An ancient eclipse computer

By Tilemahos Efthimiadis from Athens, Greece [CC-BY-2.0 (], via Wikimedia Commons

By Tilemahos Efthimiadis from Athens, Greece [CC-BY-2.0 (], via Wikimedia Commons

Probably the most astounding artifact from antiquity is the Antikythera Mechanism discovered in 1900 at an ancient shipwreck off the Greek island of Antikythera. This gearwork was dated to approximately 100 BCE and was quickly recognized as a remarkably advanced piece of ancient technology. This degree of sophisticated gear technology which was not attained again until the 14th century in western Europe.

Over the 20th century, many theories were developed to divine the purpose of this gearwork. In recent decades, considerable progress has been made by The Antikythera Mechanism Research Project and it's purpose is now clear: this mechanism was devised as a computer for the prediction of possible dates of solar and lunar eclipses.

A new research article Eclipse Prediction on the Ancient Greek Astronomical Calculating Machine Known as the Antikythera Mechanism has just been published by lead scientist Tony Freeth. From the abstract:

The ancient Greek astronomical calculating machine, known as the Antikythera Mechanism, predicted eclipses, based on the 223-lunar month Saros cycle. Eclipses are indicated on a four-turn spiral Saros Dial by glyphs, which describe type and time of eclipse and include alphabetical index letters, referring to solar eclipse inscriptions.
The ancient Greeks built a machine that can predict, for many years ahead, not only eclipses but also a remarkable array of their characteristics, such as directions of obscuration, magnitude, colour, angular diameter of the Moon, relationship with the Moon’s node and eclipse time. It was not entirely accurate, but it was an astonishing achievement for its era.

Three aspects of the Antikythera Mechanism are particularly striking;

  • the advanced level of metal gear technology which arose in a Greek colony and was lost for 15 centuries,
  • the sophisticated understanding of the motions of the Sun, Earth, and Moon by Greek astronomers which were applied to eclipse prediction, and
  • the importance of solar and lunar eclipse predictions to ancient cultures.