Because thousands of combinations had been previously tried and had failed, it was believed at the time that only two stargates existed, connecting Earth and the planet Abydos, which was visited in the film. At the beginning of the "Stargate SG-1" series, however, a large set of additional valid coordinates were discovered engraved in ruins on Abydos. Because of the stellar drift accumulated over millions of years, other addresses were impossible to dial until Samantha Carter reworked the dialing system on Earth to account for this movement. After this, a massive network of possible connections suddenly became available. Even more addresses were later uncovered by Colonel Jack O'Neill from a repository of Ancient knowledge. In order to allow for dialing back to Earth from other locations (without altering the dialing system), it was later stated that the DHD ("Dial-Home Device") normally attached to each stargate automatically updates for stellar drift; Earth's stargate lacks its DHD, requiring other accommodation.