Wednesday, 5 June 2013

Lightning: The Sky! It's Exploding!

Written by Steve Kux, Illustrations by Geoffrey Lee

You’re out for a walk across a wide open mountain top when the sky rapidly begins to cloud over. Darkness overtakes you and rain begins to fall. Before long you are caught in a full-fledged thunderstorm. Suddenly you begin to feel an eerie tingling all over your body. A faint buzzing sound begins to grow around you. A sailor might call it Saint Elmo’s fire, but you’re no sailor. To you it’s just weird. A flash of light, and searing heat are your last sensations. You won’t be making it home for supper.

Lightning is one of nature’s most impressive displays, but the mechanics behind it aren’t much different from what happens when you shock yourself on a doorknob. Called electrostatic discharge, both the lightning and the shock are caused by electrons moving from one place to another. See, everything in the universe is made of atoms, and atoms are made of basically three things: protons, neutrons, and electrons. 

Protons and neutrons are the homebodies of the atomic world. They stay cooped up in an atom’s nucleus like an acne-ridden teenager on a Saturday night. Electrons are a little different. They like to party. 

Electrons move around, but when they do they create imbalances in the relative charges of atoms. Since electrons have a negative charge and protons have a positive charge, when electrons leave one atom and go to another, the original atom loses some of its negativity and takes on a positive charge. If you get enough charged particles in one place, you’ve got a recipe for electricity.

When you walk across a carpet wearing wool socks, the friction of your feet on the fibers in the carpet transfers electrons to your body, causing you to take on a negative charge. When you touch a metal doorknob, it acts as a conductor and ZAP! Mini fireworks show. 

The same thing happens in a thundercloud. Turbulent conditions cause the uneven buildup of charges across the cloud’s volume, once those charges reach a certain threshold it’s time to take cover.

Lightning comes in three main forms: Cloud-to-Cloud, Cloud-to-Ground, and Dark Lightning (band name anyone?).

Cloud-to-Cloud is the most common type of lightning, accounting for the majority of the 40-50 lightning strikes per second experienced around the world. Often called “heat lightning” because of its tendency to happen without the accompanying boom of thunder, Cloud-to-Cloud strikes usually occur when the positively charged “anvil” section of a thunderstorm exchanges energy with the negatively charged atoms closer to the ground.

Cloud-to-Ground lightning is basically the same thing, except instead of two sections of the cloud providing the opposite charges, the exchange happens with the earth. The tricky thing with this type of lightning is that it is unpredictable and ridiculously dangerous. Strikes that take place between the lower part of the cloud and the ground are relatively straightforward. They tend to follow a straight path and, for that reason, mostly happen directly beneath a foreboding sky.

Strikes that happen between the upper anvil portion of the cloud and the ground are where things get dicey. Since the lower portion of the cloud can act as a barrier to the transfer of electrons, bolts can travel in any crazy direction they want before finally veering towards the ground. Because of the zigging and zagging, and because storm clouds are generally pretty huge things, anvil-to-ground strikes can happen miles away from the cloud of origin. Some have even been called “bolts from the blue” since they can happen in places with little to no cloud cover, adjacent to a storm.

Last but not least, there is Dark Lightning. This is where things go from cool-but-familiar to just plain weird. Dark lightning happens roughly once for every thousand bolts of visible lightning and is thought to be the result of cosmic rays from space mixing themselves up with the already potent energy of a thunderstorm. When things reach critical mass the result is an invisible explosion of X-Rays and Gamma Rays that carries approximately one million times the energy of visible lightning. Just take a minute to let that sink it. One. Million. Times. Fortunately that energy is dissipated far and wide in every direction and not concentrated in a single bolt. Still, it is thought that dark lightning could harm anyone unlucky enough to get caught in it. Not the “burnt to a crisp” harm we typically associate with lightning, more like a “screwing up your DNA” kind of harm that is potentially way worse. Research into dark lightning is in its early stages, but it might be something to keep an eye on.

So there you have it. Lightning explained. It may be impressive enough to appreciate all on its own, but the science behind it is pretty awesome too… If only slightly less showy.