Planet math

The squares of the periods of any two planets are proportional to the cubes of their average distances from the sun. For example:

Planet Dist. from Sun Period in years Period^2 Distance^3
Mercury 0.387 0.241 0.058 0.058
Venus 0.723 0.615 0.378 0.378
Mars 2.524 1.881 3.538 3.538
and so on...

Source "Awake!" March 8,2005