Geometric Unification of Gravity and Electromagnetism from SO(4) Projection: Zero-Parameter Predictions and Observational Confirmation

We present a geometric framework in which physical space is four-dimensional Euclidean (R4) and all apparent forces arise from the projection onto the observed three-dimensional subspace. The derivation chain SO (4) to SO (3, 1) to Fᵤv to Maxwell proceeds from geometry alone, with zero postulates. A single geometric constant Pi = 2pi²/sqrt (12) = 5. 6982 determines the theory. Six independent observational tests confirm the framework with zero free parameters. --- Version 2 (08/04/2026) --- Added Test VI: Inclination distribution of prograde irregular moons of the giant planets. Key results: Kozai gap edge: 60. 37 deg vs R4 prediction 59. 99 deg (0. 12 sigma) Margaret (Uranus): i = 56. 63 deg = thetac +/- 0. 09 deg, P = 4. 2e-4 Zero free parameters throughout Dataset: 85 irregular moons, 4 giant planets Source: JPL Horizons JUP347/SAT455/SAT456 (2025) Script: irregularₘoonsₐnalysisᵥ2. py (reproducible) Added: historical reference Barthel (1940), precursor of R4 geometric intuition. DOI: 10. 5281/zenodo. 19462577