The Hubble Law
In 1929, Edwin Hubble announced that
almost all galaxies exhibited redshifts of their spectral light and therefore
appeared to be moving away from us.
This redshift appeared to
be larger for faint, presumably further, galaxies. Hence, the
greater the distance to a galaxy, the faster it is receding from Earth.
The Hubble Law describing this observation is given by
v = Hd
where v is the galaxy's radial outward velocity,
d is the galaxy's distance from Earth, and H
is the current value of the Hubble constant, a parameter to be determined by measurements.
The top right figure illustrates the Hubble law.
