Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!caip!rutgers!seismo!vrdxhq!BMS-AT!stuart
From: stuart@BMS-AT.UUCP (Stuart D. Gathman)
Newsgroups: sci.physics
Subject: Re: Gathman channels revisited; and Throop diagrams
Message-ID: <245@BMS-AT.UUCP>
Date: Sun, 12-Oct-86 14:17:46 EDT
Article-I.D.: BMS-AT.245
Posted: Sun Oct 12 14:17:46 1986
Date-Received: Mon, 13-Oct-86 05:47:09 EDT
References: <3823@ism780c.UUCP>
Organization: Business Management Systems, Inc., Fairfax, VA
Lines: 44
Summary: Some real paradoxes


Well, Gathman channels have generated some interesting discussion.  All
the proposed paradoxes so far have missed the point.  The usual misunder-
standing revolves around the usual definition of 'simultaneous' in
relativity.  Since I didn't invent "Gathman channels", it is amusing
to see my name attached.  All the flames have prodded me to do some
more thinking about them myself, however.  The examples offered so far
have assumed that the world lines of points 'connected' by channels
are parallel.  This is not necessarily the case.  My own paradox
depends on this.

First, the "throop" diagram doesn't prove anything (or the equations
supplied at no extra charge).  This diagram shows events that are
'simultaneous' under the usual definition: i.e. light from the
events would have met half way.  What is missed is that nothing new
is learned by sneaking a view of 'z' through B's frame of reference:
the observer will experience the event himself before the light arrives
at 'y'!  Clearly, 'simultaneous' needs to be redefined when Gathman
channels are in use.  My first inclination is to define the first
observation of an event to be the 'original'.  Notice that with
channels, an event can be observed many times (like with mirrors).
With nice, constant velocity channel endpoints, I still maintain
that causality is not violated (but of course channels could never
have been created unless the endpoints accelerated).

The real problems occur when the channel endpoints accelerate, as they
must to create channels in the first place.  First consider non-
parallel world lines for the endpoints.  This would be the case as 
you hold one endpoint and your friend carries the other to a distant
planet.  The faster your friend travels, the greater the time dilation.
As you watch your friend through the channel, he appears to be in
suspended animation.  As he watches you, you appear to be an indistinct
blur of activity.  Does this situation violate causality?  What happens
to light as it crosses over the channel?  Could a macroscopic object,
such as a human survive a trip through the channel?  When he was half-
way through, the time rate difference between the two halves would, I
believe, kill him.  This 'time well' effect is similar to what happens
when observing an object in a gravity field.  Does this mean that a
Gathman channel has a gravity effect tending to pull matter through
the door?

NOTE: "Gathman channels" are *not* FTL travel.
-- 
Stuart D. Gathman	<..!seismo!{vrdxhq|dgis}!BMS-AT!stuart>