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Black Hole Puzzle

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51–57 of 57 posts

Re: Black Hole Puzzle

#51
post #12

Earlier quoted context omitted.

The objects can emit photons by themselves. The problem is that (classically) when you cross the event horizon, the photons that you emit at just that moment will _stay_ _in_ _place_ forever.

> (classically) ... photons Uhhh... one of those words should go. Let's keep it fully classical and drop "photon": we're interested in gravitational effects rather than quantum ones (uncertainty, fluctuations, tunnelling, details about scattering and more). Really what we want is something to illuminate (pardon the pun) interesting null geodesics, so a thin collimated beam -- a pencil of light -- will do. The relevan…

I mean, we can say "electromagnetic wave" instead of a "photon". It doesn't really change much in this case.

I don't quite understand their diagram and their point. Are they looking at a region inside the collapsing shell of material? Then there's no contradiction here, the observer won't see anything until the reach the singularity (where the space-time stops being locally flat).

Even if we consider an observer in the center of the shell, they'll only encounter the singularity after they get hit by the infalling matter.

Re: Black Hole Puzzle

#52
post #49
post #47

Earlier quoted context omitted.

That is the core of the issue: hawking radiation would seem to be completely random, and therefore have no relation to what went into the black hole. But basically the entirety of physics works in a time-reversible fashion: if you could flip the direction of all the particles in a system, it would evolve back to its previous state (including such situations as two fluids mixing: entropy is how the precise arrangement…

> But basically the entirety of physics works in a time-reversible fashion: if you could flip the direction of all the particles in a system, it would evolve back to its previous state What does that even mean though? Certain systems may indeed time-reversible, but I would argue that most are not (practically speaking). Imagine for example a meteorite which has fallen to Earth. In order to "reverse the process", not…

The first one is talking about the quantum realm. So, absent of measurement or some kind of collapsing of the wave function, pure quantum states are 100% reversible. So the question is, where does the transition happen from the quantum world to the world we know. Whence Einstein's question about "when I stop looking at the moon does it disappear". So far, nobody knows. So far, we haven't observed any limits to how big a pure quantum system can get, and there's no "spontaneous" collapse if we don't measure something.

So the question is, could a pure quantum state model a meteor crashing into Earth? It doesn't seem like it. Friction, heat, and so on cannot be reversed classically. The question of Schrodinger's Cat even becomes moot because in an isolated system, the processes a body requires to sustain life (such as friction and heat) can't be modeled in the first place, so the cat will turn into a sloppy goop before anyone pulls the trigger. So, what's going on? Why does quantum mechanics seem to model everything that happens in the microscopic world, but in the macroscopic world we see things that it can't? Where does that crossover between microscopic and macroscopic occur? If measurement is what causes quantum wave collapse, then would none of this happen if nobody was there to measure it? And what created the measurers? 99 years since Schrodinger's equation, and we're not particularly any closer.

Black holes also seem to violate reversibility. They absorb information, but the radiation they give off is random. So, it's impossible to perform the process in reverse. This is spooky in a different way than the above because it's purely mathematical. For "regular" micro/macro quantum/classical paradoxes, we're generally talking about the classical realm of experiments. But for black holes, it's pure math, of our two fundamental theories of nature, and showing that they don't line up. Though, it's perhaps less spooky because the obvious answer is that one or both of the theories is slightly wrong, so we just need to fix it. The measurement problem, or understanding waveform collapse, I think is the more interesting problem, but that's just me.

Re: Black Hole Puzzle

#54
post #37

What this thread is really missing is a simulation. I can't promise its the enterprise (as the performance constraints are crippling), but here's a bunch of cubes instead: https://www.youtube.com/watch?v=iTw0pJvTkGw It seems that what you see is the object flattened on the shadow in front of you, and it remains flattened. Apparently past me didn't implement redshift on objects, but its likely extremely redshifted Edi…

I guess we see a bit of light coming from the top and sides that would normally be hidden, but that ray tracing is making the renderer very sad because sometimes you sample from the back of the polygon that doesn't have texture?

Or something like that, there's definitely something funky going on with the view of the top surface that's unrelated to GR.

Re: Black Hole Puzzle

#55
post #2

This is a relevant-ish short story by Greg Egan on humans jumping into a black hole: https://www.gregegan.net/PLANCK/Complete/Planck.html

Here's a short fiction idea if anyone wants to take it up.

Forward causation in time with predictive ability must imply Downward causation.

This scenario is similar to the scenario in which the time and space axes inside the black hole swap places. If that is possible within the blackhole, then it must mean that it should be possible everywhere. Similarly to how we first find the holographic effect to apply to only blackholes but then generalize to the whole universe.

Downward Causation : https://www.preposterousuniverse.com/blog/2011/08/01/downwar...

Re: Black Hole Puzzle

#56
post #37

What this thread is really missing is a simulation. I can't promise its the enterprise (as the performance constraints are crippling), but here's a bunch of cubes instead: https://www.youtube.com/watch?v=iTw0pJvTkGw It seems that what you see is the object flattened on the shadow in front of you, and it remains flattened. Apparently past me didn't implement redshift on objects, but its likely extremely redshifted Edi…

Replace Starfleet Captains with The Borg and suddenly your simulation is perfect.

Re: Black Hole Puzzle

#57
post #37

What this thread is really missing is a simulation. I can't promise its the enterprise (as the performance constraints are crippling), but here's a bunch of cubes instead: https://www.youtube.com/watch?v=iTw0pJvTkGw It seems that what you see is the object flattened on the shadow in front of you, and it remains flattened. Apparently past me didn't implement redshift on objects, but its likely extremely redshifted Edi…

I guess we see a bit of light coming from the top and sides that would normally be hidden, but that ray tracing is making the renderer very sad because sometimes you sample from the back of the polygon that doesn't have texture? Or something like that, there's definitely something funky going on with the view of the top surface that's unrelated to GR.

Its hard to explain exactly what's accurate here when you're looking at the precise shapes - part of the problem is that this rendering is extraordinarily complex to do in real time, and it relies on the size of the object (tris) being 'small' relative to the curvature of spacetime

There's actually no texturing here at all though, if you see a face disappear its because general relativity is hard. The extra disconnected pieces are something to entirely ignore as well, and occur because tris become nearly parallel with rays leading to long intersection lengths (as well as numerical issues), leading to the local flatness assumption breaking down

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