: He proved that for a gas evolving toward equilibrium, can only decrease or remain constant over time ( Significance : Since is proportional to negative entropy ( −Snegative cap S ), a decrease in
(later identified as the negative of entropy), for an ideal gas. : Boltzmann defined is the distribution of molecular velocities. Ludwig Boltzmann, 1844—1906, Whose H theorem - ...
The H-theorem was groundbreaking because it claimed to derive irreversible macroscopic behavior from reversible microscopic laws of motion. This led to two famous challenges: : He proved that for a gas evolving