A child asks why because the world has not yet convinced them that ordinary means understood.

Children keep asking because nothing has yet taught them that the common is the known. Adults stop, not from having found the answers but from having grown accustomed, which the mind files as the same thing. The questions a five-year-old asks about why the sky is that color or why people die are not naive; most of them are hard, and most adults cannot answer them.

When a child asks something you cannot answer, say so and look it up together. And borrow the habit for yourself. Asking why about something you have stopped noticing is available to you at any age, and the only thing standing in the way is the assumption that you already know.