A leading cosmologist explains our current understanding of space and timeThere was immense excitement in the scientific community and among the general public when the COBE space probe sent back data that proved not only that the Big Bang had happened but also that it had happened at more or less exactly the time that astronomers had calculated. Barrow describes these finds and then goes on to explain how they allow us to reach back and shed light upon events at the dawn of time.What does it mean to say that the universe appeared out of nothing? Did it need a beginning, and will it ever end? Why do we think that most of the universe is invisible?The ideas that cosmologists are wrestling with are challenging and extraordinary: here they are explained with unfailing fluency.