Once space-faring became profitable due to asteroid mining and vacuum manufacturing, it did not take long for humans to settle all the planets and moons of the Sol system. Naturally, this development increased the economic growth of Earth, making humans more capable than ever of reaching further into deep space. The distance between solar systems was a difficult barrier to surmount, but the discovery of Warp technology changed all that. Jump gates, using gravity coupled with negative energy to create stable wormholes between them, allowed instant travel between two points in space. The downside, of course, was that one of the Jump gates had to be physically carried to its destination point, but their advent nevertheless started off the gradual expansion of the human race to other solar systems.