An alternative theory has been proposed to dark matter and dark energy. Instead of the universe being dominated by said invisible components, it's actually gravity changing on the relevant scales.
http://www.bbc.co.uk/news/science-environment-12571965
Critics have slammed it, however it better predicts the relationship between a galaxies' rotation speed and its mass, not to mention actually addresses the "flat rotation curve" problem, one of the major unsolved problems in physics.
http://www.bbc.co.uk/news/science-environment-12571965
Critics have slammed it, however it better predicts the relationship between a galaxies' rotation speed and its mass, not to mention actually addresses the "flat rotation curve" problem, one of the major unsolved problems in physics.