Talk:Energy
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[edit] Talk page has been archived
For previous discussions, see /Archive 2. Cheers. --DavidHOzAu 02:24, 16 October 2006 (UTC)
[edit] Okay, then what IS the paragraph on exploration about, then?
Originally this section DID actually suggest going into space to look for new kinds of usable energy. The main articles referenced were oil exploration and space exploration and oil exploration wasn't discussed. I thought this extremely bizarre. And yes, it really did say: "While some scientists are busy in exploring the possibility of cold fusion (what??) many countries are diverting significant economic resources towards space exploration in the hope that new energy resources may be discovered elsewhere in the universe." And it mentioned antimatter. One gets the feeling of Captain Kirk running around looking for dilithium crystals.
In the interests of good faith and no science fiction, I assumed this paragraph was really TRYING to be about the use of compact energy sources for space exploration. No, apparently not, you say. I pointed out that "antimatter" as a way to store energy (and that is all it is-- an incredibly inefficient and dangerous storage medium) is certainly more dangerous than bombs or reactors (are you really going to argue this point??) and THAT got reverted.
And what is this going on about "artificial photosynthesis"?? That's a way of trapping sunlight for chemical purposes, but you need sunlight for this, and sunlight isn't a concentrated form of energy, even near the earth, let alone outside Earth's orbit (It's no coincidence that all outer planet probes are powered by SNAP generators). Considering all of the many alternatives to fossil fuels (including ordinary solar power in one form or another to product electricity), this doesn't rate a sentence. And it has nothing to do with space exploration, except to keep astronauts alive wtihout plants. WAY off topic. What in the world are you trying to do with this section? Decide. Don't just delete. SBHarris 05:40, 25 October 2006 (UTC)
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- So you are back with vengenance, not sense. And you have discovered a new way for carrying out discussion about the page by adding lengthy comments. Ingeneous indeed. But dear friend SBHarris, we are here not to compete but to cooperate, to make the page more useful and attractive. I hope you will give this thought a few minutes of your abundant time.
And by the way, I gave the title, if you think the paragraph needs more substance you are welcome to edit/add few more sentences on what you think is missing. Charlie 17:38, 25 October 2006 (UTC)
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- Since I cannot think of how to write a good paragraph incorporating "space exploration" and "new energy-source exploration", I can't help you. They don't really go together. Does anybody else out there want to help Charlie in his quest to marry these totally disparate subjects in a block of a dozen sentences? Or even several paragraphs? Are you thinking of solar satellites? What? SBHarris 20:16, 27 October 2006 (UTC)
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[edit] Vibrational heat capacity
Vibrational modes contribute to heat capacity of substances as soon as the temperature rises to the point where they begin to be populated. But whatever the vibrational heat capacity contribution to the total is, that extra vibrational heat capacity contribution ITSELF, is always composed of a 50% kinetic and 50% potential component (on average-- integrating though each vibrational cycle). Each of these components for each vibrational mode gets (1/2)kT per atom, when T has risen so that energy is fully (equi)partitioned and hv << kT. Please don't revert me until you have a better way of saying this, or you think I'm wrong. In which case, here's the place to make your argument. SBHarris 20:30, 27 October 2006 (UTC)
- While I don't have any problem with your statement in the article, in my experience it doesn't correspond to the way people in the field think about these concepts. The whole business of identifying "contributions" to the heat capacity is bound up with the idea that these contributions are in some sense independent of one another. Mathematically, the partition function factors, and when you take its logarithm you get a sum of terms that can be computed individually. Thus for a classical liquid, the partition function factors into kinetic and potential parts, giving you an average kinetic energy that can be evaluated by inspection (giving the appropriate multiple of kT), then you go do some hard work to get the the potential energy. This is valuable because it allows you to deduce, for example, that the velocities in a classical limit obey a Maxwell distribution in spite of the strong intermolecular forces. But this factorization fails when you move away from the classical limit, since the kinetic and potential energy operators do not commute, so the exponential of the Hamiltonian does not factor. Of course you can still write the thermodynamic internal energy as the sum of the ensemble averaged kinetic energy and the ensemble averaged potential energy, and then you can formally identify the temperature derivative of each term with its "contribution to the heat capacity", but this provides no computational simplification, and the individual terms do not, AFAIK, correspond to any experiments that are commonly done. It's just talk, and IME people in the business don't talk this way. (BTW, don't forget that kinetic and potential energy expectation values are only equal in the harmonic approximation. That's not going to be very accurate for, say, a hydrogen-bonded complex or the low-frequency torsional modes - hindered rotations - of a polyatomic molecule.)--Rparson 18:42, 30 October 2006 (UTC)
[edit] The warfare paragraph
Can we delete this? This basically says that a nuke war would blow up all our energy, so it would be a good thing to avoid. OOOOKAY. How banal is that? I could add such a paragraph to just about any Wiki that exists. A nuclear war would blow up the Eiffel tower, so should be avoided, wouldn't you think? A nuclear bomb would cause phenomenal damage to a Pearl Jam concert, so don't forget the importance of a nuclear proliferation treaty there... SBHarris 21:40, 27 October 2006 (UTC)
I agree. 128.12.108.47 02:54, 31 October 2006 (UTC)
Agree. Deleted. --24.52.254.62 22:28, 11 November 2006 (UTC)
[edit] hydrothermal vent organisms
I could be wrong about the ultimate source of the energy used by the organisms around geothermal vents. However, the Chemosynthesis article says, "Chemosynthesis is the biological conversion of 1-carbon molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic molecules (e.g. hydrogen gas, hydrogen sulfide) or methane as a source of energy, rather than sunlight, as in photosynthesis." So it seems to me that either the energy article or the chemosynthesis article is incorrect, since they contradict each other. A third possibility is that the energy needed to make the unstable sulfur compounds does actually derive ultimately from sunlight, but I don't think so; I'd assume the energy of the sulfur compounds originates from geothermal energy, and geothermal energy is mostly from (a) gravitational potential energy released when the earth came together, and (b) natural radioactivity. There is also supposed to be a huge biomass of subterranean extreomophile bacteria, much of which is down extremely deep, and I can't imagine how it could be getting its energy from sunlight. Any thoughts, Sbharris? --24.52.254.62 05:47, 15 November 2006 (UTC)
Oh, I see, I only read your edit summary, and thought you'd just reverted me. Now I see that you added an explanation in a footnote. However, I still think that's not quite right. Both the sulfur and the oxygen are thermodynamically unstable. I think these organisms are getting their energy partly from geothermal sources (the sulfur) and partly from photosynthesis (the oxygen). I've made an appropriate edit to the footnote.--24.52.254.62 20:41, 15 November 2006 (UTC)
- My thinking is that native or free sulfur *is* thermodynamically stable in anaerobic conditions (away from free oxygen). Certainly to the point that it occurs in native form without any organic input (as here from deep vents spewing stuff which has been down there for billions of years, or on the surface of say the moon Io). Absent an O2 supply, I really see no obvious "reservoir" of chemical energy lying around "free" in elemental sulfur, to be potentially used by living organisms. Ultimately, I think sulfur-burners wherever you find them are basically living off sunlight free-energy in the O2, albeit in a very tricky way. The early reports on this failed to note the crucial role of O2 in the process, because the discoverers were probably eager to have discovered something completely different. But I think by now everybody agrees that they haven't. In short, no, I don't think it's fair to count the native sulfur as an energy source per se.
And yes, the chemosythesis article should be updated to note that the energy for the process is coming from sunlight, but indirectly. Just as it does for the metabolism of other anaerobic organisms, which all use chemicals that (at least to my knowledge) must include at least ONE photosynthetically derived-one. If you can find me an anaerobic chemosynthetic bacterium which doesn't rely on ANY products previously produced by aerobic (therefore sunlight-driven) processes, that will be interesting, and I'll make no objection to adding it here. SBHarris 21:03, 15 November 2006 (UTC)
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- My thinking is that native or free sulfur *is* thermodynamically stable in anaerobic conditions (away from free oxygen). Well, O2 is thermodynamically stable if there's no hydrogen around. If the earth was in thermodynamic equilibrium, there'd be no free O2, and no free elemental sulfur, either. If you can find me an anaerobic chemosynthetic bacterium which doesn't rely on ANY products previously produced by aerobic (therefore sunlight-driven) processes, that will be interesting, and I'll make no objection to adding it here. If you look at my most recent edit, I didn't say that it gets all of its energy from geothermal sources, only that it got some of it from that, and some (indirectly) from photosynthesis. I'm a physicist, not a chemist or a microbiologist, so I could be wrong, but I think some of the organisms listed in the Lithotroph article (the section starting with methanogens) don't require any free oxygen, and might still be able to live if photosynthesis ceased entirely.--24.52.254.62 23:46, 15 November 2006 (UTC)
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