In 1901, sponge divers off the Greek island of Antikythera stumbled upon an ancient shipwreck that would soon yield one of the most extraordinary artifacts of the ancient world. Among the recovered treasures, a corroded, bronze-encrusted object was eventually revealed to be the Antikythera Mechanism, an ancient Greek analog computer of remarkable sophistication. It is the oldest known computer (or computing device) in history.
The Antikythera Mechanism, believed to date back to the 2nd century BC, has amazed historians and scientists with its complex design and advanced technology. Initially, the mechanism was thought to be nothing more than a rusty piece of metal. However, upon closer inspection, it became clear that this device was much more than just a relic.
Today divided into 82 fragments, only a third of the original remains, including at least 30 bronze gears and a sophisticated series of dials and inscriptions. The device appears to be some kind of astronomical mechanical computer that predicts the movement of celestial bodies. However, its exact purpose and operating principle have always been shrouded in mystery due to advanced degradation.
Now, more than a century after its discovery, scientists at the University of Glasgow have applied a statistical modeling technique originally designed to find gravitational waves to fill in the gaps in the Antikythera Mechanism. The study extrapolated missing features on one of the calendar dials that suggest Antikythera was used to track the Greek lunar year.
Fill in the blanks
The new study focused on the Antikythera calendar ring. Previous research using X-rays to reveal hidden features had suggested that the ring could have had between 347 and 367 holes. However, the researchers’ Bayesian analysis — a statistical method that uses probabilities to measure uncertainty based on incomplete data — revealed that the ring is much more likely to contain 354 holes. It is 100 times more likely that the ring has 354 holes than 360 holes, which previous research suggested was a possible number.
This would imply that the Antikythera Mechanism followed the Greek lunar calendar and not the Egyptian solar calendar, as previously suggested. Other components of the Antikythera Mechanism were likely used to predict lunar and solar eclipses, and perhaps display the positions of the known planets (Venus, Mars, Mercury, Jupiter, and Saturn). Additionally, it is thought to have been used to determine the timing of events important to the ancient Greeks, such as the Olympic Games.
“Towards the end of last year, a colleague showed me some data acquired by YouTuber Chris Budiselic, who was looking to make a replica of the calendar ring and was investigating ways to determine how many holes it contained,” said Professor Graham Woan, from the University of Glasgow’s School of Physics and Astronomy, who led the effort using Bayesian statistics.
“It seemed like an interesting problem to me, and I thought I could solve it in a different way over the Christmas holidays. So I started using some statistical techniques to answer the question.”
Dr. Joseph Bayley adapted techniques from the LIGO gravitational wave detectors, which record tiny ripples in the fabric of spacetime caused by massive cosmic events, such as merging black holes. This analysis suggests once again that the incomplete ring most likely contained 354 or 355 holes on a circle of radius 77.1 mm.
“It’s a neat symmetry that we’ve adapted the techniques we use to study the universe today to better understand a mechanism that helped people track the heavens nearly two millennia ago,” Woan added.
The holes were made with astonishing precision given the technology of the time, with an average radial variation of only 0.028 mm between each hole.
In previous research, scientists revealed thousands of text characters hidden inside the fragments using microfocus X-ray computed tomography. The inscriptions on the back cover include a description of the cosmos, with the planets moving on rings and indicated by marker balls.
“It gave me a new appreciation of the Antikythera Mechanism and the work and care that the Greek craftsmen put into making it – the precision of the positioning of the holes would have required very precise measuring techniques and an incredibly steady hand to drill them,” Bayley said.
The results appeared in The Watchmaking Journal.
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