THE EARTH 



IS 



" new moon " 



(Figure 10). When it has completed a 

 fourth of its journey, we see one half of its' illuminated 

 surface or one fourth of its total surface ; this is the 

 " first quarter." When it has completed half its circuit 

 and is on the opposite side of the earth from the sun, 

 we see half of its total surface or its whole illuminated 

 surface ; it is then " full moon.' 7 When it is at the third 



> --0-- 



Sun's /~l 

 ~_7iays . 



Earth 



-o- 



FIG. 10. Phases of the Moon. 



quarter, we again see one fourth of its total surface or 

 one half its illuminated surface. 



The moon rises about fifty minutes later each day 

 than on the previous day. It has moved eastward 

 from the place where it was the day before, and so the 

 earth must turn a little farther on its axis before the 

 moon comes into view at the horizon. 



The Sun. The sun is the center of, and by far the 

 largest and most important body in, the solar system. 

 All the planets of the system revolve about it and receive 



