Radio waves are knowable,there are unknown unknowns and that's not what I meant. I meant unknowable unknowns. Think a variable X that will never have value ass

Radio waves are knowable,there are unknown unknowns and that's not what I meant. I meant unknowable unknowns. Think a variable X that will never have value assigned to it. The concept seems ridiculous but on your point,for a long time the concept of the number 0 ( defining non-existance of quantity as a value) was not considered or thought of as useless thing.