Newton's law of universal gravitation (Sir I. Newton): Two bodies exert a pull on each other with equivalent and opposite forces; the magnitude of this force is proportional to the product result of the two masses and is too proportional to the inverse square of the distance among the centers of mass of the two bodies; scientifically,
F = (G m M/r2) e,
Here m and M are the masses of the two bodies, r is the distance among the two, and e is the unit vector directed from the test mass to the second.