Nicolas Léonard Sadi Carnot

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Lore & Background

Sadi Carnot was born in Paris on 1 June 1796, at the Petit Luxembourg palace, where his father Lazare resided as one of the five members of the Directory. His father named him after the 13th-century Persian poet Sadi of Shiraz. An elder brother, also named Sadi, had been born in 1794 but died in infancy the following year. Carnot was educated first at home by his father and later at the Lycée Charlemagne, in Paris. In 1811, at age 16, he became a cadet of the École polytechnique, where his classmates included the future mathematician Michel Chasles and his professors included André-Marie Ampère, Siméon Denis Poisson, François Arago, and Gaspard-Gustave Coriolis. During the Battle of Paris in March 1814, Carnot, Chasles, and other cadets participated in the defense of Vincennes—his only experience of battle. He graduated in 1814 and was admitted at the École d'application de l'artillerie et du génie in Metz, completing a two-year course, then became an officer in the French army's corps of engineers. After Napoleon's final defeat in 1815, Carnot's father Lazare was forced into exile in Magdeburg, and Carnot's position under the restored Bourbon monarchy became increasingly difficult. On 15 September 1818, at age 22, he took a six-month leave to prepare for the entrance examination to the General Staff in Paris, passed, and joined in January 1819 with the lower rank of lieutenant, remaining on call but dedicating most of his attention to private intellectual pursuits on two-thirds pay.

Reader's Guide

In Paris, Carnot befriended Nicolas Clément and Charles-Bernard Desormes and attended lectures on physics and chemistry at the Sorbonne and the Collège de France, as well as the Conservatoire national des arts et métiers. He became interested in understanding the limits to improving steam engine performance, leading to his Reflections on the Motive Power of Fire, published at his own expense in June 1824 in an edition of 600 copies. The work attracted little attention during his lifetime. In 1834, engineer Émile Clapeyron published a detailed commentary that called attention to Carnot's work. That commentary drew the attention of William Thomson (later Lord Kelvin) and Rudolf Clausius. Thomson used Carnot's analysis to develop an absolute thermodynamic temperature scale, while Clausius used it to define the concept of entropy, formalizing the second law of thermodynamics. Carnot was finally promoted to captain in September 1827, but quit the army the following April after only fifteen months of active service and without right to a pension. In a directory of alumni of the École polytechnique published in 1828, Carnot is listed as 'maker of steam engines'. In the summer of 1832 he apparently suffered from a severe bout of scarlet fever. On 3 August, he was interned in a private sanatorium run by psychiatrist Jean-Étienne Esquirol in Ivry. According to the hospital record, he was cured from 'mania' but then died of cholera on 24 August at age 36. He was buried in the old cemetery of Ivry, close to what is now the Mairie d'Ivry station. Today he is often characterized as the 'father of thermodynamics'.

Did You Know?

• Carnot's father Lazare named him after the 13th-century Persian poet Sadi of Shiraz.
• His only publication, Reflections on the Motive Power of Fire, was printed in 600 copies at his own expense in June 1824.
• Carnot participated in the defense of Vincennes during the Battle of Paris in March 1814—his only experience of battle.
• In a directory of alumni of the École polytechnique published in 1828, Carnot is listed as 'maker of steam engines'.
• Carnot died of cholera on 24 August 1832 at age 36, after being cured from 'mania' in a private sanatorium.