This law of astronomy grew out of a relationship discovered between radial velocity and distance.  
This law of astronomy grew out of a relationship discovered between radial velocity and distance.  The associated constant, also named after the same astronomer, is only known to within a factor of two.  FTP, name this law that states that the further away a galaxy is away from is, the faster it is receding away from us.
This law of astronomy grew out of a relationship discovered between radial velocity and distance.  
Hubble's law