Have you ever come across something odd, and wondered what it was supposed to do? Did you wish you could open it up and find out what was inside?
In 1900, a team of divers went looking for sponges off the coast of Greece. But what they found proved to be much, much more interesting. Wearing a waterproof canvas suit and a helmet with an air hose, the first diver was lowered into the water. When he reached the bottom of the Mediterranean sea, something strange caught his eye. It looked like a human arm. Looking around, he noticed more body parts, but fortunately, he realized quickly that these weren’t from real people. It was actually something very exciting: sunken treasure! He had found pieces of bronze sculptures from an ancient shipwreck! Soon, the Greek government organized an expedition to pull up the trove of artifacts.
The Mediterranean Sea is dotted with hundreds of shipwrecks from the ancient Greek, Roman, Egyptian, and other civilizations that ringed the sea thousands of years ago. Most ships weren’t carrying anything very interesting: containers of olive oil or wine, unsculpted marble, or other stone. But this shipwreck was different. It sank in bad weather around 60 BCE, taking with it a cargo of beautiful bronze and marble sculptures, jewelry, and colorful glassware.
It also had one other thing: an object that looked like little more than a slab of corroded metal with some obscure Greek lettering on it. About the size of a shoebox and not obviously anything, workers almost threw it back in the water. But fortunately, one of the expedition’s organizers stopped them. It’s a good thing he did, because that hunk of corroded metal turned out to be the most important treasure pulled up from the wreck.
One of those things you wish you could break open and look inside. A two thousand-year-old device that no one thought possible before.
It became known as the Antikythera mechanism, after an island near the shipwreck. Dozens of historians and scientists would work for over a century to find out exactly what it was and how it worked.
The mechanism was in bad shape when it was pulled out of the water. Originally made of bronze, it was severely corroded. Corrosion is when metal changes into other minerals when it interacts with other substances around it. Rust is a type of corrosion that happens when metals with iron in them react with oxygen in air and water. The mechanism had so much corrosion that it had clearly been in the water a long time. Workers found one big piece and many smaller pieces of the device. To make matters worse, the big piece broke into three soon after it was pulled from the water. All of the pieces were taken to the National Archeological Museum in Athens, Greece.
At first, no one really knew what to make of the device. Because of how delicate and damaged it was, researchers definitely couldn’t just open it up and look inside. You could see gears from the outside, but there was clearly an inside of the device that researchers couldn’t see. The Greek writing on the outside was very hard to read. Scholars managed to read only a few words: the names of months and planets, and numbers that seemed to relate to the phases of the moon.
A few scholars proposed that the object was some sort of navigational device or a planetarium that showed the rotations of the moon, sun, and planets. But these scholars didn’t do much to try to figure out exactly how the device worked. They didn’t have much opportunity to either, since, in the early 1900s, they had no way of seeing inside the object without destroying it.
Within a few years, interest in the Antikythera mechanism died down. For decades, not many people bothered to pull it out of the museum’s storage boxes and study it in more detail. Finally, in the early 1950s, someone took notice. Derek de Solla Price, a historian of science, had always been interested in things driven by systems of gears and clockwork. He had already studied other ancient devices used to help calculate the positions of the sun, moon, and planets. The Antikythera mechanism was older and looked more complex than any similar device. Price thought he could unravel its mysteries.
In 1958, Price got the chance to visit Athens and study the device in person. The National Museum would let him examine the pieces, and hold them in his own hands. Price set about taking the most careful measurements of the fragments that anyone had attempted so far. It was hard, detailed work, measuring gears that were half corroded, counting the tiny teeth. He drew detailed pictures and carefully pieced the fragments together like a jigsaw puzzle. He was convinced that the mechanism was an ancient astronomical computer that could not only show the rotation of the planets, moon, and sun but also predict precisely where they would be on a given date.
But despite his careful measurements and calculations, Price still wasn’t sure exactly how all the gears worked together. What no one knew was that there were still more tiny gears inside, waiting to be discovered. But you don’t just break an ancient artifact like this open, even to learn more about it. Price would need to find a way to look inside, see through the outer layers to the inner workings.
Price returned home, and for many years didn’t continue his work on the device. But in 1971, he learned about a new x-ray technology that would take images through metal objects. As soon as the museum agreed, Price was back in Athens, where he and an assistant took the images. These images showed a jumble of overlapping gears and teeth that would take some time to decipher, but they were the first peek inside the mechanism. Price counted over 30 gears in total, including 6 that couldn’t be seen at all from the outside. He was able to count the teeth on the gears. And the best part? He was able to use this information to build a working model of the device. By this time, Price thought the device probably only showed the workings of the sun and moon, not the planets. His model didn’t work perfectly, but it was progressing. The mechanism still held secrets, and it would take better technology to reveal them
It would be almost another 20 years before those new technologies would come along, and 30 before the device would be fully understood. The new efforts kicked off in 1988, with the team of Michael T. Wright and Allan Bromley. Wright and Bromley took new x-ray images using more advanced techniques. The images allowed them to make better measurements and see more clearly how things fit together when the device was new. Wright was convinced that the device also tracked the planets. The gears that still sat in the mechanism all seemed to help show the motions of the moon and sun. But Wright thought that the broken-off parts looked like they might have connected to another system of gears, and maybe these gears helped show the motions of the planets. Wright constructed a model of the mechanism based on his investigations, making intelligent guesses about the gears that seemed to be missing.
In 2005, another team came together to study the mechanism. The team included mathematicians, physicists, historians, and experts on ancient Greek artifacts and science. X-ray technology had improved even more, and they thought they could get even better images of the inside of the device. They were also able to take much better photographs of the outside of the object. They found that Wright was correct in most of his observations, and he updated his model based on the new information.
So…how DID the Antikythera mechanism work?
A dial on the front of the device showed the months of the solar year and the constellations of the zodiac. The solar year is based on the cycles of the sun. The calendar that most of the world uses now is based on the solar year, and so were the ancient Egyptian and Roman calendars. You would turn a knob on the outside to operate the machine. This turn of the knob would set in motion dozens of hidden gears inside the box. Seven pointers on the face spun around to show where the sun, moon, and five planets were relative to the constellations of the zodiac for any date you chose. The Greeks only knew about five planets, and the system reflected their belief that the Earth was at the center of the solar system, instead of the sun. Each full turn of the sun pointer equaled one solar year.
On the back were two more sets of dials, operated using the same knob. The upper dial showed lunar months–from full moon to full moon. This dial would allow you to see how days in the lunar calendar lined up with days in the solar calendar. A small dial inside this one showed when athletic games, like the Olympics, would happen. Finally, the second large dial on the back showed when solar and lunar eclipses would occur.
The Antikythera device is the most complicated machine we have from the ancient world. As far as we know, nothing else so complex was built until the middle ages.
As far as we know.
Writers in the ancient Greek and Roman world did describe complicated “planetariums” –devices that showed how the planets, sun, and moon moved through the sky. So maybe similar devices were constructed. Maybe the Antikythera mechanism was just one example. Maybe others were lost and buried, or their bronze pieces melted down to make new things. We may never know, but it’s exciting to think about the possibilities! Maybe someday, you’ll discover a mystery. If that happens, I hope you’ll ask questions, examine it from all angles, and learn from it. And maybe, you’ll solve it!
Jones, Alexander (2017) A Portable Cosmos: Revealing the Antikythera Mechanism, Scientific Wonder of the Ancient World. Oxford University Press, New York.