default gates

[deezer47]

i was just wondering how the stargate found in giza was able to operate properly. i was under the impression that the default gate on a planet was the one that over turned any other gates. i understand that maybe the ancient gate may have been disused for a while but it still had power and so would that not mean that whenever someone gated to earth they would travel to that gate instead of the giza one?

[stargatefan234]

the antartic gates dhd was frozen over, and so possibly it did not register as the default gate as any inbound travelers would be stranded.

[jelgate]

the antartic gates dhd was frozen over, and so possibly it did not register as the default gate as any inbound travelers would be stranded.

We also know that the DHD is the power source of the gate. I can imgaine with the DHD frozen that the Antartic gate wasn't getting any power in contrast to the powered Giza gate

[fxdbstargate]

The antartic gate was frozen over like an iris.
In ep. 203 "prisoners" sg1 was sent to a prison on a planet and the had no dhd to dial out.
In ep. 117 Colonel O'Neill and Captain Carter get stuck in antartica when the gate jumped. That dhd was frozen.

[Eternal Density]

I had assumed that the glacial flow had separated the DHD from the Stargate and Carter had to 'plug it back in'. Just like the Russians disconnected their DHD while they weren't using it. (And the NID with their DHD) (I assume that somehow the SGC Stargate goes back to being default because it is attached to a 'primitive' dialing computer, which is better than being connected to nothing.)

A related question is that after Carter plugged the Antarctic DHD back in, why did it not immediately supersede the SGC Stargate? Many teams went offworld looking for the lost members of SG-1 but they all returned to the SGC, not Antarctica. I suppose that even with the DHD connected, the gate system did not make the Antarctic gate primary because it had not been successfully dialed after being dormant for so long. Sam and Jack were only sent to Antarctica by mistake - even with the DHD connected the gate system would not send anyone else through until a successful dial-out had been accomplished, which would update the gate system to inform the other gates that it would be safe to route wormholes to it.

Once both gates went into active use, the NID (and later, Russian) one would have been primary when connected to the DHD, and as soon as it was disconnected from the DHD, the SGC would become primary because it has a dialing computer. That explains the observed behaviour quite nicely, I think.

If we rely on the theory that the Antarctic gate should have been primary all along but didn't work because of ice, then it should have been use for all wormholes as soon as the ice cleared. That doesn't fit with what we see - it was used a single time by accident, and wasn't use again until the NID started using it. Even when connected to the DHD, it did not start to receive wormholes until after it dialed out. (At least, we can safely assume the NID did not return from any missions until they went on their first mission, and all SGC teams returned to the SGC as planned.)


I suppose we can make a timeline as follows:
1. The Ancients leave for Atlantis. The Antarctic Stargate is the only one
2. Lanteans evacuate Atlantis 10,000 years ago.
3. Glacial flows separate Antarctic Stargate from its DHD.
4. Ra shows up on Earth. It seems to be standard proceedure for Goa'uld to bring their own Stargate (since they have their own library of addresses separate to the ones the Ancients knew). He must know about the one already on Earth but found it easier to use his own. I figure Goa'uld don't really like the cold.
3. Ra's Stargate is buried 5,000 years ago. He doesn't feel like going back, and no other Goa'uld do since it's Ra's territory, even though he's moved away. Or else they can't be bothered taking the long journey by ship (hyperdrive tech wasn't so good until recent times) or tried to go by Stargate but couldn't. (Actually, some frozen Jaffa were found. They must have been sent to check out Earth, turned up in Antarctica, couldn't dial back because of the disconnected DHD, and froze)
4. Later Earth cultures get transplanted by the Goa'uld and Asgard. This had to be by ship, as the Goa'uld had no way of transporting populations via Antarctica. The Goa'uld would have mostly stayed away, maybe only a few ventured by in ships, while others stole people the Asgard had already moved because they were closer by. Who knows?
5. Ra's Stargate is uncovered. Even though neither it nor the Antarctica one are attached to a DHD, it becomes primary because it has been used more recently. (the frozen Jaffa don't count because that was an incoming wormhole only).
6. Ernest Littlefield uses Ra's Stargate to get to Heliopolis but doesn't know how to get back. (We'll ignore time travel since it doesn't apply to the original timeline)
7. Jack O'Neill (and team) go to Abydos. They, and all subsequent missions, return to Ra's gate since it is the most recent one to dial out, and neither gate has a DHD
8. An energy overload sends Jack and Sam to the Antarctica gate, where Sam reconnects the DHD. This gate does not become primary, because they do not succeed in dialing out. This prevents the search parties from turning up in Antarctica also.
8.5. Apophis brings a gate with a DHD near to Earth. This allows dialing out, and it would have become the primary gate since it has a DHD connected. It was soon destroyed by the explosion of the Ha'tak, so it quickly became a non issue.
If the NID operation was already in place (doubtful) and they had connected the DHD at this time, which gate would have recieved incoming wormholes? Theirs, or Apophis'? I'm really not sure.

9. the NID use the Antarctic DHD and Antarctic gate. It is now primary because they dialed out. They disconnect the DHD and the SGC (Giza) gate becomes primary because the dialing computer beats the lack of DHD. As soon as they reconnect their DHD, the Antarctic gate becomes primary again (they don't need to dial out for this to happen now, as the gate has been listed as 'working'). This means they merely need to connect the DHD when it is time for their teams to return home, as well as when they want to dial out.
10. The SGC overload the Madrona Stargate to send the MALP though the Antarctic gate
11. The Antarctic gate is disconnected from its DHD (so it is not primary) and also sealed so no accidental connections can be made. This would mean that a future overload would cause the wormhole to jump to another planet rather that elsewhere on Earth.
12. The Antarctic DHD runs out of power
13. The Giza gate sinks with Thor's ship and is replaced by the Antarctic gate. It becomes primary because it is connected to the dialing computer, while the Giza gate is unattached.
14. The Russians connect the Giza DHD to the Giza Gate. It becomes primary while the DHD is connected, and reverts back to the SGC (Antarctic) gate when disconnected.
15. The Russian DHD explodes during the process of rescuing Teal'c from the buffer. Earth now has no DHDs. The SGC (Antarctic) gate remains primary due to the dialing computer.
16. Anubis destroys the Antarctic gate, which fortunately is removed from the SGC and Earth in time.
17. The Russians lease the Giza gate back to the SGC. There's no more gate contention issues since there's only one stargate.
18. The Trust beams the Stargate out of the SGC. Prometheus beams it back after they use it to send symbiote poison a few times. Not especially relevant
19. Warning Massive Spoilers for Atlantis final episode, Enemy At the Gate (which I only just realised is a pun!)

Spoiler:

The Wraith bring a Pegasus (new model) Stargate close to Earth. It has a Pegasus DHD too. Since it has a DHD, it becomes primary, so it will receive any incoming wormholes. We learn that because they are a newer model, the presence of a Pegasus gate also prevents a Milky Way gate from dialing out! This was first discovered at the Midway Station, which has both types, neither with a DHD. the problem was solved with appropriate software, but of course we can't do that in this case since we can't reprogram the Wraith's stargate right now.
Then it turns out that as it is, a Pegasus DHD isn't much use in the Milky way since the coordinate system is all wrong, but a couple of minutes of McKay programming fixes that. Then it all gets blown up and we go back to the way things were.

I think that makes sense of everything.
I should of course mention that the concept of DHDs is not at all in the original movie (which would actually require a DHD in order to power the Stargate for a return trip. I suppose no one noticed it at the time, so Daniel dialed manually and the Stargate drew power from the DHD. Hypothetically if they had seen the DHD, Sam would have been a little less amazed when she got to see it for the first time on Abydos, and everyone would have been a little less surprised that the Stargate went to multiple places.)

Did I miss any problems?

[edit] yes, I did! Some Ancients left Earth again.
Either they left through Ra's stargate while Ra was still on Earth (rather unlikely) or else they left through the Antarctic gate. Since they returned to earth 5000 years before Ra left Earth, it is most likely that those who left, left before Ra came. This gives time for the DHD to become disconnected before Ra showed up. Otherwise there would have been two stargates connected to DHDs. And if they left through the Antarctic gate after Ra left, then the Antarctic gate would become the more recently used Gate, which means... actually it's not a problem, since it will still be left without a DHD for long enough to be listed as 'idle' once the Giza gate is dug up.
Also, Merlin must have used it (the ring transporters at Glastonbury and the Antarctic outpost would have been very handy!) so we know the Antarctic gate has been used since the Giza gate was buried. However it must have sat disconnected and unused for long enough after Merlin last used it for it not to become primary the moment Sam reconnected it, otherwise the rescue teams would have returned to Antarctica.
That should cover everything. I think.

[summary]
In brief, the answer to the original question is that it is necessary for the stargate system to have a rule that if a location has more than one Stargate, and one is disconnected from its DHD and not used for a few years, the other one remains primary, even if the unused Stargate has its DHD reconnected and the other gate does not. The unused Stargate will not become primary until an outgoing connection is established from it, regardless of having 'superior dialing device status'. This could be a safety feature in case the unused Stargate has been unused for a reason, such as being on a frozen continent while the other Stargate is in a nice accessible place but lacking a DHD.

Actually... I suppose that having the dialing computer (not quite as good as a DHD but still far better than nothing) must have outweighed the DHD of the Antarctic gate which had not been successfully used for a few hundred years. If the SGC only had a gate, with no dialing computer at all, the Antarctic one would have been primary, because it at least has a DHD even though it has not been used for a long time. If the Stargate system can avoid sending wormholes through stars, then surely it's smart enough to prioritise gates based on a combination of dialing device status AND dialing device usage history.
Wow, that 'summary' was longer than I expected.