Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site caip.RUTGERS.EDU Path: utzoo!linus!decvax!decwrl!pyramid!pyrnj!topaz!caip!CREW From: CREW@SU-SUSHI.ARPA Newsgroups: net.sf-lovers Subject: Re: Time Travel Message-ID: <324@caip.RUTGERS.EDU> Date: Sun, 3-Nov-85 05:20:16 EST Article-I.D.: caip.324 Posted: Sun Nov 3 05:20:16 1985 Date-Received: Tue, 5-Nov-85 20:47:13 EST Sender: daemon@caip.RUTGERS.EDU Organization: Rutgers Univ., New Brunswick, N.J. Lines: 51 From: Roger Crew>>From: Alan Wexelblat >> It seems to me that time travel *must* imply spatial ... >> travel because if you move in time, then the spot you >> left from is going to be in a different spatial location >> when you stop moving in time. >> >> This would only be true if velocities were absolute. >> They aren't. > >From: "Keith F. Lynch" > To say that the earth was 'there' in 1955 and will be > 'over there' in 2015 is meaningless... > > [ _Timescape_ and _Tomorrow_Is_Too_Far_ both ] share the > implicit notion that it is the center of our galaxy which > is stationary. There is no better reason to regard that > as non-moving as anyplace else. Strictly speaking, velocities are relative. There is a fix, however. One of the discoveries that accompanied that of the 3-degree background radiation (...think of it as stray photons left over from the Big Bang...) was the fact that there is a measurable doppler shift in this radiation. That is, it is possible to measure the velocity of the earth with respect to the ``primordial fireball.'' Once we do that, we can ascribe velocities to the sun, the center of our galaxy, etc... Thus we have, in some sense, a universal frame of reference, with respect to which the idea of an absolute velocity vector makes sense. One could point at a certain part of the sky, say that the earth is heading that way and say that, 100 years from now, we'll ``be'' a certain distance from here in that direction... This works provided we keep the times/distances small enough (cosmologically) that the notion of frames of reference still applies (i.e., don't try to say anything about where we'll be 10^9 years from now). Note that the idea of absolute location is still meaningless. None of this saves Gregory Benford, however, since the 3-degree radiation wasn't discovered until 1967; his physicist at UCwherever in 1962 wouldn't have known anything about it.... Roger Crew -------