What is a stargate? The stargate operated by the U.S. Air Force's Stargate Command (SGC) at Cheyenne Mountain Operations Center near Colorado Springs, Colo., is one of a vast number of wormhole-generating "doors" that allow for near-instantaneous intergalactic travel. Created millions of years ago by the Ancients, one of the earliest living beings in the universe, they are scattered throughout planets, with each stargate bearing a unique address, similar to a telephone number. Each is a monumental, roughly circular structure atop a base. The operating portion is composed of giant, moveable inner and outer dials, within which a wormhole entrance appears. Some stargates have an iris that opens and closes over the wormhole entrance. This iris, when closed, rests less than 10 micrometers from the "event horizon" (the two-dimensional energy field forming the passageway to the generated wormhole). This leaves essentially no physical space through which an unwanted object or visitor can materialize.   How does a stargate work? What's it made of? Stargates are made of the element Naquadah (sometimes transliterated from the original language as Naquada), a quartzite metal not found on Earth. A teleportational wormhole is generated when charged neutrinos are applied to Naquadah, the only known element that absorbs and energizes with neutrinos. This forms a stable, artificial wormhole that connects to another stargate. The derivative Naquadria is a powerful yet unstable fuel source; prolonged exposure to its radiation can cause mental disorders.   How does one travel between stargates? The monumental inner dial of each stargate has 39 symbols, called glyphs (such as those at left), which correspond to different constellations. The outer dial has nine chevrons. When a combination of the inner dial's glyphs makes contact with seven of these chevrons, a wormhole is activated, connecting the dialing stargate with the one whose code it has been set to — just as dialing a seven-digit telephone number makes contact with another telephone. (The last symbol in a stargate sequence is always the point of origin.) When a "puddle" of energy forms from the neutrino-Naquadah interaction, a person or device can pass through the puddle to emerge from the other stargate — often on a different planet, but sometimes in deep space or in orbit of a planet. In the episode "The Fifth Race", an eighth chevron was activated (thanks to the Asgard) and Carter noted, "The extra chevron must add a new distance calculation to the existing points, like a different area code." The purpose or function of the ninth chevron is still unknown.   How does the SG-1 team determine whether an unknown destination is safe? Before any SG team ventures through the stargate to an unexplored offworld location, Stargate Command first sends through a Mobile Analytic Laboratory Probe (MALP). This probe analyzes conditions and sends back radio-wave data to help SGC determine whether it is safe for human teams to proceed through.   What other SG teams are there? There are 17 SG teams so far. Initially, there were nine, including the exploratory alpha team, SG-1. By season two's "In the Line of Duty," SG-10, -11 and -12 had been added. Two additional teams were added by that season's "Show and Tell." In the third-season opener, "Into the Fire," the final three teams were added. Not every team's specialty has been expressly stated, and some specialties' designations have changed. The known teams currently include: SG-2: Research Formerly designated Military, was originally led by Maj. Charles Kawalsky (killed in action), later by Maj. Louis Ferretti; as a Research unit, it is led by Maj. Hank Griff SG-3: Marine Combat (Alpha) Originally led by Col. Robert Makepeace; later by Maj. Lawrence; and still later by Col. Reynolds, currently of SG-5 SG-4: Medical Formerly the Russian SG team. As a Medical unit, originally led by Lt. Barber (killed in action) SG-5: Marine Combat (Beta) Led by Maj. Davis SG-7: Scientific SG-8 Formerly a Medical team; current specialty unknown SG-9: Diplomatic Originally led by Capt. Hansen (killed in action), later by Maj. Stan Kovacek, still later by Maj. Benton (killed in action) SG-10: Military SG-11: Archeological (Alpha) Formerly designated as Engineering, when originally led by Maj. Hawkins (killed in action), and later by Capt. Connor (killed in action); as Archaelogical, led by Col. Edwards SG-12: Military SG-13: Survey Col. Dave Dixon leads this team, which consists of civilian archeologist Cameron Balinsky and senior airmen Simon Wells and Jake Bosworth SG-16: Exploration (Beta) Formerly led by Col. Reynolds, later of SG-3 and currently SG-5 SG-17: Archaeological (Beta) Originally led by Maj. Mansfield (killed in action); included Lt. Elliot (killed in action) What special devices does SGC use with the stargate? Among the many specialized devices used by the SG teams are:   Dial Home Device (DHD) Activates the stargate   "Garage Door Opener" (GDO) Signals the stargate to open the iris   Zatn'kitel Energy Pistols SG-1 is equipped with Goa'uld Zatn'kitel energy pistols, commonly called by Col. O'Neill's pithy sobriquet, zats. One shot will stun a victim unconscious; a second shot immediately applied will kill; a third immediately applied in succession will vaporize the target.   Transphase Eradication Rod (TER) Detects objects operating in the light spectrum 180 degrees out of phase of human vision, such as the Reetou alien race   Jaffa Staff Weapon Teal'c sometimes uses a Jaffa Staff Weapon, a long, ornate pole with Egyptian motifs. Carried by the Goa'uld Jaffa guard, of which Teal'c was once a member, this weapon fires powerful energy blasts that can penetrate metal. Stargate Command has recently completed production of several F-302 jets. Known as the X-302 during its experimental phase, this is a fighter-interceptor air/spacecraft reverse-engineered from alien Goa'uld technology. There is also a next-generation X-303 a.k.a. Prometheus, currently in operation under commander Col. Pendergast.