...but before we get to that, here are a few of the answers to clues on Jeopardy in the last few days that I answered correctly even though all the contestants' buzzers remained silent:
What is Versailles?
Who is Grendel?
What is Remembrance Of Things Past?
What is Oak Ridge, Tennessee?
What is Lexington, Kentucky?
Enough of that. On to the subject at hand.
September 23rd was the Autumnal Equinox (even though it was the first day of Spring in Australia, go figure), one of two days in the year (the other being the Vernal Equinox in March when it is Autumn in Australia) when, I was taught and have always believed, like most of you I would guess, that planet Earth has exactly 12 hours of daylight and 12 hours of darkness. This may come as a great shock to you—it did to me— but that teaching and belief, friends, is wrong!
I'm not kidding.
I happened to be looking at my Apple phone's weather app that day, which lists temperature forecasts for each hour and also shows each day's time of sunrise and sunset, and saw that where I live sunrise occurred at 7:25 a.m. and sunse occurred at 7:35 p.m. and I was flabbergasted (British, gobsmacked). That is 12 hours and 10 minutes apart, not exactly 12 hours. I did a little investigating and will now share it with you, after a fashion, by which I mean a short summary of what I learned. To share everything I read would take far too long.
Fact one: Because of Earth's atmospher the rays of the Sun are bent a little so what we see at sunrise and sunset is a sort of optical illusion. The proof of it is that you can look directly at the Sun just at sunrise and just at sunset and not be blinded by its rays.
Fact two: The Equinox is the day the Sun's rays at noon are directly over the Equator in their continuous journey north to the Tropic of Cancer and south to the Tropic of Capricorn during the year because of the tilt of Earth's axis, which is about 23-1/2 degrees off verticle. Hold that thought.
But on the two days (one in March and one in September, remember?) that the Sun's direct rays are directly overhead at the Equator, the sunrise and sunset are not exactly 12 hours apart, precisely because of the curvature of the Sun's rays that I mentioned earlier. The definition of the word Equinox includes the word "nearly" as in "An equinox is an astronomical event when the sun appears directly above Earth's equator, making day and night NEARLY [emphasis mine] equal in length everywhere on Earth."
And because of the distortion of the Sun's rays caused by Earth's atmosphere, the day when sunrise and sunset are exactly 12 hours apart occurs a few days before the Vernal Equinox im March and a few days after the Autumnal Equinox in September.
Today, September 26th, three days after the Equinox, Apple is reporting sunrise and sunset to occur at 7:28 a.m. and 7:28 p.m., respectively, at the latitude where I live. The time will vary depending on the latitude where you live. The extremes, you may remember, occur at the North Pole and South Pole, where, because of that tilt we all know about, the sun does not set for six months and then it does not rise for six months.
I had never heard of the word Equilux before but discovered it has been in use in astronomical situations since the mid 1980s. My schooling ended several decades before that.
See there, you can too teach an old dog new tricks.
T.T.F.N.
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