Editing Ecliptic (section)

{{Short description|Apparent path of the Sun on the celestial sphere}}
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{{Use dmy dates|date=June 2020}}

[[File:Ecliptic with earth and sun animation.gif|thumb|upright=1.3|As seen from the orbiting [[Earth]], the [[Sun]] [[diurnal motion|appears to move]] with respect to the [[fixed stars]], and the ecliptic is the yearly path the Sun follows on the [[celestial sphere]]. This process repeats itself in a cycle lasting a little over [[tropical year|365 days]].]]

The '''ecliptic''' or '''ecliptic plane''' is the [[orbital plane]] of [[Earth's orbit|Earth around the Sun]].<ref name="AA2010">{{cite book |author1=[[United States Naval Observatory|USNO]] Nautical Almanac Office |author2=UK Hydrographic Office, [[HM Nautical Almanac Office]] |title=The Astronomical Almanac for the Year 2010 |publisher=[[United States Government Publishing Office|GPO]] |date=2008 |page=M5 |isbn=978-0-7077-4082-9}}</ref><ref>{{Cite web|title=LEVEL 5 Lexicon and Glossary of Terms|url=https://ned.ipac.caltech.edu/level5/Glossary/Glossary_E.html}}</ref>{{Efn|Strictly, the plane of the mean orbit, with minor variations averaged out.|name=|group=}} It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making.

From the perspective of an observer on Earth, the Sun's movement around the [[celestial sphere]] over the course of a year traces out a path along the ecliptic against the [[fixed stars|background of stars]] – specifically the [[Zodiac]] constellations.<ref>{{Cite web|title=The Ecliptic: the Sun's Annual Path on the Celestial Sphere|url=http://community.dur.ac.uk/john.lucey/users/solar_year.html}}</ref> The planets of the [[Solar System]] can also be seen along the ecliptic, because their orbital planes are very close to Earth's. The Moon's orbital plane is also similar to Earth's; the ecliptic is so named because the ancients noted that [[eclipse]]s only occur when the Moon is crossing it.<ref name=Ball/>

The ecliptic is an important [[Plane of reference|reference plane]] and is the basis of the [[ecliptic coordinate system]]. Ancient scientists were able to calculate Earth's [[axial tilt]] by comparing the ecliptic plane to that of the [[equator]].