46 GRA VITA TloN. 



.ECTION II. 



GRAVITATION. 



98, What is Gravitation? Every particle of 

 matter in the universe has an attraction for 

 every other particle. This attractive force is 

 called gravitation. 



99. Three Important Facts. In respect to 

 gravitation, three important facts have been established : 



(1.) It acts instantaneously. Light and electricity 

 require time to traverse space ; not so with this 

 force. If a new star were created in distant 

 space, its light might not reach the earth for 

 hundreds or thousands of years. It might be in- 

 visible for many generations to come, but its putt 

 would be felt by the earth in less than the twink- 

 ling of an eye. 



(2.) It is unaffected by the interposition of any 

 substance. During an eclipse of the sun, the 

 moon is between the sun and the earth. But 

 at such a time, the sun and earth attract each 

 other with the same force that they do at other 

 times. 



(3.) It is independent of the kind of matter, but 

 depends upon the quantity or mass and 

 the distance. We must not fall into the error 

 of supposing that mass means size. The planet 

 Jupiter is about 1300 times as large as the earth, 

 but it has only about 300 times as much matter 

 because it is only 0.23 as dense. 



