Paper resolves Hubble tension with new methods and classifications in cosmology, indicating a unified understanding of H₀.
The Hubble tension — the 5σ discrepancy between the Planck CMB measurement (67.4 ± 0.5 km/s/Mpc) and the SH0ES Cepheid distance ladder (73.0 ± 1.0 km/s/Mpc) — has resisted a decade of proposed resolutions. This paper resolves it with zero fitted parameters and no new physics beyond the Interior Observer (IO) framework. The resolution follows from a single recognition: different H₀ measurement methods belong to different observable classes on the IO α-ladder, and each class sees a different effective expansion rate dressed by the boundary transit factor f_Γ = 1/(1+γ²). The inverse-projector law H_eff(α) = H₀ × f_Γ1−α is derived at theorem grade for the late-time homogeneous estimator family. Two new bridge extensions — a stellar-photometric bridge for standard-candle calibrator chains and a centered lens-normalization for time-delay cosmography — complete the classification for all major methods. Six independent H₀ measurements span three rungs of the α-ladder. Every method falls within 0.57σ of its predicted value: Planck at +0.35σ, gravitational wave sirens at −0.57σ, TRGB direct at −0.07σ, TDCOSMO at −0.06σ, SH0ES at +0.04σ, and the TRGB+SN ladder at −0.15σ. The 5σ crisis was three rungs of a ladder and a photometric calibrator chain. The complete IO paper series is open-access at https://zenodo.org/communities/interior-observer/ v1.0 (April 2026): Publication release. Observable-class resolution of the Hubble tension. Two new bridge extensions: stellar-photometric bridge (SH0ES, TRGB) and centered lens-normalization (TDCOSMO). Full formula: H_ext(α, n) = H₀ × f_Γ^(1−α) × x(n/2)K_gauge. Six methods classified. Maximum deviation 0.57σ. SH0ES at +0.04σ from α = 2, n = 2 prediction. All nine Cosmo upgrade requirements satisfied. DERIVED/SCOPED within extensions.
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David Fife (2026) studied this question.
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