Evidence for the Earth gravitational shift by direct atomic-time-scale comparison

Abstract

On the basis of the height difference between the CNR cosmic-ray laboratory at Plateau Rosa, 3500 m, and Turin, 250 m above s.l., a direct measurement of the terrestrial gravitational shift has been made by the comparison of the time scales of two cesium beam atomic frequency standards of the Istituto Elettrotecnico Nazionale «Galileo Ferraris». The principle of equivalence predicts the effect Δt/t=-ΔU/c2 =3.54·10-13, corresponding to the gain of the standard at mountain altitudes Δt/t=30.6 ns/d. The results Δt/t=(33.8±6.8) ns/d and Δt/t=(36.5±5.8) ns/d, derived with two independent operating criteria, have been obtained from 1584 h of actual measurement, with reference to an atomic time scale whose linearity was continuously and carefully tested. The results are discussed in terms of the current gravitational theories and in view of future experimental researches, which will be permitted by the advancements of the metrology of time. © 1977 Società Italiana di Fisica.