📅  最后修改于: 2022-03-11 14:54:57.982000             🧑  作者: Mango
An event horizon is a theoretical boundary around a black hole beyond which no light or other radiation can escape. If someone were to be falling into a black hole, as the approach the event horizon, they would be subject to gravitational red-shift as the light climbed out of the hole's intense gravitational field.