Sister Where Does the Sun Go at Night?

Little Brother's inquisitive mind is always full of questions for Big Sister. He knows Big Sister has all the answers, because she is always reading one big fat book or another. In this book, Little Brother wonders where the sun goes at night. Does he just go to sleep after a long day at work, or does he sink down into the ocean deep to make it daylight for the mermaids who frolic there?