Lunar phase

Concerning the lunar month of approximately 29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the terminology of the four major phases (new moon, first quarter, full moon, last quarter) and four minor phases (waxing crescent, waxing gibbous, waning gibbous, and waning crescent).

The lunar phases and librations in 2022 as viewed from the Northern Hemisphere at hourly intervals, with titles and supplemental graphics
A full moon sets behind San Gorgonio Mountain in California on a midsummer's morning.

The lunar phases gradually change over a synodic month (c.29.53 days) as the orbital positions of the Moon around Earth, and Earth around the Sun, shift. The visible side of the Moon is variously sunlit, depending on the position of the Moon in its orbit, with the sunlit portion varying from 0% (at new moon) to 100% (at full moon).

Each of the four major lunar phases is approximately 7.4 days±19 hours (6.58–8.24 days), the variation being due to the eccentricity of the Moon's orbit and thus it orbiting at varying speeds.

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This article uses material from the Wikipedia article Lunar phase, and is written by contributors. Text is available under a CC BY-SA 4.0 International License; additional terms may apply. Images, videos and audio are available under their respective licenses.