Father, why is the sky blue?' - the child is not really interested in the sky as such; the real stake of the question is to expose father's impotence, his helplessness in the face of the hard fact, to present the whole chain of reasons leading to it. The blue of the sky thus becomes not only the father's problem, but in a way even his fault. The sky is blue, and you're just staring at it like an idiot incapable of doing anything about it!