Space is big. Really, really big. Worldbuilders using space as a setting often struggle with its’ immensity for two reasons: one, the vastness of space can be difficult to conceptualize and so often science fiction worlds suffer from issues with scale. And two, because space is so big worldbuilders often need to invent new ways of traveling through it fast enough that a single relevant person can actually visit different planets without dying of old age first (one manifestation of the worldbuilding distance problem). When designing fictional worlds (or solar systems, or galaxies) where people can traverse the stars, worldbuilders should first come to appreciate the scale of space. Then they can focus their efforts on designing elements (like fictional propulsion systems or teleportation gates) that allow them to use space the way they envision without generating internal inconsistencies or unbelievable timeframes in their narratives.
How long does it take to get to Mars, anyway? 30-40 mins? A decade tops, right? Worldbuilders may want to be more exact.
The Scale of Space
To get a sense of the scale of space often it is best to try to frame it in an easier to conceptualize manner. Let’s focus on how long it takes to get around our local solar system using trips taken by real spacecraft.
- Apollo 11 took 3-4 days to travel from Earth to the moon.
- It took Perseverance, a Mars exploratory rover, 7 months to get from Earth to the red planet. Future human missions generally plan for a 9-month trip to Mars.
- It took the Juno space probe 5 years to reach Jupiter.
- It took the New Horizons spacecraft 9 years to reach Pluto.
- The Voyager probes took around 33 years to get from Earth to the edge of the solar system (depending on how you define the edge). They did, however, take a bit of a round-about path to get there.
The distances and times needed to travel those distances become even more absurd at interstellar scales. Alpha Centauri, our nearest neighboring system, is 4.24 light years away. Our home galaxy, the Milky Way, spans about 200,000 light years in length (less so in width). Currently the fastest man-made object in space, the Parker Solar Probe, is traveling at 0.05% the speed of light. Which means it would take Parker 85 years to reach Alpha Centauri and 4,000,000 years to cross the Milky Way (assuming constant velocity).
The Andromeda Galaxy, our nearest neighboring galaxy, is 2.5 million light years from Earth.
Many worldbuilders will wish to avoid these types of timescales, especially in narrative-driven worlds. To do so they may invent fictional propulsion systems capable of making these journeys faster or incorporate elements that allow for other variations of faster travel, such as wormholes or teleportation gates. Generation ships or cryochambers able to allow for suspended animation are additional means by which worldbuilders seek to solve the problem of the size of space.
Advances in propulsion systems means spaceships launched at later timepoints may be significantly faster than older models and may overtake them on their way to a common destination. The first interstellar mission launched to a new location may not be the first to arrive.