Re: special relativity

["John S. Denker" <jsd@MONMOUTH.COM>]

John Mallinckrodt wrote:
> > From the electromagnetic theory, the speed of light
> > must be a constant because "c" appears as a function
> > of two constants: epsilon_0 and mu_0.
>
> I don't find this by itself to be a compelling argument and
> neither did a lot of very intelligent late 19th century
> physicists.  After all, I could (apparently) just as well say,
> "From the mechanical theory the speed of waves on a given string
> must be a constant because it appears as a function of two
> constants: T and mu."

JM has a point, both as to history and logic.  (Whether this is
pedagogically relevant is another question.)

In 1880 it was perfectly logical to interpret the equation
for waves in the luminiferous ether in exactly the same way as
the equation for waves on a string.

The Michelson-Morely experiments

http://www.nobel.se/physics/educational/tools/relativity/experiment-1.html
has been called "perhaps the most significant negative
experiment in the history of science" (Encyclopedia Britannica).

====================================

I think of myself as an experimentalist.

We should keep in mind that physics remains an experimental
science.  A lot of what we know about physics comes directly
from experiment, and it is a mistake to pretend that it can
all be deduced from logic.  (To some extent I made this
mistake in my earlier post in this thread.  In that post,
please cross out the reference to the Maxwell equations
and substitute a reference to the M-M experiment.)

In any case, in the 21st century the Michelson-Morely "no
ether drift" law must be considered one of the well-established
laws of physics, so nowadays it is fully implied (however
vaguely) by proposition (1) when it speaks of "the laws
of physics" collectively.  So the main drift of my previous
post remains on target.