In the 19th century astronomers, geologists and evolutionists first suggested that the Earth and Sun were (at least) millions of years old. By the early 20th century, many assumed that the Universe was infinitely old. Then in the 1920s Edwin Hubble's discovery of the expanding Universe, combined with Einstein's general theory of relativity, pointed to a Universe with a beginning -- the Big Bang. Taken at face value, however, Hubble's early measurements suggested that the Universe was younger than the Earth. And when scientists began to understand how stars work, it really did appear that the stars were older than the Universe itself -- and astronomy was faced with a major crisis. The work and the debate continued in the 1970s and 1980s, with great hopes pinned on the Hubble Space Telescope. In 1994 and 1995 measurements from the HST shattered this hope, by seeming to support a relatively young age for the Universe. The HST measurements concentrated the attention of astronomers worldwid e in a renewed assault on the problem. At Sussex University John Gribbin and his colleagues were developing a new technique to measure the Hubble Constant. By mid 1997 they had achieved the elusive breakthrough, which finally established that the Universe really is older than the stars it contains. The Birth of Time is an intriguing tale of false leads, blind alleys, and groping in the semi-dark towards the truth, told by a brilliant science writer who was also involved, as a research astronomer, in the final breakthrough.