The Expanding Universe

Abstract

IT is very satisfactory to find that the explanation I have given of the phenomena of the expanding universe can be freed from some of the restrictions which were introduced. The essential point in the explanation, as I pointed out, is that we have to do with an unenclosed system; if the system contains some high velocity particles, it will necessarily expand. Mr. Kosambi points out that the expansion and recession to infinity may also occur under more general conditions. But Mr. Kosambi is scarcely correct in saying that in my explanation “the material particles that form the universe are taken initially to have been enclosed in some finite space”. I used the finite occupied sphere surrounded by infinite empty space as the most striking illustration of the principle (it was the way the explanation originally occurred to me), but as I explicitly pointed out, any ‘initial’ density distribution with a concentration towards one region will give rise to the expansion phenomenon; and for the particular relativistic world-structure which I outlined the initial density-distribution extends throughout infinite Euclidean space.