Spring is just around the corner, at least according to the calendar.
The vernal equinox, which heralds the arrival of spring for those of us in the Northern Hemisphere, is set to occur on Tuesday. But what exactly does this mean? Let’s dive into the significance of how we divide the year based on Earth’s journey around the sun.
So, what is an equinox? As Earth orbits the sun, it does so at a tilt. Throughout most of the year, this tilt causes the sun’s rays to hit the northern and southern parts of Earth unevenly. However, during an equinox, Earth’s tilt aligns in such a way that both hemispheres receive an equal amount of sunlight.
The term “equinox” is derived from two Latin words that translate to “equal night.” This is because, during an equinox, the duration of day and night is nearly identical, though there might be a slight variation in minutes depending on your location on the globe.
The spring, or vernal, equinox in the Northern Hemisphere can occur anywhere from March 19 to 21, varying each year. Similarly, the autumnal equinox can happen between September 21 and 24.
But what about the solstice? Solstices are the points in the year when Earth’s tilt towards or away from the sun is at its maximum. This results in a significant difference in the amount of sunlight each hemisphere receives, making the days and nights notably unequal.
The summer solstice in the Northern Hemisphere, when it tilts towards the sun, brings about the longest day and shortest night of the year, occurring between June 20 and 22. Conversely, the winter solstice, when it leans away from the sun, results in the shortest day and longest night, happening between December 20 and 23.
Now, let’s talk about the difference between meteorological and astronomical seasons. These are simply two methods of dividing the year. Meteorological seasons are based on weather patterns, dividing the year into three-month periods that reflect the annual temperature cycles. According to this system, spring begins on March 1, summer on June 1, fall on September 1, and winter on December 1.
Astronomical seasons, on the other hand, are determined by Earth’s position in relation to the sun. Equinoxes signal the start of spring and autumn, while solstices mark the beginning of summer and winter.
This exploration into the mechanics of our seasons is supported by the Howard Hughes Medical Institute’s Science and Educational Media Group, though the content is solely the responsibility of The Associated Press.