You might have seen some headlines over the weekend saying things like "Stephen Hawking declares: 'There are no black holes,'" or "Stephen Hawking says black holes don't exist." (Via CNET, Yahoo)
Stephen Hawking is, of course, the Cambridge physicist most popularly associated with black holes for the last 40 years. (Via TED)
Hawking gained fame in 1974 after coming up with the idea for something called "Hawking radiation," a way that black holes might shed some of their mass and evaporate over time.
But unlike when Hawking published that theory, we actually have a long list of known black holes. So why is he now saying they don't exist? (Via NASA)
In his new paper called "Information Preservation and Weather Forecasting for Black Holes," Hawking isn't arguing that what we know as black holes don't exist. Instead, he's arguing that they aren't truly black. (Via arXiv)
Hawking's paper is weighing in on a debate that's been raging among theoretical physicists for the last year and a half. It's called the firewall paradox.
It has to do with the edge of the black hole, the line known as the event horizon. And more importantly, what happens when you fall in. (Via NASA)
Traditionally, physicists believed you would get squeezed and stretched like a piece of spaghetti.
"The fabric of space and time funnels you down to this point. So in fact you're being extruded through the fabric of space like toothpaste through a tube." (Via Comedy Central / "The Daily Show")
But back in 2012, some physicists began arguing that you would actually be flash-fried by high-energy particles, and that the event horizon is more like a "firewall," kicking off what The New York Times called "a high-octane debate" in the world of physics.
The issue here is that both sides — the classical side and the firewall side — appear to be right according to different general theories of physics, and reconciling the two requires at least one major facet of physics to be wrong. The new paper is Hawking's attempt to sidestep that paradox.
A writer for Discovery summarizes his argument: "Hawking thinks that the idea behind the event horizon needs to be reworked. Rather than the event horizon being a definite line beyond which even light cannot escape, Hawking invokes an 'apparent horizon' that changes shape according to quantum fluctuations inside the black hole — it's almost like a 'grey area.'"
Getting rid of the event horizon — the thing that makes a black hole a black hole instead of a grey one — seems pretty extreme. Naturally, there's some resistance to the idea from physicists.
One tells Nature: "The idea that there are no points from which you cannot escape a black hole is in some ways an even more radical and problematic suggestion than the existence of firewalls."
Another tells New Scientist: "It is not clear what he expects the infalling observer to see ... It almost sounds like he is replacing the firewall with a chaos-wall, which could be the same thing."
Back in 2012, Hawking referred to the idea that information can't escape black holes as his "biggest blunder." If his new theory is right, things that fall into the black hole aren't necessarily destroyed — though they would be scrambled beyond all recognition.