The sun is a physical body, so a physical explanation makes sense. The problem is, our subjective experience isn't actually physical so the same logic doesn't apply. Our subjective experience has no mass, no shape, no size, and can't be measured. It may correspond to movements in the brain, but the experience itself is not material. For all we know we could be in the matrix, and our subjective experpence could be just as real. In fact Elon musk thinks it's a very high probability that we are in the matrix. Since our experience of the world is not material it doesn't seem to follow that there must be a material explanation for it.