Question

which would cause the universe to collapse in on itself to make a closed universe? force of gravity critical density momentum of outward expansion hubble constant

Explanation:

In cosmology, the force of gravity acts to pull matter together. If the force of gravity is strong enough (relative to the momentum of expansion), it can overcome the expansion of the universe and cause it to collapse, creating a closed universe. Critical density is a value used to compare with the actual density of the universe to determine its geometry (open, flat, or closed), but it is the force of gravity (related to the mass - energy content which affects density) that directly causes the collapse. The momentum of outward expansion acts against collapse, and the Hubble constant is related to the rate of expansion.

Answer:

force of gravity