From page 354 "It was zero in so far as the motion of the earth in its orbit is concerned. The remaining effect, however, was large enough to be measured"
Absolutely not. Flat earthers like to cite the Michelson Morley experement but the detailed results agree with their conclusion. They also don't agree with Einstein.
You shouldn't block flat earthers for the simple fact that it's a fun thought experiment finding every-day observable proofs that the earth is round. Good logic exercise.