Storm in a Teacup: The Physics of Everyday Life(74)

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.

Once inside the camera, the path of the electrons would split, some shuffling into the computer and some into the camera itself. And the thing about electrical circuits is that in the end all roads lead to Rome, or in this case, back to the battery. The massive yellow buoy was just the skeleton for this branching flow of electrons, and the electrons themselves were generating electric and magnetic fields, pushing and pulling on camera shutters, acting as timers, generating bursts of light and recording data in a huge, intricate synchronized sequence, before shuffling back to the battery.

And all of that was happening while the buoy was being shoved around by the huge waves (25–30 feet high in some cases) of an Atlantic storm. We bobbed about on the research ship and waited, living a life where gravity was an uncertain friend and a tenuous grasp on order was maintained only by imprisoning things with Velcro or elastic bungees or rope. After three or four days, the chemical reaction in the battery had finished—it was back in its original uncharged state. There was no more stored energy left, the electrons could not be pushed around the circuits, and the dance was over. The buoy went back to being an inanimate shell of metal and plastic and semiconductors. But the data had been stored in solid state computer memory, and it was safe.

A few days later, when the storm was over, we tracked the buoy down and hauled it back on board. I’m always extremely impressed by the skill of research ship crews at fishing things out of the water. Ships don’t move sideways, and they’re slow to turn around or change direction. To stand a chance of getting the buoy back, the captain had to bring his 250-foot vessel right alongside it, managing both to avoid running it over and to get close enough for the bosun to reach over and catch it with a long boat-hook. And they usually succeeded on the first try.

Then it was our turn again. The batteries were plugged into the ship’s power supply, providing the energy to push the chemical reactions back the other way ready for the next deployment. The experiments were detached and brought inside, with the exception of the camera. This got left outside in the freezing cold, because the dance of the electrons has a downside, and my poor PhD student was about to pay the price for it.

Possibly the most fundamental physical law we know of, one that has been shown to be accurate time and time again and has never been disproved, is that of conservation of energy. It states that energy can never be created or destroyed, but only shifted around from one form to another. The battery had chemical energy, and the chemical reactions converted that to electrical energy, and then somewhere between one terminal of the battery and the other one, that energy moved on. But where did it go? Things happened—the camera took pictures, the computer programs ran, and data were recorded. But none of that stored the electrical energy in a new place. The energy just leached away, unnoticed. There is a price to be paid for moving electrons around, and it’s the generation of heat. Any electrical resistance inflicts an energy tax on the electrical energy moving through it. Even though the electrons will pick the path of least resistance, some tax must still be paid.?

The camera was housed in thick plastic, a material that transmits heat very badly. When the camera was running, all the energy of the electrons was eventually converted to heat as they flowed around the system. That didn’t matter in the water, because the ocean where we were was about 45°F and stole the heat away, cooling the housing efficiently. But air isn’t up to that task. In the lab, when the computer was running to download the data, the camera kept overheating. We did our best, but the only solution we found was to leave it outside in a bucket of iced water (helpfully, the ship had an ice machine), and so my PhD student had to spend nine or ten hours starting and stopping the downloads to keep the data flowing while preventing the camera from cooking itself. Such is the glamour of field science.