Gravity is just the label we put on something that we don’t know how it works but know that it does.
Mass depresses the fabric of space-time, creating a ‘gravity well’, or so they tell us. Every bit of mass depresses it to some extent.
If you had a universe where only two atoms of hydrogen existed, and they were a billion light years apart, they would eventually collide or settle into a stable orbit around a central point............
Makes me think of the Far Side cartoon where there is a large plain with just one tree, and one dinosaur. The dinosaur manages to walk into the tree.