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How long does the Moon take to orbit Earth?
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Moon
(Left) Near side of Earth's Moon, photographed by the Galileo spacecraft on its way to Jupiter. (Right) Far side of the Moon with some of the near side visible (upper right), photographed by the Apollo 16 spacecraft.
The time it takes for the Moon to orbit Earth depends on the frame of reference used to measure the period:
- Sidereal Month: This is the time required for the Moon to return to the same position relative to the background stars. It takes approximately 27.322 days (27 days, 7 hours, 43 minutes, and 12 seconds) to complete this orbit.12
- Synodic Month: This is the time between successive recurrences of the same lunar phase (such as from full moon to full moon). Because the Earth-Moon system is simultaneously moving around the Sun, the Moon must travel further to reach the same phase relative to the Sun. This period is approximately 29.531 days (29 days, 12 hours, 44 minutes, and 3 seconds).12
It is more accurate to state that the Moon and Earth orbit a common center of mass, known as the barycenter, rather than the Moon simply orbiting the center of Earth.1