Universal law of gravitation

 Any two masses in the universe attract each other with a force which is 

i) directly proportional to the product of the masses,

ii) inversely proportional to the square of the distance between their centres.

F=GmM/r² 

where G= universal gravitational constant.

m and M are the masses of two bodies.

r = distance between them. 

* Larger the masses , greater is the force between them.

* Larger the distance , smaller is the force.

* If the distance is halved , force increases 4 times.

* If the distance is doubled,  force becomes one-fourth.

* The force is not effected with any medium between the masses.