Even today the phenomenon of lightning is still not fully understood. It is awesome and frightening to many and because of the mystery that surrounds it, several cultures have developed different beliefs about it. Some African cultures believe that when someone is hit by lightning that he/she was cursed even before the event. The Romans and Greeks believed that the gods were fighting and this was one of their weapons. Lightning kills and injures many people, starts thousands of forest fires, and causes millions of dollars in property damage every year.
Lightning is characterized by the discharge of electricity between rain clouds or between a rain cloud and the earth. It is usually seen as an arc of extremely bright light which can be many kilometers in length, however, there are other forms as well. Accompanying the lightning is the giant roar of thunder. The thunder is caused by the expansion of air that has been heated by the lightning which then collides with cooler air, creating the sound of an explosion.
Thunderstorms are the most common types of storms, and thunder itself, although frightening, is not dangerous. It is the lightning that causes the problems. Lightning and thunder occur together, however we hear the thunder after we see the lightning. Sound waves travel about one mile in five seconds, while light travels at more than 186,000 miles per second. Therefore, lightning is seen immediately when it occurs, and thunder is heard a little later.
The different sounds of thunder (deep roar/loud crash) is caused by the different types of lightning, for example, the thunder that has the sharp crackle like sound is caused when the large trunk of lightning forks into many branches. (See types of lightning)
National Lightning Safety Institute >>
National Geographic - Lightnings >>
Ball Lightning >>