Earth and the Moon


How often do eclipses occur?

Perfect alignments of the Sun, Moon, and Earth are relatively uncommon, because the plane of Earth’s orbit around the Sun (called the ecliptic plane) is not the same as the plane of the Moon’s orbit around Earth. Thus, during the new moon or full moon phases when an eclipse might be possible, the Moon is usually located just above or below the straight line that runs between Earth and the Sun, so no eclipse occurs. All three objects—Earth, Moon, and Sun—line up just right about twice a year.


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