Lightning occurs when electricity travels between areas of opposite electrical charge within a cloud, between clouds, or from a cloud to the ground. Lightning bolts between cloud and ground start with electrons (negatively charged particles) zig-zagging downward from the cloud, drawing a streamer of positively charged ions up from the ground. When they meet, an intense wave of positive charge travels upward at about 96,000 kilometers (about 60,000 miles) per second! This process may repeat several times in less than half a second, making the lightning seem to flicker. Find out what people around the world used to believe about lightning and other scary weather events before modern science explained them. http://scijinks.gov/folklore