| Share
 

Willem de Sitter

Sitter, Willem de (vĭlˈəm də sĭtˈər) [key], 1872–1934, Dutch astronomer and mathematician. He was professor from 1908 at the Univ. of Leiden and in 1919 became director of its observatory. His early work on the motions of Jupiter and its satellites contributed to the downfall of the pre-Einstein celestial mechanics. Using Einstein's formulation of relativity, he theorized that space cannot be in a stable equilibrium, and he concluded that the universe is expanding. He suggested a dynamic universe in which there is motion but no matter, in contrast to Einstein's static universe containing matter but no motion. In the combined Einstein–de Sitter model, the universe is expanding at a decreasing rate that approaches zero. De Sitter's works in English include Kosmos (1932) and The Astronomical Aspect of the Theory of Relativity (1933).

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

More on Willem de Sitter from Infoplease:

See more Encyclopedia articles on: Astronomy: Biographies


Premium Partner Content
HighBeam Research
Documents Images and Maps Reference
(from Newspapers, Magazines, Journals, Newswires, Transcripts and Books)

Research our extensive archive of more than 80 million articles from 6,500 publications.

Additional search results provided by HighBeam Research, LLC. © Copyright 2005. All rights reserved.

24 X 7

Private Tutor

Click Here for Details
24 x 7 Tutor Availability
Unlimited Online Tutoring
1-on-1 Tutoring