Life In A Black Hole

In Black Holes by Brian Koberlein

Your spacecraft is failing, and ahead looms the dark majesty of a black hole. As its gravity pulls you ever closer, you cross its event horizon and your fate is sealed. You are trapped forever. What happens next is the subject of numerous movies. Do you travel through a wormhole and enter another universe? Do you confront the intersection of reason and faith? Do you travel back in time to communicate with your daughter? The scientific answer is much more mundane. You die, crushed by the the tidal forces of the black hole interior as you are pulled inevitably to its singularity. But perhaps there is an alternative where you are trapped but could continue to live a full life. 

There is no question that if you enter a black hole you can never leave. The event horizon of a black hole ensures that not even light can escape a black hole. To find out what happens next, you have to calculate your orbital path within the black hole, what is known as a geodesic. The simplest geodesic to calculate is for a simple mass dropped into a non-rotating black hole. What is tells us is that you are fated to be crushed by the black hole singularity in a relatively short time. In a supermassive black hole you would have a bit more time, but your days are numbered. More general calculations support this idea. In relativity, the harder you try to escape, the more energy you would need, and the gravitational pull of that energy would work against you. Entering a non-rotating black hole is a death sentence.

Calculated orbits of light and matter near a singularity. Credit: Vyacheslav I. Dokuchaev

But real black holes rotate, and this is where things get more complicated. When a black hole rotates space and time are twisted through an effect known as frame dragging. Fall into a rotating black hole, and its rotation will cause you to spiral around the black hole as you’re entering it. Calculating the geodesics for a rotating black hole interior are more complex, and have to be done numerically. But given the way black holes work it was generally thought that rotation wouldn’t save you. You might orbit the singularity a few times before reaching it, but you would still be doomed. Recently, however, it was found that this might not be the case.

Calculations of orbital paths within rotating and charged black holes shows that it is possible to have stable orbits within a black hole’s event horizon. This means it would be possible to enter a black hole and find a stable orbit around the singularity. You’d still be trapped inside the black hole forever, but you wouldn’t be doomed. In principle, you could survive inside a black hole.

The calculations are only for the ideal case of orbits in a vacuum. Any radiation in the black hole, or other infalling matter would degrade your orbit and make it unstable, so you would still be doomed inside a real black hole. But perhaps with a bit of ingenuity and luck you might be able to create a somewhat stable orbit in order to live our your life before you reach a singularity grave. It’s all pretty speculative, but at the very least it gives science fiction an answer to “what happens next?” that is a bit closer to reality.

Paper: Vyacheslav I. Dokuchaev. Is there life inside black holes? Class. Quantum Grav. 28 235015 (2011)