To : Cavalier Subj: an article I wrote. = Quoting Cavalier to John Brawley = Ca Hello, I'm

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From: Karl Lembke Posted: 26 Sep 94 02:00 To : Cavalier Subj: an article I wrote. -=> Quoting Cavalier to John Brawley <=- Ca> Hello, I'm de-lurking for a moment or two, so that I can Ca> get something cleared up. I've been reading your posts in Okay. The second law of thermodynamics states that: "For any process, the entropy change of the universe must be greater than or equal to zero. The entropy change is equal to zero only if the process is reversible." (1) "It is impossible to transfer heat from a colder to a warmer system without the occurrence of other simultaneous changes in the two systems or in the environment." (2) "It is impossible to convert the heat of a system into work without the occurrence of other simultaneous changes in the system or its environment." (2) There are quite a few processes in the universe by which energy is changed from one form to another, and ultimately to heat. Changing heat into work is more difficult to do completely, and as a result, the energy represented by heat is frequently unavailable for doing work. Specifically, if we have a reservoir of heat, the energy in that reservoir is unavailable for doing work unless there is a colder reservoir available. We can then let the heat run "downhill", tapping energy made available in the difference in temperatures between the two reservoirs. In principle, since the universe appears to be finite in size, eventually all sources of heat will have been used -- all the heat in the universe will have flowed, by conduction or radiation, to colder parts of the universe. In this long distant age, the entire universe will be the same temperature, and the total energy of the universe -- the same amount the universe contains now -- will be unavailable to do work. The second law states that the universe's supply of energy will either stay where it is, or it will flow toward areas of lower energy, but energy will never flow "uphill" to more concentrated (i.e., hotter) areas. Creationists like to portray evolution as violating the second law of thermodynamics, but this doesn't really follow from the formulations given above. Living things use energy to do work. This includes the work of gathering food, movement, growth, and reproduction. The energy to do this work ultimately comes from the Sun. The second law states that living things are unable to use -=ALL=- of the energy from the Sun for work; some of that energy will be unavailable for work, and will be lost to the rest of the universe as heat. Ca> Here's my question: Ca> The hurdle is this... if life is to become Ca> more complex, thereby defyng the 2nd law, and if the reason The relation of complexity with the second law of thermodynamics is a tenuous one, at best. How much energy is required to make a system more complex? It depends on the system. Indeed, anyone who has had to clean up a house knows that in many cases, it takes energy to make a system LESS complex. It is easy to dump the pieces of a jigsaw puzzle onto a table in a very complex mess, because there are lots of different ways to have a heap of jigsaw puzzle pieces. Assembling the puzzle, however, takes work, since there is only one way to have a correctly assembled jigsaw puzzle. Which is more complex? By what measure of complexity? In any case, the energy required to change the makeup of the system is obviously less than the energy available, since these tasks are routinely done. (For example, no one has ever starved to death while working a jigsaw puzzle.) (I don't think.) (I wouldn't put it past some people, though.) Ca> it can pull this off is because of the input of solar Ca> energy, then wouldn't the very first living creature have Ca> had to have a mechanism to transform the solar energy? ie. Ca> wouldn't it have had to have some photosynthetic process? This is a slightly different question than just "what is the second law of thermodynamics?" Given an energy gradient (a hot reservoir and a cold reservoir, in some sort of contact so energy can flow from the hot to the cold reservoir), by what mechanisms can energy be trapped to do work? Classical thermodynamics is concerned with expansion and contraction of ideal gases. This is because thermodynamics was developed to understand how to make steam engines work more efficiently. (Well, originally, it addressed the question of how to make beer more cheaply, but it was very quickly adapted by the engineers.) However, since it deals with available energy, it is applicable to all mechanisms by which energy can be converted to work, be these chemical, physical, electronic, or whatever. The earth is situated between a convenient hot reservoir (the sun) and a convenient cold reservoir (the rest of the universe). Energy constantly flows from the sun to space, and some of it hits the earth on its way out. The energy that hits the earth does quite a few things. It heats the surface of the planet and the air above it. The heated air expands, rises, and circulates, therefore we have weather. The sun's energy also causes water to evaporate from the surface of the oceans, causing clouds and precipitation. Friction within the clouds, and within masses of moving air, result in lightning, which will heat up molecules in the air, and which will also ionize them. When you heat, ionize, and otherwise abuse molecules, you often break molecular bonds, creating reactive species of molecules. These reactive species will then glom on to other molecules, often creating new and more complex molecules in the process. As a result of just this sort of process, the prebiotic earth became increasingly complex, partly because of energy trapped on its way from the sun to the rest of the universe. (I'm ignoring background radiation and geothermal energy for the moment, but they do their share.) Right now, students of chemical evolution is still working to understand the possible pathways to life. It may turn out that there is no set of chemicals that can be built from carbon, hydrogen, oxygen and nitrogen by lightning bolts, by ultraviolet radiation, by ionizing radiation or by reaction in thermal vents, which can combine to form a living system. But given the research that shows that even fairly simple systems can self-replicate, I suspect workable pathways will be discovered. There may never be any evidence that any one of these pathways is what actually led to us, but that really doesn't matter. It will have been proven to be possible in principle. (1) Tipler, Paul A.; Physics; Worth Publishers Inc, (c) 1976 p. 483 (2) CRC Handbook of Chemistry and Physics, 61st ed. p. F-126


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