The origin of Northern Lights The active Northern Lights, also known as aurora, are nature's most beautiful color display. In Finland normally just before midnight, when it is dark enough, a green glow appears in the sky, normally in the form of an arc across the whole sky, directed from east to west. Later during the night, this light might get structured, so bright as to make shadows on ground - and what is most fascinating, start moving fast, covering sometimes the whole sky! Today we know what the lights are. Electrically charged particles come down from space and hit the atmosphere. The air particles in turn, in fact oxygen atoms and ionized nitrogen molecules, get energy in the collisions with the incoming electric particles. Then the air glows the excess energy away, in the form of light emission. This light emission we know as the Northern Lights. We can detect those electric particles, which originally cause the Northern Lights, of course, by using satellite instruments. ...