Finding a way to reverse the expansion of the universe would imply time travel being possible. It hasn't happened yet, but perhaps that's just a technological limitation. And if you ask my Mac, then Time Machine is very much possible - that's just the name of the backup system.

The question starts to become very philosophical if there is a backup system for this universe. Everything being saved, for eternity, in infinite time. It would require very advanced computational power and storage, but it would probably work in binary (but that's just the kind of thing a computer engineer would say).

Maybe, though, the observable universe is rotating clockwise around a centre that is in the unobservable universe, and time is just a measure of how many rotations have been made since the Big Bang.