Spring Equinox and Spring Begins

In the Northern Hemisphere, spring begins on March 19, 20 or 21 with the equinox. The Vernal Equinox of 2007 is apparently the last to fall on March 21st. After 2007, the Vernal Equinox will fall on March 19th or 20th for the rest of our lives.

In the Southern Hemisphere the seasons are reversed. And spring begins with the equinox on September 22 or 23.

All this is due to the 23.5 degree tilt of the Earth. If the Earth didn't tilt, there wouldn't be any seasons. The Sun would always shine directly at the Earth's equator and there would be no spring, summer, autumn or winter. There would be freezing cold zones like the poles, and hot tropical zones, like at the equator and temperate zones like North America. And it would be the same all the time with no changing seasons.

People always say that on the spring equinox, day and night are of equal length. But, supposedly this is not true. The reason for this is atmospheric refraction. This is when light enters the atmosphere at an angle instead of straight on or perpendicular. The light bends and celestial bodies, such as the Sun, appear slightly higher in the sky that it really is. We can see the Sun even after it has already set. This gives us 1.5 percent more sunshine. And on the equinox, there is between 4 and 15 minutes more day than night.

During the spring equinox the sun is directly above the Earth's equator. At the equator there is even more daylight. In the Northern hemisphere, as the Sun shines more and more north of the equator, the days grow longer.

Because of the tilt of the Earth, humans, plants and animals at the South Pole experience twenty-four hours of daylight. No equal day and night there. Just day.

The vernal equinox is the only day when the Sun's path is absolutely straight across the sky. The Sun rises in the east and sets exactly in the west. It is a good time to find the cardinal directions from your home. You can follow the example of ancient peoples and mark due east or west with a stone or other object.

Works Consulted

Allaby, Michael, editor. “Atmospheric refraction”. Illustrated Dictionary of Science, Facts On File, 1995, p. 31

Dr. James Foster. “Science Question of the Week: Which of the following are connected in some way: “tax day”, the Ides of March, the Vernal Equinox, opening day in baseball, Passover, and Easter?”. Goddard Space Flight Center. http://www.gsfc.nasa.gov/scienceques2004/20050415.htm 3/20/07.

From Spring Equinox and Return to Nature in Spring