chapter  72
Noncontact Thermometers
Pages 20

In any object, every atom and every molecule exist in a perpetual motion. When an atom moves, it collides with other atoms and transfers to them part of its kinetic energy, thus losing some of its own energy in this perpetual bouncing. On the other hand, an atom that had a smaller kinetic energy, a£er a collision, gains some. A£erward, the material body consisting of such agitated atoms reaches the energetic equilibrium where all atoms, while not vibrating with exactly the same intensity and frequency, still may be described by an average kinetic energy. Such an average kinetic energy of the agitated particles is represented by the absolute temperature, which is measured in degrees kelvin. In other words, what we commonly call temperature is a measure on a macroscale of the microscopic atomic motion.