> doesn't that imply that all that matter affected its surroundings gravitationally? It did; it caused the expansion to decelerate. That was true until a few b

> doesn't that imply that all that matter affected its surroundings gravitationally? It did; it caused the expansion to decelerate. That was true until a few billion years ago, when the matter density became smaller than the dark energy density and dark energy started to dominate the dynamics.