The shortest day and the longest night of the entire year starts tonight for areas north of the equator with the arrival of the solstice. Winter Solstice, which occurs annually on December 21 or 22, marks the official start of astronomical winter in the Northern Hemisphere while signaling the start of summer across the Southern Hemisphere.
This year, the solstice takes place at 10:27 p.m. EST on Thursday, Dec. 21, marking the official start of astronomical winter in the Northern Hemisphere and the beginning of astronomical summer in the Southern Hemisphere. (For the Southern Hemisphere, the winter solstice occurs on June 20 or 21.)
This is different from meteorological winter, which starts on December 1 every year.
The winter solstice is the day with the fewest hours of sunlight in the whole year, making it the “shortest day” of the year. Thankfully, after we reach the winter solstice, the days begin to once again grow longer and longer until we reach the summer solstice—the first day of summer and the longest day of the year.
While some may feel like the long winter nights drag on, astronomical winter is the shortest season, lasting 88 days, 23 hours and 39 minutes, according to timeanddate.com. This is shorter than autumn, which lasts around 89 days; spring which lasts about 92 days; and summer which lasts for a little longer than 93 days.
Think of it this way: Although the winter solstice means the start of winter, it also means the return of more sunlight. It only gets brighter from here!
This is all thanks to Earth’s tilted axis, which makes it so that one half of Earth is pointed away from the Sun and the other half is pointed towards it at the time of the solstice. We often think of the winter solstice as an event that spans an entire calendar day, but the solstice actually lasts only a moment. Specifically, it’s the exact moment when a hemisphere is tilted as far away from the Sun as it can be, which this year will be at 4:48 p.m. EST.
According to the Old Farmer’s Almanac, winter solstice holds significance across a variety of cultures, as it signals the changing of the seasons. Some ancient peoples even marked the solstice using huge stone structures, like Newgrange in Ireland. In some cultures, the solstice traditionally marked the midway point of the season rather than the start of it, which explains why holidays such as Midsummer Day are celebrated around the first day of summer.
On the day of the winter solstice, we are tilted as far away from the Sun as possible, which means that the Sun’s path across the sky is as low in the sky as it can be. Think about the daily path of the Sun: It rises in the east and sets in the west, arcing across the sky overhead. During the summer, the Sun arcs high in the sky, but during the winter, it arcs lower, closer to the horizon.
How can we observe the effects of solstice ourselves? According to the Old Farmer’s Almanac, on the day of the solstice, stand outside at noon and look at your shadow. It’s the longest shadow that you’ll cast all year! Do this again on the day of the summer solstice and you’ll see almost no shadow.
Another way to think of this is that on the day of the solstice, the Sun’s path reaches its most southerly point in the sky. For those of us in the Northern Hemisphere, this means that the Sun’s path is as low in the sky as it can get—even at “high noon.” In the Southern Hemisphere, it’s the opposite: The Sun’s path will be high in the sky on the winter solstice—directly overhead at noon at the latitude called the Tropic of Capricorn, which is an imaginary line that circles the Earth, running through parts of South America, southern Africa, and Australia.
The word solstice comes from Latin sol “sun” and sistere “to stand still.” So, loosely translated, it means “sun stand still.” Why? For a few days before and after the solstice, the Sun’s path across the sky appears to freeze. The change in its noontime elevation is so slight that the Sun’s path seems to stay the same, or stand still.
The day after the winter solstice, the Sun’s path begins to advance northward again, eventually reaching its most northerly point on the day of the summer solstice. Then, as summer advances toward winter, the points on the horizon where the Sun rises and sets advance southward each day; the high point in the Sun’s daily path across the sky, which occurs at local noon, also moves southward each day. It’s a never-ending cycle!
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Photo Credit: Bjoern Buxbaum Conradi / Shutterstock.com