Advanced imaging software and 3-D X-ray tomography have finally let scientists create the most detailed reconstruction yet of a 2,100-year-old astronomical calculator.

The latest research of the Antikythera Mechanism shows it to be a highly sophisticated calculator that could add, subtract and divide by means of a complex and ingenious arrangement of 37 bronze gears. The gear train moved a set of pointers on dials to accurately show the changing positions of the sun and moon (with its phases), and quite possibly of the planets, and to predict solar and lunar eclipses.

Researchers now date its creation slightly earlier than previously thought: between 100 and150 B.C.

One of the key new findings is the discovery that the device mechanically reproduces the mathematics developed by the great 2nd century B.C. astronomer Hipparchus to account for the irregular movement of the moon through the heavens.

“This is a mechanical reproduction, by means of a clever [pin-and-slot arrangement in the gears] of the so-called first lunar anomaly in Hipparchus’ lunar theory,” says Francois Charette, a researcher with the Department of the History of Science, Ludwig-Maximilian University, Munich, Germany. Charette authored an assessment of the new research in a story published in the current issue of the journal Nature.

“This means that the pin-and-slot device makes the pointer for the moon on the front dial move at varying speed, following (in modern terms) a mathematical function that resembles more or less a sine curve,” Charette says.

The research team speculates that Hipparchus, who lived from about 140 to 120 B.C. in Rhodes, where the mechanism is believed to have been built, or one of his students may have had a hand in its design.

The full research results were announced at a two-day international conference in Athens last week, and published online by Nature.

The mechanism, a clockwork-like collection of bronze gears and dials inscribed with Greek text and numbers, has been slow to yield its secrets since being recovered in 1901 from an ancient wreck off the Greek island of Antikythera.

But critical new details of the gears and their relationships, along with nearly 1,000 never-before-seen Greek characters, doubling the total number identified, were revealed by means of surface imaging software recently developed by scientists at HP Laboratories and by an 8-ton, high-resolution, 3-D X-ray machine from X-Tek Systems, Tring, England.