How accurate is the science in Project Hail Mary?

The eagerly awaited science fiction film Project Hail Mary has hit theaters today. The movie depicts a scenario where alien microbes, which feed on light, deplete the sun’s energy, posing an existential threat to life on Earth. To avert this crisis, an unlikely hero—a middle school teacher portrayed by Ryan Gosling—is dispatched on a one-way mission to the star Tau Ceti, where he meets an extraterrestrial ally, Rocky.

While the story’s premise is imaginative, the science behind it is rooted in reality and perhaps more plausible than it seems.

Andy Weir, the writer of the novel that inspired the film, conducted thorough research into the physics, astronomy, and biology underpinning the plot. He also provided on-set consultation to ensure scientific accuracy during unscripted scenes with the actors.

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“Actors are very much part of the creative process, [but] sometimes the science on what they say would be wrong,” Weir explains. “And so I’d go over to the directors, and then they’d say, ‘Oh, okay, well, let’s try that again, but this time say nanograms instead of milligrams.’”

In this context, Scientific American engaged with Weir, alongside an astrobiologist, a physicist, and a couple of astronauts, to explore the real science that inspires this fictional narrative.

How do the film’s “Astrophage” work?

The film imagines alien microbes named Astrophage, translating from ancient Greek as “star eater,” which inhabit the sun and migrate between it and Venus to reproduce. Their increasing numbers diminish the sun’s light, threatening Earth’s survival.

According to Chad Orzel, a physicist at Union College, these microbes might complete a round trip between the sun and Venus if they had enough power, although the journey would require varying amounts of energy in each direction. Traveling to Venus would be easier due to the natural flow of solar particles in that direction, whereas the return trip would need additional energy to counteract solar wind.

To address this challenge, Weir envisioned Astrophage as capable of absorbing neutrinos—particles that usually pass through matter without interaction. Neutrinos, mostly emitted by the sun, carry mass and therefore energy, as explained by Einstein’s equation E = mc². Weir speculated that if Astrophage could generate neutrinos within their membranes using solar energy, they could potentially use them as propulsion. By converting the mass of neutrinos back into energy, or infrared light, Astrophage could create thrust and propel themselves.

This imaginative process provides the powerful fuel for the Hail Mary spacecraft, which transports Gosling’s character to Tau Ceti.

“The idea is out there,” Orzel comments. “If you want to completely convert matter into energy, the way you usually go about that is by combining it with an equal amount of antimatter. [But] there just isn’t that much antimatter running around.”

Are Tau Ceti, 40 Eridani and the planet Adrian real places in the universe?

Indeed, these locations are real, although Adrian is a fictional name. Tau Ceti, located about 12 light-years from Earth, and 40 Eridani, the star system afflicted by Astrophage where Rocky originates, is about 16 light-years away. Adrian refers to the Tau Ceti planet visited by the characters, known in astronomy as Tau Ceti e, despite limited knowledge about it.

In the broader view, these celestial bodies are relatively close. Weir deliberately chose stars similar to our sun for the story.

In the universe of Project Hail Mary, all known life in our galaxy’s vicinity is thought to have originated from an ancient ancestor of Astrophage that spread from Tau Ceti. Weir explains, “Since all the life in the story is distantly related, I wanted it to all be around similar stars because similar stars end up with similar elements available on the planets.”

Astrophage, much like terrestrial life, possess mitochondria, supporting the notion that both share a common ancestor, says astrobiologist Mike Wong of Carnegie Science. However, he acknowledges that mitochondria evolved on Earth.

“There’s plenty of life on Earth that doesn’t have any mitochondria, like the bacteria and archaea,” Wong notes. “If there was an origin for life in the greater cosmic neighborhood, it would seem that Earth would have to be the origin.”

Artificial gravity is a big part of this film. How close are we to making that happen?

Artificial gravity is theoretically possible and could function similarly to how it does in Hail Mary. By rotating part of a spacecraft in a circle, centripetal force could mimic gravity for those inside.

Drew Feustel, lead astronaut at the private space station company Vast and a technical consultant for the film, indicates that constructing a rotating habitat is feasible and is on Vast’s future agenda. However, he clarifies that no method currently exists to simulate gravity while on land, as depicted in one scene of the film.

Gosling’s character, a middle school teacher, trains to be an astronaut in a short period of time. How realistic is that?

NASA and other space agencies do not typically send untrained individuals into space, but varying levels of expertise have been accepted historically, says former NASA astronaut Mike Massimino.

From 1983 to 2003, NASA trained “payload specialists” to join space shuttle missions with specific knowledge crucial for their missions, including a teacher who was chosen to fly. However, payload specialists underwent less training compared to full-time astronauts, leading to significant differences in their capabilities, Massimino explains.

A review of NASA’s astronaut corps reveals diverse backgrounds, including teaching, engineering, piloting, and planetary science. The skills required depend on the mission and the capabilities of the crew, Massimino says.

At a minimum, astronauts need to know how to prepare meals, use the toilet, and handle emergency procedures.

When Gosling’s character finds himself alone in space, his lack of knowledge is evident. The film realistically portrays the challenges of mastering even basic tasks initially, potentially satirizing the glamorization of space travel in other films.

“It’s very unglamorous,” Feustel comments on space travel. “That’s the reality of it.”