Grown-up people find it very difficult to believe really wonderful things, unless they have what they call proof. But children will believe almost anything, and grown-ups know this. That is why they tell you that the earth is round like an orange, when you can see perfectly well that it is flat and lumpy; and why they say that the earth goes round the sun, when you can see for yourself any day that the sun gets up in the morning and goes to bed at night like a good sun it is, and the earth knows its place, and lies as still as a mouse.