  In the process of analyzing the axiomatic principles underlying statistical
physics, when modeling the most probable stationary macrostates of non-ergodic
closed systems, a forecast was obtained about a possible limitation purview of
the main postulate, known as the principle of equiprobability for each
realizable of microstate. It is assumed that if such a system is artificially
brought into a thermodynamically equilibrium state, in particular, by filling
it with thermal Planck radiation of the appropriate temperature, then the
subsequent evolution of the state of this system can cause the appearance of
stable polarization anisotropy of said radiation. The paper presents the
successful results of a direct verification of aforesaid prognosis on a real
physical installation. Important regularities characteristic of the applied
mathematical model are noted.
