A model of an expanding universe in which there is no matter or radiation but the expansion is driven by a cosmological constant. It was proposed in 1917 by W. de Sitter. Although this model is physically unrealistic, it introduced the idea that the real Universe might be expanding. An expansion phase which is very similar to that in the de Sitter model also plays an important role in modern theories of the inflationary universe.
Subjects: Astronomy and Astrophysics.