Today is the autumnal equinox, one of four astronomical turning points that mark the changing seasons. The scientific description of an equinox explains how, as Earth rotates on its axis, the orbital planes of the equator align geometrically with the center of the sun, causing more or less equal amounts of sunlight to shine on the Northern and Southern hemispheres at the same time. Fall and spring equinox are the two days when, no matter where you are on earth (except the polar regions), you can see the sun rise due east and set due west along the horizon. After today, the sun’s path across the sky becomes incrementally shorter. The extreme latitudes of the Northern hemisphere experience the transition much differently; folks in southern Florida may lose only about 90 seconds of sunlight per day while those in northern Alaska see almost 7 minutes of daylight disappear with each sunset. In most regions, a two- to three-minute loss of light can be expected until the next astrological turning point–Winter Solstice–happens. The result of that shift brings more hours of darkness and cooler temperatures.
Surprising Fact: Though the name itself, equinox, means “equal night,” the day fall equinox occurs does not bring exactly equal portions of light and dark as many people think. In the contiguous U.S., most regions won’t experience that phenomenon until three or four days after the main event.
Another interesting shift during this time of year is the decrease of twilight hours. No, you’re not just imagining that it gets dark more quickly during autumn. The fastest sunsets of the year occur around the spring and fall equinoxes. As the sun crosses the horizon at a slightly steeper angle, it appears and disappears from the horizon more quickly. The closer you are to the equator, the less likely you are to notice, but people living in the northern tiers of our hemisphere know that autumn gives new meaning to the term “night fall.”
With cooler days, scarlet-painted trees, fall holidays, warm sweaters and warm pie ahead, there’s much to look forward to as autumn falls on the Central Coast.