November 12, 2019
Mankind did not understand the motions of planets and moons until Copernicus, Kepler, and Newton defined the structure and workings of the solar system. Our understanding of galaxy motions is in that early stage today. There is a mystery surrounding the constant rotation rates observed for stars orbiting within galaxies unlike the solar system where more distant planets orbiting the sun do so more slowly than inner planets. Some suggest there something different about gravity in galaxies and they invented dark matter, dark energy and MOND to explain it. But proper analysis of gravity finds it is constant though its environment may vary. So the answer is otherwise.