Precession: The circular motion of Earth's axis around the pole of the ecliptic, caused by the gravitational pull of the Sun and Moon on the bulging part of the equator. One complete revolution takes approximately twenty-five thousand years to complete.

 

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Precession: The circular motion of Earth's axis around the pole of the ecliptic, caused by the gravitational pull of the Sun and Moon on the bulging part of the equator. One complete revolution takes ap . . . View Full Definition

Precession Of The Equinoxes: The gradual westward shift (about 50' each year) of the equinoctial points along the ecliptic due to the ecliptic due to the rotational movement of the poles of Earth's axis. This phenomena . . . View Full Definition

Sidereal Time: The measure of time as defined by the diurnal motion of the vernal equinox. A sidereal day is equivalent to one complete rotation of the earth relative to the equinox, which is 23 hours, 56 . . . View Full Definition

Sidereal Day: Twenty-four sidereal hours equal to 23 hours, 56 minutes and 4 seconds of clock time.

Tropical Zodiac: The circle of signs that follows the apparent path of the Sun (ecliptic). Also called the movable zodiac because it shifts slightly each year relative to the constellations of the sidereal z . . . View Full Definition

Ptolemy, Claudius: A great astrologer, astronomer and geographer of the second century (ca. 100-178 A.D.) who developed the theory that Earth is the motionless center of the universe about which the planets, s . . . View Full Definition

Great Year: The astrological year based on the time it takes Earth's axis to complete on revolution around the pole of the ecliptic, about twenty-five thousand years. A Great Year is divided into twelve . . . View Full Definition