Thousands of people have seen these luminous spheres, which seem to occur along with normal, cloud-to-ground lightning. Researchers have proposed many theories to explain ball lightning, but no one theory has been able to explain all the reports.

One idea is that ball lightning is a neutral plasma – a neutral, ionized gas. In the 1960s and 70s, scientific research on ball lightning picked up because of interest in controlling nuclear fusion in plasmas. More recently, ball lightning hasn’t gotten much attention from scientists, but most are convinced that it’s a real natural phenomenon.

As for the dangers of ball lightning, there have been reports of ultraviolet and radiation burns – and even deaths when the balls exploded near people. Luckily, it doesn’t happen very often.