Eccentricity (e) is calculated with the formula e = c/a and represents the degree of elongation of an elliptical orbit. Kepler's Third Law shows the relationship between the orbital period and the semimajor axis of a planet, and using the given data for Venus and Earth, we can confirm that they adhere to this law.
The degree of elongation of an elliptical orbit, known as its eccentricity (e), is calculated by dividing the distance f from the center of an ellipse to one of the foci (c) by the length of half the long axis (a), using the formula e = c/a.
When applying Kepler's Third Law, the square of the orbital period (P²) is proportional to the cube of the semimajor axis (a³). Using the provided data, for Venus with an orbital period of 0.62 years and a semimajor axis of 0.72 AU, we can calculate P² as 0.3844 and a³ as 0.373248; for Earth with an orbital period of 1.00 year and a semimajor axis of 1.00 AU, the values are both 1.00. These calculations are used to verify that the orbital periods and semimajor axes for planets such as Venus and Earth adhere to Kepler's Third Law.