[Xcelerate]

I find gravity interesting, because everything that exists interacts with everything via the gravitational field. This is not the case with any other sort of interaction; gravity is truly different. See this diagram showing the ways that different particles can interact in the Standard Model: https://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/El...

Photons, for instance, cannot interact directly with each other via the electromagnetic field. Gluons do self-interact via the strong interaction. But both photons and gluons interact with all types of particles via gravity (although sometimes this interaction is so small that we would never be able to measure it).

[danbruc]

Photons do interact electromagnetically [1], just not in the same direct way as gluons.

[1] https://en.wikipedia.org/wiki/Two-photon_physics

[Xcelerate]

Yeah, I was more so speaking of direct coupling but didn’t want to get too technical. That interaction is due to virtual fermion-antifermion pairs.

[100ideas]

Is it ok to mentally replace the word/concept “gravitational field” with “energy density field”?

If so it resolves the mysterious central relationship this field has for all the others.

[liberte82]

How does one particle know that is here know that there's another one over there?

[100ideas]

How does spacetime know to curve?