A historical review of how the cosmological constant has fared in general relativity and cosmology

This paper reviews the ups and downs of the cosmological constant since its introduction into general relativity theory by Einstein in 1917. Although it has never really been loved, and is a major headache to particle physicists, it keeps on coming back in various guises or with minor modifications. At present it plays a manor role in cosmology both in terms of the ‘false vacuum’ of inflationary theory in the very early universe, and as a large-scale repulsive force in the late universe, as evidenced by observations of distant supernovae. Its origin in terms of fundamental physics remains as obscure as ever.