Celebrated physicist Stephen Hawking may have solved the 40-year-old information paradox - which continues to puzzle scientists - saying one could simply pop up in another universe after being sucked into a black hole, in a new theory about where lost information ends up.

"If you feel you are in a black hole, don't give up. There's a way out," Hawking, director of research at Cambridge University's department of applied mathematics and theoretical physics, said in a public lecture in Stockholm, Sweden.

He said he had discovered a mechanism "by which information is returned out of the black hole", a place where gravity compresses matter to a point where the usual laws of physics break down.

He was speaking at the KTH Royal Institute of Technology, where the Nordic Institute for Theoretical Physics is hosting the Hawking Radiation Conference dedicated to examining the mystery of the "information paradox" – a conundrum concerning what happens to things swallowed by black holes.

Information about the physical state of something disappearing into a black hole appears to be completely lost, but according to the way the universe works, this should be impossible. Even information falling into a black hole ought to end up somewhere, The Guardian reported. According to Hawking, it does – in one of two ways.

Either it is translated into a kind of "hologram" on the edge of the black hole, or it breaks out into an alternative universe.

"The existence of alternative histories with black holes suggests this might be possible. The hole would need to be large and if it was rotating it might have a passage to another universe. But you couldn't come back to our universe.

"So although I'm keen on space flight, I'm not going to try that," he said. However it is unlikely to be in the same state in which it entered.

"The information about ingoing particles is returned, but in a chaotic and useless form," he said, adding "This information paradox. For all practical purposes, the information is lost."

"The message of this lecture is that black holes ain't as black as they are painted. They are not the eternal prisons they were once thought. Things can get out of a black hole both on the outside and possibly come out in another universe," the famed physicist added.

The theory solves the 'information paradox' which has puzzled scientists for around four decades.