If the sum of the mass and energy density in the universe yields $\varOmega$

Question

If the sum of the mass and energy density in the universe yields $\varOmega$ < 1 then the universe will recollapse in a Big Crunch.

Quizplus · Accepted Answer

This statement is true. If the sum of the mass and energy density in the universe is less than the critical density needed for a flat universe, which is approximately 5.3 protons per cubic meter, then the universe will recollapse in a Big Crunch. A value of less than 1 indicates that the universe's mass and energy density are not enough to overcome the expansion of the universe and prevent a recollapse.

If the Sum of the Mass and Energy Density in the Universe