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You have that backwards. The person falling into the black hole falls straight towards the singularity as if it was any other massive object, straight through t

You have that backwards. The person falling into the black hole falls straight towards the singularity as if it was any other massive object, straight through the event horizon without noticing anything change. The far away observer sees the falling one infinitesimally approach the event horizon, but never cross.

he0001 4y ago
This ”never cross” statement bends my mind. Doesn’t it also mean that if we are observers, observing a black hole, we should not see an actual blackness as we should only see things that are slowly falling into the hole? Regardless of how much time that has been spent from the beginning of time? I mean the event horizon is the boundary but that never happen?
- cthalupa 4y ago
  The light is increasingly redshifted, so for practical purposes it disappears from view quite quickly. The more sensitive the instrument, the longer you can observe, and this doesn't really have a limit - as sensitivity approaches infinity, so does the length of time you could continue to observe the object. But for practical purposes, we would not see a black hole as some sort of weird psuedo-magnet with all sorts of junk stuck to the edge of the event horizon.
- OkayPhysicist 4y ago
  Because of time dilation, light emitted (or reflected off of) objects very near the event horizon end up getting spaced out over (almost infinite) amounts of time. For example, lets say you dropped a beacon that flashes every second into a black hole. As it approached the event horizon, you'd see the flashes only happen every 2 seconds, 4 seconds, minute, hour, decade, etc. Meanwhile, the length of those flashes are getting longer at the same rate, while producing the same number of photons, so the light gets dimmer and dimmer.
  - he0001 4y ago
    Another factor, that other things are falling into the whole, wouldn’t that mean that the event horizon, relatively, gets closer to an earlier object? Meaning an object may reach the event horizon faster than it would originally or is that constant relatively where the object exist in its descend?
dylan604 4y ago
>The person falling into the black hole falls straight towards I guess you're assuming zero velocity by that person. But if there is velocity, wouldn't the fall not be straight towards but in an ever shrinking/decaying orbit trajectory?
dotancohen 4y ago
Terrific, thank you! I should have remembered the film Interstellar, where an observer on a spacecraft orbiting a massive planet (itself orbiting a black hole) feels decades pass whereas the landing party to the massive planet experience about an hour go by. Even wording this sentence is difficult! I'm reminded of the Persian word for time, which literally means "the thing that passes".

he0001 4y ago

This ”never cross” statement bends my mind. Doesn’t it also mean that if we are observers, observing a black hole, we should not see an actual blackness as we should only see things that are slowly falling into the hole? Regardless of how much time that has been spent from the beginning of time? I mean the event horizon is the boundary but that never happen?

cthalupa 4y ago
The light is increasingly redshifted, so for practical purposes it disappears from view quite quickly. The more sensitive the instrument, the longer you can observe, and this doesn't really have a limit - as sensitivity approaches infinity, so does the length of time you could continue to observe the object. But for practical purposes, we would not see a black hole as some sort of weird psuedo-magnet with all sorts of junk stuck to the edge of the event horizon.
OkayPhysicist 4y ago
Because of time dilation, light emitted (or reflected off of) objects very near the event horizon end up getting spaced out over (almost infinite) amounts of time. For example, lets say you dropped a beacon that flashes every second into a black hole. As it approached the event horizon, you'd see the flashes only happen every 2 seconds, 4 seconds, minute, hour, decade, etc. Meanwhile, the length of those flashes are getting longer at the same rate, while producing the same number of photons, so the light gets dimmer and dimmer.
- he0001 4y ago
  Another factor, that other things are falling into the whole, wouldn’t that mean that the event horizon, relatively, gets closer to an earlier object? Meaning an object may reach the event horizon faster than it would originally or is that constant relatively where the object exist in its descend?

dylan604 4y ago

>The person falling into the black hole falls straight towards I guess you're assuming zero velocity by that person. But if there is velocity, wouldn't the fall not be straight towards but in an ever shrinking/decaying orbit trajectory?

dotancohen 4y ago

Terrific, thank you! I should have remembered the film Interstellar, where an observer on a spacecraft orbiting a massive planet (itself orbiting a black hole) feels decades pass whereas the landing party to the massive planet experience about an hour go by. Even wording this sentence is difficult! I'm reminded of the Persian word for time, which literally means "the thing that passes".