Resolution criteria

The Hubble Tension is resolved based on which explanation best accounts for the discrepancy between space telescope measurements finding a Hubble Constant of around 70-76 km/s/Mpc and CMB measurements providing approximately 67-68 km/s/Mpc. Resolution will be determined by scientific consensus as reflected in peer-reviewed literature and major cosmology collaborations' findings. More than one answer may resolve to 'Yes' if they are all reasonable.

Background

The universe is expanding, a discovery made by astronomer Edwin Hubble in 1929. Determining the Hubble Constant unlocks answers to fundamental questions including the speed of expansion and the precise age of the universe. Recent measurements using gravitationally lensed quasars match local measurements but clash with early-universe estimates, and this mismatch could point to new physics rather than observational error.

Considerations

Proposed explanations include something being wrong with our understanding of the early universe, exotic particles, alternative theories of gravity, and early forms of dark energy. No single systematic error seems likely to fully explain the Hubble tension. Either there are unknown systematic uncertainties in measurements that skew results, or cosmology's standard model is wrong and new physics is needed.