Let’s pretend. Let’s pretend that some sort of interstellar civilisation comes about. This is SF. The question that good SF wants to ask is, “What does this mean for people?” Or, put another way, what sort of society seems likely given a bunch of star-systems
infested inhabited by humans.
== Ground Rules
My starting assumptions are:
No sapient aliens. This get complicated enough with just Homo sapiens and our eternal squabbling and irrationalities.
In other words, I see no fundamental change in human nature; we’ve not transformed into angelic superbeings just because we can travel far through space. A history of tech progress to date backs me up on this.
Several star systems. Anything from a mere three or four all the way up to dozens. A system might contain only a single inhabited planet/moon/body, or (more likely) several, including space habitats and so on.
Clearly we have some tech indistinguishable from magic that enables travel between stars. Whether that’s Faster Than Light magic, Wormholes Through Spacetime magic, Alcubierre drives, Generation Starships or something else… I don’t much care. Not germane to the point I’m interested in, and they’re all roughly equally impossible by today’s understanding of the physics and engineering required. Consult Charlie Stross for more detailed exposition.
Travel between stars is still an expensive and challenging pastime. We don’t flit about from system to system on a whim. It’s somewhat akin to a long ocean voyage in the 18th Century — doable, mostly reliable rather than the adventurous/hazard-ridden exploration of the 15th, but expensive, tedious, time-consuming, and not without its challenges. Something you might do once in a lifetime, maybe two or three times if you were afflicted with a strong wanderlust. (Not so sure of my ground with this assumption. My analogy may be too weak. Let’s live with it for now. Mostly it doesn’t matter too much.)
== What Does An Interstellar Trade Network Look Like?
Well here’s the thing: I don’t think there is a lot of trade between star systems. Nothing even close to the amount of trade and shipping between nations/regions on present-day Earth. The reason is simple.
Any society sufficiently advanced to be able to engage in regular (if expensive) interstellar travel must necessarily have solved a large number and wide range of science, technical and engineering problems that to us seem insurmountable.
If the travel magic is FTL, then we’ve discovered some seriously new physics and figured out how to control it well enough for locomotion. I’ll remind you, dear reader, that we’ve not even mastered nuclear fission sufficiently well for that purpose, and we seem to think we have a pretty good handle on the underlying physics of the process. If it’s Wormhole Shortcuts/using black/white holes, then we’ve conquered some extremely interesting manipulations of spacetime and matter-energy, including some hypothetical exotic particles and states, and managing to build useful macrostructures using them. Tall order.
Whatever the transportation tech is, we’ve figured out how to keep squishy monkeys alive and healthy for extended visits into space without the shield of a planetary magnetosphere, along with sourcing enough fuel and propellant to cross distances that takes light several (dozens/hundreds of) years. I suspect that not even nuclear (fission) fuels are up to it unless you can scavenge them as you go.
For this reason I imagine an interstellar space-ship is much more likely a small armada, consisting of one or a few central bulk-carriers — the real “star ships” with all the life-support and command-and-control and navigation smarts — surrounded a by cloud/swarm of smaller robotic vessels constantly searching out minerals/water/hydrocarbons from the ever-moving region of space surrounding the mothership(s) to keep said mothership fed, watered and fuelled.
Another possibility, explored in several SF incarnations, might be a substantial and highly-industrialised “base station” — a complex of factories and refineries anchored to some “fixed”, resource-rich site — an asteroid, perhaps, or a moon of some gas-giant — extracting, purifying and packaging suitable materials into pellets (size might range from beercan size to grain-silo) and then fired toward the receding ship at relativistic speeds (and immediately we’re back into the realms of “stuff we really have no clue how to pull off”). These supply missiles catch up with the ship, get caught in some sort of catchers-mitt, imparting their kinetic energy to the ship, so accelerating it, and maintaining a constant incoming supply of consumables to the ship. Slowing down when you approach your destination is handled by the same method, only now the “base station” infrastructure is at the far end and the missiles travel in the opposite direction to the ship. Simple, really.
Or maybe Wormholes really work and the starships that transit need not be so very complex. Just the Wormhole machinery has to be.
The point is, with that much mastery over matter-energy and spacetime, it is inconceivable to me that the civilisation in question suffers from any material wants or needs. (Change My Mind!)
As a society we’d know so much about how to manipulate matter and energy, we’d have effectively limitless energy to play around with, that we must of necessity be able to produce any material we desire in any quantities we require. We have to have those capabilities if we’re able to transit between star systems, otherwise we simply wouldn’t be able to go starfaring.
So societies without material or energy shortages.
Now: What is it you want to trade?
You’re certainly not interested in transporting mundane stuff like ores or refined minerals in any form. Easier and cheaper by far to cobble them together close to home in the first place rather than schlepping them about from one star system to the next.
Likewise foodstuffs. If you can keep interstellar travellers and crew tummies full, you can certainly do the same for your planet-bound (or habitat-dwelling) citizenry. No food trade, then.
== What’s Left, Then?
About the only useful sort of trade that’s left is trade in culture, trade in ideas, trade in what we (weirdly) call Intellectual Property. Music, stories, ideas, design. Designs for better starship engines and new cures for what ails us. (Assuming that starships can move faster than electromagnetic transmissions!) Then there are unique items that people treasure for being singular and special: handmade guitars, handmade apparel, original art-works, one-off dramatic performances by treasured/gifted performers, dance, antique teacups, artisanal beer/coffee/wine… “collectables”.
Back here on present-day Earth we do a certain amount of trade in those things. Most of that, though takes place in reverse: the buyers go to the places where customs and stories and food and music is different than where we come from, and we trade culture where it happens. It’s called tourism.
I can’t see that much changing, even if the distances involved are a bit more eye-watering.
So, aside from moving ideas and collectables about, most interstellar movement would be about moving people. Tourists, yes, and also people moving from one place to another in the hope or expectation of improving their lot — much as people move from one region to another here on Earth because “the grass is greener over there”, whether it’s to escape some disagreeable circumstance, or drawn by some real or imagined attraction or opportunity. But: Moving people about — while it’s likely to remain lucrative — is not usually what we think of when talking about ’trade'.
So my guess is that cultural trade — whichever way around it happens — would be the only useful form of trade between star-systems. Change my mind.
== And War?
War between systems seems a little bit more likely than trade-as-we-know-it. But only a little.
For the same reasons there’d be no cause for trade in basic materials, there’s no impetus to war on another party just because they happen to have Stuff You Want – like oil or cadmium or lithium or tungsten or Hydrogen-3 – because (again!) if you’re capable of interstellar travel, you’re pretty certainly able to make whatever elements you want via nucleosynthesis, and to put it together in any combinations that suit you.