Asri-unix.1102 net.space utcsrgv!utzoo!decvax!ucbvax!C70:sri-unix!A.exp@Berkeley Thu Mar 25 14:49:35 1982 Thought experiment in gen rel Isn't movement backwards in time only a virtual mathematical effect of the symmetry of particle physics? No part of the rod undergoes acceleration during the comparison of the path of the rod in the new region of the universe with the geodesic in that region. The point about it being impossible for a totally rigid rod to exist is valid, but once the rod is moved to its new position any sound can be allowed to damp until no part of the rod is in motion with respect to any other part. If the speed of light sets an upper limit on the rigidity of a material, a rod could be considered which would be arbitrarily close in rigidity to the limit. The experiment previously posed can be asked in this situation. As King was saying the solution may be that the forces between the component atoms of the rod follow the geodesic, causing the rod as a whole to follow the geodesic. If however the rod is of finite thickness won't bending it in this way cause reduction of the distances between atoms on the side of the rod which is bent towards the concave, with a resulting reactive force that would prevent the rod from quite following the geodesic? ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.