Bdtyktl

Larry Niven defines a macro-life civilisation as one that lives in interstellar spacecraft, independent of planetary resources and culture, full time and by implication keeps moving. This could mean small but self-sufficient generation ships or could entail something as vast as a ram-jetting Ringworld with a star for a fusion drive. Such a civilisation, once formed, would appear to have no resource reason to resettle on planets, (near asteroid belts yes; at the bottom of a planetary gravity well no), and in terms of long-term species survival macro-life seems, to me, the better bet.

The individual case answer will obviously vary based on cultural mores but I'm interested in the logical answer based on resources and long-term survival goals, to that end: Why would a successful macro-life civilisation give up their long held nomadic habits for a return to a planet-bound lifestyle?

Please note that for the purposes of this question it's all or nothing; either they colonise new planets or they stay interplanetary, travelling in habitats that don't need worlds and barely need star systems at all. Answers need to make a logical argument, based on long term survival, for planets being worth the effort of changing cultural norms that have existed for generations. The question makes the possibly unfounded assumption that there are suitable worlds at journey's end to be colonised at the option of these macro-life travelers.

Some contextual details that may have bearing on the question:

• the macro-civilisation in question is composed of a small fleet, of ten to a dozen, very large (20+ kilometre long) slower-than-light generation ships, each of which has traveled roughly 25,000 light years when it reaches the colonisation target area.




• the ships are capable of getting up to roughly 0.9C but accelerate at a maximum of only 0.2g.




• any single ship is completely self sufficient of the technical equipment necessary to keep in resources and repair from material gathered from asteroidal and/or cometary debris.




• any individual ship is capable of replicating itself over the course of a year of so given enough resources.




• the trip has taken at least 4 very long generations for the ruling classes, several millennia at least.




• the trip was initially undertaken for purely political reasons, the governors of the fleet left home rather than face the brewing revolt of their subjects and took large numbers of loyal subjects with them.




• the governors have absolute power they can and will enforce whichever choice on the population as a whole, period.

please note that for the purposes of this question it's all or nothing: either they colonise new planets or they stay interplanetary.

You have a problem there.

For starters, I don't think you could enforce it for a civilization. It cannot be enforced for even a small country. Throughout human history we've had people who move and people who stay, for more reasons than we can count.

Also notice that by choosing one lifestyle over the other, you make the civilization less tenacious against threats. Fleets will die when their systems fail and they are adrift in the f[expletive] void of space, whereas planets fail when a nova happens too close, or when they get bombarded by large enough asteroids or planet buster weapons.

That said, planets give you more mass than you can get in an asteroid belt (our own asteroid belt has less than 5% the mass of the Moon), and fpr non-rogue planets they can also provide you with a self-sustaining biosphere and a close-by star to syphon energy from.

Catastrophe beyond the ships' collective ability to repair. Not all the ships might be destroyed, but the remaining ships may not be able to support the influx of survivors from the damaged ships.

Piracy/Attack A variation of catastrophe--perhaps the spacefarers are forced to settle due to theft of or damage to their ships from outside attackers.

Destination Reached/Fulfillment of Prophecy Your spacefarers have reached a planet that they were either specifically headed for or unquestionably meets the criteria laid out in a prophecy.

Rebellion You say "the governors have absolute power they can and will enforce whichever choice on the population as a whole, period" but then why was there a rebellion on the home planet? Either the insurrectionists win and settle on a planet, or the governors put down the rebellion and settle the planet. This might also involve some aspects of Catastrophe. The cause of the rebellion really doesn't matter. Maybe they're just tired of living in tin cans and want to try something new.

No matter how you look at it there is no logical solution.

One of the singular most crucial factors in a species survival is its ability to adapt to change thereby allowing it to spread.

The key here is spread. The larger the area a species thrives in the larger effort nature must expend to wipe it out. The larger the effort the lower the probability of occurrence.

For example a small volcano wiping out an island and whatever unique species it holds vs a meteor wiping out the dinosaurs.

There is no natural logic in reducing conquered surface area and access to resources.

There may be a diplomatic reason:

If they encountered a militarily superior species whom segregated them to a single world, maybe out of public opposition to genocide or for biological research. That might be a semi logical reason.

From what little we know about your life forms and their situation, I think this sounds like the best bet for them, especially since they seem dictatorial...

The choice is to stay in space. This offers so many advantages:

1. Easier mobility; dealing with gravity wells is very expensive




2. Enhanced probability of species continuity; it's easier to avoid extinction if you are mobile and especially spread out at least a little bit




3. Resources in space can be detected from a distance and, if enough advance notice, intercepted with minor course corrections instead of digging through millions of tons of rock hoping that you find what you want




4. Resources in space are sometimes more pure than what you find planet-side; hence the old "sword of star material" trope since some meteor iron was purer than natural earth-bound iron

... and the list goes on, you could probably come up with dozens of reasons of your own.

Now, here's the rub...

There are advantages to being planet-side too. They just do not outweigh the first couple points mentioned for staying space-side for your people. But the biggest benefit of being planet-side is that there are some things you just cannot get in space, or at least not nearly as much as (or efficiently/easy as) on a planet. However, your people can have the best of both worlds even while they stay in space...

Your group can decide to leave a very small contingent of people on a planet with the tools necessary to acquire the resources the primary group needs. Or they could use other animals or races to do the work for them. Either way, set them up to have what you need by some deadline. Come back to this area by that time, and take the resources then continue on.

This requires that the people either stay in one area long enough to wait for those planet-side to do their work, or requires the people to double-back to this spot at some point. So it does slow them down, but they still remain nomadic.

In fact, this sounds very much like nomadic cultures ruled by a chief whose word was law. They would move around, but they would have to stop at certain areas for a while out of necessity to gather materials, build, or perform other tasks. Some of these tasks would even be difficult, possibly expensive for them, such as cutting down large trees if they did not have metal blades. They may even leave people behind to continue on and gather other resources before returning to people working on their long-running tasks.

The main difference between your people and ancient nomads is that they are wandering space from celestial object to celestial object instead of wandering on the surface of a planet from resource area to resource area. An analogy with desert nomads would be even more apt since they too would be venturing through long stretches of "empty space".

Despite the question constraint, the answer is very obviously "both".

You have an entire society focused around and specialized in maintaining an interstellar society. It makes no tactical or logistical sense to try to convert the whole society and all their equipment into terraformers.

It makes a lot of sense for both the survival of the species and the survival of the society to allow those who want to land, to do so. This along with those that the society does not wish to remain in the society. So they seed all habitable planets in their wake.

We can comply with the criteria of the question if we consider each planet in isolation, though. You could make four simple rules:

1) At each mineable planet, reproduce at least one ship.

2) At each habitable planet, use at least one ship as a seed population.

3) If the number of ships grows larger than a certain point, fork the society.

4) If it shrinks below a certain point, don't seed any more planets until you reach the necessary minimum.

This does lead us inexorably to Fermi's paradox, though: why has this not been done? (https://en.wikipedia.org/wiki/Fermi_paradox)