We all depend on sunlight, but unless you live at the equator, you won't get the same amount of it every day. Ours is a tilted world, friends. Like all the planets in this solar system, Earth rotates around an axis, an imaginary line between its North and South poles. At the same time, it orbits the sun, finishing a new lap every 365.25 days.
That cosmic ballet is an intricate dance. Relative to its pathway around the sun, Earth's axis is tilted at a 23.5-degree angle. If it weren't for that helpful tilt, seasons as we know them wouldn't exist. The skewed axis is also responsible for one of the world's most astonishing places: The Arctic Circle.
Geographers define the circle as everything at or above 66 degrees and 34 minutes north latitude. (Put simply that means the exact dividing line falls between the 66th and 67th parallels in Earth's Northern Hemisphere.)
It's a region marked by strange hours. Throughout this area, the center of the sun never climbs above the horizon during the winter solstice — the shortest day of the year. Here, the skies can be dark at high noon or sunny at midnight. Yet life persists. The Arctic Circle encompasses 4 percent of the global surface. And for hundreds of thousands of people, it's also home sweet home.
1. Eight Countries Own Land There
Jetting into the Arctic Ocean, Alaska's Point Barrow is the northernmost tip of the United States. Of course, Alaska's not the only place that penetrates the Arctic Circle. Large portions of Canada, Russia, Norway, Finland and Sweden also fall within the Arctic Circle's borders. So does the majority of Greenland, a territory held by the Kingdom of Denmark. (Sorry Mr. Trump: The Danish won't sell it.) Last, but not least, Grimsey Island — an Icelandic holding — is split by the circle.
2. Murmansk, Russia Is the Biggest City
Around 295,000 people live in Murmansk, a port city founded in 1916 at the height of World War I. One of its Soviet-era landmarks, the 236-foot (72-meter) Arktika Hotel, is the tallest building north of the Arctic Circle.
The region's second-largest city is Russian, too. Norilsk, a community of some 179,554 souls, is famous for its mining operations and the historic Nord Kamal Mosque. Outside of Russia, the Arctic Circle's most populous municipality is Tromsø, Norway, which boasts the world's northernmost university.
3. It Doesn't Plunge Into Total Darkness
Even when the sun's out of view, the twilight it produces can still illuminate the skies. And guess what? Many communities above the Arctic Circle receive plenty of twilight in the darkest stretch of the year. Consider Utqiaġvik, a city in far north Alaska. For 65 days each winter, the sun doesn't rise there. Yet during this same period, Utqiaġvik gets three to six hours of daily twilight.
But maybe that's not good enough for you. Maybe you're an Arctic tourist who'd like to experience twilight-free, star-studded darkness for days on end. (Hey, we're not judging.) That's a phenomenon called "astronomical polar night." And it's only known to take place at latitudes higher than 88 degrees 33 minutes north, far above cities like Utqiaġvik — or any human settlements for that matter. Where it occurs, the astronomical polar night lasts for roughly 11 weeks, not half the year as some sources claim.
4. The Sun Hangs Out for Months
Santa Claus has ample time to get nice and tan. At the North Pole, the sun rises on the spring equinox in March. Then it lingers in the sky — without setting — until September's autumn equinox comes along. Between those dates, the big old star reaches its highest point in the polar sky on the summer solstice every June.
Because of its penchant for extended daylight, the Arctic Circle has been nicknamed "The Land of the Midnight Sun." That said, the sun hangs around for longer stints at high latitudes — so not everyone inside the circle gets to enjoy a full six months of sunshine. Over in Tromsø, the "Midnight Sun" period goes on for just two months.
On Jan. 1, 2011, Arctic communities were treated to a rare solar eclipse (albeit, a partial one). Due to the sun's position, onlookers in Tromsø saw it unfold at 11:30 p.m. local time.
5. It's Way Colder in the Antarctic Circle
Textbooks like to say the Arctic is an ocean surrounded by continents, while the Antarctic is a continent surrounded by an ocean. Here's something you might not realize about the arrangement. All that seawater under the North Pole moderates the climate to some extent. Yet the South Pole doesn't have this luxury. As a result, the average winter temperature down there is a wicked -76 degrees Fahrenheit (-60 degrees Celsius). By comparison, the North Pole's mean winter temperature of -40 degrees Fahrenheit (-40 degrees Celsius) feels downright balmy.
Just as there's an Arctic Circle, the Antarctic has a circle of its own. This begins at around 66.5 degrees south of the equator. Unlike its northern counterpart, the Antarctic Circle doesn't have any permanent human settlements. (Research stations don't count.)
6. The Arctic Circle Is Shrinking
Nothing lasts forever. Slowly but surely, Earth's axial tilt is changing — and with it, the Arctic Circle. Every 40,000 years or so, this crucial tilt shifts from an angle of 22.1 degrees to a sharper 24.5-degree incline. Right now, we're in the middle of one such cycle. While that's going on, the boundary line that defines the Arctic Circle retreats by about 46 to 49 feet (14 to 15 meters) northward per year.
Remember Grimsey Island, the Icelandic outcrop we mentioned? Well, scientists project that the Arctic Circle will leave the island behind by about the year 2050. Locals are using a concrete ball weighing about 8.9 tons (8.16 metric tons) to mark its progress. Year by year, the sphere has moved to keep pace with the Arctic's receding circle.