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

Techniques developed to analyze 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 workings of the oldest known analog computer.

Astronomers from the University of Glasgow used statistical modeling techniques developed to analyze gravitational waves to establish the likely number of holes in one of the broken rings of the Antikythera Mechanism, an ancient artifact featured in the film “Indiana Jones and the Dial of Destiny.”

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 lunar year Greek. They also offer new insight into the remarkable craftsmanship of the ancient Greeks.

The mechanism was discovered in 1901 by divers exploring a sunken shipwreck near the Aegean island of Antikythera. Although the shoebox-sized mechanism broke into fragments and eroded, it quickly became apparent that it contained an intricate series of unusually complex gears.

Decades of subsequent research and analysis established that the mechanism dates from the second century BCE and functioned as a kind of manual mechanical computer. The outer dials connected to the internal gears allowed users to predict eclipses and calculate the astronomical positions of the planets on any 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 new details of regularly spaced holes located beneath the ring. However, because the ring was broken and incomplete, it was unclear how many holes there originally were. Initial analysis by Antikythera researcher Chris Budiselic and colleagues suggests that this figure is likely between 347 and 367.

However, in a new article published in the Watchmaking JournalGlasgow researchers describe how they used two statistical analysis techniques to reveal 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, from the School of Physics & Astronomy at the University of Glasgow, is one of the authors of the paper. He said: “Towards the end of last year, a colleague showed me data acquired by YouTuber Chris Budiselic, who was looking to create a replica of the calendar ring and was investigating ways to determine the number of holes it contained.

“This seemed like an interesting problem and one that I thought I could solve in a different way over the Christmas break. So I started using statistical techniques to answer this 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 position of surviving holes and the location of six surviving fragments 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 of Gravitational Research, Dr Joseph Bayley, had also heard about the problem. He adapted techniques used by their research group to analyze signals picked up by LIGO gravitational wave detectors, which measure tiny ripples in space-time caused by massive astronomical events like colliding black holes, during their passage through the Earth, to scrutinize the calendar ring.

The Markov chain Monte Carlo and nested sampling methods used by Woan and Bayley provided a comprehensive set of probabilistic 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 reveals that the holes were positioned with extraordinary precision, with an average radial variation of just 0.028mm between each hole.

Bayley, co-author of the paper, is a research associate in the School of Physics & Astronomy. He said: “Previous studies had suggested that the calendar ring probably followed the lunar calendar, but the two techniques we applied in this work significantly increase the likelihood that this is the case.

“It gave me a new appreciation for the Antikythera Mechanism and the work and care taken by Greek artisans in its manufacture. The precision of the positioning of the holes would have required very precise measuring techniques and an incredibly steady hand to perforate them.

Professor Woan added: “It is a careful symmetry that we have adapted the techniques we use to study the universe today to better understand a mechanism that helped people track the sky almost two millennia.

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