Worldbuilding 102: Faster than light travel
Hello again all! Your favourite alien Limax, Vivian, is back again to discuss faster than light (FTL) stuff!
Space is a big place, a really unfathomably enormously gargantuanly huge place. The moon is one light second away, that is, light takes one second to go from it and reach Earth. The sun that blesses the world with light and warmth is 8 minutes away. Alpha proxima centauri, the closest star, is 4 years away. The closest edge of the Milky Way is 2000 years. Imagine it, the light that reaches Earth today was sent out when the Roman Empire was its height! Andromeda galaxy, 2 million years away. Humanity didn’t even exist when that light left for its course toward earth! The fastest thing in the universe still takes ages to go places because of how huge space is.
Relativity, Causality, or FTL
It is said you have 3 things, relativity, causality, and FTL: pick any two, and leave the third behind. This is because you cannot mathematically have all 3 at the same time, so what happens when we leave each one out?
Relativity
Without relativity, you get what is called a Newtonian universe. Light goes at infinite speed which means every point in the universe will interact with every other one instantly, and within a fraction of a second, everything has settled in the maximum entropy possible and nothing had a blast; there were no parties. It will also be a dead universe for other reasons, primarily because stars cannot exist. They gain energy from the mass equivalence of relativity, and without it, stars have no fuel to make themselves work.
Causality
Causality is the chain of events. The ability to say that one event happened after another by the order in which they could have any influence on your frame of reference. So if you throw this away, you can have effect precede cause and the chains going back and forth, future affecting the past, the past affecting the future and all. You know the time travel paradoxes? This is it, now on steroids. Not a good time for our causal brains.
FTL
And if we have no FTL we have… what you call reality. Things work… but it goes so SLOW! 🐌
What do we do?
What do writers and worldbuilders do? 🥺 We want FTL so we can do space operas and have lots and lots of sexy aliens!
We ignore the issue. Simple as that. Yes having all 3 is a mathematical nightmare, but hey, isn’t this what willing suspension of disbelief is for?
Types of FTL
There are of course for fiction countless number of FTLs, but they can broadly be divided into 2 large categories with 2 subcategories each.
Continuous
Imagine you have Earth’s sun Sol and then Alpha Centauri. With continuous FTL methods, in some sense of the word, you will have to traverse every point between Sol and Alpha Centauri. There will be no sudden jump where you ceased to be and suddenly appeared elsewhere. Think of it like a pencil on a paper and you draw a line between two points, you are not allowed to lift the pen off the paper as you draw from one point to the other.
Metric Manipulation
“Metric” is a fancy mathematical term for what can be summarised as “A way to measure a ‘distance’ between two points”. I put distance in quotation marks because while it works the intuitive way you have about distances, it is mathematics so not really distances, we don’t deal with stinking real stuff! Anyway, what these drives do is that they change the distances between two points in space. It can be locally done where distances nearby are severely shrunken (or expanded) while travelling toward the destination. The classical example here is, of course, Warp drive from Star Trek.
I have not seen anyone do more global manipulation of the metrics, but a way that is more of a mix that I can imagine is like “Warp tunnels”, where space has been reworked in specific ways such that within the tunnel, distances are significantly decreased, and thus travelling within is way faster than outside. Though how it goes when you enter them from the side, I don’t know. Explode maybe? Wormholes and the likes are not examples of this because that is bypassing the space between points. These warp tunnels would be continuous ones where you travel through ordinary space and can treat it as normal space within as I imagine, but hey, I don’t make the rules for your tunnels! If anyone has any ideas for a purely global metric manipulation, feel free to comment below with your idea.
Alternative Space
Another alternative for a form of continuous drive is what I call “Alternative space drive”, where alternative space is quite literally another space. It is not in the usual space where planets and stars exist. This can go by many names, but “hyperspace” or “subspace” are quite famous and often used ones. Star Wars is famous for this… until the trilogy that shall not be named and does not exist. The idea is that in this alternate space, distances are different, or speed of light is different, so you can use it to traverse for way longer distances and faster than in normal space. The properties within this can be literally anything a worldbuilder or author wishes it to be to create tensions and problems.
The Warp from Warhammer 40k for example has quite literally chaos as its property in the sense that you can arrive before you left, travel time is independent of distance, there are daemons, and much else there. Welcome to hell I guess? If you do alternate spaces, be quite liberal in its properties and dangers. Where is the fun if there is no danger? 😈
Discrete
The difference from continuous drives here is that while in continuous you were not allowed to lift the pencil of the paper as you drew the path, in discrete ones you are allowed to lift the pencil, move it across the paper, and then continue drawing over there. That is, you cease to be in a spot and suddenly appear in another with no historical trace of you ever in anything in between.
Teleportation Drive
This one is quite simple actually. It is a classical jump drive. Put in the coordinates, engage the capacitors after they are charged, and WHABAM! You are now there, one jump and suddenly there. You can justify this through teleportation mechanics, or some massive technobabble bullshit about folding space in on itself so hard it wet itself and called out uncle before making a slight trip across the now very close points in space. It is quite standard.
One model I love that makes it a mix with continuous (but neither of its groups) is from the Sword of the Stars game. The Liir have what is called a stutter drive. The idea is that it does not jump across space in vast jumps or even really moves. It “Stutters”, by constantly teleporting the entire ship only a few microns (micrometres; Freedom uniters can math it out) in each instance. By doing this over and over and over again in a stuttering fashion, the ships reach FTL speed and go across space. One thing they had in there is that due to the more complex space dynamics in gravitational waves, it was slower near gravity wells, and thus you sped up as you left a system and then slowed down as you went into another.
Gate Network
These are good classical ones. You use either wormholes, jump gates, dark matter shooter, you decide what name it is. The thing that makes these unique is that they are connected into a network that forms what mathematicians call a graph. Each system is (generally) connected only to a finite fixed number of other systems (or sometimes even not at all and thus a loner). Adding or removing the connections are generally exceedingly hard and not worth the effort.
A nifty thing with gate networks is that the travel time between two systems is independent of their actual distance. All that matters is how many jumps between systems you have to do and how long it takes within the system. So you can literally have it so that it takes shorter time to travel to a system a thousand lightyears away than a system that is only a hundred light years away. A common thread in these kinds of systems is that within solar systems, there are no FTL like drives so it can take hours, days, or weeks to traverse across the system.
Potential issues
When I say issues here, I mean for the users. It can be cumbersome for a person experiencing it, and thus is an issue. Narratively speaking, and how you make and form your world, they can be great positives to create conflict, tensions, reasons for wars, etc. So what are they? Let’s dive in, shall we!? Well, not like you have a choice at this point!
Fuel
Everything on Earth requires fuel: people, machines, everything. So it is quite common in fiction to include some fancy fuel source to work with FTLs. Dilithium, for example, in Star Trek. The benefit of this is that it gives the crew on the ship something to always maintain and can, due to a miscalculation or, worse, being fucked by events, mean they cannot have time to pick up any. So they are, in the continuous case at least, halfway there, and suddenly the engines start choking as there is no fuel, and they get stuck. Things are bad! Hopefully they have some ansible tech to call for help or, by sheer stupid luck (and authorial influence), just happen to get into a system where they can get it.
This is generally not an issue for jumpdrives and networks because in the jump drive, once you have enough to make the jump, you’re there instantly. Sure, you can still have fuel and now… Well damn it! Bob put in the wrong coordinates, and there are no people to buy fictonium from! Well, it seems like we still have the benefit of fuel being here, only harder to get. For networks, it is generally rather pointless to ever have it because they are maintained by the systems on either side and thus rarely use consumed fictonium. Of course, this is not an iron clad rule. You can easily have it so that FTL requires fuel, and a system suddenly stops sending ships and information onward, assuming it uses the network for communication, and ships gets stuck in there until someone on the outside figures out to send in a large quantity of fictonium to restart their systems… hoping that was the only issue.
Time Commodity
Time is money! That is how the saying goes, right? This is important for a lot of stories, and if one does not take it into account, you quickly get “At the speed of the plot”, a trope I despise. Planets, stations, people, stars, anything is any amount of distance apart and takes different amounts of time to reach depending on how convenient it is to the plot. Continuous drives of course lend themselves toward taking time to go from one star to another proportional to both speed and distance.
This, however, cannot be said about the discrete ones. Jumpdrives generally have distance and time disconnected. As long as you can get the engine charged up and ready, off it goes and arrives instantly! Some people chose to give a max jump distance in order to add time as an issue. For networks, however, distance is generally not a thing that matters. You can have a nearby star system that takes months to get to because you have to take a long ass way around the network to find the one access point to that system, all while the star 90 times farther away is just one jump away and reached in hours. So as you can see, it depends entirely on how the network is structured.
Traceability
With this, I mean how easy or hard it is to trace where you have gone. Which is important in stories as that means whether chases can be done or not. Or just finding people. In continuous cases, tracing ships is generally fairly easy. But alternate spaces can make it difficult because maybe the sensors only work if they are in the same space! So that means you quickly have to go into the space and start looking, but depending on how you make the alternative space, it might be too late already, and gone they are. If sensors can sense in both (or however many spaces you got), then pursuits can engage. Metric manipulation generally does not have these issues historically.
Jumpdrives are a wildcard. It can be literally impossible to trace because now you’re here, now you’re not! And suddenly across the galaxy. You can create tracks if you want, but it is rarely done–but hey, you can! When it comes to networks… given they don’t have FTL within a system, it is very easy to trace where you’ve gone within the system. But if you manage to get 1 or more systems between you and pursuers, it gets increasingly more difficult to trace you, especially so if each system you pass through has 3 or more exit/entrance points. I lump them together because generally they are bidirectional but I have seen some do unidirectional ones! That was fresh.
Choke points
This is where networks shine. They create obvious choke points where the enemy must come through and leave from. This means you can fortify the system in a way that other FTLs do not allow. For jumpdrives, choke points are entirely pointless, given you don’t exist at the point where you could be stopped. But hey, maybe they have invented a “jump attraction device” which means any jump that would land near it, or maybe “pass by”, if it was continuous, forces the ship to exit near it. Then we can have fortifications again!
Continuous is also generally entirely pointless to make chokepoints because if you make it in one area of space, they can fly around and come from another angle and render it moot. It is however NOT impossible to create some regional chokepoints. In my setting and universe, I use a form of continuous drive (despite it being called Discrete drive, I’ll explain it in a practicum!), but there are particles and substances that can force you out of “Discrete space” (my form of alternative space). A system for a species that I call Tshutsi has a peculiar configuration in their Oort cloud (Lots of rocks in a spherical configuration way beyond Pluto) that makes it so that there are less than a handful of angles that you can enter the system through. If you try any other you are pulled out of discrete space forcefully and then have to slug through normal space for months before you can hope to go FTL again. At this point you’ve been detected and interception is already incoming… likely with warheads.
Information diffusion
This touches on communication, a post I already did; go and read it! A common pattern in stories, though, does exist between the categories of FTL. If you have pure metric manipulation and that is literally the only method of FTL, and no ansible tech, that means sending probes at FTL, and this can take hours, days or even weeks and months before they reach their target. For alternative space drives, there is generally a form of ansible tech and information spreads like wildfire.
Jumpdrives in their pure form are generally like the metric manipulation: probes that jump around, dump information, receive information, and keep on doing this until they need refuelling, repair, or anything else that requires a human. It would be a very boring jump if there must be organics onboard to operate the jump mechanism. I am not signing up for it! BOB! He can do the monotonous mindless repetitive job. The jumps might be quick, but it’ll be a long time before that probe needs something where Bob gets to meet another organic face.
Networks generally do not have ansibles (albeit you could use the micro wormhole idea); they are usually seen using probes that either traverse across the systems to each gate and move on until the target. More well established systems that have only a probe going back and forth in a gate where it receives and dumps information for the system's own Information Technology to deal with. Having the system do it is generally faster because of lightspeed communication, compared to a probe flying that takes days at bare minimum to cross a system.
Space battles
Space battles are of course also affected by how FTL is done. In networks, they are often done away from the gates that make it work, generally out of a fear that it will close a path for everyone. Some have made it even a war crime to destroy gates. But because of the slow speeds involved here, a battle can take hours from engagement to exchanging actual anything. This is all due to how long it takes to meet up.
For jump drives, it is the very opposite. If you are seen first, you are generally worse off because, depending on ansible tech, you can have ships suddenly appear out of nowhere and bombard you before you know what is happening. So here, being seen first is the worst thing.
For metric manipulation, it is more even, where you can find your enemy approaching and know it before it is too late. But it depends on the qualities of the drives, of course. The big difference between many who use this is if you can do battles while in FTL. Some franchises allow it, some do not. If you do not, that of course incentivises one to remain in FTL to avoid fighting. Think about ways to force someone out of FTL and prevent it then.
For alternative space drives, it all depends on how the alternative space works. Most I have seen disallow battles in the alternative space and have a way to force you out of it so space battles can be done.
Economics
When it comes to trade and economics and large space empires with FTL, most things… do not need transport. Every solar system has so much material and so much space and ability that they can produce everything. But that goes contrary to how modern economics works; does that mean things will collapse back into mercantilism? It can if you want! But jump drives are generally fantastic to circumvent this because of how fast they are, so you can still trade ordinary stuff with jump drives.
For the other drives, ordinary material is rarely ever going to be worthwhile, especially not with exotic fuels like fictonium. If you have other fictoniums that are not extremely abundant in virtually all solar systems, then trade again opens up and makes sense. After all, resources are no longer equally distributed nor so abundant that everyone has it. This excludes, of course, very specific living things and cultural items that might still be valued sufficiently high that trade is an option.
Summa Summarum
The choice of FTL method changes everything within a space opera universe. From choosing continuous or discrete drives to choosing which limitations to use and how, various elements of your world and story are affected by the choice of FTL. I cannot say everything in a blog post and won’t even try. But this should give some vague ideas on the impact your choices have in some very important aspects in society and stories.
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Copyright ©️ 2023 Vivian Sayan. Original ideas belong to the respective authors. Generic concepts such as Continuous drives methods, Gate networks, Alternative space, and micro wormholes the concept, are copyrighted under Creative Commons with attribution, and any derivatives must also be Creative Commons. However, specific ideas such as Tshutsi the species, Discrete Drive the FTL method, Discrete space the alternative space, and all language or exact phrasing are individually copyrighted by the respective authors. Contact them for information on usage and questions if uncertain what falls under Creative Commons. We’re almost always happy to give permission. Please contact the authors through this website’s contact page.
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