St. Elmo's fire
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- For the 1985 Brat Pack movie, see St. Elmo's Fire (film).
St. Elmo's Fire is an electro-luminescent corona discharge caused by the ionization of the air during thunderstorms inside of a strong electric field. Although referred to as "fire", St. Elmo's Fire is in fact a low density, relatively low temperature plasma caused by massive atmospheric electrical potential differences which exceed the dielectric breakdown value of air at around 3 megavolts per meter. St. Elmo's Fire is named after Erasmus of Formiae (also called St. Elmo), the patron saint of sailors (who sometimes held its appearance to be auspicious).
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Observation
Physically, St. Elmo's Fire is a bright blue-white glow, appearing like fire in some circumstances, often in double or triple jets, from tall, sharply-pointed structures such as masts, spires and chimneys, and on aircraft wings [1].
It is named such because the phenomenon commonly occurs at the mastheads of ships during thunderstorms at sea. Benjamin Franklin correctly observed in 1749 that it is electric in nature. It is said that St. Elmo's Fire can also appear from the tips of cattle horns during a thunderstorm, or sharp objects in the middle of a tornado, but is not the same phenomenon as ball lightning, although they are possibly related. In ancient Greece, the appearance of a single one was called Helena and two were called Castor and Polydeuces.
Other works
References to St. Elmo's Fire, often known as "corposants" or "corpusants" from the Spanish Cuerpos Santos (Holy Bodies), can be found in the works of Julius Caesar (De Bello Africo,47), Pliny the Elder (Naturalis Historia, book 2, par. 101) , Herman Melville, and Antonio Pigafetta's journal of his voyage with Ferdinand Magellan.
- "'Look aloft!!' cried Starbuck. 'The corpusants! The corpusants!' All the yard-arms were tipped with a pallid fire; and touched at each tri-pointed lightning-rod-end with three tapering white flames, each of the three tall masts were silently burning in the sulphurous air, like three gigantic wax tapers before an altar." – Herman Melville, Moby Dick.
Charles Darwin noted the effect while aboard the Beagle and wrote of the episode in a letter to J.S. Henslow that one night when the Beagle was anchored in the estuary of the Rio Plata: "Everything was in flames, the sky with lightning, the water with luminous particles [bioluminescence], and even the very masts were pointed with a blue flame."
There is a possible reference to St. Elmo's fire in Samuel Taylor Coleridge's The Rime of the Ancient Mariner:
- About, about, in reel and rout
- The death-fires danced at night;
- The water, like a witch's oils,
- Burnt green, and blue, and white.
Trivia
- St. Elmo's fire was a phenomenon described in The Lusiads in Vasco Da Gama's journey to India.
- Saint Elmo is in fact wrongfully translated as it is originally called in Portuguese São Telmo, or Saint Telmo in English. Saint Telmo was the saint of the Portuguese sailors.
- It should not be confused with the British Saint Helm.
- It is speculated that St. Elmo's fire is the cause of the "Holy fire" that appears spontaneously in the Holy Sepulchre Church of Jerusalem on the Orthodox Easter.
References
A song titled "St. Elmo's Fire" appears on Brian Eno's 1975 album Another Green World.
See also
es:Fuego de San Telmo fr:Feu de Saint-Elme fi:Elmon tuli io:Fairo di Santa Elmo it:Fuoco di Sant'Elmo la:Corpus sanctum ja:セントエルモの火 nl:Elmsvuur no:Sankt Elms ild pl:Ognie świętego Elma pt:Fogo de São Telmo ru:Огни святого Эльма sv:Sankt Elmseld zh:聖艾爾摩之火