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The March equinox or northward equinox is the equinox on the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
when the subsolar point appears to leave the Southern Hemisphere and cross the celestial equator, heading northward as seen from Earth. The March equinox is known as the vernal equinox (spring equinox) in the
Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...
and as the autumnal equinox in the Southern Hemisphere. On the
Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years d ...
, the northward equinox can occur as early as 19 March or as late as 21 March at 0° longitude. For a common year the computed time slippage is about 5 hours 49 minutes ''later'' than the previous year, and for a leap year about 18 hours 11 minutes ''earlier'' than the previous year. Balancing the increases of the common years against the losses of the leap years keeps the calendar date of the March equinox from drifting more than one day from 20 March each year. The March equinox may be taken to mark the beginning of astronomical
spring Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of water * Spring (mathematics), a geometric surface in the shape of a h ...
and the end of astronomical
winter Winter is the coldest season of the year in polar and temperate climates. It occurs after autumn and before spring. The tilt of Earth's axis causes seasons; winter occurs when a hemisphere is oriented away from the Sun. Different cultur ...
in the Northern Hemisphere but marks the beginning of astronomical autumn and the end of astronomical summer in the Southern Hemisphere. In
astronomy Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, g ...
, the March equinox is the zero point of sidereal time and, consequently, right ascension. It also serves as a reference for calendars and celebrations in many cultures and religions.


Constellation

The point where the Sun crosses the celestial equator northwards is called the First Point of Aries. However, due to the
precession of the equinoxes In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. In partic ...
, this point is no longer in the constellation Aries, but rather in
Pisces Pisces may refer to: * Pisces, an obsolete (because of land vertebrates) taxonomic superclass including all fish *Pisces (astrology), an astrological sign *Pisces (constellation), a constellation ** Pisces Overdensity, an overdensity of stars in t ...
. By the year 2600 it will be in
Aquarius Aquarius may refer to: Astrology * Aquarius (astrology), an astrological sign * Age of Aquarius, a time period in the cycle of astrological ages Astronomy * Aquarius (constellation) * Aquarius in Chinese astronomy Arts and entertainment ...
. The Earth's axis causes the First Point of Aries to travel westwards across the sky at a rate of roughly one degree every 72 years. Based on the modern constellation boundaries, the northward equinox passed from Taurus into Aries in the year −1865 (1866 BC), passed into Pisces in the year −67 (68 BC), will pass into Aquarius in the year 2597, and will pass into Capricornus in the year 4312. It passed by (but not into) a 'corner' of Cetus at 0°10′ distance in the year 1489.


Apparent movement of the Sun

In its apparent motion on the day of an equinox, the Sun's disk crosses the Earth's horizon directly to the east at sunrise; and again, some 12 hours later, directly to the west at sunset. The March equinox, like all equinoxes, is characterized by having an almost exactly equal amount of daylight and night across most latitudes on Earth. Due to
refraction In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomen ...
of light rays in the
Earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...
, the Sun will be visible above the horizon even when its disc is completely below the limb of the Earth. Additionally, when seen from the Earth, the Sun is a bright disc in the sky and not just a point of light, thus sunrise and sunset can be said to start several minutes before the sun's geometric center even crosses the horizon, and extends equally long after. These conditions produce differentials of actual durations of light and darkness at various locations on Earth during an equinox. This is most notable at the more extreme latitudes, where the Sun may be seen to travel sideways considerably during the morning and evening, drawing out the transition from day to night. At the north and south poles, the Sun appears to move steadily around the horizon, and just above the horizon, neither rising nor setting apart from a slight change in
declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of th ...
of about 0.39° per day as the equinox passes.


Culture


Calendars

The Babylonian calendar began with the first new moon after the March equinox, the day after the return of the Sumerian goddess Inanna (later known as Ishtar) from the underworld, in the
Akitu Akitu or Akitum is a spring festival held on the first day of Nisan in ancient Mesopotamia, to celebrate the sowing of barley. The Assyrian and Babylonian Akitu festival has played a pivotal role in the development of theories of religion, myth ...
ceremony, with parades through the
Ishtar Gate The Ishtar Gate was the eighth gate to the inner city of Babylon (in the area of present-day Hillah, Babil Governorate, Iraq). It was constructed circa 575 BCE by order of King Nebuchadnezzar II on the north side of the city. It was pa ...
to the
Eanna E-anna ( sux, , ''house of heavens''), also referred to as the Temple of Inanna, was an ancient Sumerian temple in Uruk. Considered "the residence of Inanna" and Anu, it is mentioned several times in the ''Epic of Gilgamesh The ''Epi ...
temple and the ritual re-enactment of the marriage to Tammuz, or Sumerian Dummuzi. The Persian calendar begins each year at the northward equinox, observationally determined at
Tehran Tehran (; fa, تهران ) is the largest city in Tehran Province and the capital of Iran. With a population of around 9 million in the city and around 16 million in the larger metropolitan area of Greater Tehran, Tehran is the most popul ...
. The Indian national calendar starts the year on the day next to the vernal equinox on 22 March (21 March in leap years) with a 30-day month (31 days in leap years), then has 5 months of 31 days followed by 6 months of 30 days.


Julian calendar

The Julian calendar reform lengthened seven months and replaced the intercalary month with an intercalary day to be added every four years to February. It was based on a length for the year of 365 days and 6 hours (365.25 d), while the mean tropical year is about 11 minutes and 15 seconds less than that. This had the effect of adding about three quarters of an hour every four years. The effect accumulated from inception in 45 BC until the 16th century, when the northern vernal equinox fell on 10 or 11 March. The date in 1452 was 11 March, 11:52 (Julian). In 2547 it will be 20 March, 21:18 (Gregorian) and 3 March, 21:18 (Julian).


Western Christendom

In Western Christendom, the March equinox is one of the factors used to determine the date of
Easter Easter,Traditional names for the feast in English are "Easter Day", as in the '' Book of Common Prayer''; "Easter Sunday", used by James Ussher''The Whole Works of the Most Rev. James Ussher, Volume 4'') and Samuel Pepys''The Diary of Samue ...
. However, the Gregorian reform of the calendar declared 21 March to be the date for the
ecclesiastical equinox An ecclesiastical full moon is formally the 14th day of the ecclesiastical lunar month (an ecclesiastical moon) in an ecclesiastical lunar calendar. The ecclesiastical lunar calendar spans the year with lunar months of 30 and 29 days which are int ...
, and it is this fixed date (rather than the date of the actual astronomical event) that is used for the Easter date calculation.


Commemorations


Abrahamic tradition

* The Jewish
Passover Passover, also called Pesach (; ), is a major Jewish holiday that celebrates the Biblical story of the Israelites escape from slavery in Egypt, which occurs on the 15th day of the Hebrew month of Nisan, the first month of Aviv, or spring. ...
usually falls on the first
full moon The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (when the ecliptic longitudes of the Sun and Moon differ by 180°). This mea ...
after the northern hemisphere vernal equinox, although occasionally (currently three times every 19 years) it will occur on the second full moon. * The
Christian Church In ecclesiology, the Christian Church is what different Christian denominations conceive of as being the true body of Christians or the original institution established by Jesus. "Christian Church" has also been used in academia as a synonym fo ...
es calculate
Easter Easter,Traditional names for the feast in English are "Easter Day", as in the '' Book of Common Prayer''; "Easter Sunday", used by James Ussher''The Whole Works of the Most Rev. James Ussher, Volume 4'') and Samuel Pepys''The Diary of Samue ...
as the first Sunday after the first full moon on or after the March equinox. The official church definition for the equinox is 21 March. The
Eastern Orthodox Church The Eastern Orthodox Church, also called the Orthodox Church, is the second-largest Christian church, with approximately 220 million baptized members. It operates as a communion of autocephalous churches, each governed by its bishops via ...
es use the older
Julian calendar The Julian calendar, proposed by Roman consul Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on , by edict. It was designed with the aid of Greek mathematicians and astronomers such as Sosigenes of Alexandri ...
, while the western churches use the
Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years d ...
, and the western full moons currently fall four, five or 34 days before the eastern ones. The result is that the two Easters generally fall on different days but they sometimes coincide. The earliest possible western Easter date in any year is 22 March on each calendar. The latest possible western Easter date in any year is 25 April.


Iranian tradition

* The northward equinox marks the first day of various calendars including the
Iranian calendar The Iranian calendars or Iranian chronology ( fa, گاه‌شماری ایرانی, ) are a succession of calendars invented or used for over two millennia in Iran, also known as Persia. One of the longest chronological records in human history ...
. The ancient Iranian peoples' new year's festival of Nowruz can be celebrated 20 March or 21 March. According to the ancient Persian mythology Jamshid, the mythological king of Persia, ascended to the throne on this day and each year this is commemorated with festivities for two weeks. Along with
Iranian peoples The Iranian peoples or Iranic peoples are a diverse grouping of Indo-European peoples who are identified by their usage of the Iranian languages and other cultural similarities. The Proto-Iranians are believed to have emerged as a separate ...
, it is also a holiday celebrated by Turkic people, the
North Caucasus The North Caucasus, ( ady, Темыр Къафкъас, Temır Qafqas; kbd, Ишхъэрэ Къаукъаз, İṩxhərə Qauqaz; ce, Къилбаседа Кавказ, Q̇ilbaseda Kavkaz; , os, Цӕгат Кавказ, Cægat Kavkaz, inh, ...
and in
Albania Albania ( ; sq, Shqipëri or ), or , also or . officially the Republic of Albania ( sq, Republika e Shqipërisë), is a country in Southeastern Europe. It is located on the Adriatic and Ionian Seas within the Mediterranean Sea and share ...
. It is also a holiday for Zoroastrians, adherents of the
Baháʼí Faith The Baháʼí Faith is a religion founded in the 19th century that teaches the essential worth of all religions and the unity of all people. Established by Baháʼu'lláh in the 19th century, it initially developed in Iran and parts of the ...
and Nizari Ismaili Muslims irrespective of ethnicity.


West Asia and North Africa

* In many Arab countries, Mother's Day is celebrated on the northward equinox. * Sham el-Nessim was an ancient Egyptian holiday which can be traced back as far as 2700 BC. It is still one of the public holidays in Egypt. Sometime during Egypt's Christian period (c. 200–639) the date moved to Easter Monday, but before then it coincided with the vernal equinox.


South and Southeast Asia

According to the sidereal solar calendar, celebrations which originally coincided with the March equinox now take place throughout South Asia and parts of Southeast Asia on the day when the Sun enters the sidereal Aries, generally around 14 April. * In Cambodia, the Angkor Wat Equinox is a solar phenomenon which dates back to the reign of Suryavarman II.


East Asia

* The traditional East Asian calendars divide a year into 24 solar terms (节气, literally "climatic segments"), and the vernal equinox ('' Chūnfēn'', ) marks the ''middle'' of the spring. In this context, the
Chinese character Chinese characters () are logograms developed for the writing of Chinese. In addition, they have been adapted to write other East Asian languages, and remain a key component of the Japanese writing system where they are known as ''kanji' ...
分 means ''"(equal) division"'' (within a season). * In Japan, Vernal Equinox Day (春分の日 ''Shunbun no hi'') is an official national holiday, and is spent visiting family graves and holding family reunions. Higan (お彼岸) is a Buddhist holiday exclusively celebrated by Japanese sects during both the Spring and Autumnal Equinox.


Europe

* Lieldienas *in
Norse paganism Old Norse religion, also known as Norse paganism, is the most common name for a branch of Germanic religion which developed during the Proto-Norse period, when the North Germanic peoples separated into a distinct branch of the Germanic peopl ...
, a Dísablót was celebrated on the vernal equinox. * Drowning of Marzanna


The Americas

* Spring equinox in Teotihuacán *The reconstructed
Cahokia Woodhenge The Cahokia Woodhenge was a series of large timber circles located roughly to the west of Monks Mound at the Mississippian culture Cahokia archaeological site near Collinsville, Illinois. They are thought to have been constructed between 90 ...
, a large timber circle located at the Mississippian culture Cahokia
archaeological site An archaeological site is a place (or group of physical sites) in which evidence of past activity is preserved (either prehistoric or historic or contemporary), and which has been, or may be, investigated using the discipline of archaeology an ...
near Collinsville, Illinois, is the site of annual equinox and solstice sunrise observances. Out of respect for Native American beliefs these events do not feature ceremonies or rituals of any kind.


Modern culture

* World Storytelling Day is a global celebration of the art of oral storytelling, celebrated every year on the day of the northward equinox. * World Citizen Day occurs on the northward equinox. * The
Baháʼí calendar The Badíʻ calendar used in the Baháʼí Faith is a solar calendar consisting of nineteen months and four or five intercalary days, with new year at the moment of Northern spring equinox. Each month is named after a virtue(e.g. Perfection, Mercy ...
year starts at the sunset preceding the March equinox calculated for Tehran. * In Annapolis, Maryland, United States, boatyard employees and sailboat owners celebrate the spring equinox with the "Burning of the Socks" festival. Traditionally, the boating community wears socks only during the winter. These are burned at the approach of warmer weather, which brings more customers and work to the area. Officially, nobody then wears socks until the next equinox. *
Neopagan Modern paganism, also known as contemporary paganism and neopaganism, is a term for a religion or family of religions influenced by the various historical pre-Christian beliefs of pre-modern peoples in Europe and adjacent areas of North Afric ...
s observe the March equinox (referred to as Ostara) as a cardinal point on the
Wheel of the Year The Wheel of the Year is an annual cycle of seasonal festivals, observed by many modern pagans, consisting of the year's chief solar events (solstices and equinoxes) and the midpoints between them. While names for each festival vary among di ...
. In the northern hemisphere some varieties of paganism adapt vernal equinox celebrations, while in the southern hemisphere pagans adapt autumnal traditions. *
International Astrology Day International Astrology Day (most often observed on either March 20 or March 21) was first asserted by the Association for Astrological Networking in 1993 and is an annual observance/holiday celebrated by astrologers and astrology enthusiasts. It ...
* On 20 March 2014 and 20 March 2018, the March equinox was commemorated by an animated Google Doodle.


See also

*
September equinox The September equinox (or southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward. Because of differences between the calendar year and the tropical year, the September equinox may occur anyt ...
*
June solstice The June solstice is the solstice on Earth that occurs annually between 20 and 22 June according to the Gregorian calendar. In the Northern Hemisphere, the June solstice is the summer solstice (the day with the longest period of daylight), wh ...
* December solstice


References


External links

* *
Spring Starts Today All Over America, Which Is Weird
(19 March 2020) {{Portal bar, Earth sciences, Astronomy, Stars, Spaceflight, Outer space, Solar System Spherical astronomy Dynamics of the Solar System Equinox Astronomical events of the Solar System