Hubble's Law

Hubble's Law was written on a small whiteboard in Miss Quill's physics classroom, expressed as:

$v=H_{0}\,d$

The board also stated that:

$z={\frac {v}{c}}={\frac {H_{0}\,d}{c}}$

And that rearranging this would give:

${\frac {r}{L_{1}}}={\frac {\mbox{distance to a galaxy}}{t{\mbox{'s speed of recession}}}}$

(TV: Detained)