The Antikythera mechanism

A geared computer from 100 BC, and nothing like it again for 1,400 years

Sponge divers working a wreck off Antikythera in 1901, at 45 metres, brought up a corroded lump of bronze that turned out to be a geared computer. It was built in the second century BC, probably between 150 and 100, and it predicted the positions of the sun, moon and planets and the timing of eclipses decades ahead, tracked the calendar and even the cycle of the athletic games. At least 30 gears survive and Michael Wright has argued the Greeks of that date could have driven many more. Nothing of comparable mechanical complexity appears anywhere for about 1,400 years afterwards, until the astronomical clocks of fourteenth-century Europe. It is not a mystery in the sense of being unexplained; it is a mystery in the sense that the knowledge to make it was lost completely. National Archaeological Museum, Athens.