The Quantum Mirror is activated by a control device. After activation, the mirror shows what would be visible in the mirror of another reality. If a person touches the mirror, he/she is engulfed in energy and transported to the other reality. Switching between realities is possible by using the control device. SG-1 discovered the Mirror on P3R-233, though the device itself was created by the Ancients.
The device is found on P3R-233 by Dr. Daniel Jackson, who upon touching it is transported through the Quantum Mirror into an alternate reality where he finds that Earth is about to be overrun by a Goa'uld invasion force, which is being led by Teal'c. Daniel discovers that his reality is facing exactly the same threat - an invasion coming in retaliation for the death of Ra - and asks the alternate versions of several of his friends to help him return to save his own world, reasoning that it is impossible for them to save their reality but the information he has acquired in this universe - including the gate address that the invasion originated from - could still be used to save his own world. Just before the alternate Stargate Command is destroyed, Daniel escapes into his reality. Afterward, the mirror is transported to Earth and stored in Area 51. (SG1: "There But for the Grace of God", "Point of View")
Nearly one year later, an alternate Dr. Samantha Carter and Major Charles Kawalsky escape their reality through the Quantum mirror. When Dr. Carter begins to suffer entropic cascade failure at the cellular level due to the presence of two Samantha Carters in one reality, Major General George S. Hammond and SG-1 decide that, to save Dr. Carter's life, they will free their Earth, which has been taken over by Apophis' forces led by Teal'c. The General also orders that, upon completion of the mission, the Quantum Mirror to be destroyed. (SG1: "Point of View")
The Quantum mirror is eventually melted down at Area 51. When the outer rim of the mirror was destroyed, the singularity that was part of the mirror detached, closed in on itself and vanished. As the personnel at Area 51 had prepared for this, all the destroyed Quantum mirror took with it was a small concrete bunker and a naquadah generator. (SGA: "Entanglement")
In 2006, when many different versions of SG-1 began to appear, Dr. Bill Lee regretted that the mirror was destroyed, although Lt. Colonel Samantha Carter noted that it would be impossible to use the mirror to return everyone to their exact realities due to the number of alternate worlds involved. (SG1: "Ripple Effect")
- Alternate reality drive; a similar function to the mirror that has the capability of transporting matter into alternate realities.
- GateWorld's article on