'Equinox' comes from the Latin words aequus (equal) and nox (night). What's that mean? It means that, at the equator, the day hours and night hours would be equal: 12 hours each (kind of*).
That's one way to understand an equinox.
Another way to think of it is this: During the spring and summer months, the sun shines more on the northern hemisphere than on the southern hemisphere--hence the longer days. At the autumnal equinox, the sun has come to 'balance' on the equator again and is about to 'cross over' to the southern hemisphere, leaving us with shorter days and them with longer ones.
In an ideal world, the equinox would be the exact moment when the sun crosses from one hemisphere to the other, but this would only work if the sun were a single point in space--which it's not. Because the sun's a giant orb this 'moment' takes 2 1/2 days. The equinox they put on our calendars is the average of that time period.
This year's autumnal equinox, by the way, is the 23rd of September. Fall officially starts on Monday!
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*NOTE: Even if you're standing on the equator during the equinox it won't actually appear like 12 hours of day/12 hours of night. This is because (1) the earth's orbit isn't perfectly circular, (2) the sun is a disc and can be seen even after the centerpoint touches the horizon, and (3) the sky refracts light, so you can see the sun's rays even after it sets. If you did away with these three inconveniences then, yes, it would be a true 'equinox'.
8 years ago
5 comments:
Hey, are you studying up to be on the show "Are You Smarter Than a Forth Grader"? Just kidding. This was actually really interesting and something I haven't thought about in a while. I think I might have known some of that information once upon a time. Of course, I haven't thought at all for quite some time.
They say when you have a kid you lose half of your brain cells. I have had two kids and therefore lost all of my brains...I think there is just playdough up there now.
Don't fret, Yamsey, you've actually still got a quarter of your brains left!
...then what's MY excuse??
That's my point. I can't even do elementary math anymore. You should see me try to do geometry. Now that's a laugh!
The equinox is the great equalizer: even in Alaska, land of the Midnight Sun (or the neverending night, depending on who you ask), we're getting 12 hours of daylight.
But we're all just completely bitching and moaning about it.
"It's so dark here now!" and "The days are so short!" are two oft-heard utterings in these parts. And it's true, when you get used to nineteen hours, twelve does seem awfully piddly.
Two of my friends made such a remark in entirely different situations over the last twenty-four hours and I had to gently remind them that, on this day, we're getting exactly the same amount of daylight as everywhere else in the world.
Maybe it seems so short because we know what's coming: after all, you pay a price for nineteen hours of daylight in the summer -- it's called five hours of daylight in the winter. You'd think we'd appreciate it and try to soak it in while it's here, but no, we take it as a big, fat, depressing messenger.
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