An Astronomical Masterpiece:

Norooz and the Spring Equinox

Sunday, March 20, 2016 - 11:38

The Iranian year will change on Sunday at 8 am on March 20, 2016, (Farvardin 1, 1395). The event marks Norooz, which has been devised based on a remarkable scientific and astronomical basis.

Norooz is the traditional Iranian festival of spring which starts at the exact moment of the vernal equinox, commencing the start of the spring. The name comes from Avestan meaning "new day/daylight". Norooz is celebrated March 20/21 each year, at the time the sun enters Aries and Spring begins.

Norooz has been celebrated for at least 3,000 years and is deeply rooted in the rituals and traditions of Iran. Today the festival of Norooz is celebrated in Iran, Iraq, India, Afghanistan, Tajikestan, Uzbekistan, Azerbaijan, Kazakhstan, and Kyrgyzstan.

The basis for calculating Norooz or the first day of a new year in the Solar Hijri calendar is the moment that the sun crosses the first point of Aries and the vernal equinox begins. If the time when this occurs and the year changes before noon, that day is considered to be Norooz but if the year changes in the afternoon, the following day is counted as Norooz. The March or Northward equinox is when the Sun appears to leave the southern hemisphere and cross the celestial equator, heading northward as seen from earth. In the northern hemisphere the March equinox is known as the vernal equinox, and in the southern hemisphere as the autumnal equinox.

The present Iranian calendar, also called the Jalali calendar, dates back to the eleventh century, when Jalal-ed-din Malek Shah Seljuq commissioned a panel of scientists in 1074-1079 AD to create a calendar more accurate than those in use at the time. Prominent among the scientists was Omar Khayyám, best known today for his poetry, especially The Rubaiyat.

The Iranian year begins on the day of the vernal equinox - the first day of spring. It consists of 12 months which have retained their Old Persian names. The first six months are each 31 days, the next five 30 days, and the last 29 (except in leap years, when it is 30 days). They roughly correspond to the signs of the zodiac. The Iranian calendar coincides with the tropical year, which is 365.24219 days long, but because of the constraints of adjusting the beginning of the calendar to the beginning of the day (at midnight), on the average, the Iranian calendar runs short of the tropical year by 5h, 48m, 45.2s each year, which is countered by adding an extra day to the end of every fourth year - the leap year. In addition, in astronomical terms, the length of a year become less by 0.00000615th of a day every century.


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