22 



FIRST YEAR SCIENCE 



ceive light for a longer time during a revolution than other places ? 

 Remove the globe to the opposite side of the light without changing 

 the direction of its axis. When the globe is revolved is there any 

 change in the length of time of illumination of the places before noted ? 

 If so, what? 



As has already been stated, the ancients considered the 

 earth as the center of the universe and thought that the 



sun and stars revolved 

 around it. We of the 

 present day, however, 

 know that it is the ro- 

 tation of the earth from 

 west to east that causes 

 the appearance of the 

 rising and setting sun 

 and thus makes day and 

 night. 



Of course it makes no 

 difference about a person 

 beginning to see a light 

 whether the light is 

 brought toward him or 

 whether he goes toward 

 the light. We are turned 

 into and out of the sun- 

 light by the rotation of 

 the earth. We speak of the sun as rising high in the 

 sky, but what really happens is that we are turned so 

 that the center of the earth, our heads and the sun come 

 nearer and nearer toward a straight line. 



When we say down we mean toward the center of the 

 earth, and when we say up we mean in the opposite direc- 

 tion. These are the only two directions that we could be 

 easily sure of, if it were not for the rotation of the earth. 



MEDIEVAL IDEA OF THE UNIVERSE. 



From a fourteenth-century manuscript. 

 Above the earth are the clouds and the 

 moon ; then the rays of the sun ; next 

 various planets ; above these the stars ; 

 and finally the signs of the zodiac. 



