cosmic time

Measure for the progress of the evolution of an expanding universe such as that of the big bang models. It corresponds to time as measured by clocks that are at rest relative to the expanding space, and that have been set to zero at the very beginning, the time of the hypothetical big bang singularity. Synonym: Age of the universe.

The basic features of the cosmological models that use cosmic time are reviewed in the chapter Cosmology of Elementary Einstein.