1. Book Three

2. Reading Preview 1. Do you know what the sky is? 2. How do rockets work? 3. Have you ever dreamed to travel in space?

3. Book Three RocketsRockets in the Sky What is the sky? Where is it? How high is it? I’m sure these questions are always asked by people. They are very difficult to answer, aren’t they? If someone asked you: “What color is the sky?” I expect you would answer: “Blue.” I’m afraid you would be wrong. The sky has no color. When we see blue, we are looking at blue sunlight.sunlight

4. Book Three Is the sky full of air? We know that there is air around the world. We could not breathe without air. Airplanesbreathe could not fly without air. They need air to lift their wings. Airplanes cannot fly very high because as they go higher, the air gets thinner. If we go far enough away from the earth, we find there is no air. Perhaps we can answer some of our questions now. What is the sky? Nothing. Where is it? It is all around the world. The sky is space. In this space there is nothingspace except the sun, the moon, and all the other stars.

5. Book Three Let’s say something about the moon, which has been greatly studied by the scientists. The moon is about 384,000 kilometers away from the earth. An airplanekilometers cannot fly to the moon because the air reaches only 240 kilometers. Then there is no air. But there is something that can fly even when there is no air. This is a rocket. How does a rocket fly? If you want to know, get a balloonballoon and then blow it up until it is quite big. Do notblow tietie up the neck of the balloon. Let go! The balloon will fly off through the air very quickly. The air inside the balloon

6. Book Three tries to get out. It rushes out through the air. It doesn’t need wings like an airplane.wings This is how a rocket works. It is not made of rubber like a balloon. It is made of strong but light metal. There ismetal gas inside the rocket. The gas is made very hot. When it rushes out of the end of the rocket, the rocket is pushed up into the air. Rockets can fly far out into space. Rockets with men inside them have already reached the moon. Several rockets without men have been sent to other worlds much farther away. One day they may be able to go anywhere in space.

7. Book Three rocket ： object driven into the air by an explosion or by gas

8. Book Three sunlight ： strong light of the sun

9. Book Three breathe ： to take air into the lungs and send it out again

10. Book Three space ： what is above the surface of the earth

11. Book Three kilometer ： 1,000 meters

12. Book Three balloon ： bag filled with gas to make it rise in the air

13. Book Three blow ： to send air quickly out of the mouth

14. Book Three tie ： to fasten or bind (with string, rope, wire, etc.)

15. Book Three wing ： two large side pieces of an airplane

16. Book Three metal ： things such as iron, steel and gold