Ecliptic

The ecliptic or ecliptic plane is the <a href="/facts/Orbital_plane/xPdMmVKP">orbital plane</a> of <a href="/facts/Earth%27s_orbit/BGGCdFag">Earth around the Sun</a>. 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 <a href="/facts/Celestial_sphere/TYAtXgor">celestial sphere</a> over the course of a year traces out a path along the ecliptic against the <a href="/facts/Fixed_stars/grlDbIPX">background of stars</a> – specifically the <a href="/facts/Zodiac/v7sWp0ef">Zodiac</a> constellations. 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 <a href="/facts/Eclipse/zXeAKwyj">eclipses</a> only occur when the Moon is crossing it.
The ecliptic is an important <a href="/facts/Plane_of_reference/otIHqWPe">reference plane</a> and is the basis of the <a href="/facts/Ecliptic_coordinate_system/28zkWwVa">ecliptic coordinate system</a>. Ancient scientists were able to calculate Earth's <a href="/facts/Axial_tilt/kt7KwL3v">axial tilt</a> by comparing the ecliptic plane to that of the <a href="/facts/Equator/CjaxbVaN">equator</a>.

Ecliptic open-in-new

Ecliptic