During the period each year when we see Mars undergoing apparent retrograde motion in our sky,what is really going on in space?
A)Mars is moving around the Sun in the opposite direction from which Earth is moving around the Sun.
B)Earth and Mars are getting closer together.
C)Earth is catching up with and passing by Mars in their respective orbits.
D)Earth and Mars are on opposite sides of the Sun.

Question

Quizplus · Accepted Answer

During the period of apparent retrograde motion, Earth is catching up with and passing by Mars in their respective orbits. This phenomenon is caused by the difference in the speed of revolution between Earth and Mars. As Earth overtakes Mars in its orbit around the Sun, it appears that Mars is moving backward in the sky. However, this is just an optical illusion, and Mars is not actually moving backward.

During the Period Each Year When We See Mars Undergoing