Question

What is retrograde motion?

Answer 1

A body has retrograde motion if it is travelling in the opposite direction to most other bodies.

Explanation:

In our solar system most planets orbit and rotate in the same direction. This direction is anti-clockwise when looking down from the north. This direction is called prograde.

If a body orbits or rotates in the opposite direction to most of the others it is said to be retrograde. The best example of this is Venus which rotates in the opposite direction to the other planets.

To get around how to describe Venus's rotation. Venus is said to have an axial tilt of `177°`. In other words Venus's north pole is pointing on the opposite direction to that of other planets.