I Break the Lightning
It was once thought that ringing church bells during a thunderstorm would protect the community against lightning. So strong was this belief, that the words, Fulgura frango, "I break the lightning" were inscribed on church bells. It was believed that the ringing church bells would ward off the evil spirits associated with the lightning, and that the sound from the bells would cause the lightning to disperse.
Nature was not impressed. In fact, not only did it storm anyway, but bell ringing became a very dangerous profession. Over a thirty-three year period during the mid-1700s, 386 church towers were struck by lightning, and 103 bell ringers were killed on the job.
Much has changed since the eighteenth century. We have learned a good deal about lightning. There are no evil spirits lurking in storm clouds, just wind, rain and electrical charges. And wisely, we do not challenge nature with church bells.
Thunderstorms are not an uncommon event. At any time, about 2000 thunderstorms exist worldwide, producing about 100 lightning flashes per second. July and August are peak months in this area for thunderstorms. On rare occasions, we have some thunderstorm activity in winter.
Without lightning, there cold be no thunder, and there are specific conditions that must occur for such storms to form. Thunderhead clouds form when warm moist air rises from the ground, going sometimes as high as three to five miles where it cools and condenses along the way. This strong vertical air movement draws more warm moist air up from the ground and causes yet more thunderclouds to form.
When the clouds begin to form, their molecules have no electrical charge, positive and negative ions being paired. As the thunderhead develops, a negative electrical charge forms at the bottom of the cloud. Exactly how this happens is not fully understood, but it is probably related to quickly rising air currents. The top of the cloud has a positive charge, and when the difference in charge overcomes the resistance of the air, lightning strikes between the top and bottom of the cloud.
At the same time, things are happening near the ground. Normally, the ground has both positive and negative charges paired and is neutral. When a thunderhead passes over the ground, it attracts positive charges from the ground below, and in the air just above the ground. At times, it can be so strong, it will make the hairs stand up on your arms. When the difference in negative and positive charges between ground and cloud gets large enough, the stage is set for the lightning show.
The show begins quite subtly, a faintly visible lightning "leader" leaves the cloud and streaks for the ground in a zig zag manner. When the leader is about sixty to one hundred feet above the ground, a return stroke of lightning explodes from the ground. This return stroke is what we actually see as "lightning" and is several inches in diameter, surrounded by about a four inch thick sleeve of superheated air. The return stroke carries a charge of 20,000 to 200,000 amperes.
It is with the return stroke that thunder occurs. Temperatures, such as 50,000 degrees Fahrenheit, superheat the surrounding air, causing it to expand violently, which we hear as thunder. As soon as the return stroke reaches the cloud, another leader forms, and several dozen cycles may occur. These strokes travel at 90,000 miles per second, and we see all these cycles as one bolt of lightning.
We hear a "clap" of thunder when the lightning stroke is very close, this is often followed by rumbling as the stroke climbs higher in the cloud, exploding the air as it ascends. We hear thunder "roll" for several reasons. If it is in a valley it will echo down the sides. The thunder may also roll If it is a very long stroke of lightning, or when several bolts occur in quick succession.
There are some people who fear thunder and lightning, and others who enjoy watching the show. But whether we love it or hate it, lightning can be deadly. Between 100 and 300 people are killed by lightning each year in the United States.
What precautions can be taken during a thunderstorm? Stay indoors, away from windows, and avoid contact with telephones, metal pipes and electrical wires. If you must be outside, get in your car with the windows rolled up! Don't stand under a single tree. If you have no other cover, lay on the ground, or crouch with your arms around your knees to minimize your contact with the ground. Oh,- and don't ring any church bells!
Copyright © 1995 - 2008
Kathy Miles, Author, and Chuck Peters, Systems Administrator
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