Time in quantum cosmology loses its meaning as a fundamental organizing principle.[12] Instead, a sensible notion of time emerges only as an intrinsic quality within each individual expanding space. The reason is that a measure of time always involves a change of one physical property relative to another. As a clock within our own universe, for example, we could use the monotonic cooling of the cosmic background radiation with expansion (although this wouldn’t be a practical unit of time to schedule your meetings). But the evolution of the temperature of the CMB in one spacetime is obviously
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