equinox (ē`kwĭnŏks), either of two points on the celestial sphere celestial sphere, imaginary sphere of infinite radius with the earth at its center. It is used for describing the positions and motions of stars and other objects.
..... Click the link for more information. where the ecliptic ecliptic , the great circle on the celestial sphere that lies in the plane of the earth's orbit (called the plane of the ecliptic). Because of the earth's yearly revolution around the sun, the sun appears to move in an annual journey through the heavens with the
..... Click the link for more information. and the celestial equator intersect. The vernal equinox, also known as "the first point of Aries," is the point at which the sun appears to cross the celestial equator from south to north. This occurs about Mar. 21, marking the beginning of spring in the Northern Hemisphere. At the autumnal equinox, about Sept. 23, the sun again appears to cross the celestial equator, this time from north to south; this marks the beginning of autumn in the Northern Hemisphere. On the date of either equinox, night and day are of equal length (12 hr each) in all parts of the world; the word equinox is often used to refer to either of these dates. The equinoxes are not fixed points on the celestial sphere but move westward along the ecliptic, passing through all the constellations of the zodiac zodiac [Gr. zoion=animal], in astronomy, zone of the sky that includes about 8° on either side of the ecliptic. The apparent paths of the sun, the moon, and the major planets all fall within this zone.
..... Click the link for more information. in 26,000 years. This motion is called the precession of the equinoxes precession of the equinoxes, westward motion of the equinoxes along the ecliptic. This motion was first noted by Hipparchus c.120 B.C. The precession is due to the gravitational attraction of the moon and sun on the equatorial bulge of the earth, which causes the
..... Click the link for more information. . The vernal equinox is a reference point in the equatorial coordinate system equatorial coordinate system, the most commonly used astronomical coordinate system for indicating the positions of stars or other celestial objects on the celestial sphere. The celestial sphere is an imaginary sphere with the observer at its center.
..... Click the link for more information. .

equinox

Either of two moments in the year when the Sun is exactly above the Equator and day and night are of equal length all over Earth; also, either of two points in the sky where the ecliptic and the celestial equator (see celestial sphere) intersect. The vernal equinox, when spring begins in the Northern Hemisphere, occurs about March 21, when the Sun moves north across the celestial equator. The autumnal equinox falls about September 23, as the Sun crosses the celestial equator going south. See also solstice.

equinox

either of the two occasions, six months apart, when day and night are of equal length

equinox [′ē·kwə‚näks]

(astronomy)

Either of the two points of intersection of the ecliptic and the celestial equator, occupied by the sun when its declination is 0°. Also known as equinoctial point.

That instant when the sun occupies one of the equinoctial points.

Equinox

the moment at which the sun’s center crosses the celestial equator in the course of the sun’s apparent annual path along the ecliptic. At the time of the equinox, the length of the day is almost equal to that of the night over the entire earth, except near the poles. The difference is a matter of only a few minutes and results from refraction and the great angular diameter of the sun.

The point at which the sun’s center crosses the equator as the sun travels from the southern hemisphere to the northern hemisphere is called the vernal equinox. The point at which the sun’s center crosses the equator as the sun travels in the opposite direction is the autumnal equinox. Since the time between two successive transits of the sun through the same equinox (the tropical year) is not the same as the length of the calendar year, the equinox changes each year relative to the start of the calendar day. In a common year the equinox begins 5 hours 48 minutes 46 seconds later than the preceding year, while in a leap year it begins 18 hours 11 minutes 14 seconds earlier. The equinox may therefore extend over two successive calendar days. At the present time (second half of the 20th century), the sun passes through the vernal equinox on Mar. 20 and 21 (start of astronomical spring in the northern hemisphere) and the autumnal equinox on Sept. 23 (start of astronomical autumn in the northern hemisphere). These dates are given in the New Style for the start of the day in Moscow time.

Hipparchus (second century B.C.) discovered that the equinoxes slowly shift along the ecliptic in the direction of the apparent annual path of the sun. This shift, owing to the precession of the earth’s axis of rotation, has a period of about 26,000 years. In 1737, J. Bradley found that the earth’s axis experiences nutation, as a consequence of which the equinoxes complete oscillatory motions with a period of 18.6 years relative to their mean positions as determined by their precessional motion. Changes in the celestial coordinates of the heavenly bodies are related to the changing positions of the equinoxes. Star catalogs give the positions of stars for given vernal equinoxes of different epochs.

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No references found			Under the moon theory, the fall equinox can vary by more than one month, which would mean that fawns may or may not drop during the period of peak nutrition. Whitetail myths & truths by Winand, C.J. / Bowhunter After the fall equinox, they sensed the power of darkness as the night steadily lengthened and the day got shorter. Natural lighting by Dues, Greg / U.S. Catholic 5 days before the Hunter's Moon, the second full moon after the fall equinox -- as the average breeding date for 1,053 does collected over a 13-year period on the coastal plain of South Carolina. Rut Timing: Calendar Versus Moon by Winand, C.J. / Bowhunter			Fales-Stuart windmill Faleshty Faliero, Marino Falih Rifki Atay Faliraki Faliscan Falk flexible coupling Falk, Peter Falkberget, Johan Falke, Dr. Falkenhayn, Erich Von Falkensee Falkirk Falkland Current Falkland Islands Falkland Islands War Falkland Islands, Battle of 1914 Falkland, Lucius Cary, 2d Viscount Falkner, William Falköping fall fall back fall block Fall Creek Falls State Resort Park Fall Creek State Recreation Area fall equinox fall forward Fall Gelb fall line Fall of a Body Fall of Constantinople fall of ground fall over Fall River Fall River County Fall River Heritage State Park Fall River State Park fall streaks fall through fall thru fall time fall velocity Fall Webworm Moth fall wind Fall, Albert Bacon Fall, The fall-pipe fall-streak hole Falla Falla, Manuel de fallacy			fall by the wayside fall by the wayside fall cankerworm Fall City Fall City Arts Fall Classic Fall Classic Fall Commanders Conference Fall Creek Falls State Park Fall Creek Falls State Resort Park Fall Creek Farm & Nursery, Inc. Fall Creek Intermediate School Fall Creek Public Library Fall Creek State Recreation Area Fall Creek Valley Fall Creek Valley Middle School Fall Creek Watershed Committee fall dandelion fall down fall down fall down fall down fall down fall down Fall Down Go Boom Fall Down Laughing fall down on fall down on the job fall drop off the radar fall due fall equinox fall exactly together Fall Festival fall fever fall flat fall flat fall flat fall flat fall flat fall flat its face fall flat on face fall flat on face fall flat on face fall flat on face fall flat on face fall flat on face fall for fall for fall for fall for fall for fall for hook, line and sinker Fall forward fall foul fall foul fall foul fall foul fall foul of fall foul of fall from fall from grace

Equinox (redirected from fall equinox)

equinox

Equinox
(redirected from fall equinox)