Black holes, according to relativity theory, warp space-time with their enormously powerful gravitation field. The effect of this gravitational field is that if an astronaut were to cross the event horizon of a black hole, time would slow down on board. Actually, time slows down in proportion to speed, the faster our astronaut travels the slower time runs. The closer the astronaut travels to the speed of light the more time slows, until at the speed of light, time would stop.
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