The length of time for the Moon to move from new Moon to new Moon is known as one synodic month.Compared with one full orbital period with respect to the star background,or one sidereal month,the synodic month is:

Question

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The synodic month is slightly longer than the sidereal month because during the time it takes the Moon to complete one orbit around the Earth, the Earth has moved in its orbit around the Sun, so the Moon must travel a little farther to get back to the same phase. This adds up to about 2 extra days, making the synodic month about 29.5 days long compared to the sidereal month which is about 27.3 days long.

The Length of Time for the Moon to Move from New