Distortions of the Background Radiation Spectrum

THE discovery of cosmic blackbody radiation with a temperature of 2.7 K is widely considered as powerful evidence for the hot, big-bang model of the universe. As first discussed by Gamow, it is assumed that a very hot, dense plasma was present during the early stages of the universe, and interaction of photons and electrons leads inevitably to an equilibrium (blackbody) spectrum. The shape of the equilibrium spectrum is preserved during the subsequent expansion and cooling, although the radiation temperature decreases to the value of 2.7 K observed today.