Hawking revisited these quantum processes but now imagined them taking place just outside the event horizon of a black hole. When a particle-antiparticle pair pops into this environment, sometimes the two particles will annihilate quickly, just as they would anywhere else. But, and this is the point, Hawking realized that on occasion they will not annihilate. Sometimes one member of the pair will get sucked into the black hole. The surviving particle, now bereft of a partner with which to annihilate (and tasked with conserving total momentum), turns tail and rushes outward. With this happening
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