Global propagation and local interaction of photons in emergent spacetime

We clarify a conceptual point that becomes crucial in models where spacetime is emergent from matter: photons may propagate through a global, effectively constructed spacetime metric, while all physical interactions with photons necessarily occur in the local spacetime of the interacting system. This separation resolves apparent tensions with Lorentz invariance and explains why high-energy photons do not probe microscopic spacetime fluctuations in their propagation speed. The argument is model-independent and applies equally to General Relativity and to emergent-spacetime scenarios.