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The Autumnal Equinox

The word equinox comes from the Latin words for "equal night." The fall and spring equinoxes are the only days of the year in which the Sun crosses the celestial equator.

From here on out, the temperatures begin to drop and the days start to get shorter than the nights (i.e., hours of daylight decline).

Questions and Answers About Fall

Question: Why aren't there exactly 12 hours of daylight and 12 hours of darkness on the fall equinox? 

Answer: On the equinoxes, the very center of the Sun sets just 12 hours after it rises. But the day begins when the upper edge of the Sun reaches the horizon (which happens a bit before the center rises), and it doesn't end until the entire Sun has set. Not only that, but the Sun is actually visible when it is below the horizon, as Earth's atmosphere refracts the Sun's rays and bends them in an arc over the horizon. According to our former astronomer, George Greenstein, "If the Sun were to shrink to a starlike point and we lived in a world without air, the spring and fall equinoxes would truly have 'equal nights.'"

Question: The autumn leaves seems to be hanging on longer than usual in my neck of the woods. Is this an indication of winter weather to come?

Answer: There's an old weather proverb that states, "If autumn leaves are slow to fall, prepare for a cold winter." Or perhaps you just haven't had the kind of wind or rain needed to shake the leaves loose from their branches. But look on the bright side—you get to look at the beautiful autumn foliage for a little bit longer!  

Signs of Fall

In many regions of North America, the landscape silently explodes with vibrant colors of red, yellow, and orange. The leaves begin to drop off the trees, providing endless hours of jumping into leaf piles for kids and raking them back up for parents! Baseball season hits the homestretch, while football season is just warming up. Temperatures begin to drop, nights begin to get longer, and all the woodland critters are storing up for the long haul of winter. 

 

Read more: http://www.almanac.com/content/first-day-fall-autumnal-equinox

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