This would suggest that as I see the entire future of the universe as I fall towards the event horizon I also see the entire future of the horizon itself... which means that I will never cross the horizon because it will at some point far in the future no longer exist.
i.e. there is no spacetime path which ever crosses the event horizon
I'm near the point where I'm going to have to learn some black hole math to convince myself otherwise. (I think I'm wrong but can't see why)
> i.e. there is no spacetime path which ever crosses the event horizon
As I understand it, there isn't, from the perspective of an observer external to the event horizon.
(warning: I am only an avid watcher of PBS Spacetime)
This is not correct. An observer outside the horizon cannot see anything at or inside the horizon; but that doesn't mean he can't calculate that there is a region of spacetime inside the horizon, from observations he can make from the outside. He can.
No, you don't. Most of the universe will never be in your past light cone as you fall to the singularity. The fact that the singularity is unavoidably in your future when you are inside the hole, does not mean it is also to the future of everything outside the hole.
No, you won't even see all of those if you fall in; the most you will see are the events that end up in your past light cone before you hit the singularity. That is only a portion of the entire spacetime region inside the horizon.
No, that's not what the post I responded to meant. That post was specifically talking about what an observer falling into a black hole and hitting the singularity would see. That is not the same as existing forever outside the hole's horizon.
To be fair until your comment I wrongly believed the moment you'd be crossing horizon you'd be hit by all light ever emitted toward that point of the horizon in the entirety of the future (assuming no hawking radiation of course).
This is one of the things shown in interstellar before he hits the tesseract and they go into pure speculative scifi. He gets bombarded with extremely energetic blue shifted particles as he moves through time while falling.
Regarding what happens at the event horizon, your question is slightly inaccurate in that the photon is what you observe so it doesn't emit anything. If you assume, say, a torch falling in facing toward you, the reason that it feels delayed is ofc that it has to move out of the gravity well of the black hole. I haven't thought about the question myself, but basically think about the entire set of photons your torch emits and assume it is a magically resilient thing that never tears apart.
Then it emits a fair few trillion packets of energy before it crosses the event horizon. Most of this is caught in the photon sphere and never makes it out (depends on incident angle and some other calculations I forget).But we will assume photons are ejected in one line out on some radius vector of the black hole. Then all photos ejected before the event horizon will eventually escape and you will see them. The last one is supposed to escape asymptotically as you approach the horizon but it is only constrained by how much energy it loses traversing that piece of space time from the event horizon to infinity (i.e. where the observer is located).
So we can deduce that it gets emitted at some point in time. We assume infinity to make the math easier but real life is quantized so it'll likely be sooner than that. I can't do any better than that unfortunately.