Kepler's third law states that the squares of the orbital periods of two planets are proportional to the cubes of the semi-major axes of their orbits. In mathematical terms, this can be expressed as:
\[ \frac{T_1^2}{T_2^2} = \frac{R_1^3}{R_2^3} \]
Where \( T \) is the orbital period and \( R \) is the orbital radius (semi-major axis).
From this relationship, one can infer that:
- The ratio of the squares of the periods equals the ratio of the cubes of the radii.
Thus, the correct choice based on the options provided would be:
The squares of the ratio of the periods equals the cubes of the ratio of the radii.