- a hypothetical form of energy whose negative pressure counteracts gravity and is assumed to be responsible for the universe expanding at an accelerating rate.
- 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. See also big bang.