University of Glasgow
Techniques developed to analyse ripples in space-time detected by one of the 21st century’s most sensitive scientific instruments are helping to shed new light on the functioning of the oldest analogue computers.
Astronomers at the University of Glasgow have used statistical modelling techniques developed to analyse gravitational waves to estimate how many holes there are in one of the broken rings of the ancient artefact featured in the film The Antikythera Mechanism. Indiana Jones and the Dial of Destiny.
While the film version allowed intrepid archaeologists to travel through time, the Glasgow research team’s work provides new evidence that one of the Antikythera Mechanism’s components was likely used to track the Greek lunar calendar – and also offers new insights into the incredible craftsmanship of the ancient Greeks.
Discovery of the Antikythera Mechanism
The mechanism was discovered by divers exploring a sunken ship near the island of Antikythera in the Aegean Sea in 1901. The shoebox-sized mechanism was shattered and corroded, but it was soon revealed to contain a series of intricately crafted gears.
Subsequent decades of research and analysis revealed that the mechanism dates back to the 2nd century BCE and functioned as a kind of manual mechanical computer: an external dial connected to internal gears allowed its user to predict eclipses and calculate the astronomical positions of the planets for any given date with an accuracy unmatched by any other device of the time.
The inscriptions on the Antikythera Mechanism led to a number of breakthroughs in the creation of the “theoretical” reconstruction of the Antikythera Mechanism. (Tony Freese et al. / Nature)
Reevaluation of mechanism specifications
In 2020, new X-ray images of one of the machine’s rings, known as the calendar ring, revealed new details about the regular rows of holes beneath it. But because the ring was broken and incomplete, it was unclear how many holes it originally had. An initial analysis by Antikythera researcher Chris Budiselic and his colleagues suggested that the number was probably between 347 and 367.
Now, Watch JournalThe Glasgow researchers explain how they used two statistical analysis methods to uncover new details about the calendar wheel.
The analysis found that the ring was far more likely to have had 354 holes, corresponding to the lunar calendar, than 365 holes, according to the Egyptian calendar, which is hundreds of times more likely than the 360 ​​holes that previous studies had suggested were a possible number.
Professor Graham Warne, from the University of Glasgow’s School of Physics and Astronomy and one of the authors of the paper, said: “Late last year a colleague pointed me to some data available from YouTuber Chris Budiselic, who was trying to make a replica of a calendar ring and was researching ways to work out how many holes there are in the ring.”
“I thought this was an interesting problem and thought there might be a different way to solve it over the Christmas holidays, so I set out to answer the question using statistical methods.”
Antikythera Mechanism (Fragment A – Front); the largest gear in the mechanism is visible, approximately 14 centimetres (5.5 inches) in diameter.CC BY-SA 3.0)
Statistical Probability and Gravitational Waves
Professor Warne used a technique called Bayesian analysis – a method that quantifies uncertainty based on incomplete data with probability – to calculate an estimate of the number of holes in the mechanism from the positions of the remaining holes and the arrangement of the ring’s six remaining fragments. His results showed strong evidence that there were either 354 or 355 holes in the mechanism’s calendar ring.
At the same time, Warne’s colleague, Dr Joseph Bailey of the University’s Gravitational Laboratory, had also heard about the problem. He adapted techniques used by the group to probe the calendar rings by analysing signals picked up by the LIGO gravitational wave detectors, which measure tiny ripples in space-time caused by massive astronomical events such as colliding black holes passing by Earth.
Warne and Bailey’s Markov chain Monte Carlo and nested sampling methods provided a comprehensive set of probabilistic results, again suggesting that the ring had 354 or 355 holes within a circle of radius 77.1 mm, with an uncertainty of about 1/3 mm. They also found that the holes were precisely positioned with extraordinary precision, with the average radius variation between each hole being just 0.028 mm.
Co-author Bailey, a research associate in the Department of Physics and Astronomy, said:
“Previous studies have suggested that the calendar ring likely followed a lunar calendar, but the dual techniques we applied in this study make it much more likely that this is the case.”
This has led to a new appreciation for the Antikythera Mechanism and the effort and care that Greek artisans put into creating it. Getting the placement of the holes exact would have required extremely precise measuring techniques, and an incredibly steady hand to drill them.”
Professor Warne added:
“This is a fascinating symmetry that allows us to apply techniques used to study the universe today to better understand the mechanisms that helped people almost 2,000 years ago understand the movements of celestial bodies.”
“While our discoveries about the Antikythera Mechanism are not as supernaturally spectacular as the Indiana Jones mechanism, we hope they will help us better understand how this incredible device was built and used by the Greeks.”
“Improving the number of holes in the Antikythera Mechanism’s calendar ring: a new analysis‘teeth, Watch Journal.
Image above: The Antikythera Mechanism on display at the National Archaeological Museum, Athens. Credit: Joyofmuseums/CC BY-SA 4.0
This article first appeared in theGravitational wave researchers shed new light on Antikythera Mechanismit has been lightly edited and the spelling has been Americanized.
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