Didn’t Stephen Hawking help create the black hole theory to which most scientists ascribe? What’s going on here? Either this is a wacky case of time travel or the great physicist has changed his mind. He’s allowed, isn’t he? In fact, now he calls his old black hole theory his “biggest blunder.” Everyone makes mistakes, dude. Don’t even worry about it.
In a paper published online, Hawking describes an impasse: that if we’re right about general relativity and quantum theory, then a black hole can’t actually be comprised of an event horizon, the border beyond which nothing can escape. According to classical theory, “there is no escape from a black hole,” says Hawking, but quantum theory “enables energy and information to escape from a black hole.” The physicist believes that a complete and accurate description of the process demands another theory, one that accounts for gravity as well as other cosmic forces, but scientists are still looking for that explanation.
The impetus for Hawking’s paper is the “black-hole firewall paradox,” which has been plaguing physicists for the last few years. This involves what would actually happen to someone who had the incredible misfortune of falling into a black hole. Per math based on Einstein’s theory of relativity, an astronaut would get stretched out and pulled in, and eventually get crushed at the core, or the singularity, of the black hole. A few years ago, physicists realized that, per quantum theory, this wouldn’t happen. Instead of reaching a core of nothingness, that poor astronaut would pass through an incinerating “firewall.” They can’t both be right. This is all theoretical, which is why it can be so damn maddening.
Hawking now proposes that black holes don’t have an event horizon, and that the fireball can be generated without one. He believes that there’s no boundary for an event horizon because space-time varies so much around the region. So instead of an event horizon, he proposes an “apparent horizon,” which suspends light trying to escape the core.
Instead of the apparent horizon and event horizon being distinct—one sometimes extending beyond the other—which many physicists previously held, Hawking suggests that the apparent horizon is the boundary. He says, “The absence of event horizons means that there are no black holes — in the sense of regimes from which light can’t escape to infinity.”
It’ll be interesting to see what other experts say to the idea that there’s no event horizon. Don Page, a physicist who collaborated with Hawking in the 1970s, calls the suggestion “radical,” but admits, “these are highly quantum conditions, and there’s ambiguity about what space-time even is, let alone whether there is a definite region that can be marked as an event horizon.”
Hawking also suggests that an apparent horizon could disappear if it shrinks enough, which is startling because it means that, in principle, matter could escape a black hole. It wouldn’t be in particularly good shape if it did, though. Hawking’s paper, titled “Information preservation and weather forecasting for black holes” compares trying to figuring out the black hole paradox to forecasting the weather: it’s theoretically plausible, but practically, it’s nearly impossible to be accurate. In other words, who the hell knows? But hey, that’s one thing we all have in common with Stephen Hawking.