Hubble's Law

Hubble's Law was written on a small whiteboard in Andrea 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)
Category:Physics from the real world