Dark Energy

Form of energy that is gravitationally repulsive, due to a negative effective pressure. Dark energy is spread almost uniformly throughout space and appears to contribute about 70% of the present energy density of the universe. Its existence was recently inferred from observations of distant Type Ia supernovae from combining CMBR anisotropy measurements with measurements of the density of dark matter. The cosmological constant is a particular form of dark energy.

Some or all content above used with permission from J. H. Wittke.