This post was written by Dianne Choie, Educational Programs Specialist at the Library of Congress.
You might notice that it gets darker outside earlier and earlier as the weather turns colder. Did you know that the tilt of the Earth is the reason that happens? Instead of spinning on a straight axis like a top, our planet spins on an angle. During the summer, the northern hemisphere is tilted toward the sun, resulting in longer days and warmer temperatures. If you’ve visited the Library of Congress in the summer, you know how hot and sunny Washington, D.C. can get at that time of year!

The northern hemisphere is tilted away from the sun in the winter, which makes shorter days and cooler temperatures. The southern hemisphere has the reverse experience of the northern hemisphere, which is why their wintertime is our summertime and vice versa. Learn more about how the Earth’s tilt affects seasons in this Library of Congress Everyday Mysteries blog post.

“Winter solstice” is what we call the day of the year when the Earth’s tilt means the sun is farthest away, resulting in the shortest period of light in the da