Could a civilisation exist as 'space-nomads'?

Question

In a civilisation similar to humans (although not necessarily humanoid) living on a planet the size of Earth, could the whole civilisation (no limits on size, although I was thinking a few thousand at least) exist in space as space nomads?

This would involve moving from planet to planet, settling for a few weeks or months, then moving again. The nomads are not limited to just planets, though; any sort of planetary body will suffice.

Living as space nomads would also require a stable lifestyle; food, water, shelter, entertainment and above all defence should be no problem for our civilisation. However, the civilisation does not need to live together; tribes would no doubt develop and split off, and wars could possibly begin.

This civilisation is advanced enough to be able to live on planets such as Mars, but the tolerance of temperature, atmospheric density ect. does not differ from human tolerance.

What factors would drive a civilisation to become nomadic tribes that fare deep space?

Answer 1

Generation ships are probably the most realistic form of interstellar travel without superscience. So if the originating civilization has some reason to have interstellar travel that justifies the use of resources, generation ships will be likely.

A civilization that has colonizaed its own solar system might turn to exploring other stars almost by default. They'd also have the necessary resources and technology to actually build the generation ship. So the original reason might simply be that it is the only method of expansion left. There would also be economic benefits from the technology developed for the project and the insurance factor of not being limited to one system.

This makes more sense if the civilization is factionalized. Then a competition similar to the space race between the superpowers would be possible, even likely. Being the first to reach a new star system would gain you lots of prestige and combined with the increased technology and manufacturing base might be worth the expense. In the real world many expensive projects have been funded for similar reasons. And the results haven't actually been that bad. Ideally after the project is over all those highly trained engineers and specialists will move on to commercially viable projects that will help national economy and give the funding faction a technological and economical advantage.

After the generation ship reached the next star system, it would initiate a similar colonization of the system as had already occurred in the home system. The new colonies would then be linked to the home system with light speed communications. While direct trade would probably be unfeasible, there would be some prestige and, in the long run as the colony population increases, possibly a cultural and scientific advantage from the larger population base. For the first few systems there would certainly be a scientific advantage from being able to study more planets from close range than competition.

Now, here is the part that is actually relevant to the question. You'd still have the generation ship, resupplied and retrofitted with the resources of the new system. You'd still have the people who had spent generations living in that generation ship and who would have no attachment to having a star system. Indeed whose purpose for generations had been to reach another star system. What would they do? They'd leave for the next system.

They would have become nomads. If they'd come to an empty system they'd stay long enough to establish colonies linked to the baseline culture, resupply, and then move on. Possibly from time to time they'd build new generation ships, although more likely those would be built by the star systems for reasons similar to the original generation ship.

Over time the generation ships would come to have very strong identities, not just as individual ship cultures, but as a group separate from the less mobile people. Also, the ships would eventually start meeting each other and travelling in already colonized star systems, further developing a shared and separate cultural identity. If the ratio of colonization to visit got low enough the nomads and sedentary cultures would become separate civilizations.

The relationships would likely be relatively peaceful, as the generation ships would by necessity be largely self-sufficient and only require fairly low cost resupply. I think they could pay for those with "cultural products" such as art, design, entertainment... They'd probably be welcome visitors in the colonies. Older, more established systems might be less welcoming. And there would also be questions of the relationship between the homeworld and the colonies. Which might be different for colonies of different factions and ages. And which would impact relations with the nomads. And probably make the nomads more likely to identify with each other, not with their system bound cousins.

Answer 2

The main reason I can think of for leaving one's planet entirely is exhaustion of resources — be they food, energy, breathable air, disease free habitat, space to put new born people... But to actually become nomadic, you either have to

• deplete the resources of the new planet
  • your nomads only leave rarely
  • your nomads are very numerous
  • they actually pillage the planet they get on to stock up on resources
• need seasonal resources (planets from cluster 1 can provide for half a time cycle and planets from cluster 2 can provide for the other half of a cycle)
• need localized resources (some things you can only get from planets in cluster 1, some others from planets in cluster 2)
• your nomads benefit specifically from moving
  • because of trade
  • to escape oppression

In the end, because of the enterprise it would be to become nomadic, I believe the decision to do so would have to come from a combination of all these factors linked to a great ease for interstellar travel and a cultural tendency to be nomadic.

Following a comment from @Falco above, I'd like to add his idea to this post: if the planets within your reach are all occupied (and would make you pay some sort of tax to stay) and that space travel has become relatively cheap, it might be that the future of homelessness is endless space faring...

Answer 3

One very good example that immediately comes to mind is the Outsider race in the Known Space series by Larry Niven.

The Outsiders naturally travel from planet to planet, trading information with the locals on the planet. Since information can only be sold once on any star system with a global communication system such as the Internet, it therefore necessitates that once they have sold all the information that the client star system is able and willing to buy, they will have to leave the star system and approach a different star system to sell information.

While the Outsiders are organisms that naturally live in outer space, there is no reason a humanoid species cannot sustain the same lifestyle. With a sufficiently large ship, they can simply stop by star systems to restock, and then continue selling information. If a sufficiently large proportion of star systems are uninhabitable to the humans but habitable to other sentient races, this could be a very good way of making a living.

Answer 4

It obviously depends a great deal on the exact style of interstellar travel the nomads have available, and there are plenty of good answers here already, but I'll add another potential reason: Killing time. Given a means of safely traveling at relativistic speeds and knowledge of some interesting or beneficial event that will happen in the distant (even cosmologically distant) future, a civilization or group may decide that the best way to ensure they live to see this event is to simply spend as much time in transit as possible.

Depending on the amount of time that they want to travel through and how fast they can go, it may be necessary to stop for supplies. And this, in turn, requires them to spend longer at lower speeds (accelerating and decelerating)- which means longer subjective time, and more required supply stops, and so on.

Answer 5

What makes such a scenario highly unlikely is the mind-bogging amount of energy space travel actually requires.

The energy to put a few humans into low Earth orbit with supplies lasting only for a couple of weeks is approximately the same as required to live a modern lifestyle for a year in the USA, with all the wasteful driving with a car to do grocery shopping, so in a resource-strained world probably enough for a whole community to live for quite some time. And you traveled only a few hundred km away from your planet. You need much, much more to leave the solar system, and to reach another star system in less than a few million years you will need to travel at a significant proportion of the speed of light. This will take many orders of magnitudes more energy. Don't forget the supplies you need to bring with you for such a lengthy journey, plus the tools required to live at your destination and extract the resources for yet another journey! And that's just for a couple of people, not a whole civilization!

This makes a space-nomadic lifestyle highly impractical, if not completely implausible. It's like you don't like your job and you would consider moving to a neighboring city for a better job, but the travel would cost you 100 billion dollars.

Planets are large. You would find a lot more materials and would be much better protected on a planet, even a completely barren and dead planet, than on any spaceship. If you had the technology to "effortlessly" travel to other systems and colonize them, you could much more easily terraform your planet, or just live in orbital habitats around it.

If you have the technology and the resources to move a whole civilization through space you pretty much achieved (or are close to achieving) singularity, and settling on planets and using their meager fossil or fissile resources would be completely pointless. You would probably require much more energy just to stop at the planet and then accelerate again after you are done, than all the resources the planet could ever offer!

Answer 6

One possible scenario could be dependence on a certain resource, which can be harvested from many planets, but which is depleted quite quickly and needs a long time to regenerate.

The nomads would travel to a planet and live there, while there collectors are collecting all of the resource, which could take days/weeks/months however you like. In this time they could also hunt/farm or trade on the planet and settle in a little. Once the resource is depleted, they will travel to the next planet on their route. Overall they will have a cycle with maybe hundreds or thousands of planets they will visit. Depending on the numbers it could be years or generations until they visit the same planet again - in this time the planet has regenerated the natural resource and they can collect it again.

One possible option could be some kind of cosmic energy, which gets trapped in the gravitational field of a planet and can be harvested by collection satellites which are released into lower orbit and take several weeks to will their capacitors. Once all the energy is collected, the nomad ships can travel for Months using this energy as a source. If the planet has local inhabitants they don't care, because the cosmic radiation doesn't have any practical use for them - most likely they don't even know about it. And the planet will take some years to regenerate the radiation up to a level where an optimal collection is possible.

Answer 7

You could take a cue from The Culture, who prefer living in constructed habitats over existing planets, keeping the planets as wildlife sanctuaries.

So your evolution to spacenomads could like like this.

1. Due to overpopulation, someone has to leave the planet.
2. After colonizing several planets, your civilization comes to the conclusion that all this taking over planets and destroying the local flora and fauna is a Bad Thing(tm)
3. Your civilization leaves for deep space/interstellar constructed habitats.

Answer 8

I can imagine two things that would cause this to happen, trade and monsters.

Trade

A group of traders would have good reason to be nomadic. Travelling from planet to planet and trading for the unique goods produced by a certain planet for other goods collected during travels would provide a powerful motivation for moving from place to place. Earth's finest cheeses could be worth a fortune on the fifth moon of Antares, who in turn ship back ingots of raw unobtanium from their highly advanced factories. Shuttling goods back and forth may be a multi-generational prospect without FTL, but if the payoff is high enough it could make the nomadic traders quite wealthy.

Monsters

Nomads could also be driven from planet to planet by intergalactic monsters that will find and devour them if they settle in one place for too long. The nomads may be capable of living for long periods of time on their spacecraft, but occasionally need to land and gather raw materials for building more ships or replenishing their supplies. The same could be true if the nomads themselves are the monsters, occasionally landing to gather fresh prey, and taking off before the local authorities can arrive to stop them.

Answer 9

Well, there is an old TV series "Battlestar galactica" that deals with the subject. They leave their home solar system because they were invaded. Go out to deep space is never a good choice. Movies like Interstellar make use of the idea just because it is a romantic idea. The only and unique factor that could be a logical justification to leaving your home planet permanently is total and permanent annihilation of the planet. Any thing else is romantic but not practical. Is ever preferable to fix the problem. A 1000 years winter started by a meteor hit is hard to delivery but is Infinitely more easy to enduring than scape to space into a space ship.

Answer 10

Genetic Diversity.

If the level of technology is high enough that it is feasible to live on a spaceship for generations at a time, it seems reasonable that there would be some people (hermits, political refugees, space hippies, whatever) who would want to live in space full time. Over the course of time, it seems reasonable that groups of these people would form and decide to go live out in space.

One thing to remember is that space is ENORMOUS beyond your ability to comprehend. In order for space itself to get crowded there would have to be an unbelievably large number of people in the universe. People living in space could easily go millenia without running into any other groups by accident. So rather than needing a reason for these people to live in space, you need a reason for them to want to run into other groups, whether that be other space-faring groups or planetary colonies.

As others have already mentioned, one reason for wanting to encounter others is the need for refueling and other resources. The strength of that need would be determined by the level of technology.

Genetic diversity is another important need, both for the nomads and planetary colonies that they may visit. Unless your nomad groups have thousands of people in them, you're going to run into the problem of having a minimum viable population. Wikipedia gives the number as around 4,000 individuals, but I believe that assumes you are allowing the population to grow larger than that. With too few people, you'll end up having a lot of inbreeding and the genetic problems that follow. As such, they'll need to increase their genetic diversity by introducing new genetic material.

Fortunately for your nomads, fulfilling this need for genetic diversity also helps the planetary colonies they visit. As I said, the colonies will also be worried about having enough genetic diversity, so when a nomad group visits a colony it will be a two way trade. Perhaps a few members of the colony want to leave and go somewhere else? They can join the nomads for a while. Perhaps a few of the nomads want to settle down? They can stay with the colony. Perhaps some families will exchange a child with a family of the other group. There would probably also be an exchange of sperm and possibly eggs, whether by sex or artificial techniques like IVF.

How frequently they need to do this will depend on the size of the nomad group and how long they are able to stay on the planets. If there is a group numbering in the thousands (close to the minimum via population) they could go many generations between visits and not suffer genetically. If a group has fewer than a hundred people, they'd probably want to visit a planet at least once a generation. If the group can stay on a planet for long enough for multiple children to be born/conceived, they can get in their diversity needs all in one go. If they can only stay for a short time (less than a year), they will need to visit more planets. There would not be too much benefit in staying on a planet for longer than a few weeks unless it takes longer for the nomads to get the resources they need or they will be able to stay long enough to have a second round of children.

These nomads would also likely stay just beyond the edges of populated space where colonies are just being established. Once a colony has become large enough that it doesn't need to worry about genetic diversity, the nomads have less to offer the colonists and will therefore have to exchange more in order to get whatever other resources they need. If a colony is very small the colonists will be more interested in genetic diversity, giving the nomads an advantage in trading.

In short, there will be people who want to live in space but visit colonies to maintain genetic diversity.

Answer 11

Yes. Not only could it, but it's my hope and belief such civilizations will come to pass in our solar system.

Here is a video of Jupiter resonant asteroids. The first half is Hilda asteroids with a 3/2 resonance with Jupiter. The second half is of the leading and trailing Trojans at the Sun-Jupiter L4 and L5 points.

Notice at their aphelions the Hildas regularly visit the L4 and L5 regions where the Trojans dwell. At their perihelions they also pass through the Main Asteroid Belt.

So we have three substantial asteroid populations: The Main Belt, the trailing Trojans, and the leading Trojans. Each might have it's own civilization. And then there's the Hildas who regularly visit all three. I imagine the Hilda based civilization as a trading culture, a 22nd century version of Marco Polo's caravans.

There are other cycler asteroids possible. Here is an illustration from my page on possible earth to Main Belt cyclers:

The green orbits are main belt regions having 3, 3.5, 4, 4.5 or 5 years orbits. The red orbits have the same periods but with 1 A.U. perihelions. Thus the red orbits can regularly fly by the earth.

For example the red 3.5 year orbit will fly by the earth each 7 years. It could also fly by certain asteroids each 3.5 years In fact I illustrated a story based a 3.5 year asteroid and a 3.5 year cycler. (beneath each page are links to move forward or backward).

In summary, if humans break out of cradle earth, I believe nomadic cycler trader cultures are inevitable.

Answer 12

Ignoring the need to store sufficient amounts of food and take care of hygiene somehow (including waste management, see P.S.), there is one very serious problem with nomadic spacefaring: women conceived in space or present in space as embryos would likely be sterile due to the effect heavy charged particles have on the developing egg cells. Nomadic spacefaring will either require a terribly advanced way of shielding against space radiation (Earth has upper layers of atmosphere and a very strong magnetic field to keep us safe from high-energy protons and other nasty things) or faster-than-light precise travel that will allow short runs between stars (a dozen light-years’ distance) and long periods of settlement on a single planet or at least within a single system since going to space while pregnant would result in sterile daughters (should not affect male embryos much because males generate sperm during the course of their lifetime while women develop their lifetime’s supply of eggs in utero).

If the maximum speed you can afford is the speed of light then you’ll likely be limited to one move per generation (or suppose three moves per lifetime).

It is simpler if you decide to go with inorganic or outright cybernetic life forms. Inorganic is very loose term here because it still can be xenobiology not based on organic compounds (carbon). For example a silicone-based lifeform that might be driven by something other than DNA chains or a stronger-bonded analog.

A very good candidate for a spacefaring nomadic nation would be a race of sentient machines who could harvest asteroids and enormous gaseous clouds (even supernova fallout) for materials and fuel. Equipping them with reliable long-range faster-than-light communications will enable enormous hive-mind potential or exploration of other, more controversial topics.

P.S. Regarding waste management: Even small objects in space are very dangerous because damaging the hull of anything spacefaring even lightly can cause very quick breakdown and speeds are rather uninhibited (remember the comets that fly around empty space with tails as long as a planet’s diameter? They are just pieces of solid rock or ice or such and they break down so much just by hitting Sun’s energy, now imagine a flimsy hull of a ship which is essentially hollow inside). So throwing out stuff should be reserved for very slow speeds, or maybe sending your trash in one great package on a rocket into the nearest star. Enormous recycling ability would help, of course. Alternatively you could employ exceptionally rigid materials and “energy barriers” for exterior hull, but explaining such technology would be just as difficult.

Answer 13

It's possible that a civilization of sufficient size could work this way.

They would have to be in such numbers so that they need to strip a planet down to bare rock in a time period that is a high proportion of the time it took to get there, however.

Many, many times the current population of the earth, or perhaps the large amount of ships requires as much resources. More likely stars in that instance (Hydrogen).

Anything less than huge pop. and/or huge fuel requirements would make such an activity cost-preventative. And there would also have to be the need (or desire) for all of the pop to be together. Because these problems would be more easily solved by simply dispersing across the galaxy to various planets and setting up there.

But of course, there are reasons for things that are not strictly practical. Simple tradition might be enough for a massive spacefaring population to wish to all be together.

Answer 14

As other have pointed out, the economics of interstellar nomadism just don't add up without wildly futuristic FTL travel ala Star Trek or Star Wars. So maybe the people have less-than rational reasons to travel?

Perhaps they believe that their god is waiting for them on an unknown world, so they visit add many as they can, performing some kind of invocation at each one and then crossing it off the list. There could be many factions who have different beliefs about where to look, so occasionally splinter groups form which to search in another direction.

Maybe they're nomadic by instinct? For no rational reason, they gradually become dissatisfied with each world they visit and inevitably move on. Maybe they consider it a sin for a man to be born on the same planet as his grandfather.

Perhaps their lifestyle produces unwanted byproducts, either physical pollutants or something less tangible, like a taboo against making a grave within 100 miles of an existing one. In times past, the taboo ended when the papier-maché tomb eroded away, but these days they're made from a special eternium alloy made from old diapers which doesn't decompose for ten thousand years. That'll eat up land fast!

Maybe they have a reputation which follows them? They must move on as soon as the locals get word that these space-Gypsies can't be trusted (no offense to the Roma). The Ferengi were ecstatic to enter the Gamma Quadrant where no one knew about their... unsatisfied customers. This only applies if they're nomadic among settled worlds, of course.

Answer 15

As has been mentioned, without FTL travel, Generation ships are the only real possibility.

Building, supplying, and powering such ships is not going to be trivial, as has been mentioned.

So, the reasons to do this are limited, death of the Sun, maybe serious over crowding, perhaps even a surplus of wealth (maybe we're harvesting resources across the solar system, and it's going wonderfully for us).

But, there will not be an excess of resources when we arrive, so while we might have the ships to move on, it's very unlikely we'd have the fuel or supplies (although 'supplies' may not be a concern, as the ships will be closed systems, no matter will escape them, and everything that wears down or is used will be recycled).

Once the new planet is reached the quickest way to establish a settlement would be to use the ship, maybe keeping it intact, maybe breaking it down.

Either way, becoming nomads without having seriously exploited the resources of the planet would not make sense, travelling for generations between pit stops does not make sense, basically it would be like living on a train that doesn't stop, what's the point of traveling if there isn't a destination?

Obviously FTL travel without time travelling quicker outside the ship could change things massively.