The Critical Mass Density of the Universe Today Is 9

Essay

The critical mass density of the universe today is 9.5 *10 ^{- 27} kg/m³.Using (only) the currently observed amount of luminous matter, what would be the average mass density in the universe? If protons were spread evenly throughout the universe, what would be their typical separation? (Note that the typical separation between protons would be roughly equal to the cubic root of the average volume occupied by one proton, and the mass of a proton is 1.67 *10 ^{- 27} kg.)