The winter solstice marks the shortest day of the year. But where did the tradition of celebrating this lack of sunlight come from?
Marking that shortest day of the year began because ancient people noticed it, says Anthony Aveni, a professor of astronomy and anthropology and native american studies at Colgate University.
In the fall, “day after day after day as we get closer and closer to the winter solstice, we see the sun rising farther in the south of east and set farther in the south of west,” he said. “As you follow the sun from day to day, you see it’s rising farther and farther south and setting farther and farther south.”
When this happens, there is less and less sun until the solstice—or the day when the sun stands still.
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The word solstice means “sun stand,” or “sun stands still.”
“You have to imagine people in ancient times not knowing what causes this, and so they would wonder when the sun goes farther south, will it ever come back?” he said. “What must we do to praise the gods and make offerings to the gods to make the sun come back?”
Those offerings were the origins of winter solstice celebrations, Aveni says.
In the United States, Europe, and everywhere else in the Northern Hemisphere, the winter solstice is usually on December 21, and it is usually the shortest day of the year. In the Southern Hemisphere, that day is the summer solstice, and the longest day of the year.
It’s no coincidence that the solstice was celebrated by ancient civilizations all over the world, Aveni said.
Related: When Is the Summer Solstice?
“Everybody sees this all over the world,” he said. There is evidence of shortening days everywhere, from animals and birds migrating to changing colors of leaves. “All of these ribbons of nature are tuned to that seasonal cycle of the sun. So no matter where you are, you’re going to see it and recognize it.”
Ancient civilizations from all across the world celebrated the winter solstice. For example, the Greeks made offerings to the god Apollo, the Incas to the sun god Inti, and the Mayans to the god Kinich Ahau. For a week each December, the ancient Romans also celebrated the solstice by honoring the god Saturn.
“All of that ends up in our culture as being Christmas,” Aveni said. He said the time of the birth of Jesus Christ was not actually in December, but was changed to fit the season’s celebrations.
“His birth is the time when light came into the world, and winter is the time when you need light the most,” Aveni said.
The transition from recognizing natural phenomena to celebrating it is religion.
“When Christianity took hold, people began to realize the movement of the sun when you come to the winter solstice very aptly demonstrates how the light of the savior came into the world at this time,” he said. “It’s a good example of how people use phenomena that happen in nature to represent their ideas.”
Aveni said in modern times, there are more celebrations of winter solstice than summer “because that’s the time when people stress the most.”
And he’s not talking about holiday shopping.
“When they’re afraid something bad is going to happen,” he said. “When you see the winter come and the sun begin to go far away, you worry that maybe it won’t come back. That’s why you get these intense sessions of worshipping and paying homage to the gods.”