| > QED offers no explanation for gravity It does; gravitation in perturbative QED on time-dependent curved backgrounds has exactly the same explanation as General Relativity. [1] This generalizes very well. [2] One can look at it the other direction too: General Relativity guarantees flat spacetime in the neighbourhood of every point on the manifold with signature 1,3 or 3,1. As long as the radius of curvature is large compared to the system under study there is no trouble at all (QED systems are usually pretty tiny, so you're good down to and through astrophysical black hole apparent horizons). This is implicit in laboratory tests of QED. > But any physicist who’s being intellectually honest knows that we only have a rudimentary understanding of these concepts Everyone should be honest about how much she or he really knows, and how much he or she can judge how much someone else really knows. "The first principle is that you must not fool yourself — and you are the easiest person to fool" -- Feynman - -- [1] [BirrellDavies] N.D. Birrell and P.C.W. Davies, Quantum fields in curved space, Cambridge University Press, Cambridge U.K. (1982). [2] [BGZV] A.O. Barvinsky, Yu.V. Gusev, V.V. Zhytnikov, and G.A. Vilkovisky, SPIRES-HEP:Print-93-0274(Manitoba), (1993). https://arxiv.org/abs/0911.1168 |