Who wants to sit and be talked to all the time? When boys and girls are playing games, the greatest pleasure is in taking part, and it's the same way in the Wonderland of Books. Books mean most to those who "get into the game"; who help chase after the answers to things. This hunting for answers up and down among the books is one of the interesting games we're going to play; and those of you who don't come in will miss a lot of fun. That's all _I've_ got to say! Let's begin like this: * * * * * In the Greek myth stories what else was Mr. Apollo supposed to do for the world and its people besides turning on the light?[5] [Footnote 5: Answers to all these questions at the ends of chapters will be found in books you can easily get hold of--encyclopædias, dictionaries, and school-books; or books usually found in home, school, or public libraries. Words in parenthesis or italics indicate the headings where the information referred to will be found.] Why doesn't the force of the earth, whirling along as it does at 19 miles a second, cause the wind to blow us all away? (_Earth._) What is the difference between a planet and a sun? How does the earth compare in size with its brother planets of the sun family? How often would Christmas come around if we lived on the moon? What causes different phases of the moon? Why may we be said to have eclipses of the moon every month? "Moon" and "month" sound a good deal alike when you come to think of it. Don't you wonder why? "Moon" comes from a word meaning "to measure." You'll find the rest of the word-story of the moon in any dictionary that is big enough to tell about the origin of words. By the way--speaking of the timekeepers in the sky--don't forget to look up the lives of the great astronomers mentioned in this chapter. You will find, among other things, how Galileo, when only eighteen years of age, helped to give us our clocks and watches by counting his pulse-beats while watching a hanging lamp swing back and forth in the Cathedral of Pisa; how he found out who "The Man in the Moon" really is and what the "Milky Way" is made of; how he invented the wonderful glass for playing hide and seek among the worlds, and with it found four moons in one night! Yes, and how do you suppose he found that the sun is going round and round like a top, just as the earth does? It was the _simplest_ thing! You'll see!