Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!caip!nike!oliveb!epimass!jbuck
From: jbuck@epimass.UUCP (Joe Buck)
Newsgroups: net.physics,net.sci,net.philosophy
Subject: Re: A Sane Man Proposes A Time Travel Experiment
Message-ID: <340@epimass.UUCP>
Date: Tue, 29-Jul-86 22:21:19 EDT
Article-I.D.: epimass.340
Posted: Tue Jul 29 22:21:19 1986
Date-Received: Wed, 30-Jul-86 20:54:39 EDT
References: <289@axiom.UUCP> <5723@lanl.ARPA> <5594@sun.uucp>
Reply-To: jbuck@epimass.UUCP (Joe Buck)
Organization: Entropic Processing, Inc., Cupertino, CA
Lines: 43
Xref: mnetor net.physics:2497 net.sci:1107 net.philosophy:2225

>In article <5723@lanl.ARPA> dxm@lanl.ARPA (Douglas Miller) writes:
>>Time travel violates the conservation of mass and energy laws...

In article <5594@sun.uucp> lyang@sun.UUCP (Larry Yang) writes:
>I used to believe this argument, too, 'til I got my brain out of the
>classical view of the universe.  Consider time as an additional dimension.
>Now just consider time travel as moving mass/energy from one "point"
>in the space-time to another.  Thus , mass/energy is conserved in this new
>space-time "universe".  

Sorry, conservation of mass/energy applies at any instant of time,
and region of space.  It has never been observed that the mass/energy
decreases at one instant, and increases at the next, except at the
level of elementary particles.  The uncertainty principle lets you do
this though.  

Many people are familiar with		(delta x)(delta p) >= h

but there's also			(delta E)(delta t) >= h

That is, you can violate the conservation of energy if you do it for
a short enough time, since the energy of a system isn't precisely
defined unless you measure it forever (t -> infinity).
Unfortunately, the time in which you're allowed to have an extra gram
of matter around is pretty miniscule.  On the other hand, since it's
probabilistic, if you wait long enough (10^big-number times the
age of the universe) it might happen.

In the vacuum, particles and antiparticles are constantly appearing
and annihilating each other out of nothing.  One way of interpreting
this is that the positron is an electron travelling backward in time.
So the positron-electron pair is only a single particle, travelling
in a little circle in space-time.

One could imagine a macroscopic object travelling in a loop in
space-time.  No microscopic laws would be violated; only the second
law of thermodynamics (but this is a statistical law, so if you wait
long enough...).  An observer in a "normal" space-time path
might see this like a pair-production event: suddenly two identical
but opposite objects appear, move in some way, collide, and disappear.
-- 
- Joe Buck 	{ihnp4!pesnta,oliveb,nsc!csi}!epimass!jbuck
  Entropic Processing, Inc., Cupertino, California