In Gravity Falls, there exists the Natural Law of Weirdness Magnetism which creates an invisible barrier around the whole town and the surrounding area. This barrier in turn prevents any sort of weirdness from leaving the town. This barrier was initially hypothesized and periodically studied by Ford Pines, who eventually figured out an unknown equation that could collapse the barrier.
During the event of Weirdmageddon, Bill Cipher sought to find a way to remove the barrier in order to spread his weirdness all across the dimension. Bill attempted to force Ford to give him the equation that would allow this, but his efforts were ultimately thwarted, ultimately leading to his demise.
History[]
Ford Pines initially hypothesized on the barrier's existence after discovering the increased levels of anomalies and paranormal events in Gravity Falls. His research on this phenomenon lead to his discovery of Crash Site Omega, though he could not determine if the spacecraft was the causal link for the phenomenon or if it was simply more evidence for its existence.
In "Weirdmageddon 2: Escape From Reality," Bill announces his plan to spread weirdness across the globe. He immediately opens a door in the Fearamid and orders the Henchmaniacs to do so. However, they quickly fly into the invisible barrier, hitting it and falling to the ground. Bill is shocked and enraged by this revelation, but later realizes that Ford could help with this predicament.
In "Weirdmageddon 3: Take Back The Falls," Bill brings Ford to his penthouse to inform him of the barrier. Ford explains what it is and says a simple equation can cause the barrier to collapse, but of course, he refused to tell Bill what it was. Bill tried to coax him into relenting by promising that he will be all-powerful while he reshapes the world and hosts an eternal party, but Ford was persistent. With that not working, Bill tried to enter Ford's mind to find the equation himself, but that wasn't possible unless he let him in via handshake. Seeing himself at a dead end, Bill decides to try and find Ford's weakness and force him to talk, starting with torturing him.
After Ford and Stan break the zodiac over a petty fight, Bill turns the others into tapestries and demands how to remove the barrier from Ford again. After threatening to kill either Dipper or Mabel, Ford seemingly relents in letting him into his mind so he can find the equation. However, it turns out that he swapped clothes with Stan and they pretended to be each other so Bill would enter Stan's mind instead. Once inside, Ford used the Memory Gun to destroy Bill for good, but this came at the cost of losing Stan's memories.