How does the observed density of luminous matter (stars and galaxies) in the Universe compare with the critical density?
A) The density of luminous matter is far smaller than the critical density.
B) Amazingly, the density of stars and galaxies exactly equals the critical density.
C) The density of stars and galaxies is vastly bigger than the critical density.

Question

Quizplus · Accepted Answer

The observed density of luminous matter, such as stars and galaxies, is far smaller than the critical density needed to halt the expansion of the Universe. Most of the Universe's mass-energy content is in the form of dark matter and dark energy, not luminous matter.

How Does the Observed Density of Luminous Matter (Stars and Galaxies)