|An engraving from the 1800s showing ball lightning.|
Ball lightning is an unexplained weather phenomenon that is seen all over the world. Some people do not believe it exists. However, according to the National Geographic article Ball Lightning: A Shocking Scientific Mystery, as many as 1 person in every 30 thinks they have witnessed this phenomenon. Conservative estimates put those numbers at between 1 and 150; still nothing to sneeze at.
Ball lightning is what it sounds like, a ball of what appears to be electricity. It appears to occur most often, or always, near the ground, where it bounces around like a drunken version of Tinkerbell. According to some sources, it is powerful enough to melt glass and thin metal, such as window screens. It does not have as much of a record of being fatally dangerous as "normal" lightning, but it may be potentially deadly.
Over the course of written history, roughly 10,000 eyewitness accounts of ball lightning have been written. The stories are similar enough to suggest that these people are seeing the same thing. It seems unlikely that something that does not exist would have so many witnesses, pictures and reliable accounts. (Be careful if you search for pictures of ball lightning. Many online photos of "ball lightning" are not ball lightning at all. It does not strike as "normal" lightning does.)
Scientists have no idea what ball lightning is or how it happens. Because of this, it is nearly impossible to study. It lasts for roughly 10 seconds and not knowing how it is made makes it impossible to reproduce. Unless ball lightning starts appearing around scientists a lot more than it has been or scientists are able to replicate it, it is likely that we will not find out what this oddball lightning is for a long time to come. All theories are mere conjecture based on what we know about the world and electricity.