 with \(T_1\) and \(T_2\) representing the periodic times of two planets and \(a_1\) and \(a_2\) the length of their semi-major axes. A further formulation of this relationship, which is often found in the literature, is: \(a^3/T^2 = K\), which expresses with \(K\) that the relationship between the third power of the distances and the square of the times is a constant (however, see Davis 2005, pp. 171–172; for the third planetary law see especially Stephenson 1987). As a consequence of the third law, the time a planet takes to travel around the Sun will significantly increase the farther away it is or the longer the radius of its orbit. Thus, for instance, Saturn’s sidereal period is almost 30 years, while Mercury needs fewer than 88 days to go around the Sun. For the history of cosmology, it is important to make clear that the third law fulfils Kepler’s search for a systematic representation and defense of the Copernican worldview, in which planets are not absolutely independent of each other but integrated in a harmonic world system.