OPERATIONAL FORMULATION OF PRINCIPLE OF EQUIVALENCE

A formulation of the principle of equivalence is given that avoids some of the difficulties in the more usual statements of the principle. In particular, we give an operational definition of local systems for which the principle is applicable. The relation between our statement and other statements of the principle is discussed. To investigate the relation of our statement to general relativity, we construct model reference frames from physical systems whose dynamics is sufficiently simple that their behavior can be described within the framework of the general theory without the need to introduce extraneous assumptions. With the help of these reference frames, we then show that it is possible to formulate gedankenexperiments yielding results that satisfy our statement of the principle. © 1969 The American Physical Society.