The Breathing Universe: 103_Fundamental Limits and the Meaning of Physical Constants v1.0

Modern physics is built upon a small set of fundamental constants that define universal limits, including the speed of light c, the reduced Planck constant hbar, the gravitational constant G, and the Planck scales derived from them. These quantities are indispensable to physical theory, yet their role is typically axiomatic: they are precisely measured but not explained in terms of deeper physical structure. This paper examines fundamental constants within the Breathing Universe Model (BUM), in which spacetime is described as a dynamic, tension-bearing vacuum governed by a vacuum tension field H(t). Rather than treating constants as arbitrary numerical inputs or as quantities awaiting deeper derivation, the model interprets them as coherence limits arising from a single organizing principle: the balance between expansive and contractive contributions to the vacuum. This balance condition, termed the zero-line, defines a reversible interface where net vacuum tension vanishes while coherence is preserved. We show that the same zero-line balance manifests hierarchically across physical regimes, including vacuum fluctuations, particle formation, matter–antimatter annihilation, black-hole horizons, and cosmological evolution. Within this framework, constants such as c, hbar, and G emerge as markers of limiting balance states that cannot be exceeded without loss of coherence. Their invariance follows from structural necessity, and their non-computability reflects a boundary of meaningful physical description rather than an incompleteness of theory. The paper further clarifies why attempts to derive fundamental constants from deeper principles inevitably lead to dimensional closure or circularity. By reframing constants as limits rather than unexplained parameters, the Breathing Universe Model functions as a theory of boundaries, explaining why certain quantities exist, why they are invariant, and why physical explanation must legitimately stop at these points.