Capturing Lightning 'Fossils'

To the ancient Greeks, lightning was a sign that Zeus, ruler of the sky, was not having the best of days. The god would hurl the fiery-bright bolts like toothed spears, so beautiful and frightening that the bards sung of this holy light as one that could "grant the mortal life a pleasing end."

Bert Hickman, a retired electrical engineer from Woodridge, Ill., uses a particle accelerator to capture Zeus's rage in acrylic plastic. The photo shows a permanent "fossil" of an electric discharge formed when over 1.7 million volts was released from a 4-inch by 12-inch by 0.5-inch block of plastic.

The reason lightning bolts don't fall from the sky on a regular basis is because air is a terrible conductor. It takes a lot of energy for electrons to travel through the atmosphere. During stormy weather, the build up of static electricity in the clouds is so intense that the electrons, which are negatively-charged and don’t enjoy their own company, force their way out of the crowd toward the Earth's surface.

Hickman mimics the conditions that create natural lightning, by using a particle accelerator to pour a massive amount of electrons into a small block of acrylic plastic, which is also a very poor conductor. While the electrons are horded together, he pokes the edge of the plastic with a grounded point. With a spark, the electrons escape in less than 250 billionths of a second. The beautiful branching imprint left behind shows how the electrons traveled as they broke out of their plastic prison.

The pattern produced by an electrical discharge like lightning is called a Lichtenberg figure. German physicist George Christoph Lichtenberg discovered the patterns in the late 1700s using dust on the surface of charged insulating plates.

Branching is a common phenomenon in the natural world. Brain cells split off into different paths, as do blood vessels. Then there are plants, which spread out their leaves to catch the sun's rays. The mathematics that describes these kinds of patterns is called fractals.

To see more photographs of lightning fossils, visit "Bert Hickman's TeslaMania Website" at http://www.capturedlightning.com/.

Joseph Caputo, Special to NSF

Image credit: Bert Hickman, Stoneridge Engineering