travels at close-to-light-speed need incredible amounts of energy. this energy=mass is then bending the universe, so technically, what might be 50,000 lightyears could be reduced to ten miles, ten feet or even less, depending on how close you get to light speed. problem is that the static observer still feels the same way about this travel, so there would be no civilization to return to. but if aliens are this developed to travel at 0,9999 c, they might also have full control over their life/bodies so they could live forever and solve this problem.