The expansion of the Universe

Abstract

We show that, in principle, the observed galactic redshifts and microwave background radiation in the Universe can be explained by a static spherically symmetric (or SSS) universe model, in which there is a singularity which continually interacts with the Universe (rather than the once for all interaction that occurs in the Friedmann–Robertson–Walker, or FRW, universe models). However, when Einstein's field equations are introduced with a plausible equation of state, we cannot obtain a good fit to the observed (m, z) relation in a SSS universe model with all the properties we require. The standard discussions of the expansion of the Universe proceed from an unverified a priori assumption – the Cosmological Principle – and deduce that the Universe is expanding, on the basis of that assumption. Our result constitutes a proof that the Universe is expanding, which is not based on a priori assumptions about space–time geometry. Such a proof is needed if one is seriously to attempt to make cosmology an observationally-based subject. In addition, we use the SSS models to point out various features of interest that could arise in expanding, inhomogeneous universe models. Particularly, we show that an observer cannot deduce from the isotropy of the microwave background radiation, that the Universe is spherically symmetric about him; and that there may exist plausible cosmological models with a ‘continuously active’ singularity, such as is envisaged for the SSS universe models. This could have interesting implications for ‘Machian’ discussions. In such models, the observer would be situated somewhere near the centre. We point out that there could be good reasons for such a situation.