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From: gwyn@brl-vgr.ARPA (Doug Gwyn )
Newsgroups: net.physics
Subject: Re: Light as the boundary between matter and energy
Message-ID: <3237@brl-vgr.ARPA>
Date: Thu, 5-Apr-84 02:00:50 EST
Article-I.D.: brl-vgr.3237
Posted: Thu Apr  5 02:00:50 1984
Date-Received: Sat, 7-Apr-84 02:27:01 EST
References: <948@ihuxm.UUCP>
Organization: Ballistics Research Lab
Lines: 29

I have to disagree with some of what you said (as a matter of physics,
not philosophy).  Energy and momentum are not at all the same thing
expressed in two different ways; since energy is the conjugate of
time and momentum of space coordinates, that would imply an equivalence
of space and time, yet time-like and space-like coordinates have a very
different nature physically.  Energy and momentum are generally related
in a given situation but they do not measure the same thing.

Unless something has changed radically in the last few years, the
majority of people working in relativity theory still believe in
gravitational radiation as a consequence of Einstein's 1916 theory.
It is true that simple plane waves are predicted as a consequence of
linearization (indeed, two of the three modes do not carry energy),
but even a rigorous solution predicts slowing down of a rotating
massive object.  This business is complicated by the fact that energy
conservation cannot be expressed in a generally-invariant fashion,
which can be taken to mean that strict conservation of energy-momentum-
stress is not a fundamental law of nature but only a close approximation
so long as general-relativistic effects are small.

I have long held that the appearance of singularities in quantum field
theory is a sure tip-off that one has made a conceptual error by trying
to reduce everything to the action of an infinite number of particles.
Einstein instead thought it might be possible to reduce everything to a
small number of fields.  Certainly life is simpler when the field is
taken as the fundamental concept rather than particles.

I find topics like this much more interesting than discussions of high-
school physics problems.  More, more!