Ok, if you don't like nerdiness, this post is not for you. If you read on, don't say you weren't warned.
I've recently become a fledgling fan of the Stargate tv series. It's an interesting twist on the classic aliens-visited-the-Earth-a-long-time-ago sci-fi theme, has a relatively decent plot where each episodes' antagonists present different and unique challenges instead of just ever more fantastical versions of the previous episode, and it's about 45 minutes long if you download it from iTunes, which makes it a perfect way to get through a 45 minute cardio workout.
For those who are unfamiliar, the central premise is that some ancient and incredibly advanced race built a network of "Stargates" across the Milky Way galaxy. Two Stargates can link together by creating an artificial wormhole between themselves, allowing near instantaneous transportation between worlds across the galaxy. The tv show is about present day Earth taking its first baby steps in interstellar exploration, and making various friends and enemies along the way. How the Stargate functions has been explained in some pretty specific detail during the show, and here's the basic gist:
A Stargate is essentially a giant upright ring. Along the outside of the ring are 9 "chevrons", although typically the bottom 2 chevrons are buried in the SG's base and aren't visible or used (the show explains this in later episodes). There is also an inner ring, which features 37 separate symbols, or "glyphs".
Stargates work by "dialing" the address of another Stargate. A standard SG address is a specific sequence of 7 glyphs; 6 glyphs are used to define a 3-dimensional address in space, and the 7th glyph is a point of origin that matches the dialing gate. If there is a functioning gate at the dialed coordinates and if the 7th coordinate matches the point of origin, a wormhole is created that links the two gates. Now, being a nerd, I couldn't just sit down and let myself fall into the series, I had to take apart the Stargate network and figure out how it worked, at least theoretically. And as it turns out there are several problems with the stated functionality that the show doesn't address, and that nobody seems to have a good answer for. After many hours of thought, here's what I can come up with:
Problem 1: Geo-Centric Glyphs
It is firmly established in the series that the 37 glyphs on the inner ring correspond to constellations in the sky. These constellations are what make up the "coordinates" of a destination gate; if you connect pairs of constellations with interstellar planes, 3 uniqe pairs (6 constellations) will produce 3 planes that intersect at exactly one spot in space, the destination. Note that the doodle Dr. Jackson draws to explain this is correct in theory, but incorrectly uses 1d lines in place of 2d planes, leading to some initial confusion. The problem with this, though, is that constellations are extremely arbitrary groups of stars, and a team on another planet would have no idea what stars each of the glyphs corresponded to, and would never be able to get home. Furthermore, it means that a single destination has a different address for every different point of origin, a highly impractical system of transporation. Given that various characters have memorized large numbers of addresses, it doesn't seem likely that there is a unique set of glyphs for each gate.
The SG series never explicitly explains this, but if you examine the gates you notice that the glyphs on all the SGs are the same, with the exception of the origin glyph, which is unique to each gate. If this is the case, it would mean that there is a standard set of coordinates, and each destination would have only one address; the only thing a traveler would need to know is the origin glyph, which is far easier to discern. While far more practical, this introduces a more intriquing question: the glyphs all correspond to constellations as viewed by the planet Earth. What is it about Earth that makes it so special? Why choose a relatively obscure planet that's (relatively) in the middle of nowhere as your vantage point? Part of an explanation could be that Earth was, in the past, a very important place for the race who built the gates, an explanation that is born out as the series progresses.
Problem 2: Generation vs Connection and Interstellar Drift
Do the gates generate and/or define the wormhole themselves, or do they simply connect to a pre-defined, already existing, web of wormholes that's sustained by an outside mechanism? This one's actually pretty easy: we know that gates can be moved pretty much anywhere in the galaxy, even outside the galaxy, and still function properly. New gates on new planets have even been built during the series, and these work perfectly fine with the existing gates. If the gates simply connected to a predetermined web it wouldn't be possible to move gates around or create new ones, since chances are there wouldn't be an existing wormhole at the new location to connect to.
Furthermore, there's "interstellar drift". The SG series never actually explains what this problem is, only that they need to correct for it. However, as best I can figure it out, the "interstellar drift" problem is that the stars, over millions of years, have moved relative to each other and thus now look very different. More specifically, each time you want to make a wormhome, the originating gate needs to be programmed to look for a destination gate at coordinates that are the extrapolation of millions of years of movement from where the glyph coordinates actually point to. This further points to the wormholes being created by the gates themselves: if there were a fixed pre-defined network in place it would be fixed to something. Either fixed to points in space which means that the gates would've moved far away and wouldn't function after millions of years, or else fixed to gates in which case no interstellar drift compensation would be needed.