"No! It wasn't a vision or a dream or a hallucination. It was real. Now, I know this is hard for you guys to believe. But I swear to you, the entire time you thought I had disappeared on P3R-233, I was experiencing an alternate reality."
Daniel Jackson[src]

Alternate realities, or parallel universes, are a concept that stems from Hugh Everett's many-worlds interpretation of quantum mechanics. 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.


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[]

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 Catherine Langford's offer to translate the Stargate's coverstone instead of taking up the offer and solving the riddle of the Stargate. From that one event alone, several alternate realities were most likely created, carrying forward the idea that someone else opened the Stargate and went on the first mission, resulting in various realities where Ra was not defeated, and so on. (SG1: "There But for the Grace of God")

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 lower 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 Air Force and members of the Stargate Command's SG-1 team visited. (SG1: "Point of View", "Ripple Effect")

Forming the bridge[]

Main article: Matter 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 first introduced to the existence of alternate realities when they discovered the Quantum Mirror on P3R-233. This device appeared to be constructed of Naquadah, the same material used to build the Stargates, 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.

Major General George S. Hammond commanded that the Quantum Mirror in his reality be destroyed because he felt that there were some lines that were never meant to be crossed; but other means of inter-universal travel were later discovered. If one were to direct a controlled energy blast within a wormhole traveling through a black hole, one could actually open bridges among several alternate realities and another, making the wormhole's destination reality a point of confluence. This effect was reversed at the point of confluence with the use of an Asgard directed energy weapon discharged in the wormhole connected to the original point of origin's corresponding Stargate. Because the Stargate's wormhole was used to create the "inter-universal bridge," travel was only one-way, or uni-directional. (SG1: "Point of View", "Ripple Effect")

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 Asgard 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. (SGA: "McKay and Mrs. Miller")

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 Lt. 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. (SG1: "The Road Not Taken")

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.

SG1: "There But for the Grace of God"[]

Dr. Daniel Jackson is transported to a different reality via what is later called the Quantum Mirror.


  • The Stargate Program's headquarters is known as the SGA.
  • Earth is currently under attack from the Goa'uld and is slowly being wiped out with the death toll apparently at 1.5 billion.
  • Dr. Daniel Jackson was never a part of the Stargate Program, his alternate self having rudely turned down Catherine Langford's offer to work on the Stargate. It is also highly likely that he is dead as he lived in Egypt, which was heavily bombarded by the Goa'uld ships.
  • Teal'c is also not a part of the Program, and has remained the First Prime of Apophis and is currently leading the assault on Earth. Any chance of him turning or defecting to the SGA ended for good when the SGA sent a Nuclear warhead to his homeworld Chulak with the bomb killing Teal'c's people and family with Teal'c later killing O'Neill in revenge.
  • George S. Hammond is a Colonel rather than a Major General.
  • Jack O'Neill is not a Colonel, but rather a Brigadier General and commanding officer of the SGA. He also possess a single scar underneath his right eyebrow which the main timeline O'Neill would later inherit but unlike the main timeline's O'Neill who mellowed after meeting Daniel Jackson, this reality's O'Neill never met the Daniel of that reality and as such, O'Neill is still a hardened military man through and through who is still coming to terms with his son's death.
  • Dr. Samantha Carter has not joined the military and is a civilian scientist working for the SGA.
  • Jack O'Neill and Samantha Carter are engaged to be married.
  • Catherine Langford is still working as part of the SGA and she wasn't reunited with Ernest Littlefield.

SG1: "Point of View"[]

An alternate Dr. Samantha Carter and Major Charles Kawalsky come through the Quantum Mirror, fleeing Apophis's takeover of their Earth.


  • The Stargate Program's headquarters is known as the SGA.
  • Major Charles Kawalsky is still alive and working for the SGA.
  • Dr. Samantha Carter did not join the military and works as a civilian scientist for the SGA.
  • Samantha Carter discovered how to operate the Stargate in 1995 rather than Dr. Daniel Jackson, who never joined the Stargate Program.
  • Samantha Carter and Colonel Jack O'Neill had been married for just over a year by the time of the invasion.
  • Teal'c is still the First Prime of Apophis and, apparently, is very loyal to his master. He killed Jack in front of his master after Apophis' forces captured Cheyenne Mountain.
  • The uniforms worn by Apophis' Jaffa are different.
  • Teal'c had a beard, as does Apophis.
  • The symbols on the dialing computer are yellow instead of blue.
  • The people of this reality never met the Asgard, only coming into contact with them when Dr. Carter goes through the Stargate to ask for their help in freeing Earth from Apophis.

Other realities glimpsed in this episode[]

Stargate SG-1: Ouroboros[]

While experimenting with an invention of Janus's, SG-1 and General O'Neill travel to a parallel version of Atlantis


  • Daniel Jackson was assigned to join the Atlantis expedition, but had appendicitis just before they were scheduled to depart.
  • All of the expedition travelled to Athos to find a potential new power source rather than just a key team under Sumner's command, which resulted in the death of Doctor Elizabeth Weir when the Wraith came.
    • As a result of this, the expedition has become divided, with Major John Sheppard leading a small group who have joined the Athosians while Colonel Marshall Sumner and most of the military are in control of the ruins and are harvesting Wraith enzyme.
  • The fates of the Genii and Satedans are apparently reversed, as the Genii are confirmed to have been destroyed by the Wraith while Specialist Ronon Dex came to Athos explicitly to discuss an alliance with his people.
    • There is a brief appearance by a Wraith whose description matches Guide; a later meeting between Daniel Jackson and the "prime" Guide allows Daniel to talk with Guide about where his history might have diverged from his counterpart.

SG1: "Ripple Effect"[]

Several different realities are discovered and several teams of SG-1 come through the Stargate. Two realities are mostly seen on screen, where the command center is also called SGC, as in our reality. The "real" SG-1 team is distinguished as wearing "green" SGC uniforms throughout the episode.

Alternate reality #1[]

  • Lt. Colonel Samantha Carter is married and has been on a honeymoon.
  • The Ori successfully planted a second beachhead in our galaxy.
  • During the second Ori incursion, at least two planetary systems, including Dakara, were destroyed.
  • The Prometheus has recently been lost in battle.
  • Selmak/Jacob Carter is still alive.
  • Bra'tac is the leader of the Free Jaffa Nation.
  • Earth does not have access to a functioning Zero Point Module.
  • This team is desperate enough that it caused the problem with all of the alternate realities bleeding over into ours in order to steal the Prometheus and Atlantis' ZPM to protect their Earth with the Control chair in Antarctica. They ultimately fail and are sent home with nothing.
  • This team was distinguished by wearing "Black" SGC uniforms.

Alternate reality #2[]

Other realities glimpsed in the episode[]

At least 17 different SG-1s were stranded at the SGC during this episode. After the arrival of the first, "black" SG-1, Major General Henry Landry ordered that all further teams be instructed not to proceed through the gate, making exceptions only for those units that were under immediate fire and could not afford to shut down the Gate and dial out again.

  • The second alternate SG-1 to arrive, distinguished by wearing "Blue Digital Tiger Stripe" camouflage pattern uniforms, arrived from a firefight offworld. Its composition appears identical to the SG-1 of our reality, but its members are much more heavily armed than our universe's counterpart; notably, Teal'c is carrying a Staff cannon. This team was still being examined (or examined again) in the SGC's infirmary after several other SG-1s had arrived. In our reality, that camouflage pattern and color was one of the proposed designs for the USAF's Airman Battle Uniform (ABU).
  • Another SG-1 team, this one notably in "Digital Woodland" USMC MARPAT uniforms, can be seen in a side room as Teal'c, Daniel, and Landry passed by them. Mitchell, Carter and Teal'c (who, unlike the Teal'c of our reality, was still bald) were the only identifiable members of the team. Upon closer scrutiny, theirs does not appear to be of the official USMC pattern as it's missing prints of the "Eagle, Globe & Anchor".
  • Another SG-1 team is seen exiting an elevator, consisting of Mitchell and three men who appear to be Jaffa. They also appear to be wearing the Atanik armbands.
  • Another SG-1 team, in hazmat suits passes by as the "real" Teal'c, Daniel, and Landry goes off-screen. This Mitchell turns to look after Landry, Daniel and Teal'c, then smiles and continues walking down with his team.
  • Samantha Carter appeared to be a member of nearly every alternate SG-1. In the SGC's science lab, a room full of "Alternate-Carters" can be seen, some isolated and by themselves, others working together to help find a solution on the problem. The "real" Carter along with the "Black Carter" from the first SG-1 team who arrived, converses with Dr. Bill Lee on finding a solution to return the alternate SG-1's back to their realities, just before the "Alternate" Martouf steps in.

Deleted scenes[]

  • This episode was originally too long, so many scenes had to be edited and cut out for time. Joseph Mallozzi managed post the script sections of all cut scenes in his producer installment on Gateworld.

ATL: "McKay and Mrs. Miller"[]

An alternate version of Dr. Rodney McKay (known as "Rod") travels to our universe, seeking to shut down an experiment that might destroy his.


  • Since Rod's reality was never viewed directly, nearly everything we know about it is based on his description. No indication was given that Rod was lying, although our universe's Lt. Colonel John Sheppard did state that he found him "creepy".
  • Both Earth and Atlantis have working Zero Point Modules.
  • Though Sheppard's team appears to have the same composition, the personalities of the team members are somewhat different: in Rod's words, Lt. Colonel John Sheppard is an active member of Atlantis's Mensa chapter and something of a know-it-all that makes the McKay of our reality look humble, and Teyla Emmagan is hard to talk to (though Ronon Dex, apparently, is about the same). Rod himself is more easygoing and personal than our universe's McKay, and an honorary member of the Athosian council.
  • Jeannie Miller has three children; Rod, their godfather, carries photographs of them in his wallet.
  • The Ancient Personal shield emitter found in Atlantis has not yet exhausted its power source (or they found another one.)

SG1: "The Road Not Taken"[]

In this reality, Anubis's attack on Earth forced the Stargate Program into the public eye, and chaos ensued.


ATL: "The Daedalus Variations"[]

In one universe, the Earth ship Daedalus was installed with an Alternate reality drive, where it kept jumping to other universes, including our own.

Known universes[]

  • In one universe, Dr. Rodney McKay had developed the Alternate reality drive and fitted it on the Daedalus from that universe. Colonel Sobel was in command of the Daedalus rather than Colonel Steven Caldwell, and she and her crew explored other realities.
  • In one universe, Sobel and her crew had to flee the Daedalus after they couldn't figure out a way how to stop the alternate reality drive. They arrived over an abandoned, yet habitable planet, which happens to be M35-117 from our reality.
  • One of the alternate Sheppard's team found the abandoned Daedalus and later found themselves stuck for several weeks. They couldn't find a way out and eventually ran out of supplies. Eventually they starved to death.
  • In the first universe our Sheppard's team visited, Atlantis never made it to M35-117. The city was either still on Lantea, or the Atlantis expedition may not have been formed in the first place, or potentially stuck between the two planets, or located elsewhere.
  • In the second visited reality, their Daedalus was destroyed during an Asuran attack sometime in 2006. Atlantis was on M35-117 and had apparently made enemies with an unknown race of aliens, where one of their flagships attacked Atlantis. Sheppard saved them from the attack by using the Daedalus Asgard plasma beam weapons to take out the ship's main weapons as it was about to destroy Atlantis. The expedition retaliated by sending an F-302 fighter-interceptor assault against them, and protected the alternate Daedalus as thanks for the earlier save. Sheppard in this reality was also a pilot and held the same rank of Lt. Colonel.
  • In the third visited reality, the star of M35-117 was turning Red giant and swelled in size roughly 48,000 years before it was supposed to.
  • In the fourth visited reality, a massive object of some sort impacted M35-117, destroying the planet. All that remained was a field of asteroids. This may have occurred thousands, even millions of years ago.

ATL: "Vegas/Enemy at the Gate"[]

In an alternate reality very similar to ours, Detective John Sheppard had received a dishonorable discharge from the military. The Dr. Rodney McKay of this reality apparently met another alternative version of Sheppard in a situation similar to when Rod came to Atlantis. However, this reality is distinct from Rod's reality and it was not our reality's Sheppard that this version of Rodney met. When a Hive ship attempted an attack on Earth, it was quickly destroyed by the powerful Drone weapons of the Antarctic outpost. One of the Wraith Darts was shot down by a squad of F-302 fighter-interceptors and so ignored by the drones. The pilot survived and pretended to be human to try to send a signal to the Wraith in Pegasus to rescue him.

The signal transferred into our reality, informing the Super-hive of the location of Earth and warning them of the drones protecting it as well as the location of the Control chair at Area 51. This led to the Battle of the Super-hive which ended when Lt. Colonel John Sheppard destroyed the Hive ship above Earth with a nuke planted on the inside.

See also[]