On Tuesday, January 24, 2017 at 1:17:33 AM UTC-5, ewu...@gmail.com wrote:   
   > Light needs a surface to bounce off, otherwise   
   > light cannot be detected, for example when in a dark room, a light   
   > bulb or cfl is switched on then we can see the furniture, walls   
   > in that room because the light is bouncing/reflecting of those   
   objects/surfaces.   
   > When a laser pointer is pointed at a screen or at a target that spot can be   
   detected   
   > because the laser beam falls on the target and bounces back and then is   
   detected   
   > by a photosensor.   
   >   
   > But, what if it was possible to detect a spot or point of light in just air,   
   without   
   > the need of a surface for that spot/point to bounce of.   
   > What would be the practical applications of such an invention?   
      
   Your discussion sounds a bit nonsensical.  To detect a photon it has to be   
   absorbed by an atom/electron.  If you can detect a photon in vacuum,   
   that would be a good trick.  (At high enough energy you can crash two   
   gamma rays together and make an electron-positron pair.)   
      
   George H.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)