An unidentifiable energy surge occurred during an unscheduled off-world activation, and an SG-1 team from an alternate universe arrived through the stargate at the SGC. In their reality, Bra'tac had united the new Jaffa nation under his leadership, Selmak was still alive, and Carter had rejoined Mitchell, Daniel, and Teal'c on SG-1 following her honeymoon. A second Ori beachhead could not be stopped, and the Ori had sent their warships into the galaxy and had destroyed Chulak, Dakara, and most of the Jaffa strongholds. The team had traveled to PX7-455, a world under Amaterasu's control that had already been visited by a Prior. From there, they had intentionally crossed into our reality by opening the return wormhole to Earth through the black hole that had been created by the destruction of the first Ori beachhead, and then blasting a bridge into this universe, which accounted for a travel time of 3.4 seconds rather than the usual journey of 0.3 seconds, as well as the anomalous energy surge as the gate activated. Their plan had been to steal a ZPM from Atlantis and return to their own reality where they could replace their depleted ZPM and power the Ancient weapons platform in Antarctica to defend against the Ori.
Believing that the alternate team's arrival had been accidental, Carter theorized that as the wormhole bisected the singularity, subspace was ruptured, creating a rift in the space-time continuum, and that the spatial tear may have caused a ripple effect across several realities, transforming an area of subspace into a kind of funnel in which any wormhole passing near the black hole was drawn into the singularity and rerouted to the SGC of our reality as a kind of convergence point. Soon multiple SG teams began arriving through the gate, each from a different point of origin, each from a different reality, but all passing within a few degrees of the singularity. The proximity of the various realities in relation to each other may have accounted for the absence of entropic cascade failure. Gate travel to Earth was suspended and rerouted to the Alpha Site, and over 50 SG teams were turned back, but emergency arrivals under fire were permitted, and at least 16 different versions of SG-1 arrived through the stargate. One version of SG-1 included Mitchell, Daniel, Janet Fraiser, and Martouf. In their reality, Martouf had joined the SGC to be closer to Carter, and they had worked together and even lived together for quite some time, but the long distance relationship had not lasted. Dr. Fraiser had survived the mission to P3X-666, and she had joined SG-1 in place of Carter, who was on maternity leave. In their world, Earth had been ravaged by the Prior plague and hundreds of thousands had been infected as the team desperately sought a cure.
SG-1 intended to close the bridge between the multiverse by targeting the point of confluence and delivering an explosive device into the singularity, sealing the rupture but stranding all the alternate teams in this universe. However, during the mission of SG-1 and an alternate SG-1 aboard Prometheus to deliver the warhead and time dilation generator to counter the effects of the black hole, the alternate team commandeered the ship, and SG-1 learned that their mission had been intentional, with a plan to return already in place. SG-1 regained control of the ship, scrapped the mission, and returned to Earth. Instead, they reversed the circumstances that had created the bridge in the first place by firing a directed Asgard energy weapon through the stargate to reverse the space-time rupture, effectively inverting the convergence effect. All of the alternate teams were returned home by establishing wormholes that followed the inter-universal pathways already created by their initial trips, and Dr. Fraiser and her team were offered the cure to the Prior plague to bring back to their world.
Cross Reference: Alternate Reality, Alternate Reality - P3R-233, Alternate Reality - Quantum Mirror, Alternate Reality - Universal Bridge, Asgard Energy Weapon, Black Hole, Entropic Cascade Failure, Janet Fraiser, Kvasir, Bill Lee, Martouf, Prometheus
Episode Reference: Ripple Effect