In 1900 a group of sponge divers blown off course in the Mediterranean discovered an Ancient Greek shipwreck dating from around 70 BC. Lying unnoticed for months amongst their hard-won haul was what appeared to be a formless lump of corroded rock, which turned out to be the most stunning scientific artefact we have from antiquity. For more than a century this 'Antikythera mechanism' puzzled academics, but now, more than 2000 years after the device was lost at sea, scientists have pieced together its intricate workings. Unmatched in complexity for 1000 years, it was able to predict eclipses and track the paths of the Sun and the Moon through the zodiac, and probably even showed ancient astronomers the movements of the five known planets. In Decoding the Heavens, Jo Marchant tells for the first time the story of the 100-year quest to understand this ancient computer. Along the way she unearths a diverse cast of remarkable characters - ranging from Archimedes to Jacques Cousteau - and explores the deep roots of modern technology not only in ancient Greece but in the Islamic world and medieval Europe too. At heart an epic adventure story, it is a book that challenges our assumptions about technology transfer over the ages while giving us fresh insights into history itself.