Lord and Miller’s Project Hail Mary is a big-hearted space adventure that’s ultimately about a friendship between Ryan Gosling’s accidental astronaut Ryland Grace and his alien buddy Rocky. There’s a lot to like here: for starters, thousands of beautifully rendered VFX shots but no green screen. Directors Phil Lord and Christopher Miller had their crew build the inside of the Hail Mary ship as a set plus some of the ship’s exterior and boy, does it show on screen.
Gosling’s underdog charm and physical comedy are put to fantastic use — yes, you will laugh out loud, and very possibly cry — and Sandra Huller as Stratt, the brusque commander of Earth’s inter-governmental task force attempting to save the world, nearly steals the film.
Project Hail Mary | Final Trailer – YouTube
Then there’s the science. Project Hail Mary is based on Andy Weir’s ‘hard sci-fi’ book of the same name, published in 2021, six years after his earlier novel The Martian was adapted into Ridley Scott’s space blockbuster starring Matt Damon. (Bring him home!).
Penguin
Project Hail Mary
A lone astronaut.
An impossible mission.
An ally he never imagined.
An irresistible interstellar adventure as only Andy Weir could imagine it, Project Hail Mary is a tale of discovery, speculation, and survival to rival The Martian — while taking us to places it never dreamed of going.
Both times screenwriter Drew Goddard has done the adapting of book to screenplay. While you’re never going to be able to fit as much science into a film as a book, Andy Weir uses legit physics to come up with his fictional planets, organisms and materials. When it comes to space travel, gravity and g-forces, Weir does the real maths too. Let’s dig into what’s really going on when Ryland Grace is doing experiments in argon-filled laboratories and galaxy brain equations on his spaceship’s whiteboard twelve lightyears away…
WARNING! Some Spoilers ahead for the book and film of Project Hail Mary – best read after you watch the movie….
The central premise of Project Hail Mary goes a little like this: a Russian scientist named Irina Petrova discovers an infrared line in our solar system between the Sun and Venus. Then the instruments on board a Japanese JAXA solar probe named Amaterasu pick up solar measurements that show that as this ‘Petrova line’ is getting brighter, the Sun — the actual Sun — is getting dimmer. To start out, it’s 0.01% less bright than it should be.
The disaster? As Ryland Grace, who at the beginning of the story is a high school science teacher, is informed by a fellow scientist in the book: “The sun’s output will drop a full percent over the next nine years. In twenty years that figure will be five percent. This is bad.” How bad? Well, instant ice age on Earth bad.
Professor Mathew Owens is professor of space physics at the University of Reading, who is a fan of both Andy Weir’s books and the likes of Ted Chiang’s sci-fi short stories, one of which, Story of Your Life, was adapted into the 2016 film Arrival by Denis Villeneuve. Owens’ science research includes space weather forecasting — predicting a few days ahead what the Sun will be doing and how that affects satellites, power grids and astronauts in space — and space climate, which looks at how the Sun has varied over hundreds of thousands of years.
(Image credit: Amazon MGM)
“What causes ice ages is not the Sun itself changing but Earth’s orbit changing slightly,” Owens explains.
“The Earth’s orbit, over hundreds of thousands, millions of years, changes slightly and in particular our rotational poles tend to tip towards the Sun and away again. That changes the amount of sunlight we’re getting in particular areas. Those are thought to be the main reasons for ice ages.”
As for Weir’s fictional Amaterasu solar probe, in reality there are a couple of interesting sun-focused spacecraft Out There including NASA’s Parker Solar Probe, which recently made its 27th ‘swing’ around the Sun this month at a distance of just 3.8 million miles and the European ESA’s Solar Orbiter: “The Solar Orbiter has more telescopes, that are making more the kind of measurements that are in the book, whereas the Parker Probe is just measuring whatever material is around it at the time.”
Scientists are able to reconstruct the Sun imprecisely on very, very long timescales (i.e. previous ice ages on Earth) but Owens focuses on the past few thousand years. If you’ve seen the Northern Lights in the UK in the past few years, you’ve experienced the results of the eleven year solar cycle of brightening and dimming.
“It’s all to do with the Sun’s magnetic field,” he says.
“It’s like a bar magnet inside the Sun, it flips its polarity every eleven years so you get a complete cycle every twenty two. And during that time the number of sunspots on the Sun goes from virtually zero to a few hundred and then comes back down. We’ve observed this sun cycle back to about 1750. We get more space weather when there are more sunspots, the past few years there’s been a lot of Aurora because that’s been solar maximum.”
One area of interest for Owens is the Maunder Minimum or ‘little ice age’ around 1650 to 1700 where there were very few sunspots, those black patches, on the Sun and temperatures were fairly cold in Europe. But, he says, this is like putting two and two together and making five in terms of cause and effect.
“The Sun was a little bit dimmer, during this period of low sunspots, so it will have contributed a tiny bit to the cooler temperatures,” he explains.
“But the main thing was probably volcanoes. They throw ash up into the atmosphere and that reflects the light away, so that’s actually more equivalent to this idea that is in Project Hail Mary — you haven’t got ash reflecting the Sun, you’ve got ‘astrophage’ as he calls them absorbing the light before it gets to the ground.”
Otherwise, it would take some serious geoengineering efforts from humans to produce numbers like a 1% reduction over nine years and 5% over twenty years of the sunlight reaching Earth — “put some sulphur in the atmosphere or something and reflect some sunlight” — as even the Maunder Minimum was just fractions of a percent lower.
Fast forward a couple of years in the sci-fi Hail Mary timeline and Earth has sent an ArcLight probe to the Petrova line to see what’s up. They find moving black dots, tiny organisms, which Grace — after he is strong-armed into joining the mission based on a controversial molecular biology paper he once wrote on extra-terrestrial life not needing water — names astrophage. In basic terms: they’re alive and they are migrating to the CO2 of Venus’ atmosphere to breed. They’re also “eating” or absorbing the Sun’s energy and that is causing the existential threat to life on Earth.
(Image credit: Amazon MGM)
Project Hail Mary writer Andy Weir, in an interview with the New York Times, explains that he came up with the idea for an alien ‘mass-conversion’ fuel like astrophage, which stores very large amounts of energy in very small amounts of mass, first before he actually landed upon the doomsday scenario of the Petrova line, the Sun dimming and the consequences for our planet:
“What if we found some alien fuel independent of a ship? But then you use it, and it’s gone. So you have to be able to make more fuel with the fuel itself. What if it absorbs energy and makes more of itself? That sounded a lot like life. There has to be a reason that fuel ended up on Earth. If you’re a mould or something, you’d need to basically live on the surface of a star to get enough energy to do that. So I made astrophage, which is like an algae. But instead of living in the ocean, it lives on a star and spores out to other stars.”
Weir also says in his NYTimes chat that the only “true violation of physics” in the whole book is at the quantum level: in the story astrophage are able to store neutrinos using Weir’s fictional mechanism of ‘super cross-sectionality’.
One of the heart-warming details in Weir’s book is that the all-powerful Stratt and her international science chiefs are able to map other Astrophage-’infected’ stars aside from the Sun and identify the star — Tau Ceti — which seems to be immune to Astrophage partly thanks to crowdsourced amateur astronomy. The Project Hail Mary space mission goes like this: send three astronauts on a 26-year round trip to Tau Ceti, in a ship powered by Astrophage fuel, in order to figure out how to replicate the solution back on Earth. Tau Ceti is in fact a real sun-like star, just under twelve light years away and projects like SETI have listed it as a target for the search for extraterrestrial life.
In the book, Stratt has access to pages and pages of luminosity readings from amateur astronomers all over the world, normalised and corrected by supercomputers for weather and visibility conditions: Alpha Centauri, Sirius, Luyten 726-8 and so on. She explains to Grace that it’s historical data logged over the past few years: “It’s the amateurs who log data on local stuff. Like train spotters. Hobbyists in their backyards. Some of them with tens of thousands of dollars’ worth of equipment.”
(Image credit: Amazon MGM)
Professor Owens points out that professional astronomers do indeed study local stars and planets, too — pointing the James Webb Space Telescope at Jupiter for instance — but that citizen science projects like Solar Storm Watch are able to ask people with amateur set-ups all around the world to take part. In this case, to look for big eruptions from the Sun in telescope images and track how fast they’re moving via multiple images.
“I have a PhD student named Sarah Watson and she’s been using comet observations to study the solar winds,” he says.
“Comets sit in the solar wind and as structures move past them you see their tails wiggle like little tadpoles, but a lot of those comet observations are taken by amateur astronomers. You’ve got amateurs that have got really quite good set-ups and so we can observe the comet 24 hours a day because they’re dotted around the Earth.”
Another core component of the Project Hail Mary is a pure, giddy enthusiasm for science experiments. In the film, Ryan Gosling’s Ryland Grace simply looks out of the spacecraft’s window/viewing port to determine he’s woken up with no memory of how he got there or why, in space. In the book, Weir cleverly confines Grace to the Hail Mary’s dormitory and lab for the first few scenes which means all manner of dropping test tubes, timing drops with a stopwatch and acceleration calculations to figure out how much gravity he’s experiencing. The conclusion: he’s not on Earth.
Both the film and book include lots of plot-driven details around the Hail Mary ship’s centrifuge capabilities for creating artificial gravity and the way that relativity would affect how Grace and Rocky experience the length of the journeys to and from their planets. In a Project Hail Mary Reddit AMA in 2025 – which is well worth a full scroll through – author Andy Weir wrote that “as for research, people think I have a contacts list full of scientists at NASA, which I do, but Google is just quicker” and he told the New York Times that “for the movie, a lot of it was just kind of a ‘Hey, trust us’. Hopefully you believe us when we tell you that if you accelerate at 1.5 g for this long, you experience about four years of time while Earth had 13.”
The result regardless is that we, the audience, get pretty fired up about physics. It’s something high school science teachers and even physics professors will be able to identify with.
“I listened to the audiobook a few years ago and I remember really enjoying those bits,” says Owens.
“I teach first year physics and one of the things you do are these thought experiments of, well, ‘if I took a pendulum and it was on a moving train, would I still have the same value of g, the acceleration due to gravity’. It’s nice to see someone else revel in that and make use of it.”
When the Hail Mary reaches the Tau Ceti system, Grace discovers that an alien race — the Eridians from the 40 Eridani system — have decided to send scientists on the same journey to the same star for the same reasons; their star is dying too due to the astrophage invasion. The only survivor on the alien ‘Blip-a’ ship is an engineer who Grace names Rocky, on account of the fact he looks like a friendly crab made out of rocks. In an interview with the BFI, the movie’s co-director Christopher Miller said: “The second lead of this movie is an alien rock with no face. And you have to fall in love with it, too. By the end, you have to think, ‘I would die for that rock.’ And if you don’t, it doesn’t work.”
(Image credit: Amazon MGM)
Grace and Rocky’s first ‘conversations’ are super imaginative in both the film and the book: dancing, jazz hands and thumbs ups, fist bumps, alien clocks and alien numbers and, crucially, lots and lots of science. In the film, Rocky sends a model of the universe and the Petrova line in a ‘xenonite’ cylinder over to the Hail Mary to illustrate where he’s from. Once they’ve made a tunnel between the two ships, he puts a bracelet with two rings of eight beads through the airlock — representing element number eight, oxygen i.e. showing that it’s safe for Grace to remove his EVA astronaut suit.
In the book too, Rocky — who ‘sees’ sound but not light — communicates in elements, maths and materials, for instance, sending over 29 ammonia ‘necklaces’ to explain his own alien Eridian atmosphere so they can collaborate on their shared mission. Essentially, any future first contact will always start with science for safety and simplicity. In the Reddit AMA, Weir posted in answer to a question about the themes of friendship and perseverance:
“I wanted to make a story about first contact, but first contact among nerds, basically. Two aliens with a common goal working to solve it.” And elsewhere on the thread he wrote: “Yeah I’m done with dystopia. I’m a positive person with a very positive view of humanity.”
“The Hail Mary stuff really harks back to that plaque on the Voyager spacecraft,” says Owens. Voyager 1 launched in 1977 and has been “hurtling away from the Earth ever since”; it left the solar system in 2012 with Voyager 2 following in 2018. The Golden Record aboard both Voyagers includes sounds, data and images and the first images are scientific: the Solar System, DNA, human anatomy, animals, plants together with their mass, scales of time and chemical compositions. There’s also a pulsar map and a diagram of the hydrogen molecule, both of which were also included on the earlier Pioneer plaque sent out in the early 1970s.
“The hope is maybe one day someone will come across it. It tries to explain where it’s come from without using any actual language because that would be meaningless,” says Owens.
“So there’s this idea about how you would use science, something fundamental, like the hydrogen atom because there’s no way any alien would not have encountered that. And so maybe you use something like the energy level spacings in a hydrogen atom because that would be a common ground.”
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