Stargate

"It's not "door to heaven." It is "Stargate.""

- Daniel Jackson

The Stargates, also called the Astria Porta in Ancient and the Chappa'ai in Goa'uld, are a series of devices, built by the Ancients, that can create Wormholes between distant worlds. The Stargates are often considered to be the Ancients greatest creation, and the Ancients are often called the Gate Builders.

Names
The Ancients placed Stargates on thousands of worlds across galaxies, but the gate network was open to use by all, 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.

In turn, most races developed their own names for the Stargates. The Ancients called them "Astria Porta". The English word "Stargate" is a calque of the Goa'uld word "Chaapa'ai", courtesy of a direct translation by Daniel Jackson, and "Chaapa'ai" is itself a calque of "Astria Porta". The Wraith call the Stargate the Portal.

Although Stargates are present on many planets, most of the races which inhabit them are relatively primitive, and view the gates as no more than divine, sacred or terrifying relics, as evidenced by such names as "Ring of the Gods" and "Circle of Darkness". The K'Tau call their Stargate "the annulus". In the Pegasus galaxy, villagers know them as Rings of the Ancestors and variations thereof. They are also commonly referred to as as simply "the ring" or "the gate".

Technical specifications
The Stargate is essentially an enormous superconductor, capable of harnessing power from a wide variety of energy sources, especially electricity. When entering through the event horizon, the matter passing through is converted to energy, and then rematerialized at the event horizon of a Stargate. Wormholes are one way only, though it is unknown what happens if someone goes through an incoming wormhole. The inner track is a safety feature. When the gate has absorbed enough energy this track will unlock, allowing a manual dial in case something bad has happened to the D.H.D.

The Stargate has symbols (39 for the Milky Way, 36 for the Pegasus galaxy) which are combined to form a seven-symbol address. Six of the symbols, representing constellations, indicate the destination's three-dimensional coordinates in space, while the seventh indicates the point of origin. For Stargates accessing a destination outside of its galaxy, a seventh constellation symbol is necessary, bringing the total to eight. There are 9 chevrons around the device, allowing up to 9 symbols to be dialed. It is currently unknown what the ninth symbol correlates to. The Stargates on a planet link it to the so called Stargate network. How far it spans is unknown, but it is known to link the Alteran Home Galaxy, the Milky Way, Pegasus, and the Ida galaxy.

Generally, the Stargates have dialing devices (DHDs, an acronym for Dial Home Device) that can be used similarly to a telephone dial to select the place where the connection should go. The Stargate found on Earth in the initial movie was missing its dialing device. It was later discovered (in Stargate SG-1) that Russia was in possession of the missing DHD. The Russians acquired the DHD during the Second World War, when they invaded Germany. Somehow, Germany found the DHD originally.

Opening the Stargate requires an amount of energy much larger than what is required to keep the wormhole open, resulting in an unstable vortex emerging at the "front" of the device]. This energy blast will disintegrate anything in its way; however, the vortex can only form if there is a large enough space (several microns) in front of the event horizon. Devices like the iris prevent the vortex from forming.

Stargates stay open for a limited period of time; normally for a few minutes, but they are supposed to "time out" at about 38 minutes. There have been rare circumstances where a wormhole has remaining active for more than this. Since it composed of Naquadah, the Stargate is incredibly durable, with some surviving ship impacts, black holes, and even metoer impacts.

In the Pegasus Galaxy, some Stargates have been placed in space in orbit of planets, rather than on their surfaces. Rather than using a connected DHD, space-based gates are powered by three power nodes, and dialing is accessed by a panel on a ship. Puddle jumpers and Wraith Darts are both equipped with such DHDs, and are among the few ships capable of going through the Stargate. In the Milky Way galaxy, the Goa'uld used a special glider to fit through the Stargate, but they abandoned this tactic a century ago.

The Ori are known to use the Stargates, as this was the way they originally sent Priors from their galaxy to the Milky Way. This means that they are compatible with the Milky Way Stargates, but all other details about them at this point are unknown.

The Eighth Chevron's purpose was originally unknown until Colonel Jack O'Neill had the information capabilities of the Ancient's stored within his mind through their Repository of Knowledge. Using the Power Booster Device he created, along with modifications he made to the SGC's dialing computer, the Eighth Chevron's purpose was revealed. It added an extra distance calculation to the gate allowing it to travel to other galaxies.

Its been theorised that, considering the fact that the Stargate possesses 39 glyphs, then there are a potential 39 galaxies with a gate network which would be accessible from Earth's stargate

Little was known what the ninth chevron was capable of or even what its purpose was.

Matter transmission
When an object passes through the event horizon, it is not immediately transferred to the destination Stargate, but rather the portion that has passed through is dematerialized and held in a "hyperspatial buffer". An object that has not completely passed through the event horizon may be pulled out again, and its atoms will rematerialise from the buffer as it is extracted. The gate does not begin transmitting an object until it has entirely passed through the event horizon. This ensures that only complete objects are transferred. Objects in the buffer remain in a state of suspension. This has been used to "store" people in medical need, but this is a dangerous maneuver, since any disintegrated matter in the buffer "ceases to exist" if the wormhole shuts down before the signal is transmitted. Furthermore, each time the gate is activated the buffer is wiped clean to receive new information. If the control crystal of a connected DHD is removed then an event horizon will form without establishing a wormhole, allowing any memory stored in the stargate to be reintegrated.

Several facets of the Stargate are necessary for it to function as a useful personnel transporter. Matter emerging from a Stargate retains any kinetic energy it had while entering, so a person running into one Stargate will hit the ground running upon emerging from another. (Weapon projectiles also maintain their trajectory upon transit: a bullet fired through a stargate is just as dangerous as it would be otherwise) Also, the transmitting Stargate does not allow the air molecules of the local atmosphere to pass through: the Stargate differentiates between objects attempting to pass through the event horizon and things that would naturally exert pressure, such as water, air, lava, etc.

Gate obstruction
A wormhole is prevented from forming if a significant obstruction is present inside the Stargate's ring. Consequently, it is fairly common for Stargates to be semi- or permanently sealed by burying them.

Another means of controlling travel through a Stargate is by placing a barrier a minuscule distance (less than three micrometers) from the event horizon, which allows the wormhole to form but prevents the reconstitution of matter upon arrival through the gate. In other words, a connection can be made but any matter trying to exit the gate will not regain its original structure, and hence will be annihilated. The iris on the Earth Stargate and the shield on the Atlantis Stargate perform this function, and have been seen to be used as an effective defensive precaution, while still allowing radio communication through the open wormhole.

Iris-type barriers also suppress the formation of an unstable vortex by not allowing the matter to form. Such barriers, however, are not the only way to prevent the vortex. Several races, including the Asgard and the Nox, have demonstrated the ability to open a wormhole without the effect forming.

Power source
Power is always required to establish an outgoing wormhole, and is usually supplied by the DHD, but any Stargate can receive a wormhole whether it has a power supply or not; the dialing gate is the one that supplies power to both. In a few cases, Stargates have been dialed "manually" when more sophisticated means were not available. This was accomplished by providing sufficient raw power to the gate and then rotating the symbol ring by hand to lock each chevron. Power can be fed directly into the naqahdah that comprises the gate; power harnessed from lightning strikes has been shown to be sufficient. The Stargate that establishes an outgoing wormhole determines how long the wormhole is held open, and can generally close the wormhole "at will". Under some conditions, a gate only needs enough power to connect briefly, then the receiving gate can provide enough power to maintain the connection. The same is true if the outgoing gate loses power while transmitting; if the incoming gate has a DHD, it will take over powering the gate until reintegration is complete.

Secondary Stargates
Some planets are known to possess "secondary" or "backup" Stargates. The second Stargate is normally inactive, with the primary Stargate (defined by the presence of a functioning Dial-Home Device) receiving all incoming wormholes. If a Stargate experiences a power surge while an outgoing wormhole is open, the other end of the wormhole has been observed to "jump" to the next closest gate in the network. The effect can also be used as a defensive measure or to close a connection with the receiving Stargate. In the case of a planet with two gates, the closest is the inactive secondary gate. This scenario resulted in the discovery of the Beta Gate in Antarctica by SG-1.

The Antarctic gate was later revealed to have originally been the primary Stargate on Earth, built by the Ancients. The Alpha Gate, found in Giza and originally used in the SGC, was brought to Earth, by Ra, from another planet. Since Stargate addresses correspond to planetary locations and not individual gates, the new gate inherited the same address as the one in Antarctica. Because the Antarctic gate had been abandoned millennia earlier by the Ancients and no longer had a connected DHD, Ra's gate became the primary.

Durability
Stargates are very durable; the oldest in the Milky Way is probably the Beta Gate from Antarctica, 50 million years old; the power source may have been younger.

The Stargates themselves are extremely resistant to damage or destruction: in one case, a Stargate survived a direct hit from a meteor, while another was still capable of creating a stable wormhole while on a planet near a newly-formed black hole. A Stargate has also been seen to continue functioning whilst entering a sun, though it was protected by a portable forcefield for a portion of its journey. Even a naquadah bomb sent by the SGC that destroyed an entire planet left its Stargate intact.

Eventually, the United States developed a naquadria-enhanced nuclear bomb that was theoretically capable of destroying a Stargate (the "Mark IX"). However, when it was first used, it failed to destroy the intended Stargate, as an Ori shield defending the gate was being powered by the weapon attacks attempting to destroy it. A later attempt against a Pegasus Galaxy Stargate, however, succeeded by placing the bomb behind the gate, so that the energy would not be absorbed by the open wormhole.

Exceptions
Under normal circumstances, a wormhole can only be maintained for slightly more than 38 minutes. However, on a few occasions, this limit has been surpassed. The first breach of this general rule occurred to Earth's gate connected to a planet in the proximity of a black hole. This method was also used intentionally by the Ori. The second incident occurred when energy-rich liquid beings maintained the power for a gate while a Russian vehicle had its transmitter stuck. The third exception happened when Anubis used a Stargate destroyer to slowly feed energy to the Beta Gate at the SGC. The gate remained active and eventually exploded. Finally the fourth exception happened after Earth ordered an attack on the Asuran home planet, after it was discovered that they were building warships. The Asurans responded by sending a satellite containing a stargate to Lantea, which activated and a powerful beam came through hitting Atlantis' shield. The expedition had hoped that the Stargate would shut down after 38 minutes, but, as Dr. Meredith Rodney McKay stated, the Asurans had a sufficiently large number of ZPMs to power their Stargate indefinitely.

Susceptibility
The Stargate network is susceptible to computer viruses. A virus created by Dr. Jay Felger and altered by Ba'al once temporarily disabled the entire Stargate network. Although not intentional the virus was altered by Ba'al to take the network down.

Other uses
Several times, the Stargate network was used for a purpose other than interplanetary travel, although these extra features were almost always discovered by a fluke, and were not intended in the design of the Stargates. Two such occurrences regard the Stargate's interaction with time, first discovered by SG-1 when they accidentally traveled backward in time to the year 1969, as a result of the matter transmission stream passing through a solar flare. In the year 2010 in an alternate timeline, Samantha Carter intentionally used this phenomenon to send a message back in time. Time was also a when a scientist created a time loop, using a failed time machine built by the Ancients to isolate a region defined by 14 Stargates from the rest of the space-time continuum.

A Stargate could also be as a weapon capable of destroying an entire solar system. Samantha Carter used this effect when she dialed into a planet in close proximity to a black hole. The gate, protected by a force field, was then sent into a star. The resulting loss of mass caused the sun to go supernova, destroying the solar system and Apophis's fleet, which was orbiting the star at that time.

The dialing computer utilized by the SGC, an imperfect replacement for a DHD, was sometimes nearly the cause of disaster. Once, the bypassing of a system error caused a Stargate to introduce atoms of plutonium into the center of a star, causing the star to become unstable. Later, an unknown device and/or method was used to connect different realities and was reversed by use of an Asgard beam weapon.

Later still, it was revealed that one Stargate could be caused to dial multiple other gates simultaneously. This allowed a blast wave such as that of the Dakara Superweapon to extend almost indefinitely throughout the galaxy.

Ori Supergates
A Supergate is a massive Stargate developed by the Ori, spanning three to four hundred meters across. All known Supergates have been used for the specific purpose of establishing permanent footholds in distant locations in the universe, permitting the rapid passage of the Ori Army's enormous motherships across intergalactic distances.

Orlin's homemade Stargate
The outcast Ancient, Orlin built a miniature Stargate in Samantha Carter's basement. Its components included 100 pounds of pure raw titanium, 200 feet of fiber optic cable, seven 100,000 watt industrial strength capacitors, and a toaster. This gate was hooked up to the main power supply of the house and only connected once, to Velona, before it burnt out.

Tollan Stargate
The Tollan were an extremely advanced human civilization. Among their most impressive technological accomplishments was the construction of a new stargate.

With the destruction of the original Tollan homeworld, the Tollan's Stargate was lost. Their new homeworld, Tollana, had no original Stargate, and with the assistance of the Nox, a new gate was built.

The Tollan gate was smaller and slimmer than the Ancient's Stargates, and has a pale white color. However, it seemed to lack a DHD, or even an inner track for manual dialing, suggesting more advanced remote dialing. Eventually the Tollan Stargate was presumably destroyed by the Goa'uld, as reported by Narim to the SGC.

McKay-Carter Intergalactic Gate Bridge
The McKay-Carter Intergalactic Gate Bridge was a project to place a chain of Stargates in the void between the Milky Way and Pegasus galaxies was initiated, to allow rapid transit between Atlantis and the SGC without the need of a ZPM to power the Stargate. At the time, only the Atlantis gate had a ZPM available, meaning that the return trip from Earth required a three-week journey in a hyperspace-capable Daedalus-class battlecruiser. To this end, Stargates were "harvested" from the surface or orbit of uninhabited planets and deposited accordingly on both ends. When Atlantis' ZPM was depleted, the project took on an added urgency and was made operational shortly afterward.

The bridge (named as such by its co-creator Rodney McKay, recognizing Samantha Carter for the original idea) consists of seventeen stargates from the Pegasus network and another seventeen from the Milky Way network. A macro program written by McKay and uploaded to the gates' operating systems before dialing causes them to store incoming matter in their buffers, forwarding travelers from one gate to the next along the bridge, rather than emerging from the gate that is initially dialed.

Travelers will then exit at the Midway space station, halfway between galaxies, which serves as a transfer point. There, they will then use the other gate network (and a second macro program designed for that network) to continue on to their ultimate destination: travelers from Atlantis would use a Milky Way gate to travel on to Earth and similarly, travelers from Earth would use a Pegasus gate to travel to Atlantis. Even with this, the travel time between galaxies is just slightly over thirty minutes, making it far more efficient than traveling by hyperdrive.

When the first test of the gate bridge was conducted, only the framework of the station had been completed, so a gateship was used. The test was a complete success, and the bridge was declared operational. It was later revealed that, since the last gate in the bridge must dial the exit gate, normally either Atlantis or Earth, the macro can be rewritten to dial a different exit gate in the destination galaxy. The Midway station has since then been destroyed by the Wraith.

Asuran Stargate Satellite
The Asurans had developed an eight-chevron variant of a Stargate that was created as a satellite weapon. Its components included a shield generator, sensors and a hyperdrive allowing it to orbit its intended target. Once this is accomplished, a wormhole would be activated after which an intense red energy beam reaches out and strikes the target which, in this case, was the city of Atlantis. The beam would originate from an Asuran stronghold which would both power the satellites defenses as well as maintain an ongoing wormhole.

The satellite also had the added effect of preventing Stargate travel through the Atlantis Stargate as long as the satellite maintained its connection to the dialing Stargate, as both gates would be attempting to use the Atlantis coordinates. The satellite was able to receive the incoming wormhole from the Asurans, indicating that it could override the Atlantis Stargate, the dominant Stargate on the planet due to its being connected to a DHD. It appeared as a satellite with a Stargate in the center of its form which allowed it to maneuver and, thus, direct the energy weapon.