Question: Does the Postulate of Constant Light Speed apply also to mechanical processes? For example, is a cannonball or a sound wave required to move at the same speed independent of the motion of the "emitting" or "recieving" body? If so, what is the reasoning that leads to this requirement? If not, cannot a mechanical clock be built whose rate of ticking is independent of its motion? The objection that such a clock would allow speed to be determined appears invalid, because the speed calculated would be the relative speed of the two observers.