The northern lights, or Aurora Borealis, are an incredible natural phenomenon not totally understood by scientists. But if you’ve ever seen this breathtaking display of beauty in the night sky, you won’t soon forget it. The “simple” answer to what causes the northern lights is that electrically charged particles accelerate along the Earth’s magnetic field lines into the upper atmosphere, where they collide with gas atoms, causing the atoms to give off light. The northern lights are constantly in motion because of the changing interaction between the solar wind and the earth’s magnetic field.

In Finnish folklore, they are called “revontulet,” which means “fox fires,” a name derived from an ancient fable of the arctic fox starting fires or spraying up snow with its brush-like tail.

The aurorae appear over the Earth’s polar regions in what are known as the auroral ovals. The oval normally extends over northern Finland and Scandinavia, Canada, and the northern United States, Alaska, and Siberia.