ABSTRACT
Although the laws of quantum mechanics act on an atomic scale, they also affect the macroscopic properties of gases, liquids, and rigid bodies. Quantum mechanics and quantum statistics-that is, statistics of indistinguishable particles-allowed one to obtain correct and consistent descriptions of thermal, magnetic, and many other properties of large ensembles of particles. Here a special place is occupied by quantum theory of crystals, which allowed one to remove several unsolvable contradictions of classical theory, to obtain quantitative description of electromagnetic properties of some classes of matter, to explain the superconductivity and superfluidity, etc.
