Yes. It’s not only possible, but we have actual time travelers walking among us today. According to the Theory of Relativity, it is possible for speed or gravity to make time pass differently for separate observers. If that sounds vague and science-y, maybe a real-world example will help: if highly accurate, atomic clocks are aligned perfectly on earth, and one of those is sent into space, then one of those clocks will run faster than the other one. This is not caused by a mechanical problem with the clock, but happens through time itself being bent by the forces involved in space travel. So, all of those astronauts hanging out on the space station? Their time is passing faster than ours, and when they return to earth, they are actually younger than they would be if they had remained here. Ok, so not much younger, but it’s still true. Michael Finke and Peggy Whitson, who have spent more time on the space station than any other American man and woman, are 0.0093 and 0.0092 seconds younger, to be exact. And the man who has spent more time on the space station than anyone in history—Russia’s Sergei Krikalev, with 803 days in orbit—is a full 0.02 seconds younger! Maybe one day we will be able to reverse the time dilation, and these explorers can tell us about the wonders of life half a second in the future!