From the moment it was discovered more than a century ago, scholars have been wondering about the Antikythera mechanism, a remarkable and astonishing astronomical calculator that survives from the ancient world.
The hand-powered, 2000-year-old device displays the motion of the universe and predicts the motion of the five known planets, the phases of the moon and the solar and lunar eclipses. But it is difficult to unravel how it has achieved such impressive achievements.
Now UCL researchers believe they have solved the mystery – at least in part – and tried to reconstruct the device, gears and all to test whether their proposal works. If they can build a replica with modern machinery, they aim to do the same with techniques from antiquity.
“We believe our reconstruction fits with all the evidence that scientists have picked up so far from the existing remains,” said Adam Wojcik, a materials scientist at UCL. While other scholars have done reconstructions in the past, the fact that two-thirds of the mechanism is missing has made it difficult to know for sure how it worked.
The mechanism, often described as the world’s first analog computer, was found by sponge divers in 1901 amid a large amount of treasures rescued from a merchant ship that had a disaster off the Greek island of Antikythera. The ship is believed to have formed in a storm in the first century BC when it passed between Crete and the Peloponnese from Asia Minor to Rome.
The battered fragments of corroded copper were initially barely noticed, but decades of scientific work have revealed that the object is a masterpiece of mechanical engineering. The mechanism was originally housed in a one-foot-high wooden case with inscriptions – a built-in user manual – and contained more than 30 bronze gear wheels attached to hands and pointers. Turn the handle and the sky, as known to the Greeks, moves in motion.
Michael Wright, a former curator of mechanical engineering at the Science Museum in London, has written extensively on how the mechanism operated and built a working replica, but researchers have never had a complete understanding of how the device works. The remnants that survive in 82 separate fragments did not help their efforts, which is tantamount to the task of rebuilding it to the solution of a battered 3D puzzle that most pieces are missing.
The UCL team writes in the journal Scientific Reports and describes how they used the work of Wright and others, and uses inscriptions on the mechanism and a mathematical method described by the ancient Greek philosopher Parmenides, to work out new gear arrangements. which the planets and other bodies in the right way. With the solution, almost all the gears of the mechanism can fit within a space of only 25 mm deep.
According to the team, the mechanism showed the motion of the sun, moon and the planets Mercury, Venus, Mars, Jupiter and Saturn on concentric rings. Because the device assumed that the sun and planets revolved around the earth, their paths were much more difficult to reproduce with gears than when the sun would be placed in the center. Another change the scientists are proposing is a double-pointed pointer that they call a ‘dragon hand’ that indicates when eclipses should occur.
The researchers believe the work brings them closer to a true understanding of how the Antikythera device displayed the sky, but it is not clear whether the design was correct or could have been built using ancient manufacturing techniques. The concentric rings that make up the screen must rotate on a set of nested, hollow axles, but without a lathe to form the metal, it is unclear how the ancient Greeks would have made such components.
“The concentric tubes at the core of the planetarium are where my confidence in Greek technology is faltering, and where the model may be faltering as well,” Wojcik said. “Lathes would be today, but we can not assume they had those for metal.”
Whether the model works or not, there are more puzzles. It is unclear whether the Antikythera mechanism was a toy, a teaching tool or had another purpose. And if the ancient Greeks were capable of such mechanical devices, what else did they do with the knowledge?
“Although metal is precious and therefore would be recycled, it is strange that nothing from a distance similar was found or excavated,” Wojcik said. “If they had the technology to make the Antikythera mechanism, why didn’t they also extend this technology to the design of other machines like watches?”