The black hole information paradox is one of those physics problems that can keep scientists up at night. It strikes at the heart of one of the crucial problems in modern physics: the fact that we can’t reconcile general relativity and quantum mechanics. And it is all black holes’ fault.
Both quantum mechanics and general relativity are pinnacles of human knowledge and ingenuity. Truly, we should be very proud of ourselves and how well we understand the universe. Still, the two do not work together very well, and when it comes to certain extreme objects or events, they break down – and that is a big problem. The black hole information paradox is one of these cases.
In both classical and quantum physics, information about the properties of a system allows us to determine the state in the past and in the future. Black holes appeared to be an exception to that. In the 1970s, British physicist Stephen Hawking realized that the properties of a black hole depend on just a handful of global parameters: its mass, electric charge, and angular momentum. And that’s not all. Once they’re not actually feeding, black holes lose energy in the form of what is now called Hawking radiation, which according to his original calculations, was independent of the initial state. The expression “a black hole has no hair” comes from this.
The Hawking radiation would have no past, and anything falling into a black hole would suddenly have no future. Information falling into a black hole would be irretrievably lost. This would be a massive problem for physics if it were the case – but it is believed that information is indeed saved and gets out of a black hole. What physicists are uncertain about is how it gets out.
So black holes definitely have hair, but we don’t know if it’s a stubble or a Dolly Parton-style do! Ok, a blonde wig might be an exaggeration, but terms like the “fuzzball resolution” and the “soft-hair solution” (from Hawking and collaborators) have been proposed to solve this paradox. But there is no single agreed-upon solution yet.
The different ideas are a major focus in physics because they might reveal possible ways to make quantum mechanics and relativity work together – not just in black holes, but across the whole universe. Some researchers claim that it is possible to solve it without any new physics, which is exciting on the one hand but a bit disappointing on the other.
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Dr. Thomas Hughes is a UK-based scientist and science communicator who makes complex topics accessible to readers. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
