How does the geometry of a gravity-dominated universe relate to its density?

Question

Quizplus · Accepted Answer

The geometry of a gravity-dominated universe is determined by its density. A flat universe means that the density is equal to the critical density, which is the density required for the universe to be flat. If the universe is closed or open, then its density is either greater than or less than the critical density, respectively. But a gravity-dominated universe cannot be open because it would not have enough gravity to prevent expansion, and its geometry would be hyperbolic rather than Euclidean.

How Does the Geometry of a Gravity-Dominated Universe Relate to Its