Blow Minds With This Cool Geometric Torus Trick Using a Piece of Paper 

If your family is easily impressed by feats of paper, this is for you!


If you’re filled with Thanksgiving dread because your NaNoWriMo novel remains unfinished and you’re the only cousin who has neither found nor hitched that perfect soulmate, Inverse has one solid piece of advice: Bust out this nifty trick on Thursday, preferably after the uncles have polished off that third bottle of Merlot, and everyone younger than 10 and older than 65 will be so momentarily wowed they’ll forget you’re going to die alone, cat nibbling the toes of your stiffening corpse.

This bit of geometrical and paper wizardry comes from Tadashi Tokieda and the good YouTubers at Numberphile. The set-up is fairly simple: Cut three sides of a rectangle out of the center of a piece of paper, so that you’ve got what looks like a trapdoor. As Numberphile’s Tadashi Tokieda puts it, the result is a paper switch with two modes, either up or down.

But you can’t flip between modes without having the person holding the flap letting go, right?

Not if geometry has anything to do about it. The secret — and watch the video to get the full effect — is to roll the edges of the flap into twin circles, and then rotate the circles 180 degrees toward the feet to make, in essence, a torus. For those of us whose math classes are faint memories, a torus is the three-dimensional doughnut you get when you spin a circle about a point (as long as the circle doesn’t touch itself on the way around).

A torus becomes a sphere by shrinking the revolutionary axis.

Kieff  via Wikimedia

Once you’ve mastered your toroidal skills, the only thing you have to do is make sure your captive audience keeps their eyes closed until the reveal for the full effect. Next stop: cherished offspring city, population you.