XPost: sci.physics.relativity   
   From: jl@glen--canyon.com   
      
   On 12 Feb 2026 16:23:57 GMT, ram@zedat.fu-berlin.de (Stefan Ram)   
   wrote:   
      
   >john larkin  wrote or quoted:   
   >>Do photons have the same gravitational effects as their mass   
   >>equivalents?   
   >   
   >  The electromagnetic stress-energy tensor bends spacetime. To see the   
   >  Hilbert stress-energy tensor T of a source-free electromagnetic field   
   >  F, please see the section "Electromagnetic stress-energy tensor" on   
   >  the Wikipedia page "Stress-energy tensor". (I think this also is   
   >  equation 4.2.27 in "General Relativity" (1984) - Robert M. Wald.)   
   >   
   >  A single photon does not have mass, while a pair or gas of photons can   
   >  have mass.   
   >   
      
   That's what most sources say: m means mass as used by Newton and   
   Einstein, and is what's in gravitational equations, and photons don't   
   have any.   
      
   So when two gammas collide and create a particle pair, mass appears   
   where there was none.   
      
   Right so far?   
      
      
   John Larkin   
   Highland Tech Glen Canyon Design Center   
   Lunatic Fringe Electronics   
      
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