Why Does Mass Warp Spacetime and How Does Energy Fit In?

[Fredrik]

inre: "photons themselves cause gravitational curvature"

i do not think this is true. a photon has no location, and does not cause curvature of spacetime.

A classical electromagnetic field certainly contributes to the stress-energy tensor of the fields in spacetime, and therefore to the metric (which determines the curvature).

Things get more complicated with photons. The term is defined by quantum electrodynamics, so now we're talking about a quantum field's contribution to the metric. We seem to need a quantum theory of gravity to determine that, but there's no reason to think that it would be zero.

 

[DimReg]

inre: "photons themselves cause gravitational curvature"

i do not think this is true. a photon has no location, and does not cause curvature of spacetime.

Actually, you have it the wrong way around. General relativity works worse for point particles (not test particles) than for spread out fields. By photons, I was referring more to classical light than to the quantum description of the photon. But classically at least, the electromagnetic field, and thus light, has a stress-energy tensor and does in fact cause gravity. The electromagnetic field is the limit of the quantum field the photon is part of, and that's why I say that "photons cause gravitational curvature".

 

[Naty1]

[Things get more complicated with photons. The term is defined by quantum electrodynamics, so now we're talking about a quantum field's contribution to the metric. We seem to need a quantum theory of gravity to determine that, but there's no reason to think that it would be zero.

Hopefully that result will be the theory that 'corrects' GR and current quantum mechanics near space-time singularities...divergences...like the big bang and the 'center' of a black hole.