Northern lights
Aurora borealis is a well-known phenomenon on the winter sky in northern Norway. It is not necessary for it to be cold or dark outside for the northern lights to appear. If we want to see the aurora with our own eyes, however, the sky has to be dark and mostly clear of clouds. That usually means the weather can be quite cold as well.

Aurora Borealis is the international name of the northern lights, meaning "dawn of the north". Northern lights come from a zone high above the ground surface and can be seen at night in the polar regions. The phenomenon happens when energy particles from the sun get shot up in the atmosphere led by the Earth's own magnetic field. Particles hit the air molecules, which mainly consist of oxygen and nitrogen and between 100 and 300 kilometers from the Earth, some of the impact energy is emitted as light.

Facts about the northern lights
Mythology and superstition
Observing the northern lights
Photographing the northern lights
Solar activity and northern lights