Without doubt the Universe has been expanding since the Big Bang but it is by no means clear that it will continue to expand forever. If there is less than a certain amount of matter in the universe than the mutual gravitation of the receding galaxies it will be insufficient, to stop the expansion and the universe will run away forever. But if there is more matter than we can see hidden away in black holes say or invisible hot gas between the galaxies then the universe holds together and partakes in a very Indian succession of cycles, expansion followed by contraction, cosmos upon cosmos, universes without end.