Hubble tension

The Hubble tension is the inconsistency in current determinations of the Hubble constant (H₀), the current rate of the Hubble expansion. Such determinations are in the general range of 65-to-75 (km/s)/Mpc, but two independent methods that each ought to have little uncertainty, each show the results of the other method to be highly improbable. Determinations using the CMB are in the range of 66-68 whereas those based upon the cosmic distance ladder (particularly Cepheid variables) are in the range of 72-75. The inconsistency has been a motivator for reanalysis to detect any flaws in existing determinations, more efforts (including observations) to determine the constant, and theorizing regarding new science that could explain why the conflicting determinations might be measuring different values. Like the sigma-8 tension, it is one of the major anomalies regarding the Lambda-CDM model and current observation.