Unified Light: A Spacetime Conversion Framework — Light and Matter as Two Phases of a Single Reality

We propose a theoretical framework in which light and matter are two phases of a single underlying reality, with gravity serving as the universal conversion force between them. The framework reinterprets Einstein’s mass-energy equivalence E = mc² as a phase transition law and derives a spacetime conversion expression, 2ρ²c³, which governs the coupling intensity between matter and light phases at all density scales. This expression decomposes as the product of matter density and the radiative intensity of its own mass-energy, making it structurally incapable of existing unless both phases are real and coupled. At Planck density, the expression produces exact unity ratios for gravitational binding energy to rest energy and for gravitational frequency to Planck frequency, identifying the Big Bang as a phase decompression event rather than a thermal explosion. The framework generates testable predictions including correlations between supernova progenitor mass and heaviest elements produced, and provides continuity with Newtonian gravity and general relativity as density-specific limits of a unified conversion spectrum. Five companion papers extend this framework to black hole phase boundaries, force unification, and planetary core dynamics.