Wikipedia:Reference desk/Archives/Science/2009 February 3

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February 3

Front and back

There is a form of Antipredator adaptation where the front end of an animal looks the same as it's back. What is this called? (... and do we have a page?) 76.97.245.5 (talk) 00:18, 3 February 2009 (UTC)

The Rubber Boa when threatened hides its real head under the rest of its body and uses its fat stumpy tail as a decoy to lure predators into attacking its back end rather than the front. Its apparently convincing judging by individuals observed with quite a number of scars on the tail. I don't know if this type of mimicry has a particular name. 152.16.15.23 (talk) 01:03, 3 February 2009 (UTC)

Then there's the creepy earwig. StuRat (talk) 15:04, 3 February 2009 (UTC)

Just found the name for it: Automimicry 152.16.15.23 (talk) 01:33, 3 February 2009 (UTC)

Thanks a million.--76.97.245.5 (talk) 01:46, 3 February 2009 (UTC)

Breeding budgies and cockatiels

Is it possible to work out what the baby birds will look like, just by looking at the colour and markings of the parents and not knowing anything about their genetics or pedigree? The Budgerigar colour genetics and Cockatiel colour genetics articles don't really answer my question and use wording that I don't really understand. --84.68.231.212 (talk) 00:44, 3 February 2009 (UTC)

To help with understanding the wording, I would start by looking at Dominance (genetics) and dominance relation. If you can look at your birds and determine their phenotype you can hazard a guess at their genotype and do a Punnett square to determine what patterns of genes the offspring will receive. Once you know the genes the offspring have, you can hazard a guess at what phenotype they will have. You probably will not be able to determine appearence absolutely as there are many genetic factors which interact with one another (see Variable Expressivity and Penetrance) and some aspects of appearence are determined randomly. It may help if you can describe what varieties of birds you have: i.e are they an albino variety? Have a look at the list of common names for Budgerigar varieties and that mess of description in Cockatiel colour genetics. 152.16.15.23 (talk) 01:29, 3 February 2009 (UTC)

btw (sorry, don't have an answer - I never breed my birds for colour), those '...colour genetics' articles (which I've been minimally involved with) could probably do with a good cleanup and some rewriting from a more general perspective. Hint, hint... ;) --Kurt Shaped Box (talk) 02:51, 3 February 2009 (UTC)

Antidepressent

Medical question removed SteveBaker (talk) 02:26, 3 February 2009 (UTC)

I'm not sure that this question:

"This section says that semen has antidepressant properties. What would be the effects of injecting semen intravenously? Would shooting up semen (that's a horrible pun :) ) give you a better mood? flaminglawyer 01:10, 3 February 2009 (UTC) "

-constitutes a request for medical advice. The Flaming Lawyer is simply posing a hypothetical question (as lawyers do).

The answer, by the way, is that you'd most likely die suddenly from the semen embolism lodging in your cerebral arteries (causing a stroke) or coronary arteries (causing a myocardial infarction). So don't do it!

The Semen article does mention the putative antidepressant qualities of semen, based largely on an article published in New Scientist, in which the authors claim that women engaging in unprotected penile-vaginal intercourse scored better on depression scales than women who used condoms. It doesn't seem terribly responsible to promote unprotected sex, when at best their results indicate only an association, and not causation. The article speculates about the antdepressent effect of orally and anally administered semen, but has no supportive data. That's why the WP article uses the phrase "may have antidepressent qualities".

Stay safe! Mattopaedia (talk) 06:33, 3 February 2009 (UTC)

On further thought, it could also be very much like an amniotic fluid embolism. Still another reason to heed my previous advice - don't do it! Mattopaedia (talk) 13:05, 3 February 2009 (UTC)

Perhaps depressed women insist on condom use because they are depressed - they fear an undesired outcome and that is related to being depressed. If this is true, condom use is an effect, not a cause. —Preceding unsigned comment added by 98.17.34.148 (talk) 17:19, 3 February 2009 (UTC)

Or perhaps, despite the best efforts of condom manufacturers, unprotected sex is just more enjoyable. --Tango (talk) 19:50, 3 February 2009 (UTC)

The authors claimed to have eliminated potential sources of bias from their study design, but, as can be seen from these two responses, that would be essentially impossible in this case. There's innumerable potential associations and confounding factors. I suspect the study lacks sufficient scientific merit to be published in a peer-reviewed journal. The other problem is that claims of this nature seem to prompt people to make socially irresponsible comments that might encourage impressionable youths to engage in unsafe sexual practices. I don't think unwanted pregnancies and sexually transmitted diseases are particularly enjoyable, or have any antidepressant qualities. Mattopaedia (talk) 03:08, 4 February 2009 (UTC)

It has been suggested that chronically depressed women insist on the use of a condom during intercourse because of their greater fear of undesired consequences. This leads to the question of whether car drivers (men and women) who have depression syndrome take more care in driving than other persons do. Statistics on injuries to drivers in car accidents would be a source of information on this. Furthermore, do persons with depression syndrome take more care to avoid accidents of all types than other people do? Hospital statistics on patients hospitalized by accidents would be a source of information. If happy people are more accident prone, can it be said that, to some degree, they are happy-go-lucky? —Preceding unsigned comment added by 98.17.34.148 (talk) 10:21, 4 February 2009 (UTC)

If happy people are more accident prone, maybe they should be called happy-go-unlucky. —Preceding unsigned comment added by 98.17.34.148 (talk) 13:56, 4 February 2009 (UTC)

Brain wave crosstalk

Is it theoretically possible for one person's brain waves to spill over into another nearby person's brain and affect its functioning? NeonMerlin 02:15, 3 February 2009 (UTC)

No. The signal strength is VASTLY too small - and there is nothing in our heads that is even remotely like an antenna. SteveBaker (talk) 02:25, 3 February 2009 (UTC)

(after ec): Given the frequency range of the brain waves is roughly 1 - 100 Hz, most people think it is not possible. Many household and industrial appliances of the last 100+ years produce or used to produce much stronger electromagnetic emissions in that range than your neighbor's brain ever will. Still, there are no reports I am aware of that link any of these appliances to any systematic disruption or alteration of the thought process. --Dr Dima (talk) 02:32, 3 February 2009 (UTC)

Theoretically, could brain waves be transferred over a wired connection between two brains, as a matter of interest? --Kurt Shaped Box (talk) 02:36, 3 February 2009 (UTC)

Yes. You can use electrodes of appropriate types to inject any current(s) into any area(s) of the brain, provided your experiment conforms with the ethics requirements. You can therefore record a signal from one brain, amplify it, filter it, and inject it into another brain. That process will, most likely, not transfer any thoughts or qualia, though. For example, simply injecting current into a primary visual cortex location may produce a percept of a phosphene (small flash of light) at the corresponding retinotopic location; but not much more. Injecting a more complicated waveform is likely to have the same result, as the brain activity of the "donor" and "recipient" is neither coherent nor even necessarily similar. So a USB port on someone's forehead is still quite a few years away :) . On a somewhat related subject, you can also look at the deep brain stimulation article. --Dr Dima (talk) 03:08, 3 February 2009 (UTC)

Look there are (literally) a trillion neurons in your head. Maybe 10% of them are firing at the same time. That makes about a hundred billion teeny-tiny electrical signals...the total 'transmission' would be like all of the cellphone calls from the whole of planet earth all mixed up together...times about a thousand! If you don't have a trillion wires - you can't carry all of the information. But worse still (MUCH WORSE STILL) the arrangements of the memories and neural connections in my brain are TOTALLY different from yours. It's not a matter of connecting neuron A in my brain to Neuron A in yours, then B to B, C to C. My thoughts relate to my memories in ways that totally don't translate to those in your brain. So this isn't gonna work...and it's technically ridiculous. SteveBaker (talk) 03:23, 3 February 2009 (UTC)

Heidi (my wife) often knows what I'm thinking :) -hydnjo talk 04:03, 3 February 2009 (UTC)

'::::::Please explain "qualia." Edison (talk) 05:37, 3 February 2009 (UTC)

Women's Intuition, man's terra incognita.--Lenticel ^(talk) 05:39, 3 February 2009 (UTC)

Qualia. Richard Avery (talk) 08:34, 3 February 2009 (UTC)

Although "brainwaves" don't spread person to person, emotions can. Recent research in social networks has shown that happiness, sadness, and even obesity and smoking spread through social networks. --Shaggorama (talk) 08:57, 6 February 2009 (UTC)

There isn't a lot of reliable evidence for this, but there have been reported instances where a person's brain waves caused nearby objects in a room to fly all over the place, and a report of telephone interference. There was also an experiment where a robotic arm moves coloured balls into a container with random movements, and with the presence of a person, the robot was able to move the balls into the container in as little as two movements. Yawning is contaigous. ~AH1^(TCU) 17:37, 7 February 2009 (UTC)

Islam ... previous article

Removed Welcome to the Wikipedia Reference Desk. This is a place for people to ask questions that they are having trouble finding the answers for themselves. It is not a chat board or discussion site. There are many forums you can visit if you would like to expound your views on religion; this is not one of them. Thank you. 79.66.57.25 (talk) 08:20, 3 February 2009 (UTC)

Well, it's certainly great to see such an unbiased search for knowledge! Can we have the soap box back when you're done?

Anyway, I'll play along: if you think that people 1400 years ago didn't know that an embryo turned into a fetus, and so forth, you're wrong. (Furthermore, a fetus doesn't first grow bones and then cover them with flesh, so if that's what Mohammed thought, he was wrong.)

Likewise, the idea that you can only feel if you have your skin is wrong. (In fact, that's so obviously wrong that it boggles the mind. Haven't you ever heard of a toothache, for example?) If you mean that you can only experience a touch through skin, that's also wrong -- although it's certainly true that there may be no sensation in burned skin, the human somatosensory system also works in muscles and even bones. It's just that we aren't usually aware of such sensations. (What, you think they didn't have third degree burns 1400 years ago?)

As for what it would take to convince me that God exists, hey, I'm easy. A miracle will do just fine. It doesn't have to be a big miracle, either, it just needs to be unambiguous. He could use his awesome power to levitate me for a moment. Or he could appear to me and tell me to get with the program. Or he could turn someone I know and love into a pillar of salt, give me a dose of that Old Testament tough love. Trust me, I'll convert in a flash. I'd probably end up being a real zealous bastard, too. -- Captain Disdain (talk) 08:43, 3 February 2009 (UTC)

If God's going to turn people into pillars of salt, make sure he turns a few into pillars of pepper, for those of us who need to avoid salt in our diets. :-) StuRat (talk) 14:57, 3 February 2009 (UTC)

Trolling... —Preceding unsigned comment added by 129.67.37.225 (talk) 14:00, 3 February 2009 (UTC)

The OP sounded to me like someone who is genuinely ignorant of basic anatomy rather than a troll, though yes this is a reference desk for asking questions rather than just pushing ones opinion. Dmcq (talk) 15:31, 3 February 2009 (UTC)

Anyone who tries to push such opinions on this Reference Desk typically gets their arguments ripped to tiny little shreds under the withering force of actual science...I don't know what they think they might achieve by doing that - but for sure it ain't gonna make any converts. Quite the opposite in fact! SteveBaker (talk) 16:34, 3 February 2009 (UTC)

Even if you were made to levitate or to turn into a pillar of salt, you couldn't even rule out the possibility of it being an advanced alien species fucking with your brainBastard Soap (talk) 17:34, 3 February 2009 (UTC)

Well I'm willing to give the OP the benefit of the doubt and concede that God is a possible cause if I see someone transformed into a pillar of salt. Can't say I'd be particularly worried if it is god or an advanced alien species. Would it make much difference? Dmcq (talk) 18:22, 3 February 2009 (UTC)

I agree, there is little difference between a god and a super powerful alien that can turn people into salt (a feat that would require a Level 3 god, by Steve's classification). Seeing someone turn a person to salt wouldn't make me believe they had created the universe (although I would certainly listen to what they had to say on the subject). --Tango (talk) 19:10, 3 February 2009 (UTC)

Yes I'd certainly be willing to listen to them. As in what do you call a 200Kg gorilla with a machine gun?. (answer) Dmcq (talk) 20:36, 3 February 2009 (UTC)

Yes - transmutation of atoms (which I guess is what's required to turn someone into a pillar of salt) is a pretty impressive trick - but it's not proof of god-hood. We can do limited, small scale transmutation ourselves...so it's only just barely a "level 3" kind of a trick. Given the probabilities of each I'd definitely wield my mighty "+2 Razor of Occam" and go with "high tech alien" or perhaps even "Area 51 human". I'm not believing in any god who is unable to convince me that they can change the value of PI at will...although if they plan to actually DO that - would they please pick another universe to do it in! I don't really want to suffer the consequences of circles not joining up properly anymore! SteveBaker (talk) 20:42, 3 February 2009 (UTC)

The boundary between level 3 and 4 is highly subjective. Level 4 can be thought of as a variable level that increases as you learn about the universe, and approaches level 3. A level 3 god could certainly do it (there's nothing in the laws of physics to forbid rearranging protons, neutrons and electrons into a new pattern), very advanced level 4 gods probably could too. Creating a universe is a rather difficult feat to place - level 3 gods might be able to do it if you don't mind it being identical to the one they started in (barring initial conditions), however they wouldn't be able to observe the new universe in any way (it would probably look like a black hole to them, at least according to one multiverse theory). A level 2 god could observe it (and make it slightly different, too) by fiddling around with the speed of light in order to travel between universes. So, I think a god on a par with the Abrahamic god would need to be at least level 2. Heaven and Hell might require some level 1 stuff, though. I'd be happy if a god could prove themselves at least level 2, I think asking for level 0 is a bit much (primarily because thinking about them gives me a headache). Of course, power itself does not make one worthy of worship (a god that murders people for harmless curiosity doesn't sound worth worshipping to me...). --Tango (talk) 22:28, 3 February 2009 (UTC)

Quite interesting this Steve's classification! So level 0 corresponds to the top: still I don't understand why your classification doesn't leave a chance for further more powerful levels. Since there is no limit to the human imagination, I think that an open scale system should be more suitable (e.g. something likethis! ). Notice that the Cathar heresy exactly stated that the standard God (the old testament one) was not the top level (and was also quite a bad guy too), and that there was another God above! pma (talk) 23:18, 3 February 2009 (UTC)

I actually did agonize over that. Firstly, I'm a computer geek and counting from zero is "What We Do". It's really tough to conceive of something more powerful than changing mathematical truths (I certainly can't think of something more amazing than that). The idea that "there is no limit to human imagination" is something the Disney corporation would like to tell you...but actually, I think there are almost certainly limits - and I hit mine at "Level zero". It's tough to even imagine how much power level 0 would give you...let alone imagine something significantly more powerful than even that. I decided that if you could think of such a thing, you'd still be free to use negative numbers. I specifically didn't want to anthropomorphise the system too much by placing the zero point at where we are and then counting upwards towards the 'changer of mathematical truth'. My dog finds my ability to be able to make food appear as if by magic from a can to be godlike - so it's not unreasonable to need to talk about level 5, 6 and 7 abilities. As to the marginal difference between level 4 and 3 - I wanted a level corresponding to about where our science is - and a higher level representing the "Any sufficiently advanced technology is indistinguishable from magic" idea - hence I decided to separate 3 and 4 (it also fitted what I wanted to explain in that Ref Desk answer). I suppose you could say "Level 4 amazes SOME humans", "Level 3 amazes ALL humans". At level 4, you can influence people's thoughts - have telepathy - it's a REALLY powerful thing...fundamentally more than we can currently do...but certainly not more than we could imagine. Well, whatever, it's just a silly idea that enabled me to more easily explain a point - if you don't like it, feel free to make up your own scale! Let's not get too anal about it! SteveBaker (talk) 02:08, 4 February 2009 (UTC)

Mm. I was, of course, saying that these things would be enough to convince me. (Accompanied by a clear message that this was caused by God, of course; otherwise I could mistake it for any number of other things I haven't previously believed in.) I mean, if my ass were to be lifted off this seat right now by some kind of an invisible and impossible force, and a big, booming, and downright divine voice told me that this is the miracle, now get with the goddamn program, that'd probably convince me of God's existence. (That said, I did use the word "unambiguous" in there, so it'd have to be pretty clear-cut -- a picture of Jesus in my oatmeal wouldn't do it.) I'm sure I could come up with other scenarios, such as aliens, or delusions, or whatever, but once you go far enough with that, I might as well start wondering if I'm just a butterfly who's dreaming that he's a man, you know? No, I'd probably just go with it, at least as a strong working assumption.

It probably wouldn't make me like God, though. I mean, I'm fine with horrible things happening because that's just the way things are in our chaotic universe, but if there's a guy out there who could do something about it, but can't be bothered, and yet demands worship, that doesn't strike me as someone I'd love and respect. But I'd probably believe that he exists. -- Captain Disdain (talk) 01:19, 4 February 2009 (UTC)

That bothers me too. After I sat down and actually read the Bible from cover to cover (mostly to see what the big fuss was all about) - I got the clear impression that this God was an evil bastard. No consistancy - a vicious streak a mile wide - certainly not "fair" or "moral" by our modern standards. If he existed....sheesh...that doesn't bear thinking about. I certainly wouldn't feel like worshiping him - but on the other hand a literal infinity of the worst kind of pain and torment is a lot to bear for a point of view. But I don't think I could ever honestly like him - and for sure he's gonna know that. So what's the point in bothering? I guess that proof of the existence of the christian god would be a really bad-news kind of a day! SteveBaker (talk) 02:13, 4 February 2009 (UTC)

Which reminds me of this review of Alexander Waugh's book "God: A Biography" - "Alexander Waugh relates the following story in his book, God – The Biography. Randolph Churchill, son of Winston, had been annoying his friends by talking too much. They wagered he could not keep quiet for a week. Churchill, a keen gambler, thought he could win the bet by reading the Bible. But he didn't last long. After a few pages, he was heard to exclaim, "God! God's a shit!" If you read Waugh's book, then you will draw the same conclusion. For God is vindictive, blood-thirsty and, quite clearly, as mad as a hatter." DuncanHill (talk) 02:31, 4 February 2009 (UTC)

Personally, I've always thought the wonderful little bet God has with Satan about whether Job really is faithful to God illustrates the point beautifully. Now, Job was a big shot. He had seven sons and three daughters, and he had thousands of lambs, camels, and other animals, as well as a plethora of servants. He was like the Donald Trump of his age, except, you know, he's a nice guy, and full of faith. Probably made do without a comb-over, too.

So, Satan shows up one day after walking the Earth, and God essentially starts to brag about how loyal and righteous Job is. Satan scoffs at this; his argument is that it's no great feat for Job to love God, because God protects him from harm. To Satan, Job is like a guy who makes a big deal out of not being a racist when he lives in a white gated community and doesn't even know a single black person. God isn't having any of this, of course; He insists that Satan is full of crap, Job loves Him because Job is thoroughly righteous, no matter what. To prove His point, God withdraws His protection from Job so Satan can see if he can crack Job.

And Satan doesn't mess around, given this opportunity. He goes to town on poor Job's ass. His kids? Dead. His cattle? Dead. His servants? Dead. Job gets horribly and disgustingly sick, but he doesn't die, because that's where God draws the line -- after all, if Job dies, he can't settle the bet. Job wails and rips his clothes and is generally miserable, as anyone would be. Some of his friends try to talk some sense into him and suggest that he must've done something to piss off God, but while Job is sad that his life is utter shit, and he wishes he could die, he still insists that his friends are nuts; God is an awesome dude and He doesn't need to explain Himself to anyone. In fact, Job gets mad at his friends for messing with his head, and hopes that God does something soon before his buddies manage to convince him -- which, to me, sounds like Job knows reason when he hears it, but denial, well... it's not just a river in Egypt. This all goes on for a good while, even by the Bible's standards. Basically, Job keeps saying "shut up, I'm righteous, God giveth, God taketh away, I really, really hate my life and everything in it, but that's how it has to be if God lets it happen, you guys don't know what you're talking about, I sure hope God lets me make my case to him soon, shut up already."

Finally, God, who has been listening to Job's incessant whining and gotten sick of it, makes an appearance and basically tells Job that he should just shut the hell up and take it like a man, because He made everything and Job wasn't even there then, so who's Job to talk back? He flexes His awesome muscles and Job is humbled (presumably, he wasn't quite humble enough yet, since he dared to point out that all this wasn't a lot of fun). Job quickly says that God is right, yea, verily the Lord is awesome beyond belief and if Job spoke out of turn, he's awfully sorry. So God is happy to hear this, and then turns to Job's friends and gives them stern talking-to for all their sass, but He lets them off easy, because they're Job's buddies and presumably at this point even God's kind of aware that He's gone overboard and He should wrap it up. I know how He feels. Bear with me, I'm almost done.

So, to make up for all this horrible insanity He has inflicted on Job (or, technically, let Satan inflict, but the difference strikes me as insignificant), and also to reward Job for letting God win His little bet with Satan, God gives Job twice the cattle he had before, and even new sons and daughters, and Job lives to be a 140 years old and see a whole bunch of grandchildren.

Which kind of makes for a nice ending, I guess, but somehow I'm not seeing the part where this makes up for, oh, the murder of Job's offspring and the servants. And yet somehow the moral of the story is supposed to be that Job was a pretty smart guy to stick with God, and look how well off he ended up, and that's how we should all go about our business. The part about God being a complete rageaholic bastard about the whole thing isn't something people generally remark on, and yet it strikes me as the key element in the entire story. -- Captain Disdain (talk) 03:53, 4 February 2009 (UTC)

people as comunities need rules,regulations,because different cultures do see things from anthor aspects ... where hitting women considered to be barbarian act some where ... some where else its acceptable ... what do look like wrong for you its the most right for me ... so whats wrong and whats right ... what is the basic scale were i can judge actions . thats the idea of god ... humans is on the earth for ever and they never agree ... war never stops ... people kill each other for money ... for oil ... what seems to you as war for freedom in iraq ... to me its occupation .

so ... to belive in god is to admit his right to guide you throug your live ... to give you away of live ... some rules and regulation for you to follow ...

then ... the big question is ... if there is agod how should he prove his existence to you ... what is the ultimate proof to you ... will ... god wont do a miracle for each one of us ... so that he chose to send prophet , maybe its to hard to belive , but it could be the truth ... iam not trying to convert any body ... iam just looking for the truth just like you ...i hope some day i will see the naked truth just in front of my eyes .. thank you for helping ...?? —Preceding unsigned comment added by 79.173.236.134 (talk) 12:13, 4 February 2009 (UTC)

That's a common argument - but it doesn't hold true when you hold it up to the light of scientific enquiry.

Your hypothesis is that we need a god because we need limits on our behavior. OK - an experiment to determine whether that was true would be to look and see if our jails are full of atheists and if there were very few religious adherents who wind up doing terrible things.

But just look at how many people who claim religious devotion are in jail (or worse) - and look at how many atheists live good, "moral" lives obeying the laws of the land and standards of common moral decency. I don't have the numbers - but it's pretty clear that if this is what religion is "for" - it's largely ineffective in that goal. So I declare your hypothesis to be a false one.

Let's pick an atheist at random...me for example. I have never been to jail in my life - the only laws I've ever knowingly broken have been that I habitually drive faster than the speed limit (hardly a moral issue - and one that none of the great holy texts have much to say about!)...but yet I'm a hard-core atheist. For me, god or gods are PRECISELY as believable as Santa Clause and the Tooth Fairy - yet I believe that I live a good and moral life. I believe that following the laws of the country I'm living in is important...and there are other 'moral' standards that I believe we should all follow in order to make life pleasant and interesting. So I help little old ladies across the street - I give money to charity (not religious ones) - and I do good works (like answering questions for curious people on this reference desk) - I don't pirate video games or music. Next week I'm giving a pro-bono lecture to students at UT Austin on color theory. Not because I'm being paid for it (I'm not) - but because I believe we need to help our kids to know more. I do this without any concern that if I don't, I won't spend eternity with 47 virgins - or on some fluffy cloud with Angels playing annoying harp music at me ("Hey God - could you get these angels to do some Metallica songs for me? Oh - they can't violate the copyright...uh - OK - back to the Brahms then. K'thks."). I don't worry for an instant that I might be tossed into a fiery pit for eternity no matter how I behave. I do what I do because that's a comfortable way to pass my time. So without god or gods - I'm still living a life that I think most religious people would say was pretty much OK...apart from the lack of praying or church attendance and my annual(ish) speeding ticket fine.

In your view - why shouldn't I go off and commit all sorts of horrible crimes because I don't have a god to tell me what to do? But like most atheists - I don't. On the other hand - the most frequently shop-lifted book in the USA is the Bible. Our jails are full of religious people. Their beliefs didn't even slow them down when it came to them performing all sorts of heinous acts.

We have laws - both the ones passed by our governments and the ones we agree are a part of 'common decency'. Humans clearly don't need an entire complicated mythological structure along with the threat of eternal damnation to keep 'reasonable' people obeying those laws. Yet even in the presence of those religious strictures, religious people STILL end up in jail in vast numbers. So what on earth makes you think we need god(s) to do that? Religion is both unnecessary and ineffective when it comes to keeping people on the moral high-ground. That's not just my opinion - it's what we see happening around us every day.

SteveBaker (talk) 13:36, 4 February 2009 (UTC)

Personally, I find the idea that belief in God or fear of Hell somehow keeps us moral kind of frightening. I mean, I avoid doing evil because it's the right thing to do, not just because I'm afraid of the consequences. -- Captain Disdain (talk) 14:16, 4 February 2009 (UTC)

"Let's pick an atheist at random...me for example." Hey! That wasn't very random! APL (talk) 16:35, 4 February 2009 (UTC)

It was perfectly random - but taken from a VERY small sample size! :-P SteveBaker (talk) 19:18, 4 February 2009 (UTC)

the big question will be ... if there is a god , what is the proof you will need to admit his existance ... ??? if you can answer this question , then we could start to look for this possibility ... and the next question will be do god exist? ... thank you —Preceding unsigned comment added by 79.173.236.134 (talk) 20:09, 4 February 2009 (UTC)

What proof would you need that Santa Claus exists? I'm guessing you'd need to see a fat guy in a red suit zipping across the sky in a sleigh pulled by flying reindeer who can actually deliver toys to a large fraction of the population of the earth in one night. OK - well, for me, this is a comparable thing. So I'll settle for a god who can prove his/her existence by clearly demonstrating the power of omnipotence. This requires the god to perform an action that could not conceivably come about in any other way...changing the value of PI for example...let's have the god change the ratio of the ratio of the diameter to the circumference of a planar circle to 3.0 for the whole of Thursday - then put it back how it was again on Friday. I'd be pretty convinced. You see, you misunderstand the problem here. Nothing that's just "out there" in nature will convince an Atheist. We're happy to find scientific explanations for even the weirdest things (Quantum theory for example) because it's vastly easier to believe that than some unfalsifiable assertion like an arbitrary omnipotent being. But if I have to pick one - let's see your god change the value of pi or make 2+2 equal 19.74 for a few hours next week - he can do absolutely anything - right? The typical problem with this approach (at least for most christians) is that they'll tell you that god refuses to prove his existence in such crass and obvious ways because he wants to test your faith. Well, for those of us who have no faith - that's simply a ridiculous cop-out. The guy is omniscient for chrissakes - he can just look into your brain and SEE whether you have faith - why does he need to "test it"? So really - he has to do something active. Failing that, you have a "God of the gaps" problem - where your god can only be obvious in the teeny tiny cracks where science doesn't yet have the answers. Every year those gaps get smaller and smaller as we learn more about the universe and have less and less 'need' to have things explained with a shrug of the shoulders and a "Well God must have done it then". If you expect me to point to one of those tiny gaps and say "Well, I don't understand why the speed of light is exactly what it is - perhaps you could use that to convince me of the existence of god." SteveBaker (talk) 21:10, 4 February 2009 (UTC)

Changing the value of Pi seems rather ... destructive.

I'm not sure that I want the fundamental nature of geometry, and possibly even mathematics itself altered to satisfy SteveBaker's curiosity. (Admittedly, I wouldn't mind learning a few cosmic truths myself.)APL (talk) 02:55, 5 February 2009 (UTC)

P.S. Your last sentence sort of trails off at the end there, it could mean a couple of very different things depending on how you finish it.

Well, if a god has the power to change pi - then I'm sure (s)he can fend off the worst of the adverse consequences! You have to admit it would be interesting. I'm actually becoming more interested in having the god change the value of 2+2 to something a little less boring than '4'. 19.73 would be much more fun! Maybe I should pray for that to happen? "God answers all prayers" gets 3.1 million google hits - but then "God ignores silly prayers" only gets 900,000 ghits. So I guess on balance, it should work - right? SteveBaker (talk) 16:18, 5 February 2009 (UTC)

Well, as long as you're praying to have God change a fundamental constant, please have Him, Her, or It change it so that it encodes a message in ASCII. Your way only gives us a Yes/No answer, and there's so much more we could learn about the nature of the Universe. We don't want to have to keep doing this! APL (talk) 16:41, 5 February 2009 (UTC)

In 1997, the Federal Bureau of Prisons released the professed religious adherence rate of those in the U.S. Federal Prison system:

"Christians make up about 80% of the American population AND prison population. However, Atheists make up about 8% of the American population but only 0.2% of the prison population. On the flip side, only about 1-3% of Americans are Muslim, but 7.2% of inmates are Muslim."

Being a christian makes you 40 times more likely to break the law and wind up in jail than if you are an atheist. So these rules laid down by god to stop all of this misbehaving REALLY aren't working so well are they? Muslims are at least 80 times more likely to offend than an atheist. That's not a borderline finding - that's pretty amazingly decisive! The inescapable conclusion is that religion most certainly DOES NOT help people to stay on the straight and narrow. To the contrary! It amazes me that if you believe your god is going to toss you into a pit of fire and brimstone for all of eternity - that you'd even consider taking one tiny step away from being a model citizen...but aparrently, that's not the case. Actually (but hardly less controversially) the reason for this is probably that better educated people have a much higher incidence of atheism than the general population - and better educated people are much less likely to commit crimes. That hardly helps the OP's argument though! SteveBaker (talk) 20:43, 4 February 2009 (UTC)

I believe the comparatively high percentage of Muslim inmates when compared to the percentage of Muslims outside of prison has to do with a lot of people converting into Muslims while in prison, either because of a religious conviction or simply because being a part of the Muslim community in prison makes life easier. In fact, now that I Googled a little, this article seems to support that. Notably, apparently only 20% of inmates remain Muslims after they're released, which would suggest to me that convenience plays a big part in it... -- Captain Disdain (talk) 21:25, 4 February 2009 (UTC)

And you could certainly argue that the numbers are small - so you don't have a decent statistical sample - and that perhaps the US legal system discriminates against Muslims after 9/11...there are lots of possible reasons for there to be proportionately twice the number of Muslims than Christians result. But the 40:1 ratio of christians and/or muslims to atheists is a really dramatic result. You can't explain that away so easily. Certainly no matter what you argue - you can't conclude that people need religion in order to teach them right from wrong - as our OP claims. The evidence is completely the opposite. Religion somehow ENCOURAGES bad behavior. Quite how that would be is a little mystifying - but the evidence is right there in the numbers. SteveBaker (talk) 22:18, 4 February 2009 (UTC)

Oh, I agree. I just wanted to say that people shouldn't read the statistics to mean that Muslims commit a particularly great number of crimes, because a lot of these people became Muslims after they were convicted. It'd be interesting to see some statistics on what they were before that. The guy in the article compares Islam to Christianity, so he was probably a Christian before his conversion, but of course that's just one man. Still, I'll take a semi-educated guess and say that most of these converts probably weren't atheists before. -- Captain Disdain (talk) 22:35, 4 February 2009 (UTC)

To OP (79.173.236.134): I personally do not believe in the God that you believe in (the omnipotent, omni-everything-else type). I don't study physics, so I have no idea whether a God can exist, as in one that set the laws of the universe pre-big bang - assuming there is only one universe (tautology?). I do however, know with a 99.9% probability that there is no heaven or hell. The main reason being because I am an organism and I cannot suffer/feel pleasure eternally. Homeostasis states that the pleasure/suffering will just become normal, so it will no longer be suffering/pleasurable. I also have never seen heaven or hell, nor heard of any evidence proving its existence. I sometimes do wonder though, if heaven or hell did exist, which form of you would go there? A person who dies aged 89, would they be the 89-year-old of them? PS: The 0.1% uncertainty comes from the brain in a vat problem, which I'm just willing to risk doesn't exist, and even if it does, that still doesn't prove that there is a heaven or hell. --Mark PEA (talk) 22:05, 4 February 2009 (UTC)

The homeostasis thing is nicely addressed in Dante's Inferno. It's an odd book - but worth the read. But if your god is omnipotent and the 'thing' you're in while you are in heaven/hell is not a normal earth-issue body - then homeostasis might just not apply anyway. If God wants you to suffer he can just magic away your adaptability to pain. Similarly, heaven sounds a bit...well...boring really...but perhaps he can magic away your boredom too. When faced with literal omnipotence, all bets are off. SteveBaker (talk) 22:18, 4 February 2009 (UTC)

Some good refutes. However in the end, I am still an organism whose behaviour is determined by my genetics (nature) and my upbringing/environment (nurture). God punishing me for illegally downloading copyrighted material because I'm very frugal and prioritise a mortgage over a DVD is like me smashing my computer up because it throws errors at me. The reason I'm frugal may be a form of risk-aversity (debt is risky), possibly due to a higher than average number of D₂ dopamine autoreceptors [1]. The reason my computer throws errors at me may be due to the software or operating system being coded badly. --Mark PEA (talk) 01:42, 5 February 2009 (UTC)

will ... i dont think that will perform americal for each one ... i dont know if its possible to convince you that god do exist.

but from an anthor hand ... we use the princible of heaven and hell ... even with our children (if you behave god you will be agood boy ,,, moral award ,,, and if you dont you will be abad boy ) so god will use the same way with us ... heaven and fire . and god can make the whole world to belive ,,, to show him self so we will see him ,,, but belive me we will start to say mabye its some alien want to control us ... even if he changs the value of pi ...we will find some explanation . or should god will makes us all to belive in him without even thinking ... in other words treats us like animals.

the abillity to think is the only difference between us and other creation ... free will ...this is the only thing that could makes us humans ,,, if we couldnt belive in god without miracles ... we will never do . —Preceding unsigned comment added by 79.173.218.112 (talk) 09:22, 5 February 2009 (UTC)

Well, that's a problem. These stories that you religious types put up are deliberately 'unfalsifiable' - we can't prove that there isn't an omnipotent being because anything we might come up with could be something the god(s) intended for us to see - if a god doesn't want to be proved, (s)he can simply make our experiments come out differently or use magic to make our brains fail to register the truth. It's very hard indeed to prove a 'negative'. So we can't ever prove the nonexistance of something like that. Worse still, since (we're told) these gods have decided they don't want to prove that they DO exist - there is no way for us to prove that either. So without some actual "miracle" (such as changing the value of pi) there is absolutely no proof either way - and no prospect of there ever being proof.

However, what we CAN and ARE doing is proving that god's aren't necessary in order to explain everything we see around us. Science has made wonderful progress in the last 50 to 100 years in explaining things. We can explain everything from the first fraction of a second after the big bang until the present. We know why there are galaxies, stars, planets, plants, animals and people. We have a completely consistent story that requires only a relatively simple set of 'initial conditions' to explain everything that's around us and how everything works. We simply don't NEED there to be a god for the universe to function as it does.

So what's left? We don't need for there to be gods - and we can't prove that they are there. Should the fact that something we don't need cannot be proven to not exist imply that it does exist? Not really. We don't need pink aardvarqs playing piano's on the dark side of the moon and we can't prove they don't exist - so should we believe in them just in case? No! So why believe in god(s)?

You say "we use the principle of heaven and hell ... even with our children" - we most certainly do not all do that!! I made a very great effort in bringing up my son to explain to him WHY "bad behavior" was a problem and I did not to make arbitary threats of retribution from the skies. Failure to brush his teeth before going to bed would result in a careful explanation about the consequences of failing to do that. I would not EVER say "Do this or you get punished". This possibly explains why so many religious people end up in jail. If their parents threaten them with divine retribution and it never happens - perhaps god forgives them...so they go out and re-offend and sooner or later wind up in jail. If children of atheists are raised to understand why bad things are bad with reasoning and logic - perhaps that message 'sticks' a lot better. It seems to be working out for me at least!

As for the "the ability to think is the only difference between us and other creations" - that's just complete nonsense. Every statement I've ever heard about "The difference between us and animals" has been knocked down sooner or later. We used to say we were the only ones who use tools - then that became the only ones who MAKE tools - then the only ones who have wars - then the only ones with an awareness of self...all of those things turned out to be untrue. This crazy assertion is right up there with the others. Nobody who has ever played with a dog or a cat for more than a few minutes could possibly deny that they think. They obviously dream - they learn - they reason things out - and they laugh too. They are a LOT like us - simpler, yes - but there is no way you can put them onto a different 'level of existence'. As for free will - I'm not at all convinced that we humans have free will (we have another thread on that topic) - but if we do, then I'm 100% certain that the higher animals have it too. If your assertions about religion hinges on humans being different in those respects, then I'm sure we can prove that you're wrong.

You ask: "should god make us all believe in him without even thinking" - well, if you believe he exists - how do you know he isn't doing that to you? You believe without ANY evidence...then if there is no god then you are really looking pretty foolish...but if god does exist then perhaps he's somehow forcing you to believe in him? How would you ever know? The question you need to ask is not why he's not forcing me to believe in him - but why it is that you believe in him without evidence? Doesn't that seem a bit odd to you?

SteveBaker (talk) 16:07, 5 February 2009 (UTC)

Wikipedia:Reference_desk/Science#Free_will_doesn.27t_exist. If you have arguments/evidence for free will, post it there. --Mark PEA (talk) 16:24, 5 February 2009 (UTC)

more than 1000,000,000 human in iraq were killed to free the iraqi people ... were the actual reason was for oil ... in other words stealig ... what did atheist countreis do ,,,absolutly no thing more than 1200 human were killed in gaza to punish them for elect hamas ...and again..what did atheist countries do just the same ... absolutly no thing . morals is avariable... keep changing with profit ,,, benifet ,,, in the atheist world ,,, morals do matter while they go along with the benfits ... and if they dont, acts will be decorated to look like moral ... —Preceding unsigned comment added by 86.108.46.207 (talk) 18:57, 5 February 2009 (UTC)

There were not a billion people killed in Iraq, such obviously nonsensical claims only serve to make you look stupid. What do you mean by "atheist countries"? What did "religious countries" do? --Tango (talk) 19:13, 5 February 2009 (UTC)

soory ... i mean 1000,000 ... and there is no religious country ,,,??? —Preceding unsigned comment added by 86.108.46.207 (talk) 19:46, 5 February 2009 (UTC)

I don't know what you mean by "atheist country" and "religious country", so I have no idea if there are any or not. I only know what "atheist" and "religious" mean in reference to people. (Technically, I should be saying "theist" not "religious", please excuse me inexact use of language... I should know better!) --Tango (talk) 19:54, 5 February 2009 (UTC)

thank you for this discussion ... but you know ... i had been raised to be areligiuos since i was akid ... so if there is agod i hope he will help you find him ,and if there is not i hope my mind will help me to see the truth thank you again . —Preceding unsigned comment added by 86.108.46.207 (talk) 21:53, 5 February 2009 (UTC)

Don't make the assumption that the USA or UK are "atheist countries". The majority of people living in these countries, especially those with power, are in fact christians. Although it isn't asking about theism, belief in creationism relies on the belief of a god, and according to this data (http://en.wikipedia.org/wiki/File:Views_on_Evolution.svg), the USA is a highly non-atheist country. --Mark PEA (talk) 00:04, 6 February 2009 (UTC)

Map projection where area is proportional to a statistic

Resolved

I've read somewhere that it is possible to generate a map where the areas of the countries are proportional to some statistic (such as population), however, the countries are still recognizable. Any info on that? —Preceding unsigned comment added by Lev (talk • contribs) 07:58, 3 February 2009 (UTC)

There's a little bit at cartogram. Both this and the main map article are disappointingly short, though. --Anonymous, 08:54 UTC, February 3, 2009.

While the article isn't great, you can find some maps from a search. E.g. Population 1 Population 2 GDP per capita (2000) Nil Einne (talk) 09:33, 3 February 2009 (UTC)

You may want to read our article on Geographical information system which is much longer, and may be what the OP is talking about. --Jayron32.talk.contribs 12:32, 3 February 2009 (UTC)

Wikipedia call these "Area cartograms", but density equalizing maps seems more common. The primary website for the maps that have been circulating in the media is www.worldmapper.org. EverGreg (talk) 21:04, 8 February 2009 (UTC)

What the weather feels like

Resolved

On the news they say the temperature is 3 deg C, but it feels like 0 deg C. The latter is attributed to the wind chill factor. Then how do they measure these two temperatures? Why aren't they the same?--DFS454 (talk) 12:13, 3 February 2009 (UTC)

The two articles you should read are Wind chill and Heat index, the former tends to make us feel colder, and the latter warmer. With both of these, the relevent measurement is how fast your body dissipates heat. How warm or cold you feel is a factor of how fast your body is losing energy. This will be dependent on ambient temperature, but it is ALSO dependent on other factors as well. With wind chill, the wind (moving air) will tend to pull heat from your body faster, making you feel colder. With heat index, high humidity will make you sweat less, thus decrease your rate of cooling, thus make it feel warmer. Your perception of the temperature is largely based on how fast your body cools off, not on any direct measurement of the temperature outside of your body. Thus, "wind chill" and "heat index" corrected temperatures tend to be more useful to people, who, after all, are mostly concerned with how to correctly dress for the outdoors based on what they will feel like... --Jayron32.talk.contribs 12:30, 3 February 2009 (UTC)

As for how to measure wind-chill, use a wet bulb thermometer (a normal thermometer with a wet rag tied around it). A dry bulb thermometer (just a normal thermometer which is kept dry) is used to measure the regular temperature. StuRat (talk) 14:49, 3 February 2009 (UTC)

What's going on is that a layer of air is trapped close to your skin (eg by hair or clothing) which is close to body temperature. This insulates us from feeling the 'true' temperature of the air. When the wind blows harder - that layer of air is moved out of the way and we feel more accurately what the TRUE air temperature is. So when there is no wind, 3degC feels a certain way - but when the wind blows, it feels colder. Someone in the dim and distant past figured that 3degC with a 10mph wind feels like 0degC with no wind (or whatever it is) so we have this concept of 'wind chill'. Similarly at temperatures above body heat - when it's 40degC here in Texas - you feel cooler when there is NO WIND than when there is wind...same deal, the air near our skin has been cooled by sweating - but when the wind blows you feel hotter. Sadly, this is far from being exact science - if you have more or less clothes on then your experience of the wind chill will be different than the forecasters have stated. Humidity can also affect our feelings of high temperatures (hence "Heat Index") because when the air is very humid, sweat cannot evaporate anymore and we can't cool ourselves off naturally. When the air is very dry, sweat evaporates more easily and we feel cooler - even though the temperature is the same. So, again, we have this somewhat ad-hoc concept of 'heat index' that takes that into account and says that even though the air temperature is (say) 35 degrees C, it "feels like" 38 degrees because it's so humid. Of course if you've covered every inch of your body with antiperspirant...your mileage may vary! SteveBaker (talk) 15:01, 3 February 2009 (UTC)

(It has been pointed out to me that I shouldn't be encouraging people to cover every inch of their bodies with antiperspirant...I kinda thought that was inherent in what I just said - but just to be REALLY, REALLY CLEAR: If you cover yourself with to much antiperspirant, your body will be unable to shed heat - if you get into any kind of warm situation - you could easily get a life-threatening dose of hyperthermia. That's hypERthermia - not hypOthermia.) SteveBaker (talk) 16:29, 3 February 2009 (UTC)

Excellent thorough answers, thanks everyone--DFS454 (talk) 17:06, 3 February 2009 (UTC)

Which is more prestigious as an honour;FBA or FRS

Both there are regarded as apex academic honours in Britain.Which is more prestigious? —Preceding unsigned comment added by 212.247.70.129 (talk) 13:53, 3 February 2009 (UTC)

FRS. There is also the business that people outside science need an honour like that so they know whether the person is distinguished or not whereas for the FBA they would be known for what they did anyway without it. Dmcq (talk) 15:20, 3 February 2009 (UTC)

Is that really true? My uncle (an economist) was made an FBA, but I doubt many people outside his field (or his sideline as a chess problemist) would have heard of him. In any case, the two awards apply to different areas, so they aren't directly comparable (is there anyone who has both?). I would guess that more people are familiar with FRS than with FBA. AndrewWTaylor (talk) 15:30, 3 February 2009 (UTC)

Answering my own question, it seems there are plenty of people with both awards]. AndrewWTaylor (talk) 15:31, 3 February 2009 (UTC)

The reason I asked teh question was that I have difficulty accepting Amartya Sen FBA is any less distinguished than many FRS's.Also there have been many FRS's who have nothing to do with science-Margaret Thatcher,Lord Hailsham and in the past people like Erasmus Darwin or Samulel Pepys. —Preceding unsigned comment added by 212.247.70.129 (talk) 09:43, 4 February 2009 (UTC)

Um... Amartya Sen has a Nobel Memorial Prize in Economics. I don't think many people are worried about whether his FBA is distinguised enough. Can't speak of Margaret Thatcher or Lord Hailsam but I wouldn't give much weight to 19th century holders. It's often true that various awards etc had a lot more to do with who the person knew and how much money they had then what they achieved in the past, it isn't necessarily a good indication of what the award means nowadays. Personally being unaware of either abbreviation, when I saw what they were I did recognise the FRS much more then the FBA (actually I still don't think I've heard of the FBA much) but perhaps that simply reflects the fact I have much more of a science background. Edit: Somewhat proving my point perhaps, his article didn't even mention he was a FBA until I added it as a cat. I didn't add it to prose 'coz I wasn't sure where to fit it Nil Einne (talk) 10:38, 4 February 2009 (UTC)

Erasmus Darwin was a scientist. Algebraist 11:47, 4 February 2009 (UTC)

My apolgies.I meant his son Robert Darwin the father of the famous son!!!He was a doctor and had nothing to do with science as such! —Preceding unsigned comment added by 212.247.70.129 (talk)

Same thing though. I wouldn't say anything that old has any relevance to awarding practices today. More importantly perhaps, medicine is definitely a science and while young doctors especially nowadays primarily practice/diagnose existing techniques etc, leading medical doctors particularly in those days were often involved in research and experimentation which they may publish i.e. science. Let's not forget there's a Nobel Prize in Physiology or Medicine (there's none in biology, a biological discovery/invention has to go to physiology/medicine, chemistry or physics). Nil Einne (talk) 11:20, 7 February 2009 (UTC)

Margaret Thatcher got an honours degree in chemistry and worked as a food technologist until she entered politics. Some might say she should have stayed as a food technologist... --TammyMoet (talk) 13:36, 4 February 2009 (UTC)

Protein Supplements in diet

If you are doing significant amounts of anaerobic workouts, with an eye to maximum power gain in the relevant muscles and muscle mass gain, every 2 - 3 days; when is the best time in relation to working out to supplement your diet with extra protein? Would it be before working out, so that it is in your system as soon as your body starts repair the damage; or would it be after so that the protein comes in when the body is doing most of the growth over the next few days? Are there any other specifics or dietry supplements other than protein that can aid muscle growth without causing you to build up fat? —Preceding unsigned comment added by 129.67.37.225 (talk) 14:07, 3 February 2009 (UTC)

There was a question on the reference desk quite recently about this, see: Wikipedia:Reference_desk/Archives/Science/2009_January_18#Muscle_Tone_and_Protein_Intake. The general consensus is to eat protein as soon as possible after the workout. Read the studies for further information. --Mark PEA (talk) 16:47, 3 February 2009 (UTC)

Concerning your other question about building muscle while not fat, my answer is that's not a simple thing to do in the same day or even week for that matter. If your goal is to build muscle than you definitely want to have a daily caloric excess with a lot of protein. This means you'll be taking in more food than you are working to burn off. It is possible to have balance that allows muscle growth with fat loss, but you don't have to do that (its a lot easier to build with an excess). Most professionals alternate every 3-4 months between a muscle growth regimen and a fat cutting regimen. So they build muscle for 3 months with a caloric excess (picking up some body fat along the way is guaranteed). Then for 3 months they run (a lot) while maintaining a caloric deficit but still consuming protein post-workout. The result in the long run is (relatively) large, well defined muscles. --Mrdeath5493 (talk) 04:17, 4 February 2009 (UTC)

Boolean logic

A+(B+C)=(A+B)(A+C) and A+(!A)B=(A+!A)(A+B)

It struck me that if you consider A+ as a single varible things seem to make sense

Let A+=Z

Z(B+C)=(ZB)(ZC) and Z(!A)B=(Z!A)(ZB)

I wanted to ask if this method of considering things makes some sense or not? Bastard Soap (talk) 17:29, 3 February 2009 (UTC)

You have turned a boolean variable and an OR operation (+) into a different variable, and an AND (multiply) operation. This is not generally a valid conversion. In the case you provided, it looks like the resulting equations were valid, but this is because of distributivity, not because of your conversion. See boolean algebra to review notation and valid operations. Nimur (talk) 17:50, 3 February 2009 (UTC)

A couple other thoughts:

• What does Z actually mean? What is represented by "A or"? What's its truth table? If your intermediate step doesn't have meaning, then it's a bad route to pursue. Consider the invalid proof of 2=1 where symbols are used to disguise a divide-by-zero operation.
• Consider the trivial case of A+B. How does ZB (by your proposed conversion) evaluate?

So yeah -- as above, no, this is not the way to proceed. — Lomn 18:54, 3 February 2009 (UTC)

Yeah - you're definitely on the wrong track by "considering A+ as a single variable"...there is no way that can be the right thing. Can you give us a bit more context? (You might also want to take this to our Math desk - it's not really a science question). SteveBaker (talk) 20:04, 3 February 2009 (UTC)

I can see a way you might be able to formalise such an approach using group actions. "A+" is an element of a group (actually, it may not be a group, but that's not important) which acts on whatever set it is that these variables take values from (the power set of the universe? I don't do logic...). If it works at all, it would end up being equivalent to the standard approach (where + is a binary operation), I think, just more confusing. (The set A+ is a member of is isomorphic [as whatever type of object it is] to the set A is a member of, so you just have a set acting on itself, which basically gives you a binary operation). --Tango (talk) 20:15, 3 February 2009 (UTC)

So it is kind of like a recursive function in programming? Just seemed to me that if A+(B+C)=(A+B)(A+C) is valid the reverse operation should also be valid.Bastard Soap (talk) 08:01, 5 February 2009 (UTC)

More importantly, A+(B+C)=(A+B)(A+C) simply isn't valid. Do the truth table: for ABC {FFT} and {FTF} A+B+C ~= (A+B)(A+C). Also, because of the law of the excluded middle, your second tautology actually reduces to A+~AB=A+B. --Shaggorama (talk) 08:51, 6 February 2009 (UTC)

Gluing MDF

Which is best? Im using PVA but it doesn't seem to work that well.--GreenSpigot (talk) 18:57, 3 February 2009 (UTC)

We have an article, Wood glue, that may help. PVA ought to work, are you applying enough pressure while it dries? You'll probably need to put it in a clamp, or put some very heavy weights on it, applying pressure by hand isn't likely to be enough. --Tango (talk) 19:04, 3 February 2009 (UTC)

MDF is pretty loose fibrous stuff - glue alone won't hold it unless you are gluing over a very large area. Screws and nails don't work well either. I generally use metal or plastic brackets and screw through those using a PVA glue to stop gaps from opening if the joint flexes. If glue is the only answer, I'd try Gorilla Glue (which is just amazing stuff). But make sure you follow the instructions - Gorilla Glue is catalysed by water so the surfaces have to be slightly dampened - it also foams and expands and if you don't clamp it really firmly - it just pushes the joint apart instead of being forced into the pores of the wood. Also - whether with PVA or Gorilla Glue - make sure you're working somewhere warm - most glues don't set well at very low temperatures. SteveBaker (talk) 20:01, 3 February 2009 (UTC)

Im coating both surfaces with pva before sticking together but the glue really soaks into the mdf. Should I size the mdf first?--GreenSpigot (talk) 20:31, 3 February 2009 (UTC)

Re Linking abbreviations to disambiguation pages or not linking at all: I think I've got it figured out: Maryland Deathfest and Paralyzed Veterans of America. Right? --NorwegianBlue ^talk 20:58, 3 February 2009 (UTC)

And we do in fact have an article on Gorilla Glue. --NorwegianBlue ^talk 21:02, 3 February 2009 (UTC)

sorry for inexact link. PVA should of course link to Polyvinyl_acetate--GreenSpigot (talk) 01:19, 4 February 2009 (UTC)

Also, I dont believe I linked Medium-density_fibreboard--GreenSpigot (talk) 01:22, 4 February 2009 (UTC)

I've also used (a product similar to) Gorilla Glue (in Australia it's also sold as a variety of the Selleys product "Aquadhere") & I'll agree with Steve that it's an amazing product, but it has to be firmly & evenly clamped. If you're trying to end-glue MDF, this may not work so well. In that case, or as an alternative, you could also try using a contact adhesive like "Liquid Nails" Which doesn't tend to penetrate the timber so much. It also has to be firmly clamped though. In either case, its probably best to leave the job clamped for at least 24 hours to allow full curing of the glue to give maximum bond strength before stressing the join. —Preceding unsigned comment added by Mattopaedia (talk • contribs) 03:30, 4 February 2009 (UTC)

I've not had a lot of luck with gluing MDF and have pretty much given up on trying. Use a combination of prefab wood dowels and Minifix knockdown fittings (Don;t know a generic name. I just buy them out of the drawer at my "home improvement" center.) This is what they look like [2]) Or use cross-dowels [3] and wood dowels. If you measure and work with high precision you'll get a tight joint and you can use a dab of glue on the dowels if you like. OR Used to be you had to cut your own dowels from dowel rod stock, but now most "big box" stores carry the prefab ones and they're real easy to use.

76.97.245.5 (talk) 00:00, 5 February 2009 (UTC)

Sorry I didn't explain. I am trying to glue 2 sheets of [Bendy MDF] together to form a curved surface.--GreenSpigot (talk) 01:33, 5 February 2009 (UTC)

Gorilla Glue or contact adhesive should work, but they still need to be clamped. Perhaps you need some kind of template or formwork piece to hold the sheets in shape, and use something like a bunch of ratchet straps to apply the pressure evenly across the piece. Mattopaedia (talk) 13:01, 5 February 2009 (UTC)

Yes Matt, I have found what you say to be true--GreenSpigot (talk) 01:08, 13 February 2009 (UTC)

Space

I am asking this question by making some amendments. How many countries have succesfully landed on space through their scientists? Which are thsese countries? —Preceding unsigned comment added by 196.200.102.42 (talk) 19:06, 3 February 2009 (UTC)

What does "landed on space" mean? Space isn't a solid object... --Tango (talk) 19:11, 3 February 2009 (UTC)

It's also worth noting that all spaceflight endeavors have required contributions from scientists around the world. No one redevelops Keplerian laws of motion, von Braun's rocketry advances, or innumerable other necessary scientific or engineering advances that make spaceflight possible. As Isaac Newton famously noted, those who see farther do so only by "[standing] on the shoulders of giants." — Lomn 19:19, 3 February 2009 (UTC)

No country has gone into space without a lot of help from scientists from other countries. The Russians and Americans would have taken a lot longer to do what they did without all of the German scientists they took on board at the and of WWII. The Chinese, Indians and Japanese used Soviet era Russian and US technology to a large degree. It's truly an international thing. The physicists who worked out the principles came from all over the world.

Please try to phrase your question more clearly. It's really not very clear what exactly you are asking. SteveBaker (talk) 19:50, 3 February 2009 (UTC)

Your phrase "through their scientists" makes it sound like you mean those involved in actually developing space flight, as not all travelers are scientists . (Not sure of the percentage.) However, if you mean those who have actually gone into space, we do have a list of space travelers by nationality.Somebody or his brother (talk) 22:57, 3 February 2009 (UTC)

It is worth noting that this questioner's IP address maps to Eritrea, and it is probable that she/he is a non-native English speaker. Judging from Languages of Eritrea, it is likely that the questioner will understand at least one of the following articles:

• Veicolo spaziale (italiano)
• مركبة فضائية (Arabic/ عرابي )
• صاروخ

Our English articles, Spacecraft and Spaceflight, are available in many other languages as well. Hopefully this will help... Nimur (talk) 15:50, 4 February 2009 (UTC)

It's true. Chronology isn't clear from the article Spaceflight at least... ~ R.T.G 21:54, 6 February 2009 (UTC)

Electric motor speed

In the syncronous motor speed formula RPM = 120 f / P where 120 is constant, f is frequency, and P is number of poles, what does the constant 120 represent and how is it derived? —Preceding unsigned comment added by 167.75.254.253 (talk) 19:43, 3 February 2009 (UTC)

Well, revolutions per minute is 60 times revolutions per second (which is what 2f/P would be, since frequency is presumably measured in Hertz, or s^-1). I'm not sure where the factor of two comes from. --Tango (talk) 19:53, 3 February 2009 (UTC)

There are two axles. —Preceding unsigned comment added by 82.124.81.87 (talk) 19:54, 3 February 2009 (UTC)

(ec) Well, if 'frequency' is in Hertz, (seconds^-1) and the answer is in revolutions per minute - then that 120 is really 60 x 2 because there has to be a factor of 60 to convert seconds to minutes. So we really need to ask where does the constant '2' come from? I don't know the answer to that - but it's a lot easier to explain a factor of two than a factor of 120! SteveBaker (talk) 19:54, 3 February 2009 (UTC)

I'm betting the 2 comes from a standard motor having 2 poles, and thus you're back to frequency. — Lomn 21:17, 3 February 2009 (UTC)

The number of poles was already in the equation as P, so that can't be right. What about the 2 pulses of electricity what make up each cycle of the alternating current? That makes sense to me. --Anonymous, 07:12 UTC, February 4, 2009.

That P is also in the equation does not mean a constant cannot be conceptually related to it. However, phases of electricity seems to also be a reasonable guess. — Lomn 13:53, 4 February 2009 (UTC)

I think P refers to pairs of poles, hence could explain where the 2 comes from. You wouldn't have pairs in anything but pairs. Zunaid 17:05, 5 February 2009 (UTC)

Photons having momentum

How do photons have a momentum, when they are massless? Is it because we can equate energy to be mass (e=mc2), and they have a large velocity, therefore a large momentum? —Cyclonenim (talk · contribs · email) 20:24, 3 February 2009 (UTC)

It's not their velocity that gives them energy, it's their frequency (E=hf). You can assign a photon a relativistic mass, but I don't think it's particularly useful to do so. Instead, you need a more general definition of momentum (which I can't remember without finding my GR notes, which are several hundred miles away). I'm sure this has been discussed quite recently on this desk, though, so perhaps searching in the box at the top for 'photon momentum' would help. --Tango (talk) 20:31, 3 February 2009 (UTC)

I thought the general definiton of momentum was mass x velocity? In which case, frequency doesn't particularly help. Relativistic mass, however, might? —Cyclonenim (talk · contribs · email) 20:37, 3 February 2009 (UTC)

Nevermind, I found the answer here. Seems I walked right into a common misconception. —Cyclonenim (talk · contribs · email) 20:38, 3 February 2009 (UTC)

We now live in a world of Quantum Mechanics. So although it seems photons ought to be massless waves they exhibt particle-like behaviour also. See Wave particle duality. You and I also have a wavelength although it is of the order 10E^-50m. See De Broglie's wavelength on the duality link --DFS454 (talk) 20:45, 3 February 2009 (UTC)

The conventional definition of momentum, mass*velocity, is only one way of defining momentum. It can also be defined as a derivative in position-space coordinates, $\mathbf {p} ={\hbar \over i}\nabla =-i\hbar \nabla \,\!$. See this section for details of the mathematics and physics behind such definitions. Nimur (talk) 16:26, 4 February 2009 (UTC)

How long will it take to go to Mars?

How long is the Orion spacecraft is supposed to take to go to Mars in 2020? And if, hypothetically, we use the same spacecraft, how long would it take to go from earth to Pluto? --Emyn ned (talk) 21:39, 3 February 2009 (UTC)

See Colonization of Mars#Getting there – it's in the order of 6-9 months, but I don't think that Orion are anywhere near advanced enough in their planning to have fixed a passage plan. Bearing in mind that orbital patterns and gravitational effects play a big part in getting from one planet to the other, I couldn't safely say if the same spacecraft could make it to Pluto at all. If you wanted you could do a direct comparison of the orbital radii of Earth, Mars and Pluto and work out how many times further the minimum distance is, then assume the average speed is the same, but be warned that the result would probably be out by huge factors from reality. Bigbluefish (talk) 22:37, 3 February 2009 (UTC)

Earth-to-Mars spacecraft often use a Hohmann transfer orbit, which requires about 260 days of transit. Barring an unexpected revolution in spacecraft propulsion, that's a good estimate for Orion. Per the formula in the article, a Hohmann transfer from Earth to Pluto would require 46 years. Clearly, a different spacecraft, designed for a different sort of orbital transfer, would be required. The New Horizons probe, for instance, is using gravity assist to reach Pluto in less than 10 years -- of course, it's not stopping at Pluto, so that's not an acceptable mission parameter for Orion, either. — Lomn 22:47, 3 February 2009 (UTC)

Unmanned probes often use a Hohmann transfer orbit, or something close to it. Manned craft could well use something quicker (one plan I've seen is to send most of the equipment on a slow Hohmann orbit and then send the people along later on a quicker orbit - this means you only have a fairly light craft [relatively speaking] going along the high-energy orbit). --Tango (talk) 22:54, 3 February 2009 (UTC)

Melting tarseal

These [4] NZ news articles describe problems with the Desert Road tarseal melting. What temperature would it have to reach for this to be a problem? The air temp is only 28°, but the direct sunlight would heat the road beyond that, of course. (NB. tarseal is unknown to WP: it's an NZ word, but I don't know if it's more correctly defined as tarmac, bitumin, asphalt, asphalt concrete....) It is also worth noting that tarseal melts regularly in Auckland, on a smaller scale. Gwinva (talk) 21:55, 3 February 2009 (UTC)

this site suggests that asphalt road base doesn't really melt, per se, but gets more and more liquid as it reaches 250-300degrees F. --Mdwyer (talk) 23:45, 3 February 2009 (UTC)

I've seen asphalt get like that. In particular, when trying to change a tire on such asphalt, the jack just sank into it. StuRat (talk) 00:03, 4 February 2009 (UTC)

It sounds like "tarseal" is probably the same thing as chipseal. --Carnildo (talk) 01:18, 4 February 2009 (UTC)

I agree, and have been bold (just a little) in creating a redirect for tarseal. --Scray (talk) 02:11, 4 February 2009 (UTC)

I seem to recall reading the temperature of the ground reaching 50 degrees C somewhere when researching this but can't remember where and can't be bothered looking to see if I can find it. Whatever the case, I'm sure the temperature is quite far from 120 degrees C. Note as I mentioned in a reply to your post while undoutedly the surface temperature reaches a lot higher, I think you've missed the point. It's likely roads in tropical countries e.g. Malaysia, parts of Australia reach the same or higher surface temperature regularly and indeed may be laid under such conditions. Definitely it's common the road is literally too hot to walk upon without shoes although I guess that isn't that uncommon here either Nil Einne (talk) 13:08, 7 February 2009 (UTC)

Sorry, I didn't want to cast doubt (or misunderstand) your comment about different roads to suit hot conditions at the Misc desk...I just wandered off on a tangent wondering what temp it would be, and why the Desert Road was so problematic, when other places in NZ cope with just minor melting. And yes, roads can get too hot to walk on: have burned my feet often enough (and got them covered in melted tar). Gwinva (talk) 01:34, 10 February 2009 (UTC)

Bathymetry

Now that Google Earth allows users to view the inside of the world's oceans, I was wondering when was the seabed first mapped in its entirety? And how often does this need to be updated? Ottre 23:48, 3 February 2009 (UTC)

This surely depends on the resolution of the mapping you're talking about. You could sail across an ocean and check the depth a few times on the way and call it mapping. The history since then approximates a progressively more detailed map, and I'm sure that when some oceans first started getting mapped in high detail, other "less interesting" ones were still mapped with crude radar techniques. There probably wasn't really a "eureka" moment. Bigbluefish (talk) 01:41, 4 February 2009 (UTC)

I dont think all the seabed has been mapped as yet. Its not quite as easy as taking a photo from space!--GreenSpigot (talk) 02:54, 5 February 2009 (UTC)

Not quite, but close: the height of the ocean surface changes based on the depth of the water (seabed + mountain has higher gravity than seabed - trench). Use radar on a satellite to map the average height of the water and you can get a pretty good idea of what's underneath. --Carnildo (talk) 22:34, 5 February 2009 (UTC)