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Born: June 1, 1796, Paris, France
Died: Aug. 24, 1832, Paris, France

Sadi Carnot (NICOLAS-LÉONARD-SADI CARNOT) was a French scientist who described the Carnot cycle, relating to the theory of heat engines.

The problem occupying Carnot was how to design good steam engines. Steam power already had many uses — draining water from mines, excavating ports and rivers, forging iron, grinding grain, and spinning and weaving cloth — but it was inefficient.

Convinced that France's inadequate utilization of steam was a factor in its downfall, Carnot began to write a nontechnical work on the efficiency of steam engines. He saw that, in a steam engine, motive power is produced when heat "drops" from the higher temperature of the boiler to the lower temperature of the condenser, just as water, when falling, provides power in a waterwheel.

Although formally presented to the Academy of Sciences and given an excellent review in the press, the work was completely ignored until 1834, when Émile Clapeyron, a railroad engineer, quoted and extended Carnot's results. Several factors might account for this delay in recognition; the number of copies printed was limited and the dissemination of scientific literature was slow, and such a work was hardly expected to come from France when the leadership in steam technology had been centred in England for a century. Eventually Carnot's views were incorporated by the thermodynamic theory as it was developed by Rudolf Clausius in Germany (1850) and William Thomson (later Lord Kelvin) in Britain (1851).