XPost: sci.electronics.design   
   From: ram@zedat.fu-berlin.de   
      
   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.   
      
     Usually, the space-time curvature generated by realistic light is   
     small and therefore rarely has an observable effect. However, in   
     the early universe it once dominated over matter.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)