Follow-up: Details of the Antikythera Mechanism mysteries unveiled

Details of the newest research on the ancient astronomical calculator called the Antikythera Mechanism have been published online by Nature magazine in advance of Thursday's international conference in Athens.

The 2,000-year-old device is a complex of hand-cut bronze gears and dials, inscribed with numbers and astronomical terms. It was found a century ago by accident in a wreck off the Greek island of Antikythera and has baffled scientists for much of the time since then.

Researchers in recent years have clarified the device was used to calculate and display the relative positions of sun and moon, and possibly the five then-known planets. But many mysteries remained.

Now there are fewer remaining. The latest research, aided by advanced imaging software and 3-D X-ray computed tomography, confirms some previous insights by researcher Michael Wright and expands on them. The mechanism is revealed as a sophisticated mechanical calculator that displayed a variety of astronomical events and periods, including the sun and moon moving through the zodiac, accurately predicted solar eclipses, and apparently displayed movements of the known planets.

Nature has a general story about the mechanism and its historical context, coupled with material available only via paid subscription or institutional license: diagrams, a detailed technical paper from the Antikythera Mechanism Research Project and a technical summary by science historian Francois Charette. The latter two documents were made available to Network World.

Roughly the size of shoebox, the mechanism's front has two concentric scales, the inner one showing the Greek Zodiac with 360 divisions, the outer, moveable scale is the Egyptian 12-month calendar, widely use then in Greek astronomy. The Egyptian names for the months are written in Greek letters. Pointers show the relative positions in the Zodiac of the sun and moon, and a device showing the moon's phase was probably attached to the moon pointer. On the back of the device are two dials, each based on spiral design, whose pointers show time based on two astronomical cycles.

The new research shows the following:

* The device was built between 150 to 100 B.C., somewhat earlier than previously thought. The shipwreck took place about 65 B.C. The date is significant, as is the assumption (based on some circumstantial evidence) that the ship, traveling a busy sea route, was heading to Rome from Rhodes, where one of the greatest of Greek astronomers, Hipparchus, lived and worked from about 140 to 120 B.C. Researchers speculate that he or one of this students could have influenced the design, and possibly the building, of part of the mechanism.

* One especially remarkable arrangement of gears creates an anomalous motion for the moon, simulating visually the mathematics created by Hipparchus to account for moon's observed, irregular orbit around the Earth.

* One of the two back spiral dials is now shown to simulate what's called the Saros eclipse cycle, in which a given solar or lunar eclipse will be repeated 223 lunar months later.