Poincaré, (Jules) Henri[pwa karay]
Mathematician, born in Nancy, NE France, the cousin of Raymond Poincaré. He studied at Paris, where he became professor in 1881. He was eminent in physics, mechanics, and astronomy, and contributed to many fields of mathematics. He created the theory of automorphic functions, using new ideas from group theory, non-Euclidean geometry, and complex function theory. The origins of the theory of chaos are in a famous paper of 1889 on real differential equations and celestial mechanics. Many of the basic ideas in modern topology, triangulation, and homology are due to him. He gave influential lecture courses on such topics as thermodynamics, and almost anticipated Einsteins's theory of special relativity, showing that the Lorentz transformations form a group. In his last years he published several books on the philosophy of science and scientific method, and was also well known for his popular expositions of science.