Fresh research on waves in the structure of space-time suggests that the nearly 2,000-year-old cosmic calculator followed the lunar calendar instead of the solar one.
The hand-powered “Antikythera Mechanism” was recovered in parts from a sunken shipwreck in the Aegean Sea in 1901, sparking more than a century of research into how the device was made – and why. The box-shaped mechanical computer used gears and dials to track ancient astronomical events such as solar eclipses and planetary movements.
Now scientists are using cutting-edge work surrounding gravitational waves, which are ripples in space-time caused by events such as black hole mergers or interstellar collisions, to help unravel the mechanics of the ancient Greek gears of Antikythera. (The device is named after the Greek island near where it was found.)
“It gave me a new appreciation for the Antikythera Mechanism and the work and care that Greek craftsmen put into making it—the precision of the placement of the holes would have required highly precise measuring techniques and an incredibly steady hand to punch them,” study co-author Joseph Bayley, a research scientist in the Department of Physics and of astronomy at the University of Glasgow, said in a statement.
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The new study builds on previous research from 2021, which used X-rays to show “fresh details of regularly spaced holes” beneath one of the mechanism’s broken rings, the statement said. According to the British Horological Institute, this part, known as the “calendar ring”, is marked with the ancient Egyptian names of the months engraved in ancient Greek.
Computed X-ray imaging “also revealed inscriptions describing the movements of the Sun, Moon and all five planets known in antiquity and how they were depicted in front as the ancient Greek cosmos,” according to an older 2021 study published in Nature.
This 2021 study also noted the interdisciplinary nature of the Antikythera mechanism: “Solving this complex 3D puzzle reveals a creation of genius – combining cycles from Babylonian astronomy, mathematics from Plato’s academy, and ancient Greek astronomical theories.”
A new study in the Horological Journal suggests that scientists can predict how many holes there were in the calendar ring using statistical models derived in part from gravitational wave research. The team found that the calendar ring probably contains 354 openings, which follows a lunar year of 354 days (or 12 cycles of the waxing and waning moon). Unlike the 365-day solar year that most of the world uses today, the ancient Egyptian calendar followed a lunar year, as does the Islamic calendar, which is still widely used around the world.
The team also drew inspiration from YouTuber and machinist Chris Budiselica’s Clickspring channel. Budiselic builds a replica of the Antikythera Mechanism and conducts independent research. Budiselic’s team suggested that the ring could contain between 347 and 367 wells.
One form of analysis, led by Glasgow astrophysics professor Graham Woane, came from Bayesian statistics. It “uses probability to quantify uncertainty based on incomplete data,” the statement said.
The second part, from gravitational wave research led by Bayley, was adapted from statistics used with data from the Laser Interferometer Gravitational-Wave Observatory (LIGO), which searches for ripples in space-time. (Woan is also a LIGO researcher.)
Both statistical studies independently suggested that the ring has either 354 or 355 holes. Previous studies have suggested that the lunar calendar was more important to the creators of the Antikythera mechanism, but the new study “makes it very likely that it was,” Bayley said in a statement.
“It’s a neat symmetry,” Woan added, “that we’ve adapted the techniques we use to study the universe today to better understand the mechanism that helped people observe the heavens nearly two millennia ago.”