Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

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

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

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

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

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

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

March 12

Looking for a bird

Does anyone know of a complete list of species featured in The Life of Birds? In particular, I am looking for one bird species, it must have been in "Signals and Songs" (episode 6). Its song sounded like early electronic analogue synthesizers, or someone rapidly turning a ham radio dial. I think Attenborough's commentary mentioned that it had to learn to produce something like 40 different sounds in order to get its song right. I think it was North American, small, and dull-coloured (mostly brown). Thanks in advance! ---Sluzzelin talk 01:22, 12 March 2010 (UTC)

Well no doubt the bird with the strangest vocals in that series was the Lyre bird, that's the one that can imitate other birds and even things like camera shutters and chainsaws, but I don't know if anyone's brought a Moog for it to imitate:) . However it's not American, and its tail is a big give away, but I distinctly remember that in a lot of close shots with the tail mostly if not totally cropped out it looks small and dull colored. Vespine (talk) 04:24, 12 March 2010 (UTC)

Thanks, I too remember the supreme superb lyre bird distinctly, but as amazing as it is, it isn't it. The one I'm looking for isn't mentioned in the article. It didn't imitate. It just had its entirely own spacey sound. :-) ---Sluzzelin talk 04:31, 12 March 2010 (UTC)

I think I found it. This page mentions the cowbird using "40 different notes, some so high we can't hear them". Judging by the sound sample on this site, it's the Brown-headed Cowbird. My memory had something slightly more spectacular in storage, but this is definitely it. Thanks again. ---Sluzzelin talk 06:05, 12 March 2010 (UTC)

(I realize I was the one asking, but maybe others are interested too): The Brown-headed Cowbird article doesn't mention its song, but I found something under Lateralization of bird song. ---Sluzzelin talk 12:24, 12 March 2010 (UTC)

Reflex subwoofer query

I made a ported (reflex) sub-woofer with a vertically upward firing drive unit and a vertically downward firing port for bass instrument reproduction. I found that increasing the distance between the port and the floor (to about twice the ports diameter) seems to give a much richer sounding bass then when I used only a single diameter spacing (as recommended in some sources as the min). Why is this, and how does the spacing between port and floor affect the response/efficiency of the system? In particular, why do larger spacings seem to give more 'fruity' bass with apparently increased high frequency response?--79.76.188.14 (talk) 01:47, 12 March 2010 (UTC)

Sound pressure waves emitted from the port are reflected by the floor so creating a resonant column of air. Raising the woofer increases the height of the column so lowering its resonant frequency. That reduces the "boxyness" of the sound in the same way as would enlarging the cabinet. The sound frequencies are too low for a floor carpet to provide effective damping but you might notice some improvement from filling the whole space between the port and floor with a roll of carpet felt or foam. Cuddlyable3 (talk) 11:08, 12 March 2010 (UTC)

I find myself wondering whether more of the sound emitted by a downward facing speaker doesn't end up in the apartment below you than in your own. StuRat (talk) 12:31, 12 March 2010 (UTC)

Depends how stiff the floor is.--79.76.188.14 (talk) 20:27, 12 March 2010 (UTC)

Likely outcome of an all-out thermonuclear war between the US and Russia at the height of their nuclear capabilities?

US and USSR nuclear stockpiles during Cold War

One of many possible fallout scenarios from a mid-1980s attack on the US

Obviously no-one can 'win' a global nuclear war, as such - but I remember reading somewhere that in the event of a full-on nuclear exchange where everyone threw everything at everyone else, it was hypothesized by that it would likely be that Soviet Union that would 'continue to exist' in some form in the aftermath (mainly due to its greater land mass and more dispersed population), whilst the US (and all of Europe - West and East) would be almost completely destroyed. Am I remembering correctly here? Does anyone know the piece of research I am referring to? Does this sound at all plausible? Thanks. --95.148.106.148 (talk) 02:22, 12 March 2010 (UTC)

Just for reference, according to that infallible source, Wikipedia, the peak of the cumulative US-USSR nuclear stockpiles was in 1986, at 63,977 total warheads (23,254 US, 40,723 USSR). That would also be a period of considerable technological sophistication in delivery vehicles—ICBMs, SLBMs, MIRVs. So that's a lot of destruction.

The main problem here has and continues to be that calculating that kind of destruction is pretty hard. Most estimates probably under-estimate the destructive power of the weapons—they exclude good predictions of fallout and fire effects, or the long-term effects of kicking up that much (radioactive) dust into the atmosphere (which would probably have effects on the climate as well). Lynn Eden's book Whole World On Fire discusses this at some length. Certain weapons effects are "easy" to model—blast pressure, prompt neutron radiation, gamma rays, etc.—and some are quite hard—firestorms, fallout, etc. As a result, most calculations focus on the "easy" bits and exclude the hard bits, even though the hard bits actually do a huge amount of the damage (most of the destruction in Hiroshima and Nagasaki was caused by fire, not radiation).

But I think it is clear that if the US were hit by a large nuclear exchange, depending on the weather patterns, the fallout itself would be pretty destructive to its ability to continue as any kind of a nation. It would also surely lose a huge, huge percentage of its population, clustered as they are in big cities on the coasts. The USSR would probably do a little better, though I'm not sure it would be all that enviable. The interior would surely be targeted (as would the US's) because that's where its factories and silos were (as with the US; note the FEMA fallout map picture that shows how hit the midwest is for this reason). The resulting fallout would coat the interior areas pretty good. The lands would not be productive without massive cleanup and long-term birth defects and etc. would be rampant amongst any survivors not living far underground in mythical Strangelove-esque fallout shelters.

If you pick an earlier point in time, when the stockpiles are not so huge and the delivery mechanisms are not so good, then the USSR does a lot better—bombers are not going to saturate the interior so much. The US also probably does a lot better, as Soviet delivery mechanisms were really quite poor until the late 1950s. --Mr.98 (talk) 02:41, 12 March 2010 (UTC)

I think another major issue would be the reliability of the payload delivery systems. Many articles I have read over the last few years suggest that many, many Russian delivery systems and payloads themselves are faulty, and would likely not launch correctly, if at all. Beach drifter (talk) 03:55, 12 March 2010 (UTC)

Is this referring to now, or then? I know that the Russian nuclear arsenal has supposedly fallen into disrepair somewhat since the end of the Cold War. Thanks for the answers so far, by the way. It boggles the mind that things ever got to the point where people needed to sit and calculate this stuff and that there were people who would be prepared to actually carry it out (or put the choice to do so in the hands of computers!) - it seems completely insane, not to mention quite obscene. --95.148.106.148 (talk) 04:03, 12 March 2010 (UTC)

Many people, including me, disagree on your last point, but this is not a discussion board. 74.212.140.226 (talk) 07:08, 12 March 2010 (UTC)

To clarify: The objective of having those weapons was as a deterrence. In order to deter, it was 100% essential that the enemy be utterly convinced that you'd push the button. Hence, even if you had no intention of ever doing such a crazy thing - you had to convince them that you would. Thus, at least the public face had to be that you'd do it. Although it pains me to say it - it worked. There was no world war three. The Soviets didn't invade Europe - despite having conventional forces that were easily capable of doing so. The US didn't extend it's power throughout the world in a way that the Soviets would have found unacceptable. The American people got so sick of the idea of war that it became difficult for them to carry through with them - the Russians ran out of money. We got through that period with nothing more than a few minor skirmishes - and it was actually a fairly peaceful time for the participants. The push that the cold war gave to technology has given us cheap computers, satellites, GPS and the Internet to name but a few. I don't like it - but it did work exactly as advertised and it had significant positive outcomes. The problems the world has now relate to the fact that one side of the conflict regards Mutually assured destruction as an acceptable outcome so deterrence doesn't work. SteveBaker (talk) 13:47, 12 March 2010 (UTC)

It's of note though that there is a fair consensus that the massive build-ups led to situations of overkill, well above and beyond what was probably necessary for deterrence (and there is a lot of evidence that the Cold War politicians and military people never actually really accepted deterrence as their goal—many were explicitly interested in the possibility of a debilitating first strike and feared that the other side was pursuing it as well). And there is a debate about whether creating the realistic possibility of mega-deaths really was preferable to the Soviets running Western Europe. I think there are many who would disagree that all of the skirmishes in that period were "minor"... a few million people died on all sides in Korea, Vietnam, Afghanistan, etc. At virtually no point were the Cold War powers not engaged in some kind of costly warfare. The idea that the Cold War powers acted as logical agents here is a somewhat naive reading of the history. It is luck as much as anything else that prevented nuclear exchanges, and there were some very, very close calls. --Mr.98 (talk) 16:40, 12 March 2010 (UTC)

I wouldn't say the Russian delivery systems are faulty. Russia has a better track record than the USA developing reliable rockets. Quest09 (talk) 10:21, 12 March 2010 (UTC)

It's really pretty hard to know if the delivery systems would have worked on either side. The US in particular only did component testing (they fired exactly ONE live rocket with a live warhead on it in the entire Cold War—and even that wasn't a stockpile warhead, if I recall). The essential problem is that you can't test whether everything would work correctly without actually using it, which means death. This problem and its historical consequences is discussed in depth in Donald MacKenzie's Inventing Accuracy: A Historical Sociology of Nuclear Missile Guidance, which is a really interesting book if you care about such things! --Mr.98 (talk) 16:40, 12 March 2010 (UTC)

One thing to consider is that the *vast* majority of US nuclear strategy was focused on destroying the Russian nuclear force, and presumably the Russians had a similar idea. This means that a total exchange would be very unlikely as each successful hit by one side means that many fewer warheads for the other side to launch. --Sean 13:28, 12 March 2010 (UTC)

How do you figure? Unless you do something to prevent the weapons launch, there will be a warning of 15 minutes or so for central missile silos. More then ample time to launch the weps, so if you target enemies silos, unless you have a way of masking your hundreds of launches, you are not going to destroy very many opposing warheads. Googlemeister (talk) 14:02, 12 March 2010 (UTC)

Nuclear weapons installations were the main targets of each side's nuclear forces. --Sean 16:30, 15 March 2010 (UTC)

Yes, I think your logic is wrong here. It's a "use 'em or lose 'em" scenario. There is enough time between launch and detection for the other side to launch theirs—that's why the big missile silos are out in the middle of the land masses (to give more time), and a considerable part of the force is kept in hard-to-detect submarines. That's why in the FEMA fallout diagram above, Montana, North Dakota, and Wyoming gets plastered so hard—they are assuming that in a full nuclear exchange, the Soviets would be seeking to really saturate the air force bases out there that were basing Peacekeeper and Minuteman missiles at the time. That does not necessarily mean at all that the Soviet hits would be successful in knocking out US capabilities—the missiles could easily pass each other on the way there. --Mr.98 (talk) 16:40, 12 March 2010 (UTC)

So you're suggesting the Soviets were planning on plastering those missile bases after the missiles were gone? That makes no sense. Counterforce -- knocking out the other guy's nukes -- is the reason very accurate missiles were considered destabilizing and were even banned in some treaty proposals and the reason SLBMs were considered (mostly) stabilizing (their missiles had lesser accuracy (implying countervalue strikes) and less ability to be countered since they were basically undetectable). --Sean 16:30, 15 March 2010 (UTC)

I'm suggesting that the Soviets would not have attempted to figure out which missile silos had launched and thus remove them from their target list. I'm also suggesting that they would have not had time to do this in a true second-strike scenario. --Mr.98 (talk) 18:45, 16 March 2010 (UTC)

A strange game. The only winning move is not to play. How about a nice game of chess? Coreycubed (talk) 15:20, 12 March 2010 (UTC)

I don't understand this discussion. An all-out nuclear war would, most likely, result in Nuclear winter, which would wipe out most of the world. Whether the US or USSR would fare better is completely irrelevant (after the first month or two). A 2007 study (using modern climate modelling techniques, which are pretty reliable) predicted that if all of the current stockpiles were launched, which are about 1/3 the size of the peaks, then the results would be:

A global average surface cooling of –7°C to –8°C persists for years, and after a decade the cooling is still –4°C (Fig. 2). Considering that the global average cooling at the depth of the last ice age 18,000 yr ago was about –5°C, this would be a climate change unprecedented in speed and amplitude in the history of the human race. The temperature changes are largest over land ... Cooling of more than –20°C occurs over large areas of North America and of more than –30°C over much of Eurasia, including all agricultural regions.

Those kind of drops would leave North America and Eurasia in Arctic conditions, there would be no significant agriculture. I haven't found estimates of death toll, but I would personally guess that we're talking at least 90% of the world's population being killed before the climate started to get back to normality (and that is assuming there isn't a Snowball Earth scenario where you get a runaway cooling which leads to thousands of years of global ice). --Tango (talk) 17:21, 12 March 2010 (UTC)

Assuming it is a USA vs. USSR war, the Southern Hemisphere would probably do much better than the North with respect to nuclear winter. Stratospheric wind patterns make it hard for dust injected in one hemisphere to cross the equator and reach the the other hemisphere (as shown by high latitude volcanic eruptions). Dragons flight (talk) 17:39, 12 March 2010 (UTC)

Contrary to the 1957 nuke fiction On the Beach (novel). In his book for some reason the fallout radiation levels do not decay to a very low level in a couple of weeks as most sources predict, but continue lethal for years. Edison (talk) 18:09, 12 March 2010 (UTC)

Indeed, radiation is a risk for those reasonably close to targets shortly after they are bombed. They may be a statistical increase in cancer risk for others, but that's about it. --Tango (talk) 19:38, 12 March 2010 (UTC)

If there is appreciable fallout in their food supply/land/water (as one would expect from a 1980s exchange of thermonuclears), the cancer and birth defect risks would be more than "statistical". --Mr.98 (talk) 01:56, 13 March 2010 (UTC)

That's true - as the quote says, it will be worst in North America and Eurasia. We can expect the southern hemisphere to fare better, but we're still talking a several degree temperature drop for years, which would be enough to ruin agriculture. Most of the population is in the north anyway. --Tango (talk) 19:38, 12 March 2010 (UTC)

I do not have the reference available, but I read a comment by someone who once was tasked with aiming US nukes at Russia, to the effect that it is easy to select the first several hundred targets, but by the time you are down to the 20,000th most important target, it is likely worth less than the bomb and its delivery system. 300 bombs could hit every US city with 100,000 people. 500 more could hit every military base in the U.S. Picture the Russian planner selecting target number 40,000: The courthouse in a small U.S. county? A 2 lane highway bridge? An electrical substation? A shopping center? Edison (talk) 18:03, 12 March 2010 (UTC)

A survey of basically all fiction about nuclear war, with some notes on its accuracy or lack thereof, by Paul Brians is available at [1]. Edison (talk) 18:21, 12 March 2010 (UTC)

Russia was known to have developed a crude anti nuclear missile technology (that the US may have duplicated too), which consisted of simply planning to detonate nuclear warheads in the direct path of incoming nuclear missiles. You don't have to be very precise that way. As I recall, the response to this technology was to plan to supersaturate certain targets, e.g. aiming 30 missiles at Moscow, so that at least one would get through and destroy the city. When you have a huge excess of warheads it is easier to make plans like that. Dragons flight (talk) 21:16, 12 March 2010 (UTC)

The Russian technology in question was the ABM-1 Galosh. It would have only been stationed around a few major cities. The American response was to ramp up MIRV development—make it so that there are 10 offensive missiles to every one defensive one. I don't think the US ever developed anti-missile technology of this sort, but they did have anti-bomber technology that worked this way (MIM-14 Nike-Hercules). Fun stuff. --Mr.98 (talk) 01:56, 13 March 2010 (UTC)

The non-negligible chances of missiles not launching cleanly and warheads not detonating also make it wise to send several to each target. Edison still has a point, though - even if you launch 30 at each target you still need about 1000 targets, which is more than enough to include every major city and military base. --Tango (talk) 21:32, 12 March 2010 (UTC)

Though it does get kind of ridiculous. In the 1960s (according to Richard Rhodes), Robert McNamara asked the air force how many missiles their force requirement calculations would say were necessary for Hiroshima. The response was that according to their up-to-date calculations, it would take three bombs of 80 kt each to shut down Hiroshima during World War II... or some 18X what was actually required to do "the job." The Eden book I cited earlier discusses in some detail the origins of these calculations and why they tended towards crazy levels of overkill. It is hard not to see some of this as just being about "we've got the money and can do it so let's do it" rather than serious questions about the necessity or consequences. Compare this with China's strategy, which is just about seeing how few missiles you can have and still maintain a viable second-strike deterrence—which they've concluded is about 200 or so. Much cheaper, less dangerous, and makes no pretensions of being a first strike force. (Which, for all that we talk about second-strike deterrence today, was in fact what the US policymakers were trying to do at the time, as the historical records have shown. Which is scary.) --Mr.98 (talk) 01:56, 13 March 2010 (UTC)

Speaking of games, this may be a subject relavent to game theory, zero-sum games and the Nash equilibrium. Shortly prior to the peak in Soviet warheads, the incident involving Korean Air Lines Flight 007 occured, and the Soviet Union may have planned a preemptive attack against the US in 1984. ~AH1^(TCU) 02:51, 13 March 2010 (UTC)

The US certainly planned for preemptive (first strike) attacks against the USSR all through the Cold War. There were a load of close calls: Cuban Missile Crisis, Stanislav Petrov, Able Archer 83, etc. The idea that things were perfectly rational, stable, and that military and political officials in the US and USSR actually took deterrence seriously is demonstrably historically false! It is the kind of pat reassurance given by TIME magazine, but it is not serious history. --Mr.98 (talk) 19:48, 13 March 2010 (UTC)

Just read the Stanislav Petrov article. So the scenario described in the song '99 Red/Luftballoons' nearly actually happened? Holy crap. --95.148.105.19 (talk) 22:34, 13 March 2010 (UTC)

For another list of "close calls", take a look at World War III. ~AH1^(TCU) 23:41, 13 March 2010 (UTC)

csi

whats a good article on here about evidence collection like dna fingerprints ect. in real life —Preceding unsigned comment added by 67.246.254.35 (talk) 05:42, 12 March 2010 (UTC)

Forensic science would be a good launching point; be aware that CSI is 99% bullshit. Its good theatre, but not good law work. Forensic science is a pretty good omnibus article on the topic. Much of CSI centers around the analysis of Trace evidence, but they also discuss many other aspects of forensics. Also see the CSI effect, a real problem in the forensic science world where people tend to believe that the stuff they see on CSI is somehow real, and it makes it hard for real forensic scientists to work with people like prosecutors and juries who have an unreal expecatation about what their job is like. (Full disclosure: My wife works in forensic science for a large police agency). --Jayron32 06:04, 12 March 2010 (UTC)

is it true they can take DNA from skin cells if someones arm or something brushes against an object? —Preceding unsigned comment added by 67.246.254.35 (talk) 06:33, 12 March 2010 (UTC)

Yes, but this also means that skin cells from many people are likely to be on any object. This makes it not so useful. You can say "Your skin cells are on the murder weapon", but they can say "So what, a dozen people's skin cells are on the murder weapon". StuRat (talk) 12:43, 12 March 2010 (UTC)

For lovers of CSI, I recommend: http://xkcd.com/683/ SteveBaker (talk) 13:31, 12 March 2010 (UTC)

This is also good. http://www.phdcomics.com/comics/archive.php?comicid=1156. --Mark PEA (talk) 16:21, 12 March 2010 (UTC)

orbit of moon

Is the expansion of the moon's orbit related to the expansion of the Universe? 71.100.11.118 (talk) 12:23, 12 March 2010 (UTC)

No, it's because the Moon is outside the Earth's geosynchronous orbit distance of 26,200 miles. Orbits below that distance will decay inward and those above that distance will decay outward, due to tidal interactions. StuRat (talk) 12:36, 12 March 2010 (UTC)

Does this explanation apply to the solar orbits of the planets? 71.100.11.118 (talk) 12:50, 12 March 2010 (UTC)

Yes, with all planets being outside that range, so having their orbits decay outward. However, the effect is tiny for the Moon, and even more so for the planets, as the tidal effects of the Moon on the Earth are far greater than the tidal effects of the planets on the Sun. Mercury, being the closest, would have the greatest effect, but even that might be too small to ever measure. StuRat (talk) 15:45, 12 March 2010 (UTC)

Also does this explanation mean that the moon has never orbited closer than 26,200 miles? 71.100.11.118 (talk) 12:54, 12 March 2010 (UTC)

Yes, unless something like a third body pushed it out of a closer orbit. StuRat (talk) 15:45, 12 March 2010 (UTC)

No, the rotation period of the Earth was originally ~8 hours / day, meaning geosynchronous orbit would have been much closer. Hence the moon also could have been closer (e.g. as close as 13000 miles). Most of the change in rotation rate is in fact attributed to the moon. Dragons flight (talk) 17:33, 12 March 2010 (UTC)

Good point. StuRat (talk) 19:10, 12 March 2010 (UTC)

The second paragraph at Orbit_of_the_Moon#Tidal_evolution_of_the_lunar_orbit is a very nice explanation of how the tidal bulges on the Earth coupled with the Earth's rotation cause the moon's orbit to increase. Does that help? Zain Ebrahim (talk) 13:03, 12 March 2010 (UTC)

So the interaction of Earth's spin, tides, are entirely responsible for expansion of the moon's orbit rather than the expansion of the Universe. 71.100.11.118 (talk) 13:20, 12 March 2010 (UTC)

Yes, Expansion of the universe has zero effect on the orbit of the moon. Dauto (talk) 13:28, 12 March 2010 (UTC)

Interestingly, by calculating how much the Moon's distance from Earth should increase if Hubble's law would be correct for such small distances, I get 28 mm/year, on the same order of magnitude as the 38 mm/year in measured increase of the distance, but I guess that is coincidence. Icek (talk) 18:05, 12 March 2010 (UTC)

I just did that calculation too (having not refreshed the page since you posted) and concur. It is a pretty amazing coincidence, but it is a coincidence. Our understanding of tides (which are based on very simple physics) predicts a recession of very close to the measured amount, so that understanding would have to be totally wrong for it to be caused by anything else. If our understanding of tides is wrong then our understanding of cosmology doesn't stand a chance of being right. --Tango (talk) 18:30, 12 March 2010 (UTC)

is there intelligent sleep like beauty sleep?

If you google beauty sleep, you get a whole lot of hits, at least some of them quite credible. Moreover, if you've ever seen the harried look of someone who's gone with very little sleep over many days, it is obvious that they're not quite well. It's ugly. Now, I wonder if there is an analogous effect on intelligence. Is someone intellectually "harried" by prolonged insufficient sleep? Do they absorb things they learn less, and so forth? I have a more specific question: when we say "sleep deprivation" we mean considerably less than 6 hours of sleep per day, maybe as little as 2-3 hours per night. (By the way, if anyone wants to edit the sleep deprivation article, it certainly doesn't define the amount of time of chronic sleep deprivation. Is it less than 3 hours per night, less than 4, than, 5, than, 6, than, 7, or what?)

Anyway I have a specific question. When people talk of BEAUTY SLEEP they don't mean "don't be sleep deprived", ie don't sleep just 3 hours. What they really mean is: don't sleep too little, only 5-6 hours. Sleep 8 or 9 hours instead.

Now, insofar as this works at giving people a healthier look, I wonder: does it have an intellectual effect as well? Does it make sense likewise to talk of 'intelligence' sleep like 'beauty sleep'.

Specifically, I know that it is hard to absorb and digest information if you are not able to sleep on it, severe, chronic sleep deprivation of only 2-3 hours of sleep per night wreaks havoc on one's cognitive capabilities...

but is there an EXTRA intellectual benefit, like the beauty benefit, to sleeping, say, 9 hours per night while learning a lot, as compared with only sleeping 6? Where is the cutoff on the return? Surely 12 hours per night doesn't make you any better at absorbing information and so forth than 9 hours per night, but surely 6 hours is much better for you with respect to the same cognitive effects versus 2 hours... so, is there a graph someone could show, or the specific cutoff points on the return?

I can imagine several possible graphs: I wonder which one is correct. Thank you. —Preceding unsigned comment added by 82.113.106.93 (talk) 13:09, 12 March 2010 (UTC)

I hope someone turns up with some studies to cite soon, but until then I can tell you from experience that there is such a thing as being intellectually not-at-full-strength because you don't get quite enough sleep for days on end: talk to some parents. I can also tell you that you're unlikely to find graphs in the form you want that can be generalised, because different individuals have different sleep needs, and this can vary depending on circumstance. For example: when I start a new job, I find I need more sleep for the first week or two. 86.178.167.166 (talk) 01:25, 13 March 2010 (UTC)

Not sure about specific studies, but some relavent articles include Sleep#timing, sleep and creativity, lucid dreaming, delayed sleep phase disorder, insomnia, psychomotor learning and health and intelligence. ~AH1^(TCU) 02:33, 13 March 2010 (UTC)

According to a book I read by a sleep doctor (can't recall the title), 95% of people require 8 hours of sleep per day on average- and that less sleep will lower your efficiency. It complicates things, because a person low on sleep sleeps DEEPER, but stills needs to make it up later. (By the way, the other 5% requires as little as 6 hours total to as much as 10 hours.) If I remember the title, I'll post it. Mxvxnyxvxn (talk) 23:16, 16 March 2010 (UTC)

Lorentz invariant

If two inertial systems (x, y, z, t) and (x', y', z', t') are moving relative to each other, with their origins coinciding at t = t' = 0, and at that moment a light pulse is emitted from the origin, then x² + y² + z² - c²t² = x'² + y'² + z'² - c²t'² = 0. To show that x² + y² + z² - c²t² = x'² + y'² + z'² - c²t'² is true in general, my textbook just applied the Lorentz transformations to (x, y, z, t) and crunched the algebra. Is there a simpler way (that is, by considering some sort of thought experiment or something) to show that x² + y² + z² - c²t² is invariant under a change of reference frame? —Preceding unsigned comment added by 173.179.59.66 (talk) 14:40, 12 March 2010 (UTC)

The book did that calculation just to double check the consistency of the theory. In fact that equation is nothing more than the statement that the speed of light is the same for all observers. This is the starting point of the theory and is usually taken as a postulate. No gedanken experiment is necessary. Dauto (talk) 17:04, 12 March 2010 (UTC)

After edit conflict:

Sure. Imagine the event E with coordinates (x,y,z,t) and (x',y',z',t'). Let's call the common origin event O. Let's work with c=1 and let's forget about y and z. I assume that's what the textbook does as well. (which book do you have?)

First assume t^2 > x^2. Assume a clock present at events O and E, which was also set to t"=0 at O. The unprimed/primed systems have a speed v resp. v' w.r.t. this clock. Then clearly v^2=x^2/t^2 and v'^2=x'^2/t'^2. Through the time dilation equations, the proper time t" on that clock satisfies t = t" / sqrt(1-v^2) and t' = t" / sqrt(1-v'^2). This implies that t" = t sqrt(1-v^2) = t' sqrt(1-v'^2). Substituting the values for v^2 and v'^2, we get the result.

Then assume t^2 < x^2. Assume a rod stretched between events O and E, and a system in which this rod is at rest. The unprimed/primed systems have a speed v resp. v' w.r.t. this system. (these v and v' differ form the previous ones!) Then clearly (see spacetime diagram!) 1/v^2=1-x^2/t^2 and 1/v'^2=1-x'^2/t'^2. Through the length contraction equations, the proper lenght x" of that rod satisfies x" = x / sqrt(1-v^2) and x" = x' / sqrt(1-v'^2). This implies that x / sqrt(1-v^2) = x' / sqrt(1-v'^2). Substituting the values for v^2 and v'^2, we get the result again. DVdm (talk) 17:45, 12 March 2010 (UTC)

Thanks, and I have Intro to Mechanics (Kleppner/Kolenkow). Oh and to Dauto: I don't think the Lorentz invariance thing is a statement that the speed of light is constant with respect to different inertial reference frames. The (x, y, z) coordinates don't have to be the point occupied by a light particle, just any point in general, so I don't think that you can extrapolate that because x² + y² + z² - c²t² = x'² + y'² + z'² - c²t'² = 0 for a beam of light, x² + y² + z² - c²t² = x'² + y'² + z'² - c²t'² is true for any event (x, y, z, t). If I'm wrong, please let me know! 173.179.59.66 (talk) 17:57, 12 March 2010 (UTC)

That's the reason why I elaborated. By the way, this Kleppner/Kolenkow is a very good textbook. Stick with it :-) - DVdm (talk) 18:43, 12 March 2010 (UTC)

You are correct, but what I said is also correct. There is no need for a gedanken experiment showing that the relativistic interval $dS^{2}=(cdt)^{2}-dx^{2}-dy^{2}-dz^{2}$ is an invariant. This is a postulate of the theory. In other words, you can define the Lorentz transformations as the set of transformations that respect the invariance of the relativistic interval the same way that you can define rotations as the set of transformations that respect the invariance of space-vector lengths. Dauto (talk) 18:42, 12 March 2010 (UTC)

Oh I see, thanks. 173.179.59.66 (talk) 02:23, 13 March 2010 (UTC)

I agree, but in many (older) books the invariance is not postulated, but rather derived from the "classic" postulates. DVdm (talk) 18:49, 12 March 2010 (UTC)

do you retain information better if you sleep on it?

this is related to the question above. My question is: do you retain information better if you've slept on it versus being tested the same day?

I don't mean because of the additional time since you learned it: say you compare learninng at 8 AM and being tested same day at 8 PM versus learning at 8 PM and being tested the next morning at 8 AM. Thank you. 82.113.121.104 (talk) 17:46, 12 March 2010 (UTC)

Several recent studies indicate this is the case. Even an afternoon nap can help. Graeme Bartlett (talk) 17:54, 12 March 2010 (UTC)

How did they control for tiredness? --Trovatore (talk) 17:55, 12 March 2010 (UTC)

According to Tony Buzan, your recall improves shortly after you have studied something (because your brain has sorted the information out) and then rapidly falls off. He recommender (and I found this works well) is to review the learn material 10 minutes after studying it, then review it again 24 hours later. The again after a week and once more after a month. This helps the information to be retained by the ‘long term’ memory. So, back to your question. You are likely to get higher marks if tested the same day. But it is better to keep reviewing it if you what to remember it long term. From Page 54, 55 ,56. Use your Head by Tony Buzan.--Aspro (talk) 18:21, 12 March 2010 (UTC)

I'm wondering too. I would like to test if this is the case for me. Guys here is my followup question:

can someone suggest a test methodology to control for everything but having "slept on it"

I would like to test if the above is true for me, and although the sample size will be 1, nevertheless that 1 subject is the one of greatest relevance to me :).

So can someone suggest an appropriate test methodology for me, for the simple task of trying to memorize and retain 10 of the multiplications from the 1000 x 10000 multiplication table, for example,

328x340=111520
274x781=213994
163x310=50530
494x65=32110
491x753=369723
969x954=924426
667x324=216108
77x813=62601
622x647=402434
196x249=48804

How should I do this in a way that will control TIREDNESS, control the stress or interference of other aspects of my life (e.g. I might concentrate better at night, since I wouldn't be doing something better anyway, but in the morning, I might be stressing out over something more important that I should be doing instead, and not concentrate fully and so forth). Any ideas? Thanks. 82.113.121.104 (talk) 18:09, 12 March 2010 (UTC)

You can't possibly do a well-controlled experiment with yourself as subject. The most common experimental paradigm is to have two groups of subjects, let's call them A and B. Group A learn the task, take a nap immediately afterward, sleep as much as they want to during the night, and are tested on the following day. Group B do the same things except without the nap. Thus both groups have the same learning experience and are well-rested during testing -- the only difference is the nap. For a recent review of the literature pertaining to this topic, you might look at PMID 19251443, if you have access to it. Looie496 (talk) 19:03, 12 March 2010 (UTC)

Obviously I can't do a double-blind experiment with myself as a subject; that's a given. But why couldn't I do a well-controlled experiment with myself as a subject, granted it might take longer, but you can see from my methodology below that you can still have a control...

Now my deeper problem with the methodology you mention is that BOTH groups a and b get to "sleep on it"!!! I am interested in the difference between being able to sleep on it, versus not having slept between learning the material and being teested.

To this end, what about the following test methodology:

For the next 20 days, every morning I get up at 6, every morning at 8 I put aside 15 minutes for the Methodology, every night I put aside 15 minutes at 8 PM for the Methodology and go to sleep at 10 PM.

• I group my these 20 days into groups of two (call them day1 and day2 within each group). At the onset, I randomize each pair of days into either being a "group a" pair of days or a "group b" pair of days.
• Then, each day goes as follows:
• If it is day1 of a group a, I do the studying in the morning slot, and take my test in the evening slot.
• If it is day2 of a group a, then I don't do anything in either the morning or evening slot.
• If it is day1 of a group b, I don't do anything in the morning slot. In the evening slot I do the studying.
• If it is day2 of a group b, I take the test in the morning slot. I don't do anything in the evening slot.

Now what could possibly be wrong with that methodology? It has both a control (group a pairs of days and group b pairs of days) and beyond this, it has an equivalent 12 hours between the studying and the being tested - the only difference is one of the groups includes 8 hours of sleep in that 12 hours, and the other group does not. Now, if there is a statistically significant difference in this well-controlled study on myself, it can be argued that the difference is because I am "more tired" at 8 PM than 8 AM, or alternatively phrased, "more alert" at 8 in the monring, after having awoken at 6 AM. Also the effects of any coffee I would drink would have to be normalized (ie I would not drink coffee until after hte test in the mornning). Same for taking my showers. Is there any other way in which the methodology I've just proposed would fall short? Thank you. 82.113.121.104 (talk) 19:46, 12 March 2010 (UTC)

The problem is that test performance is influenced by motivational factors, and it's impossible for you to ensure that you're equally motivated to perform well under all conditions. Even if you don't realize it, you're sure to have some motivation to want one outcome rather than another. Looie496 (talk) 20:07, 12 March 2010 (UTC)

so what do I have to do? Do the test with my brother, but not tell him what I'm testing, ie he doesn't know if it's significant whether the recall test is the next day or the same day. Instead, he just thinks it's a multiday test? I guess here you're going to tell me that that's good, but not good enough: it is single-blind. Instead, I need to get my brother to do the test with someone else, WITHOUT letting my brother know that what is really being tested is whether the subject has slept on it. Obviously all this machination just to get the result "no difference" is ridiculous, when I might get the same result myself anyway, so you guys must really be convinced there's a big difference... :) 82.113.121.104 (talk) 22:51, 12 March 2010 (UTC)

If you want a real study, you need more than one subject. You need, at a minimum, a control group and a test group. By just testing your brother, you are getting nothing more than an anecdote - which is not data. Further, your statement appears to suggest that you think everyone here is involved in a conspiracy to keep a secret from you. That is silly. -- kainaw™ 22:56, 12 March 2010 (UTC)

Well, you'd need multiple subjects if you were doing this for publication, or even for a school project. If you're just trying to get an answer for yourself, you could do it by repeatedly testing a single subject -- but even then it's important that the subject not be aware of what you are looking for, in order to avoid having your subject subconsciously sway toward the result you want (or against it!). Double-blind experiments are always nice, but generally not possible in sleep studies -- you can't blind somebody to the difference between being awake and being asleep. Looie496 (talk) 23:21, 12 March 2010 (UTC)

Referring to your test numbers, some numbers have special properties including 142857. Another subject related to functioning versus sleep is sleep and creativity. ~AH1^(TCU) 02:11, 13 March 2010 (UTC)

There is also the question of what you mean by "retain" information, obviously you could take this as being able to repeat a set of numbers. But for something like understanding how a set of variables interact, sleeping can help you process the data, hence why you sleep on a decision. Now in this case you might "retain" the meaning of the information better but not be able to write down the table, equation etc precisely. 82.132.139.214 (talk) 02:20, 13 March 2010 (UTC)

center of mass

Technically, isn't it the Earth/Moon center of mass that orbits the sun making the Earth closer or further away from the Sun at times during the rotation about the center of mass? 71.100.11.118 (talk) 18:24, 12 March 2010 (UTC)

Yes, but the Earth is so much larger than the Moon that the centre of mass of the two is inside the Earth. That means the Earth wobbles a bit, but nothing more. --Tango (talk) 18:40, 12 March 2010 (UTC)

And this wobble (a few thousand km ?) is insignificant compared to the distance caused by the Earth's slightly elliptical orbit, which is on the order of 5 million km. StuRat (talk) 18:58, 12 March 2010 (UTC)

Deriving the Lorentz transformations

It seems that the common approach to obtaining the equations for the Lorentz transformations are by guessing at their form and then, by considering four seperate situations, determining the constants. From these equations, things like time dilation and length contraction can be worked out. Now, my goal was to go the other way around: starting from time dilation and length contraction, arrive at the Lorentz equations.

Suppose that in the reference frame O, the reference frame O' is moving at a speed v in the x-direction, with their origins coinciding at t = 0. An event E occurs at (x, y, z, t) in the O frame. It's straightforward to show that y' = y and z' = z. Next I considered x'. In the O frame, the distance between O' and E is x - vt. Because the ruler O' uses is shortened by a factor of γ , she will then measure the distance x - vt as being greater and O measures it, by a factor of γ. Thus, x' = γ(x - vt).

However, I'm having trouble with t'. I know that t' = γ(t - vx/c₂). I assume that the -vx/c₂ term comes from that, because O' believes that she's at rest, when the light emitted from the event reaches her, she doesn't treat herself as moving into the light, and thus there's a discrepancy as to how long before the light reaches O' did the event actually happen. Unfortunately, I can't arrive algebraically at this term. Finally, the gamma factor. I assume this comes from time dilation, but the wouldn't O' 's clock be running slower? So wouldn't the term have to be 1/γ? Can someone please tell me how to get the final Lorentz term this way? I know there are probably other, easier routes, but for personal reasons I would like to know how to do it this way. Thanks a lot! 173.179.59.66 (talk) 18:31, 12 March 2010 (UTC)

It seems that you're failing to take into account that the two observers perceive different simultaneities.Dauto (talk) 18:50, 12 March 2010 (UTC)

You might be interested in Bondi k-calculus. As I recall your desired approach is pretty much exactly that. Although the article isn't exactly detailed. 129.234.53.144 (talk) 19:43, 12 March 2010 (UTC)

Hmmm not really, Bondi starts from the Doppler shift and works from there, instead of from time dilation (his equations have a bunch of k's). And as for the simultaneity comment, I thought that by considering how long it would take the light to reach the observer in each frame, simultaneity would be accounted for (as that is how differences in simultaneity arise). And then there's the issue with the gamma factor, which I think should be 1/γ. Sorry, I'm still lost! 173.179.59.66 (talk) 04:01, 13 March 2010 (UTC)

"...the distance between O' and E is x - vt." => That is a distance between a pair of simultaneous events in the unprimed system. So these events are not simultaneous in the primed system. Then you arrive at "Thus, x' = ?(x - vt)." But that is a coordinate of the event E in the primed system. As such it denotes the distance between a different pair of events. When you draw a spacetime diagram, you see what is going on. A piece of advice: always think in terms of events, and always draw a spacetime diagram. DVdm (talk) 11:57, 13 March 2010 (UTC)

So then, how would you fix this conundrum with t'? 173.179.59.66 (talk) 12:16, 13 March 2010 (UTC)

I don't think there's anything to fix, and we surely haven't fixed the trouble with x'. We merely established that not only you are "having trouble" with t', but with x' as well. DVdm (talk) 13:12, 13 March 2010 (UTC)

The point (0, 0, 0, t - vx/c²) is the point along the O frame path that's simultaneous to E as viewed from the O' frame. In the O' frame, clocks in the O frame run slower by a factor of γ. To the O' observer, when event E happens, the clock in the O frame reads t - vx/c², and so the amount of time that has elapsed in the O' frame is actually γ(t - vx/c²). Rckrone (talk) 20:30, 13 March 2010 (UTC)

So basically, what you're saying is that we must look at the perspective of O', not O. Why would this be (afterall, we're starting with O 's coordinates, and the time dilation/length contraction all occur in O' 's frame, but this approach seems to yield the wrong answer). Sorry if I'm being a bit slow, I really want to understand this, subtleies included. 173.179.59.66 (talk) 21:16, 13 March 2010 (UTC)

We're trying to find the O' time coordinate of E, which is the amount of elapsed time that has been experienced by O' at the point where O' views event E as being simultaneous to her. So we need to consider the points simultaneous to E in the O' frame and how much time has passed in the O' frame up to those points. We already know what E looks like in the O frame: it's at point (x, y, z, t). Rckrone (talk) 21:32, 13 March 2010 (UTC)

Exactly. That's why I mentioned earlier that 173.179.59.66 was failing to take the different simultaneities into account. There is a way to avoid having to deal with simutaneities and time dilations. I'll post it later because I'm busy right now. Dauto (talk) 22:43, 13 March 2010 (UTC)

Things are making much more sense now, I eagerly await your posts! PS: how did you get the vx/c2 term?173.179.59.66 (talk) 01:18, 14 March 2010 (UTC)

Okay, I've made some headway myself, and have managed to understand why it should be t' = γ(t - ...) instead of t' = (1/γ)(t - ...). However, the vx/c² term still eludes me. Here's the work I've done: I looked at the O' frame, with the goal of getting (x,y,z,t) in terms of (x',y',z',t'), which can then be easily switched to get (x',y',z',t') in terms of (x,y,z,t). I should get t = γ(t' + vx'/c²). Now, the gamma factor comes from clocks running slower in the O frame relative to the O' frame. The vx'/c² should come from difference in percieved signal delay between reference frames. In the O' frame, the light from event E reaches O at t' + x'/(c-v). From O 's perspective, the signal delay should only be x/c, so she will conclude that E happened at t' + x'/(c-v) - x/c. x' = x/γ, so this becomes t' + x'(1/(c-v) - √1-v²/c²/c). Problem: this doesn't seem to algebraically reduce to t' + vx/c². Where's my mistake? 173.179.59.66 (talk) 03:03, 14 March 2010 (UTC)

To arrive at the expression for $x'\,$ we have to take two things into account - A space dilation/contraction and an offset. We can for instance assume that there is a ruler of length $l'=x'\,$ at rest with respect to the primed coordinate system $S'\,$ so that one end of the ruler coincides with the coordinate origin at all times and the other end coincides with the event that happens at $(t',x')\,$. Now, that ruler is at rest at the $S'\,$ coordinate system so $l'\,$ is its proper length. The length of the ruler on the unprimed coordinate system $S$ gets space contracted, $l={\frac {1}{\gamma }}l'$. That was the space dilation/contraction. The offset comes about because ot the relative motion between the two coordinate systems. From the point of view of $S\,$, by the time $t\,$ at which the event $(t,x)\,$ happens the origins of the two systems will be already a distance $d=vt\,$ apart and that distance - the offset - must be added to the length of the ruler to get the coordinate $x\,$, giving us the equation $x=d+l=vt+{\frac {1}{\gamma }}l'=vt+{\frac {1}{\gamma }}x'$. That last equation can be solved for $x'\,$ and we find $x'=\gamma (x-vt)$.

It so turns out that in order to arrive at the expression for $t'\,$ we also must take into account a time dilation/contraction and an offset. We can place a watch at rest with respect to system $S\,$ at the coordinate $x\,$ and start the watch exactly at the instant the two origins coincide (from the point of view of $S\,$). The watch will mark the time $T=t\,$ when the event $(t,x)\,$ happens. Now, that watch is at rest at the $S\,$ coordinate system so $T\,$ is a proper time, and this time interval will be seen time dilated from the point of view of the system $S'\,$. That is $T'=\gamma T$. That was the time dilation/contraction. The offset comes about because from the point of view of the system $S'\,$ the watch was not started simultaneously with the time the two origins coincided. There is a delay $D'\,$ given by $D'=\gamma {\frac {vx}{c^{2}}}$. $D'\,$ must be subtracted from $T'\,$ to get the coordinate $t'\,$. We get then the equation $t'=T'-D'=\gamma T-\gamma {\frac {vx}{c^{2}}}=\gamma (t-{\frac {v}{c^{2}}}x)$

Even though the space offset due to relative motion is very intuitive, the time delay due to non-simultaneity isn't. It is to our advatage if we manage to find the transformation without ever having to mention simultaneity or time dilation. To do that we start from the last equation of the first paragraph found using space contraction and relative motion only

$x'=\gamma (x-vt)$

We also have a similar equation obtained for $x\,$ in terms of $x'\,$ and $t'\,$. It's the same equation but with a sign difference because from the point of view of $S'\,$, $S\,$ is moving in the oposite direction

$x=\gamma (x'+vt')$

Substituting $x'\,$ from the first equation into the second,

$x=\gamma [\gamma (x-vt)+vt']$

$x=\gamma ^{2}(x-vt)+\gamma vt'$

$\gamma ^{-2}x=(x-vt)+\gamma ^{-1}vt'$

$vt+(\gamma ^{-2}-1)x=\gamma ^{-1}vt'$

$vt+[(1-{\frac {v^{2}}{c^{2}}})-1]x=\gamma ^{-1}vt'$

$\gamma ^{-1}vt'=vt+(-{\frac {v^{2}}{c^{2}}})x$

$\gamma ^{-1}t'=t-{\frac {v}{c^{2}}}x$

$t'=\gamma (t-{\frac {v}{c^{2}}}x)$

Voilla. Dauto (talk) 03:38, 14 March 2010 (UTC)

Wow that was exactly what I was looking for, thanks a lot! Really, that was a great help. I just have one final question though (sorry!): what was wrong with the signal delay approach I used above? I'm guessing it's another issue with simultaneity, but I just can't see were the problem is (or how it can be resolved, if I was inclined to use the signal delay way to avoid having to imagine clocks placed along the x-axis). I know it may seem trivial, but I want to have a thorough understanding of special relativity, and if I can't see why a certain approach is flawed then I can't say I really do. 173.179.59.66 (talk) 04:18, 14 March 2010 (UTC)

Never mind, I figured it out: I was multiplying my gammas at the wrong time. Much thanks again! 173.179.59.66 (talk) 05:35, 14 March 2010 (UTC)

Dauto, at a certain point you say: "There is a delay $D'\,$ given by $D'=\gamma {\frac {vx}{c^{2}}}$", I don't see how you arrive at this expression. Can you explain?

Perhaps I should add that I object to the explanation you have given above, as you have simply taken an equation from the inverse Lorentz transformation ($x=\gamma (x'+vt')$). Of course we all know that given any two of the four (linear) equations, the other two equations be derived algebraically. But 173.179.59.66 asked for an alternative way to derive the transformation: "...starting from time dilation and length contraction, arrive at the Lorentz equations.". I don't think that's what you did here. - DVdm (talk) 10:51, 14 March 2010 (UTC)

I didn't arrrive at the expression for $D'\,$. I took it as a postulate. The point of that paragraph was to highlight the similarities of the expressions for $x'\,$ and $t'\,$. I agrre that taking the expreesion for $D'\,$ as a postulate is not entirely satifactory and that's why I showed an alternate way to solve the problem on the third paragraph. The expression for the inverse transformation (($x=\gamma (x'+vt')$) can be obtained from space contraction in a manner similar to the one I used in the first paragraph to obtain the expression for $x'\,$, or better yet, simply use the principle of relativity and obtain the expression for $x\,$ from the expression for $x'\,$ by making the replacements $x'\rightarrow x\,$, $x\rightarrow x'\,$, $t\rightarrow t'\,$, and $v\rightarrow v'=-v$, afterall from the point of view of $S'\,$ it is $S\,$ that is moving. Dauto (talk) 15:52, 14 March 2010 (UTC)

Entirely with you now. Cheers - DVdm (talk) 16:01, 14 March 2010 (UTC)

tidal forces

For two absolutely solid bodies (such as pure diamond crystal matrix) orbiting each other and assuming no tidal forces then the spin of either body results in no geosynchronous orbit such that the orbit neither decay inward or outward regardless of the orbital distance, is that correct? 71.100.11.118 (talk) 18:33, 12 March 2010 (UTC)

You can still get friction and gravitational waves, which can remove angular momentum away from your system. Graeme Bartlett (talk) 18:48, 12 March 2010 (UTC)

The assumption that diamonds don't undergo tides is incorrect. Any matter will be affected by gravitational forces, and thus undergo tides, although solids deform much less than fluids. StuRat (talk) 18:53, 12 March 2010 (UTC)

There will always be tidal forces. I suppose if the body is sufficiently rigid that those forces don't result in significant bulges then we can discount them, though. In that case, there won't be any tidal interactions resulting in decay, in any direction for any orbit. There are other factors that will change the radius of the orbit, though - atmospheric drag, for instance (particularly for low orbits), and interactions with other objects. --Tango (talk) 18:57, 12 March 2010 (UTC)

Animals that feed only on animals of their own kind

Which animals eat nothing but other animals of its own kind? I know there are lots of animals that practice cannibalism but all cannibal species I think of usually eat other stuff too and I can't even think of any cannibal species that feeds primarily (let alone exclusively) on the animals of its own kind. I am aware that such behaviour would be very inconvenient for the survival of the species but some animals routinely eat their young and still thrive. Surtsicna (talk) 19:47, 12 March 2010 (UTC)

It's pretty obviously impossible -- since digestion is less than 100% efficient, the biomass of such a species would have to steadily decrease. Looie496 (talk) 19:59, 12 March 2010 (UTC)

Exactly. There would be no way for energy to enter the species. Even with 100% efficient digestion, not all that energy is converted to biomass. Much of it is used for locomotion, for example. --Tango (talk) 20:05, 12 March 2010 (UTC)

Agreed. You could, however, have a small portion of a species which cannibalizes the rest. I would expect that this portion would then evolve into a new species. StuRat (talk) 20:07, 12 March 2010 (UTC)

Whether they evolve into a new species would depend on whether they breed with the rest of the population or not. If they do, there won't be any speciation. It is common for, for example, dolphin pods to have different diets even in the same environment, but they still breed more generally. --Tango (talk) 20:42, 12 March 2010 (UTC)

I wouldn't expect much interbreeding between hunters and prey, both because the prey will run and hide and because the hunters will kill the prey if they find them. StuRat (talk) 16:00, 13 March 2010 (UTC)

Hmm. That argument implies all biomass comes from ingestion. What about if the animal were symbotic with something photosynthesising which lived in them? Not that I can think of any such but I am not clear it is technically impossible for an animal with a second such source of biomass to ingest only others of the species. --BozMo talk 21:14, 12 March 2010 (UTC)

In that case, it would have to either derive most of its energy from the other source or reproduce faster than it can eat. The first satisfies OP's question in letter but not in spirit - it would not technically be "eating" if it were to derive energy through photosynthesis. The second is unlikely given the normal ratio of consumption of nutrients to species reproduction found in other animals. That is to say, in my experience most creatures eat more often than they reproduce. Coreycubed (talk) 21:31, 12 March 2010 (UTC)

Well biology is not my subject but there are animals as far as I can tell which eat nothing (eg a Giant tube worm which derives its energy from non digestive processes and has no digestive tract). So variants could conceivably exist which ate only its own kind. But you have to be a long way out of the ordinary, and certainly not close to your ordinary ratios. --BozMo talk 21:51, 12 March 2010 (UTC)

Yes, but as Coreycubed says, that only satisfies the letter of the OP's question, not the spirit. --Tango (talk) 00:05, 13 March 2010 (UTC)

I seem to recall a certain species of spider where the young eat their mother for nutrition, probably Segestria florentina. Spider cannibalism is also relavent but those species do not solely depend on cannibalism for foon. ~AH1^(TCU) 02:06, 13 March 2010 (UTC)

Interesting, but I'm sure they eat more than just their mother during their lives. --Tango (talk) 02:16, 13 March 2010 (UTC)

Ants have three or more genders. If the workers, or whichever ones are non-reproductive, went around fattening themselves up and then the soldiers and queens ate them it could work like that, in the sense of enough energy gathered. ~ R.T.G 02:56, 13 March 2010 (UTC)

I wouldn't say they had more than two genders - workers are female, just infertile females. Also, I think soldiers are a type of worker. The males (drones) tend to do very little. All of that aside - what you describe would work, but it doesn't meet the OP's requirements since the workers are eating something other than their own species. --Tango (talk) 03:10, 13 March 2010 (UTC)

Terminal cancer

If someone is in the final stages of terminal cancer, why is nutrition denied?--79.76.188.14 (talk) 21:51, 12 March 2010 (UTC)

You need to be careful with terminology here, as nutrition and food aren't the same things. Nutrition is essential to survive, so to keep the patient comfortable they would need to be feel at least partially nourished, otherwise the individual will starve. As far as I know, in terminal cancer (i.e. where there will be no further medical intervention other to make the patient comfortable), food wouldn't be denied to the patient, but rather the patient may be unable to take food orally because of severe weakness associated with late stage cancer. Someone feel free to correct me there. Regards, --—Cyclonenim | Chat  23:04, 12 March 2010 (UTC)

Sorry I may have misunderstood your question, are you referring to nutrition being denied by the medical professionals, or nutrition to cells being reduced and why that occurs? Regards, --—Cyclonenim | Chat  23:22, 12 March 2010 (UTC)

Nutrition denied by medical professionals--79.76.188.14 (talk) 00:03, 13 March 2010 (UTC)

In that case, as Cyclonenim says, it simply isn't. Where have you got that from? Palliative care certainly involves feeding patients if they are willing and able to eat (and giving them intravenous nutrition if they can't/won't eat and it is appropriate to do so). --Tango (talk) 00:09, 13 March 2010 (UTC)

No, I think it is sometimes. It's a form of passive euthanasia. Generally we're talking about a patient in a coma or near-coma state, and who, if he did regain consciousness, would not likely enjoy it. --Trovatore (talk) 00:12, 13 March 2010 (UTC)

True, it is used for coma patients (although not usually in cases where they think there is a significant chance of the patient waking up). Do cancer patients typically end up in comas, though? Brain tumours sometimes cause comas, but I wouldn't expect other forms of cancer to. --Tango (talk) 00:55, 13 March 2010 (UTC)

When the body is unable to absorb nutrients due to organ failure but the nutrients continue to be supplied to the patient, conditions such as edema can occur. See also medical ethics. ~AH1^(TCU) 02:01, 13 March 2010 (UTC)

True, but by that point the patient would be at most hours from death anyway, wouldn't they? Not feeding someone for a few hours isn't unusual, even if they are perfectly healthy. --Tango (talk) 02:13, 13 March 2010 (UTC)

Some cancer patients lose the ability to process oral food weeks or even months before they ultimately die. Fluids and some nutrition can be supplied intravenously for a time, but the lack of solid food and difficulty absorbing nutrition can contribute to the sense of wasting away that is not uncommon in end stage cancer patients. Dragons flight (talk) 19:56, 13 March 2010 (UTC)

Absolutely, but that isn't nutrition being withheld. --Tango (talk) 21:22, 13 March 2010 (UTC)

Nutrition is sometimes withdrawn from terminal patients, with the consent of the relatives, in certain jurisdictions, as a legal method of euthanasia. The logic is that the patient "dies on their own", versus being injected with a poison, which would be considered murder. Of course, if they are on a ventilator, then that can be turned off as a quicker method of euthanasia. StuRat (talk) 02:09, 13 March 2010 (UTC)

There have from time to time, including recently, been reports in the UK press and media of, and legal investigations into, cases where elderly patients (some terminally ill, others apparently not) have allegedly been wrongly or over-prescribed with opiate drugs or denied nutrition and water, leading to their quicker and/or unnecessarily unpleasant and/or unnecessary deaths. One case is referenced here; I recall others I don't feel inclined to dig for. Such cases, obviously legally and emotionally sensitive, may reflect possible incompetence or wrongdoing on the part of some medical staff. 87.81.230.195 (talk) 04:23, 13 March 2010 (UTC)

The issue of over-prescribing opiates is often one of double effect - painkillers are given in the quantity necessary to deal with the pain despite the doctor knowing that dose will kill the patient. --Tango (talk) 21:22, 13 March 2010 (UTC)

So, if nutrition was not denied intravenously (say), would the patient live longer?--79.76.188.14 (talk) 22:49, 13 March 2010 (UTC)

Obviously the main factor here is how severe the cancer is, but without nutrition I imagine the patient would die sooner as they would be weaker from lack of energy. No source for that, just seems common sense. Regards, --—Cyclonenim | Chat  23:03, 13 March 2010 (UTC)

lab rats

where are lab rats and mice bought from for research purposes? —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 23:36, 12 March 2010 (UTC)

From companies that sell rats and mice for research purposes. E.g., [2] See laboratory rat. alteripse (talk) 23:38, 12 March 2010 (UTC)

i already read that it didnt help —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 03:52, 13 March 2010 (UTC)

here are several commercial suppliers: [3] [4] [5]. Note that most animal houses (individual labs rarely keep their own rats and mice these days - instead they are housed at a central specialised facility) would only buy animals if they needed a new strain or an existing strain was lost due to disease etc. Otherwise it is far easier and cheaper to breed their existing mice.131.111.185.68 (talk) 08:45, 13 March 2010 (UTC)

Also, while I haven't done work with animals myself (well, other than fruit flies) I would imagine that labs quite often give more specialised strains as gifts to other labs which need them. This is quite common practice in (academic) science - it is much less hassle than trying to agree on a price and the sharing of resources means that everyone can get on with their work without spending six months duplicating what another lab has already done.131.111.185.68 (talk) 08:54, 13 March 2010 (UTC)

galactic spiral arms

Given enough time will the stars that fill the galactic plane accrete and form "stellertoids" (similar to planetoids only made up of stars that have accreted into super giant stars or black holes) and become spaced out into planetoid like orbits around the galactic center? 71.100.11.118 (talk) 23:52, 12 March 2010 (UTC)

Not really. Depending on what the ultimate fate of the universe is, they might well all end up in black holes, but that will be long after they stop being fusing stars (they'll be neutron stars, white/black dwarfs, smaller black holes, etc.). I suppose it is possible for stars to merge, but it would be a very unusual event (and I'm not quite sure what would happen - it would depend on the masses of the stars involved, certainly). I think you may be a little confused about what a planetoid is, too - a planetoid is a small planet-like body. In the early solar system, planetoids would have accreted into planets. Given your terminology, I think you may be thinking planets merge together to form planetoids, which isn't the case (I apologise if I'm the one misunderstanding). Also, the orbits of stars around the galactic centre are very similar to the orbits of planets around stars - the spiral arms are just a kind of pressure wave caused by complicated interactions, individual stars follow normal orbits (they are slightly different because the mass of the galaxy isn't dominated by the centre like that of a solar system is, but that isn't very important, it just affects the numbers a little). --Tango (talk) 00:17, 13 March 2010 (UTC)

No, actually I am thinking of planetoids as the precursors to the formation of planets. Try to decide what terminology to use when composing an imaginary situation always runs the risk of bringing with it a misconception or the wrong idea (my naughty speller doesn't help either!). Basically what I'm asking is that in absence of any other interference such as collisions or merges with other galaxies or the Universe ending prematurely from the Big Rip or Crunch if accretion of stars into planet like orbits around the Galactic center is a reasonable consequence. (The main reason for the question is in consideration of how much space can separate such orbits since the motion of the solar system planets form spirals when you connect them as dots for regular periods of time.) —Preceding unsigned comment added by 71.100.11.118 (talk) 07:22, 13 March 2010 (UTC)

In that case, I guess the answer is "yes", but they won't be stars by the time it happens. They will be stellar remnants of various types and will merge into black holes. The same process will result in quite a lot of objects being thrown out of the galaxy altogether, though (unless something happens first, they will eventually fall into a black hole somewhere, anyway). --Tango (talk) 12:45, 14 March 2010 (UTC)

Also, before your scenario or something similar could occur, the Milky Way could likely collide with the Andromeda Galaxy to form Milkomeda. This would disrupt the spiral structure, and our galaxy could turn more elliptical. The colliding pair could also absorb numerous other galaxies such as the Large Magellanic Cloud, Small Magellanic Cloud and the Triangulum Galaxy, further disrupting the "clumps" of stars and gas in the galaxies. ~AH1^(TCU) 01:55, 13 March 2010 (UTC)

The merging of stars in the galactic disc is an excedingly rare event. Mergers are still rare but not completely negligible on higher density enviroments such as blobular clusters. Read blue stragglers to see what happens to stars after merging. Dauto (talk) 17:10, 13 March 2010 (UTC)

I assume Dauto has mistyped "blobular clusters" for Globular clusters, but I like this new term and can imagine someone applying it in the future, perhaps to non-symmetrical globulars :-). 87.81.230.195 (talk) 21:52, 13 March 2010 (UTC)

However, in the case of stars that collide with sufficient energy, they may explode in a hypernova, or if pulsars are involved then magnetic or gravitational waves may be released (I seem to recall an article involving a specific event where such a collision released energy that hit the earth's atmosphere but I can't find it right now). ~AH1^(TCU) 23:33, 13 March 2010 (UTC)

March 13

Sodium bicarbonate

I noticed that if you burn a chlorate, you get the chloride (with oxygen gas), and if you burn a carbonate, you get the oxide (with carbon dioxide gas), so what does burning a bicarbonate, such as sodium bicarbonate, produce? --70.250.214.164 (talk) 00:25, 13 March 2010 (UTC)

I don't think you really mean "burn" — more like "heat" or perhaps "pyrolyze". If I recall correctly, heating sodium bicarbonate will first drive off water, producing sodium carbonate. This reduces the question to the previous case, which you have already solved. --Trovatore (talk) 00:34, 13 March 2010 (UTC)

You could try reading the article; it answers the question directly. Looie496 (talk) 00:37, 13 March 2010 (UTC)

The mass of a singularity

Don't give out to me now. A principle of the singularity, in the big bang anyway, is that the mass could be fit into an infinitely small space. To say "infinitely small", there is no requirement of the word small, right? There is zero size, right? If that follows, could there be a singularity of some sort that requires zero mass? Could they peel open a quark, for instance, and a singularity or something pops out? Is there interesting theories or anything like that? ~ R.T.G 02:45, 13 March 2010 (UTC)

Quarks do have mass, so I'm not sure what you mean. However, singularities are usually just interpreted as a sign that we've made a mistake rather than as a genuine physical object. When the maths results in a singularity it is basically saying "I don't know". When we get a good working theory of quantum gravity, hopefully the singularities in black holes and the big bang will disappear. --Tango (talk) 03:03, 13 March 2010 (UTC)

Often in sci-fi there is something about where they have cracked open an atom or interfered with the density of a star opening a rift which could destroy a universe. Couldn't that sort of potential be a basic element? I suppose trying to write into it I am thinking well maybe pigs will fly too but the theory about it is hardly going to be in aerodynamics. Maybe if a butterfly flaps a bit all these storms will stop for the summer. Oh well never mind me. Thanks for answer anyway. ~ R.T.G 04:21, 13 March 2010 (UTC)

Tango, this is the second time recently that you've stated (in so many words) "singularities are usually just interpreted as a sign that we've made a mistake rather than as a genuine physical object. When the maths results in a singularity it is basically saying "I don't know"." First, what is your source for this? Second, the overwhelming consensus is that, e.g., the singularity of a black hole has infinite density; literally dozens of sources for this statement could be found in one bookshelf of one library. If you personally believe singularities are nonsense, that's fine -- but it is not the overwhelming consensus ... which equals the "truth" for our purposes here. 63.17.60.8 (talk) 05:33, 13 March 2010 (UTC)

It's very well known that general relativity, which predicts singularities in black holes and for the Big Bang, breaks down at such extreme energies. This is what's behind the search for quantum gravity, and is not at all controversial.

Also, to the OP: white hole? --99.237.234.104 (talk) 07:13, 13 March 2010 (UTC)

Gravitational singularity, for reference. Indeterminate (talk) 09:50, 13 March 2010 (UTC)

Indeed - Tango is correct. Our gravitational singularity article says "Many theories in physics have mathematical singularities of one kind or another ... This is generally a sign for a missing piece in the theory, as in the Ultraviolet Catastrophe and in renormalization". In the case of gravitational singularities the canonical view, which I believe originated with Penrose and Hawking, is that the physcially unrealistic conditions predicted by general relativity can only be resolved by an as yet unknown theory of quantum gravity. Gandalf61 (talk) 10:04, 13 March 2010 (UTC)

If something had zero mass but finite space, then it would either be considered a vacuum or nothing, but even a pure vacuum contains energy in the form of dark energy and vacuum energy. However even a singularity may have "volume" in the sense that it contains a geometrical shape but possibly in a different dimension as in the case of a ring singularity. Also, you may be interested in micro black holes. ~AH1^(TCU) 23:24, 13 March 2010 (UTC)

Indeed, it remains unsourced. "This is generally a sign for a missing piece in the theory" ... according to whom and based on what evidence? One can speculate that singularities are non-existent. But here the standard for "true" is the academic consensus at present, and the consensus is that singularities are consistent with the math and the physics and no better theory or evidence has emerged to render them imaginary. Again: scores of references for this are available on literally one shelf of any decent library. Just to pick one at random (from the internet, where, again, sources for this are endless): "We must rely on our untestable theoretical predictions. At this point they tell us the singularity has all the matter in the black hole collapsed to a geometric point. This singularity has a mass comparable to a star compressed to a zero volume and infinite density." See the words: "We must rely." That's what a scientist says, without resorting to speculation, in the present tense. (Here's THAT source, selected at random in ten seconds from among thousands on the internet: google "black_hole_singularity" (at a site WP blocks), by Paul Heckert, who writes: "I am a university professor who has been teaching physics and astronomy for over 25 years. I have a Ph.D. in astrophysics specializing in observational astronomy. My work has led to over 60 published research articles in journals such as Astronomical Journal, Astronomy and Astrophysics, Astrophysical Journal, The Monthly Notices of the Royal Astronomical Society, and The Information Bulletin on Variable Stars.") So, again: Besides the UNsourced WP article cited above, what are your sources for the statement about singularities? 63.17.64.195 (talk) 11:29, 14 March 2010 (UTC)

Here are some sources for the fact that the presence (and, indeed, inevitability) of singularities in general relatviity is generaly taken as evidence that the classical theory of general relativity is incomplete:

• Stephen Hawking, A Brief History of Time, Chapter 8: "All the known laws of science would break down at such a point. One might suppose that there were new laws that held at singularities, but it would be very difficult to even formulate such laws at such badly behaved points ... the gravitational field becomes so strong that quantum gravitational effects become important: classical theory is no longer a good description"
• Roger Penrose, The Road to Reality, Chapetr 27: "...it seems unavoidable that the realm of quantum gravity (or whatever is the appropriate term) will be entered, so that these expectations of the classical theory will have to be modified in accordance with this".
• F. David Peat, Superstrings and the Search for the Theory of Everything, Chapter 8: "These singularities are points at which the very structure of space-time breaks down and the laws of physics no longer apply".
• Matts Roos, Introduction to Cosmology, Chapter 10: "In a singularity, the field equations of general relativity break down, so one can only say that 'the theory predicts that it cannot predict the Universe'".
• Abhay Ashtekar, One Hundread Years of Relativity, Chapter 14: "...it is clear that the singularity does not so much present a boundary to the universe as a boundary to the classical theory. The theory predicts conditions under which it has to break down and is thus incomplete". Gandalf61 (talk) 14:41, 14 March 2010 (UTC)

the frog still alive

how possible?

http://www.youtube.com/watch?v=QLz8RK4teHM&feature=related —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 04:46, 13 March 2010 (UTC)

Twitching is not the same as living. See the article Galvanism which mentions the 18th century discovery that a severed frog's leg can be made to twitch. Cuddlyable3 (talk) 23:42, 13 March 2010 (UTC)

Frogs are pithed before dissection, severing the spinal column so they don't kick their legs. Nerve impulses from the spinal column can cause the legs of a dead/dieing frog to kick. All it takes is a volt or so. In the early 19th century, 1804, a hanged and dead man, Mr Foster, was used with his spine severed for electrical experiments. [6], [7], [8], [9] by Giovanni Aldini. A battery connected to muscle groups could make the dead man move his arms and legs, move his eyes around, and extend his arm. Frankenstein, anyone? Mary Shelley doubtless read of these experiments. A dead horse would kick its leg when a battery was applied, A chicken with her head chopped off can run around flapping her wings for a minute or so. Still dead. Edison (talk) 04:43, 14 March 2010 (UTC)

yes im aware but i think the frog was alive because iv seen suicide vids where they live when others would die —Preceding unsigned comment added by 67.246.254.35 (talk) 07:51, 14 March 2010 (UTC)

Did you read the part about how muscle from an absolutely dead animal can twitch? If parts of the brain were still functioning, or if the swimming movement in a frog can proceed from lower nerve centers like in a headless chicken, then the movement could occur without the animal being "alive" in any meaningful way. I did not intend to suggest that someone was electrically stimulating the shredded frog like Dr. Aldini did to his Franken-victim in 1803. Edison (talk) 18:17, 14 March 2010 (UTC)

Was there sex in the biosphere?

? —Preceding unsigned comment added by 67.246.254.35 (talk) 05:30, 13 March 2010 (UTC)

If you're talking about this biosphere, then the answer is an unquestionable "Yes". If you're referring to Biosphere 2, then the answer is still likely "yes" as this source suggests. Dismas|^(talk) 07:14, 13 March 2010 (UTC)

Or if you are asking about sex in space, see that article. ~AH1^(TCU) 23:19, 13 March 2010 (UTC)

Cylindrical Fuels rods??any

I have made an characterisation and optimisation study on flames with open top enclosures<Cylindrical Radial enclosure only>.It is already selected for an international Conference.I have problem in finding s field of application for it.Please anybody suggest.

Thanks in advance —Preceding unsigned comment added by SCI-hunter (talk • contribs) 05:41, 13 March 2010 (UTC)

If you can describe these fuel rods better, we may be able to help. Is this just a cylinder of flammable material ? StuRat (talk) 13:42, 13 March 2010 (UTC)

If it it can achieve a clean burn, then you have my vote to use it as a neat and nifty heat source for my one gallon Bagna càuda and save filling the room with the oily smell of burning paraffin wax. --Aspro (talk) 14:11, 13 March 2010 (UTC)

Yes i have modelled the situation with a candle flame.hence it is a cylinder of flammable material.Any way what is banga cauda stated by Aspro.Some more application preferably in industries would be welcomed. Thanks SCI-hunter (talk) —Preceding undated comment added 15:20, 13 March 2010 (UTC).

You are the same guy who thought a common candle was somehow related to a "CANDLE nuclear reactor" - which I think we can conclusively say it isn't. So somehow this confusion has resulted in you getting this "study" into an international conference!?! OMG! That's too funny! I strongly recommend that you call up the conference panel, apologize profusely and withdraw your paper ASAP. SteveBaker (talk) 15:40, 13 March 2010 (UTC)

Steve, I don't think English is their first language, so mistakes like that don't mean they are an idiot, it just means they don't speak English well. StuRat (talk) 15:54, 13 March 2010 (UTC)

OK, assuming you are talking about something with the characteristics of a candle, namely burning at one end by combustion with environmental oxygen, let's see what applications we can come up with. I would assume that this would be more expensive than fuel sources such as propane or natural gas. The advantage may then be that it's more portable, and stores well. If so, uses where other fuel supplies aren't available come to mind, such as camping or for emergencies (in a car road kit, for example). Perhaps this could be used to start a camp fire in damp weather ? I wouldn't think there would be much industrial use, as industry is likely to have cheaper sources of energy avaialble. StuRat (talk) 15:54, 13 March 2010 (UTC)

How about using as a heat source for a Fondu (that is also is like a Bagna càuda but more popular with trailer trash and nouveau riche )… A better fondu heat source could be the biggest advance in human dinner party experience since Boy Scouts first sat around the camp fire together and roasted their nuts.--Aspro (talk) 16:44, 13 March 2010 (UTC)

Thanx a lot for positive responses and let me tell "Steve" that my paper has not mentioned anything about the nuclear reactor.The innovative study methodology and subject has won a place in international conference.So i am nothing to apologize and withdraw.Looks some problem in communication. Thanx to aspro and others 220.225.98.251 (talk) —Preceding undated comment added 15:01, 14 March 2010 (UTC).

MATERIALS USED IN BATHROOMS

I WANT THE FULL DETAILSSSSSSS —Preceding unsigned comment added by Waqasiqbal175615 (talk • contribs) 08:05, 13 March 2010 (UTC)

Tile, porcelain, metal, wood, drywall, paint, glass. Do you have a more specific question? Comet Tuttle (talk) 08:26, 13 March 2010 (UTC)

Fiberglass, layered acrylic, and iron are often used for tubs[10][11]. Marble, slate, and other forms of stone. Copper and PVC pipes. Chrome. --Normansmithy (talk) 13:12, 15 March 2010 (UTC)

is it possible to boil water through the power of the mind alone?

If I put a pot of room temperature water on the stove, which is cold and turned off and to remain off, is it possible for me, or for anyone, to focus mental energy and bring the water to a boil through the power of the mind alone? If so, how would I go about developing this ability? 82.113.121.167 (talk) 11:15, 13 March 2010 (UTC)

No. If you can do it, and consistently, then get in touch with James Randi for your $1 million prize. --Mark PEA (talk) 11:28, 13 March 2010 (UTC)

You might consider asking this question on our yet to be created Wikipedia:Reference desk/Nonsense. DVdm (talk) 11:30, 13 March 2010 (UTC)

I believe this has been proposed. :) Zain Ebrahim (talk) 17:30, 13 March 2010 (UTC)

You must have lived such a sheltered live, DVdm. Here, for your edification, is an example of actual nonsense:

“ j6eZiebr4-choayoahOaspi4JlU7i&hlaxl$CetL4nlevluSwlarluThOuroumIdoa+oaf51Eqla!rlen$$swIudlEthluthlUgo*sp?u? ”

Or even:

“

Isn’t it always the heart that wants to wash
the elephant, begging the body to do it
with soap and water, a ladder, hands,
in tree shade big enough for the vast savannas
of your sadness, the strangler fig of your guilt,
the cratered full moon’s light fuelling
the windy spooling memory of elephant?

”

(That's from the New Yorker).

By comparison, my question is extremely sensible, and very specific. You've lived a sheltered life. 82.113.121.167 (talk) 11:52, 13 March 2010 (UTC)

Well, I guess you can run a Stirling engine off the temperature difference of a brain and the environment and use that mechanical energy to drive a heat pump to concentrate heat to boil water, or convert it to electricity to drive an electric heater. It will require very many brains and probably the application of the Spherical cow theorem to work, though, and it's not what you would usually call "mental energy". It would, however, be a strong testament to the "power of the mind" ;-). --Stephan Schulz (talk) 11:36, 13 March 2010 (UTC)

See A. W. Underwood. He claimed to be able to set things on fire using the power of his mind (with only a _little_ assistance from white phosphorus). Paranormal powers do show a distressing tendency to have such explanations - I can't imagine why. ;) Tevildo (talk) 11:54, 13 March 2010 (UTC)

I can. - DVdm (talk) 12:00, 13 March 2010 (UTC)

Spontaneous human combustion Graeme Bartlett (talk) 12:29, 13 March 2010 (UTC)

:-) Quoting (emphasis mine):

• "While there have been about 200 cited cases worldwide over a period of around 300 years, most of the alleged cases are characterised by the lack of a thorough investigation, or rely heavily on hearsay and oral testimony. In many of the more recent cases, where photographic evidence is available, it is alleged that there was an external source of heat present (often cigarettes), and nothing occurred "spontaneously.""

For the other desk. DVdm (talk) 13:30, 13 March 2010 (UTC)

What you don't understand, DVdm, is that in a scientific investigation, at least one time in a hundred, you are likely to see a statistically significant effect at the 99% confidence level. The only thing paranormal scientists now need to do, is take that 1 case out of 100, and somehow hone in on it, isolate it. That is the work that everyone who is rigorously interested in the paranormal must focus all of their mental energy on. 82.113.121.167 (talk) 14:20, 13 March 2010 (UTC)

Perhaps this is where I must emphasise that I'm not really all that "rigorously interested in the paranormal". I am however somewhat interested in the psychology of those who are. As this is a rather less interesting case, I think I'll sign off here. Sorry if was unable to help, but anyhow, the pleasure was mine :-) - DVdm (talk) 14:40, 13 March 2010 (UTC)

Presumably this would not be supernatural but indeed, some kind of natural phenomena. The brain really doesn't seem built to transmit the amount of energy required. It's also unclear to me how it would boil water at a distance without boiling the water in your head simultaneously (a microwave transmitter would not work if it was immersed in a bunch of water—it would heat itself). The only way I can imagine doing it (though I don't pretend to be the most imaginative) is to suppose that our brains are somehow tied to some very strange physics, the likes of which our pretty reliable theories have given no hints of, and of which an evolutionary explanation is conspicuously absent. One would also presumably expect that if concentrating on something could cause it to be physically manipulated or heated or whatever, that people who spend long periods of time in, say, solitary confinement, would have had ample time and opportunity to develop these abilities. Anyway—the answer seems pretty clearly to be "no, sorry," even if one does not necessarily believe that scientists "know everything." It simply seems implausible from a number of viewpoints, and there seems to be no reason to assume it is true other than "it would be cool" in a comic-book way.

Alas, don't be sad, your brain can accomplish much more than boiling water if you apply it in useful ways. Human brainpower, coupled with manpower and technology, have moved mountains, destroyed cities, healed millions. The human brain is a powerful thing in and of itself, with no need to appeal to the paranormal. --Mr.98 (talk) 15:28, 13 March 2010 (UTC)

This is exactly why I find it hard to believe. The human mind, of all the plants, mushrooms, and animals on Earth, literally in the millions, has the power to form coherent sentences, can formulate exquisitely abstract notions. The power of the human brain alone has allowed us to pierce the very fabric of the Universe and extract from it the secrets of electricity, which the power of the human brain has fully dominated and put at the command of every modern household; the power of the human brain has discovered and devised ways to apply atomic theory to split the atom, putting at our disposal not only vast amounts of energy in the form of nuclear fission power plants, far beyond what any plant or animal comes within many, many orders of magnitude of being able to produce, singly or in groups, but also what at this moment we are working on producing on Earth: the very process by which Sol our sun produces fusion energy, all invented, targeted, and worked upon through the power of the human brain; the human brain alone has cracked the secret of the atomic structure, the key to modern chemistry, and the human brain has realized ways of producing materials that have never appeared anywhere on Earth and have supremely useful functions for everyone. The human brain has devised magnetic levitation, wholly absent in all of nature, and uses it for locomotion at a speed that is literally orders of magnitude faster and at distances that are orders of magnitude farther than the fastest animal can sustain. Verily the human brain has cracked the cosmos; the genetic structure; problems of energy; of materials; of electricity and electronics; of land, air, sea, and space. Yet it cannot bring a pot of water to a boil? 82.113.121.167 (talk) 16:30, 13 March 2010 (UTC)

The mind can "bring a pot of water to boil", as it can do all those other things you listed. What it can't do is boil a pot of water alone, and as it happens, it can't do any of those other things alone either (one needs to be taught literacy skills to form sentences = mind not working alone). --Mark PEA (talk) 20:03, 13 March 2010 (UTC)

Again, sure it can. It's way of doing so is to instruct the body to take the pot to the stove and turn it on. --Stephan Schulz (talk) 16:52, 13 March 2010 (UTC)

Yes, we human are very clever. However, there's no reason to think that the ability to do complex maths or think in the abstract would also give the power of telekinesis. In a nutshell, just because you can imagine it (or you really, really want it), does not make it so. – ClockworkSoul 16:53, 13 March 2010 (UTC)

Right, we can boil water just fine, in a dozen different ways. The mind does this. It understands heat and fire and boiling points and everything. But it cannot impose its intentions on the world with sheer thought alone. In every case of it "doing" something, it uses a medium to translate computation into physical effect—be in hands, voice, movement of feet. It is not set up to broadcast radio waves or microwaves or lasers or large amounts of heat. Neither is your computer. The human brain computes. It does a great job of that. As I.I. Rabi said in a different context: "What more do you want, mermaids?" --Mr.98 (talk) 19:33, 13 March 2010 (UTC)

Studies show that the human brain consumes oxygen from the bloostream at a rate that is equivalent to 100 Watts. However, the activity actually conducted by the brain accounts for only about 10 Watts. The remaining energy is lost as electrical signals. These can be measured by electroencephalography (the EEG machine everyone has seen). Different wave patterns are generated by different types of brain activity. Some individuals have trained themselves to focus this brain activity in such a way that the wave pattern matches the vibrational frequency of the hydrogen-oxygen sigma bonds in water. This matching resonance frequency increases the rate of vibration, and of course this type of intramolecular vibration manifests itself as heat. The 90 Watts of power lost from the brain as electrical waves and focused on H-O bonds is more than enough to boil a liter of water. 72.94.164.21 (talk) 16:58, 13 March 2010 (UTC) (Since DVdm's WP:RD/N doesn't exist yet, I decided to post here instead.)

What if this signal can be amplified to electrify a heat source? Yes I realise this is no longer done on the mind ALONE, but with some help. --Kvasir (talk) 08:07, 17 March 2010 (UTC)

The whole human body only uses 100 watts of power. The brain consumes 20-40 watts, but there's no way to "account" for any of it; our brains can be as inefficient as they want to be for the computations they perform. You could warm water with a 30 watt lightbulb just fine from the waste heat. But brain waves are super-weak; that's why you have to attach electrodes to someone's head just to detect them.

If brain waves were the right frequency, and strong enough, to boil water, we'd be in trouble, because the brain is mostly water... It would be a neat ability, though, other than that. Paul Stansifer 17:21, 13 March 2010 (UTC)

Right. I don't see how the brain is going to boil water without boiling itself. A microwave would not work if it was immersed in water, presumably (in the sense that it would not be effective exclusively for a kettle of water kept at a distance). --Mr.98 (talk) 19:33, 13 March 2010 (UTC)

Side discussion moved to talk page – ClockworkSoul 18:08, 13 March 2010 (UTC)

...specifically, to here: Wikipedia_talk:Reference_desk#Nonsense_questions. StuRat (talk) 19:52, 13 March 2010 (UTC)

How about if we lower the pressure to where water boils right around body temp, put the person's skull in contact with the water, then have them concentrate really hard on some difficult problem ? Couldn't we then get their head to give off ever so slightly more heat, and therefore cause the water to boil ? (Of course, we'd probably need to provide a higher than normal percentage of oxygen in the air, to compensate for the lower pressure.) StuRat (talk) 20:06, 13 March 2010 (UTC)

The pressure would have to be about 6% of the atmospheric pressure. I think I would have a hard time thinking under those circumstances. Why can't we give the OP the honest answer and let him know that the whole thing is ludicrous? Dauto (talk) 21:19, 13 March 2010 (UTC)

Wikipedia has an article on a relevant topic so far unmentioned: Pyrokinesis which is a kind of Psychokinesis. Graeme Bartlett (talk) 22:48, 13 March 2010 (UTC)

I doubt there's any direct credible scientific proof on this, but brain waves may be shown to have effects external to the brain itself. For example a robot that places balls into a container within a random number of moves may be "affected" by human thought causing it to reduce its number of moves (but correlation with brain activity is not shown directly). ~AH1^(TCU) 23:18, 13 March 2010 (UTC)

Um, what? Citation needed. --Mr.98 (talk) 00:08, 14 March 2010 (UTC)

I'm sorry, what did that comment add to this discussion? You say that something might happen but you doubt there is any evidence for it. You don't even claim that anyone before you has claimed it does happen or that you have observed it to happen. You are just knowingly spouting nonsense for the sake of it... --Tango (talk) 05:13, 14 March 2010 (UTC)

Can we not assume that something is nonsense just for the sake of it? By the way, the specific example given was shown in Mystery Hunters. ~AH1^(TCU) 02:20, 15 March 2010 (UTC)

In other words, a silly, nonsensical TV show. That it sounds like you half-remembered. Great contribution, thanks. Clarified a lot. --Mr.98 (talk) 16:45, 15 March 2010 (UTC)

Radio waves

Resolved

Is there a difference between radio signals and radio waves? —Preceding unsigned comment added by Fire2010 (talk • contribs) 20:26, 13 March 2010 (UTC)

The signal is the message that is being transmitted via waves. Zain Ebrahim (talk) 20:39, 13 March 2010 (UTC)

I not sure I understand. Can "signal" and "wave" both be used when describing the transmissions and receiving of music or television channels? Are they essentially the same concept with different names or are they totally different from each other? —Preceding unsigned comment added by Fire2010 (talk • contribs) 20:45, 13 March 2010 (UTC)

Yes, both words can be used when talking about TV/radio. So the signal (which is the message) could be a TV show and your television receives the signal sent from the TV company in the form of waves. So the signal is transmitted as waves. Does that make sense? Zain Ebrahim (talk) 21:03, 13 March 2010 (UTC)

The signal is usually encoded either as modulations of the radio wave amplitude (AM broadcasting) or as modulations of the radio wave frequency (FM broadcasting). Dauto (talk) 21:13, 13 March 2010 (UTC)

To help understand the difference, consider the SETI astronomers, who scan the skies looking at radio waves generated by astronomical objects, hoping to find a radio signal (from an alien intelligence) among them. StuRat (talk) 21:11, 13 March 2010 (UTC)

I think (feel free to correct me if I'm wrong) that the difference would be that a radio signal would be a radio wave that carries information. Vimescarrot (talk) 21:51, 13 March 2010 (UTC)

Thanks everyone, I think I understand now. The "signal" is the message, and the "wave" is how it arrives. Thanks! —Preceding unsigned comment added by Fire2010 (talk • contribs)

acid reflux

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

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

See WT:RD#Medremoval. Zain Ebrahim (talk) 20:44, 13 March 2010 (UTC)

Feigning death drug

I just watched an episode of the TV series "The New Avengers" - a guy injects a substance to feign death, later wakes and says "a drug that suspends the heart and the respiration" - isn't that impossible (brain death?) or do such substances exist? Thanks for info., --AlexSuricata (talk) 23:24, 13 March 2010 (UTC)

Well, potassium chloride stops the heart and thus causes death by cardiac arrest, yes. I believe the mythical drug you're describing sort of freezes the body's operations, allowing them to resume hours later, and the subject only has a hangover, presumably. The same mythical drug was in The Dark Knight Returns graphic novel. No, no such drug exists; as you note, a stoppage of the heart and breathing does kill people. On a related note, the field of cryonics seeks to put people or other animals in suspended animation, but by means of chilling them. Comet Tuttle (talk) 00:37, 14 March 2010 (UTC)

(edit conflict) Yes, it's impossible. You would suffer massive brain damage due to lack of oxygen to the brain. That could be reduced by inducing hypothermia, but even that would be very unreliable. There are ways to significantly reduce the heart-rate and respiration, but not eliminate them entirely. Someone would appear dead at a glance, but not if someone actually made a significant effort to check (hold a mirror in front of their mouth for a minute, say). --Tango (talk) 00:38, 14 March 2010 (UTC)

The toxin in the blue-ringed octopus paralyzes and can make a person appear dead, especially when they stop breathing. However, if artificial respiration is used until the toxin clears their system, they can recover. So, while the heart continues to beat, the lack of any breathing could indeed make others assume the person is dead. StuRat (talk) 03:16, 14 March 2010 (UTC)

A similar drug like this was used in the play Romeo and Juliet. But I don't know if this mythical drug is modelled after any real substance. ~AH1^(TCU) 02:18, 15 March 2010 (UTC)

An induced coma might slow your breath and appear something like death, but not nearly enough to fool a doctor. APL (talk) 02:02, 16 March 2010 (UTC)

March 14

Is it possible to cause a prolonged temperature increase (eben a small one) in the skull just through mental activity?

Is it possible to increase the temperature of the skull, even by only a slight amount, just through assiduous mental activity? If so, what kind of mental activity is appropriate that I could do to show this effect? (Note: I'm the poster who asked about boiling water above) 80.187.97.42 (talk) 00:32, 14 March 2010 (UTC)

A metabolic PET scan can show increased glucose oxidation occurring in parts of the brain where mental activity is occurring, but actual temperature increases are too small and thermal conductivity of human tissue too poor to measure any differences overlying the scalp. (And yes, it was obvious it was the same questioner.) alteripse (talk) 05:14, 14 March 2010 (UTC)

Contrary to intuition and many claims in the popular literature, the increase in brain metabolism as a result of intense mental activity is actually pretty small, just a few percentage points. Our article Brain#Brain energy consumption gives a pointer to the scientific literature on this topic. A lot more heat is actually generated by the muscle-tensing that people tend to do when they are thinking very hard -- this can easily give rise to a misperception that it is the thinking itself that consumes energy. Looie496 (talk) 17:26, 14 March 2010 (UTC)

Certainly there is some change in the energy consumed by the brain when doing more calculations than in a resting state. That energy has to go someplace - and that someplace is heat. But the difference between the rest state and the working state is small and the energy consumed is small - so the temperature increase is undoubtedly there - but very, very tiny. SteveBaker (talk) 17:29, 14 March 2010 (UTC)

But, you have to define "resting state" - and since it is not clear what level of "rest" corresponds to "idle thinking", we can't really say with certainty that (for example) arithmetic is "more brain work" than staring at a blank wall. In other words, the biological version of the NOOP instruction might be just as energy-intensive as the biological version of the XOR. As an example, there are many digital computers which do this intentionally (to provide for extremely deterministic power consumption, for example). I see no reason to assume that the brain needs more energy when undergoing "heavy thinking" (unless somebody has a scientific source to the contrary). Nimur (talk) 17:15, 15 March 2010 (UTC)

Perhaps extreme high levels of mental activity could cause increased blood flow to the brain, thereby raising the temperature of the brain? But I'm not an expert on this. ~AH1^(TCU) 02:02, 15 March 2010 (UTC)

I'd expect increased blood flow would cool your brain down. I'm pretty sure your body uses it for coolant. This would probably be countered out by burning the extra oxygen and sugar the blood brings. So, even less of an effect. — DanielLC 04:09, 15 March 2010 (UTC)

The answer to your first question is a qualified yes, but it is not as straightforward as you may imagine.
Neuronal activity does increase local metabolism, consuming oxygen, and producing heat, which tends to heat the local tissue. However the body responds by increasing the blood supply to the region of the brain that is being used, and the effect of this usually overwhelms the direct metabolic effect. Paradoxically, the oxygenation level of the active areas of the brain increases, and the temperature (typically) falls a few tenths of a degree centigrade. However the temperature change shows considerable inter-subject variability depending upon for example, the physical activities the subject is engaged in, and their environment, since these affect the instantaneous blood and cranial temperatures. You can read more about the subject in the following articles, and the references they contain:

• Coupling between changes in human brain temperature and oxidative metabolism during prolonged visual stimulation, PNAS, 2000
• Theoretical model of temperature regulation in the brain during changes in functional activity, PNAS, 2006

These references will also give you an idea of the techniques used to measure the temperature in areas of the brain in vivo.
Typical mental activities that are used in such studies are visual simulation (fancy way, of saying show some moving pictures), or simple finger tapping, which engage the visual cortex and motor areas of the brain respectively. Abecedare (talk) 09:03, 15 March 2010 (UTC)

A silly question

I've noticed whenever I deliver rolled up papers that they are either rolled up clockwise or counterclockwise, depending upon the end of the paper I am looking at. On the other hand whenever I read a astronomy article in order to improve my brain I only seem to get more confused since the articles say that Galactic spirals only rotate in a clockwise direction. However, when you view the Galaxy from the other side, like looking at the other end of the rolled up papers, the Galaxy is spiraling counterclockwise instead of clockwise. Should I stop reading astronomy articles and just go with what I know? 71.100.11.118 (talk) 02:07, 14 March 2010 (UTC)

A spiral galaxy will look clockwise from one direction and anti-clockwise from the other, just like any other spiral. Can you give an example of one of the astronomy articles you have been reading that say otherwise? Perhaps you are misunderstanding them (either that, or you need to read better astronomy articles - we can help you there, too!). --Tango (talk) 03:25, 14 March 2010 (UTC)

The latest article (2002) I've read makes a comparison of the rotation of the central bulge and the rotation of the spiral arms as being in opposite directions. What is surprising and confusing to me is that I can find no characteristic of classification which is based on the 3-axis orientation of the Galaxies and in conjunction on clockwise or counterclockwise rotation. 71.100.11.118 (talk) 04:09, 14 March 2010 (UTC)

I can't comment on the galaxy described in that article, having not researched it, but that article doesn't say anything about galaxies being rolled up the same way from both sides... --Tango (talk) 05:09, 14 March 2010 (UTC)

The article says nothing to make clear that the opposite directions of rotation will be reversed when looking at the Galaxy from the other side. 71.100.11.118 (talk) 07:09, 14 March 2010 (UTC)

Why would the article make that clear when it is obvious anyway? --Tango (talk) 08:38, 14 March 2010 (UTC)

I think perhaps the OP is asking why we would choose to view it from one side, and not the other? What justification do we have for that? I don't know the answer, but this seems to be what they're after. Vimescarrot (talk) 09:58, 14 March 2010 (UTC)

We have no choice - galaxies are a little far away to go around behind them to get a photo. --Tango (talk) 10:30, 14 March 2010 (UTC)

There actually is a very good choice which would fix the problem. First we need a reference point and that point can be the Earth. Next we need a system which utilizes that reference and that system is already in existence and well known. That system is Spherical coordinate system. What we need when talking about any Galaxy or about some aspect of its orientation is to speak first in terms of Spherical coordinate system. I would think we could draw a line between the Earth and the Galaxy and let that line represent the coordinates of two perpendicular planes and then provide the coordinates of the axis of rotation in either the clockwise or the counterclockwise direction 'so long as it were named. Perhaps we could call the clockwise side the North side and the counterclockwise side the South side. In fact, maybe someone has already thought of this and we can adapt, refer to or use the system they have designed. 71.100.11.118 (talk) 12:08, 14 March 2010 (UTC)

The galactic coordinate system and supergalactic coordinate system are very similar to what you describe and could easily be used to define north and south sides of spiral galaxies (and, for all I know, maybe already are). --Tango (talk) 12:49, 14 March 2010 (UTC)

Very similar. Although the Earth's Geographic coordinate system is more dynamic in terms of looking at Galaxies than our Sun or the Milky Way using it as a reference point instead would allow it to be more directly or easily included in time dependent observation chart object data. Of course such a system can also be easily duplicated for any reference point. 71.100.11.118 (talk) 03:51, 15 March 2010 (UTC)

In fact it might do very well to establish such a system for every Galaxy and then use the spherical coordinates to identify the locations of all other heavenly bodies. With such information provided to a neural network model... but then I allow my imagination to go too far! 71.100.11.118 (talk) 10:38, 15 March 2010 (UTC)

Clockwise and anti-clockwise rotation as seen from Earth has been counted. See Galaxy Zoo#Progress. PrimeHunter (talk) 03:49, 14 March 2010 (UTC)

Brain acceleration?

I was staring at clock, and noticed that when I first look at it, it seems a second hand stays there for a while (more than a second), and only then it goes on at a normal pace. Same thing happens with digital clocks as well. Why does it happen? Does the brain accelerate itself in order to analyze the information given by clock, so it seems time slows down for a while? 195.238.106.80 (talk) 02:19, 14 March 2010 (UTC)

Interesting. I have never noticed this myself, but a bit of Googling shows that it is a known phenomenon, although the cause is not clearly understood. Here is a review from last year that discusses the effect, along with other temporal illusions. Looie496 (talk) 03:08, 14 March 2010 (UTC)

Just to add a bit of info, the review suggests that this is a consequence of the suppression of visual perception that occurs during saccadic eye movements -- when you move your eyes rapidly from one place to another, your visual system basically switches off during the movement, but your time perception is warped for a short time before and afterward so that you don't perceive any gap -- in effect you perceive the eye movement to occur instantaneously. Looie496 (talk) 03:14, 14 March 2010 (UTC)

It's an amazing thing that our brains can create a seemingly seamless perception of the world given that the information provided by the senses have so many gaps and delays and mismatches. Dauto (talk) 03:59, 14 March 2010 (UTC)

There is a really interesting article in this month's PopSci about this kind of stuff, entitled "How Time Flies". It is related to the brain's perception of time dilation under different circumstances and, while nothing is conclusive at this point, it elaborates on some pretty plausible theories. However, since it is the current issue, they won't have it posted on their web site for another couple weeks. —Akrabbim^talk 04:08, 14 March 2010 (UTC)

This article in New Scientist is good, and discusses the effect extensively: http://www.newscientist.com/article/mg20427311.300-timewarp-how-your-brain-creates-the-fourth-dimension.html --99.237.234.104 (talk) 04:57, 14 March 2010 (UTC)

I've experienced this too and have always been curious as to why it is. I've always just assumed that it's some sort of processing delay but never had a true understanding of why it happened. The theory regarding the movement of your eyes and the switching off of your visual system is pretty interesting.

That part is more than just a theoretical thing - some work I did in flight simulation actually relied upon it.

Back when computer graphics systems were hideously expensive it might cost you a million dollars to build a system that was less capable by far than a $100 graphics card of today. So making a large dome around the pilot and projecting computer graphics everywhere inside of it would have been prohibitively expensive. Instead, we built a system that measured the position of your head and eyes using a motion-sensitive helmet with an infrared camera that looked into your eyes and figured out where the 'blind spot' was on your retina - and from that, calculate exactly where your head and eyes were pointing. Then, we used a motorized projection system that mechanically moved a mirror and directed the graphics display to draw only in the region you were actually looking. That way we only had to draw detailed graphics in the area that actually mattered - and we filled in the 'background' with a very crude representation of sky and horizon brightnesses to keep your peripheral vision happy.

The problem with that was that the system took time to figure out how your gaze was moving and get the new image projected in the right place. So if you moved your eyes quickly, the machine couldn't keep up. Fortunately, this "Saccade" feature of the brain that "turns off" the video signal from your eyes when they are moving quickly, worked in our favor. Even though we were over a tenth of a second too late in getting the new image drawn, nobody could ever tell. In fact, you'd swear that the image you were seeing was continuously there as your eyes moved - when it was 100% certain that the computer hadn't drawn anything during all of that time.

It's one thing to talk about this stuff in the abstract - but when you see it with your own eyes (or at least don't see it!), it's downright creepy! You'd look to your left - then quickly glance over to your right and you'd be utterly convinced that you'd seen a continuous sweep of images in-between - and even be able to provide a reasonable description of what was that you'd seen there. But you could check the logs on the computer and know for sure that it never drew anything other than the image at the far left and then at the far right. Everything else was 'faked' by your brain in order to give you the illusion of continuous vision.

The brain is a deeply weird machine! SteveBaker (talk) 23:24, 14 March 2010 (UTC)

You may be interested in perception of time and time perception. ~AH1^(TCU) 01:59, 15 March 2010 (UTC)

Temperature of a high-gravity planet?

Say that there is a planet with a very strong gravitational pull. Would the gravity condense some liquids into solid form, meaning there is more ice on the surface? Or would it cause more heat due to friction? If the strength of the planet's gravitational pull was the only differing factor, would the resulting surface conditions be more likely to be hotter, colder, or about the same as an Earth-like planet? 97.104.210.67 (talk) 05:57, 14 March 2010 (UTC)

Gravity won't condense anything, pressure does that. Gravity is a factor in determining pressure, but it isn't the only one. Venus' surface pressure is about 90 times that of Earth despite having approximately the same surface gravity. --Tango (talk) 06:06, 14 March 2010 (UTC)

Excuse me for my mistake, I should have remembered that, but it is 1 AM my time. I'm just curious to know which result is more likely to occur. 97.104.210.67 (talk) 06:09, 14 March 2010 (UTC)

(1) regarding the "friction": Compression heating is only important for "young" planets. When a proto-planet forms and compresses (becomes more compact), the gravitational force performs thermodynamic work, and therefore heats up and melts the proto-planet material. Surface of young planets are therefore very hot, much hotter than their eventual surface temperature. Cooling rate depends on surface to volume ratio, presence of primordial atmosphere, and so on. But some time (10⁶ - 10⁹ years, AFAIR) after the accretion and the compression stops the surface does cool down, and eventually approaches its steady-state temperature. The core remains hot, though. Steady-state surface temperature of planets depends most of all on the balance between the heat influx from the star and the radiative heat loss into space. Slow release of trapped heat from the core and additional heating of the core by radioactive decay contribute less to the surface temperature. Tidal heating by other gravitating bodies is much weaker yet. So in the very young planets "friction" if more important while in the older ones the "friction" (compressional heating) is no longer very important as far as the surface temperature is concerned. (2) regarding the gravity & atmospheric pressure effect. On a planet without an atmosphere, surface pressure is zero regardless of the gravity strength. To have a nonzero pressure you need a nonzero quantity of material to exert that pressure from above. For example, Earth has 10 tons of atmosphere over every square meter of its surface at sea level, thus the atmospheric pressure equals the force exerted by the weight of 10 tons per square meter. As you climb the Everest, gravity pull changes negligibly but atmospheric pressure drops a great deal. It is therefore incorrect to say that gravity will condense something on the surface. You need a atmosphere to do that. However, even though 1 bar of pressure feels like a lot, it is not nearly enough to change the melting point of most solids by any significant amount. Typical slopes of melting curves of metals are in the ballpark of 1 degree Kelvin per kilobar IIRC. For water ice, it is approximately minus 10 degrees Kelvin per kilobar; that is, if atmospheric pressure on Earth was 100 times stronger, water freezing point would have been 272 K and not 273 K. --Dr Dima (talk) 08:32, 14 March 2010 (UTC)

Our article Triple point provides a pretty good overview of the story on the relationship between pressure, temperature, and phase. Looie496 (talk) 17:17, 14 March 2010 (UTC)

So I guess the answer is that there wouldn't be much difference? Okay! Thanks for answering my question. :) 97.104.210.67 (talk) 18:18, 14 March 2010 (UTC)

Is Chrysler 300 equiped with brake override system?

model: 2.7L V6

year of produce: 2006 Zhoudp (talk) 06:14, 14 March 2010 (UTC)

I should clarify that you mean an antilock brake override, so as to avoid any advice on draining out all the brake fluid... :-) StuRat (talk) 13:50, 14 March 2010 (UTC)

This may vary by model year. However, in my searching I find no references to any such switch, so I would tend to say "no". Perhaps someone with that car model can verify this (or you could always call a dealership). StuRat (talk) 14:01, 14 March 2010 (UTC)

Marine Creatures

what is the best topic for my report regarding Marine Creatures? —Preceding unsigned comment added by Gerlie gedoria (talk • contribs) 08:05, 14 March 2010 (UTC)

Cephalopod intelligence is very interesting, in my opinion, and a sufficiently obscure topic to make it a good report. --Tango (talk) 08:12, 14 March 2010 (UTC)

Diatoms are created too and they have interesting shapes! Graeme Bartlett (talk) 08:32, 14 March 2010 (UTC)

I added to the weird title to make it useful. StuRat (talk) 13:47, 14 March 2010 (UTC)

I completed tidying the title. Cuddlyable3 (talk) 11:51, 15 March 2010 (UTC)

I always retain the original title, in case it's used as a search term to find the Q.

It's much easier to write a good report if you focus on a question rather than a topic, and you will probably write a better report if you focus on a question that interests you rather than a question that somebody else suggests to you. Looie496 (talk) 18:21, 14 March 2010 (UTC)

What about the intelligence of cetaceans, shark finning, ocean acidification, hydrothermal vents, the invasion of jellyfish, or turritopsis nutricula? ~AH1^(TCU) 01:57, 15 March 2010 (UTC)

File:Vampyroteuthis2.jpg

Glow-in-the-dark vampire squid! Nimur (talk) 17:37, 15 March 2010 (UTC)

Bioluminescence is a fascinating topic; it is found in many different types of marine invertebrates and glow-in-the-dark fish. Whether you're in third grade (and just want some nice photographs and a few sound-bite science facts); a high-schooler in need of in-depth ecological analysis of the hadal zone and a food-chain based on minimal/zero solar energy; or if you're a Ph.D.-level biologist who wants to discuss photophoric production of bioluminescent protein compounds, this topic will make an excellent topic for your marine creatures report. Nimur (talk) 17:37, 15 March 2010 (UTC)

Methane

The hydrogen atoms of methane are distributed evenly over a sphere. How can you show that this angle is 108 degrees? (I don't know if I should ask this on the math ref desk). 173.179.59.66 (talk) 09:23, 14 March 2010 (UTC)

Actually, it is 109 degrees. More precisely, it is arccos(-1/3). The hydrogen atoms are at the vertices of a tetrahedron, so that is the shape you need to study. This derivation is pretty good. --Tango (talk) 09:45, 14 March 2010 (UTC)

This is the N=4 case of the Thomson problem, for which no general solution is known.83.134.168.71 (talk) 14:03, 14 March 2010 (UTC)

Cool, thanks. 173.179.59.66 (talk) 01:35, 15 March 2010 (UTC)

How can i analyse......subject

my name is sumanthdarisi...i am engineering first year student of ECE. I hav aolt of passtion in creating something new eletrical or electronic goods, but i dont know the internal working procedure of the related things of my ideas . for example : I hav an idea to get mobile numbers of others without asking them... jus by passing few invisible rays on to their mobiles...which will received by their mobile and then send back to me.....so i need to know how should i proceed my experiment......plz help me to move forward!! —Preceding unsigned comment added by Sumanthdarisi (talk • contribs) 10:40, 14 March 2010 (UTC)

I'm afraid that already exists, in various forms (eg. the iPhone "Bump" app). That's the hardest bit of inventing things - finding something which hasn't already been invented! --Tango (talk) 10:47, 14 March 2010 (UTC)

Asperger's Adam had it so good... :) 82.113.121.96 (talk) 12:13, 14 March 2010 (UTC)

Instead of using the cell phone itself for this, how about a separate rechargeable battery powered device ? Each could send and accept info like you'd find on a business card. They would need to have a very short range (only a few feet), and probably should only record contact info if you stay near the source for a minute, to eliminate contact info from everyone you walk by. At the end of the day you'd have a list of contacts, listed by time of day they were received. Many would be contacts you don't want, of people you just happened to stand by, so you'd need to go through and eliminate those. For those you keep, there could be a USB port to upload that info to your computer, cell phone, etc. However, note that there would be a privacy issue, in that not everyone would be willing to share their contact info with everyone else. StuRat (talk) 13:42, 14 March 2010 (UTC)

The electronics business isn't actually very short on ideas - the difficulty is in moving them from ideas into actual implementations - and then marketing those things to the public. To turn your idea from a thought to a thing requires quite a lot of deep knowledge. You'd need a clear understanding of stuff like bluetooth protocols or RFID scanners. It's possible that you could implement something like this on an existing cellphone (either iPhone or Android) - but that would require some fairly sophisticated programming skills.

I used to work for Philips research labs in the UK and we were told never to accept or acknowledge ideas like this from the general public - and in my present job as a computer games programmer - I have to live under the same rules. The reason for that is that these companies are not short of ideas for new products - so there is little benefit in taking an idea from outside of the company - and the risk of doing so might be that someone in the company might already be working on a similar idea and we wouldn't want to be sued for 'stealing someones idea'. Sadly, this means that unless you can do the work of going from idea all the way to a demonstrable product by yourself, the best way to get your ideas into products is to go and work for a company that does that kind of thing. There are companies who employ people only to have good ideas - but getting one of those jobs right out of college is almost impossible...you have to start in either the artistic, engineering or marketing fields and become known for having bright ideas.

In either case, you're going to have to study hard in the field you're interested in - do electronics - learn programming skills - get at least a basic understanding of math and physics. As you start to become proficient in those areas, start making things with off-the-shelf parts...I'd recommend using something like the Arduino system which consists of small, cheap computer boards (they cost about $26 online) and a relatively easy to use programming system. There are tons of online resources for how to add electronics to the Arduino - and using one of these, you could probably make some working prototypes of a short range identification exchanger...or whatever other idea you might have.

As for the idea itself, it does indeed already exist in the iPhone "bump", it's also done to some degree in the Nintendo DS where complete strangers who are in radio range can even share games and such like. The Microsoft Zune MP3 player allows music to be shared in a similar way. So this idea is already "out there" and I doubt you'd get credit for originality there.

SteveBaker (talk) 15:11, 14 March 2010 (UTC)

Just out of curiosity, WHY do you want to do this? (More specifically, why would I want you to get my phone number without my knowledge?)24.150.18.30 (talk) 16:48, 14 March 2010 (UTC)

The type of question, where the questioner has an idea for an electrical/electronic device but knows nothing of electricity/electronics, is in the tradition of such famous inventors as Samuel Morse, an idea man who relied on the work of Joseph Henry and Alfred Vail to make a telegraph that worked more than a few yards. Similarly Alexander Graham Bell knew very little of electricity and relied on Thomas A. Watson and others to make a working telephone. Being convinced a device can be made to work and finding funding for development are the important contributions an "idea man" can bring to the art of inventing and developing a device, especially if "conventional wisdom" says it won't work or is impractical based on earlier unsuccessful experiments going at it in some different way. Often the need for a device has not been seen before the inventor presents it (like the telegraph, the telephone, or the Xerox). Historically, people have also said "It has already been invented," pointing at some device which is not at all the thing proposed. In recent years, some billionaire heads of software companies, often described as software experts, have been far from their companies' best programmers, and would be lost trying to maintain or improve the present software. Edison (talk) 18:03, 14 March 2010 (UTC)

There is a world of difference though. Attaining a knowledge of simple electricity from other people in the field is childs play compared to something like (for example) understanding the software and hardware of a cellphone in order to change how it's bluetooth interface operates. You can easily summarize all you need to know to build a practical telegraph or telephone on one sheet of paper. It takes years of study to learn to program and to understand the way modern data transmission protocols work. A lot of what those early inventors did was trial and error - but that's absolutely not going to work with the kinds of sophisticated electronic and software systems that our OP is considering. It's not for no reason that largely self-educated individuals so rarely make ground-breaking technological advances anymore - and even well-educated people need the backing of teams of engineers to bring their ideas to fruition. SteveBaker (talk) 13:24, 15 March 2010 (UTC)

I'm not really sure if I understand the OP's suggestion but apps for phones using Bluetooth to automatically exchange details have I'm pretty sure existed for a very long time, probably not long after Bluetooth was first available on phones or PDAs. E.g. [12] and exchanging business cards is part of the OBject EXchange protocol. (These weren't necessarily automatic, but I strongly suspect fairly automatic options existed although likely to be turned off by default for obvious reasons, and BTW by automatic I mean does it without you asking, clearly you don't have to enter details which are already stored in the device, in other words the actual exchange would always be fairly automatic, it's just whether you automatically send the details, and automatically accept the details that I presume we're talking about here.) These do of course have compatibility issues (although OBEX is a defacto standard) and more importantly, people don't generally want to exchange details with random people (even if you don't mind receiving, few people want to give out their details to any random person), so they're of most interest at conferences and the like.

Of course Bluedating has also existing for a long time, [13] [14], these I believe work in various ways but would usually include some sort of profile (at a minimum something like man seeking woman etc). Once they meet a match within range, they may exchange additional details of that person, they may start a Bluetooth chatting app so the people can talk etc, I even heard of one that wouldn't tell you anything other then a compatible person was in range (can't remember if it was Bluetooth or even a phone or a seperate device, may have been in Japan), well obviously it must still internally exchange some details so they know your compatible which you can hack, but the idea is you're supposed to find the person yourself, I believe it would beep louder as you got closer. While these have tended to concentrate on dating, since that's the most likely case when people are going to want to exchange details with random people, I presume many allow those simply looking for friends.

Of course more generally there are apps which allow you to chat with people in range (and repeating what has already been said, exchange details with people in range). Indeed concern over privacy given all these possibilities was one of the early worries about Bluetooth (along with security) and there are the more dubious devices which allow you to monitor all devices in range and look out for anything including access things and do things you may not have been intended.

Of course while not working on a phone to phone communication level, missed calling someone has been a fairly standard way of giving someone your mobile number in many parts of Asia (also used for other things of course, as our article partially mentions) since long before Bluetooth, although still requires one party to get the number some how (not that it's that uncommon one party may have it but the other party won't, e.g. if someone sends it in an SMS) although neither of these (SMS or missed calls) are generally completely automatic. Well you could easily make a phone which saved all missed call numbers that aren't already present to the address book but still won't have details on who the person is. Evidentally you can send/receive vCards via SMS on some phones [15] [16] so it can be fairly automatic with SMS (although probably most either just type the number or add it with the phone but not as a vCard and most phones generally recognises numbers in SMSes).

Nil Einne (talk) 21:05, 14 March 2010 (UTC)

barbs

i was prescribed a barbiturate and Tylenol mix for migraines is that common? its Butalbital. will only Butalbital work or do all barbiturates work? —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 11:08, 14 March 2010 (UTC)

I'm afraid we can't give medical advice. If you want to check that your doctor has prescribed the right drugs you need to get a 2nd opinion from another doctor, not random people on the internet. --Tango (talk) 11:09, 14 March 2010 (UTC)

I'm not convinced this is medical advice. The OP isn't asking about the actual prescription of drugs but rather whether the one he/she was given is a common mixture, and whether or not that's the only barbiturate which is prescribed for migranes. Seems like a request for common information related to his experience rather than direct medical advice. What harm could come from answering the aforementioned questions? Regards, --—Cyclonenim | Chat  15:28, 14 March 2010 (UTC)

If I knew the answer, I'd give it; this is basically saying "my doctor said that I should do this, so I'm going to do it, but I'm curious how many other people are supposed to do it". Nyttend (talk) 15:45, 14 March 2010 (UTC)

In my opinion, any time a question refers to a medical situation and an answer has a potential to lead to a change in behavior, it should be considered a request for medical advice. Looie496 (talk) 17:11, 14 March 2010 (UTC)

I don't think you've thought this through. This would mean that we couldn't tell people that cigarettes cause cancer, for fear that they would change their behavior (stop smoking) as a result. What's wrong with Kainaw's criterion? Comet Tuttle (talk) 17:37, 14 March 2010 (UTC)

This book [17] and that [18] say you can buy it as a comination of substances in one medicament. And that one [19] says it is common in the US for migranes.--Stone (talk) 17:16, 14 March 2010 (UTC)

I think both Tango and Cyclonenim are right on this but I think also, that questioner would benefit from a bit of background, so as to be clearer of what they should be asking their own doctor for by way of clarification. For it is their own prescribing doctor that should answer queries about the medication and treatment. So I've added this below, which I think avoids advice.
Q. “Is it common” . Answer: A doctor may say to his patient that he is prescribing it 'off label.' This means that there is no good medical trial evidence (yet?) that it works for migraine. Therefore, the doctor has to take responsibility for using his own judgement of the risk verses the benefits to his patient. Doctors hate proscribing 'off label', so yes, from that fact alone, one can conclude that this mix is not commonly prescribed for migraines.
Q.”do all barbiturates work” Answer: The addition of a barbiturate (of any type) does not increase the analgesic effect in anyway. So 'work' is the wrong word. It is just there as a sedative to give some relief from the anxiety and distress resulting from suffering 'this type' of intense pain.
If the questioner also registers their email address with Medscape and then search for “Fioricet Oral.” The whole of the patient information leaflet stuff (which should have been included with the medication) and more besides, is there. Including what to talk to the doctor about.--Aspro (talk) 17:18, 14 March 2010 (UTC)

iv read the barbs also have analgesic effect thou. otherwise they wouldent use them for migrans cause u can die eeasy —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 19:23, 14 March 2010 (UTC)

I would add that I've never known barbiturates to be used in the treatment of migraines. More common treatments are β-blockers and Calcium antagonists. Regards, --—Cyclonenim | Chat  20:38, 14 March 2010 (UTC)

Beta blockers are usually given as prophylactics, however I believe 5-HT_1D receptor agonists are the most common treatment (triptans). --Mark PEA (talk) 23:11, 14 March 2010 (UTC)

As it happens, I've just been reading an essay by Avram Davidson in which he mentions that he was prescribed, for migraines, pills containing phenobarbital, caffeine, and ergot. This was probably at at least 50 years ago, but it shows, at least, that barbiturates have been used in the treatment of migraine. Deor (talk) 01:35, 15 March 2010 (UTC)

Whilst true, I suspect that ergot would have been the primary ingredient in that concoction as it's a vasoconstrictor and therefore useful for treating headaches, as long as you have the correct dosage. I imagine the phenobarbital was there to calm the patient rather than treat the actual complaint. Regards, --—Cyclonenim | Chat  12:32, 15 March 2010 (UTC)

Moments in space

Hi ppl. I am obsessed with the following...

1)Does centre of mass exist in outer space? 2)In space, is there moment of a force? If so, what is the pivot in a rigid uniform bar? And Lastly, 3) What exactly is the pivot anyway when it comes to taking moments. I mean, I am kindy confused about the pivot thingy as to how every point manages to turn around it while others remain in place.

I will be glad to knw the answers. Thanks

Blueberry —Preceding unsigned comment added by 122.99.98.17 (talk) 16:54, 14 March 2010 (UTC)

For your first question, see barycenter, binary system and Lagrange point. ~AH1^(TCU) 01:43, 15 March 2010 (UTC)

Let me explain why the center of mass still exists in space, and, in fact, is the same center of mass as on Earth. (I will assume that the object has a uniform density for this discussion.) The part that's confusing you is probably that you can balance an object on it's center of mass here on Earth, but not in space. But there is another way to measure the center of mass in space. If you push an object anywhere other than at that point, it will go into a spin. If you push it right at the center of mass, it should move, but not rotate. StuRat (talk) 02:41, 15 March 2010 (UTC)

A simple Buffer Question

Hi WikiRef-ers.

Hypothetical question for you...

Lets say you had a buffer solution of carbonic acid (H₂CO₃).

In this solution, the ratio of HCO3- to H2CO3 is 20:1. The [HCO₃^-] is 25 meq/L. [H₂CO₃] is about 1.2. The pH is 7.4.

Now, lets say you left the room to get some lunch, and a mischeivious co-worker sneaks in and adds a certain amount of H2CO3 to your buffer. You now know that the concentration in your solution of H2CO3 is about 1.5.

With that information, can you calculate what the pH AND the HCO3- is in the new solution?

Thanks!

--Cacofonie (talk) 18:52, 14 March 2010 (UTC)

Like most homework questions this easy. Lets look if there is the Henderson–Hasselbalch equation and after you put in all the data you get !ops! I was not allowed to answer homework questions. --Stone (talk) 19:34, 14 March 2010 (UTC)

That won't quite cut it in this case, because you don't know what the new concentration of HCO3- is (adding the carbonic acid shifts the equilibrium). You need to do an ICE table, where 1.5 is the final concentration of H2CO3, and you don't know the initial concentration. Buddy431 (talk) 19:46, 14 March 2010 (UTC)

Never mind: in this case, the equilibrium shifts so little that you can approximate it with the HH equation. Incidentally, the concentration of HCO3- is still 25, the change being several orders of magnitude smaller. Buddy431 (talk) 20:01, 14 March 2010 (UTC)

Actually, its not a homework question! I`m just trying to figure out arterial blood gases. It`s said that in Acute Respiratory Acidosis (i.e. an increase in H2CO3), for every 10 mmHg increase in the PCO2, your Bicarb increases by 1 meq. But, I`m not sure how that fits into this HH business if the quantity of bicarb produced is so minimal.

blagh --23:37, 14 March 2010 (UTC) —Preceding unsigned comment added by Cacofonie (talk • contribs)

no longer on speaking terms

Does Wikipedia have an article on the phenomena of people who are not on speaking terms? Such people are said to "not talk to one another." It is a human expression (or in-expression). It occurs between relatives, in families. It occurs between people who were once friends. It takes place between people who live in the same neighborhood, and ostensibly have to walk past one another. Is anything known about this human phenomenon? Has it been studied scientifically, methodically? Do we have an article or a subsection, on people who, due to some event or an interaction that has transpired — are no longer on "speaking terms?" Thank you in advance for any answers. If this needs to be moved to another page — fine. But I am asking mostly about the peculiar psychological condition. By the way, one interesting thing I have heard is that sometimes a point in time is reached at which the involved people no longer even remember what precipitated the situation! Bus stop (talk) 19:16, 14 March 2010 (UTC)

It seems that it's a part of social alienation and social rejection, especially the latter. There may be links more from those articles. -- Flyguy649 ^talk 19:42, 14 March 2010 (UTC)

It seems more like mutual deprivation: each one has made a calculation that there is a net gain in depriving the other of the mutual relationship of simply speaking. But that is just my own hypothesizing. Bus stop (talk) 19:55, 14 March 2010 (UTC)

Both parties appear to be using a tit for tat strategy of not giving each other value in the form of social interaction (mutual defection in Prisoner's dilemma), and are now in a "death spiral" until one of them yields. --Mark PEA (talk) 20:12, 14 March 2010 (UTC)

I don't think this is an example of social alienation, because this rarely occurs in families and usually happens to people who are not befriended by the "alienators". Relavent articles and topics may include mamihlapinatapei, zero-sum game, and wikt:estrangement. ~AH1^(TCU) 01:37, 15 March 2010 (UTC)

Our article about the strange British expression "Sending someone to Coventry" makes interesting reading too. SteveBaker (talk) 12:56, 15 March 2010 (UTC)

Drainage Systems in New York State

I have a question. What caused the development of different drainage systems in New York State? I think the answer is water erosion, but I am not sure. Could somebody help me with this? Thanks.--Lamb99 (talk) 22:05, 14 March 2010 (UTC)

DO you mean waste water drainage systems or watersheds? --Jayron32 00:57, 15 March 2010 (UTC)

Assuming that Lamb99 is referring to watersheds, I'd say that mountain formation (see also the article Orogeny) was the most important factor, with glacial erosion being another major factor. Deor (talk) 01:26, 15 March 2010 (UTC)

I mean any kind of drainage systems. This would be both waste water drainage systems and watersheds. Please give answers for both, and more if possible.--Lamb99 (talk) 21:57, 15 March 2010 (UTC)

Fission Reactors

I've been reading the articles on fission reactors. I have a good grasp of how and why nuclear fission happens. I can understand how the neutron poisons and neutron moderators slow down and speed up the fission process. What I don't understand is where the process starts. Do they have some fissile material at critical mass and then they slow down the chain reaction? Do they have some fissile material and bombard it with neutrons to get the reaction going? I don't understand where the original fission reaction starts. Anything you can say to help? •• Fly by Night (talk) 22:07, 14 March 2010 (UTC)

The atoms of the uranium or plutonium (or whatever) are spontaneously fissioning all the time at some low level - that's what radioactive materials do. Their atoms are fundamentally unstable. But the neutrons produced mostly fly out of the material as radiation. Only very rarely do those neutrons hit other atoms and causing them to fission in turn. If you increase the amount and compactness of the material, you increase that probability and eventually, at "critical mass", you get a self-sustaining reaction where there is enough material that the neutrons produced by one atom spontaneously fissioning are enough to cause (on average) more than one atom to fission as a result producing more neutrons and yet more fissioning events. At that point, you have a cascading, exponentially increasing chain reaction - an atom bomb. The trick in a nuclear reactor is to control the way those neutrons are absorbed or reflected back into the material to have enough neutrons captured to keep the reaction going at a useful level - but not so many that you get a runaway chain reaction. SteveBaker (talk) 22:31, 14 March 2010 (UTC)

Thanks, but I already know and understand all of that; just as my original question states: "I have a good grasp of how and why nuclear fission happens. I can understand how the neutron poisons and neutron moderators slow down and speed up the fission process." Let me repeat my question. Do they have some fissile material at critical mass and then they slow down the chain reaction? Do they have some fissile material and bombard it with neutrons to get the reaction going? I don't understand where the original fission reaction starts. Anything you can say to help? •• Fly by Night (talk) 22:38, 14 March 2010 (UTC)

As steve explained, the fission is happening spontaneously at a low level all the time. That's where it starts from. It starts from that low level spontaneous fission and grows from there. Dauto (talk) 23:26, 14 March 2010 (UTC)

Check out Spontaneous fission 82.132.139.87 (talk) 00:07, 15 March 2010 (UTC)

I think he might be inquiring about how the moderator and control rods are used to bring the pile to criticality. --Aspro (talk) 00:16, 15 March 2010 (UTC)

Grrr! Dauto and 82.132.139.87: I already know and understand that. But not just any old pile of radioactive material is used in a nuclear reactor. My question seems to be answered below: you start with some fissile material at (or very close to) critical mass, and the control rods keep the reaction manageable and useful. Thanks for your help, I do appreciate it. I think that you're aiming your well intended answers at the wrong level. But thanks again! •• Fly by Night (talk) 19:50, 15 March 2010 (UTC)

Let me take a stab at this, in my fumbling way:

So let's imagine we're hanging out with Fermi and the CP-1 crew underneath Stagg Field. We have a neutron detector next to our pile, which is already a critical mass, with our control rods fully inserted. We're getting some considerable blips from our uranium, just from the spontaneous fissions and maybe from a few secondary fissions from those, but it's basically the same as if we just had some uranium metal lying around (nothing particular to fissioning). We start to remove the control rods. Without something absorbing those neutrons from the spontaneous fissions, they are going to start creating all sorts of secondary and tertiary fissions and so on. Assuming we've done this in a safe way, with our control rods only partially out, there's going to be a cap on how many generations are likely to fission, so we aren't self-sustaining yet. But we're getting a lot more neutrons, a lot more fissions. We pull out the control rods more, the fissions start really taking off, and at some point we have them out enough that the reaction can be self-sustaining. Now this graph in this instance looks like this (note that at one point they change the scale to keep it from going off the paper).

Now, we don't have to create the critical mass first, with control rods already inserted, and then remove the control rods. That's just an easy and safe way to do it. You could create the critical mass incrementally and it would have the same effect. As you start getting enough material in there for the reactions to continue exponentially, they will start doubling quickly.

It's important to remember that the important part about reactors (and bombs) is that you have enough reacting material for an exponential chain reaction (each fission producing 2 or more other fissions). If you have something that is not producing much of a chain reaction, it will not be terribly impressive—a measurable but piddly collection of atoms fissioning. If you allow the reaction to start growing exponentially, it really becomes something impressive, and fast—the Wheat and chessboard problem, but with neutrons. --Mr.98 (talk) 00:35, 15 March 2010 (UTC)

Note that with a reactor, I think in most (all?) cases you can just let the reaction build up "slowly" from spontaneous fissions. With a bomb, you don't want to wait that long (you want an efficient chain reaction going off within 600 nanoseconds or so), so you use a neutron generator to just kick-start the reactions in a major way. --Mr.98 (talk) 00:43, 15 March 2010 (UTC)

So the answer to my question is that the fissile material is already at critical mass, but the control rods (acting as a neutrol poision) are stopping the fissile material from undergoing an uncontrollable chain reaction? About your question Mr. 98: I think that any pile of Uranium or fissile material will undergo nuclear decay; some of which will result in fission, and some won't. But within some finite time it will almost all decay away until it's something stable. •• Fly by Night (talk) 19:50, 15 March 2010 (UTC)

I don't think that's right. Such a reactor would be extremely dangerous, as a thermonuclear explosion would result if the control rods were withdrawn. I'd say it's best to think of a continuum between the radioactive decay that happens in naturally occuring uranium in rocks and that in nuclear reactors. That is, the rocks produce some nuclear energy, but at such a low level it's difficult to use. By refining and enriching the uranium, we can crank up the reaction rate until we get something usable for power generation but still far short of an uncontrollable chain reaction. The control rods are then used to change the rate, depending on demand, and also to shut down the reactor for maintenance, etc. StuRat (talk) 20:04, 15 March 2010 (UTC)

I'm sorry, but you are very wrong on many important points. No thermonuclear explosion (no nuclear explosion, much less a thermonuclear one). Yes, you can have the reactor at a critical mass with the control rods in (this is exactly what CP-1 was). Critical mass just means the reaction is self-sustaining. Yes, if you draw all of your control rods out of a reactor quickly, it can be dangerous. No, it will not explode like a nuclear bomb. Yes, enriching to different degrees can affect the reaction rate, but no, that is not really relevant to this question. (You can do it with unenriched, "natural" uranium if you have the right moderator. And in fact, this has been done with actual rocks!) Keep in mind that the main difference between a reactor and a bomb is that the reaction in a bomb is FAST—all of uranium fissioning in less than a second. In a reactor the reaction is dragged out, not nearly so rapid, and the energy release is done at a more manageable speed (so instead of blowing up the plant, it just heats some water). Making a reaction go off fast enough to be like a bomb is hard—that's why bombs have to have extremely enriched material, clever internal engineering, etc. --Mr.98 (talk) 21:57, 15 March 2010 (UTC)

Thermonuclear? How would fusion occur in a fission reactor? I did write above "at (or close to) critical mass". I forgot to write "or close to" in my last post. Okay, so if it's not at critical mass, then what would the neutron multiplication factor be? It must be pretty close to 1. That's why there are so many SCRAM safe guards. If you pulled all the control rods out and left them out then you'd be in some serious trouble! •• Fly by Night (talk) 20:47, 15 March 2010 (UTC)

Nuclear decay is fission. --Sean 20:51, 15 March 2010 (UTC)

Not quite. Fission is one mode of nuclear decay, but not all modes of nuclear decay are fission. See here. •• Fly by Night (talk) 21:47, 15 March 2010 (UTC)

StuRat is wrong. It can be at a critical mass. You can also do it by slowly assembling a critical mass cumulatively. Either way would work. By definition, in a non-critical reactor the multiplication factor is less than 2. In a critical reactor it is 2 or greater. And no, it won't blow something up just because it is critical! If the reaction is slow (as it is in reactors), you'll get a lot of neutrons, and a lot of heat. And in some designs, yes, if you let it keep getting hotter and hotter, you'll have a meltdown. So real-world reactor operation is about keeping enough heat for things to work well but monitoring things so that they don't get out of hand. (Meltdown isn't inevitable, depending on the design. A TRIGA for example is set up so that the increase in heat corresponds to a decrease in neutron efficiency, so it levels off naturally.) --Mr.98 (talk) 21:57, 15 March 2010 (UTC)

Some confusion appears to have crept in here. Is this clearer. Firstly it is not a 'critical fuel mass' one wants but a 'fuel loaded reactor pile' to go critical. The former condition can lower the value of the local real estate and much of the real estate most States downwind of the reactor. This is because the energy generation is so fast in a 'critical mass' that it is far beyond our technology to control it. However, the next bit of the answer depends on what type of reactor one is talking about, and so the question as asked is a bit difficult to answer. But I think it would be a fair generalisation to say that one employ the moderator(s) (and the addition of more fuel rods) to bring the reactor up to criticality over the long term time frame and use the control rods for short term fine control. In some reactors you can modify the liquid moderator to soak up some of the neutrons (with say boron) in a freshly refuel pile and then slowly adjust the mix as the fuel gets burnt. All the time using the control rods to control to adjust for short term fluctuations in output of the pile and electrical power demand placed upon the station. So no, you don't start off which a critical mass even though the pile may contain tons of fuel. That reminds me. The problem with the the Chernobyl reactor design was that this slow spongy characteristic was reversed a low power levels and so became very unstable at the hands of an ignoramus. The British Gas Cooled Reactors were extremely stable in comparison, (if a little inefficient). --Aspro (talk) 21:49, 15 March 2010 (UTC)

Just because something is a critical mass does not mean that we cannot control it. It is unfortunate that almost all of our physics in the critical mass and nuclear chain reaction articles are about bombs, but there are critical masses in reactors as well. The difference is that we control the speed of the reaction. Critical mass just means "the smallest amount of fissile material needed for a sustained nuclear chain reaction." It does not mean "out of control chain reaction". Assembling a critical mass very quickly is dangerous—bomb-like—but assembling one slowly is a source of neutrons, heat, etc., all the stuff we want from reactors. As nuclear reactor puts it: "Nuclear fission reactors produce heat through a controlled nuclear chain reaction in a critical mass of fissile material. All current nuclear power plants are critical fission reactors, which are the focus of this article. The output of fission reactors is controllable." --Mr.98 (talk) 21:57, 15 March 2010 (UTC)

(e/c) Okay, fair enough. So to ask once again: "if it's not at critical mass, then what would the neutron multiplication factor be?" (or at least a good estimate) •• Fly by Night (talk) 22:03, 15 March 2010 (UTC)

It been year since I did any any of this and I was only interested in the hard mechanical bits and control systems, so I would rather some one else carried this on. However, k = 1 is what one wants to achieve at every power level. So the rods are withdrawn or inserted to increase or decrease the flux until the required electrical power is being put into the distribution grid and then the rods are adjusted to bring it back to k = 1. Further adjustments will need to be made over time as the 'poisons' that get generated and decay have a time lag different to the power output.--Aspro (talk) 22:25, 15 March 2010 (UTC)

Imagine the evolution of your chain reaction of your critical mass reactor that has its control rods fully inserted. In the beginning your k is going to be quite low. You withdraw your control rods. k increases, to something >1 (if it were just =1 at the beginning, you would not have any growth beyond your subcritical stage). (I imagine that exactly what you want k to be at this stage varies based on the size of the reactor, the level of enrichment, the heat changes it can tolerate, etc. If k goes too high too fast, you'll have a serious problem in any reactor that is not designed to go prompt critical. Some reactors, again, can do this safely, like a TRIGA, which are designed to pulse.) At some point you don't want it to keep going indefinitely (which increases heat), and so at your optimum level, you re-insert your control rods so that k=1 again. Self-sustaining, but not out of control. Critical—but delayed-critical, not prompt critical. --Mr.98 (talk) 22:37, 15 March 2010 (UTC)

And I suppose it would be useful to reiterate at this point, that at start up ALL the neutrons needed to create the next generation of neutrons are supplied by the normal spontaneous fission within the fuel. Most designs need enriched fuel so that there are more spontaneous fissions to act a seeds. This need is dependant on mainly the efficiency of the moderator but better moderators can run on natural strength uranium. That is not to say a reactor wont produce k = >0 on a natural uranium ratio (even the Cavendish uranium reactor managed that in England before the WWII), it is just that they would be uneconomic to run. Maybe all these articles need a bit of polishing.--Aspro (talk) 23:15, 15 March 2010 (UTC)

is it possible to detect, at a distance the power of the mind?

I know you can detect mental activity with electrodes placed directly on the skull. My question is: is it possible to detect mental activity from a distance (ie not with electrodes touching the skull). I don't mean like with an infrared heat scanner, rather I mean actual thinking, so that you can detect, at a distance, whether someone is engaged in a certain intellectual activity versus just spacing out. Thank you. 82.113.121.89 (talk) 22:37, 14 March 2010 (UTC)

pet scan might interest you. Dauto (talk) 22:53, 14 March 2010 (UTC)

Neuroimaging might interest you as well. Dauto (talk) 22:57, 14 March 2010 (UTC)

Of course we can. We are not always right, but we often can understand what is going through another person's mind. There are no instruments that do that. alteripse (talk) 00:43, 15 March 2010 (UTC)

On the Reference desk, we can often detect mental activity, as well as spacing out, in our contributors, by means of keyboards plus the internet. But more concretely: neuroimaging can do the sort of thing you are talking about, if the person's head is inside a big instrument. But if you mean, could we do something like that for somebody not wearing or inside a big measuring instrument, I don't think so. Now, the catch here is that you could imagine some sort of technology in the future that stretched the bounds of "a big instrument" to mean, "within a large area of space" or "inside a specially equipped room of a building" or something like that. But I don't think we have anything that sensitive yet. The signals coming out of people's brains are probably too feeble to be measured accurately (and without interference) without something right next to their head, but I don't know that for a fact. --Mr.98 (talk) 00:52, 15 March 2010 (UTC)

It's theoretically possible, but the voltages on the skin outside the skull are already very small, and the voltage gradients in the surrounding air are orders of magnitude smaller. There must also be electromagnetic radiation, but its magnitude is infinitesimal. So it would take an extremely clean recording environment and ultrasensitive recording equipment to have any chance. I'm not aware of anybody having ever attempted this. Looie496 (talk) 05:25, 15 March 2010 (UTC)

The best research I've seen recently on something somewhat related to this was the use of magnetic resonance imaging in coma patients. For a long time it's been assumed that coma patients have no conscious thought but when these patients are placed in an MRI scanner, and asked certain questions and told to respond in a certain way, we can use the results to indicate yes and no answers. So for example you could ask the patient to think of their favorite film if they wanted to say yes, which would stimulate one part of the brain, and ask them to imagine playing hockey if they wanted to say no, and that would activate a different part of the brain. The patient can then be asked yes/no answer questions and it indicates that at least some comatose patients still have conscious thought.

Okay maybe that wasn't so relevant, but I found it incredible when I first heard it. Regards, --—Cyclonenim | Chat  12:38, 15 March 2010 (UTC)

That supposedly comatose people can be imaged in this way is not the most interesting thing: the most interesting recent result is that using the same experimental procedure you can find the same results in dead fish. (Just Google "dead salmon MRI".) I am currently working on a way to "channel" the intelligence of a dead salmon, however so far I have not been able to reproduce the consciousness effect of the above paper. 82.113.121.99 (talk) 18:34, 15 March 2010 (UTC)

Worse still, it's a matter of focus. There is likely to be almost zero useful information that can be obtained from the sum of the tiny electrical perturbations caused by around 300 trillion synapses firing at the same time (Maybe: "Is this person dead or not?"). Even with electrodes on the scalp, we can only locate signals very approximately and we get only a very broad-brush picture of what major parts of the brain are producing the most activity. Brain scanners are able to get a more precise view of what's going on - but still not down to the level where thoughts could possibly be read. So the answer to this question is "No". SteveBaker (talk) 12:50, 15 March 2010 (UTC)

But a brain scanner (like an MRI) can tell you if significant mental activity is taking place. You can see activity in various lobes, compare it to the "background" rate, and do all sorts of neat things with that. You just have to have the person inside a gigantic MRI machine first. You can't wave a wand at someone on the street and do that. They are, in fact, looking at ways that MRI machines could be used as lie detectors and things like that. I'm not sure we know what the limits of what will be able to be "read" with things like MRI and whatever the next generation of that sort of imaging will be. But I don't see it working "at a distance" (e.g., without your head inside a giant magnet) any time soon, if ever. --Mr.98 (talk) 15:06, 15 March 2010 (UTC)

Yes - it's necessary (as a barest minimum) to have detectors spaced around the head in order to localize the signals you're picking up to a particular 3D coordinate. This imposes limits that would make it utterly impossible to have (for example) a hand-held gizmo that you could point at a person from 30 feet away and say "Hey! This guy is thinking about blowing up a plane - stop him before he gets past airport security!". Hence my comment (above) about "focus" - it's not enough to pick up some overall waveform representing the output of the entire brain - you've got to know whether the neurons were firing in the temporal lobe or some other place - even more detail than that is really needed - and in the limit, you might need to know which of the 300 trillion synapses is firing and when. Without some spatial resolution, there is no conceivable way to extract significant information from a simple one-dimensional waveform. There are also severe issues of range. Because the signal strength of the electromagnetic waves falls off as the square of the distance, you've got to be really close in order to pick up those signals...there are very real physical limits on how far you can be in order to do that. Worse still, brain signals are all over the waveband - these super-faint signals would be completely swamped by cellphone, radio and TV signals washing through everything. SteveBaker (talk) 16:36, 15 March 2010 (UTC)

The above person who said

egg sexer or egg sexing

where are our articles on these? I don't mean chick sexing I mean egg sexing. 82.113.121.89 (talk) 23:24, 14 March 2010 (UTC)

If you mean determining the gender of the unhatched bird, maybe candling ? I don't think you can actually determine the gender that way, but our article is just a stub. I suppose you could do an amniocentesis, but that would be expensive, why not just wait until it hatches ?

If you mean determining the gender of a human baby using a spinning egg, I don't know where the article on old wives tales like that would be. StuRat (talk) 02:30, 15 March 2010 (UTC)

March 15

"Survival of the fittest"

Can we correct a widespread misunderstanding? If I am right (and it should be checked by an expert, which I am not), the Victorian English in which Darwin wrote this phrase has a different meaning from the one most commonly understood in modern English. "Fit" meant appropriate, not necessarily strong and energetic! What was "fittest", then, was what made the best fit, what was most appropriate. I worry that widespread misunderstanding of "survival of the fittest" has wrongly legitimised competitive behaviour, winner-takes-all, and other unhealthy characteristics of modern western society. Can Wikipedia help to shift that misunderstanding, as we move to an ever-more-urgent need for global cooperation on an unprecedented scale?124.176.69.92 (talk) 01:06, 15 March 2010 (UTC)

I believe you are referring to Social Darwinism ("competitive behaviour, winner-takes-all, and other unhealthy characteristics of modern western society"), rather than to biological Darwinism. Intelligentsium 01:13, 15 March 2010 (UTC)

(edit conflict) Yes, I was going to refer you to Social Darwinism as well. You may also want to look at our article on the expression itself, Survival of the fittest, where you will find that Darwin was not the first to use the expression, having picked it up from Herbert Spencer. Deor (talk) 01:18, 15 March 2010 (UTC)

You are right that Darwin (via Spencer) did not mean "fittest" to mean "most strong" or "most vigorous" but rather to mean "most appropriate" or "most adapted." --Mr.98 (talk) 01:19, 15 March 2010 (UTC)

I.e, Darwin's use of "fit" is the sense of Adapted to the requirements of the case; appropriate, suitable. ... LME. Biology. Possessing or conferring the ability to survive and reproduce in a particular environment. LME.. This meaning of the word is older (LME = 1350-1469) than the meaning In a suitable state for strenuous physical activity; gen. in good health. colloq. E18 (E18 = 1700-1729). Source: SOED. Mitch Ames (talk) 01:30, 15 March 2010 (UTC)

Fit certainly doesn't mean the most energetic. Consider the sloth. StuRat (talk) 02:31, 15 March 2010 (UTC)

There are a number of reasons that explain why people assume "fittest" means strongest, but I seriously doubt that it has anything to do with changes in the word's semantic content between Darwin's time and now. FWIW, Dawkins has advocated (though I'm not sure how strongly) changing the phrase to "survival of the fit enough" since resources are not necessarily scarce enough that only a handful of individuals survive; even when it is the case that a just few of the least "fit" do not pass their genes on, the same method of selective pressures effecting diachronic genetic changes are still in effect. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 06:14, 15 March 2010 (UTC)

It's also worth saying that modern evolutionary thought does not hang on the things that Darwin said. If it were discovered that Darwin's writings have been completely misinterpreted, all that would mean would be that Darwin was wrong - not that modern evolutionary theory is wrong. Hence, if this is true, then it's at best an historical curiosity. This is something that those creationists and intelligent designists would do well to bear in mind as they crawl through Darwin's writings in an effort to discredit him. SteveBaker (talk) 12:36, 15 March 2010 (UTC)

It's true, but I think the poster's original point was about popularization of the theory, in which case appeals to the Great Genius of the Past holds a lot of sway, even if it doesn't in modern scientific circles. (Though even there, scientists do love their heroes.) --Mr.98 (talk) 15:12, 15 March 2010 (UTC)

Certainly "Survival of the organism that fits best into it's surroundings" is a better line than "Survival of the organism that can run fastest and pump the most iron". There are many cases where a less energetic organism can survive with less food or other resources than a stronger one and thereby out-evolve it. Animals who live in dark caves, for example, evolve to lose their eyes - this is clearly "less fit" in terms of "healthyness" (for want of a better word) than an organism with fully functioning eyes - but a much better "fit" into the dark environment of the cave. Darwin wins the prize for being one of the first people to realize that inheritance plus mutation produces speciation. But that doesn't mean that we have to hang onto his every word as "truth" - he was a clever guy - but he didn't know a lot of things that we now understand (how inheritance works for one!). There are many cases in science where we award "naming rights" for a theory to someone who didn't get it 100% right. That's OK. What we're memorializing is the initial insight - not the precise details. Whether Darwin intended a particular meaning of "fitness" rather than another is something that's really only of interest to historians. If it turned out that it was a typo and he had really intended to say "Survival of the tallest" it would make precisely zero difference to modern science. SteveBaker (talk) 16:24, 15 March 2010 (UTC)

Applications of Quantum Electrodynamics

Are there any? 76.67.72.109 (talk) 01:43, 15 March 2010 (UTC)

Quantum Electrodynamics is the best theory we have to explain how electrons interact with electromagnetic radiation and therefore is at the heart of our understanding of all things electric or electronic. The applications are too numerous to count. Dauto (talk) 03:11, 15 March 2010 (UTC)

It may be the most fundamental but do we need so much precision? Couldn't modern electronics work with only the Dirac equation? Most products would work with only Maxwell's equations. 76.67.74.102 (talk) 03:59, 15 March 2010 (UTC)

QED is the quantum version of the theory of electron and photon and as such it includes Dirac's equation. Transistors wouldn't work were not for the quantum nature of the world. Dauto (talk) 04:24, 15 March 2010 (UTC)

The way I interpret the OP's line of thought is as an inquiry into whether the advanced physical description, which is indeed more accurate and correct, is necessary to make applications like electronics work. This is a difficult question to answer. Briefly stated, most engineers who actually build and work with electronics, including semiconductors, never need quantum theory - let alone quantum electrodynamics. However, much of their work is made possible by engineering approximations to the more exact physics - and somebody had to invent those approximations in the first place. That person would probably have benefited from a thorough knowledge of the full physics. Now, it's worth wondering whether a trial-and-error engineering approach, without the theoretical guidance of advanced QED and other conceptual ideas, could have ever led to modern semiconductor technology - but that's idle speculation, because we did have advanced physics to describe things like doping quantum tunneling, band gap energy, and the photoelectric effect. The same can probably be said for MEMS, nano-scale physical chemistry, protein folding, and all the other places where a quantum electrodynamic effect is at play. The applications have been expedited by a great theoretical understanding of the processes; but, for many of these applied areas, the subject and techniques have been sufficiently refined and approximated so that technical work can be done without resorting to a full QED treatment. Nimur (talk) 06:34, 15 March 2010 (UTC)

interstitial defects in ice

Since the hydrogen bonding structure in ice makes such large open spaces, isn't there a lot of opportunity for interstitial particles to get trapped in an ice lattice? Maybe ions like Na+ or Cl-? Why are they expelled from the lattice when water freezes? John Riemann Soong (talk) 03:56, 15 March 2010 (UTC)

Are you sure they are ? Saltwater can be frozen, right ? StuRat (talk) 04:02, 15 March 2010 (UTC)

John Riemann Soong is right. When salty water freezes most of the salt gets left behind. The reason is that salt ions are electric charged and there would have to be charge separation in order to place those ions in the gaps. That's energetically disfavored. Dauto (talk) 04:13, 15 March 2010 (UTC)

Yes but couldn't they be somewhat stabilised by the lattice? I mean the counterion would be in the next gap (or even in the same gap). Or is it more energetically favourable to just kick out the salt? John Riemann Soong (talk) 05:17, 15 March 2010 (UTC)

I also observe that freezing point depression (which tends to be independent of chemical identity) behaviour doesn't dramatically change on whether the solute is charged or not (normalising for realised concentration)... so it would seem that if you dissolved ammonia for instance, it could nicely fit somewhere. John Riemann Soong (talk) 05:24, 15 March 2010 (UTC)

Freezing point depression is caused by the enthalpy differences due to water-solute bonding vs. solute-solute and water-water (ice-type) bonding. As noted, when the water does freeze, it is pretty much pure water (see Fractional freezing) leaving the solute behind. This is true regardless of whether the solute is ionic or molecular in nature. That's because of the way that intermolecular forces work in molecular substances like water. Electrostatic effects from any solute will disturb the crystal lattice of the ice, preventing crystalization. The effects are particular dramatic (and annoying) during recrystallization processes for organic molecules. I remember my time working in an organic synthesis lab, and being frustrated by the fact that it was nearly impossible to get my desired product to crystalize if there was any impurities in it; basically wherever there was two substances present you would always end up with a pale yellow oil rather than nice white crystals, even if the substance was 99% pure. The other 1% would prevent effective crystalization. Bonding in ionic and network covalent substances is very different in this regard; silicate minerals, for example, can show surpising variation due to the presence of trace amounts of interstitial ions in the matrix. But while such interstitial ions work in ionic solids, and in network covalent solids, they do not in molecular solids, due to the way that dipole-dipole and london dispersion forces work in holding such crystal structures together. --Jayron32 18:07, 15 March 2010 (UTC)

Have you read the Clathrate hydrate article? Graeme Bartlett (talk) 09:03, 15 March 2010 (UTC)

Ammonium chloride as a Korean condiment?

I just got some "fried kelp" from a Korean market in Oakland, which I thought I'd enjoy because I like kelp, but it's covered with these colorless crystals that taste really weird. I believe it's ammonium chloride because the only thing I can think of that tastes remotely similar is salty liquorice. Is ammonium chloride used as a condiment in Korean cuisine for things like kelp? If so, what is the Korean name for it? —Keenan Pepper 05:22, 15 March 2010 (UTC)

It could well be ammonium chloride. Is there a list of ingredients on the package that can confirm? If it's a Korean product it may have the corresponding list in Korean. --Kvasir (talk) 06:13, 15 March 2010 (UTC)

No, it's like a deli item made in the market, and there's no ingredients list in English or Korean. All it says is "Fried Kelp". —Keenan Pepper 06:17, 15 March 2010 (UTC)

Hmmm. All the recipes for "Korean fried kelp" that I can find call for sprinkling it with sugar, which of course comes in colorless crystals, so I'm a bit skeptical here. Looie496 (talk) 18:25, 15 March 2010 (UTC)

I think the only way that the OP will be able to satisfy their curiosity ( and now ours ) is to return to the emporium and ask. Should they decline for trade secret reasons, just ask if there Green Card and other documents are in order. Of course, on the other hand if he bought it in the Oaksterdam area of Oakland it might be something completely different. You said it tasted “really weird” Keenan Pepper, did you start feeling really weird as well?

Come to think of it, didn't Leonard Bernstein and Sondheim immortalize this sea vegetable dish in West Side Story ...

Korea, Korea, I just ate some kelp from Korea! And suddenly I found, some Sal Ammoniac around - my fryee ....
--Aspro (talk) 19:09, 15 March 2010 (UTC)

I was thinking of suggesting that for a while, but since you already have and this is the science desk the other alternative is to analyse the crystals in some way. You can go the boring traditional chemistry route of seeing how they interact with various compounds. Perhaps JRS can help here. Or you can use some sort of mass spectrometer. Of course if you don't have access to any of these it's going to cost bucket loads and even if you do the lab supervisor may not appreciate you using them to work out what the crystals in your Korean kelp are (particularly if you tell them you haven't even asked the seller). Thinking of a recent question if you leave these crystals at a crime scene perhaps someone will analyse them for you, but unfortunately you may not be able to tell us the answer for several years in that case. Nil Einne (talk) 21:09, 15 March 2010 (UTC)

Are they perhaps crystals of monosodium glutamate? They taste a bit like salty licorice and are popular in Asian cuisine. --Sean 20:59, 15 March 2010 (UTC)

I certainly hope MSG doesn't taste like salty licorice (salmiakki) or as Salmiyuck as described here. --Kvasir (talk) 05:01, 16 March 2010 (UTC)

Oddball coordinates/geolocation

So I'm looking at a few biology papers. These have geolocation information, but I can't make sense of it. My working hypothesis it's some sort of map-related quadrangle info, but the relevant map is not cited by name (and I just don't knowhow to interpret it anyway):

(1) Hillside above State Highway 79 just south of the bridge over Buffalo Creek NW1/4 sec. 28, T54N, R1W, Pike County, Missouri.

(2)[...] on the east side of an unnamed tributary of Sycamore Creek on the Daube Ranch, NW1/4, NW1/4, SW1/4 sec. 2, T4S, R4E, Johnson County, Southern Oklahoma, Ravia 71/2'quadrangle.

Anybody can help me? Circéus (talk) 11:49, 15 March 2010 (UTC)

These use coordinates from the "township and range" system, used mostly in the American Midwest. See Public Land Survey System#Mechanics for a description of how it works. The entire system is based on a unit of land called a Survey township, which is a square mile of land. The T and R numbers refer to a coordinate system that numbers the townships around a central point defined between two lines, the "principle meridian" (N-S) and the "base line" (E-W). T is the "township number" and R is the "range number". Therefore, NW1/4 sec. 28, T54N, R1W is the Survey Township (square mile) located in the northwest quarter of Sec. 28, 54 squares north of the BL and 1 square W of the PM. Its not as accurate as latitude and longitude would be, but its not really a system for identifying points, its more for dividing land for establishing property boundaries. Each survey township would also be subdivided into plats of individual lots. Public Land Survey System#Mechanics contains pictures that show all the bits I describe here. --Jayron32 12:46, 15 March 2010 (UTC)

Thank you a lot! That really helped! Circéus (talk) 13:20, 15 March 2010 (UTC)

Three things. First, it's the section that's a square mile; the standard township is a square 6 miles on a side, containing 36 sections. Second, a section was often divided into four square lots (1/2 mile on a side), quarter-sections. But these may be further subdivided into smaller squares: what I would expect the "NW1/4, NW1/4, SW1/4" part to mean is the northwest quarter of the northwest quarter of the southwest quarter of the section, thus identifying a specific square that's 1/8 of mile on a side. And third, to avoid any confusion, that word is "principal". --Anonymous, 16:53 UTC, March 15, 2010.

gsp

what primetime episode was it where gsp gave tour of his house and said he hated his family? —Preceding unsigned comment added by 67.246.254.35 (talk) 12:12, 15 March 2010 (UTC)

This is the Science reference desk. Perhaps your question should be on the Entertainment desk instead? SteveBaker (talk) 12:26, 15 March 2010 (UTC)

And you might also want to explain who "gsp" is. StuRat (talk) 16:15, 15 March 2010 (UTC)

ufc fighter —Preceding unsigned comment added by 67.246.254.35 (talk) 16:19, 15 March 2010 (UTC)

That would appear to be Georges St-Pierre. -- Coneslayer (talk) 17:12, 15 March 2010 (UTC)

Software for synchronising separately recorded sound to HD video

I recorded three great new bands in Brighton on my HD camcorder, but Radio Reverb had loads of professional microphones and direct lines to the instruments leading to a mixing/CD recording desk, which would presumably exceed even the Dolby 5.1 internal microphones on my camera (which seem to give studio quality sound) and I agreed with them to share the media in the hope of synchronising the audio (presumably to arrive ready mixed on a CD) to my video and then on to blu-ray disk. What software can I purchase, preferably at a reasonable price, to do thus? My computer is a modern dual Pentium dual core 2.4 ghz machine with a reasonable hard drive capacity, which I might upgrade to 2 terabytes. I am running windows XP and would prefer not to upgrade to Vista in case it breaks certain applications I have written in visual basic. My existing Sony software plays the HD video quite well, though the motion is smoother on a proper HD set and blu ray player, or (when down-converted for DVD) a standard DVD and wide-screen cathode ray set, which I do not want to get rid of due to better colour contrast than flat screen HD televisions. Would it be cheaper to get this done by audio-visual professionals instead? filming (great) bands (with their permission) is my hobby and they use their copies as a free promotional tool, I do it to get the footage. —Preceding unsigned comment added by 80.1.80.16 (talk) 13:29, 15 March 2010 (UTC)

Our computing reference desk might be a better place to ask this question. SteveBaker (talk) 16:08, 15 March 2010 (UTC)

Feeding stick insects

How to feed newborn Extatosoma specimens?

They need Rubus or Quercus of course, but how can I persuade them?--87.10.128.186 (talk) 15:40, 15 March 2010 (UTC)

Is this the correct link? And this and this? Bus stop (talk) 15:52, 15 March 2010 (UTC)

Where does one procure newborn Extatosomas? DRosenbach ^{(Talk | Contribs)} 16:31, 15 March 2010 (UTC)

@ Bus stop: Thanks, but those links do not answer my question.

@ DRosenbach: I obtained eggs from an adult female bought one year ago.

But how to convince newborn specimens to eat leaves? --87.16.125.218 (talk) 17:56, 15 March 2010 (UTC)

What the Extatosoma tiaratum article does not say is that they are nocturnal feeders. Providing they have the right food; hunger should do the rest (who do you think gets them to start feeding in the wild). Examine the leaves in the morning. --Aspro (talk) 19:21, 15 March 2010 (UTC)

@ Aspro: Thanks; the problem is that they didn't eat nothing. The "oldest" has two days but unfortunatelly the leaves are still intact. I also tryed giving them a suggestion letting them sniff torn leaves left at the bottom of the tank.--Mparu (talk) 21:08, 15 March 2010 (UTC)

the 80s

This has degenerated into an excuse for the OP to editorialize about how boring the lives of people older than he was must have been. Other than an exercise in making his generation feel superior to his elders, it serves no further purpose. The article section titled 1980s#Popular_Culture should adequately lead to answers to the original question. The rest of this discussion is not within the domain of the reference desks. --Jayron32 19:32, 15 March 2010 (UTC)

what did people do in free time back then they didnt have internet wasent it boring —Preceding unsigned comment added by 67.246.254.35 (talk) 16:20, 15 March 2010 (UTC)

Believe it or not, people can interact without the internet, and in fact did so. There were sporting events before espn.com, facebook did not invent the concept of friends, and music existed before itunes. Googlemeister (talk) 16:24, 15 March 2010 (UTC)

this is not related to freinds, its about fun. in the 90s i was bored outo my mind. —Preceding unsigned comment added by 67.246.254.35 (talk) 16:27, 15 March 2010 (UTC)

Per WP:WHAAOE, we have a section and several related sub-articles about popular culture and lifestyles in the 1980s. Film, television, music, sports, toys, art, education, and so on, all existed in the 1980s. Notably, in light of your comparison to "zoning out" on the internet during periods of great boredom, the 1980s saw the mainstream rise of cable television, including 24 hour programming (a new and exciting cultural transition!) Nimur (talk) 16:33, 15 March 2010 (UTC)

Nobody has mentioned video games! At Wikipedia! For shame. Comet Tuttle (talk) 16:57, 15 March 2010 (UTC)

yea i watched tv and played the lame video games in the 90s but i was still bored outta my mind —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 17:07, 15 March 2010 (UTC)

Maybe you should have played the good ones. BBSes were fun, too. -- Coneslayer (talk) 17:11, 15 March 2010 (UTC)

Skateboarding as a popular sport developed in the 80's. Before that (in the 70s), boards were plastic with steel wheels and you couldn't do much more than slalom through some cones or something else rather lame. Some kids got into other passing fads like breakdancing or trick BMX stuff. Of those, skateboarding is the only one that I've noticed still continues with the teenagers today - at least I always see a few kids in my class bring in their boards and they are always amazed when I reference some board trick while explaining some concept in class. They can't imagine that a 40-year-old fart actually knows something about their sport. -- kainaw™ 17:33, 15 March 2010 (UTC)

Just to clarify... I am answering what people outside of the California coast did. By the time skateboarding became nationally popular in the 80's, they had been doing tricks in places like Santa Monica for nearly 10 years. Don't want to get into a debate about local interests vs. national interests. Might as well argue about when that pathetic "Valley Girl" talk spread across the country (and I like still like totally hear students like using that talk and stuff). -- kainaw™ 17:38, 15 March 2010 (UTC)

There are people that spend a lot of time being bored in the present day, too. Nothing has really changed in that respect. --Tango (talk) 17:41, 15 March 2010 (UTC)

When I was a kid in the late 70's/early 80's I played video games at arcades, such as Space Invaders, Centipede, Pac Man, Galaga, and Tempest (my fav). You may say they are "lame", but that's only in comparison with the games we have now. Those games were exciting compared with what came before (pinball). The games you currently play will also seem lame to future generations ("Aw man, this isn't even 3D, how lame !"). StuRat (talk) 17:43, 15 March 2010 (UTC)

"You mean you have to use your hands? That's like a baby's toy!" Nimur (talk) 18:12, 15 March 2010 (UTC)

Before the very, very late 90's, life was unbearably boring. So much so that a recent Economist article on the state of television mentioned that you could pretty much put anything on TV and people would watch it, out of sheer boredom. Therefore, if none of the networks were running anything interesting, then they could all still get a lot of advertising money, since millions were still tuning in. The only problem with running totally boring content was if another network was running something marginally less boring. But the bar wasn't very high: people were bored out of their MINDS. Now, fast-foward to 2010. These days, the bar for television is very high. People will NOT put up with something totally boring, they'll just turn off the TV and go on the Internet and find something a ton more interesting for them. The bar for television is REALLY high, since people aren't forced to watch whatever's on out of sheer boredom. Actually, the setting of the sun on newspapers is the same: people used to read the daily paper at some point during the day out of SHEER BOREDOM. They would have literally nothing better to do than read a whole article on something they're not even remotely interested in, just because they've read all the articles already that they find interesting in the least. The problem was when people had more time, they would run out of EVERY article in the paper, people, get this, I am NOT making this up: people used to read the obituaries for their city. ALL OF THEM (the ones with small articles). Every day. That's how bored out of their mind they were. The problem was most excarbated, of course, on Saturday and Sunday, where if there were just a daily paper, they would be through with it by 1 PM. Then what do they do? So Newspapers made Sunday editions that were vastly larger, included comics for the bored kids, and so on. Basically, to sum it up for you, when people weren't at work, at school, or some special event, they were bored out of their minds. They would do just about anything, up to and including sitting down with a game of Monopoly or Scrabble, just to get through the evening. That's a fact. 82.113.121.99 (talk) 17:55, 15 March 2010 (UTC)

The Pet Shop Boys wrote a song with the lines "we were never bored/because we were never being boring", which is supposed to be a quote from a 1920s socialite (sorry, searched Wikiquote but couldn't find the original). I can't remember being bored after I left home when I was 18: the world was too full of exciting things for me to be bored! --TammyMoet (talk) 19:22, 15 March 2010 (UTC)

why the hell was this archived this was interesting now its ruined someone un-archive it please —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 20:08, 15 March 2010 (UTC)

to jayron- im not trying point out how "boring the lives of people older than he was must have been" nor am i trying to "make my generation feel superior to his elders". i am a student of history and i like the 80s and wish i could have lived then. i am interested in how people passed the time back then. please do not mistake my motives. i like to hear about the past. the article you linked dosent help unfortunately. to whoever has been archiving it-please stop. i like hearing other peoples answers.

suicide

why is it thought that young people have a high rate of suicide? isint the average age like 68? —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 16:25, 15 March 2010 (UTC)

Perhaps successful suicide follows multiple attempts. DRosenbach ^{(Talk | Contribs)} 16:29, 15 March 2010 (UTC)

i dont think so, if u fail u will prob be crippled —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 16:37, 15 March 2010 (UTC)

That would depend on the method attempted. Googlemeister (talk) 16:41, 15 March 2010 (UTC)

Instead of speculating, why don't you check some statistics? Fast Stats from the Center for Disease Control is a good brief overview, and it links to a detailed statistical report, National Vital Statistics Report, as well as a Suicide Trends among Youths report, a Trends by Age Group report; and if you want more, here is a Google search query for more. Nimur (talk) 16:50, 15 March 2010 (UTC)

(ec) The original poster is asking why it's thought that young people have a high rate of suicide, despite the facts. He appears to be correct about the facts; this page from the WHO has links to PDF files showing the rates by gender, and by gender and age, for lots and lots of countries. Here are the rates (both genders) per 100,000 in the US:

Age 5-14:    0.7
Age 15-24:  10.0
Age 25-34:  12.4
Age 35-44:  14.9
Age 45-54:  16.4
Age 55-64:  13.8
Age 65-74:  12.5
Age 75+:    16.8

So, young people have a lower suicide rate than older people, at least in the US. Our article teenage suicide in the United States does not mention this (although it will shortly) and does not talk about the gap between the facts and perception. This is WP:OR but I will guess that youth suicide is thought of as more sad or tragic than adult suicide, and heavy media coverage might lead people to believe there is some sort of epidemic underway. Just a guess. Comet Tuttle (talk) 16:56, 15 March 2010 (UTC)

An important missing bit of data is evidence that suicide really is popularly thought that young people have a higher rate of suicide. DMacks (talk) 17:00, 15 March 2010 (UTC)

Googling teen suicide epidemic yields 62,000 hits, which is anecdotal, and some of the hits are on local "epidemics", but it supports the premise. Comet Tuttle (talk) 17:11, 15 March 2010 (UTC)

Exactly. So "why is it thought" (emphasis mine) might be directly answered from them. Gotta be careful to avoid a self-fulfilling mediafest though (OTOH, that may really be the reason?). Just because teens to it and it's reported as such, the stories I usually see focus on teen-suicide as a symptom/involved with other teen issues. Not "only teens do it" but "teens do it for teen reasons"--the bias is in choice of separate topics, not necessarily ignoring an included subset of the topic. None of which addresses why non-teen groups are not discussed as much, right back to the initial question:( DMacks (talk) 17:22, 15 March 2010 (UTC)

Come on people, the answer is obvious. The rates of young and old are similar, but suicide is a top cause of death among young people and way down in the list for 40-70 yr olds, even though the per capita rates are similar. alteripse (talk) 17:10, 15 March 2010 (UTC)

That's probably a factor, yes. Comet Tuttle (talk) 17:11, 15 March 2010 (UTC)

In addition, those statistics are I'm guessing successful suicides and don't include attempted suicides. Suicides may of course be a cry for help particularly among teens and may not be truly intended so succeed although in some cases, e.g. if Panadol or weedkiller is used, the person may still die even if they later regret it. While these may not seem as serious a problem, they are still a concern. In addition even if they are more serious about it (and ultimately it's a continuum anyway), teens are generally less experienced and have access to less resources and are more likely to have some dependence on and close connection to parents or guardians, so teens attempting suicide may be more likely to be rescued in time compared to adults. In other words, even if fewer teens successfully commit suicide, there may still be more attempted suicides from teenagers. Nil Einne (talk) 18:28, 15 March 2010 (UTC)

the The rates of young and old are NOT similar. old is much more —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 17:23, 15 March 2010 (UTC)

Are you sure? from the table above we have for the US (Age 25-34: 12.4) and (Age 65-74: 12.5). Icall that similar. Dauto (talk) 17:55, 15 March 2010 (UTC)

The OP is I believe 19 so 45-54 may be old to them. Nil Einne (talk) 18:28, 15 March 2010 (UTC)

Something that's always bothered me is that the term "suicide" is used to include two entirely different things. One, as in most teen suicides, is choosing to end a life that would otherwise continue normally. The other, as in most elderly suicides, is choosing to end a life that will soon end anyway, often in extreme pain, from a terminal disease. StuRat (talk) 17:30, 15 March 2010 (UTC)

It's still suicide though. You can argue mental pain vs. physical pain, but in the end taking your life is still technically suicide. — The Hand That Feeds You:^Bite 19:19, 15 March 2010 (UTC)

It is, in English, but that's just semantics. I wonder if other languages have different terms for those two concepts. For example, ritualized suicides may have different names, such as "seppuku" (hara-kiri) in Japanese. StuRat (talk) 19:49, 15 March 2010 (UTC)

Regardless clearly the idea there are two "entirely" different things is somewhat simplistic. At the extreme edges, perhaps but it's much more of a continuum and in fact even that's too simplistic since it isn't a 1 dimensional thing. For example if someone who is diagnosed with cancer with an expected average lifespan of 5 years, but the possibility of living significantly longer if treatment is successful and the expectation that they will still be able to live a resonably painfree life for perhaps the next 3 years commits can't be said to be having their live end "soon anyway". If you're resonably young and have beaten cancer once but suffer a relapse, there's a resonable chance you may beat it again, although you're always likely to be living with cancer and the coming weeks and months are probably going to be painful whatever happens and at the end, you may die anyway. Someone who has just commit a serious crime, in a country without the death penalty live will go on, but it's hardly going to be normal and they could be in prison for a long stretch of time. Someone on death row who commits suicide is probably going to die soon (although there's still the possibility of clemency). Someone who owes a lot of money to a loan shark which they can't pay may not necessarily expect to die, but may expect to find live very unpleasant or they may simply not really know what to expect. For an extremely depressed teenager or whatever (e.g. someone who's just lost a partner) it may seem to an outsider that for them live will go on and should even eventually start to become better, but the problem is often while perhaps they kind of realise that in the back of their minds, it's not something they can really 'understand' and most likely in some ways to them it seems life will always be this depressing, unbearable existance (some may realise their life is not going to end soon which may give them an impetus to commit suicide but equally I expect some just can't/don't think about that). Of course there are also who commit suicide for other reasons (e.g. to make a point, some sort of socially expected ritual, because they think they'll transcend to become aliens) but we aren't really discussing those I guess Nil Einne (talk) 20:55, 15 March 2010 (UTC)

Young people in industrialized countries die of accidents in the traffic and of suicide and very few from illnesses, the chance that that happens is low because most of us get old. The percentage of suicide as cause of death for young people is high. The low number of people dieing at young age multiplied with the the high percentage gives the moderate number quoted above. --Stone (talk) 19:10, 15 March 2010 (UTC)

... I really can't parse what you're saying here. — The Hand That Feeds You:^Bite 19:20, 15 March 2010 (UTC)

I think he/she is basically repeating what Alteripse said Nil Einne (talk) 20:56, 15 March 2010 (UTC)

A.I. Apollo Program

Imagine the USA decided to spend billions on creating a self-aware artificial intelligence. Given a huge commitment of labor and resources how long would it take from today to reach that result?

Before you say we don't have the technology or quote Raymond Kurzweil or Moore's law keep in mind the Moore's Law is not a hard rule but rather a benchmark manufacturers aim for. Given subsidies we could surely accelerate the growth rate of processing power and perhaps even leapfrog far ahead given some advanced research. TheFutureAwaits (talk) 19:28, 15 March 2010 (UTC)

I don't think any amount of time or money would do, because we lack even the theory as to how to make a machine self-aware (versus making it pretend to be, which we can do now). StuRat (talk) 19:40, 15 March 2010 (UTC)

(edit conflict) Its likely an unanswerable question until you define your parameters for what you mean by Artificial intelligence. The term is extremely broad; however truly sentient machines would require a complete fundemental change in the way we currently construct hardware and software, especially for a machine that would pass the Turing test. It isn't a question of simply making faster and faster computers that can do more complex calculations. All modern computers are fundementally still Turing machines, that is with an arbitrarily large memory and enough time, every single computer, from the ENIAC to your cell phone, could all perform the exact same tasks. Any computer can model sentient responses to stimuli, but they do it in a non-sentient way. To design a sentient machine would require starting from scratch, some interesting developments are happening in the way of Artificial neural network, either virtual or actual hardware-based ones, since they actually behave the way real brains do, and thus stand the best chance of replicating actual sentience. --Jayron32 19:42, 15 March 2010 (UTC)

As far as I've read, there is no known reason to believe that a hardware change is required for sentient machines besides the ongoing increase in computing capacity.

There is no evidence that our own sentience or the primitive self awareness of some other animals isn't based on deterministic, physical phenomena. APL (talk) 21:45, 15 March 2010 (UTC)

(edit conflict) (I knew this would happen)

I think that right now, the biggest hurdle in creating a self-aware AI is that we would need to understand how self awareness works. Right now, we have only the vaguest idea how the human brain works, and if we want to replicate those abilities, we would first need to know how our brain works in detail. This is something we have been working on for a long time and it is very hard to gauge our progress. We simply do not have a good answer for this question. Googlemeister (talk) 19:44, 15 March 2010 (UTC)

(ec) The real problem is, as far as I understand it, is that we probably don't know the scope of the problem. This isn't a "simple" engineering problem where you scale up some existing things, with a large margin of error for unknown unknowns. We don't even know what the end-situation should look like—how we could make something that was "self-aware" or not. We don't really know how that would go. Scaling up existing A.I. work does not (as far as I know) look like it would create something "self-aware" in any real sense (whatever that even means!). If we defined our outcome by some kind of more obvious metric (calculations per second; ability to play chess better than a human; ability to read and contribute to Wikipedia as good as some of our better contributors), we could probably come up with a reasonable estimate. But "self-awareness" is a vague concept at best when applied to computational thinking.

To take another historical project as a point of comparison, the Manhattan Project did not really begin until the basic engineering constraints of the problem were pretty well understood. It was still a gamble and required discovering a lot of new things in a very small amount of time, but the theoretical basis for knowing what might be possible was pretty well understood. I'm not sure A.I. work is quite at that stage yet—or, put another way, I'm not sure we understand the cognitive functioning of biological brains well enough to make "artificial" ones yet that function similarly. Perhaps someone more informed about the current state of things would have more to add on that specifically. --Mr.98 (talk) 19:45, 15 March 2010 (UTC)

all of the posters above are quite wrong. Granted, no amount of money would bring about self-aware AI by tomorrow evening at 8 PM -- not even if you were to spend say $60 trillion on it, which is one year's of the world's GDP. In theory the entire world could somehow borrow a year's worth of GDP, ie $60 trillion. But even if the world did do that, and put the entire money into self-aware AI, it would not happen by 8 PM tomorrow. You just can't move money into project at that scale that fast. On the other hand, if the world were to borrow 1 year of it's GDP and put it all into creating self-aware AI as fast as possible, then I think it would be done within a matter of months with that money. Probably the way to do it would be to split the 60 trillion into bets, different avenues, and even if you make 1000 such bets, each bet gets $60 billion funding. Now, just off of the top of my head I can list about a dozen of these bets, each of which I wouldn't be surprised at succeeding. (if you must know they include:

• starting from the now sequenced human genome, ie analyze it and extract from it. In this scenario you spend your $60 billion (or more, if there are fewer bets) on human brain power, the best in the world, to try to reverse engineer the roughly 1 cd-rom of data. I think $60 billion might be woefully inadequate to properly reverse engineer it, but who knows; it just might be. I consider this scenario unlikely to succeed.
• starting with more precise brain imaging, ie spend $30 billion on scanning and imaging a brain and $30 billion on hardware that will run it at 1/1,000,000th realtime speed. Bam! A consciousness, albeit it will be pretty trippy for it, considering a year goes by every 30 seconds it's conscious.
• do highyl parallel molecular/DNA computing to do highly parallel computing. I have no idea how you get intelligence out of it, but the idea is if intelligence evolved in the real world, then if you spend $60 billion on goo that does highly parallel _________, maybe you can induce and brute-force an evolution of an intelligence. I don't know if this one would even be considered "artificial" though -- why isn't it just real intelligence?
• For $60 billion, you can probably get around the proscription on certain human experiments, and somehow reverse engineer an actual human not with brain imaging, but layer by layer peeling away neurons however compensating for them electronically at each step. Actually $60 billion is woefully inadequate for this proposal, probably more like $1 trillion would let you do it.

) That's just off of the top of my head. Basically, it's just a question of money. Even the bets I just listed aren't very sure with $60 billion, and if you start with 1 year of the world's GDP, you can only make a thousand such bets. If, however, you a hundred year's of the current world's GDP at your disposal, then you can make a thousand such bets funded at $6 trillion each (or some of them funded more). Now we're really talking. If you had that much money for this project, you could probably be 100% confident of achieving the goal within 9 months.

But why would the world want to put itself into dept at 100 times it's annual GDP to produce, in addition to the six point eight billion people who can currently convince you that they are conscious and awake, cognizant of their surroundings, etc, one non-person who can convince you that it is conscious and awake, cognizant of its surroundings, etc.???

I mean it's an interesting result and all, but it's already doing something that we KNOW is possible given the physical laws of the universe and, oh, about 3 pounds (the weight of the human brain) and less than a CD-ROM worth of source code with some mild compression. (The human genome).

I mean, you're not even going to get something that is as small or as useful as the human brain. You spend 100 times the world's GDP, and get a building-sized supercomputer capable of basically the same function we have 6.8 billion biological specimens of. Meanwhile, the world is probably not going to live down the effects of the intellectual orgy you've gotten it into maybe for 200 hundred years (optimistic) or maybe it will simply never reach the level it would have if you hadn't entered it into such a crushing debt burdon. Basically, the reason we're not spending even as much as the moon missions on reproducing consciousness, a known possibility, is: why would we? 82.113.121.99 (talk) 20:21, 15 March 2010 (UTC)

. Comet Tuttle (talk) 20:26, 15 March 2010 (UTC)

You don't need a citation to point out that if something exists then it is possible. More specifically, you would need a citation if what I just said (I'm the same poster, maybe my IP has changed slightly) either could or could not be the case. But it is not a possibility that it is not the case: you could not read, a la the Goedel incompleteness theorem, a published proof that it is impossible for a body of finite mass to be self-conscious. Just imagine for example the idea that we would abandon the idea of ever making artificial AI, because there is now a proof floating about that, for any such AI that can exist, it must be infinite in mass. A mathematical proof like that. Just imagine it. You can't imagine it, because it is preposterous and absurd, given that we know that three pounds of stuff can do it, and we know it six billion times over. So the idea that you would need a citation, whereas the alternative state of affairs is prima facie preposterous, is absurd. 82.113.106.100 (talk) 20:49, 15 March 2010 (UTC)

It is not absurd to ask for references on a reference desk, particularly when you invent a bunch of numbers to support your points. Comet Tuttle (talk) 22:23, 15 March 2010 (UTC)

Personally, I think the final answer will be a proof that we are not "conscious" in any special way after all...that all sufficiently complex systems have a rudimentary self-awareness. However, I believe that raw complexity is the solution here. I suspect (without proof) that if you built a computer with comparable complexity to the human brain - had it run a neural network simulation at comparable speed to the brain - with cameras and microphones hooked up to it appropriately - and took it through the same kinds of developmental and learning processes that a baby goes through in the womb and for the first half dozen years of life - then there is a good chance that it would exhibit all of the properties of a conscious human. Sadly, we're perhaps 50 years of solid Moore's law expansion away from being able to do that. However, the odds are extremely high that if we did that - and it worked - then we'd learn nothing whatever of value from doing this since we don't have a way to prove that a being truly is "conscious" - or even a practical definition of what that means - and the likely complexity of a computer that would exhibit conscious-like behavior would probably be comparable to the complexity of the brain of a "higher animal" - and therefore as far beyond our ability to analyse as a real human brain. SteveBaker (talk) 21:30, 15 March 2010 (UTC)

I concur with the others who say that there's an immense theory gap. No amount of effort or money will help us if we don't know precisely what intelligence is in the first place. If NASA didn't have a handle on where the moon was, they couldn't have made it to the moon with a rocket that was 100 times as efficient. We can make computers succeed at some tasks that intelligence can also solve, but we don't know how people solve those tasks in the first place, so we don't even know whether we've made progress or not. Paul Stansifer 22:31, 15 March 2010 (UTC)

I just want to clarify that just because there is a large theory gap does not mean it is not possible to throw a lot of money at it and get results. It just means that estimating the amount of money necessary is probably not possible ahead of time. It may be, as SteveBaker posits, that the theory gap is illusory. But we don't know have great ways to know that at the moment. There is a difference between saying, "we can't do this" and "we don't know how much it would cost to do this." I think the latter is true and the former is probably false.

Just as a point of comparison, we've thrown a lot of money at cancer research in the last century. It turns out to be a very non-trivial problem—a different sort of medical problem than, say, finding a vaccine for polio, which took only a couple of decades to develop after real money was put behind it. This is a comment on the apparent nature of the problem, not the nature of science itself. Cancer is hard. Is A.I. hard? Opinions differ on this. If the answer is "yes" then it means that it's possible that huge amounts of money won't do much other than tell you exactly why it is hard. If the answer is "no" then huge amounts of money can get rapid results. A lot of problems are obviously in between these two extremes. The thing is, I don't think we know where self-aware A.I. falls in this spectrum. --Mr.98 (talk) 22:41, 15 March 2010 (UTC)

If NASA sent up enough rockets they would have found the moon eventually! Seriously, there are parts of the problem that could be worked on in the hopes that other parts would fall into place later. Specifically large computers. (Would throwing more money at computer engineering significantly increase the rate of progress? It's already a well funded industry.) Also, with an unlimited budget some vast parallel supercomputers could begin work on the type of experiment that Steve describes above. (And other proposed types of emergance intelligence.) If nothing else, dead-ends could be eliminated from future consideration.

Of course, even if they didn't know where it was, NASA would have recognized the moon when they landed on it. Would we recognize a sentient AI if we saw one? (Is Commander Data sentient? He'd never in a million years pass a rigorous Turing test. Neither would HAL9000.) APL (talk) 22:52, 15 March 2010 (UTC)

The question is not, "would throwing money at it get some kind of results." It surely would. The question is, "would a crash program work like Apollo or would it work like the War on Cancer?" Or, more specifically, could we possibly know ahead of time? (And a secondary question is, "is this the best thing to be spending resources on?", which is not a question that science alone can answer.) --Mr.98 (talk) 22:55, 15 March 2010 (UTC)

What made cancer difficult was that it turned out not to be just one disease with one cause - but hundreds of separate diseases with hundreds of separate causes. The push to cure it did an amazing amount of good. There are now dozens of cancers that we can cure - there are dozens more that we can detect early and at least have a good shot at curing - and dozens and dozens of causes that we have eliminated from our environment. The moon shot was just about the opposite of that. It was a single clear goal with a small set of distinct problems to resolve to get there. The quest for AI is yet a different problem - we don't even really know what the question is yet - and we wouldn't recognize the answer if we solved it tomorrow. How would we know if the Internet was sentient? How do we know that it isn't? That puts it a long way from getting a man on the moon - and probably further out of reach than curing all possible cancers. But we honestly don't know. It's perfectly possible that we already have machines of sufficient complexity that they are already "conscious". It's also perfectly possible that there is really no such phenomenon. The answer to this question is "We don't know - and we don't even know why we don't know." SteveBaker (talk) 23:16, 15 March 2010 (UTC)

If successful AI means anything, a minimum is an ability to carry on a coherent natural-language conversation. And the simple fact is that nobody currently knows how to build a machine that can do that, for any amount of money. Looie496 (talk) 01:56, 16 March 2010 (UTC)

The problem is in part that we don't really know how people do that, and people seem quite exceptional in their ability to do that. I think one of the main A.I. problems in general is that human language and abstract reasoning capabilities are pretty off-the-map. It's what we do; it took millions of years of evolution. Until we figure out how it works (and from what I've read, it's not just "add more neurons and it'll spontaneously emerge"—things are a lot more specialized and complicated than that), we're going to have a hard time making a machine do it well. Doesn't mean it's impossible... just that we're not really sure how complicated a problem it is, even though we've had a lot of people working on it for quite some time now. We'll probably find an answer—it's not magic—but it's not clear that just throwing money at it alone is going to turn up a shortcut. --Mr.98 (talk) 02:22, 16 March 2010 (UTC)

Sneezing and hair length

A general wonderment. If I measured the distance my head moves when I sneeze, and the time it takes for my hair to land back down on my head, could I calculate the length of my hair (assuming my hair grows pretty straight). If so, any ideas what I'd need? Would I have to use things like gravity formulas and calculating air resistance, or is there a nice simple way with a bit of maths and angles? Edit: Actually thinking about it your head doesn't go straight down when you sneeze so there might need to be some force directiony things to that I did in maths a long time ago. —Preceding unsigned comment added by Jimothyjim (talk • contribs) 21:20, 15 March 2010 (UTC)

Well, if you had good numbers for the mass of your head, the elasticity of your neck, the velocity and mass of material ejected during the sneeze, the shape of your scalp and the springyness, density and cross-sectional area of the hairs - then a mathematical model (probably a differential equation of some kind due to the distributed nature of mass along the length of the hairs and the curvature of the scalp) could be used to calculate the hair length from the bounce time. But ask yourself this: What are the error bars like? I could believe that you could measure the bounce time accurate to 10% - but there would be at least a 10% error bar on each of the other numbers - some of them possibly more like a 50% error. When you multiply out all of those sources of error and take an honest look at the size of the total error in the length estimation you'd get as a result, the answer would be something like "Between 5cm and 50cm"...which, to be honest, is something you already knew! So it's certainly possible - but without good data, the result isn't much use. SteveBaker (talk) 23:07, 15 March 2010 (UTC)

You might start by assuming a spherical head and one strand of hair. 24.12.190.7 (talk) 03:47, 16 March 2010 (UTC)

Well, what if you made a few assumptions like, momentum form things expelled from the nose being negligble and things like that, and concetrated on the more important things like the elasticity/snap back of the neck after the sneeze and the hair mass and such alike, and recorded the sneeze with a slow-mo video camera so you could accurately get the times and distances via a computer 81.102.54.39 (talk) 08:23, 16 March 2010 (UTC)

March 16

3,3-Dimethylmalic acid

I'm looking for a reference for the acid dissociation constants for 3,3-Dimethylmalic acid. I checked my usual source, the CRC, which didn't have it. I did a google search, where I only found a little bit about the compound at all, and nothing about the acid constant (here, for example). I have access to a lot of journals at my university, so any citation would be welcome. Thanks. Buddy431 (talk) 01:21, 16 March 2010 (UTC)

SciFinder reports a value of the pKa as 3.41±0.15 (no information on the second or further deprotonations). This was calculated using ACD/Labs Software V8.14. The 7 references that SciFinder has for this compound (CAS Registry Number: 73522-92-6) don't appear to be studying the physical properties. 24.150.18.30 (talk) 01:51, 16 March 2010 (UTC)

since it is a fairly simple compound, I think that the calculated pKa would be fairly trustworthy. Anyone have any other opinions on ACD predictions?. 24.150.18.30 (talk) 01:51, 16 March 2010 (UTC)

Thanks for the quick response. That's better then nothing, I guess. I'd rather have experimental results, and I'd really like the second dissociation constant, if possible. Buddy431 (talk) 02:02, 16 March 2010 (UTC)

Squirrel identification

Hi, can anybody identify either of these two squirrels for me. It should be easy since they only get a few species. I'll add them to the species articles upon response, thanks in advance. --Benjamint 06:00, 16 March 2010 (UTC)

• 
  Taken at the base of Bukit Timah hill, Singapore
• 

It looks at first shot to be a Plantain squirrel, another pic [20] Richard Avery (talk) 08:33, 16 March 2010 (UTC)

Compression of purely digitally animated films

Consider a purely digitally animated film such as shrek or Finding Nemo. I wonder what the difference is between the file size of the film (stored in some sufficiently-high-resolution pixel-based format) and the size of the original dataset used by the software to render the film (in which the characters are described as a set of coordinates that presumably need to be stored only once, their movements can be described using instructions like "move a certain joint by a certain amount of degrees"). 83.134.160.19 (talk) 06:44, 16 March 2010 (UTC)

Useful stats can be gathered from open movie projects such as Elephants Dream and Big Buck Bunny. For Elephants Dream it's available at 1080p resolution at 815MB for a 11 minute film, compressed with MPEG4. In contrast the production files (texture, models, animation, sound, etc.) are split across 2 DVD's. I do not have an exact figure but 2 DVD's are about 9GB worth of data. For Big Buck Bunny the 1080p MPEG4 compressed version is 890MB, but the entire studio backup is over 200GB. --antilived^{T | C | G} 07:01, 16 March 2010 (UTC)

Thanks! I'm surprised the original data is actually larger than the film itself. I would have expected the opposite. 83.134.160.19 (talk) 07:08, 16 March 2010 (UTC)

a question about light

can we move an object using light... —Preceding unsigned comment added by Avinashmani (talk • contribs) 09:12, 16 March 2010 (UTC)

Yes. solar sail, radiation pressure 157.193.173.205 (talk) 09:22, 16 March 2010 (UTC)