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meopemuk
meopemuk is offline
#3
Oct9-07, 12:52 PM
P: 1,743
Quote Quote by kev View Post
Can someone clear up what is observed in Shapiro time delay experiments.
As I understand it a delay is seen in the round trip signal time of a radar signal sent to a distant planet on the opposite side of the sun due to gravitational effects. The signal path would be longer than the straight line path to the calculated position of the planet in its orbit due to deflection by the gravitational field of the sun. This longer path would introduce a geometric delay. Would it be right to assume the Shapiro time delay is a measured delay over and above the the simple geometric delay?
Yes, there is some additional delay due to the non-straight path of light. But it is much smaller than the main effect. In my opinion, the main origin of the Shapiro delay is the fact that light propagates slower in the vicinity of massive objects.

Eugene.