If you jumped into a black hole, you would probably be stretched to shreds – but there’s a chance you could survive and end up in a strange place where there’s no way to know what will happen next.
The way we view the world is based largely on determinism, the idea that the past dictates the future. If you have all of the information about an object and the forces acting on it, you can predict what the object will do next. Throw a ball, and you can calculate where it will land.
But at the University of California, Berkeley and his colleagues have found that determinism ends inside certain types of black holes. And a person might be able to survive a trip there.
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Crunch of death
Every black hole has an event horizon, the boundary at which anything that passes through will never be able to escape the tug of gravity. Black holes that have an electric charge contain another boundary within the event horizon called the Cauchy horizon. This is where determinism breaks down.
Astrophysicists and mathematicians have predicted that Cauchy horizons should never be stable. If the object that collapsed to become a black hole wasn’t perfectly spherical, the Cauchy horizon should become a singularity, crushing everything that comes near it.
This crunch is due to the way gravity stretches time near a black hole. Matter and energy that fall into the black hole get denser and denser, so that if you were attempting to cross the Cauchy horizon, you’d feel a massive wave of it hit you, and you’d die.
“The amount of stuff that falls into the black hole within an hour of time measured by someone outside the black hole, reaches you in an interval of a second,” says Hintz.
Expansion stops annihilation
But Hintz and his colleagues calculated that the accelerating expansion of the universe could counteract the deluge, spreading out all that energy and making it possible to pass through the Cauchy horizon without annihilation. “If you don’t hang around for an hour and just cross the Cauchy horizon quickly, it will be a rough passage, but it may not kill you,” he says.
“Once you cross that horizon, all of the information about the entire history of the universe behind you is revealed,” says at the University of Waterloo in Canada. “But even with all of that information, you cannot predict what happens next.” And what happens next could be almost anything.
The past no longer uniquely determines the future; any action you take could have nearly infinite possible effects in part because space-time can be deformed in unexpected ways. Throw a ball here, and forces beyond your knowledge could make it fly sideways or turn around and hit you in the face.
“Given that we don’t know what happens past the Cauchy horizon, it could be crazy things as long as they’re mathematically possible,” Hintz says, including things that seem “completely haywire.”
Escape through a wormhole
For example, he says, the space beyond the horizon could act like a wormhole. You could escape the black hole into a parallel universe if you steered your spaceship carefully to avoid the crushing singularity at the centre of the black hole.
Because the laws of physics break down at a singularity and the space within the Cauchy horizon is not shielded from that in any way, the space within that horizon could be filled with all sorts of strange things, says Mann. “[The singularity] could emit elephants, planets, radiation – basically anything,” he says.
There is one caveat. The calculations done by Hintz and his team only apply to black holes with an electrical charge, and those are unlikely to exist in the real world. However, Hintz and Mann say that it’s likely that rotating black holes – which do exist and have been detected – could have similar properties.
“This could plausibly happen in the real world,” says Mann. “If you jump into a black hole, you might hit a singularity, but you might jump into another universe, and we don’t know what could happen there.”
Physical Review Letters
