Wikipedia:Reference desk/Archives/Science/2009 February 7

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February 7

Red Alert!

Now then, when I was at school, my physics teacher introduced us to an idea about perception of colour: my mum takes a red apple and points to it and says 'red, red'. Perhaps what I am seeing is what my mum would refer to as purple, but I never question this and take it as 'red'. Is our perception of colour entirely our own, in that we may all see different colours in our own experience and interpret them in our own way, or is it most likely that, because of genetic inheritance, our eyes and brains are wired up to interpret the same colour as the same thing?

Thanks for your perspectives —Preceding unsigned comment added by 86.138.239.146 (talk) 01:34, 7 February 2009 (UTC)

see Color vision, Color theory and Visible spectrum. You might also find Synesthesia interesting. 76.97.245.5 (talk) 01:45, 7 February 2009 (UTC)

Most people have the same 3 basic types of cone cells in their retinas, so yes, most people see colors the same way. That does not mean that people name colors the same way, or have the same fixed associations between colors and objects. You learn the names of different colors (and of different objects) from the people you interact with during your early childhood. --Dr Dima (talk) 01:46, 7 February 2009 (UTC)

I guess you can't know what I see when I see red. It seems obvious that the basic spectrum follows the frequency range of the light at least roughly, but one look at a van Gogh I think shows that our perceptions differ. And at the divide between, say, blue and green, I know we differ (ask my wife). Around the world, too, colors have different connotations according to the culture they're being perceived within; in many places, red is the color of happiness, whereas in the USA, I think, it's more the color of passion or blood. In many places, white is the color of death, whereas here it's the color of purity, and black is the color of death. These culturally foisted attitudes toward a color will affect our perception of it. For me, yellow is foody—butterscotch, lemon, banana—but for you it might be sunlight and your long-lost rubber duckie. There is an interesting discussion about the differences between Russian and English ideas about color here. One item is that Russian distinguishes two shades of blue, a light and a dark, with the same degree of distinction English shows between red and pink. --Milkbreath (talk) 02:07, 7 February 2009 (UTC)

I once took a class from a very well-respected scholar in the field of color physiology. She explained to me that we have no reason to suspect that people don't generally interpret the same spectra of colors as being roughly the same, barring the occasional differences in eye structure. That isn't quite the same thing as being able to assert the contrary, though. As far as I can tell, we'd know if colors were randomly distributed differently in other people's heads—color theory wouldn't work out the way it does. But if the entire spectrum was slide down a notch or two, I'm not sure we'd be able to tell. --98.217.14.211 (talk) 03:03, 7 February 2009 (UTC)

Also see trichromatic theory, which pretty much says the above answer. —Cyclonenim (talk · contribs · email) 08:19, 7 February 2009 (UTC)

Colour perception and categorisation is largely a matter of the physiology of the way the eye works for the main groupings; primary and secondary colours. However, there is an element of cultural differences as one drills down in to finer distinctions of hues and shades. There have been many studies of this sort which ask participants to group samples together by colour, this one for example. The most common differences are in the blue/green area but there are also languages which do not distinguish oranges, they are all variations of brown. SpinningSpark 12:55, 7 February 2009 (UTC)

Surely all the OP is asking about is qualia? Not that people make different distinctions between colours, not that different cultures name them differently, not that some people are more sensitive to some colours, but that we can all be calling our experience of a given wavelength 'red' without knowing what each other's experience is. So I could experience what you would call 'purple' when interpreting the wavelength we both call red. I would call this experience 'red', as you call your experience on viewing this wavelength 'red', but we are experiencing different colours for the same wavelength. We would never know, or have a way of knowing. Without some sort of mindreading powers, I don't see how this question could ever be settled. 79.66.57.25 (talk) 15:31, 8 February 2009 (UTC)

Yes, the qualia artcle deals with the questions you raise. Dang, beaten again. ReluctantPhilosopher (talk) 16:28, 8 February 2009 (UTC)

Greed not genetic?

A friend of mine says he does not think there is a gene responsible for human greed (given its complexity and its presence in non-humans), or that greed (or any other psychological failing of human nature) will ever be solved through genetic engineering. Given how permanent and universal greed, lust, gluttony, wrath, and blind faith (which IMO is the eighth deadly sin) seem to be in humans, where but in the genome could these traits reside? NeonMerlin 02:55, 7 February 2009 (UTC)

(Why would its presence in non-humans be evidence against it, and not for it? Most human genes are present in non-humans. The number of uniquely human genes is very small. Human didn't evolve the eye from scratch, either.) While I agree with your friend that the common definition of "greed" is hardly a scientific description of a personality trait or a behavior, the idea that the imprecision of our language in describing the term somehow rules it out of the genetic realm seems to me a bit false on the face of it. It's been shown in a few different ways that traits that look quite complicated in humans can be abstracted down to a fairly finite number of interacting rules—robots given just a few behavioral guidelines (try to get close to the green light but not too close and avoid robots trying to steal it from you) end up reproducing a wealth of behaviors that we can identify as being similar to the actions of love, hate, etc., without all of that gloss of intellectualism and culture. In any event, there capacity for greed and so forth must surely be built into the genes somewhere, and the idea that the brain is just an infinitely flexible capacity machine seems false (given how readily predictable most people are). So there's probably some germ of greed in all of us. And why shouldn't there be? The selective value of a little greed is obvious, just as the selective value of a little altruism (but not too much) is obvious. This isn't to say we should all be greedy—we certainly have the capacity to examine our habits and inclinations and determine what we consider to be ethical, good, etc., and this seems fairly uniquely due to our big ol' brains—but to try and get out of a bad habit by denying that it lies at the very core of whatever we call "human nature" seems the wrong approach. --98.217.14.211 (talk) 03:10, 7 February 2009 (UTC)

I would expect greed to have a genetic component. The only animals I'd expect not to exhibit any greed are insects like ants and bees where the workers can't directly pass on their genes. Therefore, being a greedy worker wouldn't have any advantage for them in terms of being more likely to survive to pass on their genes. StuRat (talk) 09:05, 7 February 2009 (UTC)

Not even entirely true of ants. Workers can produce sons (not daughters) from an unfertilised egg (see haplodiploid sex-determination system) but the queen usually prevents this happening by chemical means (pheremones). Workers have been known to produce eggs outside the chemical range of the queen in order to raise sons. SpinningSpark 12:03, 7 February 2009 (UTC)

I think greed has to be genetically encoded—I don't see any plausible alternative—but that's totally different from saying that there's a "greed gene" whose removal would cause a person to not be greedy while remaining otherwise the same. The existence of such a gene is a logical possibility, but there's no reason to think that that possibility is realized in the actual genome, and it's certainly not implied by the claim that greed is genetic. If your friend really is claiming only that (a) there's no gene for greed, and (b) we will never eliminate greed through genetic engineering, then you may not disagree at all. -- BenRG (talk) 13:40, 7 February 2009 (UTC)

See Sociobiology for a nice summary of the issues you and your friend are talking about. Also, don't think of it as though there is a "gene" that greedy people have that non-greedy people (if there are such people) do not have. We are all greedy sometimes and altruistic at other times. We ALL have two copies of EVERY gene. There are many different genes that influence behavioral responses to environmental situations, and those genes all come in a variety of "flavors" (alleles). The precise combination of alleles that you inherited from your parents will influence your behavioral responses. Some day we might have a reasonably good understanding of the interactions between all of these genes and complex behaviors, but we are still quite ignorant of how it all works. I would agree with E.O. Wilson that self-interest (greed) is an intrinsic part of the human condition that is probably "hard-wired" in our genetic make-up. We certainly don't have the technology to "solve" this or any other perceived "problem" by genetic engineering, although one could imagine that natural selection might shape our behaviors over evolutionary timescales. For example, in a situation where food, resources, and mates were limited (i.e. for much of human history), you would expect that the more "greedy" individuals would reproduce at a higher rate than others and therefore contribute a higher fraction of the alleles in the overall gene pool, leading to an increase in "greed". If resources were abundant, perhaps there would be less selective advantage to the "greedy" ones and other alleles would be more prominent in gene pool (especially if altruistic individuals somehow had a reproductive advantage due to being more highly regarded by potential mates). This raises the issue of the cultural aspects of the equation that critics of Sociobiology have raised. It's complicated. --- Medical geneticist (talk) 14:42, 7 February 2009 (UTC)

I don't agree that "We ALL have two copies of EVERY gene". Male humans have only one X and one Y chromosome, so there's the potential to have a single copy of a gene on either of those. StuRat (talk) 15:43, 7 February 2009 (UTC)

You're technically correct but missing my point. I was trying to remind the OP that it isn't a "gene" that somehow pops up in a person with a particular trait/disease/behavior but that genes are shared amongst all of us. Perhaps I should have said "we all have two copies of every autosomal gene" but of course there would be other "exception-to-the-rule" examples that you could cite, including the number of olfactory receptors, people with cytogenetic abnormalities, etc. We also have copy number variation that affects the number of copies of large stretches of DNA, some of which include genes such that some people have three or more copies of a gene. It doesn't change the fact that a complex trait such as "greed" is polygenic and complicated, and for many of the genes that influence the behavior, we inherit a copy from our mother and a copy from our father and it is somehow the combined output of those two alleles that influences the phenotype. --- Medical geneticist (talk) 16:35, 7 February 2009 (UTC)

There is an enzyme called diglyceride acyltransferase, which is essential for the synthesis of triglycerides, which is what is stored in your fat tissue. This quote comes from the Wikipedia article:

Mice with genetic disruption of the dgat1 or dgat2 genes have been made by the Farese laboratory at UCSF. Surprisingly, DGAT1 mice [1] are healthy and fertile and have no changes in triglyceride levels. These mice are also lean and resistant to diet-induced obesity, consequently generating interest in DGAT1 inhibitors for the treatment of obesity.

Of course, this doesn't prove that there is a gene for "greed" and you might argue that I've gone slightly off-topic, but it is evidence that there could be a gene whereby some people are unable to store fat whilst others are. --Mark PEA (talk) 22:26, 7 February 2009 (UTC)

I was reading about personality in my psychology textbook last night. Good timing. Personality traits have 20% correlation in fraternal twins and 50% correlation in identical twins, which shows that there is a significant genetic component, but you probably wouldn't be able to eliminate it without making the opposite very common. In addition, eliminating greed isn't necessarily a good idea. It's vital to capitalism, and is a great motivator. In addition, it's easier to tell how much you're accomplishing with capitalism than something like communism. — DanielLC 16:21, 8 February 2009 (UTC)

Not only greed, but most of the "deadly sins" seem necessary, to some degree, for survival and progress. StuRat (talk) 19:31, 8 February 2009 (UTC)

heavy menstrual cycle

Sorry, but we cannot answer medical questions here. Please consult a doctor if you are concerned about this subject. --Anonymous, 06:24 UTC, February 7, 2009.

Comment was removed by User:208.76.104.133. TenOfAllTrades(talk) 14:28, 7 February 2009 (UTC)

Colour vision

This "bump in the red cone's absorption spectrum" thing, can someone find me a reference for that? None of the relevant Wikipedia articles seem to mention it... We have a graph of the relevant spectra here, and I don't see a bump. --Tango (talk) 13:14, 7 February 2009 (UTC)

Uh are you referring to a previous question? Or did mention of this bump come from somewhere else? I.E. I think we need more context to understand what bump/why your asking about a bump in the red cone sbsorption spectrum Nil Einne (talk) 13:31, 7 February 2009 (UTC)

He's referring to the discussion "Prism's and white LED's." above (February 5) — Matt Eason ^{(Talk • Contribs)} 13:37, 7 February 2009 (UTC)

The mention in "Prism's and white LED's" above sounds suspiciously like an answer I gave to a ref desk question last year. Mea culpa. The information came from a very old (1968) training information sheet. Tango, I don't have a book reference but I can scan my document and e-mail it if you like. SpinningSpark 13:43, 7 February 2009 (UTC)

Yes, please. Special:EmailUser/Tango should work. --Tango (talk) 15:22, 7 February 2009 (UTC)

It's been mentioned a few times here, I expected those that regularly read the colour related questions (of which there seem to be a lot) to know what I was talking about, sorry! --Tango (talk) 15:22, 7 February 2009 (UTC)

For the rest of us - does "bump" = "shoulder" as shown here http://homepages.wmich.edu/~korista/web-images/human_cone_action_spectra.gif and elsewhere (shoulder in the blue)? —Preceding unsigned comment added by 87.102.43.12 (talk) 16:58, 7 February 2009 (UTC)

That looks like it, thanks! It would be a bump if that graph didn't stop abruptly half way through it (it looks like an artifact of their methodology, rather than anything real). --Tango (talk) 18:21, 7 February 2009 (UTC)

Interesting... here's another Wikipedia image that shows a bump and appears very different to the two linked to above: File:CIE1931 XYZCMF.png. Are these graphs all showing slightly different things, or are some of them just wrong? --Tango (talk) 18:30, 7 February 2009 (UTC)

I haven't checked in the case of these two images - but there are (at least) two ways two obtain these graphs

• 1 Take a visible light spectra of the compunds
• 2 Obtain the sensitivity from human based responcis (sic) to different light frequencies

Note that a bump in the spectra (1) doesn't neccessarily mean it the substance produces an (neural) responce when in the eye. (it probably does - I'm just suggesting caution...)

I'm fairlt certain that the first image is of type 1. and the second of type 2. For yourself check the labels of the y axis. —Preceding unsigned comment added by 87.102.43.12 (talk) 20:23, 7 February 2009 (UTC)

I should have linked to the proper web pages, not the images - see here http://homepages.wmich.edu/~korista/color-bb.html

This page also has the same spectra with explanation http://www.unm.edu/~toolson/human_cone_response.htm —Preceding unsigned comment added by 87.102.43.12 (talk) 20:30, 7 February 2009 (UTC)

File:CIE1931 XYZCMF.png should not be equated with the response of the human eye. It is a standard response for the purpose of defining a particular colour space, see CIE 1931 color space#Color matching functions. Although one could reasonably suppose that it bears some relationship to the actual human response. SpinningSpark 21:21, 7 February 2009 (UTC)

Presumably it needs to be an approximation of human responses in order to be useful. It may be a compromise between accurately simulating what humans see and what's easy to produce on a computer screen, but it can't be too far off or the photographers would complain even more than they do! --Tango (talk) 21:25, 7 February 2009 (UTC)

It needs to bear some resemblance, but you cannot make any assumptions about how closely it matches real humans. The main reason it is necessary is not because of mathematical or practical convenience but because real humans have a large variation of responses. We don't even all have the same type of red receptor (there are at least two different sorts with peaks in different places). A "standard observer" needs to be defined before you can accurately define a colour space and a messy human just will not do. It is perfectly possible to get good colour reproduction when the model deviates significantly from the human observer, human colour vision just ain't all that good. It is a fact that all colour reproduction systems based on three pigments/phosphors cannot reproduce all colours that the human eye could see. These are the so called "super-saturated" colours. That is a big innaccuracy but we don't have a problem with most "natural" scenes because of it. Similarly, there could be some deviation in the standard observer response but still result in acceptable colour reproduction. SpinningSpark 21:58, 7 February 2009 (UTC)

Isn't the incomplete gamut due to not being able to make certain colours out of your choice of primary colours, rather than not knowing what the required responses are? Those you can make you need to make pretty close to how humans see them, or it's useless. An object that emits yellow (monochromatic) light and an object that emits red and green light will look the same to a human, so they need to look them same when displayed on a computer monitor (which will show both as a combination of red and green). The variation between different humans is one of the reasons why you can only get an approximation at best, but you need to be pretty close. --Tango (talk) 22:09, 7 February 2009 (UTC)

The XYZ color matching functions don't need to approximate the human cone responses to be useful, they only need to be independent linear combinations of the human cone responses. Think of it this way: the actual cone responses, whatever they are, project from the infinite-dimensional vector space of possible spectra (physical colors) to the three-dimensional vector space of perceptual colors. The cone responses define a "preferred" coordinate system for that three-dimensional space, but actually for most purposes it doesn't matter what coordinate system you use as long as you're covering the same space. XYZ is a different coordinate system for the same space.

XYZ has nothing to do with RGB or any other color reproduction technique. The XYZ color matching functions are not spectra (that is, vectors in the physical color space), they are linear functionals on the physical color space. You can't identify X, Y, and Z with physical colors for two reasons: first, because you lost an infinite number of degrees of freedom in the projection and the reverse mapping would be extremely far from being unique, and second, because the image of physically possible spectra (with all frequency components nonnegative) only covers a part of the XYZ space, and the XYZ basis vectors lie outside of that. In fact, since the XYZ vectors have negative components in the cone response basis also, they aren't psychological colors either.

Because so many degrees of freedom are lost in the projection, virtually any three physical colors suffice to reproduce the whole range of perceivable hues. The only requirements are that they form a triangle on this diagram that contains the white point. Cyan, magenta and yellow would work—you could still get red, green, and blue from them, though the maximum saturation would be low.

I don't actually know whether the L cone has a second sensitivity peak in the blue-violet range, but the important thing is that it doesn't matter in the slightest. The brain has no idea that there's such a thing as monochromatic light, or that the monochromatic frequencies map to a funny curved shape in cone-response space whose convex closure defines all perceivable colors. It doesn't know that the line between violet and red is "false". It's just a three-dimensional color space to the brain, and it puts the circle of hues wherever it wants. There's no reason in the world why the highest monochromatic frequencies can't venture into the purple part of that circle. You don't need a secondary peak in the L cone for that to happen. -- BenRG (talk) 01:12, 8 February 2009 (UTC)

I still don't get it. How can you make a yellow object look yellow on my computer screen without knowing what combinations of red, green and blue my eyes will see as yellow? To know that, you need to know the cone responses to red, green, blue and yellow in order to work out how to combine the first 3 to get the 4th. --Tango (talk) 21:40, 8 February 2009 (UTC)

You don't because the cone responses are (almost exactly) linear in the intensity of the incoming light, and the XYZ coordinates are linear combinations of the cone responses. (The evidence is the fact that you can define linear XYZ color matching functions.) So if you can express the color you want as a linear combination of your phosphors in XYZ coordinates, it will be the same linear combination in cone response coordinates. The cone responses are known, though (see LMS color space) and are useful for some things. -- BenRG (talk) 01:02, 12 February 2009 (UTC)

So, like, ...what's been happenin in science lately?

Any new discoveries or anything?ScienceWorkshop (talk) 16:36, 7 February 2009 (UTC)

They started turning on the Large Hadron Collider, but it blew up... once they get it fixed we should get some interesting new stuff out of there. That's the big thing in physics at the moment. I don't know of anything particularly big in other fields, but that says more about me than them. There are minor discoveries made all the time that are probably very significant in their area, but don't get noticed by the general public. If there is a particular field you are interested in, try reading relevant journals. If you want something more general, try New Scientist. There are online copies of lots of stuff, so you don't necessarily have to buy the magazines/journals. You could try the BBC News website's Science and Environment section, they have some interesting stuff there from time to time ([2]). Other news sites probably have similar sections. --Tango (talk) 16:44, 7 February 2009 (UTC)

Discover magazine also has some info on recent scientific developments, news, opinions, thoughts, discoveries, columns, etc. ~AH1^(TCU) 17:25, 7 February 2009 (UTC)

Giant snake! --Sean 21:54, 7 February 2009 (UTC)

Poking around the science reddit works too. --Shaggorama (talk) 22:59, 7 February 2009 (UTC)

Depending on how long you've been out of touch, Quantum theory, Theory of Relativity and the earth goes round the sun. DJ Clayworth (talk) 22:04, 9 February 2009 (UTC)

And when are they gonna update the periodic table!?

It's been over 40 years, hasn't it? There's got to be more elements out there!ScienceWorkshop (talk) 16:43, 7 February 2009 (UTC)

Check out Transuranium element. --Tango (talk) 16:45, 7 February 2009 (UTC)

In the past 40 years, they have isolated and discovered the following elements: Bohrium, Meitnerium, Hassium, Darmstadtium, and Roentgenium, as well as some unconfirmed discoveries. We actually have an article: Timeline of chemical elements discoveries.-RunningOnBrains 16:53, 7 February 2009 (UTC)

The problem is that many of the newer elements only exist in a laboratory for a fraction of a second, so we don't know their properties in much detail, and it really isn't all that useful to know about elements that only exist for a fraction of a second in a lab, in any case. (Although an isotope of chemical element 105, dubnium-268, has a half-life of 15-29 hours, which isn't bad.) There may be some more stable elements out there around element 120, though, so we might want to update the table if we can synthesize those. See island of stability. Still, you have a good question as to why the usual periodic table still only goes up to element 103, even though we have good info on several elements beyond 103. StuRat (talk) 17:14, 7 February 2009 (UTC)

How do we know how many elements are out there? Isn't creating an element cheating? We could just keep combining molecules, isotopes, etc. and get an unlimited amount, right?ScienceWorkshop (talk) 20:00, 7 February 2009 (UTC)

I think you need to read up on what a chemical element is. Molecules are made up of elements, not the other way around. --Tango (talk) 20:11, 7 February 2009 (UTC)

Additionally, no, you probably couldn't just keep smashing things together and creating new elements. Eventually there will be a stage where an atom is just too unstable to exist, considering the human-sythesised elements are already incredibly unstable, existing for only very, very short periods of time. —Cyclonenim (talk · contribs · email) 20:25, 7 February 2009 (UTC)

And generally speaking, no, it's not considered "cheating" to make elements artificially. That's the whole point, nowadays, when people "discover" an element. --98.217.14.211 (talk) 16:11, 8 February 2009 (UTC)

Radioactive Decay/Bombardment

Hello. Why can radioisotopes not emit alpha and beta particles together? Thanks in advance. --Mayfare (talk) 17:20, 7 February 2009 (UTC)

Because once they have emitted one of them they would be a different particle. While there are often different ways a particle can decay, it can only do one of them and usually there will be one that is more likely than the others. I expect there are alpha emitters than decay into beta emitters and vice versa, though. --Tango (talk) 18:06, 7 February 2009 (UTC)

On the latter point, it is definitely so. The radon decay chain is a simple example of this. --98.217.14.211 (talk) 22:45, 7 February 2009 (UTC)

Solid when warm, liquid when cold

Is there a substance that will turn solid the warmer it gets and will turn to a liquid the colder it gets?– Elliott  21:10, 7 February 2009 (UTC)

There are a number of thermosetting materials such as epoxies but the process is irreversible. SpinningSpark 21:24, 7 February 2009 (UTC)

Specifying temperature is not enough. You must say what the process is. For example you can raise the temperature while pressure is kept constant, or you can raise the temperature while volume is kept constant, or you can change temperature by isentropic compression or expansion, and so on. Also, what kind of substances are you asking about? Pure elements? Alloys? Polymers? Something else? --Dr Dima (talk) 23:08, 7 February 2009 (UTC)

Mater to Energy conversion (Moved from Reference_desk/Computing

I was wondering how far along we have gotten in converting mater to energy and back again, also i was wondering how far along we have gotten in converting human thoughts to a digital format. —Preceding unsigned comment added by 98.238.145.106 (talk) 18:39, 7 February 2009 (UTC)

Well, it isn't very modern, but I find my keyboard is very effective in translating my thoughts into digital formats. Did I leave the iron on? --Mdwyer (talk) 19:36, 7 February 2009 (UTC)

We aren't anywhere in converting thoughts to digital format if you mean by simply taking them out of the brain. We don't even have a good physical definition of what a "thought" is.

As for matter to energy, well, there's always nuclear fission. Or for the more exotic and efficient, we have indeed played around with tiny amounts of pure antimatter. Converting energy into matter is part of the process (creating antiprotons). The antimatter stuff is the purest form of the energy/matter conversions, but it's very, very hard (it takes a huge amount of energy to make even a tiny bit of matter). It's waaay easier to just use nuclear reactions. --98.217.14.211 (talk) 19:48, 7 February 2009 (UTC)

Very intresting question, but i think of a few follow up questions; What do you mean in matter to energy conversion? Do you mean like the Transporter (Star Trek), or in Fission? As for 'converting human thoughts to a digital format' are you asking if something like in Ghost in the Shell the ability to transfer to a robotic body?– Elliott  20:16, 7 February 2009 (UTC)

Matter and energy are the same thing....

The idea of converting matter to energy and vice versa is incorrect. Matter does not convert into energy, nor does energy convert into matter, one does not become the other. Matter and energy are the same thing, or rather, there is only energy. Like states of matter (solid, liquid, gas, plasma), matter is a state of energy.

Consider this analogy..... The universe is a big blob of energy, one hundred percent energy. I liken it to a pot of gravy. It's gravy through and through, but there are lumps. Those lumps are still gravy, just like the rest of the contents, simply higher densities of gravy.

In the universe, those lumps of higher concentrations of energy are what we (wrongly) differentiate as matter. Matter is merely higher density concentrations of energy, IE matter is the 'solid state' of energy.

Thus, converting mass to energy is more accurately described as lowering the density of energy in a 'particular' space. This particular volume of space we can refer to as... an electron, or a neutron, a quark, a muon etc. These atomic and sub atomic particles are not mass which contains energy, they simply are energy packed in tight.

Thus, a nuclear explosion fission reaction is not releasing the energy contained in a particle, it is lowering the density of energy in that volume which we have referred to as mass. The tightly packed energy is being spread out to a level ambient to the density of energy in it's immediate environment. —Preceding unsigned comment added by 98.238.137.150 (talk) 20:24, 7 February 2009 (UTC)

It's more complicated than that. Matter is a particularly form of energy, yes, but there's more involved than just density. As I understand it, a strong electric field could have the same energy density as a proton (for a given definition of the volume of a proton) without there being any matter there. That high energy density would cause matter/anti-matter pairs to be created and destroyed more often, but there still wouldn't be any non-virtual matter. --Tango (talk) 21:34, 7 February 2009 (UTC)

We aren't anywhere in converting thoughts to digital format. Yes we are, see brain-computer interface and brain implant. SpinningSpark 21:41, 7 February 2009 (UTC)

True, we've made some very limited progress on that front. Extracting a couple of bits isn't much, but it's fascinating research. --Tango (talk) 21:45, 7 February 2009 (UTC)

I assumed the OP meant something more than the very limited success that has been made in the last few years (training the neurons to fire at the right time, taking very blunt neuron signal information and using it in simple ways). But yeah, the research is good. But we aren't anywhere close to, say, making a digital record of someone's internal brain states. We can do some neat stuff with the motor cortex and even a little with vision but as far as I know we aren't anything close to what we'd call the seats of consciousness. Even the motor cortex and vision stuff is very primitive by sci fi standards. --98.217.14.211 (talk) 22:54, 7 February 2009 (UTC)

Move Earth rocks to Mars

What rock from Earth if place on Mars would create an Earth-like breathable atmosphere in time, assuming enough of the rock is brought up? —Preceding unsigned comment added by 86.4.10.166 (talk) 22:13, 7 February 2009 (UTC)

None. What makes you think rocks can single-handedly create an atmosphere? See Terraforming of Mars for ideas of how to actually create an breathable atmosphere on Mars. --Tango (talk) 22:18, 7 February 2009 (UTC)

buddy of mine asked me a load of science questions that i couldnt answer. different subjects. —Preceding unsigned comment added by 86.4.10.166 (talk) 22:30, 7 February 2009 (UTC)

He's probably thinking of whether microbes from earth could colonize mars and so terraform it. There might I suppose be some that could live there but I don't see they'd be able to do much with the place, they'd have to live slow like the lichen in the ice in Antarctica, they don't exactly flourish Dmcq (talk)

That's pretty much how the Earth's atmosphere became brethable for animals; the oxygen on Earth is far to reactive to stay around for very long if it weren't for plants and microbes dumping it back into the atmosphere. However, the process that made Earth's atmosphere oxygen rich took something like a billion years. If were were to innoculate Mars in some way to cause it to happen there, we could expect a similar timeframe. Too slow to be practical. --Jayron32.talk.contribs 05:29, 8 February 2009 (UTC)

It depends on how you define rock, I would say. I think most scientists would agree that planetary-scale atmospheric changes require life, probably in the form of large masses of algaes or microbes. The current understanding of the origin of life is abiogenesis - that is, life develops out of the presence of some chemical elements in some combination under some conditions. Given that all pre-life chemical elements are geological or cosmological in origin, it seems plausible to me that "transplanting" enough inert, inorganic, rocks with enough seed chemical elements might be sufficient to spawn off some microbial critters. This process would probably take billions of years (and since we're not talking about earth, it may be better to use some other time measure... 10⁶⁰ planck times?) Of course it's hard to say for sure whether all of the necessary prerequisites for life can really exist in rock form - the best scientific theories for abiogenesis still have a lot of details to work out. This also doesn't even begin to consider whether conditions are suitable for the transmogrification from inorganic elemental forms into complex organic molecules... who knows what combination of local solar radiation levels, temperature and pressure, and a variety of other unknowns are also prerequisite. Nimur (talk) 11:05, 8 February 2009 (UTC)

Life can convert an atmosphere, it can't create one. If Mars had a CO₂ atmosphere of similar pressure to Earth then a bit of algae may be all you would need to make it breathable, but it has just a thin trace of atmosphere. Even if it was 100% oxygen it wouldn't be anywhere near enough to support humans. You need to create a thick atmosphere first, then you can worry about making it breathable. (If you can heat the planet up enough the frozen CO₂ in the polar caps will sublime, giving you a good start.) --Tango (talk) 13:51, 8 February 2009 (UTC)

I think the answer is "No" and I think the reason is that it's pretty likely that rocks from Earth are already on Mars. We know that high energy meteor impacts on Mars have sent significant amounts of Mars rock to the Earth - it seems likely that at over enough millions of years, at least a small amount of rock has gone back the other way (although the earth's gravity is larger and we're closer to the sun...but because there is SO MUCH material from Mars it's hard to imagine that nothing every had the impact energy to make it back the other way. SteveBaker (talk) 03:18, 10 February 2009 (UTC)

These Questions are doing my head in

What common item has the chemical formula from below?

http://i5.photobucket.com/albums/y198/tank666/72293_Thumb.jpg

What material has the following visual spectrum?

http://i5.photobucket.com/albums/y198/tank666/emissionspectrum.png

im sorry i couldnt figure out how to display the pictures —Preceding unsigned comment added by Tank666 (talk • contribs) 22:43, 7 February 2009 (UTC)

This looks an awful lot like homework. --Shaggorama (talk) 23:01, 7 February 2009 (UTC)

its not. a friend of mine asked me these questions(he's a chemist) said if i get them right he'd pay for my beer on a night out. ive looked for the first 1 for about an hour on wiki but since i dont know how to write it out properly i cant get an answer--Tank666 (talk) 23:07, 7 February 2009 (UTC)

The first is a sugar or carbohydrate of some sort. For the second, there is no clear way to tell from that information. If we had a list of actual wavelengths, then maybe. But just trying to read it from the colors is impossible. --Jayron32.talk.contribs 05:26, 8 February 2009 (UTC)

The first looks like a common vitamin to me. The spectra I have absolutely no clue. Is this your friend's homework or something, or some sort of chemist hazing? :) --Bennybp (talk) 06:32, 8 February 2009 (UTC)

I'm pretty sure the first is a sugar with a ketone group. Take a look at Ketohexose, yours is a deoxy sugar variant of one of these. The emission spectrum looks pretty darned near impossible to decipher by sight alone... there's a lot of lines in there Nimur (talk) 11:21, 8 February 2009 (UTC)

Cellulose? That ketone oxygen really trips me up, because it's often drawn as a single bond and a polymer "..." continued to the next cellulose. Nimur (talk) 12:10, 8 February 2009 (UTC)

I looks like Vitamin C/Ascorbic acid to me. (Found by drawing it in Chemsketch and searching for the IUPAC name it gave me). It looks to close to some of the sugars mentioned (off by an OH group on the little branch) --Bennybp (talk) 15:46, 8 February 2009 (UTC)

Glucose if one H got cropped off your picture? The answer to 2 might be "glass" if he's trying to pull your leg.Lisa4edit (talk) 14:00, 8 February 2009 (UTC)

Either you or 'your friend' is playing games with us. The emission spectrum is an exact duplicate of the iron emission spectrum (File:Emission spectrum-Fe.png) from our article Emission spectrum. TenOfAllTrades(talk) 14:48, 8 February 2009 (UTC)

How did you figure that out? --Sean 13:35, 9 February 2009 (UTC)

Pancreatic Cancer

What is the incidence of pancreatic cancer over the past several decades in the US...increasing or not98.238.64.140 (talk) 23:16, 7 February 2009 (UTC)

Here is a link [3]that shows it is pretty stable between 1977 and 2001. The 1 year survival rate has increased. Richard Avery (talk) 08:13, 8 February 2009 (UTC)