We’ve all heard thunder before, but now we can see it! Scientists have found a way to capture sound energy and make it into pictures. This tool, called acoustic (sound) imaging, is an excellent tool for studying thunder and lightning. But predicting when and where lightning is going to strike is difficult. To make sure they are ready to take the photograph, researchers shoot rockets at clouds to create lightning!
Researchers at a US military base in Gainesville, Florida get lightning on demand by creating super long lightning rods. They shoot rockets with copper wires trailing down to the ground into stormy skies (Watch here ). Special microphones capture the sound to make acoustic maps around the bolt of lightning. The different colors show the different loudness of the sound.
Lightning is caused by electricity in the air. Electric charge builds up in clouds during storms as a result of tiny bits of water and ice bumping into each other. Positive charges form at the top of the cloud and negative charges at the bottom of the cloud. When the positive and negative charges find a path to reach each other within the cloud, or between the cloud and the ground, we see a bolt of lightning.
Thunder, a sound caused by quick air movement, is heard right after lightning because of how quickly the lightning heats the air. The scientists’ new pictures of sound energy showed that the loudest sound is where the lightning bolt meets the ground. The colorful pictures show in detail how energy radiates from lightning bolts.
Scientists want to use acoustic imaging to improve our understanding of lightning. According to lead scientist Maher Dayeh, “Lightning strikes the Earth more than 4 million times a day, yet the physics behind this violent process remains poorly understood.” The lightning triggered by the rockets comes down in a straight line. The next step is to figure out how to create acoustic images of zigzagging and branched lightning.