There’s a reason Syfy’s thrilling series The Expanse has collectively won our space geek hearts: it’s jam-packed with drama, microgravity fights, and of course, dazzling trips across the solar system. But one of the most fascinating—and relevant—aspects of the show is its exploration of how our bodies will change as we settle down in off-Earth environments.


Set 200 years in the future, The Expanse imagines a solar system that’s been completely colonized by humanity. It follows the lives of a police detective, a United Nations executive, a spacecraft captain and his crew, who unravel a conspiracy that could lead to all-out war between the solar system’s biggest political factions, Earth, Mars, and the Outer Planets Alliance. After a gripping first season, the show returned this month for its second.

Despite the creative liberties it (frequently) takes, on the whole the show does a great job of getting the science right. This is no accident, considering the two people who wrote the books the series is based on—Daniel Abraham and Ty Franck, collectively known as James S. A. Corey—have some serious science chops, as does as the series’ showrunner, Naren Shankar, who holds a PhD in electrical engineering and applied physics from Cornell University. In particular, the show offers a terrifyingly accurate portrayal of the challenges space will pose to squishy life forms adapted for life in a gravity well beneath a protective atmosphere.

One of the most obvious examples of how life in space will change our bodies is evidenced through the “Belters,” who are taller and lankier than people from Earth, a consequence of having grown up in low gravity-environments in the Asteroid Belt. Scientists and science fiction authors have long speculated that, freed from the constraints of gravity, humans will stretch out into beanpoles, a phenomena modern-day astronauts get a taste of when they spend time up on the International Space Station. But due to financial constraints—and the realities of working with Earth-born actors—the Belters from the show are a bit less dramatic-looking than they are in the books.


“One of the things that was in the novel that we couldn’t quite do in the show was that all Belters were really tall and skinny,” Shankar said. “On a television show, we would have to change every single frame to show this, which would have been some very expensive special effects work.”

There’s also an ethical reason behind this change.

“We could [have cast] all the actors as being over 6-foot-five inches,” Shankar said. “But one of the deeper themes in the show is this notion of tribalization, and the tendency for human beings to tribalize.” Shankar noted that if the Belters are all portrayed as very tall and skinny “it makes it very easy to say that those people aren’t human.”


The Expanse also gives viewers a taste of more subtle effects of growing up in a low-gravity environment, touching on how the Belters have “brittle bones” and poor musculature development. For instance, in the very first episode of The Expanse, “Dulcinea,” a Belter is tortured by UN officials, who use Earth’s higher gravity against him. “He’s just kind of propped up on his arms because he can’t move his chest against the full gravity, since his musculature isn’t well-developed,” Shankar said.

Again, this is not dissimilar to what astronauts risk when they go to space—on average, astronauts exercise two hours a day to maintain bone, muscle, and cardiovascular function.


Beyond the Belters’ anatomical changes, Shankar said the show has will continue to delve into more biological affects of life in space, including how it could impact our immune systems.

“Later in season two, we get to Ganymede Station,” he said. “There’s a character in the latter part of season 2, that because she grew up in Ganymede, she has a unique immunodeficiency, which is partially the result of where she was raised.” While we still know very little about how exactly spaceflight will impact our innate ability to fight disease, it probably won’t be good: experiments on mice have shown that heightened levels of radiation (e.g. x-rays and gamma rays) compromised the animals’ immune systems significantly.


“When one group self-identifies, then refers to another group of people as something other, that’s often when war starts to happen.”

The ever-present danger of radiation, and its potentially devastating effect on the human body, is but one of many harsh environmental realities woven into the fabric of life in the Belt, where people live in asteroids or beneath protective domes to prevent themselves from becoming riddled with cancers. In the ninth episode of season one, two of the main characters find themselves in a near-fatal situation after they’re exposed to high levels radiation. Miraculously, both survive—but are forced to undergo rigorous cancer treatments for the rest of their lives.


Beyond what’s shown in the The Expanse, it’s worth noting that in real life, spaceflight appears to affect everything from our brains to our genetic code, as evidenced by a number of ongoing studies conducted in collaboration with NASA and astronauts on the International Space Station. For instance, a recently-published study from the University of Michigan found that the microgravity changes the volume of gray matter in the brain, causing it to increase in some areas and decreases in others.

Gray matter is responsible for many key functions, including muscle control and memory. While the implications for long-term cognitive function are not yet clear, if relatively short stints in space can affect the brain, we might expect more drastic changes for those who grow up in space, like the characters in The Expanse.


Then, of course, there’s NASA’s Twin Study—a 10-part investigation with the purpose of studying how extended spaceflight has affected twin astronaut-brothers Mark and Scott Kelly. Last month, the agency released preliminary results revealing that astronaut Scott Kelly’s recent Year in Space had a dramatic impact on the DNA level. The protective caps of Kelly’s chromosomes, called telomeres and associated with biological aging, lengthened while he was in space, completely surprising NASA scientists, who now plan to investigate what this could mean.

Our emerging understanding of how the human body responds to life in artificial and low gravity environments could very well have an impact on the rest of the show. “You know, if it’s story-topical, we absolutely will consider using it,” Shankar said.


Of course, the show isn’t always accurate. Perhaps in the end, it’s too generous with how easily humans will be able survive in off Earth environments—though certain billionaires might disagree. At least it accurately captures how perfectly willing humans are to destroy each other, even in the majesty of the final frontier.