AUGUST ON THE East Antarctic Plateau is still and silent. While the northern hemisphere basks in summer, Antarctica spins in the darkness on the bottom of the world. On the high mountain range that stretches right across the plateau, it’s almost the end of a night that has lasted four months. Very little snow falls here, but the surface ice is still 650 yards thick. The weather is calm. Heat energy is constantly leaching away into the starry night, and there is no sunlight to replace it. This deficit means that along the high mountain range, the winter temperature is regularly -112°F. On August 10, 2010, one mountainside sank to ?135.76°F, the coldest temperature ever recorded on Earth.
In the ice crystals making up the snow, heat energy is stored as movement energy as the atoms jiggle about their designated location in the solid ice. So the answer to the question “How cold can it get?” sounds straightforward: The coldest possible temperature must be the point when the atoms stop moving completely. But even at the coldest place on our planet, where there is no life and no light, there is still movement. The whole plateau is made up of atoms that are quivering, and they’ve got about half of the movement energy that they would have just before the ice melts at 32°F. If you could take away every last bit of that energy, they would be as cold as it’s possible to get. We have a name for this temperature: absolute zero, defined as ?459.67o F. It’s the same for every type of atom and every situation, and it means that there is no heat energy at all. Compared to that, even freezing winter Antarctica, the coldest place on our planet, looks pretty warm. Fortunately, perhaps, it’s very difficult to slow atoms down to a complete stop. It takes a lot of ingenuity to make sure that nothing nearby is going to give away any of its energy to your sample and spoil it all. But there are scientists who are devoting their lives to inventing extremely clever methods of removing heat energy from matter. This is the field of cryogenics, and it’s opening the door to devices that are useful even in the nice warm world where we live, especially improved magnets and medical imaging technology. Most of us, however, are far more interested in keeping warm. We find it very uncomfortable even to think about being really cold. So watching ducks waddle about barefoot on ice can be very puzzling.
Winchester is a pretty little place in the south of England, with an ancient cathedral and a colony of very English teashops serving hefty scones on dainty plates. It can be spectacular in summer, with colorful flowers and a bright blue sky making the whole place look picture-postcard perfect. But one year I took a friend there on a snowy winter day, and it looked even better. Bundled up in scarves and thick coats, we stomped all the way down to the end of the high street, until we reached the modest river and the soft blanket of undisturbed snow on its banks. My favorite thing about Winchester has nothing to do with stone buildings or King Arthur or scones. What I had dragged my friend all the way through town on a freezing cold day to see was far more prosaic: ducks. We crunched our way through the snow for a short distance along the river path, and there they were.
Just as we arrived, one duck on the bank waddled across the last bit of ice and hopped into the water. And then it did exactly what all the others around it were doing: It faced the stream, started paddling like mad, and reached down to dabble in the water in front of it in search of food. The river is very shallow at this point, but the water flows very quickly. There are plants growing on the bottom, just within reach, but the ducks have to paddle furiously to stay in one place in order to forage. The river in Winchester is a treadmill for ducks, and I find it endlessly entertaining. They paddle continuously, all facing the same way, and they never seem to stop.
A small child next to us looked down at her snow-covered boots, then pointed to a duck that stood on the ice on the bank and asked her mother an extremely good question: “Why don’t his feet get cold?” Her mother didn’t answer because at that moment, the real comedy show began. One of the paddling ducks had got a bit too close to one of the others, provoking a burst of quacking and flapping and pecking. The funny bit was that as soon as the scrap started, both of them forgot to paddle, and so they both whooshed off downstream with the flow, quacking as they went. After a few seconds, they realized how fast they were moving, forgot about each other, and started trying to paddle back upstream to where they had started. It took a while.