A replica of the Antikythera Mechanism, a stunningly complex 2,100-year-old celestial computer.

Credit: The Antikythera Mechanism Research Project

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PARIS: A 2,100-year-old clockwork machine whose remains were retrieved from a shipwreck more than a century ago has turned out to be the celestial super-computer of the ancient world.

Using 21st-century technology to peer beneath the surface of the encrusted gearwheels, stunned scientists say the so-called Antikythera Mechanism could predict the ballet of the Sun and Moon over decades and calculate a lunar anomaly that would bedevil Isaac Newton himself.

Built in Greece around 150 to 100 BC and possibly linked to the astronomer and mathematician Hipparchos, its complexity was probably unrivalled for at least a thousand years, they say.

"It's beautifully designed. Your jaw drops when you work out what they did and what they put into this," said astronomer Mike Edmunds of Cardiff University in Wales. "It implies the Greeks had great technical sophistication."

The Antikythera Mechanism is named after its place of discovery, where Greek divers, exploring a Roman shipwreck at a depth of 42 metres in 1901, came across 82 curious bronze fragments.

At first, these pieces, thickly encrusted and jammed together after lying more two millennia on the sea floor, lay forgotten. But a closer look showed them to be exquisitely made, hand-cut, toothed gearwheels.

It was clear that, within this find, 29 gearwheels fitted together, possibly making some sort of astronomical calendar. But of what, exactly? For a quarter of a century, the textbook on the strange find was a work written by a historian of science and technology, Derek de Solla Price.

He hypothesised that the Mechanism in fact had 31 gearwheels, and did something pretty astonishing - it linked the solar year with a 19-year cycle in the phases of the Moon. This is the so-called Metonic cycle, which takes the Moon 235 lunar months to the same phase on the same date in the year.

Edmunds' team, gathering experts from Britain, Greece and the United States, has now taken the tale several chapters forward.

In a paper published today in the British journal Nature, they describe how they used three-dimensional X-ray computation tomography and high-resolution surface imaging to peek beneath the Mechanism's surface without damaging the priceless artefact.