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From: hes@ecsvax.UUCP (Henry Schaffer)
Newsgroups: sci.physics
Subject: Re: A Question
Message-ID: <2182@ecsvax.UUCP>
Date: Sun, 26-Oct-86 22:06:24 EST
Article-I.D.: ecsvax.2182
Posted: Sun Oct 26 22:06:24 1986
Date-Received: Mon, 27-Oct-86 22:29:26 EST
References: <230@sri-arpa.ARPA> <572@epimass.UUCP>
Organization: NC State Univ.
Lines: 29

> In article <230@sri-arpa.ARPA> JDM%SMVL%rca.com@CSNET-RELAY.ARPA writes:
 ... 
>     o  Given the old "accellerating-elevator-in-space" experiment,
>        how can one within the elevator tell the whether he is
>        accellerating or under the influence of gravity?
> 
> You can't tell the difference.  This is the heart of general
> relativity.
> 
> 
> -- 
> - Joe Buck 	{hplabs,ihnp4}!oliveb!epimass!jbuck
>   Entropic Processing, Inc., Cupertino, California

I've wondered about one "difference" which I once read about.

Hold a ball in each hand, say 1 meter apart, and level with the floor.
Then let go of them, and they will "drop" to the floor - mark where
they hit.  In the accelerating-at-1g-elevator-in-space they will hit 
exactly the same distance apart.  On the 1-g-surface-of-earth
they will be slightly closer together because they fall along
radii converging at the center of mass of the earth.

What is the loophole here?  Can gravity produce parallel paths
of the falling balls, or does the elevator test only allow one ball,
or ... ?  (Please help - I'd hate to discard general relativity
because of this. :-)

--henry schaffer  n c state univ  (not physics dept)