Near the beginning of Interstellar, the protagonists harvest an old Indian army surveillance drone that buzzed over their property. Its passage seems random until shortly thereafter when all the huge automatic combines and harvesters in the area converge on the farm house.

What summoned these vehicles to the farmhouse? Why? If the answer is "gravitational anomalies," why would agricultural equipment and surveillance drones pursue such anomalies?


Yes, the answer is gravitational anomaly and agricultural equipment and surveillance drones actually pursue such gravitational anomalies. Because both of those machines require GPS system to control them; to give them exact location at exact time. Gravitation makes clock slower and GPS system uses calculations of General Relativity to keep time matching with the ground. But gravitational anomalies can disturb those calculations used in GPS system and make those machines to lose or misunderstand (roughly speaking) their positioning and timing commands.

Edited to add: One can find this in 'The Science of Interstellar' by Kip Thorne

The GPS system that Cooper has adapted to control harvesting machines, as they roam through corn fields, has also gone haywire, and a bunch of harvesters have converged on his farmhouse. He attributes this to gravitational anomalies that screwed up the gravity corrections that any GPS system relies on.

  • I just rewatched the movie and can state that the movie never explicitly states this but I agree that it is the only thing in the movie which explains the behavior of these machine. Cooper does state that if it were a magnetic anomaly they would have noticed the behavior when they moved in. The only anomaly that could explain the behavior that occurred in movie was the gravitational anomaly. – Jim2B Apr 12 '15 at 20:58

I think TARS reprogrammed them when he was in the Teseract. So he actually was the ace in the self-serving paradox. If true, AI saved humanity. Brilliant really, as how could humans save themselves? The universe is a simulator and "they" is AI.

Whoops, I took the Red Pill.


I think the gravitational anomaly caused by Murph's bedroom messed up the GPS signals that the harvesters were relying on. Then when they lost navigation (or for any malfunction) they were probably programmed to drive themselves back to the farmhouse (by dead reckoning) for maintenance.

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