KinexiaLEARN PHYSICS

Hubble constant

The Hubble constant gives the current expansion rate of the universe: galaxies recede at about 70 km/s for every megaparsec of distance. Unlike SI defining constants it is MEASURED from observations, and its exact value is still debated (the 'Hubble tension' between early- and late-universe measurements).

Used in

  • Hubble's law: recession velocity v = H₀d
  • Estimating the age of the universe (~1/H₀)

Source: Planck 2018 / SH0ES (measured, value approximate)