Is there a real chance that there is a multiverse?

[Alex K]

The big thing is that he could show evidence for entanglement between the sound quanta emanating outside the horizon and the ones falling in, just like with Hawking radiation coming from pairs of virtual particles created spontaneously near the event horizon where one comes out and one with negative energy falls in.

Oh, wow.  I didn't realize what a parallel a sonic black hole could be.

I have a question, but it might be a bit dense.  Does the negative energy particle, which is inside the event horizon, think IT'S in a vast expanse of space, and that its partner is the one trapped?  Is it possible that the apparent curvature has an inverse relationship depending on which side of the line you fall on?

The question is certainly not absurd because there are many such dualities in physics.
I think for ordinary schwarzschild black holes, the answer is most likely no. If you trace mathematically what a particle does inside the event horizon (and one can do that uniquely, because the apparent singularity at the Schwarzschild horizon can be avoided mathematically by going to suitable time-dependent coordinates), it falls into the central singularity in finite time as measured by the particle itself. That seems to be objectively different from the experience an outgoing particle has.

That being said, mathematically ideal eternal electrically charged and rotating black holes could serve as wormholes leading to white holes spitting stuff back out. Even weirder, and that will go in your direction, Hawking and others posited that black holes and white holes might in fact be the same thing, so would the particles coming out have fallen in some time. I don't know enough about it, and whenever I think I understood it, I always get confused again. I think it falls flat because there are no such objects in the universe.