XPost: sci.electronics.design   
   From: nospam@de-ster.demon.nl   
      
   john larkin  wrote:   
      
   > On Thu, 12 Feb 2026 19:39:50 +0100, nospam@de-ster.demon.nl (J. J.   
   > Lodder) wrote:   
   >   
   > >john larkin  wrote:   
   [-]   
   > >> Do photons have the same gravitational effects as their mass   
   > >> equivalents?   
   > >   
   > >Yes.   
   > >(there is no such thing as 'mass-equivalence, there is only mass-energy)   
   >   
   > If e and m are the same thing, why do people use two symbols?   
      
   Guess you mean E.   
   And the answer is backward compatibility.   
   E = mc^2 has been reduced to merely a trivial conversion between units.   
   (even more trivial because c = 1 in any half-way decent unit system)   
      
   So E and m have been given different meanings,   
   making the new general connection E^2 = m^2 + p^2.   
      
   > Do photons attract one another? Do they bounce off one another?   
      
   Certainly. See under photon-photon scattering.   
   (too weak to observe under lab conditions, except indirectly)   
      
   And no, you really shouldn't try to visualise photons   
   as tiny billiard balls.   
      
   > If you apply Newton's law of gravitation to photons, the force will be   
   > enormous when they get in a close intersection.   
      
   See above.   
      
   > Wouldn't that fuzz up images at cosmological distances? [1]   
   >   
   > Just asking.   
      
   Wait for answers from a theory of Quantum Gravity,   
   or better yet, the Theory of Everything,   
      
   Jan   
      
   [1] Photon-photon scattering does have observable consequences   
   at cosmological distances because very high energy gamma rays   
   must scatter off the cosmic background.   
      
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