# The Antikythera Mechanism: The Ancient Computer Found by Sponge Divers In 1900, a storm drove Greek sponge divers to a tiny island, where they found a Roman-era shipwreck. Among the statues was a corroded lump of bronze that turned out to be a geared machine for predicting the sky, built more than 2,000 years ago. - Source: https://amazingfactss.com/stories/antikythera-mechanism - Published: 2026-11-14; updated: 2026-11-14 - Topic: Ancient technology - Publisher: Amazing Facts editorial team (https://amazingfactss.com/editorial-policy) - Illustrations are AI-generated reconstructions, not photographs. ## Quick facts - **Where:** Shipwreck off Antikythera, between Crete and the Peloponnese, Greece - **Wreck found:** Spring 1900, by sponge divers from Symi - **Mechanism noticed:** 1902, by the archaeologist Valerios Stais - **Made:** 2nd or early 1st century BC (debated); the ship sank about 70 to 60 BC - **What survives:** 82 fragments, including 30 bronze gears - **Where to see it:** National Archaeological Museum, Athens In the spring of 1900, two boats of sponge divers from the island of Symi were heading home from the waters off North Africa. A storm blew up, and the captains, Dimitrios Kontos and Fotis Lykoudis, took shelter beside Antikythera, a small rocky island between Crete and mainland Greece. When the weather calmed, they did what sponge divers did: they went down to look. What one of them found on the seabed changed the history of technology. ## The divers who saw "dead bodies" The divers wore canvas suits and heavy copper helmets, with air pumped down from the boat. One of them, Elias Stadiatis, went down near the island's rocky shore. According to the story the divers told afterwards, he came back up shaking and almost unable to speak. He described a heap of rotting corpses and horses lying on the seabed. Kontos went down himself. The "bodies" were statues of bronze and marble, scattered around the remains of an ancient ship at a depth of roughly 45 to 55 metres. He brought up a bronze arm as proof. ![A diver in a copper helmet sits on a boat deck looking shaken](https://amazingfactss.com/img/stories/antikythera-diver.jpg "Illustration: an AI-generated reconstruction of a diver of the period, not a likeness of Elias Stadiatis.") ## One of the first great underwater excavations The divers reported their find to the Greek authorities in Athens. With the support of the government and a navy ship, the same sponge divers began recovering the wreck in late 1900. It was one of the first major underwater archaeological operations in history, and it was dangerous. Working at that depth with no understanding of decompression, one diver died and two were left paralysed by what we now call the bends. Over about ten months they recovered an extraordinary cargo: bronze statues, including the figure now known as the Antikythera Youth, the bronze head of a bearded philosopher, dozens of marble statues, glassware, pottery, jewellery and coins. Coins from the wreck suggest the ship went down in the 70s or 60s BC. It was probably a large merchant ship carrying luxury goods from the eastern Aegean towards Rome. ## A gear inside a lump of bronze Among the finds were several shapeless, corroded lumps of bronze and wood. They were taken to the National Archaeological Museum in Athens, where for months they attracted little attention while the statues were studied and restored. In May 1902, the archaeologist Valerios Stais looked more closely at one of the lumps, which had split apart as its wooden parts dried out. Inside he saw a gear wheel, with precise triangular teeth, and faint inscriptions in Greek. Some scholars thought it must be an astronomical instrument. Others argued that geared machinery of this kind was simply too complex to be ancient, and that it must have come from a later wreck. ![A greenish, corroded fragment with the outline of a gear wheel visible inside](https://amazingfactss.com/img/stories/antikythera-fragment.jpg "Illustration: an AI-generated impression of a corroded fragment. The real fragments are in Athens.") ## Seeing inside with X-rays For decades, the mechanism stayed a puzzle. The breakthrough came in the 1950s, when the British physicist and historian of science Derek de Solla Price began studying it. Working with the Greek radiographer Charalampos Karakalos, he used X-ray and gamma-ray images to count gear teeth hidden inside the fragments. In 1974 he published Gears from the Greeks, arguing that the device was a calendar computer that modelled the movements of the Sun and Moon. Michael Wright, a curator at the Science Museum in London, later corrected and extended Price's work and built working reconstructions. Then, in 2005, the Antikythera Mechanism Research Project brought a powerful X-ray CT scanner to Athens. The scans revealed hidden gears, and thousands of characters of text that had been invisible for two thousand years, some of it effectively a user's manual engraved on the device. ![A monitor displays an X-ray scan revealing gears inside a fragment](https://amazingfactss.com/img/stories/antikythera-xray.jpg "Illustration: an AI-generated scene. The real scans were made with an X-ray CT system in 2005.") ## What the machine could do Today, 82 fragments survive, containing 30 bronze gears. The largest gear is about 13 centimetres across, with 223 teeth. The complete device sat in a wooden case about the size of a shoebox and was operated by turning a handle or knob on its side. On the front was a large dial with two rings: the signs of the zodiac and the 365-day Egyptian calendar. Pointers showed the positions of the Sun and Moon. A small ball, half pale and half dark, rotated to show the phase of the Moon. Inscriptions and fragments of the front plate suggest that the five planets visible to the naked eye, Mercury, Venus, Mars, Jupiter and Saturn, were also shown. On the back were two large spiral dials. One tracked a 19-year cycle that keeps lunar months in step with solar years, used for calendars. The other followed the 223-month Saros cycle, which allowed eclipses of the Sun and Moon to be predicted, with symbols noting the month and time of day. A smaller dial showed the four-year cycle of Greek athletic games, including the Olympics. ![A bronze dial with a half-dark, half-silver ball showing the phase of the Moon](https://amazingfactss.com/img/stories/antikythera-moon-dial.jpg "Illustration: an AI-generated impression of a lunar phase display.") One of the most impressive details is a pair of gears linked by a pin and slot, which made the Moon's pointer speed up and slow down. This copies the way the Moon really appears to move faster at some points in its orbit, a theory associated with the astronomer Hipparchus in the 2nd century BC. In 2021, researchers at University College London published a new model showing how the planets might have been arranged on the front dial, based on the inscriptions and the surviving gears. ## Who built it, and when? Nobody knows who made the mechanism. Its astronomy draws on centuries of Babylonian observation and Greek geometry. Some researchers have linked it to Rhodes, a centre of astronomy where the philosopher Posidonius worked. The month names on its calendar, though, point to a Corinthian colony, possibly Syracuse in Sicily, the home of Archimedes, who died more than a century before the ship sank. Its date is also debated. The wreck shows that it was made before about 60 BC. Studies of its inscriptions and of the eclipse cycle have suggested dates ranging from the late 3rd century to the early 1st century BC. Ancient writers mention devices like it. The Roman statesman Cicero describes a bronze sphere built by Archimedes that showed the movements of the Sun, Moon and planets, and another made by Posidonius. Until the mechanism was understood, these accounts were easy to dismiss. ## A lost technology What makes the Antikythera mechanism so startling is not that it was impossible, but that nothing like it survives for a very long time afterwards. The next known machines with comparable gearing are the astronomical clocks of medieval Europe, built more than 1,400 years later. Somewhere along the way, the knowledge needed to build such devices was lost, or at least no physical example has survived. The wreck has also not finished giving up its secrets. Jacques Cousteau's team dived on it in the 1950s and 1970s, and new excavations since 2014 have recovered more finds, including human remains in 2016. The fragments are on display at the National Archaeological Museum in Athens. They look modest: greenish slabs of corroded metal in a glass case. But inside them is the oldest known geared calculating machine in the world, found because a storm happened to push a few sponge divers towards a small island. ## Legend or fact? - **Claim:** It is so advanced it must be alien or 'out of place' technology. **Verdict:** Not quite. Its astronomy matches known Greek theories, its inscriptions are in Greek, and ancient writers such as Cicero describe similar devices. It is remarkable, but it fits its time. - **Claim:** It is the world's first computer. **Verdict:** Partly true. It is often called the oldest known analogue computer because its gears calculate astronomical positions. It could not be programmed, so it is better described as a mechanical calculator. - **Claim:** The first diver to see the wreck thought he had found dead bodies. **Verdict:** True. According to the story told by the divers, Elias Stadiatis surfaced terrified, describing corpses and horses on the seabed. They were bronze and marble statues. - **Claim:** Nothing as complex is known for more than a thousand years afterwards. **Verdict:** True. No surviving object comes close until the astronomical clocks of medieval Europe in the 14th century, though written sources suggest other geared devices existed in antiquity. ## Timeline - **2nd century BC:** The mechanism is probably designed and built, drawing on Babylonian and Greek astronomy. - **c. 70 to 60 BC:** A large cargo ship carrying luxury goods sinks off Antikythera. - **Spring 1900:** Sponge divers sheltering from a storm discover the wreck. - **1900 to 1901:** Divers recover statues and other finds with the Greek government's support; one diver dies. - **1902:** Valerios Stais notices a gear wheel in a corroded lump of bronze. - **1974:** Derek de Solla Price publishes Gears from the Greeks, based on X-ray images. - **2005 to 2006:** CT scans reveal hidden gears and thousands of characters of inscription. - **2021:** A UCL team publishes a new model of the mechanism's display of the planets. ## Questions people ask ### What did the Antikythera mechanism do? Turned by a handle, it showed the positions of the Sun and Moon in the zodiac, the phase of the Moon, the dates of eclipses and a calendar of the four-year cycle of Greek athletic games. Researchers believe it also showed the planets known at the time. ### How old is the Antikythera mechanism? The ship sank around 70 to 60 BC, so the mechanism is at least that old. Studies of its astronomy and lettering suggest it was made in the 2nd or early 1st century BC. ### Who made the Antikythera mechanism? Nobody knows. Its astronomy draws on ideas linked to Hipparchus, and its calendar has links to Corinthian colonies in the west, such as Syracuse, but the maker is unknown. ### How big is the Antikythera mechanism? It was housed in a wooden case roughly the size of a shoebox, about 34 by 18 by 9 centimetres. ### Where is the Antikythera mechanism now? The fragments are displayed at the National Archaeological Museum in Athens. ## Sources - A Model of the Cosmos in the ancient Greek Antikythera Mechanism, Freeth et al., Scientific Reports 11 (2021) - Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism, Freeth et al., Nature 444 (2006) - Gears from the Greeks: The Antikythera Mechanism, a Calendar Computer from ca. 80 BC, Derek de Solla Price, Transactions of the American Philosophical Society (1974) - Decoding an Ancient Computer, Tony Freeth, Scientific American (2009) - Antikythera mechanism, Wikipedia, and the sources it cites - Antikythera wreck, Wikipedia, and the sources it cites