March equinox

Illustration of astronomical calculations of northward equinox and Nowruz

The March equinox (or Northward equinox) is the equinox on the earth when the Sun appears to cross the celestial equator, heading northward. The March equinox is the vernal equinox in the northern hemisphere and the autumnal equinox in the southern hemisphere.

The equinox can be as early as March 19 or as late as March 21, the precise time being about 5 hours 49 minutes later in a common year, and about 18 hours 11 minutes earlier in a leap year, than in the previous year. It is the balance of common years and leap years that keeps the calendar date of the equinox from drifting more than a day from March 20 each year.

Northward equinox solar year

The March equinox is one point in time commonly used to determine the length of the tropical year. The mean tropical year is the average of all the tropical years measured from every point along the earth's orbit.^[2] In 1983 the mean March equinox fell at 1.48 AM GMT on 23 March. When tropical year measurements from several successive years are compared, variations are found which are due to nutation, and to the planetary perturbations acting on the Sun. Meeus and Savoie (1992, p. 41) provided the following examples of intervals between northward equinoxes:

Constellation

The point where the horizon crosses the sun's disk at the celestial equator northwards is called the first point of Aries. However, due to the precession of the equinoxes, this point is no longer in the constellation Aries, but rather in Pisces. By the year 2600 it will be in Aquarius (some Archeoastronomers and Astrologers believe that will be the start of the approximate 2,150 years of "the Age of Aquarius", while others think it may have already started, and varying calculations in between).

• The northward equinox passed from Taurus into Aries in the year −1865, passed into Pisces in the year −67, will pass into Aquarius in the year 2597, and will pass into Capricornus in the year 4312. It passed along (but not into) a 'corner' of Cetus on 0°10' distance in the year 1489.

Movement of the horizon in relation to the Sun

At the equinox, the sun's disk crosses the horizon directly in the east at dawn and crosses directly in the west at dusk. However, because of refraction the sun will usually appear slightly above the horizon when its "true" middle is rising or setting. For viewers at the north or south poles, the sun moves steadily just above the horizon, not obviously rising or sinking apart from the movement in "declination" (and hence elevation) of a little under a half (0.39) degree per day.

Human culture

Calendars

The Persian calendar begins each year at the northward equinox, observationally determined at Tehran.^[3]

The Indian National Calendar starts the year on the day next to the vernal equinox on March 22 (March 21 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.^[3]

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 March 10 or 11.

The date in 1452 was March 11 11:52 (Julian) ^[4] In 2547 it will be March 20 21:18 (Gregorian) and March 3 21:18 (Julian).^[5]

Commemorations

Bas-relief in Persepolis – a symbol Iranian/Persian Nowruz – on the day of an equinox, the power of an eternally fighting bull (personifying the Earth) and that of a lion (personifying the Sun) are equal.

Chichen Itza pyramid during the spring equinox – Kukulkan, the famous descent of the snake

Abrahamic tradition

• The Jewish Passover usually falls on the first full moon after the northern hemisphere vernal equinox, although occasionally (currently three times every 19 years) it will occur on the second full moon.
• The Christian churches calculate Easter as the first Sunday after the first full moon on or after the March equinox. The official church definition for the equinox is March 21. The Eastern Orthodox Churches use the older Julian calendar, while the western churches use the Gregorian calendar, 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 Easter date in any year is March 22 on each calendar. The latest possible Easter date in any year is April 25.^[6]

West Asia

• The northward equinox marks the first day of various calendars including the Iranian calendar. The ancient Iranian new year's festival of Nowruz can be celebrated March 20 or March 21. 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. These festivities recall the story of creation and the ancient cosmology of Iranian and Persian people. It is also a holiday celebrated in Azerbaijan, Afghanistan, Pakistan, Turkey, Zanzibar, Albania, and various countries of Central Asia, as well as among the Kurds. As well as being a Zoroastrian holiday, it is also a holy day for adherents of the Bahá'í Faith and the Nizari Ismaili Muslims.^[7] The Bahá'í Naw-rúz is calculated using astronomical tables - the new year always starts at the sunset preceding the vernal equinox calculated for Tehran.^[8]
• In many Arab countries, Mother's Day is celebrated on the northward equinox.

North Africa

• 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 vernal 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.

• It marks the beginning of the new year of the Tamil calendar and is celebrated in the South Indian state of Tamil Nadu.
• This day is celebrated as the last day of the year according to the Bengali calendar and Assamese calendar in West Bengal, Assam, Tripura, Bangladesh and throughout Eastern and North Eastern India. The day is known as Chaitra Sankranti in Bengali. The following day is celebrated as the Bengali New Year's Day and Assamese Bihu.
• Andhra Pradesh, Karnataka and Maharastra people celebrate new year ugadi set by Satavahana on the first morning after the first new moon from the sidereal vernal equinox. Also the calculations of the great Indian mathematician Bhaskaracharya proclaim the Ugadi day as the beginning of the New Year, New month and New day.
• In the Indian state of Odisha, this day is celebrated as the new year around April 14. It is known as 'Vishuva Sankranti' (meaning "equal" in Sanskrit). In Kerala though the new year is on Chingam 1, the beginning of sidereal zodiac Leo, sidereal vernal equinox is celebrated much more than new year as 'Vishu'.
• The traditional New Year celebrations in Cambodia, Laos, Myanmar and Thailand take place on 13 to 15 (or 16) April.

East Asia

• The traditional East Asian calendars divide a year into 24 solar terms (节气, literally "climatic segments"), and the vernal equinox (Chūnfēn, Chinese and Japanese: 春分; Korean: 춘분; Vietnamese: Xuân phân) marks the middle of the spring. In this context, the Chinese character 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.

Europe

• Lieldienas
• in Norse paganism, a Dísablót was celebrated on the vernal equinox.^[9]

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.^[10]
• In Annapolis, Maryland in the 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.^[11][12]
• Neopagans observe the March equinox as a cardinal point on the Wheel of the Year. In the northern hemisphere some varieties of paganism adapt vernal equinox celebrations, while in the southern hemisphere pagans adapt autumnal traditions.
• International Astrology Day
• On March 20, 2014, the March equinox was commemorated by an animated Google Doodle.^[13]

References

See also

• Solar eclipse of March 20, 2015

External links

• "Ancient Equinox Alignment". Loughcrew, Ireland. 
• Dates and times of the Northward equinox