system
Given the following post, respond as if you're commenting on Reddit:
human
Instead of the universe expanding at an increasing rate which is accounted for with the term dark energy, could there be an outside force pulling the universe and as the galaxies get closer the pull gets stronger, causing them to speed up?
gpt
Yes. You can imagine that by chance we are just living in an underdense region, which would expand faster than the rest of the Universe.

The problem is that the expansion seems to be isotropic (=the same in all the directions). So it would mean we are almost at the center of this bubble. It's highly unlikely and cosmologists don't like to assume our position is special. But it's a possibility we should consider and try to rule out from the observations.