The Stargates, also called the Astria Porta in Ancient and the Chappa’ai in Goa’uld, as well as various other names across the universe are a series of devices, built by the Ancients, which create artificial subspace wormholes, allowing for near-instantaneous transportation between two distant points in space. The Stargates are often considered to be the Ancients’ greatest creation, and thus the Ancients are often refereed to as the Gate Builders. The Ancients, the Asurans, the Tollan (with the help of the Nox), and the Ori are the only known races capable of constructing Stargates.
The Ancients placed Stargates on thousands of worlds across several galaxies. They have long since reached Ascension, but the network remains accessible to any with the knowledge of how it works, and continues to be a convenient form of travel for many races. Some races, such as the Goa’uld, grew their ways of life around the gates, which became integral to the functioning of their culture. They are among the oldest examples of Ancient technology found in the Milky Way galaxy; the Stargate found in Antarctica on Earth has been estimated to be over 50 million years old.
Although Stargates are present on many planets, most of the races which use them are relatively primitive, and view the technology as divine in nature, as evidenced by such names as “Ring of the Gods” and “Circle of Darkness”. In many cases the references to gods or evil in the names come from the Goa’uld.
The Stargate creates a stable, artificial wormhole between itself and another Stargate, allowing near-instantaneous travel from the dialing gate to the destination gate, but not vice versa. When activated, a Stargate produces a violent burst of energy known as an unstable vortex or “kawoosh”. This is due to the large amount of energy needed to form a stable wormhole, while keeping one open is much less power-intensive. This event will destroy any matter it comes into contact with; however, if the event horizon is blocked to within a few microns, the vortex will be suppressed. Technologies such as the Iris on Earth’s Stargate can achieve this. The vortex settles into the event horizon, nicknamed the puddle for its liquid appearance. Travelers enter through the event horizon, which dematerializes them for transport through the wormhole, to be reassembled on the other side. The Stargate will remain open so long as matter or energy continues to pass through it, to a maximum of 38 minutes. Beyond this point, massive amounts of power are needed to sustain a wormhole, which ordinary sources cannot provide.
Travel through a Stargate is strictly one-way: from the dialing gate to the receiving gate. This is not a limitation of the wormhole, but of the technology; wormholes will transmit anything that enters them, but no solid matter could survive the process. Thus, each gate in the pair takes on a specific role: the dialing gate converts the traveler into its most basic components (sub-atomic particles) and transmits it, while the receiving gate reassembles the transmitted matter back into its original form. Doing the reverse is not only fatal for the traveler, but would just result in the dialing gate deconstructing the object upon arrival, converting it into energy much like the process of ascension.
The Stargate is an enormous superconductor composed almost entirely of Naquadah, and is capable of harnessing power from virtually any source, though some sources are apparently inferior to others. Its design renders it incredibly durable; direct meteor impacts have failed to destroy a gate, and they have also survived within a crashing vessel unharmed. The naquadah construction of a Stargate allows it to hold many times the necessary amount of power for a wormhole to form, but it does have a limit. Surpassing this limit will create an explosion of considerable size, enough to potentially kill all life on a planet the size of Earth.
Though Stargates vary in design, they share several common elements. First, all Stargates have a group of glyphs spaced around the inner ringa nd nine chevrons spaced equally around the outer edge. The glyphs on Milky Way and Pegasus gates represent constellations, while Destiny-style gates use some sort of abstract symbols for lack of consistent stellar landmarks. These two features are used as a coordinate system for the gate to target and form a connection with another gate; each chevron is locked to a specific glyph, thereby allowing the gate to connect to another. This is known as an address for a gate; gate addresses are described in terms of how many chevrons are needed to dial them, seven at the least and nine at the most.
For a standard seven-chevron address, the first six glyphs represent points in space, forming three-dimensional coordinates. The seventh represents the point of origin, a glyph which is unique to each gate. For Stargates to access a destination outside of their galaxy, eight chevrons are used; the first six target a destination as normal, while a seventh glyph prior to the point of origin adds a distance calculation to the address, targeting a gate outside the galaxy as opposed to a local one. A nine-chevron address is more of a code than a location, and this allows connection to specific Stargates – regardless of their location.
The Stargates within a galaxy are linked to each other in a network, usually by means of a Dial Home Device (DHD for short). This network compensates for stellar drift, allowing every gate with a functioning DHD to properly connect to other gates. In the absence of this, the gate will either fail to connect entirely or roughly eject the passengers due to unexpected deviations in the position of the gate.