One of the most distracting things in storytelling is when an author takes the time to line up a vast swath of details for their story, fact checking them to make sure they all comport with reality, but misses one. There’s an excellent example of this in Andy Weir’s Project Hail Mary, which we’re going to use as our example for discussion today, so be warned that there will be spoilers for the movie. Most likely the book as well but this is a rare case where I haven’t read the source so I cannot say for certain.

That said, we will need to discuss some minor spoilers to make the case so if you haven’t had a chance to watch this film (or read the book) and you wish to engage with it fresh then I won’t mind if you come back later. I can wait. If you aren’t interested in the film, I will be covering the relevant details here.

Let me start by saying that I was pleased with Project Hail Mary and what we’re about to discuss here amounts to nothing more than a nitpick in the grand scheme of things. That said, there are still useful things to think about encapsulated here. So, the premise of Project Hail Mary is simple. An astronaut named Ryland Grace wakes up on a ship called the Hail Mary orbiting the star Tau Ceti with no memories of why he’s there and must figure out his purpose and complete it with no input other than that of the ship’s AI.

Project Hail Mary is a pretty tightly written and enjoyable romp that falls into the genre of hard scifi. The primary defining trait of hard scifi is that all the technological and scientific concepts discussed in it should be grounded in real scientific knowledge of the day. The Hail Mary, for example, is not a faster than light ship. It travels near the speed of light and uses a special fuel that is incredibly energy dense (one of only two speculative elements the story introduces) but it doesn’t use some kind of entirely theoretical system to go faster than light like a hyperdrive or warp drive. If we had the right fuel, we could build the Hail Mary now.

Everything else about Weir’s story is just as grounded. Its orbital mechanics, the environmental effects of the sun slowly darkening (which, it turns out, is the puzzle Grace is trying to solve) and even its brief jaunts into bacteriology. It’s a very solid story, except for one little detail.

See, Grace wakes up with no memories because he was put in a kind of rudimentary cryosleep. Since the Hail Mary is limited by the speed of light it takes a little over eleven years of travel for it to reach its destination and it doesn’t have nearly the carrying capacity to bring along enough food and water for Grace and the other two people on board. They have to be put into hibernation in order to make the trip practical, especially because they may have to spend months or years studying Tau Ceti to figure out what’s going on and why that star isn’t dimming like the sun is. All supplies need to be saved for that part of the trip… right?

Well, maybe not.

Without getting too deep into the weeds, the laws of relativistic physics state that when an object starts moving close to the speed of light the way it experiences time changes when compared to the rest of the universe. A particle moving at the full speed of light arrives at their destination near instantaneously. So how much time did Grace experience on the Hail Mary during his trip? The film doesn’t say. Which raises the question of whether he really needed to be put into cryosleep in the first place.

This is a relevant issue as the cryosleep procedure is integral to the plot. Grace is the only one of the Hail Mary’s three occupants that survives cryosleep and wakes up at Tau Ceti. It’s also integral to understanding his character development and motivations. If cryosleep isn’t necessary for him to survive the journey its use in the story begins to look like a contrivance intended to make the story function, since it’s necessary for the other elements of the plot to fall into place. Yet the movie never addresses this factor.

Now, based on a little research I’ve done it turns out that Grace and his companions probably did need to enter cryosleep. Even if they reached 99% of the speed of light for most of their trip they still would have experienced about a year of travel time on the Hail Mary and, given the realities of acceleration and deceleration it would certainly take longer than that. However, ignoring this issue in the script of the film raises questions and distracts the audience. It’s minorly dissonant. The audience shouldn’t have to do a google search and find a time dilation calculator to figure these things out.

It’s particularly glaring in this instance as the entire story is structured around the necessity of cryosleep where ideas that are less important to the story are explored in some detail. This omission did keep drawing my attention back to that particular story element. However, it didn’t do so in a way that underlined its importance to the plot but rather in a way that pulled me out of the plot and made me question its integrity. And it did it in no small part because so much of the rest of the film fit squarely into the expectations of the hard scifi genre.

It was a clear point of dissonance and it had an impact on the story. Again, not a big one but an impact none the less. It would have been nice to see it corrected. That’s the price of holding yourself to a standard, after all. The closer you get to it, the more glaring any deviation becomes. It’s a lesson in taking care with your stories, no matter what the standard may be.