Gravitational Wave Scientists Are Unraveling the Mysteries of the World’s Oldest Analog Computer

A new study challenges a core assumption about the Antikythera mechanism, a 2,000-year-old device that inspired the latest “Indiana Jones” film

Antikythera mechanism
Created more than 2,000 years ago, the Antikythera mechanism tracked the movements of celestial bodies. Louisa Gouliamaki / AFP via Getty Images

More than two millennia ago, a device known as the Antikythera mechanism was used to predict the movements of celestial bodies using a complex system of gears. The artifact is known today as the world’s oldest computer.

Ever since divers recovered it at the site of a Mediterranean shipwreck in 1901, the mysterious device has sparked fascination. It even inspired the creative team behind the Indiana Jones franchise, which invented a fictionalized version of the artifact for last year’s Indiana Jones and the Dial of Destiny.

Now, two astronomers at the University of Glasgow have added a new wrinkle to the Antikythera mechanism’s story. In a study published this month in the Horological Journal, co-authors Graham Woan and Joseph Bayley offer a new interpretation of the mechanism’s calendar ring, a piece of the device that once featured hundreds of holes.

Because only fragments survive, the exact number of holes is unclear. For many years, researchers thought the ring may have been used as a solar calendar, with 365 holes representing the days of the year. Woan and Bayley dispute this, arguing that the ring once functioned as a lunar calendar and featured 354 holes.

The lunar calendar theory was first proposed in a 2020 study led by Chris Budiselic, a YouTuber and independent researcher. When the Glasgow astronomers learned of Budiselic’s work, they were intrigued: What if they could use techniques from their field to solve the mystery?

“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,” says Woan in a statement.

Using a technique called Bayesian analysis, which relies on probability to answer questions about incomplete data, Woan calculated the likely number of holes in the calendar ring based on the spacing of the surviving holes and the position of the ring’s surviving fragments. He found that the ring likely contained either 354 or 355 holes, about the length of a lunar year.

Meanwhile, Bayley decided to approach the problem by adapting techniques typically used in gravitational wave astronomy, which studies ripples in spacetime caused by the movements of massive cosmic objects, to “scrutinize the ring.” This analysis also suggested that the ring most likely contained 354 or 355 holes.

“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,” says Woan in the statement.

The astronomers’ findings contradict widely accepted assumptions about the device. “It’s a slightly contentious idea,” Woan tells the New York TimesBecky Ferreira. He adds that although he and Bayley are not experts on the Antikythera mechanism, “the evidence is rather clear.”

Not everyone agrees. Mechanical engineer Tony Freeth, who is an expert on the mysterious artifact, tells the Times that the study’s conclusion is “just wrong,” noting that the machinery already contains a more precise lunar calendar. Why, then, would the inventors include another?

Meanwhile, other researchers have praised the new study. Mike Edmunds, an astrophysicist who chairs the Antikythera Mechanism Research Project, tells the Times that there is “no obvious reason to doubt” the new estimate of 354 holes. However, he doesn’t think those holes necessarily represent a lunar calendar. “It is not at all clear how it would work and how it would relate to the markings on the front of the calendar ring,” he says.

Diomidis Spinellis, a software engineer at the Athens University of Economics and Business, found the new research to be convincing. “The Antikythera mechanism is a gift that keeps on giving,” Spinellis, who has researched the device but was not involved in the study, tells Live Science’s Owen Jarus. “Despite its severe corrosion and many missing elements, the application of increasingly sophisticated technologies and innovative cross-disciplinary analysis continues to provide impressive insights into this remarkable artifact.”

The device is a technological marvel that was far ahead of its time. It featured gear wheels, dials and pointers “more than a millennium before 13th-century Europeans invented the first mechanical clocks,” as Smithsonian magazine’s Meilan Solly wrote last year. “The ancients used it to predict eclipses, track the movement of the sun and the moon, and even see when sporting events like the Olympics were scheduled to take place.”

The latest research has given enthusiasts more to marvel over—even if the new findings are perhaps “less supernaturally spectacular than those made by Indiana Jones,” says Woan in the statement. The two scientists hope their work will provide a “[deeper] understanding of how this remarkable device was made and used.”

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