Lunar phase
From The Art and Popular Culture Encyclopedia
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A lunar phase or phase of the moon is the appearance of the illuminated (sunlit) portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun. The half of the lunar surface facing the Sun is always sunlit, but the portion of this illuminated hemisphere that is visible to an observer on Earth can vary from about 100% (full moon) to 0% (new moon). The lunar terminator is the boundary between the illuminated and unilluminated hemispheres. Aside from some craters near the lunar poles such as Shoemaker, all parts of the Moon see around 14.77 days of sunlight followed by 14.77 days of "night" (there is no permanently "dark side" of the Moon).
See also
- Blue moon
- Lunar effect
- Lunation
- Observing the Moon
- Planetary phase
- Planetshine
- Seven-day week
- Tides
- Week
