10 Mind-Bending Theories About Time Travel

Physicists and other scientists have long theorized about whether time travel is possible and how it might work. The folks at AllTime10s give us ten mind-bending theories about time travel that you probably didn’t know.

For example, the Tipler Cylinder is a theoretical cylinder of infinite length that is ten times the mass of our Sun. If spun at a few billion revolutions per minute, it could send a spaceship back in time. Or the doughnut vacuum (coincidentally, our nickname at our first job out of college), which would use focused gravitational fields that could bend space-time and allow you to travel back in time.

No word on whether scientists have finalized any theories on what would have happened if Marty McFly had kissed his mother a second time.