but that's the reality for locations north of the Arctic and Antarctic Circles. During these times, it's referred to as a polar night. The opposite, polar day, occurs when there is 24-hour daylight.

Under the sea ice during the Arctic’s pitch-black polar night, cells power photosynthesis on the lowest light levels ever observed in nature. Most of life’s engines run on sunlight. Photons filter ...

However, a deep freeze, thanks to the polar vortex dipping down from Siberia, is bringing an even harsher arctic blast to million Americans this week. Maps show what to expect as the cold front ...

all that icy air stays tightly locked around the arctic, keeping the freezing temperatures up north. But just like when a top starts to slow down and wobble, the polar vortex can sometimes get out ...

In my last article, From Musandam to the Rooftop of Africa, I wrote about climbing Mount Kilimanjaro. That adventure was made ...

A blast of arctic air from Canada has brought the season's coldest weather to most of the United States. The system, known as a polar vortex, is forecast to bring subzero temperatures to the ...