Sadi Carnot's only book sold almost nobody, yet founded thermodynamics
In 1824 a young army engineer paid to print 600 copies of a short book asking how much work a fire can ever deliver. It vanished from shops and libraries, and he died at 36 in obscurity. A decade later other scientists rediscovered it, and Sadi Carnot became known as the father of thermodynamics.
Sadi arrived on 1 June 1796 inside the Petit Luxembourg palace in Paris, where his father Lazare, a mathematician and revolutionary general, sat on the ruling Directory. Lazare named him after the Persian poet Sadi of Shiraz. He entered the Ecole polytechnique at 16, the youngest age allowed, taught by the likes of Ampere, Poisson and Arago, and with fellow cadets helped defend Vincennes in 1814, apparently his only taste of battle.
After Napoleon's fall his father went into exile, and Sadi's career in the army engineers stalled; his reports on fortifications seemed to be ignored. From 1819 he lived in Paris on reduced pay, attending lectures on physics, chemistry and economics. A reserved man, he played violin, fenced, swam and skated, but struck most people as aloof. He left the army for good in 1828 without a pension.
Steam engines of his day turned only about 5 to 7 percent of their fuel into useful work, and engineers experimented with higher pressures and other fluids. Carnot asked whether there was a hard ceiling. Although he pictured heat as a weightless fluid called caloric, he reasoned that an engine's maximum efficiency depends on the temperatures between which heat flows, not on the working substance. He even described the Niepce brothers' dust-burning engine in detail.
Summer 1832 brought scarlet fever, then a stay in a private asylum at Ivry, and he died of cholera there on 24 August. In 1834 the engineer Emile Clapeyron explained the book in a detailed article, which reached Rudolf Clausius and the future Lord Kelvin, William Thomson. Kelvin built an absolute temperature scale on it, and Clausius used it to define entropy and state the second law. His nephew, also named Sadi Carnot, became President of France in 1887.
Source: Nicolas Léonard Sadi Carnot
