On the planet on which Harry Maybourne had settled, SG-1 found a small spacecraft of Ancient design which contained a device bearing little resemblance to any Ancient designs previously encountered. SG-1 concluded that the device was probably meant for time travel, and that it most likely manifested an energy field that encompassed the entire ship, allowing the traveler to literally fly through time. The discovery was the first evidence that the Ancients had actually mastered time travel, and writings on the pillars of the temple ruins were discovered to be a historical log compiled by an Ancient who had once traveled through time to study the evolution of life on the planet. The writings were only a couple of hundred years old, suggesting that the Ancient traveled to the future, then back to the recent past to leave the historical record, which described events that had yet to happen, including the return of Ares to reclaim the planet. The ship had been abandoned on the planet, and SG-1 was able to bypass the time device in order to power and activate the spacecraft in defense of the planet. The SGC took possession of both the spacecraft and the time travel device and they were brought back to Area 51 for study.
Like many pieces of Ancient technology, the time travel device requires the presence of the Ancient gene for activation, and the scientists at Area 51 were unable to engage the device. O'Neill possesses the Ancient gene, and although SG-1 had agreed not to use the device because of the danger of adversely affecting the timeline, they reconsidered the idea of time travel after the discovery that a ZPM might have been present on Earth during Ra's reign in ancient Egypt. The device only works in time jumps longer than a couple hundred years, but the technology is very intuitive, and because it is controlled by the mind, it is able to extrapolate a target destination based on the user's concept of time. By concentrating on the year 3000 BC, O'Neill was able to engage the time travel device while the spacecraft was in orbit. The device pulsed, creating an energy field that enveloped the ship and seamlessly sent the team into the past.
SG-1's presence in the past changed history, and in an alternate timeline, the team was unable to return, and the spacecraft and the time travel device remained buried in ancient Egypt for 5000 years before being uncovered in an archaeological dig and turned over to the military for study. Realizing that history had been changed, a team under O'Neill's command undertook a mission in the spacecraft to Chulak with orders not to activate the time travel device. However, the ship came under attack, and the time device provided the only means to escape and to correct the altered timeline. Once again the team traveled to ancient Egypt, and in the year 2995 BC they led the revolt that overthrew Ra and freed Earth from the Goa'uld, just as history was meant to be.
Cross Reference: Ancients, Ancient Gene, Ancient Spacecraft, King Arkhan, Egypt, Time Travel, Time Travel 3000 BC, Zero Point Module
Episode Reference: It's Good to Be King, Moebius