We all know thunder! The sound of it kind of scared you when you were little, in your room, at night, but did you ever wonder what it looks like?
If the answer is yes, then you will be very pleased to know that researchers working in San Antonio, Texas at the Southwest Research Institute, have manage to turn thunder into an image, by following its acoustic signature.
How is thunder created?
As clouds ascend higher into the atmosphere, the water inside them starts to freeze and something called graupel is formed. Graupel is a material composed of half frozen water drops and slushy ice.
As the wind blows, these particles start rubbing against one another and they develop positive and negative charges. The graupel (since it is heavier) will sink to the bottom of the cloud, while the light ice will remain at the top of the cloud. Thus, the negative charges and the positive charges become separated. The negative and positive charges star accumulating in the cloud and when a critical mass is reached, they release the energy in the form of a lightning. The lightning is the one that births the sound of thunder.
This discharge is so intense, that it moves faster than the speed of sound and it produces a shock wave that reaches up to 10 meters around the location where it struck. Thunder is so loud in the location where it strikes that it can cause permanent hearing loss. So if you see lightning nearby you might want to stay inside!
So how did scientists managed to capture thunder on film?
The team decided that the best way is to create a controlled lightning that they could record. So they rigged a small rocket tied to a copper wire and launched it where they thought thunder might struck. The conductive wire enabled them to record the way the thunder travelled down and placed 15 microphones in the area to record everything.
After post-signal processing and after they amplified the data recorded by the microphones, they managed to recreate a visual image of the sound that lightning creates when descending rapidly down a copper wire.
Thunder storms are such a common occurrence on Earth that it strikes its surface more than 4 million times a day and thanks to this experiment, scientists are closer to understanding the physics and mechanics that goes on behind this violent meteorological phenomenon.
Image Source: dsx weather