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From: tan@ihlpg.UUCP (Bill Tanenbaum)
Newsgroups: net.physics
Subject: Re: Do Positrons Have Negative Mass?
Message-ID: <1138@ihlpg.UUCP>
Date: Mon, 26-Aug-85 16:46:15 EDT
Article-I.D.: ihlpg.1138
Posted: Mon Aug 26 16:46:15 1985
Date-Received: Wed, 28-Aug-85 20:17:18 EDT
References: <636@astrovax.UUCP>
Organization: AT&T Bell Laboratories
Lines: 27

> > There's a discussion on net.scifi-lovers relating to negative mass -
> > the hope is to produce an FTL drive somehow. This triggered off a
> > memory and I'm hoping someone can contribute.
> > 
> > In about 1966 I attended a seminar by Prof. Fairbanks who researched
> > at Stanford U (I think). He was trying to slow down positrons for long
> > enough to tell if they fell upwards or downwards.
> > 
> > Does anyone know how this turned out? If this experiment did not get
> > completed, has there been any other work?
> --------------------
> [Brian Sutin]
> 	There is a theorem of particle physics which states that all
> particles with a negative mass travel backwards in time.  This means
> that the positrons will fall upward, but they do it backwards, so one
> sees a downward fall forwards in time.  Since all the effects of a
> negative mass cannot be distinguished from positive mass, all
> particles are labeled with a positive mass just to keep things simple.
> All this comes from charge, parity, and time symmetry arguements.
> --------------------
Mr. Sutin's theorem is correct, but since particle physics (without gravity)
deals only with inertial mass, not gravitational mass, it does not say
anything about how positrons behave in a gravitational field.  To answer
that question, you need also the gravitational mass of the positron.
The equivalence principle of General Relativity is needed here.
-- 
Bill Tanenbaum - AT&T Bell Labs - Naperville IL  ihnp4!ihlpg!tan