Lightning is a visible electric discharge that shoots through the atmosphere. It rarely occurs alone and it is usually accompanied by thunder and rain. The discharge can occur between two regions of the atmosphere or between the land and a region of the atmosphere.
Although lightning be very destructive when it hits an object, it is also beneficial in that it causes oxides that are soluble in water when the nitrogen in the discharge combines with free oxygen. Rainwater carries the oxides into the soil where they act as natural fertilizers.
Whenever an electrical current jumps across the air between two points of differing electrical potential it forms an electric arc. This is seen as a spark in the atmosphere and is the principle behind the occurrence of a bolt of lightning. The bolt can be anywhere between a few hundred feet to several miles in length and the current could be as strong as 200,000 amperes. A typical bolt of lightning only lasts for a fraction of a second.
The electric charges that cause lightning are stored in the cumulo-nimbus clouds, often called thunderclouds that produce precipitation. Experiments conducted on the formation of lightning conclude that positive and negative charges become separated by drops of water. When the drops are large, internal forces split them in half and this causes the build up of positive and negative charges in the clouds. If there is another area of an opposite charge in the general area, the discharge results in a flash of lightning.
Each lightning bolt consists of several arcing discharges of electrical current. The action starts with a small discharge, called the leader or pilot streamer. A series of discharges follow the first one, which are called the stepped leaders. This leaves a charged path and a bolt jumps across this path producing the flash of what can be seen from the ground as lightning.
A lightning bolt can take many different forms. It can present itself as a zigzag shape in the sky, as beads of light or even as a sheet. When it is seen as a sheet, it can be seen over quite a large distance because the lightning comes from within the cloud. Heat lightning is the common term for the type of lightning in which you can see the flash, but cannot hear any thunder. This is because the lightning is so far away it is impossible to hear the resulting crash. Another type of lightning that can occur is called ball lightning. In this occurrence, the lightning appears in the sky as a red ball that explodes in less than 5 seconds.