Will o' the wisp
Scientists try to use a natural explanation. Some say they are a gas, like methane, that goes up from the ground and burns. Other people say they are electric things, like ball lightning. One flying ball of light was explained: it was an owl that had a bright stomach. Sometimes animals or fungus make some light - this is called bioluminescence by scientists or foxfire. Sometimes diphosphine (P2H4) is also produced over marshes, which are highly flammable. Therefore, it burns in air and causes a flickering glow.