Light is well understood but the explanation depends on what level of abstraction you require. There are quantum, classical and naive explanations of light and each are radically different. It's not our understanding that is flawed but rather the assumption that if there's two different explanations of the same physical phenomenon it indicates a lack of knowledge (rather than an abundance of knowledge).
That just moves the problem to "which layer of abstraction should I use".
Ex. If I'm developing a new material that interacts with light, should I consider light to have mass, or not? Well if it's a space sail, photos have mass, if it's not a space sail, light has no mass.
But I'm not sure if this new material is a space sail....which abstraction should I use?
