🚀 go-pugleaf

brahm@cco.caltech.edu (David E. Brahm) writes:

>sichase@csa1.lbl.gov (SCOTT I CHASE) writes:
>> What makes the speed of light any more fundamental than the charge
>> of an electron, or the electroweak mixing angle?

>Forgive me for jumping into a thread I haven't followed, but the obvious
>answer is that the speed of light has *dimensions*, and thus is determined
>by (or *defines*) the units you work in.  Once you set up (Planck) units
>where c=G=hbar=1, the remaining physical constants (the dimensionless ones)
>are the interesting ones.

In partial defense of Scott, you *can* just as easily define some
coupling constant to be 1 (thereby making the question of "why does
it have that value?" meaningless) and push the corresponding information
into the speed of light.  This is exactly what atomic physicists do
when they use units in which Coulomb's Law has a coefficient of 1
and the speed of light is 137.  Then the question "Why is the
electromagnetic coupling constant what it is?" becomes "Why is
the speed of light what it is?"

The point is that physics as now practiced has a certain number of
fundamental free parameters, and one of the jobs of future physics
is presumably to find explanations for them;  but the way particle
physicists usually express those free parameters, c is not one of
them.  The question "Light travels at some speed.  Why that speed?"
becomes part of "Why do things made of matter have the sizes and
run at the speeds that they do?" which is really a question about
masses and coupling constants.
-- 
Matt McIrvin