Einstein's Equivalence Principle and its relation to understanding gravitation

Dawson Huth

Einstein’s Equivalence Principle is a fundamental postulate of General Relativity and as such must be tested to high precision for our current understanding of gravitation to remain valid. Many attempts at unifying relativistic gravitation with the Standard Model of particle physics predict a violation of the equivalence principle. An upper bound has been placed on any violation due to forces exerted by Galactic dark matter to one part in 105, a significant improvement upon earlier bounds. Similarly, a violation due to the gravitational field of the Sun has been constrained to a few parts in 1013.