Wikipedia:Reference desk/Archives/Science/2010 September 7

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

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 Wikipedia. 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)