Planets don’t suddenly change direction in space — but from Earth, it can look that way. What you’re seeing here is called retrograde motion. It happens because planets don’t all orbit the Sun at the same speed. Earth moves faster on a smaller, inner orbit. When we catch up to and pass a slower outer planet like Mars, our viewing angle changes against the background of distant stars. From our moving viewpoint, the planet appears to: • slow down • stop • and briefly move backward in the sky But n