Stargate address numbering P3X-421

One of the nice things about taking the odd walk (to try and get more healthy / lose weight) is I get 20 minutes to ponder something totally random - like how are the Stargate address numbers worked out?

This is a matter of some debate. Basically, the show references gate addresses by a code, e.g. P3X-421, rather than by the gate symbols which would be tricky (though we later find they do have names / sounds that can be strung together to make words of a sort). An address is actually 6 (non repeating) gate symbols from a set of 38.

[Someone commented as a linguist that the idea of the gate symbols having sounds that make up the names of planets was crazy as no way the location in space and the name would happen to line up. They missed an obvious point that the people naming the planet may have been the Alterans and they named the planet using the sounds from the planet's gate address. But that is beside the point]

Anyway, back to these gate numbers. The Milky Way gates are almost all P something. This suggests that maybe the letter is not part of the address (P=Planet), but even the odd exception (M=Moon) does not quite fit, and a B and K have also been used. With no doubt deliberate irony the Pegasus gates start M.

This leaves 5 alphanumeric characters to define a gate address. Even if you take all letters and numbers (36 combinations), 36^5 is only 60,466,176, but there are 1,987,690,320 possible 6 figure addresses (38*37*36*35*34*33). So it cannot be a simple mapping to the gate address.

Except, and this is where the pondering whilst walking around the block comes in, let's pretend we accept the original description for how a gate address works.

The way it is described is that the 38 symbols (apart from point of origin) are constellations as viewed from Earth (which they are, you can work out which they are even), and that they represent points in space. You need 6 so as to make three lines which intersect at the destination, and then to "plot a course" you need a 7th (point of origin).

OK, here are a few of the issues:-
  • A constellation is not a point in space, the "stars" that make it up are at different distances and some may even be very distant galaxies.
  • Even if these symbols represented a point in space, the chances of ever making three lines that intersect exactly out of 38 arbitrary points is, well, slim at best. The chance that such an intersection is actually where you want to go (hits a planet, or even a solar system) is even slimmer. It is just not a way to address points in space
  • Obviously, even if using points in space as a reference, you can make a target using just one line and one point. Even so, the possible points are nowhere near enough to address a planet or solar system in the galaxy from 38 control points.
  • The fact you used reference points means that actually the expansion of the galaxy is likely to ensure gate addresses do stay the same, yet apparently they stop working after a while.
  • You obviously do not need a point of origin - the origin is "here". If you did, then how come it does not also take 6 symbols to define it. Also, does that mean by dialling a different symbol as the 7th you create a wormhole from some distant gate to some other gate in the galaxy?
OK, let's forget all of that, it is a film, let's pretend it makes sense, and that is how gate addresses work.

Well, that may solve the gate numbering issue. Each line is a pair of symbols, but clearly it does not matter which way around they are as they make the same line. So that reduces the combinations by 8 (2 for each of the three lines). Also, the order of the 3 lines does not matter, so that reduces the combinations by 6.

So instead of 1,987,690,320 gate addresses, we have only 41,410,215. This is smaller than 36^5. In fact it can be covered by 34^5 which is nice, as I would leave out "I" and "O" to avoid confusion with "1" and "0".

So yes, in theory, the Pxxxxx could be a full gate address using just the 5 letters and numbers. And the "P" could indicate type of destination somehow.

Of course, what the actual mapping is, is a different matter. It is very likely they are just random.

As an aside, why can't film makers employ a geek for a few days whilst making the screenplay. I would be trivially cheap for them, but things like this could be made to a proper scheme of some sort and have some consistency. They could have avoided the whole "points in space" crap and maybe gone for just "it's like a telephone number" which would have been way easier to explain and not tied their hands as much. Even if they just pinned down the made up rules and made up physics at the start they could avoid making inconsistent story lines later. Oh well.


  1. Bit of a shame someone on SX didn't appreciate you attempting to apply logic to the issue. This is why I stopped editing on Wikipedia.

  2. Nothing about Stargates, but yes - a walk is a brilliant time to sort through ideas in your head. I try for a morning walk every day and it really helps me sort out what I'm going to do when I get to my desk.

    I see other people walking with headphones on, presumably listening to music or audio books, but I can't help feeling that would make the thinking time less effective.

  3. You might enjoy Stephen Wolfram's discussion of being a nerd consultant on Arrival: http://blog.stephenwolfram.com/2016/11/quick-how-might-the-alien-spacecraft-work/

    As for lines between arbitrary points being unlikely to intersect, you solve that (and increase the number of gates) by treating the symbols pairwise as defining a plane. While you need three points to define a unique plane in three dimensions, I think you'd only need two for a unique plane if you know the major spatial dimension. Then, you still have a single unique point in space defined by the intersection, although it isn't necessarily inside a box defined by those points.

    This has the nice side-effect of making Castiana, Sahal and Vegonbrei's three-into-one idea meaningful, although I don't think it works with the addresses used on screen.

  4. If only this much thought had been put into IPV6, it would be amazing :-)

  5. Personally, I've always taken the Pxx-xxx system as just the SGC's index code in their gate address database...

    1. That was my take as well - it was allocated when they added new gate addresses. THink this was talked about in series 1 - I'll need to go back an watch to refresh my memory :)


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