New Cosmology V: The Physical Dynamics of Light

New Cosmology V develops a physical reinterpretation of light within the Primordial Particle Background (PPB) framework established in the preceding papers of the New Cosmology series. Rather than treating light as either an independently traveling microscopic particle or a purely abstract wave, this study proposes that light may be understood as a dynamically stable, organized mode of directional force–momentum transmission formed through temporary PPB composite structures. The paper distinguishes the fundamental PPB constituent from PPB composites, radiative transmission modes, fields, and localized detection events. It examines the generation, propagation, wavelength structure, stability, interference, diffraction, matter interaction, absorption, detection, and possible structural relaxation of light. The model also connects the characteristic propagation speed of light to the collective transmission properties of the PPB and introduces a stability framework intended for later mathematical development. Long-distance structural relaxation, possible contributions to redshift, and residual low-frequency modes are presented separately as extended, testable hypotheses rather than as necessary premises of the core light model. The study also identifies observational constraints from atomic spectroscopy, quantum optics, gravitational light propagation, the cosmic microwave background, radio backgrounds, and high-energy astrophysical observations. The paper is intended as the conceptual foundation for the mathematical development planned in New Cosmology VI, where the proposed PPB transmission structure, stability conditions, conservation laws, and coupling mechanisms must be quantitatively derived and tested.