6 Matter Is Gravitative
The law of gravitation is held as being universal. According to it every particle of matter in the universe attracts every other particle. The evidence for this law in the solar system is complete. Sun, planets, satellites, comets and meteors are all controlled by gravitation, and the movements of double stars testify to its activity among the more distant bodies of the universe. The attraction does not depend upon the kind of matter nor the arrangement of molecules or atoms, but upon the amount or mass of matter present, and if it be of a definite kind of matter, as of hydrogen or iron, the gravitative action is proportional to the number of atoms.