" But those other realities don’t really exist.” “Actually, they’re just as real as the one you and I are experiencing at this moment.” “How is that possible?” “It’s a mystery. But there are clues. Most astrophysicists believe that the force holding stars and galaxies together—the thing that makes our whole universe work—comes from a theoretical substance we can’t measure or observe directly. Something they call dark matter. And this dark matter makes up most of the known universe. "

― Blake Crouch , Dark Matter