A popular idea in fiction that features
Time Travel is the idea that time is not really any different from space—for whatever reason,
we just can't perceive it as a spatial dimension or travel through it without
technological assistance. Varying explanations are given for this.
In
Real Life, it's (more or less) generally accepted that there are three spatial dimensions that we can perceive and interact with. Time is recognized as a fourth dimension, but with fundamental differences in how it works versus how space works; obviously, we can't just "turn around" and walk backward in time, or "turn around" and "remember" the future.
The idea of time as a spatial dimension has some roots in reality, as time is recognized by
Real Life physicists and theoreticians as being closely tied to the dimensions of space, but not as a physically identical dimension. Additionally, string theory posits that there may be as many as
eleven spatial dimensions that we just haven't evolved to perceive due to our inability to interact with them—a common (and very limited, but go with it for now) analogy is to imagine an ant that can only travel in two dimensions (barring its ability to climb up things, an ant cannot jump or fly), so the ant has naturally evolved to perceive the universe as two-dimensional.
Note that the most common way to play this trope is to have time portrayed as a fourth dimension, which explains why it's mostly encountered in fiction about
Time Travel, but the core idea of the trope is simply that there are more than three spatial dimensions. A work that explores the ramifications of string theory's eleven dimensions, then, would be an unusual, but perfectly valid, example.
One of the earliest explorers of the idea of 4+ spatial dimensions was mathematician and
Science Fiction author Charles Howard Hinton, who coined the term "tesseract", a four-dimensional cube. It's worth noting that
any mention of a tesseract in fiction is practically a stock example of this trope. Hinton also coined the terms "ana" and "kata"
^{note }From Greek roots meaning "up toward" and "down from" respectively, now frequently used to refer to movement along the axis of a fourth spatial dimension (in the same sense as up/down for height, left/right for width, and forward/backward for length).
Note that this trope is
not about just any work that features
Time Travel, nor is it about a work that casually refers to time as a fourth dimension, unless it's made clear that time is being treated as "just another dimension like space".
Frequently found overlapping with
Alien Geometries. The distinction between the two is that under normal circumstances (well, as normal as this sort of thing can be anyway) an object occupying more than four dimensions will still follow all standard rules of normal euclidian geometry
^{note }perpendicular angles are 90 degrees, parallel lines never intersect, squares have straight edges, the angles of a triangle add to 180 degrees, ect.. If the additional dimensions are
curved, however, normal geometry points to
M. C. Escher and
grabs a bucket of popcorn.
Not to be confused with Another Dimension or any of its
Sub-Tropes—this is "dimension" in the sense of geometric dimensions, not parallel worlds or universes. Of course, the two may overlap.
Examples
Anime and Manga
- Doraemon: There are at least four dimensions in existence, as the titular Doraemon's Bag of Holding is referred to as a "Fourth-Dimensional Pocket".
- In The Melancholy Of Haruhi Suzumiya, Mikuru Asahina describes Time Travel as moving in a four-dimensional direction across a series of stills, as in an animation.
- In the world of Tenchi Muyo!, there exist 22 dimensions, each with a 'supervisor' that oversees it. The Choushin Goddesses exist in the 'hyper-dimension' beyond dimensional space, and created the 22 dimensions as an experiment. This is a major plot point of the third OAV.
Comic Books
- In Whatever Happened to The Man of Tomorrow?, Mxyzptlk, an inhabitant of the Fifth Dimension, reveals his true form. Lois Lane struggles to describe it afterwards:
It had height, length, breadth, and a couple of other things. [...] Looking at it made my head hurt.
Fanworks
Film—Live-Action
- Cube 2: Hypercube takes place inside what the film interchangeably refers to as both a "hypercube" and a tesseract. The film is not totally consistent with whether the fourth dimension is, in fact, time, or a fourth spatial dimension in addition to time; it's mostly a Timey Wimey exploration of Alien Geometries.
- Interstellar features unseen higher dimensional entities going through a lot of trouble to provide higher dimensional travel for humans on a dying earth. One scene in particular has these entities attempt to illustrate their perception of time by mapping the timeline of a specific point of space three dimensionally as a tesseract that can be navigated ana and kata.
Literature
Live-Action TV
- Discussed briefly in the first episode of Doctor Who, "An Unearthly Child," demonstrating how strange Susan Foreman is. Worth noting that she's supposedly a 15-year-old girl at this point.
Susan: [About a math problem] It's impossible unless you use D and E.
Ian: D and E? Whatever for? Do the problem that's set, Susan.
Susan: I can't, Mister Chesterton. You can't simply work on three of the dimensions.
Ian: Three of them? Oh, time being the fourth dimension, I suppose? Then what do you need E for? What do you make the fifth dimension?
Susan: Space.
- The Journey of Allen Strange: While wandering around a human high school, Allen overhears a physics class and walks in to "correct" the teacher with Xelan physics, which includes at least fifteen dimensions.
- The first season opening narration of The Twilight Zone starts as follows: "There is a fifth dimension beyond that which is known to man."
Tabletop Games
- Dungeons & Dragons, using "BD&D Immortals" rules. In-Universe, there are five known spatial dimensions. The first three are the standard ones (length, width and depth). The fourth is hyperspace (AKA the "shortcut dimension") and is used for teleportation. The fifth is a horrid alien space called the Nightmare Dimension. It is possible for an Immortal to see into or even enter the 4th and 5th dimensions. There are creatures that exist in the 3rd-5th dimensions: we view them as monsters (and vice versa).
Video Games
- While this moment is easy to write off as mere Technobabble, Calabi-Yau manifolds are a type of N-dimensional shape/coordinate system/mathematical model with...strange...properties deeply related to the shape of space, time, and the curled up dimensions found in string theory. See The Other Wiki's article for more details, but for our purposes a Calabi-Yau manifold can be summed up as "a map of the Timey-Wimey Ball".
- In the sister franchise Portal, there is a related Shout-Out to this same model in the swirling particles seen when the portal gun is fired: their paths trace out a simple 3d cross-section of a Calabi-Yau manifold. This would seem to imply that either Aperture Science independently stumbled across the same trick, or that the resistance has been attempting to reverse engineer their research based on incomplete notes.
- Miegakure is an in-development (as of December 2014) Puzzle Platformer in which the player explores a world that has four dimensions, but only three are visible at any given time.
Web Comics
- In xkcd strip #721, Cueball apologizes to a two-dimensional square named A. Square for having given him a hard time when he had trouble understanding three-dimensional space. Playing a four-dimensional game called Miegakure has made Cueball more sympathetic to Square's situation.
Western Animation
- The Adventure Time episode "The Real You" centers on Finn gaining super-intelligence. He invents a bubble blower that can create two-dimensional bubbles with one-dimensional shadows, three-dimensional bubbles with two-dimensional shadows, and fourth-dimensional bubbles with three-dimensional shadows. That last one just existing creates a black hole.
Real Life
- A real-life example of this trope is found in numerous attempts to explain how gravity works. To put it in layman's terms, gravity is quite weird. So weird, in fact, that the simplest way to explain the effects it has on time, space, and matter seems to be that it operates in additional directions than the three we can access. Theoretical models range anywhere from 5 dimensions (our three, time, and wherever the heck gravity is) to 11 (which would make our understanding of space look like a toddler's drawing if you could see all the dimensions that exist).
- Going in the opposite direction, the holographic principle is a theory that there are actually only two spatial dimensions, and either the third or time are an illusory byproduct of the universe existing.
- If wormholes are conclusively found to exist, they would essentially prove the existence of additional spatial dimensions. One especially interesting theorized form of wormhole is a Timelike Curve, which would allow the type of Time Travel which we here at TV Tropes know as a Stable Time Loop. This has led to physicists spending large amounts of time trying to prove they do not exist—mostly in the hopes of ending the migraines caused by thinking about all the horrible things a Timelike Curve could do to physics.