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Samantha Carter from an alternate reality

A alternate reality (which may also be referred to as an alternate quantum reality, alternate timeline or parallel timeline) is a self-contained separate reality. It is believed there are an infinite number of different realities, some more similar than others. Sometimes there are the same people, places, and objects, but with notable differences. The terms "alternate universe" or "parallel universe" are sometimes also used to refer to alternate realities, however such usage is inaccurate; a universe is a distinct separate place, divided from other universes by higher dimensions (and may have its own alternate timelines), while an alternate reality is merely a different quantum facet of any one universe, with the same laws of physics, just different histories.

As understood by quantum theory, any event creates an infinite number of possible outcomes, all of which are played out in alternate quantum realities. Each alternate reality is ordinarily separate from the others, and distinguished by its unique quantum signature. Alternate realities, together with alternate universes (and their own alternate realities), form the multiverse. In theory there are an infinite number of realities, ever branching with one for every infinite outcome. As of the 2370s Starfleet had records of 285,000 different quantum realities.


Two major timeline theories have been shown to exist: (1) alternate realities (also known as alternate universes or parallel universes) and (2) alternate timelines. Alternate realities are presented when various versions of SG-1 live in parallel universes, some almost identical; others, so extremely different so as to be unrecognizable. Alternate timelines are presented when it appears that the timeline in which "our" SG-1 exists is modified by a time traveling event.

Bridging alternate realities[]

Multiverse theory[]

The SGA, an alternate SGC

In a Multiverse, there exist a near-infinite number of universes, or realities, that are each created to reflect a different outcome to a decision. One could use the fork in the road as an analogy, where going in one direction defines the individual's current reality, whereas the roads not taken represent the alternate realities. These realities are progressing through time at the same rate as ours, but different paths are being taken, thus the term parallel universes is also used to describe them. Additional terms for "alternate realities" have included "alternate universes", "quantum universes", and "parallel worlds", and all have basically been used interchangeably, even though there are some differences in their definitions. These differences have not been expounded upon, and thus, the two more widely used terms "alternate reality" and "parallel universe" describe the same thing. Some of these alternate realities have been created through the impact of a time traveling event (see Alternate timeline), but most were the results of a decision so that all possible outcomes have their own realities. For example, one alternate reality included Dr. Daniel Jackson's turning down Colonel O'Neill's offer to join the Stargate Program instead of taking up the offer and exploring the universe. From that one event alone, several alternate realities were most likely created, carrying forward the idea that someone else joined SG-1 and went on the first mission, resulting in various realities where Ra was not defeated, and so on.

Forming the bridge[]

In order to travel to an alternate reality, one must form a link, called a "trans-universal bridge" or the more commonly used "inter-universal bridge", between the two realities. Various means of creating the bridge between realities have been discovered by Stargate Command. SG-1 was introduced to the existence of alternate realities when they discovered the Quantum Mirror on P3R-233. This device appeared to be constructed of Naquadah, and might have been the creation of the Ancients, but its actual origin was never determined. Using the hand-held remote control of the Quantum Mirror, an individual could "dial" an alternate reality, touch the mirror-like device, and be transported into that reality. As long as the link between the two realities was maintained, a traveler could go back and forth, but if the Mirror was turned off, the traveler would have to use a control device in their current reality to find the reality from which they had originally traveled. The method of determining the correct reality was purely by visual confirmation through the Mirror, as neither the Mirror nor its remote control seemed to record the placement of the originating reality or the last reality dialed. Another means of creating a unidirectional inter-universal bridge was developed by Dr. Rodney McKay and his sister, Jeannie Miller, to draw Zero point energy from a parallel universe . A traveler could traverse this uni-directional bridge (from the reality from which the energy was being drawn) if he was beamed across with beaming technology while wearing an Ancient Personal shield emitter. This attempt to draw zero point energy into a containment field created universe-destroying exotic particles, and their research had to be abandoned. Similar research was done in an alternate reality by Major Samantha Carter and Dr. Bennett, but that research was destroyed in a power overload when they accidentally tapped into SG-1's reality and drew Colonel Samantha Carter into their reality while she was inside a contained field and out of phase. Major Carter and Dr. Bennett were totally annihilated in the explosion that resulted when Carter was drawn in. With the help of an alternate Dr. Rodney McKay, Carter was transported back to her own reality through another inter-universal bridge, but how her specific reality was determined as this bridge's destination was not revealed.

Entropic cascade failure[]

Dr. Samantha Carter experiencing entropic cascade failure

Traveling between alternate realities comes with some problems, the main one being Entropic cascade failure. This phenomenon results when two people representing the same person, such as two Major Samantha Carters, exist in the same reality at the same time, and is when the visiting person, the one out of his/her own reality, will start to suffer a physical breakdown at the cellular level due to temporal distortion. A traveler who has no living counterpart will not suffer from this breakdown.

Based on this definition, the more "in sync" two realities are, perhaps having only a few differences in their "paths", the less the chance becomes that the traveler will suffer from these fatal effects. Entropic Cascade Failure was observed when the civilian Dr. Samantha Carter who worked at the SGA visited SG-1's reality, but not when several Carters who were in the Starfleet Marine Corps and members of the Stargate Command's SG-1 team visited in 2381.

Alpha-numeric designations[]

After 2345 Starfleet Command began to designate all nearby parallel universes with Greek alpha-numeric coded names, this is a listing of all currently designated dimensions.

Alternate realities[]

During the run of the Stargate Program, several alternate realities and timelines have been glimpsed briefly, providing an insight on how several alternate realities may have turned out.

Alternate reality #1 (also known as diverged prime reality or alternate quantum reality)[]


Alternate reality #2[]


Alternate reality #3[]