A nonequilibrium universe of stars and radiation

A model for a relativistic gas of macroscopic objects and black-body radiation is constructed using kinetic theory and the assumptions that the macroscopic objects form a perfect fluid and scatter the radiation isotropically in their rest frame. The model is applied to the Robertson-Walker metric and the nonrelativistic and ultra-relativistic limits are given. Equilibrium occurs in the limit that the temperature of the gas of macroscopic objects approaches zero