"If you feel you are trapped in a black hole, don’t give up. There is a way out."
Are we one step closer to solving the black hole information paradox? According to a recent paper by Stephen Hawking: yes, we are.
Back in January, Hawking excited the physics community when he announced that he had found a possible solution to this black hole information paradox. His paper was published on the pre-print site arXiv.org so that physicists from around the world could review and critique the work. And now, six months later, the research has finally been published in the peer-reviewed journal Physical Review Letters.
What is the paradox? According to Einstein’s Theory of General Relativity, everything that crosses the event horizon of a black hole is lost forever — not even light can escape its grasp.
However, in the 1970s, Hawking proposed that a type of radiation — Hawking radiation — can indeed escape from a black hole thanks to the laws of quantum mechanics. Simply put, when a black hole gobbles up a particle-antiparticle pair, one half is swallowed, while the other radiates into space, stealing away a little energy from the black hole. Eventually, this process causes black holes to evaporate and disappear, leaving only Hawking radiation behind.
Hawking’s previous calculations suggested that the radiation would not contain any useful information about what the black hole consumed, meaning this information would be lost forever. But this goes against our current understanding of physics, which states that even though things may be destroyed, their “information” should live on, explained Dennis Overbye of The New York Times. Hence the paradox.
What’s the solution? According to Hawking, his original calculations that the information inside a black hole would be lost forever were wrong, and instead, black holes have a halo of ‘soft hair’ surrounding them that can store information. This hair is not like what’s found on the top of your head, but rather low-energy quantum excitations that are capable of carrying a signature of everything that has even been gobbled up by a black hole — even long after it has evaporated.
"It is important to note that this paper does not solve the black hole information problem," wrote physicist Gary Horowitz from the University of California, Santa Barbara, in a commentary paper published in the journal APS Physics. However, it is a promising step towards solving the paradox.
According to Horowitz, more research is required to determine whether all the information consumed up by the black hole can be transferred to the soft hair — rather than the hairs just being an energy signature of everything that’s been lost.
However, he admits, that it is "certainly possible that [...] further investigation will uncover more hair of this type, and perhaps eventually lead to a resolution of the black hole information problem."
What does this discovery mean for you and me? Not much, but the physics behind the discovery does carry a rather uplifting sentiment. According to Hawking, who at the time was giving a talk at the KTH Royal Institute of Technology, "[black holes] are not the eternal prisons they were once thought. If you feel you are trapped in a black hole, don’t give up. There is a way out."
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