Falling body experiments have shown gravity is not an attraction. It is a force of all elements moving toward a target in uniform acceleration regardless of their differences in composition, shape, size, and distance. Only one momentum can build such one way concentrative force, head-on congregation from gentle pairing to high speed collision. It can be started by electromagnetic attraction-repelling or disturbance in the environment. A terrestrial planet, for example, is the coalition of elements. It grows in the process of construction. The coalition builds the body and the force of keeping it together, gravity.
Natural and mankind build structures from ground up. Out of fundamental elements to complex living organisms. I believe this is the principle of creation and growth. Large structure is the collection of sub-structures. Higher level structure can not exist unless it's components were made. The gathering builds a body and force of coalition. The Kepler Mission of NASA have discovered many "nomad" planets floating through the galaxy with no star like our Sun to anchor them. I also believe we will continue to discover more planets. It would multiply outnumber stars with the improvement of our night vision.