LAS VEGAS (AP) — Universal started out its CinemaCon presentation with the big one: New footage from Christopher Nolan’s “Oppenheimer.” “I know of no more dramatic tale, with higher stakes, twists and turns, paradoxes,” Nolan told a room full of theater owners Wednesday in Las Vegas. “In learning about that story, I wanted to be in that room and see what that must have been like.” “Oppenheimer,” due in cinemas on July 21, is about J. Robert Oppenheimer, the brilliant, charismatic physicist who, along with his peers at Los Alamos, developed the atomic bomb and changed the world. Cillian Murphy, a frequent Nolan collaborator going back to “Batman Begins,” plays the title role in a starry cast that includes Matt Damon, Emily Blunt and many more.