A
Stargate is an
Einstein–Rosen bridge portal device within the
Stargate fictional universe that allows practical, rapid travel between two distant locations.
[1] The devices first appeared in the 1994
Roland Emmerich film
Stargate, and thereafter in the television series
Stargate SG-1,
Stargate Atlantis, and
Stargate Universe. In these productions, the Stargate functions as a
plot device, allowing the main characters to visit alien planets without the need for spaceships or any other type of technology. The device allows for near-instantaneous travel across both
interstellar and
extragalactic distances.
Within the Stargate fictional universe, Stargates are hyper-advanced large rings capable of harnessing any source of energy and applying it to maintain artificial stable Einstein–Rosen bridges for the purpose of interplanetary and intergalactic travel, allowing the one-way travel of matter and energy (radio transmissions can travel either way through an open wormhole).
A stargate's destination is not fixed, but is singled out by a process known as "dialing". Once a three-dimensional destination is selected by the traveler, the Stargate generates a stable wormhole between itself and a complementary device at the destination, by being supplied with a threshold amount of raw energy.[9] Objects in transit between gates are broken down into their individual elemental components, and then into energy as they pass through the event horizon, and then travel through a wormhole before being reconstructed on the other side.[10]
Akin to a rotary dial, each Stargate has nine prominent points (chevrons) spaced equally around its circumference, which are used to determine the address being dialed. On the inner ring is a set of unique glyphs; on Milky Way and Pegasus gates, the glyphs represent constellations, while the meaning of the glyphs on Destiny-style gates is unknown. The number of glyphs is dependent on the network to which the gate belongs; Milky Way gates feature 39 glyphs, while Pegasus and Destiny gates have 36. Of these symbols, 38 and 35 for Milky Way and Pegasus gates, respectively, can be used to select a destination. One symbol represents one's own location, the so-called point of origin. The first seven of a Stargate's chevrons and glyphs are "maps" used to isolate the location of another gate and establish a connection.[citation needed][10] Chevrons one-through-six are used to designate points in space (i.e. star clusters, constellations and planets) and form three-dimensional coordinates for the destination, while the seventh chevron is coded to the Stargate's current position, to provide a point of origin for the Einstein–Rosen bridge. When sufficient power is available, the eighth chevron can be used to connect to another galaxy, effectively acting as an "area code" connecting to an entirely different network of Stargates. The ninth chevron enables a connection to a specific Stargate with its own unique nine-symbol address, regardless of distance or location.
The show is consistent with the mechanics of address-dialing. The process involves associating a unique symbol of the inner ring to each of at least the first seven of the chevrons on the outer circumference. The main "address" is invariably dialed first, and the last symbol is the "point of origin", representing the gate being used, which acts as the final "send button" trigger for the completion of the address sequence.[11] As each symbol is dialed, the chevron is said to "engage" or "encode" and usually responds by lighting up or moving. When the final symbol of an address is dialed, that chevron is said to "lock" and the wormhole opens (this terminology is arbitrary and often interchangeable, but preferred by the recurring character Walter Harriman).[11] If the address is incorrect or does not correspond to an existing or otherwise functional stargate within that three-dimensional space, the last chevron will not lock, and all of the chevrons will "disengage".[9]
Each location in the
Stargate universe has its own unique "address", which is a combination of six or more non-repeating symbols appearing on the dialing stargate.
[citation needed][12] By "dialing" these symbols in the correct order, the traveler selects a three-dimensional destination.
The symbols dialed are often referred to as "coordinates", and are written as an ordered string; for example, this is the address used in the show for the planet Abydos: 
(corresponding to the constellations of Taurus, Serpens Caput, Capricornus, Monoceros, Sagittarius and Orion). As explained by Dr. Daniel Jackson in the movie, the Stargate requires seven correct symbols to connect to another Stargate. As shown in the picture opposite, the first six symbols act as co-ordinates, creating three intersecting lines, the destination. The Stargate uses the seventh symbol as the point of origin allowing one to plot a straight line course to the destination. With the stargates of the Milky Way, with 38 address symbols and one point of origin, there are 1,987,690,320 possible six symbol co-ordinates (leading to 38!/(38-6)!/8/6=41,410,215 addresses as the six symbol addresses are composed of three tuples that can be permuted in 6 ways and the two symbols within each tuple are invariant for 8 more permutations.). With the stargates of the Pegasus or Destiny, with 35 address symbols and one point of origin, there are only 1,168,675,200 possible six symbol co-ordinates.
This diagram illustrates how Stargate symbols translate to physical coordinates.
By identifying six constellations in space, a single sextangulation point can be interpolated that corresponds to the destination desired.[10] As only a small portion of the possible combinations of Stargate symbols represent valid addresses, dialing the Gate at random is largely futile. In "Children of the Gods", SG-1 discovers a room on Abydos with a list of valid Stargate addresses and (luckily) a map that allows the SGC to compensate for thousands of years of stellar drift. In the series, the fictional planet Abydos could be dialed because it is relatively close to Earth, although in the film, Abydos was located in the fictional Kaliam Galaxy.[10] It was initially believed that the Goa'uld created the Stargates, but this was proven false in "The Torment of Tantalus" when the SGC discovered that Earth had accidentally dialled an address in 1945 that was not on the Abydos cartouche. Following this revelation, a larger list of Stargate addresses is provided by Jack O'Neill in "The Fifth Race" from knowledge downloaded into his mind by a repository of the Ancients, allowing them to travel to worlds unknown to the Goa'uld.[13] In "Rising", a list of Stargate addresses in the Pegasus galaxy is found in the Atlantis database.[14] The SGC assigns designations to Stargate-accessible planets in the form Pxx-xxx or Mxx-xxx. Samantha Carter explains in "The Broca Divide" that the designation "is based on a binary code the computer uses for extrapolation".
Eight-symbol addresses are introduced in "The Fifth Race", opening up new plot lines by connecting Stargates to different galaxies. The additional symbol acts as a type of "area code". Such connections, in comparison to seven symbol codes, require substantially more energy to complete a functional wormhole – much more than any standard dialing method can provide. In the first instance, opening an intergalactic wormhole is shown to exceed the total power generation capacity of the SGC at the time. O'Neill fashioned an additional power source using spare parts and the liquid naquadah power core of a staff weapon using the same enhanced knowledge that had allowed him to determine this address in the first place,[13] but this new power source only functioned twice and required repair work to operate the second time.[15] A fully charged Zero Point Module (ZPM) can provide enough power for regular travel between galaxies.[14][16][17] The 8th chevron is a key element in the Stargate Atlantis series, allowing travel to the Pegasus Galaxy. With the stargates of the Milky Way, with 38 address symbols and one point of origin, there are 63,606,090,240 possible seven symbol co-ordinates. With the stargates of the Pegasus or Destiny, with 35 address symbols and one point of origin, there are only 33,891,580,800 possible seven symbol co-ordinates.
Stargate Universe introduces the concept of a nine-symbol address, the purpose of the ninth chevron never having been explored in the previous series.[18] The nine-symbol addresses act as codes to dial specific Stargates, with the only two known nine-symbol addresses used to dial from the Milky Way galaxy to Destiny, a massive Ancient vessel that was part of a project to explore the universe, with the project being abandoned when they started researching into ascension among other things, and from Destiny to Earth. It is unknown if any other Stargates are reachable with a nine-symbol address, or if this is a feature unique to the Stargates on Destiny and Earth. Like eight-symbol addresses, the dialing of this address requires a significant amount of power, such that the scientists on Icarus Base had to tap into the planet's naqahdriah core. With the Stargates of the Milky Way, with 38 address symbols, there are 1,971,788,797,440 possible eight symbol destinations. With the Stargates of the Pegasus or Destiny, with 35 address symbols, there are only 948,964,262,400 possible eight symbol destinations. Provided the ninth symbol is your point of origin. If the ninth symbol can also be added to the destination, even 59,153,663,923,200 combinations with a Milky Way stargate or 25,622,035,084,800 combinations with a Pegasus or Destiny Stargate are possible.
