March 21, The Vernal Equinox

by Sumana Saparamadu

March 21 is an important date in the calendar. Do you know why? Some of you readers may know the reason. I'll explain it for the benefit of those who do not know.

You would have noticed that the evenings are getting longer now; there is daylight much longer, unlike in December and early January. Why? Because the sun is coming closer to us, our country.

What do I mean when I say ‘the sun is coming closer to us'.

The sun does not move. It seems to be moving because the earth is moving constantly. In a geography lesson you would have learned about the equator and the tropics. The equator is an imaginary line round the middle of the earth.

The tropics are two parallel lines (again imaginary) round the earth 23.5 degrees north and 23.5 degrees south of the equator. The line in the north is called Tropic of Cancer, and the line in the South, Tropic of Capricorn.

The sun seems to move between these two topics – north to south, and south to north; and as it moves north and south it crosses the equator twice a year, once on March 21 when it is going north and again on September 23, on the Southward journey. That is why March 21 is a very important day in the calendar.

The sun reaches the Tropic of Cancer on June 23, the following day it begins to move south and crosses the equator on Sep.23 and goes southward to reach the Tropic of Capricorn on December 23 from the next day the sun begins to move northwards and reaches the equator on March 21. These two days-March 21 and September 23 are called the equinox.

On March 21 and September 23 the sun is directly overhead the equator and day and night are of equal length – 12 hours day light and 12 hours darkness, at the equator.

From March 22 the sun is moving northward to the Tropic of cancer and in the first week in April, from about the 5th to the 9th, the sun will be directly overhead Sri Lanka. During this time we will have long hours of daylight, and it will be very hot.

March 21 is called the vernal or spring equinox, because it marks the beginning of spring in the northern hemisphere. In countries north of the Tropic of Cancer, the earth will slowly wake up from its long winter sleep and the trees and plants will begin to put out new shoots, and animals will begin to move away from where ever they were sleeping in the cold winter months.

In ancient times the people were keen observers of nature and the positions of the sun, moon and stars. They were aware of the days when daylight and darkness (day and night) were equal.As long ago as 2000 BC the Sumerians in Mesopotamia calculated the new year by the new moon nearest the spring equinox. Do you know a long long time ago, long before the birth of Christ, March was the first month of the year. Those ancients observed that Nature wake up from its winter sleep at this time, when day light began to increase.

They must have taken this to be the beginning of a new year. In Iran today the New Year is celebrated on the day of the equinox-March 21. So, as in ancient Rome in Iran the year still begins in March.