Thunder, the crashing sound of crackling echos through the sky. Bright explosions sparkle in the clouds but disappear within seconds. Thunder and lighting have been around since the beginning of time. Many scientists have studied what causes lighting and its companion, thunder. Lightning is an electric current. Within a thundercloud way up in the sky, many small bits of ice (frozen raindrops) bump into each other as they move around in the air. All of those collisions create an electric charge. After a while, the whole cloud fills up with electrical charges.
