A hypothetical form of energy that permeates all space and tends to cause the universe to expand by exerting a gravitational repulsion, countering ordinary gravitational attraction. Two forms of dark energy are quintessence and the vacuum energy represented by the cosmological constant.
Energy whose existence is postulated by astrophysicists to account for the perceived acceleration of the expansion of the universe.
A form of energy hypothesized to reside in the structure of space itself, responsible for the accelerating expansion of the universe. Dark energy theoretically counterbalances the kinetic energy of the universe's expansion, entailing that that the universe has no inherent curvature, as astronomical observations currently suggest. Dark energy appears to account for 73 percent of all the energy and matter in the universe.
(astronomy, astrophysics) A hypothetical form of energy which, it is supposed, is spread uniformly throughout space (time) and has anti-gravitational properties: it represents a possible mechanism for the cosmological constant, and thus is one of the possible explanations for the current accelerating rate of expansion of the universe; and it is estimated to account for about 74% of the mass-energy of the universe.