The moment of the beginning of time is one of science's Holy Grails, pursued by devotees and obsessives across the ages. Few were more committed than Bishop James Ussher who lost his sight in his 50 year quest, laboriously outlined in his 2000 Latin pages of Annals - a chronology of all known history - that is now famous only for one spectacularly inaccurate date: 4004BC, the creation of the world. Theology failed Ussher, just as it thwarted Theophilus of Antioch and many others before him. Geology was next to fail the test of time: the Comte de Buffon, working out the rate at which the earth was supposed to have cooled came up with age of 74,832 years even though he suspected this was far too little. Biology had a go in the 18th century in the hands of Johann Scheuchzer, who alleged that a fossil he had found was of a man at the time of Noah's flood; regrettably what he had was a large salamander. And so science inched forward via Darwinism, thermodynamics and radioactivity - each new discovery being applied to the enduring mystery: when had time begun.