"Bulfinch's Mythology" relates that in Norse mythology, the armour of the Valkyrior "sheds a strange flickering light, which flashes up over the northern skies, making what Men call the 'aurora borealis', or 'Northern Lights' ". There appears to be no evidence in Old Norse literature to substantiate this assertion. The first Old Norse account of "norðrljós" is found in the Norwegian chronicle "Konungs Skuggsjá" from AD 1230. The chronicler has heard about this phenomenon from compatriots returning from Greenland, and he gives three possible explanations: that the ocean was surrounded by vast fires; that the sun flares could reach around the world to its night side; or that glaciers could store energy so that they eventually became fluorescent.