Originally Posted By: ImagingGeek
I don't think that works - if it were the case that bubble of denser material should be collapsing in, due to its own gravity. We would see that at blue-shifted light in the CMB. Instead we see red-shifted light.

Bryan

The idea is that our visible universe is a bubble of lower density, not higher density, hence it being evacuated into the surrounding invisible universe. It's rather like the formation of galaxy superclusters and the voids between them.

"Time is what prevents everything from happening at once" - John Wheeler