Question

what is the ratio of force between two masses kept at a certain distance in air to force between them when kept in any other medium ?

Answer 1

fGravitational force does not depend on the medium. There will be no change in the force on each other.

However, the force may increase due to the medium attracting the objects. When I say the force will not change, I mean the force due to the objects themselves will not change. That is, the medium does not hinder or boost the ‘force fields ’ if you will.

The medium will separately attract both the objects towards itself if it is something placed only in between the objects.

Different case is if the medium is a large fluid or other material which completely envelopes the objects on all sides to infinite distance. Something like dropping 2 balls in the ocean. In that case, the force will remain same.

This is in stark contrast to electromagnetic force which does depend on the medium.