In this paper the unified description of the thermal excitation of atoms, molecules and nanoparticles was formulated. The formulae for the relaxation times and velocities of the thermal energy transport are obtained. It was shown that the relaxation times, velocities and excitation energies depend on two fundamental constants: alpha = 1/137 - fine structure constant for electromagnetic interactions and beta = m(e)/m(p) - ratio of electron to proton mass.