18

We've seen incoming activations of a stargate and before the wormhole forms, the wheel on the gate starts spinning, which helps provide a warning an incoming wormhole is about to form. Since the wormhole isn't formed yet (there's no event horizon at this point), that means the originating gate is in contact with the destination gate, even before a wormhole is created.

If one stargate is attempting to create a wormhole between itself and another gate, once it has the coordinates, it will need to connect to the gate to to open a wormhole to it.

Stargates have created wormholes over extremely vast distances light years apart. How do they communicate with each other over those distances before they open a wormhole?

12

There's a fair bit of evidence that there is a subspace communication of some kind in the SG universe. Furthermore, it is a known fact, from SG:U, that there is some kind of a very strong shock in subspace, sent when gates dial. Specifically, it's how the Control Ships find Destiny. Therefore, I'm going to hypothesize that the gates somehow communicate with each other via a subspace connection of some kind before they make the connection.

More proof of this is that in the episode Common Descent, Eli takes a subspace transmitter from a stargate and uses it to communicate with Destiny.

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    Subspace communication is fast, but it's not instantaneous like gate connections - otherwise the communication stones wouldn't have still been in use. That's why I didn't consider it in my answer. – Izkata Feb 17 '12 at 14:07
  • @Izkata: Subspace communication is real-time, but it does not cover a huge distance. Plus the communication devices allow for other methods of communication. – PearsonArtPhoto Feb 17 '12 at 14:09
  • Then, what about the Earth gate connecting to Destiny? Even if it is real-time (which I doubt; I think it's simply fast enough to appear near-real-time between the adjacent 4 galaxies the series takes place in), if distance is the issue it still wouldn't account for that connection. – Izkata Feb 17 '12 at 14:12
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    @Izkata: I'm speculating here, but the energy needs to dial Destiny were enormous. If the distance that one can communicate over subspace is proportional to the energy somehow, then the increase of energy would increase the distance, allowing for the proper communication. – PearsonArtPhoto Feb 17 '12 at 14:14
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    Also, the Destiny stargates probably have different setup than the SG1 or SGA gates, not having a DHD and all. They probably have that functionality built into the gate since they are not designed to be used by non-Alterans. – Tyson of the Northwest Feb 17 '12 at 17:51
7

Actually the Gates don't talk to each other before they connect, they don't have to. Each gate has 38 reference points programmed into them. To open up a connect you enter the 6 coordinates based off those reference points, which projects the beginnings of a wormhole near the target gate. We can tell this because the gate draws large amounts of power as it is being dialed, not just when the 7th chevron locks. It is mentioned at various times when dialing 8th and 9th chevrons that even the attempt to dial the 8th or 9th chevron would be too expensive unless they were sure it was going to lock.

If there is a functional gate within range it draws that pre-wormhole to it. The exact range of this is unknown, but I assume it is a fairly large distance. Otherwise as the planets and their solar systems move through the galaxy they would leave the target area pretty quickly. This throw/catch mechanism is necessary since even with 38 available points of reference it would be virtually impossible to hit the tiny and (relatively) fast moving target of a stargate across interstellar distances.

This capturing is indicated by the spinning of the receiving gate. This spinning could either be the receiving responding to an attempted connection in it's vicinity, or the receiving gate responding to the power being given it by the sending gate, it is unclear from the shows. I liken it to how a lightning rod "draws" lightning to it, not by acting on the lighting, but providing it the shortest path to "ground". You can also extend this metaphor to explain why a wormhole will jump to a second gate within the target range. If one gate becomes too energy saturated it ceases to be the shortest path to "ground", and the wormhole jumps to the next shortest path, the second wormhole. How stargates determine target precedence is a different question.

If nothing goes wrong by now the 7th chevron on the origin gate locks and all chevrons on the target gate lock. This is where the Kawoosh comes in, when the unstable wormhole interacts with the stargate's disintegration/reintegration. Then the stargates can communicate with each other to negotiate matter transmission, energy transmission, etc.

As long as the reference points in the stargate are fairly up to date, say within 2-3,000 years, all you need to dial is a power source and an address. If you are receiving you don't even need that, leading to the occasional one way trip. However, over time as stellar drift moves both the points of reference and the stargates out of the target area. This is why Abydos was the only gate the Earth gate could reach, in Children of the Gods Carter estimates within a few thousand more years even that address wouldn't work. Once they discovered the Abydos DHD and Daniel showed them the cartouche temple, the SGC had a baseline list of addresses that should work. From there they could determine a way tweak the stargate's reference points to access those worlds recorded by Ra. Later, during The Fifth Race, with the Ancient knowledge in his brain, O'Neill creates a better program to compensate for stellar drift allowing for a more precise reset of the stargate's points of reference.

To counter this the DHD's communicate with each other using the Correlative update system. The DHD's at random intervals, on would assume every few hundred years depending on their planet's relative motion, dial out to other gates they have records of and probably communicate with the DHD on the other side, exchanging data on how the target gate is drifting from the target area compare their update records and update each other with the most recent data. DHD's do store addresses of dialed gates, but not in an easily queryable way. It is how the Adria was able to track SG1 in The Quest, among other times. If the target is shifting then the DHD runs some internal program, then updates the stargate's points of reference.

Because the Earth gate was sealed for so long it was unable to update in this manner. So the DHD could never update the points of reference programmed into the Stargate to account for stellar drift. Each time it missed an update the stargate's points of reference got more and more out of date.

  • Sources, please? – Iszi Feb 17 '12 at 17:54
  • This of course does not cover the SGU gates, them not having DHDs. I assume that this is because they are designed for easy access to resources not supporting a world spanning civilization. As such they may use other means to communicate with each other, subspace probably, and that communication could be detected by the Control Ships. – Tyson of the Northwest Feb 17 '12 at 17:55
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    This is mostly true, but I highly doubt that SGC had subspace technology prior to using the stargate. It also doesn't explain how Stargates can open wormholes without any kind of a DHD. – PearsonArtPhoto Feb 17 '12 at 18:24
  • I thought I made that clear with the role of the DHD to detect stellar shift and adjust the stargate's points of reference accordingly. Will edit to clarify. – Tyson of the Northwest Feb 17 '12 at 18:42
  • This answer doesn't even address the question, as far as I can tell: The Stargates spin and/or light up on an incoming connection, before the wormhole is established, and even when there isn't a DHD, like with the Tau'ri gate. – Izkata Feb 17 '12 at 19:02
3

Most likely with the same (or similar) technology as the Ancients' Long-Range Communication Stones, which were able to connect for instantaneous communication across galaxies - even across a large chunk of the universe in Stargate Universe.

I would guess the communication stones work by way of some sort of quantum entanglement, which would explain why they're always used in pairs. The pairs were likely created together.

Stargates could use similar technology, a type of physics relating to quantum entanglement that we know nothing about.

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    This would suggest that all the gates are entangled together. That seems unlikely. – geoffc Feb 17 '12 at 4:28
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    I too thought of the communication stones, but if they're always used in pairs, then I have to agree with @geoffc. If there are n gates in the galaxy, the number of unique communication stones/crystals/devices each gate will have to contain will be nP2. A gate within a 1000-gate network will need to contain almost a million such units. There are other problems too. Only gates that were constructed together would work together. But we know that the Tolans built a brand new gate. And the Destiny gate can dial gates made by seed ships. – HNL Feb 17 '12 at 8:49
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    @geoffc & HNL: Hence my last sentence. A physics relating to quantum entanglement that we know nothing about. The communication stones themselves seem to be older than the Stargates - there were two in the Ori galaxy paired with two from our galaxy, which suggests the original design was from before the creation of the Gate network (before the Ancient/Ori split). – Izkata Feb 17 '12 at 12:40
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    Technically, there could be one hidden communication center that each gate connects to, and at the center acts like a telephone operator. Thus, each gate only communicates with one source, but all gates are linked. – Chris Lutz Feb 17 '12 at 17:52
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    @chris-lutz if that were the case it would have been a treasure trove of Ancient tech and a single point of failure for the system. By the time of the show the Goa'uld are familiar enough with the stargate network to reprogram it. I would think that if they had that level of knowledge they would have noticed a central source and either taken control of it or destroyed it. – Tyson of the Northwest Feb 17 '12 at 21:28
-1

Actually, there is considerable inconsistency on-screen with regards to these issues. Here's the problem; it would not be possible for an incoming wormhole to cause a Stargate to activate and start spinning BEFORE the originating gate had completely finished dialing... however, this type of "cutting back and forth" editing is prominently featured in multiple episodes of Stargate. Imagine that you were dialing a telephone to call a friend... the phone at your friend's house could not possibly start ringing before you finish dialing, because the phone does not know WHO you are dialing until you dial the very last number. The same would be true with a Stargate connection. The Stargate can't know what your destination is until you enter all the symbols (or at least the first six symbols). Nevertheless, the Stargate on the receiving end is frequently shown to start spinning even as the address is still being input on the originating end of the connection. The only way this would be possible would be if EVERY Stargate that you MIGHT be dialing (thousands of Stargates on thousands of worlds) were to simultaneously activate and start spinning at the same time as you begin to dial out. Then, with each additional symbol entered the gates that were eliminated from being the one you intend to dial would deactivate until only the final gate... the one you wished to connect to... would remain active. Certainly, there is no on-screen evidence to suggest that anything like this is happening. The DESTINY gates are a bit different... they must communicate with one another via subspace because they need to notify other gates when they are within range, whereas Milky Way and Pegasus gates do not seem to be subject to range limitations.

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