"Jesse Mazer" wrote in message
...


Androcles wrote:

In a reference frame in which the apparatus is stationary, x and y
don't
change as the apparatus is rotated (assuming x and y are the
arm-lengths).


Exactly. So you prove nothing. However, Einstein's postulate is
"light is always propagated in empty space with a definite velocity
c which is independent of the state of motion of the emitting body"
Reference :
http://www.fourmilab.ch/etexts/einstein/specrel/www/

The Earth is moving in the empty space, which is the reference frame.
Are you trying to deliberately obfuscate the problem?


Empty space doesn't have a particular reference frame in Einstein's
theory.
Then light will be source dependent.
Androcles.