The vernal equinox takes place each year on March 20th or March 21st and signals the start of spring in the Northern Hemisphere and fall in the Southern Hemisphere.
What is an equinox?
During the vernal equinox, the amount of daylight and darkness is nearly the same in length. This explains the origin of the word equinox, which comes from the Latin “aequus,” meaning equal, and “nox,” meaning night.
The equinox is driven by the Earth’s tilt. The Earth is tilted at an angle of 23.5 degrees on its axis relative to its plane around the sun. An equinox occurs when the Earth’s axis doesn’t tilt towards or away from the sun. Someone standing on the equator during an equinox will see the sun pass directly overhead. Equinoxes are also the only two times a year that the sun rises due east and sets due west.
Six months after the vernal equinox, another equinox occurs around September 22nd or 23rd. Since the Earth actually takes about 365.24 days to orbit the sun, equinoxes happen around six hours later from year to year, before moving back a day on leap years. This is why the first day of spring and fall shifts.
The start of spring is a cause for celebration in many places around the world. The vernal equinox is a holiday in Japan, called Shunbun no hi. The holiday is marked by honoring nature, spending time with family, and tending to ancestral graves.
Persian New Year, or Nowruz, is a holiday that begins on the vernal equinox and it’s celebrated by millions of people, primarily in the Middle East and Central Asia. The holiday is commonly observed by deep cleaning of homes, celebrating a season of new life, and wishing for good luck in the year ahead.
Celebrations also occur at the ruins of Chichen Itza in Mexico. The Pyramid of Kukulcán was constructed to be completely aligned with the sun during the equinox. As the sun goes down, shadows that resemble the body of a snake appear on the side of the building. The shadows symbolize the descent of the Kukulcán god that fertilizes the ground for the upcoming harvest season.
Spring Has Sprung
According to a Gallup Poll, 36% of Americans say spring is their favorite season, making it the most popular response. Spring directly follows the least popular season, as only 11% of respondents named winter as their favorite.
There are numerous pieces of scientific evidence that back up the love of spring. The warmer temperatures and longer daylight hours have a marked impact on mental health. A 2005 study from the University of Michigan linked spending 30 minutes or more outside in warm, sunny spring weather to a positive mood and better memory.
And the return of wildlife can have a positive impact as well. A 2017 study found that the more birds people could see in their neighborhoods, the better their mental health.