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From: weemba@brahms.BERKELEY.EDU (Matthew P. Wiener)
Newsgroups: net.physics
Subject: Re: Bogus physics reamplified
Message-ID: <12702@ucbvax.BERKELEY.EDU>
Date: Thu, 27-Mar-86 01:26:47 EST
Article-I.D.: ucbvax.12702
Posted: Thu Mar 27 01:26:47 1986
Date-Received: Fri, 28-Mar-86 05:50:26 EST
References: <368@ihnet.UUCP> <2057@jhunix.UUCP> <2874@sjuvax.UUCP>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: weemba@brahms.UUCP (Matthew P. Wiener)
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Organization: University of California, Berkeley
Lines: 30
Keywords: general relativity, justifying assertions, name-calling

In article <854@lanl.ARPA> jlg@a.UUCP (Jim Giles) writes:
>>In article <556@lanl.ARPA> jlg@a.UUCP (Jim Giles) writes:
>>>Note: I have always said 'local reference frame', which in GR is ALWAYS
>>>a Lorentz frame.
     ^^^^^^^ ^^^^^
>	"... The geometry of spacetime is locally Lorentzian everywhere."
                                                  ^^^^^^^^^^
Lorentz frame is not the same as Lorentzian geometry.  And your assertion
is completely false as stated.

>The emphasis is theirs.  There is, therefore a local Lorentzian frame
>everywhere (actually, an infinity of them).  On page 23 the text goes on
>"... these theorems [about spacetime] rise above all coordinate systems in
>their content.  They refer to intervals or distances." "All coordinate
>systems" here refers to the infinity of available Lorentzian frames which
>you might select for computational purposes.  Any non-Lorentzian coordinate
>system causes the theorems in question to be completely reformulated for
>that system (mainly because the metric (a word which actually doesn't
>appear yet) is no longer valid - intervals don't behave properly in a
>non-Lorentzian coordinate system).

Read what you just quoted.  There are no non-Lorentzian coordinate systems
in a Lorentzian geometry.  But whatever you are talking about, the theorems
in question rise above coordinate systems, just like MTW said in your quote,
and unlike your last sentence.  If a law or theorem is expressed in covariant
form, ie with tensors, it is true in all coordinate frames.  That is why we
use tensors in the first place: to identify the underlying geometric meaning
behind the coordinate systems.

ucbvax!brahms!weemba	Matthew P Wiener/UCB Math Dept/Berkeley CA 94720