Abstract
Dark energy, or the cosmological constant Lambda, was introduced by Einstein in 1917, to describe a model of a static Universe. Wolfgang Pauli soon tried to interpret it as the energy of the quantum vacuum, extrapolated to the Universe, but found that the orders of magnitude were far from adequate. Later, the missing mass discovered in clusters by F. Zwicky and in galaxies by V. Rubin gave rise to exotic dark matter in 1984. Numerous experiments have been attempting to detect it directly or indirectly for forty years. Dark energy was rediscovered in 1998 through the acceleration of expansion. The nature of the dark sector will be explored.
