Long story short: I only run on flat roads these days, and the only flat road in my neighborhood is a paved nature/walking path. The path is unlit, so running there at night is difficult. Still it's my only option. And, with these days being short, the sun is setting near 5:00 (5:01 today, in fact), and it's hard for me to get home, get changed, and get out and back before it's too dark to see.
So, I looked at a sunrise/sunset chart for my area, to see how long I'll have to put up with this inconvenience of nature. And there I noticed something I don't understand.
Sunset today is 5:01 PM. And this is the earliest sunset will be, all year. Actually, it set at 5:01 on November 29 and will do so every day until December 12 - but it never gets earlier. (We'll pretend minutes are the smallest possible unit of time)
On the other hand, sunrise today was at 7:10 AM and gets progressively later until Jan 1, when it peaks at 7:25 AM (and stays there until January 13, when it starts getting earlier again).
So, the peak sunrise time happens about a month after the sunset time peaks (inversely). Which I did not expect. I'd always assumed the two of them peaked together on the solstice, then diverged again until the summer solstice when they both reached their opposite peaks. Not so.
Also, the website says that the solar noon (time when the sun reaches its highest point) reaches its earliest time in mid November - which is obviously out of sync with both sunset and sunrise times and the solstice.
So, um, what's going on here ?
This is related to the fact that the Earth’s orbit around the Sun is not circular and as a result the length of a day(solar noon to solar noon) varies during the year
I’m no astronomer but I think it has something to do with the tilt of the earth and where you are on earth in relation to the equator.
In the winter you see the sunset stabilize and the sunrise moves a little later until you have the shortest day of the year. In the summer you should see the sunrise stabilize and the sunset move a little later until you have the longest day of the year.
I am sure it has to do with the combination of the tilt of the earth and our non-circular orbit.
By the by, consider yourself lucky. Today for me the sunrise was at 9:26 and the sunset at 15:33. Of course I get that back in the summer when the sunrise is 4am and doesn’t set until midnight. Late June and early July it doesn’t ever even get totally dark out.
Wow, nice link pking. Beat me to the punch.
the “equation of time”. i’m glad it has such a grand name!
You’re quite welcome cleek. The equation of time is often shown graphically as a figure-eight on globes. Here is a site with several beautiful composite phtographs showing th apparent motion of the sun through the sky.