During thunderstorms, a bright flash of light caused by the discharge of electricity in atmosphere results in lightning. The discharge of electricity causes the air to heat up rapidly producing a sound called thunder. Thunderclouds have electric potential of millions of volts with temperature of thousands of degrees. When difference between positive and negative charges of electricity (within the clouds or between the clouds and the earth) increases at greater rate, it causes electricity discharge thus resulting in lightning. Increase in atmospheric heat and moisture is another factor for more intense thunderstorms.
Thunderstorms cause a lot of damage through lightning strikes. Each day, about 8.6 million lightning strikes occur all over the world. These lightning waves move at a high speed of more than 320,000 km/hr and produce a huge amount of electricity.
Scientists are still solving the mystery "Why lightning reaches earth in zigzag manner (steps)?" From the last 50 years, scientists are arguing about zigzags and how zigzag pattern is related to thundercloud. The physics of lightning has stumped the scientific minds for decades.
University of South Australia (UniSA) plasma physicist published papers that solved both mysteries, but there hasn’t been a definitive explanation until now.
Lightning - an electrical discharge caused by imbalance between thunderclouds and ground, or within the clouds.
Dr. John Lowke, former CSIRO scientist and now a UniSA Adjunct Research Professor, explains:
“There are a few textbooks on lightning, but none have explained how the zig-zags (called steps) form, why the electrically conducting column connecting the steps with the cloud remains dark, and how lightning can travel over kilometers.”
The reason for lightning are "Singlet-delta metastable Oxygen molecules". When electrons strike oxygen molecules in the atmosphere, they form high energy singlet delta oxygen molecules. After collision, enough of the metastable states are created to detach a significant number of electrons. The detached electrons redistribute electric field forming successive steps.
Lightning rarely hit humans. Mostly buildings (especially tall and isolated), aircrafts, trees etc. are affected by lightning strikes. So, it is important to understand lightning formation to protect buildings, aircrafts as well as people from being affected.
An illustration of how lightning forms intra-clouds and clouds-to-ground.
"We need to understand how lightning is initiated so we can work out how to better protect buildings, airplanes, skyscrapers, valuable churches, and people." Dr. Lowke says.
Protection from lightning has been a great concern for scientist from a long time period. Benjam Franklin, an American polymath, in 1752 invented a thick fencing wire which is to be attached on the top of buildings and connected to ground on the other end. This lightning rod was designed to save the buildings from being damaged. This rod attracts lightning and earth the electric charge.
But, still, there are a lot of the structures which could not be protected from the lightning. Scientists are still discovering the methods to protect the remaining structures as well.
Explaining the importance of understanding lightning formation, Dr. Lowke says:
“Improving lightning protection is so important now due to more extreme weather events from climate change. Also, while the development of environmentally-friendly composite materials in aircrafts is improving fuel efficiency, these materials significantly increase the risk of damage from lightning, so we need to look at additional protective measures. The more we know about how lightning occurs, the better informed we will be in designing our built environment.”
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