LONDON, July 21: After nearly 30 years, British mathematician Stephen Hawking admitted on Wednesday that his commanding theory about black holes as bottomless pits in space, sucking in all matter and energy like a giant vacuuum cleaner, was flawed.

Stephen Hawking postulated in 1975 that a black hole was so powerful that anything which crossed its boundary, called the event horizon, would be swallowed up in its maw and never escape.

But in a major revision of his landmark theory, Hawking acknowledged it may not be a one-way trip. Hawking presented new calculations at an astrophysics conference that, he said, showed the surface of a black hole had fluctuations that could allow information to leak out.

Hawking had said in 1974 that black holes emit energy - a phenomenon that became known as Hawking radiation - and gradually lose mass, shrinking before disappearing in a final, cataclysmic blast.

Critics of this mathematical approach asked how it could respect one of the laws of quantum physics - that all information must remain in balance as the Universe evolves and can never be completely lost.

If so, they argued, there would be enormous repercussions for our notion of time. If information is lost, it means that no-one could be certain of the past or be able to predict the future.

Until now, Hawking, a Cambridge University professor, argued that black holes exercised a gravitational force that was so mighty that quantum laws were overturned. In his revision, black holes do not completely destroy everything that crosses the event horizon.

They continue to emit radiation for long periods and eventually open up to disgorge information from within. Hawking's about-turn means that he and theoretical physicist Kip Thorne of the California Institute of Technology have lost a bet with an opponent of the one-way-street idea, John Preskill, also of Caltech.

Hawking and Thorne are expected to present Preskill with an encyclopaedia of his choice. -AFP