Electron-photon Interaction and Thermal Disequilibrium Irreversibility

Atoms continuously interact with the photons of the electromagnetic fields in their environment. This electromagnetic interaction is the consequence of the thermal nonequilibrium. It introduces an element of randomness to atomic and molecular motion, which brings to the decreasing of path probability required for microscopic reversibility of evolution. In any atomic electron-photon interaction an energy footprint is given to the atom, and the emitted photon looses energy. The emission of radiation isn’t time reversible and this causes the irreversibility in macroscopic systems.