When Ryland Grace reaches Tau Ceti in Project Hail Mary, about four years have passed for his human body and fragile psyche. But, because of the effects of time dilation, about 12 to 14 years have passed on Earth. And that’s just at the beginning of the story. By the end of Project Hail Mary, decades have passed on Earth, but Grace is barely older. In the book, he says he’s 54 years-old, even though 71 years have passed on Earth since he was born. In both book and movie, Grace is younger than he should be considering how much time has passed on Earth.
For those who have not read Andy Weir’s novel, there’s a lot more math and science-y explanations about Grace’s trip in the prose than the movie reveals. As Grace tells us at the end of the book: “I’ve done a lot of time-dilated travel.” This refers to travel with extremely high gravity, or approaching the speed of light, which causes time to move relatively slower for the traveler. So, does the math check out in Project Hail Mary? How does this all work? And, does Rocky really not understand anything about relativity?
