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.
Why didn’t they escape? Each one of those extra negatively charged electrons was being repelled by the others—any route away would be better than staying put. But my boots stopped them from leaving via the floor. There is another common escape route: moist air. Humid air contains lots of water molecules, each with a positive segment that could host an extra electron for a while. Most days, my extra flock of electrons would have escaped one by one, as they hitched a ride with floating water. But cold days after a heavy snowfall are often dry. There is very little water in the air, so the air offered no way out.
And so, every dry, snowy day, I’d walk down the path from the cottage to my car, completely unaware of the billions of negatively charged passengers, at least until their opportunity knocked. My car sat on the ground, a vast reservoir of balanced electrons and nuclei. The split second when my bare fingers first made contact with the metal of the car was like the opening of an escape tunnel. Metal is an electrical conductor, so electrons can flow through it very easily. My electron passengers surged through the skin of my finger tip, finally free when they met the car. The nerve endings in the skin jangled as the mob whooshed past, directly stimulated by the flow of electrons: an electric current. And I would curse, the magic of the snow temporarily forgotten.