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From: gjphw@iham1.UUCP (wyant)
Newsgroups: net.physics
Subject: Re: Definition of mass in relativistic mechanics
Message-ID: <464@iham1.UUCP>
Date: Mon, 14-Oct-85 16:37:03 EDT
Article-I.D.: iham1.464
Posted: Mon Oct 14 16:37:03 1985
Date-Received: Wed, 16-Oct-85 05:23:30 EDT
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Organization: AT&T Bell Laboratories
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    There certainly has been a shift in emphasis over the last ten years
 concerning the use of mass and relativity.  When I began graduate school (over
 ten years ago), I recall that the standard treatment of mass used the
 relativistic mass (gamma * rest mass).  By the time I completed school, the
 thinking had changed so that rest mass was in more common usage.  This shift
 is due, in part, to the increased prominence of high energy particle physics
 and their way of dealing with concepts of nature.

    Concepts change with time and fashion, and tend to follow the most
 glamorous fields.  Particle physics and its stalking of a unified field theory
 (or grand unified field theories) is the glamor area of physics right now.
 Like the lower class people imitating the upper class, a lot of physics has
 adopted the mannerisms and formalisms of particle physics.  While the energy-
 momentum four-vector and the invariance of the rest mass were known to the
 ancients (or at least the founding fathers of relativity (what, no mothers?)),
 it was the relativity and not the invariants that were stressed.

    Einstein claimed that his General Theory supported E. Mach's concept for
 the origin of inertia (gravitational interaction between a body and the whole
 universe), but there are differences between Mach's inertia and Einstein's
 inertia.  A recent experiment performed by someone at the National Bureau of
 Standards seems to uphold Einstein's inertia as formulated in GR and not
 support Mach's inertia.  Oh well...


                             Patrick Wyant
                             AT&T Bell Laboratories (Naperville, IL)
                             *!ihwld!gjphw