This is a reminder that there will be spoilers.
Meanwhile back on Earth, a now adult Murph is a scientist working alongside Professor Brand, father of scientist/astronaut Amelia Brand. Prof. Brand concocted two plans to save the human race: Plan A consists of building space stations capable of transporting people to whichever planet is deemed best. Plan B is to use the ferilized eggs onboard Endurance to populate one of the planets. The twist is that Prof. Brand knew that Plan A was never going to work because he couldn’t resolve the math. He also knew that without Plan A, the government wouldn’t fund the project.
The crew of the Endurance arrive on Mann’s planet, only to find out Mann falsified the data so that NASA would send a shuttle and he could go home. The fiend!
Anyway, stuff happens, Romilly and Mann are dead, so Coop and Brand have no choice but to take their damaged spacecraft to Edmunds’ planet. In order to do this, they must first slingshot around the wormhole and drop the ship’s weight. The robot TARS was ejected into the wormhole so it could collect data and send it back to Earth.
Side note: Anyone else expect Coop to say, “I hate funny robots,” at some point in the film?
Just me then?
Coop disengages his shuttle from Endurance so that Brand will have an even better chance at reaching her destinaton. Then Coop hits the eject button. What happens next is best explained by someone far smarter than I, because it gets more than a bit timey wimey.
Anyway you look at it, Coop and Romilly’s decision to go to Mann’s planet was the correct call. It doesn’t matter if the decision was based on data, logic, instinct, selfishness, or whatever. If they had gone to Edmunds’ planet without ever going to Mann’s planet, it would have caused a paradox that I won’t even try to explain. Yes, I know that the Doctor claims that paradoxes tend to work themselves out, by and large, but Christopher Nolan would never be able to get away with it, because haters.
Interstellar also proved something that I think we all knew in the backs of our minds: The least threatening thing in the universe is Topher Grace holding a lug wrench.