The universe is full of matter and the attractive force of gravity pulls all matter together.
a long time ago, the universe was actually expanding more slowly than it is today
So the expansion of the universe has not been slowing due to gravity, as everyone thought, it has been accelerating
Dark Matter is a form of matter thought to account for approximately 85% of the matter in the universe and about a quarter of its total energy density.
Dark Energy is an unknown form of energy which is hypothesized to permeate all of space, tending to accelerate the expansion of the universe
It turns out that roughly 68% of the universe is dark energy.
