Editing Ecliptic (section)

==Sun's apparent motion==
The ecliptic is the apparent path of the Sun throughout the course of a [[year]].<ref>
{{cite book 
 | author = U.S. Naval Observatory Nautical Almanac Office
 | editor = P. Kenneth Seidelmann
 | title = Explanatory Supplement to the Astronomical Almanac
 | publisher = University Science Books, Mill Valley, CA
 | date = 1992
 | isbn = 0-935702-68-7}}, p. 11</ref>

Because Earth takes one year to orbit the Sun, the apparent position of the Sun takes one year to make a complete circuit of the ecliptic. With slightly more than 365 days in one year, the Sun moves a little less than 1° eastward<ref name="celes direc"/> every day. This small difference in the Sun's position against the stars causes any particular spot on Earth's surface to catch up with (and stand directly north or south of) the Sun about four minutes later each day than it would if Earth did not orbit; a day on Earth is therefore 24 hours long rather than the approximately 23-hour 56-minute [[sidereal time|sidereal day]]. Again, this is a simplification, based on a hypothetical Earth that orbits at a uniform angular speed around the Sun. The actual speed with which Earth orbits the Sun varies slightly during the year, so the speed with which the Sun seems to move along the ecliptic also varies. For example, the Sun is north of the celestial equator for about 185 days of each year, and south of it for about 180 days.<ref>''Astronomical Almanac 2010'', sec. C</ref> The variation of orbital speed accounts for part of the [[equation of time]].<ref>''Explanatory Supplement'' (1992), sec. 1.233</ref>
 
Because of the movement of Earth around the Earth–Moon [[center of mass]], the apparent path of the Sun wobbles slightly, with a period of about [[Orbit of the Moon|one month]]. Because of further [[Perturbation (astronomy)|perturbations]] by the other [[planet]]s of the Solar System, the Earth–Moon [[barycenter]] wobbles slightly around a mean position in a complex fashion.