[X Q mano]

"Time-travelling" forward wouldn't be impossible I think, but back again? Hmmm...

I suppose, if you could make a ship travelling at far above light-speed or something, then time would be different for the occupants on that ship compared to earth. But back again, that would be a problem methinks...

And there are people who claim to be time-travellers... But more often than not we lock them up in rooms with padded walls...