Correspondence of classical and quantum irreversibilities

The reversibility of classical mechanics is broken by the Carnot principle; in quantum mechanics, the time inversion invariance is broken by the principle of state decoherence. In both cases, a greater complexity produces a faster irreversibility. These principles are applied to problems related to absorption and diffusion of light. It appears that Raman scattering in extremely low-pressure gases shifts the frequency of the incident light, is space coherent and thus may be confused with the Doppler effect: the Raman scattering produces at least a part of the galactic redshift; the expansion of the universe is reduced or possibly cancelled.