The enigma of the lightning

Monsoon is at our doorstep. It’s the season of roaring skies and lightning strikes. Lightning is the giant spark of electricity in the sky unleashed due to the dynamics between the clouds, air and ground. Scientists believe that this electricity is a result of a massive build of charges in the clouds when tiny hail particles, called graupel, bounce off small ice particles as they are pushed upwards by air. When the high charge build-up breaks the insulation capacity of air, it is released as a big spark. A lightning strike is so powerful that it could heat up the surrounding air to temperatures greater than the sun’s surface, and have a voltage as high as a billion volts.

Each second, about 45 flashes of lightning occur on earth. But they aren’t all the same. The most common type of lightning is cloud-to-ground lightning where negative charges from the cloud move downward, and a stream of positive charges, from tall objects like towers, trees or poles, reach upwards. When they connect, a powerful electric current begins to flow. In some cases, the electric flashes do not reach the ground. They remain in the cloud (intra-cloud lightning) or travel between clouds (cloud-to-cloud lightning) or reach the air around the cloud (cloud-to-air lightning).

Lightning can be caused by not only thunderstorms, but also volcanic eruptions, intense forest fires, nuclear explosions, heavy snowstorms, and large hurricanes. Sometimes, instead of the familiar silver streaks, lightning can appear colourful because of light absorbed or diffracted by haze, dust, moisture, raindrops and any other particles in the atmosphere. In rare cases like snowstorms, lightning could also appear to be pink or green.

When lightning strikes the earth, it fuses dirt and clay into a glassy, tube-like rock called fulgurite. It also damages trees by killing the wood along its path. Rarely, lightning current may enter buildings and move along wires and plumbing lines, damaging them. Of course, it can also kill people and animals. Although at times disastrous, lightning is needed to create ozone and achieve an electrical balance between the Earth and atmoshere.

Spoorthy Raman