We develop a systematic analogy between the behavior of light and that of chemical mixtures, going beyond the standard pedagogical comparison (white light = "mixture of colors"). The analogy is organized around five regimes of increasing interaction strength — dilution, concentration, separation, saturation, and coagulation — each of which has a precise photonic counterpart in established physics. The five regimes: Dilution → Linear superposition of electromagnetic waves (ideal solution, non-interacting components)Concentration → Nonlinear optics: Kerr effect, second-harmonic generation, four-wave mixing (non-ideal solution, effective photon-photon interactions)Separation → Prisms, diffraction gratings, Fabry-Pérot cavities (chromatography, selective precipitation)Saturation → Planck blackbody spectrum (saturated solution at thermodynamic equilibrium)Coagulation → Bose-Einstein condensation of photons, optical solitons (precipitation, crystallization) The central thesis: linear superposition is the dilute limit of a richer vibrational interaction, not its fundamental description — exactly as Raoult's law is the dilute limit of thermodynamics, not a fundamental law of nature. The vibrations are always potentially coupled; they appear independent only when the coupling is negligible. The framework gains a geometric dimension from the observation that Maxwell's equations are intrinsically rotational (∇×): light is a self-sustaining vortical exchange between electric and magnetic fields. Optical vortices carrying orbital angular momentum (Allen et al., 1992) make this structure explicit. We organize vortex phenomena across physical domains into a stability hierarchy — from transient acoustic vortices to permanent particle-like excitations in quantum fields — and show that each of the five mixture regimes corresponds to a mode of vortex interaction: independent rotation (dilute), vortex-vortex scattering (concentrated), spatial sorting by circulation (separation), maximum vortex density (saturation), and coherent vortex merger (coagulation). The vortex perspective connects to three active research programs: analog gravity (Barceló, Liberati, Visser — sonic horizons reproduce the Hawking effect via vortex flows), topological matter (Volovik — superfluid helium-3 contains topological defects whose dynamics reproduce the standard model particle spectrum), and skyrmion physics (topologically stable vortex-like configurations that behave as particles). These programs share a structural principle: stable vortices in a continuous medium behave as particles. This is a conceptual paper. No new experimental results or calculations are presented. We organize known physics into a unified interpretive framework connecting phenomena usually discussed in separate chapters: nonlinear optics, cavity QED, blackbody radiation, photon condensation, optical vortices, and topological matter. The analogy's limitations (interference has no chemical counterpart, quantum statistics vs. distinguishability, reversibility) are explicitly documented. The paper raises two open questions: (1) what organizing principles determine which vibrational mixtures are stable? and (2) is there a universal principle governing vortex stability across substrates, from fluids to quantum fields? The convergence of independent research programs toward the same vortex-based particle picture suggests that such a principle may exist.
Thierry Marechal (Thu,) studied this question.