Question

Based on inventoried matter in the universe, including dark matter known to exist in galaxies and clusters, the actual density of the universe is what fraction of the critical density?

A) 1 percent
B) 10 percent
C) 26 percent
D) 74 percent
E) 100 percent

Answer 1

The actual density of the universe is approximately 100 percent of the critical density, taking into account ordinary matter, dark matter, and dark energy.

Step-by-step explanation:

Based on the composition of the universe, including dark matter and dark energy, the actual density of the universe is approximately 100 percent (Option E) of the critical density.

This is derived from contributions of approximately 5% from ordinary matter (including luminous matter in stars and galaxies, hydrogen, helium, neutrinos), about 27% from dark matter, and the remaining 68% from dark energy.

The interplay of these components suggests that we live in a critical-density universe, where the sum total of matter and energy meets the requirement for a flat universe.