The nature of gravity and its relationship to quantum mechanics is still an open question in theoretical physics. While gravity is well-described by Einstein's general theory of relativity, which is a classical theory, it has not yet been successfully reconciled with quantum mechanics.
Gravity is understood as a fundamental force of nature that governs the interactions between massive objects. General relativity provides a classical framework for describing gravity as the curvature of spacetime caused by the presence of mass and energy. It has been highly successful in explaining gravitational phenomena on large scales, such as the motion of planets, the bending of light, and the behavior of black holes.
On the other hand, quantum mechanics describes the behavior of matter and fundamental particles on very small scales. It has been highly successful in explaining the behavior of subatomic particles and the fundamental forces except for gravity. Quantum mechanics relies on the notion of discrete energy levels, probabilistic behavior, and wave-particle duality.
The challenge arises when attempting to combine general relativity with quantum mechanics to form a theory of "quantum gravity." The current leading candidate for a theory of quantum gravity is string theory, which posits that fundamental particles are not point-like but rather tiny, vibrating strings. However, string theory is still under active research and has not yet produced definitive experimental predictions.
Quantum gravity aims to provide a framework that unifies the principles of general relativity and quantum mechanics, allowing for a consistent description of gravitational interactions at a quantum level. However, due to the extreme conditions and energies involved, experimental verification of quantum gravity effects has been challenging.
In summary, while gravity is not yet fully understood within the framework of quantum mechanics, theoretical physicists are actively working towards developing a theory of quantum gravity that can reconcile these two fundamental pillars of modern physics.