BIO

Dissertation: N/A

Highest degree: N/A

Fields of interest:

• astronomy

Biography:
After grammar school in Arnhem, Willem de Sitter went to Groningen to study mathematics However he did some experimental work for his physics curricula at the astronomical laboratory of the famous astronomer Jacobus C. Kapteyn. The latter was involved in measuring photographic plates from the Cape Observatory in South Africa, in collaboration with Sir David Gill to chart the southern skies. During a visit to Groningen Gill invited de Sitter to Cape Town, de Sitter accepted the invitation and decided to become an astronomer. He left in August of 1897 and among others worked on measurements of the four Galilean satellites of the planet Jupiter.
Towards the end of 1899 de Sitter returned to Groningen and obtained his Ph.D. degree there in 1901. The title was Discussion of Heliometer Observations of Jupiter's Satellites. In South Africa he also had met his wife Elanora Suermondt. The thesis, and in particular later work resulted in better orbits for these satellites, where also the mutual gravitational influences on each other s orbits were corrected on. This entailed new mathematical tools and approaches.
In 1908 de Sitter was appointed in Leiden as professor in theoretic astronomy and in 1918 he was appointed as director. Together with Kapteyn he reorganised the Observatory, where previously the work concentrated on fundamental observations of positions and motions of stars on the sky, the new observatory also concentrated from then on on astrophysics and theory. In spite of administrative duties, de Sitter still found time for studies on various aspects of astronomy and astrophysics. In particular his work on the General Theory of Relativity that Einstein had formulated, is universally known. He showed that the field equations that Einstein had formulated then very recently before also allowed a solution for the structure and evolution of the universe where it was expanding, contracting or oscillating. The first is now known to be the case. The most simple solution of the field equations for the expanding universe is called the Einstein-de Sitter Universe.
In 1919 de Sitter was operated for gallstones. However, the overdose of ether he was given resulted in a continuing poor health. Among others he suffered from tuberculosis, which made it necessary to spend two years in Arosa in Switzerland. He still succeeded in doing research and he arranged an agreement with the Union Observatory in Johannesburg, to jointly carry out observational studies. Also he took measures for two expeditions to Kenya to improve absolute positional measurements of stars on the sky. He received various important honors, among which the Gold Medal of the Royal Astronomical Society (1931) and the Bruce Medal of the Astronomical Society of the Pacific (1931). He was president of the International Astronomical Union from 1925 to 1928.

Residence

• Leiden 

Occupation

N/A

Education

N/A

Membership

• Koninklijke Nederlandsche Akademie van Wetenschappen
  Member Afd. Natuurkunde 15-05-1912
• International Astronomical Union
  President 1925 - 1928

Provenance

• Sitter, W. de, Proceedings 37, 1934, p. 734-737 door J. van der Hoeve.

Publications

• Outlines of a new theory of Jupiter's satellites Year: . Pages: 21. (PDF format)
  
• Outlines of a new theory of Jupiter's satellites. (continued) Year: . Pages: 10. (PDF format)
  
• On the orbital planes of Jupiter's satellites, as derived from measurements made at Berlin Year: . Pages: 7. (PDF format)
  
• Planetary motion and the motion of the moon according to Einstein's theory Year: . Pages: 16. (PDF format)
  
• Theory of Jupiter''s satellites. I. The intermediary orbit Year: . Pages: 9. (PDF format)
  
• On the relativity of rotation in Einstein's theory Year: . Pages: 7. (PDF format)
  
• On the figure of the planet Jupiter Year: . Pages: 5. (PDF format)
  
• On Absorption of Gravitation and the moon's longitude. Part I Year: . Pages: 18. (PDF format)
  
• On the orbital planes of Jupiter's satellites Year: . Pages: 15. (PDF format)
  
• Theory of Jupiter's satellites. II. The variations Year: . Pages: 7. (PDF format)
  

Wiki and VIAF

Wiki Data: Q313059
VIAF: http://viaf.org/viaf/190428276

View obituary (PDF format)

BIO

Dissertation: N/A

Highest degree: mr.

Fields of interest:

• law
• politics
• freemasonry
• literature

Biography:
N/A

Residence

N/A

Occupation

• member 1835 - 1850 - Tweede Kamer der Staten-Generaal
• lawyer 
• banker 

Education

• law student  - 1815, Leiden

Membership

• Gezelschap ter Beoeffening der proefondervindelijke Wijsbegeerte in ’s Hage
  member (literature department), member of the board and secretary (1819) 1815 - 1824~
• Genootschap ‘Pro Excolendo Jure Patrio’ - Groningen
  member 
• Provinciaal Utrechtsch Genootschap van Kunsten en Wetenschappen
  member 
• Orde van Vrijmetselaren
  member and director 
• Union Royale
  director 
• Maatschappij ter bevordering van de Landbouw
  founding member and director 1847
• Genootschap voor tuin- en landbouw ‘Dordrechtsche Flora’ - Dordrecht
  honorary member 

Provenance

• Naamlijst der leden van de Maatschappij voor natuur- en letterkunde (Den Haag 1824).
• Molhuysen, P.C., P.J. Blok en L. Knappert (redactie), Nieuw Nederlandsch Biografisch Woordenboek. Deel 5. (Leiden 1921) 340.
• http://natuurwetenschappen-diligentia.nl/geschiedenis-3/bestuurslijst/

Publications

N/A

Wiki and VIAF

Wiki Data: N/A
VIAF: N/A