But, then, the shield itself worries me. Any innocent who comes across the gate address of Atlantis and wants to come and benefit from its benificence and wisdom finds themselves splatted and dead without having any warning of this fact. It's like shooting all visitors dead on sight, without posting notices announcing this intention. I fear there are also parallel universes in which the Elizabeth who went back in time followed all the standard Atlantis closedown procedures that she'd been taught, pressed the "activate shield" button, and caused the entire Atlantis expedition to get splatted as soon as they stepped through the gate. (It would not, I fear, be a very rewarding AU to write.)
The gate itself worries me, though I'm well aware that the answers may be contained in the other Stargate shows, which I've not watched. How does the gate know when to close down? I was watching Sateda the other day, when Rodney goes through the gate and says that the others will be coming close behind him, only for the wormhole to close behind him. How did the gate know that the rest of his team had just been hit by tranquiliser darts? Has it got eyes? Is it in league with the villagers? We've previously been told that it will stay open for 38 minutes at a time, so why does it shut down in this case, and in other similar cases? Does it go off and sulk if no-one is actively passing through it? But we know that the Wraith dial out of planets to stop others dialing in, and I don't imagine that they have a huge line of 500 Wraith all ready to walk through the gate one after another to stop the wormhole from closing down in a sulk. Though, actually, I rather wish that they did, since it would be fun to write their story.