Will you feel the equinox slip into place tomorrow at 4:05 a.m. EST, 9:05 Universal Time/GMT?

Probably not. We call this the autumnal or fall equinox in the northern hemisphere, and the spring or vernal equinox in the southern hemisphere. We have four seasons, but two equinoxes.

This has interested us from the times of those ancient first “observatories” that tracked the sun’s progress (such as Machu Picchu in Peru) to that science class where you tried to understand that an equinox is either of two points on the celestial sphere where the ecliptic and the celestial equator intersect. In much simpler terms,  it is one of two times each year when the Sun crosses the equator, and the day and night are of approximately equal length.

After the Sun passes this point (on about 23 September each year), the nights begin to grow longer than the days. They will continue to do so until the Winter Solstice in December.

For those of us in the northern hemisphere, summer is over, plants are dying off and we get hints of that transition to winter.

I have always like the autumn season best with its cooler weather, bursts of foliage and colored forests, the crunch of leaves under feet,  the scent of a wood fire in the distance, hot drinks in cold hands and the sound of geese overhead.

The name ‘equinox’ comes from the Latin aequus (equal) and nox (night).  But,  since the Earth never stops moving around the sun, these days of equal sunlight and night will change quickly.

You will notice the later dawns and earlier sunsets. Maybe you can observe the arc of the sun across the sky each day.  It is shifting toward the south and many birds and butterflies are following the path of the sun.

In the night sky, Fomalhaut – the Autumn Star – is making its way across the heavens each night. It is so named because it is the only first-magnitude star in the autumn sky of mid-northern latitudes. It has been recognized by many cultures of the northern hemisphere, including the Arabs, Persians and Chinese, and archaeological evidence links it to rituals dating back to about 2500 BC. Fomalhaut is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in the sky. Fomalhaut can be seen low in the southern sky in the northern hemisphere in fall and early winter evenings.

The sun rises due east and sets due west at the equinox, and that’s true no matter where you live on Earth. Those two cardinal directions in the weeks and months ahead, because the Earth has moved on in its orbit around the sun, will move the sunrise and sunset points southward.

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