In Search of Cosmic Time: Complete Observables and the Clock Hypothesis

This article considers a new and deeply challenging aspect of the problem of time in the context of cosmology, drawing on the work of Thiemann. Thiemann argues for a radical response to the cosmic problem of time that requires us to modify the classical Friedmann equations. By contrast, we offer a conservative proposal for the solution of the problem, by bringing together ideas from the contemporary literature regarding reference frames, complete observables, and the model-based account of time measurement. On our approach, we must reinterpret our criteria of observability in light of the clock hypothesis and the model-based account of measurement in order to preserve the Friedmann equations as the dynamical equations for the universe.