Experiments by optical resonators (Maser, Laser) were done to verify the "Null result" of the MM-Experiment by extreme high accuracy. Null result means that the light speed is not depending on direction (= isotropy of light speed).
The latest results have been published 2007 by Eisele and Herrmann.
Result: The maximum value of the ratio difference in frequencies in different directions to frequency is 10 exp -17.
Question 3: What can be concluded by this result?
Choice of possible answers:
A) Resonator experiments verified the null result of MM experiment with such a high accuracy that it has to be accepted.
B) Null result of MM experiment is still questionable