In 1900, a group of sponge divers were blown off course in the Mediterranean Sea. During what must have been a traumatic experience, they happened across an Ancient Greek shipwreck dating back to around 70 BC.

Lying unnoticed for months among their hard-won haul was what appeared to be a formless lump of corroded rock. What it turned out to be was a stunningly intricate bronze device.

It took over 100 years to crack the mystery of the Antikythera mechanism, and Jo Marchant unravels the tale with a detective's flair in her book Decoding the Heavens.

Scientists now believe the Antikythera mechanism was an intricate astronomical calculator. It seems that the Ancient Greeks invented everything - including computers. Finding the Antikythera mechanism was "like finding a steam engine on the ancient, pitted surface of the Moon" according to Marchant.

With the help of X-ray technology, a study published in the journal Nature in 2008 revealed bronze cogs and gearwheels, dials, scales and lettering can be seen within the box-like structure. It looks strikingly like modern clockwork - but it was made two millennia before historians thought it possible to create such a device.

No other civilisation is known to have created anything as complicated for another thousand years. Medieval cathedral clocks were the next objects to achieve a similar level of sophistication.

Decoding the Heavens tells this remarkable story for the first time, and made the shortlist for the Royal Society Prize for Science Books for 2009.