What element does the Perfect Cosmological Principle add to the standard CP?
Answer
Temporal homogeneity
The Perfect Cosmological Principle (PCP) is an extension of the standard Cosmological Principle (CP). While the CP concerns spatial uniformity (homogeneity and isotropy across space at a given time), the PCP adds the dimension of time. It posits that the universe looks the same not only everywhere in space but also at every moment in time; it asserts temporal homogeneity. This concept was foundational to the discredited Steady State Theory. Strong observational evidence, such as the observation that distant quasars are more numerous than nearby ones, demonstrates that the universe evolves and changes over time, definitively proving the PCP is false, even though the CP holds true for any single cosmological epoch.
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