On thermodynamic equilibrium in a static Einstein universe

Abstract

It has now become evident that the transformation of matter into radiation taking place throughout the universe and the red-shift observed in the light from the extra-galactic nebulae appear to imply a non-static quality in the universe which can be treated with some success with the help of a non-static cosmological line element.(1) If the quantity which gives the dependence of this non-static line element on the time is set equal to a constant, if is found that the line element then becomes the same as Einstein's original line element for a static universe. Hence the Einstein static universe may be regarded as a special case of the more general non-static universe, and we must continue to be interested in the properties of the Einstein universe not only because it is a limiting case of the more general model for the universe, but also because it represents a situation which might arise in the course of the evolution of the actual universe. The present article will deal with the thermodynamics of the Einstein universe, and in particular will treat the conditions for thermodynamic equilibrium between matter and radiation in such a universe assuming the possibility of their transformation into each other.