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Entropy is a concept of disorder. A drop of blue ink inside a glass of water only has 10^10 factorial possible ways of being an ink drop, but it has 10^11 factorial possible ways of being an ink soup. This means as we roll the dice over and over again, the state that fills most of the possible tree paths is the state we're most likely to observe. This thermodynamic time is a consequence of parts of the ink drop leaving their place of origin.

If we reversed time though, all those parts of the ink drop would all point towards the future ink drop. Similarly, if all spacetime paths of all parts of a blackhole point towards one location, then thermodynamic time is running in reverse.

My question is if this logic is valid, and if this phenomenon implies that observers who are created within the blackhole would look like they're time-reverse form our perspective (assuming we could see inside a black hole), and if this same phenomenon can be applied to us? If all our spacetime paths point towards a singularity (the big bang), but because thermodynamic time points away from the destinational singularity, are we actually going back in time? From our perspective, we will come to a drawn out heatdeath which, in time reverse perspective, looks like particles turning into photons that become more and more redshifted, exactly the reverse of what happens to matter falling into a black hole, from the matter's perspective. Are we in a black hole?

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  • $\begingroup$ Why do you think all our spacetime paths point towards the Big Bang? $\endgroup$ – G. Smith May 19 at 3:57
  • $\begingroup$ We cannot see "inside a black hole", there is no way to talk about how the inside would look from the outside. To postulate that is to postulate that the two causally disconnected regions are not actually disconnected. $\endgroup$ – ACuriousMind May 19 at 9:45
  • $\begingroup$ @ACuriousMind The stuff inside a black hole is causally disconnected from us, yes, but not necessarily disconnected from the other stuff falling in together. The question is asking about the relationship between the stuff falling in together. Also, not being able to perceive inside something, like a box, does not necessarily mean we cannot conceive inside something, like a cat. $\endgroup$ – Jurhas May 19 at 13:52
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You are saying that inside the BH, entropy decreases. Now in reality it should be the opposite.

Please see here:

Can we have a black hole without a singularity?

Where John Rennie says:

I think there is a semi-plausible way to explain why the matter can't avoid collapsing into a singularity, but don't take this too literally. I've mentioned above that if the escape velocity at the event horizon is the speed of light, the escape velocity inside the event horizon must be faster than light. But all forces, e.g. the electrostatic forces that hold you in shape, propagate at the speed of light. That means inside the event horizon the electrostatic force can't hold matter in shape because it can't propagate outwards fast enough. This also applies to the weak and strong forces, and the end result is that no force is able to resist the inwards fall of the matter into a singularity.

So basically, inside the theoretical escape velocity is greater then the speed of light, and no force can withstand the pull of gravity, and so EM cannot hold atoms together, and the strong force cannot hold nuclei together, so matter will just be a sea of quarks and electrons.

Now you are saying that, all spacetime paths point towards the big bang. Now it is a misconception that the big bang happened at a point. In reality, it happened everywhere at the same time in the universe. There is no center of the universe, where the paths would lead to.

Please see here:

https://physics.stackexchange.com/a/479850/132371

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  • $\begingroup$ The singularity is not at some precise location, it's "everywhere" inside a black hole just like the big bang is "everywhere" inside our universe. Regarding your quote, free falling objects stay together until tidal forces pull them apart. Which is exactly the reverse of what happened after the big bang. So according to your model, the big bang was a high entropy system and entropy has decreased since then, maybe because the contents of the big bang were not in a defined single location. $\endgroup$ – Jurhas May 19 at 14:12

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