Poincaré, (Jules) Henri (1854–1912)

French mathematician who developed the theory of differential equations and was a pioneer in relativity theory. He suggested that Isaac Newton's laws for the behaviour of the universe could be the exception rather than the rule. However, the calculation was so complex and time-consuming that he never managed to realize its full implication.

Poincaré wrote on the philosophy of science. He believed that some mathematical ideas precede logic, and stressed the role played by convention in scientific method.

He also published the first paper devoted entirely to topology (the branch of geometry that deals with the unchanged properties of figures).

Poincaré was born in Nancy and studied in Paris at the Ecole Polytechnique and the Ecole des Mines. He was professor at the Sorbonne from 1881.

In his 1906 paper on the dynamics of the electron, Poincaré obtained many of the results of the theory of relativity later credited to Albert Einstein.

In the field of celestial mechanics, Poincaré studied the mutual gravitational and other effects of three bodies, or n bodies, close together in space. He developed new mathematical techniques, including the theories of asymptotic expansions and integral invariants. From his theory of periodic orbits he developed the new subject of topological dynamics.