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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
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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  
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