The Physical Ontology of Spacetime: An Interpretation of Relativistic Physics

Contemporary physics provides highly successful mathematical descriptions of spacetime, matter, and gravitation, yet the ontological relationship between spacetime and its physical contents remains an open foundational question. This paper develops a unified perspective on spacetime, gravitation, and relativistic phenomena based on the established mathematical structure and empirical content of relativistic physics. Motivated by the historical development of ideas concerning the ether, relativity, and spacetime, it explores whether material entities, fields, and spacetime can be regarded as different dynamical processes within an underlying continuous structure. Material entities are understood as localized, persistent excitations of the continuum; motion is interpreted as the propagation of localized excitation states, and inertia is associated with the dynamical resistance of such configurations to changes in their state of propagation. Mass is interpreted in relation to energy sustained in localized and dynamically coherent configurations. The invariant speed of light is associated with a fundamental propagation constraint of the continuum, while relativistic effects are interpreted in terms of changes in the internal dynamics of moving excitations. Gravitation is interpreted as the response of the spacetime continuum to localized energy configurations, with their collective macroscopic manifestation as spacetime curvature. The framework distinguishes the continuum from classical ether theories: it is not an independent mechanical medium and therefore defines neither a preferred state of rest nor an ether wind or drag. Grounded in the established mathematical and empirical structure of relativity, the framework recognizes that universal intrinsic properties of spacetime may not be independently isolable through comparative measurement.