Story by Jess Thomson •
Image of the Antikythera Mechanism (main) and gravitational waves (inset). The same statistical analysis used to study gravitational waves was used to predict the number of holes on a broken ring of the mechanism.
Special techniques used to study ripples in the universe may have helped researchers solve an ancient mystery.
Statistical modeling methods that were developed to study gravitational waves have been used to predict the structure of a broken section of a millennia-old artifact, according to a new paper in The Horological Journal.
These techniques allowed researchers to tell how many holes there were in one of the broken rings of the Antikythera mechanism, the ancient computer featured in Indiana Jones and the Dial of Destiny.
The Antikythera mechanism is an ancient Greek analog device dating back to between 100 and 200 BC that is considered the world's first known computer. Discovered in 1901 in a shipwreck off the coast of the Greek island of Antikythera, the device is thought to have been used to predict astronomical positions and eclipses for calendrical and astrological purposes.
The mechanism is composed of a complex system of bronze gears and dials housed in a wooden case. It has 30 gears, which is an incredibly sophisticated design for its time.
Its complexity suggests that the ancient Greeks had developed advanced knowledge of gear-based technology, far more advanced than previously thought for that era.
Related video: Gravitational Waves Create A 'Cosmic Symphony' That Scientists Are Tuning Into (Space) Duration 3:41 View on Watch
Modern imaging techniques, such as X-ray computed tomography, have been used to study the internal structure and functions of the mechanism. It has slowly become apparent that it was used to calculate the locations of the planets, predict eclipses, and track the months and years.
Thanks to X-ray imagery in 2020, one of the device's rings was discovered to have regularly spaced holes. Because the ring was broken, it wasn't clear how many rings it had originally, but researchers estimated between 347 and 367.
According to the new paper, the ring is likely to have had 354 holes, corresponding to the moon's cycle. According to their calculations, the ring having 354 holes is hundreds of times more likely than having 360 holes.
"We present a new analysis of the positions of holes beneath the calendar ring of the Antikythera Mechanism," the researchers wrote in the paper. "We significantly refine their estimate for the number of holes that were present in the full ring. Our 68 percent-credible estimate for this number, taking account of all the data, is 355.24 [plus or minus about 1.4].
"If holes adjacent to fractures are removed from the analysis, our estimate becomes 354.08. A ring of 360 holes is strongly disfavoured, and one of 365 holes is not plausible, given our model assumptions."
This mystery was solved using similar statistical modeling techniques as those used to study gravitational waves, which are ripples in the fabric of spacetime created by the movement of massive objects traveling outward from the source.
"Towards the end of last year, a colleague pointed to 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," paper co-author Graham Woan, a professor at the University of Glasgow School of Physics & Astronomy, said in a statement.
"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."
After using this technique, the scientists discovered the number of holes was likely 354 or 355.
"Previous studies had suggested that the calendar ring was likely to have tracked the lunar calendar, but the dual techniques we've applied in this piece of work greatly increase the likelihood that this was the case," co-author Joseph Bayley, also a researcher at the University of Glasgow, said in the statement.
"It's given me a new appreciation for the Antikythera mechanism and the work and care that Greek craftspeople put into making it – the precision of the holes' positioning would have required highly accurate measurement techniques and an incredibly steady hand to punch them."
While we will never truly know how many holes the ring actually had, the analysis gives pretty strong evidence for there having been 354.
"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," Woan said.
"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."