A synodic month is about two days longer than a sidereal month.Why?
A) The Earth-Moon system is revolving around the Sun.
B) The Moon's orbit around Earth is tilted with respect to Earth's orbit around the Sun.
C) The Moon must follow the ecliptic.
D) The Moon's distance from Earth varies across its orbit.

Question

Quizplus · Accepted Answer

A synodic month is the time it takes for the Moon to return to the same phase (e.g. full moon to full moon) as observed from Earth. This takes longer than a sidereal month (the time it takes for the Moon to return to the same position relative to the stars) because the Earth-Moon system is also revolving around the Sun. As the Moon orbits around Earth, Earth is also moving along its orbit, which means that the Moon has to travel a bit further to return to the same phase as observed from Earth. This takes about two additional days.

A Synodic Month Is About Two Days Longer Than a Sidereal