When you add a proper description of the physical vacuum to describing the immediate environment near the event horizon of a black hole, the virtual electron-positron particle pairs that are always flashing in and out of existence, become separated by the strong gravitational tidal forces near the horizon. One of the particles may then escape while the other falls into the hole, thereby the event horizon is not black but from the viewpoint of a distant observer it is constantly emitting particles. Over time, this 'Hawking radiation' would steadily reduce the gravitational mass of the black hole, causing it to eventually evaporate.

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