Lightning has fascinated mankind for thousands of years. The powerful blasts of electricity even inspired Benjamin Franklin and his kite!
Lightning is traditionally found in the swirling winds of a thunderstorm. One area develops a positive charge of energy, while another area develops a negative charge. When that difference becomes too great, a discharge occurs and the power flows from the positive to negative areas to equalize the charges. That discharge is the lightning we see.
The discharge can occur between a cloud and the ground, or even different parts of a cloud. The energy is so powerful that the air is heated up to 50,000 degrees in an instant. This immediate expansion of air creates a shock wave, which we hear as thunder.
Lightning strikes average about 6 miles in length from where the bolt begins to where it ends, and can contain up to a billion volts of energy. Across the earth, there are about 100 lightning strikes every second. In the US, around 200 people die each year because of a lightning strike.