## The Black Hole Information Paradox, Stephen Hawking’s Greatest Puzzle, Is Still Unsolved

“Despite our best efforts, we still don’t understand whether information leaks out of a black hole when it radiates energy (and mass) away. If it does leak information away, it’s unclear how that information is leaked out, and when or where Hawking’s original calculations break down. Hawking himself, despite conceding the argument more than a decade ago, continued to actively publish on the topic, often declaring that he had finally solved the paradox. But the paradox remains unresolved, without a clear solution. Perhaps that’s the greatest legacy one can hope to achieve in science: to uncover a new problem so complex that it will take multiple generations to arrive at the solution. In this particular case, most everyone agrees on what the solution ought to look like, but nobody knows how to get there. Until we do, it will remain just another part of Hawking’s incomparable, enigmatic gifts that he shared with the world.”

When anything falls into a black hole, it adds to the black hole’s mass, electric charge, and angular momentum, which is what General Relativity predicts. But there’s also quantum information encoded in what falls in, and that information can’t be destroyed. There’s a neat solution for that: information can be encoded on the event horizon of a black hole, getting “smeared out” from the perspective of an outside observer. But then, what happens to this information when the black hole evaporates via Hawking radiation? Hawking himself predicted that information was lost, which is now thought to be wrong. But the question of exactly how that information gets encoded onto the outgoing radiation is still a matter of massive uncertainty. Despite declarations by many (including Hawking) that the paradox has been resolved, the fact is that the black hole information paradox is still an open area of study.