Willem de Sitter

Biography

He studied mathematics and physics at the University of Groningen. He worked at the Leiden Observatory and became its director. He engaged in intensive correspondence with Einstein and other physicists, discussing the nature of space-time.

Key discoveries

• De Sitter universe — an exponentially expanding model with a cosmological constant. Prediction of the redshift of galaxies before its discovery. Studies of Jupiter's moons and fundamental astrometry.