This random creation and destruction of matter happens everywhere and usually has no effect. But when such particles are created near a black hole. Hawking had shown, the black hole's gravitational field sometimes drags in only one of the paid while the other flies off into free space. These escaped particles give off the radiation that seems to come from inside the black hole.

More than 500 listeners recently jammed Science Center C to listen to each of Hawking's three lectures on gravitational collapse. Hawking explained that gravity can force matter to collapse into black holes and that time seems to end for particles trapped inside because outside observer can no longer determine what happens to them. Saying this theory has provoked "the greatest crsis physics of all time added. "It seems to indicate that time itself has a beginning and in end".

Black holes have attracted a lot of attention in the past few years, spawning pinball games, adventure movies, and dozens of sci-fi novels. Hawking says he's very glad to see all the popular interest, but he's not always so pleased with the form it takes. For instance. Walt Disney invited him to be a consultant for its film. "The Black Hole." Although he turned them down, he did accept an invitation to the movie premier. "It was an awful film," he says.

Part of the popular fascination with black holes comes from their origins. When stars use up all of their nuclear fuel and become too cold to produce the pressure needed to withstand the force of gravity, they collapse, forming black holes.

But Hawking's scenario for doamsday does not include the earth vanishing into a black hole that was once the sun Only stars about and a half times as big as our sum have enough mass to form one.

Instead, Hawking thinks nuclear was is "by far our most dangerous worry." He endorses the new disarmament movements in Europe and hopes they'll at least succeed in removing nuclear weapons from Britain and the continent "I thin that we should all disarm now and not wait for the other side to do so first. The survival of the human race is much more important than the difference between capitalism and communism."

But in the face of nuclear war. Hawking is far from depressed. He retains his underlying optimism no matter what prospects he's discussing. If we can survive the next 100 years, he says, then the human race will be able to improve itself through genetic engineering and perhaps colonize the entire galaxy. "But on the other hand," he says, "maybe that is a depressing prospect."

Hawking and many other physicists are now seeking a theory to explain all the physical qualities of the universe by a single basic force. Finding such a force would not mean that scientists could predict the weather or the color of babies' hair, but it would prove that the universe is orderly at every level.

Hawking believes that we could find such a theory within 20 years. But other people have also been convinced that they've found an all-encompassing model for the universe, he says, and they have been proved wrong. The new theory might also be wrong, he says, but at least it would be closer to the truth. "There may be discoveries that will modify our ideas, but I don't think they'll ever change them completely."