St. Elmo's fire, also known as corposant, Hermes fire, furole, witchfire, or witch's fire, is a weather event where glowing light appears around objects like ship masts, church spires, chimneys, or animal horns when electricity in the air is strong. Pilots have also seen this glowing light on the front parts and windshields of airplanes.
The brightness of the glow, which is usually blue or violet and may make a hissing or buzzing sound, depends on how strong the electricity in the air is. This phenomenon is most often seen during thunderstorms or volcanic eruptions.
St. Elmo's fire is named after St. Erasmus of Formia, also called St. Elmo, who is the patron saint of sailors. Sailors noticed this glowing light before lightning struck and sometimes believed it was a sign of good luck.
Cause
St. Elmo's fire is a type of plasma that can be shown again and again. The electric field around an object splits air molecules into charged particles, creating a soft light that is easy to see in the dark. This light often appears during thunderstorms, when large differences in electrical charge exist between clouds and the ground below. An electric field of about 100,000 volts per meter is needed to start a spark in moist air. The strength of the electric field depends on the shape and size of the object. Sharp points require less voltage because electric fields are stronger in areas with sharp curves, causing sparks to form more easily and strongly at the tips of pointed objects.
The nitrogen and oxygen in Earth's atmosphere make St. Elmo's fire glow blue or violet, using the same process that makes clear neon lights glow (without special coatings), but with a different color because of the different gases involved.
In 1751, Benjamin Franklin suggested that a pointed iron rod might light up at its tip during a lightning storm, looking similar to St. Elmo's fire.
In a study published in August 2020, scientists from MIT's Department of Aeronautics and Astronautics found that St. Elmo's fire behaves differently on objects in the air compared to those on the ground. They discovered that objects not connected to the ground collect electrical charge more easily in strong winds, unlike the type of electrical discharge seen in objects that are grounded.
Research
Scientists at Rutgers University have created a way to make vacuum ultraviolet light using different types of lighting. They do this by placing thin, conductive needles inside a thick gas, such as xenon, in a sealed container. They apply a very high negative voltage to the needles in the xenon-filled container, which produces vacuum ultraviolet light efficiently. This process is similar to St. Elmo's Fire. Scientists think this method might be used for lighting if a stronger power source is used, which could increase efficiency by more than 50%.
Notable observations
St. Elmo's fire is mentioned in writings by Julius Caesar (De Bello Africo, 47) and Pliny the Elder (Naturalis Historia, book 2, paragraph 101), as well as in Alcaeus frag. 34. Earlier, Xenophanes of Colophon had referred to the phenomenon.
In 15th-century Ming China, Admiral Zheng He and his associates created the Liujiagang and Changle inscriptions, which are two writings about the Ming treasure voyages. These inscriptions mention St. Elmo's fire as a sign of Tianfei, the goddess of sailors and seafarers.
The power of the goddess was shown in past times and again in the present. During a storm, a bright light appeared at the top of the ship's mast. When this light appeared, the danger lessened, and people felt safe even when the ship was in danger of capsizing.
— Admiral Zheng He and his associates (Changle inscription)
St. Elmo's fire is also described in Antonio Pigafetta’s journal from his 1519 to 1522 voyage with Ferdinand Magellan. It is also called "corposants" or "corpusants," from the Portuguese phrase "corpo santo" ("holy body"). This term is used in The Lusiads (1572), an epic about the voyages of Vasco da Gama.
Robert Burton wrote about St. Elmo's fire in his book Anatomy of Melancholy (1621). He mentioned that a Lithuanian duke named Radzivilius called the phenomenon "Sancti Germani sidus" and saw it during a storm in 1582 while sailing from Alexandria to Rhodes. This refers to a voyage by Mikołaj Krzysztof "the Orphan" Radziwiłł in 1582–1584.
On 9 May 1605, during the second voyage of John Davis, led by Sir Edward Michelborne, an unknown writer on the ship Tiger described St. Elmo's fire: "In the middle of our storm, we saw a flame the size of a large candle at the top of our main mast. The Portuguese call this 'Corpo Sancto' and believe it is a sign that the worst of the storm is over. As God be thanked, the weather improved afterward."
Pierre Testu-Brissy was an early French balloonist. On 18 June 1786, he flew for 11 hours and made the first electrical observations while rising into thunderclouds. He used an iron rod to draw electrical discharges from the clouds and also saw St. Elmo's fire.
William Bligh wrote in his log on 4 May 1788, while on board HMS Bounty: "Corpo-Sant. Some electrical vapor was seen near the iron at the yard arms, about the size of a candle’s flame." This event occurred in the South Atlantic, near Cape Horn, while traveling to the Cape of Good Hope and west of Tristan da Cunha. The ship's location was recorded as latitude 42°34′S, longitude 34°38′W.
William Noah, a silversmith who stole 2,000 pounds of lead in London, recorded two observations of St. Elmo's fire in his journal while traveling to Sydney on the ship Hillsborough. The first was in the Southern Ocean between Cape Town and Sydney, and the second was in the Tasman Sea near Port Jackson:
26 June 1799: At 4 a.m., the wind began to blow strongly with heavy rain and hail, and thunder and lightning were very loud. A "Cormesant" (a glowing ball of fire) appeared at the top of the foretopmast. It was followed by more thunder and lightning, which caused the fire to fall and burst on the main deck. The electrical force from the explosion shook several people on the deck and had the same effect on the gun deck and orlop (lower decks) among the convicts.
25 July 1799: Heavy thunder and lightning surrounded the ship, and a "Cormesant" hung at the top of the mainmast. A flash of lightning struck the Cormesant, causing it to burst and hit two sailors, who were blinded for several hours. Many others were hurt in their eyes.
While the exact nature of these weather events is unclear, they seem to describe two instances of St. Elmo's fire, possibly mixed with ball lightning or a direct lightning strike to the ship.
On 20 February 1817, during a severe electrical storm, James Braid, a surgeon at Lord Hopetoun’s mines in Lanarkshire, had an unusual experience while riding a horse:
On Thursday, 20th, I saw flashes of lightning from the west, repeating every few minutes. At about 9 p.m., I noticed the tips of the horse’s ears and the edges of my hat glowing. Soon after, a shower of snow fell, and the horse’s ears became wet, losing their glow. My hat’s edges stayed glowing longer.
I saw many small sparks flying toward the horse’s ears and the edge of my hat, creating a beautiful effect. Unfortunately, the snow stopped the glowing.
The air in this area was very electrified for about eight to ten days. Thunder was heard from 15th to 23rd February, and the weather was unstable, with frequent hail, snow, and rain.
No one in this area had seen such a bright glow or so much lightning before, and no one had heard so much thunder at this time of year.
In Vermont and New Hampshire, a luminous snowstorm occurred on 17 January 1817. St. Elmo's fire appeared as static discharges on rooftops, fence posts, and on people’s hats and fingers. Thunderstorms were common in central New England.
Charles Darwin described St. Elmo's fire during his voyage on the Beagle. He wrote in a letter to J. S. Henslow about one night when the Beagle was anchored in the Río de la Plata estuary:
"Everything is in flames – the sky with lightning, the water with glowing particles, and even the masts are lit with blue flames."
— Charles Darwin, 1832
He also wrote about this night in his book The Voyage of the Beagle:
"On another night, we saw a beautiful display of natural fireworks. The top of the mast and ends of the yard arms glowed with St. Elmo's light. The shape of the ship’s vane could almost be seen, as if it had been rubbed with phosphorus. The sea was so bright that the tracks of penguins left fiery trails, and the sky was briefly lit by vivid lightning."
— Charles Darwin, 1832
In Two Years Before the Mast, Richard Henry Dana Jr. also described similar phenomena.
In popular culture
One of the earliest known mentions of the phenomenon is found in Alcaeus's Fragment 34a, which refers to the Dioscuri, or Castor and Pollux. It is also mentioned in Homeric Hymn 33, which connects the Dioscuri to the phenomenon from Homeric times. It is not known whether the Homeric Hymn was written before or after Alcaeus's fragment.
The phenomenon is first described in the Gesta Herwardi, a text written around 1100 that refers to an event from the 1070s. However, one of the earliest direct mentions of St. Elmo's fire in fiction appears in Ludovico Ariosto's epic poem Orlando Furioso (1516). This reference is in the 17th canto (19th in the 1532 revised edition), after a storm has punished the ship of Marfisa, Astolfo, Aquilant, Grifon, and others for three days. The text links the fire to hope:
"But now St. Elmo's fire appeared, which they had so longed for. It settled at the bows of a fore stay, the masts and yards all being gone, and gave them hope of calmer airs."
— Ludovico Ariosto, 1516
In William Shakespeare's The Tempest (c. 1623), Act I, Scene II, St. Elmo's fire is associated with a negative meaning, appearing as evidence of a tempest caused by Ariel under the command of Prospero.
The fires are also called "death fires" in Samuel Taylor Coleridge's The Rime of the Ancient Mariner.
Later in the 18th and 19th centuries, literature often linked St. Elmo's fire to bad omens or divine judgment, matching the themes of Romanticism and Gothic novels. For example, in Ann Radcliffe's The Mysteries of Udolpho (1794), during a thunderstorm above a castle:
"And what is that tapering of light you bear?" said Emily, "see how it darts upwards—and now it vanishes!"
"This light, lady," said the soldier, "has appeared to-night as you see it, on the point of my lance, ever since I have been on watch; but what it means I cannot tell."
— Vol. III, Ch. IV, The Mysteries of Udolpho
In Jules Verne's Journey to the Centre of the Earth (1864), the fire is described during a subterranean electrical storm:
"On the mast already I see the light play of a lambent St. Elmo's fire; the outstretched sail catches not a breath of wind, and hangs like a sheet of lead."
In Herman Melville's Moby-Dick, Starbuck mentions "corpusants" during a thunderstorm in the Japanese Sea in Chapter 119, "The Candles."
St. Elmo's fire appears in The Adventures of Tintin comic Tintin in Tibet, where Tintin identifies the phenomenon on Captain Haddock's ice-axe.
The phenomenon is mentioned in the first stanza of Robert Hayden's poem The Ballad of Nat Turner and referred to as "corposant" in his poem Middle Passage.
In Kurt Vonnegut's Slaughterhouse-Five, Billy Pilgrim sees the fire on soldiers' helmets and rooftops. In The Sirens of Titan, the phenomenon affects Winston Niles Rumfoord's dog, Kazak, the Hound of Space, during solar disturbances.
In Robert Aickman's story Niemandswasser (1975), the character Prince Albrecht von Allendorf is nicknamed "Elmo" because of the fire that appears to emanate from him.
In On the Banks of Plum Creek by Laura Ingalls Wilder, St. Elmo's fire is seen by the girls and Ma during a blizzard. It is described as rolling across the floor and not burning it, though this is more similar to ball lightning.
In Voyager, the third book in Diana Gabaldon's Outlander series, the main characters experience St. Elmo's fire during a thunderstorm at sea.
St. Elmo's fire is also mentioned in Castaways of the Flying Dutchman by Brian Jacques.
It is referenced multiple times in Stephen King's Pet Sematary.
It is also mentioned in Jim Butcher's The Dresden Files series, especially during magical conflicts or when describing magic effects.
In Larry McMurtry's Lonesome Dove (1985), St. Elmo's fire appears twice during thunderstorms on a cattle drive:
"To his amazement he saw that the cattle seemed to have caught the lightning—little blue balls of it rolled along their horns… 'Ride off the cattle,' he said. 'Don't get close to them when they got the lightning on their horns. Get away from 'em.'"
On the children's TV show The Mysterious Cities of Gold (1982), St. Elmo's fire is shown affecting a ship near the Strait of Magellan. A real-life interview with sailor Fukunari Imada is included, stating that the fire was considered a bad omen because it disrupted compasses and equipment.
On Rawhide, in the 1959 episode "Incident of the Blue Fire," cattle drovers see the fire on their steers' horns and regard it as a deadly omen. In a 1965 episode of Bonanza, religious pilgrims believe St. Elmo's fire is the work of Satan.
In The Waltons episode "The Grandchild" (1977), Mary Ellen sees St. Elmo's fire while running through the woods.
In the Western miniseries Lonesome Dove (1989–1990), lightning causes the horns of cattle to glow blue during a storm.
On Futurama in the episode "Möbius Dick," Turanga Leela refers to the phenomenon as "Tickle me Elmo's Fire."
In the Netflix series Trese (2021), the Santelmo (St. Elmo's Fire) is one of the protagonist Alexandra Trese's allies, contacted using her Nokia phone by dialing the date of the Great Binondo fire, 0003231870.