Sous-lieutenant Nicolas Léonard Sadi Carnot (; 1 June 1796 – 24 August 1832) was a French mechanical engineer in the French Army, military scientist and physicist, and often described as the "father of thermodynamics". He published only one book, the Reflections on the Motive Power of Fire (Paris, 1824), in which he expressed the first successful theory of the maximum efficiency of heat engines and laid the foundations of the new discipline: thermodynamics. Carnot's work attracted little attention during his lifetime, but it was later used by Rudolf Clausius and Lord Kelvin to formalize the second law of thermodynamics and define the concept of entropy. Based on purely technical concerns, such as improving the performance of the steam engine, Sadi Carnot's intellect laid the groundwork for modern science technological designs, such as the automobile or jet engine. His father Lazare Carnot was an eminent mathematician, military engineer, and leader of the French Revolutionary Army. Life Nicolas Léonard Sadi Carnot was born in Paris at the Palais du Petit-Luxembourg into a family that was distinguished in both science and politics. He was the first son of Lazare Carnot, who chose his son's third given name Sadi (by which he would always be known) after the Persian poet Sadi of Shiraz. Sadi was the elder brother of statesman Hippolyte Carnot and the uncle of Marie François Sadi Carnot, who would serve as President of France from 1887 to 1894. His father Lazare Carnot knowing his son's potential, sent him to Lycée Charlemagne in Paris to prepare him for the examinations to École polytechnique. In 1811, at the age of 16, the minimum age possible, Sadi Carnot became a cadet in the École Polytechnique in Paris, where his classmates included Michel Chasles and Gaspard-Gustave Coriolis. The École Polytechnique was intended to train engineers for military service, but its professors included such eminent scientists as André-Marie Ampère, François Arago, Joseph Louis Gay-Lussac, Louis Jacques Thénard, Jean Nicolas Pierre Hachette, Jean-Henri Hassenfratz, Antoine André Louis Reynaud, and Siméon Denis Poisson. Thus, the school had become renowned for its mathematical instruction. After graduating in 1814, Sadi went to study in École du Génie at Metz to study the two year course in military engineering. Sadi then became an officer in the French army's corps of engineers. His father Lazare had served as Napoleon's minister of the interior during the "Hundred Days", and, after Napoleon's final defeat