The astonishing physics of the Hail Mary project dates back to ancient China

Part way through tracking The Hail Mary Project I gasped lonesomely in a full IMAX theater. I wondered why no one else was shocked by what I had just seen, and realized it was because I was a physicist.

Let me explain with an extremely mild spoiler: there is a scene in the middle of the movie where the spaceship Hail Mary suddenly moves forward. Ryan Gosling’s character, Ryland Grace, is not strapped into his seat and his head is bumping sideways into the screens in front of him. If it was real, he would definitely die. Of course, I see movies all the time where people are thrown and punched in the face and dropped from heights that would break their bodies but survive. I am usually able to suspend disbelief.

What set this viewing experience apart was the careful attention paid to properly understanding the science of space motion. Instead of asking their scientific advisors to help them make the invented science look real, directors Phil Lord and Christopher Miller evidently asked the NASA team to help make their sci-fi film look real.

Momentum matters here. If you have ever been riding a bike very fast and had to stop suddenly, you have a sense of momentum. With a heavier bike, it is harder to stop; it’s also harder to stop when you’re going fast than when you’re going slow. One way to think about momentum is that it’s how much force you and the bike carry together. It is proportional to your speed and your weight. For related reasons, trucks should therefore follow cars at a greater distance than smaller vehicles; they are more massive and have a longer stopping time.

One of the wonders of physics as a body of knowledge is that momentum applies everywhere in the universe. Isaac Newton’s Second Law codified this notion of momentum and the idea that it was a literally universal phenomenon. When an astronaut leaves Earth, they still have to deal with it in new and unexpected ways. When you throw the fact of Newton’s second law into conversation with Newton’s first law, life in space quickly becomes interesting.

The first law states that an object in motion will remain in motion, while an object at rest will remain at rest. This never seems to be the case in everyday life because there are other forces at play here on Earth. In a cricket match, when the batsman makes contact with the ball, even if it flies for a while, it eventually hits the ground. Earth’s gravity opposes the force of contact between the bat and the ball. The ball does not stay in motion. In space, far from a massive source of gravity, there is no obstacle; the ball will continue.

This is exactly what happens to Grace in the movie when his spaceship moves forward. Without a seat belt to hold him down, he flies. When his head and the spaceship panel collide, they do so with a high level of momentum because there is no force to counteract the force of the contact – so I was expecting a bone-crunching death. (The fact that this doesn’t happen shows that physics can’t always override the plot of a movie).

There are a number of little moments like this in the film that stressed me out. Honestly, I felt like hell at times, not because the movie was bad, but on the contrary – because much of the physics (if not the physiology) was portrayed so well. Sometimes it was beautiful too. There’s a scene where Grace throws an object out of her spaceship, and I loved the simplicity of watching it continue in a perfectly straight line, without slowing down, which would never happen on Earth.

Four years ago, I wouldn’t have had the same experience watching a movie like this The Hail Mary Project. Throughout my career I tried to keep a distance between myself and Newtonian physics, preferring the realm of relativistic and quantum sciences. As a first-year university student, I found these thought experiments involving speeding cars and sports balls flying through the air somewhat dated. I wanted big, space science. As a professor, I have since recognized that this is the best way to introduce students to the ideas that will follow them into places like the quantum realm, where the concept of momentum gains importance in a rather spectacular way. But it was a reluctant acceptance at first.

Everything changed when I was looking for my new book, Edge of spacetime. I wanted to write about how we try to understand and conceptualize space, and in the process I realized that, of course, Newton’s first law in particular is part of that story. Imagine my surprise when I learned that more than a thousand years before Isaac Newton was born, the philosopher Zhou Mozi and his followers had already written something like this into Mo Ching.

I spent three weeks down the rabbit hole studying the only three known English translations Mo Chingemerging with a new sense of why movement fundamentals matter. Reading those Mo Ching passages convinced me to read Newton’s original words in Principia in both Latin and English. I was suddenly fascinated. Decades after earning my first degree in physics, I still have my world tilted by new lessons about it. And importantly, it would not have been possible without the translation work of my humanities colleagues who spend time with ancient languages.

My viewing time The Hail Mary Project it was a real moment of synergy: scholars advised some artists who created art dependent on the translation work of humanists. I anxiously gripped my chair and emerged with some criticism of the story (and its author, Andy Weir). But I also left the theater satisfied with all the ways I had trained my mind to see the universe in action, and grateful to all the people who allowed me to witness it.

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