The Bruce Medalists


  portrait Photo courtesy Yerkes Observatory, University of Chicago
Willem de Sitter
6 May 1872 1931 Bruce Medalist 20 November 1934

Willem de Sitter studied mathematics at the University of Groningen, where a chance meeting with David Gill led to an invitation to work at Her Majesty’s Observatory at the Cape of Good Hope. After four years of heliometer measurements of stars and especially Jupiter’s Galilean satellites, de Sitter returned to the Netherlands and became a mathematical astronomer, earning his doctorate under J.C. Kapteyn with a thesis on the satellites’ motions. He spent most of his career at the University of Leiden, where he directed and expanded the astronomy program. He continued to work extensively on the motions of the satellites of Jupiter, determining their masses and orbits from decades of observations. He redetermined the fundamental constants of astronomy and determined the variation of the rotation of the earth. He also performed statistical studies of the distribution and motions of stars, but today he is best known for his contributions to cosmology. Since Holland remained neutral in World War I, de Sitter was able to be the liaison between scientists in warring countries, notably A.S Eddington in Britain and Albert Einstein in Germany. De Sitter’s 1917 solution to Einstein’s field equations showed that a near-empty universe would expand. Later, he and Einstein found an expanding universe solution without space curvature.

Presentation of Bruce medal
Meyer, W.F., PASP 43, 125-129 (1931).

Other awards
National Academy of Sciences, James Craig Watson Medal, 1929.
Royal Astronomical Society, Gold medal, 1931, awarded by A.C.D. Crommelin, MNRAS 91, 422-34 (1931).

Some offices held
International Astronomical Union, President, 1925-28.

Biographical materials
Blaauw, A., Dictionary of Scientific Biography 12, 448-50.
Blaauw, A., Biographical Encyclopedia of Astronomers (Springer, NY, 2007), pp. 1063-64.
Club Astronomique du Val de Loir [in French].
De Sitter-Suermondt, Eleonora [wife], Willem de Sitter, een Mensenleven (Tjeenk Willink & Zoon, Haarlem, 1948) [in Dutch].
Díaz Pazos, Patricio T., AstroCosmo [in Spanish].
McCrea, W.H., J. Brit. Astr. Ass. 82, 178-181 (1972).
Tenn, Joseph S., “Willem de Sitter: The Twenty-Sixth Bruce Medalist,” Mercury 23, 5, 28 (1994).
O’Connor, J.J. & E.F. Robertson, University of St. Andrews, The MacTutor History of Mathematics archive.
v[an] H[elden], A[lbert], in K.v. Berkel, A.v. Helden, & L. Palm, eds., A History of Science in The Netherlands (Brill, Leiden, 1999), pp. 558-60.

Chant, C.A., JRASC 29, 1 (1935).
Hins, C.H., Hemel en Dampkring 33, 1-18 (1935) [in Dutch].
Oort, J.H., Observatory 58, 22-27 (1935).
S[pencer] J[ones], H[arold], MNRAS 95, 343-347 (1935).
New York Times editorial, 25 Nov 1934 [reprinted in PASP 47, 65-66 (1935)]
More obituaries

AIP Center for History of Physics
AstroCosmo (sketch)
AIP, with Einstein, Ehrenfest, Eddington, and Lorentz
Johan Hidding, University of Groningen
Instituut voor Nederlandse Geschiedenis (with biography in Dutch)
Yale University, with Frank Schlesinger

Named after him
Lunar crater De Sitter
Minor Planet #1686 De Sitter
de Sitter space

More references

The Bruce Medalists

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