astronomy

Willem de Sitter

Willem de Sitter is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Willem de Sitter rather than just read about it. In short: Willem de Sitter (6 May 1872 – 20 November 1934) was a Dutch mathematician, physicist, and astronomer. He is known for the de Sitter universe, which is a cosmological model that was named after him.

Key takeaways

Willem de Sitter belongs to astronomy; place it in that map before memorising details.
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Reproduce the core statement of Willem de Sitter from memory before moving on to harder problems.

Reference excerpt

Willem de Sitter (6 May 1872 – 20 November 1934) was a Dutch mathematician, physicist, and astronomer. He is known for the de Sitter universe, which is a cosmological model that was named after him.

Life and work

Born in Sneek, Netherlands, de Sitter studied mathematics at the University of Groningen 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. He was director of the Leiden Observatory from 1919 until his death. De Sitter made major contributions to the field of physical cosmology. In 1916-17, he published a series of papers describing the consequences of Albert Einstein's theory of relativity to the understanding of astronomy, which directly inspired Arthur Eddington's 1919 expedition to make measurements of a solar eclipse. He co-authored a paper with Einstein in 1932, with whom he had a lengthy correspondence, in which they discussed the implications of cosmological data for the curvature of the universe, comparing "space to a cloth". He also came up with the concept of the De Sitter space and De Sitter universe, a solution for Einstein's general relativity in which there is no matter and a positive cosmological constant. This results in an exponentially expanding, empty universe. De Sitter was also well-known for his research on the motions of the moons of Jupiter, and was invited to give the George Darwin Lecture at the Royal Astronomical Society in 1931. His research helped to launch inquiries into relativistic cosmology. Willem de Sitter died after a brief illness in November 1934.

Honours In 1912, he became a member of the Royal Netherlands Academy of Arts and Sciences.

Awards James Craig Watson Medal (1929) Bruce Medal (1931) Gold Medal of the Royal Astronomical Society (1931) Prix Jules Janssen, the highest award of the Société astronomique de France, the French astronomical society (1934)

Named after him The crater De Sitter on the Moon Asteroid 1686 De Sitter De Sitter universe De Sitter space Anti-de Sitter space De Sitter invariant special relativity Einstein–de Sitter universe De Sitter double star experiment De Sitter precession De Sitter–Schwarzschild metric

Family One of his sons, Ulbo de Sitter (1902 – 1980), was a Dutch geologist, and one of Ulbo's sons was a Dutch sociologist Ulbo de Sitter (1930 – 2010). Another son of Willem, Aernout de Sitter (1905 – 15 September 1944), was the director of the Bosscha Observatory in Lembang, Indonesia (then the Dutch East Indies), where he studied the Messier 4 globular cluster.

Selected publications De Sitter, W. (1911). "On the bearing of the Principle of Relativity on Gravitational Astronomy" . Monthly Notices of the Royal Astronomical Society. 71 (5): 388–415. doi:10.1093/mnras/71.5.388. hdl:2027/mdp.39015019246357. De Sitter, W. (1913). "A proof of the constancy of the velocity of light" . Proceedings of the Royal Netherlands Academy of Arts and Sciences. 15 (II): 1297–1298. Bibcode:1913KNAB...15.1297D. "Ein astronomischer Beweis für die Konstanz der Lichtgeschwindigkeit" [An astronomical proof of the constancy of the speed of light]. Physikalische Zeitschrift. 14: 429. 1913. De Sitter, W. (1913). "On the constancy of the velocity of light" . Proceedings of the Royal Netherlands Academy of Arts and Sciences. 16 (I): 395–396. Bibcode:1913KNAB...16..395D. De Sitter, W. (1913). "Über die Genauigkeit, innerhalb welcher die Unabhängigkeit der Lichtgeschwindigkeit von der Bewegung der Quelle behauptet werden kann" [On the accuracy within which the independence of the speed of light from the motion of the source can be asserted]. Physikalische Zeitschrift. 14: 1267. Bibcode:1913PhyZ...14.1267D.

On Einstein's theory of gravitation and its astronomical consequences: De Sitter, W. (1916-07-14). "On Einstein's Theory of Gravitation and its Astronomical Consequences. First Paper". Monthly Notices of the Royal Astronomical Society. 76 (9): 699–728. Bibcode:1916MNRAS..76..699D. doi:10.1093/mnras/76.9.699. ISSN 0035-8711 – via Oxford University Press. De Sitter, W. (1916-12-08). "On Einstein's Theory of Gravitation and its Astronomical Consequences. Second Paper". Monthly Notices of the Royal Astronomical Society. 77 (2): 155–184. Bibcode:1916MNRAS..77..155D. doi:10.1093/mnras/77.2.155. ISSN 0035-8711 – via Oxford University Press. De Sitter, W. (1917-11-09). "On Einstein's Theory of Gravitation and its Astronomical Consequences. Third Paper". Monthly Notices of the Royal Astronomical Society. 78 (1): 3–28. Bibcode:1917MNRAS..78....3D. doi:10.1093/mnras/78.1.3. ISSN 0035-8711 – via Oxford University Press.

See also De Sitter double star experiment De Sitter precession De Sitter invariant special relativity De Sitter space De Sitter universe Anti-de Sitter space The Dreams in the Witch House

References

External links

O'Connor, John J.; Robertson, Edmund F., "Willem de Sitter", MacTutor History of Mathematics Archive, University of St Andrews P.C. van der Kruit Willem de Sitter (1872 – 1934) in: History of science and scholarship in the Netherlands. A. Blaauw, Sitter, Willem de (1872–1934), in Biografisch Woordenboek van Nederland. Bruce Medal page Archived 2020-02-16 at the Wayback Machine Awarding of Bruce Medal: PASP 43 (1931) 125 Awarding of RAS gold medal: MNRAS 91 (1931) 422 de Sitter's binary star arguments against Ritz's relativity theory (1913) Archived 2009-01-29 at the Wayback Machine (four articles)

Obituaries AN 253 (1934) 495/496 (one line) JRASC 29 (1935) 1 MNRAS 95 (1935) 343 Obs 58 (1935) 22 PASP 46 (1934) 368 (one paragraph) PASP 47 (1935) 65

Illustrations

Worked examples

Example 1 — a first encounter with Willem de Sitter

Start with the simplest possible case. Write down what Willem de Sitter claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Willem de Sitter before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Willem de Sitter ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Willem de Sitter

In research: Willem de Sitter appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Willem de Sitter in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Willem de Sitter is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1872 births, 1934 deaths, 19th-century Dutch astronomers, so understanding it makes those chapters shorter.
In everyday life: Look for Willem de Sitter outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Willem de Sitter in 20 minutes

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Frequently asked questions

What is Willem de Sitter in simple terms?

Why does Willem de Sitter matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Willem de Sitter?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Willem de Sitter.