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April 12

DNA samples and testing time

Two sets of multi-part questions on the subject of DNA testing:

—SeekingAnswers (reply) 02:44, 12 April 2011 (UTC)

(1) How easy is it to get DNA samples?

In some films and television shows, the police find DNA everywhere. They can get it by dabbing the inside of a person's mouth with a swab, or from a cup that a person has drunk out of. I think I've even seen cases of police getting it from surfaces that a person has touched with the tip of his or her finger.

On other films and television shows, getting DNA samples seems to be really hard: the police have to draw blood from the person they want to test, and samples seem to get corrupted and become unusable all the time. (In fact, the difficulty of getting a DNA sample seems to be most correlated to whether the plot demands a successful or unsuccessful DNA test...)

Are dead skin cells scraped off with casual contact with any surface sufficent for a DNA sample, or are bodily fluids necessary? Which bodily fluids? (That is: saliva? urine? blood? semen? vaginal lubrication?)

If getting DNA samples is very easy, then in cases of rape, even if the rapist used a condom so that semen could not be collected for DNA testing, it should be easy for the police to get DNA samples from skin cells left on the body of the victim, correct?

—SeekingAnswers (reply) 02:44, 12 April 2011 (UTC)

You can DNA samples from any of the above; however the chance of recovering enough usable DNA is slimmer the smaller and deader the sample. DNA tends to degrade over time; however since the advent of PCR, even the most minute amount of DNA can be replicated and magnified into as much as you need to do tests. Very recently, there have been a few studies on extracting DNA from samples as small as fingerprints, and work is being done to reliably extract DNA from a single hair, but the work has not been expanded into clinical viability (i.e. tested and retested to the level where the method is reliable enough to stand up in a court of law). However, DNA has been extracted from cigarette butts and coffee cups before. If you've touched it, you've left your DNA on it; the question becomes whether you've left enough to be useful. We're very close to that point; it may be likely that within the next decade or so we'll have perfected the "DNA from fingerprints" technique, making actual fingerprinting moot. --Jayron32 04:07, 12 April 2011 (UTC)

I give a thumbs-up to Jayron32's response above, with a few twists. Actual fingerprints will remain useful in situations where DNA would be poorly preserved; some circumstances will favor the long-term survival of the prints, others may better protect DNA. I suspect that databases of fingerprints are larger and more comprehensive than databases of DNA, though the difference is probably eroding. Collecting and processing fingerprints still generally requires less-costly equipment and can be done faster than DNA typing. Finally, DNA plus fingerprint may perform better in court than either test alone (particularly if someone ever successfully mounts a Daubert challenge against fingerprint evidence).

While it is technically possible to extract utterly miniscule amounts of DNA from samples – with modern PCR techniques, a single cell's worth from a suspect should in principle suffice – the risk of error or cross-contamination also rises as one becomes able to amplify smaller and smaller amounts of DNA. Consider a hypothetical case where a cigarette butt is recovered from the crime scene. DNA on the butt matches one of the suspects, but there is also DNA from a second unidentified individual. Defence attorneys get the evidence excluded as unreliable, or insist that the mysterious second person is the actual murderer. What happened? A single skin cell was shed by a cigarette plant worker; the cell settled on the cigarette packaging and fell onto the outside of the cigarette filter, from which it was eventually recovered by forensic investigators.

Sound far-fetched? Something similar has already happened in Germany: story. DNA at forty different crime scenes over a span of more than a decade was linked to the same woman, dubbed 'The Phantom of Heilbronn' by the press. The Phantom's DNA never matched any of the suspects in any of the cases; police were stumped. Investigators eventually came to believe that The Phantom was just a careless worker in a factory that manufactured cotton swabs used by forensic investigators. Sloppy manufacturing processes allowed traces of the employee's DNA to contaminate the swabs, causing her DNA to 'appear' at crime scenes across Germany.

Biochemists and molecular biologists who do high-sensitivity proteomics experiments are familiar with this problem. Labs routinely ignore any hits for keratin as irrelevant in their mass spec results, because that protein is abundant in skin, hair, and nails and contamination with it is virtually impossible (or horrifically inconvenient and expensive) to avoid. TenOfAllTrades(talk) 16:18, 12 April 2011 (UTC)

For extra credit, you can visit Murder of Meredith Kercher and associated talk archives... Wnt (talk) 21:10, 12 April 2011 (UTC)

(2) How long does DNA testing take, and why?

On television shows like CSI: Crime Scene Investigation, DNA tests take just a few hours, or sometimes just minutes.

In the real world, I've seen news articles about police, lawyers, and/or suspects waiting for months for DNA tests. Are these cases unusual?

How long do DNA tests usually take in real life? And why would they take so long? The chemical reactions involved surely can't be so slow that they take months to run their course.

—SeekingAnswers (reply) 02:44, 12 April 2011 (UTC)

It is strictly a matter of economics and priorities (or lack of them). Some jurisdictions are requiring DNA testing for shoplifting;^[1] others set very low priorities on testing of rape specimens when no immediate suspect is known. Evidence can sit around for years untested.^[2] I'd love to see these statistics broken down by the race and income of the victim. Wnt (talk) 03:24, 12 April 2011 (UTC)

The actual DNA test can be done in hours. It consists of a) isolation b) PCR c) DNA fingerprinting. The entire sequence can be completed by a technician within a few hours; the average DNA analyst can, by staggering procedures, probably churn through several in a day. The reason that real cops and prosecutors wait weeks or months for results is that there is a backlog of submitted evidence. Occasionally, a high-profile case will get rushed, but generally it is first come-first served, and everyone waits in line. It just takes time for the DNA analyst to get through all of the cases that got to his/her office before yours did. It doesn't matter how much you want your case done; the 50 other prosecutors and sherrifs and whatnot that submitted evidence before you did want their evidence just as much, and you're not any more important than them... --Jayron32 04:12, 12 April 2011 (UTC)

So...why aren't jurisdictions hiring/training more technicians and buying more equipment? That DNA testing can take months for a process that should only take hours and thereby clogs up the entire criminal justice system shows that DNA testing facilities are grossly understaffed, to an extreme degree, worse than any understaffing of police, prosecutors, prison guards, etc. No doubt criminal justice systems have many inefficiencies, but this has to be one of the worst. If police and prosecutors are all waiting months for DNA tests, then it would seem that DNA testing is the obvious limiting factor in the criminal justice system, and therefore one of the most pressing problems that needs more budgeting. —SeekingAnswers (reply) 05:55, 12 April 2011 (UTC)

They would love to. I'm am certain that if you have several million dollars, and would like to donate it to start a trust fund with which to provide both the capital investment in new equipment, and ongoing funding for both its maintenance, and for more technicians to do this work, your local crime lab would LOVE to work with you. Most places in the world, and especially in the U.S., are so strapped for cash that they are actually furloughing or outright laying off workers in these areas just to avoid having to file bankruptcy. In North Carolina, where my wife works as a forensic chemist, there's been a hiring freeze; they can't even replace the analysts who they've lost through deaths, retirement, or quitting, never mind expanding capacity... --Jayron32 06:07, 12 April 2011 (UTC)

Yeah, but what I don't get is this. In the news, I constantly hear about plans to "add a hundred more officers to the streets next year" (for mid-size cities) or "add a thousand more officers to the streets next year" (for large cities). It would seem that some of the money going to those hundred/thousand extra officers for next year would surely be better served hiring more technicians and buying more equipment. There's no way that it's cheaper to hire and arm a thousand police officers than it is to hire and equip ten more technicians, so clearly, money can be found from somewhere. The problem doesn't seem to be (or at least, not just) a lack of money; it's that the money is going into the wrong places and being inefficiently allocated. —SeekingAnswers (reply) 06:16, 12 April 2011 (UTC)

Putting more officers on the streets is often more about politics. Politicians in the UK are always boasting about how they are going to put more police on the "frontlines" (instead of doing office/paperwork) because when people are asked what they what from the police force, it's always more police on the streets. Recent suggestions that budget cuts will lead to reductions in the number of police have led to a furore in local press. No-one ever says, "But what about the evidence processing?!" Technical work is not high-profile (unless something goes very wrong), and tends not to get funding. In fact, the UK's government-owned Forensic Science Service is being shut down, and the work contracted out to private companies, which (sorry, personal opinion here) is going to be an absolute disaster.--Kateshortforbob _talk 09:23, 12 April 2011 (UTC)

As I hinted above, even if the police have somewhat sufficient capacity, it's likely to be wasted. It takes only a stroke of the pen to demand that all shoplifters be tested, that people be tested on arrest simply to fill a database, etc. I suppose there's a feeling that if you actually do budget for increased capacity, it will only be wasted anyway. (In fact, I think that by collecting too much DNA information, countries greatly harm themselves, because in future generations it may be impossible for them to send a spy to another country without the target finding out who they sent, who the agent's family is, etc.) Wnt (talk) 00:59, 13 April 2011 (UTC)

Efficiency of fixed wings vs. rotors

Long-distance aircraft tends to be fixed-wing aircraft rather than rotary. Is this because fixed wings are inherently more efficient than rotors?

—SeekingAnswers (reply) 04:09, 12 April 2011 (UTC)

Fixed-wing aircraft can run on jet engines, which are orders of magnitude more efficient than propellers are. Helicopters are propeller planes, by necessity, which is why they aren't as efficient. --Jayron32 04:18, 12 April 2011 (UTC)

On a fundamental level, how does a jet engine differ from a propeller? Both are big fans that generate thrust by spinning rapidly and pushing air behind them, so what exactly is the basic difference between them?

Would it be possible to attach a jet engine to the back of rotary aircraft to generate thrust and counter torque from the main rotor while that main rotor generates lift?

—SeekingAnswers (reply) 04:37, 12 April 2011 (UTC)

A jet engine is a Reaction engine it is fundamentally completely different to a propeller engine. The fans inside certain types of jet engine are NOT what actually cause the thrust, they are the intake, compression and exhaust stages; they move the fuel and gas around but it is the combustion gas that creates the actual thrust. There are several jet engine designs which completely lack any kind of propellers or fans. Vespine (talk) 04:53, 12 April 2011 (UTC)

As for rotary aircraft, the main problem is the rotating wing has to travel "backwards" at some point. When the aircraft begins to approach a speed comparable to the speed of the blades, in essence when the blade is traveling backwards it has a zero airspeed and generates no lift. If you strapped a jet on for speed, you'd also need to use it for lift beyond na certain velocity, at which point, your whole "rotor" mechanism just becomes dead weight to a conventional jet aircraft. We have tilt rotor aircraft which combines the benefits of rotary aircraft and fixed wing aircraft, but if you haven't noticed, there aren't many around in civilian use because they have their own whole set of challenges and difficulties. Vespine (talk) 05:02, 12 April 2011 (UTC)

Fundamentally different? Large airliners universally use turbofan engines, essentially a ducted many-bladed propeller driven by a gas turbine in the middle. The fundamental difference between that and a turboprop is just that the latter has a gearbox between the turbine and the propeller and no duct. Modern helicopters also, as far as I understand, tend to be driven by gas turbines. –Henning Makholm (talk) 12:16, 12 April 2011 (UTC)

Hmm, well I'm not an expert but I think you are wrong. In a turbofan engine, it's NOT the "fan" that creates the thrust but the exhaust gasses. The exhaust gasses are NOT created by the fan but by fuel combustion, which is what creates the thrust AND also powers the fan. The fan is there to provide compression and exhaust stages to the engine. Read the turboprop article again: The engine's exhaust gases contain little energy compared to a jet engine and play a minor role in the propulsion of the aircraft. A turboprop is powered by a jet turbine, that's like a jet engine except the primary role of a turbine is to turn a shaft (like in a helicopter), not create thrust like a jet engine. Fundamentally different methods of propulsion. Vespine (talk) 23:00, 13 April 2011 (UTC)

Have another look at Reaction engine. Jet engines are reaction engines whether they have fans in them or not. Propeller engines are NOT reaction engines whether they are driven by internal combustion or a turbine. Vespine (talk) 02:09, 14 April 2011 (UTC)

In a turbojet engine (or pure jet engine) there is only the exhaust gas leaving the engine, and it is responsible for all the thrust. In a turbofan engine there are two streams of gas leaving the engine - firstly, the hot stream which has passed through the fan, the compressor, the combustion chambers, the turbines and finally the nozzle, and is analogous to the exhaust gas in the turbojet engine; and secondly, the cold stream which has passed through the fan but not through the compressor or the combustion chambers. In a low by-pass turbofan engine the thrust from the hot stream is greater than that from the cold stream, but in a high by-pass turbofan engine the thrust from the hot stream is less than that from the cold stream. The cold stream has a lower speed than the hot stream and it causes a turbofan engine to achieve higher propulsive efficiency than a turbojet. In a propeller engine, the air leaves the propeller at a slower speed than even the cold stream of a turbofan so at slow speeds a propeller-driven aircraft has higher propulsive efficiency than a turbofan. The downwash from the rotor of a helicopter is even slower than the flow through the propeller of a propeller-driven aircraft, so the lift generated by a helicopter is done fairly efficiently but nowhere near as efficiently as the lift generated by a fixed-wing. Also, helicopters are condemned to be much slower aircraft than fixed-wing aircraft so the fuel consumed per unit of horizontal distance will always be higher for a helicopter than for a fixed-wing aircraft of similar payload capacity. Dolphin (t) 07:08, 16 April 2011 (UTC)

Maximum carrying capacity of aircraft

Our article on the Airbus A380 says that it is certified to carry up to 853 passengers, almost a thousand people. That got me wondering, just how big can we theoretically make aircraft, assuming that cost-benefit-risk ratios were not much of a factor? (What sort of actual physical limits would there be on the size of aircraft?) What would be a good estimate for the upper limit on the number of passengers a long-distance airplane could theoretically carry (again, assuming cost-benefit-risk ratios were not much of a factor)? Could an airplane for 2,000 people be built? 5,000? 10,000? 20,000? 50,000? 100,000? Would such an enormous airplane fly more efficiently with fixed wings or with rotors?

—SeekingAnswers (reply) 04:09, 12 April 2011 (UTC)

Roughly speaking, larger aircrafts need larger engines and more fuel to operate; and they must be able to lift their own engines and their own fuel. What this means is that the larger an aircraft is, all other things being equal, the larger the proportion of its weight will be taken up fuel and engines, and thus the smaller the proportion of its weight will be availible for passengers and cargo. Given a set of materials and general construction mechanisms, there is an upper limit for any aircraft design, in terms of size. This probably varies depending on the exact aircraft type, but there is a limit. --Jayron32 04:16, 12 April 2011 (UTC)

The above comment needs sources. While the first part – that larger aircraft will require larger engines – is reasonable, the second assumption – that larger aircraft must use proportionately more mass for engines and fuel – doesn't (ahem) fly. Fuel efficiency in transportation#Aircraft notes that a 747 uses about one-sixth the fuel per passenger mile of a Gulfstream business jet. I strongly suspect – though I would welcome a search for valid numbers – the thrust-to-weight ratio of turbofan engines generally improves slightly as the engines get more powerful, and not the other way around. Upper limits on aircraft size are governed by the maximum capacity of airport facilities (including gate and taxiway spacings) and the amount of time it takes to load and unload passengers and cargo from a hypothetical extremely large passenger aircraft, rather than physical limitations on aircraft efficiency. Few routes carry enough traffic to justify aircraft carrying more than five hundred passengers, and even on high-traffic shorter-haul routes an airline my prefer to use two fast-loading jets instead of one big craft that spends a long time at the gate. Aircraft manufacturers have no incentive to design aircraft that won't be able to land at existing airports and which airlines won't want or need to buy. TenOfAllTrades(talk) 16:41, 12 April 2011 (UTC)

Airports preparing for the A380 had to extend and widen runways, and modify terminal facilities so people could get on and off the plane in a sensible time. The same would apply for bigger planes, only more so. HiLo48 (talk) 06:01, 12 April 2011 (UTC)

So, assuming you have unlimited budget and no concern for profit, does anyone have any actual maximum passenger estimates? My thinking is that at some size, even with unlimited budget and no concern for profit, you would still encounter insurmountable problems because of fuselage stress issues (as in, compressive stress, tensile stress, etc., would make aluminum and titanium no longer viable options for construction), and you would have to turn to increasingly exotic construction materials. —SeekingAnswers (reply) 06:27, 12 April 2011 (UTC)

I'm not sure that there is an upper limit, if we ignore costs/benefit analysis. After all, you could just chain multiple airplanes together and call it a single airplane. As for a large, single fuselage plane, perhaps a ground effects airplane (no article ?) that launches and lands in water would work best, since that would eliminate the need for runways, and would limit fuel req's. See Spruce Goose (if we made this out of aluminum or composites it would be far more practical). StuRat (talk) 06:55, 12 April 2011 (UTC)

There is an article at ground effect vehicle, and I've now created a redirect from "ground effects airplane". But yes, my question regarding an estimate for the upper bounds of passengers is for a single-fuselage plane. I'd also be interested in any comments people have for the type of construction materials to use for this theoretical maximum-size aircraft. —SeekingAnswers (reply) 09:53, 12 April 2011 (UTC)

According to this there is a worldwide limit at air terminal gates of 80 meters wing span. The A380 fits at 79.8 meter wing span but the "Spruce Goose" is too large at 97 meters wing span. Cuddlyable3 (talk) 13:07, 12 April 2011 (UTC)

Also, the Spruce Goose would need to have the runway flooded! Alansplodge (talk) 20:34, 14 April 2011 (UTC)

I've seen a documentary about 10 years ago in which it was pointed out that flying wing designs become more efficient for very large planes and that an optimal design for a plane capable of carrying many thousands of passengers would look like a giant flying saucer. Count Iblis (talk) 14:24, 12 April 2011 (UTC)

You might want to read about the Antonov An-225 which is the world′s heaviest aircraft and also longer than the Spruce Goose (although not as wide). Our article says it can carry 640 tonnes, so I guess you could equip it to carry more people than the A380 can if you wanted to. SmartSE (talk) 15:15, 12 April 2011 (UTC)

A regulatory limitation, as opposed to a physical limitation, is the requirement that the airplane be capable of evacuation in 90 seconds, limiting travel distance and requiring increasing numbers of exits. Acroterion (talk) 17:05, 12 April 2011 (UTC)

Giant Sequoia

How long do Giant Sequoias live up to? 174.114.236.41 (talk) 04:19, 12 April 2011 (UTC)

According to our Giant Sequoia article, the "oldest known Giant Sequoia based on ring count is 3,500 years old." —SeekingAnswers (reply) 04:38, 12 April 2011 (UTC)

Taxonomy/Etymology question...

Opossum

Possum

I understand that the Australian Possum and the North American Opossum are only very distantly related; they belong to different orders. Still, I have a question about the etymology of the Australian Possum name specifically. It seems that the North American Opossum gets its name from an Algonquin word. That makes sense; they were here before the English speakers, and lots of native New World animals and plants have derived their English name from Native American names. I am quite sure that is also true about Australian animal and plant names; many of them derive from Aboriginal names of the same critters. Still, I am thus confronted with an interesting conundrum: How is it that these two marsupials should have similar names at such a geographic distance. I am left with some unsatisfying possibilities:

• That the Australians took the name of the American animals and applied it their own. This doesn't seem to make much sense; other than being marsupials, Possums and Opossums don't look all that much alike; Opossums are more rodent-like in appearence, Possums more resemble primates like Lemurs or Bushbabys. Furthermore, the entire idea that Australians would appropriate a Native American name, to describe a native Australian species seems a bit weird, if you ask me, and any path that would take the name from North America to Australia seems quite convoluted.
• The Australian Possum is derived from an Aboriginal name after all. This seems equally weird; Aboriginal languages and Native American languages are linguisticly so far apart, I can't imagine one influencing the other, and yet this would be an example of the most bizarrely close False cognates I;ve heard, how random that both Aborigines and Native Americans would have given similar names to small marsupials.

So, to sum up this insanely long question: What is the actual etymology of the Australian Possum's name? --Jayron32 05:28, 12 April 2011 (UTC)

Dictionaries that I consulted are unanimous in stating that "possum" is derived from an abbreviation of "opossum." I don't find this puzzling at all, actually. The Americas were settled by Europeans much earlier (by centuries) than Australia was (late 18th century), so the word "opossum", and its informal abbreviation of "possum", would already have been well-established in the English language. Thus, while it would be strange for Australians to appropriate a Native American name, it would not be strange for them to appropriate an American or a common English language name, which is probably what they thought it was. I doubt the first Australian settlers were even aware that the word "opossum" was of Native American origin; they probably just thought of it as another regular word in the English language. They're both marsupials. And to the layman, opossums and possums look very much alike. Just look at the photos (File:Opossum_2.jpg and File:Trichosurus vulpecula 1.jpg, which I also posted to the right) in the infoboxes at the top of the articles (as of this current writing) for the two respective animals; those photos look a lot alike at a casual glance. —SeekingAnswers (reply) 06:08, 12 April 2011 (UTC)

My Australian Macquarie Dictionary suggests that the two words are connected and interchangeable, so yes, Australia did borrow the American word. HiLo48 (talk) 06:11, 12 April 2011 (UTC)

Just by the way, hardly anyone actually says opossum in the States, at least outside of a scholarly context. In normal colloquial speech they are called possum. Using the two words distinctively is likely to lead to confusion. --Trovatore (talk) 19:07, 12 April 2011 (UTC)

According to Wiktionary, the phrase "playing possum" is documented back to 1822. I think the Australian possum does the same thing but I'm not sure. Actually, the Australian Possum doesn't look like an opossum to me - because of its face it makes me thing more of kangaroos and koalas than the opossums I've seen - I suspect it's the creature's behavior that has given it its name. Wnt (talk) 21:25, 12 April 2011 (UTC)

Note that although only one species of opossum is found in the United States, several dozen species can be found in South America. (A few extend as far north as Mexico.) Some of the South America species, such as the Gray Short-tailed Opossum, look quite a bit more like an Australian possum than the Virginia Opossum does. Looie496 (talk) 21:35, 12 April 2011 (UTC)

The power of noise

What proportion of the power of a jet engine or car engine is wasted in producing noise? My notion is that the most efficient engine would be silent. In other words, by how much would the ratio of output/input power increase if all noise energy was redirected to the output power? Do high efficiency modern engines tend to be quieter? Thanks 92.15.21.224 (talk) 13:23, 12 April 2011 (UTC)

Only a very small portion of the energy goes into sound itself. However, a loud engine may be indicative of other inefficiencies, such as friction, turbulence, cavitation (on prop attached to boat engine), an unbalanced engine, or missing cylinders (internal combustion engine), which tend to waste most energy as wear, heat, and vibration. So, a silent engine likely would be more efficient, yes. (Note that this logic doesn't apply to noise which is produced by the engine but then muffled in some way; this actually reduces engine efficiency.) StuRat (talk) 17:26, 12 April 2011 (UTC)

Before starting, I should say that so far as I've seen, measurements regarding sound are nearly always dishonest or actively misleading. Either a manufacturer wants you to believe something is more powerful than it is, or a polluter wants you to think it is weaker. Numbers are usually given in "decibels", but the decibel is a relative unit, i.e. meaningless on its own, tied to one of many different arbitrary reference levels - the article gives some of the many sub-definitions used. A particularly obnoxious trick is the usage of a "filter" (dBA) which supposedly reproduces the characteristics of human hearing - by means of a simple mathematical curve which underestimates the impact of low frequencies. And even that is relative to a curve generated by psychoacoustic measurements... I take particular exception to the low-frequency business because people do hear infrasound and suffer physiological effects from it, but it is claimed, not "consciously" (i.e. they don't call the vibration/sensation they feel a sound); for those deemed unable to hear things which are plainly audible, psychology rapidly wears out its welcome. Another use of psychoacoustics is frequently seen when a polluter takes data that people surveyed on a form said that a 10 dB increase is only a 2-fold increase (even though it's more), and uses it to say that their newest proposal will only "sound" twice as loud.

Now that hopefully I've emphasized the need for you to take such data with a truckload of salt, I'll point you to sound power, which gives some energy figures. Though I am quite suspicious that an excavator is quieter than a heavy truck, for example. To convert these to a few other sound measures, see [3]; probably there are others. But the bottom line is that if the figures in the article can be trusted, vehicles generally emit less energy, perhaps much less, by sound than from their headlights. Wnt (talk) 22:05, 12 April 2011 (UTC)

Yea, that 1/100 of a watt for helicopter noise seems particularly low. That article needs some work. StuRat (talk) 22:12, 12 April 2011 (UTC)

A jet engine delivers "noisy" i.e. irregular thrust. Longitudinal pressure variation in the output stream is just the way it delivers useful power and all the jetstream is good, though not for your ears if you stand behind a jet aeroplane. The only wasted sound power is that emitted radially (and, at subsonic speed, forwards) from the engine. A car's reciprocating combustion engine cannot be silent because of its pulsing exhaust. By dimensioning the intake and exhaust tracts to resonate at particular engine speeds, high efficiency (which can be variously defined) is obtainable with the inconvenience of loud noise. (Formula One racers are very noisy.) Two-stroke engines can only work with a resonant exhaust so they are always noisy, while four-stroke car engines are usually muffled in a compromise with efficiency but will not be completely silent. Cuddlyable3 (talk) 22:14, 13 April 2011 (UTC)

What will happen if bicycle tyre will be filled using Helium gas?

What will happen if bicycle tyre will be filled using Helium gas? — Preceding unsigned comment added by Mayank3 (talk • contribs) 13:37, 12 April 2011 (UTC)

It's an interesting question! What sorts of effects do you expect might happen? DMacks (talk) 14:05, 12 April 2011 (UTC)

The compressed helium in the tire would weigh slightly less than the compressed air when the tire was inflated to the same pressure. One would have to know the volume of gas contained in the inflated tire to calculate the exact weight difference. The weight of the gas in the tire might be very insignificant compared to the weight of the tire and the bicycle: helium in the tires would not make the bike lighter than air, for instance. The helium would likely leak out of the tire quicker than air leaks out, since it is monatomic compared to the larger and heavier molecules of the component gases in air. It might have a lower viscosity, and circulate more freely inside the tire. It would have greater thermal conductivity than air. Being an inert gas, it would not react chemically with the rubber of the tube or tire as would the oxygen in air. Edison (talk) 14:10, 12 April 2011 (UTC)

To expand a bit on Edison's response, the helium in the tire will weigh proportionally quite bit less than the same volume and pressure of air: about 85% less, in fact. In absolute terms, however, the mass of air in the tires makes a negligible contribution to the bicycle's – or even the tire's – weight; there's only a few grams of air in each tire, accounting for something like 0.1% of the total weight of the bike. TenOfAllTrades(talk) 15:17, 12 April 2011 (UTC)

Furthermore, the tire would go flatter much faster; Edison lights on this but fails to name the effect, which is called Graham's law of diffusion. A mathematical treatment of Graham's law is covered in that article if you are interested. --Jayron32 15:34, 12 April 2011 (UTC)

Filling it with hydrogen gas instead may give spectacular effects in case of an accidental tire puncture :) Count Iblis (talk) 14:16, 12 April 2011 (UTC)

Only if punctured with something that is also on fire. Hydrogen is not spontaneously combustable; perhaps you are thinking of the Hindenburg disaster, whose explosion cause was unknown, however given the properties of hydrogen all of the serious hypothesis revolve around a source of either fire or electricity as the initial cause. Hydrogen itself will not explode without sufficient cause, and merely puncturing the tire is not sufficent cause. --Jayron32 15:34, 12 April 2011 (UTC)

Yes, but then the so-called "inversion temperature" of hydrogen is lower than room temperature. This means that when under pressure and then expanding into the environment, it will heat up, not cool down like most other gasses, due to the Joule-Thomson effect (the temperature of an ideal gas will not change. While due to exansion it would cool down , the energy goes into kinetic energy of the gas; it shoots out of the puncture, that kinetic energy is subsequently dissipated and heats up the gas again). This is why hydrogen is never stored under pressure at room temperature (which complicates implementation of green energy technologies that depend on hydrogen to store energy, e.g. generated from wind energy). Count Iblis (talk) 15:48, 12 April 2011 (UTC)

Er, hydrogen is frequently stored (and readily available) as a room-temperature compressed gas; see for example hydrogen tank for some specs. Google offers lots of additional pictures: [4]. And a bicycle tire – starting at perhaps six atmospheres of pressure – is never going to reach the autoignition temperature of hydrogen through simple expansion. TenOfAllTrades(talk) 17:00, 12 April 2011 (UTC)

I see! I blame my old Prof. for giving a misleading homework problem on this issue a long time ago, although I should have been able to see that you don't get problems with tires. Count Iblis (talk) 01:45, 13 April 2011 (UTC)

What eventually happens to a beam of light?

Does it keep getting red-shifted for eternity? Imagine Reason (talk) 16:09, 12 April 2011 (UTC)

If the red shift doesn't get it, extinction will. --Sean 17:19, 12 April 2011 (UTC)

How could the photon change? Where would the energy go? Metric-expansion red shift never really made sense to me, so I don't really understand how it happens. My best guess is that it's only the relative difference in velocity between the objects in space and the photon that changes (so it only redshifts relative to you), but I'm not clear on how the energy budget is worked out. Ariel. (talk) 01:53, 13 April 2011 (UTC)

Do the articles Red shift and Photon help? Cuddlyable3 (talk) 14:07, 13 April 2011 (UTC)

Your guess is right. The redshift happens because the source of light and the detector are moving away from each other. The energy at emission will not be the same as the energy at detection because they are measured in two different inertial frames. Dauto (talk) 18:35, 13 April 2011 (UTC)

Eliminating sex

(sorry my English) One of the common themes in a lot of science fiction tales is a society that no longer repruce by bilogical sex. I wonder to wich extent that would be possible with current technology. For example, suposse a relatively isolate community (something like the Amish) Then imagine this community decide to apply chemical castration to all its male babys and oly reproduce by artificial insemination. Could this community efectivily erase both the desire and the need of sex in a generation or two? --83.59.47.204 (talk) 17:43, 12 April 2011 (UTC)

How is chemically castrating all the males (which probably would erase the desire in all males anyway, simply greatly reduce it) going to erase the desire in females? In addition, I'm doubtful chemical castration has ever been tried on male babies and even ignoring the ethical considerations I would guess given the way most forms of chemical castration work it's going to cause a great degree of feminisation of the males as they develop to the point where you will have trouble getting sperm for the artificial insemination and who knows what other problems. Nil Einne (talk) 17:53, 12 April 2011 (UTC)

Many science fiction tales seem to be based on the idea that you can't totally erase the human instinct to have sex and/or reproduce naturally. See the film THX 1138 for example. I don't know about eradicating human sexual desire...but I imagine that, in theory, it is possible to sustain a human population through artificial reproduction, and that over many generations, we might evolve to a point where we have no sexual desires. But that's just speculation. Quinn ^☂THUNDER 18:03, 12 April 2011 (UTC)

I expect that removing testes and ovaries at birth (or before), then reproducing by cloning, would pretty much eliminate sexual desire. You could also have all males or all females, and thus at least eliminate any hetero sex. StuRat (talk) 19:00, 12 April 2011 (UTC)

That all presumes that the sexual drive is a purely reproductive one, but the sexual act itself is done for all sorts of reasons, social, emotional, etc. To eliminate the reproductive desire does not necessarily eliminate the other sorts of reasons why people have sex; its why efforts to sterilize or chemically castrate males who have committed sex crimes have limited success in stopping them; they aren't committing sex crimes because of a desire to reproduce; as often as not its about establishing power relationships or other issues which have nothing to do with reproduction. --Jayron32 19:23, 12 April 2011 (UTC)

That's where the "at birth (or before)" part comes in. If you wait until adulthood to remove them, then the hormones will have already altered the brain in a sexual way. You must remove them before the brain becomes sexualized. All other sexual stimuli, like porno movies and pictures, would also need to be removed. If your brain has no concept of sex, then it can't have any concept of rape, either. (Of course, there are many other ways to humiliate people, like defecating on them, which might then become more prevalent.) StuRat (talk) 19:30, 12 April 2011 (UTC)

Well, you hit on one big point there; sexual abuse is in many ways the symptom of other social problems; removing sex as an option would not necessarily change rapists into fine people. It may very well just change the mode of abuse without altering the underlying causes that make some peopel want to be abusive. --Jayron32 19:39, 12 April 2011 (UTC)

Every life form currently living on Earth has excelled at one thing: reproducing. In vertebrate species, reproduction is usually sexual. If any behaviors are determined by evolution and genetics, copulation (i.e. 'having sex') is the most likely. Lastly, in order for some sort of asexuality to be 'evolved' it would have to be advantageous under selective pressure. You may be interested in the species which have evolved parthenogensis. This is common among the insects, such as aphids, and even some lizards and fish can reproduce this way. We suspect that this lack of sexual recombination may lead to an evolutionary bottleneck, and ultimately the extinction of the species. SemanticMantis (talk) 20:57, 12 April 2011 (UTC)

In Brave New World (1932), reproductive sex is banned but recreational sex is encouraged. Most people are infertile anyway because of the chemical treatment they receive during their pre-natal development in an Artificial uterus. Fortunately, science has not yet devised one. Alansplodge (talk) 20:25, 14 April 2011 (UTC)

UV emission from electric arcs

What is the actual mechanism of ultra violet emission from electric arcs.--92.28.38.62 (talk) 18:05, 12 April 2011 (UTC)

Electric arcing causes a lot of non-specific excitation of electrons, across a broad spectrum of wavelengths. Generally, certain types of wavelengths are closely associated with certain types of excitation (for example, the infrared wavelength is particularly correlated with vibrational modes, while radio waves are found in the range of nuclear magnetic resonance). In a situation like an electric spark, you are basically exciting electrons non-specifically, so they tend to promote to higher energy levels, and re-emit photons as they relax, between nearly every allowable transition within the material. Basically, they don't just emit in the ultraviolet, they emit in the ultraviolet along with emitting in just about every frequency from radio waves through to the UV. Radio waves emitted by simple electric sparks was, for example, one of the cornerstone areas of research that eventually led to modern radio technology, see Heinrich Hertz. --Jayron32 19:18, 12 April 2011 (UTC)

Farmer's action plan?

There is a large farm located on the Eastern shore and the farm grows corps, and to many bugs is destroying the crops and the farmer last year sprayed heavy doses of pesticides, this year the farmer was asked not to use the same chemicals and wants to control the amount of soil that is being washed into the stream. What is an action plan that will help the Bay and the farmer —Preceding unsigned comment added by 71.191.176.79 (talk) 22:07, 12 April 2011 (UTC)

Sounds suspiciously like homework, but, in case it's not, here's some thoughts:

1) Plant crops which are more resistant to "bugs".

2) Introduce natural predators of those "bugs".

3) Utilize "no till" planting methods.

4) Plant trees at the edges of fields to limit both wind and rainwater losses of soil. StuRat (talk) 23:30, 12 April 2011 (UTC)

Don't forget Bt corn. This would be easier to answer if we knew the crop, the bug, and the pesticide. Wnt (talk) 00:54, 13 April 2011 (UTC)

The farmer could also plant cover crops in the fall (like alfalfa, which, aside from simply reducing weather-based erosion, restores favorable levels of nitrogen in the soil). Juliancolton (talk) 02:14, 13 April 2011 (UTC)

Just for the benefit of the readers who aren't familiar with Atlantic Seaboard of the U.S. geography, the Eastern Shore refers to the Maryland and Virgina parts of the Delmarva Peninsula. The Bay referenced would then be the Chesapeake Bay. The region is known for agriculture, large industrial chicken farming, and crab fishing. --Jayron32 05:32, 13 April 2011 (UTC)

light-bulb

hows the glass attached to the metal in this http://www.traderscity.com/board/products-1/offers-to-sell-and-export-1/mr16-gu10-halogen-light-bulb-240-volt-energy-saver-gu10-lamp-50w-189861/ — Preceding unsigned comment added by Wdk789 (talk • contribs) 23:32, 12 April 2011 (UTC)

Since the late 19th century a substance called "vitrite" was used to join metal of the incandesent lightbulb shell to the glass bulb. Edison (talk) 05:14, 13 April 2011 (UTC)

Wikipedia does have a brief article on it: Vitrite. --Jayron32 05:25, 13 April 2011 (UTC)

Note where the info about vitrite came from. Wikipedia previously called it "vitrit."

Mining of thick seams

some of the ways of mining thick seams are :

• blasting gallery method
• inclined slicing method
• horizontal slicing method
• sublevel caving

can anybody explain the methods? — Preceding unsigned comment added by Him.12.pat (talk • contribs) 23:33, 12 April 2011 (UTC)

I just looked on Google, there are websites which cover this. I think you could find out most of this information yourself. Your question sounds like homework.217.158.236.14 (talk) 12:24, 13 April 2011 (UTC)

wrong named structure

• 

To my mind the structure shown on the picture should be named 3-Methyl 4-propyle-octane because you have to choose the main-chain with the most branches. I dont participate very often in the en wp so id like to ask sb from here to either correct the structures name or to (let) deleate it. Greetings --Oliver s. (talk) 23:38, 12 April 2011 (UTC)

Straight from the IUPAC themselves:

The longest chain is numbered from one end to the other by Arabic numerals, the direction being so chosen as to give the lowest numbers possible to the side chains. When series of locants containing the same number of terms are compared term by term, that series is "lowest" which contains the lowest number on the occasion of the first difference. This principle is applied irrespective of the nature of the substituents.

See also IUPAC_nomenclature_of_organic_chemistry#Alkanes. Your rule (main-chain with the most branches) is used only when there are two or more possible main chains of the same length. Buddy431 (talk) 23:51, 12 April 2011 (UTC)

3-methyl 4-propyl is lower numbered than 4-(1-methylpropyl), so far as I know. When I search for "3-methyl 4-propyl octane" I get a few serious-looking mentions, whereas the other name only gets me derivatives with a lower numbered substituent, and Wikipedia hits. (including a talk page discussion about someone being wrong for naming the compound that way) Wnt (talk) 00:52, 13 April 2011 (UTC)

The OP is correct. I assume the molecule is being used to demonstrate how to name a molecule with a branch off of a branch, but it doesn't work because there ARE two main chains of the same length (both octanes) and in that case you choose which octane has the most branches. So the 3-methyl-4-propyloctane is a better name for that reason. It also works with the rule quoted above, because the alternate name, being 4-(1-methylpropyl)octane has the "occasion of the first difference" on carbon 4, whereas the 3-methyl-4-propyloctane has it on carbon 3. Since it has the lowest number of first difference (3 vs. 4) its the better name. Using either rule, that's still a badly named compound. --Jayron32 01:23, 13 April 2011 (UTC)

Good catch Jayron. I was counting 7 carbons on the chain the OP wanted to be the main one. They say organic chemists only need to be able to count to 8, but it doesn't even look like I can do that. Buddy431 (talk) 03:20, 13 April 2011 (UTC)

• so I have to recommend to deleate the missleading picture: http://commons.wikimedia.org/wiki/Commons:Deletion_requests/File:Iupac-alkane-5.png --Oliver s. (talk) 14:19, 13 April 2011 (UTC)

April 13

Speed of Earth's orbit around the sun

I read that earth orbit's the sun at a speed of 107,000 KM/H, which seems mighty fast. Given this imense speed, I find it somewhat surprising that we do not feel any wind resistance here on earth. I mean if you stuck your head out of a car window travelling at 100 KM/H you would feel a strong gust of wind in your face, yet we are tearing through space at 107,000 KM/H without so much as a feint breeze? Perhaps somebody might be able to enlighten me as to why this is! Kind Regards. Paul —Preceding unsigned comment added by 79.71.91.21 (talk) 02:09, 13 April 2011 (UTC)

If you keep your head inside that car window, and keep the window closed, you also don't feel any breeze, yet you're still travelling at 100km/h relative to the road surface, because the air in the car is also travelling with you at 100km/h. Same with the Earth. Its air comes with us as we hurtle along, so we don't feel a thing. — Preceding unsigned comment added by HiLo48 (talk • contribs) 02:22, 13 April 2011

Yes, the speed of the Earth relative to the sun is very fast, but the sun is a very long way off. The sun is at such a great distance that even though the relative speed is 107 km.hr^-1 it takes the Earth one whole year to complete one trip around the sun. That is an angular speed of only 0.0411 degrees per hour which is extremely slow. There is no atmosphere between Earth and the sun, and no atmosphere means no wind when moving relative to the sun.

Earth's linear speed relative to the other planets in our solar system is also extremely large, but the angular speed is extremely small so we experience no effects from our speed relative to those planets.

A jet airliner might pass overhead at a speed of 1000 km.hr^-1 and a height of 40,000 feet (12 200 m) but you experience no effects because of the great distance between you and the airliner. If the jet airliner passed near you (close to ground level) you would experience many effects! Dolphin (t) 06:48, 13 April 2011 (UTC)

Paul you may be interested in the Michelson–Morley experiment that was carried out in an attempt to detect some kind of "wind" due to the Earth's motion, and is famous for having completely failed. (I simplified this story). Cuddlyable3 (talk) 13:52, 13 April 2011 (UTC)

Those experiments strongly (and unexpectedly) demonstrated a phenomenon that the then-current theories were totally unable to explain. For a physical experiment, that counts as a spectacular success -- the opposite of a complete failure. –Henning Makholm (talk) 16:14, 13 April 2011 (UTC)

Once again proving that there are no failures in science; a negative result is still a result, and it is all data. --Jayron32 18:56, 13 April 2011 (UTC)

Well, you can have failures, like when an experiment results in a vague result that's of no use at all, or when different people doing the experiment get different results. These usually mean the experiment was poorly designed. StuRat (talk) 06:33, 14 April 2011 (UTC)

No Henning Makholm. Lorentz-Fitzgerald length contraction was a theory that explained the negative result of the MM experiment. If Albert had not come along later with his special relativity we would probably still find Lorentz's aethereal hypotheses plausible. Cuddlyable3 (talk) 21:31, 13 April 2011 (UTC)

I would like to point out that the diameter of the Earth is 12,750 km, so the planet takes seven minutes to travel its own width. Meanwhile, your car travels its own width in a tenth of a second and a turtle walks its own width in maybe five seconds. If you were watching the Earth from above, it would look very slow. —Preceding unsigned comment added by 205.193.96.10 (talk) 16:03, 13 April 2011 (UTC)

Using decay heat in a nuclear reactor to spin a turbine

I did a presentation in a class of mine, and part of it discussed nuclear energy. The professor asked me if it was possible to use the decay heat produced in a nuclear reactor in a scram situation to spin a turbine which would power a water pump to cool the reactor. I was fairly certain that this idea was not possible simply because it does not generate enough steam to spin a turbine, but I'm not entirely sure. I'm pretty sure they disconnect the reactor from the turbine anyway during a scram for safety reasons. Can anyone confirm my guesses? ScienceApe (talk) 02:33, 13 April 2011 (UTC)

In principle the waste heat could be used to turn a turbine, though probably not the main turbine(s) used for regular electrical generation (the initial decay heat will be less than 10% of the reactor's regular output, and this will decline in the days following the scram). In practice, adding a second turbine (with all of the associated mechanical complexity and necessary preventive maintenance on parts that would be in working contact with radioactive coolant) isn't worth the complexity and cost over other solutions to drive the pumps. (Generally, grid power as the first option, and backup diesel generators as the second.) TenOfAllTrades(talk) 03:27, 13 April 2011 (UTC)

Wasn't that a system in place at Chernobyl that they were testing when the accident occurred? And I thought they referred to s similar system at the Fukushima 1 plants. A scrammed reactor should produce plenty of steam for a while to ruin emergency cooling pumps. Nuke plants are all about complexity and cost, with backups to backups. Edison (talk) 16:14, 13 April 2011 (UTC)

Did you mean to say "run" instead of "ruin" ? StuRat (talk) 06:27, 14 April 2011 (UTC)

The system being tested at Chernobyl was to run the cooling pumps off the residual kinetic energy of the turbine for the 60 seconds it would take to activate the emergency generators. --Carnildo (talk) 00:17, 14 April 2011 (UTC)

This system exists already, at least on french nuclear reactors (PWR). I think it exists also in the US since french reactors were originally constructed with a Westinghouse licence. This kind of steam turbine was also in place in Fukushima I nuclear reactors but you still need a cooling function to remove heat from the system if you want to operate with a closed cycle. You also need a minimum electrical supply to control it (this can be supplied with batteries). — Preceding unsigned comment added by Franssoua (talk • contribs) 12:49, 14 April 2011 (UTC)

whey gel

what exactly is whey gel? —Preceding unsigned comment added by 80.1.216.243 (talk) 03:39, 13 April 2011 (UTC)

It is a gel formed from Whey protein. You can read both of those articles to learn both what a "gel" is and what "Whey protein" is. --Jayron32 04:03, 13 April 2011 (UTC)

Universe = black hole, for some of time... or wait, only in the sideways version of time, which is length (*confused mumbling*)

OK I've been doing some thinking about the universe. Let's say there's this guy, and he's just chilling looking at our universe from the outside right before the big bang. Now, because the universe is ridiculously massive and small, it will appear to him like a black hole. And he is sitting right outside the event horizon (naturally this is the mother of all black holes - being the mass of the universe at ~1.6×10^55 kg and a Schwarzschild radius of approximately a two trillion light years [5] [6] - can this be right?!).

Now do I understand properly, that because he is outside the event horizon, everything that occurs within will be unobservable to him? Time on the surface of the event horizon is frozen for him, and time inside is on an entirely different plane of existence (piece of trivia: I heard one theoretical physicist put it this way: time bends on the fourth dimensional level, and length becomes time, and time length). As such, the big bang will never exist for our friend on the outside of the black hole. At best, current theories indicate he might (or might not) be able to deduce what occurs inside only from an extremely accurate reading of the Hawking radiation (see Holographic principle#Black hole information paradox).

Thus, if I understand properly, it is entirely possible that we live in a universe which is encapsulated within another universe, but the second universe will remain forever unattainable to us. No matter how much the universe expands, because we are dealing with infinitely small meters and units of time (on the event horizon, from the perspective of the outside... god knows what the hell happens inside), we will never reach that universe. I realize this isn't an entirely new concept (I saw Leonard Susskind explain it similarly), but it... kind of made sense to me for the first time tonight, when I thought it up on my own.

So I have some questions about all this:

1. If something were to enter the black hole from the outside, when and how would we perceive it on the inside?
2. Could it be, with the super-screwed-up-ness of time and space, that tracing back to the big bang is really just tracing back to the beginning of the existence of the black hole? And we would experience it entirely backwards (instead of matter falling in, vice versa), in a mad confusing turn of events because time is all goofed up.
3. Addendum to above: possibly all matter that can fall in has already fallen into the black hole before the big bang? And the entire external universe has already all ended, because it took infinite time for even a second to pass within? I'd have to assume Hawking radiation turned out incorrect. Thus we experience the big bang as the beginning of time, but really it's the end of time for the external universe. Much in the same way as someone traveling on a photon would have the entirety of time pass before experiencing even a second.
4. My understanding is that, given the right conditions of a spinning black hole, the singularity can be exposed to the outside world. What would happen then? What would it look like?

OK, I hope I haven't textwalled here too much, and I've stated this clearly enough that you all can understand it. I know I haven't stated it clearly. Anyway, am I making any sense at all?Magog the Ogre (talk) 06:37, 13 April 2011 (UTC)

Unlike some of the people here, I'm no expert, but aren't there a couple of problems with treating the big bang as a black-hole style singularity. I believe time and space came about in the big bang, standing outside it makes no sense. (unlike standing outside a black hole, of course) Isn't the concept of observing anything flawed with no concept of time and space? Grandiose (me, talk, contribs) 08:18, 13 April 2011 (UTC)

I have two questions:

1) can black hole return to expand or exploding to produce new objects?

2) about the big bang and expanding of universe ,there is no boundary and centre for universe , is there remnant matter in first point which big bang started?(this helps imagining )-78.38.28.3 (talk) 08:37, 13 April 2011 (UTC)

[Fixed your formatting for clarity, 78] In brief:

1) It is thought that, given long enough, all black holes will eventually evaporate by giving off Hawking radiation, but the time this takes is in some inverse proportion to their size, so black holes of star-mass or larger might take longer than the Universe itself will exist to evaporate (from the first link: "For a black hole of one solar mass . . . we get an evaporation time of 2.098 × 10⁶⁷ years"). Otherwise (we think), no.

2) There is no one "first point where the Big Bang started" because that point itself has now expanded to form the whole of the Universe. The Big Bang was also an expansion of space (and time) itself, not just of some matter within pre-existing space. To put it another way, everywhere is that "first point". This is, of course, very difficult for us to visualise. {The poster formerly known as 87.81.230.195} 90.197.66.111 (talk) 12:53, 13 April 2011 (UTC)

The error in your hypothetical scenario is subtle—it presumes that there is somewhere for an observer to sit outside the Universe, where he can watch the show. (That scamp Douglas Adams can be blamed for this perception, as he offered us the Big Bang Burger Bar as the natural complement to Milliways, The Restaurant at the End of the Universe.) Outside the Big Bang singularity, there just isn't any space to be in, and no way to watch the big...bang as it happens. TenOfAllTrades(talk) 15:10, 13 April 2011 (UTC)

4 It look like black hole from outside —Preceding unsigned comment added by 77.127.207.138 (talk) 15:47, 13 April 2011 (UTC)

Outside ? It's confusing to think about these things because of the tendency to think of the metric expansion of space being like a 2-sphere expanding into 3D space....but it isn't. Sean.hoyland - talk 16:10, 13 April 2011 (UTC)

"Big bang theory". Phewy, bah humbug, hogwash. I can think of no other scientific postulation which has received such resounding, universal acceptance based on such flimsy empirical evidence(other than perhaps the flat earth theory). Oh yes another one might be "god done it". The big bang is no more an explanation than the bible is. Think about it.190.149.154.194 (talk) 17:08, 13 April 2011 (UTC)

Perhaps I should clarify. Befor the existance of time or space or the universe,(something?) went bang and brought everything including itself into existance. What? Metaphysical mumbo jumbo.190.149.154.194 (talk) 17:21, 13 April 2011 (UTC)

Read Big bang#Observational evidence for the empirical evidence for the big bang. Dauto (talk) 17:48, 13 April 2011 (UTC)

The Big Bang theory is one of the best-evidenced scientific theories in the world, provided you understand its inherent limitations (briefly, that it describes effects and not cause). — Lomn 17:50, 13 April 2011 (UTC)

Thanks guys. I have no difficulty with hubble's expansion conclusions or with penzias and wilsons observations of residual electromagnetic radiation. I do however have a problem with the general assertion that the logical back track of those observations indicate the origin of the universe. It seems clear that what is being learned is part of the history of the universe, not neccessarily the origin. I think that basically sums up my argument.190.148.132.153 (talk) 19:07, 13 April 2011 (UTC)

I think that most (if not all) cosmologists would agree, these days. -- BenRG (talk) 20:38, 13 April 2011 (UTC)

but agine it cold be cycle in time , and be black hole agine . —Preceding unsigned comment added by 77.125.91.113 (talk) 22:35, 14 April 2011 (UTC)

Contrary to popular belief, you can put a big bang cosmos inside a larger universe that didn't start at the big bang, at least in classical general relativity. From the outside, the big bang cosmos has the same gravitational field as any other object with that mass. (This means the mass has to be finite—which means that the homogeneous cosmos that we find ourselves in has to have an edge out there somewhere—but that's consistent with observations if the edge is far enough away.) The big bang appears from outside as a white hole. In a black hole there's an event horizon that can only be crossed from outside to inside, and anything that does cross it ends up at the singularity, while anything that doesn't cross it ends up at future infinity. A white hole is the time-reversed version of that: there's an event horizon that can only be crossed from inside to outside, and anything that crosses it started out at the singularity (the big bang singularity, in this case), while anything that doesn't cross it started out at past infinity. The big bang singularity is inaccessible from the outside universe, but all of the matter that originates from it crosses the event horizon, after which there are no restrictions on two-way travel between the big bang and non-big-bang regions.

However, if there's a positive cosmological constant, then long-distance travel eventually becomes impossible. In the real world, assuming future expansion is dominated by the cosmological constant, I think that it's already too late to reach the edge of the visible universe, much less the edge of the whole big bang cosmos (if there even is one). Also, I don't know how quantum gravity alters this picture. Classically, the white hole has to have existed forever from the outside universe's perspective, but I don't see why it wouldn't Hawking-radiate away once you add quantum effects. It may be that nothing I said above makes sense in quantum gravity. (And all of it is almost certainly wrong in any case, even if it works in theory.) -- BenRG (talk) 20:38, 13 April 2011 (UTC)

Finally I love supernovae for their brightness in exploding (as many people suppose they are new ) and their rule in sending our body and our earth elements here and their heart (neutron star )which have palpitation such as our heart does

akbarmohammadzade--78.38.28.3 (talk) 04:16, 14 April 2011 (UTC)

BenRG - thank you for your response. At the risk of sounding nasty, I'm getting kind of tired of hearing it repeated ad nauseum on RD/S that "time doesn't exist outside of the big bang" (I've run into this paradigm problem when asking questions here before). It's just wrong - from the perspective inside of the big bang, time outside would not exist if I'm not mistaken (hence the white hole). But there is no reason that anything outside of it couldn't exist. Now the only question is: how would a white hole that massive appear to the outside? And what would the time scales look like? Is it even possible it might appear like a black hole? Magog the Ogre (talk) 01:53, 17 April 2011 (UTC)

you need as i imagin to divide what is happening in our condition of life and way of our sensing the time and relativistic time, and the way which do our mind think , then comparing those to find better way of imaginary,and intering to place there is no time. the subject and question brout below I think be useful for you .

. akbarmohammadzade--78.38.28.3 (talk) 03:32, 17 April 2011 (UTC)

how dos god see us ?

Imagine the piston of your car , you do start your car and run , after one hour you may go 70 KM your car weels did rotate 70000 times and motor piston moved 180000times , for you time spends slowly and for apoint on car weel middle and for a point on piston very fast. our brain thinks abslotly free from time , so the future and passed time and recent is equal for it ,we are seeing big bang and its events with ability of our strong brain and its modeling , and out standing not to be nessesery. we round earth axis one time per day , our year is 365 days , but one day for sun is 27days and one year for sun is 225 million years . there is in holy kuran that one day in after death time equals our 50000years , and the earth had created in 6 days ,of course those are not equal our recent days . we dont know troughly god's mind .and his way of creation , some things will appear to us after death . that was examined for miones reached to sea side and observed on top of hill , the time spending is very slovly for mion and its half life .(for its speed %99.9C)

akbarmohammadzade--78.38.28.3 (talk) 03:32, 17 April 2011 (UTC)

Bear pit

The article says that a bear pit trap can deter bears from approaching a cabin. How could that be? If bears are smart enough to avoid falling in it, wouldnt they be smart enough to simply walk around it? Thanks 92.15.19.232 (talk) 13:11, 13 April 2011 (UTC)

Perhaps bears are just smart enough to keep away from anything that looks dangerous or smells human, but not up to complex route planning. Here is the editthat added the information to the article Bear pit. You might leave a message to the editor on their Talk page or raise the question at the article talk page. Cuddlyable3 (talk) 13:37, 13 April 2011 (UTC)

It's unreferenced and sounds pretty questionable to me. I'd just remove it and maybe leave a note about it on the talk page. --Sean 19:32, 13 April 2011 (UTC)

What about the girzzly bear that watched its mother and probably other older siblings get killed by a hunters and then continued to watch as the hunters gathered arount the mother to take pictures with it. The juvenile bear must have watched for a while as the hunters "hugged" and "played" with the mother. Later the same hunters were back and had the juvenile in their sights when the bear rolled over on its back and played dead showing submissive behavior while slowly coming closer to the hunters. it let them pet it and touch it as if saying here do what you want but don't kill me. it was on TV and it changed the hunter's life forever. —Preceding unsigned comment added by 98.221.254.154 (talk) 02:07, 14 April 2011 (UTC)

Maybe they are so "smart" that they know if they see 1 pit in the area there is likely to be others that they might not see.98.221.254.154 (talk) 02:50, 14 April 2011 (UTC)

That's what I think was implied, but that seems a bit beyond bear intelligence, to me. StuRat (talk) 06:23, 14 April 2011 (UTC)

Not really, did you read the question? He's asking why they DIDN'T walk around the one they saw. Does the juvenile bear's behavior in my previous example also seem beyond bear intelligence to you? —Preceding unsigned comment added by 165.212.189.187 (talk) 13:42, 14 April 2011 (UTC)

I was under the impression that bears were a fairly intelligent group of animals. Googlemeister (talk) 15:29, 14 April 2011 (UTC)

Fairly intelligent yes, probably on the order of dogs. But seeing one trap and then extrapolating that there may be others requires that it think about what you are thinking ("He's trying to trap me !"), getting into game theory. This is likely beyond all but the most intelligent animals. Although I suppose there might be a way to figure it out using less intelligence. If I found something bizarre in the woods, I might look for it again in the same spot, even if I had no idea who or what caused it to appear there and what their motivation, if any, might be. Perhaps a bear can work on this level. StuRat (talk) 18:14, 15 April 2011 (UTC)

Well, I may not be any smarter than the average bear, but I'm fairly certain the implication in that article is that the pit has to go 360 around your cabin. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:41, 17 April 2011 (UTC)

Would that be called a pit ? That's more of a trench, or, if filled with water, a moat. StuRat (talk) 21:04, 17 April 2011 (UTC)

The key question is: Never mind the bear walking around the pit... how can you ensure that he will take a path that will even lead to the pit in the first place? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:06, 17 April 2011 (UTC)

Mass-energy conversion of the human body

One of the sources I've read claims that the conversion of the human body mass to energy would produce a 200-300 TNT megaton explosion, Another source, however, states that because the basic human body components - carbon, hydrogen, oxygen and nitrogen - have low molecular weight and a lower proportion of internal energy, the released energy would be far less than that from the nuclear weapons. Which is right?--89.76.224.253 (talk) 16:17, 13 April 2011 (UTC)

My suspicion is the difference is in how you are proposing to convert the mass to energy. If you're talking about throwing a human into a human-sized chunk of anti-matter (a more or less pure conversion of mass into energy), then you'd get something like a massive nuclear explosion. If you're talking about any other, more conventional method (e.g. burning alive), you're getting considerably less than that. --Mr.98 (talk) 16:20, 13 April 2011 (UTC)

Going by the mass–energy equivalence, the human body would be around 4.5 to 11 EJ (ballpark estimate for adults - ~50 to ~120 kg). That is, very roughly, between 1000 and 2600 megatons of TNT. By comparison, the biggest bomb ever created by humans was around 50 megatons of TNT. --Link ^(t•c•m) 17:10, 13 April 2011 (UTC)

Evaporated Water Consumption

If one consumes water with absolutely no salts, what are the major disorders one might run into? Most of the disorders found in wiki and google search are caused by a single salt/mineral deficiency. Also what specifically does the body go through when there are no salts present in the water consumed? Does this affect kidneys? Is it true that salt deficiency causes body to borrow salts from bones resulting in calcial erosion of bones in process? —  Hamza  ^{[ talk ]} 17:29, 13 April 2011 (UTC)

Does this help? --TammyMoet (talk) 18:12, 13 April 2011 (UTC)

Actually, I think Water intoxication is more relevent; water intoxication is caused when consumed water causes the electrolytes (salts) in the bodies fluids to become diluted to a dangerous point. --Jayron32 18:53, 13 April 2011 (UTC)

Water intoxication can (and in practice usually does, as it's what people usually drink) involve regular tap water and mineral-containing spring water; it's not confined to demineralized or distilled water, and indeed the trace minerals present in most water don't make an appreciable difference to body or blood electrolyte levels. TenOfAllTrades(talk) 19:39, 13 April 2011 (UTC)

Note that you can get the salts you need from food, they needn't be in the water. StuRat (talk) 02:05, 14 April 2011 (UTC)

How did the hills of Rwanda form, and how old are the soils?

Rwanda is the "land of a thousand hills", but I can't work out how they were formed. In the UK, AFAIK, most hills were formed by the last glaciation - how do hills form on the equator? On a related note, can anyone find out roughly how old the soils in the south of Rwanda are (we'll be talking millions of years)? _{(google is not being my friend today)} SmartSE (talk) 18:35, 13 April 2011 (UTC)

Rwanda lies in the western branch, pretty much right under those two red triangles

Rwanda lies on the western fork of the Great Rift Valley, see the map to the right. The hills in Rwanda are thus caused by Plate Tectonics, i.e. in this case the area is literally being torn into two pieces as the Somali Plate seperates from the African Plate. Along plate boundaries, you get a lot of geologic activity, from volcanism to subduction to folding, and I suspect that, given where Rwanda is, despite being such a small country, you can find ample evidence of all of this. In geology, all of these process are called Orogeny, which roughly means "mountain birth". Sadly, I cannot find any articles on the Geology of Africa or of the Rwanda region. The template below, filled with redlinks, shows that this is likely a MUCH needed area of Wikipedia. Alas, I hear there is a new Pokeman coming out soon, so I think this is going to be pushed to the back burner for a bit longer while more important work gets done.--Jayron32 18:48, 13 April 2011 (UTC)

The geology of Rwanda is pretty complicated so it probably depends on which hills you are talking about. Generally speaking though, in the tropics like elsewhere, landforms like hills are formed by climate+the nature of the rocks+the biological activity...only much faster. Rock can be turned into soils through chemical weathering and high rainfall, transported away somewhere else either by water or landslides/soil creep/slow flow processes etc pretty quickly in the tropics. Well, that and whatever else is going on geologically that could effect the landscape like rifting, volcanic activity etc etc. Sean.hoyland - talk 19:12, 13 April 2011 (UTC)

I was going to go start linking the geography articles of those respective countries, then I realized... Not the same thing at all. Falconus^{p t c} 22:41, 13 April 2011 (UTC)

Follow-up on cleaning apple juice bottles for recycling

Referring to this question, I am happy to say I finally threw out the first of about half a dozen apple juice bottles.

Using hot water and dishwashing liquid, but mostly repeating the process of filing the bottle with water and adding dishwashing liquid and shaking it up every now and then when I prepared my bottles for recycling, I finally looked at one bottle and realized it was clean enough to go.

The others still look a mess. I suppose I could take them, but someone would have a lot of work to do and they might just reject them at whatever facility processes them.

Yes, it has been over a year. I had no idea.Vchimpanzee · talk · contributions · 18:40, 13 April 2011 (UTC)

At least you didn't send them to the recycling center Bluefist ^talk 13:26, 14 April 2011 (UTC)

It seems that you may have the wrong idea about what recycling is. It's true that if you wash out a bottle and put something else in it you can say that you recycled it, but that is not how a recycling facility does it. At a commercial recycling facility the sorted plastics are melted down and reformed into other products. Any contaminants (such as apple juice and other stuff) are iliminated by processing and melting. Therefor a simple rinse out one time with water will aid the processing slightly. It is not neccessary to make them clean enough to put food into.190.56.16.167 (talk) 20:18, 13 April 2011 (UTC)

Another thought. If your bottles are made of glass the same thing applies. The glass will be smashed up and melted down to make other bottles or maybe a window. You dont need to make them clean enough for food. Germs will not survive the melting process.190.149.154.28 (talk) 21:00, 13 April 2011 (UTC)

Where I live the recyclers say to just recycle the item without any cleaning at all, just leave remaining food or juice on it. I suspect it will get washed later anyway. Graeme Bartlett (talk) 21:39, 13 April 2011 (UTC)

My understand was the washing of recycling was more to prevent Rats or Cats or whatever other street creature from making a mess of your recycling box to get at that last bit of baked beans your tin didn't get clean (similarly to reduce smell given that my recycling is only collected once a fortnight). ny156uk (talk) 22:06, 13 April 2011 (UTC)

What is your goal? to help the environment? if so then you might want to consider all the electricity for the hot water, the good, clean potable water that you wasted cleaning the bottles, the soap you wasted and added to the once good water that now has to be removed by some water treatment facility. all because you wanted to clean some organic biodegradable material off the glass bottles? think a little farther than your nose. —Preceding unsigned comment added by 98.221.254.154 (talk) 02:17, 14 April 2011 (UTC)

I don't know what my goal is. I just didn't want to put those filthy bottles in with the regular recyclables. Ordianrily, the stuff left in the bottles will get washed out easily and the bottles will be clean. These were bottles I waited too long to wash out and they're disgusting. Maybe they would accept them. I do know if I'm not careful to clean some of the items, the perfectly good recyclables in the bin could get messed up. By the way, I didn't waste soap. I waited until the bottle of dishwashing liquid was nearly empty. I probably did waste water.Vchimpanzee · talk · contributions · 19:32, 14 April 2011 (UTC)

I'm surprised you responded to the IP's "think a little farther than your nose" comment. I'm sure the environmental impact of the equipment and infrastructure he used to post that comment far exceeded your bit of water and soap. Sean.hoyland - talk 19:58, 14 April 2011 (UTC)

That's stupid. Nobody bought a computer just to reply to this post.

The goal here presumably isn't to put the bottles in the recycling bin. The goal is to make a positive impact by doing so as opposed to throwing it in the trash. (By saving glass.)

98.221 made a perfectly valid point that water and energy have been wasted in the attempt to save a little glass. APL (talk) 15:07, 15 April 2011 (UTC)

I could be wrong, but it seems unlikely your recyclables are kept separate when they leave your bin. In other words, it doesn't really matter how clean your recyclables are, they're going to get 'messed up' by other people's recyclables... Nil Einne (talk) 20:40, 14 April 2011 (UTC)

I'm surprised they don't make an effort. We have a giant container we throw all the recyclables in. At one time the different types were separated. I don't have a bin of my own because recycling is a recent introduction in my community. I still take everything 'to the dump" as I always did. If I asked for a bin like my neighbors have, I'd have to remember to put it out every Monday. Chances are I wouldn't.Vchimpanzee · talk · contributions · 22:50, 14 April 2011 (UTC)

For those who may wonder, my father took the trash on Saturday, and at some point I started going with him but it was always after lucnh. I'm still in the habit of going at that time or, if the college library near my house is closed, later in the day. The recyclables go in what look like milk crates. I'm not sure how we started doing that. Once the town got trash pickup, I chose to keep doing what I always did, even after they added recycling pickup.Vchimpanzee · talk · contributions · 21:13, 15 April 2011 (UTC)

Do we feel heat from the sun because of Infra Red, or because of the energy in the entire spectrum?

Whenever people talk about being warmed by infra red radiation from the sun, I always grumble and say that the entire spectrum of light contains energy, and that infra red just happens to be the frequency that warm bodies on earth emit, and so we think of that as heat.

However, I recently read in [7] that "Far infrared waves are thermal. In other words, we experience this type of infrared radiation every day in the form of heat." So this NASA site seems to be saying that there really is a difference between IR light and other light when we are feeling heat from the light source. Is that right? Have I been confused all along? Can we not get warm from just the visible/UV spectrum of the sun (if there is enough of it)?

Thanks! — Sam 71.184.188.110 (talk) 22:30, 13 April 2011 (UTC)

You are not wrong. The sentence you quoted is about perception, we experience some frequencies as vision, and others as heat. But both can cause warming. However there is a somewhat more light energy available as infrared than as visible light (from the sun), so most warming is from the infrared. Ariel. (talk) 22:41, 13 April 2011 (UTC)

But you can have very bright, but "cold" light right? Vespine (talk) 22:44, 13 April 2011 (UTC)

I think the reflectance characteristic of each frequency is very relevant. See Spectral reflectance curve. The frequencies we associate with visible light are readily reflected from opaque surfaces and that is one of the reasons we can see things with the naked eye, but little of the energy with those frequencies is transmitted into the opaque surface to raise its temperature. The frequencies we associate with the infra-red band are not so readily reflected from opaque surfaces so most of the energy in the IR band is transmitted into the opaque surface and so raises its temperature. Also see Infrared#Heat and Thermal radiation. Dolphin (t) 22:55, 13 April 2011 (UTC)

The so called "cold" light is a light bulb that produces little Infrared while producing visible light. Of course, visible light is also a form of heat so "cold" light does produce heat. Dauto (talk) 23:58, 13 April 2011 (UTC)

"But you can have very bright, but "cold" light right?" Not if the source is blackbody radiation. The spectrum emitted because of thermal energy is a well-defined function, and the intensity is rigidly bound to the frequency-distribution. Both of those parameters are determined by the source object's temperature.

A non-thermal source of radiation can provide any spectral distribution; it can radiate at specific frequencies (observable as individual spectral emission lines), or can radiate over a wide range of frequencies, with continuously varying intensities.

But again, if the source is due to thermal emission, then the total amount of energy radiated is defined by the temperature of the source (which also defines the spectral distribution that gets radiated). The mathematical formula that defines this relationship is Wien's displacement law. Loosely speaking, it's not possible to have very bright radiation from a very cold source: decreasing the temperature decreases the total amount of radiated power and changes the shape of the spectrum. Nimur (talk) 00:17, 14 April 2011 (UTC)

Just as an aside - "cold" lightbulbs, such as a cold cathode fluorescent lamp, are not thermal radiators: they fluoresce (producing photon-emission via a totally different physical process), and thus are not a blackbody radiator. This is very different than an incandescent lightbulb. Nimur (talk) 00:20, 14 April 2011 (UTC)

Not if the source is blackbody radiation But we're not talking about "the source", we're talking about the "light" it self. if you have some IR and heat shielding that transmits only visible light, then that light can be bright and "cold" right? As in if you shine it on a thermometer it won't heat it up? Vespine (talk) 02:00, 14 April 2011 (UTC)

The only thing that matters is the total irradiance, and how well light of that wavelength is absorbed. If a surface has equal absorptivity for visible light and infrared, then a 1 W beam of infrared will heat it up exactly the same as a 1 W beam of visible light. Talking about light being "cold" is meaningless.--Srleffler (talk) 02:38, 14 April 2011 (UTC)

Correct. The mathematical model of color temperature is an attempt to fit a black-body curve to a light-source. But if the light source isn't black-body-like, then its effective temperature has very little physical meaning. Nimur (talk) 02:49, 14 April 2011 (UTC)

Heat is the sum of all of the kinetic forms of energy experienced by a molecule, these are usually classified into 3 types of motion: translation (that is, moving in a straight line), rotation (spinning around an axis) and vibration (deformations of the molecule along bonds). Photons in the IR range cause molecules to vibrate, basically by exciting the electrons that occupy the molecular orbitals that hold the molecule together. The article and section Infrared_spectroscopy#Theory and stuff in that area describes how IR photons do that, and the various ways that a molecule can vibrate. Here's the important connections to make, for the layperson: Vibration of molecules is heat. Its not that we "perceive" it as heat, it not that we "sense" it as "warmth" or anything like that: vibration is heat. Since IR photons cause electrons to become excited in such a way as to cause molecules to vibrate, quite literally IR light causes heat. In a very direct sense, by the most basic definition of what heat is. --Jayron32 02:23, 14 April 2011 (UTC)

But visible light and UV cause heat too. Anytime electromagnetic radiation is absorbed in a material, the result is heat.--Srleffler (talk) 02:38, 14 April 2011 (UTC)

Not necessarily. Absorbed light will always cause electronic transition from one quantum state to another. However, this transition does not necessarily cause the substance to gain thermal energy. Thermal energy (heat) is only that energy that involved increases in kinetic energy of the molecules themselves; an electron moving to a higher energy quantum state does not necessarily cause the molecules of the substance to move faster; it MAY cause that to happen, but only in situations where there is significant coupling between, say, electronic states and vibrational states (vibronic coupling). Absorbed light may cause other things to happen as well, such as chemical reactions (Homolysis being a major one), fluorescence, phosphorescence, or simply immediate re-emission of the same wavelength photon. --Jayron32 04:07, 14 April 2011 (UTC)

Jayron, you're making the very common mistake of confusing the word heat (which is energy transferred to a substance by a variety of methods including radiation - IR, UV, visible, etc, all included) with the internal kinetic energy. Besides, most of the visible light that is not reflected and does get absorbed eventually does find its way into the vibrational modes of the molecules. Dauto (talk) 14:52, 14 April 2011 (UTC)

Procession of the Perihelion

Prior to the acceptance of GR what other attempts had been made to explain the peculiar mercurial motion. So far I have:

1. Planet Vulcan
2. Gravity as an $r^{2.00000016}$ instead of $r^{2}$ law

Please add to the list if you know of any! Thanks. —Preceding unsigned comment added by 92.20.205.185 (talk) 22:46, 13 April 2011 (UTC)

For one thing, gravity is a $r^{-2}$ law, not a $r^{2}$ law. (Sorry for the nitpicking). Dauto (talk) 00:07, 14 April 2011 (UTC)

Why not at all, Newton claimed the source mass required to produce a unit force on a test particle at a distance $r$ scaled as $r^{2}$. —Preceding unsigned comment added by 92.20.205.185 (talk) 00:46, 14 April 2011 (UTC)

April 14

Pseudoscience: suspended water

I know this seems ridiculous, but there is no harm in asking. This video on youtube (of course) has a person do a magic trick where he removes a cup leaving water in suspended animation. I highly doubt this as possible and is probably just a joke, but how did he fake it in the first place? Even faking this stunt seems inconceivable. Bugboy52.4 ¦ =-= 03:28, 14 April 2011 (UTC)

Looks like CGI to me. The "suspended" water seems to be obviously added in post production; it becomes even clearer when frame through the video. There are certain frames where it seems rather obvious that the water isn't "sitting" on the desk. This sort of thing is relatively easy to fake with pure CGI alone. Modern computer animation is fully capable of placing an animated object in a virtual 3D space and tracking camera movements such that you can view the object from all angles. I see no reason why a sufficiently talented animator couldn't have done this. --Jayron32 04:38, 14 April 2011 (UTC)

I found something for you: [8]. It seems you can find glitches in his animation; where for a few frames, the "suspended" water jumps illogically; in the middle of a normal pan, for a few frames, the water moves the wrong way before resuming normal motion. Its plainly an effect added after the fact. --Jayron32 04:45, 14 April 2011 (UTC)

I spotted another glitch myself. If you watch the inverted image of the countertop behind the "suspended water", around the 1:45 mark, the image illogically jumps from one place in the "suspended water" to another, without a smooth transition. There's no reason it should do that. If you play the 2-3 seconds before it, and the 2-3 seconds after it, you can see what I mean. Just rock back and forth over that, and you see where there's an obvious glitch in his animation. --Jayron32 04:49, 14 April 2011 (UTC)

Ha, very good! I wonder how many people will "try it". lol.Vespine (talk) 05:43, 14 April 2011 (UTC)

If I were going to fake this, I'd use clear gelatin or a carefully frozen cup of ice to get the basic form and then animate in effects to make it look more like free-standing water. a good afternoon's work, but easy enough or a bored high-school kid with time on his hands. no complex cgi involved. --Ludwigs2 06:10, 14 April 2011 (UTC)

Probably a parody of this comic strip by B. Kliban that has been making the rounds on the internet recently. Flicker Link.

I'd like to see someone try that second one. APL (talk) 13:27, 14 April 2011 (UTC)

I don't know, I'm not convinced about this. The image through the water seems amazingly believable, and above all... where does the water come from when he breaks the water cone? I'm leaning toward believing that there is some kind of physical transparent membrane involved. I see the slight dimming at 1:45, but that might plausibly be the effect of reflection hitting the videocamera's light meter. The shift to include more at the top of the image in the water cone matches a slight lowering of the camera. If it's a CGI fake it's pretty impressive! And the cartoon seems more a parody of this than the other way around. Wnt (talk) 05:03, 15 April 2011 (UTC)

Spilling water across a surface isn't a difficult thing to animate... --Jayron32 05:19, 15 April 2011 (UTC)

1) Prank "Science" videos are very common on YouTube. They're practically a genre in and of themselves.

2) The match-moving techniques needed for this sort of thing were impressive and Hollywood-only a few years ago, but commonplace now.

3) The guy who posted this is a computer animator!!! Look at his other videos!

Also, the cartoonist I just linked died twenty years ago, he's not drawing parodies of youtube videos. APL (talk) 14:56, 15 April 2011 (UTC)

FIBONCCI NUMBER

what cause the nature to obey fibonacci number? --78.38.28.3 (talk) 05:38, 14 April 2011 (UTC) —Preceding unsigned comment added by 78.38.28.3 (talk) 05:37, 14 April 2011 (UTC)

The fibonacci series is a type of power series; in that way it nicely models growth patterns. In other words, things tend to grow from themselves; one cell produces additional cells, which produce additional cells themselves, and so on. One way to model this is through exponential growth, but that only works where the growth occurs via individuals (i.e. one free bacterium divides into two, each of those divide into two, etc. etc.) When you have a situation where you have growth which is restricted by the new copies, for example the way a Chambered Nautilus shell grows is that each successive growth can only occur at the opening of the shell. The shell cannot grow in all directions, only in a highly constricted direction. This growth will not occur exponentially, since parts of the shell which have already produced new shell are now "surrounded" by that shell, and don't have any room to produce any more shell around them. It will only occur at the leading edge of the shell, and this is better modeled by an additive power series rather than a multiplicative one. Hence, the connection to the fibonacci series, the best known example of an additive power series. --Jayron32 05:57, 14 April 2011 (UTC)

Point of clarification for the purposes of general education. Nature does not obey mathematical formulae. Mathematical formulae are human inventions that describe different aspects of nature, often without any real understanding of why nature might behave in that fashion. Never forget the basic paradigm of modern science: if your formulae say one thing and nature does something else, it's not nature that's made a mistake. --Ludwigs2 06:19, 14 April 2011 (UTC)

True, that's why I stated that nature is modeled by the fibonacci series and exponential growth. Those are human-created explanations for nature. I recall what a chemistry professor of mine once said... "Molecules do what molecules do, and if they don't obey the rules that we give them, that's our problem and not theirs." The same is true for all of science. --Jayron32 17:28, 14 April 2011 (UTC)

On the other hand, Julia Robinson looked at it the other way around, that the mathematics of numbers is "the one real thing". Sean.hoyland - talk 18:25, 14 April 2011 (UTC)

The continued fraction expansion of the fibonacci number tells us that it is the number that is least good approximated by rational numbers. Depending on the physical context, this helps to avoid resonances. 95.112.246.93 (talk) 09:31, 14 April 2011 (UTC)

See http://www.evolutionoftruth.com/adm/contents.htm. -- Wavelength (talk) 23:17, 14 April 2011 (UTC)

I'm not sure spamming links to pseudoscience sites is appropriate here. Look, I am a professing evangelical Christian, and Jesus Christ is my lord and savior, and that website is still unmitigated bullshit. --Jayron32 05:18, 15 April 2011 (UTC)

Cardiomyopathy

What is the meaning of the term "constrictive cardiomyopathy"? aniketnik 08:21, 14 April 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

A number of useful definitions turn up when you google your term. Eg. [9]. Aaadddaaammm (talk) 09:02, 14 April 2011 (UTC)

Pycnodeuterium

How credible is the existence of Pycnodeuterium ? My google hits all relate it to cold fusion which raise some extra doubts about it. 95.112.246.93 (talk) 09:39, 14 April 2011 (UTC)

Palladium is well known to absorb large amounts of hydrogen (of which deuterium is an isotope) into its crystal lattice: see Palladium hydride. I'm not sure what the particular qualities are attributed to "Pycnodeuterium" are: is it just deuterium adsorbed into the palladium crystal structure? Because that absolutely does happen, even if it doesn't allow cold fusion. Buddy431 (talk) 23:29, 14 April 2011 (UTC)

The article tells of "ultrahigh density deuterium lump" and does not mention simple hydrogen. As D is a boson whereas H is not, Bose–Einstein condensate comes to mind. Regrettably, the article does not even specify how "ultrahigh" the density really is. 95.112.143.65 (talk) 08:46, 15 April 2011 (UTC)

Here's the journal article that it came from: [10], and the pdf of the full article where it is specifically mentioned that both regular hydrogen and deuterium are absorbed similarly. The fusion they're talking about is real , hot fusion that occurs in stars (where pressure forces the deuterium to form a metallic solid). The authors were exploring the possibility of reproducing this hot fusion that occurs in stars by forcing deuterium into a palladium crystal, essentially forcing the hydrogen (deuterium) into an orderly metallic solid state, due to the nature of the palladium crystal. The ideas and terms from the paper might have been misappropriated by cold fusion advocates, but it looks like the research is relatively sound, if not nearly as exciting as some would like us to believe. Buddy431 (talk) 16:53, 15 April 2011 (UTC)

physical education

what are the effects of physical activities in human body? —Preceding unsigned comment added by 41.59.1.50 (talk) 10:28, 14 April 2011 (UTC)

As from my experience, mostly Abrasions and Hematoma, but probably this is not what you are asking for. 95.112.246.93 (talk) 12:02, 14 April 2011 (UTC)

See physical exercise. --Tango (talk) 12:56, 14 April 2011 (UTC)

Hmm, "Physical exercise is any bodily activity that enhances or maintains physical fitness and overall health and wellness." (from physical exercise). If so, then it is well different from what our (or at least, my) teachers forced us to do at school. At times I was so depleted I had to vomit. I remember a class mate left with a broken nose. But as the OP's question is probably homework, this is no thing to say to the teacher who is in power to have get your nose broken and get away with it. 95.112.246.93 (talk) 17:24, 14 April 2011 (UTC)

Differences between conservative and liberal brain

Please help to expand this article. — Preceding unsigned comment added by Brain Researcher (talk • contribs)

No, see wp:MEDRS in relation to single sourced studies and media reports. There's no literature review available on the field, the article ought to be deleted until multiple studies are available. Remember cold fusion? Fifelfoo (talk) 11:34, 14 April 2011 (UTC)

(after EC) The reference desk is a good place to ask questions or request information. If you have questions about the article in question, feel free to post them. However, as it appears that you created the article in question and are now trying to recruit assistance in its development so that it doesn't get deleted, my questions are "why should we expand the article, and with what?" These types of juicy, controversial findings are quick to grab the attention of news agencies (ABC, NY Daily News, Fox as cited in the article) or blogs, but I happen to agree that the subject is not worthy of its own encyclopedic article and should be merged into another existing article or dispensed with entirely until the results have been replicated and better understood. --- Medical geneticist (talk) 11:37, 14 April 2011 (UTC)

Well, afd will be the right place for this discussion. BTW, I was not aware of wp:MEDRS when I created this article. I think since the study is covered by major news organizations, it meets WP:N. So the article can be renamed like Kanai's study of political orientation and brain structure?? --Brain Researcher (talk) 11:43, 14 April 2011 (UTC)

See [11][12][13][14]--Brain Researcher (talk) 11:46, 14 April 2011 (UTC)

This appears to be based on a single small study - hence is likely not-notable ubnder WP guidelines at all. Collect (talk) 11:49, 14 April 2011 (UTC)

Comment: There are previous studies on this topic [15] So we have resolved the single study issue. --Brain Researcher (talk) 11:50, 14 April 2011 (UTC)

And the smallness of the study? Seems conclusively not-notable. Collect (talk) 11:51, 14 April 2011 (UTC)

Please see these links: 1. study published in Nature Neuroscience by New York University and UCLA scientists in 2007 [16], 2. online survey by psychologists in 2009 [17], 3. study in New Scientist in 2008 [18] So we now have multiple studies. And it is not "the study", it "the studies". --Brain Researcher (talk) 11:57, 14 April 2011 (UTC)

AFD commenced. Fifelfoo (talk) 12:00, 14 April 2011 (UTC)

Perhaps this information would be best summarized as a subheading under political psychology (which itself is a pretty mangy article in much need of help). That being said, the main caveats to these studies will remain a small sample size, lack of independent confirmation, and very little insight into causation. --- Medical geneticist (talk) 15:04, 14 April 2011 (UTC)

The people who want this deleted will oppose it no matter what. Debating their issues is pretty much a waste of your time. Something I tried to include earlier, only to run into multiple instant reverters for the faith wherever I put it:^[19]

According to the ASA, IQ data from the "Add Health" survey averaged 106 for adolescents identifying as "very liberal", versus 95 for those calling themselves "very conservative". An unrelated study in 2009 found that among students applying to U.S. universities, conservatism correlated negatively with SAT, Vocabulary, and Analogy test scores. According to a 2004 study by the Pew Research Center, liberals were the most educated ideological demographic and were tied with the conservative sub-group, the "Enterprisers", for the most affluent group. Of those who identified as liberal, 49% were college graduates and 41% had household incomes exceeding $75,000, compared to 27% and 28% as the national average, respectively.

Wnt (talk) 20:31, 14 April 2011 (UTC)

xrays and vitamins

what effect if any would airplane xrays (the ones for checked baggage) have on vitamin supplements and their efficacy? 70.31.58.245 (talk) 11:51, 14 April 2011 (UTC)

The short answer is 'none'. This discussion starts off with a good list of links to sources, though most refer to the smaller, lower-power scanners used for carry-on bags. This post is from a health physicist who measured the dose absorbed by checked luggage on a number of occasions, measuring doses ranging from 35-211 millirem; that's equivalent to between about one and six months' exposure to natural background radiation. TenOfAllTrades(talk) 13:36, 14 April 2011 (UTC)

thank you, that was an awesome answer. much appreciate your time. 70.31.58.245 (talk) 23:09, 14 April 2011 (UTC)

Are there any trends in the half-lifes of isotopes?

If there is, how accurate can we predict an isotope's half-life that is undiscovered?--Inspector (talk) 15:05, 14 April 2011 (UTC)

The island of stability discusses this a bit — theoretical trends make it seem like there might be superheavy elements with relatively long half lives. However it is unclear if this will be true in practice — when you start loading up nuclei to levels that we've never seen before, it's possible that other sorts of effects start to kick in (e.g. deformation of the nucleus, or quantum tunneling) which would affect their stability. My qualitative take away from the article, reading between the lines, is that there are trends, there are theoretical models, but the confidence in these theories being accurate is heavily qualified. Perhaps someone else can give a more informed answer... --Mr.98 (talk) 15:19, 14 April 2011 (UTC)

There are some very general trends. A greater difference in number of neutrons from the that of stable isotopes correlates with shorter half-life. One can see these general trends in graphs such as the one at right. For example, the half-life of undiscovered ¹¹He is likely to be shorter than the 2.7×10⁻²¹ half-life of ¹⁰He (but there is no guarantee). 148.177.1.210 (talk) 15:32, 14 April 2011 (UTC)

But how accurate can we make predictions? I doubt the validity of some isotopes listed in the isotope articles, after I checked out the references below, because it did not cite any other sources. It's like anyone can make a number as long as it looks reasonable. Are there any academic sources discuss about the formula and accuracy of the predictions?--Inspector (talk) 13:26, 15 April 2011 (UTC)

shivers down my spine -- are they endorphins?

Sometimes if I'm listening to a piece of good music (or something particularly touching) or make some sort of epiphany, I can feel a wave of relaxation, etc. wash over me. Are they endorphins being released? I'm not sure if it's purely nervous, because the effect lingers well after the initial stimulus. John Riemann Soong (talk) 16:17, 14 April 2011 (UTC)

I don't know, but I think the phenomenon you describe falls under the umbrella of ASMR, "Autonomous Sensory Meridian Response". This term may help you find related information, though it doesn't seem to have much serious scientific study devoted to it. You may be interested in this recent thread on metafilter [20], which gives several audio and video examples that trigger this response. SemanticMantis (talk) 16:51, 14 April 2011 (UTC)

The term "Autonomous Sensory Meridian Response" seems to be purely an internet phenomenon -- it gets zero hits on Google Scholar or Google Books. Shivers down the spine are also known as "chills" or a frisson (French for shiver), but regardless of what they are called, not a great deal is known about their physiology. They are clearly related to "piloerection", i. e. the hair on the back of the neck standing up, and it has been suggested that the response depends on opiates, but that doesn't seem to be proven. This freely available paper summarizes what is known about them, and this paper describes their brain activity correlates and discusses the evidence regarding what causes them. Looie496 (talk) 22:03, 14 April 2011 (UTC)

Looie, for "not a great deal known" that paper you posted certainly has a lot of info. When I was in school studying this stuff, I recall it being considered part of the fight or flight response. Your info is better.OrangeMarlin ^{Talk• Contributions} 22:08, 14 April 2011 (UTC)

Shaking all over deliberately and involuntarily. (videos) Cuddlyable3 (talk) 12:46, 15 April 2011 (UTC)

Breacking neck

Why breacking neck is fatal while breacking other body parts is not?--89.76.224.253 (talk) 17:11, 14 April 2011 (UTC)

Because the neck contains the spinal cord which carries signals from your brain to other parts of your body. If you sever the spinal cord in the wrong place, your brain can no longer send signals to, say, the muscles that make you breathe. That would be contraindicated in for those seeking a long life... --Jayron32 17:21, 14 April 2011 (UTC)

There are rather important things protected by the cervical vertebrae... — Scientizzle 17:22, 14 April 2011 (UTC)

First, breaking your neck is not always fatal. (See Paraplegia and Quadraplegia) Where it is fatal, it is usually because the neck is broken and the spinal cord is severed high up (C1, C2, C3). This cuts the messages from the brain to the body and essential functions, like breathing and heartbeat, are stopped. Bielle (talk) 17:25, 14 April 2011 (UTC) (Sorry to those who answered above. I didn't get an "ec", or I would not have written. Bielle (talk) 17:26, 14 April 2011 (UTC)

Mike the Headless Chicken survived for a while. Cuddlyable3 (talk) 12:28, 15 April 2011 (UTC)

sorry for the ignorance. What does 'ec' mean.190.56.107.170 (talk) 20:15, 14 April 2011 (UTC)

It (normally) stands for edit conflict - more information on that there. Grandiose (me, talk, contribs) 20:49, 14 April 2011 (UTC)

Why half-life is more important than total decay?

Although I may be wrong.--89.76.224.253 (talk) 17:14, 14 April 2011 (UTC)

I'm not sure I follow the question. Can you explain what you mean by "more important" and in what context you are asking? --Jayron32 17:19, 14 April 2011 (UTC)

Maybe you're wondering why we measure the time for half of a sample to decay, rather than the time for the full sample to decay (the "full-life")? This is because atoms decay exponentially, which means that the rate of decay slows down in such a way that the "full-life" would mathematically be infinite. So the only thing which can be meaningfully measured is the time until some chosen proportion decays, and 1/2 seems like a natural choice for a proportion to measure. (I'd assumed that half-life would explain this, but it doesn't seem to address the question specifically.) Staecker (talk) 18:18, 14 April 2011 (UTC)

The half-life article may be a little confusing because it seems not to contain a graph. this graph may make it easier to understand. If the half-life is one year, then it takes one year for it to decay by half, and then another year for what's left to decay by half again, and another year for what's left to decay by half again... So in two years, you will approximately a quarter of the original substance left, and in three years you will have an eighth of the original substance left. In ten years you will have 0.0009% of the substance remaining, and there may still be a tiny bit of stuff remaining after 100 years. This is why the "full" decay isn't something you can really measure. Note that this isn't some special property of radioactive decay, it's a property of statistics. If everyone flips coins and you discard all the tails, then half will be discarded after one flip, then half of what's left will be discarded after the second flip, etc... — Sam 63.138.152.135 (talk) 18:59, 14 April 2011 (UTC)

What is special about radioactive decay is that it is probabilistic, unlike e.g. Newtonian mechanics. In the coin example, it is not exactly half the coins that come up tails, that is merely the expected value. In a given toss of 100 coins, we may only see 10 tails. Half-life works well for macroscopic samples due to the law of large numbers, so the chance of seeing significant deviations from the expected 1/2 decay is vanishingly small. SemanticMantis (talk) 19:50, 14 April 2011 (UTC)

Ionization of d-block elements

In the d-block of the periodic table I've read that when atoms of elements in there ionize becoming cations, the electrons are pulled from the highest s-orbital with principal quantum number n where n is the row of the periodic table in which the element is found, instead of from the d-orbital which, though it has a lower principal quantum number by one, has more energy than the s-orbital. Why aren't the first electrons to go the ones with the most energy? 20.137.216.64 (talk) 18:10, 14 April 2011 (UTC)

The energies are all negative so by most you actually mean least and by more you actually mean less. Dauto (talk) 18:39, 14 April 2011 (UTC)

The reason is that the organization of the resultant ion is going to be different than the organization of the neutral atom. Don't think of it as "removing an electron", as though you come and pluck a little ball from its orbit outside of the atom, and the rest of the electrons keep going as though nothing happened. The electrons and nucleus system is always interacting, and any change at all to the system affects the whole system. Compare the following configurations:

• Fe⁰: [Ar] 3d⁶ 4s²
• Fe²⁺: [Ar] 3d⁶

At first it looks like what was done was that the 2 4s electrons were removed from the iron atom. However, it doesn't work that way. Electrons a) don't stay put and b) are indistinguishible from one another. Two electrons are removed. That is all we can say. The way that the *Fe²⁺'s configuration is derived is exactly the same way that the *Fe⁰'s configuration is derived: The configuration comes from the lowest energy solution to the Schrödinger equation for Fe²⁺. Pedagogically (that is, to teach this stuff to students) there are derived certain heuristics or mnemonics or "rules" to describe how to write the configuration correctly, i.e. the Aufbau principle, the diagonal rule, the periodic table method, etc. etc. These rules are merely descriptive of the end result of the Schrödinger equation for any particular system; they are not the real reason why the configuration is as it is. That's why there's all of the exceptions (like copper and chromium) that we have to create new, more convoluted rules. Solving the Schrodinger equation for any system has mathematics that is beyond the average first year chemistry student (indeed, at this point in my life, 15 years from when I learned this stuff, it's beyond MY ability as well), which is why all of the rules are taught to students. --Jayron32 20:48, 14 April 2011 (UTC)

Lugol's iodine

is "true" Lugol's iodine 2 % or 5 % is this it? http://www.amazon.com/J-Crows-Lugols-Iodine-Solution-2/dp/B001AEFM9Y — Preceding unsigned comment added by Wdk789 (talk • contribs) 19:56, 14 April 2011 (UTC)

You deleted my answer here: [21]. I don't know why you did that. To restate it again, you can find the answer for the composition of Lugol's Iodine at the wikipedia article titled Lugol's Iodine. It has a recipe in the article, so you can answer the question yourself. --Jayron32 02:58, 15 April 2011 (UTC)

Magnetism

What creates magnetism I always believed it was the circular movement of the electrons that gave magnetism but I am not entirely sure. Also if magnetic monopoles do exist not if they don't why cannot we detect them why don't we see evidence them in everyday life if they do exist.—Preceding unsigned comment added by 82.38.96.241 (talk) 22:20, 14 April 2011

Magnetic fields are always associated with electric current, the effect can be described in a number of different ways such as Ampère's circuital law. A loop of current will give rise to a magnetic dipole, that is, a pair of magnetic poles. The motion of an orbiting electron amounts to a current loop, and even more strongly, the spin of electrons generates a magnetic field. Materials where these spins align in the same direction are ferromagnetic.

It is not possible to create a single magnetic pole, a monopole, with current loops. However, there is nothing in the laws of physics that forbids them from existing but no one has yet discovered any. Some versions of grand unified theory (GUT) require them to exist but no GUT has yet been generally accepted - it is still possible magnetic monopoles simply do not exist, and this is the reason that they have not been discovered. SpinningSpark 22:47, 14 April 2011 (UTC)

April 15

Why is DC voltage used in public transportation

Help my boyfriend sleep better at night. He's currently tormented by the idea that today's worldwide subway, tramway, and electric train system use brutally inefficient DC Voltage rails to power motors. Since voltage must be supplied over a long distance (a whole rail, or at least have a long cable going up to the rail in question) there would be a lot of energy lost even when there is no train going on the rail (leaking capacitor).

So why does subway, maglev, tramways, and train use DC third rail exclusively? Esurnir (talk) 02:40, 15 April 2011 (UTC)

Electric motors operating on direct current (DC) are readily controlled to vary the speed. This allows the vehicle driver to choose the speed at which the vehicle is traveling. Electric motors operating on alternating current (AC) rotate at synchronous speed, or some fraction of synchronous speed, such as 3600 revolutions per minute (or 3000 or 1800 or 1500 rpm etc.) It would be feasible to have the distribution system supplying alternating current, and for each vehicle to have an AC motor coupled to a DC generator, and then have one or more DC motors driving the traction wheels, but that would double the cost, double the weight, and double the electrical losses.

Variable-speed AC motors are now available, but in the past they were not, and they are more temperamental than DC motors. Very-long-range power distribution is often done with direct current because of lower losses. Dolphin (t) 02:51, 15 April 2011 (UTC)

(ec) DC power lines are "leaky capacitors"; AC power lines are "giant antennas"; both suffer losses due to physical limitations. But, it's rarely a good idea to try to apply "first principles" physics to complicated, sophisticated engineering projects; estimating the losses requires detailed analysis of specific technologies and parameters for any particular project. While AC power has certain theoretical advantages, it also has certain practical disadvantages. In today's technology, high-voltage DC is probably more efficient than AC for long-distance power transmission, though in any particular instance, specific engineering details may sway the balance one way or the other. DC systems are usually supplied by AC from a power plant, so there is a conversion loss to worry about; but you never have to worry about phase matching, nor radiative losses. We have numerous articles on electric train topics; the most helpful will be Railway electrification system, which discusses AC and DC systems. Nimur (talk) 02:53, 15 April 2011 (UTC)

I don't get it - if HVDC is so efficient, why has everyone been drilled into thinking that long-range transmission requires AC? Wnt (talk) 05:09, 15 April 2011 (UTC)

High-voltage AC is easy to convert to low-voltage AC. It's harder with DC. --Trovatore (talk) 05:18, 15 April 2011 (UTC)

Yes, in a word transformers. These are only available for AC (except in network theory books). High voltage (sometimes as high as 400 kV) gives less loss over long distances but is unsuitably high for most power stations to generate directly (around 25kV is normal for anything with a turbine) and is way too high to be safe in a factory or a home. SpinningSpark 11:30, 15 April 2011 (UTC)

The AC vs. DC dispute is old, see War of Currents. Cuddlyable3 (talk) 12:18, 15 April 2011 (UTC)

The article link that Nimur provided in his comment provides a good discussion, but briefly, HVDC transmission makes economic sense only for long runs with few 'taps' off them. First, there is a small loss incurred each time current is converted from AC to DC or back again, so the line has to be long enough that the increased efficiency on the line more than makes up for the bigger losses in AC/DC conversions at the ends. Our article puts the break-even distance as about 50 km for undersea cables and 600-800 km for overhead cables, but it doesn't have a supporting reference. Second, each tap off the HVDC line needs to have an installed high-voltage inverter (to convert DC to AC) before the transformer, this increases the cost of each tap. TenOfAllTrades(talk) 16:33, 15 April 2011 (UTC)

Diagnosing an electrical problem

In my house all the lights on the even circuits are blinking, computers are rebooting on their own, etc., while the odd circuit numbers are fine. There are two "phases" coming into the house, one which feeds the even circuits, and one which feeds the odd circuits. So:

A) This indicates to me that the source of the problem is external to the house. Is this correct ? In this case, how can I convince the power company it's their problem ? (The power company is Detroit Edison.)

B) Is there any danger to continuing to use the even circuits until it's fixed ? (I installed an uninterruptable power supply for the computer, to stop it from rebooting when the voltage drops.) The other approach is to use extension cords from the odd circuits, but I doubt if the whole house can be run on half power like that, especially if this isn't fixed by the time we hit A/C weather (we use window air conditioner units). StuRat (talk) 03:59, 15 April 2011 (UTC)

No, the problem can be at the transformer, or it can be in the house. If you have a high-resistance arcing connection in the panel, disconnect or meter socket, you could have a fire. This should be checked out immediately. If you run any 240V equipment, it won't work efficiently, and if it's a 240V motor, like a heat pump or high-output air conditioner, you'll burn out the unit. Intermittent loss of one leg (it's technically not a phase) is often a sign of a failing circuit breaker - in this case, the main breaker. Have it checked as soon as possible by an electrician. Acroterion (talk) 04:17, 15 April 2011 (UTC)

There's no sound or smell of arcing, so it doesn't seem likely that's happening within the house. Nothing is running 240 in the house (we have gas heat, water heater, and dryer, and small window A/C units). StuRat (talk) 05:59, 15 April 2011 (UTC)

If the problem is at a transformer, neighboring homes will also be affected (unless yours is the only one on that transformer.) We had a situation years ago where some circuits were fine; others had no power. They had to replace the transformer to fix that.

I get the impression this situation has gone on for some time. If the power company won't check the situation, perhaps the only way to get their attention is to have an electrician tell them the fault is in their equipment. I'm quite sure our power company would be out quickly to check the transformer if I reported such a problem.

The above is just speculation. As Acroterion says, Have it checked as soon as possible by an electrician. Wanderer57 (talk) 05:28, 15 April 2011 (UTC)

You can have high-resistance connections and arcing without sounds or smells. My money would be on either a transformer fault or a breaker fault (I had a similar issue with a 50A 240V breaker for a range - the oven wouldn't heat all the way and half the burners didn't work - replacing the breaker fixed it), but the possibility of a faulty connection is sufficiently dangerous to warrant immediate investigation and action. An electrician can provide ammunition if it's the power company's fault; I got my power company to add a transformer for my house and my neighbors after convincing them that six houses on a transformer was too many - we had serious voltage drops every time somebody turned on a load. Get it checked out immediately: it's potentially dangerous. Acroterion (talk) 13:06, 15 April 2011 (UTC)

Thanks so far. How would an electrician determine if it's the main breaker or the transformer ? StuRat (talk) 18:06, 15 April 2011 (UTC)

Measure the voltage before the breaker with a graphing multimeter. You could probably do it yourself if you like to take risks, the wires are accessible in the box. You could probably attach a light before the breaker, and one after and watch them. It's risky though - you have no protection against shorts while working on it. Also, ask your neighbors, if it's only you it's your breaker, or meter, or wires, or junctions. Ariel. (talk) 19:33, 15 April 2011 (UTC)

What Ariel said; the main feed lugs are normally shielded, but can be accessed by a very careful person, ideally one who is used to doing this. Since it's intermittent, some time will be needed, which are further grounds for leaving to an electrician, who will have the right clamps. If there's a load on the leg and the problem is internal, there may be visible damage or heat somewhere in the panel - the main breaker may be hot.. Bear in mind that conductive tools inside a live panel can be dangerous for the uninitiated; an arc flash (vaporized copper) in your face can blind you. Acroterion (talk) 19:41, 15 April 2011 (UTC)

Relativistic mass

Hello. Mass in special relativity#Controversy explains that some researchers have rejected the concept of "relativistic mass", but apart from saying that it is "a troublesome and dubious concept", the article doesn't go into any depth regarding why they reject relativistic mass. Could someone please tell me what is fundamentally wrong with this concept? Thank you. Leptictidium (mt) 06:17, 15 April 2011 (UTC)

It just seems like a fudge factor to me. That is, when the numbers didn't add up, they just decided to say that the mass was changing. Imagine if your tax accountant could do that: "well, the balance sheet doesn't balance, so I will say that this is 'dynamic cash' and changes quantity as needed to make everything balance". StuRat (talk) 06:40, 15 April 2011 (UTC)

Isn't this just what the central banks do all over the world? 95.112.143.65 (talk) 09:02, 15 April 2011 (UTC)

It's not a fudge factor and it is a occasionally useful concept. For instance, if you put a block on a scale to measure its mass, then you heat it up to a higher temperature increasing its internal energy, its relativistic mass also increases and that should be measurable by the scale in principle (In practice the effect is too small to be measured). The problem is that the concept causes more confusion than it's worth and the modern convention is to reserve the word mass for the rest mass as BenRG points out below. Dauto (talk) 15:08, 15 April 2011 (UTC)

What's troublesome and dubious is thinking that you can plug relativistic mass into equations that have an m in them, such as F=ma, and get something that makes sense. Generally, you can't. To the extent that relativistic mass is just energy divided by c², it's a well-defined concept, but there's no point having two names (energy and relativistic mass) for the same thing. The modern convention is to call it energy, and reserve the word "mass" for rest mass (which is often written in units of energy as well). -- BenRG (talk) 09:23, 15 April 2011 (UTC)

I think it's quite the opposite - if you don't include relativistic energy in equations such as f=ma you will get incorrect results. This energy has inertia and momentum and causes gravity. Which is why I prefer to call it mass. But the hard part is that the mass of an object is relative, it's not fixed. This can make calculations all but impossible. For example, what is the mass of a magnet? If I turn on an electromagnet on the other side of the planet, the magnet in my hand is now heavier (relative to that electromagnet anyway). Ariel. (talk) 19:30, 15 April 2011 (UTC)

If you use the proper form $F={\dot {p}}$ with the three-momentum $p=\gamma mv$, you can easily dispense with "relativistic mass". Here's a quote from a book by Taylor and Wheeler: "Our viewpoint ... is that mass is an invariant, the same for all free-float observers... In relativity, invariants are diamonds. Do not throw away diamonds!" Modern physics understands relativity as a geometrical theory, a theory of the structure of space-time, not as a dynamical theory as suggested by the concept of relativistic mass. In relativity, energy and mass remain distinct physical quantities; "relativistic mass" obfuscates that distinction. Having said that, if the energy is in internal degrees of freedom of a composite body (not center-of-mass motion), then this energy does indeed show up in the effective mass of that body. That's where the mass deficit of, say, the helium nucleus comes from. --Wrongfilter (talk) 20:38, 15 April 2011 (UTC)

Triplet v.s. Singlet Oxygen

According to the formula for calculating the bond order for diatomic molecular species, both triplet and singlet oxygen species have bond orders of 2. This does not make sense to me - triplet oxygen cannot have a double bond and concurrently be a diradical. I think the reason for this is that the formula ignores electron spin direction. Is this true, and does triplet oxygen have a bond order of one? Or, do I have it wrong? Plasmic Physics (talk) 08:17, 15 April 2011 (UTC)

Sure it can. You cannot draw a proper lewis structure for O₂ with a bond order of two and still have it be a diradical, but that's just a limitation of lewis structures. The molecular orbital diagram at the lower right corner of triplet oxygen shows how it works. The diradical occurs in the two degenerate π* antibonding orbitals. The bond order is calculated as: (bonding electrons - antibonding electrons)/2, which (8-4)/2 = 4/2 = 2. The reason that the Lewis Structure doesn't work out is that the geometry of the molecular orbitals does not work easily in a 2D representation, and lewis structures ignore the whole "antibonding" thing all together. --Jayron32 12:17, 15 April 2011 (UTC)

I was not using the Lewis model approach. Each oxygen has 6 valence electrons, if it has a bond order of two, that means that each atoms makes a net contribution of two electrons to the bonding orbital. This means that each oxygen has four remaining valence electrons. If triplet dioxygen is a diradical which I believe it is, then each atom has only one electron pair and two unpaired elecrons, not just one (according to a two bond order system).

I used the MO diagram for my argument, from it I used two factors - the total number of valence electrons, and the total number of unpaired electrons. Plasmic Physics (talk) 12:50, 15 April 2011 (UTC)

You can't consider the electrons of each atom separately when you're looking at their arrangement in the combined molecule. Electrons that are unpaired for the independent atoms are not required to remain unpaired in the final molecule. Do you understand how the orbitals are filled in the MO diagram at triplet oxygen, and how to calculate bond order based on filling of bonding and antibonding orbitals? TenOfAllTrades(talk) 13:51, 15 April 2011 (UTC)

@ Plasma Physics: To expand on what TOAT said above, when considering the organization of the electrons in the O₂ molecule, you cannot consider each atom as retaining any individual characteristic. The whole thing with Molecular orbital theory is that you treat the entire molecule as a single entity, and calculate the quantum states of the electrons based on that presumption. The system cannot be accurately modeled (for these purposes) as individual atoms which are merely sharing a few electrons (which is how both valence bond theory and hybridization theory model bonding). Molecular orbital theory models the O₂ molecule as a 16-electron system with two nuclear charges of 8+, and calculates the shapes and populations of the various orbitals that way. For convenience, the molecular orbital diagram referenced above only looks at the valence electrons, but the actual calculations are based on all of the electrons. Its the organization and shapes of these molecular orbitals that gives rise to the particular properties of triplet oxygen, that being that it has a second order bond (or "double bond") and is diradical. You can easily arrange all of the electrons in orbitals to get this result; in the case of triplet oxygen you have a total of 8 valence orbitals: five of them have 2 electrons in them, two have one electron each, and the last one is empty. That's 8 orbitals, a double bond, and a diradical. This is empircally confirmed by things like the bond strength and length of the O=O bond in O₂ (compare the bond lengths of O=O with the average peroxide bond length of O-O here, which gives O=O a bond length of 121 picometers, and O-O a bond length of 148 picometers. This is on par with the 20 picometer difference between C-C and C=C), and with the magnetic properties of ground state(triplet) O₂, which is experimentally confirmed to be paramagnetic, as would be expected of a diradical. To sum up; the experimental evidence indicates that oxygen is BOTH second bond order (double bond) and a diradical. Molecular orbital theory predicts both facts about oxygen (again, check the MOT diagram at triplet oxygen), so it is the model which is perhaps best in describe the organization of the oxygen electron cloud. There's actually even MORE evidence that confirms this model of triplet oxygen (vis-a-vis chemical reactivity and spectroscopy), which I'll not go into in the interest of not extending this discussion to the TLDR point. If you are using a model that leads you to a structure which contradicts the empirical, observed properties of oxygen, then simply put, the model is inadequate and needs to be discarded for this purpose. --Jayron32 14:33, 15 April 2011 (UTC)

Well, it's just that the molecular modelling program I'm using does not like the idea of a double bonded dioxygen diradical. It seems to have the least problems when the unpaired electrons are on the same atom. Yes, I have to specify where the unpaired electrons are. One more thing, why do I find lewis structures of single bonded triplet oxygen on google images? Plasmic Physics (talk) 20:47, 15 April 2011 (UTC)

The usual skeletal diagram notation doesn't work so well for complex MO situations. The line between two atoms represents a covalent bond, which means a shared pair of electrons. But the diradical isn't a shared pair making one bond--that's impossible if they have the same spin. Instead (again, exactly as the MO diagram illustrates) it's two shared lone electrons each in separate orbitals that are orthogonal to each other. The limitation is in your modelling program and meaning implied by the diagram style (or at least in the the modelling program's interpretation of the diagram style). Drawing it as a single-bond with a single electron on each atom at least gets the idea of "electrons are not paired, and therefore easily have same spin" correct, at the cost of error in the estimated bond-length. Drawing it as a double bond would imply (to those that don't know the details) that ³O₂ would undergo reactions characteristic of other pi bonds, which is not true. DMacks (talk) 21:03, 15 April 2011 (UTC)

OK, helpful. What do you think, should there be two bond order formulae, one for calculating the total net bond order, and one for calculating spin matched bond order? In the spin matched bond order, only electrons of the same spin cancel, this kind of formula can distinguish between a true bond, and a quasi-bond, which is really what triplet oxygen has. Triplet oxygen has an effective bond order of one and two halves. Plasmic Physics (talk) 21:34, 15 April 2011 (UTC)

While I'm on topic, while I studied the consequences of particle spin at Univeristy, I have no idead what spin actually is. All I know about it, is that it is some kind of description of a particle's kinetics. Does an electron cycle around an actual locus? If it does, what are the constraints? Does the locus describe a point, line, or a surface? Does the locus lie within the electron? Plasmic Physics (talk) 00:07, 16 April 2011 (UTC)

Period food

Are there any studies into what foods women particularly crave on their periods? I know sugary food is pretty common, and iron-rich food, as well as the more specific chocolate, but I'm interested in if anything has looked in more detail or more broadly. I don't have access to most of the paid-for literature at the moment, so public-domain or summaries would be appreciated. 86.164.75.102 (talk) 09:48, 15 April 2011 (UTC) Brain-fart, I meant freely available, not actually released into the public domain. I think. 86.164.75.102 (talk) 15:22, 15 April 2011 (UTC)

Binge eating occurs in a minority of menstruating women. This may be due to fluctuation in beta-endorphin levels. Source: Price WA, Giannini AJ (November 1983). "Binge eating during menstruation". J Clin Psychiatry 44 (11): 431. PMID 6580290. See also Premenstrual dysphoric disorder.

Thanks, that's an interesting start, although I cannot read the paper (even its summary). The Wikipedia article is an interesting read, as the more recent findings on variable response to hormones fits with some of the stuff I've been reading about different women's responses to different versions of the pill, suggesting years more profitable research to be done. So thanks. For this question, I suppose I'm looking more for research into food cravings experienced by women in the 'normal' range, rather than eating associated with various interesting disorders. 86.164.75.102 (talk) 15:22, 15 April 2011 (UTC)

Pinion?

what is racken pinion —Preceding unsigned comment added by 175.157.66.79 (talk) 14:09, 15 April 2011 (UTC)

Did you mean to start a new question? (I've reformatted this, because I think you did..) Are you perhaps thinking of Rack and pinion steering in an automobile? SemanticMantis (talk) 14:54, 15 April 2011 (UTC)

See also rack railway.--Shantavira|^{feed me} 16:57, 15 April 2011 (UTC)

Design pattern: both for software and art

Is there a design pattern which can be applied both to works of art and software? Quest09 (talk) 15:40, 15 April 2011 (UTC)

You may be interested to read the works of Lawrence Lessig et al. The so-called "free culture movement" inherited its philosophical inspiration from the free software movement. Nimur (talk) 17:18, 15 April 2011 (UTC)

I'm not sure that I necessarily understand your question correctly but you may also be interested in Carlos Amorales' modular "Liquid Archive" approach to making his art. Sean.hoyland - talk 17:46, 15 April 2011 (UTC)

I also am not sure what your question means. could you be thinking of fractal geometry? as in the Mandelbrot set.190.148.136.166 (talk) 19:32, 15 April 2011 (UTC)

Live vs. recorded sound

Why do they sound so different? Quest09 (talk) 15:42, 15 April 2011 (UTC)

You mean Acoustic music vs. electronically recorded music played back through electronic amplifiers and loudspeakers? Pfly (talk) 15:50, 15 April 2011 (UTC)

Live sound reaches your ears as each sound source sends out waves which bounce around rooms and off surfaces and arrive at your ears. Recorded sound can only approximate all of these relationships, and generally (unless you are an audiophile with a shitload of cash and time) most people listen to recorded sound from a set of earphones/headphones or speakers which are at a fixed location, and so do not accurately model the actual source sounds. They do a passable job for most people who just want to listen to the latest Lady Gaga song, but there is a noticable difference in the sound of hearing her come from the speakers on the stereo in your living room, and hearing her sing in your living room. --Jayron32 16:01, 15 April 2011 (UTC)

Also, consider a piano, for example, vs. a recording of a piano played back through loudspeakers. There's a huge difference between what is making the sound. Loudspeakers are nothing like pianos. A piano's sound board alone is a resonating surface far larger and different in design and function than a loudspeaker. The amazing thing is that loudspeakers can even come close to sounding like so many different things, from pianos to people singing to cymbals and so on. Still, loudspeakers do a poor job of reproducing the experience of sitting close to the front of an orchestra, or listening to a powerful pipe organ playing full bore. Pfly (talk) 16:14, 15 April 2011 (UTC)

But if the question is about live, as in performed in "real time" vs. recorded, as in created in a studio, then the answer is something to do with live performance vs. the process of building something slowly and in pieces. Something like theater vs. film. Pfly (talk) 16:12, 15 April 2011 (UTC)

No, I asked in the sense that you pointed to at your first reply. But, what's the difference in the wave that hits my ears when coming from a recording or coming directly from an instrument? Which properties are different? Quest09 (talk) 16:33, 15 April 2011 (UTC)

The waveform is different; and to be strictly accurate, the only real reason is because the wave field is different. It is difficult (but not impossible) to completely re-synthesize the entire wavefield; instead, electronic recording only resynthesizes a sampled waveform. For most purposes, your human ears are a stationary set of two single points that sample the pressure level of a multidimensional acoustic wave field; a more complete description of the total wavefield must account for its extent in 3 spatial dimensions, plus the pressure, velocity, and other non-linear acoustic properties of sound waves in air. Most electronically recorded sound waveforms only seek to sample the pressure as a function of time at one (or maybe two or more locations). (They accomplish this by recording pressure fields, placing a microphone as a pressure transducer at one or more fixed locations). For most purposes, this totally replicates the "99th-percentile" of the audible experience; but it is a known fact that the perception of sound waveforms is actually more complicated. A good friend of mine worked on a project to synthesize a multidimensional surround-sound experience; you can read "artistic" and technical descriptions at the technical specifications page. Nimur (talk) 17:27, 15 April 2011 (UTC)

From the list of sound wave properties, frequency, wavelength, and wavenumber are basically the same in this context, as are amplitude, sound pressure, and sound intensity. "Speed of sound" doesn't seem relevant in this context. So that leaves three basic properties, frequency, amplitude, and direction (Nimur addressed wave shape issues above I see, which curiously isn't included in that properties list). A few quick comments:

• Frequency: typical consumer-grade loudspeakers have trouble with very low and very high frequencies. Not uncommonly they drop off below 40-60 Hz and fall off somewhere around 15,000 Hz or perhaps around 20,000 Hz, depending on quality. Subwoofers can handle very low frequencies, but typical consumer-grade, not-super-expensive subwoofers are not very good at producing strong stable pitches, tending more toward booms and rumbles. Compare pipe organs, which can produce extremely low pitches--sometimes so low you feel them more than hear them. No subwoofer can make a sound like a big 32' pipe on a pipe organ. I was lucky enough to get to watch this pipe organ being installed. The sound of the 32' pipes was intense. If I recall right, that beast can accurately and loudly produce pitches down to 8 Hz or so. There's further issues regarding the recording medium, which limit and distort the frequencies in various ways (see Sound recording and reproduction).
• Amplitude: With electronic amplification you can make acoustic instruments much much louder than they could ever be themselves. It is common, I think, to listen to recorded music at louder volumes than would be normal for acoustic instruments (at least the quieter ones like guitar). Plus, when music is put together in a studio it is typical to mix the amplitudes of different instruments in "unnatural" ways--a quiet singer overpowering a drum kit, for example. In olden times you needed a operatic voice to overpower loud instruments. Today on a recording a whisper can overpower a marching band, if desired.
• Direction: The sound from stereo loudspeakers comes from two relatively small, usually non-moving places. Surround sound systems up that to five or so. Compare a live modern orchestra, where the sound comes from well over 100 sources. Even a single acoustic instrument, say a piano, produces sound from multiple sources—the strings, the sound board, etc. Pfly (talk) 18:05, 15 April 2011 (UTC)

To clarify: if you are only modeling the sound pressure level, you are only modeling p wave; this is the straightforward "acoustic wave equation" that is suitable for describing sound in a gas (like air). But in reality, air is not ideal; it has some viscous properties; and you should use a suitable elastic wave equation, such that the velocity of any individual particle is not equal to the velocity of the wavefront. It is unlikely that most human ears can perceive this difference, but we absolutely can measure this phenomenon using sophisticated equipment. A typical condenser microphone only responds to pressure, not to velocity; but a scientific-grade acoustic transducer will be able to record pressure and at least one component of the 3-dimensional acoustic velocity vector. Sampling and recording this information would be critical to a total and exact re-synthesis of the wavefield. And as always, I will re-emphasize the caveat; the goal is to mathematically model the physical effect to some specified level of accuracy/detail. We can always make a more complicated model to account for the 99.999999...th percent effects. Most human ears only "hear" or perceive stereo sound (i.e., two pressure-waveforms) sampled at 40 kHz, so it's not necessary to record more data. Nimur (talk) 18:12, 15 April 2011 (UTC)

Nimur, your technical understanding is way beyond mine. This brings up a question I've wondered about. Human hearing range doesn't normally reach much beyond 20 kHz (if that), and one often hears how it is therefore unnecessary to record or reproduce frequencies above 20 kHz or so. But I wonder--is it possible, or even common, for frequencies above 20 kHz bouncing around a room after, say, a gong is struck, to interact with other waves bouncing around, with the room itself, etc, such that lower, audible frequencies are produced and heard? Something akin to a resultant tone (or better, combination tone), but at the high end? I've long wondered if this is possible and if so, how common it is. And if so, whether it would have an effect on music with lots of very high overtones/harmonics--making it sounding richer live, with all those ultrasonic waves existing and bouncing around, than recorded, with no ultrasonic frequencies in the first place. ? Pfly (talk) 18:55, 15 April 2011 (UTC)

Certainly I feel that way, but my preference is actually for the recording. The clash of real cymbals in the highest frequencies is just so painfully loud that it cuts up the rest of the song. Wnt (talk) 23:37, 15 April 2011 (UTC)

Regarding technical understanding... Anyone can understand mathematical descriptions of physical phenomena if they spend enough time analyzing them. I have spent, and continue to spend, a lot of time thinking quantitatively about daily mundane things. It also helps to have academic or formal training in physics or mathematics. Anyway - regarding wave mixing. It is a fundamental assumption of linear system theory that frequencies are preserved by systems. In other words, the simplest model forbids a high frequency from "reflecting" and producing a lower frequency. On the other hand, a nonlinear wave model (such as the elastic wave model) does permit nonlinear, frequency-altering interactions. For most purposes, the amplitude of such an effect is very small, so we safely ignore it for day to day ordinary sound waves. I can think of at least one case where we cannot ignore these effects! A broken loudspeaker results in a nasty rattle that is nothing like the intended waveform; what is happening is that energy is coupling nonlinearly into the torn paper cone of the speaker, which is then buzzing and sounding awful! Nonlinear acoustics are therefore not merely a theoretical concoction of bored physicists! Nimur (talk) 02:25, 16 April 2011 (UTC)

two questions about electromagnetic waves

1.I have no imagination of photons as particles. I mean we can think of electrons as particles moving (or present) in regions called orbitals. do photons have a certain measurable "area of influence" or something like that?

2.In the emission or absorbtion spectrum of different elements,there are lines that show different transitions in energy levels.well, according to the formalae, each kinds of transition must produce a single kind of electromagnetive wave(E(n2)-E(n1)=hf). but when we look at the spectrums there are neighbours of wavelengths, not "exactly one" wavelength.I mean although the neighbourhood may be small, but it is still a neighborhood, otherwise we couldn't see it.

It's REALY hard for me to ask such questions in English, so I'm sorry and I hope you understand what I mean.Thanks! —Preceding unsigned comment added by 178.63.158.171 (talk) 16:55, 15 April 2011 (UTC)

For question #1, a single photon's "area of influence" is probably best thought of by defining a particular fall-off in the electric field intensity (or, for one single photon, the probability of measuring an electric-field at a particular intensity). There's going to be a "soft edge" for the photon; for any radius r from the photon's "center location," there's going to be a lower probability that the photon can interact with anything. This is described mathematically as a wave packet, which has finite extent in space and time. (We also have wellenpaket in German).

For question #2, see hyperfine structure (also available in German at Hyperfeinstruktur). Nimur (talk) 17:57, 15 April 2011 (UTC)

(EC) The answers to both of your questions involve the Heisenberg uncertainty principle.

Similar to how you can't say with certainty exactly where within an orbital an electron is, there is also a "fuzziness" as to where exactly a photon is. For example, if you shine a monochromatic light on a circular aperture, the light intensity behind the aperture will form a diffraction pattern known as an Airy disk, rather than a solid circle as one would expect if each photon traveled along an infinitely thin line.

Spectral lines not having zero width is due in part to excited states having a finite lifetime, which causes an uncertainty in the emitted photon's energy, as explained in Uncertainty principle#Energy-time uncertainty principle. Red Act (talk) 18:18, 15 April 2011 (UTC)

The German articles on the topics I mentioned are Heisenbergsche Unschärferelation, Beugung (Physik), Beugungsscheibchen, Spektrallinie and Linienbreite. Red Act (talk) 18:34, 15 April 2011 (UTC)

Discovery of rimantadine and references

In the past few days a history section was added to the rimantadine article. An anon-IP editor has added several references to verify the claims, but I am having difficulties verifying the claims, mainly of two reasons: 1) Chemistry is not something I am familiar with. 2) English is not my native language. Can someone with knowledge in chemistry please have a look at the references, and explain whether the references really verifies the claims or not, and perhaps explain why – since I, as a layman am not able to understand the references given at first sight. Thanks in advance. ^Talk/♥фĩłдωəß♥\^Work 18:02, 15 April 2011 (UTC)

Head rotation

Is it theoretically possible by surgical means to make the human neck safely rotate the head at 360 degrees or so (bearing in mind that it's not fatal in some birds)?--89.76.224.253 (talk) 18:16, 15 April 2011 (UTC)

No, this is not possible. The structure of our spine and neck is different from birds. Nimur (talk) 18:20, 15 April 2011 (UTC)

I'm pretty sure birds don't rotate 360 - they probably do 180. Ariel. (talk) 19:23, 15 April 2011 (UTC)

OP, what birds are you referring to? The usual example of a bird rotating their head to an extreme is the owl. And according to our article on the owl, "Owls can rotate their heads and necks as much as 270 degrees in either direction". Or do you mean 360 from one extreme to the other? Dismas|^(talk) 19:41, 15 April 2011 (UTC)

Screen-width Problem in computer

The ratio of width-to-height in new laptops is considerably different than traditional desktops. Does that mean that everything will appear deformed i.e. stretched along horizontal axis ? —Preceding unsigned comment added by 124.253.130.232 (talk) 21:52, 15 April 2011 (UTC)

Please don't ask the same question on multiple ref desks, especially when it has already been answered on one of them (Computing). Looie496 (talk) 22:16, 15 April 2011 (UTC)

Seafloor river bed in Toyama Bay, Honshu from Google Earth

Hi. On Google Earth, a long river valley appears carved onto the seafloor leading out from Toyama Bay in Japan, extending toward the bottom of the Sea of Japan. It is most likely not volcanic or tectonic in origin, and also does not extend from the mouth of the Shinano River, which lies closer to Niigata farther northeast. It appears to wind itself around the eastern edge of some continental shelf and steadily drops off in elevation on the seafloor, tracing a path from a reverse-delta toward the north. In fact, the main undersea channel appears to be a merger of the Shō River and the Jinzū River. The channel appears to have a lower sea bottom elevation on Google Earth than its surroundings and stretches for about 590 km before ending at the edge of a deep basin, at which point it is closer to Sapporo than to Tokyo. At the point equidistant between the two cities, the elevation at the bottom of the channel is about 2800 metres below sea level, It is noticeably longer than any other apparent seafloor river channel in the area and may be one of the longest in the world. Also, the channel appears to bypass the edges of a few underwater volcanoes, suggesting that sea levels were lower or the river has enough power to carve this deep channel even when underwater. At various points, the channel itself lies an average of 145 metres lower than the surrounding ocean floor. Any information on what was responsible for creating this channel, whether it was an ice age event or a phenomenon similar to the conditions today, and how this particular locale compares to any similar channels worldwide? Thanks. ~AH1 ^(discuss!) 22:59, 15 April 2011 (UTC)

Apparently it's called the Toyama Deep-Sea Channel.^[22] Wnt (talk) 00:02, 16 April 2011 (UTC)

I don't know about that one specifically, but our article on submarine canyons give information (or at least speculation) about how such things form. Looie496 (talk) 00:05, 16 April 2011 (UTC)

"Submarine canyons are well developed around the Japanese Islands. Three major large-scale submarine canyons are the Kushiro Canyon, the Toyama Deep-sea Channel, and the Boso Canyon. The Kushiro Canyon greatly encroached on the continental shelf and deeply eroded the continental slope. This characteristic is markedly different from other canyons. The Toyama Deep-Sea Channel is characterized by the length of over 500 km, considerably meandering, a vast submarine fan, and well-developed submarine natural levees. The Boso Canyon has significantly incised meander 100 km in length."^[23] Looks like 3.6 million articles just aren't nearly enough. ;) Wnt (talk) 00:10, 16 April 2011 (UTC)

Question about gravity and absolute zero temperature?

As both [Einstein’s and Newtonian] models of gravity are independent of temperature therefore “Does gravity cease and clocks stop or slow down at Absolute zero temperature?” Also this might help: http://www.jupiterscientific.org/sciinfo… 68.147.41.231 (talk) 02:47, 16 April 2011 (UTC)Eclectic Eccentric Khattak#1