Planet Mercury (m = 0.3301 x 10^24 kg ) is in a circular orbit about the sun (M = 1.989 x 10^30 kg ) at r = 57.91 x 10^6 km.
Show that this slight shortening of the period amounts to the observed precession (gradual rotation of the semi-major axis ) of Mercury's orbit which is 43 seconds of arc per century. This agreement between Einstein's calculations and the observed precession was one early piece of evidence confirming Einstein's relativity.