What is St. Elmo's fire?

Search: st elmo's fire

Why: In Extremely Loud and Incredibly Close by Jonathan Safran Foer, Ruth Black tells Oskar:

Static electricity buildup is so mammoth on top of the [Empire State] Building that, under the right conditions, if you stick your hand through the observatory fence, St. Elmo's fire will stream from your fingertips. Lovers who kiss up there may find their lips crackling with electric sparks.

I assume she's not talking about that movie (which I have never seen).

Answer: Well, it's very complicated. In short, it's a weather phenomenon that occurs when there is a significant imbalance in electrical charge, causing molecules to tear apart, spark, and glow blue. The effect is similar to what happens inside a neon tube or in a plasma globe. The blue "flames" often manifest on pointed objects, like the mast of a ship, a steeple, or the wing of an airplane.

St. Ermo's fire is named after St. Erasmus or St. Ermo, the patron saint of Mediterranean sailors. Sailors believed the fire was a sign of salvation from the saint, since the phenomenon occurs most often toward the end of a storm. St. Ermo probably looked like this:

Source: How Stuff Works

The More You Know: From WeatherNotebook.org:

In 1947, General Electric engineer John Anderson undertook an interesting demonstration of the fair weather electrical potential. The Empire State Building is a well grounded structure, and thus the whole building has the same potential as the ground. Standing on a high floor, Anderson extended his arm from an open window. The strong potential difference between the atmosphere at that height and his arm still at ground potential made his finger tips glow from the potential-generated ionization, a form of St Elmo’s fire.