Kepler’s second law is based on

Kepler’s second law, often known as the law of equal areas, is a principle related to the conservation of angular momentum.

It claims that the line connecting the Sun to a planet and that line sweeps out an equal area in equal times. The planet moves with higher orbital speed when the distance is minimal from the Sun or perihelion, and it will be less fast when at the other extreme position or at aphelion. The orbit speed variations will ensure constant areas of sweeping for the same line segment connecting the Sun and the planet over time.

The underlying physical reason for this behavior is that angular momentum is conserved. Angular momentum depends on the mass of the planet, the distance of the planet from the Sun, and its velocity. For a planet in orbit, if no external torques act on it, then the angular momentum will be constant. If the planet is closer to the Sun, then the distance is less, and its velocity must be greater to conserve angular momentum. When the distance increases, the velocity will decrease.

This principle therefore reflects the balance of the gravitational forces and the planet’s motion. It would therefore give an elegant explanation of Kepler’s second law and the observed behavior of planetary orbits.