Science inspires, but does not limit, Andy Weir’s fiction
Ryland Grace, played by Ryan Gosling, must save Earth in the new film Project Hail Mary, based on a book of the same title. The movie’s backdrop features realistic readouts calculated by author Andy Weir and the movie’s science advisers.
(Photo by Jonathan Olley.)
This story contains minor spoilers about the plot of Project Hail Mary.
Amount of fuel required. Mass of ship. Distance, in light-years, to destination. Those are some of the values in the Excel spreadsheet Andy Weir made when writing his 2021 novel, Project Hail Mary. The book centers on an astronaut who wakes up in a star system 12 light-years from Earth with little memory of how he got there. A series of misadventures follows. A movie adaptation hits theaters on 20 March.
Weir says he enjoys making his novels’ spreadsheets more than writing. “I set things in motion very specifically,” says Weir, who also wrote The Martian (2011) and Artemis (2017).
To generate story ideas, Weir muses about what-ifs and lets the answers determine whether the story is worth telling. “I try to set up an interesting scenario and then just see where it goes,” he says. The Martian began with the question of how an astronaut could survive alone on Mars. Weir solved the problem iteratively, posting his drafts online for readers to weigh in. He created a spreadsheet to calculate launch windows according to orbital trajectory calculations. “If you say Sol 417, I could look it up in my spreadsheet and find the calendar date [in the story],” Weir says. The book and the 2015 movie earned praise for the realistic depictions of space engineering and the Martian environment (see PT’s review of the science in the film ).
In Project Hail Mary, a light-eating space microbe dims the Sun, which cools Earth’s surface by 6 to 8 degrees Celsius and throws the planet into an extinction-level event. The protagonist, Ryland Grace, could rescue Earth if he could remember who he is and how he got into space.
Weir tinkers with the story’s numbers to devise the most-thrilling scenarios. “If I haven’t defined enough of those starting conditions, then that means I get to go back and retroactively decide things,” says Weir. He gives the example of adjusting the amount of fuel in Grace’s spaceship to keep the story exciting.
A former software engineer, Weir consults websites for educators and students as sources for his science information. “I have a really tough time reading scholarly papers,” he says. Although he knows scientists he could ask, he finds that Googling is a faster way to answer his questions. Science motivates Weir’s stories, but he doesn’t let it get in the way of a good plot. “If I don’t like a fact, I change it,” Weir says.
Project Hail Mary features a mixture of realistic, plausible, and fantastical scenarios. The ship at the heart of the story is “something that we could do with five or ten years and a few trillion dollars to play with,” Alex Howe, an astrophysicist and science communicator who reviews science-fiction books, wrote on his blog.
The habitability of Venus’s clouds is another plot point in the story, and that is an active area of research. In a paper published in Nature Astronomy in 2020, researchers claimed they had found evidence of phosphine gas in the clouds of Venus. Phosphine comes exclusively from biotic sources on Earth, and the authors stated that there is no known abiotic source on Venus. Several subsequent analyses of Venus data failed to find phosphine (see PT’s 2022 coverage ). Several missions to Venus by the mid 2030s are being considered.
One fictional exoplanet, Erid, at the heart of the story, was inspired by a nearby three-star system, 40 Eridani, that is the target of exoplanet searches. Catherine Clark, an astronomer who studies multistar systems, has studied the stars of 40 Eridani. No exoplanets have been confirmed there, says Clark, “but as a nearby bright star, 40 Eridani A is a good candidate for future planet searches.”
On the more outlandish end of the spectrum, Weir invented the concept of “super cross-sectionality” to explain how the space microbe stores energy. The movie summarizes the concept with a quip from Grace, played by Ryan Gosling, who says that the microbes “toot to scoot.” The film skims over many of the other science plot points that come up later in the book.
Andy Weir likes to imagine scenarios for his books through calculations on spreadsheets, like this Excel sheet for the physics of Project Hail Mary.
(Image courtesy of Andy Weir.)
Weir crunched more numbers for the film. Much of the movie takes place on a spaceship, and the directors wanted realistic readouts on the ship’s screens. Weir calculated the distance of the ship to its destinations, the current velocity with respect to the target star, and other values depending on where a scene occurred. Weir says that a physicist on set would at times double-check his math and that NASA engineers reviewed cuts of the film. “They told us little things like, ‘Yeah, this is wrong, but it doesn’t matter.’ Or ‘This is wrong, and it does matter.’ ”
Having explicit math featured in his stories also opens it up for critique. One criticism, pointed out by readers online, is about the atmospheric pressure of the exoplanet Erid. In the book, Erid is said to have an air pressure 29 times as high as that of Grace’s spaceship. That is incorrect. What Weir meant is that Erid’s atmospheric pressure is 29 times as high as Earth’s at sea level—the spaceship’s internal air pressure is kept at 0.4 atmospheres. “It’s not perfect. I make mistakes,” Weir says. Changing the book in subsequent printings is harder than a simple find and replace, says Weir. “We just don’t bother making those changes.”
Weir acknowledges that the scientific scenarios he investigates aren’t novel in and of themselves. “I’m not even the first person to strand someone on Mars in fiction. I just like to do things my own way: meticulously, nerdishly, scientifically.”
