COSMOLOGY SPACE AND TIME GRAVITATIONAL PHYSICS A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z           HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site dark energy Credit: NASA/WMAP Science Team A property of empty space, allowed by Einstein's general theory of relativity, that acts as a large, negative pressure and pushes the Universe apart at a faster and faster rate. Its existence has been hypothesized to explain observtions which indicate that the expansion of the Universe is accelerating. Current observations suggest that about 74% of the mass-energy of the Universe is in the form of dark energy. A further 22% consists of dark matter; the remaining 4% is ordinary matter. The exact nature of dark energy has yet to be established. However, dark energy is believed to be extremely homogeneous (evenly spread throughout space) and of very low density, roughly 10-29 grams per cubic centimeter. Various models of dark energy have been proposed, including a cosmic field associated with inflation; a different, low-energy field called quintessence; and the cosmological constant, or vacuum energy of empty space. Unlike Einstein's famous fudge factor, the cosmological constant in its present incarnation doesn't delicately (and artificially) balance gravity in order to maintain a static universe; instead, it has negative pressure that causes expansion to accelerate. Related categories    • COSMOLOGY    • SPACE AND TIME    • GRAVITATIONAL PHYSICS    • SCIENTIFIC MYSTERIES Archived news Dark energy makes galaxies keep their distance (Jan 31, 2008) Giant space-time ripples may cause cosmic expansion (Mar 20, 2005) Evidence of dark energy missed 30 years ago (Mar 12, 2005) Moon measurements might explain away dark energy (Feb 20, 2005) Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP