What is Lightning? What is Thunder?
    Lightning is a discharge of electricity from cloud to cloud, or from cloud to ground. Thunder is simply the sound that lighning makes. Lightning forms in thunderstorms when rapid heating and cooling inside the cloud produces violent activity. Some drops of freezing water become charged with positive electricity. Air currents will then cause these water droplets to rise to the upper part of the cloud and form a positive charge center. Ice crystals at the top of the cloud are charged with negative electricity and because of their weight, sink to the lower part of the cloud. As the clouds continue to form, a strong positive charge on the ground begins to form. Since opposite forces attract, the negatively charged particles in the cloud travel down to meet the positively charged earth. This is what causes the brilliant flash that you see. Thunder is created by the lightning because lightning heats up the air quickly as it travels towards the earth. This causes the gases to expand faster than sound which creates a loud clash. Thunder is heard after the lightning because light travels much faster than sound. Lightning is the number one cause of forest fires.


Last revised April 23, 1998