In Praise Of Fall’s First Day

A pocket of fall color catches the eye a week ago on the Superior Hiking Trail above the Manitou River in northeastern Minnesota. Bob King

“What’s your favorite season?” Lots of us ask or are asked this question, and the most common answer I hear is “fall.” People like the colors, the cooler temperatures and the get-down-to-business feel of the season after a summer of heat, sloth and mosquitos. For me, fall and winter are equals followed by spring and summer. Summer used to be in second place, but it’s become so humid and fire-smoke-filled in recent years, I’ve reluctantly shuffled it  to the end of the line.

Earth’s axis maintains a 23½° tilt as it orbits the sun, but its changing position in orbit causes the axis to point toward, away and sideways to the sun during the year. On the first day of fall, Earth is neither tipped toward nor away, so all areas of the planet receive equal illumination with day and night of about equal length, 12 hours and 12 hours. Sonoma University with additions by the author

But just like my kids used to holler “Ready or not, here I come” when playing hide-and-seek, fall begins this evening at 8:54 p.m. (Central Time) whether we’re ready or not. That translates to 9:54 p.m. Eastern, 7:54 Mountain and 6:54 Pacific. The sun’s been dropping south ever since the first day of summer, when it stood highest in the sky. This evening at the appointed time, it crosses an invisible circle sketched across the sky called the celestial equator headed south. The celestial equator is an extension of Earth’s equator into the sky. It begins at the due east point on the horizon, passes directly overhead, and arcs back down to the due west point. We see only a semi-circle’s worth because the other half looping around the backside of the planet out of sight.

On the first day of autumn, the sun crosses the celestial equator moving south. The sun’s apparent motion across the sky over the year is caused by Earth’s revolution around the sun. Bob King

From the Earth’s equator the sun will shine directly from overhead at local noon today. Then, in the coming days, we’ll see it slowly move into the southern sky. At the north pole, the celestial equator coincides exactly with the 360-degree horizon. Today, the sun will circle the horizon for 24 hours, never setting.

But not for long. In a few more days, as it moves south of the celestial equator, the sun disappears below the horizon and won’t return to view until next year’s spring equinox on March 20. From the mid-northern-latitude city of Chicago, the equator’s about halfway up in the southern sky, so the sun is likewise about halfway up today. As it continues to moves south, the sun will sink lower and lower into the Chicago skyline until Dec. 21, the first day of winter, when it will reach its lowest point in the south, about two fists high at noon.

Changing maples set and a glacial erratic (large boulder dropped by a glacier) along the Superior Hiking Trail on Horseshoe Ridge make a pleasing fall scene. Bob King

Earth makes a face-on presentation to the sun at the fall equinox — neither hemisphere is tilted toward or away from the sun, so we all get the same amounts of daylight and darkness: 12 hours and 12 hours. Lighting equality rules the world on the fall equinox if only for a day. All these seasonal ups and downs are courtesy of two properties of our planet: a tilted axis combined with its annual revolution around the sun.

I love the crunchy, colorful leaves, tangy woodland smells, cooler temperatures and sweatless nights. Happy equinox and may you find balance today.