Cosmic Birefringence: A Geometric Prediction from the Tetrahedral Substrate of Spacetime

We present a parameter-free geometric derivation of cosmic birefringence—the rotation of the polarization plane of CMB photons—as a natural consequence of the intrinsic chirality of the tetrahedral spacetime lattice (the Cosmic Mesh). Within this framework, where the fine-structure constant acts as a "cosmic odometer" of the lattice’s residual torsional frustration (δ ≈ 2. 034), light propagates as a traveling wave of free energy whose polarization vector is guided by the chiral metric background. By coupling the microphysics of the Planck-scale FCC lattice to cosmological distances via the Scale Bridge Hypothesis, we derive a closed-form integration for the polarization rotation. For CMB photons at the Last Scattering Surface (z ≈ 1100), our model predicts a uniform rotation angle of: β = 0. 272° ± 0. 03° This prediction contains no free fitting parameters and is remarkably consistent with recent observational hints from Planck and ACT. To distinguish this geometric mechanism from exotic axion-like fields or localized astrophysical Faraday rotation, we propose four distinct discriminant tests: 1. A non-linear monotonic redshift dependence β (z) governed by the cosmic acceleration transition. 2. Anisotropic spatial fluctuations β (θ, φ) that correlate directly with the mapped Large-Scale Structure (LSS). 3. A highly distinct, non-dispersive frequency scaling where the birefringence scales as λ⁻² (suppressed at radio wavelengths, amplified in the optical/UV). 4. A non-zero cross-correlation signal (CₗTβ) with CMB temperature anisotropies. This work demonstrates that cosmic birefringence does not require the postulation of undetected, fine-tuned pseudo-scalar fields, but stands as the first direct, falsifiable evidence that spacetime is an intrinsically chiral, discrete, and elastic medium under physical relaxation.