The movie begins with a dad named Cooper who has two kids, Murph and Tom. They live in the future where the world is plagued with a crop blight and a second Dust Bowl, leaving even the smartest of people (Cooper, a former NASA pilot) to become farmers. Murph is convinced that she has a ghost in her room who drops books and leaves messages in Morse code. Cooper helps her decipher one of the binary messages left in dust and it leads them to the old NASA location that has been “shut down”. https://www.youtube.com/watch?v=_fOwJQpBl5c However, a team of researchers led by Professor Brand has been working on a mission to save humanity. Their goal is to transport Earth’s population to a new home planet through a wormhole. This Plan A is meant to harness 5th dimensional physics and use gravity to launch space station to transport earth’s population to safety. However, he has a secret Plan B in which he wants to launch embryos to a habitable planet and start a new colony as he knows Plan A is impossible. With his kids’ lives and humanity on the line, Cooper is coerced to man a mission to scope out habitable planets with Brand’s daughter, her boyfriend Doyle, and another physicist, Romilly. He leaves on bad terms with his daughter but promises that he will be back. An interesting thing he tells her is that they might even be the same age when he returns, hinting at a time travel element that appears later on. https://www.youtube.com/watch?v=4UmRtfP3b8E When they do make it to space, the only way to reach their planets is through a wormhole that allows them to travel a vast distance of space that would take much longer to travel, faster than the speed of light. It is like a shortcut or tunnel through space of warped spacetime. When imagining a 2-dimensional surface, one would just fold it over, creating this wormhole bridge. It was placed there by earth’s future civilization that had a grasp on 5th dimensional physics. This is an example of a causal time loop in which the future civilization placed the wormhole for Cooper and his crew to travel through, so they could establish this future civilization, so they could create this wormhole and on and on. There was a prior mission that Cooper was not aware of that sent 13 astronauts to explore 13 planets in hopes of finding a habitable one. Unfortunately, only three survived. The first made it to a planet that has a surface covered in three feet of water but that also huge storm waves that would kill anyone in its path. That planets position in relation to the black hole makes time distorted. This black hole was created by mass imploding on itself. In essence, it has a gravitational field so intense that no matter can escape. So, one hour on this planet is over 7 years on earth. Cooper, Brand, and Doyle go to this planet, Miller’s World, while leaving Romilly on the main ship. While on the planet, Doyle gets killed by a wave while Cooper and Brand barely make it off. When they return to the ship in orbit, Romilly is visibly older and tells them 23 years have passed, when they only spent three hours on the planet. Cooper panics and tries to find a way to reverse time, but this is impossible as the arrow of time argument shows. Although time at the microscale is time reversal invariant, meaning that time can flow backward, at the macroscale, it cannot as the physics is not time-reversal invariant. https://www.youtube.com/watch?v=e6ZxU7PxPxc When they reach the second planet, the astronaut that was left there, Dr. Mann is awakened from cryosleep. He put himself to sleep hoping for their arrival to begin repopulating the planet, or so we think. Mann’s World has temperatures too cold without a spacesuit but still “habitable”. Mann then tries to kill Cooper. He reveals that Plan A was never the actual plan. However, Mann dies in an explosion when trying to connect his ship to the station. Brand and Cooper are now the only ones alive, but they are running out of fuel to make it to the last planet, leaving no choice but for Cooper to jettison himself and the excess weight off the main ship. https://www.youtube.com/watch?v=HbsPgGpfKpU This will leave Brand to slingshot up the black hole to reach the last planet with the fuel they have left. It is important to distinguish that Brand does not enter the black hole, but only follows the light cone path right before the horizon, where then nothing can be seen or can escape. Cooper, on the other hand, jettisons himself into the black hole but does not fade from existence. It is understood today that when one enters a black hole, their image will forever be stamped on its surface and they will cease to exist. However, Cooper manages to stay alive and even escapes it down the road. Instead, there is a pocket inside the center of the black hole where Murph’s entire life exists at the same time as when he left her, where she is still a child. However, the only part that he can see is her bedroom. Cooper is trapped in this tesseract, a 4-D cube, that is a 5th dimension and his only form of communication is through time with the use of gravity. This is due to gravity being the only thing that can transcend space and time. According to Einstein’s theory of relativity, gravity bends 4-dimensional space-time into a curvature, a geodesic. Seeing that holograms are 3-D pictures on a 2-D surface, and the fourth dimensions is displayed in observable three dimensions, the fifth dimension is essentially the spacetime fabric. This fabric is smooth, continuous, and can curve when acted on by energy or matter. From this, he pushes books off of her bookcase to send a message through Morse code. His message spells out S-T-A-Y, the phrase that Murphy had told her father her ghost had sent to her before he left. However, at the time he didn’t believe her and ended up going on the mission anyway. He was also the one to line the floor with dust that left them the coordinates that they used to find NASA. While trapped here, he sees the day that he leaves, and tries to warn himself not to go. He even manages to fling a book across the room where his earth self sees, hesitates, but continues to leave. https://www.youtube.com/watch?v=xo3N9Brp2CU However, no matter how hard he tried to get himself to stay, his attempts would have been futile as Cooper was not free of his acts. It is claimed that no one, at any time between arrival in the past and departure in the future, is free in any of their acts. He had to travel to space and go through the black hole in order to leave the messages to Murph when she was a child. Therefore, this black hole was designed specifically for him and his daughter as a means of communication, eventually saving the earth as Murph goes on to study Professor Brand’s work and figures out a solution to save humanity. Once Cooper relays this information to Murph, he is jettisoned out of the black hole, his mission complete, to the side of the universe of Earth where nearly a century has passed in earth’s time. https://www.youtube.com/watch?v=GtTkcM9BfXM When he returns, his daughter is now on her deathbed, when Cooper himself hasn’t really aged at all. Their reunion is cut short as she forces him to leave as she has now accepted his absence all those years and does not want to have her father watch his own child die. https://www.youtube.com/watch?v=ECjYsWLgy3I Cooper agrees and ends up stealing a rocket ship to go back into space to find Brand on Edmund’s World where she is starting the colony with the embryos. In essence, humanity only survived because Cooper was sent into space and into the black hole to communicate with Murph. He had already made the journey before, proving to her that time travel was real. This led her to find the flaws in Professor Brand’s equation, master gravity and save earth.