From: PointedEars@web.de   
      
   Thomas 'PointedEars' Lahn wrote:   
   > Ross Finlayson wrote:   
   >> "Optical light is special", ....   
   >   
   > "Optical light" is a pleonasm.  _Visible_ light is only special in that   
   > humans can see it with their naked eyes.  That is how visible light is   
   > defined by humans: it is light in the *human*-visible part of the   
   > electromagnetic spectrum.   
   >   
   > Historically it was the other way around: first, "light" was defined by   
   > humans as a phenomenon that could be seen with the human naked eye, and then   
   > subsequently electromagnetic radiation had been discovered (at least three   
   > times by accident, and named so accordingly by their discoverers: infrared   
   > [lit. "below red"], ultraviolet ["above violet"], and X-rays ["X" for   
   > "unknown"]) that was invisible to humans because their eyes, specifically   
   > the photoreceptors cells in their retina, are not sensible to it (the energy   
   > of each of those photons is either too low or too high to enable the   
   > required biochemical reaction; although too high energies can damage or even   
                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^   
   > destroy cells).   
     ^^^^^^^^^^^^^^^   
      
   I should be more precise, to avoid propagating the common misconception that   
   energy is a physical object instead of a physical quantity:   
      
   I meant _photons_ whose energy is too _large_, because they give off that   
   energy to electrons and nuclei; electrons with too large an energy are no   
   longer bound to the nucleus of their atoms, thereby molecular or ionic   
   binding involving them becomes impossible, too; nuclei with higher energy   
   may change (by radioactivity) to nuclei of other chemical elements or   
   isotopes which changes the chemical properties of a molecule and can even   
   destroy it, too.   
      
   --   
   PointedEars   
      
   Twitter: @PointedEars2   
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