Black holes -- sometimes incorrectly described as the “vacuum cleaners” of the universe -- hold an unending fascination for astronomers and science fiction writers alike. These bodies, whose gravitational pull is so intense that nothing, not even light, can escape once it passes the event horizon, have long been considered regions of space-time where, inexplicably, the usual laws of physics break down.
A long-standing conundrum related to black holes deals with something known as the “information paradox.” In a nutshell, the laws of quantum mechanics tell us that everything in the universe is encoded with information about its constituent particles’ quantum states. And, this information should never entirely disappear, not even if something gets sucked into a black hole. The fact that this information seems to get irretrievably lost when a black hole inevitably evaporates has frustrated physicists for nearly four decades.
During a lecture at the KTH Royal Institute of Technology in Stockholm on Tuesday, famed British physicist and cosmologist Stephen Hawking presented an idea about how this paradox can be solved. According to him, the quantum-mechanical information about particles falling into black holes doesn’t actually enter the black hole.
“The information is not stored in the interior of the black hole as one might expect, but in its boundary -- the event horizon,” Hawking said, adding that the information is encoded in two-dimensional holograms known as “super translations.”
“The idea is the super translations are a hologram of the ingoing particles,” Hawking said. “Thus they contain all the information that would otherwise be lost.”
So, while the information is not technically lost, it is preserved in a “chaotic, useless form,” Hawking added. “For all practical purposes, the information is lost.”
And what happens to the stuff that does fall into the black hole? According to Hawking, they travel down a one-way path, eventually winding up in a different universe.
“The hole would need to be large and if it was rotating it might have a passage to another universe. But you couldn’t come back to our universe. So although I’m keen on space flight, I’m not going to try that,” Hawking said. “The message of this lecture is that black holes … are not the eternal prisons they were once thought. Things can get out of a black hole both on the outside and possibly come out in another universe.”