Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site brl-tgr.ARPA Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!whuxl!whuxlm!akgua!sdcsvax!dcdwest!ittvax!decvax!genrad!panda!talcott!harvard!seismo!brl-tgr!gwyn From: gwyn@brl-tgr.ARPA (Doug Gwyn ) Newsgroups: net.misc,net.physics Subject: Re: perpetual motion Message-ID: <9347@brl-tgr.ARPA> Date: Tue, 19-Mar-85 19:35:23 EST Article-I.D.: brl-tgr.9347 Posted: Tue Mar 19 19:35:23 1985 Date-Received: Sat, 23-Mar-85 04:24:28 EST References: <608@vortex.UUCP> <368@talcott.UUCP> Organization: Ballistic Research Lab Lines: 18 Xref: watmath net.misc:7614 net.physics:2285 > ... The conservation of > momentum is so fundamental (and easy to verify) that even most laymen be- > lieve it; ... Also, conservation of momentum is a direct consequence of spatial translation invariance of the fundamental laws of physics, and conservation of energy is a result of time translation invariance. The general relativist would point out that the corresponding exact physical law (vanishing divergence of stress-energy-momentum tensor) shows that the exactly-conserved quantity is not purely physical, and the purely physical quantity is not exactly conserved. However, I know of no "perpetual motion machine" that claims to exploit this. I certainly don't think professional physicists have a monopoly on truth, but the odds are very much against a "backyard inventor" being able to overthrow well-established theories of physics without himself having a coherent mathematical theory.