Time slows immensely for someone at the event horizon of a black hole. From the viewpoint of an observer outside the black hole, it appears time stops at the event horizon.

How can we know the actual relationship between the relative amount of time that passes within and outside of the black hole? Is there an equation? If I am in a black hole with mass x and, from my perspective, 10 seconds pass, how much time specifically passes for someone outside the black hole?

  • $\begingroup$ @safesphere If time inside “starts” after time outside “ends”, but it doesn’t end, does that mean time inside never progresses or moves forwards? $\endgroup$
    – arara
    Commented Jan 20, 2023 at 19:17
  • $\begingroup$ @safesphere I’m not sure I follow. Earlier you said time on the inside starts “after” time on the outside ends. Here you say that something like a second passes by on the inside while on the outside you ‘approach’ eternity. Also, you say ‘as you approach the horizon’ — but do you ever actually reach the horizon? How does the relationship (or lack of one) change before/after reaching the event horizon? Maybe this needs a more fleshed out answer … $\endgroup$
    – arara
    Commented Jan 21, 2023 at 6:28


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