Gravitation and Experiment

The confrontation between Einstein’s gravitation theory and experimental results, notably binary pulsar data, is summarized and its significance discussed. Experiment and theory agree at the 10 level. All the basic structures of Einstein’s theory (coupling of gravity to matter; propagation and self-interaction of the gravitational field, including in strong-field conditions) have been verified. However, some recent theoretical findings (cosmological relaxation toward zero scalar couplings) suggest that the present agreement between Einstein’s theory and experiment might be naturally compatible with the existence of a long-range scalar contribution to gravity (such as the dilaton, or a moduli field of string theory). This provides a new theoretical paradigm, and new motivations for improving the experimental tests Talk given at Princeton’s 250th Anniversary Conference on Critical Problems in Physics (Princeton, October 31 – November 2, 1996); to appear in the Proceedings to be published by Princeton University Press.