Explanation of the EPF experiment in terms of gravity gradients

TL;DR

This paper explains the EPF experiment results as a classical systematic effect caused by ambient gravity gradients, rather than a new force, highlighting the importance of considering environmental factors in precision gravity tests.

Contribution

The paper provides a novel classical explanation for the EPF results based on gravity gradients, challenging previous interpretations of the data.

Findings

Gravity gradients caused false signals in the EPF experiment.

Time variation of gravity gradients contributed to the results.

Different sample shapes affected gravitational force measurements.

Abstract

Results of the E\"otv\"os Pek\'ar and Fekete (EPF) equivalence test were used by Fischbach and coworkers in 1986 as an argument in favor of a hypothetical fifth force. Although this hypothesis was abandoned in view of the negative experimental results that followed, we still miss plausible explanation of the EPF results. This situation motivated us to investigate the EPF test in terms of gravity gradients. This paper presents arguments that the results can be explained as a classical systematic effect related to the ambient gravity field. We found that gradients of the ambient gravity field caused a false equivalence violation signal. Firstly, this was due to the time variation of gravity gradients, in spite of the fact that the experimenters were aware of it and designed a method to cancel it. Second, the EPF samples had different shapes and therefore the gravitational force was necessarily different in a constant, but inhomogeneous gravity field. We demonstrate that there is an ambient gravity field where these effects can fully reproduce the EPF results.