Lightning is one of the most dramatic and frequent natural phenomena on Earth. Every second that passes without stopping, approximately 100 lightning strikes hit the Earth's surface from clouds, and at any given time, there are about 2,000 thunderstorms occurring simultaneously around the world.
Lightning forms when electrical charges build up in storm clouds. In towering cumulonimbus clouds, there are strong upward and downward air movements. Ice particles in the upper part of the cloud collide with water droplets in the lower part, resulting in the transfer of electrical charges. The top of the cloud accumulates positive charges while the bottom accumulates negative charges.
When the difference in charge between the cloud and the ground reaches a sufficient level, the air, which usually acts as an electrical insulator, can no longer hold the charge. A narrow conducting channel called a "stepped leader" descends from the cloud, and when it meets a rising channel from the ground, a very high voltage is released in a very short period β this is what we see as lightning.
The temperature of lightning can reach up to 30,000 Kelvin or nearly five times hotter than the surface of the Sun. This extremely rapid and sudden heating of the air expands the air abruptly, creating a shockwave sound that we hear as thunder. Lightning itself lasts only a few milliseconds, but the energy released can reach one billion volts.
Although lightning appears dangerous β and indeed it can be deadly β lightning also plays an important role in Earth's ecosystem. Lightning helps convert atmospheric nitrogen into a form that can be absorbed by plants, contributing to the natural fertility of the soil. Every year, lightning produces about 100 million kilograms of nitrogen in a useful form for plants.