A form of radiant energy similar to this, but not acting on the normal retina, such as ultraviolet and infrared radiation. Interplay between light rays and the atmosphere cause us to see the sky as blue, and can result in such phenomena as glows, halos, arcs, flashes, and streamers. During thunderstorms, static electricity builds up within the clouds. A positive charge builds in the upper part of the cloud, while a large negative charge builds in the lower portion. When the difference between the positive and negative charges becomes great, the electrical charge jumps from one area to another, creating a lightning bolt.
Most lightning bolts strike from one cloud to another, but they also can strike the ground.
These bolts occur when positive charges build up on the ground. Then a positively charged leader, called the return stroke, leaves the ground and runs into the cloud. Lightning bolts can heat the air to temperatures hotter than the surface of the sun. This burst of heat makes the air around the bolt expand explosively, producing the sound we hear as thunder. Since light travels a million times faster than sound, we see lightning bolts before we hear their thunderclaps.