a lot more going on than meets the 

 eye, scientists say. 



Inside that cloud, a complicated 

 chain of events is in the works. And it's 

 about to create the first bolt of lightning. 



Vin Saxena, a physical meteorologist 

 at North Carolina State University, ex- 

 plains how lightning forms. 



Even in fair weather, there is an elec- 

 trical field spread over the Earth, Sax- 

 ena says. 



For example, from your waist down, 

 you are continually being bombarded 

 with about 120 volts per meter of elec- 

 tricity—an amount similar to that in an 

 electrical outlet. In industrial areas, the 

 electrical field can be as much as 360 

 volts per meter, Saxena says. 



But in a thunderstorm, the electrical 

 field becomes exaggerated. 



When hot and cold air masses mix, a 

 thunderstorm starts brewing. The top of 

 the thunderstorm cloud becomes posi- 

 tively charged, and the bottom nega- 

 tively charged. 



Down below, the positively charged 

 surface of the Earth reacts to that law of 

 nature that says opposites attract. The 

 more negative the base of the cloud 

 becomes, the more positive the Earth's 

 surface becomes. 



The air between the two acts as an 

 insulator until the voltage difference 

 reaches 3 million volts per meter. 



At this point, the insulation breaks 

 and lightning begins to form. 



A line of current races from the base 

 of the cloud toward the Earth, search- 

 ing for the quickest way to the ground. 

 It finds the tallest point— a tree, a radio 

 tower, a church steeple. 



The positive charge of the target leaps 

 up to meet the negative charge from 

 the cloud, creating a connection between 

 the two and a blinding flash of light. 



Photo from National Oceanic and Atmospheric Administration 



This is called the return stroke. And 

 contrary to the popular belief that the 

 flash moves from cloud to ground, it's 

 the return stroke that's actually visible. 



With the return stroke, the air becomes 

 super heated, raising the temperature 

 instantly to 30,000 degrees. By compar- 

 ison, the sun's outer disk is 5,800 

 degrees. "That flash increases the tem- 

 perature to five times the sun's outer 

 disk," Saxena says. 



The violent shock that the tempera- 

 ture creates results in the sound we 

 hear and feel as thunder. 



So far, that's just one bolt of lightning. 

 Now the process starts again, and will 

 happen over and over until the cloud 

 and the Earth have neutralized their op- 

 posite charges. 



"Lightning is nature's magnificent 

 process of organizing all this energy," 

 Saxena says. "In one thunderstorm 



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