Decoding an Ancient Mystery

No one realized it at the time, but this lump would become known as one of the most mysterious archaeological discoveries ever. It was an ancient computing device now called the Antikythera mechanism. Scientists would spend the next century trying to understand how it worked. Their search would shed new light on what we know about ancient Greece.

“We don’t have anything else like it from ancient times,” says Alexander Jones. He is a historian at New York University. “We’re amazingly lucky that the shipwreck had something like this on it.”

For nearly a year, the strange artifact sat in storage in a Greek museum, gathering dust. Then, in 1902, a government official named Spyridon Stais came across it. By that point the fragile lump had broken into several smaller fragments. Some were covered in faint writing. Stais noticed something strange sticking out of the pieces: gears. The gears were complex, with neat triangular teeth like those inside a clock. They were unlike anything researchers had ever seen on something so old. 

“We knew of gears in the ancient world, like for windmills and watermills—simple mechanical gears,” says mathematician Tony Freeth. He is part of a research team devoted to studying the Antikythera mechanism at University College London in England. “But the gears in this mechanism are absolutely tiny, with teeth about a millimeter long.” 

The researchers in 1902 realized that the seemingly insignificant lump was actually the remnants of an elaborate bronze device. They determined that the device came from ancient Greece and that it dated back to sometime between 200 and 100 B.C. Yet, somehow, it contained technology that wasn’t thought to exist for another 1,400 years. For context, that’s like finding an Xbox in the ruins of a medieval castle! 

For nearly a year, the strange artifact was in a Greek museum. It sat in storage, gathering dust. But in 1902, a government official came across it. His name was Spyridon Stais. By that point the fragile lump had broken into several smaller pieces. Some pieces were covered in faint writing. Stais noticed strange gears sticking out of the pieces. The gears were complex. They had neat triangular teeth like those inside a clock. They were unlike anything researchers had ever seen on something so old.

“We knew of gears in the ancient world, like for windmills and watermills—simple mechanical gears,” says Tony Freeth. A mathematician, he is part of a research team at University College London in England. The team studies the Antikythera mechanism. “But the gears in this mechanism are absolutely tiny, with teeth about a millimeter long.”

The researchers in 1902 realized something: What seemed like an unimportant lump was actually parts of an complicated bronze device. They determined that the device came from ancient Greece. It dated back to sometime between 200 and 100 B.C. But somehow it contained technology that was not thought to exist for another 1,400 years. For context, that is like finding an Xbox in the ruins of a medieval castle!

Researchers quickly came up with several theories to explain the object.

“People got very excited about figuring out what it was,” says Freeth. “And they mostly got it wrong.” Some thought it was a navigation device, like a compass. Others argued that it was too advanced to have been built so long ago. They said it must have dropped into the sea during the Middle Ages (500-1500 A.D.).

Around 1905, German researcher Albert Rehm identified the device. He said it was a type of astronomy calculator. The people of ancient Greece were fascinated by the universe. They measured the passage of time based on the cycles of the sun and moon.

Rehm thought that the device was used to track the motion of the sun, moon, and planets. But he had no way to confirm his theories. The pieces of the Antikythera mechanism were very delicate. And they were battered after spending 2,000 years underwater. Researchers like Rehm could only examine the surface of the fragments. There was no way to look inside without destroying them.

That changed in the 1970s, with a British science historian named Derek de Solla Price. He used X-rays to reveal the artifact’s inner workings for the first time. The fragments contained about 30 overlapping gears.

Price and his team agreed with Rehm. They concluded that the machine had been made to track the movement of objects in the sky over time. Price hypothesized that each gear calculated the position of a specific object. For example, he found that one of the gears matched the rotation of the moon over a 19-year period.

Price used data from the X-rays to create the first model showing how the machine may have worked. But his model was not complete. He still could not figure out what most of the gears were designed to do.

Nearly 30 years later, Freeth, the mathematician, began studying the mechanism. In 2005, he and a team of researchers from the United Kingdom and Greece got permission to take 3-D scans of the fragments. These scans showed the interlocking gears in great detail. They also revealed a clearer view of the writing on the fragments—some of which described how the mechanism worked! 

One of the gears was used to predict eclipses. (An eclipse is the total or partial hiding of a star, moon, or planet by another.) Other gears tracked the planets. 

“It was a prediction machine,” says Freeth. “You could turn the input knob and for a future date find out where the planets are going to be, the phase of the moon, and whether there’s going to be an eclipse.” 

The mechanism also contained a countdown to the Olympic Games, which were founded in ancient Greece in 776 B.C. The Olympics “had nothing to do with astronomy but were important to Greek culture,” says Jones, the historian. The Games “united all the Greek-speaking people throughout the Mediterranean world.”

Nearly 30 years later, Freeth began studying the mechanism. In 2005, the mathematician worked with a team of researchers from the United Kingdom and Greece. They got permission to take 3-D scans of the fragments. The scans showed the interlocking gears in great detail. They also revealed a clearer view of the writing on the fragments. Some of that writing described how the mechanism worked!

One of the gears was used to predict eclipses. (An eclipse is the total or partial hiding of a star, moon, or planet by another.) Other gears tracked the planets.

“It was a prediction machine,” says Freeth. “You could turn the input knob and for a future date find out where the planets are going to be, the phase of the moon, and whether there’s going to be an eclipse.”

The mechanism also contained a countdown to the Olympic Games. The Olympics were founded in ancient Greece in 776 B.C. They “had nothing to do with astronomy but were important to Greek culture,” says Jones, the historian. The Games “united all the Greek-speaking people throughout the Mediterranean world.”

Scientists have now been studying the Antikythera mechanism for 120 years. Their work has offered insight into ancient Greek astronomy. It also has revealed that ancient Greek astronomy was more advanced than previously thought. The civilization was able to predict lunar eclipses, right down to the exact date and time. That took complex mathematical calculations, Jones says.

Still, many questions remain unanswered: Who built this device? How did it end up on the doomed ship? And why have we not found anything else like it?

“The Antikythera mechanism has told us things about ancient Greek technology that we had no idea could possibly be true,” says Freeth. But, he adds, “it hasn’t given up all its secrets yet.”