Enigmatic relic was an eclipse calculator

The mystery over the purpose of a sophisticated geared "calculator" built in the 2nd century BC has finally been solved.

The so-called "Antikythera mechanism" was found in 1902 by sponge divers exploring a shipwreck off the Greek island of the same name, but its exact use had puzzled scientists.

The relic consists of numerous fragments, including brass gears embedded in thick mineral encrustations. The device is thought to have once been housed in a wooden box about the size of a carriage clock and is more complex by far than any other machine known to have existed on the planet for the following 1000 years.

Now a team led by Mike Edmunds at Cardiff University in Wales has shown that the Antikythera mechanism was designed to predict solar and lunar eclipses from the relative positions of the Earth, Moon and Sun.

Edmunds's team used an industrial CT scanner to map out the gear trains within the mineral-encrusted fragments. The scans allowed them to determine how the components fit together and to work out their function. The team also found fragments of previously hidden text engraved on the metal.
Long tradition

"The real significance of this is just how sophisticated the device was – much more complex than a modern wristwatch," says Edmunds. "It is beautifully designed and must have come from a long tradition of making these kinds of devices."

The team is constructing a virtual model of the mechanism, which they hope to have completed within a few months.

But questions still remain, says Edmunds. There are various written references to devices like the Antikythera mechanism and yet no other examples are known. One reason may be that the bronze from which the machine is made would have been extremely valuable and so similar devices may have been melted down.

"It may be significant that the only example we have has come from a shipwreck and so couldn't have been melted down," Edmunds says, adding that the only examples of bronze statues from the same period also come from shipwrecks.