Vernal Equinox

Well, spring is officially here. Friday March 20th was the vernal (spring) equinox, the sun shining directly on the equator, day length roughly equaling night length. The first two days of spring were gorgeous in the mid 60s and sunny, it really felt like spring. Yesterday, however, our great mother seemed to forget that it is officially spring and sent us a major wind storm mixed with brief moments of snow. The high was only 46 degrees Fahrenheit!


I knew that the spring equinox was when the day and night length were equal, but I wanted to learn more about it so I did some research and this is what I found. The term equinox is derived from Latin aequus - equal and nox - night. The day length and night length are not quite equal on the day of the equinox. Day length is different depending where you are on the Earth. The day is slightly longer in places farther away from the equator because the sun takes longer to rise and set in these areas. Also, the Earth's atmosphere bends the Sun's light when it is close to the horizon so it appears a bit higher in the sky than it really is, causing the sun to appear above the horizon a few minutes earlier than it really is.

The vernal equinox can occur on March 20th or March 21st, however, it sometimes falls on March 19th.

Resources:

The March Equinox Explained, (n.d.). Retrieved March 23, 2009 from Time and Date.com: http://www.timeanddate.com/calendar/march-equinox.html.

Roach, John. Vernal Equinox 2009: Facts on the First Day of Spring (March 19, 2009). Retrieved March 23, 2009 from National Geographic News: http://news.nationalgeographic.com/news/2009/03/090319-vernal-equinox-2009-spring.html.