Answer: True
Explanation: Dark energy is the name given to the mysterious force that is accelerating the rate at which our universe is expanding. ... Some repulsive force is pulling the universe apart and this force was dubbed “dark energy”. Riess and Livio describe the three main hypotheses to explain the nature of dark energy. The leading theory to explain the accelerating expansion is the existence of a hypothetical repulsive force called dark energy. ... "Usually this repulsion is ascribed to a mysterious dark energy that would uniformly permeate the cosmos, but nobody knows what it is nor why it behaves this way," Villata said in an email. Dark energy is believed to be responsible for the expansion of the universe, counteracting gravity, and is considered to be the fifth force acting on matter, after gravity, the electromagnetic force, and the strong and weak nuclear forces.