There is more than one way to measure temperature. Daniel Fahrenheit, a German working in Amsterdam as a glassblower in the early 1700s, developed the mercury thermometer and the temperature scale still familiar to Americans. He built on work dating back to just after the time of Christ and modi?Ed by the likes of Galileo, who used wine instead of mercury, and Robert Hooke, appointed curator of the Royal Society in 1661, who developed a standard scale that was used for almost a century. In 1724, Fahrenheit described the calibration of his thermometer, with zero set at the coldest temperature he could achieve in his shop with a mixture of ice, salt, and water, and 96 set by sticking the instrument in his mouth to, in his words, "acquire the heat of a healthy man." He found that water boiled at 212 degrees. With only a minor adjustment to his scale, he declared that water froze at 32 degrees, leaving 180 degrees in between, a half circle, reasonable at a time when nature was believed by some to possess aesthetic symmetry.
Anders Celsius, working in Sweden, came up with the Celsius scale in 1742. Conveniently, it put freezing water at zero and boiling water at one hundred degrees. Less conveniently, it set in place a competition between two scales. An Australian talking to an American has to convert from Celsius to Fahrenheit, or the American will think of Australia as too cold for kangaroos. An American talking to an Australian has to convert from Fahrenheit to Celsius, or the Australian will think of America as too hot for anything but drinking beer. The Australian is forced to multiply by two and add thirty-two, or the American is forced to subtract thirty-two and divide by two. Or, as more often happens, they drop the matter of temperature altogether.
Lord Kelvin realized in 1848 that both Fahrenheit and Celsius had set their zero points way too high. He understood that heat could be entirely absent. At least conceptually, absolute zero was a possibility. He came up with his own scale, based on degrees Celsius, but with zero set at the lowest possible temperature, the point at which there is no heat. Zero Kelvin is 459 degrees below zero Fahrenheit. Just above this temperature, helium becomes a liquid. Anywhere close to absolute zero, and all things familiar to the normal world disappear. Molecular motion slows and then stops.
A new state of matter, called a "super atom" -- something that is neither gas nor liquid nor solid -- comes into being. But Kelvin's understanding of the strange world that exists within a few degrees of absolute zero was theoretical. By the time he died, in 1907, his colleagues were struggling to force temperatures colder than 418 degrees below zero, 41 degrees above absolute zero, and helium had not yet been liquefied.
One of the physicists who first achieved a temperature low enough for the formation of a super atom, which did not occur until 1995, had this to say: "This state could never have existed naturally anywhere in the universe, unless it is in a lab in some other solar system."