DHAKA: Stephen Hawking has shocked physicists by admitting `there are no black holes`. In a paper published online, Professor Hawking instead argues there are `grey holes`.
`The absence of event horizons means that there are no black holes - in the sense of regimes, from which light can`t escape to infinity,` he says in the paper, called Information Preservation and Weather Forecasting for Black Holes.
He says that the idea of an event horizon, from which light cannot escape, is flawed.
He suggests that instead light rays attempting to rush away from the black hole’s core will be held as though stuck on a treadmill and that they can slowly shrink by spewing out radiation.
Hawking told the journal Nature: `There is no escape from a black hole in classical theory. [But quantum theory] enables energy and information to escape from a black hole`.
A full explanation of the process, Hawking admits, would require a theory that successfully merges gravity with the other fundamental forces of nature.
However, that is a goal that has eluded physicists for nearly a century.
`The correct treatment,` Hawking told Nature, `remains a mystery.`
The professor’s grey hole theory would allow matter and energy to be held for a period of time before being released back into space.
Hawking’s latest work was prompted by a talk he gave via Skype to a meeting at the Kavli Institute for Theoretical Physics in Santa Barbara, California, in August 2013.
It tries to address what is known as the black-hole firewall paradox, which has puzzled scientists for almost two years.
It stems from a theory where scientists tried to imagine what would happen to an astronaut unlucky enough to fall into a black hole.
Black hole expert Don Page, of the University of Alberta in Edmonton, Canada, admits: `The picture Hawking gives sounds reasonable.`
But theoretical physicist Joseph Polchinski of the Kavli Institute is sceptical and insists: `In Einstein’s gravity, the black-hole horizon is not so different from any other part of space.
`We never see space-time fluctuate in our own neighbourhood: it is just too rare on large scales.`
Raphael Bousso, a theoretical physicist at the University of California, Berkeley, and former student of Hawking`s, admits many physicists will find Hawking’s work “abhorrent”.
He says: “The idea that there are no points from which you cannot escape a black hole is in some ways an even more radical and problematic suggestion than the existence of firewalls.
`But the fact that we’re still discussing such questions 40 years after Hawking’s first papers on black holes and information is testament to their enormous significance.`
A BRIEF HISTORY OF PROFESSOR HAWKING`S WORK
In the 1970s, already confined to a wheelchair, he produced a stream of first class research, including probably his most important contribution to cosmology.
This was the discovery of Hawking radiation, which allows a black hole to leak energy and gradually fade away to nothing.
By applying quantum mechanics to black holes, he had taken the first steps to combining quantum theory and general relativity.
One describes the universe at the sub-atomic level, and the other at very large scales.
Bringing the two theories together is one of the great unfulfilled goals of modern physics.
In the 1980s, Prof Hawking and Professor Jim Hartle, from the University of California at Santa Barbara, proposed a model of the universe which had no boundaries in space or time.
The concept was described in A Brief History Of Time, which sold 25 million copies worldwide.
Source: Dailymail
BDST: 1230 HRS, JAN 25, 2014
