What Causes Lightning

Lightening put simply, is a bright flash of electricity, caused during a thunderstorm. Besides thunderstorms, lightning can also be observed during volcanic eruptions, surface nuclear explosions and forest fires. It travels up to speeds of 60,000 meters per second and has the power to kill more people each year than a hurricane or a tornado. Over a 100 people die and over 250 people are injured from lightning each year in the United States. Florida in the US, has the maximum number of lightning strikes each year than any other part of the US. This natural phenomenon which occurs in the form of a luminous zigzag pattern in the sky is something that has interested people for generations. Curiosity has caused people to ask the question: What causes lightening?

What Causes Lightning?

There are several theories stating how lightening is formed, and these theories have generated scores of controversies as well. Scientists have still not succeeded in figuring out this phenomenon completely. However, the polarization mechanism in clouds is the theory which is widely accepted across the globe.

Formation of Cumulonimbus Clouds (Thunder Clouds)
Water from the lakes, rivers, ponds, oceans and all other water bodies on the surface of the Earth evaporates and rises into the Earth's atmosphere in the form of gas by a process called convection. Water evaporated from the aerial parts of plants by the process of transpiration also rises into the atmosphere. As this warm, evaporated water rises into the atmosphere, it is encountered by cold air, which causes the warm air to rise even more rapidly and form large, dense and tall cumulonimbus clouds (thunder clouds) at a height of 15000-25000 feet above sea level. At such a height some of the water particles in the clouds are converted into ice or snow particles.

Electric Charge Formation and Ionization
During thunderstorms, what happens is that strong air currents cause the water particles and ice particles inside the cumulonimbus clouds to collide against each other. Scientists believe that these collisions in the clouds create an electric charge: positive and negative. Further, the positive and negative charges separate from one another, wherein the negative charges moves towards the bottom of the cloud and the positive charges dwell in the upper and middle regions of the cloud. The negative charges cause positive charges to develop in the area surrounding the cloud and on the ground below. The electric charges get stronger and makes the cloud negatively charged and the surface of the Earth positively charged. The electric charge caused between the Earth and the cloud serves as the perfect platform for the occurrence of lightning.

Lightning Formation
When the difference in electric charge is large enough, the huge charges inside the cloud ionize the air and make it a good conductor of electricity. The air acts as the bridge between the ground and the cloud and thus a path is formed. Further, a giant spark is generated which causes electricity to flow through the air to another point of opposite charge. This flow of electricity between regions of opposite charges is called a leader stroke and can occur between two clouds (cloud to cloud lightning), from the cloud to the ground (cloud to ground lightning) or from one part of the cloud to another part of the same cloud (in-cloud lightning). Once the connection between the opposite charges are formed and the path is set, the positive charges leap upwards in the path to meet the negatively charged particles, thereby causing the zigzag path of the negative charges to light up. Often people think that lightning comes from the clouds, on the contrary the path of lightning is from the ground to the cloud. This is called the production of a main stroke of lightning. The zig zag pattern of lightning appearing to us is because of the uneven ionization of the air in all directions. All this occurs in less than a millionth of a second. Lightning bolts have temperatures ranging from 30,000 to 50,000° F, which is extremely hot, even hotter than the surface of the Sun. Once the air, the Earth and the cloud have been neutralized by the lightening, it will not strike again. However, at times more than one strike is required for neutralization and this is known as a lightning storm.

Thus, we see that lightning formation as believed by scientists starts by the creation of electric charge in the cumulonimbus clouds and ends with the neutralization of the electric charge on the Earth's surface, air and clouds. Lightning is dangerous and can kill you, so if you observe dark storm clouds in the distance, quickly find shelter.