It seems feasible that we could have a spacecraft that hurtles toward the sun becoming a comet. The idea would be to apply acceleration at various orbital points that maximize speed with minimum expenditure. If we can go fast enough the relativistic effect would compensate for our lack of resources. After sufficient orbits we could then rejoin the Earth. To us it would seem that we had been gone a few months or even years, but we would have moved forward in time by hundreds of years.
It should be possible to do some science at the outer boundary of our orbit. Measure the cosmic radiation, red shift, various observations of deep space. Maybe our UFO’s are other primates who are moving forward in time in order to avoid us.
The reason of course is that once we had rejoined humanity, assuming that we are still here, we could then ask them, after we figured out how they spoke:
-What do you think of Donald Trump?
They would answer: