The question of whether spacetime must be quantized within the framework of quantum field theory (QFT) and general relativity (GR) is still an open topic of research and debate in theoretical physics. Currently, there is no consensus on a definitive answer.
Quantum field theory describes the behavior of matter and forces within the framework of quantum mechanics, while general relativity describes the gravitational interactions in terms of the curvature of spacetime. The problem arises when attempting to combine these two theories into a unified framework, commonly referred to as quantum gravity.
Quantizing spacetime is one approach to reconcile QFT and GR, and it has been a fruitful line of research in areas such as string theory and loop quantum gravity. These approaches propose that spacetime itself should be quantized at a fundamental level, much like particles and fields are quantized in QFT.
However, alternative approaches also exist. For example, some researchers explore the possibility of emergent spacetime, where the notion of spacetime arises as an effective description from more fundamental, non-spatial, and non-temporal entities. In such scenarios, spacetime may not be inherently quantized but rather emerges as a collective behavior of underlying constituents.
Ultimately, the question of whether spacetime must be quantized or whether quantizing spacetime is the most obvious solution remains an active area of research. It is an ongoing endeavor to develop a consistent theory of quantum gravity that successfully merges the principles of quantum mechanics and general relativity.