In the boundless expanse of science fiction, crafting immersive and captivating worlds is an art form as essential as warp drives and laser blasters. Let’s journey into the imaginative cosmos of sci-fi worldbuilding. In this article, we’ll unlock the secrets of crafting otherworldly landscapes, species, and technologies that will leave your readers and players spellbound.

Whether you’re a seasoned author seeking to enrich your narrative or a game master looking to sculpt a unique gaming experience, we’ve got you covered. And what better way to embark on this cosmic journey than with World Anvil, the ultimate platform for harnessing the power of your creativity and enhancing your sci-fi worldbuilding endeavors? 

So, fasten your seatbelts, set your phasers to stun, and let’s embark on a thrilling expedition into the universe of sci-fi worldbuilding.

Sci-Fi Worldbuilding Approach and Process

One crucial aspect of sci-fi worldbuilding is the delicate balance between creativity and scientific credibility. While imagination knows no bounds in this genre, it’s important to ground your ideas in plausible scientific principles. This adds a layer of authenticity that allows readers or viewers to truly immerse themselves in your created world.

When we discussed fantasy worldbuilding, we recommended an “inside out” approach, starting with your core premise and extrapolating outward. From a certain point of view, sci-fi worldbuilding works in the opposite direction. We recommend that you start BIG and “out there,” looking at the astrophysics of your star system. Then working your way down to the planet, then the aliens and sapients who live there, and finally the minutiae of everyday cultures.

And yes, technology is also an important element of sci-fi worldbuilding. But technology is often a reflection of the values, resources and goals of a culture. So those things should be constructed first. Furthermore, in fiction, technology is often dependent on plot. Your world often has a specific gadget, weapon or spacecraft because the story can’t progress without it.

Okay, so with our overall process and approach defined, let’s start building a star system! 

Astrophysics for Beginners: Structuring Your Sci-Fi Universe  

Stars are formative for their planetary systems, as well as the geography, species and cultures of those planets! Stars can be:

  • Non-“planet hosting” (i.e. with nothing orbiting them – space is very empty!)
  • The center of a planetary system.
  • Part of a star system, a small number of stars that orbit each other, which may also host a planetary system.

Out of these options, the best bang for your sci fi worldbuilding buck will be a star system. A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A star system gives you multiple planetary setting options, without needing to deal with the question of faster-than-light travel. 

If you’re creating a star system, here are a few things to keep in mind to ensure you’re following plausible astrophysics principles.   

  • Smaller and lighter stars orbit bigger & heavier ones
  • Balanced systems are usually hierarchical, with stars divided into two groups, each traversing a larger orbit around the system’s center of mass.
  • Unbalanced systems can shoot stars off into space!

Tip: If you’re building your science fiction setting in World Anvil, the Geography article template is a perfect starting place! You can select star systems, planets, asteroid belts or even galaxies from the Type drop-down! 

Strange New Worlds: How to Build a Planet (or Several)

Now that you have your star system, it’s time to build some worlds for your game or story setting! As before, it’s a good idea to base your planets on plausible science. A moon made of cheese might be a fun (if smelly) idea, but it’s not exactly believable science fiction. 

On average, a planetary system has 10 planets, although they may have fewer or more. Common planet types are Gas Giants, Super-Earth, Neptunian and Terrestrial. Your inhabited worlds will likely exist within the “Goldilocks Zone” – meaning it’s neither too hot nor too cold to support life. According to NASA, about half the stars in the same temperature range as our sun could have a rocky planet that fits the bill. 

Some other considerations can make a difference for the inhabitants of your planet. It’s worth bearing in mind that planets that are closer to their stars are warmer, and have shorter years (because they have shorter, faster orbits). Planets that spin faster have shorter days, and also more volatile weather conditions. The tilt of the planet, as well as “orbital eccentricity” (how round or elliptical the orbit is) affect the seasons and their relative duration. 

Now that we’ve got the scientific credibility covered, let’s dive into the more creative aspects of planet-building. 

Sci-Fi Planet and Star System Tropes

On the less hospitable side of things, there are broken planets, tomb worlds, and relic worlds. These kinds of planets are great settings for exploration and uncovering the mysteries of long lost civilizations or finding valuable artifacts. At the other end of the spectrum are Gaia planets and Ecumenopolis planets. These worlds either represent a utopian environment or a thriving cosmopolitan setting, which can work better for stories centered on political intrigue, interplanetary espionage or other plots that require large populations. If you’re looking for something stranger, you could consider rogue planets, machine planets, and shielded or shrouded planets. 

Aside from habitable planets, there are fringe locations that are mainly uninhabitable, but can make good locations for things like pirate or rebel bases or corporate mining outposts. These include asteroids, gas giants, frozen or molten worlds, and toxic or radioactive locations. They can create tension for your characters, as they’re not just trying to reach their goals but also survive in a fundamentally hostile place.    

Planetary Trope Definitions

Rogue planets: Planets independent of a planetary system (these really exist!)

Broken planets: Planets destroyed at some point the past; broken, somewhat spherical ruins

Gaia planets: Idyllic, habitable Eden-like worlds

Tomb worlds: Barren, lifeless planets, homes to a civilization long gone

Ecumenopolis: Planet-wide cities (e.g. Coruscant in Star Wars)

Relic: As tomb worlds, but filled with still active technology

Machine planets: Remanufactured with all their resources used as infrastructure by robots

Shielded planets: Planets entombed by an Energy shield (nobody in – nobody out)

Shrouded planets: Mostly hidden/phasing in and out, hidden in a nebula

Alien Species and Civilizations

Next up, you’ll need to populate our worlds with interesting human and alien species! One big question in sci fi worldbuilding is sentience versus sapience. “Non-Sentient” species are unable to experience emotions or consciousness. This generally includes fungus, plants, microbes, and some animals. 

“Sentient” beings have the ability to feel or perceive, allowing them to think and experience emotions. This would necessarily include consciousness, and arguably includes some animals. “Sapient” beings have the capacity for intelligence, wisdom, and logic along with the ability to solve problems, learn, and understand. This is what is often referred to in science fiction as “intelligent life.”

It’s important to note that many species in popular sci fi are humanoids out of practical necessity. Before advanced CGI, television and movies needed aliens that could be represented by humans in a suit and prosthetics. But outside of humanoids, there are a lot of possibilities!

  • Machine
  • Mammalian
  • Reptilian
  • Avian
  • Arthropoid
  • Molluscoid
  • Fungoid
  • Plantoid
  • Lithoid
  • Necroid
  • Aquatic

Other considerations when you are developing alien species include anatomy & morphology, perception & extrasensory capabilities, genetics, reproduction, growth rate, habitat, and habits.

All of these (and more), with definitions and examples, are available in the species worldbuilding template on World Anvil.

Sci Fi Worldbuilding: Tech and Transport

Okay, so now you have people (aliens, humans, robots and so on) inhabiting your worlds. It’s time to equip those beings with some tools and transportation. Let’s talk technology and spaceships

When looking at the overall level of advancement for a society, there are a few different areas to consider. How plentiful is energy, and how adept is the civilization at harnessing it? What areas of science and technology have they poured the most research into advancing? 

It might be useful to think of a whole civilization like a single character in a roleplaying game, and branches of technology as different skill trees. Some societies will be moderately advanced in several branches. Others will be very advanced in only one or two. Only the very oldest civilizations may have “maxxed out” every branch.   

Branches of Technology

Biology: Agriculture, Medicine, Genetics, Bioweapons, Cloning 

Physics: Lasers, Shields, Anti-Gravity

Engineering: Robotics, Armor, Projectiles, Missiles 

Informatics: Computing power, AI, etc.

To go a bit deeper, consider major milestones for these interplanetary societies. Which “deep secrets” of technology have they unlocked? This might be dark matter, meta materials, psionics, or transcendence. You should also consider faster-than-light travel and communications. How do they manage it? By traveling outside “normal” space, teleportation, stable wormholes, or jump gates? Was their first contact with aliens hostile or peaceful and cooperative? 

These are important elements of history to sketch out for your sci fi worlds, but it’s also good to remember the “holy triangle” of technology (or magic, in fantasy worldbuilding). The holy triangle describes the balance between power (what it can do), cost (what it requires) and limitations (what it can’t do). If your technology can do everything, costs nothing, and has no limits, that can make it hard to craft a satisfying story that meaningfully challenges your characters. 

Worldbuilding Sci Fi Cultures

When you’re creating alien civilizations, it’s common to see a planetary or species-wide monoculture, or “planet of hats.” That means the entire population has a single culture, or expresses a single point of view on a subject. This is common when you are merely spotlighting a world or people, but it is avoidable. 

Within a single species, you can show different cultural groups, reflective of how humans work. Cultures can be formed and affected by:

  • External factors, like climate, weather, resources
  • Biological factors like lifespan or reproduction
  • Inherited history and origin
  • Internal factors, like religion and politics

Those factors will bear out in the elements of culture, such as food and cuisine, religion, traditions and taboos, politics and philosophy, as well as language, art and architecture. These cultural elements are great “show don’t tell” opportunities to display culture, for example setting a scene during a meal, or using a community ceremony, rite of passage or holiday observance as part of the set up for an adventure. Your characters might need to do some digging to find clues to a mystery by learning about the symbols, gestures or rituals of a specific culture. 

Tip: The World Anvil Culture template offers plenty of prompts like these, including naming traditions, genders, courtship practices, and descriptions of fashion, art and architecture.


In this exploration of sci-fi worldbuilding, we’ve uncovered the key takeaways that can turn your creations into breathtaking works of art. By grounding your sci-fi world in scientific truths, you create a more believable experience. 

Whether it’s crafting advanced technologies, alien species, or astrophysical phenomena, blending science with imagination will make the extraordinary feel plausible. Creating complex societies and civilizations breathe life into your world. This rich backdrop can serve as tools to advance your narrative, introducing suspense, drama, and unexpected twists.

So, whether you’re a writer penning a novel set in a distant galaxy or a game master preparing to lead adventurers through the cosmos, remember that the universe is yours to shape. Explore World Anvil, and embark on a journey into endless possibilities. Your sci-fi worldbuilding adventure awaits, and the stars are yours to command!