On Monday, July 21, 2014 5:55:26 PM UTC-4, RichD wrote:   
   > Let's say you radiate a pulse of energy from    
   > a dipole antenna at 100 MHz, equal to a single    
   > photon. Sort of tiny, but elctrical engineers    
   > are a clever lot, I'm sure they're up to it.   
      
   >    
   > Rich   
      
   Rich can I change your question to something that is kinda doable?   
      
   So say a set up a light source on earth. Maybe it's monochromatic, but that   
   shouldn't really matter.  And I can put attenuators in the beam such that I   
   can reduce the intensity to ~1 photon/ second*.  Now on the moon I set up a   
   big array of PMT's.  (and    
   I also shut off the sun and all other light sources :^) We'll imagine the   
   array covers the beam spread.  And now I monitor the PMT's.  What do I see?    
   (Except for dark counts and stray light and all that.)        
   I see a detection in one PMT and then a different one.. etc, the beam is   
   spread out over many miles or whatever.  But I still get one count at a time.     
      
   George H.    
      
   *maybe 10^6 per second.  PMT's are fast and I can probably do the timing to   
   1us.   
      
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