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From: pmk@prometheus.UUCP (Paul M Koloc)
Newsgroups: net.physics
Subject: Re: Electron radius
Message-ID: <177@prometheus.UUCP>
Date: Mon, 2-Sep-85 03:50:45 EDT
Article-I.D.: promethe.177
Posted: Mon Sep  2 03:50:45 1985
Date-Received: Wed, 4-Sep-85 05:17:32 EDT
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Organization: Prometheus II Ltd., College Park, MD
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TERRY%LAJ.SAINET.MFENET@LLL-MFE.ARPA
Terry of Science Applications Incorporated? at LLNL Magnetic 
Fusion Energy? picks up on inconsistencies:

> I see no basis for the assumption that the rest mass of an electron is
> due entirely to the mass of its electrostatic energy.  The following
> equation is then given:
>         m*c^2 = e^2/r
> radius is ~ e^2/(m*c^2).  Where did the approximation come in?  
> . .. e is proportional to the charge, without giving the constant of
> proportionality ...  . .  a number for his use of e.
> The value for r is then given as ~ 3*10^15 meters.  Is this really correct? 

> . .. . poor little electron which has been shown by experiment to be 
> indistinguishable from a point particle. 

Clearly the electron has energy tied up in electrostatic energy, and
to a lesser degree magnetic energy.  We only used the approximation
m*c^2 ~ e^2/r + ... .  to show that an electron has real physical size
and is not  a "zero extent" or point particle. Certainly, the electric
energy doesn't exceed or exactly equal the electrons rest mass (energy). 
But, assuming that all of the rest mass energy was due to entirely to 
its electrostatic energy gives us a lower bound for the radius of an 
"at rest" electron.  

The numerical value given was INCORRECTLY copied from a previous article 
and should read ~ 3*10^(-15) meters.  
"e" is defined as follows: 
         "e^2" = "q^2/(4*pi*8.854*10-12 newton {meters squared}) 

      where "q" is  electron charge (equals 1.6 * 10^{-19}coulombs). 

I know of NO experiment which has the appropriate sensitivity that 
shows an electron is indistinguishable from a point. There are 
equations which can reduce the earth's mass as acting from a point 
to obtain an usable result. That doesn't mean that the earth's radius 
is an infintesmal. The mathematical treatment in such cases are not 
complete, and should not be extrapolated beyond the limit of its
assumptions. 
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