Shortest Day of the Year

Today, Decemeber 21st, is the Winter Solstice (in the Northern Hemisphere), the shortest day of the year. This is good news, because from tomorrow until the Summer Solstice, each day will be a little longer then the last! So what's going on? 

Hourly images of the Sun were captured in Bursa, Turkey, on key days from solstice, to equinox, to solstice. The lower path is shorter and in winter, the higher path is longer and in summer. The middle path is spring or fall. Image credit: APOD and Tunc Tezel

As I explained in my Summer Solstice post, we have solstices and equinoxes because of the Earth's tilt on its axis. While the Earth orbits the Sun, one hemisphere is tilted toward the Sun while the other is tilted away. Right now we are tilted away from the Sun in the Northern Hemisphere, and so are in winter. Today is the day that we are tilting most away from the Sun, so it is the shortest day of the year. In Peoria, we have about 9 hours of sunlight, and 15 hours of darkness.

On the Winter Solstice, the Northern Hemisphere is tilted away from the Sun, causing the day to be short and the night long. Image Credit: Wikipedia Commons.

You have probably noticed the Sun rising later and later, and setting earlier and earlier. Did you also notice the sunrise creeping toward the southeast, and sunset creeping toward the southwest? As the Earth orbits the Sun and the axis points away, the Sun rises later and farther south. Now that we have had the shortest day, the sun will rise earlier and move easterly again. On the Spring Equinox, the Sun will rise due east and set due west. 

This video has a nice explanation of the seasons and the Earth's tilt: 

I always find the Winter Solstice hopeful. I know that every day after this will be a little longer. We still have several cold months ahead of us, but it is easier to deal with the cold when the Sun is shining. And we are on our way to the Spring Equinox, the official beginning of Spring, on March 20. 

Happy Solstice from all of us here at the Peoria Riverfront Museum! If you need something to do over the holidays, stop by for a planetarium show or two, or bring your kids to our Holiday Boredom Busters!