A will-o'-the-wisp, sometimes called a ghost light, is a spectral illumination that appears at night, often near marshy areas. In folklore, these lights often lured unwary travelers away from paths and into the deep forest or bog, where they might vanish without a trace. While the actual cause of these lights remains in dispute, the most widely accepted explanation is chemical luminescence and the oxidation of swamp gases.
Will-o'-the-wisps and similar phenomena exist in the folklore of many countries. Typically, the stories claim that the lights are created by faerie folk or wandering spirits who seek to waylay travelers either for their own entertainment or for malicious purposes. Some tales identify the lights as gateways to hidden treasure, no doubt increasing the number of victims who follow them into the dark swamps.
While the most prevalent theory blames the lights on chemical reactions in the complex gases that arise from decomposition, there are other possible explanations. Fireflies and other bioluminescent species can cause lights in the swamp, and birds with vivid white plumage like barn owls may reflect the moon's light as they fly. Flashes of light could also be caused by piezoelectric reactions created by geologic stress, the cracking of rocks under pressure at fault lines.