Absolute Zero: The Third Law of Thermodynamics

By Steven Holzner

In physics, absolute zero is considered the lower limit for the temperature of any system, and the third law of thermodynamics can be formulated in terms of this temperature. The third law of thermodynamics is pretty straightforward — it just says that you can’t reach absolute zero (0 kelvin, or about –273.15 degrees Celsius) through any process that uses a finite number of steps. In other words, you can’t get down to absolute zero at all. Each step in the process of lowering an object’s temperature to absolute zero can get the temperature a little closer, but you can’t get all the way there.

Although you can’t get down to absolute zero with any known process, you can get close. And if you have some expensive equipment, you discover more and more strange facts about the near-zero world. One researcher has discovered how liquid helium works at very, very low temperatures — below two-thousandths of a kelvin. For example, the helium will climb entirely out of containers by itself if you get it started. For these and some other observations, he and some friends got the Nobel Prize in Physics in 1996, the lucky dogs.