A planet's speed at perihelion (the point in its orbit closest to the Sun) is faster than its speed at aphelion (the point furthest from the Sun).

Here's why:

* Conservation of Angular Momentum: Planets follow elliptical orbits, and their orbital speed is governed by the principle of conservation of angular momentum. This means that the product of a planet's mass, orbital speed, and distance from the Sun (the orbital radius) remains constant throughout its orbit.

* Inverse Relationship: As a planet gets closer to the Sun (perihelion), its orbital radius decreases. To maintain a constant angular momentum, its orbital speed must increase. Conversely, at aphelion, where the orbital radius is larger, the speed decreases.

Think of it like a figure skater spinning: When they pull their arms in close to their body, they spin faster. Similarly, a planet "pulls in" closer to the Sun at perihelion and speeds up.