What is the Nature of Light? In the Modified Einstein Spherical (MES) Universe Model, light is reimagined as a Quantum-Geometric Body, unifying its wave-particle duality and relativistic invariance through synchronized spacetime oscillations. By redefining time as a Chaotic Phase-Locked Variable tied to universe-scale entanglement (Zjk) and oscillatory dynamics (Cjk), this framework predicts modulated light propagation, superluminal quantum correlations (SMES>2√2), and spectral phase encoding of universal dynamics. High-precision numerical simulations and multi-platform cross-validation validate these predictions, resolving light’s role as Both a Quantum Entity and a Geometric Medium for Cosmic Entanglement. Key results include: → Local Lorentz invariance: Simulations confirm light speed constancy (c = constant) in inertial frames, with cosmological deviations ∆c/c ~10-15 over τ = 10 Gyr. → Enhanced Bell violations: Numerical solutions of the Zjk-mediated entanglement network yield SMES≈3.11, surpassing quantum limits. → Universal spectral modulation: Frequency shifts (∆v/v ~10-15) emerge from chaotic spacetime oscillations, detectable via next-generation spectrographs. This work bridges quantum optics, general relativity, and cosmology, offering testable pathways to validate the MES Universe paradigm.