The deepest identification in Pentagon Physics: coherence is light. Not metaphorically — physically. Light is coherence in its propagating form. Matter is coherence in its standing form. The distinction between light and matter is not a distinction of substance — it is a distinction of state. A photon is a mode of coherence propagating below the self-referential threshold. An electron is a mode of coherence that has crossed the threshold, paid the mass cost of self-reference, and frozen into a standing wave. E = mc² is the exchange rate between these two states of the same thing.