The Cosmological Principle in Newtonian Universes

Abstract

The cosmological principle normally employed in Newtonian cosmology is briefly reviewed, and a wider interpretation is proposed which does not include the assumption that the equivalent reference frames are similarly oriented. This leads to a formulation based on groups of motions of a Euclidean 3-space, and thus analogous to that of homogeneous world models in general relativity. The usual linear-velocity universes are obtained as one of two possible cases; the other is a new class of Newtonian universes having a partly non-linear velocity function.