galaxies?
Galaxies (like everything else in the universe) are composed of atoms, and there are some intriguing similarities between an atom with its electrons orbiting the nucleus, and the solar system with the planets orbiting the sun. However, the physical laws governing the atom are very different from the laws that govern the solar system and galaxies. For atoms, quantum mechanics governs the behavior, while for galaxies and planetary systems, gravity plays the major role.
