The time for the Moon to repeat its cycle of phases is equal to
A)its sidereal period.
B)one day.
C)one hour.
D)one year.
E)its synodic period.

Question

Quizplus · Accepted Answer

The synodic period is the time for the Moon to return to the same phase (e.g. full moon to full moon) as observed from Earth. This takes into account both the Moon's orbit around the Earth and the Earth's orbit around the Sun. The other options are not correct because: A) the sidereal period is the time for the Moon to complete one orbit around the Earth (not the same as the time for its phase cycle); B) one day is the time for the Earth to complete one rotation on its axis; C) one hour is a unit of time and not a relevant period for lunar phases; D) one year is the time for the Earth to complete one orbit around the Sun (not the same as the time for the Moon's phase cycle).

The Time for the Moon to Repeat Its Cycle of Phases