Wisconsin Nature

Celebrating the Spring Equinox

We all look forward to the arrival of spring, with warming temperatures, increased sunlight, and the budding of new life. The kick-off to the season begins with an astronomical event called the spring equinox, also called the vernal equinox. The equinox which translates to “equal night” from the Latin, means that daytime and nighttime are of equal length on this day. This year, the spring equinox occurs at 4:37am on the morning of Saturday, March 20.

The Movements of the Sun and Earth

There is a complex relationship between the movement of the sun and the earth. The focal point of the sun’s light hits the earth and travels across its surface as the earth spins. If you looked at a record of this point moving across the surface of the earth over time, it would look like many lines crisscrossing the planet. On the spring equinox, the point of sunlight passes directly over the equator, heading north, with the sun sitting directly overhead. It is a moment in time.

On March 20 in the Northern Hemisphere, this corresponds to the beginning of spring. In the Southern Hemisphere, it’s the beginning of fall. The day can vary over time because the calendar doesn’t equate exactly to astronomical time. Because of leap year every four years and other alterations in the calendar, however, the spring equinox always occurs within a day of March 20.

The Moment of the Seasons

An equinox also takes place in fall in the Northern Hemisphere, which corresponds to spring in the Southern Hemisphere. As the spring and fall equinox signal the beginning of their respective seasons, the solstices signal the beginning of their respective summer and winter seasons. While the lengths of day and night are equivalent on the equinoxes, the summer solstice is the longest day, and the winter solstice the shortest.

Movements Through the Zodiac

The earth orbits around the sun in our solar system. The earth tilts at a 23.5-degree angle in its orbit. As it spins, it wobbles, which is called the earth’s precession. This angle and the different positioning of the earth through time in relation to the sun produces the seasons. The solar system also orbits through the galaxy. So, though astronomical events like the equinox take place close to the same date every year, the position of the earth and sun in the galaxy is different. The position of the sun during the equinox has shifted by about 1° every 73 years because of the earth’s wobbling. The sun travels through the constellations of the zodiac, and every zodiac sign will host a spring equinox. Since 68 BCE, the equinox has taken place while the sun is in the constellation Pisces. By AD 2597, the spring equinox will happen in Aquarius.

Celebrating the Spring Equinox

Many people across the globe celebrate the spring equinox as a time of rebirth and renewal. In England, some visit Stonehenge in ancient tribal garb and walk the grounds at sunrise on the day of the spring equinox. In India and Nepal, the Holi festival is celebrated. It is a Hindu custom known as the “festival of colors,” in which people toss colored powder on each other and dance in the streets.

Other cultures throughout history and pre-history have watched the movements of the sun and stars closely. In Mexico’s Chichen Itza, the Mayans built a pyramid around AD 1000. On this pyramid, the sun’s light creates a display at the beginning of the seasons. On the spring equinox, it looks like a snake slithering down the side. The day is known as the “return of the Sun serpent.”

Watch for the spring equinox on March 20 this year and consider celebrating with a walk in nature at the Center.