The many differences between the Project Hail Mary film and the book are causing some friction. The sci-fi adventure blockbuster, starring Ryan Gosling and directed by Phil Lord and Christopher Miller, is based on Andy Weir’s 2021 novel of the same name. Including the $3 million price for acquiring the rights to the novel, Amazon MGM Studios has spent nearly $250 million on the film’s production (though that was cut to around $200 million after tax credits). Even so, like any adaptation of a popular book to the silver screen, many scenes were cut, some storylines were altered, and a few elements were added. That said, unlike the 2015 movie The Martian that is based on another novel by Weir, the author is one of the producers of the film and was a part of the approval process for any changes the movie made.

Changes to the Project Hail Mary book were inevitable

From the outset, it would be clear by anyone who has read “Project Hail Mary” that any film adaptation of the nearly 500-page novel would need to be revised or edited out. The original story, which follows science teacher Ryland Grace on a space mission to save the Earth after it’s discovered that the sun is effectively dying out due to an energy-sucking organism dubbed the Astrophage, is full of thorough, grounded scientific explanations and a lot of internal dialogue from Grace himself. While both of these traits are hallmarks of Weir’s writing, these are difficult to translate through the visual medium of a film.

Meanwhile, directors Lord and Miller are known for adding a slice of comedy to their productions, which include 21 Jump Street, Spider-Man: Across the Spider-Verse, and The Lego Movie. The same goes for screenwriter Drew Goddard, who was also responsible for adapting The Martian (which humorously won “Best Motion Picture – Musical or Comedy” at the Golden Globes). So it would be expected that the screenplay for the film would not be as serious in tone as the novel is.

Still, book fans who have watched the movie, which had early screenings on March 16 as part of an Amazon Prime promotion, have expressed their disappointment on the movie’s simplification of the science in a thread on . Several comments say that Grace could have described the unique properties of the Astrophage more and that the movie could have explained that the drug Grace is injected with intentionally causes memory loss and gradual recall (which is why he starts the film not knowing what has happened and why he’s on a spaceship to Tau Ceti in the first place). The book’s exposition on the hibernation pods and DNA testing were cut down too, particularly the section that shows the laborious trial and error Grace goes through to breed taumoeba, an organism that eats Astrophage.

The film instead chooses to streamline the novel’s explanations to keep the runtime manageable and prevent the audience from being snowed by math and science. As noted by RadioTimes, the movie uses montages and bite-sized messages that Grace sends back to Earth to convey the science expediently. The movie then reduces the amount of time it takes for the scientist to connect his ship to the spacecraft of Rocky, the sentient stony-looking spider creature who quickly becomes the heart of the story.

The Project Hail Mary film alters the source material in many ways

That’s hardly the only place where the movie separates itself from the source material. Lord and Miller, in an interview with Gizmodo, revealed that they added a “Don’t Go Crazy” room to Grace’s ship. This section of the craft, as seen in trailers, projects full 360-degree screens of different environments as way of maintaining the mental well-being of the passengers. While this zen-like room isn’t in the book, it’s inspired by passages describing how the team on Earth were concerned about astronauts having cabin fever and going nuts having to look at the same walls every day and night.

In addition, the film introduces different states of gravity for each room on the ship to give it more personality and visual surprise. This allowed the directors to convey how disorienting it is for Grace to wake up on the ship, as a way of interpreting his thoughts, of which there are many in the book, without having to explain the situation with internal dialogue. Lord explained that they “spent a lot of time trying to find ways that were in line and harmony with the soul of the book,” ways that would be “additive to the book” so that the film could be seen as a “great companion piece.”

Many of the changes in the film were made to emphasize the emotional companionship between Grace and Rocky by removing or changing several plotlines. It cuts out a subplot about Eva Stratt, the leader of the Project Hail Mary initiative, choosing to hit the polar ice caps with nuclear weapons to release methane, artificially causing climate change. As dramatic as this is, it has little to do with the main characters.

Another alteration in the middle of the film has Grace watching over Rocky’s unconscious body after it saves him, making the creature’s survival less assured than it is in the book. Then for the ending, the film omits the part where Rocky tells Grace that the probes he sent to Earth with samples of the taumoeba led to the sun being restored; instead, it shows a scene where Stratt receives the probes without Grace knowing if his efforts paid off. This makes Grace’s decision to leave Rocky’s planet, which both the book and the film make ambiguous, a stronger tug on the heartstrings.

Taking this all into consideration, most of the comments in the aforementioned Reddit thread understand why the film chose to make a beeline through the science and focus on the relationship between Grace and Rocky. A handful who had read “The Martian” and then saw the movie had a similar reaction to Project Hail Mary, saying that it would take some time for them to accept the changes the movie made. This is despite Weir having cleared the changes himself. A few hope that an extended version of the film will be made that includes scenes that were left on the editing room floor. But even with the numerous edits, many still describe the adaptation as being “faithful” to the original story and appreciate the theatrical version as much as the source material.