This sounds suspicously like a fanboy physicist trying to salvage the Superman-flies-really-fast-around-the-earth-reversing-its-rotation-thereby-turning-back-time scene. From the article:
In theory, it should be possible to travel back to any point in time after the time machine was built, reports Ori in Physical Review Letters1. One slight snag is that he has not worked out how to generate the gravitational doughnut, although he has some ideas. "It's wild speculation, but you may need to move large masses rapidly in a circular motion," Ori says.
