photo #5864109

Scandinavians in the Middle Ages referred to the aurora borealis as norðrljós (‘Northern Lights’). The earliest documented mention of norðrljós is in the thirteenth-century Old Norse text Konungs skuggsjá (‘King’s Mirror’), which was written for the education of King Magnus Lagabøte (c.1238-1280). The author describes the ‘peculiar nature’ of the Northern Lights, how ‘the darker the night is, the brighter they seem’ and how ‘they always appear at night but never by day, most frequently in the densest darkness and rarely by moonlight.’ Then they go on to summarise three possible explanations for the Lights.Some, they explain, think the Northern Lights are the illumination of the sky from ‘fires that encircle the outer ocean.’ Others think they’re the result of powerful glows emanating from glaciers. And some suggest that ‘during the hours of night, when the Sun’s course is beneath the Earth, an occasional gleam of its light may shoot up into the sky.’ We now know auroras are caused by the dynamic interaction between charged particles from the Sun, known as solar wind, and our magnetosphere, the region of Space around Earth under the influence of its magnetic field. The charged particles energise the magnetosphere as they become trapped in it. Over time, they distort its shape and stretch it out, until eventually the magnetic field snaps back, hurling electrons and protons into our atmosphere at high speeds. They collide with and excite the atoms and molecules of gases in our upper atmosphere which, as they return to their original states, release photons of light. These we see as the green and pink curtains of light dancing across the night sky. That said, if you give it another 800 years, this explanation will likely sound as fanciful as those told to King Magnus Lagabøte.Aurora borealis with Altocumulus undulatus spotted over Inari, Finland by Kees Neve (Member 57,271).