THE UNIVERSAL FORCE. 
199 
If we lay two blocks of wood on the table, 
they undoubtedly attract each other, but the attrac¬ 
tion is not strong enough to overcome the hold¬ 
ing-back force of friction and move them toward 
each other. 
Reasoning along this line, Newton concluded that 
every particle of matter in the universe attracts every 
other particle, and if they were not kept apart by 
other forces they would be drawn together. By 
mathematics Newton computed that a man standing 
on this planet is attracted three thousand six hundred 
times as much by the earth as he is by the moon, 
supposing the two spheres to be of like density. That 
is, the amount of gravitation is proportionate to the 
mass, and increases as the square of the distance be¬ 
tween the bodies diminishes. The force exerted upon 
a stone on the earth’s surface by the earth, is to the 
force exerted on that stone by the moon as the 
square of sixty is to the square of one, the distance of 
the moon from the earth’s center being sixty times 
the distance from the earth’s surface to its center. 
If the moon did not have a moving force of its own, 
which tends to carry it on in a straight line, it would 
quickly be drawn to the earth. 
Newton’s two laws, then, are: The attraction of 
gravitation between two bodies varies (1) directly ac¬ 
cording to their mass; (2) inversely as the square of 
the distance between them. No laws promulgated by 
science have been more positively proved by both 
astronomers and physicists than these two. 
