THE EARTH AS A PART OF THE SOLAR SYSTEM 525 



five times that of the largest cratnr on the earth. Immense 

 mountains are also found on the moon, some ranging from 

 six to seven miles in height, exceeding any mountain on the 

 earth. These craters show that formerly there was much 



I'IG. 208. Features of the moon as seen in a telescope, showing the large number 

 of volcanic craters. 



volcanic activity on the moon; but now the moon has 

 cooled down so that it is extremely cold. 



There is no air on the moon, and there is no water. Hence 

 there are no clouds and there is no diffused light. Only 

 those objects can be seen that stand in the direct sunlight. 

 As there is no air, no sound could be heard. The force of 



