STEM Around Us: Catching Lightning in a Bottle

The high voltage breakdown of plexiglass creates beautiful fractal patterns called Lichtenberg figures
The high voltage breakdown of plexiglass creates beautiful fractal patterns called Lichtenberg figures. Credit: Bert Hickman

“Catching lightning in a bottle” is an idiom for a nearly impossible goal. While trapping lightning in a bottle is still out of reach, we can trap lightning in plexiglass or acrylic with some clever science.

To start with, lightning is a giant electric spark that occurs in a cloud, between two clouds, or between a cloud and the ground. All forms of electric spark occur due to the movement of electrons. Electrons are particles with a negative charge. When a large number of electrons accumulate in the clouds, they discharge to form lightning. 

In the same way, when plexiglass is passed through an electron accelerator (a device that produces a beam of electrons), it becomes loaded with electrons. This charges the glass with a million volts. The trapped electrons are released manually by making a sharp tap on the glass which produces miniature lightning. The energetic sparks create microscopic cracks and tubes along the glass, and the patterns they form are called fractal patterns. These are beautiful, branched structures, and this type of fractal pattern is called Lichtenberg figures. This is the path that the sparks took while passing through the glass slab, so these figures are, in a way, ‘fossils’ of the spark. This method is used in making branch-like patterns in glass paperweights.

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