The grandfather paradox is just one of the thorny logical problems that arise with the concept of time travel. But one physicist says he has resolved them.

It's a monumental head-scratcher known as the 'grandfather paradox', but a few years ago ... system," Tobar explained back in 2020. "However, Einstein's theory of general relativity predicts ...

Einstein came up with an example to show the effects of time dilation that he called the "twin paradox." It's a lot like the Time Traveler game you just played. Let's try it out with a pair of ...