THE MOON 



15 



The Moon. We have learned that certain of the planets 

 are accompanied by smaller bodies which are called satel- 

 lites or moons. These moons revolve about their planets 

 just as the planets revolve around the sun. Our own 

 moon revolves 

 around the earth at 

 an average distance 

 of about 240,000 

 miles and makes the 

 circuit of its orbit in 

 a little less than a 

 month. Primitive 

 people measured time 

 by "moons." This 

 is the origin of the 

 word month. 



The moon turns 

 only once on its axis 

 during a revolution 

 around the earth, 

 and so it always 

 keeps the same side 

 toward us. Its 

 periods of daylight 

 and darkness are, 

 therefore, about 14 

 of our days long. 

 The moon has a diameter of about 2000 miles and its 

 weight is about one-eightieth of that of the earth. It has 

 no air or water on its surface. Since it has not the leveling 

 influence of wind and rain and freezing water, the surface 

 is very jagged. It is covered with great crater like 



PHASES OF THE MOON 



Showing roughly the varying positions of the 

 sun, moon, and earth. 



