What is light?
Light is a ripple in the way neighboring patches of the world translate each other's readings, a wave with nothing inside it to maintain. Every patch holds its own set of reference directions, and across each seam two neighbors keep a translation from one set to the other. Where everything has settled, those translations fit together, and they can also ripple. A ripple has no core of disagreement for repair to keep fixing, so it costs nothing at rest. That is why the photon is exactly massless and travels at the top speed. Only two ways of rippling survive across the direction of travel, which is why light has two polarizations and why polarized sunglasses stop cutting glare when you tilt your head. As the seams get finer, the ripples obey Maxwell's equations, and their quanta are photons.
Also in Chapter 17: Why Is There a Speed Limit?, Chapter 35: What Is Anything Made Of?.
This answer comes from OPH, Observer Patch Holography. OPH is a rigorous, consistent and complete description of the unified, self-creating computational Universe we inhabit. Its consistency is machine-checked: the fixed point at its core is constructed explicitly, and a theory with a model contains no contradiction.
To understand OPH and check every step yourself, start with the free book Reverse Engineering Reality. It builds the theory from the ground up, and the OPH Notebook answers your questions while you read.
read the free bookask the notebookor ask sage:read chapter 28: What Is a Particle, What Is a Wave, and Why Does It Look Like Both?watch a universe make its own particles