General relativity predicts something extraordinary at the event horizon: time dilation becomes extreme. An observer watching someone fall toward a black hole would see them slow down, their light redshifting until they appear to freeze at the event horizon. From the outside, they never quite cross it. They just fade to a dim, red smear.

But for the person falling in, nothing special happens at the event horizon itself. They cross it at normal speed and only realize they are past it when they discover that every direction — even "outward" — leads deeper in.