Scientists are pointing to studies of tree-rings in Ireland which have revealed that about 2,354-2,345 BC there was an abrupt change to a colder climate.

They have also highlighted discoveries by archaeologists in northern Syria of a catastrophic environmental event at about the same time. This is also about the time that Bronze Age civilisations collapsed.

Firework displays of meteors

Dr Bill Napier, an astronomer at Armagh Observatory, and Dr Victor Clube, from Oxford and Armagh universities, say the evidence points to a comet hitting the Earth, and have called for more research.

Writing in Frontiers, the magazine of the Particle Physics and Astronomy Research Council, Dr Napier suggests that the Comet Encke, first observed in 1786, might be a remnant of the object along with its associated stream of meteors, called the Taurids.

This giant mother-comet is thought to have been disintegrating as recently as 5,000 years ago.

At this time, and for some millennia afterwards, the night sky would have been lit up by a bright light caused by dust particles, cometary fragments, and firework displays of meteor storms.

The scientists highlight ancient civilisations' preoccupation with the sky.

Cosmic icons were widespread

Dr Napier wrote: "People have assumed that this was driven by the need for a calendar for both agricultural and ritual purposes.

"However, this explanation does not account for the doom-laden nature of much cosmic iconography and early sky-centred cosmic religions associated with these societies."

Icons apparently depicting comets were widespread among early civilisations.

The new evidence also ties in with ancient prophecies, including the Book of Revelations in the Bible, which appears to describe cataclysmic events involving objects falling from the sky.

Dr Napier said the ancient swastika, a symbol of great antiquity stretching back to at least 1400 BC and found from China through India to the New World, may also be a cometary image.

Comets are giant dirty snowballs in space, made of ice and dust. Unlike asteroids, which are rocky, there is no known upper limit to their size, and the largest can measure several hundred kilometres across.

Every 100,000 years or so one of these rare, giant objects enters an orbit that crosses the path of the Earth.