Black holes are powerful engines of pure
gravity, capable of pulling on objects so intensely that they can't possibly escape.
When those objects near the event horizon, they're accelerated to incredible velocities. Now, some physicists are suggesting harnessing the gravitational pull of black holes to create ferocious particle accelerators. The trick, the new study finds, is to carefully set everything up so that
particles don't get lost forever in the insatiable black hole. This new insight may help us identify black holes from the streams of particles blasting away from them.
Falling together
Let's say a particle starts falling into a black hole. As it gets closer to the black hole, it speeds up, just like a ball speeds up as it rolls down a hill. In fact, it's much worse than a ball rolling down a hill, because the gravity of a black hole is so strong that particles can fall in faster than the speed of light
The event horizon — the distance from the black hole where infalling particles reach the speed of light — defines the boundary of the black hole.
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