The Pantheon+ sample (1,701 Type Ia supernovae spanning z = 0 to 2.3) infers H₀ ≈ 73.3 ± 1.0 km/s/Mpc with the SH0ES Cepheid calibration, statistically incompatible with Planck CMB-derived H₀ ≈ 67.4 ± 0.5 km/s/Mpc at the 5σ level (Brout 2022; Riess 2022). The discrepancy persists across systematic checks and reanalyses spanning more than a decade.
The standard model assumes a single global FLRW expansion history with constant Λ. Every probe of H₀ at every redshift, in every direction, must converge on one universal value. Pantheon+ supernovae sample the local-to-intermediate-z universe; CMB samples the integrated history from recombination forward. The two methods cannot disagree if the model is right, and the model has no way to absorb a real difference.
SCT replaces the hot-dense-center with a superluminal collision and the thermalized debris field that became our visible universe. From this single change, Λ stops being a fundamental constant. It becomes the dynamical ratio Λ_eff(x,t) = κ · U_local(x,t) / U_parent(x,t) (P17). Different probes integrate this field along different spatial paths and over different redshift ranges, so they correctly report different H₀ values.
Pantheon+ supernovae at low-to-intermediate z predominantly sit inside or near the KBC supervoid, a roughly 20% underdense region extending out to 300 Mpc. Less local mass means lower U_local, which raises the Λ_eff ratio and pushes the locally inferred H₀ about 2 to 3 km/s/Mpc above the cosmic average (P19). Independently, the parent-frame mesh has been progressively weakening since recombination through ordinary three-body ejection and dynamical friction (P14, P15, P16). That secular weakening adds another 2 to 3 km/s/Mpc to the gap between the local-volume Pantheon+ inference and the global-volume Planck inference (P18). The two contributions sum to the observed 6 km/s/Mpc tension, with no fitted parameters.
The same mechanism resolves the SH0ES Cepheid distance ladder, the H0LiCOW time-delay lensing, the megamaser disk distances, and the S₈ clustering deficit. Pantheon+ is one more observational window onto the same underlying field. There is no need to invoke evolving supernova systematics, peculiar distance-ladder calibrations, or modified-gravity models. Both Pantheon+ and Planck are correctly measuring what they measure; they are not measuring the same H₀ because there is no single H₀ in a dynamical-Λ_eff universe.
Splitting Pantheon+ by host-galaxy environment (cluster-member vs field, void-direction vs overdensity-direction) and finding zero systematic offset in inferred H₀ at greater than 2σ would refute the M5 environmental-Λ_eff explanation. DESI peculiar-velocity surveys plus environment-tagged supernova analyses can perform this test within the next few years.