Wikipedia:Reference desk/Archives/Science/2010 December 15

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December 15

computable universe

Episode 1 of "Through the Wormhole" with Morgan Freeman has left me with a flurry of thoughts. Someone talked about reality as we know it to be a possible computer simulation of a "god" programmer... which leaves us with the eternal question - "Where did this godlike programmer come from?" - but this is not my question. What was stated was that the universe has a finite resolution or pixellation and if so, the entire universe can be computed or duplicated in a simulation. They talked about computers being able to perform realistic simulations in 5 years time (computers about 500 times more power than today's) so why not universe-scale simulations in hundreds of years given that the universe is 13 billion years old? My questions: does reality have a finite resolution? What if there are smaller subatomic particles than currently known to science - then the resolution would get finer not so? Would it ever be possible for any computer to simulate the entire working of the universe? How can this be, given that the computer is always made up of fewer elementary particles than the universe itself? Sandman30s (talk) 04:50, 15 December 2010 (UTC)

The limit is the size of the smallest possible black hole. Since black holes have no hair, anything smaller than that does not matter. What this means is that whenever there is too much "stuff" inside a given sphere to resolve it all on the surface of that sphere the mass is too much and it collapses into a black hole. Hence the surface area of the observable universe can easily contain all the information inside it.

Added: Where are the fnording links between Simulated reality and Holographic principle? Hcobb (talk) 05:43, 15 December 2010 (UTC)

Yes, the universe does appear to be pixelated. At a fine level many things are quantized and can only change in discrete amounts. Why this is is not known. Regarding the computer - it's pretty obvious that a computer can only simulate a universe that is smaller than itself - probably much smaller. This could mean that there is a huge chain of computers each simulating ever smaller universes. It's impossible to know. For all you know your entire life could be an RPG played by someone in our parent universe (sound kind of like religion and heaven, doesn't it?). However I should point out that currently computers are not getting faster, but they are getting more parallel, then again, reality simulation is a pretty parallel process - especially since the speed of light means that distant computation units don't have to talk. But it's impossible to know, so I've chosen to live my life as if I were real, and not a simulation. BTW the Simulated reality article is quite excellent. Ariel. (talk) 08:35, 15 December 2010 (UTC)

The "simulated reality" article is excellent in the sense that there's a large overlap between the type of people who edit Wikipedia and the type who are prone to that kind of superstition, so it gets a lot of attention. It's not science, though. It's essentially a form of religious belief. -- BenRG (talk) 09:08, 15 December 2010 (UTC)

It's excellent because it covered many possibilities and described the implications and limitations of each. If you define "religious belief" as a desire to explain the origin of the universe without evidence then sure, but to me religious belief also includes an element of worship, which this topic does not have. To me this topic is speculative, not religious. Ariel. (talk) 11:03, 15 December 2010 (UTC)

Well... it's entirely possible that the universe is discrete/finite in some way. There isn't what I'd call clear evidence for it, or against it. It's not even entirely clear what it would mean for the universe to be discrete/finite. The idea of "computer simulation" seems to me rather silly, since computers are physical devices whose existence and correct operation depends on the laws of physics. You might be able to ask "is the universe computable?", using an abstract mathematical notion of computability, but to ask "is the universe run on a computer?" suggests to me a certain failure of imagination.

"The limit is the size of the smallest possible black hole" doesn't make sense to me. You may be talking about the Bekenstein entropy bound, whose physical significance isn't entirely clear. I don't think there should be links between "Simulated reality" and "Holographic principle", since I can't see any connection in either direction.

Morgan Freeman is an actor whose main marketable skill appears to be his awe-inspiring voice. I haven't seen the show in question, but I'm going to go out on a limb and guess that it's full of cringeworthy nonsense. They mostly are, these days. -- BenRG (talk) 09:08, 15 December 2010 (UTC)

Cringeworthy? Nice word, lol. Thanks for the responses guys. Sandman30s (talk) 09:42, 15 December 2010 (UTC)

I question the claim that the Universe is pixellated. Pixellation implies that a continuous reality is identified only by samples and the intervening reality is invalid. Ignoring reality between samples is the source of Sampling error and the incorrect (aliassed) appearance of fine detail - see Nyquist–Shannon sampling theorem for a frequency-domain explanation. One encounters infinite (not quantised) precision in math identities such as the square root of 2 and Transcendental numbers such as e and the ratio pi, and in fractals. Is the claim saying that math does not apply to reality between the pixels? Cuddlyable3 (talk) 10:22, 16 December 2010 (UTC)

It's not that the intervening reality is invalid, but that things can only change by discrete amounts - which matches quantum physics quite well, and the "sampling error" does actually show up, in for example, things like blackbody radiation. Math is not a thing, it's an idea, so can take on any value desired - a physical circle on the other hand not have exactly Pi ratio of circumference to diameter, the ratio is slightly changed because the atoms have finite resolution. Ariel. (talk) 22:56, 16 December 2010 (UTC)

The answer to the OP's "Where did this godlike programmer come from?" given by this frequently-mentioned-here speculative philosophical paper is that: it came from us. WikiDao ☯ (talk) 21:10, 16 December 2010 (UTC)

The simulation of the entirety of reality brings up the problem of determinism vs. Free will. Of course, then there are the numerous chaotic components that fully exist even in a deterministic system. What about the potentially computable multiverses and possibility of retrocausality given the quantum Zeno effect? ~AH1^(TCU) 02:53, 18 December 2010 (UTC)

At least your brain is simulating a virtual environment based on the input it receives from the external world. What you experience is always the events in that virtual world, not the real world. It is just that the simulation mimics real world events (unless you are dreaming or hallucinating), that you are fooled into believing that whatever you are experiencing happens exactly like you are experiencing it in the real world. Optical illusions clearly demonstrate this fact.

The conclusion thus has to be that we are all algorithms that exist in a big universe that is running all these algorithms. The universe itself is presumably also just an algorithm. There may not be a physical world at all, it could be that all that exists is pure math. Count Iblis (talk) 22:21, 19 December 2010 (UTC)

Full name for "Issiki", Japanese Lepidoptrist active ~1930 - ~1960

Hi all,
Yet again, pet peeve is authorities without biographies. One "Issiki" is binomial authority for N. elongata, N. nipponensis, N. matsumurana, and many more. Who is this Moth-man? (nb: "Issiki" looks like Kunrei-shiki romanization. "いしっき" would probably more likely romamised as "Isshiki" - see Wikipedia:Manual_of_Style_(Japan-related_articles)#Romanization). Thanks again. --Shirt58 (talk) 11:03, 15 December 2010 (UTC)

Full name appears to be Shūchi T. Isshiki (in Hepburn romanization) – see these papers. Physchim62 (talk) 15:06, 15 December 2010 (UTC)

Nice work! I spent half an hour on that without any luck. Ginger Conspiracy (talk) 16:06, 15 December 2010 (UTC)

I don't know if it matters at this point, but your hiragana version of the name doubled the wrong consonant: it should be いっしき. ja:ヨトウガ mentions an 一色周知 who is presumably the same person, but there's no biography and no other mention in the Japanese Wikipedia. -- BenRG (talk) 21:37, 15 December 2010 (UTC)

どっ!--Shirt58 (talk) 12:59, 17 December 2010 (UTC)

It appears he is a Japanese biologist, I found an obituary for him (in Japanese here), I'll summarize some of it it if anyone's still interested.

He was born in Wakayama prefecture, educated first in Japan, professorship in Taiwan in the 1930s-50s then returned to Japan to do more teaching eventually passing away in 1978? at the age of 86. The main text doesn't say anything about his work, just the circumstance of the last few days of his life in hospital. It's kind of amusing if you're interested in this kind of thing. 173.183.68.27 (talk) 01:57, 16 December 2010 (UTC)

"ELSC0501: Error is occurring in displaying full Text PDF file."

"Because PDF file may be displayed normally, please act bellow."

"1. Search again because of the case of the close of the session."

"2. Change your browser's setting to accept Cookie because of the case that your browser doesn't accept Cookie."

Did all of the above, but still no joy for for me. --Shirt58 (talk) 13:44, 17 December 2010 (UTC)

Milk Powder

I want to know how milk powder are produced ?... I used to think it is produced from orignal milk but now I doubt it.. as it seems impossible to do that.... —Preceding unsigned comment added by 220.225.96.217 (talk) 12:54, 15 December 2010 (UTC)

We have an article, powdered milk. Feel free to come back here if you any unanswered questions from that article. CS Miller (talk) 13:08, 15 December 2010 (UTC)

Article was very helpful thanx.... :) —Preceding unsigned comment added by 220.225.96.217 (talk) 13:23, 15 December 2010 (UTC)

What if Newtonian mechanics were the correct model of reality?

How would a universe in which Newtonian mechanics were the correct model of reality differ from a relativistic universe? --J4\/4 <talk> 13:39, 15 December 2010 (UTC)

Let me paraphrase a (possibly apocryphal) story attributed to Johannes Keppler. Apparently, one of his students asked him "Wasn't it kinda stupid that people a few generations ago thought the sun moved around the Earth" and Keppler's response was "If they had been right, how would it have looked different?" The fact is that, for most people, living their lives as though Newtonian mechanics is reality works; which is why it is still a good, workable theory. After all, if I'm trying to calculate the torque in my car's engine or the energy evolved in a chemical reaction, Newtonian mechanics works quite well, and there's often little need during most people's day-to-day lives to invoke quantum mechanical calculations and explanations. Answering how the universe itself would appear different if the laws of quantum mechanics didn't work is kinda nonsensical; we might as well ask how things would look if "magic" were real. --Jayron32 13:58, 15 December 2010 (UTC)

I don't think it's quite on par with asking if "magic" worked. The theories give different predictions, unlike "magic". At this stage it is hard to imagine such a change because many of the questions and investigations we've asked since then only make sense in light of the theories themselves. (To ask what Bell's theorem would look like with quantum mechanics is obviously nonsensical, for you need the latter to even conceive of the former's existence, much less truth.) But one could say, "if Newtonian mechanics was correct, there should not be any black holes," for example, (if that is true, I don't know). One might even be able to come up with a cosmological model (steady state, expanding, big bang?) that is or isn't compatible with Newtonian mechanics, though I imagine that is a bit too much work for the Ref Desk. --Mr.98 (talk) 14:41, 15 December 2010 (UTC)

In a newtonian universe, objects can reach infinite speed in a finite amount of time. I wish there was a wikipedia page about this but apparently there isn't, so see http://plus.maths.org/content/outer-space-twos-company-threes-crowd 157.193.175.207 (talk) 15:09, 15 December 2010 (UTC)

In a relativistic universe, objects can reach infinity in finite proper time (always traveling at sublight speed). I think this is related to the Newtonian result. -- BenRG (talk) 04:19, 16 December 2010 (UTC)

Speed is acceleration times time. How can an object reach infinite speed without either infinite acceleration or infinite time? The former is ruled out because by Newton's 2nd law F=ma infinite acceleration could only be obtained by an infinite force (impossible) or a zero-mass object (impossible). Cuddlyable3 (talk) 09:52, 16 December 2010 (UTC)

The linked article does not in fact directly assert that the objects reach infinite speed in finite time. It says that they become infinitely separated in finite time. That must mean that the speed approaches infinity over that interval, but neither the speed nor the acceleration would have to actually become infinite at any moment before the actual singularity. Once you reach the time at which they are infinitely separated, presumably the whole analysis breaks down; for example, if the physical universe is modeled as R³, then there is no such thing as two infinitely separated points. --Trovatore (talk) 10:03, 16 December 2010 (UTC)

What do you suppose is the object's finite average speed during the acceleration to infinite separation? Did Newton have any reason to disbelieve that his stated laws apply throughout an infinite universe? Cuddlyable3 (talk) 10:48, 16 December 2010 (UTC)

Suppose for example that an object's position for t<0 is k/t, where k is some constant. Then its position approaches infinity as t approaches 0. The speed as a function of time is -k/t², which is finite for t<0. The average speed is infinite. There is a singularity at t=0 when the object "reaches infinity", but no singularity before that moment. That's the kind of situation being talked about here. Yes, it's weird, and the physical significance of it isn't clear. (Well, Newtonian physics is wrong, but the physical significance of the relativistic version isn't clear.) -- BenRG (talk) 14:13, 16 December 2010 (UTC)

There's something a little flaky about the claims on the webpage, though. Newtonian mechanics may be wrong, but I'm not aware of anything in it that contradicts conservation of energy. Nevertheless it appears that the total energy of this five-particle system is supposed to increase without bound prior to the singularity. There's a piece missing here; I don't know what it is. Maybe the linked page is just wrong? Or maybe it's leaving something out of the informal description. --Trovatore (talk) 20:47, 16 December 2010 (UTC)

Conservation of energy holds just fine in Xia's example of a non-collision singularity in a 5-body problem. The source of the craziness is that according to Newton's theory of gravity, between two point particles there's an infinite amount of potential energy available to be consumed. The gravitational potential energy between point particles of mass m and M is U= - GMm/r. So the potential energy at any finite separation is infinitely greater than the potential energy at r=0. Xia's construction basically shows a way to turn that infinite potential energy into infinite kinetic energy. Non-collision singularities in the Newtonian n-body problem are discussed in more technical detail here. Unfortunately, there appears to be only three sentences covering non-collision singularities in the article space, at n-body problem#Singularities of the n-body problem. Red Act (talk) 22:24, 16 December 2010 (UTC)

Ah, that makes sense. I hadn't realized they were point particles. --Trovatore (talk) 22:47, 16 December 2010 (UTC)

Black holes wouldn't exist, so they wouldn't have accretion disks emitting x-rays. So maybe they would be even darker neutron stars. Ginger Conspiracy (talk) 16:21, 15 December 2010 (UTC)

Stars themselves wouldn't exist. Newtonian mechanics doesn't have a means to adequately deal with nuclear processes like fusion and fission; it's not that its somehow wrong about them, it just completely doesn't deal with it. The big problem with Newtonian mechanics isn't its wrongness, its that it simply ignores or doesn't deal with many issues that make our Universe exist in any meaningful sense. The question doesn't make any sense because it assumes that modern physical theories have supplanted "classical" physical theories because the classical theories were "wrong". That isn't all that true. The classical theories work just fine. Its just that there are huge parts of the universe that the old theories simply don't deal with at ALL, so attempting to construct a universe where those phenomena which can only be explained by post-classical theories like quantum mechanics doesn't make sense. At all. Unless we go back to designing a universe that operates on epicycles and the Music of the Spheres, there just isn't a way to answer the OPs question in any meaningful sense. --Jayron32 16:44, 15 December 2010 (UTC)

Why is relativity necessary for fusion or fission? I thought they're a strictly quantum chromodynamic and electroweak-nuclear force interaction process independent of relativistic constraints. Ginger Conspiracy (talk) 18:09, 15 December 2010 (UTC)

Because relativity explains mass-energy equivalence. Quantum theory is useful for explaining the mechanics of nuclear reactions, but the core concept that mass and energy are two expressions of the same thing comes from relativity. And both relativity and quantum theory are post-Newtonian theories. The OP asks what would happen if the universe only worked by the laws of Newtonian mechanics. I was merely pointing out that it is a nonsensical question because Newtonian mechanics ignores major observable phenomena. It doesn't get these phenomena wrong, which is what the OP implied, it just doesn't deal with them at all. --Jayron32 19:00, 15 December 2010 (UTC)

Fission and fusion are not fundamentally much different from chemical reactions: you rearrange some particles into a new binding state of higher or lower total energy, either storing or releasing some energy in the process. I don't see why nuclear reactions require E = mc² any more than chemical reactions do. On the other hand, I don't see how the standard model of particle physics can work nonrelativistically, since all of its fundamental fields are massless and the massive particles that we see show up through secondary mechanisms. In particular, most of the mass of protons and neutrons is actually the strong force binding energy of the quarks. I don't know how one could make a nonrelativistic version of that mechanism, but I wouldn't be willing to bet that it's impossible. -- BenRG (talk) 04:19, 16 December 2010 (UTC)

Atoms would not exist. Hcobb (talk) 17:17, 15 December 2010 (UTC)

Why not? Ginger Conspiracy (talk) 18:09, 15 December 2010 (UTC)

In a purely Newtonian world, an electron circling a nucleus, as in the Rutherford model, would emit electromagnetic radiation as per the Larmor formula, losing potential energy in the process, causing the electron to spiral in toward the nucleus until it collided with it. See Bohr model#Origin. Red Act (talk) 20:09, 15 December 2010 (UTC)

Even if the universe was Newtonian except for nonrelativistic quantum mechanics, the masses of atoms would be significantly different, because the mass defects of the nuclei would be zero. Red Act (talk) 20:31, 15 December 2010 (UTC)

In a quantum but not relativistic world, chemistry involving heavier elements would also be different, because relativistic effects of atomic orbitals become significant in heavy elements. For example, gaseous Hg₂ would exist, and gold would appear white. See Relativistic quantum chemistry. Red Act (talk) 20:57, 15 December 2010 (UTC)

Wow! Thanks both Red Act and Jayron. Ginger Conspiracy (talk) 02:42, 16 December 2010 (UTC)

What distance is a Newtonian Light-year? If you answer that it is about 63 000 Astronomical units then how long does it take for the light of the Sun to reach the Earth and why is this not immediate? Cuddlyable3 (talk) 09:58, 16 December 2010 (UTC)

It would be the same distance. There are two possibilities:

1. Photons are particles, and NOT waves, and the speed would vary based on the relative motions of the emitter and receiver, i.e. light would act like small bullets which are launched at a certain speed, but which can be speed up or slowed down by the motion of what launched them.
2. Photons are waves, and travel in Ether.

It's not possible to have non-relativistic photons that are both particles and waves. Ariel. (talk) 20:57, 16 December 2010 (UTC)

Ariel there is contradiction between saying that the distance light travels in a year is always the same, and that the speed of light varies. Newton wrote in "Optics" that light is a particle. Wave/photon duality would only be an issue raised by Young long after Newton died. Cuddlyable3 (talk) 01:02, 17 December 2010 (UTC)

The distance as measured from the emitter. Not as measured by all observers. So I guess Newton was self consistent with his theory? Obviously Newtonian mechanics is not sufficient to explain things, this is just a "what if". Ariel. (talk) 03:19, 17 December 2010 (UTC)

No Ariel, in Newtonian mechanics there is no relativism of distance measurements, In his 1704 book Opticks, Isaac Newton reported Rømer's determination of the speed of light and he explained Newton's rings not in the modern terms of wave interference but instead supposed that the light particles were altered or excited by the glass and resonated. He would have considered neither quantum nor relativistic mechanics as useful explanations because the laws of classical mechanics seemed accurate in all circustances. Cuddlyable3 (talk) 20:43, 18 December 2010 (UTC)

I don't see any problem with building the basic tenets of quantum mechanics, such as wave-particle duality, on a Newtonian background. (Some parts of quantum mechanics wouldn't work, but many parts would.) You'd probably have to treat photons as actual particles with a non-fixed speed, but we can observe wave-particle duality with electrons and other massive particles traveling at non-relativistic speeds, so I don't see any reason the same couldn't be true of hypothetical photons having non-fixed speed. Dragons flight (talk) 04:48, 17 December 2010 (UTC)

If I traveled at exactly the same speed as the photon what would I see? (BTW This is the question that Einstein asked which led him to relativity.) Unlike regular particles, photons can not exist if their frequency is 0. Ariel. (talk) 06:05, 17 December 2010 (UTC)

binary stars in Centauri system

Do scientists know if alpha and beta Centauri are tidally locked with each other? Googlemeister (talk) 17:19, 15 December 2010 (UTC)

Um, I'm gonna say no, since Alpha Centauri is 4 light years from earth, and Beta Centauri is 525 light years away. --Jayron32 17:24, 15 December 2010 (UTC)

My bad, I mean Alpha Centauri A and Alpha Centauri B. Googlemeister (talk) 17:35, 15 December 2010 (UTC)

(ec) I assume OP meant alpha Centauri A and B. No they're not. The orbital period of the system is 79.9 years, the rotation periods of the two stars are 22 days and 41 days, respectively. If they were tidally locked, all of these periods would be the same. --Wrongfilter (talk) 17:36, 15 December 2010 (UTC)

Do we know of any tidally locked binary stars? Googlemeister (talk) 14:08, 16 December 2010 (UTC)

Yes: [1], [2]. (Google "tidally locked binary" for more; it looks like tidal locking has interesting effects on the convective mixing of the stars' atmospheres.) TenOfAllTrades(talk) 14:25, 16 December 2010 (UTC)

Earth Rotation

Assuming the earth is orbiting the sun in a circular motion, how many days would be in a year? —Preceding unsigned comment added by 96.61.186.193 (talk) 18:31, 15 December 2010 (UTC)

The orbit being circular rather than a non-circular ellipse doesn't change the length of the year. The orbital period (that is, the duration of the year) is a function of the distance from the earth to the Sun (see Kepler's laws of planetary motion#Zero eccentricity). There some more info at Earth's orbit. -- Finlay McWalter ☻ Talk 18:45, 15 December 2010 (UTC)

Also, the earth's orbit is nearly circular. It is literally an elipse, but only barely so. The orbital eccentricity of the earth is 0.016, which means that average deviation from a perfect circle is only 1.6%. I'd have to do the calculations, but I believe that both of the foci of the elipse of the Earth's orbit actually lie within the sun itself. --Jayron32 18:55, 15 December 2010 (UTC)

Yes, they do. Physchim62 (talk) 19:01, 15 December 2010 (UTC)

A body travelling in an elliptical orbit will move faster when it is closer to what it is orbiting and slower when it is further away. The average of that speed is how fast something in a circular orbit of the same length would travel at, giving the same length of "year" for both. Vespine (talk) 21:37, 15 December 2010 (UTC)

For the record, Earth rotates around its (shifting?) North-South axis while it revolves around the Sun, so this subsection should've been named Earth Revolution. 66.108.223.179 (talk) 23:53, 15 December 2010 (UTC)

Why didn't anybody try swinging a rock from a long enough string in a still enough place to notice that the rock kept alignment with the fixed stars instead of the Earth sometime shortly after the invention of string? Hcobb (talk) 00:01, 16 December 2010 (UTC)

You mean like a Foucault pendulum? Generally, one would need a reason to construct one. --Jayron32 00:04, 16 December 2010 (UTC)

Anyway, the answer to the original question is that we can't say, because the original poster didn't specify which particular circular orbit is intended. But if the intention is that the orbital radius would be equal to the average of the actual aphelion and perihelion distances, then the length of the year would be the same as it really is. --Anonymous, 01:45 UTC, December 16, 2010.

Siping rubber soles?

Our article on siping says that the inventor of the process originally used it to improve the traction on his shoes in a wet slaughterhouse environment. I can find plenty of information on siping automobile tires, but little on shoes. I would like to try siping my soles to improve traction on ice/snow. Can anyone advise me on ideal number / depth of cuts to make? How about the geometry? Thanks, SemanticMantis (talk) 20:43, 15 December 2010 (UTC)

*checks soles* Try v-shaped grooves three to four millimeters deep in a crosshatched pattern every centimeter or two, especially where the soles appear already worn, as you'll have more pressure there. Ginger Conspiracy (talk) 00:58, 16 December 2010 (UTC)

Thallium(III) hydroxide

What is its appearance? Gray? --Chemicalinterest (talk) 21:22, 15 December 2010 (UTC)

White. All thallium(III) salts are white unless the anion is coloured. Physchim62 (talk) 23:07, 15 December 2010 (UTC)

Really? IIRC oxide is not colored. --Chemicalinterest (talk) 23:15, 15 December 2010 (UTC)

The Properties list in the article you link to states "brown-black", C. 87.81.230.195 (talk) 01:39, 16 December 2010 (UTC)

That seems to be a confusion. Thallium(I) oxide is black, thallium(III) oxide is colourless (which means white, if it's an amorphous powder). Physchim62 (talk) 15:47, 16 December 2010 (UTC)

Grass as edible food source for humans

Other than feeding it to other animals and have them produce meat or milk, is there any artificial method to more efficiently turn grass into edible food for humans? Disregarding taste of course. ScienceApe (talk) 22:39, 15 December 2010 (UTC)

Grass organic matter could be burned and converted into energy, and the energy could be used to clone chicken meat. Disregarding the taste of course, because apparently cloned chicken meat tastes like wet sponge. 173.183.68.27 (talk) 22:43, 15 December 2010 (UTC)

Do you get to choose which species of grass are involved? Many species of grass have grains that are commonly eaten by humans. Wheat, barley, oats and rye are all even in the same subfamily (Pooideae) as many of the common lawn and pasture grasses. Corn and bamboo (which has edible shoots) are also in the "true grasses" (Poaceae) family. Red Act (talk) 23:22, 15 December 2010 (UTC)

Oh, rice is a grass, too. Three grasses – rice, wheat and corn – provide more than half of all calories eaten by humans. See Poaceae#Food production. Red Act (talk) 23:33, 15 December 2010 (UTC)

(ec)What are the aspects of grass that make it inedible? I assume we're talking about the "lawn grass" sense, not the larger group that includes cereals which are already commonly eaten by humans? Probably some enzymes exist that could break down certain components. For example, if cellulose is the problem, cellulase could convert it to glucose. Heck, if you have a high-cellulose-content grass, right there is a neat way to convert it to a sugar that could be separated for consumption. Can grass be fermented? I know a lot of college students seem to live on a fairly steady diet of ethanol. Or else that could free up other crops (corn, barley, etc.) to be used for human food (your grass wouldn't directly be turned into food itself, but it would lead to production of it). DMacks (talk) 23:29, 15 December 2010 (UTC)

Sure grass can be fermented, but it would usually be considered silage. — Preceding unsigned comment added by SemanticMantis (talk • contribs) 00:40, 16 December 2010 (UTC)

Remember that 'grass' normally refers to the leaves of Poaceae spp, but 'cereals' refers to their seeds. CS Miller (talk) 12:21, 16 December 2010 (UTC)

Right, and silage is made "using the entire green plant (not just the grain)". Obviously the types of plants and proportions of plant parts will vary, but fermented leaves of Poaceae spp. are a large component of silage. SemanticMantis (talk) 15:28, 16 December 2010 (UTC)

If you're just trying to make use of the grass clippings from mowing your lawn, the grass clippings can be composted, and then the compost can be used as fertilizer in your vegetable garden. Red Act (talk) 00:23, 16 December 2010 (UTC)

Yeah I'm just talking about regular lawn grass that you find everywhere, but can't be digested by humans. ScienceApe (talk) 01:29, 16 December 2010 (UTC)

Disregarding taste, fermenting your lawn clippings would allow you to gain some calories from ingesting them. If you are interested in efficiency, grass is not the way to go. Our article addresses many environmental concerns, including runoff of insecticides and fertilizers, as well as high water usage. I'd rather gain efficiency by not having a lawn, rather than finding ways to make grass into human food.SemanticMantis (talk) 15:39, 16 December 2010 (UTC)

Yes, I recall hearing a radio programme about grass being put through a machine which opened the cells and turned it into a green 'milk' which was fed as an effective health supplement to malnourished children in South America. I also recall hearing about one or two enthusiasts for the human consumption of grass in Britain. Edit: searching Google finds the Chayen Impulse Process, described here, http://books.google.co.uk/books?id=M42stMBW_VwC&pg=PA458&lpg=PA458&dq=chayen+grass&source=bl&ots=bmab0CI4id&sig=i369bvSAcT5WPzjAUBV0MqSwjJs&hl=en&ei=kjYKTfrYNZK0hAfWsdnIDw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCcQ6AEwAg#v=onepage&q=chayen%20grass&f=false but the radio program I heard was a lot more recent than that, and perhaps was done with just a small machine. Correction: it may have been leaf protein they were eating in South America, but that coulsd include grass perhaps. eg http://scholar.google.co.uk/scholar?hl=en&as_sdt=2000&q=chayen+grass+malnourished 92.28.247.44 (talk) 15:51, 16 December 2010 (UTC)

building on buoyant coral

I'm working on a relatively complex sci-fi concept, and I'm trying to develop the idea with a realistic (though implausible) explanation of how it works. Basically the goal is to have some sort of living biological system that grows in equilibrium with the other organisms that it consists of, at least one having a buoyancy in high-seas so great that were the system large enough, it could float a city above (and/or below) it. It's a little more complex than just a huge forest of microbial cork though, because building on it would obviously cause it to lose buoyancy (and raise the water level), so the system would have to be in a state of balance with the water level in that submerging it caused it to grow faster > buoyancy, or perhaps made it more buoyant for some other reason. That's why I think this would make more sense as being the result of biochemical relationships between a number of organisms, living at different levels above/below the water.

Some species of coral (or rather, the fossil remains of them) are known to float spontaneously when air slowly? replaces some of the water inside, but the buoyancy wouldn't be enough and the coral is obviously dead, so that doesn't really work. Given that this is sci-fi, I'm thinking more along the lines of splicing characteristics from a number of organisms together, so for example a coral-like bacteria could be genetically engineered to secrete something vastly less dense than calcium carbonate.

I'm basically at a road block, because I can't get my head around the process that would allow the system to modify its buoyancy dynamically with the amount of force applied to it, and simply "modifying coral to make it better" doesn't really seem like a good feasible premise for a sci-fi concept lol. Any ideas? I'm not much of a biologist so any examples from nature that I've missed would be great! Thanks! 173.183.68.27 (talk) 22:41, 15 December 2010 (UTC)

One of the advantages of sci-fi is the ability to branch out into fantastic, but realistic, life forms. I'm not sure I have a direct solution (maybe an organism that's a giant air bladder is part of the ecosystem?) but an author you should perhaps look to for inspiration is biologist Julie E. Czerneda. Her life forms are fantastically well detailed and researched, especially their ecological background. Her "Species Imperative" series really does a good job of inventing some spectacular ecosystems and life forms which still obey the basic rules of ecology. --Jayron32 22:45, 15 December 2010 (UTC)

The nautilus uses a neat system called a siphuncle to adjust its buoyancy, maybe you could design something around that. Mikenorton (talk) 23:01, 15 December 2010 (UTC)

See floating island for something sort of similar. Looie496 (talk) 23:35, 15 December 2010 (UTC)

Your system has muscular swim bladders. They are attached to the surface with long spiracles. Submerging the top of the spiracle stimulates the bladder to open, and exposing it to too much air stimulates it to close (but this stimulation is very slow, so it ignores waves). If the bladder stays fully open, it stimulates the organism to grow another, and if it stays closed for too long it atrophies. Be aware that normally the muscles in a bladder squeeze, which is the opposite of what you want, so yours has two contracting muscles on either side that pull it open instead. Additionally in the spiracle it has a sphincter that can close the bladder (so the pulling muscles don't have to be constantly working). Ariel. (talk) 00:39, 16 December 2010 (UTC)

A strange "living" island floating in the ocean features in the book Life of pi. It has a spongy floor with "trees" and pools of "clean water," but it's also like a carnivorous plant after the sun goes down. But it's not really "real" it's sort of a dream or metaphor or something related by the protagonist, it's hard to explain. I personally don't recommend the book, it was recommended to me but i didn't like. Actually i just thought to google it and there's a straight dope article about it. Vespine (talk) 04:55, 16 December 2010 (UTC)

Here's one idea that springs to mind, and is (kind of) feasible. When extra weight is placed upon the floating mass, more of it becomes submerged. As more is submerged, the outer shell of the submerged parts expand as water absorbs into them. This expansion causes the internal spaces to expand, and this expansion draws in more air through the parts which are above the water-line. When more air has been drawn in, the buoyancy stabilises. When weight is removed, the reverse happens. The outer shell dries out more, decreasing the size of the outer shell, which squeezes the air pockets more tightly, which cause less air to be held, and the buoyancy decreases. This system would provide a consistent level of buoyancy. Hope this helps! Zzubnik (talk) 10:25, 16 December 2010 (UTC)