A Proposed First-Harmonic Optical Test of Preferred-Frame Effects in Dielectrics with Translational Molecular Mobility

We propose an encounter-based phenomenological method for estimatingpossible preferred-frame optical signals in stationary dielectric mediawith thermally driven molecular translational mobility, and a tabletopinterferometric test of the resulting prediction. The physical pictureis direct: even a stationary localized optical probe samples not onlymolecules along its geometrical path but also new molecules arriving atits location through thermal motion, at a rate proportional to ρσv_th.The total number of such waiting encounters during transit thereforedepends on the residence time in the medium, which isorientation-dependent at first order in β = v/c in a preferred-framemodel. In the minimal normalization used here the predictedfirst-harmonic differential fringe shift is ΔN(θ) = 2χ_t (n−1) β (v_th/c) (L/λ) cos θ, where χ_t = 1 corresponds to the simplest residence-time convention andisolates an order-unity microscopic prefactor not derived here. Theclean experimental observable is the change in differential phase undera 180° rotation of the apparatus, for which the sign reverses whilestatic path offsets do not. The signal scales with n−1 in dilute gases,vanishes in solid dielectric controls, and cancels in single-mediumround-trip geometries — explaining why most high-precision opticaltests would be insensitive to it. The effect is distinct from Fresneldrag; the same encounter bookkeeping reproduces the relativisticFresnel–Fizeau result in the rigid-body bulk-motion regime, serving asa methodological check. The proposed implementation is a two-mediacounterpropagating ring interferometer.