More than a hundred years ago an extraordinary mechanism was found by sponge divers at the bottom of the sea near the island
of Antikythera. It astonished the whole international community of experts on the ancient world. Was it an astrolabe? Was in an orrery or an
astronomical clock? Or something else? For decades, scientific investigation failed to yield much light and relied more on imagination than the facts. However research over the last half century has begun to reveal its secrets. It dates from around the 1st century B.C. and is the most sophisticated mechanism known from the ancient world. Nothing as complex is known for the next thousand years. The Antikythera Mechanism is now understood to be dedicated to astronomical phenomena and operates as a complex
mechanical "computer" which tracks the cycles of the Solar System.
An ancient astronomical calculator, built around the end of the second century BC, was unexpectedly sophisticated, a study in this week''s Nature suggests. Mike G. Edmunds and colleagues used imaging and high-resolution X-ray tomography to study fragments of the Antikythera Mechanism, a bronze mechanical analog computer thought to calculate astronomical positions. The Greek device contains a complicated arrangement of at least 30 precision, hand-cut bronze gears housed inside a wooden case covered in inscriptions. But the device is fragmented, so its specific functions have remained controversial. The team were able to reconstruct the gear function and double the number of deciphered inscriptions on the computer''s casing. The device, they say, is technically more complex than any known device for at least a millennium afterwards. The text is astronomical with many numbers that could be related to planetary motions, and the gears are a mechanical representation of a second century theory that explained the irregularities of the Moon''s motion across the sky caused by its elliptical orbit.