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Is the early cosmos subject to gravitational time dilation?

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Since the early universe was much more dense and clumpy (evidence are the SMBHs detected by JWST at high redshift) than today, gravitational time dilation due to the stronger gravitational potential of matter should result. But why do cosmologists ignore these effects and agree on a linear cosmic time scale and a corresponding continuous cosmological redshift for describing the evolution of the universe?

asked Sep 7 in Astronomy by rhkail (0 points) [ no revision ]
recategorized Sep 8 by Dilaton

The relation between redshift and look-back time can be found for example in Bergström, Goobar "Cosmology and Particle Astrophysics". This look-back time is the difference in cosmological time between "now" and a given event in the past. The derivation in the book is based on the Robertson-Walker metric and thus presupposes a homogeneous and isotropic universe (i.e., no clumpiness (at least not on cosmological distances)).

As for clumpy matter: The effects of time dilation are most notable in the vicinity of the clump. Viewed at large scale, such a clump is a "particle" in an on average homogeneous universe.

commented Sep 9 by Flamma (110 points) [ no revision ]

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