What is Phosphorescence?

   Phosphorescence is the condition in which certain organic or mineral matter and certain plants and animals give off light without the presence of heat. Also known as "afterglow," phosphorescence has been known to persist for a period of only a few seconds up to several days.
   The scientific explanation of phosphorescence is that the substance absorbs radiant light energy which increases the energy of some of the electrons in the substance. When the electrons slowly return to their original state, they emit this extra energy in the form of light. If the radiation of a substance fades immediately after the light is stopped, the process is called fluorescence. If light continues, however, the process is called phosphorescence.
   In ancient times, phosphorescence was, of course, seen and recorded as it appeared in nature. However, the earliest record of serious investigation and experimentation of this phenomenon comes from Bologna, Italy, where a cobbler and alchemist named Cascariola conducted extensive research with a barium compound.
   The delayed luminescence of phosphorescence is the result of the object being subjected to an exciting light source. The time during which phosphorescence persists is known to decrease with an increase in temperature of the substance. The principles of phosphorescence are being applied in many new areas of research, using especially the highly phosphorescent ruby.