Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!mgnetp!ihnp4!houxm!vax135!cornell!uw-beaver!tektronix!hplabs!sri-unix!STEINBERG@RUTGERS.ARPA From: STEINBERG@RUTGERS.ARPA Newsgroups: net.sf-lovers Subject: conservation of momentum Message-ID: <13198@sri-arpa.UUCP> Date: Thu, 6-Sep-84 12:38:27 EDT Article-I.D.: sri-arpa.13198 Posted: Thu Sep 6 12:38:27 1984 Date-Received: Thu, 13-Sep-84 06:58:23 EDT Lines: 30 From: Louis Steinberg Carl Weidling note that matter transmission does not necessarily imply violating consevation of momentum, but notes that classical conservation of momentum implies that the center of mass of the the universe is not altered while matter transmission does seem to alter it. I have two comments: If momentum is conserved, then you come out of the matter transmitter with the same momentum you went into it with. Since your mass doesn't change (we hope!), your velocity doesn't change. The problem is that the place you transmit to may be moving with a quite different velocity. E.g. if you transmit from one point on the equator to another point on the equator exactly on the other side of the earth, you will come out moving about 2000 mph relative to the ground. Interplanetary MT is even worse. I vaguely remember one of the series of short stories on MT used this device to limit the range of MT for the first few stories. Eventually a method was developed that allowed the momentum to be transfered to some large mass somewhere in the process of transmitting you. (This was the series including the story Flash Crowd.) While conservation of momentum is a well established law, the question about center of mass of the universe is not a real issue. In fact, the term "center of mass of the universe" does not even make much sense in a relativistic universe. Presumably one defines this by taking the position and mass of every particle at some instant. The problem is that there is no consistent way to define "the same instant in time" for two particles that are moving relative to each other at some noticable fraction of the speed of light. -------