The Mirror Universe is a curious place. By many of the standards known to Federation science it should not even exist at all, yet it does. Not only that, but it remains remarkably similar to the Federation Universe, down to duplicates of individual people. The Federation's few contacts with the Mirror Universe have given scientists only a limited understanding of the physics involved in the creation and sustaining of such a parallel universe. This chapter covers where the Mirror Universe "is" in relation to the Federation Universe, how to get there, and (more important from a Federation standpoint) how to get back.
For more information on parallel timelines and dimensional travel in general, consult the All Our Yesterdays sourcebook from Last Unicorn Games.
The Mirror Universe, like all parallel timelines, is believed to lie parallel to the Federation Universe in a six-dimensional continuum: three dimensions of space, and three of time. The dimensions of space (height, width, and depth) are familiar. The linear motion of time (past-present-future) can be considered one "dimension" of time. Time's other dimensions are made up of probability fields that are the "height" and "width" of time. In essence, these temporal dimensions encompass every possible past, present, and future that could exist, and does, "elsewhere" in the continuum.
In these higher temporal dimensions lie a potentially infinite number of timelines, running parallel to the familiar Federation Universe. The amount of divergence between universes - essentially the difference between their quantum signatures - determines how "far apart" they are in temporal terms. The Mirror Universe lies quite "close" to the Federation Universe in a dimensional sense, one of the reasons it was the first parallel dimension encountered by visitors from the Federation Universe.
Everything in a particular timeline has a unique energy "signature" that can be measured on the quantum level, and cannot be changed by any means known to Federation science. This quantum signature is normally of little interest, since it is common to everything in the universe. However, objects from outside the universe have a different quantum signature. This includes people and objects from a parallel dimension. A quantum scan can determine whether or not something is from the same universe as the scanner. If the quantum signature of the subject's home dimension is known, then it can also be identified. This requires a Moderate (7) Personal Equipment (Tricorder) Test.
Note that at present the quantum signature of the Mirror Universe is not widely known in the Federation and vice versa, so correctly identifying the universe of origin for either requires some time and a computer records search (a Moderate (7) Computer (Research) Test).
Although the quantum signature of matter cannot be altered by any known means, it is possible to place matter in a state of quantum flux. This causes the affected matter to become "unstuck" in the space-time continuum, shifting "sideways" through time into another dimension. Transporters have the potential to place matter into a quantum flux state, and use a component known as a quantum resonance oscillator to keep the matter stream in the correct quantum state with relation to the rest of the universe, preventing it from going into quantum flux. As we will see, a failure of the quantum resonance oscillator can lead to quantum flux, along with a number of other high energy phenomena.
The Mirror Universe is unusual, even for a parallel dimension. Most parallel dimensions known to Federation science are what might be termed alternate histories. They diverge from known Federation history at a particular place in space-time, known as the divergence point. From that moment on, they follow their own history, but before the divergence point, they are identical to the Federation Universe, save for a difference in quantum signature.
Some parallels appear to have diverged from Federation history so long ago that it is difficult to determine the divergence point. These parallels are quite different from the Federation Universe, up to and including vastly different life forms evolving on Earth, Vulcan, and other planets of the galaxy. The further the divergence point is from the Federation present, the less likely it is for the parallel to have anything even remotely resembling Federation Universe history.
The Mirror Universe appears to be the exception. Although Mirror Universe history is quite different from Federation Universe history, going back centuries at the very least, many aspects of the Mirror Universe are remarkably similar to the Federation Universe, including the presence of certain individuals in both universes. For example, when Captain Kirk and his crew first encountered the Mirror Universe, they accidentally beamed on board an Enterprise that was an almost exactly duplicate of their own, down to the presence of an acid stain Dr. McCoy recalled from his own sickbay. Although the Terran Empire differed radically from the Federation in terms of politics and culture, it still had many of the same people.
With a history that diverged even decades previously, much less centuries, the odds of the Mirror Universe having a duplicate Enterprise, with an almost identical crew, are astronomical. The odds of there being a Benjamin Sisko and a duplicate crew of Deep Space Nine nearly a century after Kirk verges on the impossible. The events described by Intendant Kira, including the fall of the Terran Empire at the hands of the Alliance, should have so scrambled the human gene pool that Sisko and co. should never have been born. And yet they exist in the Mirror Universe, along with duplicates of many other people from the Federation Universe. Why?
The exact answer is uncertain, but Federation scientists who have studied the phenomenon of the Mirror Universe have offered a theory. They suggest that the Mirror Universe represents some kind of "quantum inversion field," an almost literal "mirror" of the Federation Universe. The inversion field creates a universe that duplicates the Federation universe on a macroscopic scale, while altering events and personalities on a smaller scale. Take the example of looking at your reflection in a mirror. The image looking back at you appears nearly identical to you, but if you were to hold up a book or a sign, the writing in the mirror appears backwards. So it is with the Mirror Universe. The large-scale things are nearly the same: planets, people, and even starships and space stations, but many of the details, the "writing" of the universe, are the opposite of what they are in the Federation Universe.
This "quantum inversion field" theory implies a strong relationship between the Mirror Universe and the Federation Universe, a kind of interdependency. Events in the Federation Universe may serve to dictate or at least influence events in the Mirror Universe. It may be that the Mirror Universe is only that, a reflection of the Federation Universe. If the Federation Universe was destroyed, the Mirror Universe might cease to exist as well. Of course, it is equally possible the Federation Universe is actually the reflection, and the Mirror Universe is the "real" one, or that they are both equally "unreal," reflections of some "higher" reality. Still, the strong relationship between the two realities on the quantum level seems to be what makes travel between them relatively easy compared to other quantum phenomena.
One result of this theory about the nature of the Mirror Universe is what scientists call "quantum mirroring." This essentially describes the fact that events and individuals often appear duplicated in both universes despite the larger-scale differences between them. For example, the lives of individuals from both universes are often extremely similar, even down to the smallest details, despite larger difference in personality and attitude.
Dr. McCoy's acid stain is a prime example. Although the Dr. McCoy from the Federation Universe was clearly a very different person from his Mirror Universe counterpart (who was described as "weak-willed" and prone to drinking excessively) both men experienced an identical accident that left an identical stain on their respective workbenches. Likewise, the Benjamin and Jennifer Sisko from the Federation Universe and their counterparts from the Mirror Universe were both married, although the Federation Jennifer died during the Borg assault on Wolf 359, while the Mirror Jennifer separated her husband and continued her work as a scientist. The list of similarities goes on and on.
Quantum mirroring somehow "synchronizes" certain events between the two universes. Scientists are uncertain how this happens, or why certain events are mirrored almost exactly, while others are distorted or altered, and some events are not mirrored at all. They speculate that it may be possible to influence the events in the Mirror Universe through a greater understanding of the phenomenon, but to what degree remains unknown.
The only known means of travel between the Federation Universe and the Mirror Universe involves putting a subject into a state of quantum flux matched to the particular quantum resonance of the other universe. The affected matter shifts out of one universe and into the other. Returning to the original universe is a matter of once again placing the subject in a state of quantum flux and matching the resonance of the original universe. This is somewhat easier, since the subject's natural quantum signature always matches that of the subject's home universe.
This technique was first discovered accidentally by the crew of the U.S.S. Enterprise in 2267, when an ion storm over the planet Halka caused a failure of the quantum resonance oscillator in the ship's transporter system. When members of the bridge crew attempted to beam aboard, they entered a state of quantum flux and shifted into the Mirror Universe. At the exact same moment, the bridge crew of the I.S.S. Enterprise shifted into the Federation Universe. The two crews being on (essentially) the same mission, and beaming back to their vessels at the same moment is another example of the quantum mirroring between the two universes. Enterprise Chief Engineer Montgomery Scott was able to reverse the quantum flux process to return the crew to their home universe, while at the same time the crew of the Mirror Enterprise was returned to their universe.
Although some scientific investigation of the Enterprise mission took place, the Federation Council decided on a policy of non-intervention in the Mirror Universe. Although Captain Kirk's actions in the Mirror Universe could be interpreted as a violation of the Prime Directive, the Council decided that the Directive did not specifically cover interference in the history of a parallel universe. Captain Kirk's actions were overlooked, and the definition of the Prime Directive was extended to include the Mirror Universe. Research into the nature of the Mirror Universe has been necessarily limited as a result.
The primary means of access between universes remains the quantum flux transporter. By modifying the quantum resonance oscillator of a standard transporter system, it is possible to place the matter stream in a state of quantum flux, shunting objects into a different universe during the re-materialization process. Targeting the transporter requires the quantum signature of the target universe; otherwise the subjects may become lost in the space-time continuum.
Making the necessary modifications to a transporter requires a Difficult (14) Systems Engineering (Transporter) Test, with a Challenging (11) Shipboard Systems (Transporter) Test to operate it successfully. A failure on either test means the transporter does not function as a means of interdimensional travel, although no harm comes to the subjects of the transport. A dramatic failure on either test results in the transporter sending the subjects to a random parallel universe, then burning out (leaving no means for the travelers to return). Because of the potential danger to the travelers, and the possible complications of contact with other parallel universes, the Federation and Starfleet restrict dimensional travel to times when it is absolutely necessary.
Apparently, the Terran Empire (and later the Klingon-Cardassian Alliance) modified the quantum resonance oscillators of their transporters systems to make quantum flux transport impossible, most likely to keep people from fleeing their grasp by escaping into parallel timelines. The existence of the Federation Universe was kept secret from most people, out of concern that knowledge of parallel timelines might inspire hope and rebellion in subject populations. Still, residents of the Mirror Universe have modified transporters to function as quantum flux transporters, and have used them to visit the Federation Universe.
Normally wormholes provide a "shortcut" to a different point in space-time. Thus far, all the wormholes known to the Federation connect different points within the same timeline; that is to say wormholes appear limited to the three dimensions of space and the linear dimension of time, rather than extending into the "sideways" temporal dimensions. However it is theoretically possible for a wormhole to connect two parallel timelines. Such a wormhole would most likely be short-lived, formed by high-energy interactions in the vicinity of strong subspace or gravitic forces (such as an active warp field or possibly a black hole). A ship could use an interdimensional wormhole as a means of traveling from one universe to another.
Experience has also shown that a resonant warp field applied to a normal wormhole can cause anything inside the warp field to enter a state of quantum flux, shifting it between universes. This occurred in 2370, when a Federation runabout carrying Major Kira Nerys and Dr. Julian Bashir suffered a warp malfunction inside the Bajoran wormhole, sending the ship and its crew into the Mirror Universe. By modulating the warp field exactly, it is theoretically possible for a ship entering a wormhole to travel to a parallel universe intentionally. Doing so would require a Difficult (14) Propulsions Engineering (Warp Drive) Test to successfully modify the ship's warp field. A failure on the test means the ship does not enter quantum flux, while a dramatic failure can catapult the ship into another timeline altogether rather than the desired destination.
A quantum singularity is a point of incredibly intense gravity, so powerful that neither light nor normal matter can escape from its pull. The gravity emitted by a quantum singularity can stress local space-time in such a way as to cause spatial and temporal distortions. Chroniton particle emissions are common around quantum singularities, which may interact with subspace to cause unusual phenomena. The Romulans use a forced quantum singularity as a power source for their starships rather than a Federation-type antimatter engine.
An encounter with a quantum singularity in deep space, or the failure of an artificial singularity like those found aboard Romulan vessels, could accidentally induce a state of quantum flux. For example, a battle between a Federation and Romulan vessel could lead to the formation of a quantum fissure, or simple phase shift both vessels out of normal space-time into another universe. Returning in such a case would require the cooperation of both vessels and crews.
A vessel might be able to channel the energies of a quantum singularity, in conjunction with a warp field, to place matter in a state of quantum flux. The Klingons and Romulans experimented with a similar technique to shift a cloaked vessel out of phase with ordinary matter, not only making the vessel completely undetectable by conventional scanners, but also allowing it to pass through ordinary matter unharmed. All the experiments ended in disaster and were abandoned by both Empires. Two experimental phase cloak vessels vanished entirely, never to be seen again. It is possible they were phase shifted out of the universe entirely and into a parallel universe (although not the Mirror Universe, apparently).
Deliberately using a quantum singularity to phase shift a vessel into a parallel universe would be a Difficult (14) feat of Propulsion Engineering (Warp Drive) at best. Failure would most likely disable the vessel's warp drive at the very least. A dramatic failure could lead to anything from the disappearance or destruction of the ship to strange temporal phenomena to a visit to an undiscovered parallel universe (accompanied by a burnout of the warp drive, making it very difficult to get back).
A quantum fissure is a weak point in the space-time continuum where different parallel timelines come in contact. It can be thought of as a kind of "quantum keyhole" between different universes. Normally, quantum fissures are extremely small, and short-lived, of little concern to anyone. However, certain high-energy subspace interactions, particularly warp fields, can cause quantum fissures to grow and de-stabilize, creating a more volatile interface between dimensions. Exposure to such a quantum fissure can place objects in a state of quantum flux, causing them to shift between different parallel universes.
In 2370, the U.S.S. Enterprise encountered an unstable quantum fissure, which caused hundreds of thousands of parallel universes to begin converging with the Federation Universe. The crew used a broad-spectrum warp field to safely seal the fissure and return the other timelines to their proper orientation in space-time. Sealing an unstable fissure in a similar manner requires a Challenging (10) Propulsion Engineering (Warp Drive) Test.
A quantum fissure could theoretically be used as a means of travel between parallel universes, but a means of controlling the fissure and choosing a destination would be required. A very precise application of warp fields might accomplish this, but any error would lead to a destabilization of the fissure. Such a technique should be Nearly Impossible (Difficulty 15+) for Level Six civilizations like the Federation. Alien technology - like that of the Iconians - might employ artificial quantum fissures as a means of dimensional travel.
There are a number of other possibilities for travel between parallel universes. The options presented here are based used a plot devices rather than technologies the Crew can rely on with any certainty. They are good for "accidental" dimension travel stories or when the Narrator wishes to introduce a unique form of dimensional travel into the series. Narrators should feel free to expand on the ideas presented here for use in their own games.
Warp field and warp drive technology is an integral component to many of the modes of interdimensional travel above. Warp fields have the ability to alter the properties of local space-time and, as the Traveler has pointed out, the Federation's understanding of the relationship between warp fields and reality is in many ways only beginning. A static warp bubble once created an alternate reality, so it is quite possible an application of warp fields might provide a means to travel to parallel universe.
Warp fields mixed with exotic phenomena like quantum fissures, singularities, cosmic strings, and so forth create a recipe for sending a starship nearly anywhere (and anywhen) a Narrator wants, including into a parallel like the Mirror Universe. Getting back may involve duplicating the circumstances of the original accident - often involving a short-lived interstellar phenomenon, like an unstable wormhole or quantum fissure. Or the Crew may need to find another way to return home.
Time travel normally involves moving along the linear dimension of time, but it is possible some methods of time travel could - intentionally or accidentally - permit movement "sideways" through time into a parallel universe. Experiments involving time travel and the nature of time, such as Paul Manheim's experiment from "We'll Always Have Paris" (TNG), could open a "window" into the Mirror Universe, or simply catapult the scientist and the Crew into the Mirror Universe altogether, with or without a means of getting back home.
The different methods of time travel, and parallel universes in general, are covered in more detail in the All Our Yesterdays sourcebook from Last Unicorn Games.
It may be possible to psionically induce quantum flux in an object, causing it to shift from one universe to another. This Quantum Shift ability is a Psionic Skill, albeit one unavailable to player characters and largely unknown in the Alpha Quadrant. The difficulty of a Quantum Shift Test is based on the parallel universe the character wishes to visit. Parallels "close" to the Federation Universe have a Moderate or better difficulty, while those "farther away" in a dimensional sense are more difficult. The difficulty also varies based on the local field density and other phenomena, which may shift from time to time, allowing the Narrator to make using this ability more of less difficult as desired.
Quantum shifting is best reserved for strange alien beings like the Traveler or the Q. A powerful Quantum Shifter could bring a Crew (or even a whole ship) along for the ride. This offers a good way of getting the Crew to a parallel universe without necessarily giving them the ability to get back (especially if Q isn't feeling particularly generous at that moment).
"Artifacts" covers any advanced, alien technology that provides the ability to travel between dimensions. The technology most likely comes from an alien race that is long extinct, like the Iconians, the Preservers, or the mysterious builders of the Guardian of Forever. It is technology so advanced that Federation species are like cavemen in comparison.
Most of these ancient races built their technology to last (the Guardian of Forever is billions of years old, for example). Generally, the instruction manuals haven't survived along with the device, so the Crew has to rely on trial-and-error in order to make it work. Most often, an alien artifact is activated accidentally and shifts the Crew (and possibly their ship) to another dimension before they can do anything to stop it. Getting back requires figuring out how to make the device work again, which isn't always the same as what made it work the first time.
With advanced dimensional travel technology, it is quite possible an ancient species or two visited the Mirror Universe (and other parallels) long ago. In fact, the Preservers or Iconians of the Mirror Universe may have been the same race from the Federation Universe, or perhaps the two parallel races were in contact with each other. Of course, it's equally possible the builders of the Guardian of Forever went to war with their Mirror counterparts, resulting in the destruction of both their civilizations.
Like psionic dimension travel, alien artifacts fall under the control of the Narrator, who can introduce them as plot devices to get the Crew to the Mirror Universe and (possibly) back.
One particular alien artifact deserves special attention: the Tantalus Field. Discovered by the Mirror Captain James Kirk "in the laboratory of a dead alien scientist," the Tantalus Field is a device that granted the Captain much of his power and fearsome reputation.
The Field consists of a small viewscreen and a few simple controls. By adjusting the controls, the operator can call up a view of any point within orbital distance (up to 10,000 kilometers away). No know screens or other technology can block the Tantalus Field's view. This ability alone is quite useful for covert surveillance, but the Tantalus Field's true power allows its user to "lock on" to anything in the device's field of view and destroy it with the touch of a button.
The Tantalus Field operates on a principle of quantum interference. It disrupts the target's normal quantum resonance signature. In essence, the target no longer "belongs" in normal space-time and instantly ceases to exist, vanishing in a momentary flash of light. This is more than mere disintegration; the subject is banished from reality all together. There is no known defense against the Tantalus Field; once it has you in its sights, you are as good as dead. The field has no Damage Rating or game statistics for this reason. It requires only a Routine Personal Equipment (Tantalus Field) Test to destroy anyone or anything within the field's range.
The Tantalus Field remained in the Mirror Kirk's possession until the Mirror Spock discovered its existence in 2269. With the aid of the Tantalus Field, Spock seized power on board the I.S.S. Enterprise. He used the Tantalus Field as one of his prime weapons in his own ascent to power in the Empire.
However, even the power of the Tantalus Field was no match for the invasion of the Klingon-Cardassian Alliance. The Field has not fallen into the hands of the Alliance, and its whereabouts remain unknown. It is rumored Spock's mysterious "disappearance" was the result of a subordinate using the Tantalus Field to assassinate him. More likely Spock still has control of the Tantalus Field, and is most likely using it to keep watch on activities in the Alliances and elsewhere, perhaps eliminating those that threaten his long-term plans, whatever they may be.