How accurate is the science in Project Hail Mary?

The much anticipated sci-fi film Project Hi Maria are out at the cinema today. In it, light-emitting alien microbes extract the sun’s energy, threatening life on Earth with extinction. To find a solution, an unlikely hero – a middle school teacher played by Ryan Gosling – is sent on a one-way mission to the star Tau Ceti and encounters an alien sidekick nicknamed Rocky along the way.

The premise is fantastic, but the concepts that inspired the story are real – and not as unlikely as you might think.

Andy Weir, the author of the eponymous book that inspired the film, carefully researched the physics, astronomy and biology that govern the action, and he even consulted on set to preserve scientific accuracy while the actors adlibbed during scenes.

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“Actors are very much part of the creative process, (but) sometimes the science of what they’re saying will be wrong,” Weir says. “And so I’d go up to the directors, and then they’d say, ‘Oh, okay, well, let’s try it again, but this time say nanograms instead of milligrams.'”

In that spirit, Scientific American spoke with Weir, as well as an astrobiologist, a physicist and a pair of astronauts about the real science that inspired this work of cinematic fiction.

How does the movie “Astrophage” work?

The film’s premise is that alien microbes called Astrophage (roughly translated from ancient Greek as “star eater”) colonize the Sun and travel between our star and Venus to breed. As the population of star-hugging Astrophage grows, it dims the Sun’s light, endangering life on Earth.

Microbes could make a sun-Venus round trip with the right amount of power, but the journey would require different amounts of it in each direction, says Chad Orzel, a physicist at Union College. “From the Sun to Venus would not be that difficult because there is already a steady stream of (solar) particles going in that direction,” he says. However, the return trip “would require a bit more effort” to counteract the solar wind.

Weir’s way of dealing with this problem, he says, was to imagine Astrophage as capable of absorbing neutrinos, so-called ghost particles that don’t tend to interact with other matter. A neutrino can slide untouched right through a light-year’s worth of lead, for example, and every second tens of billions of them pass through every cubic centimeter of Earth—and through you, dear reader. Most of these neutrinos come from the Sun, which constantly spews them out as it shines. But these ghost particles do carry mass (and thus energy via Albert Einstein’s practical equation E = mc²). If Astrophage could use the sun’s energy to create neutrinos in their cell membranes (“science” gets very hand waved here), thought Weir, perhaps they could use the particles as propellant. Astrofag can convert most of the neutrinos’ mass back into energy (or essentially infrared light) which they will then emit to produce thrust.

This (imaginary) process would be efficient and powerful. In the film, Astrophage is the fuel that drives Hi Maria, the ship that takes Gosling’s character to Tau Ceti.

“The idea is out there,” Orzel says. “If you want complete convert matter to energy, the way you usually go about it 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?

Yes, these places really exist, even if Adrian is a fictitious name. Tau Ceti is a star about 12 light-years from Earth, and 40 Eridani, the Astrofag-plagued star system from which Rocky hails, is about 16 light-years from Earth. Adrian, the Tau Ceti world that the characters visit really exists in astronomers’ exoplanet catalogs as Tau Ceti e (although we know very little about it).

In the grand scheme of things, these places are not that far apart. Using nearby stars similar to ours in the story, says Weir, was a deliberate choice.

IN Project Hi Maria universe, all life in our solar system’s part of the Milky Way comes from an ancient ancestor of Astrophage that long ago radiated from Tau Ceti, says Weir. “Since all life in history is distantly related,” he says, “I wanted everything to be around similar stars because similar stars end up with similar elements available on the planets.”

Just like much life on Earth, Astrophage has cell organelles called mitochondria, which would be consistent with the idea that terrestrial life and Astrophage share a common ancestor, notes astrobiologist Mike Wong of Carnegie Science. However, we know that mitochondria evolved on Earth, he adds.

“There is plenty of life on Earth that has no mitochondria, such as the bacteria and archaea,” he says. “If there was an origin for life in the larger cosmic neighborhood, it would seem that Earth must be the origin.”

Artificial gravity is a big part of this movie. How close are we to achieving that?

Artificial gravity could exist in theory and could work much like it does on Hi Maria. A part of a spacecraft can rotate in a circle, and the resulting centripetal force can simulate gravity for the passengers inside.

Drew Feustel, lead astronaut at the private space station company Vast and one of the film’s technical consultants, says building a spinning habitat is not only possible, but also on Vast’s list of upcoming priorities. But he points out that there is no known way to simulate gravity on land (which happens at one point in the film).

Gosling’s character, a middle school teacher, is training to become an astronaut in no time. How realistic is that?

NASA, or other public space agencies, are not in the business of throwing anyone into space. But there has historically been a sliding scale of qualifying expertise, says former NASA astronaut Mike Massimino.

Between 1983 and 2003, NASA trained “payload specialists” to fly as Space Shuttle crew members with niche, mission-critical knowledge. And famously, a teacher was indeed selected to go to space. But overall, payload specialists received less training than full-time astronauts. “There was a big difference, of course, in what you could do,” says Massimino.

A quick look at NASA’s past and present astronaut corps shows that its members have very diverse backgrounds, from teaching to engineering to piloting to planetary science. What an astronaut needs to know depends on the mission and the skills the other crew members possess, says Massimino.

At the very least, “what you need to be able to do is cook a meal and use a toilet and know all the emergency procedures.”

When Gosling’s character is stranded in space without his crew, the gaps in his knowledge become apparent. But the film does a remarkably realistic job of showing how even the basics can be hard to pull off at first, perhaps even hinting at romanticized films about outer space.

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