The Photon

@beecee The rabbit hole of what underlies something understood as fundamental. If spacetime is emergent then it is emergent from something more fundamental, which would need a whole new set of theories for whatever spacetime emerges from. True, the speed of light as a constant still holds to this day with no need for a physical medium. Yes, General Relativity is very successful, but the problem is with linking Quantum Mechanics and General Relativity, and gravity. Gravity is not treated with the SM of Particle Physics as there is no QFT for gravity. What little I know of LQG, space and time are quantized, probably also emergent from something more fundamental. In string theory, spacetime is likely to be emergent also. It is, but string theorists, LQG theorists and other physicists have the idea that space and time is emergent from something more fundamental than space and time. Nima Arkani-Hamed is vocal about it for example.

Really? So spacetime is then here to stay? I am hoping so, because replacing spacetime with something else just makes the rabbit hole go deeper.

Any ideas from physicists that will replace spacetime? Will spacetime be replaced by some underlying material aether medium that light waves propagate on and visible matter as disturbances in the medium? There's superfluid vacuum theory but I don't know what the photons and matter is in the theory, and the speed of sound in the superfluid may exceed the speed of light. String theorists like Gross and Witten also predict the emergence of spacetime from something more fundamental. What evidence to date leads physicists to replace spacetime with something else?

I am interested in studying physics and research in String Theory. String theory is interesting to me, but I've also read that there isn't any experimental support for the theory yet and many physicists doubt the theory. Still, the idea of unifying all particles into a single string and all forces into one force is appealing.

A microwave photon can not pass through a microwave mesh. If photons are point-like particles, I am confused how a photon of certain frequencies can not pass through a hole that is of significant size. When a photon of the same frequency or a photon from a radio station for example is absorbed by a material it does not excite a large group of molecules, it gets localized, hence the confusion.