Spring and autumn equinox

phrase that explains what the equinox, assumes at least a basic knowledge of astronomical terms, because the very Equinox is a phenomenon being studied is this science.

necessary knowledge astronomical terms

our star makes his move along the ecliptic, which is the saying unscientific language, the plane of Earth's orbit.And the moment when the sun, making their way along the ecliptic intersects the celestial equator, is a large range of air and airless space, parallel the Earth's equator (the plane of the same, and both are perpendicular to the axis of the world), is called the equinox.Terminator (this is also the astronomical concept has nothing to do with Schwarzenegger) is a line that divides any celestial body in the sunlit part and "night".So, on the day of the equinox is the terminator passes through the geographic poles of the Earth and divides it into two equal semi-ellipse.

characteristic feature encased in the title

In the name laid down the notion that the day of the equinox night

and day are equal.From a scientific point of view, the night is always a little shorter and the sun rises and sets are not exactly in the east and west and a little north.Still, since childhood, we know that on June 22 - is not only the first day of the war, and school graduation balls (as in Soviet times), but also the day of the summer equinox.However, it is called and 22 December days of summer and winter solstice.This happens because the sun during these periods of time, or is at the highest point above the horizon, or the lowest and farthest from the celestial equator.That is the day of the equinox light and dark part of the day is almost equal.

number, characteristic for dates days equinoxes and solstices

During the solstices, some of them - either day or night - more than most other.Equinoxes and solstices are notable for the fact that are the beginning of the change of seasons.It is noteworthy these dates, and always someone from the family members said that, they say, now the longest or shortest day, or what day it is night.And that it highlights in a series of consecutive days.Almost always, the date of these moments becomes the number 22, but in fact there are leap years, and other aspects of astronomy and the phenomena affecting the displacement of the date of 21 or 23 numbers.Months of March, June, September and December are the ones that fall on the equinoxes and solstices.

Holidays, came from ancient times

Of course, they are known since ancient times.Our ancestors observed them and communicate with these dates his life, to take dozens of witnesses.The ancient Slavs with each of these days is associated a certain holiday, and it lasts usually a week (Christmas carols, Rusal, Shrovetide).So, on the winter solstice falls Kolyada, holiday, later dedicated to Christmas.Velikden or Komoeditsa, aka Mardi Gras - the name marks the vernal equinox, the birth of the young sun.From this day begins the astrological solar year, and our star goes into the Northern Hemisphere from the South.Maybe that's why March 20, the feast has to astrology.Midsummer (aka Ivan-day Solstice), or a summer confrontation - the big summer holiday of ancient Slavs, covered with legends, the glory of the brave men walking in the night to look for a fern flower.Ovsenev-Tausen, autumnal equinox, after which winter slowly begins to come into its own, and the nights grow longer.So our ancestors Svyatovit (another name) lit candles - the most beautiful was put on a place of honor.

special climatic zone of the Earth

All these serve as a benchmark date for the commencement of certain activities necessary for life - seasonal types of farming, construction or reserves for the winter.The days of vernal and autumnal equinox is characterized by the fact that the sun gives its light and warmth in equal measure and the Northern and Southern hemisphere, and its rays reach both poles.These days it is over the territory of a climatic zone of the Earth, as the tropics (in Greek language means the turntable).The opposite sides of the equator to 23 degrees with a slight, are parallel to the northern and southern tropics.A characteristic feature of the area enclosed between them is that on them twice a year, the sun reaches its zenith - once on June 22 over the northern tropics and the Tropic of Cancer, the second time - over the South, and the Tropic of Capricorn.There is 22 December.Typically this for all latitudes.North and south of the zenith of the sun in the tropics does not happen ever.

One of the consequences of the displacement direction of the Earth's axis

at the equinoxes and solstices it intersects the celestial equator at a point in the constellation Pisces (spring) and Virgin (autumn), and in the days of maximum and minimum distance from the equator, thethere during the summer and winter solstice - in the constellation Taurus and Sagittarius respectively.From the zodiacal constellation Gemini into Taurus point of the summer solstice has moved in 1988.Under the influence of gravity of the Sun and the Moon slow the Earth's axis shifts its direction (precession - another astronomical term), resulting in a shift, and the point of intersection of the light with the celestial equator.Spring dates are different from the number of autumn, and if falls on the September 22-23 th, then the question, "When the day of the vernal equinox?" The answer would be as follows - 20 March.It should specify that the date for the Southern Hemisphere will be swapped - will spring autumn, because there is the opposite.

role zodiacal constellations

As noted above, the equinoxes are called points of intersection of the celestial equator and the ecliptic, and they have their zodiac symbols corresponding to the constellations in which there are: spring - Aries, summer - CancerAutumn - Libra winter - Capricorn.It should be noted that the period of time between the two equinoxes of the same name is called the tropical year, the number of sunny days which is different from the Julian calendar by about 6 hours.And only thanks to a leap year, repeated once in 4 years, fleeing forward the date of the next equinox, returning to the previous number.On the Gregorian year, the difference is negligible (tropical - 365.2422 days, Gregorian - 365.2425), because the modern calendar is designed so that even in the long term, the date of solstices and equinoxes occur in the same number.This happens because in the Gregorian calendar provides a pass 3 days once in 400 years.

One of the most important practical problems in astronomy - the establishment of the equinox

dates range from 1 to 2, not more days.So how do you determine in the coming years, when the equinox?It has been observed that due to the presence of small fluctuations, the earliest date that is 19 numbers account for leap years.Naturally, the most recent (22) fall directly onto the previous leap year.Very rarely earlier and later dates, their memory is kept for centuries.So, back in 1696, the vernal equinox fell on March 19, and in 1903 - Autumn on September 24.Such deviations will not see contemporaries, because the repetition of the record in 1696 will be in 2096-th, and the latest equinox (September 23) will not happen before the 2103rd.There are nuances associated with local time - deviation in the figure of the world happens only when the exact date falls on 24:00.After west of the starting point - the zero meridian - a new day has not yet come.