A Stargate address is a coordinate system used by a Stargate to determine the position of a target gate in the Stargate Network. They are composed of a series of glyphs, at least seven depending on the intended destination, which when entered in the correct order allow the Stargate to establish a wormhole with another gate at the destination.
A Stargate address consists of two distinct parts: the destination and the starting location. The first six chevrons mark a three-dimensional area of space as the target. The last chevron is the point of origin, identifying where the Stargate is dialing from. Seven chevrons are used to dial within a galaxy, while the eighth and ninth are required for greater distances. The point of origin is always the last chevron, apart from the nine-chevron address, while any between it and the first six are modifiers that change how the system interprets the coordinates given. Assuming the dialing gate has enough power and neither is obstructed in any way, the wormhole will then form, allowing passage.
Because of stellar drift, most addresses are invalid by themselves. Dial Home Devices contain automatic update transceivers which allow the network to correct for stellar drift. This correlative update system causes the DHDs to occasionally dial other gates and update their position in the network. The Stargate on Earth lacks a DHD, so Stargate Command developed their own equation to compensate for stellar drift. A supercomputer using this equation was able to turn out two or three every month. While under the influence of the Ancient Repository of knowledge, Colonel Jack O'Neill developed a much more efficient equation for calculating stellar drift. (SG1: "Children of the Gods", "The Fifth Race", "Avenger 2.0")
Types of addressesEdit
A seven-chevron address is the basic operating mode of the Stargate, allowing the gate to connect to any other within a galaxy. The first six mark the destination and the seventh is the point of origin. This kind of address uses the least amount of power. The DHD present with most Stargates has a power source sufficient to dial such addresses nearly indefinitely; the oldest known Dial Home Device found in Antarctica was still capable of dialing fifty million years after it was created, though its cold fusion reactor core was depleted shortly after it was recovered.
Eight-chevron addresses are used to dial extra-galactic gates. In this address, an additional chevron is added between the destination and the point of origin, which serves as a distance calculation. Intergalactic addresses require more power than is provided by a standard Dial Home Device, requiring 10 times the power input of a standard seven-chevron dialing, but most advanced races are able to substitute in their own power sources to easily dial intergalactic destinations. DHDs are incapable of dialing such addresses without a special control crystal, which is present only on Atlantis or another system which can calculate extragalactic addresses, like the Stargate Command's modified dialing computer. It is not known whether Milky Way galaxy DHDs possess these control crystals; as they were only specifically excluded from Pegasus DHDs because of the presence of the Wraith in that galaxy.
A nine-chevron address is used to connect to the 1st Generation Stargate on-board Destiny, and back to Earth from Destiny; these have been the only two nine-chevron addresses known to have been dialed. The ninth chevron triggers link-layer addressing (the language used in the show is "dialing specific Stargates"). It bypasses the normal, more useful location-based network addressing in favor of hardware-based addressing. Thus, the ninth chevron is used for traveling to a specific gate, or place with a gate that doesn't have a fixed point in space. For example, Destiny; is a ship which doesn't have an exact point in space (it is always moving). Dialing nine chevrons for a specific gate, is like a password for that gate, akin to calling a specific cellphone by dialling its serial number. In the case of dialing Destiny, the point of origin had to be Earth, regardless of where dialing from. This allowed specific travel to Destiny's gate, and the address would never be invalid as long as the symbol for Earth was the 9th chevron. Both 8th and 9th Chevron dialing cannot be achieved without additional power, dependant on the distance involved between the two gates, that being a ZPM (Zero Point Module) or other power source with an equivalent boost in power, such as O'Neil's Power Booster Device or the Naquadria core of an Icarus-type planet.
There are three popular theories regarding the mechanics of such addresses. One of which suggests that every active Stargate has its own 9-glyph address (2nd and 3rd generation Stargates having been built after 1st generation models, they are likely compatible with them, much like how the 3rd generation Stargate on Atlantis can dial Earth's 2nd generation model). The second theory states that the glyphs on Destiny-style Stargates represent some form of Ancient numeral system, and that the address is based on the direction and distance of the destination gate relative to the dialing gate. The third theory states that nine-chevron addresses can and are used in Stargates that are located in or around 'top-secret' or 'need to know' Ancient facilities. Since nine-chevron addresses are not based upon a location in space, the destination can not be located via triangulation, using the six points in a normal seven or eight-chevron address, thus making use of this method of dialing a secure way. This theory also addresses why neither the SGC or Atlantis have found Ancient facilities that are used in space faring civilisations, such as ship construction or manufacturing, knowledge about these worlds and how to access them would be strictly controlled by those who have a higher standing in their civilisation, such as the Lantean Council, and not common knowledge amongst others.