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

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.

November 15

DNA Bank of endangered species

Is there a project that collects and saves DNA from endangered species as "insurance" in case of extinction (assuming we could possibly clone them later)? I am specifically curious about the technical aspect of DNA collection and storage. I'm also interested in any ethical "arguments" against "re-animating" an extinct animal. Any info about any or all of this would be appreciated. Thanks! Quinn ^{❀ BEAUTIFUL DAY} 01:49, 15 November 2011 (UTC)

One argument against bringing extinct animals back is that at least some of them were destined to become extinct without human intervention, and thus bringing them back is counter to what evolution would have done. Extinction is important to make room for new species, just as death makes room for new individuals. Pandas, IMHO, are one such species, that, while cute, just don't seem to have what it takes to survive.StuRat (talk) 02:01, 15 November 2011 (UTC)

Right. While I am interested in the ethical aspects, I am more so interested in any ongoing project that saves the DNA of such animals (like pandas). Just clarifying, as these questions can get off track pretty quickly. Quinn ^{❀ BEAUTIFUL DAY} 02:06, 15 November 2011 (UTC)

Any actions by humans are as much a part of "nature" and "evolution" as are the eating of a deer by a lion. Humans are not "outside nature." Edison (talk) 02:28, 15 November 2011 (UTC)

That sounds like an animal version of eugenics. I think religious objections are far more prevalent. The same thing that opposes genetic engineering, cloning, stem cell research, etc. as these are supposed to "playing god".-- Obsidi♠n Soul 05:56, 15 November 2011 (UTC)

Yes yes, and all scientists are atheists out to destroy faith and morals wherever they see them. Or, instead of constructing wild strawmen of opponents to casually throw into conversation, we could find out what the actual beliefs and reasoning of various people are, even if we disagree with them, and refrain fron misrepresenting them. Honestly, have you ever heard someone actually opposed to all stem cell research, let alone using the phrase "playing God" to articulate their objection? These are common in mocking representations of opponents, but I have never heard anyone use them to describe their own beliefs. 86.163.1.168 (talk) 12:28, 15 November 2011 (UTC)

Er... projecting much? What strawman arguments? I have very grave misgivings about GMO's and genetic engineering myself, and I'm acutely aware of the failures of well-meaning attempts of biological control and ecological management. I was merely pointing out that I've never heard of the argument about tampering with the natural course of evolution being used as a reason for opposing conservation. Much less Pandas. And please don't downplay the significance of Playing God (ethics). It figures very prominently in the objections against the mentioned fields. Remember Christian Science#Medical controversies? What about arguments against prophylactics (particularly birth control) and abortion (no matter how dangerous it is to the mother)?-- Obsidi♠n Soul 14:31, 15 November 2011 (UTC)

We have the short article Gene bank, but it appears that this is much more common with plants than animals.. There are several Seedbanks, where the seeds are stored in case there's a catastrophe and the crops need to be replenished (most famously at the Svalbard Global Seed Vault in Norway). For animals, do you mean just sequencing the genome, or are you looking for actual tissue storage? Because sequencing's being done at its own steady pace (including to several endangered animals) by the scientific community, but I'm not aware of any projects to specifically sequence endangered animals. The list of organisms with sequenced genomes is still relatively small [1]. You can look at all published genomes (including multiple sequences of the same species) at NCBI site. You can also see (perhaps incomplete) lists at List of sequenced bacterial genomes and List of sequenced eukaryotic genomes. Buddy431 (talk) 03:07, 15 November 2011 (UTC)

Specifically conservation-aimed gene banks aside from the already mentioned Svalbard Global Seed Vault, include Frozen Ark (our article for which is dreadful), the Royal Botanic Gardens, Kew's Millennium Seed Bank (and its Plant DNA Bank), the Animal Gene Storage Resource Centre of Australia (commonly known as the "Australian Frozen Zoo"), the United States' National Plant Germplasm System (specifically the National Center for Genetic Resources Preservation), San Diego Zoo's Frozen Zoo (not to be confused with the former), etc. Some countries also have local facilities including Australia, Korea, Brazil, etc. for native species or for specific groups (livestock, mosses, rice and other crops, reptiles, infectious diseases, etc.) Zoos also usually have facilities for them. They actually seem to be fairly common though we don't have a lot of articles about them. Just google "gene bank".-- Obsidi♠n Soul 06:27, 15 November 2011 (UTC)

I'd also like to mention Garden Organic's Heritage Seed Library, where members can access old varieties of seed, grow them in their gardens and replenish the stock of seed for the future. --TammyMoet (talk) 10:44, 15 November 2011 (UTC)

About what sturat said, I don't see why it matters if something is fit to survive or not. If we want them to survive, then that's the only reason we need. Are chihuahuas fit to survive in the wild? Are miniature horses? Does it matter? If we want pandas to live, then we'll make sure they do because we like them. That seems like a good enough reason to me. If we don't have a genebank of endangered animals, we should. The white rhino went extinct recently, personally I would like it if we could bring it back to life. I'm sure it would make a lot of other people happy too. ScienceApe (talk) 15:07, 15 November 2011 (UTC)

Actually the white rhino did not go extinct recently. What was recently declared extinct is the Western sub-species of the Black Rhino - [2]. Roger (talk) 15:28, 15 November 2011 (UTC)

Rayleigh scattering

It says here, http://en.wikipedia.org/wiki/Rayleigh_scattering#Reason_for_the_blue_color_of_the_sky "A portion of the light coming from the sun scatters off molecules and other small particles in the atmosphere. It is this scattered light that gives the sky its brightness and its color. As previously explained, Rayleigh scattering is inversely proportional to the fourth power of wavelength, so that shorter wavelength violet and blue light will scatter more than the longer wavelengths (yellow and especially red light). "

Ok fair enough, blue is scattered the most, so that's why the sky is blue. But then the article says, "The reddening of sunlight is intensified when the sun is near the horizon, because the volume of air through which sunlight must pass is significantly greater than when the sun is high in the sky. The Rayleigh scattering effect is therefore increased, removing virtually all blue light from the direct path to the observer. The remaining unscattered light is mostly of a longer wavelength, and therefore appears to be orange."

Err what? That contradicts what was said before, the sky is blue because blue is scattered. Now it's saying the sky is orange near sunset because orange is unscattered. ScienceApe (talk) 03:10, 15 November 2011 (UTC)

Light isn't "scattered" or "un-scattered", all of it is scattered, but blue scatters more then orange. The sky appears the color of the light which is scattered "a bit" (not the technical term). So most of sky above you has enough atmosphere to scatter blue light "a bit" and orange light "only a little" so you see blue more then orange. The thicker the atmosphere, the more scattering, so through the thicker volume of atmosphere you have to look through to the horizon, the blue is now scattered so much you can't even see it and the orange light is now scattered "a bit" so you see more orange then blue. Vespine (talk) 05:16, 15 November 2011 (UTC)

Isn't refraction of blue light a more significant effect than Raleigh scattering with regard to red sunsets? Or are the redness of the sun and the redness of the sky different issues? SpinningSpark 08:05, 15 November 2011 (UTC)

No, refraction is not the reason for the red sunsets. Scattering is.

Then why does it say the remaining unscattered light is mostly of a longer wavelength and therefore the sky appears orange? ScienceApe (talk) 14:51, 15 November 2011 (UTC)

Nvm. You're saying there's a "sweet spot" so to speak between where light is scattered too much and not enough and that's what gives the sky a particular hue? ScienceApe (talk) 14:53, 15 November 2011 (UTC)

Think about it. If you have a beam of light with all the colors in it and the blue is scattered off of it, you are left with a orange-red beam of light. Now, if more scattering happens from that beam, the sky becomes orange-red since those are the colors still left in the beam. Dauto (talk) 15:58, 15 November 2011 (UTC)

Or, put another way, the more light is scattered, the more like the sun the sky will look, since it's made up of more of the sun's light (I don't get what you were saying about light being scattered too much - it may bounce around a bit more before it gets to your eye, but it will either reach the ground or go into space, and there's basically a 50/50 chance of both regardless of how much scattering is going on). That doesn't explain why it goes beyond white (the colour of the sun, give or take) and into red and orange. I think that is due to refraction (particularly when the sun is touching the horizon - the image of the red light from the sun drops below the horizon a few minutes after the image of the blue light, so the sun gets very red when just before it goes below the horizon). Dust in the atmosphere is also significant (you get spectacular sunsets after volcanic erruptions), which is probably scattering (but since dust particles are a lot bigger than nitrogen molecules, they scatter very differently - I don't know the details, but it wouldn't surprise me if they scatter red light more than blue). --Tango (talk) 18:03, 15 November 2011 (UTC)

I don't understand what scattering means. When you say "scattered" are you basically saying that the air molecules are reflecting light? The more light is "scattered" the more the sky will look like the sun? Like you said the sun is white, not red or yellow so that can't be true. I do know that the thicker the atmosphere is, the more light is attenuated. There's this website, http://panoptesv.com/SciFi/LaserDeathRay/Visible.html, it basically says that the higher frequencies (blue, green) are attenuated at less distance than shorter frequencies (yellow, red). So basically is blue attenuated completely by the atmosphere near sunset while red and yellow are able to "make it through" while scattering red or yellow light into our eyes? ScienceApe (talk) 23:00, 15 November 2011 (UTC)

Yes, that's basically the correct idea. Because air scatters blue more efficiently, at sunset by the time that a light beam reaches you pretty much all of the blue has been scattered and removed from the light beam. So, whatever light is scattered from it now will be in the yellow to red range giving the sunset's sky it's typical colors. If there is a lot of dust in the atmosphere which is more effective at scattering light than molecules, even the yellow and orange will be gone, giving the sky a bloody red appearance. Dauto (talk) 04:28, 16 November 2011 (UTC)

Tango, almost everything you said in that last post is wrong. Let me make a list

1. The sky doesn't look more like the sun as light gets scattered. The scattering separates the bluer rays from the redder rays making the sky less like the sun which has all the colors together.
2. Refraction has nothing to do with it.
3. The blue image of the sun sets just a fraction of a second before after the red image. If that was not the case, the sun would look smeared. For an effect caused by refraction read green flash.
4. Dust also scatters Blue light more than red light. Just more so.

-- Dauto (talk) 04:20, 16 November 2011 (UTC)

Ok, then. You explain why sunsets are red. So far, you haven't. Your point (1) is incorrect, anyway: with no scattering, the sky is black, completely unlike the sun, with a bit of scattering, it becomes blue, a little more like the sun, if all the light were scattered (as it is when it's cloudy), then it would be white, just like the sun. If your other 3 points are correct, then why are sunsets red and why are they even more red when there is a lot of dust in the atmosphere? So far, you haven't given any explanation that makes sense. You've just talked about more scattering, but as I've said, that would result in white, not red. --Tango (talk) 17:54, 16 November 2011 (UTC)

Let me try that again. The light coming from the sun at sunset has no blue in it because the blue has been removed by scattering at an earlier point in the trajectory of that light beam towards you. Since it has no blue left in it, you cannot possibly get blue skies out of it (Or white skies which also require blue). By the way, that's also why the green flash is green instead of blue (There is a little bit of green left, but not much). Since All of the blue and most of the green is gone, any light scattered off of that beam will look yellow, orange, or red. Dust is more efficient at Rayleigh scattering than clear air, so when there is a lot of dust in the atmosphere, the Rayleigh scattering processes intensifies, removing green and yellow from the light beam as well. By the time the beam reaches your location all that's left in it is the orange and the red. Therefore any scattering that happens at your location will give the sky an orange-red (sometimes blood red) color. A cloud contains water droplets which are even more efficient than dust at scattering light. So efficient that all the content of the light beam becomes immediately scattered, completely eliminating the light beam. Since all of the light is scattered at one location, the sky (cloud) at that location becomes white (Except at sunsets because the beam already lost its blue component so the sky (cloud) looks yellow-orange-red). One last comment: I think my previous explanations made sense. It's not my fault you couldn't understand them. -- Dauto (talk) 19:33, 16 November 2011 (UTC)

How long has the importance of blood pressure to human health been known

How long has the importance of blood pressure to human health been known, and when were routine blood pressure checks begun? 109.253.251.166 (talk) 09:35, 15 November 2011 (UTC)

Based on sphygmomanometer, the technology to measure blood pressure became widespread around 1900. Dragons flight (talk) 09:59, 15 November 2011 (UTC)

Hypertension#History gives more information. It states that: "Studies in the 1920s demonstrated the public health impact of untreated high blood pressure" and that, in the US after World War II, "public health campaigns to increase public awareness of hypertension and the advice to get blood pressure measured and treated. These measures appear to have contributed at least in part of the observed 50% fall in stroke and ischemic heart disease between 1972 and 1994." Obviously the position in other parts of the world varies considerably. Ghmyrtle (talk) 10:12, 15 November 2011 (UTC)

This paper describes the history of blood pressure measurement and notes Samuel Siegfried Karl von Basch's work in the 1870s and 1880s as "the first investigations into haemodynamic pathology", connecting high blood pressure with arteriosclerosis; von Basch is also credited as the inventor of the sphygmomanometer. --Colapeninsula (talk) 17:08, 15 November 2011 (UTC)

I thank you a lot for help! thanks 109.253.131.172 (talk) 21:14, 15 November 2011 (UTC)

What would be the evolutionary and epistemological basis for Aliens being "too alien" for human communication?

I was reading the Stanisław Lem article and got linked to the Fermi paradox article, particularly the section on They are too alien, where it states "Another possibility is that human theoreticians have underestimated how much alien life might differ from that on Earth. Alien psychologies may simply be too different to communicate with human beings, to understand the concept of communication, or to even be interested in other lifeforms at all, and so they may be unable or unwilling to make the attempt. Human mathematics, language, tool use, and other concepts and communicative capacity may be parochial to Earth and not shared by other life."

Can anyone provide any websites, articles, or books that explore this concept?

Specifically I would be interested in learning about the biological evolutionary and epistemological origins of a incommensurably radically different Alien consciousness, mathematics, perception, cognition and science. --Gary123 (talk) 12:12, 15 November 2011 (UTC)

Why do you think these aliens are biological? What makes you think they evolved? :) - Nunh-huh 12:22, 15 November 2011 (UTC)

Well presumably if intelligent ETs come into existence though naturalistic means it would be through some form of self-replicating mechanism. That is all I would mean by "life". So I wouldn't discount any possibility of a non-carbon based lifeform, perhaps silicon. But I would assume that even Hypothetical types of biochemistry would still be "biological" and "evolved" by selection in a general sense. If your referring to the possibility of singularity and/or advanced AI. Thats another possibility, but it would assume that an advance biological lifeform had invented the AI 1st. --Gary123 (talk) 12:32, 15 November 2011 (UTC)

It is certainly possible that there are things out there that are beyond our ability to conceive, but by definition we can't really discuss them. Something which we would recognise as complex life probably needs to have followed some kind of evolutionary path (or, have been created by something that did) - how else would that complexity arise? As for whether the lifeforms are biological or not, that's just a matter of how you define "biological" and isn't an interesting question. --Tango (talk) 12:55, 15 November 2011 (UTC)

Perhaps carbon-based intelligent life is just a short intermediate step to a higher silicon-based civilization. --Stephan Schulz (talk) 13:01, 15 November 2011 (UTC)

While the possibility of life so unlike us in nature that we can't meaningfully interact with it is a fun thing to think about on a rainy day, I think the more meaningful way in which ETI's would be different form us is in technology. Even if you restrict your definition of ETI to only include beings very similar to us, we still couldn't interact with them very well. The human race has existed for at least 50,000 years (longer for most definitions of "human race"), but we've only had the ability to communicate with other star systems for a few decades (and even that ability is highly limited). Given the current rate of technological advancement, it is pointless to try and predict what technology will look like even 25 years in the future. If we look 100 years in the future, we'll be dealing with technology so different to that which we have today that it would all be gibberish to us (we tend to assume that interstellar communication will happen by radio transmission, but we've only known about radio for about 100 years - 0.2% of our existance as a race - beings 100 years ahead of us could be using something we couldn't even dream of to communicate). What are the odds that another race of intelligent beings out there at the moment is at a sufficiently close level of technological development to ours for us to be able to interact? Even assuming a 200 year window in which communication could happen, that's a ridiculously small length of time to expect it to overlap with the same window in another race. --Tango (talk) 12:55, 15 November 2011 (UTC)

I often wonder if the theories that there are more dimensions than the 4 we know of are true, and if so, would there be life in the other dimensions that wouldn't exist in our dimension, or if it did, would we recognise it as life? --TammyMoet (talk) 13:26, 15 November 2011 (UTC)

You might be interested in Chris Adami's TED talk "Finding life we can't imagine", which talks about the information-theory characteristics that could be used to differentiate life from lifelessness, without being bound by worrying about the chemistry or biology of what that life might be. That seems like a sensible approach when you consider "life" to be something that reorganises matter for its own convenience. When it comes to technology, the dominant signature of our technological civilisation is that we've dug around in the crust of our planet to extract, and then refine, metal. We've then strewn that metal over the surface both as objects and as metal particulates (latterly as radioactive metal particulates). So if you were to look at the sedimentary strata of Earth in the distant future, you'd see a profound metal layer corresponding particularly with the industrial revolution. A corollary of that is if you see a similar surplus metal (Fe,Cu,Zn,Sn,Pb) elsewhere (either in Earth's sedimentation, which you don't, or on another place on the cosmos) you'd have to suspect life of some kind of "life" had induced this. Once you get to life that doesn't affect matter in a statistically interesting way, I think you'd be into guessing at best. -- Finlay McWalterჷTalk 13:50, 15 November 2011 (UTC)

Just had an out-of-the-box moment reading you guys, I hope I will be able to phrase this right. Ahem. Look at the stars, and then look around you. There are creatures even on Earth with whom we are not able to properly communicate. So, extrapolating, perhaps, the same could be true for our 'neighbours' from among the stars - even if living close, like your everyday birds, animals and the like, they could be so different that any level of even simplest understanding could prove difficult, if not impossible. --Ouro (blah blah) 15:26, 15 November 2011 (UTC)

Well, there is currently only one intelligent species of animal on this planet, so it's not surprising that we can't communicate with non-intelligent animals. (There are lots of very clever animals, but none even close to the level of humans) Goodbye Galaxy (talk) 15:47, 15 November 2011 (UTC)

<facepalm> That argument is exactly why it would be very difficult for humans to communicate with any other sentient life. We tend to define "intelligence" only from our own perspective. -- Obsidi♠n Soul 16:13, 15 November 2011 (UTC)

"We can't talk with language-less animals" is why it would be difficult for us to communicate with other sentient life? That doesn't follow at all. First of all, sentience isn't what we're talking about-- intelligence is. I'd say language is a necessary prerequisite for any intelligent civilization. Is that an inference based on life we see on earth? Of course it is, but that doesn't invalidate it. Intelligent creatures need some mechanism to pass on knowledge and ideas between individuals and generations. Whatever way this occurs would necessarily be "language". Goodbye Galaxy (talk) 17:47, 15 November 2011 (UTC)

What is your definition of language? Sounds? Symbols? Gestures? Chemicals? Colors? Human language is unique in its complexity, but it is not unique to humans. I suppose you also expect aliens to conveniently communicate with sound waves as well as perceive visually and aurally? -- Obsidi♠n Soul 18:52, 15 November 2011 (UTC)

I would consider all of those as examples of language, so long as they are capable of communicating abstract ideas and thoughts. "Animal language" is a misnomer, in my opinion, and I would argue that humans are the only animals on Earth with language. Most "animal languages" are either instinctual, and not learned, or a sort of 1:1 copycat behaviour (eg. whales teaching their young hunting techniques by showing them). Additionally, while I think language is necessary for intelligent civilization, it's by no means the only requirement. Goodbye Galaxy (talk) 19:10, 15 November 2011 (UTC)

Saying "most animal languages" betrays that you are already aware that there are examples that contradict your assertions. There are numerous studies on abstract concepts (including grammar) in animals. We make arbitrary rules about what should constitute a language, when in fact we are merely defining our language. You are, in effect, declaring that because you can not understand them, they don't possess a language.

Dolphins, for example, are able to exhibit remarkably coordinated complex behavior that are in addition, cultural. That already clearly shows there is non-trivial communication involved. We don't know yet how or why simply because even in a fellow mammal, there is a vast communication and perception rift between us and them. Most of the sounds dolphins make are out of our hearing range, for one, and we can only imagine how they perceive their environments with echolocation because we don't have one. And this is given that dolphins and humans are relatively very closely related lifeforms, how much more for more distant relatives or non-relations at all? Heck, there are organisms that undoubtedly senses things through some way that we haven't been able to detect or understand the full mechanisms of yet.

And exactly. Language is not the only requirement for intelligence, in fact the argument that language is a requirement at all is questionably anthropocentric. What about swarm intelligence for example? Exemplified already by social animals like ants. Taken individually, they are stupid. Taken as a whole, they have remarkably complex behavior communicated primarily through chemical scents (simple automated signals that can't really be considered language). Our brain itself is an alliance of billions of individual cells, each living and dying independent of the others. In an intelligent lifeform that developed on such lines, there would be no need for civilization or language. All individuals are part of a single mind, it doesn't need to communicate because it has always been alone.

Convergence is a reasonable thing to expect, of course, but that also fails to take into account that convergence would only work if we are the norm and not the exception. You are taking way too many things for granted, including time perception below. Given your username, I would have expected you to already realize how important a frame of reference is and how it affects perception.-- Obsidi♠n Soul 20:56, 15 November 2011 (UTC)

Again, I wouldn't call that "language." It might be a language "ancestor" if you will, but dolphins have no way to communicate abstract ideas like, "1+1=2", assuming it ever occurred to them. Also, you're not taking societal interest into account. If we discovered aliens, there would be a HUGE amount of funding put into developing means to communicate with them. How much funding is put into learning to communicate with dolphins? Also, do you have a link to the studies on abstract concepts and grammar in animal languages? Goodbye Galaxy (talk) 21:16, 15 November 2011 (UTC)

No. Just some of the more interesting ones with a few minutes of googling:

• Louis M. Herman (2010). "What Laboratory Research has Told Us about Dolphin Cognition" (PDF). International Journal of Comparative Psychology. 23. International Society for Comparative Psychology: 310–330.
• Adam A. Pack (2010). "The Synergy of Laboratory and Field Studies of Dolphin Behavior and Cognition" (PDF). International Journal of Comparative Psychology. 23. International Society for Comparative Psychology: 538–565.
• Ramon Ferrer-i-Cancho & Brenda McCowan (2009). "A Law of Word Meaning in Dolphin Whistle Types". Entropy. 11 (4): 688–701. Bibcode:2009Entrp..11..688F. doi:10.3390/e11040688. ISSN 1099-4300.
• Sayaka Tsutsumi; Tomokazu Ushitani & Kazuo Fujita (2011). "Arithmetic-Like Reasoning inWild Vervet Monkeys: A Demonstration of Cost-Benefit Calculation in Foraging" (PDF). International Journal of Zoology. 2011. Hindawi Publishing Corporation: 1–11. doi:10.1155/2011/806589.
• Zhanna Reznikova & Boris Ryabko (2011). "Numerical competence in animals, with an insight from ants". Behaviour. 148 (4). BRILL: 405–434. doi:10.1163/000579511X568562.
• Kate Arnold & Klaus Zuberbühler (2008). "Meaningful call combinations in a non-human primate". Current Biology. 18 (5): R202–R203. doi:10.1016/j.cub.2008.01.040. PMID 18334192. S2CID 31058104.
• Margaret S. Livingstone, Krishna Srihasam & Istvan A. Morocz (2008). "The benefit of symbols: monkeys show linear, human-like, accuracy when using symbols to represent scalar value". Animal Cognition. 13 (5). Springerlink: 711–719. doi:10.1007/s10071-010-0321-1. PMC 2921054. PMID 20443126.

And you mean human language precursors of course, because you've already decided that human language is completely separate from modes of animal communication and that all languages must strive to achieve the paradigm of human speech. That's the problem with the "funding" assertion. Given that you apparently only classify language and intelligence through the filter of human language and intelligence (i.e. they have to resemble human sentience), you wouldn't recognize a sentient species in the first place if it didn't talk or think enough like a human.-- Obsidi♠n Soul 06:45, 16 November 2011 (UTC)

Humans can communicate with animals. We can't hold conversations, but can train them to perform tasks and obey orders, understand their mental/emotional states to a degree, etc, although there is still much that is mysterious about animal behaviour. This does depend on the definition of intelligence and communication - I'm not sure in what way we could communicate with a virus. --Colapeninsula (talk) 17:17, 15 November 2011 (UTC)

You guys are thinking far too simply here. You're assuming that an alien life will be fundementally similar to earth life, and it will simply be a matter of working out the translation. Expand your imagination for a moment: Imagine a highly intelligent life form which operates on an entirely different time scale: how do you communicate with that? If it takes 1000 years for such a life form to communicate the equivalent of a single word, how do we communicate (or even recognize) such a life form. Or at the other scale: what about a highly intelligent life form where a single life span is less than 1 second. An entire life lived in the blink of an eye; how do we communicate with that. Where in our models is the means to communicate with collective intelligence as opposed to individual intelligence (see Ender's Game for an exploration of such a problem)? There are an almost infinite number of variations on the form that intelligent life may take, and there are a finite number of those variations we could reasonably communicate with. That's the core of the Fermi paradox; infinity minus a finite number is still infinity, so even presupposing the existance of another intelligent life form, the chances are infinitessimal that we could communicate with it. --Jayron32 18:53, 15 November 2011 (UTC)

I don't buy it. Life may arise in any number of possible ways, but there must be ways that are more probable. A creature with a lifespan of 1 second? How would that come about? How does it reproduce? Also, why would a highly intelligent lifeform take 1000 years to formulate one word? That doesn't sound very intelligent to me. But that's all besides the point. If we discovered such beings (and this discussion is about the difficulty of communicating with them, so discovery is implied), I have no doubt we would eventually figure out a way to communicate. It might take extremely long time periods, and would be extremely rudimentary at first (likely math based, prime numbers, or some such). Goodbye Galaxy (talk) 19:18, 15 November 2011 (UTC)

On the contrary, what is magical about the timescale that earth-based life works on? You've made no really convincing arguments that say that life working on other timescales is impossible, or even improbable. To expand a bit: Why couldn't something live in the span of a single second? What is preventing it from doing so? Yes, life based on earth based chemistry which is familiar to us couldn't, but what makes you so certain that life based on completely different systems would have to operate on a similar time scale to ours? --Jayron32 20:17, 15 November 2011 (UTC)

There's no such thing as Earth-based chemistry. There is just chemistry. Goodbye Galaxy (talk) 20:23, 15 November 2011 (UTC)

Obviously. That isn't what I was saying. Your limitations on what life can look like are based on an understanding of life based on a known carbon-based (and moreso, a specific subset of carbon-based) chemistry. Life could be based on other sorts of molecules and chemical reactions for which we have no analogues on Earth (and thus which we may not have even considered to start studying yet). That's the whole point; it's not that the laws of chemistry itself may be different elsewhere. They plainly and obviously would not be. It's that our knowledge of those sorts of chemistry may be non-existant, which is why you are unable to conceive of life working vastly differently than it does on earth. Earth-based life works at a certain speed because it all works on a certain type of reaction kinetics, but an entirely different system of life would have an entirely different system of kinetics, and it is not outside the realm of possibility for such systems to be many orders of magnitude off in terms of timescales. I can do a chemical reaction which goes to completion in a nanosecond, and I can do another one that goes to completion in longer than a second: That's an order of 1 billion-fold difference in time scales. Why would such distinctions in reaction kinetics NOT apply to possible life systems? The issue is not that the rules of chemistry are different, it is that our understanding is limited by where we live, we cannot and should not limit our expectations to that which is familiar to us. That is dangerously and rediculously short-sighted. --Jayron32 20:30, 15 November 2011 (UTC)

This is orthogonal to the original question, (I already asserted that we would eventually figure out ways to communicate with creatures on vastly different timescales) but it's still fun and interesting to think about, so I'm going to continue debating it. We have a pretty firm understanding of elemental distribution in the universe, and the range of characteristics found on planets. The reactions you're describing seem to be either extremely rare, unstable, volatile, short-lived, etc. Does this mean it's impossible for life to form utilizing such reactions? No. But it does make it much more unlikely. A creature that took millions of years to think and move around would have to deal with cataclysmic cosmic events (nearby supernovae, asteroid impacts, its star dying, etc), not to mention natural selection. If I was hungry, I'd love to gobble up a big slow alien that can't react to save its life (literally!). Carbon and water and prevalent throughout the universe in large quantities, and they're both so good at what they do! The article Hypothetical types of biochemistry is a good read! Goodbye Galaxy (talk) 21:07, 15 November 2011 (UTC)

The reactions which describe life on earth could easily be described as "extremely rare, unstable, volatile, short-lived, etc." The reason we find them likely is that we find them familiar; but if you view biochemistry with a completely neutral eye, trying to ignore the fact that you know alot about earth-based biochemistry because you are made of it, you quickly become aware of how completely impossible it looks. I'm not sure that, without already having the examples at hand, we could have invented such a convoluted, complex, and strange chemistry from whole cloth. It is only because we have the examples around us that makes it understandable and known at all. If we didn't, I'm not sure we would have thought of it on our own. Sure, basic building blocks exist in the universe (methane, ammonia, water). But the way in which methane, ammonia, and water have come together on Earth to produce life is quite insane, when you think about it. All I am saying is that, given the same building blocks (or even given different building blocks), an equally insane but vastly and incomprehensibly different biochemistry could have developed. If your only defense of the chemistry of Earth-based life is that it doesn't seem rare because we're familiar with it, doesn't mean it isn't actually rare or unusual or bizzare. --Jayron32 21:17, 15 November 2011 (UTC)

Does alien life need to even be biochemical ? Perhaps a purely electromagnetic life form can arise in the interior of stars. Or perhaps dark matter, whatever it is, is alive. Or, even if we talk about biological life forms, I believe there are bacteria which live deep underground that have much slower metabolisms than those we are familiar with. Yes, they aren't intelligent, but perhaps more complex organisms can exist with a similarly slow metabolic rate. StuRat (talk) 21:25, 15 November 2011 (UTC)

What Stu said. One of my favorite thinkers in this regard was the humorist Douglas Adams. A major theme of his is the Fermi paradox. I don't recall where all of the examples from his works are (they kinda run together for me); but there were the Dolphins trying to warn humans about the impending destruction of Earth (whose language we constatly misinterpret as cute tricks), there was a fun speculation about intelligent Rhinoceri who sense their world primarily via smell, and thus have difficulty communicating with life forms who sense via sight and sound, there was once when he propsed a "hyperintelligent shade of the color blue". Which is not to say that Adams was anything resembling a serious xenobiologist; but he DOES represent the sort of imaginitive thinking that people need to have to drive forward scientific thought. We don't get very far if the only kind of world we can imagine is the one we (think that we) live in. --Jayron32 01:45, 16 November 2011 (UTC)

The article cites a broken link, a lecture by James Schombert at the University of Oregon. I think that lecture is here: [3]. It mentions the idea only very briefly, as follows:

ET has no interest in conversing with lesser beings. Problem: with millions of possible civilizations, someone would have some curiosity.

So the idea as it appears in the source is far less elaborated than in the article, and says nothing about "psychologies too different to understand the concept of communication". Also: of course human language is parochial to Earth, duh. This is very different from the idea that human mathematics might be parochial. It would be surprising if intelligent aliens couldn't do sums, but absurd if they spoke Dutch.

- In fact, I have taken a violent dislike to that paragraph in the article and have pruned it back radically (and fixed the link to the source).  Card Zero  (talk) 19:50, 15 November 2011 (UTC)

I used archive.org to check the source myself, and the part most relevant to my question is this section: "# They Develop Different Mathematics * Mathematics is the universal language. But humankind may have a unique system of mathematics that ET cannot understand. Problem: then where are their incomprehensible signals? " --Gary123 (talk) 22:01, 15 November 2011 (UTC)

Holocene epoch

Why is the Holocene considered a distinct epoch when (from what I've read) it appears no different from the many other interglacial periods that occurred during the Pleistocene? --Lazar Taxon (talk) 13:33, 15 November 2011 (UTC)

Humans as a species have profoundly changed the Earth that I do think we qualify quite easily for a faunal stage very distinct from the stages/ages preceding it and the epoch that contained them. - Obsidi♠n Soul 14:13, 15 November 2011 (UTC)

That's correct. for instance: Mammoths are no where to be found within Holocene layers. Dauto (talk) 16:18, 15 November 2011 (UTC)

Probably helps that we've caused the extinction of more organisms than any other (all the other?) organism(s) combined. I'm not proud of it. Heck froze over (talk) 18:20, 15 November 2011 (UTC)

And being the most recent it is represented by the top sediment layer, and therefore different from buried or eroded ones. Graeme Bartlett (talk) 02:09, 16 November 2011 (UTC)

2 x 4 wall cavity

what is the maximum amount of fiberglass insulation That you can put inside a 2 x 4 wall cavity? r-10, r-12, r-14 ect — Preceding unsigned comment added by 208.86.2.203 (talk) 14:57, 15 November 2011 (UTC)

Most people won't know what you mean by a 2 x 4 cavity. Dauto (talk) 16:21, 15 November 2011 (UTC)

I think the OP means the cavity between wall studs, built of "2x4" structural elements (nominally two-inches by four inches, explained in greater detail in our article on dimensional lumber). The exact r value depends on not just the dimensions, but the quality of the insulation you're buying. Nimur (talk) 17:46, 15 November 2011 (UTC)

Yes, I know that's what he meant. I was just pointing out that some people might not understand that. Dauto (talk) 18:29, 15 November 2011 (UTC)

I feel that listing the nominal size is misleading to anyone who doesn't understand 2x4. He is asking how thick can the insulation be that could be put into a cavity with a depth of 1.5 inches. -- kainaw™ 18:32, 15 November 2011 (UTC)

You mean a depth of 3.5 inches, don't you? Dauto (talk) 19:15, 15 November 2011 (UTC)

There are three kinds of nominal 3.5" batts sold: R-11, R-13 and R-15. R-13 is the most common these days. The difference has to do with the fiber matrix and resin binder, and I don't think R-15 is available at all in formaldehyde-free formulation. Fiberglass is extremely sensitive to correct installation procedure. Just mashing it in will not result in the advertised value, it must be cut to fit snugly without much compression.Acroterion (talk) 21:41, 15 November 2011 (UTC)

[www.habitat.org/env/pdf/wall_insulation.pdf] covers the subject well. Rmhermen (talk) 02:02, 16 November 2011 (UTC)

2 inch foam board insulation

I was working with some 2 inch r – 10 foam board insulation. It seems so rigid anddense it seems like it would have a greater R-value than r – 12 fiberglass bats. Does anyone else agree with me on that? Have there been any tests to compare R-value? — Preceding unsigned comment added by 208.83.61.203 (talk) 15:00, 15 November 2011 (UTC)

10 is less than 12. Dauto (talk) 16:16, 15 November 2011 (UTC)

It's worth noting the difference between thermal mass and thermal conductivity. R-value nominally describes conductivity, not heat capacity. Nimur (talk) 17:48, 15 November 2011 (UTC)

Thermal conductivity and density are usually in opposition, there are grades of foam insulation (for using under walkways and slabs) that are denser, and they have poorer thermal performance. R-value for expanded polystyrene (white beadboard) is about 4 per inch. For extruded (the blue, pink or green non-beaded stuff) is 5 per inch. Fiberglass varies greatly, but is about 3 per inch. R-11/R-13 fiberglass batts are 3-1/2" thick. Acroterion (talk) 21:34, 15 November 2011 (UTC)

wet insulation

Can anyone tell me if there is any insulation that retains its full R-value when wet? I am wondering also, what percentage R-value most insulation retains when wet? For example, fiberglass, cellulose, Styrofoam pellets, rock wool? — Preceding unsigned comment added by 208.83.61.203 (talk) 15:03, 15 November 2011 (UTC)

Styrofoam (the slab, not the pellets) and rocks being waterproof likely retain their full R-values. The other ones will absorb water which conducts heat better than the air it replaces reducing the overall R-value. Dauto (talk) 16:15, 15 November 2011 (UTC)

Styrofoam (as Dauto says, the extruded kind, not the beaded kind) is commonly used underground and in wet applications. Practically all other materials will absorb water and lose efficacy. Acroterion (talk) 21:37, 15 November 2011 (UTC)

Survival experts [4], state that wool and synthetic fibers such as polypropylene and Polarguard retain much of their insulating value when wet, unlike cotton or down. If you are interested in building insulation, see Building insulation materials. Those which absorb water, like fiberglas batts, cotton batts, cardboard, or rockwool, would lose much of their insulating ability. Insulation impervious to water would keep a high percentage of its R value. (Paradoxically, sawdust, straw and woodchips were historically used to insulate blocks of ice in 19th century icehouses, sometimes piled directly around the ice, so they must have retained appreciable insulating value even when wet.) Here is an article discussing various types of roof insulation's equilibrium moisture content at various relative humidities. They cite one research on the ratio of wet thermal resistance to dry thermal resistance (TRR). Here is the book "Thermal insulation, materials and systems...] with considerable discussion of wet insulation problems and measurements.Pages 563-661 cover moisture effects on insulation R value. Your library should be able to get the book for you via interlibrary loan. Here is a 1991 research paper, all viewable, with TRR data for several types of building/roof insulation. Edison (talk) 20:29, 16 November 2011 (UTC)

Non-finger interaction with iPad touchscreen -- how to generate touches with objects

Hi all,

The iPad uses a capacitance touch screen. According to the the article, "capacitive screens respond to only materials which are conductive (human finger used most commonly) ...A standard stylus cannot be used for capacitive sensing unless it is tipped with some form of conductive material, such as anti-static conductive foam."

I am trying to get the iPad to recognize a touch without touching it. I have dropped both a cube of antistatic foam (from a microchip package) and a wad of steel wool and neither one of them triggered a touch event, unless I was touching the foam or wool with my finger. I also tried a sponge that had been slightly dampened with salty water and it didn't work (although I would prefer this not to require wetting object).

Any suggestions on what material I could use such that I could place it on the screen and generate a touch event? Thanks! — Sam 63.138.152.219 (talk) 15:13, 15 November 2011 (UTC)

I suggest an iPad stylus. There is a large market of them from very cheap (less than $10) to rather expensive (over $50). -- kainaw™ 15:17, 15 November 2011 (UTC)

I'm looking for something I can make myself. — Sam 63.138.152.219 (talk) 15:21, 15 November 2011 (UTC)

Sure. If you google for "how to make an ipad stylus" you will find a lot of examples such as: A guy who cut up a pair of $15 socks to make a $5 stylus. A guy who wrapped a pencil in about $20 worth of copper wire to make a $5 stylus. A guy who converted a $250 oscilloscope to work as a $5 stylus. Etc... -- kainaw™ 15:40, 15 November 2011 (UTC)

Almost every single one of those hand-made iPad styluses require the hand to be touching them. The $5 ones you're referring to also require a hand. My whole question is: how can I create some sort of surface that doesn't require the magical properties of a human hand to work? I don't want a stylus, bought or handmade. I want a surface that mimics the properties of a hand. Sorry if this wasn't clear...

Anyway, with some more research I've found that the salt-soaked sponge occasionally works. If I drop the sponge or move the sponge with a pen, I can get occasional touch events. However, I'd love some material that didn't need to be wet in order for it to work (anti-static foam? That should work, why doesn't it!). Thanks — Sam 63.138.152.219 (talk) 17:26, 15 November 2011 (UTC)

The objects you are using are likely too small to trigger the touch. Try connecting them to some large conductive object such as a metal chair or something. Dauto (talk) 17:45, 15 November 2011 (UTC)

There are some styli that I presume work without the hand, look for those which are advertised for gloved hands. You can also try the bottom of a 1.5V battery or the non sharp side of a row of staples or the back of a spoon or fork which seems to work on occasion to me (when dropped gently or rested) on a capacitive touch screen and don't require getting the screen wet. I can't guarantee any of these, particularly the battery are good for the screen. I can also say the paw pad of a live cat works when I tested it on a capacitive touch screen. Parts with fur like the tail do not. None of this was with an iPad, if you're willing to send me an iPad I can test if it work with that. Although it may take a few days for the cat test since unfortunately the former test subject is no longer alive, so I'd need to get assistance from someone else. And before any joker asks, no I did not test the cat's paw pad after it died. Nil Einne (talk) 18:43, 15 November 2011 (UTC)

Hmmm... I've tried all of those now except the cat, and none of them seem to work. The staples and battery require a finger, the fork and spoons don't work at all, but I assume that this is related to the type of metal used (they look stainless). Barring using live cats for this experiment, I guess I may need to invest in one of the higher-end styli... It seems like it ought to be possible to make this yourself, though. The now-drier salty sponge still works, but I expect it won't work when it's completely dry. — Sam 63.138.152.135 (talk) 19:21, 15 November 2011 (UTC)

I should perhaps clarify the spoon and fork which are just ordinary cheap stainless steel ones (bought at quite different times too) seem to work okay (not all the time but it's not hard for me to get them to work) when rested on the phone, perhaps supported by a plate or something else so it makes decent contact (although with the iPad you could perhaps just rest the whole spoon on the iPad). I don't have much experience with the iPad but if there's some way you can make it so it's obvious if it's sending you can try moving the phone and spoon around and then move your hands away and see if it's still being detected. The batteries also sometimes work when rested on the phone although but from further testing it's harder then I thought initially. You can also try with a thin plastic bag (of the sort you get in the supermarket in places that haven't banned them) below the spoon, I found out a while ago these work with fingers but they also seem to work when combined with the spoon, although I don't know if there's much chance they will work since your iPad doesn't work with the spoon itself. BTW most of these (can't remember about the cat one) were with an LG P500 which was a low mid end phone (but does have a capacitive touch screen). Nil Einne (talk) 20:34, 15 November 2011 (UTC)

I don't know about iPads, but I worked in a low-temperature research lab. When wearing thermal gloves it was impossible to manipulate laptop touchpads, but we found that you could consistently control the touchpad if you added a thin polyethylene glove (like this [5]) on top of the thermal glove. I would imagine that if you make something that looks like a thermal gloved finger with a polyethylene wrapper then you'd have a good chance of triggering an iPad. (I'm implicitly assuming that iPads and laptop touchpads use similar technology, though I don't actually know that to be true.) Dragons flight (talk) 17:55, 15 November 2011 (UTC)

That's interesting, I wonder if there's something special about polyethylene. I'll have to see if I can get my hands on some. I wouldn't be surprised, though, if what worked on a different touch pad didn't work on an iPad... — Sam 63.138.152.135 (talk) 19:21, 15 November 2011 (UTC)

It's photons all the way down.

Do all particle annihilations lead towards producing photons? Given any starting particle-antiparticle annihilation, then taking the particles produced by this, and annihilating them with their respective antiparticles, and so forth and so forth, will you always end up with photons? If this is the case, what is the significance of photons? Is it just that they are massless? Seems weird to me that the carrier particle of just one of the four fundamental forces would be the trunk of the particle tree. --Goodbye Galaxy (talk) 15:56, 15 November 2011 (UTC)

Yes, it is (almost) true that eventually all that will be left will be photons. That happens because photons are massless and non-confined by the strong force. Confinement prevents the production of free gluons. The reason I said almost true is because the production of gravitons is also possible but gravitational force being a million trillion trillion trillion times weaker than electricity leads to a negligible chance of graviton production that way. Dauto (talk) 16:11, 15 November 2011 (UTC)

Are not neutrinos also ultimate end products of some annihilations? Scratch that: I see that they annihilate with anti-neutrinos to form Z-bosons. {The poster formerly known as 87.81.230.195} 90.193.78.25 (talk) 16:36, 15 November 2011 (UTC)

Neutrino--anti-neutrino pairs can exchange a W-boson particle turning into a virtual electron--positron pair which annihilate into a pair of photons. But the cross section for such reaction is extremely small. Dauto (talk) 16:57, 15 November 2011 (UTC)

hormone change

simple question! can a girl hormone change to a guy hormone??? try sending answer at (email redacted) — Preceding unsigned comment added by 78.101.36.81 (talk) 18:10, 15 November 2011 (UTC)

email redacted Heck froze over (talk) 18:17, 15 November 2011 (UTC)

Depends on what you mean by "can change". It can be changed by someone who has some knowledge of organic chemistry, but it doesn't spontaneously change as if by magic. The structures of testosterone and progesterone are very similar, so such a change could be done in a little beaker on a lab bench. Both are subclasses of a group of hormones called Corticosteroids, so the process by which the human body makes each of them from raw building blocks is roughly similar, with slight tweaks. The group of female hormones called estrogens are more distantly related to those two, chemically, and so would be much tougher to synthetically convert to testosterone. --Jayron32 18:46, 15 November 2011 (UTC)

(EC) Yes. According to this chart, during natural steroidogenesis in humans, progesterone, which is a "girl hormone", can get turned into testosterone, which is a "guy hormone", in a three-step process. Red Act (talk) 19:03, 15 November 2011 (UTC)

Mar's Low Gravity

Ok so Mars has .376g and Earth has 1g. My weight is 110lbs so on Mars it would be 68lbs. Could you just wear weighted clothes (42lbs) to counter the effects of low gravity? Oh and did I even figure this out correctly? Matthew Goldsmith 18:37, 15 November 2011 (UTC)LightylightMatthew Goldsmith 18:37, 15 November 2011 (UTC)

It might help, but it wouldn't be the same, since the weight wouldn't be distributed as it is in your body. Also, your math is a little off. At 0.376g you would weigh about 42 pounds, so your clothes would have to be about 181 lbs (on Earth) to make it feel like you were your normal weight on Mars, since they would weigh less as well. --Goodbye Galaxy (talk) 19:03, 15 November 2011 (UTC)

(EC)No, you did not figure it out correctly. 37.6% of 110 lbs is about 41.4 lbs, not 68 lbs. A weighted suit would counter some of the effects of low gravity, but not all. Dauto (talk) 19:13, 15 November 2011 (UTC)

And it would make movement very hard - the inertial mass is the same on Mars and Earth, i.e. to accelerate your 50-pound sleeve you would still need to use plenty of force (and the same to stop it from moving). --Stephan Schulz (talk) 20:02, 15 November 2011 (UTC)

What effects are you trying to counter ? For the most part, lighter gravity is better, in that you can carry more objects, move faster, work longer without getting tired, etc. There is the negative effect that the body becomes accustomed to the reduced gravity, and the thinner bones and reduced muscle mass are problems when you go back to Earth. So, your idea might make some sense, for that reason. However, don't just add weights to your clothes, add something useful, like extra oxygen tanks, a spare spacesuit, satellite antenna, etc. StuRat (talk) 22:01, 15 November 2011 (UTC)

Sham-Wows and the Hudson River

How many sham-wows would it take to absorb the entire Hudson River? Also, how much would they cost? Smartyllama (talk) 19:45, 15 November 2011 (UTC)

That would be difficult to answer, because it isn't easy to define how much water is in the Hudson River. It isn't a static body of water, so the amount of water in the river varies greatly over time. If you were to choose a body of water whose volume was easier to measure, it could be done trivially. Based on the claim that a ShamWOW can hold 12x its weight in water, simply weigh a ShamWOW, multiply it by 12, and then take that number and divide it into the weight of the water in the desired body. For example, lets say I had a 1.25-ounce piece of shamwow. 12x 1.25 ounces is 16 ounces, which is one pound. If I have a 5 gallon jug of water, that weighs 40 pounds (water is 8 pounds to the gallon). It would then take 40 Shamwows to absorb all of that water; just multiply that by the cost of each of them. The same calculations would work for larger bodies of water as well, you just need to replace the size of my jug of water with the size of the Hudson River (assuming you can do that reliably) and do the exact same sequence of calculations. You'd also have to get the correct weight for a Shamwow, because I made up that number as well. --Jayron32 19:57, 15 November 2011 (UTC)

An average shamwow can hold less than 2 cups of water. The Hudson river does not have a constant amount of water due to the rise and fall of water levels. It is in the millions of gallons. There are 16 cups to a gallon. So, if you pick some estimate, such as 16 million gallons of water, you can calculate how many cups that takes and divide by two. -- kainaw™ 19:57, 15 November 2011 (UTC)

Oddly enough Kainaw, I came up with a Shamwow holding the same amount of water (2 cups of water weighs exactly one pound), though I was basically making stuff up. --Jayron32 20:01, 15 November 2011 (UTC)

Am I the only one wondering WTF a ShamWow is? Vince Offer#ShamWow! [6] [7] Nil Einne (talk) 20:47, 15 November 2011 (UTC)

It's obviously something that makes you go "wow" after you discover it was a sham. --140.180.3.244 (talk) 23:04, 15 November 2011 (UTC)

It's a synthetic chamois cloth. Chamois is pronounced roughly as "Sham-wah". Hence, "ShamWOW!" --Jayron32 23:10, 15 November 2011 (UTC)

In my part of the USA, we pronounce "chamois" as "shammy". Since "chamois" is a public-domain word, the inventors of the "Cham-Wow" had to come up with something unique. That product would seem to not be the most efficient. I wonder how large a kitchen sponge would have to be, to soak up the Hudson at a given moment. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:23, 16 November 2011 (UTC)

In my experience, a kitchen sponge can hold approximately its own volume in water. So, to absorb the Hudson River, you'd need a sponge as large as the Hudson River. --Carnildo (talk) 02:17, 19 November 2011 (UTC)

As the Hudson River page says, its average flow is 21,400 cubic feet per second (610 m³/s). Google tells me that 2 cups is equal to 0.000473176473 cubic meters. So, if these things absorb 2 cups each, and unless my math is as bad is it sometimes is, you'd need over 1,280,000 per second during an average flow of the river. Pfly (talk) 04:18, 16 November 2011 (UTC)

Kangaroos and the Fourth Dimension

Not sure if this should go in entertainment or here. In the TV show Flashforward, on certain occasions, kangaroos would show up at random places right after people woke up from global (or local) mass blackouts/loss of consciousness (i.e. the "Flashforwards"). I happen to know that kangaroos are unable to step backwards (in the third dimension). Is it possible that this could also hold true in the fourth dimension, and thus that after Flashforwarding, they would be stuck in the future? Also, note that at least one of the flashforwards/GBOs (and possibly more) happened within a few minutes of the "future vision point" for a previous GBO, which is when the human (and at least some animal) consciousnesses flashforwarded to. Also, is there anything particularly unusual about kangaroos' brains, particularly the hippocampus? It may have played a major role in the show if it hadn't been cancelled. Finally, could someone please answer the last question for black camels also. Smartyllama (talk) 19:53, 15 November 2011 (UTC)

The laws of physics are not required to behave correctly (or even make sense) in works of fiction. Asking how physics "happens" in a fictional work is a pointless exercise, if the writers have made it explicit you can get your answer from the work of fiction itself. If they have not, then there is nothing we could factually say here which could be an appropriate answer. --Jayron32 19:59, 15 November 2011 (UTC)

Except cartoon physics. ~AH1 ^(discuss!) 03:20, 16 November 2011 (UTC)

Note that our article for the 2009 television series is capitalized as FlashForward. -- 203.82.66.198 (talk) 23:11, 18 November 2011 (UTC)

natural selection in medicine?

Can people use natural selection for producing drugs?for example, taking a population of mice(lab mice), infecting them with HIV for many generations and see if any of them shows any resistance.Has it been done before?--Irrational number (talk) 20:20, 15 November 2011 (UTC)

...how would that help you combat HIV? Natural selection is great for producing genetic changes over big populations over time, but it's unclear how you're going to take genetic changes from a rat and apply them in a way that's useful for a human. There might be some conceivable mechanism from your HIV-resistant rat that could be transferrable, but it seems like a pretty long shot given the sizes of the populations and the time you'd need to see useful mutations. --Mr.98 (talk) 20:31, 15 November 2011 (UTC)

It wouldn't necessarily require new mutations. A small portion of humans seem to be immune to AIDS, and perhaps the same is true of rats and other diseases. If you could develop a strain of rats resistant to the disease in question, then perhaps we could figure out what the difference(s) are in those rats, and invent a gene therapy for humans to make those same changes. However, why wait for natural selection, when you could hurry it along with artificial selection, by breeding the healthy rats and killing the sickly ones ? StuRat (talk) 21:36, 15 November 2011 (UTC)

Since we don't have gene therapy at all yet, and really have no practical way of imagining how it would work, this is still a pretty sci-fi explanation. That's kind of my point. --Mr.98 (talk) 02:01, 16 November 2011 (UTC)

(edit conflict)That's theoretically feasible, but there's no need to develop naturally resistant mice in the lab. A very small percentage of the population already is naturally immune to HIV —or to any other virus/illness you can think of— and, actually, those people are one of the most important sources of information for finding a cure for the illness. --Cerlomin (talk) 21:37, 15 November 2011 (UTC)

True, but they tend to object to us performing autopsies on them to study the differences in their bodies. :-) StuRat (talk) 21:39, 15 November 2011 (UTC)

I suspect you were joking, but if not, do you have any evidence suggesting that HIV-immune people tend to object to such studies? Also, I'd imagine that a blood sample is enough for studying HIV resistance; what advantage would a dead body have? --140.180.3.244 (talk) 22:56, 15 November 2011 (UTC)

The problem is not getting evidence from people who are resistant after they are dead. The problem is finding out who is naturally HIV resistant. You're not going to get a lot of support for a "expose 10,000 people deliberately to HIV, and then see which two or three of them are resistant" sort of study. If you did for some reason know that someone was naturally resistant I doubt you'd have too much trouble getting permission to study them, alive or dead. --Mr.98 (talk) 02:01, 16 November 2011 (UTC)

Mr.98 and 140.180 are of course right, there are plenty of studies being done on those who have been identified which have provided a variety of clues [8] [9] [10] CCR5. The first and big problem is finding them, next is identifying genes which contribute to their resistance. Which is related, as it usually relies on correlation analysis, so you need to identify a fair number of people who are resistant. While StuRat is right you can't be as invasive as you could be with labratory animals, in particular you can't kill them to study them in ways you can't while alive, I don't think that's really that big a limitation. With modern biology and HIV I don't think that's really that useful particularly since you're studying people who just don't get the disease. Perhaps a slightly more significant limitation is related to Mr.98 said, even if you know they have some natural resistance it would still be extremely unethical and of course you're unlikely to get consent to expose them to HIV, nor for that matter anyone with the gene you identify as being a likely candidate. Nor for that matter can you produce clones bar that gene (or more likely with a different, functional allele) to test or anything like that (although I don't believe knockout clones for mice is easy enough to be feasible yet anyway). However on the flipside your working on your target rather then some model system so any genes and info you gather probably has more relevance. Nil Einne (talk) 02:27, 16 November 2011 (UTC)

Note that HIV resistance can mean two things: 1. Resistance to HIV infection (no HIV, despite exposure) or 2. long-term non-progressors (no AIDS, despite HIV). In the first case, I don't see why you wouldn't find enough test persons to be analyzed in a non-invasive way. There is no need to expose anyone deliberately to an HIV infection. In the case of 1. you have long-term partners of HIV positive people and children of HIV positive mothers, but 2. is more tricky, since you'll need a HIV positive person, who does not get antiretroviral drugs and does not develop the AIDS. 88.8.67.30 (talk) 11:57, 16 November 2011 (UTC)

Calling all frog-experts

Sorry if you dislike reposts, but I'm not sure if I could reference my previous post on the village pump. Any ways, it's about a photo I took of a frog while at Bamburgh Castle. I am clueless to which species it is, and someone from the village pump suggested I asked the science reference desk, as they usually give quick and accurate replies. It wouldn't surprise me if it's just the common frog, to be honest. John Aplessed (talk) 21:40, 15 November 2011 (UTC)

The mystery frog

— Preceding unsigned comment added by 77.98.243.16 (talk) 21:38, 15 November 2011 (UTC)

To be as quick and accurate as I can, I think it's a Common toad.Richard Avery (talk) 21:55, 15 November 2011 (UTC)

a-theorem?

Just saw an article in Nature News that I completely don't understand: [11] We don't have an article a-theorem and "komargodski" returns no results. The theorem, now reportedly proved in 2 and 4 dimensions, "says that the number of ways in which quantum fields can be energetically excited (a) is always greater at high energies than at low energies." But how is this number of ways counted, and how can an apparent mathematical proof be offered about it, etc...? Wnt (talk) 21:43, 15 November 2011 (UTC)

This isn't an answer to your question, but for reference, the proof referred to in the article is here. Red Act (talk) 22:13, 15 November 2011 (UTC)

Thanks for the link... now, if only I understood dilatons... this is quite the proverbial rabbit hole. ;) Wnt (talk) 14:36, 17 November 2011 (UTC)

Scum on my teeth

When I eat a banana, my teeth feel "slimy", yet also dry. I've noticed that eating a banana with oatmeal doesn't cause this effect, presumably because the oats wipe the slime off my teeth. I've also noticed the same slimy teeth effect from pomegranates. Noting that both of those are high in potassium leads to my question: Is this scum some form of potassium ? StuRat (talk) 21:53, 15 November 2011 (UTC)

It has nothing to do with potassium. You're talking about astringency. Tannins are the culprit. Both pomegranates and bananas are rich in tannins when unripe, and when ripe, there are still plenty in those parts of the fruit that you don't normally eat (especially the skin, but also the three stringy strips that the length of the banana). Another fruit that is highly astringent when unripe is the persimmon. As these fruits ripen, the tannins break down and the fruits lose their astringency. The tannins cause proteins in saliva to clump together and form a coating on the tongue and teeth. And you get a dry, "puckery" feeling in your mouth. Oatmeal is very high in protein. There probably aren't enough tannins in the ripe bananas your eating to effective cause clumping of so much protein (at least that's my best guess). Dominus Vobisdu (talk) 23:26, 15 November 2011 (UTC)

You can get the same effect with strong tea too. 86.169.18.74 (talk) 16:33, 16 November 2011 (UTC)

Thanks. I wonder if anyone is working on ways to fix this, as it makes it rather unpleasant to eat those items. StuRat (talk) 04:51, 17 November 2011 (UTC)

Tannins aren't exactly optional though. At least one of their functions (one of the most apparent anyway) is antipredator defense. It keeps unripe fruits from being eaten while still not ready, as aside from causing astringency, they give an unpalatable bitter flavor and interfere with digestion of proteins in large herbivores (they can even interfere with drug absorption in humans). They are also toxic to insects and antibacterial. They are so prevalent in plants that tannins cause some rivers that run through forests to turn black due to tannins from decaying leaves, the blackwater rivers.-- Obsidi♠n Soul 05:50, 17 November 2011 (UTC)

StuRat, have you considered waiting until the banana is actually ripe?? Tip: Bananas aren't ripe until there is no green on the skin anywhere, even up by the stem, and there are at least a few little brown spots on the peel lower down. --Trovatore (talk) 06:23, 17 November 2011 (UTC)

I do wait until there's no green, but by the time there are brown spots there are frequently large spoiled spots inside and a swarm of fruit flies around (of course, they are put off by the tannins as much as I am, but having the tannins only in the skin could prevent that). I also once bought a variety of tiny bananas at an Indian store that appeared ripe, but were far worse, as far as tannin content, than the Cavendish bananas I usually get. StuRat (talk) 17:48, 17 November 2011 (UTC)

Persimmons, on the other hand, are never ripe — they go straight from unripe to rotten. See bletting. My only advice for that problem is, don't eat persimmons. At least not raw — they can be pleasant in breads and maybe in preserves. --Trovatore (talk) 06:33, 17 November 2011 (UTC)

My advice, on the other hand, is that there are few things finer in life than gorging yourself on icky-looking, half-rotten American persimmons "fresh" off the tree. It's the only fruit I know that can compete with durian.

"Rotten" is not necessarily bad. Essentially, all fermented foods are "rotten": wine, cheese, pickles, sauerkraut, miso etc. In fact, the finest German wines are made from grapes that are left to rot on the vine, and are decomposed by the Botrytis fungus, also called the "noble rot".

I live in Poland now, and every year, the large Oriental persimmons appear in grocery stores and fruit stands. The locals don't know that you can't eat the fruit until it turns a bit mushy, and thus the fruit hasn't really caught on (the taste of an unripe persimmon is enough to turn anyone off for ever). A lot of the persimmons go unsold and are put up for sale at reduced price, and that's when I have a field day. No comparison with American persimmons, though.

By the way, the large attractive persimmons you see for sale in America are all oriental varieties. American persimmons are not sold in stores (at least I've never seen them). You either have to find them growing wild or have a tree planted in your yard. The trees on our property were incredibly productive, and even with seven hungry boys in our family, we still had plenty left to make lots of persimmon pudding and cake. Dominus Vobisdu (talk) 08:52, 17 November 2011 (UTC)

Hmm, well, I think we just have different tastes. I can't stand durian. To me it tastes like rotting fish. Don't particularly like German wine either — prefer Italian or Californian. --Trovatore (talk) 19:14, 17 November 2011 (UTC)

I love durian. I'm beginning to think the affinity to the smell of durian is genetic. My friends can also neatly be divided into two groups: those who can't stand the smell of durian, and those who actually describe it as "fragrant" (like me). I really don't understand though, it smells nothing like sewage, rotten fish, etc. that you guys usually describe it as. It's very strong, yes, but it's a plant-like smell (very much like vanilla really), and the taste is like sweet custard or melted icecream. -- Obsidi♠n Soul 07:59, 18 November 2011 (UTC)

On the other hand, I can't stand the smell of most cheeses.-- Obsidi♠n Soul 08:03, 18 November 2011 (UTC)

And I don't think that skunk spray stinks. It can be quite strong, yes, but isn't inherently unpleasant, to me. I must come from a long line of skunk herders, to have evolved in this way. StuRat (talk) 20:56, 18 November 2011 (UTC)