The event horizon is the gravity field of a black hole where the space-time is so bent that light cannot escape it. The event horizon creates a region in space where nothing can escape, if nothing can go beyond the speed of light. Thus when something enters the event horizon, it will vanish without a trace. Should the object be emitting something, after it is enveloped by the event horizon, not even the emissions that traced its existence will escape the black hole.

This creates something called the cosmic censorship hypothesis, proposed by Roger Penrose, that can be summarized as "God abhors a naked singularity" (Hawking 114). This means that no one outside of the event horizon of a black hole is capable of observing the breakdown of classical physics inside a black hole (Hawking 115). However, the black hole is also unforgiving towards those who would dare enter the event horizon (Hawking 115).