1. Gravity via Acceleration
Gravity is useful to humans. It drags toxic particles out of the air, keeps us going in the right direction, and makes sure coffee stays in your cup. In zero-g, everything just floats around, and then there are health issues like bone loss and muscle atrophy. Most science fiction stories assume we’ll figure out how to generate artificial gravity via some kind of techno-wizardry. While there’s nothing inherently wrong with that conceit, The Expanse goes one better: spacecraft generate gravity via the constant thrust of their engines.
If you’ve ever been pressed into your seat by an accelerating car, you know how this works. If a ship accelerates at 9.8 meters per second squared, anything inside it will experience an Earth-like level of gravity. Since space is big and empty, there’s nothing to stop ships from accelerating as long as they like. While this kind of thrust isn’t available right now, it’s within the realm of possibility. The Expanse simply asks that we accept a more efficient form of fusion drive, rather than a semi-magical warp core.
Ships in The Expanse are built with decks perpendicular to the direction of thrust, like flying through space in an office tower with an engine in the basement. When the ship reaches a halfway point, it turns around and thrusts in the other direction to slow down, creating more gravity.
In The Expanse, races between ships are as much about endurance as they are about speed. It’s the human crew that limits how fast their ship can travel. We meat sacks can only sustain so much g-force, after all. While the engine might be capable of a g-force acceleration of ten or more, that would liquefy any humans aboard. Instead, what’s important is how well-designed the ship’s force-absorbing crash couches are and what kind of drugs the crew has to keep themselves alive. Exercise is also very important, as a crew member in poor shape can force the ship to slow down at a critical moment.
More than once, Corey uses these simple physics to create harrowing scenes. The protagonists feel the weight of mountains rolling over them as the ship accelerates. Warning lights flash when one character’s vitals drop dangerously low. Now the others must decide: Do they slow down to care for their flagging comrade, thus giving up the chase?
The books also make drama out of catastrophic deceleration. Without spoiling anything, scenes in the later books show ships slammed from high speed to near zero in seconds, causing damage to crew and mechanical systems alike. Those fortunate enough to survive must split their time between helping wounded shipmates and keeping the life support systems online.
2. Fragility of Artificial Environments
As anyone at NASA can tell you, keeping humans alive in space is hard. There’s no air, no water, and no gravity, to say nothing of all that radiation. On Earth, there are hundreds, thousands of little processes keeping us alive that we never think about. Plants and algae scrub carbon dioxide from our air, swamps filter gunk from our water, and gravity helps our body drain fluids properly. All of this must be created artificially in space, and it’s damned difficult. Even the relatively small International Space Station requires constant maintenance and resupplying. Imagine what it would take to create a habitat for thousands tunneled into the ice of Ceres.
Earth’s ecosystem is resilient. Even in the face of extreme environmental pollution and a skyrocketing human population, it goes on keeping us alive. In space, we don’t have that luxury. When the algae oxygen farms fail, it puts added pressure on the emergency carbon dioxide scrubbers, which then draw more power from the grid, which causes grow lamps to shut off in the hydroponics bay, etc. In the second book, one character labels this a cascade effect. Artificial environments exist in a delicate equilibrium, and it’s easier than anyone thinks to shock them into collapsing.
When catastrophe strikes, things get bad fast. Even with super-powered fusion drives, help is days or weeks away. Since other artificial habitats exist in the same precarious balance, they may not have anything to send. Food stockpiles dry up and air thins out. In the midst of catastrophe, short-sighted humans hoard what little resources are left. They gun each other down over a few tins of protein or fight tooth and nail for a place on evacuation ships.
This behavior only makes things worse. Fighting damages the habitat’s remaining systems, and refugee ships have nowhere to go. Other habitats can’t risk a large influx of people without upsetting their own delicate balance. This type of scenario creates conflict most writers would kill for, and Corey doesn’t waste it.
When Ganymede’s artificial environment is devastated by fighting, the story follows Praxidike Meng through the apocalyptic aftermath. Praxidike is an environmental scientist, so he can’t help but notice how everything is going to hell, even while struggling to survive. The story teaches a powerful lesson: the only way through such a catastrophe is cooperation. Stabbing your fellow human in the back might get you a meal, but it won’t save you. These events define Praxidike’s character for the rest of the book.
3. Space-Based Culture Clash
It’s the future, and everything we knew about culture has changed. While national identities survive on Earth, the old divisions don’t mean much in space. Mars’s Mariner Valley is descended from a mix of East Indian and Texan immigrants, resulting in a population that’s largely Hindu but speaks with a Texas twang. In the Asteroid Belt and outer planet colonies, humans have mixed so thoroughly that names like Mohammed Wong are commonplace.
Cultures of The Expanse are fractal. A Belter is anyone born past the orbit of Mars, even though a native of Ceres has little in common with someone raised on Europa. Residents of Earth, Luna, and Mars are often lumped together as inner-planet types. Reinforcing these distinctions, those humans raised in low gravity environments are physically distinguishable from those who live at the bottom of a gravity well. Belters have longer bones and larger skulls than anyone from Earth, and this sets the groups apart.
Beyond what they look like, there are broad differences between cultures. People raised in artificial environments often have a fanatical devotion to air filters. On Earth, high levels of productivity have created a world where no one has to work if they don’t want to. Earthers take a relaxed approach to life, certain that the basics will always be provided. Martians are the opposite. The grand project of terraforming their planet has lead to a culture that practically worships hard work and struggle. Of course, cultures have great internal variance as well. It’s a complicated world.*
With the passing of old divisions come entirely new ones. Even though they are all still humans, the differences in physical appearances allow for the kind of discrimination that’s painfully familiar. Racists on Earth see everyone born off-planet as mooching off the mother planet; Belters and Martians see Earthers as lazy and indolent. While people are more similar than they are different, that doesn’t stop the closed-minded from exploiting the differences that exist.
The protagonists come from a range of backgrounds, which causes friction between them. The retired Earth naval officer has difficulty relating to the hot-shot Martian pilot. Romance between them is even more complicated, especially when the concept of meeting parents is raised. Where many sci-fi stories show us a relatively homogeneous version of humanity, Corey shows us as the complicated primates we really are.
4. Politics of Resource Scarcity
On the one hand, expansion into the solar system has created a flood of new wealth for humanity. On the other, it’s stretched resources farther than ever. Asteroid mining provides near endless raw material, but moving it around is difficult. At the same time, Earth produces more than enough food and air for everyone, but these resources can’t always get where they need to go. When you’re dealing with the vast distance of space, distribution becomes a problem.
Humanity’s far-flung habitats in the solar system form a complex, interdependent relationship – one that isn’t easy to see. For instance, Earth depends on the raw materials being shipped in from space. Even with vast recycling programs, there aren’t enough materials on the planet to keep vital infrastructure running. Reactionary Terran politicians refuse to acknowledge this reality, claiming that since Earth has always been self-sufficient, it can remain so. Perhaps even more sinister, some in positions of power think military force is the answer to this dependence. They seek to control the solar system by sinking untold fortunes into the navy, spending more and more of humanity’s resources on tools of violence.
Mars, the Belt, and the outer planets are in the opposite situation. They have all the raw materials they could ask for, but are short on either labor, air, water, food, or all four. Many in the Mars government take the same position as the politicians on Earth: if they can build enough ships, the solar system will have no choice but to bend to their will. Meanwhile, nationalists in the Belt expound the virtues of independence, ignoring how much they need regular shipments from Earth.
Ironically, the xenophobic distrust is a self-fulfilling prophecy. Fearing Belter separatism, Earth deploys more ships to the outer planets. Belters, seeing their freedom threatened, strike out with acts of sabotage. Mars builds a new class of warship to counter an expanding Earth navy. Earth sees this new Martian ship and, in a panic, expands its navy. The political divisions between Earth, Mars, and the Belt are what drive the story. Who doesn’t love a little space-based intrigue?
5. War by Remote Control
I’ve said it before: space is really big. Unimaginably big to us humans. To cross it in any reasonable amount of time, ships have to move really fast – so fast that, should they get into a fight, human reaction time won’t be able to keep up. Unlike most sci-fi stories, The Expanse accepts this and uses it.
Space battles in The Expanse are more like games of chess than Star Wars-style dogfights. Torpedoes accelerate so quickly that no human pilot could hope to evade them – even if the acceleration required to do so wouldn’t kill everyone on board. Instead, the ship relies on point defense cannons (PDC), automated machine guns that shoot incoming torpedoes down. The pilot’s job is to plot a course that gives their PDCs the best firing solution while denying that same opportunity to the enemy.
Gunners don’t aim their weapons manually. Instead, they prioritize targets based on data fed to them by an electronic warfare (EW) officer. Since distances are too vast to look out a window, the EW officer has the job of determining which nearby objects are hostile. Battles don’t hinge on human reaction time but rather on our ability to plan.
With this dynamic, Corey makes every space battle a dread-filled waiting game. The characters plot their flight plans, assign their targets, and wait as the g-force of acceleration pushes down on them. For a handful of seconds, there’s nothing they can do but hope.
These scenes are so well written, and use enough real science, that no one asks why these ships have crews on them at all. Logically, a ship with no squishy humans to keep alive would have far greater performance, and the setting’s AI is more than advanced enough. That’s The Expanse’s secret. It’s not 100% accurate, but it’s close enough that even nerds like me don’t ask questions. We’re willing to suspend our disbelief because everything else is so good. No series can get everything right, but The Expanse proves there’s value in trying.
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