Northern Lights

Seeing the Northern Lights for the first time will leave you mesmerized. It is magic and impressive. It looks completely different from the pictures we know. The shapes may look familiar, but it seems less colorful. At the same time it moves much more than we could have imagined.
(The celestial phenomenon over the German city of Nuremberg on April 14, 1561)
Also in history, sights of the Northern Lights made big impressions on people. Different explanations were given, from reflections of icebergs to blood of deceased. The Inuit in Greenland referred to the moving light curtains as dancing children that were playing high in the skies.
At the Native American tribes they were referred to as deceased people dancing in the skies. The stories can be told in many variants, since they were shared over multiple generations and over large distances.

(Frederic Edwin Church, Aurora Borealis, 1865)

Once in a while, the Northern Lights were visible further down south and would be more red colored. In many European countries, this was taken as a sign for upcoming wars. This has been the case before the French Revolution, the 1870-1871 French-German war and the Russian occupation of Finland (1714-1721).

(Le Monde Illustré, on October 29, 1870)

Also the American civil war appears to have been predicted by red Auroras. On the other hand, in Japan, being born under Norther Lights is treated as a sign for a happy life.

An other word used for the Northern Lights is Polar light. Polar light is a more common name for this occurrence, wherever it is seen in the world. The Northern Light name refers to this Polar light being seen in the Northern Hemisphere. Hence the name on the southern hemisphere is Southern Light. These can be seen on Antartica. Both Northern and Southern Lights often occur at the same time. The Latin name for Polar light is Aurora. Where Aurora Borealis refers to the Northern Lights and Aurora Australis is the Southern Light. Also in the English language the word for Polar light is aurora.

But what are these lightning areas, rays and curtains high in the sky? There is a bit of physics required to explain: Northern lights are nothing more than energy-rich oxygen and nitrogen atoms, high in the atmosphere. In certain circumstances, they will send out photons and light up. When the sun ejects enough energy through a mass ejection, this may end up being guided by the earth magnetism to the polar regions and hit the oxygen and nitrogen atoms in the polar atmosphere. This will get the atoms from their ground state into an exited state:

After they collide, there is enough energy for these atoms to release a photon in the visible spectrum (e.g red or green color). This allows them to fall back into their preferred ground state:

The mechanism is roughly the same as the fluorescent tubes we used to use in offices and at school before the leds. In these tubes the mercury gets its energy through electricity and will to release it's added energy through a photon, which lights up the office or classroom. Like Northern Lights in a tube. (images from NASA/Goddard)