A mystery that has puzzled scientists for the past 50 years may finally be unraveled: why lightning zigzags as it strikes. The discovery was made by a scientist at the University of South Australia and was published in an article that also reveals how the phenomenon travels for kilometers.
The answer, given by physicist John Lowke, lies in a different oxygen molecule formed during storms: delta-singlet oxygen. This variation of the element used in our breathing has a different configuration in its electrons that allows electricity to be conducted through the air.
The formation of lightning occurs thanks to the difference in electrical potential between a cloud and the ground. In the process, moving electrons collide with oxygen molecules, forming delta singlets.
The zigzags formed by the rays, also called steps, are the result of the accumulation of these molecules and electrons. A short, extremely conductive step is formed in the process and the light we see is released.
Like a lightning bolt?
When lightning strikes, a handful of “leaders” emerge from the cloud and propagate through the air until one of them encounters an object on the surface, generating an electrical discharge that travels at over 320,000 km/h. Leaders left behind are extinguished as electrical charge flows along the path formed by the leader that hit the ground first.
The leader steps up the steps, which glow for about a millionth of a second. Then, the brightness fades for about 50 millionths of a second until a new step forms at the end of the previous one. It is during this period that the accumulation of delta-singlet oxygen occurs.
This state of oxygen is not completely stable, but it lasts long enough to conduct electricity during a lightning storm. The process progresses until reaching the floor, when the discharge is released.
The agitated molecules created in the previous steps form a column to the cloud. The entire column is then electrically conductive, with no need for an electric field and with little light emission.
Why does it matter?
For Lowke, understanding how lightning works is important to protect people and property from its effects, especially with the increase in the incidence of severe storms thanks to climate change.
Even lightning rods may not be in sufficient quantity to protect buildings in a city. The development and use of new materials, such as composites for aircraft – aiming at better energy efficiency – also poses new challenges for the protection of these vehicles.
“The more we know about lightning, the better informed we are to think about our built environment,” says Lowke.
Source: Journal of Physics D: Applied Physics Via: University of South Australia
