Spring is nearly upon us, at least according to the calendar.
The vernal equinox occurs on Thursday, signifying the commencement of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. At the equator, the sun will be positioned directly overhead at midday. Equinoxes are unique in that they are the only instances when both poles receive sunlight simultaneously.
These events have been commemorated globally for centuries. For instance, Nowruz, the Iranian New Year, is timed to coincide with the spring equinox. Furthermore, at the Mayan archaeological site of Chichen Itza in Mexico, people congregate during the equinox to observe the sun’s shadow casting a serpent-like image down the El Castillo pyramid.
But what exactly is transpiring in the sky? Here’s what you should understand about how the Earth’s orbit dictates our yearly divisions.
What is the equinox?
As the Earth orbits the sun, it does so on a tilted axis.
For much of the year, the Earth’s axis leans either towards or away from the sun. This results in an uneven distribution of solar energy and light across the northern and southern halves of the globe.
During the equinox, the Earth’s axial tilt and its orbital path align in such a way that both hemispheres receive an equal amount of sunlight.
The term “equinox” originates from Latin words meaning “equal” and “night.” This is because, during the equinox, the duration of day and night is nearly identical, although a slight difference of a few minutes may occur depending on your location.
The Northern Hemisphere’s spring (or vernal) equinox can occur between March 19 and 21, contingent on the year. The autumn equinox can occur between September 21 and 24.
What is the solstice?
Solstices mark the points in the year when the Earth’s tilt relative to the sun is at its most extreme. This results in the most significant differences in the amount of sunlight received by each hemisphere, leading to the most unequal day and night lengths.
During the Northern Hemisphere’s summer solstice, the upper half of the Earth is tilted towards the sun, resulting in the longest day and shortest night of the year, occurring between June 20 and 22.
Conversely, at the winter solstice, the Northern Hemisphere is tilted away from the sun, leading to the shortest day and longest night of the year, which falls between December 20 and 23.
What’s the difference between meteorological and astronomical seasons?
These represent two distinct methods of dividing the year.
While astronomical seasons are determined by the Earth’s movement around the sun, meteorological seasons are defined by weather patterns. They divide the year into three-month periods based on average temperature trends, with spring commencing on March 1, summer on June 1, autumn on September 1, and winter on December 1.
“`