Gravitation 5 



earth could fall into the sun, and it would do so, if it 

 were not swinging around the sun so fast. You will 

 see how this keeps it from falling into the sun when 

 you come to the section on centrifugal force. 



Why there is a place where things weigh nothing. 

 Now about the place where gravitation has no effect. 

 Since an object near the sun is pulled more by the sun 

 than it is by the earth, and since down here near the 

 earth an object is pulled harder by the earth than by 

 the sun, it is clear that there must be a place between 

 the sun and the earth where their pulls just balance; 

 and where the sun pulls just as hard one way as the 

 earth pulls the other way, things will not fall either 

 way, but will float. The place where the pulls of the 

 sun and the earth are equal is not halfway between the 

 earth and the sun, because the sun is so much larger 

 and pulls so much more powerfully than the earth, that 

 the place where their pulls balance is much nearer the 

 earth than it is to the sun. As a matter of fact, it can 

 be easily calculated that this spot is somewhere near 

 160,000 miles from the earth. 



There are other spots like it between every two stars, 

 and in the center of the earth, and in the center of 

 every other body. You see, in the center of the earth 

 there is just as much of the earth pulling one way 

 as there is pulling the other, so again there is no up 

 or down. 



Application 1. Explain why the people on the other 

 side of the earth do not fall off; why you have weight; 

 why rivers run downhill; why the world does not fall 

 down. 



