What we really know about photons is virtually be inference and deduction as we only observe photons with a material interface. We know the speed of light and have tested it so there is little doubt that is true however we have never caused photons to interact with each other not even with a laser. Photons are predictable and we can size and shape them with frequency and wavelength analogies but again both of those attributes of photons are derived from observing them interacting with mater at a material interface. We also know there is no evidence of interference of photons with out both the double slit experiment screen and with the background material interface used to detect the so called interference which puts that interference directly at the point where the photons hit the screen upon which they are observed or detected. That means they stimulate mater to that effect or interfere with mater to give the interference effect. ...