Storm in a Teacup: The Physics of Everyday Life(70)
It’s a weird phenomenon, but we humans have learned to make use of it in ways that now permeate our lives. It starts with coins and paper clips and fridge magnets, but ultimately, magnets are essential to the way we generate power for our world. At the heart of every single device that feeds electricity into our power grid, there’s a magnet. However, magnets don’t do it alone, and magnetism is only half of the story. It’s linked in a very fundamental way to electricity, something so vital to modern society that we hardly notice it anymore.
It was the science-fiction writer Arthur C. Clarke who said that “any sufficiently advanced technology is indistinguishable from magic.” Electricity and magnetism together are responsible for more magically advanced technology than almost anything else. When you look really hard at the physics, you can see that these invisible forces are two sides of the same phenomenon: electromagnetism. They are bound together, each influencing the other. But before we look at the connection, let’s dig a little bit deeper into the side that we’re most familiar with: electricity. Unfortunately, the first time most of us experience electricity in a direct way, it hurts.
RHODE ISLAND IS a tiny, friendly fragment of the American north-east, and it was my home for two years. Its official nickname is the Ocean State, and the locals have entirely missed the irony of nicknaming the smallest state in the United States after the most gigantic feature on the planet. The mentality of Rhode Islanders rests on two pillars: the coastline and the summer. Life there is about sailing, crab shacks, snail salad,? and the beach. But the winters were cold. The tourists vanished, the locals hibernated, and the olive oil in my kitchen solidified if I turned the heating off when I went out.
On the best winter days, I woke to a distinctive stillness that told me before I had even opened my eyes that snow had fallen overnight. For someone brought up in gray, damp Manchester, this was always hugely exciting. I loved it all, apart from one single repeated moment. After pulling on snug winter boots, shoveling the snow from my path, and laughing at the squirrels digging in the white stuff, I’d stomp out to my car in the stillness. And every single snowy morning, as I touched the car for the first time, I’d be greeted with the sharp snap of a painful electric shock. I never quite remembered in time. Ow!
It always felt as though it must be the car’s fault in some way, but with hindsight, it wasn’t the car that was to blame. As I walked down the path, I was carrying a small flock of sneaky passengers looking for an escape route. The pain was just a side effect of their jumping ship. These passengers were electrons, incredibly tiny fragments of matter and some of the most fundamental building blocks of our world. The wonderful thing about electrons is that you don’t need a fancy particle accelerator or a sophisticated experiment to know that they’re moving about. In the right situation, our bodies can detect their movement directly. It’s just a shame that our bodies register this astonishing detection as pain.
It all starts with what’s in an atom. At the core of each one, there’s a heavy nucleus that makes up almost all the “stuff” of the atom. This nucleus has a chunky positive electric charge, so it will almost never be alone. Electric charge is a strange concept, but it holds our world together. There are only three building blocks that make up almost everything we see—protons, electrons, and neutrons—and they each have a different electric charge associated with them. Protons are much more massive than electrons, and they have a positive charge. Neutrons are similar in size to protons but have no electric charge. And each electron is minuscule by comparison but has exactly enough negative electric charge to balance out one proton. This mixture of building blocks dictates the structure of our world. In the center of each atom, protons and neutrons cluster together to form a heavy nucleus. But an atom needs to be electrically balanced. Electric charges affect the world because different charges attract and like charges repel (as we saw with my magnets and coins). So tiny electrons swarm around the massive nucleus because they are negatively charged, and therefore attracted to the positive charge in the center. Overall, the positives and negatives cancel each other out, but the attraction holds the atom together. All the matter that we see is full of electrons, but because everything is balanced we don’t notice them. They become noticeable when they move.?
The problem is that when you’ve got tiny, nimble players like electrons in the game, things don’t always stay balanced. When two different materials touch, electrons quite often hop from one to the other. It happens all the time, but it doesn’t normally matter because the extra ones will usually find a way back quite quickly. Walking around my cottage in socks wasn’t a problem—a few electrons were hopping from the nylon carpet to my feet with every step, but they’d soon find their way back. As soon as I pulled on my fleece-lined, rubber-soled boots, things changed a bit. The wandering electrons were hopping from the carpet to the rubber soles, just as before. But, nimble though electrons are, there are some materials they can’t make their way easily through: These are called electrical insulators, and rubber is one of them. The rubber has plenty of its own electrons, but it can’t easily soak up any extras. As I was packing my bag for the day, finding my coat, and tidying up from breakfast, I was accumulating electrons as they quietly hopped on board. This led to extra electrons spreading themselves out around the outside of my body. By the time I stepped outside, I was the vehicle for a few thousand billion extra electrons, a gigantic number but still a minuscule fraction of my body’s own electron cohort.