Editing Lunar day (section)

==Main definition==
Relative to the [[fixed stars]] on the [[celestial sphere]], the Moon takes 27 Earth [[day]]s, 7 hours, 43 minutes, 12 seconds to complete [[orbital period|one orbit]];<ref name="ebmonth">{{cite web|url=http://www.britannica.com/EBchecked/topic/390962/month#ref225844|title=Month|publisher=[[Encyclopædia Britannica]]|accessdate=15 April 2015}}</ref> however, since the Earth&ndash;Moon system advances around the Sun at the same time, the Moon must travel farther to return to the same phase. On average, this [[synodic period]] lasts 29 days, 12 hours, 44 minutes, 3 seconds,<ref name="ebmonth" /> the length of a [[lunar month]] on Earth. The exact length varies over time because the speed of the Earth&ndash;Moon system around the Sun varies slightly during a year due to the [[orbital eccentricity|eccentricity]] of its elliptical orbit, variances in [[orbital speed|orbital velocity]], and a number of other periodic and evolving variations about its observed, relative, mean values, which are influenced by the gravitational [[perturbation (astronomy)|perturbations]] of the Sun and other bodies in the [[Solar System]].

As a result, daylight at a given point on the Moon lasts approximately two weeks from beginning to end, followed by approximately two weeks of '''lunar night'''.