The force between them decreases, as the square of the distance.
For example ...
-- If you move them apart to double the original distance, the force becomes (1/2²) = 1/4 of the original force.
-- If you move them apart to 3 times the original distance, the force becomes (1/3²) = 1/9 of the original force.
-- If you move them apart to 5 times the original distance, the force becomes (1/5²) = 1/25 of the original force.
(Gravity works exactly the same way.)
