From Stargate Wiki
- "...an ancient device capable of instantaneous transportation to other planets by means of a sub-space wormhole."
- — Samantha Carter
A Stargate, known as an Astria Porta in Ancient and Chappa'ai in Goa'uld is a device created by the Ancients to access numerous worlds by the use of a stable wormhole connecting Stargates together over vast distances and allowing for near-instantaneous travel in galaxy wide networks.
The Stargate was built by the Ancients however other races such as the Ori, Nox, Asurans and the Tollan have been known to build them as well. The original Stargate idea was though up by an Alteran known as Amelius. It is unknown if he is the one responsible for building the Stargate or just coming up with the idea. (Stargate: The Ark of Truth)
The name Stargate comes from the Goa'uld word chappa'ai which originally comes from the Ancient Astria Porta. Races from across the Milky Way and Pegasus gave the Stargate numerous names, usually referring to it as the ring or the gate, such as the K'tau who call it the annulus, other people call it the Ring of the Gods, the Medieval villagers call it the Circle of Darkness and the Wraith call it the portal. (SG1: "Children of the Gods", "Avalon, Part 2", "Red Sky", "The First Commandment", "Demons", ATL: "Midway")
When the Stargate receives adequate power and a valid address is supplied, a wormhole is formed. The event horizon will dematerialize any matter that passes it barrier and hold the energy until the entire unit has entered the wormhole which then will transmit the energy to the receiving gate where it is rematerialized in the same form it entered. (SG1: "The Enemy Within", "Shades of Grey", ATL: "Thirty-Eight Minutes")
Matter can only travel one way through the wormhole but certain forms of energy such as radio waves and gravitational distortions can pass either way through. If the dialing end loses power then the receiving end will supply the power needed to complete the transit process. If the receiving end is incapable of providing power then the travelers will be stored in the Stargates buffer, or in some cases will be reduced to its most basic components and released into space. The buffer stores the entire energy pattern of the traveler to ensure that it has received the entire object before it is reassembled. Every time the gate is activated the buffer is reset to ensure that no information will be mixed up with older material. (SG1: "Red Sky", "48 Hours")
The journey through a Stargate will seem instantaneous to both the traveler and observers on either side but actually takes 0.3 seconds on average. There was one exception to that; when an alternate SG-1 used a Stargate to dial into our reality to steal a ZPM, the connection took 3.4 seconds. A traveler will exit the gate at the same velocity in which they enter under normal circumstances. However if the Stargate is powered by an unstable power source, the velocities of the travelers are greatly increased. Depending on the range of the instability of the power fluctuations velocities tend to increase, most likely due to the affects of the instability of the wormhole.(SG1: "Ripple Effect", "Upgrades")
When connected to a more stable power source such as a ZPM the wormhole experiences no ill effects. When O'Neill had the repository of knowledge downloaded into his brain he constructed a device to provide power to the gate to dial the Ida galaxy, which due to the crudeness of the device, resulted in O'Neill exiting the gate very differently then how he entered. When SG-1 traveled to K'tau and the wormhole traveled through K'tau's sun, the wormhole was affected by the star and SG-1 exited the gate much faster than they entered. In comparison, when the Atlantis expedition traveled to Atlantis there was no change in velocity due to the more stable power source of the ZPM. (SG1: "The Fifth Race", "Red Sky", ATL: "Rising")
When Destiny was dialed using the unstable radioactive core of Naquadria, all of the travelers were flung out of the gate, many of them sustaining injuries. Col. Everett Young was the last to go through just as the planet was exploding and was flung right across Destiny's gate room. Similar effects happened when the Lucian Alliance gated into Destiny. (SGU: "Air, Part 1", "Incursion, Part 1")
If a traveler enters through the back of the wormhole of a Stargate, the traveler will simply exit the puddle at the front and be caused no ill effects. If a traveler enters an incoming wormhole they will simply be deposited back to where they entered from at the same velocity, unless prevented from doing so.  (SG1: "A Hundred Days")
Most Stargates get their power from the DHDs for outgoing wormholes but not required for incoming wormholes unless power from the dialing end is interrupted. Stargates, being made of Naquadah, can absorb many forms of energy from electricity, heat and radiation. Stargates require significantly small amounts of power to initially connect the wormhole, which then the receiving end will take over powering the wormhole. (SG1: "The Torment of Tantalus", "Prisoners", "1969", ATL: "Home")
Due to the Naquadah that the Stargates are built of, they are incredibly durable, capable of outliving most other structures and withstanding huge amounts of force and energy. The early versions of the Stargate such as those deployed by the seed ships are more fragile than future versions capable of only withstanding a single powerful blast before being irreparably damaged. Future gates can withstand graviational effects, direct meteor strikes, intense heat and even weapons of mass destruction. (SGU: "Common Descent", SG1: "A Matter of Time", "A Hundred Days", "Exodus", "Chain Reaction")
Stargates however have a limit to how much they can withstand before damage ensues. If enough explosive force impacts the gate it will be destroyed such as specially designed weapons like the Mark IX. Stargates are also susceptible to subspace interference like that created by the Attero device which causes the Stargate to build up its energy reserves until it explodes. Also with age some Stargates may stop functioning. (SG1: "Beachhead", ATL: "First Contact", SG1: "The Fifth Race")
Each Stargate has several safety features installed in their programming to ensure safe use. The Stargate will not, unless overridden, be capable of dialing a planet on the opposite side of a Star to protect the chemical reaction of the star, the event horizon also has a feature to prevent things which naturally exert pressure on the event horizon such as liquids and gases from entering the gate, unless enough force is exerted on the event horizon. Stargates also peridoically dial one another to transmit their location to negate the effect of stellar drift. (SG1: "Red Sky", "Watergate", "Children of the Gods", ATL: "Inferno")
The Stargate is also capable of dialing all other Stargates in range, but it is unknown what happens if a traveler passes into one of the active gates. The Stargate is also capable of time travel effects such as when the wormhole passes too close to the solar flare of a star which can cause the wormhole to loop upon itself exiting at either gate in the past of future. An Ancient time machine can access the Stargates subspace field and create time distortions outside of subspace, however its range is limited. The Stargate can also access alternate realities when the wormhole passes through a black hole. (SG1: "Avenger 2.0", "Reckoning, Part 2", "1969", "Window of Opportunity", "Ripple Effect")
- Main article: Glyph
Glyphs are the symbols on Stargates which allow for a co-ordinates system to be used for interplanetary, interstellar and intergalactic travel. These glyphs are locked into place by the Chevrons on the Stargate. The original Stargates used an unknown word-meaning system  for glyphs but on later versions it became based on star constellations. The Milky Way Stargates have 39 distinct symbols on them, the Pegasus galaxy and Destiny-style Stargates have 36 symbols on them. (Stargate, SG1: "Touchstone", ATL: "The Brotherhood", SGU: "Air, Part 2")
- Main article: Chevron
Each Stargate has nine chevrons equally placed around its surface. The chevrons indicate how many symbols have been dialed by lighting up, the top chevron on Milky Way version Stargates locks downward while other versions do not move at all. Destiny-style Stargates have white chevrons, Milky Way Stargates have orange chevrons and Pegasus Stargates have blue chevrons. The only use of all of the chevrons is the ninth chevron used to dial Destiny.
Dial Home Device
- "On most planets, found along with the ring, is what we call a DHD. It's a dialing device."
- — Daniel Jackson
- Main article: Dial Home Device
The Dial Home Device, more commonly called a DHD, is used in the dialing of the Stargate. Most DHD's are short pedestal-shaped devices with a rounded inclined surface on the top with two concentric circles of buttons, for each of the symbols on the Stargate, surrounding the center button. The DHD can allow for faster dialing of the gate by not allowing the inner ring of the gate to spin. The DHD also serves as the main power supply for the Stargate as well as containing all the necessary dialing data and the correlative update program. The Destiny-style Stargates do not possess DHD's and instead need to be dialed with a remote. (SG1: "Children of the Gods", "48 Hours", "The Quest, Part 2", SGU: "Air, Part 3", "Lost")
Milky Way version
The Milky Way versions of the Stargate are the second version built by the Ancients, these versions are an analogue type which have an inner track of Glyphs, which spins around to place the appropriate symbol beneath the top Chevron to lock it into place, the subsequent chevron will glow orange to signify it has been locked. These gates are dark grey in color, made of Naquadah and weigh around 29 tons (64,000 pounds). (SG1: "Children of the Gods", "Redemption, Part 2")
These Stargates are capable of manual-dialing by rotating the inner track until the appropriate symbol is beneath the top chevron, power is provided which causes the Stargates programming to lock the symbol. They are found in both the Milky Way and Ida galaxies, these Stargates are the most common with thousands located in the Milky Way. Most of these Stargates are situated in stone platforms with a stairway to provide access, most likely built by the Ancients. (SG1: "The Torment of Tantalus", "1969", "The Fifth Race")
When the Ancients moved to the Pegasus galaxy, they constructed a new version of the Stargates. These versions are digital in nature as opposed to the previous more analogue versions, are also built of Naquadah and consist of more of a silvery blue appearance with blue chevrons. There is no inner track that moves, instead the symbols stream through and light up the chevrons as they go, because of this these versions cannot be manually-dialed. These versions are incapable of dialing intergalactic addresses without a special control crystal, they also override older versions when in proximity becoming the dominant one. Many of these gates are situated in the ground with no platform and some are placed in orbit of planets as spacegates. (ATL: "Rising", "Home", "Midway", "The Last Man", "Enemy at the Gate")
- "Rush figures that this gate predates all the others we know of, like a prototype."
- — Eli Wallace
The Destiny-style Stargates, the one on Destiny and those planted by the seed ships and are the prototype version of all others. The gates do not have an inner track of glyphs but instead the entire gate spins to move the glyph to the top. The glyphs do not represent star constellations but instead an unknown word meaning.  and light up for each address. The Stargates chevrons light up white and stay lit until the wormhole is established. These versions are less advanced that their future counterparts and incapable of intergalactic distances and only capable of short distances to relatively close Stargates. (SGU: "The Stargate Room", "Air, Part 3", "Lost")
The planetary Stargates are situated on travel bases that consist of a ramp leading up to the Stargate. The Stargates may not be made of, or primarily made of, Naquadah as they have been shown to be somewhat weaker than future versions. It is apparent that the Destiny style Stargates have a subspace connection with the Destiny and communicate with nearby gates to provide data on address and Stargate status. The Stargate on Destiny also features an orb at the top connected to the roof of the room, which lights up when the gate is active, the function of which is still unknown. When wormholes are deactivated, two vents on either side of the Stargate open and release some form of gas. (SGU: "Air, Part 3", "Cloverdale", "Common Descent", "Aftermath")
- Main article: Supergate
To accommodate their large ships the Ori built at least three Supergates, consisting of several dozen individual pieces, actually ships, and hundreds of meters in diameter, these gates are powered by a black hole and capable of sending ships across the universe. The segments are sent through a regular Stargate and form into the shape of a circle, energy passes between the segments and the wormhole is formed. (SG1: "Beachhead", "Camelot", Stargate: The Ark of Truth)
- Main article: Tollan Stargate
The Tollan built, with help from the Nox, a Stargate to get to their new homeworld, Tollana. This gate was pale in color, much smaller and thinner than other gates, possessed no Dial Home Device, had no discernible glyphs on it and no light-up chevrons. This version no longer exists after Tollana was invaded by the Goa'uld and the Stargate was destroyed to prevent escape. (SG1: "Pretense", "Between Two Fires")
- Main article: Mini Stargate
The deascended Ancient Orlin built a miniature Stargate in Samantha Carter's basement as a means to return to Velona to stop SG personnel from activating a weapon and bringing the wrath of the ascended Ancients. The gate was not made of Naquadah but instead constructed of various Earth materials such as titanium, fibre optic cable and a toaster and was only able to dial out once before it burnt out. (SG1: "Ascension")
McKay-Carter Intergalactic Gate bridge
- Main article: McKay-Carter Intergalactic Gate Bridge
While not a variant of the Stargate, the gate bridge was constructed as a means to traverse the three million light year void in between Atlantis and Stargate Command, the McKay-Carter Intergalactic Gate bridge was a connection of 38 Stargates that stored the patterns of the travelers and allowed safe and (relatively) quick passage between the two. At the midway point is the Midway Space station which is used to exit one gate system and enter another as well as quarantine travelers for any number of reasons. (ATL: "The Return, Part 1", "Midway")
Asuran Stargate satellite
- Main article: Asuran Stargate satellite
The Asurans built a small ship, consisting of a shield generator, hyperdrive and sensors, built around a Stargate. When it arrived in place, the shield protected it until the Stargate was dialed when a powerful beam is shot through the wormhole to attack a target. The offworld source provides power not only for the weapon but also the shield for the device. The proximity of the satellite also overrides the Stargate on nearby planets. (ATL: "First Strike")
Behind the scenes
- The Stargate prop on Destiny does not entirely spin, only the front half does, unlike the location Stargate which entirely spins. 
- Occasionally some of the Pegasus Spacegates were shown to have only 8 chevrons. This is actually a production goof when these CGI shots were made. (ATL: "First Strike")
- Amelius' notebook has Milky Way style Stargates and similar glyphs despite the generation of Stargates first built being much different from his designs. (Stargate: The Ark of Truth, SGU: "Air, Part 1")
Similarities in other media
- In Tomb Raider: Legend, the portal to Avalon is a large circular ring which spins around.
- The original movie was parodied in the South Park episode "Imaginationland". The US Army builds the gate and have a team sent through led by Kurt Russell and the similarities are actually mentioned in the episode.
- In the MMORPG EVE Online, 'Stargates' are used to send spaceships across systems, however they are of a different design.
The Stargate manufacturing area on a seed ship
- Mini Stargate
- Stargate Network
- Dial Home Device
- Ancient Remote
- Stargate Travel base