Hovering blue flames that flicker over bogs and marshes have inspired ghostly folktales for centuries. Known as “will-o’-the-wisp,” “jack-o’-lantern,” “corpse candle” and “ignis fatuus” (“foolish fire ...

For centuries, will-o'-the-wisp has puzzled scientists and travelers alike. According to folklore, it is the product of faeries, demons, and spirits. More recently, scientists have attributed ...