Gravitational wave researchers shed new light on the mystery of the Antikythera mechanism

Techniques developed to analyze the ripples in space-time detected by one of the most sensitive pieces of scientific equipment of the 21st century have helped shed new light on the function of the oldest known analog computer.

Astronomers from the University of Glasgow have used statistical modeling techniques developed to analyze gravitational waves to determine the likely number of holes in one of the broken rings of the Antikythera Mechanism – an ancient object featured in the film ‘Indiana Jones and the Dial of Fate.”

While the film version allowed the intrepid archaeologist to travel through time, the Glasgow team’s results provide new evidence that one of the components of the Antikythera mechanism was most likely used to track the Greek lunar year. They also provide new insights into the extraordinary craftsmanship of the ancient Greeks.

The mechanism was discovered in 1901 by divers exploring a shipwreck near the island of Antikythera in the Aegean. Although the shoebox-sized mechanism was broken into fragments and corroded, it soon became clear that it contained a complex series of gears that were unusually intricate tools.

Decades of subsequent research and analysis have proven that the mechanism dates back to the second century BC and functioned as a type of mechanical handheld computer. External forms connected to internal gears allowed users to predict eclipses and calculate the astronomical positions of the planets on any given date with an accuracy unmatched by any other known contemporary device.

In 2020, new X-ray images of one of the mechanism’s rings, known as the calendar ring, revealed fresh details of the regularly spaced holes that lie beneath the ring. Since the ring was broken and incomplete, however, it was not clear how many holes it originally had. Initial analysis by Antikythera scholar Chris Budiselic and colleagues suggested it was likely somewhere between 347 and 367.

Now, in a new paper published in Horological magazineGlasgow researchers describe how they used two statistical analysis techniques to uncover new details about the calendar ring.

They show that the ring is much more likely to have had 354 holes, corresponding to the lunar calendar, than 365 holes, which would have followed the Egyptian calendar. The analysis also shows that 354 holes is hundreds of times more likely than a ring with 360 holes, which previous research had suggested as a possible count.

Professor Graham Woan, of the University of Glasgow’s School of Physics and Astronomy, is one of the authors of the paper. He said, “Late last year, a colleague showed me data obtained 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.

“It struck me as an interesting problem and one that I thought I could solve in a different way over the Christmas holidays, so I decided to use some statistical techniques to answer the question.

Professor Woan used a technique called Bayesian analysis, which uses probability to quantify uncertainty based on incomplete data, to calculate the likely number of holes in the mechanism using the positions of the surviving holes and the placement of the six fragments survivors of the ring. His results showed strong evidence that the mechanism’s calendar ring contained either 354 or 355 holes.

At the same time, one of Professor Woan’s colleagues at the University’s Institute for Gravitational Research, Dr. Joseph Bayley, had also heard of the problem. He adapted techniques used by their research group to analyze signals received by the LIGO gravitational wave detectors, which measure tiny ripples in space-time caused by massive astronomical events such as colliding black holes as they pass by across the Earth, to examine. calendar ring.

The Markov chain Monte Carlo and nested sampling methods used by Woan and Bayley provided a comprehensive probabilistic set of results, again suggesting that the ring most likely contained 354 or 355 holes in a circle of 77.1 mm radius, with an uncertainty of about 1/ 3 mm. It also reveals that the holes were precisely positioned with remarkable accuracy, with an average radial difference of only 0.028 mm between each hole.

Bayley, a co-author of the paper, is a research associate in the School of Physics and Astronomy. He said, “Previous studies had suggested that the calendar ring was likely to have tracked the lunar calendar, but the dual techniques we applied to this piece of work greatly increase the likelihood that this was the case.

“It has given me a new appreciation for the Antikythera Mechanism and the work and care that Greek craftsmen took to make it – the accuracy of the positioning of the holes would have required very precise measuring techniques and an incredibly steady hand to strike them .

Professor Woan added, “It is a neat symmetry that we have adapted the techniques we use to study the universe today to understand more about a mechanism that helped humans keep track of the heavens nearly two millennia ago.

“We hope that our findings about the Antikythera Mechanism, although less supernaturally spectacular than those made by Indiana Jones, will help deepen our understanding of how this remarkable device was created and used by the Greeks.”