Science

The Black Hole Firewall Hypothesis Says a Black Hole Would Incinerate You on the Spot

Most people know that if you fell into a black hole, you'd never get out. You might even know that, in theory, you'd be stretched so much by the extreme gravity that you'd be "spaghettified." Well, there's another possibility: the moment you passed the edge of the black hole, you'd be annihilated in a fiery death. Meet the black hole firewall hypothesis.

A Fiery Paradox

Black holes are plagued with problems, scientifically speaking. The strange phenomena spring from Einstein's theory of general relativity, which says that the more massive an object, the more it warps spacetime.

Black holes arise when an object, like the shrinking core of a massive star, packs all of its mass into an infinitely small point that warps spacetime so much that not even light can escape. But if nothing can escape, then information about every particle that enters the black hole is destroyed forever. And quantum mechanics says that's not possible. The quantum principle that puts a stop to this is called unitarity, which says that information can't be destroyed.

In the 1970s, theoretical physicists Stephen Hawking and Jacob Bekenstein showed that a black hole's event horizon, or the border that defines where you can and can't escape, emit energy known as Hawking radiation. Every bit of Hawking radiation, they said, was emitted in entangled pairs of particles that form near the event horizon (for more on quantum entanglement, check out this article). For every particle in that pair that shoots out as radiation, the other falls into the black hole. Over a long time, all that escaping mass will make the black hole start evaporating into oblivion — not a good sign for unitarity. Hawking and Bekenstein said the information must be escaping as Hawking radiation. No problem!

But hold on a minute. Every entangled pair has one particle that escapes and one particle that falls in, but eventually, that particle that fell in is going to escape, too — and it'll need an entangled particle to fall in, in turn. That causes a paradox. A particle can only be entangled with one other particle at a time, but for information not to be destroyed, it has to be entangled with more than one particle. What to do?

The only way to resolve this paradox is to assume one of the three fundamental theories at play in this scenario is wrong. The first we already described: the unitarity principle, or the fact that information can't be destroyed. The second is the equivalence principle, another tenet of general relativity that says there's no difference between inertial motion and gravity — it's also the reason you feel heavier climbing in an elevator, and why aviators can refer to their acceleration in terms of the earth's gravity (or gs). Finally, there's quantum field theory as a whole, the laws that govern how physics works — even if those laws break down inside the black hole.

There's no way around it, it seems. One of these principles has to go.

Behind The Curtain

Enter: the black hole firewall. First proposed in 2012 by University of California, Santa Barbara researchers Ahmed Almheiri, Donald Marolf, Joseph Polchinski, and James Sully — often referred to as "AMPS" — the hypothesis says that particles are entangled with more than one other particle, but that entanglement is broken the moment it forms. That would create extreme quantities of energy at the event horizon, creating a curtain of fire that incinerates anything that passes through.

There are a lot of scientists that have big problems with this hypothesis. And yet, no one has disproven it. In 2013, researchers from University of York published a paper that seemed to fix this issue with entanglement, and in 2016, researchers from the University of Victoria in British Columbia posed a new hypothesis that said yes, you'd burn up when entering a black hole, but just because of your acceleration — no firewall necessary. Even so, the firewall paradox still nags at physics — that is, until a convincing solution comes along.

Can Black Holes Have Firewalls?

Written by Ashley Hamer December 4, 2017