Stephen Hawking spent his scientific life exploring some of the deepest questions a human caught in the Einsteinian opera of space and time could ask.
Although Einstein himself never really accepted it, his general theory of relativity predicted that if enough mass or energy were concentrated at one point, space would sag like mattress and eventually close itself off, creating a black hole from which nothing, not even light, could escape.
It would be Hawking’s fate to explore these imagined monsters and ask what their presence portends for the universe, and for those of us who live inside it.
In 1970, building on work in Hawking’s doctoral dissertation, he and Penrose show that there had to be a singularity at the beginning of time — in other words, a big bang.
That is to say, he showed that the universe had a beginning.
Quantum physicists object, saying the universe can’t forget, initiating a 40-year argument about the fate of information.
Hawking concedes in 2004 but does not say how information is preserved in a black hole, and the argument continues to this day.
In their picture of cosmic history, space-time is like a globe of the Earth. Time starts at the North Pole and goes south as the universe gets fatter. Asking what came before the Big Bang, in this case, is like asking what is north of the North Pole, they said.
Moreover, just as nothing weird happens at the North Pole of the Earth, nothing strange happens to the laws of physics at time zero. Earth abides and so does physics, obviating the need for a creator.
“In an infinite universe there must be other occurrences of life,” he said. “Or do our lights wander a lifeless universe? Either way, there is no bigger question.”
But he is sure about time travel. In 1991, he enunciated what he called the chronology protection conjecture, that will, as he put it, “keep the world safe for historians.” It says that the laws of physics do not allow time machines.
In 2016, working with Andrew Strominger of Cambridge University and Malcolm Perry of Harvard, Hawking took a small step toward a solution of the infamous information paradox. He announced that information about what falls into a black hole might be preserved on the surface, or event horizon, of a black hole.
The universe will remember us, which is no small thing, he declared.
If the rules break down in black holes, they may be lost in other places as well, he warned. If information disappears into a gaping maw, the notion of a “past” itself may be in jeopardy — we couldn’t even be sure of our own histories. Our memories could be illusions.
“It’s the past that tells us who we are. Without it we lose our identity,” he said.
Copyright 2024 New York Times News Service. All rights reserved.
