Zero - Charles Seife [60]
Thomson is better known as Lord Kelvin, and it is for Kelvin that the universal temperature scale is named. In the centigrade scale, zero degrees is the freezing point of water. In the Kelvin scale, zero degrees is absolute zero.
Absolute zero is the state where a container of gas has been drained of all of its energy. This is, in actuality, an unattainable goal. You can never cool an object to absolute zero. You can get very close; thanks to laser cooling, physicists can chill atoms to a few millionths of a degree above the ultimate coldness. However, everything in the universe is conspiring to stop you from actually reaching absolute zero. This is because any object that has energy is bouncing around—and radiating light. For instance, people are made up of molecules of water and a few organic contaminants. All of these atoms are wiggling about in space; the higher the temperature, the faster the atoms wiggle. These wiggling atoms bump into one another, getting their neighbors to wiggle as well.
Say you are trying to cool a banana to absolute zero. To get rid of all of the energy in the banana, you’ve got to stop its atoms from moving around; you have to put it in a box and cool it down. However, the box the banana is in is made of atoms, too. The box’s atoms are wiggling around, and they will bump the banana’s atoms and set them in motion again. Even if you get the banana to float in a perfect vacuum in the center of the box, you can’t stop the wiggling entirely, because dancing particles give off light. Light is constantly coming off of the box and striking the banana, getting the banana’s molecules to move again.
All of the atoms that make up a tweezer, a refrigerator coil, and a tub of liquid nitrogen are moving and radiating, so the banana is constantly absorbing energy from the wiggles and radiation of the box it is in, from the tweezers you use to manipulate the banana, and from the refrigerator coil you use to cool it down. You cannot shield the banana from the box or the tweezer or the coil; the shield, too, is wiggling and radiating. Every object is influenced by the environment it’s in, so it’s impossible to cool anything in the universe—a banana, an ice cube, a dollop of liquid helium—to absolute zero. It is an unbreakable barrier.
Absolute zero was a discovery that had a very different flavor from Newton’s laws. Newton’s equations gave physicists power. They could predict the orbits of the planets and the motion of objects with great accuracy. On the other hand, Kelvin’s discovery of absolute zero told physicists what they couldn’t do. They couldn’t ever reach absolute zero. This barrier was disappointing news to the physics world, but it was the beginning of a new branch of physics: thermodynamics.
Thermodynamics is the study of the way heat and energy behave. Like Kelvin’s discovery of absolute zero, the laws of thermodynamics erected impenetrable barriers that no scientists can ever cross, no matter how hard they try. For instance, thermodynamics tells you that it is impossible to create a perpetual-motion machine. Avid inventors tend to swamp physics departments and science magazines with blueprints for incredible machines—machines that eternally generate power without any source of energy. However, the laws of thermodynamics state that it is impossible to create such a machine. It is another task that cannot be done, no matter how hard you try. It is impossible even to get a machine to run without wasting energy, frittering some of its power