I have to disagree there regardless of how one interprets “know”.
If you mean “know intuitively”, then we don’t, precisely because we have no sensors for it and hence no experience with it. We intuitively know light, because we sense it and know what to expect in a closed room with no light source.
If you mean it scientifically, then light and magnets are extensively studied and far from “know nothing about it”. Our knowledge of light, magnetism and sound is very good on all levels.