Caelum Incognitum — The interactive encyclopedia of ufology
Will-o’-the-wisp
Explanations & misidentifications
Small bluish flames seen above marshes and graveyards in European folklore. They are linked to the spontaneous combustion of decomposition gases (methane, phosphines). It is one of the folkloric ancestors of mysterious lights, to which the 1966 Michigan “swamp gas” explanation is compared.