THE ENIGMA of a priceless Bronze Age disc seems to have been solved by a Hamburg scientist who has identified it as one of the world’s first astronomical clocks.

The 3,600-year-old Sky Disc of Nebra, which surfaced four years ago when German grave robbers tried to sell it on the international market, shows that Bronze Age man had a sophisticated sense of time.

“We have been dramatically underestimating the prehistoric peoples,” said Harald Meller, chief archaeologist of Saxony-Anhalt, where the disc was found.

The bronze disc is about 30cm in diameter, has a blue-green patina and is inlaid with a gold sun, moon and 32 stars. Robbers using metal detectors found it in 1999 alongside a pile of bronze axes and swords in a prehistoric enclosure on top of a hill in deep forest 112 miles (180km) southwest of Berlin.

The Nebra settlement is close to Europe’s oldest observatory in Goseck. The site appears to have had deep spiritual significance in the Bronze Age. From the hill it is possible to see the sun set at every equinox behind the Brocken, the highest mountain peak of the Harz range. And there are about 1,000 barrows, burial grounds for warriors and princes, in the nearby forests.

Since police tracked down the thieves in Switzerland in 2002, archaeologists and astronomers have been trying to puzzle out the disc’s function. Ralph Hansen, an astronomer in Hamburg, found that the disc was an attempt to co-ordinate the solar and lunar calendars. It was almost certainly a highly accurate timekeeper that told Bronze Age Man when to plant seeds and when to make trades, giving him an almost modern sense of time.

Herr Hansen first tried to explain the thickness of the moon on the disc. “The crescent on the Sky Disc of Nebra seems to be equivalent to a four-day moon,” he said.

He consulted the 7th and 6th century BC mul-apin collection of Babylonian documents in the British Museum. It appears that the users of the 3,600- year-old clock made similar calculations. The disc was used to determine when a 13th month should be added to the lunar year, which has shorter months than the solar year. Herr Maller said: “Probably only a very small group of people understood the clock.”

But the knowledge was somehow lost, and scientists say that the clock would have been used for only about 300 years. Herr Maller said: “In the end, the disc became a cult object.”