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$\begingroup$ Thank you for the great answer! $\endgroup$
– Charles Averill
Commented Sep 8, 2021 at 0:48
$\begingroup$ "The light that reaches infinity will be less energetic that it was" - The energy of an ascending photon doesn't change when measured in the same coordinate system. If a photon arrives to me "redshifted", then in my coordinates it was emitted already "redshifted" and never changed its energy or color. So the redshift here refers to the fact that energy is generally frame dependent, but not to the energy of a photon changing in flight. $\endgroup$
– safesphere
Commented Sep 8, 2021 at 6:06
$\begingroup$ "Time passes slowly in a gravitational well. The deeper in, the more slowly. So it takes longer to escape than you might expect. - It takes only a fraction of a second for light to escape far enough from any physically meaningful distance, even from a Planck length. $\endgroup$
– safesphere
Commented Sep 8, 2021 at 6:25
2

$\begingroup$ "Inside the event horizon [...] Light pointed outward does not travel outward." - How do you point "outward" (or "inward") inside the horizon? These are directions in time, not in space. How do you point a flashlight to yesterday? $\endgroup$
– safesphere
Commented Sep 8, 2021 at 6:32
$\begingroup$ @safesphere - Your objections are correct. I was talking too loosely. I have made some edits, but I don't know that it improves matters. I will say that a fraction of a second can be significant. GPS would not work in Earth's gravity without relativistic corrections. $\endgroup$
– mmesser314
Commented Sep 8, 2021 at 14:50

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