Ball lightning is an unexplained and potentially dangerous atmospheric electrical phenomenon. The term refers to reports of luminescent, spherical objects that vary from pea-sized to several meters in diameter. Though usually associated with thunderstorms, the phenomenon lasts considerably longer than the split-second flash of a lightning bolt. Two reports from the nineteenth century claim that the ball eventually explodes, leaving behind an odor of sulfur. Some reports; however, describe ball lighting to last longer than a split second according to additional accounts included below. The actually existence of this lightning ball phenomena is not proven, but appears to have a variety of accounts from people through the world in the past centuries. Until the 1960s, most scientists treated reports of ball lightning skeptically, despite numerous accounts from around the world. Laboratory experiments can produce effects that are visually similar to reports of ball lightning, but how these relate to the natural phenomenon remains unclear.