Humans using faster than light-speed (FTL) travel have found and begun populating other planets, planetoids, asteroids, etc. Local societies farm; they ranch and mine; they are bootstrapping light manufacturing.

As these new civilizations grow, they seek trade over distances to local planets and other bodies, and even to other solar systems. When needs for many raw and refined materials, for transportable agricultural products, for desired cultural and light manufactured items (clothing, art, shelter pods, mining ray guns) are met and even surpassed, what media will be most sought to store and exchange value?

I think of several categories for trade:


  • technologies like how-to;
  • navigation like charts of what’s-there;
  • information like about other places or societies

—- artifacts:

  • items of human or found alien ancestry
  • wampum from shell beads to diamonds with O₃ entrained
  • origin-unique art & cultural objects
  • Hand tools, machine parts, tires

—- certain materials:

  • bulk metals like gold, silver, platinum highly refined
  • materiel especially for construction of weapon & ammunition
  • tooling from router bits to bearings, cryogenic parts to micro-manipulators.

Lots of things have value, but the further it has to be transported, the greater its combined [value / size::mass] ratio should be. What has a high enough value then for traders to put in cargo and carry to another solar system, and what medium can have near universal trade value at other stops on the route?

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    $\begingroup$ Luckily, civilization is about 5,000 years old. Put yourself in the sandals of a savvy Sumerian merchant who lived 5,000 years ago. What commodity available in his time would be still valuable today? Slaves? No, we don't buy and sell slaves any more. Silver? Not really, the price of silver today is some 20 times lower than it was then. Cloth? Absolutely not, cloth is about 1,000 times cheaper. So the question is, how could the savvy Sumerian merchant have any opinion worth considering about what we will find valuable 5,000 years later? $\endgroup$
    – AlexP
    Jun 18, 2023 at 13:07
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    $\begingroup$ Are you sure about that? There's 50 million slaves on Earth right now. More than at any point in history: npr.org/sections/goatsandsoda/2022/09/13/1122714064/… $\endgroup$ Jun 18, 2023 at 13:31
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    $\begingroup$ @SurpriseDog As far as I know, slave trade is no longer a major business even though there are more slaves today than ever: that figure, 50 million, includes also debt slavery and such, where people are not captured and sold but their effort is exploited via economical means. But it is nonetheless possible that as long people can exploit each other, some form of enforced labor is going to exist. $\endgroup$ Jun 18, 2023 at 14:14
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    $\begingroup$ What kind of FTL travel is available in your world? Without this information it is not very clear what is worth the effort. Also related question: worldbuilding.stackexchange.com/questions/15364/… $\endgroup$
    – FrogOfJuly
    Jun 18, 2023 at 14:55
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    $\begingroup$ The answer depends on what the societies are like (the origin and destination) and what are their differences and similarities and the effort to transfer the goods, eg. whether one lives in abundance and the other in scarcity, or one has free markets and the other one controlled markets (eg. drugs are valuable because they are illegal), and what the societies value (scarce items can become such just because they are scarce) etc. Without knowing anything of these, it is impossible to provide even good guesses. $\endgroup$ Jun 18, 2023 at 15:42

3 Answers 3


It depends on your world

The big question — that you need to answer yourself — is:

Is there fiat money or not?

enter image description here

Science fiction fiat money (image credit: Midjourney AI)

Fiat money is currency that has no intrinsic value, it only represents value.

In order for fiat money to work, there needs to be some kind of centralisation or at least some kind of framework that dictates what value this currency represents. In the world today, within one economic zone, this is usually handled by some kind of central bank.

The value of different currencies in relation to each other is what we typically call the exchange rate. This can be governed both centrally, and by the market.

So, follow-up questions:

  • Is there perhaps one big currency used by all interstellar systems, like in the Elite franchise?


The Elite setting uses the same currency everywhere, called "Credits" (image source)

  • Or does your "world" have any kind of economic zones, with centralised government of the money in these zones, but not throughout the whole setting, kind of like Earth today, where there are different currencies that can be national or regional, where some currencies where "everywhere" and some not.

  • Or is there no trade of money, and instead only commodity/service/goods trade?

All of the answers to these question, only you know. Only you can tell what kind of interplanetary governance exists.

And then there is the other big question...

Is money even needed?

Currency exists because of scarcity. Scarcity means that value is limited. Currency exists to manage the value, and maintain some inertia in how value is traded, and to allow the different traders to maintain control over their acquired value.


What if the value is not limited, or if it is irrelevant?

In a post-scarcity economy, money is not needed, because the amount of value that is so large that withdrawing some does not deplete the available amount, or people simply do not care about "losing" such value.

One example of this kind of commodity is air. We can refine air and create goods with it...

  • Carbon dioxide
  • Dry ice
  • Liquid nitrogen
  • Noble gasses such as argon

On Earth, we have since the start of industrialisation taken our first steps towards post-scarcity. You notice this in how the grand-parental and great-grand-parental generations of today refrain from throwing things away and instead save their goods, because that is what they were taught: goods and commodities are scarce, and if you do not save and fix them, you might lose them.

Younger generations know there is always more to be had, so we acquire, use, and throw away / recycle instead.

In summary

There is no singular answer to your question without knowing these things:

  • Is there scarcity or post-scarcity?

  • Are there centralised governance of economics zones that extend beyond planetary nations / planetary federations / planets / planetary systems? How far out do they extend?

  • Is there a money trade between these economic zones, or are there only services / goods / commodities being traded?

  • How diverse is your "world"? Is there a spectrum, where — at the one end — you have thriving post-scarcity utopias, and — at the other end — you have struggle-for-survival subsistence economies?

I hope this helps in making you ask the right questions to yourself, and thus allow you to shape the economy/economies of your "world". :)

  • $\begingroup$ By leading your answer with the phrase "It depends on your world" you're admitting the question is too story-based (a VTC reason). Worse, you end your answer with a list of clarifying requests. So this isn't an answer... it's a very long comment. $\endgroup$
    – JBH
    Jun 19, 2023 at 14:31
  • $\begingroup$ Answers also have minimum standards, and they begin with Answer well-asked questions. You recognized this wasn't a well-asked question - and answered it anyway. The goal of senior users (theoretically, such as yourself) is as much to help people learn how to answer questions as to ask them. If you believe that I'm coming across as too much the policeman when I police the rules of the Stack... that's your problem. Rules exist for many reasons, including to enhance the quality of the service. $\endgroup$
    – JBH
    Jun 19, 2023 at 15:22
  • $\begingroup$ You didn't fully address at least [any] part of the question. You posted a bunch of clarifying question requests and concluded by saying, in effect, "it depends." It is not true that "any benefit I perceive the OP may receive" is a qualifying condition for answering a question that isn't well-asked. $\endgroup$
    – JBH
    Jun 19, 2023 at 18:45

Genes, not necessarily people, but their genetics. Especially on small colonies which probably have little genetic diversity. Sending actual human beings raises the issue of slavery in various forms which may or may not be in favor for a given society. Also a small number of new people will probably viewed as an exotic attraction, while large numbers may be seen as an alien invasion. Frozen sperm and ova are easier.

Possibly plant seeds and animal embryos. Seeds would easier. Embryo either require same species females to implant them or artificial wombs to gestate them.

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    $\begingroup$ Resolving genetic stagnation. That's a clever idea. +1. $\endgroup$
    – JBH
    Jun 19, 2023 at 14:32

Everything: Because Opportunity Cost is Never Equal

In economics, there is this huge misconception that just because you can make something yourself means that you will make it yourself. Every world can grow its own food, supply its own power, produce it's own materials, etc... but they wont all share the same set of opportunity costs.

  1. The more things your economy does for itself, less available labor you have, and the more difficult it gets for employers to find and afford labor, and the harder it becomes to train an eclectic workforce that can work in every industry. So, if your planet only has 1 major industry, and a neighboring planet has 50 major industries, the very fact that you have such a thin labor market, and simple educational requirements means you have a more poor population with fewer employment options willing to work for less meaning the 1 industry you have can, must, and will be able to produce and sell a large cheap surplus. This also means that, in many cases, its worth while to import something that you can in theory produce more cheaply domestically simply because in practice, your workforce is spread too thin and better employed elsewhere doing other things at a higher profit. So in your case of all worlds being able to have all 50 major industries locally, economy of scale and market forces will drift towards planets each specializing in some of those industries and trading for other products that other planets specialize in.

  2. There are also culture differences from one place to the next where the education, public services, government subsidies etc. all work together in a way to produce a place that is better at doing some things than others. So sure, every planet can bootstrap thier meta-material mills and thier aeroponic farms and such, but each planet will also have innovators who are improving on and experimenting with those bootstrapped systems. So, while 10 worlds might be able to supply the exact same, perfectly cloned, aeroponically grown strawberries, the 11th world might have a whole subculture of artisan strawberry geneticists and culinary artists and relaxed genetic engineering laws which produce 1000s of new varieties of strawberries and strawberry derived products each year that are not part of the standard template library, and these strawberry products would be valuable trade commodities because everyone knows Sigma-B strawberries are the best darn strawberries in the universe.

  3. Lastly some trade deals exist purely to overcome the inconveniences of nature. For example, many South American countries sells fruit like apples, oranges, and pears to the United States, and in return, the United states sells them.... fruits like apples, oranges, and pears... which sounds ridiculous right? But here on Earth, we trade between hemispheres to equalize food availability. Likewise your planets may go through any number of natural cycles that cause bull and bust economic factors at predictable intervals that can be offset through mutual trade. For example Planet-A may be a highly volcanic planet. When a major volcano erupts, the the sky gets blotted out, global temperatures fall, and even though they could keep growing indoor crops, heating and artificial lighting becomes much more expensive; so, they rebalance a lot of thier power grid to heating homes and keeping people alive while they import food from Planet-B... but when the dust clears, they have abundant fertilizer from all the volcanic ash allowing them to out produce thier sister planet; so, they start selling food right back to the guys who they were just buying food from.

Bootstrapping Production wont prohibit trade, but shipping costs may.

The only real limit to how much your society will deal in trade is how much it costs to transport goods between worlds. If it's supper expensive, then only very high value/low mass goods will be considered, but the less fuel and time it takes to get between worlds, the more things you will want to work in bulk goods.

  • $\begingroup$ +1 to the cost of transport - with realistic space travel it's not economical to ship 99+% things from one planet to another, you'd only ever trade extremely valuable stuff, absolutely NOT raw ore (think shipping it by air on Earth, but much worse). HOWEVER if you have FTL, you can define your shipping costs any way you like. Just make sure it's self-consistent within the story. $\endgroup$ Jun 20, 2023 at 12:18

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