Antikythera Mechanism: Ancient Greece’s Astronomical Computer

A testament to the prowess of ancient Greeks in astronomy on advanced technology, the Antikythera mechanism is a sophisticated astronomical computer. Since it was found in 1991, this hand-powered tool with complex configuration has been baffling scientists and astronomers.  Its complex configuration, the capability of tracking eclipse and celestial events, etc., still intrigue people with a keen interest in astronomy. 

Let’s dig deeper into the Antikythera mechanism: the ancient Greek computer ever found on Earth.  

Antikythera Mechanism

Antikythera mechanism is a hand-powered orrery that ancient Greeks used to calculate and predict eclipse decades and astronomical events in advance. Besides celestial observation, this advanced mechanism was used to display the positions of the planets, sun, and moon in the sky. Archaeologists and researchers predict it to be manufactured in ~100 B.C.E. This astronomical calculator is thought to be the world’s first-ever analog calculator.

The remnants of this iconic device are stored and displayed in the National Archaeological Museum in Athens. 

Different Parts of Antikythera Mechanism

The device is made of bronze with the following parts:

• Gears: The mechanism comes with small gears of different sizes interlocked with each other. These gear wheels were designed to precisely move and calculate. At the core of the mechanism are the gears that drive other functions. These are driven by the “main drive wheel”.
• Pointers: On the dials, there are pointers designed to show the positions of the planets, the sun, and the moon. Attached with the “Main drive sheel”, these pointers rotate with the gear system for accuracy.
• Scales and Inscriptions: The mechanism comes with a range of scales and inscriptions used to track the solar cycles, lunar cycles, and calendars and predict astronomical events.
• Main Drive Wheel: The main drive wheel lies at the center of the mechanism and orchestrates and initiates the motion of the gear wheels. As you know, all functions of the system are regulated by this drive wheel.
• Dials: You will find the front and back faces of the mechanism having a number of dials that display astronomical events and celestial data. For example, its back has around five dials: two large displays, the Metonic and the Saros, and three smaller indicators, the so-called Olympiad Dial.
• Parapegma: An additional component of the mechanism, parapegma helps track celestial events whilst keeping it aligned with celestial cycles.

How Antikythera Mechanism was Discovered

The discovery of the Antikythera mechanism traces back to 1900 when a team of Greek sponge divers were on a voyage to explore a trade shipwreck off Antikythera Island in the Mediterranean Sea. It’s thought to have sunk in the first half of the 1st century. When the divers stumbled upon the wreck, they thought it to be a cluster of bronze fragments that corroded over time. Little did they have the idea of these seemingly insignificant remnants being the bedrock of modern archaeological excellence. 

However, due to heavy corrosion over time, the device was fragmented into 82 pieces, posing a great challenge to archeologists and scientists to put them back together correctly. This fragmented and corroded condition also made it difficult for researchers to decipher the actual look and operating process of the mechanism.

Scientists could defy the challenges and demonstrate how the mechanism was used for astronomical observations. For example, in 2005, different successful studies were conducted to understand how the Antikythera mechanism could predict eclipses. The success of these studies have led researchers to try to replicate the entire mechanism using modern materials.

Scientists also successfully comprehended the back of the mechanism, but how the gear system at the front operated is still a mystery. The researchers of the University College London published a study trying to solve this jigsaw puzzle and decipher the gearing process of the Antikythera mechanism.

Findings of the University College London

For the study, the researchers of the University College London (ULC) used the remnants of the mechanism that, despite being fragmented and corroded, provided detailed information about the inscriptions and mechanical components of the mechanism.

To understand the gear system, they used high-resolution imaging techniques, X-ray computed tomography (CT) scanning, and macro X-ray fluorescence scanning to better understand the gearing process. The implementation of these advanced technologies allows them to decode the structure of the mechanism. The inscriptions they discovered at the front of the device clearly describe the motion of the moon, sun, and planets.

Through this study, UCL researchers got a comprehensive understanding of the complex mechanism of the world’s analog computer, highlighting the precision of ancient Greek craftsmanship. They could successfully reinvent the model for the front of the mechanism, which is claimed to be the first-ever in history to match all the details in the scientific inscriptions engraved on the mechanism itself. The rebuilt model shows different mechanisms the instrument contains, for example, mechanisms to track planetary movements, lunar phases, and the Moon’s position in the Zodiac, lunar phases, and planetary movements. It also comes with a ring system that has output. It incorporates a ring system with outputs for various celestial bodies, ensuring accuracy and alignment with the inscriptional evidence found on the device.

Another key feature of the mechanism was the Dragon Hand, a double-ended pointer that demonstrated the possibility of an eclipse. There are index letters for synodic events on the planetary rings sitting on the display.

University of Glasgow Revealed New Findings

Over time, subsequent studies have explained the operating process of the mechanism. Researchers demonstrated how the exterior dial is linked with the internal gear and facilitates astronomical observations. They could also decipher the calendar ring in the gear system through X-ray images and reveal the details of the holes in it in 2020. However, how many holes the system actually contains was still a mystery. The predicted number of holes was between 347 and 367. In 2024, researchers from the University of Glasgow reported that the calendar ring had 354 holes, which is closely related to the lunar calendar. There are 354 days in it. The association of the holes with the lunar calendar implies that the system was designed to track lunar events. The research strongly approves the probability of the mechanism having a 365 calendar which corresponds to the Egyptian calendar – a solar-based year-count system.

It also disagrees with the 360-holes hypothesis as the 354-house design best aligns with the purpose of the mechanism. 

Antikythera mechanism, an example of technical and intellectual prowess of our ancestors, serves as the bedrock of modern astronomical and computational devices.