Science: Travelling faster than the speed of light can save you
12 Sep 2008
The world’s largest scientific instrument, the Large Hadron Collider (LHC), was switched on in Switzerland this week. Some people are worried that the LHC may cause the world to be swallowed up by a black hole, especially when it starts to operate at full force.

What would happen if you fell into a black hole?

Neil deGrasse Tyson, director of the Hayden Planetarium at the American Museum of Natural History, who wrote the definitive account Death by Black Hole, imagined the experience as “the most spectacular way to die in space”.

A black hole is a place where the force of gravity is so powerful that you would need to be travelling faster than the speed of light to escape its pull. Since nothing in the universe is faster than the speed of light, nothing that falls into a black hole can ever escape. The border at which gravity becomes strong enough to create that phenomenon is known as the “event horizon”; it marks the outer boundary of the black hole.

Closer to the centre, gravity is even stronger. If you were caught by the pull of a black hole, you would be sent into free fall toward its centre. The pulling force would increase as you moved toward the centre, creating what’s called a “tidal force” on your body. That is to say, the gravity acting on your head would be much stronger than the gravity acting on your toes (assuming you were falling head-first). That would make your head accelerate faster than your toes; the difference would stretch your body until it snapped apart. You’d be reduced to a bunch of disconnected atoms. Those atoms would be stretched into a line and continue in a processional march. No one knows what happens to those atoms once they reach the centre, or “singularity”, of a black hole.

In a small black hole — like the one predicted by the LHC doomsayers — this dissolution would occur almost immediately. In fact, for all but the largest black holes, dissolution would happen before a person even crossed the event horizon, and it would take place in a matter of billionths of a second.

The more matter a black hole gobbles up, the bigger it gets. As a black hole increases in size, the differences in gravitational force become less dramatic. If you fell into a large enough black hole, your last moments would be a little bit like being on the inside of a one-way mirror. No one outside would be able to see you, but you’d have a view of them. Meanwhile, the gravitational pull would bend the light weirdly and distort your last moments of vision.