Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!rutgers!aramis.rutgers.edu!athos.rutgers.edu!nanotech From: doom@portia.stanford.edu (Joseph Brenner) Newsgroups: sci.nanotech Subject: Re: A practical nano-mechanical perpetual motion machine (?) Keywords: thermodynamics, perpetual motion machine of the second type Message-ID: Date: 6 Mar 90 22:23:54 GMT Sender: nanotech@athos.rutgers.edu Organization: Stanford University Lines: 45 Approved: nanotech@aramis.rutgers.edu --------- About JoSH's objection: Certainly the "rubbery" nature of the cylinder I was proposing causes problems, but how would you prove that they make the device impossible? I might try and argue that the kinetic energy is not be equal, just the thermal energy, and that the somewhat greater stiffness of the cylinder might let you see the motion of the gas molecule as a very small "signal" on top of the thermal "noise" of the cylinder. Another way to look: can you build a piezoelectric crystal so small that it's thermal fluctuations can be detected as a voltage across the crystal? I would guess that if you could, you'd have a 2nd law violation, hence I expect you can't, but why not? In general about these comments: It seems to me that the nature of this game is that you can't just say "this contradicts the second law, therfore it's impossible". The idea is to find an inherent design flaw working from the ground up, and hence verify the second law. I would be suprized (to say the least) if I get anything out of this than a somewhat improved understanding of thermo... So, I'll re-read Drexler on the Maxwell's nano-Demon disproof, and I'll even try flipping though some recent SA's to see if I can trace Henry Cobb's reference. Thanks for the comments. -- Joe B. [I don't know that anything about nano-Demons is in EoC--I couldn't find anything in a quick review. Look at Cellular Automata Machines by Toffoli and Margolus (and papers by either, and by Fredkin) and the oft-mentioned Emperor's New Mind by Penrose for a nice overview of entropy matters (skip the AI part). I would imagine you get some voltage variation in any material directly due to the electronic component of the thermal energy, it doesn't have to be piezo-electric. The same arguments would apply to it as to mechanical motion--you'll have as hard a time building a diode for nano-voltages as a ratchet for nano-motions. There is no proof in my original reply--it was just explanatory. The proof, if you need one, would have to be built up from the reversibility of physics at the micro-level. --JoSH]