Jean Baptiste Joseph Fourier (21.03.1768 —16.05.1830) was a French mathematician and physicist, a member of the Paris Academy of Sciences (1817) and from 1822 its secretary. He was born in Auxerre, where he graduated from the military school and worked. In 1796 — 98 he taught at the École Polytechnique.
His main research was in mathematical physics. He was the founder of the theory of heat conduction and the author of the well-known work “The Analytical Theory of Heat” (1822), which played a significant part in the development of mathematics. He developed the method of representing a function by trigonometric series, the so-called Fourier series, widely used in various branches of physics. He derived the differential equation of the propagation of heat inside a solid body and gave precise definitions of the units of heat. He constructed the first mathematical theory of thermal radiation. In 1822 — 23, independently of H. Ørsted, he rediscovered the thermoelectric effect, showed that it has the property of superposition, and built the first thermocouple. He studied the elasticity of gases at various temperatures. He was the first to apply dimensional formulae.
He was a member of the St Petersburg Academy of Sciences (1829) and a Fellow of the Royal Society.