Comment on “Measurement of the speed-of-light perturbation of free-fall absolute gravimeters”

Abstract

Abstract. The paper (Rothleitner et al. 2014 Metrologia 51, L9) reports on the measurement of the speed-of-light perturbation in absolute gravimeters. The conclusion that the perturbation reaches only 23 of the commonly accepted value violates the fundamental limitation on the maximum speed of information transfer. The conclusion was deluded by unaccounted parasitic perturbations, some of which are obvious from the report. 1. The “2 3 result ” and its interpretations The speed-of-light perturbation in absolute gravimeters is due to the fact that the laser beam reflected from the test mass delivers the information on its position with some delay. The light reflected at the moment t reaches the beam splitter at a later moment t′, so that t ′ = t+ z c, (1) where z is the distance traveled by the light, c is the speed of light (fig.1). Figure 1. The delay of the laser beam. The paper [1] reports on the experiment which agrees better with the formula t ′ = t+ 2