Ground measurements of the gravitational redshift questioned:re-establishing the physical bases

TL;DR

This paper critically reexamines the Pound-Rebka experiment, clarifying that it measured gravitational redshift as originally predicted, countering recent claims of a Doppler shift interpretation.

Contribution

The authors correct a misunderstanding about the Pound-Rebka experiment, reaffirming its measurement of gravitational redshift and clarifying the physical interpretation involved.

Findings

The Pound-Rebka experiment measured gravitational redshift as predicted by Einstein.

Misinterpretations of reference frames led to incorrect conclusions about the experiment.

The original experiment's results are validated as a measurement of gravitational redshift.

Abstract

Motivated by alleged inconsistencies in the scientific and educational literature, Asenbaum, Overstreet and Kasevic \href{https://doi.org/10.1088/1402-4896/ad340c}{(2024)} aim to clarify some fundamental concepts in the physics of gravitation. To this end they reexamine the first experimental measurement of the gravitational redshift by Pound and Rebka in 1960, claiming that it did not in fact measure the gravitational redshift predicted by Einstein almost half a century earlier, but rather a Doppler shift originating from non-gravitational reaction forces. We show that their conclusion arises from a misunderstanding of the reference systems involved, along with an unphysical interpretation of non gravitational forces. Thus, our work restores the Pound and Rebka experiment to its rightful place in Physics.