Past exam of the mathematics course of the University of Cambridge 2006 iii Paper 61 2 b Solution Created 2026-10-03 Updated 2026-10-14
For a photon, and the null displacement along the ray is parallel to . Consequently , and the first term of the momentum law vanishes. Write with an appropriate path parameter. ThenFor a static potential, a photon emitted and received by laboratories at rest in the background frame has energy proportional to . Using , the scalar-force gravitational redshift isRestoring , the leading fractional shift is , where is the dimensional Newtonian gravitational potential. Near Earth's surface, an upward displacement has , hence : the receiver sees a redshift.
Thus yes: the predicted weak-field frequency shift agrees with the Pound-Rebka experiment. The calculation concerns stationary emitter and receiver, with identical local transition-energy standards; it does not add a Doppler shift due to their relative motion. Agreement with this gravitational redshift measurement alone does not establish the tensor theory of general relativity.