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Lightning
LightningLightning is a large electrical discharge produced by well-developed thunderstorms, a huge spark followed by a rumbling noise of thunder . Lightning can happen within the cloud (intra-cloud), between two clouds (inter-cloud), or from the cloud to the ground. A lightning bolt can heat the air as much as five times hotter than the surface temperature of the Sun , or about 54,000°F (30,000°C). This heated air causes expansion in the air as an explosion, starting a shock wave that turns into a sound wave upon reaching the human ear. Thunder travels in all directions (radially) from the lightning at the speed of sound, approximately 738 mph (1,188 kph) at sea level. Because it takes the sound about five seconds to travel each mile (about three seconds for one kilometer), the time between the lightning and the thunder can give a rough estimate of how far an observer is from a thunderstorm. The quick flash that can be seen as lightning occurs as a complex series of events. In order to have lightning, separate regions of electrical charges must be present in a cumulonimbus cloud. There are several hypotheses as to how this occurs. One mechanism may involve falling ice particles within the cloud that transfer ions. This results in a positively charged upper part and a negatively charged middle part in the cloud. The bottom of the cloud is also mostly negatively charged, causing part of the ground underneath to become positively charged. In the insulating dry air an electrical field builds up, and when it reaches a threshold potential, the air is no longer insulating and, as a current flows, lightning occurs. Cloud-to-ground lightning (arguably the best understood among the different types of lightning) starts inside the cloud when a critical value of the localized electric field is reached along a path, so a surge of electrons will move to the cloud base, then gradually down to the ground. A short (165 ft, or 50 m) and narrow (4 in, or 10 cm) conducting channel is created by ionized air molecules, which are produced by the electron flow out of the cloud. These surges of electrons move downward in a series of steps for about 165–328 ft (50–100m), then they stop for about 50-millionths of a second, and continue for another 165 ft, creating a stepped leader form of transit. Near the ground, a current of positive charge goes up from the ground to meet the stepped leader, and when they meet, many electrons flow into the ground, and a bright return stroke moves up, following the path of the stepped leader up to the cloud, releasing heat, thunder, and charges. The subsequent leader is called the dart leader and, for subsequent flashes, the same processes reoccur in a similar cycle. Usually, a lightning flash has approximately three or four leaders, each of them accompanied by a return stroke. To distinguish the several different appearances of lightning, the forms are assigned special names. Heat lightning (also termed clear-air lightning) occurs when lightning can be seen but the following thunder cannot be heard. Forked lightning occurs when a dart leader moving toward the ground diverges from the original path of the stepped leader, so that the lightning seems to be crooked or forked. When the wind moves the ionized channel between the return strokes, the lightning looks like a ribbon hanging from a cloud, so it is called a ribbon lightning. Bead lightning looks like a series of beads on a string, and it occurs as the lightning channel disintegrates. Sheet lightning appears as a white sheet, and it occurs either when clouds obscure the lightning, or when the lightning flash happens within a cloud. St. Elmo's Fire, named after the patron of sailors, is a corona discharge, a nonstop supply of sparks in the air, which happens when a positive current moves up on pointed objects. Ball lightning often appears as a luminous, floating sphere in the air. The various mechanisms underlying the varying forms of lightning remain a subject of intensive meteorological research. During a thunderstorm, usually the tallest object in the area is struck because this provides the most rapid form of current transit to lowest energy state. At any moment, there are about 2,000 thunderstorms worldwide, generating about 100 lightning flashes per second. A lightning stroke can deliver a current as great as 100,000 amperes, which can cause electrocution in humans and animals. About 100 people die in a year in the United States alone from lightning, and lightning causes billions of dollars in damage each year. See also Atmospheric circulation; Atmospheric composition and structure; Atoms; Clouds and cloud types; Meteorology |
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"Lightning." World of Earth Science. 2003. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "Lightning." World of Earth Science. 2003. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1G2-3437800350.html "Lightning." World of Earth Science. 2003. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3437800350.html |
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lightning
lightning electrical discharge accompanied by thunder , commonly occurring during a thunderstorm . The discharge may take place between one part of a cloud and another part (intracloud), between one cloud and another (intercloud), between a cloud and the earth, or earth and cloud; more rarely observed is the electrical discharge sometimes called "upward lightning," a superbolt between a cloud and the atmosphere tens of thousands of feet above the cloud. Lightning may appear as a jagged streak (forked lightning), as a vast flash in the sky (sheet lightning), or, rarely, as a brilliant ball (ball lightning). Illumination from lightning flashes occurring near the horizon, often with clear skies and the accompanying thunder too distant to be audible, is referred to as heat lightning. There are numerous theories on why charges accumulate in the atmosphere. It is thought that temperature and water vapor pressure in thunderstorm clouds are associated with the positive and negative ions that cause lightning. Long-lasting lightning flashes with lower current are more damaging to nature and humans than shorter flashes with higher currents. Benjamin Franklin , in his kite experiment (1752), proved that lightning and electricity are identical (see lightning rod ). |
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"lightning." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "lightning." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-lightnin.html "lightning." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-lightnin.html |
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lightning
light·ning / ˈlītning/ • n. the occurrence of a natural electrical discharge of very short duration and high voltage between a cloud and the ground or within a cloud, accompanied by a bright flash and typically also thunder: a tremendous flash of lightning. ∎ poetic/literary a flash or discharge of this kind: the sky was a mass of black cloud out of which lightnings flashed. • v. [intr.] (of the sky) emit a flash or discharge of this kind: what's a person supposed to do when it starts to lightning? • adj. [attrib.] very quick: a lightning cure for his hangover galloping across the country at lightning speed. PHRASES: like (greased) lightning very quickly. |
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"lightning." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "lightning." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O999-lightning.html "lightning." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-lightning.html |
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Lightning
246. LightningSee also 27. ATMOSPHERE ; 87. CLOUDS ; 345. RAIN ; 394. THUNDER ; 417. WEATHER .
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"Lightning." -Ologies and -Isms. 1986. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "Lightning." -Ologies and -Isms. 1986. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1G2-2505200257.html "Lightning." -Ologies and -Isms. 1986. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-2505200257.html |
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lightning rod
lightning rod a rod made of materials, especially metals, that are good conductors of electricity, which is mounted on top of a building or other structure and attached to the ground by a cable. By virtue of its position, shape, and conductivity the rod attracts lightning discharges much more readily than the building on which it is mounted. When struck, the connecting cable carries the discharge safely into the ground, preventing any damage to the building. Benjamin Franklin , in his kite experiment (1752), proved that lightning and electricity are identical and subsequently invented the lightning rod. |
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"lightning rod." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "lightning rod." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-lightni-ro.html "lightning rod." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-lightni-ro.html |
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Lightning
409. Lightning (See also Thunder.)
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"Lightning." Allusions--Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. 1986. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "Lightning." Allusions--Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. 1986. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1G2-2505500418.html "Lightning." Allusions--Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. 1986. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-2505500418.html |
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lightning
lightning Awe-inspiring phenomenon regarded by ancient peoples as a manifestation of the power of deities. By the Hebrews it was also associated with God's revelation at Sinai (Exod. 19: 16) and it was a feature of Ezekiel's inaugural vision (Ezek. 1: 13–14). Lightning is mentioned in connection with the angel who announced the resurrection (Matt. 28: 3), which is a kind of theophany; and in apocalyptic passages (e.g. Matt. 24: 27) the lightning image of the OT reasserts itself.
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W. R. F. BROWNING. "lightning." A Dictionary of the Bible. 1997. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. W. R. F. BROWNING. "lightning." A Dictionary of the Bible. 1997. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O94-lightning.html W. R. F. BROWNING. "lightning." A Dictionary of the Bible. 1997. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O94-lightning.html |
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lightning rod
light·ning rod • n. a metal rod or wire fixed to an exposed part of a building or other tall structure to divert lightning harmlessly into the ground. ∎ fig. a person or thing that attracts a lot of criticism, esp. in order to divert attention from more serious issues or to allow a more important public figure to appear blameless. |
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Cite this article
"lightning rod." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "lightning rod." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O999-lightningrod.html "lightning rod." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-lightningrod.html |
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Lightning
Lightning P-38 a heavily armed fighter-interceptor aircraft used in World War II by the U.S. Army Air Force. The P-38 was the primary fighter escort for medium U.S. bombers in Europe, and was also used in the Pacific theater.
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"Lightning." The Oxford Essential Dictionary of the U.S. Military. 2001. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "Lightning." The Oxford Essential Dictionary of the U.S. Military. 2001. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O63-Lightning.html "Lightning." The Oxford Essential Dictionary of the U.S. Military. 2001. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O63-Lightning.html |
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lightning
lightning like (greased) lightning very quickly.
lightning never strikes the same place twice often used as an encouragement that a particular misfortune will not be repeated; proverbial saying, mid 19th century. |
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ELIZABETH KNOWLES. "lightning." The Oxford Dictionary of Phrase and Fable. 2006. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. ELIZABETH KNOWLES. "lightning." The Oxford Dictionary of Phrase and Fable. 2006. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O214-lightning.html ELIZABETH KNOWLES. "lightning." The Oxford Dictionary of Phrase and Fable. 2006. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O214-lightning.html |
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lightning
lightning Flash of light accompanying an electrical discharge between clouds or between clouds and the surface. The potential difference causing the discharge can be as much as 1000 million volts.
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"lightning." World Encyclopedia. 2005. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "lightning." World Encyclopedia. 2005. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O142-lightning.html "lightning." World Encyclopedia. 2005. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-lightning.html |
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lightning
lightning XIV. Special use of lightening, vbl. sb. of LIGHTEN1, with differentiated sp.
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T. F. HOAD. "lightning." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. T. F. HOAD. "lightning." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O27-lightning.html T. F. HOAD. "lightning." The Concise Oxford Dictionary of English Etymology. 1996. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O27-lightning.html |
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