Astronomers from the University of Glasgow utilized statistical modeling techniques developed for gravitational wave analysis to determine the probable number of holes in one of the damaged rings of the Antikythera mechanism-an ancient artifact featured in the movie "Indiana Jones and the Dial of Destiny."

While the film's version allowed the famous archaeologist to travel through time, the Glasgow team's findings provide fresh evidence that a component of the Antikythera mechanism was likely used to track the Greek lunar year. Additionally, they highlight the remarkable craftsmanship of the ancient Greeks.

The mechanism was discovered in 1901 by divers exploring a shipwreck near the Aegean island of Antikythera. Despite being broken into fragments and eroded, it was quickly recognized for its complex and intricately-tooled gears.

Decades of research and analysis have determined that the mechanism dates back to the second century BCE and functioned as a hand-operated mechanical computer. Exterior dials connected to internal gears enabled users to predict eclipses and calculate the astronomical positions of planets with unparalleled accuracy for its time.

In 2020, new X-ray images of one of the mechanism's rings, known as the calendar ring, revealed details of regularly spaced holes beneath the ring. However, the exact number of original holes was unclear due to the ring's incomplete state. Initial analysis by Antikythera researcher Chris Budiselic and colleagues suggested a range of 347 to 367 holes.

In a new paper published in the Horological Journal, the Glasgow researchers described using two statistical analysis techniques to reveal new details about the calendar ring. They demonstrated that the ring most likely had 354 holes, corresponding to the lunar calendar, rather than 365 holes, which would follow the Egyptian calendar. Their analysis showed that 354 holes are hundreds of times more probable than the previously suggested 360-hole count.

Professor Graham Woan of the University of Glasgow's School of Physics and Astronomy, a co-author of the paper, stated: "Towards the end of last year, a colleague pointed me to data acquired by YouTuber Chris Budiselic, who was looking to make a replica of the calendar ring and was investigating ways to determine just how many holes it contained. It struck me as an interesting problem, and one that I thought I might be able to solve in a different way during the Christmas holidays, so I set about using some statistical techniques to answer the question."

Professor Woan used Bayesian analysis, a technique that quantifies uncertainty based on incomplete data, to calculate the likely number of holes using the positions of the surviving holes and the placement of the ring's remaining six fragments. His results strongly indicated that the calendar ring contained either 354 or 355 holes.

Meanwhile, Dr. Joseph Bayley, a colleague at the University's Institute for Gravitational Research, also heard about the problem. He adapted techniques used by their research group to analyze signals from the LIGO gravitational wave detectors, which measure tiny ripples in spacetime caused by astronomical events like black hole collisions, to examine the calendar ring.

The Markov Chain Monte Carlo and nested sampling methods used by Woan and Bayley provided a comprehensive probabilistic set of results, suggesting that the ring most likely contained 354 or 355 holes in a circle of radius 77.1mm, with an uncertainty of about 1/3 mm. The analysis also revealed that the holes were positioned with extraordinary accuracy, with an average radial variation of just 0.028mm between each hole.

Dr. Bayley, a co-author of the paper, noted: "Previous studies had suggested that the calendar ring likely tracked the lunar calendar, but the dual techniques we've applied in this work greatly increase the likelihood that this was the case. It's given me a new appreciation for the Antikythera mechanism and the care that Greek craftspeople put into making it - the precision of the holes' positioning required highly accurate measurement techniques and an incredibly steady hand to punch them."

Professor Woan added: "It's a neat symmetry that we've adapted techniques we use to study the universe today to understand more about a mechanism that helped people 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 made and used by the Greeks."

Research Report:'An Improved Calendar Ring Hole-Count for the Antikythera Mechanism: A Fresh Analysis',

Related Links
University of Glasgow
Understanding Time and Space