Will-o'-the-wisp appears in folk tales and traditional legends of numerous countries and cultures; notable will-o'-the-wisp include St. Louis Light in Saskatchewan, The Spooklight in Southwestern Missouri, Marfa lights of Texas, the Naga fireballs on the Mekong in Thailand, the Paulding Light in Upper Peninsula of Michigan and the Hessdalen light in Norway. While urban legends, folklore and superstition typically attribute will-o'-the-wisps to ghosts, fairies or elemental spirits, modern science explains them as natural phenomena such as bioluminescence or chemiluminescence, caused by the oxidation of phosphine (PH3), diphosphane (P2H4) and methane (CH4) produced by organic decay.