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 ...

Arctic air surging south could glaze Colorado ... RELATED: Everything you need to know about the polar vortex bringing extreme cold to Colorado “We’re used to driving on snow here in Colorado ...