The term that gives the novel its title, dark matter is the theoretical substance that comprises most of the universe. Physicists hypothesize dark matter exists to account for observations of astrological phenomena that can’t be explained by currently established scientific laws, such as the law of gravity and general relativity. There is no way to measure or observe dark matter; it does not emit or interact with electromagnetic waves, but it exerts a gravitational pull on objects around it. Dark matter is integral to the universe as we know it: The universe would be structured differently without its presence.

In the novel, dark matter symbolizes love. Just as dark matter exerts an invisible gravitational pull, the unseen force of love pulls Jason ever towards Daniela and Charlie. Both dark matter and love are responsible for Jason’s ability to travel between worlds to get back to his family. Both are undeniably real, but neither is observable on its own. In Chapter 6, Jason2 explains to Daniela that dark matter may be the key to the multiverse. He likens the world they inhabit to a small pond. Daniela replies, “So all these other thousands of ponds are all around us, right at this moment—but we just can’t see them?” (113).