Are there any theories of gravitation and spacetime that don't require the existence of dark matter to explain the peculiar rotation of galaxies and don't require dark energy to explain the expansion of space? I would love some links. These things just seem suspiciously like luminiferous ether to me. I would be absolutely fascinated by an explanation of the universe that doesn't require 95% of the universe to be invisible, because of course invisible things are often imaginary. It doesn't matter to me how crackpot the theories seem as long as they explain those two phenomenon without resorting to dark matter or dark energy.