We know how much dark energy there is because we know how it affects the universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27%. read more
Dark matter around,on surface, and inside the earth would not amount to a quantum greater than what would fill a bottle of coke. Yet every trillionth of a second, trillions of dark matter particle zoom through all life and all matter on earth at the speed of light without any obstruction from any particle. read more
Dark Energy, Dark Matter In the early 1990s, one thing was fairly certain about the expansion of the universe. It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time went on. read more