from The Century Dictionary and Cyclopedia
- n. Luminosity due to the spontaneous vibratory motions of the particles of the luminous body. All bodies heated above red heat are self-luminous, whereas in most cases of luminescence the light emitted is due to excitation from without. The glowing of radium, and of other radioactive substances, is an instance of self-luminosity and it is in describing this phenomenon that the term is usually employed.
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