The mechanism, or at least a large section of it, was found at the beginning of the 20th Century by sponge divers who discovered a shipwreck off the coast of the Greek island, Antikythera. The piece had corroded significantly but enough of it had survived to indicate this was a sophisticated machine. It wasn’t until many years later, however, that scientists realised this Hellenic invention was similar in many respects to an analogue computer or calculator. By entering a future date, probably by turning various levers to move the gears, the machine could tell you the position of the moon and the sun at that time as well as indicating the phase of the moon.
It was based on something they had got from the Babylonians called the Metonic cycle – they worked out there were almost exactly 235 full moons in 19 years
It is probable that the ancient Greeks used a lunar calendar instead of a solar one and this would have presented problems because a complete number of lunar months does not fit into a year.
Professor of Astrophysics at Cardiff University, Mike Edmunds, who has led a team of international scientists investigating the Antikythera Mechanism, told Humans Invent, “One of the things this device definitely did was to show the relationship between the lunar month and the year. It was based on something they had got from the Babylonians called the Metonic cycle – they worked out there were almost exactly 235 full moons in 19 years.”
This meant, for example, that the Antikythera mechanism could inform you when there was going to be a full moon many years in advance – this was useful in discerning which day festivals could be held that were celebrated according to a particular phase in the moon’s cycle.
When we started about 700 Greek characters were known, and now it is up to 2,000 – 3,000
It is believed the machine was also used to work out when there would be an eclipse as well as showing the movement of other planets. Edmunds says, “It is fairly probable, almost certain, that it also displayed the position of the planets in the sky as well – the planets they knew about: Mercury, Venus, Mars, Jupiter and Saturn.”
X-ray computed tomography (CT scans) has been incredibly important in revealing the secrets inside the corroded machine, especially as there are engravings throughout the mechanism. Edmunds says, “This imaging has revealed not only the gearing but it also allowed for much more reading of the inscriptions. When we started about 700 Greek characters were known, and now it is up to 2,000 – 3,000. So it really has been extremely helpful in revealing the underlying texts.”
These instructions have led to a much better understanding of the functions behind the machine. Before this, many theories on its use were based largely on speculation. What makes this machine so remarkable is how far ahead of its time it was. It wasn’t until the 14th Century, some 1400 years later, that astronomical clocks, which used similar gear designs to the Antikythera mechanism, started to appear in Europe.
Scientists and researchers have become fascinated with the machine over the last ten years, so much so, that former Science Museum curator Michael Wright made a woking re-production of the machine – it is most certainly one of those occasions where you have to see it to beleive it…