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

Techniques developed to analyze the ripples in spacetime detected by some of the most sensitive 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 artefact showcased in the film ‘Indiana Jones and the Dial of Destination.”

Although the film version allowed the intrepid archaeologist to travel through time, the results from the Glasgow team 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 remarkable craftsmanship of the ancient Greeks.

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

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

In 2020, new X-rays of one of the mechanism’s rings, known as the calendar ring, revealed new details of regularly spaced holes located beneath the ring. However, because the ring was broken and incomplete, it was not clear how many holes there were originally. Initial analysis by Antikythera researcher Chris Budiselic and colleagues suggested it was probably somewhere between 347 and 367.

Now, in a new article published in the Clockwork Magazinethe Glasgow researchers describe how they used two statistical analysis techniques to reveal new details about the calendar ring.

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

Professor Graham Woan, from the University of Glasgow’s School of Physics & Astronomy, is one of the authors of the paper. He said: “Late last year, a colleague pointed me to data from YouTuber Chris Budiselic, who wanted to make a replica of the calendar ring and was investigating ways to determine how many holes were in it.

“It seemed like an interesting problem, and I thought I could solve it in a different way over the Christmas holidays. So I started working with 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 remaining holes and the placement of the six surviving ring fragments. His results provided strong evidence that the mechanism’s calendar ring contained 354 or 355 holes.

At the same time, a colleague of Professor Woan 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 the signals picked up by the LIGO gravitational wave detectors, which measure the tiny ripples in spacetime caused by massive astronomical events such as the collision of black holes, as they pass through Earth to go. the calendar ring.

The Markov Chain Monte Carlo and nested sampling methods used by Woan and Bayley produced an extensive probabilistic set of results, again suggesting that the ring most likely contained 354 or 355 holes in a circle of radius 77.1 mm, with an uncertainty of approximately 1/3 mm. . It also shows that the holes are precisely positioned with extraordinary accuracy, with an average radial variation of just 0.028mm between each hole.

Bayley, co-author of the paper, is a research associate at the School of Physics & Astronomy. He said: “Previous studies have suggested that the calendar ring probably followed the lunar calendar, but the dual techniques we employed in this paper 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 put into its making – the precision of the positioning of the holes would require extremely precise measuring techniques and an incredibly steady hand to make them to beat.

Professor Woan added: ‘It’s a nice symmetry that we’ve adapted techniques we use to study the universe today, to understand more about a mechanism that helped humans keep an eye on the sky almost two millennia ago .

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