394] 



Our Earth and Its Fellow Planets 



sunshine goes far beyond the Pole, making long days (summer) 

 on the northern half of the earth. When the earth reaches a differ- 

 ent stage in its journey around the sun so that the North Pole- 

 always pointing in the same direction begins to tip further and 

 further away from the sun, daytime on the northern half of the 

 earth grows shorter: Winter is approaching. 



If the earth's axis were not tilted if the axis were straight up 

 and down in relation to its path around the sun, the sun would 

 always appear directly over our equator, and throughout the earth 

 the days and nights would be of equal length. 



WHY WE HAVE CHANGING SEASONS 



The slant of the sun's rays affects the earth's seasons. In 

 the United States the rays are most nearly vertical coming almost 



SPRING 



SUMMER 



WINTER 



AUTUMN 



SEASONS CHANGE AS THE EARTH TRAVELS AROUND THE SUN 

 The variation in the way the sun's rays reach us causes the seasons of spring, 

 summer, autumn and winter; and the variation results because the earth's axis is 

 not exactly perpendicular to its path around the sun, but is tipped toward the 

 north. The axis always points in the same direction, but the fact that it is tipped 

 causes the North Pofe to pofnt away from the sun during our winter and toward 

 the sun in summer. We receive only one two-billionth of the sun's energy. 



