Scientists say they have solved one of science’s biggest paradoxes, first identified by Stephen Hawking.
He highlighted that black holes behave in a way that puts two fundamental theories into conflict.
Black holes are dead stars that have collapsed and have a gravity so strong that even light cannot escape.
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New research claims to have resolved the paradox by showing that black holes possess a property they call “quantum hair”.
“The problem has been solved!” Xavier Calmet, from the University of Sussex, UK, exclusively tells BBC News.
He was among the scientists who developed the mathematical techniques they say solved the paradox.
At the heart of this paradox is a problem that threatens to undermine two of physics’ most important theories. Einstein’s general theory of relativity states that information about what goes into a black hole cannot come out, but quantum mechanics says that is impossible.
Calmet and his colleagues claim to have shown that the star’s components leave an imprint on the black hole’s gravitational field.
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Scientists called the brand “quantum hair” because their theory would supplant an earlier idea called the “baldness theorem” developed by Professor John Archibald Wheeler of Princeton University in New Jersey in the 1960s.
Wheeler suggested this name because it conveys the mathematical description of a black hole: an entity that has mass, spin, and charge, but otherwise has no other physical characteristics—bald, if you will.
Calmet’s “hair theorem, yes” published in the scientific journal Physical Review Letters is revolutionary. It claims to resolve Hawking’s paradox, which has deeply intrigued physicists since it was introduced in the 1970s.
British physicist Stephen Hawking outlined some of the most important theories about black holes — Photo: Santi Visalli/Getty Images via BBC
The paradox raised the possibility that quantum mechanics or general relativity could be flawed, which is a terrifying prospect for theoretical physicists because they are the two pillars on which most of our understanding of the Universe is based.
The “hair theorem, yes” claims to resolve the paradox by bridging the gap between general relativity and quantum mechanics. The notion of “quantum hair” allows information about what goes into a black hole to come out again without violating any of the important principles of any theory. It’s a simple and elegant solution.
“But it’s going to take some time for people to accept it,” says Calmet.
That’s because it’s a big question in the world of theoretical physics.
“Hawking introduced the paradox the year I was born,” he notes.
Since then, several famous physicists around the world have been working on it, proposing somewhat dramatic things to explain the paradox, including some who have suggested that certain aspects of quantum mechanics are wrong.
“So it’s going to take a while for people to accept that you don’t need a radical solution to solve the problem,” he says.
If the “hair theorem, yes” stands up to scrutiny, he believes that could be the first step in connecting the theories of relativity — which concerns gravity — and quantum mechanicswhich mainly focuses on the other three forces of nature, which are electromagnetism and the two nuclear forces.
“One of the consequences of Hawking’s paradox was that general relativity and quantum mechanics were incompatible. What we’re finding is that they are quite compatible.”
The research team, which also includes Professor Roberto Casadio from the University of Bologna in Italy and Professor Stephen Hsu from Michigan State University in the US, drew on the work of Professor Suvrat Raju from the International Center for Theoretical Sciences in Bangalore. , in India.
Raju believes that together they solved Hawking’s paradox.
“In recent years it has been recognized that the baldness theorem fails due to quantum effects and this solves Hawking’s paradox,” he says.