Principles of Equivalence: Their Role in Gravitation Physics and Experiments that Test Them

Modern formulations of equivalence principles provide the foundation for an efficient approach to understanding and organizing the structural features of gravitation field theories. Since theories' predictions reflect differences in their structures, principles of equivalence also support an efficient experimental strategy for testing gravitation theories and for exploring the range of conceivable gravitation physics. These principles focus attention squarely on empirical consequences of the fundamental structural differences that distinguish one gravitation theory from another. Interestingly, the variety of such consequences makes it possible to design and perform experiments that test equivalence principles stringently but do so in markedly different ways than the most familiar experimental tests.