Someone offers the following account of the Pound and Rebka measurement (1960): 'The…
PHYSICS · Subjective · Fermi University Physics · Relativity & Gravitation · The equivalence principle and gravity as geometry · The equivalence principle and gravity as geometry
The Geometry of Gravity, Ch Redshift, local inertial frames and the failure of flat spacetime
Problem
Someone offers the following account of the Pound and Rebka measurement (1960): 'The 22.5 m tower and its clocks are just standing still on the ground: no force is needed to keep a clock at rest, so they are inertial observers in flat spacetime. As the emitted gamma ray climbs the tower it does work against Earth's gravity and loses energy ΔE=mg⊕ℓ with the photon's effective mass m=hν/c2; this gives Δν/ν=−g⊕ℓ/c2, which is the measured shift. Because the whole account uses only ordinary energy conservation for a photon moving through flat spacetime, with the towers themselves undisturbed inertial observers, the Pound-Rebka result requires no revision of special relativity.' Find the error in this argument, and state what is actually true of the tower's clocks.