The fact that the Earth-Moon system orbits the Sun (covering 30° per month) while the Moon orbits Earth means that, compared to one lunar orbital (sidereal) period, the time between successive full Moons (the synodic month) is
A) about 2 days longer.
B) about 2 days shorter.
C) about twice as long.
D) zero because these periods are always the same, by definition.

Question

Quizplus · Accepted Answer

The synodic month is about 2 days longer than the sidereal month because as the Earth-Moon system orbits the Sun, the Moon has to travel a little further to reach the same phase, resulting in a longer cycle between successive full Moons.

The Fact That the Earth-Moon System Orbits the Sun (Covering