What Is the Vernal Equinox?

How much do you know about the first day of spring?

Woman's finger touches cherry blossom,. orchard
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The vernal equinox is the first day of spring, on March 20 or 21 each year. “Vernal” and “equinox” are Latin terms meaning “spring” and “equal night” respectively.

Is the Vernal Equinox Really Equal?

The idea is that on the first day of spring there are exactly 12 hours of daylight and 12 hours of darkness, but it rarely works out that way.

There is always a time each spring, and again each fall, when the hours of light and darkness are equal, but it usually occurs before the vernal equinox and after the autumnal equinox.

First Day of Spring--Above and Below the Equator

The vernal equinox signals the start of spring in the Northern Hemisphere, but it also corresponds to the autumnal equinox—the first day of autumn—in the Southern Hemisphere. Conversely, the autumnal equinox in the north, which occurs in late September, is the first day of spring south of the equator.

Facts About the First Day of Spring

Here are a few other interesting facts about the first day of spring:

  • If you were standing on the equator during either the vernal or autumnal equinox, you would see the sun pass directly overhead, the only two times in the year when that is true.
  • The two equinoxes are also the only times during the year when the sun rises due east and sets due west.

  • In spring, the Earth’s axis is tilted toward the sun, increasing the number of daylight hours and bringing warmer weather that causes plants to bring forth new growth.

  • Under global climate change, certain spring phenomena are starting to shift in time: tree leaf out, flowering, and caterpillar emergence happen earlier. The arrival of birds from their spring migration does not necessarily follow the same shift - a problem called phenological mismatch

There is a persistent myth that at the vernal equinox, and only at the vernal equinox, can you stand a raw egg on its end.

There is an equally persistent rebuttal that says it’s not possible at any time to balance a raw egg on its end. Neither assertion is true. With a little patience (or sometimes a lot), you can balance a raw egg on its end at any time of year. The first day of spring has nothing to do with it.

Edited by Frederic Beaudry