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Definition of DARK ENERGY
: a hypothetical form of energy that produces a force that opposes gravity and is thought to be the cause of the accelerating expansion of the universe
First Known Use of DARK ENERGY
The dominant component (about 70 percent) of the universe. Its nature is not well understood, but it differs from matter in being gravitationally repulsive. Dark energy is detected by its effect on the rate at which the universe expands. Many explanations have been proposed for dark energy; the simplest is that it is an energy density inherent to empty space.