Correct with this (relatively new) definition of the meter, which makes use of c
in my second sense (i.e., the speed at which light actually does travel. Of course the
definition is predicated on the assumption that c _doesn't_ change - i.e., that it's
identical with c in my first sense. Logically we ought to designate these by different
symbols, c1 & c2. What we know now is consistent with c1 = c2. It's easier to
understand how c2 could change with time than c1.
George L. Murphy