Black holes, as they're commonly portrayed, are the universe's trash compactors. The supermassive black hole Sagittarius A*, the dancing duo—they're the product of collapsed stars, regions of unimaginable density where gravity is so strong nothing can escape its grip. Once caught, any victim, whether interstellar voyager or hapless photon, is destined to be slowly but steadily torn apart in an eternal prison where time itself seems to come to a standstill.
Stephen Hawking, one of the physicists who helped pioneer this modern conception of black holes, however, thinks we may have got it wrong. Or, at least, not entirely right. He says that though something like a black hole is certainly out there—there's tons of evidence for them, after all—black holes as they're commonly conceived don't really exist. But their grip, he says, is not quite so enduring or destructive as we thought. Essentially, he wants to do away with the idea of the black hole's iconic “event horizon" and turn this ultimate gravitational cliff into something a little less steep.
Hawking's rebellion against black holes began back in, at least, 2004. As New Scientist wrote at the time, Hawking talked his way on to the stage at the 17th International Conference on General Relativity and Gravitation to present his new idea.
"He sent a note saying 'I have solved the black hole information paradox and I want to talk about it'," says Curt Cutler, a physicist at the Albert Einstein Institute in Golm, Germany, who is chairing the conference's scientific committee. "I haven't seen a preprint [of the paper]. To be quite honest, I went on Hawking's reputation."
Though Hawking has not yet revealed the detailed maths behind his finding, sketchy details have emerged from a seminar Hawking gave at Cambridge. According to Cambridge colleague Gary Gibbons, an expert on the physics of black holes who was at the seminar, Hawking's black holes, unlike classic black holes, do not have a well-defined event horizon that hides everything within them from the outside world.
In essence, his new black holes now never quite become the kind that gobble up everything. Instead, they keep emitting radiation for a long time, and eventually open up to reveal the information within. "It's possible that what he presented in the seminar is a solution," says Gibbons. "But I think you have to say the jury is still out."
Fast forward to today, and Hawking is back. This time, Nature reports, Hawking has a new preliminary study outlining his idea to replace the sharp “event horizon” with a squishier sort of “apparent horizon.”
In Hawking's “new” idea, black holes are less like death pits and more like cosmic prisons: they hold on to matter and information, they break it down and change it, but eventually the swallowed material is set free.
Physicists, says Nature, seem impressed with Hawking's formulation. But there's still one problem. Just like in 2004, Hawking can't actually prove this new concept of black holes one way or another.
A full explanation of the process, the physicist admits, would require a theory that successfully merges gravity with the other fundamental forces of nature. But that is a goal that has eluded physicists for nearly a century. “The correct treatment,” Hawking says, “remains a mystery.”