well.. taking the theory of relativity into account, time slows as you move closer to the speed of light. also, there are theories that go along with that that state that once you pass the speed of light you start to effectively move backward in ralation to a place with constant time. however, there is one major flaw with a practical application of these theorys.

]as an object accelerates closer to the speed of light it's mass increases as well in direct proportion to it's speed. that poses the main problem to practical application. there would have to be a power source to propel the object or craft that could handle the stresses of propelling an exponentially increasing mass.

so, in short, it all works out on paper but unless there is a discovery of a power source that can accomodate that type of load it cannot happen anywhere but on paper.