The Antikythera mechanism, an ingenious calculator made 2,200 years ago, has inspired awe and enchantment ever since it was recovered from a shipwreck near a Greek island in 1901. Generations of researchers have unraveled many mysteries about the device, which is often described as the world’s first analog computer, though much remains unknown.
A study published this month in The Horological Journal challenges a core assumption about the mechanism that could upend understanding of the complex timepiece’s form and function. But rather than using standard tools of archaeology, the scientists reached their conclusions by drawing from the methods of gravitational wave astronomy, a field that tunes into subtle ripples in space-time that result from cosmic disruptions.
Graham Woan, a professor of astrophysics at the University of Glasgow, and Joseph Bayley, a research associate there, said that the mechanism’s calendar ring, a circular feature that survived only in fragments, had once contained 354 holes, which corresponds to a lunar calendar of 354 days. That result conflicts with earlier research that identified the ring as a solar calendar, lined with 365 holes.
“It’s a slightly contentious idea,” said Dr. Woan, who acknowledged that he and Dr. Bayley are not experts on the device. “However, the evidence is rather clear.”
If the calendar ring does represent a lunar year, it would invalidate current models of the mechanism. For that reason, some Antikythera scholars remain skeptical of the new study.
“It’s just wrong,” said Tony Freeth, an honorary professor at University College London and an expert on the Antikythera mechanism. He noted that there was already a much more precise lunar calendar, based on the 19-year Metonic cycle, embedded in the machinery.
“Why put a second lunar calendar on the mechanism when you’ve already taken a lot of trouble to construct a lunar calendar of great accuracy and sophistication?” Dr. Freeth said.
The Antikythera mechanism is no stranger to controversy and speculation, in part because it was so ahead of its time in the second century B.C. Its intricate mesh of gears, dials and plates produced a model of the cosmos that tracked cycles of the moon, the sun, the planets and constellations, while also predicting eclipses and marking the timing of athletic games, such as the ancient Olympics. The artifact also inspired the titular “dial of destiny” in the latest Indiana Jones movie.
For decades, researchers have viewed the calendar ring as a solution to the mathematically finicky solar year, which lasts 365.24 days. Just as leap years are built into our calendars, the holes in the ring allowed it to be manually rotated by one day every four years so it didn’t drift off track.
The solar model was first called into question in a 2020 study by a team of researchers and enthusiasts. By analyzing X-ray images of the mechanism’s remaining holes, the study claimed to “displace the century-long assumption of a 365-day calendar on the Antikythera mechanism, proposing instead that it is a 354-day lunar calendar.”
Dr. Woan and Dr. Bayley thought that the methods they were using to analyze gravitational waves could place tighter constraints on the original number of holes.
“It’s such a well-defined and clear problem that we couldn’t resist analyzing it in the same way as we would analyze an astronomical problem,” Dr. Woan said.
They ran measurements of the surviving holes, including size and spacing, through their astronomical software. The results strongly favored a complete ring with 354 holes.
Mike Edmunds, an emeritus professor of astrophysics at Cardiff University in Wales and the chair of the Antikythera Mechanism Research Project, said there seemed to be “no obvious reason to doubt” the study’s estimate of 354 holes. Still, he remained unconvinced that the mechanism carried a redundant lunar calendar.
“The suggestion that 354 represents a lunar calendar does not seem to have any other support from within the mechanism — 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,” Dr. Edmunds said. “But the establishment of the count may perhaps tell us something about the level of precision in construction judged necessary and used by the mechanism’s builders.”
Whatever was the original nature of the calendar ring, the new study demonstrates that the Antikythera mechanism is not a static relic, but a dynamic puzzle with many missing pieces yet to be found.
The mechanism “keeps giving us new stuff,” Dr. Freeth said. “It’s extraordinary. Year after year, we’ve found these astonishing things in it.”