St. Elmo’s Fire…!

Wild Weather Explanations by Non-Scientists: St. Elmo’s Fire

Written on Feb 27, 2018 by Gerard West —

Earth is a mysterious place. Scientists still struggle to explain some phenomena, and weather events are at times some of the most difficult to decipher. Once science figures it out, however, looking back on previous explanations by lay-persons can be amusing. One such misinterpreted weather event is known as St. Elmo’s fire.

Guiding Spirit, Sign of a Saint, or Omen of Doom?

St. Elmo’s fire is a recorded phenomenon throughout history from ancient Greece to modern times. Different cultures thought it to be a myriad of different things, but the descriptions of its characteristics remained a constant.

St. Elmo’s fire appears as a bright blue or violet glow, sometimes looking fiery in nature. It always appears on sharp, tall objects such as lightning rods, masts of ships, or the tips of aircraft wings. The glow is often accompanied by a buzzing sound.

There are dozens of descriptions from different times and cultures that deduce the phenomenon to be a sign of a benevolent spirit, god or goddess, or patron saint. The name “St. Elmo’s fire” comes from a reference to St. Erasmus of Formia, the patron saint of sailors. Welsh mariners referred to it as “candles of the Holy Ghost” or “candles of St. David”. 15th-century Ming China believed St. Elmo’s fire was a divine omen of Tianfei, the goddess of seafarers.

There are many literary examples of St. Elmo’s fire as well. In some cases, the phenomenon is described in a negative light. In Shakespeare’s The Tempest, Ann Radcliffe’s The Mysteries of Udolpho, and Samuel Taylor Coleridge’s The Rime of the Ancient Mariner, St. Elmo’s fire is described as a bad omen, portending imminent death or bad luck.

The Truth Behind St. Elmo’s Fire

Despite the popular religious opinions throughout history, scientists now know the true cause of St. Elmo’s fire. In 1899, Nikola Tesla tested out a Tesla coil in his laboratory and created St. Elmo’s fire. Blue and violet light was seen around the coil and even lit up the wings of butterflies as they flew around. Other instances of St. Elmo’s fire have been observed or created since then so the phenomenon could be better understood.

During thunderstorms, the high voltage differentials between clouds and the ground work with the shape and size of a sharp object to produce plasma. Sharp points lower the necessary voltage for this phenomenon to occur. The nitrogen and oxygen in Earth’s atmosphere cause the fluorescent blue or violet light. Neon lights glow via a similar mechanism.

In 1995, a University of Alaska research flight over the Amazon observed St. Elmo’s fire. The team was able to record St. Elmo’s fire’s optical spectrum.


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