10 Massive Stargate Plot Holes
9. Incoming Travelers Gives A Lot Of Notice
When dialing a Stargate address from the SGC, the process takes up to a minute while the computer locks on to the address. This is explained due to the amount of power it takes to connect and compute the distance, with Earth technology paling in comparison to Ancient technology in this (and many other) respects. However, usually when a Gate is dialed via a DHD, off-world, the wormhole activation is seemingly instant.
There are many occasions in SG-1 where the base alarm will go off, with the distinctive voice of Walter Harriman ringing through the complex warning of an unscheduled off-world activation. There are many times when people have time to drop what they are doing, walk to the command centre and watch as the Gate continues to spin, lighting up each chevron along the way.
It is absolutely concievable that if the incoming wormhole is coming from a world that has a dialing system much like Earth's own, then it would take a little longer to connect, thus allowing the Stargate time to whirl and light up. However, if the connection is instant, from a world with a DHD - with it being stated many times in the show that a wormhole won't establish until it is connected on both sides - then there shouldn't be enough time for this to happen.
So why does it do this?
Because it looks cool, dammit!