Marian Smoluchowski (28.05.1872 — 5.09.1917) was a Polish physicist. He was born in Vorderbrühl, near Vienna. He graduated from the University of Vienna (1895). He furthered his studies in the laboratories of G. Lippmann, W. Thomson and E. Warburg. In 1899-1913 he worked at the University of Lviv (professor from 1900). From 1913 he was professor at the University of Kraków (rector in 1917).
His main research concerned molecular physics, thermodynamics and statistical mechanics, in particular the kinetic theory of gases and liquids, the theory of Brownian motion, and molecular statistics. In 1898 he gave a theoretical basis for the temperature jump at a “gas — solid” boundary, which had been discovered experimentally in the 1870s, and this was a fairly strong argument in favour of molecular kinetics. Smoluchowski's further studies of Brownian motion and of the limits of applicability of the second law of thermodynamics supported and developed the ideas of L. Boltzmann. Starting from the kinetic law of energy distribution, he created (1905 — 06) a theory of Brownian motion, which proved the validity of the kinetic theory of heat and helped to establish it finally.
He established (1904) the laws of fluctuations of equilibrium states in molecular systems, which he used to support Boltzmann's idea that R. Clausius's classical treatment of the second law of thermodynamics, which led to the “heat death” of the Universe, was of limited validity. His theory of thermodynamic fluctuations made it possible to determine the time after which a new anomalous state of a system arises, and dealt a serious blow to the hypothesis of the “heat death”. His research also concerned aerodynamics and the physics of colloids.
The Polish Physical Society established the M. Smoluchowski Medal.