GRAVITY, GAUGES AND CLOCKS

We discuss the definitions of standard clocks in theories of gravitati on. These definitions are motivated by the invariance of actions under different gauge symmetries. We contrast the definition of a standard Weyl clock with that of a clock in general relativity and argue that t he historical criticisms of theories based on non-metric compatible co nnections by Einstein, Pauli and others must be considered in the cont ext of Weyl's original gauge symmetry. We argue that standard Einstein ian clocks can be defined in non-Riemannian theories of gravitation by adopting the Weyl group as a local gauge symmetry that preserves the metric and discuss the hypothesis that atomic clocks may be adopted to measure proper time in the presence of non-Riemannian gravitational f ields. These ideas are illustrated in terms of a recently developed mo del of gravitation based on a non-Riemannian spacetime geometry.