Again the Schneiders, who have created so many fine excursions for young people into the world about them, handle difficult material in a lucid, simplified manner. In brief, easy-to-digest sections, the reader is introduced to his world and universe -- the relative size and properties of the earth, the sun, moon, stars, planets, space and the phenomena of night and day; ""up and down"" in relation to our earth; gravity; and such natural questions as, ""how do we know the earth is round?"", ""why can't we see the stars in the daytime?"", ""what is the sky?"" are answered with a direct appeal to the child's imagination and his observation.