For centuries, tales of mysterious blue lights above swamps fascinated people. Modern experiments now explain that microlightning sparks between charged methane bubbles from decomposing plants produce the eerie glow known as will-o’-the-wisps.For centuries, tales of mysterious blue lights above swamps fascinated people. Modern experiments now explain that microlightning sparks between charged methane bubbles from decomposing plants produce the eerie glow known as will-o’-the-wisps.