Decoding the Heavens, By Jo Marchant

Clockwork marvel before its time

Sunken treasure. A mysterious artefact. Scrambled inscriptions. Warring academic egos. Technology 1,000 years before its time. The tale of a wondrous relic related in science journalist Jo Marchant's first book sounds like pulp fiction. But it is all true. One piece of complex clockwork challenges all conventional accounts of the history of invention, and puts ancient Greece in a whole new light.

The modern story of the Antikythera mechanism – named for the Greek island off whose shores it was recovered – began in 1900. A crew of sponge divers equipped with cumbersome diving suits happened upon a 2,000-year-old wreck. They were astonished to find the cargo, including massive bronze and marble statues, still recognisable. Heroic effort saw some of it brought in triumph to the National Archaeological Museum in Athens. Among the haul were obscure fragments of a mechanism, so corroded as to be almost unrecognisable. The statues got all the attention.

Later, the museum realised that along with their classical treasures they had something harder to credit. It was a book-sized, complex assembly of beautifully made bronze gearwheels, once mounted in a wooden frame, inscribed with what seemed to be instructions for use. It was unprecedented – as big a surprise, the historian of technology Derek de Solla Price said, as finding remnants of an internal combustion engine in Tutankhamen's tomb. Price was trying to talk up the significance of his favourite relic in the 1950s, but he was hardly exaggerating.

Recent scrutiny, with better imaging and more scrupulous counting of gear teeth, revised Price's reconstruction. Thanks to the laborious efforts of the redoubtable British Museum curator Michael Wright and the late Australian astronomer Allan Bromley, the calendar computer envisioned by Price was reborn as an exquisitely crafted planetarium. Still more detailed examination, using X-ray CAT scans, has shown the mechanism was used to predict eclipses, and possibly keep track of dates for the Olympic games.

Marchant's book should stand for a while as a full account of this amazing, intricate device, and the men who became obsessed with it. But solving the puzzle of those tantalising fragments leaves enormous questions. Who built the thing, and why? How many others adorned Greek culture? And if they could engineer such a model of the heavens, why did it take another 1,000 years for the techniques to find other practical uses?

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