Boltzmann Ludwig (1844–1906), Austrian physicist who was a spirited advocate of the atomic theory and a pioneer in developing the kinetic theory of gases and statistical mechanics. Boltzmann’s most famous achievements were the transport equation, the H-theorem, and the probabilistic interpretation of entropy. This work is summarized in his Vorlesungen über Gastheorie (‘Lectures on the Theory of Gases,’ 1896–98). He held chairs in physics at the universities of Graz, Vienna, Munich, and Leipzig before returning to Vienna as professor of theoretical physics in 1902. In 1903 he succeeded Mach at Vienna and lectured on the philosophy of science.
In the 1890s the atomic-kinetic theory was attacked by Mach and by the energeticists led by Wilhelm Ostwald. Boltzmann’s counterattack can be found in his Populäre Schriften (‘Popular Writings,’ 1905). Boltzmann agreed with his critics that many of his mechanical models of gas molecules could not be true but, like Maxwell, defended models as invaluable heuristic tools. Boltzmann also insisted that it was futile to try to eliminate all metaphysical pictures from theories in favor of bare equations. For Boltzmann, the goal of physics is not merely the discovery of equations but the construction of a coherent picture of reality. Boltzmann defended his H-theorem against the reversibility objection of Loschmidt and the recurrence objection of Zermelo by conceding that a spontaneous decrease in entropy was possible but extremely unlikely. Boltzmann’s views that irreversibility depends on the probability of initial conditions and that entropy increase determines the direction of time are defended by Reichenbach in The Direction of Time (1956).
See also ENTROPY , MACH, MAXWELL, PHI- LOSOPHY OF SCIENCE , REICHENBAC. M.C.