Hubble's law
![Full-sky image derived from nine years' WMAP data](/Images/godic/202501/18/Ilc_9yr_moll40963915.png")
![Fit of redshift velocities to Hubble's law.[30] Various estimates for the Hubble constant exist. The HST Key H0 Group fitted type Ia supernovae for redshifts between 0.01 and 0.1 to find that H0 = 71 ± 2 (statistical) ± 6 (systematic) km s−1Mpc−1,[24] while Sandage et al. find H0 = 62.3 ± 1.3 (statistical) ± 5 (systematic) km s−1Mpc−1.[31]](/Images/godic/202501/18/Hubble_constant3915.JPG")
![A variety of possible recessional velocity vs. redshift functions including the simple linear relation v = cz; a variety of possible shapes from theories related to general relativity; and a curve that does not permit speeds faster than light in accordance with special relativity. All curves are linear at low redshifts. See Davis and Lineweaver.[36]](/Images/godic/202501/18/Velocity-redshift3915.JPG")
![The age and ultimate fate of the universe can be determined by measuring the Hubble constant today and extrapolating with the observed value of the deceleration parameter, uniquely characterized by values of density parameters (ΩM for matter and ΩΛ for dark energy). A](/Images/godic/202501/18/Friedmann_universes.svg3916.png")
Hubble's law is the name for the observation in physical cosmology that:
Hubble's law is considered the first observational basis for the expansion of the universe and today serves as one of the pieces of evidence most often cited in support of the Big Bang model. The motion of astronomical objects due solely to this expansion is known as the Hubble flow.