Vernal Equinox Arrives Today

The orbit of the Earth around the Sun produces variations in the seasons with four orbital positions having particular significance. Today, March 19, 2020, the Sun will pass directly overhead at the equator. The exact time will be 11:49 p.m. EDT (0349 GMT March 20, 2020). We can rejoice that the vernal equinox arrives today!

This is the earliest equinox in the United States in 124 years! As you can see in the diagram, the usual date for the vernal equinox is March 20 or 21, depending on where you live on the Earth. The reason it arrives on the 19th this year in North America is somewhat complicated, but it has to do with leap years and daylight saving time. We won’t get into that, but I thought we should explain why the diagram differs from this year’s dates.

There is wonderful history of how the Greek scholar Eratosthenes of Alexandria used the equinox to measure the circumference of the Earth. He knew that on the equinox, a pole stuck vertically in the ground left little or no shadow at noon, depending on location. He compared the length of the shadow of a pole in Syene, a town in southern Egypt, with one in Alexandria in northern Egypt. Using the difference in the shadow lengths, he calculated the circumference of the Earth. His calculation was very close to the known circumference today, and it proved the Earth was round. He did that in 245 BC, long before Columbus sailed.

The four polar positions roughly predict the seasons that have been used by every culture to control planting, harvesting, and preparing the soil. In Genesis 1:14, God said, “Let there be lights in the expanse of space to divide the day from the night, and let them be for signs, and for seasons, and for days, and years.” God not only instituted day and night, but He also positioned the Sun and Moon so they could be used to mark the seasons we would need to live on this planet.

As the vernal equinox arrives today, we wish you a happy equinox!! Enjoy the season and the official end of winter in the Northern Hemisphere. We will have more on the spring equinox tomorrow.

— John N. Clayton and Roland Earnst © 2020