At night, in damp marshy places, mysterious dancing lights appear. Their strange glow and no less peculiar «behaviour» fill most people with superstitious dread. But what are they, and should we be afraid of them? A strange phenomenon. The strange marsh lights have another name – will-o'-the-wisps. They appear suddenly and move at incredible speed – up to 30,000 km/h. In appearance they resemble a small glowing ball, or the flame of a candle wick. Their colour can vary – greenish, yellow, white. But most often, belated travellers encounter lights with a mysterious blue glow. Despite research carried out all over the world, their nature still remains unexplained. There are several theories, but none of them is official. Theory one, the scientific one. Scientists suggest that the cause of the formation of these little dancing balls on the marsh is self-igniting methane. It is released by the marshy soil. The thing is, the remains of animals lie at the bottom of marshes. Various plants also grow and die in damp places. Against the background of decay, marsh gases form. The gas bursts to the surface, comes into contact with the air and instantly ignites. That is how spontaneous combustion occurs. The constant «dancing» of the lights is explained by their remarkable lightness – after all, they weigh almost nothing. Any movement of the air can set them on their way. Theory two, the mystical one. Will-o'-the-wisps frightened both ancient man and the enlightened resident of the Renaissance era… and what is more, they can leave you stunned even today. One cannot help but recall ancient legends and grim tales of the dead and of hidden treasure, of the souls of the innocently slain, of the ghosts of fearsome bandits. The will-o'-the-wisp from a mystical point of view, as in the animated film «Brave». The ancients believed that marsh lights were souls. Meeting them boded no good, so the Celts, finding themselves on a marsh on the eve of Samhain, hurried to get home as quickly as possible. There are many stories in which marsh lights saved a person from death, or, on the contrary, led them into the most fatal of places. According to scientists, there is nothing mystical in this, only pure chance. The thing is, it is impossible to catch up with the ultra-light balls. A running person pushes the air ahead of himself, and this only spurs on the light flying in front. And then it suddenly disappears. This is explained by the fact that the gas has burned out. Another version. Academician Willoughby of the University of Queensland put forward yet another version. In his opinion, marsh lights are mirror mirages emanating from small sources of light. The sources themselves may be located several kilometres away. Whether this is so or not, time will tell. For now, all that remains for us is to marvel at the mysteries that nature keeps tossing our way.