COSMOLOGY: SOME CURRENT PROBLEMS

Summary: This article starts with a summary of the history of the Universe, as given by big-bang cosmology about a decade ago. It attemps then to review some of the main developments that have taken place since that. Refined studies of the relative abundances of the light elements hydrogen, helium and deuterium have yielded improved limits upon the value of the baryon: photon ratio X] . There have been extended assessments of the amounts of dark matter associated with galaxies and systems of galaxies. In combination with the estimates of 77 , these have facilitated discussion of the amount of nonbaryonic mass that may exist in the Universe. This is naturally related to work upon the possible rest-mass of the neutrino, but precise inferences are not yet forthcoming. Recent work on the large-scale structure of the Universe is mentioned and this leads to a discussion of the origin of condensations in big-bang cosmology. A sketch of a model for galaxy formation indicates that big-bang cosmology seems capable of accounting for this, provided a theory of the origin, in this cosmology, of inhomogeneities of any sort is forthcoming.