Eager to increase his understanding, I put a lamp in the middle of the floor to act as the sun, got down the world globe, and used a tennis ball for the moon. Then I walked around the "sun", carrying the globe and turning it, explaining how we are suspended in space, constantly moving. It was the universe in a nutshell - sun, earth, moon, stars, seasons.
My son watched the production with silent, squint-eyed attention. When I finished, he said to me, "You don't expect me to believe that, do you?"