March equinox

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Illustration of astronomical calculations of Northward equinox and Nowruz
UT date and time of
equinoxes and solstices on Earth[1]
event equinox solstice equinox solstice
month March June September December
year
day time day time day time day time
2010 20 17:32 21 11:28 23 03:09 21 23:38
2011 20 23:21 21 17:16 23 09:04 22 05:30
2012 20 05:14 20 23:09 22 14:49 21 11:12
2013 20 11:02 21 05:04 22 20:44 21 17:11
2014 20 16:57 21 10:51 23 02:29 21 23:03
2015 20 22:45 21 16:38 23 08:20 22 04:48
2016 20 04:30 20 22:34 22 14:21 21 10:44
2017 20 10:28 21 04:24 22 20:02 21 16:28
2018 20 16:15 21 10:07 23 01:54 21 22:23
2019 20 21:58 21 15:54 23 07:50 22 04:19
2020 20 03:50 20 21:44 22 13:31 21 10:02

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 22, 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[edit]

Main article: tropical year

The March equinox is one point in time commonly used to determine the length of the tropical year. The length of Northward equinox solar year is relatively stable in the time from 6000 BCE to 10000 CE at 47:37 to 49:20 in excess of 365 days and 5 hours.[2]

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:

time in excess of 365 days and 5 hours
min s
1985–1986 48 58
1986–1987 49 15
1987–1988 46 38
1988–1989 49 42
1989–1990 51 06

Constellation[edit]

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 year −1865, passed into Pisces in year −67, will pass into Aquarius in year 2597, will pass into Capricornus in year 4312. It passed along (but not into) a 'corner' of Cetus on 0°10' distance in year 1489.

Movement of the horizon in relation to the Sun[edit]

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

For observers in either hemisphere not at the poles, the further one goes in time away from the March equinox in the 3 months before that equinox, the more to the south the Sun is seen, and for the 3 months afterwards the sun is seen more and more to the north.

Human culture[edit]

Calendars[edit]

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[edit]

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 tropical year is about 11 minutes and 14 seconds less than that. This had the effect of adding about three quarters of an hour every four years. The effect accumulated from 325 until by the 16th century, when the northern vernal equinox fell on March 10 or 11.

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

Commemorations[edit]

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 (7 times every 19 years) it will occur on the second full moon.[citation needed]
  • 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; however, as the Eastern Orthodox Churches use the older Julian calendar, while the Western Churches use the Gregorian calendar, both of which designate March 21 as the equinox, the actual date of Easter differs. The earliest possible Easter date in any year is therefore 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 stationary; the new year always starts at sunset March 20.[8]
  • In many Arab countries, Mother's Day is celebrated on the Northward equinox.
North Africa
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.

East Asia
Europe
Modern culture

References[edit]

  1. ^ United States Naval Observatory (2010-06-10). "Earth's Seasons: Equinoxes, Solstices, Perihelion, and Aphelion, 2000-2020". 
  2. ^ http://individual.utoronto.ca/kalendis/leap/Solar-Year-Length-Variations.pdf
  3. ^ a b Dr. Irv Bromberg, University of Toronto, Canada. "The Lengths of the Seasons". Individual.utoronto.ca. Retrieved 2013-07-06. 
  4. ^ Ivan Smith (2002-05-10). "Vernal Equinox, 1452 - 1811". Ns1763.ca. Retrieved 2013-07-06. 
  5. ^ Ivan Smith (2002-05-10). "Vernal Equinox, 2188-2547". Ns1763.ca. Retrieved 2013-07-06. 
  6. ^ Cooley, Keith (2001). "Keith's Moon Facts". Hiwaay.net personal pages. 
  7. ^ "Navroz". The Ismaili. Islamic Publications Limited. Retrieved 2011-07-04. 
  8. ^ "With Spring comes the Baha'i New Year". Bahai.us. National Spiritual Assembly of the Baha'is of the United States. Retrieved 2011-07-04. 
  9. ^ "Disablót". Nationalencyklopedin (Swedish).
  10. ^ "World Citizens Day - World Unity Day". Consultative Assembly of the Peoples Congress (2007).
  11. ^ "Annapolis Welcomes Spring by Burning Socks". First Coast News.[not in citation given]
  12. ^ Rey, Diane. "Hillsmere Joins in Sock Burning Tradition". Annapolis, MD: The Capital. Retrieved 25 April 2011. 
  13. ^ Gander, Kashmira (2014-03-20). "Spring equinox 2014: First day of spring marked by Google Doodle". The Independent (independent.co.uk). Retrieved 2014-03-20. 

External links[edit]

See also[edit]