Science fiction is under no obligation to be scientifically accurate, and some shows, like Star Trek, flagrantly violate the laws of physics with every warp jump. But others make an earnest effort to get the science right, and few of these hard science fiction shows have seen more commercial success than The Expanse, the Amazon Studios series set in a future where humanity has colonized the Solar System and political drama unfolds on a cosmic stage.

In The Expanse, there are no artificial gravity machines or teleportation devices. Humans have expanded beyond Earth, but it hasn’t been easy. On Mars, people live out their lives underground, dedicated to a multi-generation terraforming effort that might allow their great-great-grandchildren to breathe air on the surface. The “Belters” who live beyond Mars, meanwhile, have no illusions of ever seeing a sky. Instead, they build giant greenhouses on Jupiter’s moons and mine asteroids for resources that they can sell to denizens of the inner Solar System. Without any faster-than-light tech, trips across the Solar System can take weeks or even months, not unlike traveling from Europe to the Americas several centuries ago.

Weaving all the messy complexities of physics and biology into a show that includes epic space battles and ancient alien technology isn’t easy. The Expanse’s knack for doing so—without subjecting the audience to long expository dumps about fusion reactors—can be chalked up largely to Daniel Abraham and Ty Franck, who wrote the books the series is based on under the pen name James S.A. Corey, and to executive producer Naren Shankar, who holds a Ph.D. in electrical engineering and applied physics from Cornell University. With Season 5 of The Expanse launching on December 16, The Science of Fiction spoke with Shankar about how his scientific background has shaped his approach to the show, how hemming to the laws of physics opens up new opportunities for drama, and how sometimes, scientific realism must be sacrificed for the sake of cool space maneuvers.

This conversation has been lightly edited for clarity.

Maddie Stone: You’re clearly a person with some serious science credentials. How has your scientific training informed your work on The Expanse?

Naren Shankar: I think the way it’s really informed it is I was never even tempted to get rid of the things that Hollywood has traditionally dispensed with in science fiction shows. Gravity, and dealing with it in space, is complicated. That’s why people, most of the time, act like they’re in airplanes. They walk around, there’s gravity on the ship when you need it, there isn’t when you don’t. Those kinds of things are just normal conveniences because it makes [a show] easier to produce.

For me, what was attractive in actually doing this show was, in the books, they turn real physics and the realities of space into a character in the story. And there are all sorts of things you can really use to great dramatic effect if you’re rigorous about it. So that was a real opportunity. It was a way to do a space show and get into action sequences and situations that most people just ignore. So that was an attraction to me.

Maddie Stone: And as you just mentioned, you had some great source material to work off, books that tried to make space travel as accurate as possible. But I’m still curious: when you want to do something new in the show and you want it to be scientifically realistic, what’s your process like?

Naren Shankar: Well, to Ty Franck and Daniel Abraham’s credit, they’ve done a tremendous amount of research just getting the books right. So most of the time, when we’re trying to recreate those sequences on the show, a lot of the research has been done. Ty and Daniel know it really, really well. They’ve been in the writers’ room since day one. They’re always there to kind of keep us on track.

Aside from that, we just try to get things as right as we possibly can. Astronauts have come from NASA to coach our cast about how to move properly in zero-g, we have all sorts of things that give us the ability to create the illusion of weightlessness when we need it. The way we reflect it on the visual effects side is the ships move the way objects in space move. You can’t put on the brakes and put your car into reverse. Those kinds of things don’t happen [in space]. And then, I think it goes back to Star Wars, pretending that spaceflight is like World War 2 fighters in the Pacific is just not the way things move in space. So those are the things we tried to stay away from.

We occasionally get things wrong. There’s some extraordinarily complex motion, and when you’re trying to connect visual effects and graphics and physical photography, sometimes you miss it. Hopefully, we don’t do too much of that but it does happen.

Maddie Stone: Have you ever been called out by a scientist for getting something egregiously wrong?

Naren Shankar: Um, I called myself out once.

We did a sequence in Season 2 where Alex, the pilot on the Rocinante, this is him basically doing a non-thrust trajectory to get back to Ganymede, so he’s slingshotting around the moons [of Jupiter]. The way it was portrayed was very false, in the sense of he was dipping from moon to moon so absurdly fast. So we hadn’t really portrayed it very authentically. There were a number of reasons that conspired to get to that point. I’m not big on social media, but I did write a little blog for James S.A. Corey’s blog talking about that scene and promising to get it right the next time.

And then what we did at the start of Season 3 Episode 7, an episode called “Delta V,” that I think was a much more authentic gravity assist trajectory. So, we tried to fix it.

Sometimes, when you’re in the writer’s room, you’re talking about conservation of angular momentum and how it affects the motion of these objects and it gets fairly complex fairly quickly. And so you can’t always translate that exactly.

Maddie Stone: So while it sounds like it can be a challenge to be technically accurate, you mentioned a moment ago that trying to portray space travel realistically also opens up dramatic opportunities. Can you give an example of that?

Naren Shankar: The one that came up the earliest was we were talking about light delay, and we were writing an action sequence and [the other writers] were saying the characters have to be talking to each other. But they can’t talk to each other, because it takes three hours for the signal to get there. And what we realized when we were talking about it was if we play into the idea that one side doesn’t know what’s happened until after it’s happened, it actually can create drama for you.

One of the writers said it’s like we solved the cell phone problem, which is that many modern thrillers are ruined by the existence of a cell phone. Just the fact that you can be in instant contact with somebody, you know, that throws out thirty years of great movies. [In the past] you just couldn’t get in touch with somebody to tell them what was happening. So it does open up possibilities, but you have to be open to them.

And there are so many other [space travel] examples. Science fiction, especially in movies and television, has not done a good job of this. People have learned the wrong lessons. I remember we did a moment in Season 1 where a Belter has a problem inside his helmet and he kind of pops open his visor and just breathes out and fixes it, and somebody said ‘oh, their head would explode.’ But that’s actually not true! So all of these things that people think, in way, we’re un-teaching people.

And that really does come back to Ty and Daniel, because they chose to tell the story that way. And it has really given the show a unique vibe and a unique visual signature, which is part of the fun.

Maddie Stone: I want to ask you about Earth. We haven’t seen a whole lot of Earth in the show outside of some glitzy UN buildings, although having read the books I suspect we’re going to see more of it in Season 5. But we know Earth is struggling to support its large population, and there are hints that it has faced some pretty severe environmental challenges in the past. How have the problems facing humanity today informed the show’s portrayal of Earth in the future?

Naren Shankar: You know, it is one of the things that, sometimes you can be a little limited in television as opposed to features and bigger canvasses. I think we all would love to show more of Earth. We get a little taste of it when Bobbie is in New York in Season 2, when she gets out of the Martian embassy and goes to see the ocean. I think we really would have liked to have shown more. You see a lot more of it in Season 5 as you pointed out, so that’s going to be a treat for people.

But in the background of the show, we have talked about the problem of Earth being that most people don’t have jobs. And that there’s a universal basic income for people to give them essentially subsistence. But the idea of having a job, something that you can put your effort and thought and intelligence into, that’s something a lot of people aspire to. That’s why they have lotteries to become a mechanic. That’s why people tend to go off into the Belt, because there are jobs you can actually engage in.

Again, in the deep background of the books, Ty and Daniel talked about the reason Earth is under a planetary government. The roots of that are in a significant environmental catastrophe, a climate catastrophe, that sort of required collective action from Earth. These things, we hint at often in the show. In the reality of the series, so much of the drama is not on Earth, and so much of the drama on Earth is refracted through Avasarala, who is at the pinnacle of the political, economic, and social structure, so it’s limited our perspective of the planet, I think, in some ways.

Again, it is one of the nice things we’re doing in Season 5. We’re getting a much better look at Earth in the time of The Expanse than we have in previous seasons.

Maddie Stone: I was pretty jazzed about Season 4 taking place on a planet with a lot of lithium because, as an environmental reporter, I write a lot about lithium’s importance in our future energy supply. What do you think future people will be using lithium for?

Naren Shankar: Well for Ty and Daniel, it’s for fusion. Helium-3-lithium is a fusion fuel. [Editor’s note: Nuclear fusion is not a viable energy source on Earth today, but helium-3, in conjunction with lithium, has been proposed as feedstock for future fusion reactors.] Because lithium is only created in [novae], the supply is finite, it’s not something you can make and it’s a highly precious commodity.

Maddie Stone: Without giving much away, can you talk about any particularly interesting thing you learned while working on Season 5?

Naren Shankar: There is a very complicated ship maneuver that happens at the end of the season that was… very difficult to understand. [Laughs.] That was extremely counterintuitive. And we got one of the graphics not right, it fell through the cracks and was too late to fix so it vexes me a little bit when you see it, but so it is a very complicated ship motion that figures into the end.

Maddie Stone: But will it be more scientifically accurate than the Jupiter multi-moon gravity assist?

Naren Shankar: Yes. Yes, it will.

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Top image credit: Amazon Studios

Update: This article has been updated to clarify that lithium is created in novas, a distinct astronomical event from supernovas.