Poincaré, Henri, << `pwan kah` RAY, on REE >> (1854-1912), was a French mathematician and physicist. He worked in nearly every branch of mathematics and mathematical physics known during his time.
Poincaré made important contributions to a branch of mathematics called topology. Topology deals with certain properties of geometric figures that cannot be changed by stretching, squeezing, or twisting (see Topology ). Poincaré had published in 1894 the first detailed paper devoted entirely to the topic. In 1904, Poincaré made a famous conjecture (unproven statement) about the topological properties of spherelike figures with three-dimensional boundaries. This idea became known as the Poincaré conjecture. For almost 100 years, it was considered one of the most important unsolved problems in mathematics. The Russian mathematician Grigori Perelman finally proved the conjecture in 2002.
Poincaré also worked in probability theory, the mathematical study of chance and randomness. He examined the stability of planetary orbits over time. This work led him to the mathematical conception of chaos—the idea that tiny changes in a system’s starting conditions can lead to vastly different results (see Chaos theory ).
Poincaré’s work in mathematics and physics led to insights about relativity, differences in space and time experienced by observers in different frames of reference. His work contributed to the theories of relativity developed by the German-born physicist Albert Einstein.
Jules Henri Poincaré was born on April 29, 1854, in Nancy, France. He attended the École Polytechnique in Paris, where he won many prizes in mathematics. From 1881 until his death on July 17, 1912, he taught at the Sorbonne, now part of the University of Paris. He created an enormous amount of published work, including about 500 papers and 30 books. Several of his books became popular classics, particularly Science and Hypothesis (1902).
