What 'Project Hail Mary' gets right—and wrong—about astrophysics

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"Project Hail Mary," the Ryan Gosling-led adaptation of the best-selling sci-fi novel from Andy Weir, is being praised for putting the science in science fiction. Although aliens, sun-draining microorganisms and galaxy-spanning spaceflight are all a part of the story of a scientist sent on a suicide mission to save Earth, the film and its source material are not afraid to delve into the kind of astrophysics that would make most people's heads spin.

But just how accurate is the science depicted in "Project Hail Mary"? Does fact lose out to fiction? Astrophysicist Jacqueline McCleary said viewers might be surprised by what the film gets right and wrong.

The way "Project Hail Mary" approaches concepts in astrophysics, orbital mechanics and even spacecraft engineering is "treated very fairly," said McCleary, an assistant professor of physics at Northeastern University. On the whole, even as the film wades deeper into fiction and pushes against the current limits of science, its scientific foundation grounds the story, she explained.

"This story in particular falls on the line of close enough to be enjoyable and, more importantly, self-consistent," McCleary said. "It's a grammar unto itself, but it's legible."

The core concept of "Project Hail Mary" is, oddly, where it jumps the shark, McCleary noted.

The film follows scientist Ryland Grace (Gosling), who wakes up from a coma and finds that he is the last living member of a mission that has traveled to another solar system to unearth why Earth's sun is dimming. It turns out that the culprit is a sun-sucking microbe called astrophage that has infected other nearby stars, causing an ice age on nearby planets. Grace and his team members, who did not survive the induced coma, were sent to a nearby star, Tau Ceti, to investigate how it managed to resist the astrophage.

The idea that a microorganism-like astrophage could absorb sunlight or even survive the sun's atmosphere is a stretch, McCleary said. The organism's behavior is based on how real microbes do absorb sunlight and use it for energy, but "there's orders of magnitude mismatch between what a microbe could store … and what the sun actually puts out in terms of energy," McCleary said.

The energy emitted by the sun is 10²⁶ joules per second, millions of times more than the annual energy use of all of Earth in a few seconds. That's not to mention that the astrophage would have to endure the extreme conditions of the sun's atmosphere, which is upwards of 5 million degrees Fahrenheit, to even absorb that energy in the first place.

The astrophage aside, one of the film's wackier science fiction elements is also one of its more plausible.

During his mission, Grace encounters an unlikely ally: an alien whose own species is facing the same existential threat. Rocky, as Grace calls him given his rock-like appearance, becomes the film's second protagonist, as he and Grace work together.

Although it's purely speculative, McCleary said the depiction of Rocky is likely more accurate than many sci-fi alien creatures based purely on "how weird Rocky is."

"People are now starting to talk about sentient plasmas as a potential lifeform," McCleary said. "The notion of a completely different biology, completely different body chemistry adapted to different conditions is very clever."

Rocky doesn't even use what humans would consider speech, instead communicating in musical-sounding tones. Unlike in "Star Wars," where members of different species are universally able to understand each other, Grace and Rocky have to first learn to communicate.

McCleary laughed at the concept of a multi-year induced coma for a potentially lifesaving team of scientists—"You'd have brain damage"—but the Hail Mary, the spaceship that Grace uses to traverse the galaxy, itself is a clever extension of real-world physics, she said.

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The ship is designed with both a propulsion system in the back like a regular rocket, but the front half can also detach and spin to create gravity so the crew can live and work in a "normal" environment. While a ship like this hasn't yet been built, McCleary said it's based on "totally conventional, well-accepted physics."

That's because the design makes use of centrifugal force, which pushes rotating objects away from their central point of rotation. When someone turns quickly in a fast-moving car and gets pushed in one direction, that's centrifugal force at play.

"That's a force, and if it's a reasonable rate of speed, not so fast that you feel dizzy, that force that you feel pushing you back will feel like gravity," McCleary said.

For McCleary, the most strikingly accurate piece of "Project Hail Mary" is how, in its depiction of Grace and Rocky, it cuts to the core of who scientists are.

"We like to come together to solve problems or learn something new about the universe," McCleary said. "In this case, for our heroes, it's both. You're willing to bridge wide gaps in order to work together to solve what's fundamentally an intellectual problem. That was something that read so true to me."

"Project Hail Mary" is, ultimately, still fiction. It may drift to the outer reaches of reality's orbit but remains tethered by science. Despite the film's stumbles, in its genuine attempt to bring astrophysics down to earth and its earnest appreciation for scientists, McCleary sees in "Project Hail Mary" the real value of science fiction stories.

"It exposes people to real scientific ideas who might not otherwise see it," McCleary said. "It may still make new scientists."

Key concepts

Planets & planetary systemsSpace & astrophysical plasmaXenobiology

Provided by Northeastern University

This story is republished courtesy of Northeastern Global News news.northeastern.edu.