Abstract
By examining the effects of rotational and orbital motions of the Earth on wave propagation in the global positioning system and an intercontinental microwave link, it is pointed out that the Earth's orbital motion has no influence on these earthbound wave propagations, while the Earth's rotation does contribute to the Sagnac effect. As the propagation mechanism in the Michelson-Morley experiment cannot be different from that in the aforementioned ones, it is concluded that due to the Earth's rotation, the shift in interference fringe in this famous experiment is not exactly zero. However, by virtue of the round-trip propagation path, this shift becomes second order and hence is too small to observe within the present precision.