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DickR · 12-19-2022, 12:03 PM

One decent source of sunrise and sunset times, length of day, etc. for any place is here:https://ptaff.ca/soleil/?l1pays=USA&...w+the+graph%21

The times and length of day follow a sine curve pattern. The variations are due to the 23.5 degree tilt of earth's axis from perpendicular to the orbit plane. The fact that the dates of earliest sunset and latest sunrise are about two weeks to either side of December 21 (shortest daylight length) is due to our orbit around the sun being somewhat eliptical, rather than spherical. Actually, we are closest to the sun in early winter (northern hemisphere winter). In 2023, this happens on January 4 at 11:17 A.M. Eastern Time. But since earth's axis is tilted from "vertical" so that the north pole is aimed somewhat away from the sun, incoming solar gain is spread over more area in winter, the weather is cooler now. The north pole actually is in earth's shadow around the clock right now. In early July (the 4th in 2023), the earth will be farthest from the sun, but tilted toward the sun (northern hemisphere), so the daytime solar gain is less spread out and the temps are warmer.

12-19-2022, 12:03 PM	#3
DickR Senior Member Join Date: Apr 2008 Location: Moultonborough Posts: 735 Thanks: 4 Thanked 254 Times in 166 Posts	One decent source of sunrise and sunset times, length of day, etc. for any place is here:https://ptaff.ca/soleil/?l1pays=USA&...w+the+graph%21 The times and length of day follow a sine curve pattern. The variations are due to the 23.5 degree tilt of earth's axis from perpendicular to the orbit plane. The fact that the dates of earliest sunset and latest sunrise are about two weeks to either side of December 21 (shortest daylight length) is due to our orbit around the sun being somewhat eliptical, rather than spherical. Actually, we are closest to the sun in early winter (northern hemisphere winter). In 2023, this happens on January 4 at 11:17 A.M. Eastern Time. But since earth's axis is tilted from "vertical" so that the north pole is aimed somewhat away from the sun, incoming solar gain is spread over more area in winter, the weather is cooler now. The north pole actually is in earth's shadow around the clock right now. In early July (the 4th in 2023), the earth will be farthest from the sun, but tilted toward the sun (northern hemisphere), so the daytime solar gain is less spread out and the temps are warmer.