Scientists have just calculated the maximum speed of sound. This is a big surprise
Usually the speed of sound is around 340 meters per second, which means that the sound wave needs just over 3 seconds to cover a kilometer. Meanwhile, a photon traveling at the speed of light travels nearly 900,000 kilometers within 3 seconds. When we see a lightning bolt, and only after a few seconds we hear a sound boom, then we can calculate how far the storm is.