The Antikythera mechanism

Divers used standard dress suits such as the one shown here to recover artefacts User friendly: the Antikythera mechanism was recovered from a roman cargo ship X-rays of the machanism revealed gearwheels hidden inside Decoding the Heavens, £12.99

Elias Stadiatis surfaced after just five minutes in the water, agitated and shaking as his crewmates pulled him into their tiny boat and twisted off his copper helmet. Stadiatis breathlessly recounted what he had seen on the sea bed. His captain, Dimitrios Kontos, immediately went to investigate. As he dropped through the cold water, a tumbled mass of figures loomed out of the blue. They weren’t corpses but statues. Some were marble, while others had the green tint of ancient bronze. This ship had been carrying treasure.

The divers had stumbled across the greatest hoard of ancient riches ever found. What’s more, lying hidden among the statues was an ancient machine; a device so sophisticated it would take more than a century to decode.

It was autumn 1900. Kontos and his men were sponge divers from the Aegean island of Symi. Greek divers had earned a living cutting sponges from the sea bed for thousands of years, swimming naked and weighed down by stones. But in the 1860s, the industry was transformed by the introduction of the diving suit, which allowed divers to breathe air fed through a hose from a compressor in a boat above. Thick folds of canvas were sealed with rubber and bolted onto a large copper collar and breastplate. Screwed on top was a heavy round helmet.

Divers could now reach 70m below the surface, staying down much longer than before. Every spring, fleets of flimsy wooden boats – each carrying up to 15 divers who shared one battered suit and air compressor – left Symi and the surrounding islands and travelled as far as north Africa. In the autumn they would return, laden with cargo and ready for one huge party.

Kontos and his crew had been sailing home from their summer fishing grounds off Tunisia when they were blown off course by a gale, and took shelter by a barren islet called Antikythera. When the winds eased, they found the ancient treasure.

Taking a bronze arm from one of the statues as proof, Kontos announced the discovery to the Greek government in Athens, which hired the men to salvage what they could. A few days later, the divers returned to Antikythera, accompanied by government archaeologists and a navy transport ship. It was a treacherous expedition. The waters around the island are cold and prone to storms and sudden currents. But the biggest challenge was the depth. At 60m down, the wreck was out of reach of any navy in the world at the time. The divers had no understanding of the diving tables or decompression stops used for safe diving today, so the bends was a constant danger. The exertion of hauling statues in the unwieldy suits exaggerated the effects of nitrogen narcosis. And the mud and sand clouded visibility as soon as the divers moved anything.

Yet they brought up find after find. As well as statues, there were swords, a lyre, gold jewellery, glassware and even an ornate bronze throne. The treasures were transported to Athens, where they were put on display in the National Archaeological Museum. Crowds flocked from across Greece to see the long-lost artefacts. At Antikythera, the work was taking its toll. By the time work stopped in 1901, two divers had been paralysed by the bends, and one was dead. Nevertheless, the government congratulated itself on a successful project. It was the first-ever archaeological survey of a wreck, and it yielded treasures beyond anyone’s imagination.

Busy museum staff struggled to cope with the huge influx of objects, so nobody noticed a corroded lump of bronze and wood lying in a crate. But as it dried and shrivelled, the lump cracked open to reveal traces of gearwheels, along with some faint inscriptions in ancient Greek.

This ‘Antikythera mechanism’ caused excitement and consternation. The gearwheels, and what looked like scales and pointers, suggested a clockwork device for making calculations and displaying the answers on a dial. But that was far beyond anything the Greeks were thought to have been capable of. Not one example of a gearwheel or scale from ancient times had ever been found. For decades, experts were unable to make head or tail of the mechanism, and it sank into obscurity.

Archaeologists studying the wreck and the rest of its cargo made more progress. They concluded that it was a 50m-long Roman cargo ship that sank in the first century BC. Sailing west from the eastern Mediterranean, it was probably carrying stolen Greek treasures to Rome.

But it took more divers – the explorer Jacques Cousteau and his friend Frédéric Dumas – to pin down its exact timing and origin. They visited Antikythera in 1976; their team equipped with sleek scuba gear, flood lamps and a powerful suction pipe that devoured whatever was in its path and pulled it up to the surface.

They were rewarded with an array of artefacts including an oil lamp, giant ship nails and the magnificent Spartan-style crest of a bronze helmet. Cousteau was especially pleased with two bronze statuettes on rotating bases. But the most significant find of all was a misshapen lump of metal. It was a stack of silver and bronze coins, fused together by the chemical action of the sea. They came from the cities of Pergamon and Ephesus on the Asia Minor coast, and the latest dated to the 60s BC.

At that time, a fearless Roman general called Pompey was sweeping through Asia Minor, ravaging the Greek colonies there. He shipped home the booty in hundreds of ships, enough to hold the greatest triumphal parade in Rome’s history in 61 BC. The Antikythera ship may have been carrying Pompey’s treasures of war.

Since Cousteau’s dives, the battered fragments of the Antikythera mechanism have been X-rayed to reveal the gearwheels hidden inside. After decades of work, scientists have recently concluded that the device was a clockwork computer, for predicting the motions of the heavens. When the user turned a handle on the side, gearwheels drove pointers on dials that displayed the positions of the sun, moon and planets in the sky, showed the timings of the Olympic games, and even predicted eclipses. It has rewritten our understanding of ancient Greek technology.

There are still many questions, however, such as who made the device and how it ended up on Pompey’s ship. To help answer them, archaeologists hope to return to Antikythera. Modern sonar scans could produce a 3D image of what lies beneath the sea bed, showing whether the hull of the ship is still intact. And divers using gas mixes such as heliox or trimix could stay at depth longer, enabling a more thorough excavation of the site. With any luck, more artefacts will be found entombed in the sediment, and who knows – maybe even another astronomical computer.



Jo Marchant is the author of Decoding the Heavens: Solving the mystery of the world’s first computer, published by William Heinemann and priced £12.99. For details, go to http://www.decodingtheheavens.com