Atmosphere And Weather

What causes Lightning



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Intricate flashes of light shatter the darkness with their beauty, as well as potential danger. Lightning is one of nature's most beautiful sky shows, but has proven itself to be one of the most dangerous. Unfortunately, the aesthetic features of lightning are often superseded by the safety issues of it. Due to the high voltage that results when lightning is being formed, safety precautions must be taken to avoid all of its dangers.

Lightning is instigated within the cloud when the particles in the cloud begin to grow and interact (Stokley 101). During this interaction some of the particles become charged through collisions; smaller particles tend to acquire a positive charge while larger particles often obtain a negative charge (Rinerd 138). Under the influence of up drafts and gravity these particles separate until the upper portion of the cloud acquires a net positive charge and the lower portion becomes negatively charged (Rinerd 138). The separation of the charges produces an enormous amount of electrical potential both within the cloud as well as between the cloud and the ground. This festering electricity results in millions of volts when the electrical resistance breaks down and the flash begins (Rinerd 138). Lightning, therefore, is basically an electrical discharge between the positive and negative regions of a thunderstorm. This high voltage can result in a stroke averaging six miles long with a peak power of about 10^12 watts (Lightning Primer, n.p.). The temperature of the return stroke can reach up to 50,000 degrees Fahrenheit, which is 39,000 degrees hotter than the surface of the sun (Cori, n.p.). These storms average six to ten miles long and travel at an average rate of twenty-five miles per hour (Cori, n.p.).

Lightning can be classified into four basic categories, cloud to ground, Intra-cloud, inter cloud, and cloud to air. While it is the most dangerous, and the most understood, cloud to ground lightning is not the most common (Ellett n.p.). This type of flash originates near the lower-negative charge center and delivers the negative charge to earth (Rinerd 139). Some cloud to ground flashes do have a positive charge, but these bolts always occur during the dissipating stages of the storm, and usually during storms that take place during the winter months (Rinerd 139). The most common type of lightning is intra-cloud lightning, which occurs between oppositely charged centers with in the same cloud (Ellett n.p.). The entire cycle of an intra-cloud flash usually occurs within the cloud, but occasionally a flash will exit the cloud's boundary. It is not known, however, what causes the flash to remain within, or to exit the cloud (Ellett n.p.). The third type, inter-cloud, or cloud-to-cloud lightning, occurs between two charge centers in two different clouds (Ellett n.p.). The discharge resulting bridges a gap of clear air between the two clouds (Ellett n.p.). The last type of lightning occurs from cloud to air. The electricity forms with in the cloud, similar to intra-cloud lightning (Rinerd 139). The charge that results is dissipated into the air, making no contact with the ground.

Lightning can be further classified into smaller categories, most of which are determined by its appearance, and can vary depending on the position of the observer in relation to the strike. Major forms include forked, streak, ribbon, bead, and chain lightning (Uman 265). Ball lightning and a glowing light called Saint Elmo's Fire are considered to be separate forms of lightning, but little is understood about these forms (Uman 265). Ball lightning appears as a glowing, fiery ball that floats for several seconds before disappearing. It is normally seen after ordinary lightning has already occurred and has been described as a red, yellow, or orange ball that may be as large as a grape fruit. This mysterious lightning has been reported floating along the ground and inside houses, barns, and airplanes (Uman 265). St. Elmo's Fire is a likewise mysterious phenomenon. This light resembles ball lightning in many ways, but also encompasses its own characteristics. St Elmo's fire is caused by electrical discharges from a sharp object during a thunderstorm. It sometimes appears around airplanes, the masts of sailing ships, towers, and treetops (Uman 265).

Through the centuries of man, lightning has been one of the greatest mysteries of nature, and is still not completely understood. Ancient Greeks and Romans believed it to be a weapon of the gods, and some African cultures believed that people and places struck by lightning were cursed. Even into the eighteenth century some people in Europe and America believed that lightning could be kept away by the ringing of church bells (Uman, 263). Perhaps when lightning is fully understood it will not be such a risk. For now, however, due to the high voltage that results when lightning is being formed, safety precautions must currently be taken to avoid all of its dangers. Unfortunately spectators will be forced to enjoy nature's lights from afar, in the safest environment possible.



Works Cited

"Cori's Lightning Facts and Safety Tips About Lightning." On-line. Available: http://www.parzen.com/cori/litfacts.html.

Ellett, Will. "A Lightning Primer from the GHCC." On-line. Internet. Available: http://thunder.msfc.nasa.gov/primer/primer2.html.

Kithil, Richard. "National Lightning Safety Institute Safety Issues." On-line. Available: http://www.lightningsafety.com/letter.html.

Rinerd, Judith E. Powers of Nature. Washington DC: National Geographic Society.

Stokley, James. The New Book of Popular Science, vol. 2. Grolier, Inc.

Uman, Martin A. Lightning. World Book Encyclopedia, vol. 12. New York: World Book Inc..

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