When Newton said, "I have stood on the shoulders of giants", he was referring, above all, to the astronomers, Johannes Kepler and Tycho Brahe. Kepler was an obsessive, devout teacher, many of whose astronomical theories were quite mad, yet he had an analytical ability second to none. Brahe, by contrast, was an arrogant, cruel, extravagant aristocrat who believed the Sun orbited the Earth, yet he was one of the best observational astronomers of all time. Their serendipitous meeting in Prague in 1600 led to an extraordinary - and uneasy - alliance and resulted in a huge leap forward in the understanding of astronomy. Brahe's observational data and Kepler's genius combined to produce the first three laws of planetary motion. Set in one of the most turbulent and colourful eras in European history, at the turning point where mediaeval gave way to modern, this book tells the story of a major watershed in the history of human thought.