Einstein does not define the units for distance (m) and time (s) independently of the speed of light c. Special relativity defines a time interval as distance divided by c and distance as time interval multiplied by c:
c = 300.000.000 m/s
s = 300.000.000 m/c
m = cs/300.000.000
If, in the equations above, we substitute s or m with their respective definitions we obtain:
c = 300.000.000m/300.000.000m/c <=> c=c
The statement c=c is surely always true independently of the actual value of c. This is a classical example of a circular argument. If the units of measurement are defined by nothing more then the postulate of the universal constancy of c then it shouldn’t come as a surprise that measurements utilizing those units can’t but confirm the universal constancy of c.
It appears as if in special relativity units of measurement have no physical meaning. They seem to be pure mathematical scaling factors which are set for each reference frame in such a way, that the universal constancy of c is maintained.
Is relativity still a theory of nature or is it just a theory of mathematics?
Is there a difference between mathematical and physical?
The complete argument can be found on my blog http://hellenicflame.blogspot.com