When light (EMR) moves through a transparent medium, its velocity is less than 'c'. The traditional explanation seems to be that the photons pause for a while as they meet each atom in the medium, and then head on in EXACTLY THE SAME DIRECTION at 'c' velocity, until they reach the next atom in their travels. If the direction was different, the medium would become opaque. When trying to understand the mechanism of this, I'm drawn to the Transactional interpretation of QM. Unless we consider the reality of EM moving from one solid to another as an holistic and contained process in itself, the movement of EM through transparent mediums poses serious questions that no one seems to be able to answer. So instead of seeing particles moving through space, we have to (surely?) consider something more like an energy exchange. The nature of this exchange is that it will only ever be detected at one point in spacetime. Its a bit like someone scribbling on a piece of paper, and the observers only seeing where the pencil is on the x axis. In our case its less than half the picture that we're seeing. And we cannot ignore what this says about the nature of matter. It is (surely?) matter that gives the quantum nature of EM, its not a fundamental property of the photon. I agree with Cramer - to me Einstein won his Noble prize for his one actual mistake (the Photoelectric effect), whereas the man himself thought the Gravitational Constant was his mistake. He mistook the qualities of his emitters and detectors as properties of what he was trying to study. I'd really appreciate some reasoned rebuttals, my lack of formal education on these things means I could be missing something obvious to everyone else.