Equal or Not?
As I was driving the kids to the bus stop this morning I remembered yesterday was the Fall Equinox. I asked them if they knew what it meant and after saying, "NO" in unison I proceeded to dig deeper and asked if they knew what "Equi" meant. After no deliberation they told me it was equal day and equal night and then I said, "Yep, it means we have 12 hours of sunlight and 12 hours of darkness."
What I didn’t know is that isn’t exactly the truth. Looking into the Equinox a little more I found out way more information then one would ever need to know. Stuff like the Pope had a calendar and Julius Ceasar had a calendar and there’s something called the Tropical astronomical year and if we didn’t have leap year every four years then we’d be celebrating Christmas in June, or something like that.
I did find the following information from the National Geographic Website informative.
Sunrise is defined as the moment the top edge of the sun appears to peek over the horizon. Sunset is when the very last bit of the sun appears to dip below the horizon. The vernal and autumnal equinoxes, meanwhile, occur when the center of the sun’s disk crosses what’s known as the celestial equator, an imaginary line that projects outward from Earth’s Equator, Chester noted. What’s more, Earth’s atmosphere bends sunlight when it’s close to the horizon, making the sun appear to rise a few minutes earlier than it actually does. "Those factors all combine to make the day of the equinox not the day when we have 12 hours [each] of light and darkness," Chester said.
I guess I didn’t remember the fact the Spring and Fall Equinox are the only two days the sun rises exactly in the East and sets exactly in the West. I do know that before the sun actually rises it produces light just as it does after it sets. This in addition to the fact the sun is a moving object, light refracts, the earth tilts and most people can’t see the horizon without obstruction confuses the issue even more.
What I learned is that 12 hours of darkness and 12 hours of light doesn’t happen until after the Autumn Equionox. That day has a special name, "This day is commonly referred to as ‘equilux’ to distinguish them from the equinox. The equinox is a point in time, but the equilux is a day," Devgun explained.
Very interesting indeed. I can say we have noticed how dark it is now when we drive to the bus stop. We used to come over the hill and be blinded by the sun in our eyes and now it hasn’t even started to peak out from beneath the horizon. I guess some day around the 25th of this month we’ll actually have equal hours of light and dark. Then the hours of light will continue to dwindle until the Winter Solstice when once again the hours of light will increase. I for one am looking forward to the Spring Solstice.
We’re still outfitting groups into the Boundary Waters and Quetico Park but the days are numbered and I can’t help but look forward to next summer when the days are long and the nights are short and I’m paddling beneath the rays of the summer sun once again.