Intra-terrestrial verification of the gravitational shift

Abstract

Einstein predicted a change in the energy of photons in the proximity of a gravitational field, the change being directly proportional to the distance from the gravitational source. In the early 1960s, Pound and Rebka (Phys. Rev. Lett. 3, 439 (1959)) set out to verify Einstein's prediction. The experiment was reprised with even higher precision by Pound and Snider (Phys. Rev. Lett. 13, 539 (1964)). Later, Vessot (Phys. Rev. Lett. 45, 2081 (1980)) reprised the experiment in space at a much improved precision. In this paper, we will present an approach to the experiment that goes exactly in the opposite direction by descending towards the center of the Earth. Our new approach is less expensive, introduces stronger effects, and showcases an unprecedented second-order effect. PACS No.: 03.30.+p