The Light we are seeing now is called incoherent because it is coming from all directions.  It is coming from the prime source, the sun.  It is being beamed to the earth, and in its process of being beamed, it is radiating in a ll directions, so the paths of the light rays are incoherent.  (The definition of incoherent meaning coming from many directions.)  The light is coming from a single source but it is being radiated from the millions of miles separating the sun and the earth, and the light is being scattered on the way.

Coherence is the process of passing this light thru a device ( a laser, a crystal, etc.).  With the laser, you have two parallel surfaces and you pulse this (zeon) flash (as with a flashlight) into a specifically cut ruby.  The light passes thru, hits a window and bounces back with the speed of light.  It then meets the wavelength of light that is just being generated as well.  These 2 wavelengths amplify each other and build a signal.  The 2 now act as one.  These two together hit a surface, bounce and pick up another wavelength going to further amplification, going back and forth.  When they emerge from this partly silvered surface, they are coherent, meaning altogether, not scattered, not going in a ll directions, but lasing:  LASER:  Light Amplification by the stimulated Emission of Radiation.  When it starts to Lase, it will Continue…  “Perpetual Motion”.


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