Question

select the correct answer.
what is responsible for the difference between the time the moon takes to go through a complete set of phases and the time it takes to complete one complete revolution of the earth?
a. the movement of the earth along its orbit
b. the changing speed of the earths rotation
c. the synchronous rotation of the moon
d. the tilt of the earth about its axis

Explanation:

The Moon's orbital period (sidereal month, about 27.3 days) is the time it takes to complete one revolution around the Earth relative to the stars. The lunar phase cycle (synodic month, about 29.5 days) is the time between identical lunar phases. During the Moon's orbit, the Earth is also moving along its orbit around the Sun. So, the Moon has to "catch up" a bit more to show the same phase again relative to the Sun - Earth - Moon geometry. The changing speed of Earth's rotation affects day - length, not lunar phases. The Moon's synchronous rotation (same side always facing Earth) is about its rotation - revolution relationship (tidally locked) and not related to phase - orbital period difference. The Earth's axial tilt affects seasons, not lunar phase - orbital period difference.

Answer:

A. the movement of the Earth along its orbit