Ball Lightning refers to luminous, usually spherical, atmospheric objects which vary from a few centimetres to several metres in diameter. They are usually associated with thunderstorms. Anecdotal reports suggest that they can 'pass through' solid objects.
Although extensively documented and even photographed, Ball Lightning is currently unexplained.
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.
See : Wikipedia
Quote from Emeritus Professor Bob Crompton of the Australian National University
“I don't believe there is any satisfactory explanation so far”
“[The theories] don't satisfy me and I don't think they satisfy anyone who looks at the evidence objectively.”
source ABC Science , 2008.
Further reading : First Spectrum of Ball Lightning from the American Physics Society, 2014