, and it is very difficult to "tune" X-ray sources to give a controlled frequency: effectively, we have to make do with what nature provides us with! To give an idea of how accurate you have to be, you can take a look at our article on Mössbauer spectroscopy, which isn't exactly the same effect but is very similar: the gamma rays for Mössbauer spectroscopy have to have their energies tuned to within a few parts in 10¹², which is done by simply moving the sample and using the Doppler effect: apparently, it's not that simple with hafnium! Physchim62 (talk) 14:57, 7 September 2010 (UTC)

Do you aim the photon at the electron to make the electron give up a photon? Is the photon higher or lower in energy than the photon given up? In the case of hafnium, what would you aim the photon at? ScienceApe (talk) 15:01, 7 September 2010 (UTC)

For normal stimulated emission, the photon has to be of (almost) exactly the same energy as the one that will be emitted: but the photon that does the stimulation is not lost, so you get amplification of the light (and other interesting phenomena such as coherence). Physchim62 (talk) 15:11, 7 September 2010 (UTC)

We also have a more specific article on induced gamma emission. TenOfAllTrades(talk) 15:41, 7 September 2010 (UTC)

For ScienceApe, the difference here is that it is the nucleus emitting the photons, not electrons jumping in the shells, as you may normally expect for xrays. A hafnium atom with an inner shell electron in a higher energy would only have a sub picosecond lifetime in its excited state. Graeme Bartlett (talk) 22:02, 7 September 2010 (UTC)

Cooling the Chilean miners

It is very hot where the Chilean miners are trapped. 1) Would there be any point in pumping chilled air down to them, or would the air simply warm up again on its way there? 2) Would pumping normal unchilled air help cool them, or would it be already hot by the time it got to them? 3) Is there a Wikipedia article somewhere about the trapped miners? 92.15.12.116 (talk) 14:53, 7 September 2010 (UTC)

For 3), see 2010 Copiapó mining accident. -- Finlay McWalter ☻ Talk 15:12, 7 September 2010 (UTC)

The mine is geothermally heated so it would be very tough to maintain a cooler environment through a 4" pipe. Maybe if they pumped some liquid air down there? The good news is that 85F is warm, but only about 15F above room temp. Googlemeister (talk) 16:47, 7 September 2010 (UTC)

What nonsense? 85F is normal air temperature Nil Einne (talk) 17:20, 7 September 2010 (UTC)

Yes, 30C isn't "very hot". Sean.hoyland - talk 04:54, 8 September 2010 (UTC)

Where does the figure of 85 degrees farenheit come from please? Perhaps people are not aware that the temperature rises as you get deeper. The Geothermal gradient article says: "Very deep mines, like some gold mines in South Africa, need the air inside to be cooled and circulated to allow miners to work at such great depth." The Geothermal energy article says: "the geothermal gradient of temperatures through the crust is 25–30 °C (77–86 °F) per kilometer of depth in most of the world."

The 2010 Copiapó mining accident says "at 700 meters deep and under high temperatures and high humidity" and "Many of the miners developed severe skin problems due to the hot and wet conditions." So the miners have to cope with high humidity and high temperature without any breeze either. 92.15.20.52 (talk) 23:40, 8 September 2010 (UTC)

This CNN story says: "To stay hydrated in the 85-degree Fahrenheit (29 Celsius) heat, each miner must drink eight or nine pints (4 liters) of water per day". -- ToE^T 14:57, 9 September 2010 (UTC)

I can't imagine that air would do anything but equilibrate in temperature, unless you pumped a gale down the hole... which you can't do. You could send down Dewars of liquid nitrogen, but that has its own problems in a mine! Seriously, dumping down a generous number of bags of ice seems like the obvious solution, together with many thin cloths to soak with ice water or keep dry to wipe off with. Wnt (talk) 06:42, 10 September 2010 (UTC)

Florida winter isotherm for indoor heating

Hello, I would like to know at about what winter isotherm does indoor heating start to become common in Florida? Or in the Southern U.S., for that matter. I know that in Southern Florida, around Miami, most people only have small one-room heaters they take out occasionally in January, but I have no idea if the winter temperatures in the rest of Florida warrant a need for indoor heating during most of the winter months.

This is my guess, but I imagine Northern Florida would definitely need indoor heating during all the winter months, every year. In general, at about what isotherm or latitude do homes and buildings in the Southern U.S. need indoor heating? Thanks —Preceding unsigned comment added by 201.21.183.191 (talk) 15:50, 7 September 2010 (UTC)

The science of sex, and female libido

On the one hand the female human should not be adapted to random, indiscriminate copulation as it is not an evolutionary sound strategy since reproduction is far more demanding on the female body than it is on the male body (one night of sex vs. nine months of pregnancy and a subsequent child), explaining why women tend to be choosier about their sexual partners than males are (see here). The female, in terms of what she is evolutionarily adapted to, should theoretically want sex only a few times in her life. Yet if you read some internet forums and women's magazines females themselves will discuss the fact amongst themselves that they are masturbating 4 times a day, having multiple orgasms, always wanting sex with their boyfriend, or if they don't have one they will go out and find a guy to have sex with, and it's all about the latest sex tips and how to look good and please a man and so on. Females do have a menstrual cycle that men do not have, and they have different hormones, which explains some of it, but not all. Who is right - Glenn Wilson (who proposes the biological evolutionary theory) or the girls who masturbate/have sex every day of their own free will (which seems to happen with some of them)? It would seem that enjoying sexual stimulation is a generally masculine characteristic? It's known that females are choosier about who they have sex with, and most of these girls who have very regular sex are in a committed relationship (although the practice of serial monogamy confuses things further). Perhaps social attitudes changing does play a role, but I am always convinced that instinct, nature, trumps society and is ultimately a lot more important in determining behaviour.--Querydata (talk) 16:08, 7 September 2010 (UTC)

For example - compare exhibit A and exhibit B (especially as you go past the first page of responses, many females are stating that their libido is actually greater than that of their male partners which totally contradicts the other link). Assuming that exhibit B contains the responses of actual females and isn't some sort of psychological operation on unsuspecting males, the two websites are inconsistent.--Querydata (talk) 16:17, 7 September 2010 (UTC)

It's possible that higher female testosterone could produce a higher libido in women, see here, so that it varies with the individual to some extent. But there's still a massive contradiction in terms between the two examples listed above. Women can have multiple orgasms and go on and on, but once a man's nutsack has been drained of sperm, he won't feel much like sex (and vice versa).--Querydata (talk) 16:24, 7 September 2010 (UTC)

That's a long ramble that doesn't really get to any sort of point. Having men wanting sex all year round and women only wanting sex at a certain time of the year makes no sense whatsoever. If there was a specific time of year humans had sex, both men and women would come into season at the same time, as animals do. But they don't, because there's no specific human breeding season. 71.170.245.203 (talk) 16:27, 7 September 2010 (UTC)

Echoing the above, female libido is as strong as male libido. Women, even when pregnant, often want sex. Anyone saying women don't have as stong libido as men are misogynists. 86.203.239.106 (talk) 16:34, 7 September 2010 (UTC)

There is no equality in nature. Why are the two sources that I picked out inconsistent? One of them must be wrong. Who is it - those who go by Charles Darwin or the readers of Cosmopolitan magazine? I also believe that concepts like 'sexism', (as well as things like 'racism' and 'antisemitism') are meaningless terms artificially imposed upon society by the proponents of cultural Marxism in order to nullify biological instincts and render society powerless. Do you wonder if in the wars of the ancient world, one tribe killing the men of another tribe and raping the women was called 'racist' and 'sexist'?--Querydata (talk) 16:51, 7 September 2010 (UTC)

"One of them must be wrong" Perhaps their both wrong. 84.42.138.38 (talk) 17:23, 7 September 2010 (UTC)

Or both right...? Wikiscient (talk) 18:24, 7 September 2010 (UTC)

If you are "always convinced" then there's no point asking a question on the RD, whatever your question actually is (I only counted two question marks and they both seemed more rheotorical). Nil Einne (talk) 16:36, 7 September 2010 (UTC)

Really, there's so much variation that whatever people blog and otherwise confess online in terms of their personal arousal and need to be aroused is more reflective of the topic being less taboo than of anything else. The few sex-specific tidbits I'm aware of:

1. males peak early (teens and following), then it's downhill from there—we pretty much all knew that;
2. women peak late (30's, 40's) as the body revs up the hormones for one more last shot at maternity—we pretty much all knew that;
3. orgasm in the female releases chemicals which imprint the female on the male—something to consider for the gals if the guy is great in bed but not so much the rest of the time. :-)

For what it's worth. PЄTЄRS J VЄСRUМВА ►TALK 16:55, 7 September 2010 (UTC)

P.S. Marxists in bed? Would that be Groucho, Marco, Chico, Zeppo, or Karl? PЄTЄRS J VЄСRUМВА ►TALK 17:02, 7 September 2010 (UTC)

P.P.S. On the multiple versus not, female versus male, male = single = with same female again, new female is different. PЄTЄRS J VЄСRUМВА ►TALK 17:02, 7 September 2010 (UTC)

I've heard all of those things. The last one in particular (about the female getting imprinted by the stimulation of one particular male) is associated with the tendency of females to desire to be more monogamous than males. I agree that sex differences are not absolute, but the biological aspect is the most important thing. Pornography should be viewed as a harem simulation for men due to their polygynous instincts. However since it's not real pornography can only do so much.--Querydata (talk) 17:06, 7 September 2010 (UTC)

To boil all this down; theories by a biologist vs Facts. Women say they masturbate and enjoy sex. They obviously do otherwise they wouldn't masturbate and have recreational sex. So it seems rather evident that whatever theories there are saying women only want sex a limited number of times are wrong. 174.56.218.72 (talk) 17:27, 7 September 2010 (UTC)

We have some good background articles on this very complex (and interesting) topic. Evolutionary psychology, though, as a science, is always going to try to account for the data as best it can. So you may find that it is not, on the whole, in opposition to, or contradiction of, the eg. "Cosmo" POV (as you cite it so well above). (In perhaps annoying-to-you Marxist/Hegelian terms, there is a synthesis to be found to the "dialectic" you present here, if you look for it carefully;). Wikiscient (talk) 18:48, 7 September 2010 (UTC)

BTW, Querydata, we have a whole portal devoted to topics like this -- good for further pursuit of the answer to your question and a good place to start contributing yourself if you're ever interested: Portal:Sexuality. Best regards, Wikiscient (talk) 20:02, 7 September 2010 (UTC)

OK. Well, I know about the Hegelian dialectic thing as well. Alright. Enough of this conversation for now. Many women do enjoy sex, there are just variations in the generalised male and female attitudes to sex, although these are not 100% absolute like a dichotomy where you can just draw a line in the sand and say that men like sex and women don't, and there are also differences between individual persons of the same sex. Ultimately it doesn't matter in the end because the doom is coming.--Querydata (talk) 20:23, 7 September 2010 (UTC)

Yes. Wikiscient (talk) 21:29, 7 September 2010 (UTC)

"Female should theoretically want sex only a few times in her life", No, even from a purely darwinist point of view, in a situation where natural selection occurs, they should want sex many, many times, as long as they are not pregnant. And then, they should want sex with their man, because it pleases him, and therefore he is more likely to stay and to help providing food for the baby later. --Lgriot (talk) 11:46, 8 September 2010 (UTC)

How to make 3-methylbutyl ethanoate?

Give a detailed account of how you would prepare a pure dry sample of 3-methylbutyl ethanoate from ethanoic acid, concentrated sulfuric acid and an alcohol which you should choose. You will need to make use of the physical properties you discussed earlier. (Boiling points, solubility in water and odour of caboxylic acids, alcohols and esters). Dust429 (talk) 18:47, 7 September 2010 (UTC) —Preceding unsigned comment added by Dust429 (talk • contribs) 18:45, 7 September 2010 (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. TenOfAllTrades(talk) 19:00, 7 September 2010 (UTC)

Fischer esterification might be a good article to read. -- 140.142.20.229 (talk) —Preceding undated comment added 19:50, 7 September 2010 (UTC).

This  is not helpful. I sincerely hope that users like yourselves who visit the Reference Desk regularly would care to provide more adequate answers. Dust429 (talk) 20:48, 7 September 2010 (UTC)

We care to note the very clear statements and guidelines against doing people's homework for them when they don't even demonstrate a teensy effort to try to help themselves first. You're obviously welcome to go somewhere else and say "please do this homework for me", but WP ref-desk is definitely not it. The way I would do it is to tell my students to do it and then pick the answer of whoever gave me a chocolate donut. DMacks (talk) 20:52, 7 September 2010 (UTC)

What part of the problem are you having trouble with? Look at the name: 3-methylbutyl ethanoate (aka acetate). Note which part is the acetate and which part is not. This gives you a big clue about which alcohol to use. This isn't difficult, you aren't even trying to reverse a cyclic aldol condensation. John Riemann Soong (talk) 20:55, 7 September 2010 (UTC)

Also look at Fischer esterification, and ask anything you don't understand. John Riemann Soong (talk) 20:59, 7 September 2010 (UTC)

Also, you can get isoamyl acetate solution from my Asian supermarket. Win! John Riemann Soong (talk) 20:57, 7 September 2010 (UTC)

If you check the posters history, you will find that he is a troll, so you should probably ignore this question. Ariel. (talk) 21:08, 7 September 2010 (UTC)

"style"

This question was moved to Wikipedia:Reference_desk/Miscellaneous#.22style.22

Rotation of the Earth...

Ok... so the Earth is spinning very fast, however it is so big that it seems so slow to us. My question is this... If you was to stand directly on the North Pole or South Pole, would you be able to feel the effects of the spin? Also, wouldn't you be spinning at an extreme speed? —Preceding unsigned comment added by 74.218.50.226 (talk) 19:59, 7 September 2010 (UTC)

No, if you stood on the north pole, you would only spin around once every 24 hours. The earth does not spin fast in RPMs, only 0.00069 RPM, but the surface near the equator speeds past at speeds of around 1000 mph.--Chemicalinterest (talk) 20:13, 7 September 2010 (UTC)

Actually you got it backwards. The earth is spinning very slow, however it is so big that it seems so fast to us (1000 mph). --Chemicalinterest (talk) 21:28, 7 September 2010 (UTC)

I think the OP is saying that traveling from one day to the next sure seems to take a long time (1 day) going at 1000 mph (at the equator, which is very "big"). At the exact center of rotation, you are at rest (ie. not moving at all) with respect to the center of the Earth.Wikiscient (talk) 21:46, 7 September 2010 (UTC)

The Coriolis effect is a measure (roughly) of the rate of change of your rotational speed as you move north or south, so this is greatest at the poles. But in terms of "human-scale" lengths and times (a few metres and a few minutes) it is still very small. A Foucault pendulum is one way to observe the Coriolis effect. If you set up a pendulum at the pole swinging through an arc of 1 metre, the pendulum precesses so the endpoint of its swing moves sideways - but only at the tiny speed of about 36 micrometres per second - less than a hair's width. It would take four and a half minutes for the endpoint of its swing to move sideways through a distance of 1 centimetre. Gandalf61 (talk) 08:55, 8 September 2010 (UTC)

Springs squirting out of the ground

Do springs commonly squirt out of the ground? I have explored many streams to their source and only saw large amounts of grass and undergrowth. I never see a distinct spring. Do they even exist? --Chemicalinterest (talk) 20:44, 7 September 2010 (UTC)

Yes, flowing artesian wells behave in this manner. — Lomn 20:51, 7 September 2010 (UTC)

But in all my explorations, I never saw an artesian well? Do squirting springs only exist in very rocky terrain? --Chemicalinterest (talk) 21:00, 7 September 2010 (UTC)

See also Hydrology#Hydrologic transport and the main article Hydrological transport model. Water is "flowing everywhere" - in liquid and in vapor form. A "spring" is just a region where that flow is "useful" and rises to the surface. It can occur underneath a lake (where a net flow of water actually flows up from the bottom - as is postulated for the Sea of Galilee); through a specific bore-hole in an otherwise water-tight seal rock, or percolating through a sediment or sandy area until it reaches the surface; it can even be an outlet of an otherwise subterranean river. A spring can be modeled as a single point-source, as a "line source", or as an entire region with a positive fluid flux. Spring (hydrosphere) shows many photos of different kinds of springs. To "squirt" out of the ground, the water would need to be under significant pressure - more than is sustainable by normal hydrological processes - and that would be an artesian well, where a sufficiently water-tight rock layer squeezes water; the hydrostatic head can be large, and the water can actually "gush" from the ground. Nimur (talk) 21:03, 7 September 2010 (UTC)

I cannot speak to the breadth of your explorations. I'll note, though, that springs will generally fill in low areas so that what could be a free-flowing artesian well ends up being a submerged spring simply because of the geography. Rocky or hilly terrain, though, is not a prerequisite. This USGS page illustrates the geography of the Brunswick, GA area on the Atlantic coast, which is quite flat. — Lomn 21:06, 7 September 2010 (UTC)

OK, now I see. The spring fills up the surrounding area, making a wetland? --Chemicalinterest (talk) 21:10, 7 September 2010 (UTC)

Yes -- sometimes. Or a lake, or a river, or some other hydrological formation. — Lomn 21:31, 7 September 2010 (UTC)

In the Ozarks I saw a small pond fed by an artesian spring. The spring itself was at the base of a low rock cliff, and the pond mostly a bit below there. While the spring itself was underwater you could see the water surface welling up where the spring was. There are other, more obvious springs in the Ozarks. The largest one is Big Spring (Missouri). An awful lot of water is welling up from the ground, forming a river. It's not "squirting" into the air though. There was a town in Washington, I think, that in early times dug a well and released a powerful artesian spring, a literal gusher. Unfortunately I cannot remember what town right now. Some kind of fountain-like structure was built around the spring, and the town became locally famous for its natural gushing fountain. Over the years and decades, however, the pressure weakened and the fountain slowly died, becoming just a small spilling out of water. I wish I could remember the town so I could give a reference. But the point is I suspect a "squirting" artesian well is likely to weaken over time as the pressurized water is released, even if it isn't submerged. (PS, the Greer Spring (Ozarks) page has a photo of a more obviously "welling up" spring). Pfly (talk) 13:05, 8 September 2010 (UTC)

Most springs I have seen were just water seeping through the ground, i.e. big patches of wet grass.--178.167.223.93 (talk) 17:56, 8 September 2010 (UTC)

... and most springs where I live are the sources of small streams, but they come out of the rock horizontally and under very little pressure. Dbfirs 13:55, 10 September 2010 (UTC)

Reduction of copper(II) oxide to copper(I) oxide

I reacted ascorbic acid solution with copper(II) oxide. It turned from black to gray. I checked it after a day and it was red. Was this reduced to copper or copper(I) oxide? Is there a way I can find out? --Chemicalinterest (talk) 21:07, 7 September 2010 (UTC)

You could check for conductivity with a multimeter (possibly after drying out the material), or you could do a chemical check for oxygen. Also if you try to melt it, copper metal should fuse to a metal bead unlike the oxide. Another test could be to see if molten solder sticks or not. Graeme Bartlett (talk) 21:51, 7 September 2010 (UTC)

There's probably some coordinating solvent in which the oxide is soluble but that is not strong enough redox to dissolve the metal itself. Maybe chloride or ammonia? DMacks (talk) 01:18, 8 September 2010 (UTC)

Well the article says it can dissolve in ammonia solution or hydrochloric acid. Copper metal will not do so in the absence of air. Graeme Bartlett (talk) 12:07, 9 September 2010 (UTC)

Laplace pressure and bubbles

The bending of the surface of any liquid creates excess pressure, known as the Laplace pressure. Consider a T-shaped pipe with two bubbles of different diameters blown at the two ends across from each other. How will the two bubbles behave?

After doing some googling, I found that the smaller the bubble, the larger the Laplace pressure. So I figure, if the two bubbles were connected through a regular pipe, the small bubble would shrink while the larger bubble would expand, because the pressure inside the smaller bubble is greater and would force the air towards the larger bubble. I'm not sure if this is right, or how the situation changes when the linear pipe is replaced by a T-shaped one. My intuition says they would both deflate as air leaves the T-pipe, because pressure inside the pipe has to be greater than pressure outside the pipe, by the Laplace pressure thing. Am I on the right track? 74.15.136.172 (talk) 22:07, 7 September 2010 (UTC)

What do you mean by "blown"? As in glass or soap bubbles? Why Other (talk) 06:06, 8 September 2010 (UTC)

Soap. 74.15.136.172 (talk) 13:24, 8 September 2010 (UTC)

In a normal pipe of constant diameter, the two soap films will assume the same shape (but one may be thicker if you put more soapy water there): a spherical cap. Whether it bulges outwards or inwards depends on how much air was trapped inside. Putting any hole in such a pipe (or making it a T) will make the pressure inside and outside equal (air doesn't have surface tension, so no Laplace pressure) and so the films will be flat (regardless of their radii or thicknesses). In the case where one end of an otherwise closed pipe is narrower than the other, the film at the narrow end will be a subset of the film at the wide end (that is, they will be caps from spheres of the same radius). --Tardis (talk) 14:57, 8 September 2010 (UTC)

Why don't we use human waste for fertilizer?

Topic says it all. ScienceApe (talk) 22:19, 7 September 2010 (UTC)

We do. I don't know the details, but solid waste residue from UK effluent treatment plants is routinely tankered off and spread on farmland. --Tagishsimon (talk) 22:21, 7 September 2010 (UTC)

The US does and the newspapers have been full a food poisoning outbreaks.--Aspro (talk) 22:29, 7 September 2010 (UTC)

I don't think that last comment is accurate, but human waste has routinely been used for fertilizer, see night soil. Looie496 (talk) 22:33, 7 September 2010 (UTC)

There are concerns about build-ups of metals & other pollutants. Example article discussing the pros & cons. --Tagishsimon (talk) 22:42, 7 September 2010 (UTC)

Human waste is used for a variety of purposes. For some of the processes used in developed countries see Sewage treatment. Dolphin (t) 22:45, 7 September 2010 (UTC)

I believe the reason why it is not more widely used is because untreated Human feces is full of E.coli. This is the reason I read why you should not put human or dog feces into compost. Vespine (talk) 23:26, 7 September 2010 (UTC)

Many places do, but it's processed first. Using it raw is very likely to cause bacterial contamination of your crops. APL (talk) 23:19, 7 September 2010 (UTC)

One of my favorite chuckles is the Abe Books Weird Book Room. One of the books featured is called The Humanure Handbook. [1] I haven't read it, but ... there is is. Antandrus (talk) 23:29, 7 September 2010 (UTC)

And a link: Humanure (contrast with Night soil). Ariel. (talk) 00:15, 8 September 2010 (UTC)

Manure of any mammal should be composted before it is used. The harm is not as much from e. coli as it is from larger intestinal fauna such as trichinosis and other worms. Composting and sewage treatment will replace flora and fauna which live inside you with those that do not. I don't know where the idea that heavy metal contamination is a problem comes from, and I seriously doubt it. Those and other poisons are more likely to accumulate within fish, game fowl, and game mammals. The primary danger from e. coli is when human feces are directly applied to above-soil vegetables by farm workers in unsanitary working conditions. Why Other (talk) 06:18, 8 September 2010 (UTC)

I think I can remember reading some gardening book that mentioned that the manure of herbivores is useful as fertilizer for home gardens, but the manure of omnivores and carnivores isn't. Try investigating that angle, like the example Why Other gave above about fowl.--Brianann MacAmhlaidh (talk) 06:22, 8 September 2010 (UTC)

If one's human waste is processed and sold for a profit does one have a legitimate claim for royalties? The term "royalties" does not mean the question is limited to those who spend time sitting on the throne. Cuddlyable3 (talk) 12:24, 8 September 2010 (UTC)

It depends on the originality of your work... ;) Wnt (talk) 16:20, 8 September 2010 (UTC)

There was a Japanese company making jewellry from sewage. The product was dark in colour with that "oil on water" rainbow effect. I guess it never took off as there are very few online mentions of it now. SpinningSpark 12:33, 11 September 2010 (UTC)

lemon

My sister is into science stuff. Apparently lemon juice can be used to charge power? How is their electricity in lemon juice? —Preceding unsigned comment added by Evlwty (talk • contribs) 22:24, 7 September 2010 (UTC)

read Lemon battery. --Aspro (talk) 22:30, 7 September 2010 (UTC)

To fix a misconception in the question, the lemon doesn't actually provide the electrical power. The electrical power is provided by the electrodes, which are merely two different chunks of metal (like, say, copper and zinc). The lemon merely provides the medium to transport ions between the electrodes; it is what is known as a salt bridge. --Jayron32 23:48, 7 September 2010 (UTC)

Yes, almost any chemical can be used instead; try sodium chloride. --Chemicalinterest (talk) 00:00, 8 September 2010 (UTC)

Actually, the lemon works better than ordinary salt water because the acid present provides a better cathode reaction; there's not much hydrogen ions in pure salt water, and the cathode (copper) reaction in the case of the lemon battery is the reduction of hydrogen ions to hydrogen gas. Most redox reactions happen better in either acid or base than pure water because pure water actually makes a lousy oxidant or reductant. Sodium ions are even more bulletproof in this regard. If you did the reaction in something like weak hydrochloric acid, or perhaps something like vinegar, it would work better than plain salt water. --Jayron32 00:08, 8 September 2010 (UTC)

Offtopic, but what do you think generates electricity in a salt water galvanic cell? --Chemicalinterest (talk) 00:11, 8 September 2010 (UTC)

It depends on the nature of the electrodes present, and the specific construction of the cell. If you stick a copper and a zinc electrode into pure salt water and hook it up to a voltmeter, you will generate a tiny voltage, but it won't be terribly high. That's because the cathodic reaction depends on the reduction of H+ ions, of which there are only 10^-7 M concentration in pure water. --Jayron32 00:20, 8 September 2010 (UTC)

I made a kinda powerful battery with a zinc and pure sodium chloride and a carbon electrode. I think it was reducing oxygen from the air to hydroxide. --Chemicalinterest (talk) 10:53, 8 September 2010 (UTC)

ChemicalInterest made a cell similar to a Leclanché cell (see article). The reason that different conductive materials are used for the two electrodes is that the voltage produced depends on the electrode materials having different Electrochemical potentials. (Note: Pure sodium chloride is a solid. It is useable as an Electrolyte when diluted in water.) Cuddlyable3 (talk) 12:15, 8 September 2010 (UTC)

In the cell, there is a reducing agent, zinc. Copper is not the oxidizing agent. --Chemicalinterest (talk) 14:59, 8 September 2010 (UTC)

Good for your sister. Imagine Reason (talk) 01:29, 9 September 2010 (UTC)

September 8

Ancient bread

Surely bread before modern times was of the no-sugar-added, whole wheat variety? 67.243.7.245 (talk) 01:47, 8 September 2010 (UTC)

History of bread is where anything we have about it would likely be found. DMacks (talk) 01:56, 8 September 2010 (UTC)

As our article on flour says, refined flour first came into wide use in the 19th century. And before the 20th century, pretty much all bread used a starter or sponge rather than purified yeast, so no sugar was necessary to get the rise going. There were however types of bread that had sugar or honey added to sweeten them, dating back at least to the middle ages. Looie496 (talk) 04:06, 8 September 2010 (UTC)

The middle ages is a bit late in the game for sweet bread. There are sources from ancient Mesopotamia citing "sweet bread". 99.11.160.111 (talk) 06:39, 8 September 2010 (UTC)

As with my comment below, it seems unlikely to me all bread used a starter or sponge, as there was likely plenty of places where unleavened bread was uncommon, as there still is nowadays Nil Einne (talk) 09:29, 8 September 2010 (UTC)

It would seem rather unlikely to me that all ancient bread was 'whole wheat' considering not everywhere had much wheat yet it's likely some of these places had some form of bread Nil Einne (talk) 09:27, 8 September 2010 (UTC)

Following on from Nil Einne. Old European text often refer to the 'black bread' that the peasants' ate. Wheat has always been the most expensive cereal for bread, whereas black sourdough rye bread (made without yeast) was cheaper. History of bread appears to omit this nugget. Freeing the grain from the head of the wheat stalk was also labour intensive -especially 'spelt'. Modern verities are easier. --Aspro (talk) 12:48, 8 September 2010 (UTC)

I read that ancient bread probably had a load of other stuff like wool and straw and bits of wood, because they bulked it out to save the wheat. Quadrupedaldiprotodont (talk) 14:16, 8 September 2010 (UTC)

Note that crystallized cane sugar was described by Pedanius Dioscorides, who regarded it as a sort of honey. Wnt (talk) 15:00, 8 September 2010 (UTC)

Traditionally, bread was made with whatever was available. In a good harvest year in Britain, much more of the population would eat wheat bread, and the poorer might eat bread with barley or rye or oats mixed in. In average years, the reliance on hardier crops would be greater, and the poorest would be likely to eat bread with dried ground beans and peas mixed in. In bad years, the poor would be eating mostly oats and beans, and even the rich would have other corn mixed with their wheat. White bread was an aspirational food, and bolting (sieving through fabric) the flour for the finest bread was extremely time consuming and required finely woven fabric: even the rich only ate small manchet loaves, supplemented with coarser bread. Only the poorest ate the cheap, wholegrain loaves: other loaves were made from flour with more or less of the bran removed, and people used the bran for animal feed. 86.164.78.91 (talk) 18:03, 8 September 2010 (UTC)

Desert heat

I just moved to Phoenix from San Francisco. Needless to say it is much hotter here, the daily high has been over 100 F just about everyday (highest I have seen is 112 F) and it rarely gets bellow 85 F at night. I understand that the temperature effected by a number of factors, but it is the intensity of the sun that confuses me. I'm only four or five hundred miles further south, but the sun feels much much stronger, it is like standing under a heat lamp (In the middle of the day) and is nothing like the sun in the Bay Area. Are there other factors beyond latitude that effect the intensity of the sun? —Preceding unsigned comment added by Daniel J. Leivick (talk • contribs) 04:37, 8 September 2010

Air temperature has a profound effect on the sensation of heating from the sun. If the air is 90F the sun feels very intense. If the air is only 60F the sun feels much weaker, even though it is the same sun and you are at the same latitude. If the air is below, say 30F, the sun feels almost insignificant. Our skin is actually an inaccurate instrument for sensing the power of the sun (or any other radiant source.) The sensation of heating from the sun is dependent on the temperature of our skin. Dolphin (t) 05:33, 8 September 2010 (UTC)

Also, you'll get used to it after a while. Sean.hoyland - talk 05:44, 8 September 2010 (UTC)

There is a little information at Thermoception. Dolphin (t) 06:22, 8 September 2010 (UTC)

Thermoception is a word ? I did not know that. Marvelous. Sean.hoyland - talk 06:25, 8 September 2010 (UTC)

Large bodies of water (the Pacific Ocean in your case) help reduce the difference between day and night temperatures (and summer to winter). Also the oceanic gyres move the heat further up the coast. CS Miller (talk) 09:45, 8 September 2010 (UTC)

Thermoception relates to how you feel yourself affected (not "effected"!) by the ambient temperature. Cuddlyable3 (talk) 12:00, 8 September 2010 (UTC)

Thermal convection of the atmosphere is bringing moist air inland during the day (from the chilly seawaters off the SF coast). This air is no doubt, absorbing some of the heat rays (and rises in the process to be replaced by more cool moist air). The cooler air also help to take more of the heat away from the skin. On top of that, SF has a 1000 foot of extra atmosphere. Out of all the factors, I think it is the very low humidity days when I have noticed the heat lamp effect at the places I've been. Just a water mister can have quite an effect on the microclimate of the back yard. Does that seem plausible to you?--Aspro (talk) 13:20, 8 September 2010 (UTC)

Here in Barcelona, on the Mediterranean coast, the daily maximum temperatures in July are 4–5 °C (7–9 °F) lower than in Lleida, which is just a hundred miles inland (temperatures in Madrid, which is right in the middle of the Iberian peninsula, are similar to those in Lleida): that gives you some idea of the cooling effect of the sea in summer. The cooling effect for San Francisco is even greater, beacuse the currents in the Pacific off SF are cold: if we take the city of Murcia, which is the same latitude as SF and almost on the coast, the July average daily maximum is 28.4 °C (83 °F), as oposed to 20.1 °C (68.2 °F) in SF. Physchim62 (talk) 14:06, 8 September 2010 (UTC)

The effects of the Pacific Ocean are quite stark in San Francisco; I am surprised that someone who lived there never noticed the regular differences between San Francisco and the East Bay; on any given day it can be ten degrees or more hotter in Oakland than in San Francisco. Compare the climates in the articles. The average July high in Oakland is 72.7. In SF it is 68.2 Four degrees in average difference of temperature is pretty good for a few short miles. --Jayron32 02:07, 9 September 2010 (UTC)

The original question is not about air temperature as measured by a thermometer. It is about the perceived heating power of the sun. Daniel has written … it is the intensity of the sun that confuses me. … The sun feels much, much stronger. Dolphin (t) 04:10, 9 September 2010 (UTC)

AH. In that case, it's still a water issue, but likely an issue regarding water vapor in the air. Humid air has a higher specific heat than does dry air, water vapor itself having a relatively high specific heat (lower than liquid water, but higher than, say, nitrogen). That means that humid will tend to resist changes in temperature more than dry air; it also means that on a dry day the sun will feel hotter, since the air around you absorbs less of the heat energy , being of lower specific heat than on a humid day, with the temperatures being the same. This effect is not the same reason why a humid day in the shade feels hotter than a dry day; that is because when the air is closer to the saturation point, sweat evaporates less rapidly, providing less cooling. If we are specifically talking about the perceived heat of the direct sun in dry air vs. humid air, at identical temperatures, the difference is caused by the difference in specific heat of dry air vs. humid air. To sum up, humid air has a higher specific heat, so absorbs more heat energy before it gets to your skin. Dry air, of a lower specific heat, allows more of that energy to get to you faster. --Jayron32 04:36, 9 September 2010 (UTC)

humid air ... absorbs more heat energy before it gets to your skin No! Air is transparent and the solar radiation passes straight through. The sun doesn't heat the atmosphere directly. It heats the Earth's surface and then the surface heats the atmosphere by the process of convection. Close to the Earth's surface the air is warm but at progressively higher altitudes in the troposphere the air is progressively colder. Dolphin (t) 06:20, 9 September 2010 (UTC)

Nothing you said controadicted a single word of my answer, so using the word "No!" is inappropriate. Air is not at absolute zero temperature, so at some point it needs to absorb energy from something. The path it takes to get there is irrelevent, the heat capacity of humid air is still higher than the heat capacity of dry air. It's irrelevent whether that heat source comes from above, below, or the side. It still has a higher heat capacity. --Jayron32 03:34, 10 September 2010 (UTC)

Another thing that has come to me, is sitting in front of large bay windows, with the sun shining through on a very icy cold but very dry days. The heat lamp effect has been too much for me to remain sitting there. Found a simple graph of the sun spectrum and absorption ( in blue) and the transparent windows (yellow). The ESPERE Associaton. As you can see most of the long wave infra-red is absorbed by water vapour. Theory and experience seem to agree. So this would aply to cold dry deserts too.--Aspro (talk) 11:17, 9 September 2010 (UTC)

Thanks a lot for all the well thought out answers, but I'm still a little confused. We have a couple of possibilities as to what causes this "heat lamp" effect.

• 1. The air temperature is higher and increases the perceived intensity of the sun.
• 2. Lower humidity causes less infrared radiation to be absorbed increasing the intensity of the sun.

Of course could certainly be a combination of the two, but I wonder which has a greater impact. I have also experienced the bay window event Aspro was talking about. Which makes me lean towards option 2. On the other hand I don't think I can recall feeling the intensity of the sun outside on a cold but very dry day. --Leivick (talk) 23:22, 9 September 2010 (UTC)

Atmospheric carbon scenario difference projections on math desk

There was earlier ambiguity about whether this question should have been on the math desk or the science desk, but the way it is stated now, it is solely a probability density optimization problem (please correct me if I am wrong), so I copied it out on to the math desk. Why Other (talk) 05:42, 8 September 2010 (UTC)

Your question seeks a rational conclusion in economic policy making. It has human variables so it is not solely a mathematically soluble problem. Cuddlyable3 (talk) 11:55, 8 September 2010 (UTC)

de Broglie wavelength

Dear All,

Hello everybody,

1) how to find the de broglie wavelength of a 1 eV electron ?
2) how to find the momentum and energy of an X-ray with a wavelength of 0.5 A ? ( the A here with a bubble on top )

THANK YOU —Preceding unsigned comment added by Jameskiki (talk • contribs) 08:45, 8 September 2010 (UTC)

See De_Broglie_wavelength. Also, we won't do your homework for you. TomorrowTime (talk) 09:08, 8 September 2010 (UTC)

and see Angstrom and photon#Physical_properties 157.193.175.207 (talk) 09:10, 8 September 2010 (UTC)

For 2b, the relevant formulae are E=hf ; c=fλ      CS Miller (talk) 09:52, 8 September 2010 (UTC)

Bees - five eyes

Apart from the two large compound eyes, what is the purpose of the other three eyes? 92.28.242.240 (talk) 09:51, 8 September 2010 (UTC)

See Simple eyes in invertebrates. The ocelli seem to monitor general light levels rather than form images. So for example, in the case of Apis mellifera, if you paint over its ocelli it will start foraging later in the morning and finish earlier than foragers without covered ocelli and if it's cloudy they won't even leave the nest. It reduces their sensitivity to light by about 10x apparently. James and Carol Gould did some very nice experiments where they adjusted the light levels of a lamp (=fake sun) and when the light level reached a certain point the bees with painted over ocelli reoriented their waggle dances from oriented relative to the light source to oriented relative to gravity whereas the unpainted dancers carried on as usual. So they ended up using different dialects and workers trying to read the dances ended up going to the wrong locations. Sean.hoyland - talk 10:46, 8 September 2010 (UTC)

The article Evolution of the eye explains the origins of insect eyes that are so different from human eyes. This difference may be accounted for by the origins of eyes; in cephalopods they develop as an invagination of the head surface whereas in vertebrates they originate as an extension of the brain. Cuddlyable3 (talk) 11:43, 8 September 2010 (UTC)

Why do your muscles ache when you have the flu?

I have a flu and i also know one of the symptoms is aches and pains. I'm a (high school) biology student so i find this stuff rather interesting. We have done immunology but the teachers often tells us just simply something does happen without actually explaining how. I do some reading on my own but on a cursory glance i couldn't find much on this. Any insight would be greatly appreciated.

(I have also done endocrine and nervous system and protein synthesis if that helps to gauge my knowledge for the right response)

Kingpomba (talk) cheers kingpomba

See our article on influenza. The technical term for muscle aches and pains is myalgia (although that article doesn't really answer your question). Also, try this article for a general discussion about the mechanisms underlying many symptoms of viral infections. The take-home message from the article is that myalgia is the result of cytokine release. For example, tumor necrosis factor causes active breakdown of muscle protein in response to illness, probably as a mechanism to mobilize amino acids. There is also a role of prostaglandin E2 which can mediate pain by stimulating nerve endings. --- Medical geneticist (talk) 12:37, 8 September 2010 (UTC)

The body is under a lot of stress fighting the flu so everything else suffers as a result. Like a leaky pipe lowers pressure. Quadrupedaldiprotodont (talk) 14:13, 8 September 2010 (UTC)

The explanation I've heard (which may be specious, but is worth considering) is that one of the approaches the body uses to fight off viruses in raising body temperature, and muscular activity is one of the main sources for doing that. In extreme forms this produces shivers, but the body can also use muscular tension or sub-perceptible activity to achieve the same ends. Body aches, then, are the same kind of soreness one will get after any unaccustomed physical effort. --Ludwigs2 16:28, 8 September 2010 (UTC)

Neil Armstrong tie clip

My grandfather had a tie clip he claimed belonged to Neil Armstrong. He told me the tie clip was made from melting the legs of the lunar module down and all the astronauts got one. He told me it was registered. He passed away and I have it now and want to authenticate this. Any clues?

-Shari Morgan —Preceding unsigned comment added by 207.235.214.120 (talk) 12:49, 8 September 2010 (UTC)

The lunar modules were not melted down. The tie clips were made from the medallions that the astronauts wore. Each astronaut received one medallion, so they are very rare. What you would need to do is figure out how to explain why Neil Armstrong decided he didn't want to keep his. -- kainaw™ 12:57, 8 September 2010 (UTC)

NASA had a number of items made for presentation to VIPs and others as a goodwill gesture. We don't have such a photograph of one on Wikipedia. Can you photograph it and upload it to us or get someone else to please. It will likely have a serial number on it to prevent forgeries. Can you see any marks or numbers. Use a spy glass as there might be some minute letters to identify the stamping die. Any such serial number would be a start to establish a Provenance. Did your grandfather keep a diary in which he may have recorded the event? It is quite possible that it incorporates metal that came back from the voyage – but of course not the leg of lunar module --Aspro (talk) 13:58, 8 September 2010 (UTC)

The legs of the lunar modules were part of the descent stage, and were left on the moon (except for the LMs that never went to the moon in the first place) in order to save weight. Paul (Stansifer) 14:16, 8 September 2010 (UTC)

I agree that you should take a photo of it with any markings or numbers visible. Don't mean to be a spoil sport but no one else has said it yet, I think it's probably much more likely that it's not that at all. Stories tend to "build up" over time, even quite innocently and honestly, no one has to lie or be deceitful for it to happen. It's just human tendency to embellish stories over time as they are told and retold. We know that at least part of the story is not accurate (the bit about the melted down module legs), of course you would say "oh but it was something like that", unfortunately, once you add up all the it was something like that's you often end up with a completely different story. Of course I'm not saying it's not worth investigating, my argument does NOT rule out the possibility it was really Neil Armstrong's pin, and even if it wasn't it might still be something that makes a great heirloom. Vespine (talk) 01:28, 9 September 2010 (UTC)

Surely if anyone is going to be able to authenticate this it's NASA. I would suggest communicating with their Public Inquiries Office, being ready to send a photo if they ask for it. I won't post the email address here but you can easily find it with Google. --Anonymous, 03:50 UTC, September 9, 2010.

I detect some doubting Thomases out there, so I'll explain some more why I think this has a good chance of being from Armstrong. Nixon et. al. understood, that if you give out exclusive gifts to high profile people, who meet a lot of other high profile people, they will not be able to resist showing it off. In doing this, the gift 'announces' Hey, the US got to the Moon first! In other words, this was a PR exercise which was politically driven. It was grudgingly supported by NASA because they needed the tax-payers dollar -or rather several billion of them. Too much should not be read into the leg issue because astronauts have to repeat things so many times that they tend to sail through public functions on auto-pilot and frequently over simplify things. If the poster's grandfather was not an engineer this could easily lead to confusion. For instance: Armstrong could have mentioned that the next mission (Apollo 12) went on a little jaunt to retrieve bits from a Luna lander. What is there to distinguish this from the Luna lander modules or LM's. Amongst other things they removed were parts from its struts. The engineering name for leg is strut. I'm not saying this is what happened in this case but rather to show how lay people might get things confused by over simple explanations from a lunanaut who could well be suffering from jet lag. Also, although the lunanauts dumped much non essential equipment on the moon surface before leaving, they still brought back stuff that had no intrinsic scientific value -such as the moon rock boxes. Metal from such items gets regularly included in approved gift items ( unapproved ownership is illegal in the US) to give them a mystic. Therefore, it is quite possible that if the poster's grandfather did something in an official roll for Armstrong, when Armstrong was present in an official capacity, then Neil could have well given him one of the many tie clips that had been allotted to him. The probability can be higher than one at first imagines. A photo uploaded to here would be nice and we might be able to place it in an article. As an aside: The thought's gone through my mind as to whether there was ever a cover for the Apollo plaque on the LM leg. Could it have been inscribed with a eulogy in case it landed with far too much of a bump. This is something that they would have wanted to bring back if it existed. On the video I don't see them pulling a cord and a little curtain opening, so was the removal of such a cover what was meant by the phrase 'unveil the plaque'? --Aspro (talk) 12:52, 9 September 2010 (UTC)

I was hoping we'd at least get a photo. Given the lack of evidence, I'm going to stick to my doubting thomas theory. Vespine (talk) 23:47, 12 September 2010 (UTC)

hand

Explain http://j.imagehost.org/0021/213232.png —Preceding unsigned comment added by Mind345 (talk • contribs) 13:46, 8 September 2010 (UTC)

Dreadfully inaccurate drawing. I have yet to see a hand that actually folds that way. Also, next time show some manners. TomorrowTime (talk) 14:13, 8 September 2010 (UTC)

The questioner may be learning english. The grammar of asking questions is difficult. 92.15.20.52 (talk) 16:55, 8 September 2010 (UTC)

Is it? I don't quite agree with that, and I also don't think the word "please" is a terribly advanced one. At the very least, the inclusion of "please" would make this more of a question and less of an order. TomorrowTime (talk) 17:58, 8 September 2010 (UTC)

To illustrate what it may be like for the OP, how would you ask their question politely in Japanese or Korean? 92.15.3.53 (talk) 10:28, 9 September 2010 (UTC)

To someone raised with a different language and culture to you, it is not going to be obvious that 'please explain' is a polite question, while 'explain' is an order. Hell, I've seen Americans puzzled when they get slightly cold treatment, because they don't use certain 'polite' words as often as English people expect. I've seen and heard a lot of EAL students mangle questions in English, because forming them is not straightforward. Please try to extend courtesy to those who may be struggling. 86.164.78.91 (talk) 22:08, 8 September 2010 (UTC)

Oh yes, I ran into that in London, when I was browsing at a bookseller's display, and someone near me was smoking, and I wondered if he might be willing to move a bit. He scolded me for not saying "please". To my ear the word "please" would have been slightly offensive in that context, a sort of pseudo-politeness that masks what's really an order. --Trovatore (talk) 02:00, 9 September 2010 (UTC)

Erm, I was raised in a different language and culture, if by that you meant English. English is a foreign language to me. And assuming that non-English speakers have a hard time grasping such rudimentary concepts of the English language as the difference between orders and questions and words like "please" is, frankly, a little condescending. The OP is just being rude, plain and simple. TomorrowTime (talk) 23:10, 8 September 2010 (UTC)

But you have absolutely no idea whatsoever whether the person is or is not being intentionally rude. Someone thinking something is rude does not make it so. There is no evidence to support your conclusion so one wonders why you are answering questions on a science reference desk. Perhaps saying "show some manners" is rude too. It certainly seems rude to me given that "Explain" is about as concise as you can get. They didn't include a question mark. Many languages don't include an equivalent of please as part of a question, things get lost in translation and the world keeps turning. Even if the questioner is a native speaker of English there is no obligation on their part to conform to someone's unknowable personal model of acceptable human behavior in discourse. It doesn't say "Remember to add please to your question" or "Try to be Christian in your discourse" or "Please remember to add Insha'Allah to the end of your question" at the top of this page. There is however an obligation on our part to, as it says at the top of the page, "Be polite and assume good faith, especially with users new to Wikipedia" when we answer questions here. It would be lovely if everyone phrased their questions as "Would you be so kind to answer the following question" etc but it's not going to happen. Sean.hoyland - talk 03:01, 9 September 2010 (UTC)

I should add that my comment is in no way intended to discourage further culture clashes which are always welcome given their potential for hilarity. Sean.hoyland - talk 04:09, 9 September 2010 (UTC)

I suspect that he's asking "Why do the fingers have such dramatically different lengths when straight, but fold down to roughly the same level?"

If you look at your fist from the 'top' (ie: The business end of your fist.) you'll notice that the pinky bends a lot 'sooner'. Your fingers haven't changed length or anything, they've just all folded relative to their length so you can grab stuff easily.

I think I've explained that dreadfully, but the basic idea is that it's all in how they fold. There's no unexaplained paradox.

Did that answer your question? APL (talk) 14:53, 8 September 2010 (UTC)

In effect, the answer is "evolution". ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:02, 8 September 2010 (UTC)

Saying that the answer is "evolution" is a bit vague, methinks. We might as well say that it's caused by "biology", or even "science". Without a specific elucidation of the selection pressures that favored the given outcome, "evolution" as the answer doesn't help the original poster much more than saying "magic". TenOfAllTrades(talk) 00:01, 9 September 2010 (UTC)

To get back on track, look at your own hand. You'll see the base of each finger is set at different heights, as are the tips, such that when folded into a grasp they all come down to the same level. I don't believe this is accidental - it likely has something to do with the most effect grasp, especially on tree branches where the entire hand must wrap around for grip. It would be interesting to see if all the grasping apes have this property. SamuelRiv (talk) 01:18, 9 September 2010 (UTC)

glue

i have a wood baseboard that it peeling off in 1 spot from moisture. what kind of glue should i use to secure it. is PVA glue strong enough? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 16:12, 8 September 2010 (UTC)

I'm not sure what you mean by "baseboard", but PVA is unlikely to be strong enough, by quite a long way. Wood that is bending because of moisture (even thin sheets) usually needs to be replaced to give a repair that will last more than a few days. Physchim62 (talk) 16:17, 8 September 2010 (UTC)

baseboard = skirting board, although I cannot answer the question. 86.164.78.91 (talk) 17:41, 8 September 2010 (UTC)

I'd say you'd need nails, although I think it would be safer and more aesthetically pleasing to replace. —Preceding unsigned comment added by 178.167.223.93 (talk) 17:53, 8 September 2010 (UTC)

You can use No More Nails as a glue for bonding skirting board to walls - I do it. Though to be honest that's not your biggest issue - the issue you'll need to take action on is the Damp - it ain't really an ideal thing to have in a home (assuming it is skirting board you're interested in fixing). No more nails and its equivalents are very good - I remember a great advert for it when I was little of a chopped in half Mini glued to a bill-board to highlight the strength of the bond. ny156uk (talk) 21:43, 8 September 2010 (UTC)

what kind of glue is No More Nails? is it super glue? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 21:54, 8 September 2010 (UTC)

I'm not sure - here it is on Amazon's website (http://www.amazon.co.uk/no-more-nails-DIY-Tools/s?ie=UTF8&rh=n%3A79903031%2Ck%3ANo%20More%20Nails&page=1) it's made by Unibond. Honestly i've never had any trouble with it and it bonds a very large number of materials. ny156uk (talk) 22:15, 8 September 2010 (UTC)

is it water proof? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 22:56, 8 September 2010 (UTC)

It's a gap filling adhesive. Gripfix, Gripfill and Liquid Nails are all similar. It won't bond to damp or dusty surfaces. As ny156uk points out above, you need to sort out the source of the damp before you worry about re-fixing the timber. Trugster | Talk 18:11, 9 September 2010 (UTC)

... and it's certainly not strong enough for your purpose, though some use it for straight skirting-boards that are not under any sort of pressure. I agree that sorting out the damp is a priority, but, meanwhile, screwing the skirting-board back in place will be a better solution if you can get a firm fix into the damp wall. Dbfirs 13:46, 10 September 2010 (UTC)

successor representation

Could someone explain this psychological terminology for me? Thanks! —Preceding unsigned comment added by Chimonanthus-madder (talk • contribs) 16:50, 8 September 2010 (UTC)

It's a highly technical concept introduced by Peter Dayan as a way to improve the performance of a mathematical reinforcement learning algorithm. The paper that introduced it is available online here, but you will need extensive background knowledge to make sense of it. Where did you come across the term? Looie496 (talk) 17:39, 8 September 2010 (UTC)

Studying ice

Is there a name for the study of the cryosphere? Thanks, --The High Fin Sperm Whale 17:27, 8 September 2010 (UTC)

Glaciology, I think would be it. Looie496 (talk) 17:45, 8 September 2010 (UTC)

Glaciology is only about glaciers, cryology is used to describe the study of ice in general. Smartse (talk) 21:31, 8 September 2010 (UTC)

Wrong, and wronger. Looie496 (talk) 22:04, 8 September 2010 (UTC)

I don't really know but it's possible there might not be a field narrowly defined as "study of the cryosphere". Study of the planets is still just called planetary astronomy, so maybe it's something like arctic or polar climatology or something. Vespine (talk) 23:14, 8 September 2010 (UTC)

I agree. The American Geophysical Union, which would include many people that study the cryosphere, simply has the "Cryosphere Focus Group" that is charged with dealing with "Cyrosphere Science" or "Cryospheric Science". I also agree with the above that "Glaciology" is not broad enough to capture the entirety of the cryosphere. Dragons flight (talk) 03:53, 9 September 2010 (UTC)

Bolides

What exactly is a bolide? The section about it defines it very poorly. I always thought it was a rock that skipped off the atmosphere like a pebble on a pond. And how high up do they occur? --The High Fin Sperm Whale 18:24, 8 September 2010 (UTC)

I can't imagine what sort of answer you are expecting. Why do you think there is a better answer than the one the article gives? Looie496 (talk) 18:32, 8 September 2010 (UTC)

It can be summarized as "a really bright fireball." -- kainaw™ 19:00, 8 September 2010 (UTC)

The answer is the IAU does not specify what constitutes a bolide, so it is not surprising that our article also poorly defines it. Googlemeister (talk) 19:27, 8 September 2010 (UTC)

So it's basically a very bright meteor? Then what is the name for a meteor the skips through the atmosphere? --The High Fin Sperm Whale 20:47, 8 September 2010 (UTC)

Earth-grazer. Rmhermen (talk) 22:26, 8 September 2010 (UTC)

But note that that term has another meaning, as you see from the fact that you linked to a disambiguation page. --Anonymous, 03:53 UTC, September 9, 2010.

As noted in the article, geologists have a different use of "bolide" that has nothing to do with fireballs. In their usage, a bolide is a large asteroid or comet that actually impacts the surface and creates a crater. In that context "bolide" is thus largely synonymous with "impactor". Dragons flight (talk) 17:42, 9 September 2010 (UTC)

why do we laugh when someone falls?

hi, why do we laugh when someone falls? —Preceding unsigned comment added by 122.164.221.178 (talk) 19:54, 8 September 2010 (UTC)

Check out Physical comedy and see where it takes you. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:59, 8 September 2010 (UTC)

I can't laugh at people hurting themselves badly. A lot of people can't.--178.167.223.93 (talk) 20:22, 8 September 2010 (UTC)

I do not laugh when people fall over. Its not at all funny. I'd be ashamed to laugh at someone else's distress. 92.15.30.158 (talk) 21:05, 12 September 2010 (UTC)

Perhaps this is why I never found America's Funniest Home Videos very entertaining. P. D. Cook ^{Talk to me!} 20:45, 8 September 2010 (UTC)

Well I can laugh at a lot of stuff like that. If someone falls into water or something. But if they smack their back on a concrete curb I flinch with disdust.--178.167.175.240 (talk) 22:29, 8 September 2010 (UTC)

Sometimes it is just amusing. If someone young and in good health slips on a condom on grass (I've seen it happen) then it's hilarious to me so long as there is no injury beyond slight bruising. If on the other hand an old woman falls and breaks her hip, it's not in the slightest bit amusing. Regards, --—Cyclonenim | Chat  21:35, 8 September 2010 (UTC)

A common quip is that comedy is tragedy plus distance (or time). So when Blackadder falls off of his horse (around the 00:50 mark), we can laugh without remorse, since we also know that he's not actually hurt. (And because Blackadder is a horrible fellow.) In any case slapstick is a pretty old form of comedy. I don't know if it is universal to all human cultures but I would not be surprised if it was — it is something everyone can relate to, grappling as we all always are with the damnable physical world. I'm not sure there's much more of a "scientific" answer available than this kind of speculation, though. --Mr.98 (talk) 22:51, 8 September 2010 (UTC)

A scene with neanderthals in the BBC series Walking with Cavemen makes the suggestion that physical comedy (choking and coughing up meat after eating too fast) was a type that could be very much appreciated by apes and humans, whereas more abstract jokes (A giraffe walks into a bar; the bartender says, "Why the long face?") would require an advanced mind like that of Homo sapiens. Here is a free article that talks about the evolution of humor. Very interesting question. SamuelRiv (talk) 01:23, 9 September 2010 (UTC)

You may also want to have a look at our "Schadenfreude" article, which discusses some studies that have looked into this particular phenomenon. Wikiscient (talk) 01:53, 9 September 2010 (UTC)

I have found that groups tend to laugh at individuals in pain, whereas individuals rarely laugh at another individual in pain. See Herd mentality Quadrupedaldiprotodont (talk) 14:19, 9 September 2010 (UTC)

Some have claimed that "if I fall on my ass, it is a tragedy, but if you fall on your ass it is a comedy." To me, the absence of serious injury is more important then whether it is you or I who suffers the incident. It seemed pretty funny to me when my feet flew out from under me on the icy front steps one morning and I landed on the sidewalk with no serious injury. Comedy, not tragedy. I once saw a man in a carwash in Michigan when the temperature was far below freezing. He put his money in the coin acceptor, and extended the washing wand at arms length above his car, waiting for the flow of high pressure hot soapy water to begin. He was standing on ice. When the water started squirting forcefully from the wash wand, Newton's Law sprang into action, as surely as if he were doing a space walk using a small jet to maneuver. The force moment created by the stream of water caused the man to rotate, worse than if he had slipped on ice, since after his feet left the ground as he started to fall the wand kept accelerating his rotation. He was literally upside down by the time his head hit the ground. Had he broken his neck and died, it would not have been funny. Rather he sprang up and looked around to see if anyone had witnessed his hyper-pratfall. In fact, it was hilarious, a real thigh-slapper, since he had a real-life fall equal to anything in the Three Stooges but experienced no apparent serious injury. Edison (talk) 03:30, 12 September 2010 (UTC)

Arsenic cyanide

Does arsenic form cations? Is the resulting arsenic cyanide more toxic than either arsenic or cyanide alone? --75.33.216.97 (talk) 20:43, 8 September 2010 (UTC)

Arsenic is known to form covalent bonds to cyanide (see for example Diphenylcyanoarsine), so you could presumably have something like As(CN)₅ as triphenylarsine but it would not really be a salt containing As⁵⁺ ions (as per the "arsenic cynanide" name you propose for a Group 5 element) in the way that NaCN is a salt of Na⁺. There are a bunch of arsenic-based chemical weapons, but they are not listed as acutely highly poisonous in their typical use (nor is even diphenylarsine described that way--sounds unline standard symptoms of either simple poison--organometallic compounds are neat!). DMacks (talk)

Googling on "arsenic cyanide" I found this link, from Nature in 1892, which refers to As(CN)₃ by that name. I don't know if there's a more contemporary nomenclature that calls it by a different name. (But in any case it would certainly not be triphenylarsine — I guess it could be tricyanoarsine or something.) --Trovatore (talk) 22:43, 8 September 2010 (UTC)

Ah dangit, that's what I get for posting without proofreading. Tricyanoarsine would be it per one standard naming scheme. It is CAS# 1115-98-6 , we don't seem to have a WP article on it. DMacks (talk) 22:49, 8 September 2010 (UTC)

Arsenic and cyanide poison you in different ways, so it's hard to say that one would be more poisonous than the other. It's a bit like asking if apples are healthier for you than oranges. Arsenic tends to be a fairly slow acting poison, wheras cyanide is quite quick in fatal doses, so I would guess that the cyanide would kill you first: but a lot depends on dose, mode of administration, individual sensitivity, etc. Physchim62 (talk) 23:51, 8 September 2010 (UTC)

Primary source of a wavelengths table

On X-ray_fluorescence there is a table of wavelengths that I want to use in a book. I need to know the PRIMARY SOURCE so I can obtain a copyright permission. That site has been updated recently, can the author tell me the source of the data? 71.23.85.98 (talk) 20:46, 8 September 2010 (UTC)

You'll need to ask User:LinguisticDemographer. He or she hasn't been terribly active lately (last edit back in April), but you might get a response on his/her talk page. Clarityfiend (talk) 21:10, 8 September 2010 (UTC)

This was the edit where he or she added the table, along with an acre of other stuff. Comet Tuttle (talk) 21:15, 8 September 2010 (UTC)

You can also use Moseley's law, which is the special case of the Rydberg formula, which is a simplification of a more thorough quantum mechanical treatment of emission spectral lines. These values should be easy to calculate and independently verify from the fundamental principle, using a simple spreadsheet or calculator. All you need is to understand the notation (e.g., K-alpha, see also, Siegbahn notation). And, you need the Rydberg constant, which is available on our article, with a citation, (and probably appears in any text book on spectroscopy or basic atomic physics / chemistry if you want to verify). Nimur (talk) 21:23, 8 September 2010 (UTC)

(In the US) You can't copyright a table of factual data see: Feist v. Rural, so you don't need permission. Ariel. (talk) 21:29, 8 September 2010 (UTC)

Actually, it looks like Wikipedia has a copyright problem here. The table that is quoted in X-ray_fluorescence is obviously a selection of the primary data that's available, but the selection criteria are neither clear nor objective. I would guess that the table has been copied from a manufacturer's handbook, in which case it's copyvio. Physchim62 (talk) 22:57, 8 September 2010 (UTC)

The most quoted source of primary X-ray data is NBS 14. This is technically under copyright (even though it is a U.S. government work) and so you need to ask NIST in order to make a commercial reproduction that doesn't fall under fair use. Physchim62 (talk) 23:07, 8 September 2010 (UTC)

yellow

is white PVA glue the same as yellow PVA glue ? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 22:01, 8 September 2010 (UTC)

Oops sorry meant to say - read Carpenter's glue. ny156uk (talk) 22:38, 8 September 2010 (UTC)

September 9

Laser beam expansion rates?

I've seen a few articles recently about laserstrikes on commercial aircraft coming in to land at various airports around the world, including a few discussing arrests of the perpetrators. The articles always mention how the laser fully illuminates the cockpit, and in one case the pilot was temporarily blinded and the co-pilot had to land the plane. That makes me wonder how wide the laser beam is at these altitudes. Considering it's only 1 or 2 mm wide at the point of emission, how wide would your average Class 2 laser be at 2000 feet? Or are these people using Class 3+ lasers to do their dirty work? Masked Booby (talk) 01:50, 9 September 2010 (UTC)

Do you have links to these articles? --Jayron32 01:56, 9 September 2010 (UTC)

This one was on BBC News some time back: Police fight back on laser threat. Nimur (talk) 01:58, 9 September 2010 (UTC)

There are many, if you had bothered to look, Jayron. Google News results Masked Booby (talk) 02:31, 9 September 2010 (UTC)

My 50 mW green laser pointer (very typical for the kind used in these laser attacks) has a beam that's 5 mm wide at 383 cm, so that's a beam angle of 0.0013 radians. At 1000 m, for example, it would be 1.3 m wide; at 2000 m, 2.6 m wide. --99.237.234.104 (talk) 03:10, 9 September 2010 (UTC)

Yes, but there will also be a loss of luminosity commensurate with the spreading of the beam. A beam that puts a dot of radius 1.3 meters will be (1.3/.005)² times less luminous, at those levels it may not even be noticed... --Jayron32 03:17, 9 September 2010 (UTC)

Slight correction: the laser beam is 2 mm at the origin, which makes the beam angle only 0.00078 radians. The beam would only be 0.8 m wide at 1000 m.

Pilots definitely do notice green lasers being shone at them at distances on the order of 1000 m. Pilots coming in for landing routinely suffer flash blindness from them, sometimes forcing the co-pilot to take over and land the plane. --99.237.234.104 (talk) 03:25, 9 September 2010 (UTC)

. Please cite sources; this is a Reference Desk. Comet Tuttle (talk) 17:09, 9 September 2010 (UTC)

Um, what I said about the pilots comes directly from the links that the OP gave. As for my own experiment, I admit that's OR. --99.237.234.104 (talk) 07:08, 10 September 2010 (UTC)

Hostage survival rates in modern times?

Here's an unusual question for you - has anyone ever studied/compiled statistics on the survival rates of hostages in modern times? By modern times I mean since the widespread prevalence of involuntary hostage-taking as opposed to the centuries old practice of exchanging people as collateral of sorts. Masked Booby (talk) 02:36, 9 September 2010 (UTC)

The FBI have apparently tried to do something with their HOBAS system but it only covers the US and Canada. See here for example. It gets a mention in FBI_Crisis_Negotiation_Unit#Initiatives. Sean.hoyland - talk 05:07, 9 September 2010 (UTC)

Stamp protection

The last time I bought pre-stamped envelopes from the post office (United States, btw), the stamps were actually pre-printed to the envelope. I took a good look at them, and there doesn't appear to be anything special about the stamps. They seem to be made of normal ink, and I can't see anything distinctive between them. Is there any kind of hidden protection on the envelopes or in the printed stamp to prevent someone from getting a high quality scan of the stamp and printing their own? Someguy1221 (talk) 09:50, 9 September 2010 (UTC)

In the UK stamps have, I understand, invisible phosphorous markings which allow their amounts to be automatically read. Your envelopes may have something similar. You would probably have to fake the envelope as well, which would cost more than the cost of the stamps. One of the stamps articles says that stamps often have hidden information coded into them, so there may be a secret code that signifies that design of envelope it should be with. On pragmatic grounds as well as ethical, do not do it as you will probably be found out. 92.15.3.53 (talk) 10:53, 9 September 2010 (UTC)

An interesting side note; a few years ago as an experiment I made a postage frank in mspaint (I don't have a scanner), printed it onto an envelope with a inkjet printer, and mailed it to myself. It arrived 82.44.55.25 (talk) 11:11, 9 September 2010 (UTC)

And technically, one could use a 50 year old stamp or older (with sufficient postage) and it would not have the same hidden markings, but would still be a valid stamp. Googlemeister (talk) 13:02, 9 September 2010 (UTC)

I wasn't aware of the word "franking" in that context. It's perhaps appropriate that the Canadian satirical magazine Frank got into a bit of trouble for publishing fake stamps with bizarre and/or humorous saying and pictures on them. Despite Canada Post claiming that they used state of the art scanning technology to prevent fraud of this kind, the writers found that virtually all their illicit mail was delivered, regardless of how obviously fake the stamps were. I get the impression that the amount of fraud taking place is so low that it would be more trouble than it's worth to crack down on it. Matt Deres (talk) 13:37, 9 September 2010 (UTC)

All US stamps have been tagged (read this article by someone from the American Philatelic Society) since the 1970s. As Googlemeister notes, it's possible to use older stamps; as a stamp collector buying from other collectors, I've often gotten envelopes franked with lots of older stamps from when first-class postage was a lot less than it is today. Nyttend (talk) 00:58, 10 September 2010 (UTC)

Over-efficiency as a cause of extinction

If evolution favors those species which are relatively best at adapting to their environment, can over-efficiency then be considered a cause of extinction? For example, if a predator evolves over time to succeed 100% of the time, and its prey does not recover, and the predator adapts no alternative prey, then the said predator goes extinct (for the purpose of this question at least). Now if a predator is successful only 5% of the time but thrives, then could it be said that efficiency is not a favored trait (unless it is relative to the evolution of its prey's efficiency of escaping), so a species that is "over"-efficient, or "uber-adaptable", may go extinct. I somewhere heard this could be applied to saber-toothed cats. Is this a valid concept and where can I find a good article on this? (using a dynamic IP; may change) 64.85.214.138 (talk) 10:07, 9 September 2010 (UTC)

Sounds akin to Malthusianism and the Malthusian catastrophe - albeit I get the impression he was more concerned about humans outgrowing the carrying capacity of the earth. --Tagishsimon (talk) 10:19, 9 September 2010 (UTC)

I was speaking more towards an already extinct species, one that did not employ agriculture or domestication of other animals. I don't mean this as an overpopulation/humans-are-bad question. Sorry for not clarifying. 64.85.214.138 (talk) 10:35, 9 September 2010 (UTC)

The model still applies. Malthus may have been concerned with humans, but (AFAIK) was one of the first to suggest that populations of any sort are limited by resources available to them. I'm sure your extinction concept is valid, though I cannot point you at examples. --Tagishsimon (talk) 10:38, 9 September 2010 (UTC)

The Lotka–Volterra equations describes what typically happens in predator-prey cycles. Occasionally there is a boom of prey, this is followed by a boom of predator. This causes a crash of prey, followed (inevitably) by a crash of predators. It only rarely drives one of the species to extinction. However, some prey have evolved solutions that have made their predators extinct; see the 13 year cicada for an example, although that idea might not be correct. CS Miller (talk) 12:03, 9 September 2010 (UTC)

I have heard of this, with snowshoe hares I think, but this type of boom-bust cycle has had time to evolve so that it settles at some kind of equilibrium, and then swings in favor of the other species, then temporary equilibrium, then swings in favor of the other other species, etc. In your cicada example, you refer to when prey out-evolve their predator, what I am referring to is when a predator out-evolves its prey -- when no equilibrium has time to evolve. It is just boom- but no -bust; it's boom-you're prey is extinct and then boom-you yourself are extinct. When prey win, adaptability pays off; when predators win, they have no food (unless they can create or grow their own -- I'm focusing only on predators that hunt or scavenge). (using a dynamic IP; may change) 64.85.220.14 (talk) 12:40, 9 September 2010 (UTC)

The Lotka-Volterra equations may be a bit of a red herring for the purposes of this questions. The solutions to those equations are not stable limit cycles, but neutrally stable. This means there is nothing internal to the model that prevents the kinds of extinctions that the OP suggests. As I see it, the problem that the OP describes is not extinction through `over efficiency', but extinction due to over-specialization. Basically, if a species' ability to grow/reproduce is tied too tightly to a single other species, then the extinction of one can cause the extinction of the other. This has probably happened many times through history. This does cause evolutionary pressure. For instance, many plant and animal pathogens have evolved NON-lethality, essentially to circumvent the problem the OP describes. I suspect very few predators are limited to EXACTLY one prey species, and many exhibit prey-switching behaviour based upon prey density. SemanticMantis (talk) 19:11, 9 September 2010 (UTC)

Oh, and the LV equations WILL produce the single boom, both bust when parameterized as the OP describes above. SemanticMantis (talk) 19:13, 9 September 2010 (UTC)

Headache + lack of exercise

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 talk page discussion (if a link has been provided). --TenOfAllTrades(talk) 14:17, 9 September 2010 (UTC)

k1

are there any k1 kickboxing deaths?—Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 13:28, 9 September 2010 (UTC)

Try the Entertainment desk. Brammers (talk/c) 06:18, 10 September 2010 (UTC)

power

How does the teethbrush charger transfer power to the teethbrush, when both parts are plantic because they get wet? Plastic doesn't conduct electrity —Preceding unsigned comment added by Whovandr. (talk • contribs) 13:38, 9 September 2010 (UTC)

Electromagnetic induction --Tagishsimon (talk) 13:39, 9 September 2010 (UTC)

Inductive charging, specifically. -- Finlay McWalter ☻ Talk 13:40, 9 September 2010 (UTC)

Why can't we remove scars?

When I was seven I got a tiny burn to the side of my face.

It looks like tere is a layer of skin missing from the shape of the burn and its pretty much invisible.

If skin cells are constantly regenerating why do we have scars?

There is no scar tissue from the wound its just looks like a tiny portion/layer of skin is missing.

I know its not possible to remove a scar with any of the current methods available. but would it ever be possible to remove a scar/ what would have to be done scientifically to remove a scar? —Preceding unsigned comment added by 139.62.222.73 (talk) 13:53, 9 September 2010 (UTC)

With MatriStem Wound Powder, a lady grew back part of her pinky finger. source: http://www.cnn.com/2010/HEALTH/09/09/pinky.regeneration.surgery/ 20.137.18.50 (talk) 14:30, 9 September 2010 (UTC)

yea, I heard about that but that is a little off topic.

Anybody else got info? —Preceding unsigned comment added by 139.62.86.190 (talk) 09:11, 10 September 2010 (UTC)

We sort of answered this question already here. The problem with scars is that the collagen gets deposited in a linear fashion to bridge the defect and hold it together, instead of in a random "basketweave" fashion which is what happens during normal skin development. In order to "remove" the scar, we would have to have a way to re-organize the dermal collagen. From a technical standpoint, this would require either a cell-based therapy involving injection of cells programmed to degrade the scar and re-establish the connective tissue correctly (remotely possible with current tech), or perhaps more futuristic technology like nanorobots (i.e. Sci-Fi). --- Medical geneticist (talk) 16:44, 10 September 2010 (UTC)

Ceramic pastes with high R values

I have these little metal rings used for holding eggs in while you fry them to keep them from running all over the place. These metal rings have stainless steel loop handles that stick up which get so hot as to be untouchable with unprotected fingers. I want to coat the top part of those stainless steel loop handles with some kind of material that is very resistant to changing its temperature. What commercially available product would fit the bill here? Thanks. 20.137.18.50 (talk) 14:24, 9 September 2010 (UTC)

I am dubious that a suitable material exists that you could successfully apply non-industrially (I wouldn't recommend asbestos!), though I'm open to enlightenment. Have you considered the alternative of using an oven glove or a similar but makeshift device? 87.81.230.195 (talk) 17:03, 9 September 2010 (UTC)

Wood? 92.29.121.183 (talk) 19:00, 9 September 2010 (UTC)

First: are you cooking on a gas range with it turned up really high? I fry eggs in a hot pan but turn the gas back down low. Once the albumin has turned white round the edges it should be possible to take the ring off and finish cooking. The loops tend to remain coolish (although you may have different ones). Have you tried lifting them off with a Carving Fork? Or an inverted wire coat hanger? Back to your question about R values. Polytetrafluoroethylene has good heat resistance whilst reaming a good insulator. Likewise there is Silicone rubber. The boots of the Luna astronaut where soled with this stuff to avoid them getting toasted tootsies. A way of getting very small quantity would be to take a ring to an electrical wholesaler and ask to see some cable for connecting hot water immersion heaters or other high temperature cable. The cable outer sleeving may just be the right size to slip over the loop. What would Gordon Ramsay use? His teeth? --Aspro (talk) 19:03, 9 September 2010 (UTC)

Your best bet may not be insulation, but active cooling. Soldering a large number of copper fins to the handles, or making handle extensions from loosely-coiled thin steel wire, may let natural convection cool the handles (or extensions) to the point where you can safely touch them. --Carnildo (talk) 22:03, 10 September 2010 (UTC)

Scientists break the speed of light

Are there any comments about such rumors? I can see them coming up again.--Email4mobile (talk) 14:45, 9 September 2010 (UTC)

We have an article on faster-than-light phenomena, including quantum tunneling as cited in the first Google result I looked at. It appears that this specific phenomenon is the 50-year-old Hartman effect. — Lomn 15:08, 9 September 2010 (UTC)

How about the two German scientists' (Sorry may be the 2nd older result about NEC reasearch)?--Email4mobile (talk) 15:20, 9 September 2010 (UTC)

The Hartman effect linked above specifically names the German scientists in question. Note that the article is now 3 years old. — Lomn 15:50, 9 September 2010 (UTC)

Potassium iodate used in bread

I always see this chemical used in bread. What does it exactly do? The articles are not specific. Would potassium chlorate be a cheaper alternative? --Chemicalinterest (talk) 15:31, 9 September 2010 (UTC)

It's used to ensure that people get enough iodine in their diet for correct thyroid function. Potassium iodate is commonly added to table salt for the same reason. A little bit of excess dietary iodine does you no harm, but a deficiency causes goitre. So no, you couldn't use potassium chlorate as an alternative! Incidentally, they use the iodate rather than the iodide because the iodide will slowly oxidize to elemental iodine, which wouldn't look too pretty in your bread or your salt. Physchim62 (talk) 15:35, 9 September 2010 (UTC)

A relevant paper abstract is here. Potassium bromate used to be used instead, as a bread improver. Brammers (talk/c) 15:37, 9 September 2010 (UTC)

No, the reasons for adding the two salts are different. Potassium bromate used to be used as a flour improver (apparently it strengthens the dough that is formed), although this rare nowadays. The potassium iodate that is added to flour in some countries is at a much lower concentration (about 2 ppm seems a common level), probably too low to have a useful effect on the strength of the dough. Physchim62 (talk) 15:59, 9 September 2010 (UTC)

I live in the US, if that helps. --Chemicalinterest (talk) 16:04, 9 September 2010 (UTC)

I do not see anything about iodine-enriched bread. The KIO₃ articles says it is used as a maturing agent. --Chemicalinterest (talk) 16:43, 9 September 2010 (UTC)

KI is added to my salt. Not the oxidizing anion iodate. --Chemicalinterest (talk) 16:43, 9 September 2010 (UTC)

Some countries use iodate for iodizing salt [2]. As for iodized flour (which will make iodized bread), our article on iodine deficiency mentions it with a reference. Physchim62 (talk) 16:58, 9 September 2010 (UTC)

In NZ, iodised salt is used to make iodine fortified bread [3] [4] [5]. I know folic acid fortified flour is used for bread in some countries including Australia (as also mentioned in our article), in NZ the plan was to add it during baking to enable organic breads to be excluded (I believe) [6] but the plan was deferred by the new government. Nil Einne (talk) 18:03, 9 September 2010 (UTC)

postman opened my door?

Question and responses removed. Questions that contain the phrase "Can I sue them" are requests for legal advice and should not be answered. Seek a lawyer if you intend to sue anyone. --Jayron32 04:21, 10 September 2010 (UTC)

Giants

As we know, there are many myths related to the existance of giants. However, in reality, actual "giants" are rare and those who have existed (eg. Robert Wadlow) are not as tall as those of the myths. So, my question is: what are the factors that limit people from growing 10, 12 or 20 feet tall? Many animals are bred for specific characteristics (eg. the Clydesdale horse); giraffes are tall and elephants are huge; in the past, there were many varieties of megafauna. So why not humans? 142.46.225.77 (talk) 15:58, 9 September 2010 (UTC)

It depends on how widely you're willing to apply the term 'human.' See Gigantopithecus, for example. Restricting ourselves to H. sapiens and close relatives, it seems that the right circumstances happened not to arise favouring development in that direction, but in principle they might in the (far) future. However, the necessary evolutionary changes would not be insignificant: consider that, like Robert Wadlow whom you mentioned, many human giants suffer from foot/leg/back problems because current human anatomy is not 'designed' to support their weight (square-cube law and all that). 87.81.230.195 (talk) 16:54, 9 September 2010 (UTC)

Our article Human height ought to answer this question, but does not; it just says, frustratingly, that growth subsides at a certain age. Once we've had a great answer here, could a knowledgeable editor improve Human height by adding the answer? Comet Tuttle (talk) 16:57, 9 September 2010 (UTC)

The ref to Gigantopithecus reminded me of a curious idea relating to human's body size (and brain size). Terrence Deacon, in his book The Symbolic Species, proposes a theory about why human brains differ from other primates. The way human brains, and bodies, develop (in the womb and in early childhood) "can perhaps best be described as though a human child is growing a brain from a much larger primate species. The human pattern of brain growth is appropriate for a gigantic ape, while the pattern of body growth is appropriate for a large chimp." How large an ape? Something around the size of Gigantopithecus. He explores the idea that humans did not evolve larger brains so much as smaller bodies. Or put another way, evolved larger brains by slowing the development of body growth but not brain growth. A key point is that humans don't simply have "larger brains" than other primates. Each part of the brain differs in how much larger or smaller than they "should be" for a human sized ape. The prefrontal cortex is the most "enlarged" (over 200%) and the olfactory bulbs the most "reduced". There's more to it than just this, of course, but it struck me as a curious notion. Perhaps a link to human neoteny? Pfly (talk) 19:36, 9 September 2010 (UTC)

Hmm, similar to some of Elaine Morgan's stuff in The Descent of the Child. She adds that the apparently anomalous lifespan of humans, compared to other apes our size, is in line with the size of our brains. So, that would be another way that we are more 'large with small bodies' than 'small with large brains'. 86.164.78.91 (talk) 13:16, 10 September 2010 (UTC)

There is little doubt that humans could be bred to be much larger than we are. But it would take hundreds of years of selective breeding. Who would go to the trouble? Looie496 (talk) 22:51, 9 September 2010 (UTC)

This guy's parents? Googlemeister (talk) 14:24, 10 September 2010 (UTC)

87.81.230.195 (talk · contribs) made some very good points "changes would not be insignificant" and "current human anatomy" re carrying that amount of weight. For a human to be that tall they would have to be so many changes that they might no longer be 'human', as we recognise them. Note that Wadlow at least looked rather thin and still had great problems related to his height /weight combination.("he required leg braces to walk, and had little feeling in his legs and feet.") He was 'only' 8 ft 11.1 in (2.72 m) and and weighed 485 lb (220 kg) at his death at 22.

• Lets compare a 6 footer to a 12 footer, keeping all dimensions in proportion so that they remain human. Height x 2, breadth x 2, depth x 2, I believe that their weight would therefore be 2³ = 8 x. However, all else being equal, muscular strength is relative to Muscle cross-sectional area (see point 2), so their muscles if remaining proportional, would only be 2x2=4. Weight x 8 but strength x 2 means that they would be half as strong as a 'normal' sized person.

• The bottom surface of the feet would also be x 4, with 8 x weight so twice as much weight per surface area.(look at elephant feet, very broad/flat and the legs, relatively short and very thickened bones. Highly modified from their distant ancestors and they are a quadruped).

• The spines cross section would also only x4 be while carrying 8x as much weight.

• Cooling might also be a problem, as the bodies volume has increased x8 but the Body surface area likely by a lesser amount. Not sure and I haven't calculated this. Elephants though tend to have large ears that are are also used as cooling devices.

♦ It seems our Giant human would live a (possibly) short life with constantly aching flat feet, if they could walk at all, scoliosis of the spine, and be very feeble. They could develop hugely thickened leg (and other) bones and huge feet. Or they would need to walk supporting the upper body on their knuckles (somewhat like Mountain gorillas) to spread the weight, becoming essentially a quadruped.

♦ There are probably other factors making giants unlikely that I have not covered, ie. blood pressure changes and food supply. If there are any flaws in my reasoning here, please point it out. 220.101 talk^\Contribs 05:31, 11 September 2010 (UTC)

Anatomy of a brain

Are human brains wired basically the same, the anatomy the same? Is it the chemicals and hormones that differ in each person, which control the strength of the signals among other things that make us unique? —Preceding unsigned comment added by 71.137.244.210 (talk) 16:09, 9 September 2010 (UTC)

To both of your questions, the answer is "yes and no." At the level of "gross anatomy" (what you can see by eye when you dissect a brain) the neuroanatomy is basically the same. Everyone generally has the same major structures, linked together by the same main bundles of axons. We also have generally the same wiring when you look at those structures under a microscope, for example the main cell layers of the cerebral cortex, the main cell layers cerebellar cortex, etc. However, it is safe to say that everyone has a unique microscopic arrangement at the level of the actual distribution of neurons in any given layer at any particular part of the brain, and a unique set of connections between neurons, etc. Secondly, in a general sense, we all have the same neurochemistry, meaning that our brains use the same neurotransmitters and neurotransmitter receptors to transmit signals between neurons. We share the same basic groups of neurons in various parts of the brain that use particular types of neurotransmitters. However, at a cellular level there will be all kinds of differences and fluctuations in terms of the strength of individual synapses. --- Medical geneticist (talk) 17:42, 9 September 2010 (UTC)

Right. There are hormonal factors that have important effects on personality, and probably anatomical differences that correlate with intelligence, but those things don't really make us unique. What makes us unique is memory, in combination with other effects of experience. Looie496 (talk) 22:48, 9 September 2010 (UTC)

What do you mean or if you could provide examples would be anatomical differences that correlate with intelligence? —Preceding unsigned comment added by 71.147.4.67 (talk) 03:19, 10 September 2010 (UTC)

See Neuroscience and intelligence. Lots of that stuff is pretty iffy in my opinion, though. Looie496 (talk) 06:13, 10 September 2010 (UTC)

Integrated theory

The reason I've asked about breaking light speed rumors is that some are trying to reformulate physics and its laws reasoning that under the name of Integrated theory like this web under construction.

I will quote his introduction here:

"There is a need for a single unified theory, could explain all the phenomena of nature. and reduce all theories of physics in one, able to explain and interpret what interpreted by earlier theories and give more than all. predict conclusions of the future, of the realities of the universe. And interpretation of what all theories can not be interpreted or understood. Then put a convincing philosophical theory, based on scientific facts that are not in doubt, the aim to unification of the human thinking so not to be dispute. Uniting all forces of nature on the grounds that is properties of the material. And give causal explanation of all events and phenomena. And be simple and streamlined, universe simpler. And re-explanation of what other theories failed to interpret. This theory is different and collide with the old concepts, but not with the truth, a single, unified, comprehensive and integrated basis on truth. Most importantly, uniformity of laws, which apply to the solar system with atom Laws. it is causal theory of distinction. most of our concepts of physics, was based on erroneous grounds. such as Characteristics of the wave for the particles, and zero mass, and the idle talk about the fourth dimension, and the madness of Mathematics at super string theory, and leaps electrons Bohr, and the shortsightedness of the Big Bang theory. Theory relies new foundations and the most important is the new atomic model, adds particles to atom, smaller than electrons. and focuses on the structure of elementary particles. We got to know that this theory interpret black holes, dark matter, and sunspots. In short, tell us the truth about the universe. Relates to the impact of global warming of Earth's surface. Focus on the gravity, and develop a new understanding of energy. And provide a deeper understanding of the so-called forces of nature, and give a causal definition of the charge, and then address the speed of light, it have the ability to give causal answers to, all phenomena of nature. At first it seems weird and difficult to understand, because they contradict with the foundations of earlier theories, but after you complete the understanding it will be simple and very easy, and not to forget, and internally consistent, and enable us to conclude everything easily.", Dr: Sadi Said Mona

Do you think this mas is serious?--Email4mobile (talk) 17:03, 9 September 2010 (UTC)

Serious? Sure. Correct? Unlikely. See Fringe science and Pseudoscience. People claiming to have re-invented large segments of the study of physics are pretty common on the Internet, and Wikipedia's WP:V verifiability policy came into being largely to stop physics cranks from posting their fringe theories as articles here. Comet Tuttle (talk) 17:13, 9 September 2010 (UTC)

It's important not to conflate fringe with crank. The high-risk-high-reward area of any discipline is always on the fringe. Unfortunately the well-intentioned practice of saying fringe when you really mean crank has tainted the former word, and we now probably need a new one. --Trovatore (talk) 21:15, 9 September 2010 (UTC)

You're right; I'll be more careful in the future. Comet Tuttle (talk) 19:11, 10 September 2010 (UTC)

Feynman Famous?

Hello again, this is sort of a follow-up to a previous question I asked a few weeks ago about how to pronounce his name. After reading "Surely You're joking", I started on a collection of his letters, and was struck by a passage that said how Feynman was very famous with the general public, almost as much as Stephen Hawking or Albert Einstein. However, when I told a few people that I was reading the letters of Feynman, only two people from the twenty I asked knew who he was (one was my Physics teacher, who I don't think counts as the general public); yet I have no doubt they would all have know who Einstein or Hawking were.

Is Feynman simply much more famous in the US? (I live in the UK)--HarmoniousMembrane (talk) 17:25, 9 September 2010 (UTC)

I would say that Feynman (and also Hawking) have largely been known in the public for their efforts to popularize science. People who are effectively spokesmen for science tend to be known during their lifetimes, but the public forgets about them relatively quickly after they die. By contrast, Einstein is known to the public for his actual science (other examples might be Newton or Galileo). When the science itself becomes part of the public awareness, then the person behind it tends to have a much longer legacy. Of course Feynman also did top notch science, but that was never really why he was known to the general public. Dragons flight (talk) 18:05, 9 September 2010 (UTC)

If Feynman had had crazy hair and his work could be put in a nutshell as compactly as $E=mc^{2}$ his image and therefore identity might have also been conveyed to Joe Six-pack via cartoons and other cultural pellets consumed by the general public. 20.137.18.50 (talk) 18:10, 9 September 2010 (UTC)

Good point! Path integrals just don't have the same simplistic elegance. P. D. Cook ^{Talk to me!} 18:22, 9 September 2010 (UTC)

From the Rogers Commission Report article regarding Feynman's role in investigating the Space Shuttle Challenger disaster: "During a televised hearing, Feynman famously demonstrated how the O-rings became less resilient and subject to seal failures at ice-cold temperatures by immersing a sample of the material in a glass of ice water." That may have been the point at which he got the most attention from the general public. Wikiscient (talk) 19:02, 9 September 2010 (UTC)

Surely it's more impact than compact that gives $E=mc^{2}$ and its discoverer lasting fame. --Sean 22:52, 9 September 2010 (UTC)

It's definitely true that the association with nuclear weapons boosted that particular equation's notice in the public eye (graphically depicted in this Time magazine cover from 1946), but Einstein was actually already pretty famous before the atomic bomb, on account of the widely publicized and popularized success of theories after the Solar eclipse of May 29, 1919, and because of his very public activism during World War I and against the Nazis. He was already a public figure long before the bomb, but the bomb really capped it off. --Mr.98 (talk) 23:46, 9 September 2010 (UTC)

Nazis were World War II. SpinningSpark 01:14, 10 September 2010 (UTC)

The Nazis took over and did all sorts of nefarious things related to Einstein well before WWII. (Much less if we taken into account their pre-power hijinks as well.) See Deutsche Physik, among other things. Einstein was known for his anti-Nazi stance years before the war had started. --Mr.98 (talk) 01:23, 10 September 2010 (UTC)

And Einstein was active in the pacifism movement during WW1, even though Wikipedia's article about him doesn't seem to mention it. See Martin Gilbert's book on the war, for example. So "during WW1 and against the Nazis" was quite correct. --Anonymous, 03:51 UTC, September 10, 2010.

Oh, yes, I didn't realize that was the part under dispute. Einstein was very active during World War I as well, I guess I should clarify. He was one of the most prominent German scientists who was outspoken against German militarism (most of the others climbed on the Kaiser's bandwagon without hesitation). Wikipedia's Einstein article is presently a huge mess and seems to have been taken over by at least one POV-pusher, so I wouldn't put much faith in it myself, unfortunately! --Mr.98 (talk) 12:43, 10 September 2010 (UTC)

Einstein was a popular figure starting in 1919, amplified in the 1930s, sanctified in the 1940s, and at his death became the symbol of "science" around the world. Hawking on the other hand was mostly popularized through A Brief History of Time in the late 1980s, if I recall correctly. Hawking is culturally poignant not because of his scientific work, but because of his "brain in a ruined body" symbolism. I don't think he's quite on the same level as Einstein as a cultural icon, but the symbolism is pretty strong. I suspect that in the long run, he will be more of a Feynman-level of popular understanding — someone that smart, science-nerds know about, but not the general public (unlike Einstein). Incidentally, though, my wife had a shirt on the other day with Einstein's photo on it, and someone (who happens to be quite uneducated) asked her, earnestly, if it was George Washington. So I suppose we should not overestimate even his penetration into the mind of the common man! --Mr.98 (talk) 01:28, 10 September 2010 (UTC)

FWIW, I think Feynman wrote in that book that in WWII Americans knew Einstein as a mathematician; few people knew what physics is. Imagine Reason (talk) 21:50, 10 September 2010 (UTC)

Lumen Loss

All other things being equal, what would be the approximate lumen loss of a 130v 150w halogen lamp operating from a 120v source compared to a 120v 150w halogen lamp operating from that same 120v source (nominally 2400 lumens). This (marketing?) technique is sometimes used to advertise a longer lifetime or enhanced ruggedness but of course at the expense of lumens. hydnjo (talk) 20:09, 9 September 2010 (UTC)

Wrong question: Marketing? The nominal voltage may be 120 but 50% of the consumers live close enough to the sub-transformer to be supplied with 120 plus volts. This would shorten the life of a 120 volt rated bulb filament dramatically. Hence the 130 rating. Make sense?! --Aspro (talk) 20:53, 9 September 2010 (UTC)

Also, The human eye is more sensitive to sorter wave lengths (ie. 550 nm). An over-run bulb will run hotter (but not more efficiently). It will appear brighter (more energy being converted into light) and in wave lengths the eye is more sensitive to ) but to quote Tyrell: 'The light that burns twice as bright burns half as long, and you have burned so very very brightly, Roy. Look at you. You're the prodigal son. You're quite a prize! [7] --Aspro (talk) 21:05, 9 September 2010 (UTC)

The two products are sold side by side from the same manufacturer. One (the 120v 150w rated} has no claim as to extended lifetime or increased ruggedness. Right next to it is the 130v 150w rated one with the claims mentioned. I'm pretty sure that the two lamps are intended to be sourced from the same 120v (nominal) supply, I'm trying to find out what the reduction in lumens would be if I opt for the 130v version (claimed lifetime of 4000 hours if operated at 120v) vs the 120v version (claimed lifetime of 2000 hours if operated at 120v). Does that clarify? hydnjo (talk) 21:14, 9 September 2010 (UTC)

There is about a 9% difference between 120 and 130 volts. If your board voltage is 130 v you should be asking yourself if you want to run up and down the steps changing blown bulbs or not. If your at, or below 120v, then it don't really mater and its academic. The human eye adapts and I don't think you will notice, so it's a pointless question asking about lumen. In photography I think it will be less than a third of a stop. For what earthy purpose prey, do you neeeed to be sooo precise? Get someone to meter your supply and tell you how many volts you're getting (important:switch some things on so you have some load -like a cooker). THAT voltage should indicate what bulbs you buy, rather than how many lumens you feeeel you need. If however you really mean lumens, then please repost on Reference desk/Trivia --Aspro (talk) 21:46, 9 September 2010 (UTC)

Just in case anyone gets confused over in the UK or Australia. There they have an asymmetrical nominal voltage declaration. Bulbs carry the 240 volt rating, which is correct for the average voltage delivered. This takes account of the higher voltages that occur nearer to the sub-station. The voltage supply is of much better quality and thus, two voltage options on bulbs are not required.--Aspro (talk) 21:50, 9 September 2010 (UTC)

This has gone way beyond my intended concern but here goes anyway. The security floodlights around my residence are doubly housed 150w halogen lit. My home is powered by a nominal 120v service. I need to replace one or two of the bulbs at this time. For reasons of aesthetics I don't wish to have one lamp significantly less bright than its 150 cm away neighboring lamp. I was hoping to get a response as to how much (qualitatively) brightness difference I might expect to perceive from opting for the 130v version as opposed to the nearby 120v version - that's all! This thread has gone way off track from my original question perhaps because of my in-artfull presentation but if you think you know what I'm asking please chime in. Thanks hydnjo (talk) 22:41, 9 September 2010 (UTC)

Power varies to the square of voltage. Assuming the load resistance does not change with the lower voltage (not an entirely accurate assumption - cooler running = lower resistance) and the efficiency is linear with power (also not entirely accurate) the radiant output will be (120/130)² = 85% of previous output. You will be 15%, or 360 lumens down. This book suggests that a more accurate formula is 3.38 rather than 2 as the exponent. Using that gives you a loss of 24% rather than 15% from the simplistic calculation. SpinningSpark 00:37, 10 September 2010 (UTC)

We have an article on this Lamp rerating. --Gr8xoz (talk) 00:50, 10 September 2010 (UTC)

• Thanks to both SpinningSpark and Gr8xoz, you both figured out exactly what I was asking and both of you provided excellent references. Looks like I should stick with the same 120v lamps that are all around the house as the luminosity difference with the 130v lamps would be quite noticeable and annoying and not worth the extra life expectancy. And Gr8xoz you've shown once again that WHAAOE! hydnjo (talk) 01:32, 10 September 2010 (UTC)

This analysis has been done in detail constantly by lighting engineers since about 1881, with tradeoffs between efficacy and lifetime carefully measured and analyzed. Edison (talk) 05:27, 10 September 2010 (UTC)

I'm sure that's true, but without providing any links or information that answer the question (as SpinningSpark and Gr8xoz did), you haven't really added anything to the answer. Did you mean to include a link? 86.164.78.91 (talk) 13:04, 10 September 2010 (UTC)

It is not a requirement to provide a link or reference with every posting. Sometimes a lifetime of study of a subject provides insights which may be helpful. One may have read something in a reference work which is miles away in a library and not easily citeable. An additional point is that empirical formulas derived for, say ordinary tungsten filaments in vacuum may not be accurate for a bulb filled with inert gases, or those for a bulb filled with inert gas may not be accurate for halogen, and formulas accurate for 240 volt filaments may not be accurate for 120 volt or lower rated filaments. These are not laws of physics like an ideal gas law or Ohm's law. Edison (talk) 15:16, 10 September 2010 (UTC)

• OK - resolved without the template. Additional thanks to Edison for his pragmatism and to 86.164.78.91 for their support after some of the earlier comments. Edison is right, this has lots of scientific study and empirical evidence available. The reason for there being two such similar products next to each other is that a compromise product (the 130v version operated at 120v) has been found to be marketable with the portable "rough duty" customers who are less concerned about the amount of light loss (20% - 30%) than the ability to withstand rough handling. The 120v version is the optimal choice for the average user with a fixed (non-bumpy) location and provides the appropriate balance of luminosity and life expectancy. hydnjo (talk) 21:03, 10 September 2010 (UTC)

Asbestos: regulation and risk to neighbours in the UK

Hello.

It seems that most asbestos legislation in the UK deals with occupational safety - the safety of workers and the responsibility of employers. Most of the science I can find deals with the same thing. I am interested in the risk to the general public - and nearby neighbours in particular - that may or may not be caused by work such as demolition.

So, my question to Wikipedians who wish to help me is:

What are the known risks to occupants of neighbouring buildings, of the demolition of nearby buildings which are known to contain asbestos? What precautions - in relation to those residents - are prudent? What precautions are required?

I've tried to research this myself, but all I can find are general medical and scientific studies of the dangers of asbestos, and laws and regulations relating to occupational safety and procedures. I have tried hard, but I cant find any information to help me answer my question.

Please note: I am definately not asking for legal or medical advice - I am purely looking for background information, as this seems like a hole in the regulatory system here in the UK.

I would be very grateful for any links that may be of interest.

Many thanks to anyone who wishes to answer.

Contactless (talk) —Preceding undated comment added 21:52, 9 September 2010 (UTC).

The general law in the area is section 3 of the Health and Safety at Work etc. Act 1974:

General duties of employers and self-employed to persons other than their employees.
3.—(1) It shall be the duty of every employer to conduct his undertaking in such a way as to ensure, so far as is reasonably practicable, that persons not in his employment who may be affected thereby are not thereby exposed to risks to their health or safety.
(2) It shall be the duty of every self-employed person to conduct his undertaking in such a way as to ensure, so far as is reasonably practicable, that he and other persons (not being his employees) who may be affected thereby are not thereby exposed to risks to their health or safety.
(3) In such cases as may be prescribed, it shall be the duty of every employer and every self-employed person, in the prescribed circumstances and in the prescribed manner, to give to persons (not being his employees) who may be affected by the way in which he conducts his undertaking the prescribed information about such aspects of the way in which he conducts his undertaking as might affect their health or safety.

Of particular relevance to demolitions is regulation 29 of the Construction (Design and Management) Regulations 2007:

Demolition or dismantling
29.—(1) The demolition or dismantling of a structure, or part of a structure, shall be planned and carried out in such a manner as to prevent danger or, where it is not practicable to prevent it, to reduce danger to as low a level as is reasonably practicable.
(2) The arrangements for carrying out such demolition or dismantling shall be recorded in writing before the demolition or dismantling work begins.

With regard to asbestos, the prudent approach is to remove as much of the asbestos as possible before demolition; otherwise, the whole demolition job would need licensing under the Control of Asbestos Regulations 2006. I don't know of any specific studies done on the risks to neighbours during demolition work. Court cases are only just getting round to dealing with the health damage to neighbours of asbestos processing plants: these people are at far more risk because the (potential) exposure is longer. Physchim62 (talk) 22:54, 9 September 2010 (UTC)

It depends on whether the demolition of the building containing asbestos is conducted according to regulations or not, and the size of the building/amount of asbestos. If the demolition abides by the regulations, airborne asbestos levels will be very low and I don't think health precautions are necessary for neighbors in standard cases. As mentioned above, larger projects might be different. If you're particularly worried and it's a windy day, then you could stay inside and keep doors and windows shut, or use a mask. If you want to see more information on the aforementioned regulations, check out this link. Regards, --—Cyclonenim | Chat  23:00, 9 September 2010 (UTC)

Thanks to both of you for putting the effort in to reply. I should probably have said that I had found the legislation Physchim62 kindly found, and the HSE link that Cyclonenim gave. Thanks for those though guys! But it does seem strange that, other than the very general duty of care to others contained in these regulations, there is little mention of risk to others such as neighbours. Dont you think?

The HSE has lots of information about worker's safety - respirator types, fibres per cc of air, decontamination procedures, licensing rules etc. - but none that I can find about precautions for the general public. It is strange to see, on a construction site, workers in full plastic hazard gear, with gas masks and disposable boots - even mobile decontamination shower units - while only feet away are members of the public watering their pot-plants in t-shirts! It just seems like a slight disconnect to me.

Anyway, thanks a lot for your help.

Regards Contactless (talk) 00:32, 10 September 2010 (UTC)

This is not legal or technical advice, just an observation. I once underwent "official" training in US asbestos removal procedures. The jist of it is that asbestos had to be removed only in an environment (plastic sheeting, negative air pressure via HEPA filters) where it was not dispersed in the environment. The problem area was enclosed with layers of plastic to constitute a sealed area. It was wet down and then scraped off the beams, pipes, boilers, ceilings, or whatever by workers with respirators and protective suits, and bagged for disposal. When they were done, and showered, the suits went into disposal bags and the inner plastic walls, floor and ceilings went into disposal bags. Then the air was monitored to make sure there were no fibers drifting around, before all the plastic was removed. Those regulations would not have permitted open air removal with the fibers drifting around the neighborhood. Just knocking down the building and letting the fibers drift around would not seem in accord with the US standards I was familiar with. Edison (talk) 05:22, 10 September 2010 (UTC)

Exactly the same (or a very similar) system is used in the UK, and licensed contractors go to great lengths to ensure that no asbestos fibres escape to the outside environment. You should be aware, however, that asbestos and other potentially carcinogenic particles exist (in a very small quantity) in normal atmosphere in the UK (and probably elsewhere). The risk from these (and from most demolition work) is so low that most of us don't bother to wear special masks when going about our everyday tasks. If you are really worried, perhaps you should ask to see certificates of asbestos removal which should have been obtained before demolition work stated. There are always some "cowboys" who ignore regulations. Dbfirs 13:03, 10 September 2010 (UTC)

Thanks a lot for helping me out - those are good, reassuring answers. I'm definately not one to make a fuss about health - I just wanted to make sure that the protection rightly afforded to workers (who are obvioulsy at much greater risk) was not to the exclusion of the general public, especially as this is a very high density residential neighbourhood.

The contractor is definately licensed for the task and reputable. I think I'll just write a quick letter to the council (who approved and gave notice of the demolition) and just ask them to confirm that reasonable measures have been taken to minimise any danger to residents.

Thanks again for your help.

Regards Contactless (talk) 23:00, 10 September 2010 (UTC)

Particle board

is it possible to make particle board with epoxy or yellow PVA glue or urethane glue instead of formaldehyde resin —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 22:54, 9 September 2010 (UTC)

I suppose it is possible to create your own particle board at home using your own matrix and binder system; any suitible binder should work. However, I imagine that quality control would be an issue. The stuff that's made in big factories tends to have better uniformity of properties and conforms to higher standards than something you whip together in your workshop with sawdust and glue. --Jayron32 05:45, 10 September 2010 (UTC)

The article Fiberboard, which covers the class of building materials that includes particle board, mentions some of the issues with formaldehyde-based resin systems, and mentions some alternatives which are in production. --Jayron32 05:48, 10 September 2010 (UTC)

How do frogs get into an isolated marsh?

This is a question that has intrigued me. I will give an example.

As I like to do, I explored a dry drainage ditch to its source beside a shopping mall. There was a small pool of water and mud. As I walked past, several small frogs jumped in. The nearest frogs were in a pond about 1/2 mile away.

So: How did the frogs get there? --Chemicalinterest (talk) 23:14, 9 September 2010 (UTC)

Although virtually all frogs have to breed in water, they frequently don't have to live in it, and many species spend much of the year out of it (though often sheltering in shaded and moist nooks and crannies, especially during daylight), during which they can disperse considerable distances in search of 'greener pastures.' The frogs you saw might easily have travelled more than half a mile to this intermittent pond (though it's not unlikely that some live closer than that without your realising). Alternatively, they may be a small population living permanently around the site, breeding when water is seasonably available and sheltering in the aforesaid nooks etc when not.

It used also to be said that frogspawn is dispersed by its sticking to wading birds' legs and being transported by them from one body of water to another, but I'm not sure how much of this was merely assumption rather than observationally confirmed. 87.81.230.195 (talk) 23:46, 9 September 2010 (UTC)

The area is developed, so it is easy to spot marshes. --Chemicalinterest (talk) 00:16, 10 September 2010 (UTC)

Are you certain that they were true frogs, not just tree frogs? Nyttend (talk) 00:54, 10 September 2010 (UTC)

Yes, they are true frogs. Bronze frogs, most likely. They are one of the most common frogs in my area. --Chemicalinterest (talk) 10:55, 10 September 2010 (UTC)

Also, don't forget that there would be a very large and complex subterraneal storm water drainage system that I imagine frogs would love to travel around in. Vespine (talk) 02:29, 10 September 2010 (UTC)

Frogs like light more than darkness. The storm drain is at the end of the stream. The frogs are at the beginnning of the stream. The spring at the beginning of the stream has dried up, although the water is still high. That is why there is still a puddle there. Frogs normally like mud, too. It gives them a better place to hide. Cement is hard to hide in. --Chemicalinterest (talk) 10:55, 10 September 2010 (UTC)

Frogs can wind up in odd places. I once found a somewhat dehydrated and emaciated but quite lively frog in a small recess in a television mast on top of a house. I cannot picture the frog climbing up the wall of the house, and my best guess is that he was grabbed by a bird and subsequently dropped while the bird was above the house or perched on the mast. So a frog in an "isolated" pool is not at all surprising. Edison (talk) 05:12, 10 September 2010 (UTC)

That is strange. It reminds me of something similar. Many times when it rains, we find earthworms on our porch. The porch is about 2 1/2 feet above the soil. --Chemicalinterest (talk) 10:58, 10 September 2010 (UTC)

See Raining_animals#Frogs_and_toads for referenced, documented cases of frogs raining from the sky. It is rare, but it apparently does happen. Checking earlier in the article, apparently waterspouts and tornados can carry water-borne creatures some distance, resulting in rains of fish and frogs and other oddities. --Jayron32 05:16, 10 September 2010 (UTC)

Here's one possible answer. As our frog article says: Some frogs inhabit arid areas such as deserts, where water may not be easily accessible, and rely on specific adaptations to survive. The Australian genus Cyclorana and the American genus Pternohyla will bury themselves underground, create a water-impervious cocoon and hibernate during dry periods. Once it rains, they emerge, find a temporary pond and breed. Looie496 (talk) 06:11, 10 September 2010 (UTC)

I live in the eastern US, if that helps any. --Chemicalinterest (talk) 10:58, 10 September 2010 (UTC)

I saw a bird carrying a frog once, and then it dropped it. The frog was unharmed and hopped away to safety. Maybe that's how they got there Quadrupedaldiprotodont (talk) 14:19, 10 September 2010 (UTC)

Here in Ireland I have seen Common Frogs in a wooded area near my house from time to time even though the nearest lake is about half a mile away. I see them very rarely but they travel this far away from water nonetheless.--92.251.241.196 (talk) 18:19, 10 September 2010 (UTC)

For true frogs in genus Rana, half a mile is not a big distance. While adult frogs normally stay in the same pond, juveniles disperse to large distances in search of new ponds. This paper gives the dispersal distance of about 1000 m (0.62 mile) for the wood frog Rana sylvatica; but of course the dispersal distance depends on weather, terrain, and the species of frog. Half a mile is not a problem. In fact, many species of frog breed more successfully in vernal pools and other ephemeral bodies of water, as the absence of large fish guarantees reduced predation and reduced competition. It is probably also an evolutionary adaptation for the species to be able to spread to the new available habitats. --Dr Dima (talk) 18:21, 10 September 2010 (UTC)

They were young frogs, I could tell by the splash instead of the plunk. . --Chemicalinterest (talk) 20:09, 10 September 2010 (UTC)

September 10

Remote controlled almost self-replicating small production systems.

Has there been any practical experiments with self-replicating machines using mostly “bulk” material?

Large-scale space-activity require production in space since the launch cost from earth is so high. Before large-scale production in space is implemented it is extremely expensive to have a human workforce in space. Production should therefore be remote controlled or automatic.

The current global industrial complex is able to replicate itself and to a large extent automated but it is way to complex and big to be a god model for something to send to the moon, asteroids or the moons of Mars. Most of the work on self-replicating machines seems to be either theoretical or using prefabricated parts. I would be interested in attempts to build machines that can replicate most of its mass from bulk material, parts that are hard to build such as semiconductor chips will of curse need to be prefabricated. I know that we don't have the technology to build self-replicating machines that uses raw material such as lunar-regolith but machines that uses simpler bulk material such as plastic granulate is an important step.

I find the RepRap-project interesting but limited since it is built mostly of prefabricated steel bars and need to be mounted manually. Are there similar research projects that are more ambitious and professional? Have they build functioning prototypes?

I have read Self-replicating machine and Clanking replicator Gr8xoz (talk) 00:23, 10 September 2010 (UTC)

Based on your interests, you might find this old Soviet SF short story interesting: Crabs on the Island, Masked Booby (talk) 01:30, 10 September 2010 (UTC)

I havent had time yet to reed it but it sounds intresting thank you for the link.Gr8xoz (talk) 11:43, 10 September 2010 (UTC)

I don't know whether you can say the RepRap isn't 'ambitious'. Their goal is indeed that most (well theoretically all, but I think most would acknowledge that's a very far off dream) of the machine be self-replicatible i.e. the number of 'vitamins' be kept to a minimum. And there is the Kartik M. Gada prize that's been offered related to the RepRap [8] which requires, amongst other things, 90% of the volume be printable. (See for example [9] one of the projects which is aiming to eventually meet the requirements of the prize.) Note that one of the goals of many developers for the RepRap includes work on making printed circuit boards and perhaps even assembling the boards via some sort of pick and place technique. However it's true they're centred on low cost and earth usage so some self assembly isn't usually seen as a big deal provided it's something most people can do without needing much training or experience, but I don't think you can say this isn't ambitious, they just have a different goal from what you're looking for. In particular, building or assembling something that is the same size as the device building it raises several issues potentially requiring the device is capable of moving by itself rather then occupying a fixed space and building something that requires no human involvement requires a very high degree of reliability or otherwise the internal ability to fix problems that arise (even the KMG prize allows one printer head jam to be fixed) and a resonably consistent degree of built quality. Of course being ambitious doesn't mean you don't recognise the limitations you currently face, hence why the RepRap team is concentrating on building something that works and then improving it until it can make most of itself. Nil Einne (talk) 07:11, 10 September 2010 (UTC)

I was more looking at the current prototype than the overall project goal. A useful self-replicating system in space need of curse be able to move it self or it's offspring any way to avoid crowding. I did not rule out human intervention but the intervention should be performed by remote control. A robotic arm on wheels produced by the RepRap system would be an interesting step towards self assembly.Gr8xoz (talk) 11:43, 10 September 2010 (UTC)

pimelea linifolia......flax leafed riceflower;

does this plant normally be pink? i have two pink ones but i thought they were only white.i am 67 and have never before seen pink. i know there is pink in a different riceflower but this is the flax leafed riceflower & the other is a more rounded leaf. i live on the midcoast, n.s.w. australia02:23, 10 September 2010 (UTC) —Preceding unsigned comment added by 123.208.80.32 (talk)

Our article on Pimelea linifolia says that the flowers are white, but this says that there is a subspecies which can have pink flowers. Smartse (talk) 12:36, 10 September 2010 (UTC)

Polar night and midnight sun

According to the Barrow, Alaska article, the polar night lasts for about 65 days, while the midnight sun lasts for 82 or 83 days. Why are these durations not the same? —Bkell (talk) 02:31, 10 September 2010 (UTC)

The article polar night gives a clue "but in regions that are located at the inner border of the polar circles where midnight sun is experienced, this is not true. Because of twilight, these regions experience polar twilight instead of the polar night. In fact, polar regions typically get more twilight throughout the year than equatorial regions." This implies that "twilight", when the disc of the sun is below the horizon but where the suns light is still detectable, do not count as "night". However, midnight sun must be when the disc of the sun is actually visible. The other 18 days of the year must be times when the sun is just below the horizon; that is not actually visible, but too bright to be considered "night". --Jayron32 03:26, 10 September 2010 (UTC)

See also atmospheric refraction, which makes the sun appear higher over the horizon than it would in a vacuum. PhGustaf (talk) 03:32, 10 September 2010 (UTC)

I thought about atmospheric refraction, but I didn't think it alone could be responsible for that 18-day difference. The discrepancy in the definitions, as Jayron pointed out, seems to be a likely explanation; I hadn't thought of that. Thanks. —Bkell (talk) 03:46, 10 September 2010 (UTC)

In addition to the points mentioned, the Earth is nearer to the Sun during the Northern Hemisphere winter, so it is a few days shorter than the Northern Hemisphere summer. --Anonymous, 03:55 UTC, September 10, 2010.

(edit conflict) Those aren't the only reasons. The Earth's orbit is not a perfect circle, but an ellipse, so, at some points during the year, the Earth is closer to the Sun than others. When is the Earth closest to the Sun? About January 3, right in the middle of Northern hemisphere winter. Now when the Earth is (very slightly) closer to the Sun, it is moving slightly faster around its orbit, a bit like an ice skater who pulls in his/her arms to spin faster. You can see this as well in the dates of the equinoxes: there are about 186 days between the Spring Equinox and the Autumn Equinox, but only about 179 days between the Autumn Equinox and the Spring Equinox. Physchim62 (talk) 03:58, 10 September 2010 (UTC)

One would expect the polar night and polar day to be the same length only if the sun was a point source of light (instead of a circle of about 30 arc-minutes or so), and if the atmosphere did not distort light slightly like it does. I would anticipate that the polar night length and the polar day length would be the same on Pluto if it had the same orbital eccentricity and orbital inclination assuming Pluto has seasons. Googlemeister (talk) 13:02, 10 September 2010 (UTC)

What type of Machine Gun

I vaguely remember a type of Machine Gun I saw long ago. It was one of those type that are kept on ground on a tripod etc. The ammunition is fed by a magazine inserted from above (like most non-portable types). The peculiar thing about this was the fact that when you fire, the trigger-hand handle you are holding moves backword several inches (and the gunner has to keep his elbow-joint supple enough to accommodate the jerk !) Why would they build such a thing ? Does this mean that the gunner has to be ready to have his hand move at least a dozen times per second (when set on rapid fire mode !)  Jon Ascton  (talk) 06:42, 10 September 2010 (UTC)

The only thing I can think of is the woeful French Chauchat light machine gun, where the whole barrel assembly moves (although that is bipod mounted). I believe most tripod mounted weapons are belt-fed rather than having a magazine. You could have a look at this[10] site and see if anything rings a bell. Let us know if you find it! Alansplodge (talk) 18:45, 10 September 2010 (UTC)

I'm not too specific on "tripod", it may have been on a bipod as well (please note "etc"). Yes, I know of models where barrel moves back, but what I am talking about is the hand-grip moving back. I know it sounds weird...

Indoor heating in Florida

Hello, I would like to know at about what winter isotherm does indoor heating start to become common in Florida? Or in the Southern U.S., for that matter. I know that in Southern Florida, around Miami, most people only have small one-room heaters they take out occasionally in January, but I have no idea if the winter temperatures in the rest of Florida warrant a need for indoor heating during most of the winter months. This is my guess, but I imagine Northern Florida would definitely need indoor heating during all the winter months, every year. In general, at about what isotherm or latitude do homes and buildings in the Southern U.S. need indoor heating? Thanks 201.21.183.191 (talk) 12:45, 10 September 2010 (UTC)

This map shows the average 60° isobar in January. Vulnerable people will likely turn on the heating if the temperature drops much below that. Rojomoke (talk) 14:37, 10 September 2010 (UTC)

Carrots

I head a long time ago, that drinking excessive amounts of carrot juice could turn someones skin orange. Is that true? Does wiki have an article on it? —Preceding unsigned comment added by Biskyhigh (talk • contribs) 13:47, 10 September 2010 (UTC)

See Carotenosis. --Chemicalinterest (talk) 13:49, 10 September 2010 (UTC)

It's worth noting that the colour of the vegetable has nothing to do with the colour your skin turns. Green vegetables like cabbage can produce the same effect and you don't turn green, you go yellow. Regards, --—Cyclonenim | Chat  14:43, 10 September 2010 (UTC)

Manganese as a free element

Is manganese really found as a free element? It is quite reactive and readily corrodes. I know in some meteorites it may be found, but those are not very common, IIRC. --Chemicalinterest (talk) 14:14, 10 September 2010 (UTC)

The "Occurrence and production" section deals with this Quadrupedaldiprotodont (talk) 14:17, 10 September 2010 (UTC)

Some finds of native manganese have been reported [11], but it is hardly very common. Physchim62 (talk) 14:59, 10 September 2010 (UTC)

PANCREATIC CANCER AND GENOMICS RESEARCH

MY HUSBAND DIED TO PANCREATIC CANCER AND I AM CONCERNED FOR MY CHILDREN AND GRANDCHILDREN. I HAVE RECEIVED INFORMATION FROM NATIONAL FOUNDATION FOR CANCER RESEARCH THAT A DR VON HOFFHAS IDENTIFIED SEVERAL GENETIC WEAKNESSES IN PANCREATIC CELLS. IS THERE ANY WAY THAT MY CHILDREN AND GRANDCHILDREN COULD BE TESTED TO SEE IF THE ARE PREDISPOSED TO THIS DREDFUL DISEASE? I LOOK FORWARD TO HEARING FROM YOU. THANK YOU. —Preceding unsigned comment added by 65.32.133.7 (talk) 15:12, 10 September 2010 (UTC)

Asking a doctor would be a better choice. Most of us are not doctors and might give you bad advice. --Chemicalinterest (talk) 15:26, 10 September 2010 (UTC)

In fact, Wikipedia policy forbids us to give medical advice on the Reference Desks. Looie496 (talk) 15:32, 10 September 2010 (UTC)

It is true that we here on the reference desks can't really answer your question adequately. However, your doctor may not know the answer, either. For the most up-to-date information about genetic risk for cancer, you could look for an MD or genetic counselor who specializes in clinical cancer genetics; this person will know what genetic tests are available and applicable to your family's situation. You can ask your doctor for a referral to a genetics specialist (either MD or genetic counselor). Alternatively, you can search for a nearby genetics clinic here or find a genetic counselor here. --- Medical geneticist (talk) 16:34, 10 September 2010 (UTC)

Wireless USBto

I am planing to buy and use it in India, Warpia, which is a Wireless USB Audio and Video Display adopter set.According to Wikipedia," Wireless USB is based on the WiMedia Alliance's Ultra- WideBand (UWB) common Radio Platform,Which is capable of sending 480 Mbit/s at a distance up to 3 meters and 110 Mbit/s at up to 10 meters. It was designed to operate in 3.1 to 10.6 GHz frequency range, although local regulatory policies may restrict the legal range for any given country". Would this device be compatible in India?Jayessandhu (talk) 17:36, 10 September 2010 (UTC)

muscles shaking

When an athlete finishes a grueling day at the gym, or after a marathon or weightlifting competition, their muscles are often shaky including what might look like shivering. Is this because their muscle has used up its stores of acetylcholine(sp)? Googlemeister (talk) 18:47, 10 September 2010 (UTC)

No, acetylcholine is essentially 'recycled' by your body, at least in the immediate short term. There's a good written explanation here. Regards, --—Cyclonenim | Chat  19:06, 10 September 2010 (UTC)

Your link says it is because certain chemicals produced by the neural motor units can't keep up with demand. That is what I thought, but what specific chemicals? Googlemeister (talk) 19:43, 10 September 2010 (UTC)

I was always under the impression that you don't exhaust acetylcholine, at least not after exercise as it should restore itself with time. Perhaps I'm wrong, or the shakiness is a symptom that occurs until acetylcholine supply recovers. I'll leave this to someone else! Regards, --—Cyclonenim | Chat  19:55, 10 September 2010 (UTC)

The technical term for this seems to be fasciculation. Googling "Fasciculation after exercise" got this link [www.ehow.com/how_5276858_understand-muscle-twitching-after-exercise.html] (which is 'blacklisted' by WP!. The Scientific American link is interesting, but note it is dated 1999 so may well have been made obsolete by newer research, though it sounds quite logical and technically correct. And it does seem they are speaking of acetylcholine.
Calcium is also used in triggering the contraction of muscle fibres (see Sarcomere). I'm wondering if there might be circumstances where it may actually not be a depletion, but an excess of Epinephrine/Adrenaline ? Hope this helps, 220.101 talk^\Contribs 09:01, 11 September 2010 (UTC)

Methane Toxicity

I read an article a couple of days ago (sorry, don't have a link) about a town in Pennsylvania where the ground water was flammable due to the large amount of methane dissolved in it, which the townsfolk blamed on nearby fraking operations. Obviously flammable water presents some large problems, but would it be harmful to drink it (supposing that the only "abnormal" chemical in it were methane)? The methane article seems to deal only with respiration, not ingestion. 96.246.59.38 (talk) 19:32, 10 September 2010 (UTC)

I assume it was a story like this, according to Methane#Potential health effects it shouldn't be dangerous to drink. The water itself can't be flammable though, its the gas that escapes from it that is. If methane is getting into the water, it's likely that other compounds that might be toxic also are though. Smartse (talk) 22:14, 10 September 2010 (UTC)

Very tasty hydrogen sulfide is normally found in methane deposits. --Chemicalinterest (talk) 00:29, 11 September 2010 (UTC)

Wth? Methane is not nearly soluble enough in water to make water flammable. Note that most low-proof alcoholic drinks do not ignite -- and their concentrations are much higher than you would find CH4 in a high-dielectric solvent. John Riemann Soong (talk) 06:07, 11 September 2010 (UTC)

Strength not linked to muscle size?

I'm quite a small guy, 5' 10", slim build, moderately fit.

Recently I discovered that I am stronger than a friend of mine who is 6' 1", weighs 11 stone and has visibly large muscles. What's going on here? He's also moderately fit.--92.251.241.196 (talk) 20:01, 10 September 2010 (UTC)

Two thoughts come to mind : 1) Your friend was being nice, or 2) You chose a 'test of strength' that did not test his 'visibly large muscles' but instead some other muscles that he never works out. APL (talk) 20:49, 10 September 2010 (UTC)

Well as the "test" was a physical fight and we were both angry I think neither of those hold true. He was trying to hit me but was doing no damage, and I pushed him back against a wall and held him, he was also trying to hold his ground but couldn't--178.167.172.73 (talk) 21:41, 10 September 2010 (UTC)

Another thought. I am very thin but someone else that has arms about twice as big beats me in arm-wrestling, but not easily. I can tell he is trying to, so it is not a matter of being nice. I think if muscles are not worked out, sometimes they can stay large but deteriorate internally, and sometimes get replaced by fat. --Chemicalinterest (talk) 21:06, 10 September 2010 (UTC)

Go look at professional athletes like runners. You don't see huge thighs, you see quite thin legs with very lean muscle. Size isn't everything! Regards, --—Cyclonenim | Chat  22:41, 10 September 2010 (UTC)

178.167 - fighting is hugely technique based: a professional Flyweight boxer doesn't weigh that much and isn't that big but I suspect their superior technique would mean they'd have little trouble disposing of someone (lacking the same training) twice their build in a regulation boxing match. Basically size and build are probably correlated with strength but are by no means a guarantee of. ny156uk (talk) 23:00, 10 September 2010 (UTC)

If all else is equal, muscular strength should be proportional to cross sectional area of the muscles, see Muscle_strength#Strength. Also Skeletal muscle. Genetics plays a part of course, you may have more 'fast twitch' muscle fibres allowing quicker application of force. See "Genetic variation in muscular strength" from the British Journal of Sports Medicine - 220.101 talk^\Contribs 09:17, 11 September 2010 (UTC)

tornado army tank

Is it possible for a tornado too pick up an army tank would it take EF5/F5 status too gain lift. --86.41.129.119 (talk) 20:49, 10 September 2010 (UTC)

An M1A2 tank weighs around 60-70 tons or so and an F5 has had a maximum wind speed of 300 mph. I suspect it would move the tank, but I am skeptical about it picking it up. I wonder if any photos exist of a tornado moving a bulldozer or similar, which might give an indication. Googlemeister (talk) 20:57, 10 September 2010 (UTC)

I did watch storm chasers on the discovery channel and they made a vehicle thats allot like a tank except they had too use something too prevent it from being uplifted so they can go into one but an average tank has nothing like that. --86.41.129.119 (talk) 21:12, 10 September 2010 (UTC)

The vehicles on Storm Chasers aren't truly comparable to a tank in any fashion. I can't imagine they'd top out at more than 5 tons or so; an average tank wouldn't need additional leverage. — Lomn 21:29, 10 September 2010 (UTC)

They could maybe drag it horizontally but there would be no chance of lifting it. Not even a C-130 Herculese or CH-47 Chinook can do that.--178.167.172.73 (talk) 21:56, 10 September 2010 (UTC)

C-130 Hercules is the link you want. Buddy431 (talk) 00:55, 11 September 2010 (UTC)

There is at leas anecdotal evidence of tornadoes being able to lift railroad cars [12], or [13], or [14], for example, but railroad cars are significantly larger, and somewhat lighter than a tank, so that makes the job easier. It's also unclear whether the cars are truly lifted, or rather just pushed off the tracks (still an impressive feat; see this Youtube video [15]. It's interesting that the engine, presumably significantly heavier, manages to stay upright). It also appears that this question has been asked elsewhere, with the general consensus being "no, probably not" ([16], [17], [18], [19]). While none of those sites approach being a reliable source, the comments seem quite reasonable to me. Train cars can be pushed over (and maybe lifted) because they have big sides. Tanks do not. Buddy431 (talk) 01:10, 11 September 2010 (UTC)

One TV account of a southern US tornado said it removed a concrete slab covering a storm cellar. I expect that a strong US tornado might well pick up and whirl around and crash to earth an Abrams tank. There are relatively few Abrams tanks per square mile, so the probability of empirical confirmation of the hypothesis is slight. Instead, do the analysis of a force 5 tornado versus the aerodynamics of the said tank. Could it in principle lift/launch the tank? Edison (talk) 04:40, 11 September 2010 (UTC)

For the sake of a simplified upper bound on what a tornado could lift, consider the following. Suppose the EF5 tornado has a max wind speed of 350 km / hr (100 m/s). Further suppose those winds are somehow capable of blowing directly upward from underneath the tank (very unlikely in practice, but that's why this is an upper bound). The maximum force such winds would impart is of order ${1 \over 2}\rho Av^{2}$ where v is the windspeed, ρ is the air density, and A is the surface area underneath the tank. Taking an M1 Abrams as a representative tank, A is ~30 m^2. For a force of 150000 Newtons, which implies an ability to lift an object up to ~15 tonnes. This is of course well under the 60 tonnes of the tank. So, even given an ideal flow geometry, it is probably impossible for a EF5 to lift a tank. Dragons flight (talk) 06:59, 11 September 2010 (UTC)

What happened to Ron Gellatley ?

Ron Gellatley is an Australian naturopath/medical herbalist/homeopath who wrote a book called 'How to Fight Prostrate Cancer and Win' first published in 1998 when he was in his seventies which apart from the obvious had all sorts of information about herbs and what they do. I'm wondering where he is now as I can't find ANY information about him.121.73.185.217 (talk) 21:03, 10 September 2010 (UTC)

Did you try google? You might want to read this before though. Smartse (talk) 22:01, 10 September 2010 (UTC)

?Prostate cancer

Conflicting reactions

The reactions listed at this and manganese(VII) oxide conflict. The specific reaction is the one with concentrated sulfuric acid. The first article says that it produces ozone as a "special" product. The second article says it produces manganese(VII) oxide with some left over ozone. Why do not the two reactions coordinate? Thank you. --Chemicalinterest (talk) 21:26, 10 September 2010 (UTC)

The two descriptions seem coherent enough to me: it's one of those reactions which is "messy", you don't really want to try to write a balanced equation for it, but the products are Mn₂O₇ and ozone, for as long as either of those species stay around. The exact yields of each product will depend on the exact conditions. Physchim62 (talk) 23:35, 10 September 2010 (UTC)

The one in potassium permanganate does not list the very dangerous manganese(VII) oxide formation in the reaction. --Chemicalinterest (talk) 00:27, 11 September 2010 (UTC)

I've tweaked the wording to make it clearer that you can't make ozone by this route without also making manganese heptoxide. Physchim62 (talk) 00:51, 11 September 2010 (UTC)

does Vitamin C increase or decrease the strength of the immune system?

The immune system depends on reactive oxygen species to fight bacteria...so will constantly elevated bloodstream levels of Vitamin C neutralise ROS's? John Riemann Soong (talk) 23:01, 10 September 2010 (UTC)

Have you read Vitamin_C#Immune_system? Rojomoke (talk) 23:43, 10 September 2010 (UTC)

Also relevent, Vitamin C megadosage (a therapy promoted by none other than Linus Pauling) and Megavitamin therapy. --Jayron32 01:45, 11 September 2010 (UTC)

September 11

Rainbow Falls

Hello. I just made an article on Rainbow Falls, British Columbia. Could someone please find the coordinates of it? --The High Fin Sperm Whale 03:44, 11 September 2010 (UTC)

Looks to be at about 49°23'57"N 121°44'38"W, based on user-submitted information and photos on Google Earth. -- Tom N (tcncv) talk/contrib 04:30, 11 September 2010 (UTC)

So can someone add them to the article?--81.96.185.94 (talk) 08:37, 11 September 2010 (UTC)

BCGNIS search is useful for such things, although the coordinates are rounded to minutes. There are five Rainbow Falls in British Columbia, this one is "Rainbow Falls". BC Geographical Names., I believe. Pfly (talk) 10:30, 11 September 2010 (UTC)

Sending nuclear waste to space

I recently watched a TV documentary about how difficult it is to get rid of nuclear waste. So I came to think, what's stopping us from sending it out to space in unmanned throwaway rockets? The only thing that comes to my mind is that it would be far too expensive, but are there other reasons too? JIP | Talk 09:54, 11 September 2010 (UTC)

Impracticality and risk, according to our article's subsection on space disposal. ---Sluzzelin talk 10:01, 11 September 2010 (UTC)

There are two issues:

1. We have a lot of nuclear waste.

2. Sending things into space has a reasonable high accident rate.

When you combine the two of these, it suddenly doesn't seem like a great idea. To make a significant dent in the waste problem, you have to send up a lot of rockets. That means that at least one of those is probably going to blow up when it is being launched. That means you're now spreading nuclear waste into the surrounding area. Not good. Of course, you could put some heavy duty shielding in place, right? But now you've just decreased the amount of waste you can send on each trip, meaning you have even more trips.

It's not economical and it's not safe. You're better off, in terms of the tradeoff of risk and expense, just dumping it into a deep sea trench, if you're going to consider doing that.

In any case, the real difficulty in getting rid of waste is mostly a political problem, only in a small degree a technical problem. Or, put another way, the technical problem is the political problem. In the US, for example, the law requires the government be able to certify that absolutely no people in the next 10,000 years or so (at the minimum) will ever have a negative health effect due to this waste. You basically cannot do that, not just with nuclear waste, but anything. It's an absurd standard that we don't hold any other toxic or hazardous substance to, because it's completely impossible to satisfy from a technical point of view, because of the time scales involved. If we were a bit less strict in our standards — that all that was to be avoided was an absolutely worst-case-scenario, and that the waste would be buried somewhere where its being disturbed was unlikely — it wouldn't be such a difficult technical problem. --Mr.98 (talk) 12:12, 11 September 2010 (UTC)

contradiction in electromagnetism

I have one doubt. When two similar charges are kept at a distance and if our reference frame is not moving and charges too are not moving then they repel each other. If our reference frame starts moving lets say backward from charges with some speed, then we see that charges are going away with same speed. Because charges are moving, they will create magnetic field and we should see that they attract each other (because they are moving in the same direction with respect to us.) According to me this is a contradiction. Just because of changing our reference frame how can phenomena change? Change in reference frame should not change the phenomena. —Preceding unsigned comment added by Ptamhane (talk • contribs) 10:01, 11 September 2010 (UTC)

For a charge to induce a magnetic field, doesn't it have to be moving through a conductor? Not just a "frame of reference"? Vespine (talk) 11:18, 11 September 2010 (UTC)

No, fundamentally magnetism is a relativistic effect, the electric field is (partially) transformed into a magnetic field by the moving frame. The effect is easier to understand if two lines of charges are considered instead of two isolated charges. The distance between the charges in each line will be reativistically foreshortened in a moving frame. Two lines moving in opposite directions will measure (in a frame moving with one line) the distance between charges in the other line as being less, and consequently a greater charge density leading to a greater repulsion. Two lines moving in the same direction will have less repulsion, as observed by a frame at rest. These adjsutments to the electrostatic force are the root of magnetic forces. SpinningSpark 13:06, 11 September 2010 (UTC)

Horseshoe Crabs

The article on horseshoe crabs says that they are over-harvested. But who harvests horseshoe crabs and for what? —Preceding unsigned comment added by 69.120.0.81 (talk) 12:04, 11 September 2010 (UTC)

Ummm, Your question is answered in the very same sentence.. I'll give you a hint: East coast of North America and fertilizer and bait. Vespine (talk) 12:32, 11 September 2010 (UTC)

Helium shortage

If we're running out of helium, why can't we make some more by taking radioactives (and we have plenty, via nuclear waste), and then putting them in an atmosphere. It seems like they would spit off enough alpha particles for this to be useful. Alpha particles + other stuff = slightly ionized other stuff + helium. —Preceding unsigned comment added by 69.120.0.81 (talk) 12:09, 11 September 2010 (UTC)

One problem is that the most radioactive bits of nuclear waste are not alpha emittors. Another is the scale that would need to work on. World helium production in 2009 was about 29,000 tonnes, or 7.23 gigamoles. As helium-4 has relative atomic mass 50–60 times less than that of most alpha-emitting nuclides, you would need 1–1½ million tonnes of alpha-emitting radioactive waste to decay each year to supply the world's helium consumption. Physchim62 (talk) 12:48, 11 September 2010 (UTC)

Lonely

What is the science behind lonely people? Why are some people socially retarded and lonely, unable to get a girl/boy friend? Is it evolutionary?