  Based on quantum origin of the universe, in this article we find that the
universal wave function can be far richer than the superposition of many
classical worlds studied by Everett. By analyzing the more general universal
wave function and its unitary evolutions, we find that on small scale we can
obtain Newton's law of universal gravity, while on the scale of galaxies we
naturally derive gravitational effects corresponding to dark matter, without
modifying any physical principles or hypothesizing the existence of new
elementary particles. We find that an auxiliary function having formal symmetry
is very useful to predict the evolution of the classical information in the
universal wave function.
