I'm trying to figure out how many planets have stargates in the Stargate universe, preferably separated by galaxy. I've recently thought about just how many stars there are in the galaxy, and roughly what fraction of them would have a stargate, just to run through some numbers.
Bonus points if you compare the number of stargates to the number of stars in the galaxy, distance between stargates, etc.
To my knowledge, there was never a number given for the number of Stargates in the Milky Way or Pegasus galaxies. An out of universe explanation for this is that giving such a number would limit the number of planets they could visit and thus the number of episodes they could have on different planets. Such a limit would also prevent the writers from easily doing things like pulling 17 gates from each galaxy to build an intergalactic bridge, which would further reduce the number of gates in the galaxy.
This is a pretty comprehensive list of the known gates and addresses.
On the other hand, for Stargate Universe, we know that the trail of gates left behind the seed ships have been going for 60 million years, and their FTL is pretty quick. If one ship is able to seed a gate on one planet each week, then that means there are roughly 3.13064742 × 10^9 gates spread across the universe, per seed ship.
After reading a few of the Stargate wiki pages, I rewatched a couple of episodes that I thought might provide clues. In Avenger 2.0, a season 7 episode, Felcher's assistant Chloe provides a hint to the number of gates in the Milky Way. They deploy a virus that scrambles the glyphs on a DHD so they no longer correspond to the correct coordinates. This makes it so the DHD for that gate doesn't work. This virus then spreads to other gates, and Chloe says:
If each gate only dials 2 others before adapting to the new system, the entire network will be affected in less than 2 hours.
This was several hours after they'd deployed the virus. What follows is speculation, inferring from what is in the episode. The above quote was from later in the day they deployed the virus to one gate. If we assume they deployed the virus first thing in the day, and learned of the ramifications at midday, then there are ~5 hours of the virus spreading prior to that quote. Add 2 more hours, we get 7 total. We don't know how long it takes for one gate to dial another gate and send the update, so for an upper bound on the number of gates, let's assume that it's instantaneous once the two gates connect.
One gate dials one other gate (1 infected DHD), sends the update (2 total), then both gates dial another (4 total). Then the first infected gate is done, and the 3 others dial out (7 total). Then the second infected gate is done, so 5 of the gates dial out (12 total). Next 8 of them will dial out. The number of gates dialing each time is going to follow the Fibonacci sequence.
So, now we know how long it will take to spread, and how quickly it spreads to new gates. If we assume that the dialing process takes 1 minute, it will run for 420 iterations. But that yields a number larger than the number of stars in the galaxy. By like 10^78th power. If it takes 2 minutes to dial, that comes down to 10^35th.
I hate it when writers don't do research.
In SG-1, they find the Abydos cartouche in the first episode, which gives them an estimate.
There are certainly many gates NOT on this artifact.
With the number of chevrons on the gate, and the number needed for dialing (six + Point of Origin) we can determine the number of potential gates (1,947,792 - 36 choose 6)
We can discount the random dialing the US did pre-Stargate movie - it's highly unlikely they dialed a significant number of gates using the correct 7th symbol, without which the gate would never work.
The stargate team doesn't regularly dial random numbers to try to find valid addresses. This indicates to me that they consider the odds of randomly dialing a valid gate too small to be worth the risk.
With that in mind, I peg the chances at 1% (a number for which I have no real reasoning beyond "small enough to be good, but big enough to be interesting"). It's also a nice, round number, and humans in general find those appealing.
So, assuming 1% of the possible gate addresses works (with some margin for error for buried or inaccessible gates) at approximately 20,000.
The next question is - how accurate is this estimate?
Not very - I have no support for my percentage estimate. I could be off by a significant margin (most likely in the 'too generous' direction). This could be considered an optimistic estimation, then.
Out of universe, I think this number would be called 'plausible' by the creative team in charge of the shows, as it leaves them a lot of wriggle room, enough planets for 100 20-episode seasons (assuming no repeat visits), etc.
Final Answer: 20,000 at best. (For a 37-glyph stargate)
16,500 for Pegasus (36-chevrons, though Pegasus may have a relatively higher percentage of active gates than the Milky Way)
Edit:
In Earth's network (39 glyphs): ~28,000 As someone pointed out in the comments, the Milky Way network has 39 glyphs per stargate, meaning we should do 38 choose 6 instead of 36 choose 6. The rest of the math is unchanged.
I've been thinking this through, and while my new answer is based off of Jeff's and Keen's, I think I've got a few things uniquely figured out.
First of all, there is a question about Does the order of glyphs matter in Stargate addresses?. Personally, I find it hard to believe that the order would make much of a difference as to where the coordinates end up to be, but it does seem to be that the order is important. Perhaps there can only be one given set of glyphs for a particular star, but the order must be dialed in exactly. Thus there is only a 1 in 720 chance that a particular combination is dialed correctly, assuming that the stargate map was entirely fullfilled. What this allows then is for there to be more stargates.
Given then the math in Jeff's answer, the maximum number of stargates could be as high as 2.8 million combinations. That's alot of possible stargates... Still, I doubt somehow that the number is really so high. It seems likely that most of them are empty, but it could still explain higher numbers than would otherwise be possible.
Assuming 5 minutes to dial a gate, and 2 hours total time, the number is 200,000 roughly. Assuming some dead ends, and that number is a bit lower.
Given the above information, and some story-line bits, I estimate that the number of gates is somewhere between 10,000 and 100,000, with possibly as many as 200,000. But further work would be needed to reduce that number somewhat.
A B C is not the same as C B A. Order allows you to store much more information in much less space. If I tell you the coordinates are 51.5° 0° and you punch in 0° 51.5° instead of ending up in London you'll wind up off the coast of Somalia.
Just doing some very vague maths, with (38x37...x33)/6n!= 2.759*10^6 stargates, & the volume of the galaxy 50*10^14ly^3, this gives us 1.8*10^8ly^3gate^-1. Converting that for orbs, that's over 350ly until the next stargate zone.
In season 6 ep"2001", there are 6 recorded gates within a 300ly radius, even abidos was within this distance from earth after they changed the story line that it was in the same galaxy.
From this we can conclude that the order isn't important, returning us to ~2*10^10, or the writers never had some base math to work off.
Also (season 1) with go'auld ships travelling initially at 30c, & taking initially upto 2 months from the address meant that it was 5ly away from earth. Less then abidos which for all intensive purposes was ludicrously close.
If the order doesn't matter then a gate can be placed within a 18ly radius. Looking back at 2001 & other episodes, the ancients knew of gates which correlated to 1 in possible 10,000 addresses, or 20,000 adresses, which works with how many were in the ancient database.
Y'all are all wrong. The earth Stargate is based off of the constellations as seen from earth. So each gate should have its own set of glyphs because each planet would have its own set of constellations. So the number of possibly gates could be infinite but the number of gates accessible by earth is limited by the number of glyphs available.
