Kepler's Laws

First Law - Planets orbit the the sun in elliptical orbits, using the sun as one of the ellipses two foci.

Second Law - The areas swept over by a vector (line) drawn from the sun to a planet are proportioned to the times of describing them.

Third Law - The squares of the times of revolution of two planets are in the ratio of the cubes of their mean distances. From data obtained, as orbital radius (R) increases, the period (on cycle, or T), gets bigger. The relationship between R and T were found to be:

K = R3 T2

Where:

R = orbital radius (m) - center of body 1 to center of body 2
T = period (s) - time per orbit
K = Kepler's Constant (m3/s2) - Constant only in the system it was measured in.