Science In Real Life

Almost all the physics of our daily lives is governed by electromagnetic interactions between different clumps of matter. Ninety-nine times out of a hundred, these electromagnetic interplays occur on such a small scale that we can’t see them directly. The hundredth one is called lightning. Lightning is electrostatic discharge writ large across the atmosphere.

Recall from the essay about electricity that ordinary matter is made of atoms; clouds of negative electrons surround a tightly compacted positive nucleus. For most ordinary substances, a vigorous rub is all that is required to separate a few of those electrons from their positive partners and create ions. A negative ion, or anion, is just an atom that is possessing one or more extra electrons. A positive ion, or cation, is missing one or more electrons and has nothing to do with LOLcats no matter how much you want it to.

This is the effect responsible for lightning, more or less. Scientists are still studying the exact mechanism by which charge is separated before a lightning strike, but it probably involves ice moving around inside clouds. One theory suggests that the negative ions, being slightly heavier due to excess electrons, are pulled downwards more than the positive ions, creating separation of charges. What happens on the ground is that this polarization of clouds creates a polarization on the ground by its proximity. Let’s say all the electrons in a cloud move towards the bottom, towards from the earth. Then electrons in the ground would be repelled away from that cloud, leaving a positively-charged section of earth under the negatively-charged cloud bottom. Eventually the attraction overcomes the gap and a spark jumps.

But this gap is miles wide – so the amount of charge required to overcome it is gargantuan, and we call it lightning. The actual mechanism behind the discharge has several steps. First is an actual series of steps – like the one brave boy at a school dance, with the girls on one side and the boys on the other, a “stepped leader” will jump sporadically towards the ground. Before too long, one or more positive streamers, the young ladies, will move out to meet the brave lad. Just like it always happens on TV, once the two connect and begin dancing, everyone else is: a path of massively reduced resistance is created, at which point all the positive charge from the Earth rockets up towards the cloud. This, finally, is the jagged luminous column that we actually see. Unlike the school dance, all of this happens in just a fraction of a second.

Ground-to-cloud strikes are by no means the only or even the most common forms of lighting. Far more frequent is when lightning discharges within a single cloud. Lightning can also strike between clouds, or from clouds to air. If you’re very lucky, you might even witness a form of lightning known as ball lightning. It’s exactly what it sounds like: a glowing ball of electricity that, according to eyewitness accounts, moves erratically and lasts up to a minute. Ball lightning is not yet understood, and eyewitness accounts vary wildly as to its specific behaviors. One theory is that it is created when ordinary lightning strikes a deposit of silicon, creating an electrically bound silicon aerosol, made to glow by the heat of the silicon recombining with oxygen into its usual mineral form.

There are a dozen more variations on the processes I have outlined here – suffice it to say lightning is very complex. I’ll wrap this one up by addressing some misconceptions about lightning and lightning safety:

1) Being in a car is a safe place to be during a lightning storm, but it has nothing to do with the tires. It’s your car’s metal body (presuming it has one) – it provides a conducting path around the outside of the car. Think about this: the lightning can travel through miles and miles of air (a rotten conductor of electricity), so a few inches of rubber really aren’t going to be a problem. This is known as the skin effect, and it occurs anytime you have a solid piece of an electrically conductive material.

2) Thunder is the sound of lightning. There is so much energy in a lightning bolt that the air in a column around it literally explodes, sending out shockwaves of pressurized air, also known as sound.

3) Lightning rods work (usually). They do not work by “catching” a lightning strike and sending it off harmlessly. If you see a lightning rod struck by lightning, it has failed. Lightning rods work by dissipating the excess charge accumulating on a tall structure faster than it can accumulate. No excess charge means no gargantuan discharge, aka no lightning. The geometry of creating a tapered point of conducting metal is sufficient to send extra charge pouring out of it in a continuous stream.

4) The basics. Stay away from solitary trees, they have a tendency to explode if struck. Get inside if possible. If you’re stuck out in the open, don’t lie down flat – it provides a longer route for electricity through your body in the event that the ground near you is struck. Instead, squat down on your heels, crouching as low to the ground as possible. If the ground near you is struck, the lightning will go in one foot and out the other. Bottom line of lightning safety: Don’t be the tallest thing around.