[Keysh]

> there could be empty regions of space in which billions of years more have elapsed than in e.g. a galaxy.

A problem with that idea would be that the ages of galaxies in low-density regions (including voids) tend to be younger than galaxies in denser regions, suggesting that galaxy evolution proceeds more slowly in voids.

https://www.iaa.csic.es/en/news/galaxies-great-cosmic-voids-...