Why Summer Becomes Fall During the Autumnal Equinox

autumnal equinox

A Moment of Harmony Between Our Planet and the Sun Marks the Start of Fall 

The autumnal equinox is on September 22nd, and with it comes an opportunity to regain balance and harmony as summer slips into the rearview mirror and the joys of the fall season come into view.  

Like the vernal equinox and solstices in winter and summer, the autumnal equinox is an astronomical event shaped by the orbit of our earth around the sun that humanity has long used to mark the changing of seasons. This year, welcome autumn by diving into the science behind the autumnal equinox and you just might find yourself restored by the literal reason for the fall season, the autumnal equinox.

What is the Autumnal Equinox?

The autumnal equinox officially opens pumpkin spice season, otherwise known as fall, with brief restoration of order in an otherwise topsy-turvy world. 

We get the joys of changing seasons because earth orbits at a 23.5 degree tilt as it makes its year-long trek around our solar system’s very own mass of incandescent gas that we call the sun. Without the earth’s tilt the sun would shine directly on the equator all year long and seasons would not change. Because of the earth’s tilt the sun 

Due to earth’s tilt, the sun spends most of the year north or south of the equator and shines more directly on some parts of the globe during certain times of the year than others. We experience the resulting variations in the amount of sunlight regions north or south of the equator get throughout the year as seasons. That’s why fall starts when it does, on the autumnal equinox, whether it feels any chillier outside or not (regards from Texas). 

Twice a year, in March and September, the sun aligns with the equator, day and night fall into balance, and the whole world experiences the changing of seasons with a day that’s roughly equal in duration to the night. That’s why we call these days equinoxes, from the Latin for equal (equi-) night (nox). 

When is the Autumnal Equinox?

The Autumnal Equinox occurs on the planet earth’s time, not ours, so the equinox can fall on different days in late September, depending on the year. 

Equinoxes occur in between solstices. During the solstices in winter and summer, the sun is at its furthest north or south of the equator. In the June solstice, the sun beams directly over the Tropic of Cancer, giving us the longest day of the calendar year as the first day of summer. When the sun beams directly over the Tropic of Capricorn in the December solstice, we open winter with the shortest day of the year.

During the spring and fall equinox, the sun beams right over the equator, between both tropics. Around March 21st, we experience the vernal equinox in the Northern hemisphere, and mark the start of spring, and in late September the autumnal equinox ushers in the fall season.

What About The Southern Hemisphere?

Meanwhile, in the Southern Hemisphere the equinox and solstice mark the changing of opposite seasons. While we’re welcoming fall, the Southern Hemisphere ushers in Spring with its vernal equinox, and when we welcome winter with the shortest day of our year, people south of the equator start their summers with the longest day of their year.

Celebrate the Equinox and Sneak a Science Lesson in for the Kids

Aside from an excuse to get out all the Halloween decorations and fill your home with the scent of cinnamon-spice, the equinox is a great time for her for an astronomy lesson with your kids! You can find a kid-friendly explanation on study.com for older kids, or reference the pictures and video from National Geographic to help younger kids  appreciate the changing of the seasons too.

For more health-related topics, tips, and recipes, make sure to follow along with our Hospitality Health ER blog. There you can find all of our coverage on autumnal ailments like “3 Tips for Fall Allergy Season. For giveaways, updates, and COVID-19 tips, like us on Facebook and Instagram.

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