What significant contribution did Nicolas Leonard Sadi Carnot make to thermodynamics?

Nicolas Leonard Sadi Carnot is best known for introducing the Carnot Cycle and the concept of Carnot efficiency, which are foundational in the study of thermodynamics. The Carnot Cycle is a theoretical model that represents the most efficient possible engine cycle, operating between two temperature reservoirs. Through this cycle, Carnot established a baseline for the maximum efficiency of heat engines, whereby no engine can be more efficient than a Carnot engine operating between the same two temperatures.

The concept of Carnot efficiency is expressed as the ratio of the work output of the engine to the heat input from the hot reservoir, dependent solely on the temperatures of the two reservoirs. This work laid the groundwork for later developments in thermodynamic theory and has crucial implications for understanding real-world heat engines and their limitations. Thus, Carnot's contributions are vital in shaping the principles of energy transfer and efficiency that are central to thermodynamics.