In astronomy, the rule was if you can’t see it, it’s not real. Tell that to the astronomers who discovered dark energy or dark matter … or, more recently, Planet 9. Find out how we know what we know about the latest cosmic discoveries – even if we can’t see them. Plus, did dark matter do in the dinosaurs? And the winner of the 2015 Nobel Prize in physics explains why neutrinos may hold clues to the origin of the universe.