Every year in December, we're usually wrapped up in our preparations for the holidays. Or prepping for the onset of cold temperatures and snow, depending on our location. Some might be aware of the approach of the winter solstice, but for most people it's a blip on the radar at best.
The winter solstice might not outwardly be a significant event in our lives, but it marks an extreme in the passage of time each year. It has a rich and varied history of traditions and rituals going back millennia.
Most people consider the winter solstice to be a full day on the calendar each year. But technically, the winter solstice is only a brief moment in time. Specifically, the winter solstice occurs at the exact moment when either the North Pole (for Northern Hemisphere) or South Pole (for Southern Hemisphere) is angled the furthest away from the sun.
That small point of time when the pole is at the maximum angle away from the sun marks the winter solstice. With that being said, most people consider the entire 24-hour period during which that moment takes place to be the winter solstice as well.
The winter solstice is the day when we get the least daytime and the most nighttime each year. This makes sense when you consider the definition of the winter solstice. When Earth is tilted away from the sun, we receive less exposure. So, the days are shorter. At a maximum angle, this leads to the least amount of daylight.
The exact length of the day on the winter solstice depends on how far north or south you are. In extreme northern locations like Alaska, the day of the winter solstice is incredibly short, lasting only for a few hours. Closer to the equator, the day is significantly longer.
We tend to think of the winter solstice as occurring on December 21, and it's true that the winter solstice frequently falls on that day. But the solstice is not fixed to a specific day on the calendar each year. Most of the time, it's on either the 21 or 22 of December in the Northern Hemisphere and either June 20 or 21 in the Southern Hemisphere.
The reason the date can vary from year to year is that the rotation of Earth around the sun doesn't precisely match up with the calendar year. Remember, the event of the winter solstice is tied to Earth rotating the sun. So, the winter solstice can slightly go out of synch with the calendar.
A rough translation of solstice is "sun stands still." The term comes from the Latin solstitium: the word sol means "sun" and sistere means "make stand." This definition actually reveals quite a bit about the scientific progress we've made in understanding our universe over the centuries.
Why did ancient people identify the winter solstice as a day that the sun stood still? Probably because the sun appears relatively fixed in the sky over the course of the day. During most of the year, the sun appears to travel across the sky, but this doesn't take place at and around the solstice.
Of course, we now know that Earth revolves around the sun. It's not the sun's movement that normally causes the sun to appear to traverse the sky—it's our own movement!
Ancient peoples always watched the sky carefully and were able to create some pretty remarkable calendars. From the early days of civilization, days like the summer and winter solstices were seen as special and significant, and a variety of practices and celebrations took place on the winter solstice.
One notable winter solstice celebration is the Roman holiday of Saturnalia. This festival was marked by feasting, revelry, and temporary role swaps between master and servants and slaves. But Saturnalia was far from the only winter solstice-based festival. All around the world, ancient peoples celebrated the solstice.
You might have noticed that the winter solstice happens to be pretty close to the date of Christmas. After all, December 21 and 25 only a few days apart. Look closer, and you'll notice a lot of similarities between Roman pagan traditions and Christmas.
In the early days of Christianity, it competed with a number of pre-existing religions, cults, and belief systems. Many of these religions had prominent festivals or observances on the winter solstice. In order to make Christianity more attractive and compliant with people's existing habits, it is believed that the date of Christmas was folded into some other religious celebrations.
Just because Earth is tilted the farthest away from the sun during the solstice does not mean it is at its farthest annual point away from the sun. A common myth is that the winter solstice is when Earth is physically at its farthest point away from the sun. This seems logical at first. The colder times must be when the sun is farthest from the Earth, and the winter solstice is smack dab in the middle of winter. So, the solstice must be when the Earth is farthest away from the sun, right?
It's not actually true that temperature is determined by how far Earth is from the sun, at least not on a seasonal basis. In fact, the sun is closest to Earth just a few weeks after the winter solstice.
It's probably hard to remember back to 2012 by now. If you remember anything from this time, though, it was probably the panic that the world was going to end on December 21, 2012. This prophecy centered on the ancient Mayan calendar, where this specific date marked the end of a cycle of more than 5,000 years. There was not direct textual evidence that the Mayans themselves believed that the world would end. However, they did attribute great significance to the end of this cycle.
As the date approached, people threw out a number of different predictions. They ranged from the annihilation of the planet to a new age of enlightenment. In the end, nothing much seemed to happen.
A number of monumental events have reportedly taken place over the years on the winter solstice. One such event was the landing of the Pilgrims at Plymouth Rock to found their colony in what would become the United States of America. Another significant winter solstice took place in 1898, when Marie and Pierre Curie discovered the element radium, marking the beginning of the atomic sciences. Yet another solstice milestone took place in 1968, when the Apollo 8 spaceship became the first manned space flight to travel to the moon.
One of the rarest lunar events is the full solstice moon. Since 1793, there have only been 10 full moons on the winter solstice. The last full solstice moon was in 2010; to make that occurrence even more special, it was also a lunar eclipse. If you want to see another full solstice moon, you'll need to wait for a fairly long time. The next full solstice moon will happen in 2094.