Do general relativistic effects limit experiments to test the universality of free fall and the weak equivalence principle?

TL;DR

This paper analyzes the impact of general relativistic effects on high-precision space tests of the universality of free fall and finds these effects are negligible, ensuring they do not limit such experiments.

Contribution

The study demonstrates that relativistic effects, including rotational influences, are too small to affect upcoming high-precision free fall experiments.

Findings

Relativistic effects are negligible at current experimental sensitivities.

Rotational effects do not pose a significant challenge to test precision.

High-precision experiments remain feasible without relativistic corrections.

Abstract

The Universality of Free Fall and the Weak Equivalence Principle, which are at the basis of General Relativity, have been confirmed to 1 part in 10^13. Space experiments with macroscopic test masses of different composition orbiting the Earth inside a low altitude satellite aim at improving this precision by two orders of magnitude (with the Microscope satellite, launched on 25 April 2016) and up to four orders of magnitude (with the 'Galileo Galilei' - GG satellite). At such a high precision many tiny effects must be taken into account in order to be ruled out as the source of a spurious violation signal. In this work we investigate the general relativistic effects, including those which involve the rotation of both the source body and the test masses, and show that they are by far too small to be considered even in the most challenging experiment. (Paper to appear on Physical Review D)