Where does light end up after it enters a black hole?
Many have grappled with this question since the Thirties when it became widely accepted that black holes might exist. Einstein’s theory of general relativity tells us that all mass deforms space and time, causing paths taken by particles to bend towards the mass. At the event horizon of a black hole – the boundary in space-time through which matter and light cannot escape once crossed – the deformation of space and time is so strong, there are simply no paths that lead away from the black hole. Once matter or light has crossed the event horizon, it becomes impossible to determine what happens to it afterwards, since information from that event can never reach an outside observer.
Answered by Rik Sargent.