LIGHTNING is a force of nature that fascinates as much as frightens. Here are some interesting facts about this power-disrupting phenomenon.
Although thought to be an uncommon occurrence, lightning actually hits the earth about 100 times per second. That makes about 8 million strikes per day! The United States alone experiences over 20 million lightning strikes per year. Scientists have estimated that at any given moment there are nearly 2,000 thunderstorms occurring over the earth's surface. That means about 100,000 thunderstorms annually for the U.S.
Cloud to ground lightning occurs when negative charges at a cloud's base are attracted to positive ones on the earth. A surge is created which carries current to the ground. This bolt typically contains about 1 billion volts and between 10 to 20 thousand amperes of current. What happens next is called a "return stroke" which is revealed as the bright flash.
The average lightning stroke is about 6 miles long. The flash appears wider than it actually is due to the glowing air surrounding it. Lightning's return stroke can reach 50,000° Fahrenheit. To put this blast in perspective, the surface of the sun is only about 11,000 degrees.
Lightning may occur even with a clear sky overhead. A thunderstorm need only be within 10 miles for cloud to ground lightning to originate from high altitude anvil clouds. The thunder that follows the lightning bolt can be heard up to 10 miles away.
Thunder is essentially the air around the lightning exploding due to high temperature. Lightning "cooks" the surrounding air to between 15,000° and 50,000°. The sound is relative. If the strike is close by, the louder the thunder's "bang." Rumbling thunder is the "clap" arriving at a different time due to distance of the lightning.
Annual property loss in the United States due to lightning has been estimated into the hundreds of millions of dollars. Much of this damage is to sensitive electronics that suffered surge damage as a result of a nearby lightning strike.
American Power Conversion, APC Currents, July 1997, Reprinted courtesy of Sports Turf Manager, Dec. 1998.
Turf Line News February/March 1999