#('this metaphor sorta slides back and forth between sounding like magnetism and sounding like gravity')

[ckret2]

Do you have any headcanon about why during the event of Weirdmageddon, the invisible barrier around Gravity Falls and the surrounding area created by the Natural Law of Weirdness Magnetism, had become a physical barrier that prevented Bill and the Henchmaniacs of leaving the town? And why a equation would be able to collapse the barrier?

Yeah, because they were too weird.

If somebody has like 1 Cuil worth of weirdness in their body, then the weirdness magnet would exert 1 Cuil worth of force dragging their body into town. ("What's a Cuil?" it's a unit of measurement we're appropriating because there AREN'T any IRL units to measure weirdness, just roll with it.) The weirdness of an irregularly shaped jelly bean is like, 0.1 Cuils; so 0.1 Cuils is a strong enough force to counteract the force of gravity on an object that weighs as much as a jelly bean. Ford's weirdness is like, .5 Cuils, so the force dragging him toward Gravity Falls is like,, the same as the amount of force that it would take to make 5 jellybeans roll uphill. Enough to feel a small tug but it's not gonna physically drag Ford into town.

Bill has trillions upon trillions of Cuils worth of weirdness in his body.

The force dragging him into town is like unto the force of a black hole, and the barrier is its event horizon. Bill ain't escaping that event horizon.

As long as Bill's in town, his weirdness is adding to the "mass" of weirdness in town dragging everybody in, so it's sucking like a black hole on everything. Ain't nobody escaping that event horizon.

People take "there's a simple equation to collapse the barrier" too literally.

If I told you "there's a simple equation to halve the amount of cookies this recipe produces," that doesn't mean "if you write a mathematical equation on a piece of paper, this will somehow cause half the cookies to disappear." It means "you take your recipe and its ingredients, you divide all the ingredient measurements by 2 (a simple equation!), and now the recipe will make half as many cookies."

An action (unknown) needs to be performed to collapse the barrier. There is an equation to calculate the (force, direction, weight, duration, wavelength, temperature, whatever) of the action, and maybe even to narrow down what kind of action it needs to be. Ford knows what that equation is.