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About luminescence

The term “luminescence“ refers to the emission of light (Latin: lumen) by an object without any increase in temperature. It is a form of cold body radiation. Many luminescent materials are known and there are many possibilities to produce luminescence. Very well-known is the excitation of luminescence through light. Here, the light emission may either immediately stop after turning off the light source (so-called “fluorescence”) or continue over a certain period of time (from seconds to minutes or even days) in the dark (so-called “phosphorescence”).

 

Luminescent animals, which produce the so-called “bioluminescence”, have got something magical, no matter whether they are, for example, fireflies, deep-sea fishes or other aquatic organisms. Here, the glow is directly related with life. The functions of the light emission may be manifold. Attraction of a mate, alluring the prey, communication, threatening, warning, camouflage and even mere illumination could be some of them.

 

If we think about a luminescent human, the situation is getting more complex. Is it a spiritually illuminated person? Or is it someone, who is contaminated with radioactivity, who just escaped an accident with a nuclear reactor or the testing of an atomic bomb? Or is it a genetically modified person, maybe even “genetic art”? The latter seems to be feasible through the existence of new techniques for genetic manipulation and is just waiting for realization: fluorescent fish, mice, rabbits, pigs and monkeys have already been produced! And the so-called “synthetic biology” lets us expect even bioluminescent animals in near future.

 

The luminescence of phosphorescent materials slowly decreases with time after turning off the light. Thus it also may serve as a symbol for transientness. The materials require new light to make them shining again. According to Buddhist teaching a spiritually illuminated person also has to make efforts to obtain illumination again and again. Wood, which is glowing in the dark forest, is in the status of decomposition and decay, it suffers from fungus.

 

People use luminescent materials in a similar way than animals do. They use them for signals, markings, warnings, lures or illuminations. In addition, they can make visible or emphasize objects on purpose. And they can do something very essential more: they can play with it!

 

Fluorescence and phosphorescence especially tempt to play with our optical senses. A specific characteristic of these kinds of luminescence is that the colours of the light, which were used for excitation, are not identical to the colours of the emitted light. For example, excitation with blue or ultraviolet light might result (depending on the type of pigment or dye) in colours such as blue green, green or red of the emitted light. At the same time the illuminated materials may have a completely different body colour. In combination with the different periods of light emission of the materials and different kinds and colours of light sources for excitation, this opens a vast and poetic playground for our sensory perception.
 

Lumen luminis I

Lumen luminis II