Iris (Stargate)
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StargateIris.jpg
In the sci-fi television show, Stargate SG-1, the "iris" (of the Stargate) is a large, metal protective device, similar to the shutter of a camera, which was invented by Stargate Command to prevent unwanted travelers from emerging through the Stargate's wormhole.
When closed, the iris forms a barrier within 10 μm of the wormhole's event horizon, thereby preventing most forms of matter from properly reintegrating. Objects coming through the wormhole are destroyed instead, accompanied by a ringing thud against the iris. Radio signals are able to penetrate, however, allowing SG teams to request the opening of the iris using their GDOs. The iris also suppresses the destructive "kawoosh" (the unstable vortex) generated when the Stargate opens, apparently as a side effect.
The System Lord Sokar devised a means to breach the iris by firing a particle beam through the wormhole, the subatomic particles being small enough to reintegrate in the space between the iris and the event horizon, thus heating the iris up with the intent of eventually melting it. (Season 2 "Serpents Song") The SGC used this technique themselves in a later episode to penetrate a "natural iris" that had formed over a distant world's Stargate after it had been buried while still active. (Season 3 "A Hundred Days")
Instituted in the pilot episode, the original titanium iris was destroyed in the episode "A Matter of Time" by a black hole's gravity leaking through from the other end of the wormhole. It was replaced with a new iris made of a trinium alloy.
The Iris is controlled from either the control room Iris Hand Scanner, or the manual control down in the Gate room on the left wall. Since the Iris was installed by the SGC, Earth's Stargate is the only one with such protection, though the Stargate in the Ancient city of Atlantis, as well as some Goa'uld controled Stargates have a force field that can serve the same function. The palm scanners were installed in the season 2 episode "Show and Tell", after an invisible alien came through the stargate with a team and broke into the computer system, overriding the computer and opening the iris.
Iris Deactivation Code
The Iris Deactivation Code is a code transmitted through an open stargate to request that the iris be opened to allow travellers through. IDCs are transmitted using a GDO or Garage Door Opener.
Early portrayals of its use even had it deactivating the iris against Stargate Command's wishes, such as in the Season 1 episode "Cold Lazarus". The stargate in Atlantis is not protected by an actual iris, but the term has been carried over to apply to the protective force field that fills the same role.