Our Universe - and others

Cosmological models used to explain the origin and fate of the Universe are discussed. It is argued that the evidence that the Universe is expanding, coupled with the discovery of the cosmic microwave background radiation, suggest that the Universe began in a big bang. However, in speculating as to the end of the Universe, although from conventional wisdom it will expand for ever, it is not sure that there is not sufficient material for gravity to halt the expansion and produce a collapse to a 'big crunch'. (U.K.)