Test of the Equivalence Principle Using a Rotating Torsion Balance

TL;DR

This study used a rotating torsion balance to test the equivalence principle, significantly improving limits on violations across various distances and confirming equal acceleration of different materials towards galactic dark matter.

Contribution

It introduces a highly sensitive rotating torsion balance method to test the equivalence principle, setting new stringent limits on violations over a wide range of distances.

Findings

Improved limits on equivalence-principle violations by an order of magnitude.

No detectable difference in acceleration between beryllium and titanium.

Equal attraction towards galactic dark matter within experimental uncertainty.

Abstract

We used a continuously rotating torsion balance instrument to measure the acceleration difference of beryllium and titanium test bodies towards sources at a variety of distances. Our result Delta a=(0.6+/-3.1)x10^-15 m/s^2 improves limits on equivalence-principle violations with ranges from 1 m to infinity by an order of magnitude. The Eoetvoes parameter is eta=(0.3+/-1.8)x10^-13. By analyzing our data for accelerations towards the center of the Milky Way we find equal attractions of Be and Ti towards galactic dark matter, yielding eta=(-4 +/- 7)x10^-5. Space-fixed differential accelerations in any direction are limited to less than 8.8x10^-15 m/s^2 with 95% confidence.