Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 exptools 1/6/84; site iham1.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxj!ihnp4!iham1!gjphw
From: gjphw@iham1.UUCP
Newsgroups: net.physics
Subject: Re: Could someone explain why FTL is illegal?  In small words?
Message-ID: <249@iham1.UUCP>
Date: Thu, 8-Nov-84 16:55:18 EST
Article-I.D.: iham1.249
Posted: Thu Nov  8 16:55:18 1984
Date-Received: Sat, 10-Nov-84 07:24:24 EST
References: <327@mhuxt.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 57



    Just would like to make two comments about the FTL topic under
 discussion.  The first is about what changes, or doesn't change, with
 velocity and the other is about the origin of the Lorentz
 transformation.

    One biographer of Einstein wrote that Albert's primary interest in
 exploring relativity was to discover which properties remained
 invariant at high speeds.  He was interested more in what does not
 change than what does change with velocity (reflecting most physicists'
 interest in constants of nature).  If you consider that theories in
 physics can be organized in a hierarchy, from the very concrete such as
 electrons to the very abstract such as unified field theories,
 Einstein's special theory is an example of a theory formulated
 primarily by considering the concepts surrounding an issue and not by
 appeal to experiment.  The special theory resolves a conflict between
 Maxwell's equations for electrodynamics and Newton's laws of dynamics.
 Albert said that he was not aware of the Michelson-Morley experiments
 (doubtful) but rather concentrated on resolving conflicts and seeking
 invariants.

    In Maxwell's equations, electric charge is invariant and other
 properties (e.g., magnetism) are velocity dependent.  Similarly, from
 Newton's dynamics, mass is the invariant quality with momentum and
 energy being velocity dependent (above the Newtonian expressions).
 With this convention, as it is being used in the search for grand
 unification theories, mass does not change with velocity but momentum
 does.  Even with mass being a constant, the velocity of light in a
 vacuum still remains a limit for motion as has been amply described in
 many recent submissions.

    Related to the faster-than-light discussion is the origin of the
 Lorentz transformations.  Lorentz, the foremost physicist at the time,
 was deeply interested the properties of light at different velocities.
 The behavior of light traveling through lengths of rapidly flowing
 water was carefully studied for many years before Lorentz wrote down
 his equations governing contractions and transformations.  These
 equations depended upon the speed of light in the medium and the motion
 of the medium.

    Virtually at the same time, Einstein wrote his special theory and
 named the transformation equations after Lorentz thinking that they
 had already been derived.  In fact, the equations had been derived for
 light traveling through a medium, did not reference the speed of light
 in a vacuum, and did not include time as a variable parameter.  Today,
 with the outstanding success of Einstein's formulation, we often
 overlook how close Lorentz (from an experimental perspective) and
 Poincare (from a mathematical-conceptual perspective) were to
 formulating special relativity.

-- 

                                    Patrick Wyant
                                    AT&T Bell Laboratories (Naperville, IL)
                                    *!iham1!gjphw