Wikipedia:Reference desk/Archives/Science/2009 May 15

Science desk
< May 14	<< Apr | May | Jun >>	May 16 >

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

May 15

Can tame, captive-bred animals be used to breed offspring that can be returned to the wild?

I notice that my captive-bred pet sun conure is a member of a species that is endangered in the wild. As far as I know, there are loads of sun conures in captivity. There might even be more kept as companion parrots in people's homes than there are in the wild. So, would it be possible, if the need ever arose, to breed pet sun conures and release the young ones (that weren't familiar with humans) back into the wild? Or would they be unable to survive? Thanks. --90.241.160.124 (talk) 00:03, 15 May 2009 (UTC)

Does Captive breeding answer your questions? Tempshill (talk) 01:02, 15 May 2009 (UTC)

Not really. I'm interested in knowing if animals that behave exactly like they would in the wild can ever be bred in captivity from parents that are pets? We can talk about sun conures specifically, if that makes it any easier. Thanks. --90.241.160.124 (talk) 01:39, 15 May 2009 (UTC)

Do you mean to ask if is possible to intentionally create a feral population? Dauto (talk) 02:05, 15 May 2009 (UTC)

I suppose I am, yeah. But only in the areas where the bird is or was found naturally. --90.241.160.124 (talk) 02:45, 15 May 2009 (UTC)

Amazingly we don't have an article about the parrots of Telegraph Hill. If escaped parrots can adapt to such an unnatural environment, one would think they should be able to readapt to their native environment. Looie496 (talk) 03:11, 15 May 2009 (UTC)

Reintroduction may have some information for you. There is a difference between having the same skills as a member of a wild population, being able to integrate into and survive within a wild population and having sufficient skills to survive in the wild. Just to illustrate: A captive bred conure may not know the warning call a wild one would use for a panther. If it doesn't get eaten by one, it or it's descendants may be able to learn that. The captive conure may not have the proper social skills and knowledge about nesting to make it within a wild flock. If they are bred in sufficient numbers and with sufficient diversity to form their own flock they may develop skills they can pass on to their next generation, even if those are different from wild conure behavior. For example the parrots of Telegraph Hill might have a call for "hawk" that their rainforest relatives may not have or need. This form of reintroduction usually involves a high attrition rate when scientists have tried it. Successful reintroduction programs usually involve lots of steps, close monitoring and possibly several generations. An animals survival strategy also plays a role here. Some animals just breed in such large numbers that they can stand losing a lot of individuals. Animals with low reproductive rates usually invest in longer training periods and parental care to ensure their offspring make it. Hope this helps.71.236.24.129 (talk) 04:46, 15 May 2009 (UTC)

Domestic cats can product feral offspring. If a domestic stray cat has kittens, and they are not socialised (introduced to humans) within a certain time period, they will difficult or impossible to tame or introduce successfully into a domestic environment. I'm not sure we'll ever need to breed cats for release into the wild, though. --Kateshortforbob 11:22, 15 May 2009 (UTC)

Cats are a whole different ball game. I have successfully reintroduced several feral cats into domestic environments. It just takes an awful lot of effort and a certain type of home. (A townhouse apartment won't work. A barn would be ideal.) Since our shelters are overflowing with domesticated cats shopping for a home it's usually not worth the trouble. I even used to have a semi-tame wild cat that I could pet and feed (while the door to the outside remained open.) Most experts will tell you they're impossible to domesticate. Domestic cats do not need to be reintroduced into their natural habitat - which would be people's homes. Other Felinae like Felis silvestris, Prionailurus viverrinus, Felis margarita and Felis manul are in decline and captive breeding and reintroduction programs are under way. They face many different challenges like diseases, difficulty breeding, loss of prey and loss of habitat or human encroachment. The target here is not to domesticate them, to make them pets, and then reintroduce their progeny into the wild, but to keep breeding pairs in human controlled environments or zoos and then prepare their offspring for release into the wild. Those would still not be feral cats though. With zoo raised cats you have the same issues with reintroduction as described above, which is why they usually try to keep them in reserves or sanctuaries. With both cats an conures the question becomes where the "wild" that you want to reintroduce them into can still be found. 71.236.24.129 (talk) 14:35, 15 May 2009 (UTC)

Yes I believe that individual home reared Conures can successfully survive in what is left of thier native habitat. My largest concern would be with the diversity and size of the gene pool. Geneticists will tell you that without a "certain" amount of diversity and a certain number of indivivuals (there is a formula for such)a reintroduced population is doomed to failure. Wikipedia probably has articles on genetic bottlenecking, gene pools and other relevant topics but i don't know how to link them here. 67.193.179.241 (talk) 12:03, 15 May 2009 (UTC) Rana sylvatica

Huntington's disease in Scotland

I read in one source that Huntington's disease has an extraordinarily high prevalence in "some areas of Scotland". Which ones? 99.245.16.164 (talk) 00:20, 15 May 2009 (UTC)

The Moray Firth apparently. SpinningSpark 06:28, 15 May 2009 (UTC)

Making the Rage Virus

Is it possible for scientists to create a virus that could make humans rage with anger and cause them to kill other humans and animals? 174.114.236.41 (talk) 01:20, 15 May 2009 (UTC)

It already exists -- it's called intolerance. Wikiant (talk) 01:25, 15 May 2009 (UTC)

... and it's already mutated into a virulent strain, increasingly common in urbanized areas especially where bitumen or asphalt takes up a large proportion of the land surface area, and is known colloquially as Road rage. Fortunately, there are treatments available. BoundaryRider (talk) 02:01, 15 May 2009 (UTC)

Well how about an actual useful answer? A virus like this somewhat already exists. The rabies virus turns dogs and foxes into crazed killers - but fortunately, not so in humans (although it's nasty enough without that particular symptom) - but if such a virus is possible in other mammals, I could imagine something similar happening in humans. Our article explains that "In many cases the infected animal is exceptionally aggressive, may attack without provocation, and exhibits otherwise uncharacteristic behavior."...and..."The first stage is a one- to three-day period characterized by behavioral changes and is known as the prodromal stage. The second stage is the excitative stage, which lasts three to four days. It is this stage that is often known as furious rabies due to the tendency of the affected dog to be hyperreactive to external stimuli and bite at anything near."...and also..."a new symptom of rabies has been observed in foxes. Probably at the beginning of the prodromal stage, foxes, who are extremely cautious by nature, seem to lose this instinct."

That's a virus that's transmitted in saliva and has therefore evolved to cause its victims to go nuts and start attacking and biting.

SteveBaker (talk) 02:46, 15 May 2009 (UTC)

There are lots of infectious agents which do induce delirium and brain damage in their hosts. Depending on what parts of the brain are affected, it is not unreasonable to find an infectious disease which would cause the result described by the OP. --Jayron32.talk.contribs 04:21, 15 May 2009 (UTC)

The challenge is finding a virus that consistently targets brain areas in just the right way to induce a behavior like the "furious rabies" that Steve's (useful) answer cites. I don't think scientists currently have the knowledge or tools to design such an agent. --Scray (talk) 04:57, 15 May 2009 (UTC)

It would probably be quite easy to do this, one doesn't need to know the mechanism to select for things like this. After all somebody with this level of morals wouldn't mind human testing. It is totally unnecessary though, it seems altogether too easy to get whole nations to take up arms against others and bomb and torture and otherwise behave vilely. You want a way of doing this even less controllably? 08:07, 15 May 2009 (UTC)

In case anyone has missed the reference, the "Rage virus" is the premise of the film 28 Days Later. --Tango (talk) 13:59, 15 May 2009 (UTC)

It is definitely possible, though how hard it is I don't know. What you need is a virus that can get into the bloodstream to have DNA that will code for enzymes that will synthesize a psychotomimetic. The DNA/RNA for enzymes is easy to extract from plants/fungi (ergot, atropa belladonna), but I dont think these drugs (lysergamides, atropine, respectively) would cause people to start killing each other, although people under the influence of deliriants do sometimes accidently kill themselves (I can't find the ref right now, but some english guy flew to new york and took too many nytols to overcome jet lag. He was found in his hotel room bleeding from the head, he had smashed his head in with a lamp or something along those lines. Google isn't finding it unfortunately). --Mark PEA (talk) 17:06, 15 May 2009 (UTC)

Though not a virus, if you watch the film Jacob's Ladder (film), you will see that BZ, a derivative (or ingredient) of LSD is purported to do this.--KageTora - (영호 (影虎)) (talk) 22:34, 16 May 2009 (UTC)

We have an article on BZ, which is an anticholinergic like atropine that I mentioned earlier (except it lasts longer, alot longer). Just a note, BZ is not an ingredient of LSD, nor is it anything like it in fact. LSD can be classed as a psychedelic or less specifically an hallucinogen, where as BZ/atropine are deliriants and have completely different mechanism of action. I'll might have to check out that film. --Mark PEA (talk) 22:26, 18 May 2009 (UTC)

Partial Pressure

Hello. There is an equal amount of nitrogen gas and hydrogen gas in a balloon that has a pinhole leak. There is no word of where the leak is exactly on the balloon. The temperature stays constant. Why will the partial pressure of nitrogen gas exceed that of hydrogen gas? Thanks in advance. --Mayfare (talk) 03:53, 15 May 2009 (UTC)

Sounds like homework, but anyway, you can read about Graham's law here just as well as in a science textbook. DMacks (talk) 04:12, 15 May 2009 (UTC)

Which molecules are moving faster? So which molecules will hit the pinhole more often? So which molecules will leave the balloon faster? So what happens to the ratio of the gases in the balloon? Answer these questions, or just read the Graham's law article cited above. --Jayron32.talk.contribs 04:20, 15 May 2009 (UTC)

Two! Two Graham's Law answers on WP:RD/S! Ah ah ah ah ah. Count von Count (talk) 04:49, 15 May 2009 (UTC)

I'm surprised that no one picked up on the fact that there are two answers to this question: The rate of effusion may be greater, but additionally, in air Nitrogen is much more plentiful, so even if Hydrogen were heavier, it would still eventually have a lower partial pressure in the balloon. -RunningOnBrains^{(talk page)} 18:25, 19 May 2009 (UTC)

Yet another perpetual motion machine

I know it wouldn't work. Tell me why. An electric transformer generates a voltage on one side proportional to the change in voltage on the other. If you put an exponentially increasing voltage one one side, that should generate an exponentially increasing voltage on the other, which would generate an exponentially increasing voltage on the first. This would make a self-sustaining increase in voltage. Another way to do the same basic thing would be by moving a charged particle along an exponential path. The Abraham–Lorentz force will create a force on it proportional to its jerk. — DanielLC 05:10, 15 May 2009 (UTC)

energy is lost as heat. —Preceding unsigned comment added by 82.44.54.169 (talk) 05:38, 15 May 2009 (UTC)

OP: memorize those five words, because it is (probably) the answer to most any perpetual motion machine you could think of (except the fancy stuff you could try to do with magnets, which might end up depeleting their own magnetic charges over time, and slow down for that reason). As to why, thermodynamics should give you the answer to that... —Preceding unsigned comment added by 79.122.38.222 (talk) 10:57, 15 May 2009 (UTC)

Daniel, by the Lenz's law the induced electromotive force back on the first side should opose the one you had to begin with, and not reinforce it. Read the article I linked. Dauto (talk) 12:56, 15 May 2009 (UTC)

1)The induced waveform would only be proportional to the input exponentially increasing waveform until the magnetic core material saturated. 2)There is a frequency response limitation in a transformer; it does not have infinite bandwidth, so the output waveform would not be able to reproduce an input waveform with too high of a rise time. The induced voltage from a cable thumper or lightning may not be able to travel through a power transformer, for instance, because the impulse is too brief. (Safety note: Don't experiment with this at home.).Edison (talk) 18:11, 15 May 2009 (UTC)

This would disobey the first law of thermodynamics, not just the second. As such, heat escaping wouldn't make it not a perpetual motion machine. You can't create any energy, useful or not. In any case, you could theoretically change the curve to account for any loss in voltage. The second law of thermodynamics tells me that it won't work, but not why. I still don't understand that whole thing with flux. Is the problem that there is only one flux field, and as such I can't treat the two inductions separately? That still doesn't answer the Abraham-Loretz force version. Is that one similar? I get the feeling it is, but I'm not sure. — DanielLC 19:32, 16 May 2009 (UTC)

Yes, the problem is that you can't treat the magnetic fields or voltages (whether applied or induced) separately. They are coupled together, so you must treat them together, otherwise you'll get a wrong answer. This is similar to how a differential equation cannot (in general) be solved by isolating each term and then summing over the termwise answers. As for the bit about the Abraham-Lorentz force, the article says it nicely: "the motion of the particle must be periodic (an assumption that is explicitly made in the derivation of the force)". Someone42 (talk) 05:45, 17 May 2009 (UTC)

molarity

here's the question: what volume of 36M and 1M sulphuric acid must me mixed to get 1L of 6M sulphuric acid?

i need some explanation. don't just give me hints... explain those hints too, please... i'm new to this concept. —Preceding unsigned comment added by 122.50.136.97 (talk) 05:14, 15 May 2009 (UTC)

First you need to figure out the proportions needed to get a 6M concentration. Then you can figure out the amounts to give you the total volume you need. If you add X liters of 36M (36 moles/liter) solution to Y liters of 1M (1 moles/liter) solution, figure out the total number of moles that gives you and the total volume in terms of X and Y. Now the total number of moles divided by the total volume gives you the new molarity, which you want to be 6. That gives you enough information to form an equation that you can reduce down to a ratio between X and Y. From there, it should be a simple matter of calculating the amounts of each solution needed to give you the desired 1 liter result. -- Tcncv (talk) 05:41, 15 May 2009 (UTC)

Example: Suppose you had 1M and 5M solutions and needed 1 liter of 2M solution. Using the above approach, X liters of 1M solution added to Y liters of 5M solution gives you 1X + 5Y moles in X + Y liters. To get a 2M solution, set (1X + 5Y)/(X + Y) = 2. This can be rewritten as X + 5Y = 2(X + Y) or 3Y = X. So you need three parts 1M solution to 1 part 4M solution, this works out to 3/4 liters and 1/4 liters respectively to give you the desired amount. -- Tcncv (talk) 05:51, 15 May 2009 (UTC)

Gene Accession to Protein ID conversion

I am attempting to convert a large (1000s) list of gene accession numbers into their corresponding protein IDs (SwissProt/UniProt accession). The site [[1]] performed the task, but only returned protein accession numbers for ~80% of the supplied gene accession numbers, seemingly lacking the SwissProt IDs to the more recently characterized proteins. I looked at Pubmed, and found it to be more complete; but, as far as I know, the IDs can only be retrieved individually there rather than by a large list, which is obviously inefficient. I was wondering if there is a similar program to these with (ideally) the completeness of pubmed and the speed of idconverter. (NB: in addition to the gene accession numbers, I also have, or can acquire, the gene names and common names.) Any help will be greatly appreciated!Lashyn (talk) 06:03, 15 May 2009 (UTC)

Lashyn, I don't have an answer but I suggest you ask User:AndrewGNF who runs the Protein Box Bot. The bot seeds gene articles with the type of information you are trying to get. I'm not sure if Andrew has run across the same problem or not, but its worth asking. David D. (Talk) 06:56, 15 May 2009 (UTC)

I believe that SwissProt requires a pretty high level of evidence in order to get an accession number and there simply may be no SwissProt ID for every gene ID. The NCBI RefSeq genes are highly curated but other gene IDs may be predicted coding sequences, etc. The fact that you found SwissProt accession numbers for only 80% of the gene accession numbers is probably about right. Another way to look at it would be to take all SwissProt accession numbers and then find the corresponding Gene IDs. Then you'll have a complete list of the GeneIDs that CAN be linked to a SwissProt ID. --- Medical geneticist (talk) 12:24, 15 May 2009 (UTC)

Wet, Soap, Wash, Rinse, Dry

Since Swine Flu became the new thing to worry about i've seen a marked increase in how to wash your hands posters in toilets. Fair does, it's cheap to roll out and I suspect does make people more likely to wash their hands (reminders often do - even for seemingly insanely normal things). Anyhoo my question was this...I prefer to Soap, wet, wash, rinse, dry - does that (changed) ordering make any difference? Will my hands be less clean because I didn't wet before soaping? I guess it's nothing but what are Friday afternoons for if not trying to get answers to (largely) pointless questions? 194.221.133.226 (talk) 13:25, 15 May 2009 (UTC)

I'm sorry, but your order of doing things is wrong, and you now probably have Swine Flu. Please see a doctor. (Just kidding, of course. I don't think it matters a whole lot if you put the soap on before you've wetted your hands, as long as you take the time to wash and rinse.) --98.217.14.211 (talk) 13:42, 15 May 2009 (UTC)

I agree - your imminent death soon after you fall over into a muddy puddle and roll around snorting contentedly - is now virtually certain. The soap lowers the surface tension of the water and acts as a surfactant to encapsulate whatever comes off of the surface so it can rinse away more easily. You need the soap and the water to mix completely because neither soap or water alone can perform this magic trick. Whether you add soap to water or water to soap isn't so critical...although I guess if you first cover your hands with soap and then hold them under running water, you may send more of it down the sink than if you'd first wetted your hands, then shut off the water and then added soap. However, since most people use VASTLY more soap than they need - it's probably just as effective your way. The new advice for me was the amount of time to wash for. They are telling kids to sing the alphabet song while they wash - since that's timed to be about 15 seconds. On NPR the other day - they recommended that adults sing "Bohemian Rhapsody" but since that was (at the time it was released) the longest 'single' record ever made (5 minutes, 55 seconds) - I think that NPR may have been kidding! SteveBaker (talk) 14:59, 15 May 2009 (UTC)

Damn, I've been washing my hands while humming In-A-Gadda-Da-Vida. I don't have much skin left, but I laugh in the face of swine flu! Matt Deres (talk) 16:26, 15 May 2009 (UTC)

Hate to disabuse you, Steve, but the single of "Hey Jude" lasted 7:11, and that's not the only pre-1975 single longer than "Bohemian Rhapsody." Deor (talk) 21:49, 15 May 2009 (UTC)

More released singles longer than Bohemian Rhapsody, and also released prior to Bohemian Rhapsody include: 1971's American Pie at 8:33, the 1972 single version of Papa Was a Rollin' Stone at 6:54 (the album version was 11:54), 1972's Jessica at 7:30, the 1972 7:02 single verion of Layla (more successful as a single than the 1971 2:43 version). 5:55 is long, but when released it was certainly not even close to the longest single released to that point. Sorry Steve. For the record, I sing the full album cut of the Rare Earth version of Get Ready. With lava soap and a steel brush. My hands are a bit raw, but there ain't nothing on them after that. --Jayron32.talk.contribs 01:25, 16 May 2009 (UTC)

Now you're just making fun. If you children can't play nicely together I'll turn this ref desk around! --Tango (talk) 16:50, 16 May 2009 (UTC)

My sister is a medical student and she was telling me about their lessons in washing your hands (they have a very strict way to do it, washing each part in a very specific order, but I think that's just to make sure they don't forget a bit rather than because there is anything better about that order) and the interesting thing she said is that the key thing for getting rid of viruses is the mechanical action of scrubbing/rubbing/whatever your hands. The soap doesn't do all that much and, obviously, antibacterial agents don't help against viruses. So, I think the advice to wash your hands for a significant amount of time is probably good. --Tango (talk) 17:47, 15 May 2009 (UTC)

My wife used to be an operating department nurse - and that whole scrubbing-up ritual really does get burned into the soul. She hasn't worked at that job for 5 years - but you can still catch her standing there with her hands held up like a kangaroo when she's deep in thought because she spent so long being told to keep her hands firmly above waist height after scrubbing. SteveBaker (talk) 17:57, 15 May 2009 (UTC)

What is reality ?

I am a teenager, and i have read a bit about Quantum Mechanics, its interpretations, wave function collapses, and paradoxes. My question is, Where does this all leave us ?
Can we still think that the world is deterministic, that it is written on my forehead what i will do? Is there a place for free will ? Is there reality out there, or when i close my eyes does everything turn into imaginary wave functions with respect to me ? Is physics really complete, at low velocities, ie, is QM infallible in non-relativistic situations? I understand that there is a bit of a debate over these topics, but i do want to know where the scientific community stands at this point. In short, can someone please explain, what is reality ?Rkr1991 (talk) 13:41, 15 May 2009 (UTC)

Reality is anything that does not goes away after you are utterly sick of it. For example: being unemployed is a reality for many people. 122.107.207.98 (talk) 14:12, 15 May 2009 (UTC)

"Reality is that which, when you stop believing in it, doesn't go away." - Phillip K. Dick. — The Hand That Feeds You:^Bite 21:30, 18 May 2009 (UTC)

The uncertainties of the quantum world tend to average out at the macro scale that humans live on. So for most of the time, it can be ignored and the world treated as a more or less deterministic place. However, we humans are cunning and we can magnify quantum uncertainty to the point where it becomes visible and important (eg in the Schrodinger's Cat thought experiment). But Quantum theory isn't the only source of indeterminacy. There are many systems out there which are 'chaotic' in the mathematical sense that the outcome of some experiment on these systems depends on the initial conditions with extreme (and possibly, infinite) sensitivity. You've heard of "The Butterfly Effect" where (it is said) the flapping of a butterfly's wings can change the course of a hurricane on the opposite side of the planet a year later. Well, that may be an underestimate. It's possible that a quantum fluctuation of a single electron would be enough to change the weather patterns. So determinism exists - but only strictly within non-chaotic systems - or over shorter time/distance scales - and not at very small scales. However, we can still use basic victorian-style physics to build bridges that don't fall down and airplanes the size of large buildings that seem to defy gravity by exploiting classical airflow laws. We construct amazing things that work pretty much as we expect them to - and that's only possible because determinism is reliable in most cases.

I don't believe there is free will. What goes on inside the brain is a matter of cellular biology - which is basically chemistry - which is basically physics. There is no magical 'outside' will that changes what happens in the physics - and either with or without quantum or chaotic determinism, what is the thing that is making the choice for that chemistry to either go out for Chinese take-out or stay home and cook left-overs? Ultimately, chemistry is what drives that. But it doesn't matter because it seems to us like we have free will - so we might as well act as if we do.

Whether there is a "reality" out there or not is a non-falsifiable proposition - there is no conceivable experiment you can do that would show that it's not all a figment of your imagination. You've seen "The Matrix" - right? So science takes the view that you can assume that nothing really exists and that's OK - but it's a fairly pointless thing to do. It doesn't advance your knowledge, further your career or make you happier - so you might as well assume that reality exists and carry on playing with it.

Physics certainly isn't complete. We don't know about the Higgs Boson for example - we've built this gargantuan machine to test for it - and (sadly) the machine is currently broken. But even in the realms of the "normal" world - there are unknown things. We're still having trouble figuring out WTF happens when you take a "Wint-O-Green" Life Saver into a very dark place and crush it with a pair of pliers causing it to emit a brief spark of light.

Quantum mechanics is more than just a hypothesis. It's extremely well tested. If quantum mechanics were just a theoretical possibility, the computer you are sitting at wouldn't work because the flash memory inside relies on quantum effects to do what it does. If quantum theory didn't work, we'd never have figured out how to make blue LED's.

SteveBaker (talk) 14:46, 15 May 2009 (UTC)

An illuminating answer, i must say, but still more questions. You talked about the chaos theory. Even though the effects are very hard to predict, it remains that the situation is , much like the tossing of a coin,in principle, intrinsically deterministic. So no problem with there. Reality. My question remains unanswered. Will the world be reduced to complex wave functions when i blink ? Does there or doesn't there exist things that exist whether or not i see it ? Is the electron already there, or does it choose to appear there as i have forced it to make a choice by observing it ? As Einstein said, does the moon exist only if i look at it ? And you said no free will. Which pretty much means it is already decided what choices we will take. Which pretty much means determinism. But doesn't the uncertainty principle forbid this ? If something can be anywhere now, how can it be at some particular point in the future ? I'm sorry if i sound aggressive, buut these debates have been raging in my mind for quite some time now, and i had to ask an expert.Rkr1991 (talk) 15:02, 15 May 2009 (UTC)

I think you're confused by the often-quoted point of quantum mechanics where "observing" a system changes it. I don't like this word "observed" because it implies that sentient beings have some sort of power over the laws of physics: this is not the case. "Observation" simply implies interacting with another wave/particle/wavicle, so that its position and momentum at one point in time is known (whether or not a human happens to be watching to record the evidence of that interaction).

The answer to your question is yes, as far as we know, QM is infallible. But this is easy to say, because we have defined that QM only "applies" for slow and light (think non-heavy, not photonic) objects. Through predictions, experiments, and results, scientists have narrowed down the cases where QM makes good predictions, and determined that when certain conditions are present QM spews nonsense. It's easy to say that a theory is "infallible" when you only apply it to special cases.

As far as your latest post, you ask "If something can be anywhere now, how can it be at some particular point in the future?" It isn't fair to say that just because a particle's wavefunction is non-zero everywhere that it can be "anywhere". The probability of me tunneling (think quantum, not creepy) through the earth to appear next to your computer is, technically, non-zero, but that is not going to happen.

Take all of this with a grain of salt: I am, at best, an advanced beginner at quantum physics. I'm sure SteveBaker will correct me if I'm wrong :-D -RunningOnBrains 15:50, 15 May 2009 (UTC)

Regarding the original question, the Science Desk is really not very well suited to resolve these sorts of doubts. You have to go read some books. Looie496 (talk) 16:04, 15 May 2009 (UTC)

I don't think Rkr1991 should be so quick to brush away chaos theory. The important point is that chaos theory acts as an uncertainty multiplier. The teeny-tiny uncertainty of whether the butterfly flaps it's wings now...or...(wait for it)...NOW! can make the difference between that hurricane happening or not. The chaotic nature of (for example) the weather magnifies the degree of uncertainty from something that really doesn't matter at all - to something really major. What that means is that chaos theory can magnify the literally, fundamentally, non-deterministic things that happen in the quantum world up to the macro scale where humans are affected by the results. We cannot - even in principle, with infinite computing power and perfect knowledge - usefully predict the weather more than maybe a month into the future. Taken together, quantum theory and chaos theory mean that even at the large scales where we like to think that the 'real world' consequences of quantum uncertainty is negligable - it's not. SteveBaker (talk) 17:49, 15 May 2009 (UTC)

I would like to emphasize the fact here that i am not talking about what is going to happen in practice , merely the principle. Practicality notwithstanding, since the wavefunction is non zero everywhere, the electron can indeed in principle be found everywhere. Coming to practical terms, ok, my electrons can never be found in the sun, but that doesn't mean you know where it is now. The fact lies that there is a finite measurable indeterminacy in position of the electron, and now i can say that "If something can be anywhere now, how can it be at some particular point in the future?" But you are right, i am confused a bit about that observing part... the problem is that most books are too abstract or complex for me to plough through... I just want to get the picture, the principle, the idea, not everything in its mathematical beast-like form...Rkr1991 (talk) 16:34, 15 May 2009 (UTC)

And if the universe is infinite (or even very VERY large) - then somewhere on some far distant planet - a half ton rock has indeed just jumped four feet to the left and turned into a mauve grand piano without any provocation. In principle, that could happen to you, right now. (Please let me know if it does...that would be fun to know!) It is only that the probability is so amazingly low that we may ignore it for all practical purposes...and even theoretical ones for that matter! However, it is only the quantum uncertainty of that electron "tunnelling" that enables your computer's flash memory to work...so at the level of the very small, this effect dominates the way the universe works. SteveBaker (talk) 17:49, 15 May 2009 (UTC)

Ok, I'm just going to take a shot at this, but what I think the world would look like when you close you're eyes is just atoms reacting with each other. So things that you can see when you have you're eyes open, like light, are just the photons of light hitting electrons and reflecting off into space, to be reflected off into whatever. But when you're eyes are open, you're brain and interpret these waves into the color spectrum and creates shapes and sizes. But then I think even there is still kind of low resolution, if you consider string theory. I don't know a lot about it, and correct me if I'm wrong, but tiny little vibrating strings make up everything, and some are looped into themselves while others are just wiggly lines. So if you could see the true "reality," then you'd see all these little tiny strings are that are vibrating and interacting with each other. 129.21.109.153 (talk) 17:12, 15 May 2009 (UTC)

I think the whole "blinking" or "not looking" thing is a bad interpretation. If you don't look at the Sun, is it still there? Well the tan/sunburn that you will get implies that it is. When your eyes are closed, you are just blocking light waves from reaching your retina, but I know you aren't looking at things from this perspective. You are asking whether "reality" exists if you are in a coma, for example. I guess that depends on what you define as reality, and this is more of a philosophical question than a scientific one. As for free will, I personally have no problem with accepting it doesn't exist, in fact, I feel like I have no control over my life (I realise this may just be a symptom of depersonalization disorder, but I don't fit other criteria), but I always notice how my biology affects me. If I'm in the shower and it starts to feel cold, I turn the heater up. If I'm cold I go and put my jacket on, If I see a question on Wikipedia which I believe I'm capable of producing a decent answer to, I reply to it. Etc. In terms of philosophy, I would be classified as a physicalist determinist. --Mark PEA (talk) 17:29, 15 May 2009 (UTC)

There was some recent discussion about a related topic on this very page. Make sure you read my coments as well as BenRG's. To avoid repetition I will only coment about free will here. Can anybody explain me why people equate determinism with lack of free will? That makes no sense to me. I think it is exactly the oposite. In order to have free will, we need a deterministic world otherwise people would go around doing random things instead of doing things they want to do. Dauto (talk) 19:44, 15 May 2009 (UTC)

Assuming free will refers to a conscious ability to make decisions, in a deterministic universe, all our decisions would have been determined (or determinable) before we were born. There's no space for free will there. Zain Ebrahim (talk) 08:00, 16 May 2009 (UTC)

I disagree. I think you confuse being predictable with having been determined. As I see it, determinism is essential in order to preserve true free will. Dauto (talk) 02:28, 19 May 2009 (UTC)

What are your definitions of free will and true free will? If free will is a conscious ability to excercise control over our decisions in spite of (or independently of) past events then a deterministic universe rules out free will. Btw, a random universe would rule out that kind of free will too because random decisions are not consciously made. Zain Ebrahim (talk) 07:22, 19 May 2009 (UTC)

What you're saying doesn't make sense to me. Living organisms do what they 'want'. What an organism wants to do is a calculation based upon the information they are receiving from their senses, along with their genetic code and upbringing (and diet, drugs, ...). As I posted in the previous example (with the shower and the jacket), decisions are made to try and maintain homeostasis, although some genetic code is better at maintaining homeostasis than others (e.g. those with the short allele of the 5-HTTLPR are more susceptible to commit suicide (Caspi et al. (2003). Science. 301(5631):386-389.)). This is confirmed with the needs of shelter, water, nutrition, warmth... but doesn't really explain reproduction. The explanation for the urge to reproduce is presumably due to DNA that makes us 'want' to reproduce, because without it, we wouldn't be having this conversation. --Mark PEA (talk) 22:20, 15 May 2009 (UTC)

You're a teenager and you've hit a mine of interesting thoughts. As people have said, the way you're thinking about this isn't necessarily very scientifically useful. For one thing, you seem to be mixing 'reality' up with 'your perception of reality'. But it is fun and interesting, particularly when all these ideas are new to you. Get hold of some Philip K. Dick short stories, read the Principia Discordia (although it will probably just seem silly to you), enjoy playing with these ideas. But remember that for all practical purposes, reality exists independently of you and you exercise free will. All the rest is mental entertainment (or seeking after ultimate truth. One or the other). 80.41.104.220 (talk) 20:01, 15 May 2009 (UTC)

Quantum theory provides us with a striking illustration of the fact that we can fully understand a connection though we can only speak of it in images and parables.

However the development proceeds in detail, the path so far traced by the quantum theory indicates that an understanding of those still unclarified features of atomic physics can only be acquired by foregoing visualization and objectification to an extent greater than that customary hitherto.

We have to remember that what we observe is not nature herself, but nature exposed to our method of questioning.

The existing scientific concepts cover always only a very limited part of reality, and the other part that has not yet been understood is infinite.

Whenever we proceed from the known into the unknown we may hope to understand, but we may have to learn at the same time a new meaning of the word "understanding."

Any concepts or words which have been formed in the past through the interplay between the world and ourselves are not really sharply defined with respect to their meaning: that is to say, we do not know exactly how far they will help us in finding our way in the world. We often know that they can be applied to a wide range of inner or outer experience, but we practically never know precisely the limits of their applicability. This is true even of the simplest and most general concepts like "existence" and "space and time". Therefore, it will never be possible by pure reason to arrive at some absolute truth.

The above are selected quotes from Werner Heisenberg, one of the founders of quantum mechanics. Cuddlyable3 (talk) 20:36, 15 May 2009 (UTC)

If you've managed to wrap your head around the above, here's another bummer: Have you noticed just how much "nothing" is involved in solid matter? It still amazes me how it all works together so well that you can actually have solid objects and people instead of just random particle soup :-)71.236.24.129 (talk) 22:11, 15 May 2009 (UTC)

That is because physical science is learning more and more about what turns out to be less and less. Cuddlyable3 (talk) 10:26, 16 May 2009 (UTC)

Well, i am not a professional in this, so correct me if i am wrong. Dauto had asked why i equate determinism with lack of free will. From what i understand, Free will is taking decisions ourselves, when we have a choice, even if it is obvious, it is we who will choose. Sometimes they maybe be obvious, sometimes they may not, like coming to a fork in the road and not knowing which way to go. But the fact remains that we make the decision. Now if everything is already predetermined, then it is already known, perhaps to god, what decision we would take, say the left road in the fork (see : i made a decision here ). So if god already knew it, i was just destined to type lift road here and not anything else... Spooky : since i was destined to choose the left road, did i really have a choice ? Did i really exercise my free will ? Or in other words, in a deterministic world, does free will exist ? This is something like not punishing a criminal because he was destined to commit the crime... he couldn't have done otherwise... Note that this problem wouldn't arise in an indeterministic situation  : If even GOD didn't know what choice i would take, then it was entirely upto my mind, and me, of my own free will, chose left. I may have made a mistake somewhere, if so please excuse me... Rkr1991 (talk) 04:35, 16 May 2009 (UTC)

In terms of the punishing criminals thing: If the criminal is predetermined to commit crime, society is predetermined to lock them away. If someone punched me in the face and said "Sorry, I have no free will", then I will just punch them back and say "Me neither". What it boils down to in the end is a question of fairness. Is it fair that a child gets abused and then grows up to be a criminal, and then locked away, etc. when if they had grown up in a caring family with adequate wealth they would be going on to earn good money in a good job and live outside of prison? That is just nature I guess. --Mark PEA (talk) 09:36, 16 May 2009 (UTC)

Determinism contra free will is a contradiction that is impossible to resolve by logic. However the consequence of each choice is not experienced until after the choice is made. The resulting subjective development may be surprise, guilt, pleasure. learning or something else. Whether you regard that as predetermined or not, you cannot know it in advance. Wondering about whether something unknown might matter prompted Donald Rumsfeld's dictum Now what is the message there? The message is that there are known "knowns." There are things we know that we know. There are known unknowns. That is to say there are things that we now know we don't know. But there are also unknown unknowns. There are things we do not know we don't know. So when we do the best we can and we pull all this information together, and we then say well that's basically what we see as the situation, that is really only the known knowns and the known unknowns. And each year, we discover a few more of those unknown unknowns.Cuddlyable3 (talk) 10:22, 16 May 2009 (UTC)

There is another theory about determinism that doesn't really involve god that no one has mentioned yet. If you look at everything at the quantum level then it's all random. There is no way to predict what an electron will do, and this has been going on since the big bang, and probably before that. So what if our "free will" is just the random playing out of quantum reactions? This theory includes not just our actions and choices but thoughts as well (even thoughts about god). Interesting, right?129.21.109.153 (talk) 19:13, 16 May 2009 (UTC)

Ya, i agree with the above answer. That does present an interesting possibility. In fact that is what i had in mind while asking this questionRkr1991 (talk) 06:02, 17 May 2009 (UTC)

I think watching (most of) these movies could help your quest somewhat. They'll make you think, but also will entertain (except Signs and Unbreakable which aren't so good, and Walkabout which I haven't seen. The Tarantino films don't answer much either... --Jackofclubs (talk) 20:06, 16 May 2009 (UTC)

Mark PEA's answer may explain why criminals are punished, but it still doesn't explain if there is free will or not, which is what the question is all about. Rkr1991 (talk) 06:03, 17 May 2009 (UTC)

I need your definition of free will. If it is absolutely free, it would imply that it is random, unpredictable and unconstrained. If this were the case, (nearly) every field of science with the prefix "neuro" and "psycho" would be obsolete. Studying the behaviour of people would be as about as productive as studying the behaviour of a (non-fixed) roulette wheel. I think practically everyone accepts that free will isn't "free", rather "constrained". What I'm proposing is that it is so constrained that there isn't any choice at all. I'm going to pose a quick (probably not well thought out) thought experiment:

In one condition of the experiment, you are in a room sat on a chair, wearing a blindfold and earmuffs, blocking your vision and hearing. You have also had local anaesthetic injected into your wrists 5 minutes prior to sitting, preventing pain (but not touch) from being received from your hands. You are asked to extend your hands out as far as you can, and they will touch some flat-feeling objects (you haven't seen these objects). What is your reaction after touching the objects? In the second condition, everything is the same to you, except this time no local anaesthetic is injected. When you extend your hands and touch the objects, you realise they are extremely hot (probably irons). What is your reaction?

The point of this thought experiment is to show you how your behaviour is completely controlled by the stimuli you receive, and there is no choice involved. I realise I'm going to be picked apart by many because this situation involves a reflex arc, but in my view it is just wishful thinking to believe that when a signal is calculated in certain areas of the brain (composed of neurons) "free will" is involved as opposed to other areas of the brain or other areas of the central nervous system (both also composed of neurons). What is so different about the neurons in the brain stem (heart rate/etc.)/hypothalamus (hunger/sleep/etc.) compared to those in the prefrontal cortex (personality)? If you believe in some sort of spirit, how does a lobotomy change this spirit? If you believe in a spirit or some quantum indeterminacy hypothesis for free will, how do psychoactive drugs change this free will? As I mentioned earlier (with refs), how does having the short allele of the 5-HTTLPR make one's free will more susceptible to neuropsychiatric disorders? Am I just being a blind confirmistic determinist? Because I can't see how all these changes in molecular chemistry are just very large coincidences and that subatomic indeterminism is the actual cause (not including lobotomy, which doesn't affect subatomic hypotheses for free will, only spiritual).

On another note, an interesting study involving conscious intention was published in Science just over a week ago [2] (and discussed on NewScientist [3]). I fully recommend getting the entire article (your school/college should have access to Science, IMO anyway). I can't really sum it all up, but basically, stimulation of one area of the brain caused movement of a limb that the participant was completely unaware of, where as stimulation of another area of the brain in small amplitude caused an urge to move a limb/lips/etc, and higher amplitude stimulation caused the participants to believe they had actually moved a limb/talked/etc, when they hadn't. This implies that one area of the brain is involved in conscious intention, and if activity is high enough, believes that those intentions were carried out, and these areas of the brain are actually naturally innervated by subconscious areas of the brain which cause the movement to occur. But when stimulated individually artificially, there is some mis-innervation which - depending on the area of the brain - either causes the conscious perception of having done something but actually not done it, or the actual doing something but no conscious perception of it. Sorry that isn't eloquently put, but I can't copy and paste the conclusions of the article due to copyright reasons.

I've just seen that in the same issue there was another piece of research about rhesus monkeys' decision making based upon their confidence in the correctness of that decision (which was also due to neurons in the parietal cortex - [4]), I've only read the abstract though so I'll post on here if there is anything very relevant to this discussion after I've read the full article. --Mark PEA (talk) 14:42, 17 May 2009 (UTC)

Left/right and relativity

Does the left and right side undermine the relativity theory in a sense that there is an absolute benchmark - the possessor of these extremities? If the arms for example are considered left and right from the benchmark of one's own body, does it turn non-relativist, absolute? 91.135.250.34 (talk) 13:44, 15 May 2009 (UTC)

I don't think your understanding of relativity is quite correct. In general relativity, there is still a coordinate system, which means that relative positions can and do exist. The difference in relative position (how far apart your arms are) depends on who is observing and how fast they are moving and accelerating. But, under no circumstances would they "flip sides", because they are separated by a space-like interval. Maybe you heard some discussion about chirality and mixed up some terminology? Nimur (talk) 14:01, 15 May 2009 (UTC)

Identify this military equipment

Can anyone identify this thing? This image was posted on DefenseLink with the caption,

“ 05/12/2009 - LAND SCAN - U.S. Army Pfc. David Mitchell scans the landscape surrounding Vehicle Patrol Base Badel at the mouth of the Narang Valley in Konar province, Afghanistan, May 9, 2009. Mitchell is assigned to the 1st Battalion, 32nd Infantry Battalion. The base has closed down enemy activity in the valley and in Narang, Chowkay and Nurgal districts. U.S. Army photo by Sgt. Amber Robinson. ”

I'd like to put this image in Wikipedia on the appropriate article, but I'm not sure what it is. (Maybe a reflecting telescope?) Nimur (talk) 13:45, 15 May 2009 (UTC)

I think it's more likely a BGM-71 TOW launcher along with associated aiming mechanism. See this HMMWV-based launcher for comparison. — Lomn 14:04, 15 May 2009 (UTC)

There is a "71" on the tube, so I'd call that a solid ID. Further research indicates it's probably the M220 variant of the BGM-71. Nimur (talk) 14:18, 15 May 2009 (UTC)

Since you mention checking markings on the tube, the stenciling below the eyepiece suggests it's the TOW 2B top-down attack warhead, so the BGM-71F designation looks like the most specific for the missile itself. — Lomn 15:13, 15 May 2009 (UTC)

calculation

although the title suggests a mathematical problem, it's acutally chemistry

what is the molecular mass of a substance each molecule of which contains 9 atoms of carbon, 13 atoms of hydrogen and 2.33 * 10^-23 grams of other component?

that's 108 grams of carbon and 13 grams of hydrogen. and adding them up, i get 121 grams. but how am i gonna add 2.33 * 10^-23 grams?????!!! —Preceding unsigned comment added by 122.50.132.126 (talk) 13:51, 15 May 2009 (UTC)

Well, you have made a silly mistake... See, an atom of carbon doesn't weigh 1 gram. 1 mole, or 6.023X10^23 atoms weigh 12 grams. Now i think you'll do the problem...Rkr1991 (talk) 13:55, 15 May 2009 (UTC)

I expect you want the molecular mass in Daltons or "atomic mass units", not grammes. So its 108 Da from carbon and 13 Da from hydrogen. Grammes is related to Da through Avagadro's constant, so you don't need to know what element it is, nor do anything with moles in this case.YobMod 13:56, 15 May 2009 (UTC)

Biomass

Which mammal species has the largest mass (number of individuals x average weight) on earth? Is it people? 65.121.141.34 (talk) 14:11, 15 May 2009 (UTC)

A table at Biomass (ecology) says cattle outweigh humans, for one thing. Tempshill (talk) 15:38, 15 May 2009 (UTC)

Very helpful, thanks. 65.121.141.34 (talk) 16:08, 15 May 2009 (UTC)

At one extreme, you might think of the largest animals on earth - the Blue Whale. At 172,000kg each - and with only 12,000 of them left - they total about 2 billion kg. There are about 7 billion humans and at perhaps 80kg each, we reach about 560 billion kg. Even before we started on the mass extinction of the blue whales, there were only about 300,000 of them - so 53 billion kg is the best they ever managed. So perhaps we should be looking at things that are tiny but much more numerous than us. It is estimated that there are 1,000,000,000,000,000 ants in the world - but at 0.003 grams each - that only gets us up to 3 billion kg...more than the blue whales - but nowhere near as much as all the whale species taken together (and I did cheat and take all of the ant species together). So if anything is going to beat out humans, it's got to be something in the middle range - much more numerous than whales but much bigger than ants. And that's why cattle win. SteveBaker (talk) 17:23, 15 May 2009 (UTC)

Minor detail - last time I checked, ants didn't feed their young on milk... --Tango (talk) 17:41, 15 May 2009 (UTC)

I read in The Book of General Ignorance that if you take a field of cows and weigh all the worms in the field, the worms will outweigh the cows considerably. 90.193.232.41 (talk) 17:45, 15 May 2009 (UTC)

Our article Earthworm says "Darwin estimated that arable land contains up to 53,000 worms per acre (13/m²), but more recent research from Rothamsted Experimental Station has produced figures suggesting that even poor soil may support 250,000/acre (62/m²), whilst rich fertile farmland may have up to 1,750,000/acre (432/m²), meaning that the weight of earthworms beneath the farmer's soil could be greater than that of his livestock upon its surface." - but a lot of cattle are not kept on rich, fertile farmland. Here in the western world, they are mostly cooped up in gigantic factories - and out in the 3rd world, they are on barely-grazeable wasteland. In either case, the number of worms will be dramatically lower. Weighing in at perhaps a gram or two each, 1.7 million of them might constitute 2 or 3 metric tons of biomass. A cow weighs around 800kg - so if there are less than 3 or 4 cows to the acre then maybe this claim is true. Worldwide - there are about 1.7 billon cattle - each one weighs about 10 times more than a human - so even though there are around 7 billion of us - the cattle win the biomass contest by a factor of two. The worms though...well, if we go with the 250,000 to the acre for 'poor soil' and 4x10¹⁰ acres of 'arable' land in the world - then we have 10¹⁶ worms - which (at 1 to 2 grams each) is 1 to 2 x 10¹³ kg. Which beats out the weight of cattle at 1x10¹²...by a factor of 10.

So I don't know - worms or cows? Sadly, our OP asked about SPECIES - and while there is only really one species of domesticated cattle (they can all interbreed AFAIK) - there are dozens and dozens (or maybe hundreds) of species of earthworm. So while the total weight of all worms beats out the cattle - I think the cattle still win on a species-by-species contest.

SteveBaker (talk) 18:18, 15 May 2009 (UTC)

Well that and worms are not mammals. Otherwise some termite species would probably be a major possibility 65.121.141.34 (talk) 18:40, 15 May 2009 (UTC)

So small mammals perhaps? Are there any estimates of the world population of rats, or mice? 65.121.141.34 (talk) 18:07, 15 May 2009 (UTC)

Hmmm - good point. Well, rats weigh about half a kilo - so for every cow, you'd need to have more than 1600 rats...about three trillion of them world-wide...but again, to meet the OP's requirements, they have to be all of one species - and there are about 50 species of rat...so while I can't find a number for their population size - I'd be surprised if they won. http://www.snopes.com/critters/wild/rats.asp says that there are far fewer than one rat per person in the UK - and about one per 36 people in even the most rat-infested cities. Since we're looking for more like 500 rats per person...all of one species - it seems very unlikely. Mice, even less likely still because they are so much lighter. SteveBaker (talk) 18:29, 15 May 2009 (UTC)

If you want to be picky you'd have to sort out what cells are actually "human" or "cow" and what are independent organisms. I lost the figures in my files, but a significant portion of you walking around are actually bacteria, fungi and other separate entities. It may even out in the end, though, because you'd have to do that for all the qualifying mammals. 71.236.24.129 (talk) 22:31, 15 May 2009 (UTC)

That's a point worth considering. I remember a statistic that only 10% of the cells in a typical human body are human, although I'm not sure how reliable that is and I'm not it would be as drastic if you considered it by mass rather than by number of cells. If I had to guess, though, I'd say all mammals will have roughly the same proportion, so it shouldn't matter. --Tango (talk) 23:49, 15 May 2009 (UTC)

Rabbits breed like, well, rabbits - they're mammals and they're can be found pretty widely across the globe. Contender perhaps? ny156uk (talk) 23:15, 15 May 2009 (UTC)

Or Sheep? From the article it suggest the global sheep stock is 1.059.8bn. If we say 45kg (again from the article as low point for Ewes) that would be well about 45bn kg... oh well - don't you just hate it when you realise what you've gone and estimated ends up proving yourself 'wrong'? Seems that Sheep ain't nearly enough to compare with the human estimates noted above :-( ny156uk (talk) 23:21, 15 May 2009 (UTC)

http://faostat.fao.org/site/339/default.aspx might be worth a look around. Sorry should have done all this as one answer rather than the 3 half-assed answers! ny156uk (talk) 23:23, 15 May 2009 (UTC)

EARTH

Is Earth definitely symmetrical about the axis passing through through the Northern and southern most points??? Or Is it deformed ??? —Preceding unsigned comment added by 59.165.84.9 (talk) 15:21, 15 May 2009 (UTC)

Shape of the Earth. This article is a bit technical, but it's easy to answer your own question when you think about this question: how many Mount Everests are there?-RunningOnBrains 15:56, 15 May 2009 (UTC)

See also Land hemisphere. —Tamfang (talk) 05:32, 16 May 2009 (UTC)

It is very close to be symmetrical about that axis, but not perfectly so (due to oceans, continents, hills, valleys, etc.). Around other axes, there isn't rotational symmetry because of an equatorial bulge caused by the rotation. --Tango (talk) 17:38, 15 May 2009 (UTC)

I was surprised to read about the following asymmetry today: if and when the West Antarctic Ice Sheet melts into the ocean, it will have a more pronounced sea-level-rise effect on the northern hemisphere because it's so massive that water is bunched up near it due to its own gravitational pull! [5] --Sean 18:05, 15 May 2009 (UTC)

Actually, it's pretty darned close to spherical. There was a discussion last week or so (too lazy to dig it out of the archives myself) which brought up the fact that the variations in heights on the earth surface are smaller than the tolerances allowed for regulation billiard balls, and the "equatorial bulge" which makes the earth's equatorial diameter larger than its axial diameter is also smaller than allowable variations in regulation billiard balls. Basically, the earth is actually smoother and rounder than a billiard ball. The variations look huge when placed on human scales, but when looking at the earth as a whole, they are quite tiny. Take Everest for example. It is 8.848 kilometers tall. The earth is about 6,371 km in diameter. Thus, the biggest bump on the earth represents 0.139% variation from the mean diameter. I would call that pretty darned smooth. Also, the variation between the polar and equatorial diameters is 21.3 kilometers, or 0.334% variation of the mean diameter. Again, pretty darned close to spherical. --Jayron32.talk.contribs 01:09, 16 May 2009 (UTC)

That's Quite Interesting! And I was thinking it all went pear-shaped about 6 billion years ago.--80.3.133.3 (talk) 08:25, 16 May 2009 (UTC)

I may be missing a joke here, but the Earth is only about 4.5 billion years old. --Tango (talk) 16:47, 16 May 2009 (UTC)

Our UK brethern use Pear-shaped to mean "gone awry." -Arch dude (talk) 02:32, 17 May 2009 (UTC)

What would our friends across the water say, then? 'All gone eggplant shaped'?--KageTora - (영호 (影虎)) (talk) 04:43, 17 May 2009 (UTC)

I am British, so I got that part. It was the 6 billion years part I couldn't understand. --Tango (talk) 14:31, 17 May 2009 (UTC)

units

i'm very confused about this question, not only about the procedure but about the units also.

if the velocity of light is taken as the unit of velocity and an year is taken as the unit of time, what's the unit of length? what's it called?

should i do: length = velocity of light * 1 year

and then subsitute them with their values in m/s and days, or something else....

please help me

thanx —Preceding unsigned comment added by 122.50.132.126 (talk) 15:40, 15 May 2009 (UTC)

Take a look the article Light-year and come back if you have additional questions. --Zerozal (talk) 15:57, 15 May 2009 (UTC)

... and for extra credit, ask your teacher whether their "year" is a Julian year, a sidereal year or a tropical year (but only once you understand the difference between those terms yourself). Gandalf61 (talk) 16:05, 15 May 2009 (UTC)

Dimensional analysis and the related factor-label method are concepts which are important to be familiar with (at least for science-inclined types). -- 128.104.112.117 (talk) 16:09, 15 May 2009 (UTC)