Let the earth be a coordinate system rotating uniformly relative to the universe. Then centrifugal forces would be in effect for masses at rest in the universe's coordinate system, while no such forces would be present for objects at rest with respect to the earth. The geosynchronous satellite is precisely such an object, at rest with respect to the earth, but viewed as having a centrifugal force acting on it with respect to the universe. Already Newton viewed this as proof that the rotation of the earth had to be considered as 'absolute,' and that the earth could not then be treated as the 'resting' frame of the universe. Yet, as E. Mach has shown, this argument is not sound. One need not view the existence of such centrifugal forces as originating from the motion of the earth; one could just as well account for them as resulting from the average rotational effect of distant, detectable masses as evidenced in the vicinity of
the earth, where the earth is treated as being at rest.

In quite precise language, Einstein taught that the centrifugal force on an object in the earth's rest frame (the condition satisfied by the hovering geosynchronous satellite) is inadmissible as evidence of the rotation of the earth, for in the earth's frame that force arises from "the average rotational effect of distant, detectable masses."

<font size=-1>[ This Message was edited by: Prince on 2002-08-12 18:55 ]</font>