> for example §12.2 of Wald, and problems 1 and 4 at the end of chapter 12
Literally the first paragraph of problem 1 states my exact objection.
"Since an observer outside a black hole does not lie within the causal future of the
black hole, such an observal literally cannot "see" the black hole. As is apparent from
Figure 6. 1 1 , an observer looking at a region where gravitational collapse has occurred would, in principle, see the collapsing matter at a stage where it is just outside
the black hole."
What I can't understand is how people can smoothly ignore it and calculate something that is going to happen after infinite time passes on Earth. Because those things will literally never exist, because there's simply not enough time anywhere in the universe outside of any event horizon. For the points on event horizon there's no causality line that crosses our future and there's no simultaneity line (however you define it) that crosses our future. It just won't happen, ever, in any practical sense.
> The practical sense is the binary-merger waveforms detected at LIGO, Virgo, and Kagra, which were emitted in the detectors' (and humanity's) past lightcones.
Aren't those waveforms just in agreement of theoretical prediction of what happens as the matter approaches event horizon? Because we can't have any information about it crossing it. I don't have a problem with that part. I have a problem with the part that's theorized to happen after those signals get stretched, red-shifted and stopped by gravitational dilation.
> The curve of every part of a rock chucked through a black hole horizon ends inside the horizon.
Sure at t(Earth)=infintiy.
> Coordinate divergence is not the same as curvature divergence, and different systems of coordinates on a single arrangement of mass can diverge at arbitrary radial distances, including very very large ones.
Curvature is not the only real thing. Time, which is a coordinate is also a very real thing and when it diverges to infinity at any finite point for any observer, we can't just sweep it under the rug with a coordinate change.
> "Does the ringdown overtone of a merger of two black holes encode any of the accretion history of each black hole?" is a physical rather than philosophical question and is an avenue for testing solutions of the Einstein Field Equations (including approximate ones solved numerically) against astrophysical data.
I have absolutely no problem with that. What I have problem with is postulating that anything happens (from our point of view) in that observed region of space after the ringdown overtone of a merger happens. In my opinion when the signals get too faint and redshifted for us too observe nothing ever happens there, because time there physically nearly stops for us.
Literally the first paragraph of problem 1 states my exact objection.
"Since an observer outside a black hole does not lie within the causal future of the black hole, such an observal literally cannot "see" the black hole. As is apparent from Figure 6. 1 1 , an observer looking at a region where gravitational collapse has occurred would, in principle, see the collapsing matter at a stage where it is just outside the black hole."
What I can't understand is how people can smoothly ignore it and calculate something that is going to happen after infinite time passes on Earth. Because those things will literally never exist, because there's simply not enough time anywhere in the universe outside of any event horizon. For the points on event horizon there's no causality line that crosses our future and there's no simultaneity line (however you define it) that crosses our future. It just won't happen, ever, in any practical sense.
> The practical sense is the binary-merger waveforms detected at LIGO, Virgo, and Kagra, which were emitted in the detectors' (and humanity's) past lightcones.
Aren't those waveforms just in agreement of theoretical prediction of what happens as the matter approaches event horizon? Because we can't have any information about it crossing it. I don't have a problem with that part. I have a problem with the part that's theorized to happen after those signals get stretched, red-shifted and stopped by gravitational dilation.
> The curve of every part of a rock chucked through a black hole horizon ends inside the horizon.
Sure at t(Earth)=infintiy.
> Coordinate divergence is not the same as curvature divergence, and different systems of coordinates on a single arrangement of mass can diverge at arbitrary radial distances, including very very large ones.
Curvature is not the only real thing. Time, which is a coordinate is also a very real thing and when it diverges to infinity at any finite point for any observer, we can't just sweep it under the rug with a coordinate change.
> "Does the ringdown overtone of a merger of two black holes encode any of the accretion history of each black hole?" is a physical rather than philosophical question and is an avenue for testing solutions of the Einstein Field Equations (including approximate ones solved numerically) against astrophysical data.
I have absolutely no problem with that. What I have problem with is postulating that anything happens (from our point of view) in that observed region of space after the ringdown overtone of a merger happens. In my opinion when the signals get too faint and redshifted for us too observe nothing ever happens there, because time there physically nearly stops for us.