In science, the expression "other universes" is usually employed when referring to such possibilities. The term "parallel universe" tends to be encountered mostly in science fiction.
In Star Trek, a parallel universe was first introduced in the original series episode "Mirror, Mirror". In this alternate reality, all the main characters were portrayed as being cruel and barbaric. The episode was followed up in several Star Trek: Deep Space Nine episodes, starting with "Crossover".
OverviewFantasy has long borrowed the idea of "another world" from myth, legend, and religion. Heaven, Hell, Olympus, Valhalla are all alternate universes different from the familiar material realm. Modern fantasy often presents the concept as a series of planes of existence where the laws of nature differ, allowing magical phenomena of some sort on some planes. This concept was also found in ancient Hindu mythology, in texts such as the Puranas, which expressed an infinite number of universes, each with its own gods.1 In other cases, in both fantasy and science fiction, a parallel universe is a single other material reality, and its coexistence with ours is a rationale to bring a protagonist from the author's reality into the fantasy's reality, such as in The Chronicles of Narnia by C.S. Lewis or even the beyond-the-reflection travel in the two main works of Lewis Carroll. Or this single other reality can invade our own, as when Margaret Cavendish's English heroine sends submarines and "birdmen" armed with "fire stones" back through the portal from the Blazing World to Earth and wreaks havoc on England's enemies. In dark fantasy or horror the parallel world is often a hiding place for unpleasant things, and often the protagonist is forced to confront effects of this other world leaking into his own, as in most of the work of H. P. Lovecraft and the Doom computer game series. In such stories, the nature of this other reality is often left mysterious, known only by its effect on our own world.
Often the alternate worlds theme in science fiction is framed by postulating that every historical event spawns a new universe for every possible outcome, resulting in a number of alternate histories. This literary interpretation is sometimes rooted in the many-worlds interpretation of quantum mechanics formulated by the physicist Hugh Everett, an alternative to the Copenhagen interpretation originally formulated by Niels Bohr and Werner Heisenberg. This kind of alternate universe is often the backdrop of stories involving time travel and is often used to rationalize the logical paradoxes that arise when an author allows characters to travel backward in time (for example, see grandfather paradox). The concept also arises outside the framework of quantum mechanics, as is found in Jorge Luis Borges short story El jardín de senderos que se bifurcan ("The Garden of Forking Paths"), published in 1941 before the many-worlds interpretation had been invented. In the story, a Sinologist discovers a manuscript by a Chinese writer where the same tale is recounted in several ways, often contradictory, and then explains to his visitor (the writer's grandson) that his relative conceived time as a "garden of forking paths", where things happen in parallel in infinitely branching ways. While this is a common treatment in SF, it is by no means the only presentation of the idea, even in hard science fiction. Sometimes the parallel universe bears no historical relationship to any other world; as in the novel Raft by Stephen Baxter, which posits a reality where the gravitational constant is much larger than in our universe.
One motif is that the time flow in a parallel universe may be very different, so that a character returning to one might find the time passed very differently for those he left behind. This is found in folklore: King Herla visited Fairy and returned three centuries later; although only some of his men crumbled to dust on dismounting, Herla and his men who did not dismount were trapped on horseback, this being one folkloric account of the origin of the Wild Hunt.2 C. S. Lewis made use of this in The Chronicles of Narnia; indeed, a character points out to two skeptics that there is no need for the time between the worlds to match up, but it would be very odd for the girl who claims to have visited a parallel universe to have dreamed up such a different time flow.3
It should be noted that the division between science fiction and fantasy becomes fuzzier than usual when dealing with stories that explicitly leave the universe we are familiar with, especially when our familiar universe is portrayed as a subset of a multiverse. Picking a genre becomes less a matter of setting, and more a matter of theme and emphasis; the parts of the story the author wishes to explain and how they are explained. Narnia is clearly a fantasy, and the TV series Sliders is clearly science fiction, but works like the World of Tiers series tend to occupy a much broader middle ground.
Uses in science fiction
In written science fiction, higher dimensions more commonly – and more accurately – refer to additional coordinate axes, beyond the three spatial axes with which we are familiar. By proposing travel along these extra axes, which are not normally perceptible, the traveler can reach worlds that are otherwise unreachable and invisible. One of the first works of modern science fiction, The Time Machine by H. G. Wells used time as an additional "dimension" in this sense, taking the four-dimensional model of classical physics and interpreting time as a spatial dimension in which humans could travel with the right equipment.
There are many examples where authors have explicitly created additional spatial dimensions for their characters to travel in, to reach parallel universes. Douglas Adams, in the last book of the Hitchhiker's Guide to the Galaxy series, Mostly Harmless, uses the idea of probability as an extra axis in addition to the classical four dimensions of space and time. Though, according to the novel, they're not really parallel universes at all but only a model to capture the continuity of space, time and probability. Robert A. Heinlein, in The Number of the Beast, postulated a six-dimensional universe. In addition to the three spatial dimensions, he invoked symmetry to add two new temporal dimensions, so there would be two sets of three. Like the fourth dimension of H. G. Wells' time traveler, these extra dimensions can be traveled by persons using the right equipment.
HyperspacePerhaps the most common use of the concept of a parallel universe in science fiction is the concept of hyperspace. Used in science fiction, the concept of hyperspace often refers to a parallel universe that can be used as a faster-than-light shortcut for interstellar travel. Rationales for this form of hyperspace vary from work to work, but the two common elements are:
While use of hyperspace is common, it is mostly used as a plot device and thus of secondary importance. While a parallel universe may be invoked by the concept, the nature of the universe is not often explored. So, while stories involving hyperspace might be the most common use of the parallel universe concept in fiction, it is not the most common source of fiction about parallel universes.
Time travel and alternate historyThe most common use of parallel universes in science fiction, when the concept is central to the story, is as a backdrop and/or consequence of time travel. A seminal example of this idea is in Fritz Lieber's novel The Big Time, where there is a war across time between two alternate futures each side manipulating history to create a timeline that results into their own world. Time-travelers in fiction often accidentally or deliberately create alternate histories, such as in The Guns of the South by Harry Turtledove where the Confederate Army is given the technology to produce AK-47 rifles and ends up winning the American Civil War. The alternate history novel 1632 by Eric Flint explicitly states, albeit briefly in a prologue, that the time travelers in the novel (an entire town from West Virginia) have created a new and separate universe when they're transported into the midst of the thirty years war in 17th century Germany.
The concept of sideways time travel is often used to allow characters to pass through many different alternate histories, all descendant from some common branch point. Often worlds that are similar to each other are considered closer to each other in terms of this sideways travel. For example, a universe where World War II ended differently would be "closer" to us than one where Imperial China colonized the New World in the 15th century. H. Beam Piper used this concept, naming it "paratime" and writing a series of stories involving the Paratime Police who regulated travel between these alternate realities as well as the technology to do so. Keith Laumer used the same concept of sideways time travel in his 1962 novel Worlds of the Imperium. More recently, Frederik Pohl used the idea in his novel The Coming of the Quantum Cats which is explicitly based on upon a human-scale reading of the many worlds interpretation of quantum mechanics, postulating that every historical event spawns a new universe for every possible outcome.
It can be argued that most modern alternate histories implicitly refer to parallel universes, based on the above reading of quantum theory. However, many of these works are presented as self-contained worlds in and of themselves, and can be read without resort to additional universes being present. For example, outside The Guns of the South, the large part of Turtledove's work in alternate history makes no reference to any other universes other than the ones in which the stories take place. And Philip K. Dick's classic novel The Man in the High Castle features a universe in which the Axis won World War II, and the only other universe present is fictional, in a book whose author imagines an alternate world (different from our own) in which the Allies won. Such stories bear the same relationship to the reader's world as any fantasy (such as J. R. R. Tolkien's The Lord of the Rings novel) that contradicts the reader's reality. By extension all of fiction in general could, by this reasoning, be occurring in a subcreated alternate reality.4 While this definition might be useful in some critical contexts a more generally useful definition restricts the term to fiction where there are alternate realities presented in the work itself.
Uses in fantasy
Stranger in a strange landFantasy authors often want to bring characters from the author's (and the reader's) reality into their created world. Before the mid-20th century, this was most often done by hiding fantastic worlds within hidden parts of the author's own universe. Peasants who seldom if ever traveled far from their villages could not conclusively say that it was impossible that an ogre or other fantastical beings could live an hour away, but increasing geographical knowledge meant that such locations had to be farther and farther off.5 Characters in the author's world could board a ship and find themselves on a fantastic island, as Jonathan Swift does in Gulliver's Travels or in the 1949 novel Silverlock by John Myers Myers, or be sucked up into a tornado and land in Oz. These "lost world" stories can be seen as geographic equivalents of a parallel universe, as the worlds portrayed are separate from our own, and hidden to everyone except those who take the difficult journey there. The geographic lost world can blur into a more explicit parallel universe when the fantasy realm overlaps a section of the real world, but is much larger inside than out, as in Robert Holdstock's novel Mythago Wood.
After the mid-20th century, perhaps influenced by ideas from science fiction, perhaps because exploration had made many places on the map too clear to write "Here there be dragons", many fantasy worlds became completely separate from the author's world.6 A common trope is a portal or artifact that connects worlds together, prototypical examples being the wardrobe in C. S. Lewis' The Lion, the Witch, and the Wardrobe, or the sigil in James Branch Cabell's The Cream of the Jest. In Hayao Miyazaki's Spirited Away, Chihiro Ogino and her parents walk through a long tunnel into the spirit world. The main difference between this type of story and the "lost world" above, is that the fantasy realm can only be reached by certain people, or at certain times, or after following certain rituals, or with the proper artifact.
In some cases, physical travel is not even possible, and the character in our reality travels in a dream or some other altered state of consciousness. Examples include the Dream Cycle stories by H. P. Lovecraft or the Thomas Covenant stories of Stephen R. Donaldson. Often, stories of this type have as a major theme the nature of reality itself, questioning if the dream-world can have the same reality as the waking world. Science fiction often employs this theme (usually without the dream-world being another universe) in the ideas of cyberspace and virtual reality.
Between the worlds
However, in a few cases the interaction between the worlds is an important element, so that the focus is not on one world or the other, but on both, and their interaction. After Rick Cook introduced a computer programmer into a high fantasy world, his wizardry series steadily acquired more interactions between this world and ours. In Aaron Allston's Doc Sidhe our "grim world" is paralleled by a "fair world" where the elves live and history echoes ours. A major portion of the plot deals with preventing a change in interactions between the worlds. Margaret Ball, in No Earthly Sunne, depicts the interaction of our world with Faerie, and the efforts of the Queen of Faerie to deal with the slow drifting apart of Earth and Faerie. Poul Anderson depicts Hell as a parallel universe in Operation Chaos, and the need to transfer equivalent amounts of mass between the worlds explains why a changeling is left for a kidnapped child.
Multiple worlds, rather than a pair, increase the importance of the relationships. In The Lion, the Witch, and the Wardrobe, there are only our world and Narnia, but in other of C. S. Lewis's works, there are hints of other worlds, and in The Magician's Nephew, the Wood between the Worlds shows many possibilities, and the plot is governed by transportation between worlds, and the effort to right problems stemming from them. In Andre Norton's Witch World, begun with a man from Earth being transported to this world, gates frequently lead to other worlds – or come from them. While an abundance of illusions, disguises, and magic that repels attention make certain parts of Witch World look like parallel worlds, some are clearly parallel in that time runs differently in them, and such gates pose a repeated problem in Witch World.
It was an idea in the air, as most of these are, and I would have come across a reference to it in New Scientist (one of my best friends was then editor) ... [or] physicist friends would have been talking about it. ... Sometimes what happens is that you are imagining these things in the context of fiction while the physicists and mathematicians are imagining them in terms of science. I suspect it is the romantic imagination working, as it often does, perfectly efficiently in both the arts and the sciences.Unlike many science-fiction interpretations, Moorcock's Eternal Champion stories go far beyond alternate history to include mythic and sword and sorcery settings as well as some worlds more similar to our own. However, the Eternal Champion himself is incarnate in all of them.
Roger Zelazny used a mythic cosmology in his Chronicles of Amber series. His protagonist is a member of the royal family of Amber, whose members represent a godlike pantheon ruling over a prototypical universe that represents Order. All other universes are increasingly distorted shadows of it, ending finally at the other extreme, Chaos, which is the complete negation of the prototype. Travel between these shadow universes is only possible by beings descended from the blood of this pantheon. Those "of the blood" can walk through Shadow, imagining any possible reality and then walk to it, making their environment more similar to their desire as they go. It is argued between the characters whether these shadows even exist before they're imagined by a member of the royal family of Amber, or if the shadows' existence can be seen as an act of godlike creation.
In the World of Tiers novels by Philip José Farmer, the idea of godlike protagonists is even more explicit. The background of the stories is a multiverse where godlike beings have created a number of pocket universes that represent their own desires. Our own world is part of this series, but interestingly our own universe is revealed to be much smaller than it appears, ending at the edge of the solar system.
But even works that deal with lesser beings, the structure of the multiverse may be significant. Piers Anthony depicts two worlds in the Apprentice Adept series, the SF Proton and the fantasy Phaze, such that every person born in either world has a physical duplicate on the other world. Only when one duplicate has died can the other cross between the worlds.
Fictional universe as alternate universeThere are many examples of the meta-fictional idea of having the author's created universe (or any author's universe) rise to the same level of reality as the universe we're familiar with. The theme is present in works as diverse as Myers' Silverlock and Heinlein's Number of the Beast. Fletcher Pratt and L. Sprague de Camp took the character Harold Shea in the Incompleat Enchanter series through the worlds of Norse myth, Edmund Spenser's Faerie Queene, Ludovico Ariosto's Orlando Furioso, and the Kalevala7 – without ever quite settling whether writers created these parallel worlds by writing these works, or received impressions from the worlds and wrote them down. In an interlude set in Xanadu, a character claims that the universe is dangerous because the poem went unfinished, but whether this was his misapprehension or not is not established.
Some fictional approaches definitively establish the independence of the parallel world, sometimes by having the world differ from the book's account; other approaches have works of fiction create and affect the parallel world: L. Sprague de Camp's Solomon's Stone, taking place on an astral plane, is populated by the daydreams of mundane people, and in Rebecca Lickiss's Eccentric Circles, an elf is grateful to Tolkien for transforming elves from dainty little creatures. These stories often place the author, or authors in general, in the same position as Zelazny's characters in Amber. Questioning, in a literal fashion, if writing is an act of creating a new world, or an act of discovery of a pre-existing world.
Occasionally, this approach becomes self-referential, treating the literary universe of the work itself as explicitly parallel to the universe where the work was created. Stephen King's seven-volume Dark Tower series hinges upon the existence of multiple parallel worlds, many of which are King's own literary creations. Ultimately the characters become aware that they are only "real" in King's literary universe, and even travel to a world – twice – in which (again, within the novel) they meet Stephen King and alter events in the real Stephen King's world outside of the books.
TelevisionThe idea of parallel universes have received treatment in a number of television series, usually as a single story or episode in a more general science fiction or fantasy storyline.
The most widely known and imitated example is the original Star Trek episode "Mirror, Mirror". The episode introduced an alternate version of the Star Trek universe where the main characters were barbaric and cruel to the point of being evil. The way Star Trek executed the concept was deeply influential on subsequent treatments. Enough so, that when the parallel universe concept is parodied, it is often this Star Trek episode that's being referenced. Two recent examples are from South Park in the episode Spookyfish where the evil universe double of Cartman sports a beard, like the alternate version of Mr. Spock in the Mirror, Mirror episode. In addition, while the good universe's Cartman is the most obnoxious character, the evil one is pleasant and agreeable. Another animated series, Futurama, had an episode where the cast travels between "Universe A" and "Universe 1" via boxes containing each universe, and one of the major jokes is an extended argument between the two sets of characters over which set were the evil ones.
One of the earliest television plots to feature parallel time was a 1970 storyline on soap opera Dark Shadows. Vampire Barnabas Collins found a room in Collinwood which served as a portal to parallel time, and he entered the room in order to escape from his current problems. A year later, the show again traveled to parallel time, the setting this time being 1841.
Sometimes a television series will use parallel universes as an on-going subplot. This happened as Star Trek: Deep Space Nine and Star Trek: Enterprise elaborated on the premise of the original series' "Mirror" universe and developed multi-episode story arcs based on the premise. Other examples are the science fiction series Stargate SG-1, the fantasy/horror series Buffy the Vampire Slayer and the romance/fantasy Lois & Clark: The New Adventures of Superman. Following the precedent set by Star Trek these story arcs show alternate universes that have turned out worse than the original universe; in Stargate SG-1 the first encountered parallel reality featured Earth being overwhelmed by an unstoppable Goa'uld onslaught, in Buffy, the vampires had overrun Sunnydale and Buffy and Angel were both killed trying to prevent them from massacring the human populace, while in Lois & Clark an alternate universe is visited, repeatedly, that contains a Clark Kent whose parents, Jonathan and Martha Kent died when he was ten years of age, and whose Lois Lane is apparently dead. Clark eventually became Superman, with help from the original Lois Lane, but he is immediately revealed as Clark Kent and so has no life of his own.
In addition to following Star Trek's lead, showing the evil variants of the main storyline gives the writers an opportunity to show what is at stake by portraying the worst that could happen and the consequences if the protagonists fail. The latter could also be seen as the point of the alternate reality portrayed in the movie It's a Wonderful Life (see below).
There have been relatively few series where parallel universes were central to the series itself. Two examples are the short-lived 1980s series Otherworld which transported a family from our world to an alternate Earth; and Sliders, where the characters travel across a series of alternate Earths, trying to get back to their home universe.
MoviesThe most famous treatment of the alternate universe concept in film could be considered the The Wizard of Oz, which portrays a parallel world, famously separating the magical realm of the Land of Oz from the mundane world by filming it in Technicolor while filming the scenes set in Kansas in sepia.
A later example is the Frank Capra movie It's a Wonderful Life where the main character George Bailey is shown by a guardian angel the city of Pottersville, which was George Bailey's hometown of Bedford Falls as it would have been if he had never existed. Another notable depiction of a parallel universe in movies is the second film in the Back to the Future trilogy (1985, 1989) by Robert Zemeckis, starring Michael J. Fox and Christopher Lloyd, showing an accidentally created alternate present and future. Like It's a Wonderful Life, The Big Time, and many other time travel stories using this conceit, it is clear that these alternate presents/futures are mutually exclusive with the protagonists' own – so, strictly speaking, the universes aren't parallel in that they cannot coexist, rather they oscillate between one or the other.
Another common use of the theme is as a prison for villains or demons. The idea is used in the first two Superman movies starring Christopher Reeve where Kryptonian villains were sentenced to the Phantom Zone from where they eventually escaped. An almost exactly parallel use of the idea is presented in the campy cult film The Adventures of Buckaroo Banzai Across the 8th Dimension, where the "8th dimension" is essentially a phantom zone used to imprison the villainous Red Lectroids. Uses in horror films include the 1986 film From Beyond (based on the H. P. Lovecraft story of the same name) where a scientific experiment induces the experimenters to perceive aliens from a parallel universe, with bad results. The 1987 John Carpenter film Prince of Darkness is based on the premise that the Christian Satan is actually an alien being that is the son of something even more evil and powerful, trapped in another universe. The protagonists accidentally free "Satan", who then attempts to release his "father".
Some films present parallel realities that are actually different contrasting versions of the narrative itself. Commonly this motif is presented as different points of view revolving around a central (but sometimes unknowable) "truth", the seminal example being Akira Kurosawa's Rashomon. Conversely, often in film noir and crime dramas, the alternate narrative is a fiction created by a central character, intentionally – as in The Usual Suspects – or unintentionally – as in Angel Heart. Less often, the alternate narratives are is given equal weight in the story, making them truly alternate universes, such as in the German film Run Lola Run, the short-lived British West End musical Our House and the British film Sliding Doors.
Recent films that have more explicitly explored parallel universes are: the 2001 cult movie Donnie Darko, which deals with what it terms a "tangent universe" that erupts from our own universe; Super Mario Bros. (1993) has the eponymous heroes cross over into a parallel universe ruled by humanoids who evolved from dinosaurs; The One (2001) starring Jet Li, in which there is a complex system of realities in which Jet Li's character is a police officer in one universe and a serial killer in another, who travels to other universes to destroy versions of himself, so that he can become 'the one'; and FAQ: Frequently Asked Questions (2004), the main character runs away from a totalitarian nightmare, and he enters into a cyber-afterlife alternative reality.
Comic booksParallel universes in modern comics have become particularly rich and complex, in large part due to the continual problem of continuity faced by the major two publishers, Marvel Comics and DC Comics. The two publishers have used the multiverse concept to fix problems arising from integrating characters from other publishers into their own canon, and from having major serial protagonists having continuous histories lasting, as in the case of Superman, over 60 years. Additionally, both publishers have used new alternate universes to re-imagine their own characters.
Because of this, comic books in general are one of the few entertainment mediums where the concept of parallel universes are a major and ongoing theme. DC in particular periodically revisits the idea in major crossover storylines, such as Crisis on Infinite Earths and Infinite Crisis, where Marvel has a series called What If... that's devoted to exploring alternate realities, which sometime impact the main universe's continuity.
Marvel has also had many large crossover events which depicted an alternate universe, each springing from events in the X-Men books, such as Days of Future Past, the seminal Age Of Apocalypse, and 2006's House Of M. Exiles is an offshoot of the X-Men franchise that allows characters to hop from one alternate reality to another, leaving the original, main Marvel Universe intact.
GamesA small part of EarthBound involves traveling to Moonside, an alternate universe version of the town of Fourside.
There is a secret level named "Out of this dimension" in the game Star Fox. The level is somewhat bizarre and confusing, with a slot machine boss waiting in the end.
The Dungeons & Dragons role-playing game has a thoroughly developed system of planes of existence. A popular campaign setting for the game, Planetscape, centers around travelling between these planes. Ravenloft, a Gothic horror setting for Dungeons & Dragons, is based entirely in a single demiplane.
In the Magic: The Gathering, every plane is part of a multiverse. What effects one plane, may ultimately affect others, such as what happened when a great devastation occurred on the main plane, Dominaria. All the planes around were locked in a bubble, called the Shard, where no one could get in or out. The recent expansion, Planar Chaos, explores the idea of "what if?". The set looks back at the game's history, both mechanically and flavour-wise, and imagines what the game would be like today if certain decisions were made differently. The result is an alternate color pie – some abilities that are generally only seen in one or two colours in "real Magic" are put in completely different colours. For example, the ability to tap creatures, traditionally white, is put in black. The ideals and philosophies behind the colours remain unchanged - just the abilities that represent them. White is generally a very organized, military-focused colour, and tapping creatures is generally represented as a military tactic of leading an opponent astray (as seen on cards like Master Decoy). In Planar Chaos black, however, it is more seen as either a numbing poison (Midnight Charm), leading a creature into a trap (Rathi Trapper), or flaring negative emotions like immense sadness, resulting in no will to fight (Melancholy).
In the computer game Myst a people known as D'ni colonized Earth from another universe, and kept traveling to other universes (known as Ages) through Linking Books. According to their cosmology, each universe is a leaf of the Terokh Jeruth, the Tree of Possibilities. Myst also includes the use of Trap Books as empty universes for storing criminals, although they were later converted to be complete universes of their own, called Prison Ages.
The Kingdom Hearts series makes frequent use of multiple worlds, implementing Disney properties used as source material as their own world the protagonists can travel to over the course of the game (such as Halloween Town (from The Nightmare Before Christmas) or Port Royal (from Pirates of the Caribbean: The Curse of the Black Pearl).
The Squaresoft game Chrono Cross involves the world being split into two different dimensions, due to an accident involving the fate of a boy named Serge.
The 3do series Army Men constantly has its characters jumping from the plastic dimension to ours.
In the computer game Red Alert 2, or more specifically, its expansion, Yuri's Revenge, the player must utilize a time machine and travel back in time, to a parallel universe.
The Half-Life series strongly features the concept of parallel universes. In the original game, the player visits a 'border world' named Xen. In Half-Life 2, Earth has been taken over by an imperialistic, inter-dimensional alien race known as the Combine.
The Silent Hill horror video game series incorporates a concept of parallel worlds that are related to main character's emotions, memories, fears and other projections of his or her subconsciousness. The most common distinction is between the normal world (as the world is seen in reality) and the evil world (as the world is seen when it is devoured by evil powers). Characters are switching (i.e. altering) between these two worlds numerous times during the game's plot. There is a number of ways in which a character may switch between the worlds (for example, he or she may experience a pounding headache and, after this event, he or she "wakes up" in the evil world). The architecture of the evil world (also referred as an alternative world) is basically the same as the one of the normal, "real" world (for instance, a hospital in the normal world has its equivalent in the evil world). However, images of the evil world demonstrate how the real world would look like if it would be devoured by evil powers (for example, a hospital in the real world is no longer a hospital in the evil world –-it is in fact a decent torture block full of hellish images of pain and suffering).
The massively multiplayer online game Ultima Online used the parallel universe concept to rationalize the existence of multiple instances of the game world (called "shards"), so that players could be partitioned onto multiple servers for capacity reasons.
External siteParallel Universes (Scientific American article)
Related categories• SPACE AND TIME
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Parallel universe (fiction)".
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