Black holes have long been a mystery to scientists, but they have been thought of as relatively easy to describe. Researchers only needed three parameters to describe them: their mass, their angular momentum (how fast they’re spinning), and their electric charge. However, a paradox was introduced by Stephen Hawking in 1976 that says black holes are destroying information. According to the laws of quantum physics, information cannot be destroyed. So, scientists have been trying to figure out what’s going on.
Hawking argued that black holes are destroying information because the radiation they emit (known as Hawking radiation) is thermal, which means they can’t carry information. If the radiation can’t carry information, and the information can’t stay locked in the black hole forever, it’s being destroyed. However, a group of researchers recently published a study that suggests the information isn’t being destroyed after all.
Last year, the same group of researchers published a paper that claimed black holes had what they referred to as “quantum hair.” It’s basically the idea that if you look at the way black holes warp spacetime right at their horizons, you can detect a sort of fingerprint in the quantum realm pointing to where the matter within came from. Essentially, the hair contained the missing information.
Now, the researchers have published a new study that shows the hair is the key to solving the paradox. They re-ran Hawking’s original calculations that showed the only thing coming out of black holes was information-less thermal Hawking radiation, but with one added ingredient: quantum gravity. That’s the description of gravity as it exists in the quantum realm, and it’s something Hawking didn’t originally take into account.
“While these quantum gravitational corrections are minuscule, they are crucial for black hole evaporation,” said Xavier Calmet, professor of physics and lead author on the study. “We were able to show that these effects modify Hawking radiation in such a way that this radiation becomes non-thermal. In other words, factoring in quantum gravity, the radiation can contain information.”
The study shows that Hawking radiation, contrary to historical belief, could scoop up information from black holes and carry it out into the universe. Information that had been stored in the hairs around black holes could be carried out, solving the paradox.