ningluo@acsu.buffalo.edu (Ning Luo) (12/05/90)
One thing we have to watch out in such imaginations about how efficient the nanotechnology would be is the second law of thermodynamics, which places not only an upper bound on the efficiency of any operation involving work, but also an upperbound on the efficiency of any "computation"(i.e. information processing). The ecological consequences of an economy thermodynamically very efficient are also important constraints. Imagine that the whole economy is like a huge heat engine busy in extracting energy from heat or energy sources (the sun, atoms, nuclei, etc.) and outpouring the heat directly and indirectly (i.e. after the work has been used and "useful energy" dissipated) to the only "cold bath" --- the Mother Earth. [Wrong! A much better heat sink, both from thermodynamic and environmental perspectives, is the 3K intergalactic background. It can be accessed from right here on cloudless nights, and from LEO all the time. --JoSH] I think if the quantum leap of the techno-economic revolution is to happen by whichever means (well, nanotech is one of the leading candidates for becoming the driving engine of it), and the human civilization not to be destroyed as the outcome, then man has to go to space. Only in the era of space colonization, the new technologies with too large scale impacts to be "contained" on earth can be safely explored. Space colonization will also make multiple (non-identical) copies of the H. sapien civilization, in case one collapses due to its own carelessness, the evolution lineage of this intelligence will not be terminated. This bring up another thing which bothers me from time to time when I am reading the "grand projections" in this group. Many are talking how nanotech will fundamentally change the social and economic orders. However, the pictures enlisted are usually about how cars, supermarketing, consumer behavior, etc. will be different. It reminds me the story of the White brothers. The motivation for them to invent the airplane was to have a speedy way to transport ice before it melted. They never could have imagined what their invention had meant to the world. But they did invented the plane, so nobody needs to make fun of their original motivation. Good for them. -- Luo, Ning 218 CCC Bldg Roswell Park Memorial Institute Buffalo, NY 14263 | ningluo@sun.acsu.buffalo.edu (APARNET) [Actually, the Wright brothers were simply trying to make a flying machine--that story is quite untrue. There are some good biographies of the Wrights, particularly one entitled "The Bishop's Boys", if you wish to delve further into their motivations. The fact that I am at pains to correct a couple of factual inaccuracies, however, should not be taken as invalidating your main points, which seem to be "Space colonization is desireable in the long run" and "Inventions often outstrip the necessities that mothered them." I agree with both. --JoSH]
dmocsny@minerva.che.uc.edu (Daniel Mocsny) (12/06/90)
In article <Dec.4.23.17.14.1990.24696@athos.rutgers.edu> ningluo@acsu.buffalo.edu (Ning Luo) writes: >[Wrong! A much better heat sink, both from thermodynamic and > environmental perspectives, is the 3K intergalactic background. > It can be accessed from right here on cloudless nights, and > from LEO all the time. > --JoSH] The only commercially competitive terrestrial application of which I know for this heat sink is producing ice in 3rd-world countries. (Place a shallow pan of water on top of a building or hilltop so it only "sees" the night sky. Insulate the bottom. On a calm, clear night, the water can radiate enough heat into space to freeze solid even if the air temperature is above freezing.) Radiative heat transfer across small temperature differences is very slow compared to the mechanisms of conduction and convection. Virtually all heat transfer in the process industries is by a combination of those two. In most practical heat exchanger design, radiation is minor enough to neglect. The consequence is that large-scale power generation today requires convenient heat sinks, such as rivers, oceans, and/or cooling towers. Any scheme that relied on direct radiation to space would need massive arrays of radiators and long runs of piping for all the working fluid. That in itself would probably have an environmental impact considerably greater than the impact of dumping the waste heat into the atmosphere. Just because something is theoretically available does not mean that it will be practical. I have never heard of a serious suggestion to use direct radiation to space to cool a terrestrial power plant. The problem with problematic waste is not that we *can't* deal with it, but that we can't get rid of it without generating even more waste. -- Dan Mocsny Snail: Internet: dmocsny@minerva.che.uc.edu Dept. of Chemical Engng. M.L. 171 dmocsny@uceng.uc.edu University of Cincinnati 513/751-6824 (home) 513/556-2007 (lab) Cincinnati, Ohio 45221-0171 [This underscores Mr. Luo's major point that we must get out into space, which I enthusiastically support. However, I must point out that all terrestrial conductive and convective heat sinks ultimately feed into the dark sky: it is the real sink, and the planet only a buffer. With that in mind, it's clear that we could build (in space) a radiative cooler with half the area of the earth which could sink all the contact- with-matter sunk power theoretically capable of being generated on earth. From there it's only a giant leap to a Dyson sphere... --JoSH]