Dr. Mann (Symbol)
Dr. Mann begins Interstellar as a symbol of hope for all those at NASA who believe there is a way to save humanity, and this symbolism is a prominent reason why Cooper's crew choose to go to his planet over Edmund's. Ultimately, however, Dr. Mann becomes a symbol of the great human capacity for selfishness and betrayal. The dismal conditions coupled with the knowledge that he was going to die alone on his planet poisoned his mind, turning him into a manipulator obsessed with self-preservation. That his name is literally Mann is a nod to the fact that his fate could’ve potentially been that of any human.
Cooper's Watch (Symbol)
Cooper's gift of a watch to Murph in their tear-jerking goodbye scene is a symbol of their connection across time. That Murph leaves it untouched in her bedroom for so many years represents her desire to remain detached from her father's painful memory, such that when she ultimately does return her room to retrieve the watch, it coincides with her breakthrough realization that her father is communicating to her from another dimension. Additionally, Cooper's use of the physical watch itself to establish this connection only further speaks to its symbolism of their unbreakable connection.
Voices Turning Into Narration (Motif)
One recurring motif in Interstellar is having speech turn into narration as we switch from the speaker to a new visual. This happens frequently in the beginning of the film, when the various interviewees speak first to the camera directly, and then continue to talk as we switch to scenes of the new Dust Bowl. Other examples of this motif include when Professor Brand reads aloud the Dylan Thomas poem "Do Not Go Gentle" as we switch from his video message to a view of the Endurance from space. And, of course, the film concludes with an older, bedridden Murph telling Cooper to find Brand, and her words turn to narration as we see Brand setting up camp on Edmunds' planet and Cooper commandeering a Ranger to join her there.
Silence in Space (Motif)
Interstellar consistently features shots in space that have no sound, creating a distinction between diegetic and non-diegetic audio. Diegetic elements of a film are those that exist within the world of the story, i.e. things the characters can experience and perceive, like dialogue. Non-diegetic elements exist only for the audience, like the soundtrack or narration. As there naturally is no sound in space, Nolan removes it from the shots taken "from space" entirely, grounding the audience in reality by allowing us to experience space as silently as real astronauts do. The Endurance’s retro-boosters, the docking of the Ranger with the Endurance, even the explosion Mann causes aboard the station later in the movie: all of these exciting moments happen silently. The exception to this, of course, is Hans Zimmer’s epic, non-diegetic score, which keeps the audience enthralled in the drama and helps us transition between silent space shots and sound-heavy ones inside the space crafts.
Scenes Shot From Onboard Perspectives (Motif)
During Cooper’s crash scene, we briefly experience a cinematographic choice that will become a recurring motif by the time he heads into space: Christopher Nolan chooses to show much of the film’s spacecraft action from cameras seemingly mounted on the outsides of the ships themselves. These angles mimic the externally-set cameras on many of NASA’s real-life space shuttles and rockets, which allow the viewer to experience the vessel’s journey as if they were on board. In choosing to show us many of the film's spacecraft flight maneuvers this way, such as those of the Endurance and the Ranger, Nolan places the audience in the role of astronaut alongside Cooper and his crew to deeper involve us in the onscreen action.
