Nicolas Léonard Sadi Carnot
Nicolas Léonard Sadi Carnot (Nicolas Léonard Sadi Carnot (June 1, 1796 - August 24, 1832) was a French physicist and military engineer who gave the first successful theoretical account of heat engines, now known as the Carnot cycle, thereby laying the foundations of the second law of thermodynamics. Technically, he is the world's first thermodynamicist, being responsible for such concepts as Carnot efficiency, Carnot theorem, Carnot heat engine, Carnot cycle and others.