THE BOSUN SCOWLED at the horizon, stuffed his hands deep into the pockets of his paint-splattered hoodie and swayed along the deck of the ship toward me. It was November in the North Atlantic, and I hadn’t seen land in four weeks. Everything was always either going up or going down as we clung to a heaving gray sea that merged with gray sky in every direction. The roll of electrical tape I’d just put down on the deck took advantage of my temporary distraction and skidded across the deck until it met the bosun’s boot. His thick, cheery Boston accent seemed comically out of place in this forbidding environment. “How long you gonna be?”
For me, the worst bit about doing experiments at sea has always been these final checks before letting the experiments float free. I was nervous, and this bit was my responsibility alone. To measure the bubbles just beneath the breaking waves, I was using a large yellow buoy with a variety of measurement devices strapped to it. The bosun was in charge of maneuvering this beast off the ship and into the rolling sea, but I had to make sure that it was ready. The storm that was coming would be a big one, and I desperately wanted good data from it. “I’m just about to plug in the batteries, and then I’m ready to go,” I said. The monstrous yellow buoy, 36 feet long, that carried my experiments was strapped to the deck, shackled securely until it was safe to release it. I started with the armored camera near the top and put my hand on the power connector, following the wire all the way down to the bottom of the buoy where the chunky batteries were and then plugging it in. Then back up to the acoustical resonators. Hand on the power cable, follow it down to the batteries, plug it in. Check that the connection is secure. Check again. Back again to the other camera. These experiments could carry out incredibly delicate and sophisticated manipulation of the physical world, but only when provided with electrical energy. And the providers were four cumbersome lead-acid sea batteries that weighed 88 pounds each, and whose basic design hadn’t really changed since they were invented in 1859. But they worked.
When it was time, we scientists huddled in our oilskins at the far end of the deck and the crew and crane took over, maneuvering the swaying monster over the side and into the dark ocean. As the last rope slipped free, there was a weird shift of perspective, and the huge yellow beast became a vulnerable bobbing piece of flotsam, tiny compared to the vast ocean and frequently hidden by the waves. A burst of chatter spread along the ship’s rail about how the buoy was sitting in the water and the speed at which it was drifting away from the ship. But I wasn’t thinking about any of that. I was thinking about electrons.
Below the waterline, the dance of the electrons had started. They were shuffling out of the battery, around the circuits carried by the buoy and then back into the other side of the battery. There were a fixed number of electrons held in the circuit, all just going around the same loop. The electrons don’t get used up—they just go around and around. The trick is that it takes energy to push them around, and they give that energy away as they travel. The source of that energy is the battery, and a battery is a very ingenious device.
The clever thing about batteries is that they join up a chain of events. Each link in the chain supplies the electrons that the next link needs; and so once a battery is connected to a circuit, everything is in place for electrons to flow around the loop. These sea batteries had two terminals sticking out to connect them to the outside world. Inside, each terminal was connected to one of two sheets of lead, but those two sheets weren’t touching. The space in between the lead sheets was full of acid, which is why they’re called lead-acid batteries. There are two ways in which the lead can react with the acid. There’s one that needs some extra electrons from somewhere, and there’s another one that gives away extra electrons. A lead-acid battery is charged when those two reactions have been pushed as far as they can go.
When I plugged the equipment into each battery, I was providing a path all the way from one lead sheet through my experiments to the other lead sheet. And then there was the crucial last piece to the jigsaw: Because of the chemistry at the lead plates, there was an electric field down the wire. Electrons were being pushed along the wire, away from one lead sheet toward the other. They couldn’t get there across the acid, so the only option was the outside circuit, the long way around. Once the electrons have a path with an electric field pushing them down it, the reactions can undo themselves because the chain is complete. One set of lead plates gives electrons to the acid, and then the acid passes this charge on to the lead at the other plate. The lead there takes electrons as it reacts, and the whole thing keeps going because the electrons can then shuffle around the circuit back to the first set of plates. The really important fact is that on that trip through the camera around the back, the electrons have some extra energy to get rid of. This is electricity. And if you arrange it so that on their way they have to pass through a sophisticated electrical circuit, hey presto: You can put that energy to work, and you’ve got a useful battery.
As I leaned over the rail of the ship watching that bobbing yellow buoy, I was imagining this dance. The camera would switch on, creating a pathway for electrons from the battery, and they would bounce their way up the stem of the buoy, into the camera housing. You have control over where the electrons go because you know that they’ll take the easiest path. So you arrange a path through the maze that is made of conducting material. The power cable is metal, easier for an electron to move through than the plastic coating around the wire, so you know that electricity will flow down the wire rather than escaping into the surrounding material. Beyond that, the most basic element of control is a switch. A closed switch is just a place in the circuit where two parts of electrical wire touch. They’re not glued together, but when they’re touching, electrons can move between them. To stop the flow, you just move one of the wire ends away from the other. Electrical flow stops because there is no longer an easy route through.