Context: The most rare and mysterious form of lightning is ball lightning, which occurs during thunderstorms.
- Ball lightning, also called globe lightning, is a rare aerial phenomenon in the form of a luminous sphere that is generally several centimeters in diameter.
- It usually occurs near the ground during thunderstorms, in close association with cloud-to-ground lightning.
- It is a ball of luminosity that usually occurs near the impact point of a flash and moves horizontally at a speed of few centimeters per second.
- It can penetrate closed windows, is usually accompanied by a hissing sound, and has a lifetime of several seconds.
- The color is quite variable, and the ball often ends with an explosion.
- It is not usually destructive.
- It occurs at times of intense electrical activity in the atmosphere.
- These balls are said to be plasmas. Plasma is a completely ionized state of matter, at high temperature, in which positive and negative ions freely move out.
- However, no theory has so far satisfactorily explained the behavior of a ball as scientists have not been able to reproduce it in the laboratory.