The term "retrograde motion" for a planet refers to the
A) temporary reversal of the planet's normal east-to-west motion past the background stars as seen from Earth.
B) apparent motion of a planet's moon in the opposite direction to the motion of the planet itself during half of each orbit of the moon around the planet.
C) temporary reversal of a planet's direction of spin about its axis of rotation.
D) temporary reversal of the planet's normal west-to-east motion past the background stars as seen from Earth.

Question

Quizplus · Accepted Answer

Retrograde motion refers to the apparent backward movement of a planet across the sky, opposite to the common west-to-east motion relative to the stars, as observed from Earth. This is due to the relative positions and motions of Earth and the other planet in their orbits around the Sun.

The Term "Retrograde Motion" for a Planet Refers to the