Ball lightning is an unexplained atmospheric electrical phenomenon. The term refers to reports of luminous , usually spherical objects which vary from pea-sized to several meters in diameter. It is usually associated with thunderstorms , but lasts considerably longer than the split-second flash of a lightning bolt. Many of the early reports say that the ball eventually explodes, sometimes with fatal consequences, leaving behind the odor of sulfur .
Laboratory experiments have produced effects that are visually similar to reports of ball lightning, but it is presently unknown whether these are actually related to any naturally occurring phenomenon. Scientific data on natural ball lightning are scarce owing to its infrequency and unpredictability. The presumption of its existence is based on reported public sightings, and has therefore produced somewhat inconsistent findings. Given inconsistencies and the lack of reliable data, the true nature of ball lightning is still unknown