Re: The Coulomb

[David Bowman <dbowman@tiger.gtc.georgetown.ky.us>]

Leigh writes:
> ...
> There are other kinds of units, too, including a system called
> electromagnetic units. My thesis advisor at Cal, Mike Tinkham, used to
> refer to the system he called "GOU", or "God's Own Units". The late
> Bob Karplus taught a graduate E & M course in rationalized CGS units!
> I don't much like SI (I guess I am an atheist convert to GOU) but it
> does have the virtue that it allows students to concentrate on learning
> the concepts of physics rather than becoming obsessed with remembering
> that there are 300 volts in a statvolt!

I've always thought that a rationalized version of Planck units was GOU.
(implicit smiley at the end of the above line)  Like you, "I don't much like
SI" either.  However, I disagree concerning any virtue there may be regarding
the ease with which the students can actually learn the concepts of physics
with the SI system.  SI units needlessly obscure the natural structure and
relativistic invariance of E&M.  I think that a unit system like Gaussian (or
its rationalized version, the Lorentz-Heaviside system) makes the theoretical
structure of the theory much more transparent since it keeps all factors of c
explicit and always puts them next to the time variable in Maxwell's Equations,
and it doesn't mix up the dimensions of the various components of the
electromagnetic field strength tensor and the electromagnetic 4-potential
(unlike the SI system).  The Gaussian & L-H unit systems also don't clutter up
the equations with extra gratuitous factors of epsilon_0 and mu_0 whose actual
meanings tend to be mysterious to students.

I think the biggest (possibly only) advantage of of SI units is its ubiquity.
The various pieces of lab equipment that the students use tend to be already
calibrated in units of volts, amperes, ohms, etc., so extra unit conversions
in the lab are kept to a minimum by adopting the SI system.  (Maybe this is
what you meant by the remark about 300 volts = 1 statvolt.)

David Bowman
dbowman@gtc.georgetown.ky.us

p.s. Nick's original question asked about the historical reasons for why the 
the SI system developed the way it did.  About this I'm ignorant.  Maybe
someone who has actually read the works of the relevant 19th century
physicists can supply the answer.