When Is the First Day of Fall? 13 Fun Facts About the Fall Equinox
Ready for sweater weather? Read on for surprising facts about back-to-school, apple-picking, leaf-peeping season.
Fall equinox 2019
The first day of fall in the Northern Hemisphere is September 23rd this year. At 3:50 a.m. Eastern Daylight Time, Earth’s annual trip around the sun hits the milestone we use to separate our seasons: The sun crosses over the equator to the southern half of the planet. For the next six months, the Northern Hemisphere will be getting less direct light from our star, and it will get chillier by the week. To make the most of the season, add these activities to your fall bucket list—stat.
What is an equinox?
The word equinox is Latin for “equal night,” and it’s the date when, in most places on Earth, the daylight lasts just about as long as the nighttime. It marks the midpoint between the summer solstice in June when Northern Hemisphere days are their longest (up to 24 hours without the sun setting in the polar regions) and the long, dark nights of the winter solstice in December when the sun never rises in the polar regions. Check out these facts about the summer solstice.
Day and night aren’t really equal on the equinox
On the fall equinox, the center of the sun is above the horizon for exactly 12 hours. But we consider the sun to be rising when the lip of it just comes into view, which can happen a few minutes before the center; at sunset, even once the sun’s center has dipped below the horizon, it takes a few more minutes for the rest of it to disappear. Plus, according to timeanddate.com, during the moments at the very beginning of the sunrise and the very end of the sunset, when there’s only a tiny bit of the sun visible to us, we’re actually seeing the image refracted by Earth’s atmosphere—it bends the light around to us even before the Earth has rotated far enough for the edge of the sun to clear the horizon.
Seasons happen because of the Earth’s tilt
The Earth’s axis is tilted 23.5 degrees, so it’s not directly perpendicular to our orbit around the sun. The leaning planet is what gives us our seasons—summer in the Northern Hemisphere is the period during which the top half of Earth is pointed toward the sun. On the first day of fall, the Earth is oriented so that the sun is shining most directly on its side, rather than top or bottom.
The sun goes south
At the moment of the equinox, when the sun’s rays are concentrated on the side of the Earth, the sun is directly above the equator. Fall in the Northern Hemisphere begins just as the Earth progresses a little bit farther on in our orbit—the sun’s radiation then focuses more on the Southern Hemisphere (where spring begins) and keeps bathing the Earth’s southern half in extra light until the next equinox, in March.
Other planets have equinoxes
A few planets have an axis that doesn’t tilt—Venus and Jupiter rotate on axes that are almost exactly perpendicular to the plane of their orbits around the sun, so there’s very little seasonal change over the course of a year (trip around the sun). Uranus, on the other hand, has an extreme tilt—98 degrees. That means it’s basically lying on its side as it orbits the sun. Plus, one trip around the sun takes Uranus 84 Earth years, so it only has an equinox (when the sun’s shining on its equator rather than one hemisphere or the other) every 42 years. Read about astronomy facts you never learned in school.
There’s a long-standing tale that you can stand eggs up on end during the first day of fall because of the unusual gravitational pull the sun exerts that day. According to the Miami Herald, brooms can be balanced on this special day as well. And, in fact, it is possible to balance eggs (and brooms) on the first day of fall, or on any other day of the year—an astronomer named Frank Ghigo tested it and published a paper in 1987 explaining that certain eggs balance more easily than others.
It can disrupt the communication of satellites
Although eggs don’t behave much differently on the first day of fall, some satellites are vulnerable to disruptions—lots of them orbit around the equator, so when the sun is shining directly on them on the equinox, the unusual amount of solar radiation can lead to slow internet connections and staticky radios, according to National Geographic. These “sun outages” can happen during the days before and after the equinox too, and they usually only last a few minutes.
Falling into autumn
Why does pumpkin-spice season have two names, and is one more valid than the other? The word autumn comes from Latin and began being used in England in the 1300s. People also referred to the season as “the fall of the leaves”—the phrase was eventually shortened to fall around the 1600s. A couple of hundred years later, records show that fall had become more popular in the United States and autumn had held the lead in England, but nobody’s sure why. Don’t miss these 38 stunning photos of fall across America.
Mayan astronomers marked the equinox
Although the first day of fall doesn’t attract quite the modern celebrations that the spring equinox and the summer solstice do, the ancient Mayans really played it up: At Chichén Itzá on the Yucatán peninsula, the Pyramid of Kukulkán (also known as El Castillo) is a pyramid with 365 steps—that’s one for each day of the year. On the fall and spring equinoxes, a shadow appears on the pyramid’s surface that looks like a serpent descending the steps toward a stone head at the bottom.