Lesson CCXXXIV

The Moon

Leading thought—The moon always has the same side turned toward us so we do not know what is on the other side. The moon shines by reflected light from the sun, and is always half in light and half in shadow. The moon has neither air nor water on its surface and what we call the moon phases depend on how much of the lighted surface we see.

Method—Have the pupils observe the moon as often as possible for a month, beginning with the full moon. After the suggested experiment, the questions which follow may be given a few at a time.

Experiment for recess—Darken the room as much as possible; use a lighted lamp or gas jet or electric light for the sun, which is, of course, stationary. Take a large apple to represent the earth and a small one to represent the moon. Thrust a hat pin through the big apple to represent the axis of the earth and also the axis about which the moon revolves. Tie a string about a foot long to the stem of the moon apple and make fast the other end to the hat pin just above the earth apple. Hold the hat pin in one hand and revolve the apple representing the moon slowly with the other hand letting the children see that if they were living on the earth apple the following things would be true:

1. Moving from right to left when the moon is between the earth and the sun it reflects no light.

2. Moving a little to the left a crescent appears.

3. Moving a quarter around shows the first quarter.

4. When just opposite the lamp, it shows its whole face lighted turned toward the earth.

5. Another quarter around shows a half disc, which is the third quarter.

6. When almost between the sun and the earth the crescent of the old moon appears.

7. Note that the moon always keeps one face toward the earth.

8. Note that the new moon crescent is the lighted edge of one side of the moon, while the old moon crescent is the lighted edge of the opposite side.

9. Make an eclipse of the moon by letting the shadow of the earth fall upon it, and an eclipse of the sun by revolving the moon apple between the sun and the earth. The earth’s orbit and the moon’s orbit are such that this relative position of the two bodies occurs but seldom.

Observations—1. Describe how the moon looks when it is full.

2. What do you think you see in the moon?

3. Describe the difference in appearance between the new moon and the full moon, and explain this difference.

4. Where does the new moon rise and where does it set?

5. When does it rise and when does it set?

6. Where and when does the full moon rise and where and when does it set?

7. How does the old moon look?

8. Could the crescent moon which is seen in early evening be the old moon instead of the new; and, if not, why not?

9. When and where do we ordinarily see the old moon when it is crescent shaped?

10. Does the moon rise earlier or later on succeeding nights? What is approximately the difference in time of moonrise on two successive nights?

11. Do you think we always look at the same side of the moon? If so, why?

12. Is more than one side of the moon luminous? Why?

13. How many days from one new moon until the next?

14. How long is the day on the moon and how long the night?

15. How many times does the moon go around the earth in a year?

16. What is the difference between the disappearance of the old moon and an eclipse of the moon? In both cases the moon is hidden from us.

The Physical Geography of the Moon

Questions for the pupils to think about and answer if they can—17. Since it has been proved that there is no air or water on the moon, could there be any life there?

18. Supposing you could do without air or water and should be able to visit the moon, what would you find to be the color of the sky there?

19. Would there be a red glow before sunrise or beautiful colors at sunset?

20. Would the sun appear to have rays? Could you look at the sun without being blinded?

21. Would the stars appear to twinkle? Could you see the stars in the daytime?

22. How would the shadows look? If you could step into the shadow of a rock at midday, could you be seen?

23. Could you tell by looking at it whether a mountain was far or near?

24. It is estimated that the temperature of outer space is 250 degrees below zero, and the sun’s direct heat is 500 degrees above zero. If this be correct, how hot would it be in the sunshine on the moon? How cold would it be at midnight?

25. Why is it so much hotter and colder on the moon than upon the earth?

26. If you could shout on the moon, how would it sound? If one hundred cannons should be fired at once on the moon, how would it sound?

27. Is there any rain or snow on the moon? Are there any clouds there? If there are no air and water on the moon, would the intense heat and the powerful cold affect the soils or rocks, as freezing and thawing affect our rocks?

28. Professor Newton estimated that the earth meets seven million meteorites (shooting stars) every twenty-four hours. Why do we not see more of these? What happens when a meteorite strikes the moon?

29. The moon is so small that the force of gravity on its surface is one-sixth that on the earth’s surface. If a man can carry seventy-five pounds on his back here, how much could he carry on the moon? If a boy can throw a ball one hundred yards here, how many yards could he throw on the moon? If a boy can kick a football one hundred and thirty-five feet in the air here, how far could he kick it on the moon?