The black hole is constantly generating Hawking radiation. But the interesting thing here is that, according to theory, for every Hawking particle that leaves the black hole, another version of that particle falls into the black hole. The two particles exist on separate sides of the black hole’s event horizon, or boundary. They are physically separated, but their properties are linked, or entangled. No matter how far apart they are, their properties will always be opposite. So if the Hawking particle on the outside spins up, for example, then the particle on the inside will spin down, and vice versa.