>>14005011>>14005039See
>>14004959There isn't a "problem where to draw the line". It's more like QM and GR just don't affect each other. Instead they simply ignore each other completely other than that one of them happens to happen in the environment described by the other.
You can treat quantum systems in curved spacetime just fine and calculate anything you want the same way as in flat space except the equations are a bit more complicated because of the curvature. Things will continue to work and move more or less like macroscopic matter would in curved spacetime, but the problem is that anything quantum scale will itself have essentially no effect on the curvature since there is basically no mass to speak of when compared to classical systems like planets or galaxies or anything else you would typically consider in terms of GR, so the mass, gravity and curvature will have a source outside the quantum system.
When anyone says QM and GR are incompatible what they mean is that there are no sensible answers in the *extrememal* case, like at the singularity.. There is no quantum description of space or gravity, or at least none of the models that exist can be proven without poking a black hole, more powerful particle accelerators or some other clever experiment. There are models explaining what happens, but without proof it's just an educated guess and there are multiple candidates to pick from. There should be a graviton, but who the fuck knows.
>GR is correct except about the insides of black holes (which we can't observe anyway so who cares)That's exactly what everyone cares about and the reason for the "incompatibility". Everywhere else there is no conflict at all. Your quantum system just evolves according according to the Schrödinger equation while pulled into the black hole as usual. And it hits the singularity. But then what? QM says the system MUST keep evolving, but GR says that your particles arrived at some weird place with no space and no time.
