The Catatumbo Lightning is an atmospheric phenomenon in Venezuela. It occurs only over the mouth of the Catatumbo River where it empties into Lake Maracaibo. The frequent, powerful flashes of lightning over this relatively small area are considered to be the world's largest single generator of tropospheric ozone. Photo by Fernando Flores, 31 October 2015.

Thor: (The Sound of) Thunder

 

A year ago, I covered Thor’s relationship to Thunder.

I think the phrase “God of Thunder” is a touch misleading, because when you’re the god of X, people pray to you hoping that you’ll give them X. It seems silly, though, to think that anyone would ask a god to bring them thunder and lightning. Instead, Thor is a protector, like Jupiter and Zeus (also thunderers) are gods of sovereignty and justice. It’s not that anyone ever prayed for thunder: they prayed to Thor in the hopes that he would use his mighty hammer Mjolnir to defeat the forces of chaos. Thor’s chariot, driven by the goats Tooth-Gnasher and Tooth-Grinder, was responsible for most of the noise. The sound of Thor defeating the giants and the trolls, riding in on is chariot, that was the thunder. Thor was thunder. He was the animating personification of the warrior heart, the man defending his farm, the whole community standing against invaders.

Thunder was just the outward sign that chaos was being held at bay by the storm. Lightning the hammer, thunder the chariot, all of it Thor, fighting the Jotun hordes.

But that’s just one version of the story. There are North American thunder gods, South American thunder gods, Hindu thunder gods, Chinese thunder gods, Nigerian thunder gods, a Celtic thunder god, over a dozen European Thor-cognates, and all of these myths are similar but by no means the same to those that I’ve been relating on this blog for three years now. They’re not all protectors, but they’re more orderly than chaotic. Usually fertility gods and associated with storms and rain. Always with the thunder.

Always, everywhere, trying to understand thunder, trying to use thunder as a metaphor, or an allusive element to some bigger part of being human.

And yet in the three years of writing this blog, it’s easy to just skate past the question: what’s thunder? A year ago I told you that Thor is thunder. What does that mean? What is it about thunder that inspires us? 

Thunder is the sound caused by lightning. Sounds simple, but there’s more to it than that.

First, here’s the sound of thunder. Take a listen.

It’s the loud crash at about the five second mark that really makes you pay attention. Something spectacular has just happened. You can imagine this sound had a large bolt of lightning, relatively nearby. You’re used to this sort of thing happening during a major thunderstorm, but you know it has consequences. Sometimes it’s the violence of the storm, sometimes the lightning strikes close enough that it causes damage, it can be a variety of things. But most of us have experience with this phenomenon.

This second video has a variety of thunder sounds.

These sounds are a bit more gentle. Rather than the loud, quick strike of lightning, the thunder rumbles a bit, sometimes lasting several seconds. You can imagine, if you were to witness this storm, that the lightning might be entirely cloud based, or at least that the lightning would be more off in the distance. You might not see the lightning at all, in fact, as sometimes the clouds are so thick and pervasive that the lightning isn’t visible on the ground at all.

Thunder is the sound that lightning makes. But what is lightning? What does that mean?

We know now that lightning is a discharge of plasma that occurs because an electrical pathway forms between the ground and a point in the sky. We don’t know all the specifics of how it works – a lot of what’s going on during a flash of lightning is happening when electrons get displaced from their original molecules, and while we can study things like that in labs, it’s hard to study in the field, when storms, particularly lightning-bearing storms, and especially the exact location of a single bolt of lightning, are difficult to predict.

But we’ve worked some things out.

flood-cycleLightning happens because of the water cycle, and the flow of water particles between the water and the ground. That’s part of the story anyway. Lightning can also happen during volcanic eruptions, forest fires, nuclear detonations… usually things where there are clouds, where there are particles flowing in the air. The water cycle is just the most familiar version of this process. Eventually things get to the point where negatively charged electrons have been knocked free. They start to gather in one area, typically understood to be the bottom of a cloud, and become attracted to the ground, to discharge.

Eventually, the charge becomes powerful enough that the resistance in the air can no longer prevent the discharge. A pathway between the cloud and the ground (or from one cloud to another) forms, and an extremely hot plasma briefly fills this pathway as an electric current surges between the cloud and the ground (or between clouds). This plasma is as much as 30,000 degrees Celsius – about five times as hot as the surface of the Sun. It’s about an inch in diameter, and usually extends 4-5 miles, either from the sky to the ground, or from one cloud to another.

Not every lightning strike is the same. In addition to variations between strikes between clouds, or strikes from clouds to the ground, the electricity works differently, too. Sometimes the electricity flows down, then back up, repeatedly, and very rapidly. Sometimes it’s one continuous current flowing down.

Additionally, you will have noticed that each lightning strike is, let’s say, jagged. That’s a complex process that’s determined by various air conditions during the storm: the lightning current takes the path of least resistance to its destination, which isn’t a straight line. It’s more like a series of straight lines, like a connect-the-dots kind of thing.

Thunder is what happens when the super-hot plasma causes a shockwave. It heats the particles in the air around it to that extremely high temperature, which causes the air pressure to increase right along with it, anywhere from 10 to 100 times normal air pressure. This pressure pushes outward like a wave, and because the electrical discharge happens quickly, the air cools behind it: the pressure relaxes. The shockwave turns into a sound wave, and the lightning causes a booming sound.

But the character of each sound wave is determined by the different properties of each lightning strike. The sound drives out perpendicular to the lightning strike, and since the lightning isn’t perfectly vertical (or, in the case of cloud-cloud lightning, perfectly horizontal), it manages to push out not quite perfectly straight from the strike itself.

Studies have also shown that 80% of the acoustic energy of a lightning strike is directed 30 degrees away from the perpendicular line. That means that the loud crack of a nearby lightning strike occurs both when you’re close to the lightning and, almost always, when you’re in that 30 degree zone where the power is being transmitted most powerfully. And again, remember that lightning strikes are jagged (the technical term is “tortuous”) – sometimes it looks like the lightning would be far enough away that you wouldn’t be getting much of a sound. But you’re at just the right angle to one of the “jagged edges” to get the most powerful acoustic burst.

Those lower, deeper rumbles can happen for a few reasons. First, they can happen just because you’re further away from the thunder. The sound starts to get a bit “messier” as it moves through the air, and loses some of its clarity. But more importantly, cloud-to-cloud lightning strikes will mostly be at angles where the vibrations from the shockwave are more oblique. But since a lightning bolt is four or five miles long, and you’re still getting most of the sound from its shockwave (it’s jagged!) even when it’s a cloud-to-cloud strike, you get the sounds nearest you sooner than you do the sounds from the parts of the lightning bolt further away. Which is why, as with the second video I shared above, it can take a few seconds for the thunder to finish.

So thunder, practically speaking, is amazing. Even if we don’t understand all the mechanics of what causes the electricity flows in the air, we know enough to understand that ridiculously hot temperatures cause shockwaves, and therefore sounds. Some of which are like crashes, some of which are like rumbles.

And storms aren’t just sounds. They’re fascinating combinations of light and sound and wind and rain, too. Like this.

Just to return to mythology for a moment, the pre-Christian Germanic peoples, and many other societies leading back into pre-history, were animistic in their belief system. Put simply, they thought that there was a consciousness behind everything they encountered, animals, plants, objects, even the world itself. Not one big consciousness driving everything. Not several gods who nudged everything in a few directions. Everything had a consciousness, and could to some extent be communicated with, maybe bargained with, and, without a doubt, was worth respect.

Imagine a storm, or just watch that storm video again. Put on some headphones and feel the bass in that thunder.

What’s the consciousness of that storm like? What kind of mood is the thunderer in today?

Thor is the god of protecting humans from the giants, the agents of chaos in the world, the forces of cold and fire and everything that scares you. He uses his hammer Mjolnir, which he throws as if like lightning, to defeat the giants, but also to bless weddings and consecrate graves. He helps humans feels safe.

And Thor is the thunder. He’s the crackling thunder. He’s the rumbling thunder. He’s the distant thunder, and he’s sparking thunder. His temper cannot be predicted or controlled.

Pray he’s on your side. If not, if you’re threatening humans or otherwise upsetting the Thunderer, sun-scarring heat and an ear-splitting shockwave may be coming for you.

Chris Hemsworth as Thor in the recent trailer for Thor: Ragnarok
Chris Hemsworth as Thor in the recent trailer for Thor: Ragnarok

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