Theory of Relativity

Relativistic lag is caused by real-world attempts at faster-than-light. As an object accelerated near and past the speed of light, time appears to slow down. While the object may experience a journey of only a few hours or days, time could have passed in the universe over decades or centuries.

Slipspace travel manages to circumvent this. Because the laws of physics in the slipstream are different, this allows speeds of many times the speed of light without affecting the objects perception of time to the same degree. It is still affected, but rather than decades or centuries it is by hours or days.