Consider a wormhole. Suppose its two mouths have no relative motion with each other. Therefore no time difference exists across its ends. It provides a mean to travel faster than "light in normal space". Imagine this wormhole to be at rest in frame "S" (say). If there is another frame "W"(say) in relative motion (much closer to the speed of light) w.r.t. frame "S". An observer in frame "W" will view the wormhole (rest in frame "S") as a time tunnel. Therefore accelerating another end of wormhole is not the only way to convert a wormhole to a time tunnel. Uniform Relative motion is just enough to create such a scenario.