When1: 1917
Who: Willem de Sitter [de Sitter, Willem]
What: physicist
Where: France
Detail: He lived 1872 to 1934, used curved time coordinate (in which distant clocks can run slower or faster), and demonstrated how general relativity required expanding universe [1917]. With curved time coordinate, symmetrical space with no matter or energy can have constant positive curvature (attraction) {de-Sitter space} {de-Sitter space-time}, with no expansion or contraction. (After universe origin, universe probably was like de-Sitter space.)
With curved time coordinate, symmetrical space with no matter or energy can have constant negative curvature (repulsion) {anti-de-Sitter space} {anti-de-Sitter space-time}, with no expansion or contraction. In anti-de-Sitter space, object motions are harmonic. Space boundary is constant at infinity, but space radius depends on curvature and is finite.
Physical Sciences>Physics>History>Cosmology
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Date Modified: 2022.0224