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Encyclopedia > Willem de Sitter

Willem de Sitter (May 6, 1872November 20, 1934) was a mathematician, physicist and astronomer. He was born in the city of Sneek in the Netherlands.

Willem de Sitter studied mathematics at Groningen University 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. From 1919 he was director of the Leiden Observatory.

De Sitter contributed to our concept of the universe. One of his accomplishments was to have co-authored a paper with Albert Einstein in 1932 in which they argued that there might be large amounts of matter which does not emit light, now commonly referred to as dark matter.

He won the James Craig Watson Medal in 1929 and the Bruce Medal in 1931, as well as the Gold Medal of the Royal Astronomical Society in that same year.

A crater on the Moon is named for him, as is the asteroid 1686 De Sitter.

See Also

External links


  • AN 253 (1934) 495/496 (http://adsabs.harvard.edu//full/seri/AN.../0253//0000265.000.html) (one line)
  • JRASC 29 (1935) 1 (http://adsabs.harvard.edu//full/seri/JRASC/0029//0000001.000.html)
  • MNRAS 95 (1935) 343 (http://adsabs.harvard.edu//full/seri/MNRAS/0095//0000343.000.html)
  • Obs 58 (1935) 22 (http://adsabs.harvard.edu//full/seri/Obs../0058//0000022.000.html)
  • PASP 46 (1934) 368 (http://adsabs.harvard.edu//full/seri/PASP./0046//0000368.000.html) (one paragraph)
  • PASP 47 (1935) 65 (http://adsabs.harvard.edu//full/seri/PASP./0047//0000065.000.html)

  Results from FactBites:
Sitter, Willem de (172 words)
Sitter wasn't in agreement with Einstein's idea of the Universe; the light curves because of the gravity, so any ray of light would be more and more curved till it reach it departure point again, the universe consists then in a curved space.
Sitter thought that the general theory of relativity could be interpreted for showing that the curvature is lower and that the universe always is expanding.
Sitter calculated that the universe has got a radio of 2 billion of light years and that has got eighty billion of galaxies, but this estimation of the size of the universe is too conservative.
Sitter biography (497 words)
De Sitter corresponded with Ehrenfest in 1916, and he proposed that a four- dimensional space- time would fit in with cosmological models based on general relativity.
De Sitter's work led directly to Eddington's 1919 expedition to measure the gravitational deflection of light rays passing near the Sun, results which, at that time, could only be obtained during an eclipse.
De Sitter, unlike Einstein, maintained that relativity actually implied that the universe was expanding, theoretical results which were later verified observationally and accepted by Einstein.
  More results at FactBites »



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