Combining general relativity (describing the behavior of gravity on a large scale) and quantum theory (describing the behavior of particles on a small scale) into a single coherent framework has been a significant challenge in theoretical physics. The current leading candidate for such a theory is called quantum gravity.
One of the key aspects of quantum theory is the wave-particle duality, which states that particles can exhibit both particle-like and wave-like behavior. This duality arises from the mathematical formalism of quantum mechanics and has been experimentally verified in numerous experiments.
In the context of combining general relativity and quantum theory, the challenge lies in reconciling the probabilistic, wave-like behavior of quantum theory with the smooth, deterministic geometry of general relativity. Various approaches have been proposed to tackle this issue, such as string theory, loop quantum gravity, and others, but a definitive and widely accepted solution has not yet been achieved.
It is important to note that these theories are highly complex and still under active development and research. The nature of the final theory that successfully combines general relativity and quantum theory is not yet fully understood. It is possible that new insights and theoretical advancements may eventually lead to a better understanding of how these seemingly contradictory aspects can be unified, but at present, the exact nature of such a theory remains an open question.