Geodesic motion in General Relativity: LARES in Earth's gravity

TL;DR

This paper discusses how the LARES satellite, due to its high density, serves as an almost perfect test particle for verifying predictions of General Relativity through geodesic motion measurements.

Contribution

It analyzes the correspondence between geodesic motion and extended body motion using the Ehlers-Geroch theorem, with a focus on the LARES satellite as a test of General Relativity.

Findings

LARES approximates a test particle in Earth's gravity.

Satellite measurements can test relativistic predictions.

High-density orbiting body enhances experimental accuracy.

Abstract

According to General Relativity, as distinct from Newtonian gravity, motion under gravity is treated by a theory that deals, initially, only with test particles. At the same time, satellite measurements deal with extended bodies. We discuss the correspondence between geodesic motion in General Relativity and the motion of an extended body by means of the Ehlers-Geroch theorem, and in the context of the recently launched LAser RElativity Satellite (LARES). Being possibly the highest mean density orbiting body in the Solar system, this satellite provides the best realization of a test particle ever reached experimentally and provides a unique possibility for testing the predictions of General Relativity.