The Photon: Linear Mode of Icosahedral Geometry

We establish the photon's identity within the Bootstrap Universe framework. The photon is the linear propagation mode of the same wave that, when closed on itself, constitutes the electron. Absorption is wrapping: a linear wave closes into rotation. Emission is unwrapping: rotation opens into linear propagation. Geometrically, the photon propagates as dodecahedral face vibrations through the shared 30-edge interface with icosahedral matter structure. The 12 dodecahedral faces partition under propagation symmetry into 2 polar faces (longitudinal mode, forbidden by masslessness) and two rings of 5 transverse faces, yielding exactly 2 polarisation states whose degeneracy is guaranteed by 5-fold symmetry — the highest discrete rotational symmetry in three dimensions. The electron acts as compliant counterparty through 860 wrapping modes (F × 43), accepting any photon frequency via its extended field — absorption is a field process, not a collision. The proton is transparent to low-energy photons because its vertex-dominated geometry cannot accommodate photon wrapping without ≥145 MeV excitation. The photon couples to matter via edges with area normalisation: c₂ = (E − χ²)/D² = 26/9. The hadronic prime 743 = p(V(V−1)) cross-validates between hydrogen wavelength corrections (2 ppm) and lepton g−2 (electron: 0.094σ, muon: 0.75σ). Version 2.1: Major rewrite. New polarisation derivation (12 = 2 + 5 + 5), field interaction spectrum, scattering/absorption mechanism. Supersedes v1.3 "Dodecahedral Transit Structure."