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Antikythera Mechanism: Ancient Celestial Calculator

Antikythera mechanism
This is the largest piece of the Antikythera Mechanism, which is on display at the National Archaeological Museum in Athens, Greece. (Image credit: National Archaeological Museum, Athens, Greece)

The Antikythera Mechanism has been called an “ancient calculator,” but there is so much more to it than meets the eye. The shoebox-size device has a complex gearwheel system of 30 intricate bronze gear wheels used to run a system that displayed the date, positions of the sun and moon, lunar phases, a 19-year calendar and a 223-month eclipse prediction dial. This makes it an analog computer of great complexity. No other machine of known existence shows a similarity in advanced engineering for at least another 1,000 years. 

The discovery

In 1900, a boatload of sponge divers in the Mediterranean were forced off course by a storm and took shelter nearby the island of Antikythera. The next day, they went diving near the island and discovered a 2,000-year-old Greek shipwreck, according to NOVA

The ship likely sank between 70 B.C. and 60 B.C. on a voyage from Asia Minor to Rome. The sponge divers salvaged from the ship three flat pieces of corroded bronze that later became known to be the Antikythera Mechanism. 

The device has been dated as coming from the second or early first century B.C., according to research published in the science journal Nature. Research, published in the journal Archive for History of Exact Science in 2014, found that the mechanism was timed to begin in 205 B.C.

What it does

For decades, scientists could only guess about the use of the mechanism because it is too fragile to examine by hand. Advancements in imaging, such as 3-D X-ray scanners, has allowed scientists to see the many working parts of the machine and inscriptions that offer directions on how to use the device.

It was believed that it is an ancient astronomy calculator that shows the four-year cycle of the early Greek competitions that inspired today's Olympic Games. Inscriptions on the device list names linked to the Olympiad cycle of games. 

"The first clues that suggested a link with the ancient cycle of Greek games came when the word 'NEMEA' was read near a small subsidiary dial on the mechanism," said Tony Freeth, a scientist with Images First Ltd. in the United Kingdom and coauthor on the Nature study. [Ancient Olympic Calculator Discovered]

The Nemean Games was one of the crown games in the Olympiad cycle. Other names were also found, which included 'ISTHMIA" for the games at Corinth, 'PYTHIA' for the games at Delphi, and the word 'OLYMPIA' for the Olympic Games.

Additional research and reconstruction of a working model of the device in 2006 found that it may not be Greek as formerly believed, according to Nature. It may actually be Babylonian, making the device centuries older than previously thought, which means that the Babylonians may have played a large role in shaping Greek advancements in astronomy, though this has been highly debated. 

A computer-generated reconstruction of the front and back of the Antikythera Mechanism. (Image credit: Antikythera Mechanism Research Project)

Physical description

The Antikythera Mechanism is not all in one piece. There are 82 catalogued fragments of the Antikythera Mechanism and they are kept at the National Archaeological Museum in Athens, Greece, according to the Antikythera Mechanism Research Project. Many of the pieces have been named and functions have been attributed them.

The calendar scale represents a 360-day year and is divided into 12 months of 30 days each plus a five-day extra period, which corresponds to the Greek-Egyptian calendar.  

The planetary dials list the five planets that were known at the time: Mercury, Venus, Mars, Jupiter and Saturn. It is thought that these dials may have shown planetary cycles.

The zodiac scale is a 360-degree dial divided into the 12 signs of the zodiac, which are split into a "fast" zone and a "slow" zone. These speed zones are believed to represent the varying apparent speed of the sun.

These dials had seven pointers, total, though they are lost or destroyed. The sun pointer shows the date on the calendar scale and the sun’s position in the sky on the zodiac scale. It makes a complete turn for each year. The moon pointer shows the moon’s position in the sky on the zodiac scale. 

Below the moon pointer is a revolving black-and-white ball that represents the moon’s phases. This seems to have modeled the moon's elliptical orbit around Earth rather than a circular orbit. This is at odds with Greek philosophers' belief that all heavenly orbits were perfect circles. 

There was also a handle, which researchers think was used to move the pointers back and forth.

Rumors of a hoax

There are many conspiracy theories online that claim that the Antikythera Mechanism is a hoax simply because some believe that ancient people couldn’t possibly build a device so complex. The Antikythera Mechanism Research Project stated that an examination at the National Archaeological Museum in Athens has found that the device is not a hoax.

Additional resources

Alina Bradford
Alina Bradford
Alina Bradford is a contributing writer for Live Science. Over the past 16 years, Alina has covered everything from Ebola to androids while writing health, science and tech articles for major publications. She has multiple health, safety and lifesaving certifications from Oklahoma State University. Alina's goal in life is to try as many experiences as possible. To date, she has been a volunteer firefighter, a dispatcher, substitute teacher, artist, janitor, children's book author, pizza maker, event coordinator and much more.