At 5:44 a.m. on Wednesday, December 21, the 2016 winter solstice occurs in the Northern Hemisphere, which means winter has arrived in the United States.

We know that the December solstice is the opposite of the summer solstice – it marks the longest night and shortest day of the year. The winter solstice is also referred to as Midwinter, the Longest Night, and Yule by some. But did you know these other facts about the winter solstice?

1. It Marks the First Day of Astronomical Winter

winter solsticeIn the Northern Hemisphere, astronomers and scientists use the December Solstice as the start of the winter season. Winter ends with the March Equinox, when spring officially begins.

This gets a little confusing though, as meteorologists often use December 1 as the start of winter due to the change in the weather. That’s a three-week difference!

2. “Solstice” Translates to “Sun Stands Still”

The word is derived from Latin and means “sun stands still.” It was selected because during a solstice, the sun appears to remain still in its position in the sky. Of course, this is because of the tilt of the Earth – the sun never moves!

On December 21, the sun appears to be at its lowest point in the sky. To us on Earth, it looks as though the sun stops moving southward, pauses, and then starts moving northward.

3. The Solstice Has Been Celebrated for Thousands of Years

There’s a good reason that the “holiday season” happens to coincide with this astronomical event. Since ancient times, people have celebrated the solstice and observed it with many different cultural and religious traditions.

According to historian David Gwynn, Christmas was set on December 25 to replace a Roman holiday, which had roots in a pagan cult of Sol Invictus (which means the unconquered sun).

winter solsticeIn addition, several geographical sites have ties to the solstice. Stonehenge in England, which was built between 3000 B.C. and 2000 B.C., is still a popular spot to witness a solstice, where the sun perfectly aligns with what are known as the central Altar stone and the Slaughter stone when the sun sets on the winter solstice. Newgrange in Ireland is another monument dating back thousands of years that appears to have been built in alignment with the solstice.

4. A Solstice Is Different from an Equinox

Don’t worry – lots of people get these confused. Like solstices, equinoxes happen twice a year. However, instead of the winter and summer, equinoxes occur in the spring and fall (March and October) to mark when the sun is over the equator.

5. Each Solstice Occurs in Both Winter and Summer

winter solsticeThe solstice you’re experiencing on December 21 may be the summer or the winter – it simply depends on where on Earth you are. While the Northern Hemisphere is experiencing the shortest day of the year around December 21, the Southern Hemisphere experiences the summer solstice. On this day, all locations south of the equator have day lengths greater than 12 hours. Meanwhile, all locations north of the equator have less than 12 hours of daylight.

Around June 21, the Northern Hemisphere has its summer solstice. Meanwhile, the Southern Hemisphere will have the day of the year with the least amount of daylight, the winter solstice.

If you’re a fan of longer days and shorter nights, the winter solstice is great news! Slowly, the amount of daylight hours will increase. Don’t be fooled though – in many regions, the coldest days of winter are still ahead. Bundle up!

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