If a starship cannot reach the speed of light through sheer thrust, perhaps the answer lies in bending the laws of time and space so that the distance itself is shorter. A ship could then get around the need to travel at relativistic speeds, leaving behind the problem of increased mass and negating-if not actually reversing- the effects of time dilation. In other words, if one could find a shortcut through the galaxy, it might be possible for spacecraft to travel quickly between star systems, and perhaps even travel backward in time.
Shortcuts through space and time are called wormholes. Wormholes are created naturally when black holes collapse, though they tend to close so rapidly that a ship attempting to pass through would instead encounter a singularity-a point with infinite density and a radius of zero-and be instantly crushed. But, if the technology were developed to enable a wormhole to remain open, it might become possible for spaceships to enter wormholes, travel for a few million miles, and emerge several light years away-perhaps at the point of a white hole.
White holes are theoretical objects that spew energy into the universe from unknown sources. One theory suggests that quasistellar objects (also known as quasars) are actually white holes, at the far end of which might be wormholes. Thus, it is theoretically possible to enter a wormhole in one location in the universe, and emerge from a white hole in another. Such a stable conduit could be called a jump gate.
At Progress Level 5, the technology does not exist to stabilize wormholes in order to create jump gates, though by PL 6 scientists might have developed the technology to map the exit points of wormholes. With a theoretical advance in astrophysics, humanity might be ready to make the first safe jump by Progress Level 7.