Can anything escape black holes? This question has been troubling physicists for at least four decades, and while we don’t have an answer yet, we might have just found some important clues.
Stephen Hawking, Malcolm J. Perry, and Andrew Strominger have suggested that information can indeed escape. They suggest that black holes are surrounded by vacuum energy states that can "record" the charge of particles coming into the black holes, so the information is never lost.
If this approach, presented in a paper published in Physical Reviews Letters, can be repeated for gravity, the scientists might have found a way to solve the information paradox, which has plagued black hole research since Hawking's seminal work in 1975.
According to the laws of physics, it should always be possible to reconstruct the past of any interaction. A mug falling from a table, a lightning strike, or a galaxy collision can always be imagined backward. But this is not the case for black holes.
Hawking showed that a black hole is not really black because the interactions between its surface and space-time can create particles that rob the black holes of energy. This energy, dubbed "Hawking radiation," will cause the black holes to lose mass and eventually evaporate. So particles appear in the universe without a past, and some particles (the infalling material) disappear from the universe without a future. And quantum mechanics really doesn’t like that.
The other issue comes from relativity. According to Einstein’s theory, a static black hole can be described by three parameters alone: its mass, its electric charge, and its angular momentum. Physicist John Wheeler popularized the phrase "black holes have no hair," meaning all the information that falls into a black hole is lost.
Now, the solution proposed by Hawking and his colleagues suggests that there are hairs. They are soft quantum hairs, photons that have essentially zero energy trapped on the surface of black holes. When a particle is eaten by a black hole, it excites these photons. This doesn’t change the general properties of the black hole, but as it evaporates that information is released back into the universe.
A lot of work is still necessary on this idea to truly solve the information problem; it is not clear if all information can be transferred to this soft hair, but maybe we are on the right track.
Note: IFLScience covered the pre-print of this paper in January, which you can read about here.
