Maxwell and Classical Physics

John K Clark (
Wed, 10 Jun 1998 07:56:13 -0700 (PDT)


On Tue, 9 Jun 98 (Tony Hollick) Wrote:

>Maxwell's theory does conform fully with Classical Mechanics.

No it does not, although Maxwell tried very hard to make it do so. Maxwell's
greatest triumph came when he proved that a changing electrical field creates
a changing magnetic field and a changing magnetic field creates a changing
electrical field. He then proved that this phenomena propagated as a wave at
a speed of 1/(EM)^1/2 , where E and M are the well known electric and
magnetic constants, this give a speed of 3*10^8 M/sec and this was exactly
the speed for light that was experimentally and independently found.
The match was too close, it couldn't be a coincidence, light must be an
electromagnetic wave.

There was one nagging little problem however, the electric and magnetic
constants are the same for everybody, that's why they're called constants,
and that means that the speed of light would be the same for every observer.
Maxwell thought this was a (minor) flaw in his theory, he assumed that his
derivation of the speed of light was only for an observer that was at
absolute rest, but this assumption was definitely not in the equation,
it said not one thing about the motion of an observer. Maxwell tried to
modify his theory to make his assumption explicit but he failed, 40 years
later Einstein explained why he failed and why a modification was not needed.

John K Clark

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