Whenever you're trying to fathom a mangled sample of very old hi-tech, it helps to have the manufacturer's instructions.

For over a century since its discovery in an ancient shipwreck, the function of the Antikythera Mechanism — named after the Greek island off which it was found — was a deep and tantalizing mystery.

From a few words deciphered on the twisted, corroded fragments of bronze gears and plates, experts guessed it was an astronomical instrument.

After more than a decade's efforts using cutting-edge scanning equipment, an international team of scientists has now read about 3,500 characters of text — a quarter of the original — hidden inside the 2,100-year-old remains.

They say it was a kind of philosopher's guide to the galaxy, and perhaps the world's oldest mechanical computer.