Underdense regions expand more rapidly than the Universe as a whole, whereas overdense regions expand more slowly.
I thought she had earlier said that the expansion was constant.
Does the density of the space affect its expansion, or does all the space expand but the more dense areas retain the shape of their matter because the gravitational forces are much stronger than the expansionary forces?
I have no idea if this "empty regions expand more" is one of the simplifications or not. Grr.
