The winter solstice arrives Thursday, making it the “shortest” day of the year.
The solstice occurs at 11:28 a.m., the moment the North Pole is tilted the farthest from the sun and the South Pole tilted most toward it. The 23.5-degree tilt of Earth’s axis is responsible for the seasons.
The sun will be up for just about 9 hours and 24 minutes on Thursday, and in the days immediately before and after the solstice, too. That is 5 hours and 32 minutes less daylight than Baltimore gets on the summer solstice, the “longest” day of the year.
Starting Friday, the sun spends a few more seconds above the horizon each day.
Though it is the shortest day of the year across the Northern Hemisphere, the length of daylight varies by longitude and latitude. That is because at the solstice, Earth’s tilt means that the “terminator” — the line dividing day and night that can be seen in pictures taken from space — crosses the country diagonally. (At the spring and fall equinoxes, on the other hand, the line runs essentially north-south, because at those times Earth’s axis is tilted neither toward nor away from the sun.)
To explain the variation, EarthSky.org uses the example of New York and St. Augustine, Fla. The sun rises at about the same time in both places on Thursday — 7:16 a.m. and 7:17 a.m., respectively — but it sets nearly an hour later in St. Augustine — 4:31 p.m. vs. 5:31 p.m.
It means that New Yorkers’ “shortest” day of the year is about 9 minutes shorter than Baltimoreans’. But for Floridians, it is almost an hour longer, or more, with 10 hours, 15 minutes of daylight in St. Augustine and 10 ½ hours in Miami.