Originally published on 3/20/26

If you’ve read Project Hail Mary, you know it’s packed with pages and pages of science. Between Rocky the alien and the mysterious Petrova Line in outer space to those deadly Astrophage organisms, it can be really hard to figure out what actually exists and what was made up for entertainment purposes. And with the movie coming out, readers need answers now more than ever, and who better to give them to us than the book’s author Andy Weir! To learn what he exclusively told Woman’s World about the book’s science and how it impacted the movie set, keep reading. Heads up: Major space-sized spoilers ahead!

Andy Weir shares what is real in ‘Project Hail Mary’ 

Not a scientist? No worries! Here’s what’s real and made up in Project Hail Mary. 

Is the physics in ‘Project Hail Mary’ correct? 

According to Weir, all the physics is “real, except for down at the quantum level of how Astrophage works, but all the math and all the science adds up.” 

“I’m sure I made mistakes here and there, but it’s intended to be real science,” he continues. “The trick is to explain to the reader the science that they need to understand to understand the plot, and that’s it. There’s a big difference between educating someone and bringing them up to speed. I don’t think my readers need to learn all this information and then later solve problems on a quiz, right? They just need to understand the plot.” 

Is Rocky real? 

While there is no real-life version of Rocky, Weir did say people could and have hung out with the puppet version of Rocky that they used in the film. 

“Rocky was on set all the time with his five puppeteers, who we called the Rocketeers,” the author says. “They had their little black ninja outfits, and they’d be extremely uncomfortable underneath the set or hanging from wires or whatever. Then they had to be digitally removed after the fact. It was quite an ordeal. We’d have to remove things to make room for the Rocketeers and the sticks that they’re moving around.” 

One reason that they decided to use a puppet? To make the film feel as real as possible, says Weir.

“It also gives Ryan [Gosling, who plays Ryland Grace in the film] another actor to play off of,” He continues. “James Ortiz, who is the voice of Rocky, is the head puppeteer and he and Ryan could riff off of each other. They could ad lib. They could try different ways of doing the readings and relate to each other. And there’s a lot you can do when you’re acting against another person in the puppet that you can’t do when you’re talking to a tennis ball on the end of a green stick.” 

Is the Hail Mary ship real? 

Similar to Rocky, there is no functioning Hail Mary ship, but they did build a realistic looking model. 

“There are no green screens in the whole movie. All the sets you see are practical,” Weir explains. “It’s cool because it means that Ryan can interact with his environment and ad-lib. He can flick switches on the walls because they’re there.” 

Are Planet Adrian and Planet Erid real?

If you had dreams of hopping on a rocket ship and visiting either Planet Adrian or Planet Erid, we have some sad news for you: They aren’t real. To craft them, Weir said they built some of them and used CGI for others. 

“I’m afraid Adrian was mostly south of London where all of this was filmed,” Weir says. “Ryan never went to space. He went to Earth, which is in space, but he never went to space.” 

Is the Petrova Line real? 

In Project Hail Mary, the Petrova Line is made up of billions and billions of Astrophage pieces that are destroying the sun. In real life, there is no Petrova Line, meaning that our sun is just fine. 

 You can pick up your copy of Project Hail Mary now wherever books are sold, and be sure to see the movie in theaters everywhere Friday, March 20.

Link to original: https://www.womansworld.com/entertainment/books/andy-weir-discusses-project-hail-mary-science-exclusive