The vernal equinox is a reference point in the equatorial coordinate system. The autumnal equinox signaled the time for the second harvest, the last chance to bring in the crops before the start of winter and the dark half of the year at Samhain (October 31stNovember 1st). On the Celtic calendar, autumn starts at Lughnasa (August 1st). This motion is called the precession of the equinoxes. In fact, the Celts considered the autumnal equinox mid-autumn. The equinoxes are not fixed points on the celestial sphere but move westward along the ecliptic, passing through all the constellations of the zodiac in 26,000 years. On the date of either equinox, the Sun is above the equator and night and day are of approximately equal length the word equinox is often used to refer to either of these dates. Autumnal equinox or variations, may refer to: September equinox, the autumnal equinox in the Northern Hemisphere March equinox, the autumnal equinox in the Southern Hemisphere Other uses. This occurs in March, marking the beginning of spring in the Northern Hemisphere. 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. For the rest of us, it's one of two times a year when the Sun crosses the equator, and the day and night are of approximately equal length.Īt the autumnal equinox in Sept., the Sun appears to cross the celestial equator, from north to south this marks the beginning of autumn in the Northern Hemisphere. In the language of science, an equinox is either of two points on the celestial sphere where the ecliptic and the celestial equator intersect. Seasons for the Northern Hemisphere, 2017.Seasons of the Northern Hemisphere, 2016.Clouds notwithstanding, Des Moines will get about 12 hours and 10 minutes of daylight. The alignment officially occurs this year at 8:03 p.m. The science and significance of the autumnal equinox During the autumnal equinox, the sun shines directly on the equator, and the northern and southern hemispheres get the same amount of rays.
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