" What can escape a black hole?"

Nothing that falls into a black hole can come back out again -- at least not in its original form. But a black hole may lose some of its mass. Quantum theory says that "virtual pairs" of particles sometimes wink into existence from the fabric of space itself.

These particles quickly cancel each other out and vanish. But if a pair of particles appear just outside a black hole's horizon, one may fall inside, never to make it outside again. If the one on the outside doesn't fall through the horizon, then the particles can't cancel each other out.

In essence, that "steals" a little bit of mass from a black hole. Over countless billions of billions of billions of years, the mass loss could become substantial enough to cause the black hole to vaporize.

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Material would come out, but not in its original form -- only as energy and subatomic particles. This energy is known as Hawking radiation in honor of Stephen Hawking, the physicist who first described it.

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