Luminescence's light that usually occurs at low temperatures, and's thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which's light generated by high temperatures. Historically, radioactivity was thought of as a form of "radioluminescence", although it's today considered to be separate since it involves more than electromagnetic radiation. The dials, hands,… (More on Luminescence)