A character explains Time Travel, Faster-Than-Light Travel, Teleportation, or wormholes by folding a sheet of paper (or something similar) in half to illustrate the theory of an Einstein-Rosen Bridge. Usually they indicate two points at opposite ends of the sheet, then fold the sheet so that the points touch. If they really want to get their audience's attention, they might create their metaphorical wormhole by stabbing a pen through the two points.
Truth in Television: the piece of paper explanation has become so ubiquitous that it turns up in many real-world scientific explanations of wormholes and space/time.
- A variation in Rocketship Voyager. While explaining various theories of Faster-Than-Light Travel to Tom Paris, B'Elanna Torres uses a slide rule to demonstrate folding space instead of a paper and pencil, and a bubble of alcohol floating in zero-gravity (from a squeeze-tube of illicit moonshine) to demonstrate a warp bubble.
- Happens in Déjà Vu when Doug demands a Layman's Terms explanation for how the scientists established a live feed connection to a timeline four days in the past. Denny holds up a blank sheet of paper and then folds it to explain how they folded space and time to create a wormhole into the past.
- In Event Horizon, the ship's designer William Weir (Sam Neill), demonstrates the concept with the centerfold page from a magazine.
- On the way to the wormhole in Interstellar, Romilly does some exposition talk to explain the wormhole idea to Cooper. Interestingly, the movie refers to the hole as a sphere rather than a tunnel, which is scientifically correct.
Romilly: So they say you want to go from here, to there. [holds up a blank sheet] But this is too far. So a wormhole bends space like this so you can take a shortcut through a higher dimension. [folds paper and pierces it with a pen] Okay so, to show that they've turned three-dimensional space into two dimensions, which turns a wormhole in two dimensions? ... A circle. What's a circle in three dimensions?
Cooper: A sphere.
Romilly: Exactly. A spherical hole.
- In the My Teacher Is an Alien series, a random alien explains the ship's movement using a noodle-like alien food. The book also makes a point that said alien knows the general theory but can't explain the mechanics of how it works, because he's not actually an engineer, much as how most people have only a vague idea of how an internal combustion engine works.
- Subverted in The Restaurant at the End of the Universe, in which Ford Prefect starts with a napkin, and subsequently completely fails to explain to Arthur Dent why Milliways is protected from the destruction of the Universe.
- In The Wheel of Time, Rand uses this with a cloth to explain his method of Thinking Up Portals to a female channeler. Since the Mars-and-Venus Gender Contrast is hard-coded into the magic system, she's quite disturbed by the notion of distorting and puncturing the fabric of reality, while he's equally confused by her own method of somehow turning the destination and origin points into the same location.
- In A Wrinkle in Time, the protagonists are shown an ant walking across a cloth, how it has to travel such a far distance to get from one side to the other. But, by folding the cloth so that the two ends are right beside each other, the ant can travel the whole distance by only going a few steps.
- Skeleton Crew: Not physically demonstrated but the analogy is made in "Mrs Todd's Shortcut". Homer discovers evidence that Mrs Todd's shortcuts are taking fewer miles than are in a straight line between the trip origin and its destination, something that would be impossible in reality. Mrs. Todd compares the shortcuts to folding a map to bring two points closer together, suggesting she has discovered a warped version of reality, akin to a wormhole.
- The Long Way to A Small, Angry Planet features a crew of space travellers whose job is to construct wormholes, or tunnels, for intergalactic travel in a story set in a somewhat unified galaxy. These tunnels allow the public to travel from space to space in a way that's akin to an average commute, maintaining the consistency of time despite the actual speed of light between spaces. Newcomer ship clerk Rosemary Harper gets a crash-course on how tunnelling works from ship mechanic and resident Cloudcuckoolander Kizzy Shao, who begins by using her porridge and the space above it as an example of the distance their ship travels to "punch" a hole within the fabric of space. She's about to launch a blueberry across the counter with a spoon when she remembers she "can't fold porridge", and uses a much more foldable napkin instead. It plays out pretty much similarly with all the other examples, though emphasis is made on the work involved in keeping the sublayer (the "space" between space) from ripping apart after they've punched two holes through space.
Kizzy: (Holds up clean napkin, gripping the two opposite corners) Okay. You know the big grid-like spheres surrounding tunnel openings? [...] Those are containment cages. They keep space from ripping open any farther than we want to. You have to have one cage on each end of the tunnel. (Gestures with the corners of the napkin) So if we've got one cage at this end, and another cage at this end, we've got to construct a tunnel that effectively makes it so that this - (Stretches the corners far apart from one another) - is the same thing as this. (Brings the corners together)Rosemary: (Frowns) Okay, so, the cages are light-years apart. They're not in the same place. But...they behave as if they were in the same space?Kizzy: Pretty much. It's like a doorway connecting two rooms, only the rooms are on opposite sides of town.Rosemary: So the only place the distance between those two points has been changed is...within the tunnel?Kizzy: (Grins) Physics is a bitch, right?
- In Robert A. Heinlein's Starman Jones, a character explains the "anomalies" that allow for interstellar travel by folding another character's scarf (which conveniently even has a stylized picture of the Solar System on it, allowing him to talk about the difference it makes in traveling from "Mars" to "Jupiter" with or without the scarf folded over).
- In The Ballad of Black Tom, Suydam's explanation for going Outside is: Imagine a cotton ball stuck to a strip of adhesive tape. Now imagine crumpling the tape, so that many different points touch the same cotton ball. The ball represents the room we're in.
- In Quantum Leap Sam uses the term "string theory" to explain his leaping. Imagine your life as a piece of string, with one end (birth) and the other end (death). If you ball the string up, every day of your life touches every other day out of order, so you can jump from one to another, therefore time-travelling within your own lifetime.
- Mentioned in the Stargate SG-1 episode "Enigma". When Daniel takes Omoc outside to send a FTL transmission to the Nox, he asks Omoc to explain how his message can cross interstellar distances in an instant. At first reluctant (due to the Tollan rule about not giving technology to younger races), Omoc takes a branch and bends it, so that the ends touch, explaining that the distances seem to be far away, until you merge the points together (paraphrasing). Daniel assumes he's talking about space folding, causing Omoc to shake his head in disappointment and shut up on the subject.
- In Episode 5 of Stranger Things, the science teacher uses this method to explain to our kid heroes how they could create a doorway to the "Upside Down" dimension. He takes a paper plate, folds it and pierces it with a pen.
- In Dark (2017), the inventor Tannhaus uses a rolled-up sheet of paper to demonstrate time travel via wormhole to a visitor.
- In Lighthouse: The Dark Being, Dr. Jeremiah Krick used his titular lighthouse to create a portal device. His theory follows this trope to the letter, but when he gets it working, it instead creates a portal to a Parallel Universe, which he perceives as his portal crumpling a second sheet of paper against ours.
- As noted above, in the Interstellar example, space being three-dimensional instead of two-dimensional means that if wormholes existed things would be more complicated, them being spherical and tunneling through an extra dimension—and that the similar comparison of a black hole with the funnel caused by something heavy put in an elastic sheet is a simplification; it being also a sphere. Better not to think too much about it.