EARTH 104 Study Guide - Quiz Guide: Ecliptic
7 Dec 2015
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Document Summary
Ecliptic: apparent path of the sun"s motion on the celestial sphere as seen from earth. Aphelion: the point in the orbit of earth farthest from the sun. Perihelion: the point in the orbit of earth nearest to the sun. Obliquity or tilt: the angle between earth"s rotational axis and its orbital axis, or, the angle between its equatorial plane and orbital plane. Eccentricity: a parameter that determines the amount by which a planet"s orbit around the sun deviates from a perfect circle. 0 is a circular orbit, values between 0 and 1 form an elliptical orbit. Precession: any of several gravity-induced, slow and continuous changes in an astronomical body"s rotational axis or orbital path. Equinoxes: an equinox occurs twice a year, around 20 march and 22. September, days when daytime and night are of approximately equal duration. An equinox occurs when the plane of earth"s equator passes the center of the sun.
