Willem de Sitter

Willem de Sitter (6May 187220November 1934) was a Dutch mathematician, physicist, and astronomer. He is known for the de Sitter universe, which is a cosmological model that was named after him.

Life and work

Born in Sneek, Netherlands, de Sitter studied mathematics at the University of Groningen and then joined the Groningen astronomical laboratory. He worked at the Cape Observatory in South Africa (1897–1899). Then, in 1908, De Sitter was appointed to the chair of astronomy at Leiden University. He was director of the Leiden Observatory from 1919 until his death.

De Sitter made major contributions to the field of physical cosmology. In 1916-17, he published a series of papers describing the consequences of Albert Einstein's theory of relativity to the understanding of astronomy, which directly inspired Arthur Eddington's 1919 expedition to make measurements of a solar eclipse. He co-authored a paper with Einstein in 1932, with whom he had a lengthy correspondence, in which they discussed the implications of cosmological data for the curvature of the universe, comparing "space to a cloth". He also came up with the concept of the De Sitter space and De Sitter universe, a solution for Einstein's general relativity in which there is no matter and a positive cosmological constant. This results in an exponentially expanding, empty universe. De Sitter was also well-known for his research on the motions of the moons of Jupiter, and was invited to give the George Darwin Lecture at the Royal Astronomical Society in 1931. His research helped to launch inquiries into relativistic cosmology.

Willem de Sitter died after a brief illness in November 1934.

Honours In 1912, he became a member of the Royal Netherlands Academy of Arts and Sciences.

Awards James Craig Watson Medal (1929) Bruce Medal (1931) Gold Medal of the Royal Astronomical Society (1931) Prix Jules Janssen, the highest award of the Société astronomique de France, the French astronomical society (1934)

Named after him The crater De Sitter on the Moon Asteroid 1686 De Sitter De Sitter universe De Sitter space Anti-de Sitter space De Sitter invariant special relativity Einstein–de Sitter universe De Sitter double star experiment De Sitter precession De Sitter–Schwarzschild metric

Family One of his sons, Ulbo de Sitter (1902 – 1980), was a Dutch geologist, and one of Ulbo's sons was a Dutch sociologist Ulbo de Sitter (1930 – 2010).

Another son of Willem, Aernout de Sitter (1905 – 15 September 1944 ), was the director of the Bosscha Observatory in Lembang, Indonesia (then the Dutch East Indies), where he studied the Messier 4 globular cluster.

Selected publications

On Einstein's theory of gravitation and its astronomical consequences: