Black Holes, Quantum Gravity and the Curvature of spacetime

[notknowing]

“Quantum Gravity” - Fundamentally based a quantum approach, utilizing QM (its derivatives or equivalents) and uses the Standard Model including the idea of particle exchange of gravitons (yet to be discovered) to account for gravity.

I hope you don't mean that "Quantum Gravity" implies making use of gravitons. There are other approaches too, such as described in
R. Van Nieuwenhove, Quantum Gravity : a Hypothesis, Europhysics Letters, 17 (1), pp. 1-4 (1992)), or in Puthoff's polarizable vacuum concept. Such approaches are based on considering gravitation not as a fundamental force but as derived from modified quantum vacuum properties.

 

[Anonym]

DocN:” Can one say that at the singularity, we would find such a transition from GR to quantum states? It appears that even the black hole itself is circular in shape--still a classical formation?”

juan_rod:” is it really an impossibility to say that classical and quantum physics are both one and the same; a thing of perspective rather than two different things? i am reminded of the geometrical classic Flatland and Spaceland books.”

Let me give an example (and the additional argument that it is worth to know electrodynamics):
The peaceful coexistence of quantum and classical physics is well-known in the quasi-classical approximation. One obtains that according to W. Heisenberg UR number of particles is the self-adjoint operator with continuous spectrum (P.Carruthers, M. Nieto, Rev. Mod. Phys., 40,411
(1968)). Indeed, you should use non self-adjoint operators which are relevant in QM as was demonstrated by V.A. Fock many years ago.

 

[Blackhaven]

Why does the curvature of spacetime cause matter to experience gravity?

 

[marcus]

Why does the curvature of spacetime cause matter to experience gravity?

That was the central idea of the theory of general relativity that appeared in 1915. We have a whole forum at PF that is devoted to relativity (both special 1905 and general 1915). You might try asking your question in that forum.

 

[thomheg]

Why does the curvature of spacetime cause matter to experience gravity?

Actually: curvature of worldlines would be better, since curved spacetime is a misnomer.
Since spacetime consist of events that combine a position and a time based on the state of an observer, the worldline of the observer is straight (by definition). The observer isn't a person, but the zero point of the frame of reference.
That's a free-falling observer. Seen from there other worldlines are curved, because of gravity.
The reason is - in my eyes- something different and the curvature is an outcome and not the cause.
(Personally I see gravity as an effect of interactions of 'parallel lightcones' that interact and deflect the other one, since there seems to be some kind of rotation with these cones.)