Wikipedia:Reference desk/Archives/Science/2011 March 15

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Science desk
< March 14 << Feb | March | Apr >> March 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.

March 15[edit]

Were Neanderthals more intelligent?[edit]

I recently found out that the cranial capacity of a Neanderthal(being 1400) is larger than our cranial capacity of modern humans(being 1350). This led me to think more cranial capacity will provide room for a larger, more intelligent brain to develope. A larger brain developing makes me ponder over whether they wouldv'e advanced quicker than we had. Well I mean if they never became extinct. I'm just not entirely sure. Matthew Goldsmith 02:43, 15 March 2011 (UTC) — Preceding unsigned comment added by Lightylight (talkcontribs) 02:42, 15 March 2011 (UTC)

The real thing you'd want to know is not the brain size, which doesn't tell you much, but the encephalization quotient — which is related to the ratio of brain size to body mass. The latter gives you a better understanding of whether a given species is fairly "intelligent" (broadly defined) than raw brain size alone. (If raw brain size was all that was necessary, whales would be hunting us for oil, rather than the other way around!) --Mr.98 (talk) 02:51, 15 March 2011 (UTC)
If whales had opposable thumbs we'd be in trouble. PЄTЄRS J V TALK 14:42, 15 March 2011 (UTC)
Well, the real thing you'd want to know is how intelligent Neanderthals were. We have pretty close to zero specific information about that. Presumably at some point we'll be able to draw conclusions from the Neanderthal DNA sequence, but we're a long way short of that right now. Looie496 (talk) 03:03, 15 March 2011 (UTC)
We are not entirely clueless. For one thing, they are extinct and we are not. It is impossible to know for sure why that is so, but our intelligence may very well have played a role. May be our warfare skill is what did them in... Dauto (talk) 03:21, 15 March 2011 (UTC)
Its also not just encephalization quotient alone, there are also structural difference between brains unrelated to size directly, such as the complexity of the Cerebral cortex which plays a major role in intelligence. --Jayron32 04:30, 15 March 2011 (UTC)
Hooray for pedants! Yes, of course I meant the encephalization quotient as a proxy for intelligence, lacking other information about their anatomy and behavior. And Dauto, the fact that they are extinct does not tell us very much about their intelligence. They may have just had a bad run of things, or not been clever enough in some areas as opposed to others. Perhaps they just happened to be exceptionally tasty to certain large predators. My overall point was, in any case, that raw brain size by itself is no anatomical indicator of intelligence at all — if you want to make sense of raw brain size, you have to compare it to raw body mass, and even then that is a crude (albeit not unhelpful) metric. --Mr.98 (talk) 14:40, 15 March 2011 (UTC)
There are things we can infer from the Archeological record about Neanderthal intelligence, and that's a much safer indicator than trying to guess intelligence using anatomy (generally a poor indicator). The Wikipedia article on Neanderthals mentions a burial with flowers that was found; I can recall a much stronger example of Neanderthal culture from my archeology professor (maybe someone can help me out with a specific name of this find) where a pair of Neanderthals were found buried beside each other, face up, but with the head of one next to the toes of the other. Their spears were on either side. Why would they bury valuable spears if they did not believe in some abstract significance of the event? Religious cermonies and especially beliefs in an afterlife (if that's what this burial shows) require "visualizing ahead" and long-term planning, some of the most rare and important skills of critical thought.
Since they interbred and co-existed with modern humans (see the Neanderthal wiki article), that's the strongest evidence we towards them having negligible differences in intelligence compared to us; if they had vastly different brain structures, the interbreeding process would not have gone well at all, because complex information processors (such as computers) can't just be mashed together to get a functioning result. Since most modern humans are descendents from this interbreeding, we know it went well. Their extinction was thus probably not due to them being dumber or anything, but probably due to something like starvation during the most recent ice age. They were huge and thus required a lot of food; we were small and could jog for long distances to run down prey, giving us more food options. Their leg bones do not show the "teardrop" shape that indicates long-distance running; Homo Sapiens is one of the only animals out there that can actually run cross-country because of our unusual bodies (near-hairlessness, efficicient bipedal gait, awake during the day but having stereoscopic vision, etc).
They are believed to have hunted in groups, which requires communication (and obviously language), co-ordination, and more planning. These account for pretty much all of the features we define as intelligent, so they were probably very similar to us in capacity. One could perhaps be raised to adapt to the modern world if it was alive today.—Preceding unsigned comment added by (talk) 05:36, 15 March 2011 (UTC)
Some other indicators of intelligence are art (such as cave drawings), trade (indicated by the presence of items in their camps not native to the area), sophisticated weapons and tools, a varied diet (determined by fecal analysis and animal bones), cities, and writing. I don't believe we've found any Neanderthal art, am certain we haven't found any writing or cities, do believe their weapons and tools were less sophisticated and their diet was less varied, and I'm unsure about Neanderthal trade. However, most of these would indicate that Neanderthals were less intelligent than modern humans, and humans may also be significantly more intelligent now than they were then, particularly with respect to use of language and symbolic logic. StuRat (talk) 06:20, 15 March 2011 (UTC)
I guess the counter-argument to that would be that intelligence isn't all biological; biologically they may have been equally intelligent (and they probably were, if my logic above holds about brain structures and interbreeding, an argument borrowed from Stephen Pinker) but culturally, perhaps they did not have as many good ideas floating around and accumulating over generations, and so were less intelligent because of social conditions rather than biological. Maybe that would explain the two having the same intelligent behavior on the small-scale (mystic beliefs, tool use, group hunting) but vastly different behaviors on the large scale (ie. trade, cities, advanced tools, art when it's construed as more of a learned meme rather than innate) that would involve more organized, refined societies. I'm certainly no expert on this stuff though, not being in a related field; just hypothesizing/generating discussion since the existing answer had left some things unexplored.[Special:Contributions/|]] (talk) 07:01, 15 March 2011 (UTC)
I think a general difference is that modern humans are "generalists", meaning we can adapt to many different environments and niches, while Neanderthals, like most species, were specialists, designed for a single niche. Being a generalist requires far more ability to learn, while instincts can serve a specialist well. StuRat (talk) 07:10, 15 March 2011 (UTC)
Neanderthal's use of tools and creative (not hard-wired) methods of hunting, however, were a form of generalism. They adapted to and solved the real-time environmental problems they faced. If they had been a specialist species, their hunting techniques would been programmed in as sort of an automatic routine, like a wasp building a nest, for greater computational efficiency and quicker reflex speed. Varied, special-purpose tools would suggest forethought; forethought about such things as how to get around a hunted animal's specialized natural defenses. I think all early human species filled the "generalist niche"; their hunting niche was "surprise them with something new", that is, coming up with techniques on the fly in real time that evolved defenses could therefore not keep up with.
Now, perhaps Homo Sapiens were somehow "more generalist" than Neanderthals were; but that again runs into the problem of, how did they interbreed successfully with different brain structures? Unless there is an easy way to interpolate between a more generalized mind and more specialized one (ie. a single chemical's concentration gets varied), it seems like the genes would clash and produce an unusable result.—Preceding unsigned comment added by (talk) 07:33, 15 March 2011 (UTC)
Regarding interbreeding, I was aware that this was one theory, but am not aware that it had been proven. Do you have a source for this ? StuRat (talk) 07:45, 15 March 2011 (UTC)
Yes, what I'm referring to is a recent find and you can read about it near the top of the Neanderthal wikipedia article. To both you and to SamuelRiv below, what I'm referring to is not a particular specimen that was found, but rather a genetic discovery made in 2010 (and featured on Wikipedia's front page for a while) asserting that "1–4% of the genome of people from Eurasia" was contributed by Neanderthals. So basically, that would mean that for everyone who is not African, we are part Neanderthal; the only "pure Homo Sapiens" are those of African descent. Obviously this is a very huge assertion and stands to change a lot of what we know, and people interested in science made a pretty big deal about it when it was announced. (It's also kind of an ironic find considering how it makes white-supremacist groups' rhetoric about being a "pure" race backfire. I also wonder if it explains how so many of the best long-distance runners are from Africa, since Homo Sapiens were evolved for endurance running.) Anyway, since then even another hominid species that apparently was just genetically found to have interbred with us was featured on Wikipedia's front page (edit: Found it on the Human Evolution Page: "the recently discovered Denisova hominin may have contributed 6% of the genome of Melanesians.").
This mixing of the DNA of various species that we can now find in the human genome tells us a whole lot, and allows us to infer that we were at least compatible enough as species to share brain parts and also co-exist (assuming it was an amicable co-existence and not interspecies rape or something). It seems that perhaps the final truly significant iteration of human intelligence may have spanned across a few different species with highly different bodies and hunting styles. (talk) 08:38, 15 March 2011 (UTC)
To StuRat and Unsigned: I believe you are referring to the debate over the Lagar Velho hybrid child. That link is extensive on the scientists' arguments, rebuttals, and counters for at least the first period after publication, but I'm not sure what consensus is, though it looks like they critique got the last word in solid by showing that the skeleton was within expected bounds of human morphology (comparable to northern Finns). So there is no clear hybrid, and question to biologists: do we have confidence that a hybrid would even show extensive morphological difference, that those skeletal traits wouldn't just prefer one side or another in hybridization? SamuelRiv (talk) 08:21, 15 March 2011 (UTC)
I just added a reply up above (talk) 08:50, 15 March 2011 (UTC)
Their crainal capacity was only 3.7% larger from the numbers given. This tiny difference may have been due to all sorts of reasons and is not sufficient to suggest they were more intelligent. (talk) 14:00, 15 March 2011 (UTC)

I've read somewhere some time ago that Neanderthals are believed to have grown into adulthood much faster than modern humans. And this is strongly indicative of "being less intelligent", at least in the following sense: If we could clone Neanderthals back to life and raise Neanderthal children, they would not be able to become professors. The flip side here is hat they they could be "more intelligent" when it comes to solving ad-hoc problems for which no established knowlege is of help.

This is similar to why, on the one hand, Chimps have the overall intelligence of a two year old or so, but there are certain intelligence tests in which they routinely outperform ten year olds. In one such test children and chimps were shown a box and shown a complicated set of actions, supposedly needed to open the box. Thing is that almost all of these actions are completely irrelevant and most adults will immediately see this. So, if you want to open the box, you will just open it in the obvious straightforward way. Children below the age of ten will, however, typically go through the entire routine of performing all the irrelevant actions. Chimps, however, won't and will open the box just like adult humans open it. Count Iblis (talk) 15:12, 15 March 2011 (UTC)

There's a much older reference about Neanderthal milk teeth, but a current one is [1](open access)(also see [2] for commentary). I should say that I have a problem with their plot showing that Neanderthals reach effectively age 16 by age 12, because if you look at the line they draw through the Neanderthal samples crosses the human at age 3. If you assume linear development it should start from birth, and if you assume variable development then there's only one sample which is more than a year or two ahead of the humans, so that straight line is overly bold. So I think they overstate the case a little, though I don't deny there's something of a separation.
Even so, it's hard for me to take this case all that seriously, because I know that by the time I was 15, I'd gone off to college, stopped growing, and had all four wisdom teeth mostly into their right positions. While I don't think I delivered on early estimates of future mental or physical development (some of my precocity was, indeed, just precocity), I'm not a troglodyte either. My guess is that the development time is some simple trait, probably controlled by a relatively small number of genes, which varies under selection or random drift in any species of humans. Wnt (talk) 19:34, 15 March 2011 (UTC)
I see, so things are more complicated :) Another thing that came to my mind was that Neanderthals are known to have hunted animals by attacking them from close range. This requires good eye-hand coordination and there was certainly a lot of selection pressure for that, as many Neanderthal bones show evidence of injuries. So, perhaps the brain areas involved in eye-hand coordination were far better developed than in us. This suggests that Neanderthals would likely have been better Formula 1 drivers or figher pilots than modern humans. Count Iblis (talk) 15:27, 16 March 2011 (UTC)
Someone please tell the military this right away, so we can get some Neanderthals spliced up and ask them directly. ;) Wnt (talk) 21:18, 16 March 2011 (UTC)
On the other hand, hand-to-hand combat might require more strength and less precision, making them less well-suited to the mentioned tasks. (talk) 00:06, 17 March 2011 (UTC)

atomic structure[edit]

can electrons shift dimensions i have a theory on it please help.. — Preceding unsigned comment added by Genius1109 (talkcontribs) 06:06, 15 March 2011 (UTC)

What does "shift dimensions" mean? Ariel. (talk) 06:09, 15 March 2011 (UTC)
I imagine "shift" means to translate; and dimension has a specific meaning in physics; I usually choose to say that the word "dimension" is synonymous with "generalized coordinate" in physics. So, yes, an electron can "shift dimensions" insofar as it can move along the x,y,z, axis. Such movements are subject to constraints imposed by proper solution of the position operator on a wave function that must be a solution to the Schrödinger equation. I think the OP should learn existing theory and review (or repeat) prior experiments before proposing a new theory. The theoretical solution for the electron position in the atom is the basis of modern atomic theory and has been very carefully validated by experiment for more than a century. Nimur (talk) 15:09, 15 March 2011 (UTC)
Are you perhaps referring to double-slit experiments ? One interpretation of this experiment's results is that the electrons are interfering with those in a parallel universe (under the many worlds hypothesis). Therefore, such electrons must at least pass information about themselves between these universes, which could be called "shifting dimensions" (although physicists don't call alternate universes "dimensions", this is more of a laymen's term). StuRat (talk) 07:23, 15 March 2011 (UTC)
If you look at a simple theory of the hydrogen atom, you may think that the electron orbits in a circle, in two dimensions. However using quantum mechanics you can show that the electron is not just found in a circle, but takes up 3 dimensions. Graeme Bartlett (talk) 11:26, 15 March 2011 (UTC)
And it would be better to say that the electron does not actually "orbit" as we imagine a planet to orbit a star; even if we consider it to do so in three dimensions. Instead, the better models consider the electron to exist across a probability distribution of locations (i.e. as measured over an arbitrarily long time, the shape of space that the electron may be found in with some arbitrarily high probability) without any concern for its mode or pattern of travel within that space, or we can consider the electron to be modeled as a standing wave in three dimensions organized around the nucleus; much as a guitar string represents a standing wave in two dimensions. These two concepts are nicely combined into a mathematical single concept, known as the Wave function, whose general shape and behavior is described mathematically by the Schrödinger equation. The image of a smaller ball (the electron) revolving around a larger ball (the nucleus) in some describable pattern, as we would expect it to look if it were large enough to see, is very limiting and does not actual work well to accurately model actual atomic behavior. --Jayron32 13:22, 15 March 2011 (UTC)
Sorry to nitpick the otherwise excellent response: a guitar string is a model of a standing wave in one dimension (not two). Constructing the standard wave-equation for a taut string requires an assumption of "negigibly small" deviations, such that the displacement and propagation terms are only a function of the position along the string. A 2-D model of a guitar-string would be a non-linear wave equation. A web search turned up this very nice student-report, Guitar String Tension Experiment; page 2 includes the mathematical reduction to 1 dimension (note the absence of an Fx term due its very small magnitude). Nimur (talk) 17:01, 15 March 2011 (UTC)

Space colonization[edit]

Not telling to predict anything, just a curious question. Is there any possibility of space colonization in the next 50 years that will have SIGNIFICANT impact on world economy, as opposed to extraterrestrial human presence (such as the ISS, which is year round human presence in the space for research purpose rather than economic activities)? Is it a possibility from the current state of technological progress in space exploration? Thanks! --Reference Desker (talk) 08:42, 15 March 2011 (UTC)

We could have a lot grander things than that happening in the next 50 years if the Technological Singularity (see the huge Wikipedia article) happens as early as Ray Kurzwiel predicts (using a bunch of trends like Moore's law). Any prediction of "where technology will be by XXXX year" using the current advancement rates is rendered moot if that happens. (talk) 09:10, 15 March 2011 (UTC)
Likewise, much grander things could happen if Christ returns to start his thousand-year reign of peace, or if people finally manage to tap the latent psychic powers hidden in the unused 90% of their brains. -- BenRG (talk) 22:30, 15 March 2011 (UTC)
Are you parodying me? (edit: yep, he was. You won't be laughing when I set my future robotic brain to work on destroying your logic! >:( (talk) 02:07, 16 March 2011 (UTC)
Most scientists will readily admit that there is essentially no economic benefit to space colonization - certainly not in the next 50 years. Don't take my word for it: here's some high-quality reading material for the pragmatic space enthusiast:
If you're lazy, just search these readings for the phrase "economics" or "profit" - such discussion is noticeably absent in any realistic discussion of the near- and mid-term future of space exploration. For the "layman", here's How much will Space Colonization cost? from NASA Ames.
Read a lot of different sources - draw your own conclusions - but you will notice a recurring theme. Despite the vast reservoir of public enthusiasm for space colonization, expert astronauts, scientists, engineers, bureaucrats, and politicians all know that space colonization is not profitable in the sense of "extracting resources" from other worlds. Space travel is a very expensive "luxury hobby" for our planet; and the laws of physics (particularly, gravitation and the need to launch faster than escape velocity) are not in favor of interplanetary commerce. No conceivable hypothetical technology or engineering solution will make gravity go away.
Still, space exploration has a massive economic impact: the space industry is constantly improving Earth technology, pushing the frontier of human knowledge, developing new materials, technologies, software, and scientific understanding that makes life on Earth much more efficient and sustainable. Nimur (talk) 15:43, 15 March 2011 (UTC)
You might enjoy Marshall Savage's The Millennial Project: Colonizing the Galaxy in Eight Easy Steps -- Finlay McWalterTalk 17:28, 15 March 2011 (UTC)
That appears to have no more connection to reality than Kurzweil's technological singularity. -- BenRG (talk) 22:30, 15 March 2011 (UTC)
There are fans of helium 3 extraction from the Moon (though I never got how that was supposed to work in practice), and space-based solar power (in that article I read a fascinating description of an H.G. Wells style space launch from a gun, supposedly for 10% the current price ... and people thought Saddam Hussein was crazy. ;) [3]) Wnt (talk) 21:40, 15 March 2011 (UTC)
Helium-3 mining is only useful if someone invents a viable nuclear fusion reactor. There is no way to know how long that will take. --Tango (talk) 22:04, 15 March 2011 (UTC)
Wikipedia has an article on space guns. -- BenRG (talk) 22:30, 15 March 2011 (UTC)


This may sound a bit stupid..... I'm a 21 year old male and I find myself sexually attracted to females. What I mean by sexual attraction is the desire to @#$%... Now I don't want that, if I'm attracted to a girl I only want to love her nothing more. I learned from wikipedia this is due to new hormones developing, so is there any way to remove these hormones? My body thinks very differently from my mind. Money is tight (talk) 14:24, 15 March 2011 (UTC)

Unless you feel like getting injected with female hormones or have certain parts permanently removed, I suggest you start with a cold shower. PЄTЄRS J V TALK 14:48, 15 March 2011 (UTC)
I'm having trouble understanding why you would want to do this! Despite what you may have been told, sexual intercourse is entirely natural and pleasurable. It's also not inevitable: see Platonic love. Advice on how to chemically castrate yourself would probably constitute medical advice, which we're not allowed to give. --TammyMoet (talk) 15:03, 15 March 2011 (UTC)
Chemical castration, perhaps? (talk) 15:59, 15 March 2011 (UTC) Martin.
Hormone therapy is another relevant article. In case the OP hasn't already surmised, these hormone treatments are extremely serious medical procedures with numerous physiological and psychological consequences. They aren't something that should be considered lightly on account of "social awkwardness." If the OP really wants to pursue hormone treatment, they should speak with a physician. There are many options for less-severe treatment, ranging from medication to counseling to simply "taking a cold shower" as mentioned above - we really aren't able to determine what the OP's actual needs are. Nimur (talk) 16:52, 15 March 2011 (UTC)
If it poses danger to my health, I don't think I'm that desperate. I just want to feel pure without any materialistic desires. Money is tight (talk) 18:37, 15 March 2011 (UTC)
The Refdesk does not offer medical advice. We can't reliably tell you what is safe and what isn't (even if it's nucking futs...). And you'd probably get better information on the purity of love, with or without the wet work, at the Humanities desk. Wnt (talk) 18:39, 15 March 2011 (UTC)
Though I suppose, provided that this is clear, it does no harm to mention monk's pepper, in a purely platonic sense. Wnt (talk) 21:55, 15 March 2011 (UTC)

I think you need to fix your mind, not your body. Everyone belongs to everyone else.

Ben (talk) 18:59, 15 March 2011 (UTC)

The fact you think this makes you somehow "un-pure" makes me think this is an ideological issue, if I had to guess probably a religious one. Religions just love to make people feel guilt for perfectly normal and natural feelings especially concerning physical desire. As the post above states, I think you need to work on your mind not your body. HOWEVER that's not to say people can't have objectively unhealthy obsessions or desires which lead them to commit criminal acts or leave them unable to function in social situations, if you believe this might be the case then you really need to seek the help of a relevant professional, like a doctor or therapist. Hormone therapy might be one of the solutions if there is indeed a problem, but you need to strat from the problem not from the solution. Vespine (talk) 22:28, 15 March 2011 (UTC)
It's worth remembering that unless they're straight out of a Victorian novel, females have hormones too. The object of your affections might be more than a little disappointed if your interest turned out to be purely non-physical. APL (talk) 00:21, 16 March 2011 (UTC)

Since you were born a human being, you will never get rid of materialistic desires. Becoming an adult means learning to manage those desires in a healthy way. What you're feeling is what virtually every heterosexual male feels to some degree, and there's nothing impure about it. thx1138 (talk) 22:58, 15 March 2011 (UTC)

The original post sounds like stupid trolling, but in case it's sincere, the best cure is the one nature intended: get yourself a girlfriend and $*&^!@# away. You'll love it. (talk) 06:08, 16 March 2011 (UTC)

I am being sincere. Why would I troll on an account with these many edits? I'm not under some regligious influence. Maybe I just have something wrong with my way of thinking, seeing as how everyone responded negatively. But if it helps I went through years of suffering from a loss and only recently have I felt like I'm beginning to recover. Sorry I didn't know medical advice weren't allowed here. Money is tight (talk) 11:09, 16 March 2011 (UTC)
It seems you have some very basic questions about what we are, how we got here, and why we behave the way we do as humans. Get on Amazon and pick up the book "How the Mind Works" by Stephen Pinker (Cognitive Scientist from MIT) for a very satisfying answer of those questions, including your questions about why sexuality works the way it does - that book has entire chapters devoted to the biological "economics" and the psychology of sex. So much of what I understand about science and about mankind was turned upside down by reading that book in particular.
Also, if you are actually 21 years of age, your social and emotional development as indicated by what you have typed here would suggest a sheltered upbringing. I am guessing you were raised by a religious single mother as I was. Either way, there are a lot of surprising and wonderful things that you're about to find in the world now that you are older that you may not have been aware of before, if you throw off your blinders and explore it passionately, and look into science in particular. Best of luck! (talk) 00:21, 17 March 2011 (UTC)
Yikes guys, some people legitimately want to understand and separate blind sex from love. Some people do not separate the two. It doesn't mean either one is religious or sheltered or let loose or criminal, so stop insulting the poster or making fun of him like a bunch of jr. high preteens!
Modern media outside of Hollywood seems to understand that there is an identity crisis in the Western world over free sexuality vs. traditional human monogamy, both of which obviously are evolutionarily relevant. I link to a scene from Torchwood where a character, in talking with someone from the 50s, awkwardly dances into the contradiction, and to an SMBC comic on the arbitrariness of the human reproductive act.
To OP - from what I've seen (and what Alfred Kinsey said), everybody on this planet experiences sexuality differently, so you have to pick and choose from what people might say. Sex is not without consequences, emotional and physical, until after you're 40, so discipline is an important skill, particularly against 50-year-old flower-children giving bad advice. SamuelRiv (talk) 05:30, 17 March 2011 (UTC)

Simple chalk oscillator[edit]

In this video, at 1:38, how does Prof. Walter Lewin make the dotted line on the blackboard? If I tried that, it would only screech miserably. — Sebastian 20:09, 15 March 2011 (UTC)

Lol, lot's of practice. WikiDao 20:48, 15 March 2011 (UTC)
That's some mad blackboard skills. Very nice. (I suppose the secret of the dotted line has to do with having exactly the right angle, force, and the right elasticity in how you hold the chalk). He gets less careful later in the lecture, though -- at about 15:50 there's a very releaxed rendering of . Hmm, it is just formulas versus figures -- there's really good drawing from 29:09 again.Henning Makholm (talk) 21:27, 15 March 2011 (UTC)
No doubt history will mourn the loss of these skills to the march of technology. I wonder if there's some way to preserve the dead sport for posterity - maybe give it an event at the Olympics? Wnt (talk) 21:32, 15 March 2011 (UTC)
Does he explain his easy-access banana? Admittedly, it's right there when you need it, but surely putting it in a pocket would be more convenient while sacrificing very little in draw time. APL (talk) 00:17, 16 March 2011 (UTC)
BTW he has an article: Walter Lewin. Also Walter Lewin Lectures on Physics. You could probably email him and ask - the article says he replies to emails. Ariel. (talk) 01:05, 16 March 2011 (UTC)
Good suggestion; I'll do that! — Sebastian 11:31, 16 March 2011 (UTC)
Drawing a dotted line with chalk is indeed easy. One additional variable is the distance from the board you grip it. I've found it easier with long pieces (I guess greater "bounce" per skip?). For angle, close to perpendicular is a's almost as if the dotted line is a low-frequency version of the sqeeking. Sometimes even going a little beyond perpendicular ("pushing" at an angle instead of "dragging") works. I can't do it often because I usually lean hard when doing a chalk-talk and then forget to ease up...nearly-perpendicular + long chalk stick between hand and board + high pressure against the board + crappy quality (soft and dusty) chalk == lots of broken chalk and a face-full of colored powders:( DMacks (talk) 01:35, 16 March 2011 (UTC)
There was a big mathoverflow thread[4] about some deluxe chalk from Japan that mathematicians like to use. Maybe that has something to do with it. Then again, I also don't know if physicists like Prof. Lewin are in on such secrets. (talk) 07:29, 16 March 2011 (UTC)

I just noticed that we already had a related discussion at WP:Reference_desk/Archives/Science/2009_April_9#Noisy_chalk_holders. — Sebastian 11:31, 16 March 2011 (UTC)

Grains of salt/sand/sugar in a cup[edit]

Hello all! Today in class we did a rather unimpressive activity in which we were challenged to find the number of grains of sand/salt/sugar in a cup. We were free to use anything in the lab (which was pretty well-equipped, but obviously excluding corrosive chemicals and flame) but we had nothing that could measure the mass of a single grain. The expected solution was that we count out grains until we got enough that we could measure on the scales provided. I think there was a better solution though, but unfortunately I was too busy counting the grains to figure it out :) It might have to do with volume. DOes anyone have any ideas? (PS: Rest assured this is just idle curiosity, the activity was completed in class and not homework). Thanks (talk) 22:16, 15 March 2011 (UTC)

You could have tried photographing the grains in a known volume to get a digital image, used some software to count the grains in the image, and weighted that. Graeme Bartlett (talk) 22:46, 15 March 2011 (UTC)
(ec): Not very different from your suggested solution, but you might go the other way: Using a balance, divide the cup into halves of equal weight. Divide the half-cup into quarter cups. Continue, until you have reached the limit of what can be balanced with your equipment. You could then try to continue the division process manually, by dividing the sugar into heaps of equal size, visually, on a dark surface. When the heaps are of managable size, count the grains (or take a photograph, as Graeme Bartlett suggested), and multiply to get the approximate number in the original cup. --NorwegianBlue talk 22:52, 15 March 2011 (UTC)
A different approach: count as many grains (assuming NaCl) as you can manage. Dissolve them in a small volume of destillated water. Measure the Na+ concentration. Calculate the number of micromoles/L of Na+ in the solution, multiply by the volume, get the number of micromoles in the grains that went into the solution, and get the number of micromoles per grain. Repeat with a larger quantity of salt, and calculate the number of micromoles of Na+ in the cup. Divide, and get the number of grains per cup. --NorwegianBlue talk 23:16, 15 March 2011 (UTC)
Or just walk into the building superintendent's office and say: "I will give you this fine cup of salt if you can tell me ..." –Henning Makholm (talk) 23:20, 15 March 2011 (UTC)
A microbiologist would get something with a big grid on it, like a paper cutter, and scatter the salt (or a smaller volume as is reasonable) over its entire surface. Then count a few grid squares until the standard deviation looks alright... Wnt (talk) 23:30, 15 March 2011 (UTC)
Another variation on the photographing method, but less onerous to count because it is a linear measure: photgraph the surface of the cup of salt with a digital camera. Magnify to a scale you can count the number of grains occuring in a 1mm interval. Cube to get the number of grains in 1mm3. Multiply by 1000 to get grains in 1ml. Multiply by 250 to get grains in a cup. SpinningSpark 23:44, 15 March 2011 (UTC)
Different method: Weigh your cup of sugar. Expose it to ants and count the ants as they take away grains of sugar. Ants are a lot easier to count than grains. Weigh the cup again and take the difference to the original weight. Divide this into the original weight and multiply by the number of ants counted. SpinningSpark 23:44, 15 March 2011 (UTC)
How about an hourglass approach? Make a paper cone with a small hole at the tip and put the sugar in it, count how many grains fall out in, say, five or ten seconds, depending how fast it's falling out, then time how long it takes it all to drain. Vespine (talk) 01:12, 16 March 2011 (UTC)
Does an hourglass drain linearly? I would think as an hourglass begans to empty it would slow down. John Riemann Soong (talk) 19:32, 19 March 2011 (UTC)
Going back to volume, how accurately can you measure the dimensions of a single crystal? Better do a few to account for different sizes. I bet you could convert the average volume of the crystals into their average mass pretty easily, using some known physical constant of...whatever chemical you think salt mainly is. DMacks (talk) 01:20, 16 March 2011 (UTC)
Volume is no good in this case. The listed density for sugar would be the density of the sugar itself, but the cup has a combination of sugar and air. You don't really know what part of the cups volume is air, reliably... --Jayron32 02:29, 16 March 2011 (UTC)
Volume of a crystal is a route to mass of a crystal. If you then know the total mass of some uncountably large number of crystals, what does the mass of a single crystal allow you to calculate? DMacks (talk) 03:39, 16 March 2011 (UTC)
Now if the crystals are sand, a cell biologist would find some sugar in the lab, dissolve it, and pour it into tubes in a sucrose gradient, or at least, a goopy mass of melted sugar. Then dump lots of grains into the tubes from a large height, so he can see what the average distance is that the grains travel into the sugar. The grains at the average distance are average grains, so by aspirating this band of grains, washing them and drying them, and weighing them in aggregate, he gets to the average weight of a grain. ;) Wnt (talk) 21:27, 16 March 2011 (UTC)
But a molecular biologist, presented with a cup of sugar, would simply add a little water, perhaps flour, egg, a few spices... Then knead the mixture until it is homogeneous, and roll it up into ten little balls. Cook them if desired, put them back into the cup, and answer - "ten". Wnt (talk) 21:33, 16 March 2011 (UTC)
A chemical engineer would find the appropriate documentation for that particular variety of sand/salt/sugar sold by that specific company, and look up the 'average mass per grain' entry in the specifications. If it's a standard product, there may be an entry in a standard reference book, and you may be able to bypass mass and look up the average volume and packing volume ;) (talk) 22:44, 16 March 2011 (UTC)

after effects of radiation in india[edit]

what are the possible after efeects of 2011 radiactive radiation in japan to asian countries including india —Preceding unsigned comment added by (talk) 22:41, 15 March 2011 (UTC)

Because the air moves generally from west to east around Japan, any radioactive material would have to go all the way around the world to reach India, or most other parts of Asia. It astonishes me that so many people think there is a risk to other countries -- even the US west coast, which is in the direct path of atmospheric flow, is 8000 miles from Japan, a third of the way around the world. Looie496 (talk) 22:51, 15 March 2011 (UTC)
(ec) At the moment, nothing. The amount of radiation is too low to be of significance to India or China. Even if there were a Chernobyl-style catastrophe (which is highly unlikely), the fallout plume probably wouldn't affect India in a substantial way. At its maximum, the problematic radioactive material from Chernobyl was dispersed some 2,800 km away. That's enough so that if it was going due West (highly unlikely), it would potentially end up in China or the Koreas (or the edge of Russia). Definitely not enough for India, and that would be a worse-case scenario. More problematic would be the effect on the food supply — whether it would end up in the fish sold in Asian (and world) food markets. I don't know enough about that to comment. But the current levels of radiation, though hardly ideal, are not of a level that should have any consequences as far India. Unless they sharply rise, they should not have consequences even in Japan, as I understand it. But the situation has not played itself out yet. --Mr.98 (talk) 22:54, 15 March 2011 (UTC)
The news I'm hearing is that they have four reactors and who knows how many pools of spent fuel rods all about to cook off, and the place is so radioactive they've cut 700 workers down to a skeleton crew of 50, and abandoned the control room.[5] It seems reasonable to be talking about a Level 8 nuclear disaster here. Wnt (talk) 23:26, 15 March 2011 (UTC)
There doesn't seem to even be a level 8 on the International Nuclear Event Scale... They are struggling to control the situation, but at the moment it is under control. Radiation levels outside the evacuated zone are negligible and have been throughout the incident. --Tango (talk) 00:19, 16 March 2011 (UTC)
Not yet there isn't. Wnt (talk) 00:41, 16 March 2011 (UTC)
The current situation is either a 4 or a 5 on the INES scale (depending on who you listen to), with the worst-case scenario (all three reactors undergoing complete meltdown, combined with uncontrolled fires in all the spent-fuel pools) being an INES 6. --Carnildo (talk) 02:28, 16 March 2011 (UTC)
This was a declared a level 4 by Japan when only two reactors were involved. Since then they have said nothing (3 reactors and 3 spent fuel tanks involved now). France, Finland(?) and a number of private organizations have called it a level 6 now. The IAEA apparently will not rate it yet. (talk) 04:31, 16 March 2011 (UTC)