Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!linus!philabs!cmcl2!seismo!hao!hplabs!sri-unix!crummer@AEROSPACE.ARPA
From: crummer@AEROSPACE.ARPA
Newsgroups: net.physics
Subject: Time travel
Message-ID: <284@sri-arpa.ARPA>
Date: Tue, 18-Jun-85 14:08:16 EDT
Article-I.D.: sri-arpa.284
Posted: Tue Jun 18 14:08:16 1985
Date-Received: Sun, 23-Jun-85 08:24:48 EDT
Lines: 33

From:  Charlie Crummer <crummer@AEROSPACE.ARPA>

> Received: by sri-unix.ARPA (4.12/4.16)
>         id AA26679; Sat, 15 Jun 85 00:04:41 pdt
> Message-Id: <8506150704.AA26679@sri-unix.ARPA>
> Date: Wed, 12-Jun-85 06:17:56 PDT
> To: physics@sri-unix
> From: merrill%raja.DEC@DECWRL.ARPA (Rick - Font Mgr. for Hardcopy Engineering)
> Subject: One Quick Question

> Article-I.D.: <2627@decwrl.UUCP>

> >Path: decwrl!dec-rhea!dec-kirk!williams
> >Subject: Two quick answers
> >
> >	The time traveler travels close to the speed of light in
> >relation to the inertial frame. He travels into the future.
> >...				John Williams

> One thing I'd like cleared up: does the traveler moving at CONSTANT
> VELOCITY  move FURTHER into the future the longer he travels, or
> did he move into the future by Accellerating To Speed?

> 				Rick Merrill
At any speed < c there is no time travel.  To achieve a speed >= c requires
infinite force since the relativistic mass increases without bound as c is
approached.  Cosmic rays travel very close to c (as do particles in any large
accelerator) and they do not travel backwards in time.  (See Feynman's books
for the description of a positron as an electron travelling backwards in time.
Since CPT is conserved, it seems, C amounts to T where P is conserved.
C, P, T, are charge conjugation, parity, and time-reversal.)

 --Charlie