1796 – 1832
Nicolas Léonard Sadi Carnot (1796–1832) was a French physicist and engineer who founded the science of thermodynamics. His 1824 treatise *Réflexions sur la puissance motrice du feu* established the theoretical upper limit of heat engine efficiency, introducing concepts foundational to the second law of thermodynamics. Though he died young and largely unrecognized, his work was later formalized by Clausius and Kelvin into the canonical thermodynamic framework.
Formulated the Carnot cycle, establishing the theoretical maximum efficiency of heat engines
Introduced the concept that heat engines require a temperature differential to produce work
Laid the groundwork for the second law of thermodynamics
Anticipated the conservation of energy (first law) in unpublished notes
Demonstrated that perpetual motion machines of the second kind are thermodynamically impossible