In physics cosmology and astronomy, dark energy is an unknown form of energy which is hypothesized to permeate all of space, tending to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate. Assuming that the standard model of cosmology is correct, the best current measurements indicate that dark energy contributes 68% of the total energy in the present-day observable universe. The mass<unk>energy of ordinary dark matter and (baryonic matter) contribute 27% and 5%, respectively, and other components such as neutrinos and photons contribute a small amount. The density of dark energy is very low (~7 × 10−30 g/cm3) less than the density of ordinary matter or galaxies within the universe. The density of dark energy is very low (~7 × 10−30 g/cm3) than the density of ordinary matter or galaxies within the universe. The density of dark energy is very low (~7 × 10−30 g/cm3) than the density of ordinary
zviyero