Lightning is a large electrical discharge produced by well-developed thunderstorms, a huge spark followed by a rumbling noise of thunder. Lightning can happen within the cloud (intra-cloud), between two clouds (inter-cloud), or from the cloud to the ground. A lightning bolt can heat the air as much as five times hotter than the surface temperature of the Sun, or about 54,000°F (30,000°C). This heated air causes expansion in the air as an explosion, starting a shock wave that turns into a sound wave upon reaching the human ear. Thunder travels in all directions (radially) from the lightning at the speed of sound, approximately 738 mph (1,188 kph) at sea level. Because it takes the sound about five seconds to travel each mile (about three seconds for one kilometer), the time between the lightning and the thunder can give a rough estimate of how far an observer is from a thunderstorm...