by Bruce Tyson

Created on: March 20, 2010

Vernal Equinox is the term used to describe the moment in time when the middle of the sun is observable directly overhead from a location on the equator. The Vernal Equinox happens once every year on either March 20th or 21st. The exact time of the Vernal Equinox varies each year, with it becoming about a day earlier every seventy years. The leap year rules of our calendar system compensate for this change in time. There is another equinox, the Autumnal Equinox that happens every year. Because of its association with spring, a move is being made to rename the Vernal Equinox the March Equinox to remove the biased reference of the northern hemisphere. The Vernal Equinox in 2010 was on March 20th at 17:32 UTC.

Length of Day

Several events characterize the Vernal Equinox that makes it astronomically significant. First, the length of day and night are most equal at the equator. This means that sunlight reaches the ground when no obstructions are present for almost exactly 12 hours, although the day is slightly longer than the night.

At the north and south poles of the earth, the equinox is the time when they change from either 24 hours of day to 24 hours of light.

Beginning of calendar year

The Vernal Equinox marks the beginning of several different calendars in use around the world. The Persian calendar and the Baha’i calendar, for example, both regard this as the beginning of the new year.

Celebrations

Persians celebrate the Vernal Equinox because of the new year as well as because it marks the time when a mythological king ascended to power.

Landmarks

At the Vernal Equinox, the Sun is aligned with the Great Sphinx in Egypt. Other landmarks around the world are associated with the equinox such as Stonehenge in England and the Caracol Tower at Chichen Itza in Central America.

Change of season

Finally, perhaps the most practical implication of the Vernal Equinox is that it marks the beginning of Spring in the northern hemisphere. The Vernal Equinox marks the beginning of autumn in the southern hemisphere.

Since ancient times the Vernal Equinox has been an event revered and celebrated. It continues to be a time of curiosity and celebration. In a world where it seems like everything is changing, the Vernal Equinox is a good time to remember that the more things change, the more they stay the same.

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