Willem de Sitter

Willem de Sitter was a Dutch mathematician, physicist and astronomer, born in Sneek in 1872, known for the de Sitter universe, a cosmological model named after him. He studied mathematics at the University of Groningen, joined the Groningen astronomical laboratory, worked at the Cape Observatory in South Africa from 1897 to 1899 and in 1908 was appointed to the chair of astronomy at Leiden University, where he was director of the observatory from 1919 until his death. In 1916 and 1917 he published papers describing the consequences of Einstein's theory of relativity for astronomy, which inspired Arthur Eddington's 1919 eclipse expedition, and in 1932 he co-authored a paper with Einstein. He also researched the motions of the moons of Jupiter and in 1931 received both the Bruce Medal and the Gold Medal of the Royal Astronomical Society.