Stephen Hawking has described a new theory for how our existence could escape a black hole during a lecture at the KTH Royal Institute of Technology in Sweden this week.
The theory, which builds on ideas that have been mulled over for decades now, states that when something is sucked into a black hole, it’s not lost to the universe forever as you might expect. Instead its information - defined in physics as all the properties of a particle - is retained on the boundary (or event horizon) of the black hole, and will be taken in by the universe later on.
"I propose that the information is stored not in the interior of the black hole as one might expect, but on its boundary, the event horizon," Hawking said at the event. "The message of this lecture is that black holes ain't as black as they are painted. They 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."
At a very basic level, we know that a black hole arises from a star that’s collapsed under its own gravity, and this produces a gravitational force that’s strong enough to consume even light itself. What we don’t know - and what theoretical physicists have been debating for the past four decades - is what happens to the information of an object when it’s consumed?
While quantum mechanics states that information can never be destroyed, even in a black hole situation, general relativity says it has to be, and therein lies what’s come to be known as the information paradox.
Back in the 1970s, Hawking got himself noticed when he proposed that the quantum fluctuations - a temporary change in the amount of energy in a point in space - that occur in a black hole could allow photons (light particles) to escape. "Originally he said that this radiation carried no information from inside the black hole," says Jacob Aron at New Scientist, "but in 2004 changed his mind and said it could be possible for information to get out."
In the mid-90s, American and Dutch physicists Leonard Susskind and Gerard 't Hooft addressed the information paradox by proposing that when something gets sucked into a black hole, its information leaves behind a kind of two-dimensional holographic imprint on the event horizon, which is a sort of ‘bubble’ that contains a black hole through which everything must pass. This means that while all the physical components of an object would be so totally obliterated by a black hole encounter, its blueprint lives on.
To help wrap your brain around that, think about a stack of documents going through a shredder, says Joseph Stromberg at The Verge. You can shred the paper into the tiniest imaginable pieces, but the information on them remains, and can be restored. "It's been cut into tiny pieces, but it hasn't disappeared, and given enough time, the documents could be reassembled so that you'd know what was written on them originally. In essence, the same thing was thought to be true with particles."
What Hawking is now proposing is that when photons are ejected by the black hole - a phenomenon known as Hawking radiation - they pick up the information blueprint sitting on the event horizon and carry it with them back into the universe. Not that anything could be done with this blueprint - or two-dimensional hologram - though, Hawking said at the conference: "The information about ingoing particles is returned, but in a chaotic and useless form. This resolves the information paradox. For all practical purposes, the information is lost."
What’s unclear, and what will perhaps be discussed at the conference later on this week, is how Hawking’s theory differs from what SussKind and ’t Hooft have already proposed, but perhaps what Hawking has done is resolve some of the sticking points of the theory’s earlier iteration. Rachel Feltman writes for The Washington Post:
"Nobel laureate Gerard 't Hooft, who was present for the discussion, has been thinking about information loss in a similar way, and he cited several papers he has published on the subject. It will take more discussion - and much comparing of math equations - to establish what's new about Hawking's theories in relation to 't Hooft's, and whether Hawking has overcome some of the issues associated with earlier iterations of the idea."
What can we take away from all of this? Well, perhaps black holes aren’t the quagmires of complete and utter destruction that we like to describe them as, and Hawking says we should take some comfort in that fact. "If you feel you are in a black hole, don’t give up," he said at the conference. "There’s a way out."
Just don't think about that last point too hard because in this context, the thought of becoming a "chaotic and useless form" isn't exactly the motivational pat on the back we're looking for in our darkest moments.
Watch his presentation below: