The discovery of black hole radiation also led to a 30-year controversy over the fate of things that had fallen into a black hole.Not only that, but physicists do not have a sufficiently coherent definition of information in order to make this a paradox. And even if they did, there were be no way to resolve an issue about information leaking out of a black hole.
Dr. Hawking initially said that detailed information about whatever had fallen in would be lost forever because the particles coming out would be completely random, erasing whatever patterns had been present when they first fell in. Paraphrasing Einstein’s complaint about the randomness inherent in quantum mechanics, Dr. Hawking said, “God not only plays dice with the universe, but sometimes throws them where they can’t be seen.”
Many particle physicists protested that this violated a tenet of quantum physics, which says that knowledge is always preserved and can be retrieved. Leonard Susskind, a Stanford physicist who carried on the argument for decades, said, “Stephen correctly understood that if this was true, it would lead to the downfall of much of 20th-century physics.”
On another occasion, he characterized Dr. Hawking to his face as “one of the most obstinate people in the world; no, he is the most infuriating person in the universe.” Dr. Hawking grinned.
Dr. Hawking admitted defeat in 2004. Whatever information goes into a black hole will come back out when it explodes. One consequence, he noted sadly, was that one could not use black holes to escape to another universe. “I’m sorry to disappoint science fiction fans,” he said.
Despite his concession, however, the information paradox, as it is known, has become one of the hottest and deepest topics in theoretical physics. Physicists say they still do not know how information gets in or out of black holes.
This shows the sorry state of theoretical physics, that such a non-question could be "one of the hottest and deepest topics".
As a graduate student in 1963, he learned he had amyotrophic lateral sclerosis, a neuromuscular wasting disease also known as Lou Gehrig’s disease. He was given only a few years to live.He probably had some other degenerative disease.
Dr. Hawking was a strong advocate of space exploration, saying it was essential to the long-term survival of the human race. “Life on Earth is at the ever-increasing risk of being wiped out by a disaster, such as sudden global nuclear war, a genetically engineered virus or other dangers we have not yet thought of,” he told an audience in Hong Kong in 2007.Mars will always be much more hostile to human life than the Earth, no matter what we do to Earth.
By then string theory, which claimed finally to explain both gravity and the other forces and particles of nature as tiny microscopically vibrating strings, like notes on a violin, was the leading candidate for a “theory of everything.”There is not any hope that string theory will do that.
In “A Brief History of Time,” Dr. Hawking concluded that “if we do discover a complete theory” of the universe, “it should in time be understandable in broad principle by everyone, not just a few scientists.”
He added, “Then we shall all, philosophers, scientists and just ordinary people, be able to take part in the discussion of why it is that we and the universe exist.”
“If we find the answer to that,” he continued, “it would be the ultimate triumph of human reason — for then we would know the mind of God.”
Hawking's scientific reputation rests on two things: extending the Penrose singularity theorems, and arguing that quantum effects cause black holes to very slowly radiate.