(Redirected from Planetary shift)
A natural phenomena by which stellar matter gradually drifts apart over time as the universe expands outward, eventually making some Stargate coordinates determined many millennia ago to be invalid. The Stargate networks are believed to have a built-in protocol to counter this by automatically dialing one another at regular intervals to update their positions.
These correlative updates allow the Stargate symbols to continually work after hundreds of thousands of years.
But the correction protocol depends upon a gate being connected to a D.H.D. On Earth, the S.G.C.'s dialing computer must calculate the approximate drift in order to determine if a Stargate address needs correction in order to be dialed successfully. This would be done by using the existing, 7-symbol address to locate where the planet was located in the galaxy hundreds of thousands of years ago.
Children of the Gods - While examining the Abydos cartouche Samantha Carter and Daniel Jackson realize that stellar drift is why the addresses don't work.
Avenger 2.0 - Samantha Carter speculates the Stargate network undergoes automatic correlative updates to compensate for stellar drift.