Vacuum as Structure: Admissibility, Interval, and the Architecture of Time

In physics, the vacuum is often described negatively: as the absence of matter, the ground state of fields, or the lowest-energy configuration permitted by a theory. While these descriptions are operationally useful, they obscure a deeper structural role played by vacuum across physical domains. The vacuum is treated as a backdrop—empty yet active, inert yet fluctuation-rich—without a unified account of why physical law remains well-defined in its absence of persistent structure. Recent discussions of early-universe coherence, large-scale structure, and the persistence of physical regularities increasingly suggest that vacuum cannot be understood solely as “empty space.” Instead, vacuum appears wherever structure fails to persist, while law and admissibility remain intact. This observation motivates a structural reinterpretation: vacuum as a regime defined not by absence, but by non-selection. Building on the framework developed in The Opening of Time, we propose that vacuum corresponds to the interval between constraint-locked temporal configurations. In this view, vacuum is not outside time, nor is it a precursor to structure. It is an integral component of temporal architecture: the regime of maximal admissibility that separates legible, persistent states. This reinterpretation allows vacuum to be treated consistently across contexts ranging from early cosmology to low-density astrophysical environments, without invoking new ontologies or abandoning established physical laws.