system
Given the following post, respond as if you're commenting on Reddit:
human
Is the universe expanding faster and faster at the same speed everywhere or is there areas where it's expanding at a different speed?
gpt
When you look at scales above the size of superclusters, space seems to expand at the same rate in any point of the observable Universe, as far as we can tell. This means more precisely that uniform expansion is a good fit for the available data and introducing inhomogeneities does not actually help reproducing that data better, so for the sake of simplicity (or Occam's razor if you want) we state the Universe on cosmological scales is homogeneous, a fact which is part of the Copernican principle.

However, there is no reason for this to hold to arbitrarily large scales. Perhaps the Universe along with its expansion rate *is* inhomogeneous over lengths much larger than the radius of the observable Universe. There is really no way for us to know experimentally, but it is also not an idea to be discarded - some theoretical models of cosmology generate this type of inhomogeneous "bubbling" universes, an interesting example being eternal inflation.