Spring is about to make its official entrance, signaling a change in seasons across the globe. The vernal equinox is set to arrive on Thursday, marking the beginning of spring in the Northern Hemisphere and the start of fall in the Southern Hemisphere. As this astronomical event unfolds, the sun will be directly overhead at noon along the equator. Important to note, equinoxes are unique occurrences where both the north and south poles receive simultaneous sunlight.
These equinoxes have been celebrated worldwide for centuries. To illustrate, Nowruz, the Iranian New Year, coincides with the spring equinox. Additionally, at Chichen Itza, an ancient Mayan site in Mexico, people assemble during the equinox to witness a striking shadow pattern resembling a serpent slithering down the steps of the pyramid known as El Castillo.
Understanding the heavenly mechanics behind this event is fascinating. During its journey around the sun, Earth is tilted at an angle, which throughout most of the year results in uneven distribution of sunlight between the northern and southern hemispheres. When the equinox occurs, Earth’s orbit and axis align such that both hemispheres receive an equal share of sunlight. The term “equinox” is derived from Latin, combining the words for “equal” and “night,” reflecting the nearly equal lengths of day and night experienced globally.
The Northern Hemisphere’s spring equinox, also known as the vernal equinox, can fall anywhere from March 19 to March 21, depending on the year, while the autumnal equinox occurs between September 21 and 24. On the other hand, solstices denote the extreme points in Earth’s tilt either toward or away from the sun. This results in vastly different distributions of sunlight between the two hemispheres and significantly varying lengths of day and night.
During the summer solstice in the Northern Hemisphere, Earth is tilted towards the sun, resulting in the longest day and shortest night, typically occurring between June 20 and 22. Conversely, in the winter solstice, the hemisphere tilts away from the sun, leading to the shortest day and longest night between December 20 and 23.
There is also a distinction between meteorological and astronomical seasons. While astronomical seasons are determined by Earth’s orbit and axial tilt, meteorological seasons are classified based on weather patterns and temperature cycles. Meteorological seasons divide the year into three-month intervals: spring starting on March 1, summer on June 1, fall on September 1, and winter on December 1.
