Abstract:In quantum gravity interpretations, the role of space-and time-related concepts is debated. Some argue that these concepts are not needed to describe physical reality at the Planck scale. Others object that an operational definition of magnitudes cannot get rid of spatiotemporal notions. We propose a "conceptual test" to assess if the mathematical content of a quantum gravity theory refers to some possibly verifiable empirical model. Given that any physical model describes the evolution of a set of measurables, these must be detectable in any empirical interpretation of a physical theory, including quantum gravity ones. Our test ultimately relies on considerations and studies concerning human cognitive limits in the discrimination of magnitudes.
An astonishing thesis in the philosophy of quantum gravity is that spacetime ”disappears” at the fundamental level of reality, and that the geometrical notions of ”length” and ”duration” are derived from the dynamics of the basic non–geometrical building blocks of the theory. Unveiling here the analysis of the concepts of spacetime, measure, and magnitude, given by the philosopher Nicolai Hartmann, I argue that the ”disappearance” thesis is too strong. The fundamental geometrical notions are, on the contrary, primitive and cannot be derived from the fundamental building blocks; they must be presupposed ab initio not only for epistemological, but also for methodological reasons
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