Lunar phase: Difference between revisions

The '''lunar phase''' or '''phase of the moon''' is the shape of the illuminated (sunlit) portion of the [[Moon]] as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon [[orbit]]s the Earth, according to the changing relative positions of the [[Earth]], [[Moon]], and [[Sun]]. The moon and the Earth are [[Tidal locking|tidally locked]], and therefore the same lunar surface always faces Earth. This face is variously sunlit depending on the position of the moon in its orbit. Ergo, the portion of this 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 darkened hemispheres. Aside from some craters near the lunar poles such as [[Shoemaker (lunar crater)|Shoemaker]], all parts of the Moon see around 14.77 days of sunlight followed by 14.77 days of "night" (the "dark side" of the Moon is a reference to radio darkness, not visible light darkness).

 

 

[[Image:Moon phases en.jpg|thumb|none|nofloat|800px|Phases of the Moon, as seen looking southward from the Northern Hemisphere. The Southern Hemisphere will see each phase rotated through 180°. The upper part of the diagram is not to scale, as the Moon is much farther from the Earth than shown here.]]