Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!bellcore!decvax!ittatc!dcdwest!sdcsvax!drillsys!gatech!seismo!brl-adm!brl-smoke!gwyn
From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: net.physics
Subject: Re: The death of bogus physics
Message-ID: <2049@brl-smoke.ARPA>
Date: Mon, 24-Mar-86 12:39:30 EST
Article-I.D.: brl-smok.2049
Posted: Mon Mar 24 12:39:30 1986
Date-Received: Fri, 28-Mar-86 05:07:46 EST
References: <12603@ucbvax.BERKELEY.EDU>
Reply-To: gwyn@brl.ARPA
Organization: Ballistic Research Lab (BRL)
Lines: 19

In article <12603@ucbvax.BERKELEY.EDU> weemba@brahms.BERKELEY.EDU (Matthew P. Wiener) writes:
>It is true that the theoretical justification of certain points is easier
>to do with calculations in a local Lorentz frame.

From the point of view of the more general theory, it is important
to realize that a general metric cannot be completely diagonalized
by real (differentiable) coordinate transformations, so a local
Lorentz frame is not always possible.  A theory in which it IS
always possible is one that neglects other possible metric-related
physical effects besides gravitation.

In answer to the fellow who wanted to know what the difference is
between space and space-time:  When one diagonalizes the symmetric
part of the metric (the only part considered in normal general
relativity) using real coordinate mappings, one of the four
diagonal elements will have different sign than the other three.
In the transformed (local Lorentz) frame, that coordinate will be
associated with the direction of time while the other three are
spatial.