Dear Tom,

What is the temperature of absolute zero, and also the highest temperature possible?

—Alice Thompsonn, Streeterville, Chicago

Dear Alice,

The temperature of absolute zero is 459.67 degrees below zero Fahrenheit, the lowest temperature possible. It is the temperature at which no molecular motion exists and it represents the total absence of heat energy. It is a physical limit in the sense that no lower temperature is possible. Although the range of temperatures is bounded on the cold side, there is no corresponding limit on the high end. There is no absolute highest temperature. The universe’s highest temperatures are found in the interiors of stars. Our own sun has a core temperature of 27 million degrees, but much higher temperatures probably exist in the interiors of larger stars.