The Hubble Tension as a Measurement Artifact: Quantifying the Frame-Mixing Systematic via Horizon-Normalized Coordinates

The reported 5σ Hubble tension between Planck (H₀ = 67.4 km/s/Mpc) and SH0ES (H₀ = 73.04 km/s/Mpc) is demonstrated to be substantially a frame-mixing artifact arising from comparing datasets processed under incompatible coordinate assumptions. Using the Pantheon+SH0ES dataset (1,701 SNe Ia; 43 Cepheid calibrators), we show that expressing distances in horizon-normalized coordinates ξ = d_c/d_H removes 93.3% of the apparent tension for redshift-derived distances. The Cepheid calibrators themselves imply H₀ = 69.78 ± 13.97 km/s/Mpc — between the two competing values — when analyzed independently of pipeline assumptions. The residual physical tension is ~3%, not 5σ. The tool that makes this separation visible is…