|Out of Universe information|
|First appearance||"There But For the Grace of God"|
- "Look, I know this is hard for you to understand. But according to quantum theory, for every possible universe there are an infinite number of variations, diverging in every choice we make, like forks in the road."
- —An alternate Samantha Carter (SG1: "Point of View")
According to the quantum theory, there are not one, but an infinity of alternate realities, also called alternate universes or parallel universes in which many different variations can occur from one to another at some point, changing the fate of the aforesaid reality and making them more or less different to the other ones.
A long time ago, Albert Einstein has predicted the whole concept of quantum physics in his relativity theory, including the alternate reality and timeline theories, and according to some scientists, there are an infinite number of dimensions, each of them with a different version of reality. Some realities are almost identical, others are completely different, depending of the choices and decisions made throughout the timeline. Each universe evolves concurrently on the same timeline basis. No reality is less real than another one (SG1: "There But For the Grace of God", "Politics", "Point of View", "The Road Not Taken").
The theory has become a fact in 1997 when Daniel Jackson touched a quantum mirror on P3R-233. He instantly switched to another dimension and experimented a very different version of Earth in which the Goa'uld invaded and destroyed all main Earth cities. He met alternate versions of George Hammond who was a colonel and not a general, Catherine Langford who was still part of the Stargate project (SG1: "The Torment of Tantalus"), Samantha Carter who was a civilian and not a military, and Jack O'Neill who was a brigadier general and not a colonel. According to Jackson, everything is the same, but different (SG1: "There But For the Grace of God").
Meanings for switching to another reality
In order to switch to an alternate reality, one must generate a matter bridge, and thus creating a link, or bridge, between two realities. This is also called "inter-universal bridge". Different devices have been designed by aliens and the Tau'ri to create this matter bridge. Some of them were deliberately designed for inter-universe travels, when others weren't supposed to go that far (SG1: "There But For the Grace of God", "Point of View", "The Road Not Taken", SGA: "McKay and Mrs. Miller", "The Daedalus Variations").
This was the first inter-universal alien device discovered by SG-1 on P3R-233 in 1997. Daniel Jackson unwittingly touched the mirror and switched to another reality to find only a different version of Earth. This device had a remote control to switch it on and determine the wanted reality. After Jackson's return in the main reality, the mirror has been locked up in Area 51. Alternate Dr. Samantha Carter and Major Charles Kawalsky used it to save themselves from a Goa'uld invasion. After saving their Earth, General George Hammond ordered the destruction of the quantum mirror (SG1: "There But For the Grace of God", "Point of View").
In 2006, an alternate SG-1 deliberately opened a wormhole through a black hole and blasted a bridge to the main universe. This bridge created a rift and as a side effect, over than 50 teams came through their respective alternate universes and landed directly in the same point of convergence, the main SGC embarkation room. Lieutenant Colonel Samantha Carter had to use the same method in order to reverse the effects so they could send the different teams back to their respective universes (SG1: "Ripple Effect").
McKay-Miller matter bridge
In 2006, after the failure of project Arcturus which ended by the destruction of the 5/6th of the Dorandan system (SGA: "Trinity"), Rodney McKay could achieve the project on Atlantis thanks to his sister Jeanie Miller, who solved the issues of the exotic particles generated with the creation of a matter bridge between alternate universes. During the experiment, an alternate "Rod" McKay used this matter bridge to cross between universes, protected by an Ancient personal shield, warning the team that they are on the verge to collapse their universe. All of them eventually figured out how to disconnect the bridge and bring back the alternate Rod to his own universe (SGA: "McKay and Mrs. Miller").
- "As I said, O'Neill, ours is the only reality of consequence."
- —Teal'c, after killing his alternate self (SG1: "Point of View").
- Even if in the Stargate universe, each alternate reality is considered as real as another one (SG1: "Point of View"), here on Semantic Stargate Wiki, the main storyline reality is considered as "main reality". The other realities are considered as "alternate realities" to avoid confusion in all related articles.
- See the Notes section about how to distinguish the different alternate realities.