St. Elmo’s Fire – fact or fiction?

St. Elmo's fire in an artist depiction. The image is in the public domain.
St. Elmo’s fire in an artist depiction. The image is in the public domain.

Have you ever heard about St. Elmo’s fire?

It is rather rare, and truth be told, if you do know about it, chances are you may regard it somewhat uncertainly as either tale or reality, not really knowing whether it is real or not.

Well, it is just as real as it is rare. The physics behind it is not even that much of a mystery either: The expression to look for is “field emission”, an explanation of which can be found in a rather well written article at Wikipedia here.
The idea is that an electrostatic field can draw electrons out of the pointy end of a conducting material.

The boat in the image, or rather its real-life counterparts are not made of conducting material. Yet, during a thunderstorm or during the built-up to one the air may get so electrified that this does not matter. Remember, there are very few absolutes in physics. Conducting materials have a resistance, and non-conducting materials do still have some free electrons. The higher the energy, the more of these there are.

This brings us back to the thunderstorms. If they are big, and I mean really big, the electrification of the surrounding air, i.e. the electric field in it, may just be enough to scare some sailors… 😉

PS: The image is in the public domain. I would still rather mention the artist, so if you happen to know who that is, please leave a comment below!

Now read this: Rainy day: It ain’t real if you can’t see it?

2015-03-14 18.46.20Alexander is a physicist, teacher and storyteller. You can follow him on Twitter, Facebook, and Instagram.

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