From: u502sou@beverly.kleinbus.org   
      
   Mikkel Haaheim wrote:   
   > On Thursday, February 16, 2017 at 4:32:22 PM UTC+1, Damien Valentine wrote:   
   >> On Tuesday, January 24, 2017 at 5:45:00 AM UTC-5, ewu...@gmail.com wrote:   
   >>   
   >> > 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.   
   >>   
   >> We already have those devices: they're called "digital cameras". (The   
   photons/waves don't bounce off anything -- they're focused by a lens, then   
   directly absorbed by a CCD and converted into electrical signals.)   
   >   
   > I think you are misreading his admittedly imprecise question. I think, when   
   he refers to "bouncing off", he actually means "interacts with". In your   
   example, the light is interacting with the CCD.   
   > In other words, I think he is asking what would happen if we could detect a   
   photon without interacting with that photon, either directly or indirectly.   
      
   We would violate Energy Conservation, among others.   
      
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