The actual matter density of the universe, accounting for all of the luminous matter and all of the dark matter known to exist in galaxies and clusters, is what fraction of the critical density?

Question

Quizplus · Accepted Answer

The actual matter density of the universe, including both luminous and dark matter, is approximately 25 percent of the critical density. This means that matter alone is not enough to reach the critical density needed for a flat universe, and dark energy is believed to make up the rest.

The Actual Matter Density of the Universe, Accounting for All