Here's why:
* Angular Momentum: Angular momentum is a measure of an object's tendency to rotate. It depends on the object's mass, velocity, and distance from the axis of rotation. In the case of a planet, the axis of rotation is the Sun.
* Conservation of Angular Momentum: The total angular momentum of a system remains constant unless acted upon by an external torque. This means that as a planet orbits the Sun, its angular momentum must be conserved.
* Kepler's Laws: Kepler's laws of planetary motion tell us that a planet's orbital speed is slower when it's farther from the Sun.
Putting it Together:
* When a planet is farther from the Sun, its velocity is slower.
* To conserve angular momentum, the planet must compensate for its lower velocity by having a larger distance from the Sun (increasing the "moment of inertia").
* Therefore, a planet has the greatest angular momentum at aphelion, where its distance from the Sun is maximum.
